Optical and Optoelectronic Materials and Applications

Topic Information

Dear Colleagues,

In the last few decades, advanced technologies in the fields of optical materials and optoelectronics, as well as energy storage and up-conversion luminescent applications, have played critical roles in addressing societal demands, including the increasing global energy consumption, the growing demand for sustainable clean energy, the transition to digitization, the Internet of Things, and the development of multifunctional applications such as colorful optoelectronic devices, agrivoltaics, and heat control. Herein, this topic aims to collect original research articles and review papers. Manuscripts should cover, but are not limited to, the following topics:

• Optoelectronics;
• Nanophotonics;
• Optical Materials and technologies;
• Optical fiber materials and fabrication technologies;
• Fabrication and characterization of transparent ceramics and glasses;
• Thin films for optical applications;
• Physical, chemical, and environmental optical sensors;
• Optical materials for photocatalysis, photovoltaics, etc.;
• Deposition methods and thin film processing for PV applications;
• Energy Conversion, Saving and Storage;
• Magneto-optical visualization of micromagnetic objects;
• Structured vortex beams in nanophotonic systems and devices;
• Nanomaterials for photovoltaic applications and third generation concepts, including up-conversion, down-conversion, MEG, etc.

Prof. Dr. Fabian Ambriz Vargas
Prof. Dr. Jianzhong Zhang
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	18.4 Days	CHF 2400
Coatings coatings	2.9	5.0	2011	14.5 Days	CHF 2600
Materials materials	3.1	5.8	2008	13.9 Days	CHF 2600
Photonics photonics	2.1	2.6	2014	14.9 Days	CHF 2400
Sensors sensors	3.4	7.3	2001	18.6 Days	CHF 2600

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Published Papers (71 papers)

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13 pages, 2972 KiB  

Open AccessArticle

Excitonic Evolution in WS₂/MoS₂ van der Waals Heterostructures Turned by Out-of-Plane Localized Pressure

by Weihu Kong, Zeqian Ren, Peng Chen, Jinxiang Cui, Yili Chen, Jizhou Wu, Yuqing Li, Wenliang Liu, Peng Li, Yongming Fu and Jie Ma

Appl. Sci. 2024, 14(5), 2179; https://doi.org/10.3390/app14052179 - 5 Mar 2024

Cited by 1 | Viewed by 1818

Abstract

In this study, we explore the exciton dynamics in a WS₂/MoS₂ van der Waals (vdW) heterostructure under varying pressures by integrating a laser-confocal photoluminescence (PL) spectroscope and an atomic force microscope (AFM). For the WS₂/MoS₂ heterostructure, the [...] Read more.

In this study, we explore the exciton dynamics in a WS₂/MoS₂ van der Waals (vdW) heterostructure under varying pressures by integrating a laser-confocal photoluminescence (PL) spectroscope and an atomic force microscope (AFM). For the WS₂/MoS₂ heterostructure, the exciton emission belonging to MoS₂ is too weak to be distinguished from the PL spectra. However, upon contact with a Si probe, the emission intensity of WS₂ excitons significantly decreases from 34,234 to 6560, thereby matching the intensity level of MoS₂. This alteration substantially facilitates the exploration of interlayer excitonic properties within the heterostructures using PL spectroscopy. Furthermore, the Si probe can apply out-of-plane localized pressure to the heterostructure. With increasing pressure, the emission intensity of the WS₂ trions decreases at a rate twice that of other excitons, and the exciton energy increases at a rate of 0.1 meV nN⁻¹. These results elucidate that the WS₂ trions are particularly sensitive to the out-of-plane pressure within a WS₂/MoS₂ vdW heterostructure. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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8 pages, 1969 KiB  

Open AccessArticle

Superluminescent Diodes Based on Chirped InGaAs/GaAs Quantum Well-Dot Layers

by Mikhail V. Maximov, Nikita Yu. Gordeev, Yuri M. Shernyakov, Grigoriy O. Kornyshov, Artem A. Beckman, Alexey S. Payusov, Sergey A. Mintairov, Nikolay A. Kalyuzhnyy, Marina M. Kulagina and Alexey E. Zhukov

Photonics 2023, 10(10), 1090; https://doi.org/10.3390/photonics10101090 - 28 Sep 2023

Cited by 2 | Viewed by 1472

Abstract

We study the applicability of InGaAs/GaAs quantum well-dots (QWDs) for active regions of broadband superluminescent diodes (SLDs) emitting in the 950–1150 nm spectral range; 2 mm long SLDs with a bent section and an active region based on seven chirped QWD layers show [...] Read more.

We study the applicability of InGaAs/GaAs quantum well-dots (QWDs) for active regions of broadband superluminescent diodes (SLDs) emitting in the 950–1150 nm spectral range; 2 mm long SLDs with a bent section and an active region based on seven chirped QWD layers show emission spectra centered at 1030 nm with a full-width at half-maximum of 80 nm and an output power of 2 mW. In a 250 µm long SLD with a tilted stripe that has an increased output loss, the width of the emission spectra is 113 nm at 20 °C and 120 nm at 60 °C. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 1498 KiB  

Open AccessFeature PaperArticle

Controlled Dispersion and Transmission-Absorption of Optical Energy through Scaled Metallic Plate Structures

by Hammou Oubeniz, Abdelhaq Belkacem, Hicham Mangach, Muamer Kadic, Abdenbi Bouzid and Younes Achaoui

Materials 2023, 16(18), 6146; https://doi.org/10.3390/ma16186146 - 10 Sep 2023

Viewed by 1134

Abstract

The dispersive feature of metals at higher frequencies has opened up a plethora of applications in plasmonics. Besides, Extraordinary Optical Transmission (EOT) reported by Ebbesen et al. in the late 90’s has sparked particular interest among the scientific community through the unprecedented and [...] Read more.

The dispersive feature of metals at higher frequencies has opened up a plethora of applications in plasmonics. Besides, Extraordinary Optical Transmission (EOT) reported by Ebbesen et al. in the late 90’s has sparked particular interest among the scientific community through the unprecedented and singular way to steer and enhance optical energies. The purpose of the present paper is to shed light on the effect of the scaling parameter over the whole structure, to cover the range from the near-infrared to the visible, on the transmission and the absorption properties. We further bring specific attention to the dispersive properties, easily extractable from the resonance frequency of the drilled tiny slits within the structure. A perfect matching between the analytical Rigorous Coupled Wave Analysis (RCWA), and the numerical Finite Elements Method (FEM) to describe the underlying mechanisms is obtained. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 3025 KiB  

Open AccessArticle

High Performance GaN-Based Ultraviolet Photodetector via Te/Metal Electrodes

by Sheng Lin, Tingjun Lin, Wenliang Wang, Chao Liu and Yao Ding

Materials 2023, 16(13), 4569; https://doi.org/10.3390/ma16134569 - 24 Jun 2023

Cited by 6 | Viewed by 2247

Abstract

Photodetectors (PDs) based on two-dimensional (2D) materials have promising applications in modern electronics and optoelectronics. However, due to the intralayer recombination of the photogenerated carriers and the inevitable surface trapping stages of the constituent layers, the PDs based on 2D materials usually suffer [...] Read more.

Photodetectors (PDs) based on two-dimensional (2D) materials have promising applications in modern electronics and optoelectronics. However, due to the intralayer recombination of the photogenerated carriers and the inevitable surface trapping stages of the constituent layers, the PDs based on 2D materials usually suffer from low responsivity and poor response speed. In this work, a distinguished GaN-based photodetector is constructed on a sapphire substrate with Te/metal electrodes. Due to the metal-like properties of tellurium, the band bending at the interface between Te and GaN generates an inherent electric field, which greatly reduces the carrier transport barrier and promotes the photoresponse of GaN. This Te-enhanced GaN-based PD show a promising responsivity of 4951 mA/W, detectivity of 1.79 × 10¹⁴ Jones, and an external quantum efficiency of 169%. In addition, owing to the collection efficiency of carriers by this Te–GaN interface, the response time is greatly decreased compared with pure GaN PDs. This high performance can be attributed to the fact that Te reduces the contact resistance of the metal electrode Au/Ti to GaN, forming an ohmic-like contact and promoting the photoresponse of GaN. This work greatly extends the application potential of GaN in the field of high-performance photodetectors and puts forward a new way of developing high performance photodetectors. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 3583 KiB  

Open AccessArticle

Elucidating the Effects of Interconnecting Layer Thickness and Bandgap Variations on the Performance of Monolithic Perovskite/Silicon Tandem Solar Cell by wxAMPS

by Ili Salwani Mohamad, Camellia Doroody, Wabel Mohammed Alkharasani, Mohd Natashah Norizan, Puvaneswaran Chelvanathan, Seyed Ahmad Shahahmadi and Nowshad Amin

Materials 2023, 16(11), 4106; https://doi.org/10.3390/ma16114106 - 31 May 2023

Cited by 5 | Viewed by 2342

Abstract

In this study, we investigated the pathways for integration of perovskite and silicon solar cells through variation of the properties of the interconnecting layer (ICL). The user-friendly computer simulation software wxAMPS was used to conduct the investigation. The simulation started with numerical inspection [...] Read more.

In this study, we investigated the pathways for integration of perovskite and silicon solar cells through variation of the properties of the interconnecting layer (ICL). The user-friendly computer simulation software wxAMPS was used to conduct the investigation. The simulation started with numerical inspection of the individual single junction sub-cell, and this was followed by performing an electrical and optical evaluation of monolithic 2T tandem PSC/Si, with variation of the thickness and bandgap of the interconnecting layer. The electrical performance of the monolithic crystalline silicon and CH₃NH₃PbI₃ perovskite tandem configuration was observed to be the best with the insertion of a 50 nm thick (E_g ≥ 2.25 eV) interconnecting layer, which directly contributed to the optimum optical absorption coverage. These design parameters improved the optical absorption and current matching, while also enhancing the electrical performance of the tandem solar cell, which benefited the photovoltaic aspects through lowering the parasitic loss. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 3731 KiB  

Open AccessEditor’s ChoiceArticle

High-Efficiency and Compact Polarization-Insensitive Multi-Segment Linear Silicon Nitride Edge Coupler

by Yuhao Zhang, Yi Liu, Xuhua Cao, Li Wang, Chunyuan Mu, Ming Li, Ninghua Zhu and Wei Chen

Photonics 2023, 10(5), 510; https://doi.org/10.3390/photonics10050510 - 27 Apr 2023

Cited by 7 | Viewed by 3623

Abstract

Edge couplers are widely utilized in photonic integrated circuits and are vital for ensuring efficient chip-to-fiber coupling. In this paper, we present a high-efficiency and compact polarization-insensitive multi-segment linear silicon nitride edge coupler for coupling to high numerical aperture fibers. By optimizing the [...] Read more.

Edge couplers are widely utilized in photonic integrated circuits and are vital for ensuring efficient chip-to-fiber coupling. In this paper, we present a high-efficiency and compact polarization-insensitive multi-segment linear silicon nitride edge coupler for coupling to high numerical aperture fibers. By optimizing the thickness of the up cladding and introducing air slots in the transverse direction, we have further modified the limiting effect of the mode field. This innovative edge coupler scheme boasts a compact structure and is compatible with existing mature standard processes, with a total length of only 38 μm. We numerically demonstrate that the proposed edge coupler exhibits a low coupling loss of 0.22 dB/0.31 dB for TE/TM modes at λ = 1550 nm. Furthermore, the proposed coupler displays high wavelength insensitivity within the range of 1400–1850 nm and maintains a coupling loss of less than 0.2 dB with a manufacturing deviation of ±20 nm. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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15 pages, 5922 KiB  

Open AccessArticle

Luminous Flux Utilization of Static Birefringent Fourier Transform Imaging Spectrometer with Zoomable Spectral Resolution

by Xiangzhe Zhang, Jingping Zhu, Liqing Huang, Yu Zhang, Huimin Wang, Jinxin Deng and Fengqi Guo

Appl. Sci. 2023, 13(8), 5132; https://doi.org/10.3390/app13085132 - 20 Apr 2023

Cited by 2 | Viewed by 1399

Abstract

The optical displacement calculation formula for the dual Wollaston prism is derived for any incident plane and angle using the wave normal tracing method. The validity of the calculation is confirmed by comparing it with captured photographs. The relationship between the maximum incident [...] Read more.

The optical displacement calculation formula for the dual Wollaston prism is derived for any incident plane and angle using the wave normal tracing method. The validity of the calculation is confirmed by comparing it with captured photographs. The relationship between the maximum incident aperture, incident angle, and incident surface angle is given when plane and spherical waves incident on the prism group. The aperture utilization of a novel static birefringent Fourier transform imaging spectrometer based on dual Wollaston prisms is also analyzed. The relationship of aperture utilization with the incident surface angle, incident angle, and prisms’ air gap thickness is given. The results provide a theoretical foundation for fully describing the optical transmission characteristics of the dual Wollaston prism group and developing a high-performance spatio-tempo hybrid modulated birefringent spectral zoom Fourier transform imaging spectrometer. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 4853 KiB  

Open AccessCommunication

The Densification Characteristics of Polished Fused Silica Glass and Its Scattering Characteristics

by Xiaowei Jiang, Dingbo Chen, Yuchuan Quan, Xingwu Long, Suyong Wu and Zhongqi Tan

Photonics 2023, 10(4), 447; https://doi.org/10.3390/photonics10040447 - 13 Apr 2023

Cited by 2 | Viewed by 1647

Abstract

Optical surface scattering is an important subject in the field of optics. Previous studies of surface scattering mainly focused on the influence of surface topography and often ignored the influence of the mechanical property’s change caused by polished surface densification. In this paper, [...] Read more.

Optical surface scattering is an important subject in the field of optics. Previous studies of surface scattering mainly focused on the influence of surface topography and often ignored the influence of the mechanical property’s change caused by polished surface densification. In this paper, we study the mechanical property of fused silica glass in detail and analyze the scattering behaviour of actual fused silica glass’s surface with sub-angstrom roughness, considering the topography and the change of refractive index. Experimental results show that there is a negative correlation between the height and modulus on the surface of roughly polished fused silica glass, and the correlation coefficient γ = −0.29 was determined. After super−polishing, the mechanical properties of the sample surface become significantly uniform with a roughness of Rq = 0.06 nm and Ra = 0.05 nm, and the correlation coefficient becomes γ = −0.02. Moreover, the nanoindentation test proves that silica glass surfaces have been densified during polishing. Based on the densification characteristics, the bidirectional reflectance distribution function (BRDF) was simulated by the finite element method. The result indicates that the densification characteristics will increase the scattering intensity. This work not only deepens the understanding of the properties of polished optical surfaces but also the surface scattering characteristics of optical elements. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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15 pages, 4781 KiB  

Open AccessArticle

Synthesis and Study of the Optical Properties of a Conjugated Polymer with Configurational Isomerism for Optoelectronics

by Oscar Javier Hernández-Ortiz, Damaris Castro-Monter, Ventura Rodríguez Lugo, Ivana Moggio, Eduardo Arias, María Isabel Reyes-Valderrama, María Aurora Veloz-Rodríguez and Rosa Angeles Vázquez-García

Materials 2023, 16(7), 2908; https://doi.org/10.3390/ma16072908 - 6 Apr 2023

Cited by 1 | Viewed by 2538

Abstract

A π-conjugated polymer (PBQT) containing bis-(2-ethylhexyloxy)-benzo [1,2-b’] bithiophene (BDT) units alternated with a quinoline-vinylene trimer was obtained by the Stille reaction. The chemical structure of the polymer was verified by nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FT-IR), and mass [...] Read more.

A π-conjugated polymer (PBQT) containing bis-(2-ethylhexyloxy)-benzo [1,2-b’] bithiophene (BDT) units alternated with a quinoline-vinylene trimer was obtained by the Stille reaction. The chemical structure of the polymer was verified by nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FT-IR), and mass spectroscopy (MALDI-TOF). The intrinsic photophysical properties of the solution were evaluated by absorption and (static and dynamic) fluorescence. The polymer PBQT exhibits photochromism with a change in absorption from blue (449 nm) to burgundy (545 nm) and a change in fluorescence emission from green (513 nm) to orange (605 nm) due to conformational photoisomerization from the trans to the cis isomer, which was supported by theoretical calculations DFT and TD-DFT. This optical response can be used in optical sensors, security elements, or optical switches. Furthermore, the polymer forms spin-coated films with absorption properties that cover the entire visible range, with a maximum near the solar emission maximum. The frontier molecular orbitals, HOMO and LUMO, were calculated by cyclic voltammetry, and values of −5.29 eV and −3.69, respectively, and a bandgap of 1.6 eV were obtained, making this material a semiconductor with a good energetic match. These properties could suggest its use in photovoltaic applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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24 pages, 7375 KiB  

Open AccessArticle

Optical Protective Window Design and Material Selection Issues in the Multi-Sensor Electro-Optical Surveillance Systems

by Saša Vujić, Dragana Perić, Branko Livada, Miloš Radisavljević and Dragan Domazet

Sensors 2023, 23(5), 2784; https://doi.org/10.3390/s23052784 - 3 Mar 2023

Cited by 2 | Viewed by 3908

Abstract

Multi-sensor imaging systems have a very important role and wide applications in surveillance and security systems. In many applications, it is necessary to use an optical protective window as an optical interface connecting the imaging sensor and object of interest’s space; meanwhile an [...] Read more.

Multi-sensor imaging systems have a very important role and wide applications in surveillance and security systems. In many applications, it is necessary to use an optical protective window as an optical interface connecting the imaging sensor and object of interest’s space; meanwhile an imaging sensor is mounted in a protective enclosure, providing separation from environmental conditions. Optical windows are often used in various optical and electro-optical systems, fulfilling different sometimes very unusual tasks. There are lots of examples in the literature that define optical window design for targeted applications. Through analysis of the various effects that follow optical window application in connection with imaging systems, we have suggested a simplified methodology and practical recommendation for how to define optical protective window specifications in multi-sensor imaging systems, using a system engineering approach. In addition, we have provided initial set of data and simplified calculation tools that can be used in initial analysis to provide proper window material selection and definition of the specifications of optical protective windows in multi-sensor systems. It is shown that although the optical window design seems as a simple task, it requires serious multidisciplinary approach. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 9799 KiB  

Open AccessArticle

Angle-Based Parametrization with Evolutionary Optimization for OESCL-Band Y-Junction Splitters

by Roy Prosopio-Galarza, J. Leonidas García-Gonzales, Freddy Jara, Maria Armas-Alvarado, Jorge Gonzalez and Ruth E. Rubio-Noriega

Photonics 2023, 10(2), 152; https://doi.org/10.3390/photonics10020152 - 1 Feb 2023

Cited by 2 | Viewed by 2220

Abstract

The design of passive photonic devices based on geometry optimization can lead to energy-efficient, small-footprint, and fabrication-ready geometries. In this work, we propose an angle-based parametrization method to optimize Y-junction splitters based on multimode interferometers. The selected figure of merit was the transmittance [...] Read more.

The design of passive photonic devices based on geometry optimization can lead to energy-efficient, small-footprint, and fabrication-ready geometries. In this work, we propose an angle-based parametrization method to optimize Y-junction splitters based on multimode interferometers. The selected figure of merit was the transmittance in the SCL and OESCL optical fiber communication bands. The performances of three optimization methods were compared: (i) particle swarm optimization (PSO), (ii) genetic algorithm (GA), and (iii) the covariance matrix adaptation-evolution strategy (CMA-ES). The results show that CMA-ES parametrization produces similar transmittance results (≤1.5% of difference) to PSO in the first 40 generations. The CMA-ES results are identical in the SCL (1460–1625 nm) and OESCL (1260–1625 nm) bands, whereas the GA and PSO executions are slightly different in terms of the rate and similarity of the figure of merit. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)
(This article belongs to the Section Optical Communication and Network)

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10 pages, 5318 KiB  

Open AccessArticle

Time-Resolved Photoluminescence in GeSn Film by New Infrared Streak Camera Attachment Based on a Broadband Light Upconversion

by Patrik Ščajev, Saulius Miasojedovas, Algirdas Mekys, Pavels Onufrijevs and Hung-Hsiang Cheng

Coatings 2023, 13(1), 111; https://doi.org/10.3390/coatings13010111 - 7 Jan 2023

Cited by 2 | Viewed by 2194

Abstract

GeSn coatings on commercial Si substrates have gained increased interest for application in infrared detectors and lasers. The characterization of these materials is crucial for their quality assessment and in describing device performance for commercialization. The time-resolved photoluminescence is an efficient method for [...] Read more.

GeSn coatings on commercial Si substrates have gained increased interest for application in infrared detectors and lasers. The characterization of these materials is crucial for their quality assessment and in describing device performance for commercialization. The time-resolved photoluminescence is an efficient method for contactless, time-resolved characterization of GeSn optoelectronic properties. For this purpose, in this work, we developed an infrared streak camera attachment based on the broadband upconversion of infrared photoluminescence by using powerful nanosecond 1064 nm pulses. The attachment achieved picosecond time resolution, being limited by the laser pulse duration, jitter, and temporal resolution of the streak camera. The spectral range for time-resolved photoluminescence in the 1100–2400 nm interval was obtained, outperforming the range of commercial infrared InGaAs streak cameras. The developed setup was applied for excitation-dependent time-resolved photoluminescence decay measurements in a GeSn and compared to the conventional upconversion technique with the optically delayed picosecond gate pulses. The new setup provided 2D spectro-temporal images for analysis. The photoluminescence decay times in the 30–80 ps range were obtained in the GeSn layer depending on the excitation pulse energy and spectral emission wavelength. Carrier thermalization was observed as a redshift of the photoluminescence spectra with time. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 2670 KiB  

Open AccessArticle

Nanoscale ITO Films for Plasmon Resonance-Based Optical Sensors

by Yury Zhidik, Anna Ivanova, Serafim Smirnov, Klavdiya Zhuk, Igor Yunusov and Pavel Troyan

Coatings 2022, 12(12), 1868; https://doi.org/10.3390/coatings12121868 - 1 Dec 2022

Cited by 2 | Viewed by 2066

Abstract

The developing field of plasmonics has led to the possibility of creating a new type of high-speed, highly sensitive optical sensors for the analysis of chemical and biological media. The functional conducting layers of surface plasmon resonance (SPR) optical sensors are almost always [...] Read more.

The developing field of plasmonics has led to the possibility of creating a new type of high-speed, highly sensitive optical sensors for the analysis of chemical and biological media. The functional conducting layers of surface plasmon resonance (SPR) optical sensors are almost always nanoscale thin films of noble metals. To enhance the plasmon resonance, nanostructured films of transparent conductive oxides are introduced into the optical sensors. However, such modified optical sensors operate in the infrared region of the spectrum. In this work, we demonstrate that the use of indium tin oxide (ITO) films with a high concentration of charge carriers makes it possible to shift the surface plasmon resonance into the visible radiation region. The work presents the results of the development of magnetron deposition technology for ITO thin films, with optimal parameters for optical sensors based on surface plasmon resonance operating in the visible range of the spectrum. Their optical and electrical characteristics are investigated. Excitation of the surface and volume plasmon resonance at the dielectric-ITO film interface, using the Kretschman configuration, is studied. It is shown that SPR is excited in the investigated ITO films with a concentration of free charge carriers of the order of 10²¹–10²² cm⁻³, when irradiated with a beam of light with TM polarization in the wavelength range of 350–950 nm. At the same time, the addition of various analytes to the surface of an ITO film changes the excitation wavelength of the SPR. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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16 pages, 3287 KiB  

Open AccessArticle

Research on Spectral Restoration and Gas Concentration Inversion Accuracy Based on Quasi-Trapezoidal Window

by Yusheng Qin, Xiangxian Li, Xin Han, Jingjing Tong and Minguang Gao

Photonics 2022, 9(11), 885; https://doi.org/10.3390/photonics9110885 - 21 Nov 2022

Cited by 3 | Viewed by 2069

Abstract

The Fourier transform is a popular method for analyzing and processing interference data in which spectrum leakage occurs. Generally, window function (also called apodization function) weighting is employed to limit spectrum leakage. A rectangular window with optimal main-lobe performance and the Rife-Vincent (R-V) [...] Read more.

The Fourier transform is a popular method for analyzing and processing interference data in which spectrum leakage occurs. Generally, window function (also called apodization function) weighting is employed to limit spectrum leakage. A rectangular window with optimal main-lobe performance and the Rife-Vincent (R-V) window were introduced to improve the window function performance, resulting in the establishment of a quasi-trapezoidal window function. Based on the experimental interference data, the quasi-trapezoidal window function was used in the spectral restoration process. The experimental results show that when the apodization degree of the quasi-trapezoidal window was 1.06, the spectral resolution was improved by 17.46% compared with that of the Hanning window; when the apodization degree was 2.71, the spectral signal-to-noise ratio (SNR) was improved by 130.09% compared with that of the Blackman-Harris window function. In the propane (C₃H₈) and ethylene (C₂H₄) gas concentration inversion experiment, when the apodization degree was increased from 1.06 to 2.58, the inversion precision was increased by 6.94% for C₃H₈ gas and 23.93% for C₂H₄ gas. Through the parameter adjustment, the quasi-trapezoidal window may achieve a high SNR or high-resolution spectral restoration, which can improve the accuracy of gas concentration inversion to some extent. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 7110 KiB  

Open AccessArticle

Terahertz Generation by Optical Rectification of 780 nm Laser Pulses in Pure and Sc-Doped ZnGeP₂ Crystals

by Vladimir Voevodin, Svetlana Bereznaya, Yury S. Sarkisov, Nikolay N. Yudin and Sergey Yu. Sarkisov

Photonics 2022, 9(11), 863; https://doi.org/10.3390/photonics9110863 - 16 Nov 2022

Cited by 4 | Viewed by 2373

Abstract

Terahertz wave generation through the optical rectification of 780 nm femtosecond laser pulses in ZnGeP₂ crystals has been studied. All of the possible interactions of types I and II were analyzed by modeling and experimentally. We demonstrate the possibility of broadband “low-frequency” [...] Read more.

Terahertz wave generation through the optical rectification of 780 nm femtosecond laser pulses in ZnGeP₂ crystals has been studied. All of the possible interactions of types I and II were analyzed by modeling and experimentally. We demonstrate the possibility of broadband “low-frequency” terahertz generation by an ee–e interaction (with two pumping waves and a generated terahertz wave; all of these had extraordinary polarization in the crystal) and “high-frequency” terahertz generation by an oe–e interaction. The arising possibility of achieving the narrowing of the terahertz generation bandwidth at the oe–e interaction using thicker ZnGeP₂ crystals is experimentally confirmed. It has been found that the thermal annealing of as-grown ZnGeP₂ crystals and their doping with a 0.01 mass % of Sc reduces the absorption in the “anomalous absorption” region (λ = 0.62–3 μm). The terahertz generation by the oo–e interaction in (110) ZnGeP₂:Sc and the as-grown ZnGeP₂ crystals of equal thicknesses was compared. It has been found that ZnGeP₂:Sc is more efficient for 780 nm femtosecond laser pulses optical rectification. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 3434 KiB  

Open AccessArticle

A Comparative Study of Ir(dmpq)₂(acac) Doped CBP, mCP, TAPC and TCTA for Phosphorescent OLEDs

by Despoina Tselekidou, Lazaros Panagiotidis, Kyparisis Papadopoulos, Vasileios Kyriazopoulos and Maria Gioti

Photonics 2022, 9(11), 800; https://doi.org/10.3390/photonics9110800 - 26 Oct 2022

Cited by 4 | Viewed by 3126

Abstract

In this work, we present the fabrication and characterization of solution-processable red Phosphorescent Organic Light-Emitting Diodes (PhOLEDs). The proposed approach is based on Ir(III) complex, namely Bis(2-(3,5-dimethylphenyl)quinoline-C,N)(acetylacetonato)Iridium(III), also known as Ir(dmpq)₂(acac), which was doped in four different host materials: (a) 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl [...] Read more.

In this work, we present the fabrication and characterization of solution-processable red Phosphorescent Organic Light-Emitting Diodes (PhOLEDs). The proposed approach is based on Ir(III) complex, namely Bis(2-(3,5-dimethylphenyl)quinoline-C,N)(acetylacetonato)Iridium(III), also known as Ir(dmpq)₂(acac), which was doped in four different host materials: (a) 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP), (b) 1,3-Bis(N-carbazolyl)benzene (mCP), (c) 1,1-Bis[(di-4-tolylamino) phenyl]cyclohexane (TAPC), and (d) tris(4-carbazoyl-9-ylphenyl)amine (TCTA). The metal–organic complex offers unique optical and electronic properties arising from the interplay between the inorganic metal and the organic material. The optical and photophysical properties of the produced thin films are investigated in detail using spectroscopic ellipsometry and photoluminescence, whereas the structural characteristics are examined by atomic force microscopy. This comparative study of the four different Host:Ir-complex systems provides valuable information to evaluate the emission characteristics in order to achieve pure red light. Finally, these materials were applied as a single-emissive layer in PhOLED devices, and the electroluminescence characteristics were studied. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 2775 KiB  

Open AccessArticle

Europium(III)-Doped Gadolinium(III) Complex for High-Sensitivity Temperature Sensing in the Physiological Range

by Kevin Soler-Carracedo, María Díaz-González, Inocencio R. Martin, Susana Rios, Beatriz Gil-Hernández, Gabriela Brito-Santos and Joaquín Sanchiz

Materials 2022, 15(21), 7501; https://doi.org/10.3390/ma15217501 - 26 Oct 2022

Viewed by 1762

Abstract

A new Eu³⁺-doped Gd³⁺ complex of formula [Eu_0.0135Gd_0.9865(pta)₃me-phen] was synthesized and structurally characterized (Hpta = benzoyltrifluoroacetone, me-phen = 5-methyl-1,10-phenanthroline). The photoluminescence study revealed that when the compound was excited at RT, under a 457 [...] Read more.

A new Eu³⁺-doped Gd³⁺ complex of formula [Eu_0.0135Gd_0.9865(pta)₃me-phen] was synthesized and structurally characterized (Hpta = benzoyltrifluoroacetone, me-phen = 5-methyl-1,10-phenanthroline). The photoluminescence study revealed that when the compound was excited at RT, under a 457 nm continuous laser, the material exhibited high luminescence due to the antenna effect of the ligands, as well as a good balance between the phosphorescence from the spin-forbidden triplet (from the organic ligands), and the characteristic lanthanide f-f transitions. The ratio between the previous emissions drastically changed when the sample was heated up to 62 °C inside a tubular furnace. This ratio was investigated using the luminescence intensity ratio method, to analyze the capabilities of the sample as a temperature sensor. The relative sensitivity reached a maximum of 11.4 °C⁻¹ %, maintaining a detection limit below 0.15 °C for the whole temperature range. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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23 pages, 5125 KiB  

Open AccessReview

Nano-Bismuth-Sulfide for Advanced Optoelectronics

by Zimin Li and Ye Tian

Photonics 2022, 9(11), 790; https://doi.org/10.3390/photonics9110790 - 24 Oct 2022

Cited by 12 | Viewed by 4191

Abstract

Bi₂S₃is a semiconductor with rational band gap around near-IR and visible range, and its nanostructures (or nano-Bi₂S₃) have attracted great attention due to its promising performances in optoelectronic materials and devices. An increasing number of [...] Read more.

Bi₂S₃is a semiconductor with rational band gap around near-IR and visible range, and its nanostructures (or nano-Bi₂S₃) have attracted great attention due to its promising performances in optoelectronic materials and devices. An increasing number of reports point to the potential of such nanostructures to support a number of optical applications, such as photodetectors, solar cells and photocatalysts. With the aim of providing a comprehensive basis for exploiting the full potential of Bi₂S₃ nanostructures on optoelectronics, we review the current progress in their controlled fabrication, the trends reported (from theoretical calculations and experimental observations) in their electrical properties and optical response, and their emerging applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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15 pages, 5380 KiB  

Open AccessArticle

Excitation Wavelength and Colloids Concentration-Dependent Nonlinear Optical Properties of Silver Nanoparticles Synthesized by Laser Ablation

by Tarek Mohamed, Majed H. El-Motlak, Samar Mamdouh, Mohamed Ashour, Hanan Ahmed, Hamza Qayyum and Alaa Mahmoud

Materials 2022, 15(20), 7348; https://doi.org/10.3390/ma15207348 - 20 Oct 2022

Cited by 15 | Viewed by 2390

Abstract

We reported experimental results from investigations that employed the Z-scan method to explore the dependence of silver nanoparticles’ (AgNPs) nonlinear optical properties on the excitation wavelength, AgNP concentration, and size. Using a 532 nm Nd: YAG laser beam at 100 mJ/pulse for different [...] Read more.

We reported experimental results from investigations that employed the Z-scan method to explore the dependence of silver nanoparticles’ (AgNPs) nonlinear optical properties on the excitation wavelength, AgNP concentration, and size. Using a 532 nm Nd: YAG laser beam at 100 mJ/pulse for different ablation times, AgNPs were synthesized from a silver target immersed in distilled water. UV–Vis spectroscopy and an atomic absorption spectrometer are used to characterize the optical properties of laser-synthesized AgNPs as well as their concentrations. The AgNPs’ size and shape are determined using a transmission electron microscope (TEM). The laser-synthesized AgNPs are spherical, with an average particle size of 12 to 13.2 nm. Whatever the ablation time, the AgNP colloids exhibit reversed saturable absorption and a negative nonlinear refractive index (n₂). Both n₂ and the nonlinear absorption coefficient (α₃) increase as the AgNP concentration increases. As the excitation wavelength and average size of the AgNPs increase, n₂ and α₃ decrease. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 4045 KiB  

Open AccessArticle

Molecular Cocrystals with Hydrogen-Bonded Polymeric Structures and Polarized Luminescence

by Jing-Yi Zhao, Fa-Feng Xu, Zhong-Qiu Li, Zhong-Liang Gong, Yu-Wu Zhong and Jiannian Yao

Materials 2022, 15(20), 7247; https://doi.org/10.3390/ma15207247 - 17 Oct 2022

Cited by 5 | Viewed by 2165

Abstract

Crystalline materials with appealing luminescent properties are attractive materials for various optoelectronic applications. The in situ bicomponent reaction of 1,2-ethylenedisulfonic acid with 1,4-di(pyrid-2-yl)benzene, 1,4-di(pyrid-3-yl)benzene, or 1,4-di(pyrid-4-yl)benzene affords luminescent crystals with hydrogen-bonded polymeric structures. Variations in the positions of the pyridine nitrogen atoms lead [...] Read more.

Crystalline materials with appealing luminescent properties are attractive materials for various optoelectronic applications. The in situ bicomponent reaction of 1,2-ethylenedisulfonic acid with 1,4-di(pyrid-2-yl)benzene, 1,4-di(pyrid-3-yl)benzene, or 1,4-di(pyrid-4-yl)benzene affords luminescent crystals with hydrogen-bonded polymeric structures. Variations in the positions of the pyridine nitrogen atoms lead to alternating polymeric structures with either a ladder- or zigzag-type of molecular arrangement. By using a nanoprecipitation method, microcrystals of these polymeric structures are prepared, showing polarized luminescence with a moderate degree of polarization. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 1292 KiB  

Open AccessArticle

Development and Validation of a Novel Microwell-Based Fluorimetric Method Assisted with Fluorescence Plate Reader for High-Throughput Determination of Duvelisib: Application to the Analysis of Capsules and Plasma Samples

by Abdullah M. Al-Hossaini, Hany W. Darwish, Ahmed Y. Sayed, Nasr Y. Khalil, Rashad Al-Salahi and Ibrahim A. Darwish

Appl. Sci. 2022, 12(20), 10460; https://doi.org/10.3390/app122010460 - 17 Oct 2022

Cited by 5 | Viewed by 1896

Abstract

Duvelisib (DUV) is a novel drug with a small molecular weight and characterized by dual phosphoinositide-3-kinase (PI3K)- and PI3K-inhibitory activity. The Food and Drug Administration (FDA) recently approved DUV for the management of small lymphocytic lymphoma (SLL) and relapsed or refractory chronic lymphocytic [...] Read more.

Duvelisib (DUV) is a novel drug with a small molecular weight and characterized by dual phosphoinositide-3-kinase (PI3K)- and PI3K-inhibitory activity. The Food and Drug Administration (FDA) recently approved DUV for the management of small lymphocytic lymphoma (SLL) and relapsed or refractory chronic lymphocytic leukemia (CLL) in adult patients. In the current study, a microwell-based fluorimetric (MW-FLR) method was established for the quantitation of DUV in copiktra^® capsules as well as plasma samples. The proposed MW-FLR method was carried out in a 96-microwell plate and involved measuring the native fluorescence of DUV by using a fluorescence plate reader at 405 nm after excitation at 340 nm. The preparation of plasma samples involved simple one-step protein precipitation prior to the analysis. The optimum conditions for the proposed method were established. Under these conditions, the fluorescence signals showed an excellent linear relationship with DUV concentrations in the sample solutions (r = 0.9995) in a concentration range of 25–800 ng/mL. The detection and quantification limits were 20.5 and 62.1 ng/mL, respectively. The method's accuracy and precision were acceptable as the recovery values were not less than 98.5% with low relative standard deviations (less than 6%). The presented MW-FLR method was adopted with truly good accuracy and precision to analyze copiktra capsules and DUV-spiked plasma samples. The method's results were found to be superior to those of reference methods. The MW-FLR method combined the advantages of the inherent high sensitivity of the fluorimetric measurement and the high analytical throughput of microwell-based methods. In addition, the method is characterized by the simplicity of the procedures and the green chemistry approach as it uses water as a solvent and low volumes of sample solutions. These advantages gave the method great value for the determination of DUV in quality control and/or clinical laboratories. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 2496 KiB  

Open AccessArticle

Narrow-Linewidth Single-Frequency Ytterbium Laser Based on a New Composite Yb³⁺-Doped Fiber

by Maksim Yu. Koptev, Olga N. Egorova, Oleg I. Medvedkov, Sergey L. Semjonov, Boris I. Galagan, Sergey E. Sverchkov, Boris I. Denker, Alexander E. Zapryalov and Arkady V. Kim

Photonics 2022, 9(10), 760; https://doi.org/10.3390/photonics9100760 - 12 Oct 2022

Cited by 3 | Viewed by 2518

Abstract

Fiber single-frequency lasers are currently being actively developed, primarily due to the growing number of applications that require compact and reliable narrow-band sources. However, the most developed single-frequency fiber lasers based on phosphate fibers have the disadvantages of low mechanical strength of both [...] Read more.

Fiber single-frequency lasers are currently being actively developed, primarily due to the growing number of applications that require compact and reliable narrow-band sources. However, the most developed single-frequency fiber lasers based on phosphate fibers have the disadvantages of low mechanical strength of both the phosphate fibers themselves and their splices. In this paper we demonstrate a single-frequency laser based on a new composite Yb³⁺-doped active fiber. The core of this fiber is made of phosphate glass with a high concentration of ytterbium ions and its cladding is made of standard silica glass. This structure ensures a higher splicing strength of the fiber compared to the phosphate fibers and provides high resistance to atmospheric moisture. Despite the multimode structure of this fiber, we achieved stable single-frequency lasing with an average power of 10 mW and a spectral contrast of more than 60 dB in the scheme with a short (1.1 cm) cavity formed by two fiber Bragg gratings. We believe that further optimization of this fiber will make it possible to create powerful and reliable single-frequency lasers in the one-micron wavelength range. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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54 pages, 7489 KiB  

Open AccessReview

Opto-Mechanical Eye Models, a Review on Human Vision Applications and Perspectives for Use in Industry

by André Rino Amorim, Boris Bret and José M. González-Méijome

Sensors 2022, 22(19), 7686; https://doi.org/10.3390/s22197686 - 10 Oct 2022

Cited by 4 | Viewed by 6725

Abstract

The purpose of this review is to aggregate technical information on existent optomechanical eye models (OME) described in the literature, for image quality assessment in different applications. Several physical eye models have been reviewed from peer-reviewed papers and patent applications. A typical eye [...] Read more.

The purpose of this review is to aggregate technical information on existent optomechanical eye models (OME) described in the literature, for image quality assessment in different applications. Several physical eye models have been reviewed from peer-reviewed papers and patent applications. A typical eye model includes an artificial cornea, an intraocular lens or other lens to simulate the crystalline lens, an aperture as the pupil, and a posterior retinal surface, which may be connected to a light sensor. The interior of the eye model may be filled with a fluid to better emulate physiological conditions. The main focus of this review is the materials and physical characteristics used and the dimensional aspects of the main components including lenses, apertures, chambers, imaging sensors and filling medium. Various devices are described with their applications and technical details, which are systematically tabulated highlighting their main characteristics and applications. The models presented are detailed and discussed individually, and the features of different models are compared when applicable, highlighting strengths and limitations. In the end there is a brief discussion about the potential use of artificial eye models for industrial applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 2559 KiB  

Open AccessArticle

Approach for Designing Human-Centered and Energy Saving Lighting Luminaires

by Jwo-Huei Jou, Zhe-Kai He, Deepak Kumar Dubey, Yi-Fang Tsai, Snehasis Sahoo, Yu-Ting Su and Chun-Hua Wu

Photonics 2022, 9(10), 726; https://doi.org/10.3390/photonics9100726 - 5 Oct 2022

Cited by 5 | Viewed by 2446

Abstract

Electric light has been widely adopted in numerous applications, including signage, display, and illumination. Enhancing its efficiency and quality has been the focal point until now. Long exposure to intensive blue-light-enriched white light is, however, likely to cause health concerns, such as retina [...] Read more.

Electric light has been widely adopted in numerous applications, including signage, display, and illumination. Enhancing its efficiency and quality has been the focal point until now. Long exposure to intensive blue-light-enriched white light is, however, likely to cause health concerns, such as retina damage and melatonin suppression. A good light should hence be redefined as, at least, human-friendly, besides energy-saving and high-quality. Here, we demonstrate a novel design approach toward a good light based on the state-of-the-art solid-state lighting technologies. Taking the typical phosphor converted white-light-emitting diode (LED) for lighting, for example, a 2000 K orange-white emission with a black-body-radiation chromaticity can be 5 times safer than the 5000 K pure-white counterpart from a retina-protection perspective and 3.9 times safer from an MLT-secretion perspective. Further tuning its chromaticity from black-body-radiation- to sunlight-style, the 2000 K LED can be made 303% safer in terms of maximum retina permissible exposure limit or 100% better in terms of melatonin suppression sensitivity. Moreover, its corresponding efficacy limit can be increased from 270 to 285 lm/W, while keeping light quality constant at 91, in terms of natural light spectrum resemblance index. The same approach can be extended to organic LED as well as the design of a good light for display, wherein pure-white emission with a color temperature around 6000 K is suggested to replace the bluish-white backlight to safeguard human health. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 1741 KiB  

Open AccessCommunication

Heat-Induced Emission Enhancement in a Yb:YAG Crystal-Derived Silica Fiber

by Kai Zou, Jianxiang Wen, Ying Wan, Yan Wu, Fufei Pang and Tingyun Wang

Photonics 2022, 9(10), 706; https://doi.org/10.3390/photonics9100706 - 28 Sep 2022

Cited by 3 | Viewed by 1947

Abstract

We fabricated a Yb:YAG crystal-derived silica fiber (YCDSF) by the melt-in-tube method with a CO₂ laser-heated drawing tower and explored the influences of the heat treatment method on fluorescent properties in the YCDSF. After the heat treatment, the intensity of the emission [...] Read more.

We fabricated a Yb:YAG crystal-derived silica fiber (YCDSF) by the melt-in-tube method with a CO₂ laser-heated drawing tower and explored the influences of the heat treatment method on fluorescent properties in the YCDSF. After the heat treatment, the intensity of the emission peaks and the fluorescence lifetime of the YCDSFs improved. In particular, after 1350 °C of heat treatment, a series of sharp peaks appeared in the core layer, which may form a new crystalline phase. Moreover, its emission intensity at 1030 nm was significantly enhanced, over 2 times greater than before the heat treatment. Additionally, the fluorescence lifetime of Yb ions was also increased from 129 to 621 μs, indicating the changes in local environments around Yb ions. Then, schematic models were set up to show how the local environments around Yb ions are gradually changing. These results revealed that the assessed YCDSF is of excellent performance; after the heat treatment, it may be a potential material for realizing optical amplification, light sources, fiber lasers, and so on. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 2124 KiB  

Open AccessArticle

Characterization of Cubic Zirconia as a Lens Material Suitable for Autonomous Driving

by Jae-Kun Lee, Sung Yun Chung, Eui Chul Shin, Jae Bum Kim and Jong-Kwon Lee

Photonics 2022, 9(10), 701; https://doi.org/10.3390/photonics9100701 - 28 Sep 2022

Cited by 3 | Viewed by 2831

Abstract

As the development of autonomous driving technology is now in full swing, the demand for miniaturized optical modules mounted on various sensors has increased. Particularly, the optical lens used for such autonomous driving must demonstrate stable performance and durability despite rapid changes in [...] Read more.

As the development of autonomous driving technology is now in full swing, the demand for miniaturized optical modules mounted on various sensors has increased. Particularly, the optical lens used for such autonomous driving must demonstrate stable performance and durability despite rapid changes in the external environment. In this regard, cubic zirconia (CZ) can be used as an optical lens due to its high refractive index, which is above 2.1 in visible and near-infrared wavelengths, along with its chemical and mechanical durability. Thus, in this paper, we investigated the temperature-dependent physical properties of CZ fabricated by the skull melting method. The temperature coefficient of the refractive index (dn/dT) of the fabricated CZ plate in the temperature range of 25–100 °C decreased from 9.76 × 10⁻⁵/K to 7.00 × 10⁻⁵/K as the wavelength increased from 447.0 nm to 785.0 nm. The estimated Abbe number decreased from 33.98 at 25 °C to 33.12 at 100 °C, while the measured coefficient of thermal expansion (CTE) was 9.91 × 10⁻⁶/K, which revealed that the dn/dT value of the CZ plate was more affected by the dispersion than by the CTE. In addition, the CZ samples with a high refractive index, coated with a dielectric multilayer showed a high average transmittance of 98.2% at the investigated wavelengths, making it suitable for miniaturization or wide-angle optical lens modules. To secure the durability required for automobile lenses, the variation in the surface profile of the CZ before and after the external impact was also analyzed, revealing much better performance than TAF glass. Therefore, the observed results demonstrate that the CZ material is suitable for use as an optical lens for autonomous vehicles. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 1956 KiB  

Open AccessEditor’s ChoiceCommunication

An All-Dielectric Color Filter, with a Wider Color Gamut

by Lizhen Zeng, Yuting Yang and Gongli Xiao

Photonics 2022, 9(10), 680; https://doi.org/10.3390/photonics9100680 - 21 Sep 2022

Cited by 3 | Viewed by 2267

Abstract

Due to their extraordinary abilities to manipulate light propagation at the nanoscale, dielectric resonators that generate electric and magnetic Mie resonances for minimal optical loss have recently attracted great interest. Based on an all-dielectric metasurface, made of H-type silicon nanoarrays, this study proposed [...] Read more.

Due to their extraordinary abilities to manipulate light propagation at the nanoscale, dielectric resonators that generate electric and magnetic Mie resonances for minimal optical loss have recently attracted great interest. Based on an all-dielectric metasurface, made of H-type silicon nanoarrays, this study proposed and constructed a visible-wavelength-range color filter, with high-quality Mie resonance and the ability to synthesize new colors. Using the finite-difference time-domain (FDTD) approach, we can create a larger color gamut by modifying the H-type array’s structural properties. The all-dielectric color filter suggested has a high color saturation and narrow bandwidth. The Mie resonance can be adjusted by manipulating the structural characteristics. By translating the reflectance spectrum into color coordinates and using the CIE1931 chromaticity diagram, a wide range of colors can be generated. This color filter offers a larger color range and saturation than other color filters. We produced color passband filters that span the visible spectrum using Mie resonator arrays, based on an H-type nanoresonator. This technology could have many applications, including high-resolution color printing, color-tunable switches, and sensing systems. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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Supplementary File 1 (ZIP, 153 KiB)

11 pages, 3146 KiB  

Open AccessArticle

Facile Preparation of Flexible Lateral 2D MoS₂ Nanosheets for Photoelectrochemical Hydrogen Generation and Optoelectronic Applications

by Ahmed Adel A. Abdelazeez, Amira Ben Gouider Trabelsi, Fatemah. H. Alkallas, Samira Elaissi and Mohamed Rabia

Photonics 2022, 9(9), 638; https://doi.org/10.3390/photonics9090638 - 5 Sep 2022

Cited by 8 | Viewed by 2834

Abstract

Two-dimensional (2D) materials have attracted significant attention with their high optical response due to their interesting and unique fundamental phenomena. A lateral 2D MoS₂ nanosheets was prepared via a facile one-step electrophoretic deposition method on polyethylene terephthalate (PET)/ITO. These nanosheets have been [...] Read more.

Two-dimensional (2D) materials have attracted significant attention with their high optical response due to their interesting and unique fundamental phenomena. A lateral 2D MoS₂ nanosheets was prepared via a facile one-step electrophoretic deposition method on polyethylene terephthalate (PET)/ITO. These nanosheets have been used as photoelectrode materials for photoelectrochemical (PEC) hydrogen generation and optoelectronics. The chemical structure and morphology were confirmed using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman, scanning electron microscope (SEM), and transmission electron microscopy (TEM). The optical absorbance of the 2D MoS₂ nanosheets extended to the UV, Vis, and near-IR regions with a bandgap value of 1.59 eV. The testing of the prepared photoelectrode material, PET/ITO/MoS₂, was carried out through a three-electrode system, in which the current density (J_ph) value represents the rate of H₂ gas evaluated. The J_ph enhanced under light illumination compared to the dark conditions with values of 0.4 to 0.98 mA·cm⁻², respectively. The produced photocurrent at V = 0 V was 0.44 mA·cm⁻². This confirms the great abilities of the PET/ITO/MoS₂ photoelectrode in light detection and hydrogen generation with high photoresponsivity values. Soon, our team will work on the development of a prototype of this three-electrode cell to convert the water directly into H₂ fuel gas that could be applied in houses and factories, or even in advanced technology such as spacecraft and airplane F-35s by providing H₂ gas as a renewable energy source. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 9172 KiB  

Open AccessArticle

Design and Optimization of a Compact Ultra-Broadband Polarization Beam Splitter for the SCL-Band Based on a Thick Silicon Nitride Platform

by Georgios Patsamanis, Dimitra Ketzaki, Dimitrios Chatzitheocharis and Konstantinos Vyrsokinos

Photonics 2022, 9(8), 552; https://doi.org/10.3390/photonics9080552 - 6 Aug 2022

Cited by 3 | Viewed by 3967

Abstract

The polarization beam splitter is an essential photonic integrated circuit in applications where a high-performing on-chip polarization diversity scheme is required. The lower refractive index contrast of the silicon nitride material platform compared to silicon-on-insulator constitutes the separation of polarized light states a [...] Read more.

The polarization beam splitter is an essential photonic integrated circuit in applications where a high-performing on-chip polarization diversity scheme is required. The lower refractive index contrast of the silicon nitride material platform compared to silicon-on-insulator constitutes the separation of polarized light states a challenging task since for this purpose a large difference between the effective refractive indices of the fundamental TE and TM modes is highly desirable. In this paper, we present the design and optimization analysis of an ultra-broadband polarization beam splitter based on a thick silicon nitride platform through extensive 3D-FDTD simulations. The proposed device exploits two different Si₃N₄ thicknesses that enable the discrimination of the two polarizations at the proximity of an 800 nm thick slot and a 470 nm thick strip waveguide via directional coupling. The proposed two-stage PBS achieves higher than 30.6 dB polarization extinction ratio (PER) for both TE and TM polarizations across a 130 nm span at the SCL-band. The dimensions of the PBS are 94 × 14 μm² and the insertion losses are calculated to be lower than 0.8 dB for both polarizations. The fabrication tolerance of the device is also discussed. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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8 pages, 2068 KiB  

Open AccessCommunication

Tunable Luminescence of Sm³⁺/Tb³⁺ Co-Doped CaMoO₄ Phosphors Synthesized by Microwave-Assisted Heating

by Wen-Te Wu, Kwong-Kau Tiong, Yu-Wei Lee, Sheng-Yao Hu, Yueh-Chien Lee and Wei Huang

Appl. Sci. 2022, 12(15), 7883; https://doi.org/10.3390/app12157883 - 5 Aug 2022

Cited by 4 | Viewed by 1860

Abstract

We present a series of Sm³⁺/Tb³⁺ co-doped CaMoO₄ phosphors synthesized by an efficient method of microwave-assisted heating. The prepared CaMoO₄ samples were characterized by X-ray diffraction, photoluminescence, and Commission Internationale de l’Elcairage (CIE) chromaticity diagram. The X-ray diffraction [...] Read more.

We present a series of Sm³⁺/Tb³⁺ co-doped CaMoO₄ phosphors synthesized by an efficient method of microwave-assisted heating. The prepared CaMoO₄ samples were characterized by X-ray diffraction, photoluminescence, and Commission Internationale de l’Elcairage (CIE) chromaticity diagram. The X-ray diffraction results confirmed that all synthesized CaMoO₄ samples are crystallized in a pure tetragonal phase. The photoluminescence spectra significantly show both red- and green emissions in the synthesized Sm³⁺/Tb³⁺ co-doped CaMoO₄ phosphors. It is obvious that the variations in the intensity ratio of red/green emissions depend on the molar ratio of Sm³⁺/Tb³⁺ co-doping and dominate the CIE color coordinates on the chromaticity diagram. The investigations showed the functionality of the material system as advanced color-tunable phosphors for white-LEDs as evidenced by the controllability of the light-emitting region of Sm³⁺/Tb³⁺ co-doped CaMoO₄ phosphors through the adjustment of the molar ratio of Sm³⁺/Tb³⁺ ions. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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18 pages, 3552 KiB  

Open AccessArticle

Design and Analysis of Highly Sensitive LSPR-Based Metal–Insulator–Metal Nano-Discs as a Biosensor for Fast Detection of SARS-CoV-2

by Ata Taghipour and Hamid Heidarzadeh

Photonics 2022, 9(8), 542; https://doi.org/10.3390/photonics9080542 - 3 Aug 2022

Cited by 19 | Viewed by 3157

Abstract

For over 2 years, the coronavirus has been the most urgent challenge to humanity, and the development of rapid and accurate detection methods is crucial to control these viruses. Here, a 3D FDTD simulation of Au/SiO₂/Au metal–insulator–metal (MIM) nanostructures as a [...] Read more.

For over 2 years, the coronavirus has been the most urgent challenge to humanity, and the development of rapid and accurate detection methods is crucial to control these viruses. Here, a 3D FDTD simulation of Au/SiO₂/Au metal–insulator–metal (MIM) nanostructures as a biosensor was performed. The strong coupling between the two plasmonic interfaces in the Au/SiO₂/Au cavity helped us to obtain relatively higher sensitivity. The attachment of SARS-CoV-2 changed the refractive index, which was used to detect SARS-CoV-2. Due to the higher overlapping of plasmonic mode with the environment of nano-discs, a higher sensitivity of 312.8 nm/RIU was obtained. The peak wavelength of the proposed structure shifted by approximately 47 nm when the surrounding medium refractive index changed from 1.35 (no binding) to 1.5 (full binding). Consequently, the SPR peak intensity variation can be used as another sensing mechanism to detect SARS-CoV-2. Finally, the previously reported refractive index changes for various concentrations of the SARS-CoV-2 S-glycoprotein solution were used to evaluate the performance of the designed biosensor. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 7245 KiB  

Open AccessArticle

A Multichannel Superconductor-Based Photonic Crystal Optical Filter Tunable in the Visible and Telecom Windows at Cryogenic Temperature

by Luz E. González, Lina M. Segura-Gutierrez, John E. Ordoñez, Gustavo Zambrano and John H. Reina

Photonics 2022, 9(7), 485; https://doi.org/10.3390/photonics9070485 - 12 Jul 2022

Cited by 8 | Viewed by 2970

Abstract

We design and evaluate the performance of a one-dimensional photonic crystal (PhC) optical filter that comprises the integration of alternating layers of a barium titanate ferroelectric $\left({\mathrm{BaTiO}}_3\right)$ and an yttrium oxide dielectric $\left({\mathrm{Y}}_2{\mathrm{O}}_3\right)$, with [...] Read more.

We design and evaluate the performance of a one-dimensional photonic crystal (PhC) optical filter that comprises the integration of alternating layers of a barium titanate ferroelectric $\left({\mathrm{BaTiO}}_3\right)$ and an yttrium oxide dielectric $\left({\mathrm{Y}}_2{\mathrm{O}}_3\right)$, with a critical high-temperature superconductor defect, yttrium–barium–copper oxide $\left({\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\mathrm{X}}\right)$, resulting in the ${(\mathrm{BTO}/{\mathrm{Y}}_2{\mathrm{O}}_3)}_{\mathrm{N}}/\mathrm{YBCO}/$${({\mathrm{Y}}_2{\mathrm{O}}_3/\mathrm{BTO})}_{\mathrm{N}}$ multilayered nanostructure array. Here, we demonstrate that such a nanosystem allows for routing and switching optical signals at well-defined wavelengths, either in the visible or the near-infrared spectral regions—the latter as required in optical telecommunication channels. By tailoring the superconductor layer thickness, the multilayer period number N, the temperature and the direction of incident light, we provide a computational test-bed for the implementation of a PhC-optical filter that works for both wavelength-division multiplexing in the 300–800 nm region and for high-Q filtering in the 1300–1800 nm range. In particular, we show that the filter’s quality factor of resonances Q increases with the number of multilayers—it shows an exponential scaling with N (e.g., in the telecom C-band, $Q\approx 470$ for $N=8$). In the telecom region, the light transmission slightly shifts towards longer wavelengths with increasing temperature; this occurs at an average rate of 0.25 nm/K in the range from 20 to 80 K, for $N=5$ at normal incidence. This rate can be enhanced, and the filter can thus be used for temperature sensing in the NIR range. Moreover, the filter works at cryogenic temperature environments (e.g., in outer space conditions) and can be integrated into either photonic and optoelectronic circuits or in devices for the transmission of information. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 2264 KiB  

Open AccessArticle

Finite Temperature Ultraviolet-Visible Dielectric Functions of Tantalum Pentoxide: A Combined Spectroscopic Ellipsometry and First-Principles Study

by Wenjie Zhang, Zhaohui Zeng, Tao Cheng, Tianhao Fei, Zhiwei Fu, Xiaoyan Liu, Jingyi Zhang and Jia-Yue Yang

Photonics 2022, 9(7), 440; https://doi.org/10.3390/photonics9070440 - 22 Jun 2022

Cited by 3 | Viewed by 2425

Abstract

Tantalum pentoxide (Ta₂O₅) has demonstrated promising applications in gate dielectrics and microwave communication devices with its intrinsically high dielectric constant and low dielectric loss. Although there are numerous studies on the dielectric properties of Ta₂O₅, [...] Read more.

Tantalum pentoxide (Ta₂O₅) has demonstrated promising applications in gate dielectrics and microwave communication devices with its intrinsically high dielectric constant and low dielectric loss. Although there are numerous studies on the dielectric properties of Ta₂O₅, few studies have focused on the influence of external environmental changes (i.e., temperature and pressure) on the dielectric properties and the underlying physics is not fully understood. Herein, we synthesize Ta₂O₅ thin films using the magnetron sputtering method, measure the ultraviolet-visible dielectric function at temperatures varying from 300 to 873 K by spectroscopic ellipsometry (SE), and investigate the temperature influence on the dielectric function from first principles. SE experiments observe that temperature has a nontrivial influence on the ultraviolet-visible dielectric function, accompanying the consistently decreased amplitude and increased broadening width for the dominant absorption peak. First-principles calculations confirm that the dominant absorption peak originates from the aggregated energy states near the valence band maximum (VBM) and conduction band minimum (CBM), and the theoretically predicted dielectric functions demonstrate good agreement with the SE experiments. Moreover, by performing first-principles molecular dynamics simulations, the finite-temperature dielectric function is predicted and its change trend with increasing temperature agrees overall with the SE measurements. This work explores the physical origins of temperature influence on the ultraviolet-visible dielectric function of Ta₂O₅, aimed at promoting its applications in the field of micro-/nanoelectronics. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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18 pages, 5010 KiB  

Open AccessArticle

Absorption Enhancement in a Quantum Dot Thz Detector with a Metal-Semiconductor-Metal Structure

by Hongmei Liu, Ruolong Zhang, Tianhua Meng, Yongqiang Kang, Weidong Hu and Guozhong Zhao

Coatings 2022, 12(7), 874; https://doi.org/10.3390/coatings12070874 - 21 Jun 2022

Viewed by 2244

Abstract

The low absorptivity of quantum dot nano-structures cannot meet the requirements for high-performance next-generation Thz detectors which can be used for environmental pollution detection. In this study, a novel metal-semiconductor-metal (MSM) cavity structure with a square hole array instead of a traditional planar [...] Read more.

The low absorptivity of quantum dot nano-structures cannot meet the requirements for high-performance next-generation Thz detectors which can be used for environmental pollution detection. In this study, a novel metal-semiconductor-metal (MSM) cavity structure with a square hole array instead of a traditional planar metal electrode was developed to improve and enhance the absorptivity of a quantum dot Thz detector. The possible modes and loss problems in the metal resonant cavity were analyzed using the finite-element transmission matrix, the eigenvector method, and Kirchhoff diffraction theory. The results demonstrate that the MSM cavity structure introduced in the detector can enhance absorption up to 8.666 times higher than that of the conventional counterpart. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 3144 KiB  

Open AccessArticle

High-Power, High-Efficiency Red Laser Diode Structures Grown on GaAs and GaAsP Metamorphic Superlattices

by Steven Ruder, Tom Earles, Christian Galstad, Michael Klaus, Don Olson and Luke J. Mawst

Photonics 2022, 9(7), 436; https://doi.org/10.3390/photonics9070436 - 21 Jun 2022

Cited by 1 | Viewed by 2854

Abstract

Three types of GaAsP metamorphic buffer layers, including linearly graded, step graded, and metamorphic superlattices, were compared for the purposes of virtual substrates for red laser diode heterostructures. Laser diodes were fabricated on GaAs substrates and relaxed GaAsP metamorphic superlattice virtual substrates. A [...] Read more.

Three types of GaAsP metamorphic buffer layers, including linearly graded, step graded, and metamorphic superlattices, were compared for the purposes of virtual substrates for red laser diode heterostructures. Laser diodes were fabricated on GaAs substrates and relaxed GaAsP metamorphic superlattice virtual substrates. A laser diode structure with a tensile-strained quantum well on a standard miscut GaAs substrate achieved TM-polarized emission at a 638 nm wavelength with 45% peak power conversion efficiency (PCE) at a 880 mW continuous wave (CW) output power with T₀ = 77 K and T₁ = 266 K. An analogous laser diode structure with a compressively strained quantum well on the metamorphic superlattice emitted TE-polarized 639 nm light with 35.5% peak PCE at 880 mW CW with T₀ = 90 K and T₁ = 300 K. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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18 pages, 7398 KiB  

Open AccessArticle

Low Power FPGA Implementation of a Smart Building Free Space Optical Communication System

by Rehab Ali, Hossameldin Eassa, Hesham H. Aly, Mohamed Abaza and Saleh M. Eisa

Photonics 2022, 9(6), 432; https://doi.org/10.3390/photonics9060432 - 18 Jun 2022

Cited by 5 | Viewed by 3467

Abstract

Free Space Optical (FSO) communication systems have extensively invaded the speed of smart city evolution due to the current surge in demand for wireless communication spots that can match recent challenges due to high technical leaps in smart city evolution. As the number [...] Read more.

Free Space Optical (FSO) communication systems have extensively invaded the speed of smart city evolution due to the current surge in demand for wireless communication spots that can match recent challenges due to high technical leaps in smart city evolution. As the number of users is vastly increasing throughout all networks in the form of machines, devices, and variously distinct objects, FSO is a hugely recommended robust communication system that mitigates a lot of RF disadvantages on the field with no need for licensing, fast rollout time, and low cost. This paper shows an exploit of a Low Power Field Programmable Gate Array (FPGA) based FSO communication system designed for Line of Sight (LOS) Building to Building Communication over a distance of 12 m using a 650 nm Visible Light (VL) red laser source via On-Off Keying (OOK) and higher-level Intensity Modulation (IM)/Pulse Width Modulation (PWM) schemes. The implemented system reached a doubled data rate than OOK of 230 kbps using the IM technique. Traffic monitoring and building security status can be frequently updated between adherent buildings, each scanning its zone real-time conditions and sharing them with the neighboring links. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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10 pages, 2232 KiB  

Open AccessArticle

Synthesis and Characterization of Highly Photocatalytic Active Ce and Cu Co-Doped Novel Spray Pyrolysis Developed MoO₃ Films for Photocatalytic Degradation of Eosin-Y Dye

by Olfa Kamoun, Abdelaziz Gassoumi, Mohd. Shkir, Nima E. Gorji and Najoua Turki-Kamoun

Coatings 2022, 12(6), 823; https://doi.org/10.3390/coatings12060823 - 11 Jun 2022

Cited by 31 | Viewed by 3108

Abstract

The current work deals with the fabrication of novel MoO₃ nanostructured films with Ce and Cu co-doping through the spray pyrolysis route on a glass substrate maintained at 460 °C for the first time. The phase of developed films was approved by [...] Read more.

The current work deals with the fabrication of novel MoO₃ nanostructured films with Ce and Cu co-doping through the spray pyrolysis route on a glass substrate maintained at 460 °C for the first time. The phase of developed films was approved by an X-ray diffraction study, and the crystallite size was determined between 82 and 92 nm. The optical transmission of the developed films was noticed to be reduced with doping and found between 45 and 90% for all films, and the absorption edge shifted to a higher wavelength with doping. The optical energy gap of the fabricated films was found to be reduced from 3.85 to 3.28 eV with doping. The developed films were used to degrade the harmful Eosin-Y dye under UV light. The system with 2% Ce and 1% Cu-doped MoO₃ turned out to be the most effective catalyst for photodegradation of the dye in a period of 3H and almost degrade it. Hence, the MoO₃ films prepared with 2% Ce and 1% Cu will be highly applicable as photocatalysts for the removal of hazardous dye from wastewater. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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19 pages, 6566 KiB  

Open AccessArticle

Effect of Optical–Electrical–Thermal Coupling on the Performance of High-Concentration Multijunction Solar Cells

by Qi Shi, Bifen Shu, Jingxiang Jiang and Yuqi Zhang

Appl. Sci. 2022, 12(12), 5888; https://doi.org/10.3390/app12125888 - 9 Jun 2022

Cited by 4 | Viewed by 2034

Abstract

In the process of high-concentration photovoltaic (HCPV) power generation, multijunction cells work in the conditions of high radiation and high current. Non-uniformity of focusing, the mismatch between the focusing spectrum caused by the dispersion effect and the spectrum of multijunction solar cell design [...] Read more.

In the process of high-concentration photovoltaic (HCPV) power generation, multijunction cells work in the conditions of high radiation and high current. Non-uniformity of focusing, the mismatch between the focusing spectrum caused by the dispersion effect and the spectrum of multijunction solar cell design and the increase in cell temperature are the key factors affecting the photoelectric performance of the multijunction solar cell. The coupling effect of three factors on the performance of multijunction solar cell intensifies its negative impact. Based on the previous research, the light intensity and spectral characteristics under Fresnel lens focusing are calculated through the optical model, and the optical–electrical–thermal coupling model under non-uniform illumination is established. The results show that obvious changes exist in the concentration spectrum distribution, energy and non-uniformity along different optical axis positions. These changes lead to serious current mismatch and transverse current in the multijunction solar cell placed near the focal plane which decreases the output power. The lost energy makes the cell temperature highest near the focal plane. In the condition of passive heat dissipation with 500 times geometric concentration ratio, the output power of the solar cell near the focal plane decreases by 35% and the temperature increases by 15%. Therefore, optimizing the placement position of the multijunction cell in the optical axis direction can alleviate the negative effects of optical–electrical–thermal coupling caused by focusing non-uniformity, spectral mismatch and rising cell temperature, and improve the output performance of the cell. This conclusion is verified by the experimental result. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 5068 KiB  

Open AccessArticle

A Dual-Frequency Terahertz Metasurface Capable of Distinguishing the Handedness of Circularly Polarized Light

by Bowei Yang, Mingzhao Ouyang, Hang Ren, Chenhao Ma, Yu Zhao, Yuhui Zhang and Yuegang Fu

Coatings 2022, 12(6), 736; https://doi.org/10.3390/coatings12060736 - 27 May 2022

Cited by 7 | Viewed by 2352

Abstract

Circularly polarized light can present more optical properties of chiral materials and is widely used to analyze and detect biomolecules. In this paper, a dual-frequency terahertz circular polarization detection structure, which is based on multilayer metamaterials, is proposed. The proposed structure consists of [...] Read more.

Circularly polarized light can present more optical properties of chiral materials and is widely used to analyze and detect biomolecules. In this paper, a dual-frequency terahertz circular polarization detection structure, which is based on multilayer metamaterials, is proposed. The proposed structure consists of a dual-frequency quarter-wave plate, a polyimide spacer, and a filter. The simulation results show that the structure can distinguish the handedness of circularly polarized light by filtering. The extinction ratios are 4 dB and 5.26 dB at 0.952 THz and 1.03 THz, respectively, and the maximum transmittance efficiency reaches 40%. Given the advantages of easy integration and dual-frequency operation, our design is bound to facilitate the development of multi-frequency detection in biomedical imaging devices. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 4952 KiB  

Open AccessArticle

Extending Focal Depth of Flower-Shaped Optical Vortex with Composited Spiral Zone Plate Grating

by Huakui Hu, Fulin Cao and Yue Zhao

Photonics 2022, 9(6), 371; https://doi.org/10.3390/photonics9060371 - 25 May 2022

Cited by 1 | Viewed by 2415

Abstract

By combining a spiral zone plate (SZP) and a grating, we propose a single optical element, termed a composited spiral zone plate grating (CSZPG), to generate flower mode vortices with the equicohesive petals and has long focal depths. Theoretical [...] Read more.

By combining a spiral zone plate (SZP) and a grating, we propose a single optical element, termed a composited spiral zone plate grating (CSZPG), to generate flower mode vortices with the equicohesive petals and has long focal depths. Theoretical analysis reveals that the CSZPG can generate flower mode vortices with approximately equicohesive petals, and that it has longer focal depths compared with the conventional SZP. Moreover, the performance of the CSZPG on the period, focal length and radius is investigated. The experimental results are also presented, agreeing well with the theoretical predictions. The unique characteristics of the proposed CSZPG make it attractive for many applications such as particle trapping and optical imaging. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 6062 KiB  

Open AccessArticle

Improved Exponential Phase Mask for Generating Defocus Invariance of Wavefront Coding Systems

by Jing Sheng, Huaiyu Cai, Yi Wang, Xiaodong Chen and Yushuai Xu

Appl. Sci. 2022, 12(11), 5290; https://doi.org/10.3390/app12115290 - 24 May 2022

Cited by 4 | Viewed by 2243

Abstract

Wavefront coding is an effective way to extend the depth of field of optical imaging systems. The invariant defocusing imaging feature can be obtained by adding a phase mask with a suitable form to the aperture of a typical optical system. Traditional exponential [...] Read more.

Wavefront coding is an effective way to extend the depth of field of optical imaging systems. The invariant defocusing imaging feature can be obtained by adding a phase mask with a suitable form to the aperture of a typical optical system. Traditional exponential phase mask defocusing optical characteristics exhibit strong invariance in the frequency domain, but the point spread function (PSF) variation is significant in the image plane To reduce PSF position deviation, we presented an improved exponential phase mask. The phase function of the improved mask is obtained by analyzing the relationship between Taylor expansion and wave aberration. Numerical analysis and imaging simulation are used to evaluate the performance of the proposed phase mask to that of other standard phase masks. The simulation results show that the improved exponential phase mask has a stronger defocus invariance of the modulation transfer function (MTF), and the position deviation of the PSF has been effectively controlled. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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19 pages, 9335 KiB  

Open AccessArticle

Spectroscopic and Physicochemical Studies on 1,2,4-Triazine Derivative

by Arwa Alrooqi, Zahra M. Al-Amshany, Laila M. Al-Harbi, Tariq A. Altalhi, Moamen S. Refat, Ali M. Hassanien, Gaber A. M. Mersal and Ahmed A. Atta

Coatings 2022, 12(5), 714; https://doi.org/10.3390/coatings12050714 - 23 May 2022

Cited by 4 | Viewed by 2231

Abstract

A novel 5-(5-Bromo-2-hydroxybenzylidene)-6-oxo-3-phenyl-5,6-dihydro-1,2,4-triazine-2(1H)-carbothioamide (4) “compound 4” was synthesized. The chemical structure of compound 4 was confirmed with spectroscopic techniques. Thermal analysis (TGA/dTGA) studies were conducted for identifying the kinetic thermodynamic parameters and the thermal stability of the synthesized compound 4. Cyclic [...] Read more.

A novel 5-(5-Bromo-2-hydroxybenzylidene)-6-oxo-3-phenyl-5,6-dihydro-1,2,4-triazine-2(1H)-carbothioamide (4) “compound 4” was synthesized. The chemical structure of compound 4 was confirmed with spectroscopic techniques. Thermal analysis (TGA/dTGA) studies were conducted for identifying the kinetic thermodynamic parameters and the thermal stability of the synthesized compound 4. Cyclic voltammetric studies were performed for recognizing electrochemical characteristics of the synthesized compound 4. The calculated highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the band gap were found to be −3.61, −5.32, and 1.97 eV, respectively. Using a diffused reflectance spectroscopy (DRS) technique, the estimated values of the optical band transitions of compound 4 in powder form were found to be 2.07 and 2.67 eV. The structural properties of thermally evaporated compound 4 thin films were analyzed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. It was found that compound 4 has a triclinic crystal structure. The optical transitions and the optical dispersion factors of compound 4 thin films were investigated using a UV-Vis spectroscopy technique. From the UV-Vis spectroscopy technique, $E_g^{ind}=3.6 V$ was estimated for both the as-deposited and annealed thin films. For the as-deposited film, there were two photoluminescence (PL) emission peaks centered at 473 and 490 nm with a shoulder at 422 nm. For the annealed film at 423 K, there were five PL emission peaks centered at 274, 416, 439, 464, and 707 nm with a shoulder at 548 nm. The dark electrical conduction of compound 4 thin film was through a thermally activated process with activation energy equaling 0.88 eV. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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21 pages, 4903 KiB  

Open AccessArticle

MIS-Like Structures with Silicon-Rich Oxide Films Obtained by HFCVD: Their Response as Photodetectors

by Gabriel Omar Mendoza Conde, José Alberto Luna López, Zaira Jocelyn Hernández Simón, José Álvaro David Hernández de la Luz, Godofredo García Salgado, Erick Gastellou Hernández, Haydee Patricia Martínez Hernández and Javier Flores Méndez

Sensors 2022, 22(10), 3904; https://doi.org/10.3390/s22103904 - 21 May 2022

Cited by 10 | Viewed by 2783

Abstract

MIS-type structures composed of silicon-rich oxide (SRO), thin films deposited by hot filament chemical vapor deposition (HFCVD), show interesting I-V and I-t properties under white light illumination and a response as photodetectors. From electrical measurements, it was found that at a reverse bias [...] Read more.

MIS-type structures composed of silicon-rich oxide (SRO), thin films deposited by hot filament chemical vapor deposition (HFCVD), show interesting I-V and I-t properties under white light illumination and a response as photodetectors. From electrical measurements, it was found that at a reverse bias of −4 V, the illumination current increased by up to three orders of magnitude relative to the dark current, which was about 82 nA, while the photogenerated current reached a value of 25 μA. The reported MIS structure with SRO as the dielectric layer exhibited a hopping conduction mechanism, and an ohmic conduction mechanism was found with low voltage. I-t measurements confirmed the increased photogenerated current. Furthermore, the MIS structure, characterized by current-wavelength (I-λ) measurements, exhibited a maximum responsivity value at 254 mA/W, specific detectivity (D*) at 2.21 × 10¹¹ cm Hz^1/2 W⁻¹, and a noise equivalent power (NEP) of 49 pW at a wavelength of 535 nm. The structure exhibited good switching behavior, with rise and fall times between 120 and 150 ms, respectively. These rise and decay times explain the generation and recombination of charge carriers and the trapping and release of traps, respectively. These results make MIS-type structures useful as photodetectors in the 420 to 590 nm range. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 4765 KiB  

Open AccessArticle

Examination of the Blank Error on Mirror Accuracy of Lightweight SiC Mirror and a Compensation Method

by Ping Jiang and Pingwei Zhou

Photonics 2022, 9(5), 360; https://doi.org/10.3390/photonics9050360 - 21 May 2022

Viewed by 2388

Abstract

Due to excellent characteristics of specific stiffness and thermal stability, silicon carbide-based (SiC) material is commonly selected to construct large-scale lightweight mirror. In general, the fabrication process of SiC mirror is similar to the casting process. The blank error of SiC mirror is [...] Read more.

Due to excellent characteristics of specific stiffness and thermal stability, silicon carbide-based (SiC) material is commonly selected to construct large-scale lightweight mirror. In general, the fabrication process of SiC mirror is similar to the casting process. The blank error of SiC mirror is 0~1 mm. Due to the high hardness of SiC, only the mirror surface and some positioning surface will be milled. The mirror surface accuracy will be degraded due to the fact that the blank error can cause significant changes in weight distribution. In this paper, Monte Carlo analysis is firstly performed to examine the blank error on gravity center, stiffness and mirror accuracy of a SiC mirror. It is found that according to the designed mount location, the amount of degradation is more than 2.5 nm of which the probability is 40.3%. It is known that the error of gravity center can be compensated by optimizing the axial mount location. Then inverse modeling and testing of gravity center for the SiC mirror is carried out in order to determine the optimal axial mount location. Based on the proposed method, the mirror degradation introduced by the blank error has been eliminated to the greatest extend. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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10 pages, 5360 KiB  

Open AccessArticle

ZnO@MoS₂ Core–Shell Heterostructures Enabling Improved Photocatalytic Performance

by Yu Zhong, Fengming Wang, Chuangming Liang, Zeyi Guan, Bingshang Lu, Xin He and Weijia Yang

Appl. Sci. 2022, 12(10), 4996; https://doi.org/10.3390/app12104996 - 15 May 2022

Cited by 6 | Viewed by 2488

Abstract

This work reports the fabrication of ZnO@MoS₂ core–shell micro/nanomaterials and their photocatalytic performances. First, the ZnO@MoS₂ core–shell micro/nanorods heterostructures were grown by a two-step, hydrothermal method. Second, X-ray diffraction, scanning-electron microscopy, Raman spectra, and UV-visible spectra were applied to confirm and [...] Read more.

This work reports the fabrication of ZnO@MoS₂ core–shell micro/nanomaterials and their photocatalytic performances. First, the ZnO@MoS₂ core–shell micro/nanorods heterostructures were grown by a two-step, hydrothermal method. Second, X-ray diffraction, scanning-electron microscopy, Raman spectra, and UV-visible spectra were applied to confirm and characterize the ZnO@MoS₂ core–shell micro/nanorods. Third, methylene blue was employed to investigate the photocatalytic performance of the ZnO@MoS₂ core–shell micro/nanorods heterostructures. It was found that the shape of the MoS₂ shell layer depended on the growth time. The shell layer was composed of MoS₂ nanoparticles before the growth time of 6 h and then turned into MoS₂ nanosheets. It was also found that the photocatalytic performance was significantly affected by the growth time of the MoS₂ nanosheets. When the growth time of the MoS₂ nanosheets was between 6 and 10 h, ZnO@MoS₂ core–shell heterostructures grown for 6 h exhibited a best photocatalytic efficiency value of 69.24% after 3 h catalysis. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 2987 KiB  

Open AccessArticle

Interaction between Graphene Nanoribbon and an Array of QDs: Introducing Nano Grating

by Sahar Armaghani, Ali Rostami and Peyman Mirtaheri

Photonics 2022, 9(5), 348; https://doi.org/10.3390/photonics9050348 - 15 May 2022

Cited by 2 | Viewed by 2528

Abstract

In this work, the interaction between an array of QDs and Graphene nanoribbon is modeled using dipole–dipole interaction. Then, based on the presented model, we study the linear optical properties of the considered system and find that by changing the size, number, and [...] Read more.

In this work, the interaction between an array of QDs and Graphene nanoribbon is modeled using dipole–dipole interaction. Then, based on the presented model, we study the linear optical properties of the considered system and find that by changing the size, number, and type of quantum dots as well as how they are arranged, the optical properties can be controlled and the controllable grating plasmonic waveguides can be implemented. Therefore, we introduce different structures, compare them together and find that each of them can be useful based on their application in optical integrated circuits. The quantum dot arrays are located on a graphene nanoribbon with dimensions of 775 × 40 nm². Applying electromagnetic waves with a wavelength of 1.55 µm causes polarization in the quantum dots and induces surface polarization on graphene. It is shown that, considering the large radius of the quantum dot, the induced polarization is increased, and ultimately the interaction with other quantum dots and graphene nanoribbon is stronger. Similarly, the distance between quantum dots and the number of QDs on Graphene nanoribbon are basic factors that affect the interaction between QDs and nanoribbon. Due to the polarization effect of these elements between each other, we see the creation of the effective grating refractive index in the plasmonic waveguide. This has many applications in quantum optical integrated circuits, nano-scale atomic lithography for nano-scale production, the adjustment coupling coefficient between waveguides, and the implementation of optical gates, reflectors, detectors, modulators, and others. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 6454 KiB  

Open AccessCommunication

Constraint Mechanism of Power Device Design Based on Perovskite Quantum Dots Pumped by an Electron Beam

by Yining Mu, Yanzheng Li, Peng Du, Hang Ren, Idelfonso Tafur Monroy, Makram Ibrahim, Guanyu Wen, Dong Liang, Jianshang Feng, Jiayu Ao, Xiangyue Xie and Yumeng Li

Sensors 2022, 22(10), 3721; https://doi.org/10.3390/s22103721 - 13 May 2022

Cited by 1 | Viewed by 2158

Abstract

This paper studied the constraint mechanism for power device design based on perovskite quantum dots pumped by an electron beam. Combined with device designing, an experimental system of self-saturation luminescence and aging failure was designed for CsPbBr₃ films. On this basis, we [...] Read more.

This paper studied the constraint mechanism for power device design based on perovskite quantum dots pumped by an electron beam. Combined with device designing, an experimental system of self-saturation luminescence and aging failure was designed for CsPbBr₃ films. On this basis, we further completed the self-saturation luminescence and aging failure experiment and constructed a model of self-saturation luminescence and aging failure for CsPbBr₃ device designing. Three constraints were proposed after analyzing and discussing the experimental data. Firstly, too high of a pumping current density makes it difficult to effectively promote the enhancement of luminescence efficiency. Secondly, radiation decomposition and aging failure of CsPbBr₃ films are mainly related to the polarized degree of CsPbBr₃ nanocrystals. Thirdly, by increasing the pumping electric field, the pumping energy can be effectively and widely delivered to the three-dimensional quantum dots film layer space, and there is a nonlinear relationship between the attenuation of the pumping energy density and the increment of the pumping electric field, which will effectively avoid the local high-energy density of instantaneous optical pumping. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 1963 KiB  

Open AccessArticle

Effect of Yb³⁺ on the Structural and Visible to Near-Infrared Wavelength Photoluminescence Properties in Sm³⁺-Yb³⁺-Codoped Barium Fluorotellurite Glasses

by Eric Kumi-Barimah, Yan Chen, Rebekah Tenwick, Mohanad Al-Murish, Geeta Sherma and Animesh Jha

Materials 2022, 15(9), 3314; https://doi.org/10.3390/ma15093314 - 5 May 2022

Cited by 7 | Viewed by 3295

Abstract

We report on the Sm³⁺ and Sm³⁺:Yb³⁺-doped barium fluorotellurite glasses prepared using the conventional melting and quenching method. The spectroscopic characterisations were investigated with Raman and FTIR to evaluate the glasses’ structural and hydroxyl (-OH) content. The Raman [...] Read more.

We report on the Sm³⁺ and Sm³⁺:Yb³⁺-doped barium fluorotellurite glasses prepared using the conventional melting and quenching method. The spectroscopic characterisations were investigated with Raman and FTIR to evaluate the glasses’ structural and hydroxyl (-OH) content. The Raman analysis revealed a structural modification in the glass network upon adding and increasing the Yb³⁺ concentration from a TeO₃ trigonal pyramid to a TeO₄ trigonal bi-pyramid polyhedral. At the same time, the FTIR measurements showed the existence of -OH groups in the glass. Thus, under the current experimental conditions and nominal composition, the -OH group contents are too large to enable an effective removal. The near-infrared region of the absorption spectra is employed to determine the nephelauxetic ratio and bonding parameters. The average nephelauxetic ratio decreases, and the bonding parameter increases with the increasing Yb³⁺ content in the glasses. A room temperature visible and near-infrared photoluminescence ranging from 500 to 1500 nm in wavelength and decay properties were investigated for glasses doped with Sm³⁺ and Sm³⁺-Yb³⁺ by exciting them with 450 and 980 nm laser sources. Exciting the Sm³⁺- and Sm³⁺-Yb³⁺-doped glasses by 450 nm excitation reveals a new series of photoluminescence emissions at 1200, 1293, and 1418 nm, corresponding to the ⁶F_11/2 state to the ⁶H_J (J = 7/2, 9/2, 11/2) transitions. Under the 976 nm laser excitation, a broad photoluminescence emission from 980 to 1200 nm was detected. A decay lifetime decreased from ~244 to ~43 μs by increasing the Yb³⁺ content, ascribing to concentration quenching and the OH content. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 2620 KiB  

Open AccessArticle

Low Temperature Step Annealing Synthesis of the Ti₂AlN MAX Phase to Fabricate MXene Quantum Dots

by Sophia Akhtar, Shrawan Roy, Trang Thu Tran, Jaspal Singh, Anir S. Sharbirin and Jeongyong Kim

Appl. Sci. 2022, 12(9), 4154; https://doi.org/10.3390/app12094154 - 20 Apr 2022

Cited by 9 | Viewed by 4036

Abstract

We present the synthesis of the Ti₂AlN MAX phase using two-step annealing at temperatures of 600 °C and 1100 °C, the lowest synthesis temperatures reported so far. After the successful synthesis of the Ti₂AlN MAX phase, two-dimensional Ti₂ [...] Read more.

We present the synthesis of the Ti₂AlN MAX phase using two-step annealing at temperatures of 600 °C and 1100 °C, the lowest synthesis temperatures reported so far. After the successful synthesis of the Ti₂AlN MAX phase, two-dimensional Ti₂N MXene was prepared through wet chemical etching and further fragmented into light emitting MXene quantum dots (MQDs) with a size of 3.2 nm by hydrothermal method. Our MQDs displayed a 6.9% quantum yield at a 310 nm wavelength of excitation, suggesting promising nanophotonic applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 4975 KiB  

Open AccessArticle

Expansion of Image Space in Enhanced-NA Fresnel Holographic Display

by Byung Gyu Chae

Appl. Sci. 2022, 12(9), 4148; https://doi.org/10.3390/app12094148 - 20 Apr 2022

Cited by 2 | Viewed by 2285

Abstract

The enhanced-NA Fresnel hologram reconstructs a holographic image at a viewing angle larger than the diffraction angle of a hologram pixel. The image space is limited by the bandwidth of a digital hologram. In this study, we investigate the property of image formation [...] Read more.

The enhanced-NA Fresnel hologram reconstructs a holographic image at a viewing angle larger than the diffraction angle of a hologram pixel. The image space is limited by the bandwidth of a digital hologram. In this study, we investigate the property of image formation in the extended image space beyond a diffraction zone. A numerical simulation, using the phase Fresnel hologram, is carried out to observe an extension of image space and the effect of this on the changes in the angular field of view. The phase Fresnel hologram, synthesized by restricting the angular view range to a diffraction angle, can reconstruct a uniform image without high-order noises within the primary viewing zone, which is well confirmed by optical experiments. On the other hand, the overlapping of high-order images is inevitable, when the viewing angle depends on the hologram numerical aperture. In principle, the replica noises in both the hologram and image planes would be removed during the optimization algorithm considering suitable constraints. We discuss the development of a method for expanding the image space, while maintaining the viewing angle of a holographic image. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 3798 KiB  

Open AccessArticle

A CMOS-Compatible Carrier-Injection Plasmonic Micro-Ring Modulator with Resonance Tuning by Carrier Concentration

by Jiaqi Sun, Wenwu Wang and Zhihua Li

Photonics 2022, 9(5), 272; https://doi.org/10.3390/photonics9050272 - 19 Apr 2022

Cited by 3 | Viewed by 2519

Abstract

A complementary metal-oxide-semiconductor (CMOS)-compatible carrier-injection plasmonic micro-ring modulator (CIPMRM) is designed and analyzed theoretically. The CIPMRM has a compacted footprint of 49.3 μm² (R = 2 μm), a bit rate of 36.5 Gbps, insertion loss of −9.8 dB, a static extinction ratio [...] Read more.

A complementary metal-oxide-semiconductor (CMOS)-compatible carrier-injection plasmonic micro-ring modulator (CIPMRM) is designed and analyzed theoretically. The CIPMRM has a compacted footprint of 49.3 μm² (R = 2 μm), a bit rate of 36.5 Gbps, insertion loss of −9.8 dB, a static extinction ratio of 21.7 dB, and energy consumption of 4.40 pJ/bit as 2.2 V peak-to-peak voltage is applied at 1550 nm. Besides, the method of resonance tuning by carrier concentration is proposed to compensate for the wavelength mismatch between the CIPMRM resonance and the laser, resulting from temperature and line width variation of the CIPMRM. This method has a faster response time and a greater ability to shift the resonant wavelength compared with the method of thermo-optic resonance tuning. The proposed scheme provides a route for realizing the compacted size modulator for optoelectronic integration. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 2940 KiB  

Open AccessEditor’s ChoiceCommunication

Flexible Silicon Dimer Nanocavity with Electric and Magnetic Enhancement

by Chengda Pan, Yajie Bian, Yuchan Zhang, Shiyu Zhang, Xiaolei Zhang, Botao Wu, Qingyuan Jin and E Wu

Photonics 2022, 9(4), 267; https://doi.org/10.3390/photonics9040267 - 18 Apr 2022

Cited by 1 | Viewed by 2721

Abstract

High-index dielectrics have recently been regarded as promising building blocks in nanophotonics owing to optical electric and magnetic Mie resonances. In particular, silicon is gaining great interest as the backbone of modern technology. Here, silicon dimer nanocavities with different sizes of silicon nanospheres [...] Read more.

High-index dielectrics have recently been regarded as promising building blocks in nanophotonics owing to optical electric and magnetic Mie resonances. In particular, silicon is gaining great interest as the backbone of modern technology. Here, silicon dimer nanocavities with different sizes of silicon nanospheres were constructed using a probe nanomanipulation method and interacted with a few-layered R6G membrane to investigate the enhancement of electric and magnetic mode coupling. The evidence of the enhancement of fluorescence and slightly prolonged lifetime of R6G indicated the existence of nanocavities. In addition, the simulated electric and magnetic field distributions and decomposed mode of nanocavity were used to analyze the contribution of electric and magnetic modes to the R6G enhanced fluorescence. Such silicon dimer is a flexible nanocavity with electric and magnetic mode enhancement and has promising applications in sensing and all-dielectric metamaterials or nanophotonic devices. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 1488 KiB  

Open AccessArticle

Efficient Enhancement of Second Harmonic Generation via Noninvasive Modulation

by Liqing Wu, Weiru Fan, Ziyang Chen and Jixiong Pu

Appl. Sci. 2022, 12(8), 3962; https://doi.org/10.3390/app12083962 - 14 Apr 2022

Viewed by 2653

Abstract

Second harmonic generation has been widely applied in various fields. High second harmonic intensity can facilitate optical imaging, signal sensing, and detection. Thus, enhancing the intensity of the second harmonic is a significant work. However, changing the external character of crystal or increasing [...] Read more.

Second harmonic generation has been widely applied in various fields. High second harmonic intensity can facilitate optical imaging, signal sensing, and detection. Thus, enhancing the intensity of the second harmonic is a significant work. However, changing the external character of crystal or increasing the pump light intensity to improve the intensity of the second harmonic is not always advisable in some applications, such as bioimaging, biopsies, etc. Here, we implemented a noninvasive method that constructs a specific spatial distribution field via a scattering medium to realize a high enhancement of second harmonic intensity. We studied that different scattering mediums exerted the influence on the optimal enhancement effect of second harmonic. It was found that choosing an appropriate scattering medium can greatly enhance the intensity of the second harmonic. The results can offer a helpful value for second harmonic applications such as bioimaging, sensing, and optical frequency conversion. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 2269 KiB  

Open AccessArticle

A CMOS-Compatible Carrier-Injection Plasmonic Micro-Ring Modulator (CIPMRM) with Stable Performance as Temperature Varying around 60 K

by Jiaqi Sun, Zhihua Li and Wenwu Wang

Appl. Sci. 2022, 12(8), 3947; https://doi.org/10.3390/app12083947 - 13 Apr 2022

Viewed by 1989

Abstract

A CMOS-compatible carrier-injection plasmonic micro-ring modulator (CIPMRM) is proposed and theoretically analyzed. It has a compacted footprint of 43.4 μm² (R = 2 μm), a data rate of 45 Gbps, an insertion loss of −8 dB, a static extinction ratio of 22 [...] Read more.

A CMOS-compatible carrier-injection plasmonic micro-ring modulator (CIPMRM) is proposed and theoretically analyzed. It has a compacted footprint of 43.4 μm² (R = 2 μm), a data rate of 45 Gbps, an insertion loss of −8 dB, a static extinction ratio of 22 dB, and an energy consumption of 4.5 pJ/bit when 2.5 V peak-to-peak voltage is applied. Moreover, it works well when temperature varies around 60 K. A method of tuning the resonant wavelength based on the carrier concentration is proposed here because the device is reliable when the linewidth varies within ±5%. CIPMRM provides a way to overcome the shortcomings of temperature and process sensitivity, which are characteristics of the photonic micro-ring modulator. It can be used in optoelectronic integration for its small size and stable performance. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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24 pages, 4226 KiB  

Open AccessArticle

Space Debris Detection and Positioning Technology Based on Multiple Star Trackers

by Meiying Liu, Hu Wang, Hongwei Yi, Yaoke Xue, Desheng Wen, Feng Wang, Yang Shen and Yue Pan

Appl. Sci. 2022, 12(7), 3593; https://doi.org/10.3390/app12073593 - 1 Apr 2022

Cited by 30 | Viewed by 8245

Abstract

This paper focuses on the opportunity to use multiple star trackers to help space situational awareness and space surveillance. Catalogs of space debris around Earth are usually based on ground-based measurements, which rely on data provided by ground-based radar observations and ground-based optical [...] Read more.

This paper focuses on the opportunity to use multiple star trackers to help space situational awareness and space surveillance. Catalogs of space debris around Earth are usually based on ground-based measurements, which rely on data provided by ground-based radar observations and ground-based optical observations. However, space-based observations offer new opportunities because they are independent of the weather and the circadian rhythms to which the ground system is subjected. Consequently, space-based optical observations improve the possibility of space debris detection and cataloging. This work deals with a feasibility study of an innovative strategy, which consists of the use of a star sensor with a dedicated algorithm to run directly on board. This approach minimizes the impact on the original mission of the satellite, and on this basis, it has also the function of space debris monitoring. Therefore, theoretically, every satellite with a star tracker can be used as a space surveillance observer. In this paper, we propose a multi-star space debris detecting and positioning method with constant geocentric observation. Using the multi-star tracker joint positioning method, the angle measurement data of the star tracker is converted into the spatial coordinates of the target. In addition, the Gaussian MMSE difference correction algorithm is used to realize the target positioning of multiple optical observations, and the spatial target position information of the multi-frame images is fused, thus completing the solution of the orbit equation. The simulation results show that the proposed method is sufficient to detect and position space debris. It also demonstrates the necessity and feasibility of cooperative network observation by multiple star trackers. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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15 pages, 13611 KiB  

Open AccessArticle

Asymmetric Encryption of Invisible Structured Light 3D Imaging

by Jing Zhang, Aimin Yan and Hongbo Zhang

Appl. Sci. 2022, 12(7), 3563; https://doi.org/10.3390/app12073563 - 31 Mar 2022

Cited by 4 | Viewed by 2250

Abstract

The research proposes a novel invisible structured light 3D object encryption method. The system projects invisible light on the target plane to achieve three-dimensional object reconstruction. The encryption is conducted using keys from eight stripe patterns and two fingerprint patterns using an elliptic [...] Read more.

The research proposes a novel invisible structured light 3D object encryption method. The system projects invisible light on the target plane to achieve three-dimensional object reconstruction. The encryption is conducted using keys from eight stripe patterns and two fingerprint patterns using an elliptic curve encryption algorithm to generate eight corresponding ciphertexts. The three-dimensional object is reconstructed using eight fringe patterns with the elliptic curve decryption algorithm. The proposed method greatly reduces the interference of background light in the system to achieve a better 3D imaging accuracy. The elliptic curve cryptosystem is able to ensure 3D object information transmission security. The simulation results validated the robustness and effectiveness of the proposed scheme. The proposed method has practical security-sensitive applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 3125 KiB  

Open AccessArticle

Optimized ICPCVD-Based TiO₂ for Photonics

by Aurore Andrieux, Marie-Maxime Mennemanteuil, Nicolas Geoffroy, Mélanie Emo, Laurent Markey and Kamal Hammani

Materials 2022, 15(7), 2578; https://doi.org/10.3390/ma15072578 - 31 Mar 2022

Cited by 2 | Viewed by 2140

Abstract

We propose obtaining TiO₂ films by ICPCVD for the fabrication of low-loss waveguides. The challenge is to produce a dense and homogeneous layer with a high refractive index and low absorption in the visible range. Crystallized layers with features such as grains [...] Read more.

We propose obtaining TiO₂ films by ICPCVD for the fabrication of low-loss waveguides. The challenge is to produce a dense and homogeneous layer with a high refractive index and low absorption in the visible range. Crystallized layers with features such as grains and amorphous layers have a rather low index for the application targeted, so we aimed for an intermediate state. We investigated the influence of plasma power, pressure, deposition time and annealing temperature on the structural, crystalline, and optical properties in order to tailor them. We showed that crystallization into rutile at the nanoscale occurred during deposition and under wisely chosen conditions, we reached a refractive index of 2.5 at 630 nm without creating interfaces or inhomogeneity in the layer depth. Annealing permits one to further increase the index, up to 2.6. TEM analysis on one sample before and after annealing confirmed the nano-polycrystallization and presence of both anatase and rutile phases and we considered that this intermediate state of crystallization was the best compromise for guided optics. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 4474 KiB  

Open AccessCommunication

Analysis and Simulation of the Optical Properties of a Quantum Dot on a Graphene Nanoribbon System

by Sahar Armaghani, Ali Rostami and Peyman Mirtaheri

Photonics 2022, 9(4), 220; https://doi.org/10.3390/photonics9040220 - 27 Mar 2022

Cited by 2 | Viewed by 2664

Abstract

In this work, we theoretically study the optical properties of a graphene nanoribbon with a quantum dot (QD) on it. The system consists of a graphene nanoribbon with dimensions of 400 × 3100 (nm²) and a quantum dot with a nanoscale [...] Read more.

In this work, we theoretically study the optical properties of a graphene nanoribbon with a quantum dot (QD) on it. The system consists of a graphene nanoribbon with dimensions of 400 × 3100 (nm²) and a quantum dot with a nanoscale radius. The quantum dot is symmetrically located at the center of the graphene nanoribbon to simplify the mathematical model. To calculate the optical properties (susceptibility) of the system, a broadband electromagnetic wave (0.5–2.5 μm) is applied to the structure to model dipole-dipole interaction. Considering the input field and calculating the total induced polarization, the optical susceptibility of the system is calculated. The applied electromagnetic field excites the surface plasmon on the graphene nanoribbon and the excitons of QDs. The induced dipoles in the graphene nanoribbon and the QD will interact with each other. We show that the parameters of both materials strongly influence dipole-dipole interaction. In particular, the effect of QDs (location on graphene and radius) on the optical properties of the considered system was studied. The obtained results can be used to introduce periodic optical structures in nanoscale by inserting QDs in a periodic array on graphene nanoribbon. Additionally, applications such as reflectors, couplers, and wavelength filters can be designed. Considering the presented theoretical framework, we can describe all the optoelectronic and optomechanical applications of complex nanoscale graphene and QD systems. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 2050 KiB  

Open AccessCommunication

Modeling for Generating Femtosecond Pulses in an Er-Doped Fiber Using Externally Controlled Spectral Broadening and Compression Mechanisms

by Mohamed Hemdan Abo-elenein, Salah Eldeen Ibrahim Hassab Elnaby, Amin Fahim Hassan and Afaf Mahmoud Abd-Rabou

Photonics 2022, 9(4), 205; https://doi.org/10.3390/photonics9040205 - 22 Mar 2022

Viewed by 2370

Abstract

A model for generating femtosecond laser pulses from a low-power mode-locked laser of moderate temporal half-width was proposed. This was achieved by injecting the pulse into a single-mode inverted-populated Er-doped fiber where self-focusing and absorption were avoided. To initiate spectral broadening, the pulse [...] Read more.

A model for generating femtosecond laser pulses from a low-power mode-locked laser of moderate temporal half-width was proposed. This was achieved by injecting the pulse into a single-mode inverted-populated Er-doped fiber where self-focusing and absorption were avoided. To initiate spectral broadening, the pulse was phase-modulated by subjecting a part of the fiber to an electric field of suitable intensity and frequency generated into a circular capacitor. To stimulate temporal compression, the phase-modulated pulse was introduced into a combination of two prism sets located symmetrically with respect to the x-axis. After passing the pulse through the first prism set, its spectral components were spatially separated in the y-axis. The spectral phases were manipulated by redirecting the spectral components through a slab cross-section that was subjected to a spatially modulated DC electric field. After passing the slab, the pulse is directed into the second prism set, where the spectral components were spatially overlapped and propagated outside the compressor with the same slope and dimension as before entering the compressor. Constructive super positioning of the phase-manipulated spectral components gave maximum intensity only at a specified location. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 19001 KiB  

Open AccessArticle

Research on the Coupled Modulation Transfer Function of the Discrete Sampling System with Hexagonal Fiber-Optic Imaging Bundles

by Wenxian Li, Chengshan Han, Congjun Wu, Yawei Huang and Hang Zhang

Appl. Sci. 2022, 12(6), 3135; https://doi.org/10.3390/app12063135 - 18 Mar 2022

Cited by 3 | Viewed by 2001

Abstract

In this study, we developed a numerical model of the coupled modulation transfer function (coupled-MTF) based on the discrete sampling system from the perspective of optical system imaging quality evaluation for coupled two-dimensional discrete sampling characteristics of the hexagonally aligned fiber-optic imaging bundles [...] Read more.

In this study, we developed a numerical model of the coupled modulation transfer function (coupled-MTF) based on the discrete sampling system from the perspective of optical system imaging quality evaluation for coupled two-dimensional discrete sampling characteristics of the hexagonally aligned fiber-optic imaging bundles and CCD image elements. The results show that when the spatial frequency of the input target signal deviates from the Nyquist frequency by 1%, an increase in the number of fibers leads to a faster convergence of the oscillation of the coupled-MTF, and the coupled-MTF converges to a stable value when the number of fibers reaches 1000 × 1000. The deviation of the spatial frequency of the input target signal from the Nyquist frequency is within 1%, and the oscillatory convergence of the coupled-MTF accelerates with increasing deviation. The coupled-MTF oscillates with the deviation period of the wave peak of the input target signal from the initial position of the fiber center, and the theoretical oscillation spatial period is twice the fiber diameter. This study produces important guidelines for the selection of the number of fibers, input spatial frequency, and initial position deviation of the hexagonally arranged fiber imaging bundles. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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9 pages, 6357 KiB  

Open AccessArticle

Organic–Inorganic Hybrid Film MLAs Built on the Silicon Solar Cells to Improve the Photoelectric Conversion Efficiency

by Xuehua Zhang, Yang Bi, Shun Liu, Wei Zhang and Fangren Hu

Coatings 2022, 12(3), 393; https://doi.org/10.3390/coatings12030393 - 16 Mar 2022

Cited by 3 | Viewed by 2966

Abstract

Light trapping micro-nano structures have been widely used to optimize the function of solar cell devices, especially microlens arrays (MLAs). In this article, we first prepared composite films by using sol-gel technology and the spin coating method, and then constructed heteromorphic MLAs on [...] Read more.

Light trapping micro-nano structures have been widely used to optimize the function of solar cell devices, especially microlens arrays (MLAs). In this article, we first prepared composite films by using sol-gel technology and the spin coating method, and then constructed heteromorphic MLAs on the surface of the composite films by using thermal reflow and UV nanoimprint technology; the substrate used was the silicon solar cell. Finally, the performance of the cells was improved. Optical transmission properties and surface morphology of the organic–inorganic hybrid films were detected by using a UV-Vis spectrometer and atomic force microscopy, respectively; it was revealed that the hybrid films had relatively excellent optical transmission performance in the visible light range. Surface structure of the hybrid film MLAs were detected by using SEM. At the same time, the optical imaging capabilities of MLAs were studied by using optical microscopy. Besides, the contact angles of the MLAs were also measured. It can be clearly seen that the prepared MLAs have a regular arrangement, clean appearance, and good imaging capabilities (from the actual test results). Finally, the various parameters of the silicon solar cells with hybrid film MLAs were studied. In addition, the power conversion efficiency (PCE) values increased by about 10.48% for the silicon solar cell with circular MLAs, compared to the silicon solar cell without a structure. The results show a concise and effective method to prepare organic–inorganic hybrid film MLAs on silicon solar cells, with significant improvement in photoelectric conversion efficiency. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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14 pages, 9096 KiB  

Open AccessArticle

Enhanced Single-Beam Multiple-Intensity Phase Retrieval Using Holographic Illumination

by Cheng Xu, Hui Pang, Axiu Cao and Qiling Deng

Photonics 2022, 9(3), 187; https://doi.org/10.3390/photonics9030187 - 15 Mar 2022

Cited by 1 | Viewed by 2705

Abstract

Single-beam multiple-intensity iterative phase retrieval is a high-precision and lens-free computational imaging method, which reconstructs the complex-valued distribution of the object from a volume of axially captured diffraction intensities using the post-processing algorithm. However, for the object with slowly-varying waves, the method may [...] Read more.

Single-beam multiple-intensity iterative phase retrieval is a high-precision and lens-free computational imaging method, which reconstructs the complex-valued distribution of the object from a volume of axially captured diffraction intensities using the post-processing algorithm. However, for the object with slowly-varying waves, the method may encounter the problem of convergence stagnation since the lack of diversity between the captured intensity patterns. In this paper, a novel technique to enhance phase retrieval using holographic illumination is proposed. One special computer-generated hologram is designed, which can generate multiple significantly different images at the required distances. The incident plane wave is firstly modulated by the hologram, and then the exit wave is used to illuminate the object. Benefitting from this holographic illumination, remarkable intensity changes in the given detector planes can be produced, which is conducive to fast and high-accuracy reconstruction. Simulation and optical experiments are performed to verify the feasibility of the proposed method. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 8097 KiB  

Open AccessArticle

D–π–A–π–D Initiators Based on Benzophenone Conjugate Extension for Two-Photon Polymerization Additive Manufacturing

by Shanggeng Li, Xiaolin Liu, Shuai Zhang, Yawen Zhou, Xiangyu Wan, Ning Li, Jing Li and Lin Zhang

Photonics 2022, 9(3), 183; https://doi.org/10.3390/photonics9030183 - 13 Mar 2022

Cited by 3 | Viewed by 2785

Abstract

A two-photon polymerization initiator is a kind of nonlinear optical material. With the demand for more efficient initiators in two-photon polymerization additive manufacturing, there are more and more related studies. In this paper, four conjugate-extended two-photon polymerization initiators with different alkane chain lengths [...] Read more.

A two-photon polymerization initiator is a kind of nonlinear optical material. With the demand for more efficient initiators in two-photon polymerization additive manufacturing, there are more and more related studies. In this paper, four conjugate-extended two-photon polymerization initiators with different alkane chain lengths were designed and synthesized, and single-photon, two-photon, and photodegradation experiments were carried out. Additive manufacturing experiments illustrated that the designed molecules can be used as two-photon initiators, and the writing speed can achieve 100,000 μm/s at a laser power of 25 mW. Through theoretical calculation and experimental comparison of the properties of molecules with different conjugation degrees, it was proven that a certain degree of conjugation extension can improve the initiation ability of molecules; however, this improvement cannot be extended infinitely. Solubility tests of different acrylates showed that molecules with different alkane chain lengths have varying solubility. Changing the molecular alkane chain length may be favorable to adapt to different monomers. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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Supplementary material:
Supplementary File 1 (ZIP, 628 KiB)

10 pages, 25721 KiB  

Open AccessArticle

Fabricated Flexible Composite for a UV-LED Color Filter and Anti-Counterfeiting Application of Calcium Molybdate Phosphor Synthesized at Room Temperature

by Jae-Yong Jung

Materials 2022, 15(6), 2078; https://doi.org/10.3390/ma15062078 - 11 Mar 2022

Cited by 14 | Viewed by 3099

Abstract

Crystalline CaMoO₄ and rare-earth-doped CaMoO₄:RE³⁺ (RE = Tb, Eu) phosphors were synthesized at room temperature using a co-precipitation method. The crystal structure of the synthesized powder was a tetragonal structure with a main diffraction peak (112) phase. When CaMoO [...] Read more.

Crystalline CaMoO₄ and rare-earth-doped CaMoO₄:RE³⁺ (RE = Tb, Eu) phosphors were synthesized at room temperature using a co-precipitation method. The crystal structure of the synthesized powder was a tetragonal structure with a main diffraction peak (112) phase. When CaMoO₄ was excited at 295 nm, it showed a central peak of 498 nm and light emission in a wide range of 420 to 700 nm. Rare-earth-ion-doped CaMoO₄:Tb³⁺ was excited at 288 nm and a green light emission was observed at 544 nm, and CaMoO₄:Eu³⁺ was excited at 292 nm and a red light emission was observed at 613 nm. To take advantage of the light-emitting characteristics, a flexible composite was manufactured and a color filter that could be used for UV-LEDs was manufactured. In addition, it was suggested that an ink that could be checked only by UV light could be produced and applied to banknotes so as to prevent counterfeiting. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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16 pages, 3721 KiB  

Open AccessArticle

DDGANSE: Dual-Discriminator GAN with a Squeeze-and-Excitation Module for Infrared and Visible Image Fusion

by Jingjing Wang, Jinwen Ren, Hongzhen Li, Zengzhao Sun, Zhenye Luan, Zishu Yu, Chunhao Liang, Yashar E. Monfared, Huaqiang Xu and Qing Hua

Photonics 2022, 9(3), 150; https://doi.org/10.3390/photonics9030150 - 3 Mar 2022

Cited by 1 | Viewed by 3144

Abstract

Infrared images can provide clear contrast information to distinguish between the target and the background under any lighting conditions. In contrast, visible images can provide rich texture details and are compatible with the human visual system. The fusion of a visible image and [...] Read more.

Infrared images can provide clear contrast information to distinguish between the target and the background under any lighting conditions. In contrast, visible images can provide rich texture details and are compatible with the human visual system. The fusion of a visible image and infrared image will thus contain both comprehensive contrast information and texture details. In this study, a novel approach for the fusion of infrared and visible images is proposed based on a dual-discriminator generative adversarial network with a squeeze-and-excitation module (DDGANSE). Our approach establishes confrontation training between one generator and two discriminators. The goal of the generator is to generate images that are similar to the source images, and contain the information from both infrared and visible source images. The purpose of the two discriminators is to increase the similarity between the image generated by the generator and the infrared and visible images. We experimentally demonstrated that using continuous adversarial training, DDGANSE outputs images retain the advantages of both infrared and visible images with significant contrast information and rich texture details. Finally, we compared the performance of our proposed method with previously reported techniques for fusing infrared and visible images using both quantitative and qualitative assessments. Our experiments on the TNO dataset demonstrate that our proposed method shows superior performance compared to other similar reported methods in the literature using various performance metrics. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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16 pages, 1959 KiB  

Open AccessArticle

Energy-Efficient Monitoring of Fine Particulate Matter with Tiny Aerosol Conditioner

by Sung Hoon Baek

Sensors 2022, 22(5), 1950; https://doi.org/10.3390/s22051950 - 2 Mar 2022

Cited by 1 | Viewed by 2813

Abstract

Fine particulate matter (PM) is associated with an increased risk of respiratory and cardiovascular diseases. Fine PM absorbs water molecules at high relative humidity, and then their size grows. Such hygroscopic growth causes a large error when monitoring PM concentrations. To lower the [...] Read more.

Fine particulate matter (PM) is associated with an increased risk of respiratory and cardiovascular diseases. Fine PM absorbs water molecules at high relative humidity, and then their size grows. Such hygroscopic growth causes a large error when monitoring PM concentrations. To lower the relative humidity, monitors use an indirect heating device, which is large and consumes large amounts of power. The problem with conventional particle separators is that their efficiency depends on temperature and humidity, and their traditional structure, which lets air flow downward. As such, this paper addresses these problems and presents a PM monitor with a new type of dryer that is free from these problems. The proposed monitor requires less energy and has an efficient dehumidifier and a new structure in which air flows upward. The presented experiments were conducted to compare the proposed device with a reference monitor managed by a governmental institute, and to evaluate the effect of the dehumidifier, the relative precision of the proposed devices, and the correlation with the reference monitor. The experimental results showed that the proposed monitor satisfies the U.S. EPA indicators for class III monitors. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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13 pages, 6439 KiB  

Open AccessArticle

Statistically Correlating Laser-Induced Damage Performance with Photothermal Absorption for Fused Silica Optics in a High-Power Laser System

by Zhaohua Shi, Laixi Sun, Ting Shao, Hongjie Liu, Jin Huang, Xin Ye, Fengrui Wang, Liming Yang and Wanguo Zheng

Photonics 2022, 9(3), 137; https://doi.org/10.3390/photonics9030137 - 26 Feb 2022

Cited by 12 | Viewed by 3120

Abstract

Photothermal weak absorption is useful for the diagnosis of absorbing defects on the surface of fused silica optics in high-power lasers. However, how they relate to the laser-induced damage performance remains unclear, especially for a fused silica surface that has been post-treated with [...] Read more.

Photothermal weak absorption is useful for the diagnosis of absorbing defects on the surface of fused silica optics in high-power lasers. However, how they relate to the laser-induced damage performance remains unclear, especially for a fused silica surface that has been post-treated with different processes (e.g., dynamic chemical etching or magnetorheological finishing). Here, we present a correlation study on the surface defect absorption level and laser-induced damage performance of fused silica optics post-treated with different processes using the photothermal common-path interferometer method. Statistical distribution of the absorbing defects at various absorption levels is obtained. The relationship between the defect density and the laser damage performance was analyzed. We show that the surface absorbing defects of fused silica can be affected by the post-treatment type and material removal amount. Furthermore, we show that the density of the defects with the absorption over 2 ppm is strongly correlated with the damage initiation threshold and damage density. Especially, for high-density defects at this absorption level, the damage density of fused silica optics can be well-predicted. In the low-density range, the density of this kind of defect can reflect the zero-probability damage threshold well. The study exhibits the potential of this methodology to non-destructively detect the key absorbing defects on fused silica surfaces as well as evaluate and optimize the post-treatment level of fused silica optics for high-power laser applications. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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12 pages, 3127 KiB  

Open AccessArticle

All-Optical Phase-Change Memory with Improved Performance by Plasmonic Effect

by Wei Sun, Yegang Lu, Libo Miao and Yu Zhang

Photonics 2022, 9(3), 132; https://doi.org/10.3390/photonics9030132 - 25 Feb 2022

Cited by 10 | Viewed by 3683

Abstract

The combination of the integrated waveguide and phase-change materials (PCMs) provides a promising platform for reconfigurable and multifunctional photoelectric devices. Through plasmonic enhancement and the low loss propagation of the waveguide, the footprint and power consumption of the photoelectric device can be effectively [...] Read more.

The combination of the integrated waveguide and phase-change materials (PCMs) provides a promising platform for reconfigurable and multifunctional photoelectric devices. Through plasmonic enhancement and the low loss propagation of the waveguide, the footprint and power consumption of the photoelectric device can be effectively improved. In this work, a metal double-ring structure embedded with phase change materials was proposed to utilize the plasmonic effect for enhancement of the light-matter interaction. In particular, the overall temperature difference in the PCM cell can be confined within 2 °C during the crystallization process, thus avoiding the interior heterogeneous crystallization. The insertion loss of the cell in amorphous and crystalline states at a wavelength of 1550 nm are 2.3 dB and 1.0 dB, respectively. A signal contrast ratio of 15.8% is achieved under the ultra-small footprint (50 × 90 nm²) at a wavelength of 1550 nm. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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24 pages, 12232 KiB  

Open AccessReview

Developmental Trends in the Application and Measurement of the Bidirectional Reflection Distribution Function

by Yangyang Zou, Liu Zhang, Jian Zhang, Bonan Li and Xueying Lv

Sensors 2022, 22(5), 1739; https://doi.org/10.3390/s22051739 - 23 Feb 2022

Cited by 8 | Viewed by 3985

Abstract

The bidirectional reflection distribution function (BRDF) is among the most effective means to study the phenomenon of light–object interaction. It can precisely describe the characteristics of spatial reflection of the target surface, and has been applied to aerial remote sensing, imaging technology, materials [...] Read more.

The bidirectional reflection distribution function (BRDF) is among the most effective means to study the phenomenon of light–object interaction. It can precisely describe the characteristics of spatial reflection of the target surface, and has been applied to aerial remote sensing, imaging technology, materials analysis, and computer rendering technology. This study provides a comprehensive review of the development of devices to measure the BRDF. We gathered research in the area by using the Web of Science Core Collection, and show that work on the BDRF has been ongoing in the last 30 years. We also describe some typical measurement devices for the BRDF proposed in the literature. Finally, we summarise outstanding problems related to BRDF measurement and propose directions of future research in the area. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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11 pages, 3339 KiB  

Open AccessArticle

Structural, Electrical and Optical Properties of Pyrrolo[1,2-i][1,7] Phenanthroline-Based Organic Semiconductors

by Corneliu Doroftei, Aurelian Carlescu, Liviu Leontie, Ramona Danac and Cristina Maria Al-Matarneh

Materials 2022, 15(5), 1684; https://doi.org/10.3390/ma15051684 - 23 Feb 2022

Cited by 1 | Viewed by 2260

Abstract

This work reports a study on structural, electrical and optical properties of some recently synthesized pyrrolo[1,2-i][1,7] phenanthrolines derivatives in thin films. The thin films were deposited onto glass substrates by spin coating technique, using chloroform as solvent. The obtained films exhibited [...] Read more.

This work reports a study on structural, electrical and optical properties of some recently synthesized pyrrolo[1,2-i][1,7] phenanthrolines derivatives in thin films. The thin films were deposited onto glass substrates by spin coating technique, using chloroform as solvent. The obtained films exhibited a polycrystalline structure with an n–type semiconductor behavior after heat treatment in the temperature range 293–543 K, specific to each sample. The thermal activation energy lies between 0.68 and 0.78 eV, while the direct optical band gap values were found in the range 4.17–4.24 eV. The electrical and optical properties of the investigated organic semiconductor films were discussed in relation to microstructural properties, determined by the molecular structure. The investigated organic compounds are promising for applications in organic optoelectronics and nanoelectronics. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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23 pages, 7120 KiB  

Open AccessConcept Paper

Simultaneous Up-Conversion Based on a Co- & Counter-Directions SOA-MZI Sampling Mixer with Standard & Differential Modulation Modes

by Hassan Termos, Ali Mansour and Abbass Nasser

Photonics 2022, 9(2), 109; https://doi.org/10.3390/photonics9020109 - 14 Feb 2022

Cited by 7 | Viewed by 2642

Abstract

Simulation and experimental performance analyses of simultaneous up-converted signals, for the first time, were investigated utilizing a semiconductor optical amplifier Mach–Zehnder interferometer (SOA-MZI) sampling mixer in co- and counter-directions for standard and differential modulation modes. An optical pulse source at a sampling frequency [...] Read more.

Simulation and experimental performance analyses of simultaneous up-converted signals, for the first time, were investigated utilizing a semiconductor optical amplifier Mach–Zehnder interferometer (SOA-MZI) sampling mixer in co- and counter-directions for standard and differential modulation modes. An optical pulse source at a sampling frequency of f_s = 15.6 GHz was used as a sampling signal. The IF signal channels carrying quadrature phase shift keying (QPSK) data at frequencies f_m were up-converted at different mixing frequencies up to 195.5 GHz. Using the Virtual Photonics Inc. (VPI) simulator, we realized mixed QPSK signals and studied their characteristics through a conversion gain and an error vector magnitude (EVM). Simulations of up mixing operated in a frequency range up to 158 GHz. For the standard modulation in the co-direction, the conversion gain decreased from 43.3 dB at the mixing frequency of 16.6 GHz to 21.8 dB at 157 GHz for the first channel and from 43 dB at 17.6 GHz to 21 dB at 158 GHz for the second channel. The use of the differential modulation principle improved the conversion gain by about 10 dB at 195.5 GHz compared to standard modulations in co- and counter-directions. The EVM reached, respectively, 15.5 and 17.5% for the differential modulation in both configurations, at the bit rate of 100 Gbit/s at 195.5 GHz. The benefit provided by the differential modulation was that EVM values were shifted by 20% for all channels in both configurations at 100 Gbit/s. In the real measurement, we confirmed that co-directional conversion exhibited a better performance than the counter-directional operation. In addition, the real mixed signal exhibited lower efficiency and quality in comparison with simulated signals due to the sensitivity of the receiver. Full article

(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)

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