Optical and Optoelectronic Properties of Materials and Their Applications

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Materials materials	3.1	5.8	2008	13.9 Days	CHF 2600
Nanomaterials nanomaterials	4.4	8.5	2010	14.1 Days	CHF 2400
Photonics photonics	2.1	2.6	2014	14.9 Days	CHF 2400
Polymers polymers	4.7	8.0	2009	14.5 Days	CHF 2700
Applied Sciences applsci	2.5	5.3	2011	18.4 Days	CHF 2400
Sensors sensors	3.4	7.3	2001	18.6 Days	CHF 2600

36 pages, 6509 KiB

Open AccessReview

Hydrostatic Pressure as a Tool for the Study of Semiconductor Properties—An Example of III–V Nitrides

by Iza Gorczyca, Tadek Suski, Piotr Perlin, Izabella Grzegory, Agata Kaminska and Grzegorz Staszczak

Materials 2024, 17(16), 4022; https://doi.org/10.3390/ma17164022 - 13 Aug 2024

Viewed by 1337

Abstract

Using the example of III–V nitrides crystallizing in a wurtzite structure (GaN, AlN, and InN), this review presents the special role of hydrostatic pressure in studying semiconductor properties. Starting with a brief description of high-pressure techniques for growing bulk crystals of nitride compounds, [...] Read more.

Using the example of III–V nitrides crystallizing in a wurtzite structure (GaN, AlN, and InN), this review presents the special role of hydrostatic pressure in studying semiconductor properties. Starting with a brief description of high-pressure techniques for growing bulk crystals of nitride compounds, we focus on the use of hydrostatic pressure techniques in both experimental and theoretical investigations of the special properties of nitride compounds, their alloys, and quantum structures. The bandgap pressure coefficient is one of the most important parameters in semiconductor physics. Trends in its behavior in nitride structures, together with trends in pressure-induced phase transitions, are discussed in the context of the behavior of other typical semiconductors. Using InN as an example, the pressure-dependent effects typical of very narrow bandgap materials, such as conduction band filling or effective mass behavior, are described. Interesting aspects of bandgap bowing in In-containing nitride alloys, including pressure and clustering effects, are discussed. Hydrostatic pressure also plays an important role in the study of native defects and impurities, as illustrated by the example of nitride compounds and their quantum structures. Experiments and theoretical studies on this topic are reviewed. Special attention is given to hydrostatic pressure and strain effects in short periods of nitride superlattices. The explanation of the discrepancies between theory and experiment in optical emission and its pressure dependence from InN/GaN superlattices led to the well-documented conclusion that InN growth on the GaN substrate is not possible. The built-in electric field present in InGaN/GaN and AlGaN/GaN heterostructures crystallizing in a wurtzite lattice can reach several MV/cm, leading to drastic changes in the physical properties of these structures and related devices. It is shown how hydrostatic pressure modifies these effects and helps to understand their origin. Full article

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

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15 pages, 7353 KiB

Open AccessArticle

Light-Cured Junction Formation and Broad-Band Imaging Application in Thermally Mismatched van der Waals Heterointerface

by Liyuan Cheng, Qinglin Quan and Liang Hu

Materials 2024, 17(16), 3988; https://doi.org/10.3390/ma17163988 - 11 Aug 2024

Cited by 1 | Viewed by 1542

Abstract

Van der Waals (vdW) heterostructures are mainly fabricated by a classic dry transfer procedure, but the interface quality is often subject to the vdW gap, residual strains, and defect species. The realization of interface fusion and repair holds significant implications for the modulation [...] Read more.

Van der Waals (vdW) heterostructures are mainly fabricated by a classic dry transfer procedure, but the interface quality is often subject to the vdW gap, residual strains, and defect species. The realization of interface fusion and repair holds significant implications for the modulation of multiple photoelectric conversion processes. In this work, we propose a thermally mismatched strategy to trigger broad-band and high-speed photodetection performance based on a type-I heterostructure composed of black phosphorus (BP) and FePS₃ (FPS) nanoflakes. The BP acts as photothermal source to promote interface fusion when large optical power is adopted. The regulation of optical power enables the device from pyroelectric (PE) and/or alternating current photovoltaic (AC–PV) mode to a mixed photovoltaic (PV)/photothermoelectric (PTE)/PE mode. The fused heterostructure device presents an extended detection range (405~980 nm) for the FPS. The maximum responsivity and detectivity are 329.86 mA/W and 6.95 × 10¹⁰ Jones, respectively, and the corresponding external quantum efficiency (EQE) approaches ~100%. Thanks to these thermally-related photoelectric conversion mechanism, the response and decay time constants of device are as fast as 290 μs and 265 μs, respectively, superior to current all FPS-based photodetectors. The robust environmental durability also renders itself as a high-speed and broad-band imaging sensor. Full article

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

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9 pages, 5255 KiB

Open AccessCommunication

Optical Study on Temperature-Dependent Absorption Edge of γ-InSe-Layered Semiconductor

by Wen-Te Wu, Kwong-Kau Tiong, Shih-Wei Tan, Sheng-Yao Hu, Yueh-Chien Lee, Ruei-San Chen and Chia-Ti Wu

Appl. Sci. 2024, 14(15), 6676; https://doi.org/10.3390/app14156676 - 31 Jul 2024

Cited by 1 | Viewed by 1041

Abstract

We have studied the variations in the temperature-dependent absorption edge of a bulk InSe-layered semiconductor using photoconductivity (PC) measurements. From both the X-ray diffraction (XRD) and Raman experimental results, the structural phase of the as-prepared InSe sample was confirmed to be γ-polytype. [...] Read more.

We have studied the variations in the temperature-dependent absorption edge of a bulk InSe-layered semiconductor using photoconductivity (PC) measurements. From both the X-ray diffraction (XRD) and Raman experimental results, the structural phase of the as-prepared InSe sample was confirmed to be γ-polytype. Upon heating from 15 K to 300 K, the absorption edge of PC spectra was found to shift significantly toward lower energy, and the absorption edge as a function of temperature was further analyzed by the Varshni’s relationship and Bose–Einstein empirical equation. The Urbach energy as a function of temperature was obtained by fitting the absorption tail below the absorption coefficient of the PC spectrum, and the effective phonon energy can be derived from the temperature-dependent steepness parameter associated with Urbach energy. Our study indicates that the broadening of the absorption edge in the as-synthesized bulk γ-InSe is caused by a combination of electron/exciton–phonon interactions and thermal/structural disorder. Full article

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

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11 pages, 2141 KiB

Open AccessArticle

Effect of Substitutional Metallic Impurities on the Optical Absorption Properties of TiO₂

by Eduardo Cisternas, Rodrigo Aguilera-del-Toro, Faustino Aguilera-Granja and Eugenio E. Vogel

Nanomaterials 2024, 14(14), 1224; https://doi.org/10.3390/nano14141224 - 19 Jul 2024

Cited by 2 | Viewed by 1006

Abstract

(TiO₂) is both a natural and artificial compound that is transparent under visible and near-infrared light. However, it could be prepared with other metals, substituting for Ti, thus changing its properties. In this article, we present density functional theory calculations for [...] Read more.

(TiO₂) is both a natural and artificial compound that is transparent under visible and near-infrared light. However, it could be prepared with other metals, substituting for Ti, thus changing its properties. In this article, we present density functional theory calculations for Ti_(1−x)A_xO₂, where A stands for any of the eight following neutral substitutional impurities, Fe, Ni, Co, Pd, Pt, Cu, Ag and Au, based on the rutile structure of pristine TiO₂. We use a fully unconstrained version of the density functional method with generalized gradient approximation plus the U exchange and correlation, as implemented in the Quantum Espresso free distribution. Within the limitations of a finite-size cell approximation, we report the band structure, energy gaps and absorption spectrum for all these cases. Rather than stressing precise values, we report on two general features: the location of the impurity levels and the general trends of the optical properties in the eight different systems. Our results show that all these substitutional atoms lead to the presence of electronic levels within the pristine gap, and that all of them produce absorptions in the visible and near-infrared ranges of electromagnetic radiation. Such results make these systems interesting for the fabrication of solar cells. Considering the variety of results, Ni and Ag are apparently the most promising substitutional impurities with which to achieve better performance in capturing the solar radiation on the planet’s surface. Full article

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

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13 pages, 5110 KiB

Open AccessArticle

Polarization and Incident Angle Independent Multifunctional and Multiband Tunable THz Metasurface Based on VO₂

by Rehmat Iqbal, Ubaid Ur Rahman Qureshi, Cao Jie, Zia Ur Rahman and Naveed Jafar

Nanomaterials 2024, 14(12), 1048; https://doi.org/10.3390/nano14121048 - 18 Jun 2024

Cited by 3 | Viewed by 1804

Abstract

Aiming at the limitations of single-functionality, limited-applicability, and complex designs prevalent in current metasurfaces, we propose a terahertz multifunctional and multiband tunable metasurface utilizing a VO₂-metal hybrid structure. This metasurface structure comprises a top VO₂-metal resonance layer, a middle [...] Read more.

Aiming at the limitations of single-functionality, limited-applicability, and complex designs prevalent in current metasurfaces, we propose a terahertz multifunctional and multiband tunable metasurface utilizing a VO₂-metal hybrid structure. This metasurface structure comprises a top VO₂-metal resonance layer, a middle polyimide dielectric layer, and a gold film reflective layer at the bottom. This metasurface exhibits multifunctionality, operating independently of polarization and incident angle. The varying conductivity states of the VO₂ layers, enabling the metasurface to achieve various terahertz functionalities, including single-band absorption, broadband THz absorption, and multiband perfect polarization conversion for linear (LP) and circularly polarized (CP) incident waves. Finally, we believe that the functional adaptability of the proposed metasurface expands the repertoire of options available for future terahertz device designs. Full article

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

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17 pages, 3580 KiB

Open AccessArticle

Impact of Temperature Optimization of ITO Thin Film on Tandem Solar Cell Efficiency

by Elif Damgaci, Emre Kartal, Furkan Gucluer, Ayse Seyhan and Yuksel Kaplan

Materials 2024, 17(11), 2784; https://doi.org/10.3390/ma17112784 - 6 Jun 2024

Cited by 1 | Viewed by 2062

Abstract

This study examined the impact of temperature optimization on indium tin oxide (ITO) films in monolithic HJT/perovskite tandem solar cells. ITO films were deposited using magnetron sputtering at temperatures ranging from room temperature (25 °C) to 250 °C. The sputtering target was ITO, [...] Read more.

This study examined the impact of temperature optimization on indium tin oxide (ITO) films in monolithic HJT/perovskite tandem solar cells. ITO films were deposited using magnetron sputtering at temperatures ranging from room temperature (25 °C) to 250 °C. The sputtering target was ITO, with a mass ratio of In₂O₃ to SnO₂ of 90% to 10%. The effects of temperature on the ITO film were analyzed using X-ray diffraction (XRD), spectroscopic ellipsometry, and sheet resistance measurements. Results showed that all ITO films exhibited a polycrystalline morphology, with diffraction peaks corresponding to planes (211), (222), (400), (440), and (622), indicating a cubic bixbyite crystal structure. The light transmittance exceeded 80%, and the sheet resistance was 75.1 Ω/sq for ITO deposited at 200 °C. The optical bandgap of deposited ITO films ranged between 3.90 eV and 3.93 eV. Structural and morphological characterization of the perovskite solar cell was performed using XRD and FE-SEM. Tandem solar cell performance was evaluated by analyzing current density-voltage characteristics under simulated sunlight. By optimizing the ITO deposition temperature, the tandem cell achieved a power conversion efficiency (PCE) of 16.74%, resulting in enhanced tandem cell efficiency. Full article

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

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13 pages, 5930 KiB

Open AccessArticle

The Effect of Polyvinyl Alcohol Addition on the Optical Properties and Oxygen Detection Performance of Titanium Dioxide and Methylene Blue Nanocomposite Colorimetric Indicators

by Kanokthip Boonyarattanakalin, Praphaporn Rattan, Maneerat Songpanit, Sutee Chutipaijit, Hideyuki Okumura, Keiichi N. Ishihara, Wanichaya Mekprasart and Wisanu Pecharapa

Polymers 2024, 16(10), 1400; https://doi.org/10.3390/polym16101400 - 14 May 2024

Viewed by 1396

Abstract

In this study, we investigated the impact of polyvinyl alcohol (PVA) incorporation on the optical properties and oxygen detection performance of a titanium dioxide/methylene blue (TiO₂/MB) nanocomposite colorimetric indicator for packaging applications. The nanocomposite was synthesized via mechanical milling of TiO [...] Read more.

In this study, we investigated the impact of polyvinyl alcohol (PVA) incorporation on the optical properties and oxygen detection performance of a titanium dioxide/methylene blue (TiO₂/MB) nanocomposite colorimetric indicator for packaging applications. The nanocomposite was synthesized via mechanical milling of TiO₂ nanoparticles with MB and citric acid. PVA, at varying concentrations (0, 3, 9, and 14 wt%), was introduced during the wet milling process to produce a homogeneous composite film. Spin coating was employed to fabricate TiO₂/MB nanocomposite films for oxygen detection evaluation. The influence of PVA loading on the films’ chemical functionalities and surface morphologies was assessed using Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). The indicator’s activation process, involving a color change between bleached and colored states, and its recovery time were monitored via optical imaging and UV-VIS-NIR spectrophotometry. The results revealed that a PVA content of 9 wt% yielded well-defined films with enhanced stability of the TiO₂/MB nanocomposite’s oxygen detection performance. Full article

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

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12 pages, 2896 KiB

Open AccessArticle

A Systematic Study of the Temperature Dependence of the Dielectric Function of GaSe Uniaxial Crystals from 27 to 300 K

by Long V. Le, Tien-Thanh Nguyen, Xuan Au Nguyen, Do Duc Cuong, Thi Huong Nguyen, Van Quang Nguyen, Sunglae Cho, Young Dong Kim and Tae Jung Kim

Nanomaterials 2024, 14(10), 839; https://doi.org/10.3390/nano14100839 - 10 May 2024

Cited by 2 | Viewed by 1649

Abstract

We report the temperature dependences of the dielectric function ε = ε₁ + iε₂ and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to [...] Read more.

We report the temperature dependences of the dielectric function ε = ε₁ + iε₂ and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose–Einstein statistical factor and the temperature coefficient to describe the electron–phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and p_z orbitals at the Γ-point. Full article

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

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19 pages, 11282 KiB

Open AccessArticle

Rare-Earth-Ion (RE³⁺)-Doped Aluminum and Lanthanum Borates for Mobile-Phone-Interrogated Luminescent Markers

by Katya Hristova, Irena P. Kostova, Tinko A. Eftimov, Daniel Brabant and Samia Fouzar

Photonics 2024, 11(5), 434; https://doi.org/10.3390/photonics11050434 - 6 May 2024

Cited by 3 | Viewed by 1528

Abstract

In this paper, we present the synthesis and luminescent spectra of rare-earth (RE)-doped aluminum and lanthanum borates intended to serve as narrow excitation–emission band fluorescent markers. We perform a detailed 3D excitation–emission matrix (EEM) analysis of their spectra, compare the measurements from both [...] Read more.

In this paper, we present the synthesis and luminescent spectra of rare-earth (RE)-doped aluminum and lanthanum borates intended to serve as narrow excitation–emission band fluorescent markers. We perform a detailed 3D excitation–emission matrix (EEM) analysis of their spectra, compare the measurements from both standard and mobile phone spectrometers, and outline the basic differences and advantages of each method. While smartphones have a different and non-uniform spectral response compared to standard spectrometers, it is shown that they offer a number of advantages such as contactless interrogation, efficient suppression of the UV excitation light, and simultaneous spectral analysis of spatially arranged arrays of fluorescent markers. The basic emission peaks have been observed and their corresponding electronic transitions identified. The obtained results show that the rare-earth-doped La and Al borates feature excitation–emission bandwidths as low 15 nm/12 nm, which makes them particularly appropriate for use as luminescent markers with UV LED excitation and smartphone interrogation. Full article

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

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11 pages, 2194 KiB

Open AccessArticle

Buried Depressed-Cladding Waveguides Inscribed in Nd³⁺ and Yb³⁺ Doped CLNGG Laser Crystals by Picosecond-Laser Beam Writing

by Gabriela Croitoru, Florin Jipa, Madalin Greculeasa, Alin Broasca, Flavius Voicu, Lucian Gheorghe and Nicolaie Pavel

Materials 2024, 17(8), 1758; https://doi.org/10.3390/ma17081758 - 11 Apr 2024

Cited by 2 | Viewed by 1188

Abstract

Buried depressed-cladding waveguides were fabricated in 0.7-at.% Nd:Ca₃Li_0.275Nb_1.775Ga_2.95O₁₂ (Nd:CLNGG) and 7.28-at.% Yb:CLNGG disordered laser crystals grown by Czochralski method. Circular waveguides with 100 μm diameters were inscribed in both crystals with picosecond (ps) laser [...] Read more.

Buried depressed-cladding waveguides were fabricated in 0.7-at.% Nd:Ca₃Li_0.275Nb_1.775Ga_2.95O₁₂ (Nd:CLNGG) and 7.28-at.% Yb:CLNGG disordered laser crystals grown by Czochralski method. Circular waveguides with 100 μm diameters were inscribed in both crystals with picosecond (ps) laser pulses at 532 nm of 0.15 μJ energy at 500 kHz repetition rate. A line-by-line writing technique at 1 mm/s scanning speed was used. Laser emission at 1.06 μm (with 0.35 mJ pulse energy) and at 1.03 μm (with 0.16 mJ pulse energy) was obtained from the waveguide inscribed in Nd:CLNGG and Yb:CLNGG, respectively, employing quasi-continuous wave pumping with fiber-coupled diode lasers. The waveguide realized in RE³⁺-doped CLNGG crystals using ps-laser pulses at high repetition rates could provide Q-switched or mode-locked miniaturized lasers for a large number of photonic applications. Full article

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

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15 pages, 2543 KiB

Open AccessArticle

Unraveling Broadband Near-Infrared Luminescence in Cr³⁺-Doped Ca₃Y₂Ge₃O₁₂ Garnets: Insights from First-Principles Analysis

by Wei Zou, Bibo Lou, Mekhrdod S. Kurboniyon, Maksym Buryi, Farhod Rahimi, Alok M. Srivastava, Mikhail G. Brik, Jing Wang and Chonggeng Ma

Materials 2024, 17(7), 1709; https://doi.org/10.3390/ma17071709 - 8 Apr 2024

Cited by 6 | Viewed by 2090

Abstract

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr³⁺-doped Ca₃Y₂Ge₃O₁₂ garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of [...] Read more.

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr³⁺-doped Ca₃Y₂Ge₃O₁₂ garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr³⁺ activator ions, which revealed a pronounced preference for the Y³⁺ sites over the Ca²⁺ and Ge⁴⁺ sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states ²E and ⁴T₂, along with their optical transition energies relative to the ground state ⁴A₂ in Ca₃Y₂Ge₃O₁₂:Cr³⁺, were successfully modeled using the ΔSCF method. Calculation convergence challenges were effectively addressed through the proposed fractional particle occupancy schemes. The constructed host-referred binding energy diagram provided a clear description of the luminescence kinetics process in the garnet, which explained the high quantum efficiency of emission. Furthermore, the accurate prediction of thermal excitation energy yielded insights into the thermal stability of the compound, as illustrated in the calculated configuration coordinate diagram. More importantly, all calculated data were consistently aligned with the experimental results. This research not only advances our understanding of the intricate interplay between geometric and electronic structures, optical properties, and thermal behavior in Cr³⁺-doped garnets but also lays the groundwork for future breakthroughs in the high-throughput design and optimization of luminescent performance and thermal stability in Cr³⁺-doped phosphors. Full article

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

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25 pages, 4495 KiB

Open AccessReview

Advances in Semiconductor Lasers Based on Parity–Time Symmetry

by Hongbo Sha, Yue Song, Yongyi Chen, Jishun Liu, Mengjie Shi, Zibo Wu, Hao Zhang, Li Qin, Lei Liang, Peng Jia, Cheng Qiu, Yuxin Lei, Yubing Wang, Yongqiang Ning, Guoqing Miao, Jinlong Zhang and Lijun Wang

Nanomaterials 2024, 14(7), 571; https://doi.org/10.3390/nano14070571 - 26 Mar 2024

Cited by 3 | Viewed by 2577

Abstract

Semiconductor lasers, characterized by their high efficiency, small size, low weight, rich wavelength options, and direct electrical drive, have found widespread application in many fields, including military defense, medical aesthetics, industrial processing, and aerospace. The mode characteristics of lasers directly affect their output [...] Read more.

Semiconductor lasers, characterized by their high efficiency, small size, low weight, rich wavelength options, and direct electrical drive, have found widespread application in many fields, including military defense, medical aesthetics, industrial processing, and aerospace. The mode characteristics of lasers directly affect their output performance, including output power, beam quality, and spectral linewidth. Therefore, semiconductor lasers with high output power and beam quality are at the forefront of international research in semiconductor laser science. The novel parity–time (PT) symmetry mode-control method provides the ability to selectively modulate longitudinal modes to improve the spectral characteristics of lasers. Recently, it has gathered much attention for transverse modulation, enabling the output of fundamental transverse modes and improving the beam quality of lasers. This study begins with the basic principles of PT symmetry and provides a detailed introduction to the technical solutions and recent developments in single-mode semiconductor lasers based on PT symmetry. We categorize the different modulation methods, analyze their structures, and highlight their performance characteristics. Finally, this paper summarizes the research progress in PT-symmetric lasers and provides prospects for future development. Full article

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

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11 pages, 3206 KiB

Open AccessArticle

The Control of the Expansion or Compression of Colloidal Crystals Lattice with Salt Solution

by Hongwei Zhou, Wenze Ouyang, Shuangyang Zou and Shenghua Xu

Nanomaterials 2024, 14(4), 355; https://doi.org/10.3390/nano14040355 - 13 Feb 2024

Cited by 1 | Viewed by 1528

Abstract

Tuning the lattice spacing or stop bands holds great significance in the design and application of materials with colloidal crystals. Typically, particle surface modifications or the application of external physical fields are needed. In this study, we demonstrated the ability to expand or [...] Read more.

Tuning the lattice spacing or stop bands holds great significance in the design and application of materials with colloidal crystals. Typically, particle surface modifications or the application of external physical fields are needed. In this study, we demonstrated the ability to expand or compress the lattice of colloidal crystals simply by utilizing a salt solution, without the need for any special treatments to the colloidal particles. We found that by only considering the diffusiophoresis effect we cannot explain the reversion of lattice expansion to lattice compression with the increase in the salt concentration and that the diffusioosmotic flow originating from the container wall must be taken into account. Further analysis revealed that variations in the salt concentration altered the relative amplitudes between diffusiophoresis and diffusioosmosis through changing the zeta potentials of the particles and the wall, and the competition between the particle diffusiophoresis and wall diffusioosmosis lay at the center of the underlying mechanism. Full article

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

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14 pages, 3731 KiB

Open AccessArticle

Multi-Band Emission of Pr³⁺-Doped Ca₃Al₂O₆ and the Effects of Charge Compensator Ions on Luminescence Properties

by Dejian Hou, Rui Huang, Yi Zhang, Hongliang Li, Wenxing Zhang, Zhisen Lin, Yanqing Guo, Zewen Lin, Jianhong Dong and Jin-Yan Li

Nanomaterials 2024, 14(1), 2; https://doi.org/10.3390/nano14010002 - 19 Dec 2023

Cited by 1 | Viewed by 1227

Abstract

Multi-band emission luminescence materials are of great significance owing to their extensive application in diverse fields. In this research, we successfully prepared a series of Pr³⁺-doped Ca₃Al₂O₆ multi-band emission phosphors via a high-temperature solid-state method. The [...] Read more.

Multi-band emission luminescence materials are of great significance owing to their extensive application in diverse fields. In this research, we successfully prepared a series of Pr³⁺-doped Ca₃Al₂O₆ multi-band emission phosphors via a high-temperature solid-state method. The phase structure, morphology, luminescence spectra and decay curves were investigated in detail. The Ca₃Al₂O₆:Pr³⁺ phosphors can absorb blue lights and emit lights in the 450–750 nm region, and typical emission bands are located at 488 nm (blue), 525–550 nm (green), 611–614 nm (red), 648 nm (red) and 733 nm (deep red). The influence of the Pr³⁺ doping concentration was discussed, and the optimal Pr³⁺ doping concentration was determined. The impacts of charge compensator ions (Li⁺, Na⁺, and K⁺) on the luminescence of Pr³⁺ were also investigated, and it was found that all the charge compensator ions contributed positively to the emission intensity. More importantly, the emission intensity of the as-prepared phosphors at 423 K can still maintain 65–70% of that at room temperature, and the potential application for pc-LED was investigated. The interesting results indicate that the prepared phosphors may serve multifunctional and advanced applications. Full article

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

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16 pages, 3461 KiB

Open AccessArticle

Transition Temperature of Color Change in Thermochromic Systems and Its Description Using Sigmoidal Models

by Martina Viková and Michal Vik

Materials 2023, 16(23), 7478; https://doi.org/10.3390/ma16237478 - 2 Dec 2023

Viewed by 2147

Abstract

Background: Symmetric sigmoidal models with four parameters based on an idealized S/Z-shaped curve are commonly used to analyze the optical parameters of thermochromic materials. However, our experimental findings show that this approach leads to systematic errors involving the incorrect estimation of the transition [...] Read more.

Background: Symmetric sigmoidal models with four parameters based on an idealized S/Z-shaped curve are commonly used to analyze the optical parameters of thermochromic materials. However, our experimental findings show that this approach leads to systematic errors involving the incorrect estimation of the transition temperature or the possibility of a virtual indication of the hysteresis nature of a reversible thermochromic change. For this reason, we sought to find a five-parameter model that would appropriately avoid this problem. Methods: Two commercial thermochromic pigments were used for the test and applied to a textile substrate at different concentrations. The optical properties were measured using reflectance spectrophotometry and then converted to Kubelka–Munk function values and colorimetric coordinates. The following statistics were used to assess the quality of the selected sigmoidal models: coefficient of determination, R²; adjusted coefficient of determination, AR²; root mean square error, RMSE; and Akaike Information Criterion, AIC. Results: The four-parameter models were compared with each other and with the five-parameter models using nested F-tests based on residual variance to obtain a statistical measure of superior performance. For all thermochromic color change data examined, the five-parameter models resulted in significantly better fitting. It could be shown that the five-parameter model showed significantly higher accuracy and precision in determining the transition temperature, like non-sigmoidal quantification methods. Conclusions: We concluded that the asymmetric five-parameter model is a valuable extension of the symmetric model in the investigation of thermochromic color changes, providing better parameter estimates and a new approach to investigating the mechanisms contributing to the asymmetry of the thermochromic curve. Full article

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

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16 pages, 18764 KiB

Open AccessArticle

Intensive and Efficient Design of a Two-dimensional 8 × 8 Silicon-Based Optical Phased Array Transceiver

by Yaoyuan Zhang, Rui Wang, Haibo Liu, Guobin Zhao, Ming Wei, Ruitao Jiang and Kunyang Du

Sensors 2023, 23(23), 9396; https://doi.org/10.3390/s23239396 - 25 Nov 2023

Cited by 1 | Viewed by 1455

Abstract

In recent years, the silicon-based optical phased array has been widely used in the field of light detection and ranging (LIDAR) due to its great solid-state steering ability. At the same time, the optical phased array transceiver integration scheme provides a feasible solution [...] Read more.

In recent years, the silicon-based optical phased array has been widely used in the field of light detection and ranging (LIDAR) due to its great solid-state steering ability. At the same time, the optical phased array transceiver integration scheme provides a feasible solution for low-cost information exchange of small devices in the future. Based on this, this paper designs a two-dimensional optical phased array transceiver with high efficiency and a large field of view, which can realize a dense array with antenna spacing of 5.5 μm × 5.5 μm by using low crosstalk waveguide wiring. Additionally, it can realize the conversion between the receiving mode and the transmitting mode by using the optical switch. The simulation results show that the scanning range of 16.3° × 16.3° can be achieved in the transmitting mode, and the overall loss is lower than 10dB. In the receiving mode, we can achieve a collection efficiency of more than 27%, and the antenna array receiving loss is lower than 12.1 dB. Full article

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

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11 pages, 7031 KiB

Open AccessArticle

Redirecting Incident Light with Mie Resonance-Based Coatings

by Alexander A. Shklyaev, Dmitrii E. Utkin, Zhu Zheng and Andrei V. Tsarev

Photonics 2023, 10(11), 1286; https://doi.org/10.3390/photonics10111286 - 20 Nov 2023

Cited by 3 | Viewed by 1496

Abstract

The efficiency of thin film photoelectric devices can be improved by redirecting incident electromagnetic radiation along their surface layers. Redirection can be achieved using antireflection coatings made of subwavelength dielectric particle arrays. In this study, we fabricate such coatings, consisting of Ge particles [...] Read more.

The efficiency of thin film photoelectric devices can be improved by redirecting incident electromagnetic radiation along their surface layers. Redirection can be achieved using antireflection coatings made of subwavelength dielectric particle arrays. In this study, we fabricate such coatings, consisting of Ge particles on quartz glass substrates via solid-state dewetting, transforming thin Ge films into compact particles. Using optically transparent substrates, we measure reflection and transmission spectra and determine absorption spectra, showing that substrates coated with Ge particles absorb much more strongly than substrates coated with continuous Ge films. The spectra obtained using objective lenses with different aperture angles indicate that scattered radiation is predominantly directed at glancing angles to the substrate surface. The lateral propagation of scattered radiation is the result of destructive interference, which suppresses both reflected and transmitted radiation. Full article

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

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15 pages, 5491 KiB

Open AccessArticle

An Investigation on the Use of Au@SiO₂@Au Nanomatryoshkas as Gap-Enhanced Raman Tags

by Brinton King Eldridge, Saghar Gomrok, James W. Barr, Elise Anne Chaffin, Lauren Fielding, Christian Sachs, Katie Stickels, Paiton Williams and Yongmei Wang

Nanomaterials 2023, 13(21), 2893; https://doi.org/10.3390/nano13212893 - 1 Nov 2023

Cited by 2 | Viewed by 1885

Abstract

Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. [...] Read more.

Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. Even though placing Raman molecules beneath an Au shell seems counter-intuitive, it has been shown that such systems produce a stronger surface-enhanced Raman scattering response due to the strong electric field inside the gap. While the theoretical support of the stronger electric field inside the gap was provided in the literature, a comprehensive understanding of how the electric field inside the gap compares with that of the outer surface of the particle was not readily available. We investigated Au@SiO

_{2}

@Au nanoparticles with diameters ranging from 35 nm to 70 nm with varying shell (2.5–10 nm) and gap (2.5–15 nm) thicknesses and obtained both far-field and near-field spectra. The extinction spectra from these particles always have two peaks. The low-energy peak redshifts with the decreasing shell thickness. However, when the gap thickness decreases, the low-energy peaks first blueshift and then redshift, producing a C-shape in the peak position. For every system we investigated, the near-field enhancement spectra were stronger inside the gap than on the outer surface of the nanoparticle. We find that a thin shell combined with a thin gap will produce the greatest near-field enhancement inside the gap. Our work fills the knowledge gap between the exciting potential applications of gap-enhanced Raman tags and the fundamental knowledge of enhancement provided by the gap. Full article

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

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13 pages, 3090 KiB

Open AccessArticle

Effect of Cs⁺ Doping on the Carrier Dynamics of MAPbI₃ Perovskite

by Menghan Duan, Yunpeng Wang, Pingli Zhang and Luchao Du

Materials 2023, 16(17), 6064; https://doi.org/10.3390/ma16176064 - 4 Sep 2023

Cited by 3 | Viewed by 2167

Abstract

Organic inorganic perovskite materials have received increasing attention in the optoelectronic field because of their unique properties. The ultrafast dynamics of photogenerated carriers determine photoelectric conversion efficiency, thus, it is feasible to influence the dynamics behavior of photogenerated carriers by regulating A-site cations. [...] Read more.

Organic inorganic perovskite materials have received increasing attention in the optoelectronic field because of their unique properties. The ultrafast dynamics of photogenerated carriers determine photoelectric conversion efficiency, thus, it is feasible to influence the dynamics behavior of photogenerated carriers by regulating A-site cations. This paper mainly used transient absorption spectra (TAS) technology to study the photogenerated carriers relaxation processes of organic–inorganic perovskite Cs_xMA_1−xPbI₃ materials at different x values. Three sets of time constants were obtained by global fitting at different values of x. The experimental results showed that the crystal structure of perovskite could be affected by adjusting the Cs⁺ doping amount, thereby regulating the carrier dynamics. The appropriate amount of A-cation doping not only maintained the organic–inorganic perovskite crystal phase, but also prolonged the photogenerated carrier’s lifetime. The 10% Cs⁺ doping Cs_xMA_1−xPbI₃ perovskite has potential for solar cell applications. We hope that our research can provide dynamics support for the development of organic–inorganic perovskite in solar cells. Full article

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

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10 pages, 2066 KiB

Open AccessArticle

Cap Layer Effect on Key Features of Persistent Photoconductivity Spectra in HgTe/CdHgTe Double Quantum Well Heterostructures

by Mikhail K. Sotnichuk, Aleksei S. Kazakov, Ilya D. Nikolaev, Konstantin A. Drozdov, Roman V. Menshchikov, Sergey A. Dvoretsky, Nikolay N. Mikhailov, Dmitry R. Khokhlov and Anton V. Ikonnikov

Photonics 2023, 10(8), 877; https://doi.org/10.3390/photonics10080877 - 28 Jul 2023

Cited by 3 | Viewed by 1368

Abstract

Persistent photoconductivity (PPC) spectra of HgTe/CdHgTe heterostructures with double quantum wells with different cap layers have been studied in the radiation excitation range 0.62–3.1 eV. We have shown that the material of the cap layer defines key features of the PPC spectra—local extrema—and [...] Read more.

Persistent photoconductivity (PPC) spectra of HgTe/CdHgTe heterostructures with double quantum wells with different cap layers have been studied in the radiation excitation range 0.62–3.1 eV. We have shown that the material of the cap layer defines key features of the PPC spectra—local extrema—and their origin. An unusual oscillatory behavior of the PPC spectra is demonstrated. Such a behavior is shown to be independent of both cap and barrier layers. Full article

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

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10 pages, 4061 KiB

Open AccessCommunication

Polarized Luminescence of Bismuth Active Centers in Phosphosilicate Glasses

by Alexander V. Elopov, Konstantin E. Riumkin, Fedor V. Afanasiev, Sergey V. Alyshev, Alexander V. Kharakhordin, Aleksandr M. Khegai, Elena G. Firstova, Sergei V. Firstov, Konstantin N. Nishchev and Mikhail A. Melkumov

Photonics 2023, 10(8), 860; https://doi.org/10.3390/photonics10080860 - 25 Jul 2023

Cited by 1 | Viewed by 1598

Abstract

The polarization properties of bismuth active centers (BACs) are important for many applications of bismuth-doped fibers, but they are still lacking in study. In this paper, we present the measurements of polarized luminescence (PL) of the BACs formed in a Bi-doped phosphosilicate glass [...] Read more.

The polarization properties of bismuth active centers (BACs) are important for many applications of bismuth-doped fibers, but they are still lacking in study. In this paper, we present the measurements of polarized luminescence (PL) of the BACs formed in a Bi-doped phosphosilicate glass matrix. This research was performed on phosphosilicate fiber preforms used for the drawing of active bismuth-doped fibers for efficient optical amplifiers and lasers. The degree of polarization (DOP) of luminescence of the BACs associated with phosphorus and silica (BAC-P and BAC-Si) is provided and discussed. The DOP of luminescence at the 1320 nm wavelength appeared to be around 19%, 0% and 7.5% for pumps at 1240 nm, 762 nm and 425 nm, respectively. The DOP of PL caused by resonant excitation may be described in terms of a model of a partially anisotropic oscillator with the parameters represented by the principal axes of an ellipsoid. For the resonant excitation at 1240 nm, the ratio of the major principal axis to the minor one turned out to be 5.1 and 3.0 for BAC-P and BAC-Si, respectively. Full article

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

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18 pages, 8000 KiB

Open AccessArticle

Iridium-Based Nanohybrids: Synthesis, Characterization, Optical Limiting, and Nonlinear Optical Properties

by Nikolaos Chazapis, Michalis Stavrou, Georgia Papaparaskeva, Alexander Bunge, Rodica Turcu, Theodora Krasia-Christoforou and Stelios Couris

Nanomaterials 2023, 13(14), 2131; https://doi.org/10.3390/nano13142131 - 22 Jul 2023

Cited by 4 | Viewed by 2673

Abstract

The present work reports on the synthesis and characterization of iridium (Ir)-based nanohybrids with variable chemical compositions. More specifically, highly stable polyvinylpyrrolidone (PVP) nanohybrids of the PVP-IrO₂ and PVP-Ir/IrO₂ types, as well as non-coated Ir/IrO₂ nanoparticles, are synthesized using different [...] Read more.

The present work reports on the synthesis and characterization of iridium (Ir)-based nanohybrids with variable chemical compositions. More specifically, highly stable polyvinylpyrrolidone (PVP) nanohybrids of the PVP-IrO₂ and PVP-Ir/IrO₂ types, as well as non-coated Ir/IrO₂ nanoparticles, are synthesized using different synthetic protocols and characterized in terms of their chemical composition and morphology via X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM), respectively. Furthermore, their nonlinear optical (NLO) response and optical limiting (OL) efficiency are studied by means of the Z-scan technique, employing 4 ns laser pulses at 532 and 1064 nm. The results demonstrate that the PVP-Ir/IrO₂ and Ir/IrO₂ systems exhibit exceptional OL performance, while PVP-IrO₂ presents very strong saturable absorption (SA) behavior, indicating that the present Ir-based nanohybrids could be strong competitors to other nanostructured materials for photonic and optoelectronic applications. In addition, the findings denote that the variation in the content of IrO₂ nanoparticles by using different synthetic pathways significantly affects the NLO response of the studied Ir-based nanohybrids, suggesting that the choice of the appropriate synthetic method could lead to tailor-made NLO properties for specific applications in photonics and optoelectronics. Full article

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

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18 pages, 4866 KiB

Open AccessArticle

Extinction and Independent Scattering Criterion for Clusters of Spherical Particles Embedded in Absorbing Host Media

by Jinan Zhai, Shangyu Zhang and Linhua Liu

Photonics 2023, 10(7), 782; https://doi.org/10.3390/photonics10070782 - 5 Jul 2023

Cited by 3 | Viewed by 1614

Abstract

In practical applications, the independent scattering approximation (ISA) is widely used to analyze light transfer in nanoparticle systems. However, the traditional independent scattering criterion is obtained under the assumption that the host medium surrounding particles is nonabsorbing, and thus may be invalid in [...] Read more.

In practical applications, the independent scattering approximation (ISA) is widely used to analyze light transfer in nanoparticle systems. However, the traditional independent scattering criterion is obtained under the assumption that the host medium surrounding particles is nonabsorbing, and thus may be invalid in certain circumstances. In this work, to explore the applicability of the ISA for small particles in absorbing host media, we calculate the extinction efficiency of particle clusters by direct solutions of macroscopic Maxwell equations. Using the far-field and distance-independent definitions of extinction, the computational efficiency multi-sphere method is applied for particle clusters in absorbing host, and its accuracy is verified with the discrete dipole approximation method. It is well known that for small particles, the dependent scattering in transparent host always enhances the extinction of the cluster and the criterion for the ISA is nearly independent of the particle refractive index and particle size. We show, however, that when the host medium is absorbing, the dependent scattering between particles can lead to a decreased or even negative extinction, and thus the ISA criterion depends on the particle refractive index, size, and host medium absorption index. In this result, the generalized criteria for absorbing host media may differ significantly from the conventional ones for transparent host media. The results can provide guidance in solving problems related to light transfer in nanoparticle systems, particularly in the presence of absorption in the host medium. Full article

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

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7 pages, 2424 KiB

Open AccessCommunication

Correlation between the Surface Undulation and Luminescence Characteristics in Semi-Polar

(11 \bar{2} 2)

InGaN/GaN Multi-Quantum Wells

by Mi-Hyang Sheen, Yong-Hee Lee, Jongjin Jang, Jongwoo Baek, Okhyun Nam, Cheol-Woong Yang and Young-Woon Kim

Nanomaterials 2023, 13(13), 1946; https://doi.org/10.3390/nano13131946 - 27 Jun 2023

Cited by 4 | Viewed by 1606

Abstract

Surface undulation was formed while growing InGaN/GaN multi-quantum wells on a semi-polar m-plane (1–100) sapphire substrate. Two distinct facets, parallel to

(11 \bar{2} 2)

and

(01 \bar{1} 1)

, were formed in the embedded multi-quantum wells (MQWs). The structural and luminescence [...] Read more.

Surface undulation was formed while growing InGaN/GaN multi-quantum wells on a semi-polar m-plane (1–100) sapphire substrate. Two distinct facets, parallel to

(11 \bar{2} 2)

and

(01 \bar{1} 1)

, were formed in the embedded multi-quantum wells (MQWs). The structural and luminescence characteristics of the two facets were investigated using transmission electron microscopy equipped with cathodoluminescence. Those well-defined quantum wells, parallel and slanted to the growth plane, showed distinct differences in indium incorporation from both the X-ray yield and the contrast difference in annular darkfield images. Quantitative measurements of concentration in

(01 \bar{1} 1)

MQWs show an approximately 4 at% higher indium incorporation compared to the corresponding

(11 \bar{2} 2)

when the MQWs were formed under the same growth condition. Full article

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

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11 pages, 6418 KiB

Open AccessCommunication

Polarization Selective Broad/Triple Band Absorber Based on All-Dielectric Metamaterials in Long Infrared Regime

by Haotian Zou, Bo Ni, Hua Zhou, Haibin Ni, Guohuan Hua and Jianhua Chang

Photonics 2023, 10(5), 587; https://doi.org/10.3390/photonics10050587 - 18 May 2023

Cited by 2 | Viewed by 2016

Abstract

In this paper, a polarization selective broad/triple-band metamaterial absorber based on SiO₂ all-dielectric is designed and studied. The absorber works in a long infrared band (8–14 μm). It is composed of cuboid and trapezoidal silica structures in the upper layer and metal [...] Read more.

In this paper, a polarization selective broad/triple-band metamaterial absorber based on SiO₂ all-dielectric is designed and studied. The absorber works in a long infrared band (8–14 μm). It is composed of cuboid and trapezoidal silica structures in the upper layer and metal plates in the lower layer. We calculate the absorption results of the metamaterial absorber at different polarization angles as the polarization angle of incident light increases from 0° to 90°; that is, the light changes from Ex polarization to Ey polarization. The results show that the absorption rate of the structure is more than 90% in the range of 8.16 to 9.61 μm when the polarization angle is 0°. When the polarization angle of the incident light is less than 45°, the absorption result of the absorber does not change significantly. When the polarization angle of the incident light is greater than 45°, three absorption peaks appear in the long infrared band, realizing the selectivity of the polarization of the incident light. When the polarization angle increases to 90°, the absorptivity of the two absorption peaks at λ = 9.7 μm and 12.3 μm reaches more than 85%. In addition, the sensitivity analysis of the length, width, and thickness of the all-dielectric metamaterial absorber and the calculation of the electric field of this structure are also carried out. The designed all-dielectric metamaterial absorber has polarization selection and perfect absorption characteristics and has a broad application prospect. Full article

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

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12 pages, 5430 KiB

Open AccessArticle

Efficient Second- and Third-Harmonic Generations in Er³⁺/Fe²⁺-Doped Lithium Niobate Single Crystal with Engineered Surficial Cylindrical Hole Arrays

by Caixia Xu, Hongli Wu, Yanwei He and Long Xu

Nanomaterials 2023, 13(10), 1639; https://doi.org/10.3390/nano13101639 - 14 May 2023

Cited by 2 | Viewed by 2225

Abstract

Herein, significant enhancement of second- and third-harmonic generation efficiencies in a 1 mol% Er³⁺ and 0.07 mol% Fe²⁺-doped lithium niobate single-crystal plate were achieved after ablating periodic cylindrical pit arrays on the surface. Enhanced absorption and reduced transmittance of light [...] Read more.

Herein, significant enhancement of second- and third-harmonic generation efficiencies in a 1 mol% Er³⁺ and 0.07 mol% Fe²⁺-doped lithium niobate single-crystal plate were achieved after ablating periodic cylindrical pit arrays on the surface. Enhanced absorption and reduced transmittance of light were measured when the incident light signal passed through the patterned sample. Enhanced photoluminescence and two-photon-pumped upconversion emission spectra were also explored to obtain more details on the efficiency gains. The excitation-energy-dependent second-harmonic generation efficiency was measured, and an enhancement as high as 20-fold was calculated. The conversion efficiency of second-harmonic generation is 1 to 3 orders higher than that from other lithium niobite metasurfaces and nanoantennas. This work provides a convenient and effective method to improve the nonlinear conversion efficiency in a thin lithium niobite plate, which is desirable for applying to integrated optical devices. Full article

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

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20 pages, 2046 KiB

Open AccessArticle

Extreme Refractive-, Diffractive- and Hybrid-Hyperchromats: Minimizing the Equivalent Abbe Number of a Two-Lens System

by Lukas Werner, Erik Förster, Matthias Kraus, Hartmut Hillmer and Robert Brunner

Photonics 2023, 10(5), 556; https://doi.org/10.3390/photonics10050556 - 10 May 2023

Cited by 3 | Viewed by 2046

Abstract

This work provides a comprehensive analysis of the maximum chromatic axial split of two-element hyperchromats, with the distance between the two lenses being a key variable. Purely refractive and diffractive systems are considered, as well as hybrid layouts combining refractive and diffractive elements. [...] Read more.

This work provides a comprehensive analysis of the maximum chromatic axial split of two-element hyperchromats, with the distance between the two lenses being a key variable. Purely refractive and diffractive systems are considered, as well as hybrid layouts combining refractive and diffractive elements. In order to achieve extreme chromatic axial splitting and accordingly a minimum equivalent Abbe number for lens combinations, a three-step procedure was used. In the first paraxial step, purely optical quantities such as focal lengths of the lenses, inter-lens distances and dispersion properties of the lenses were investigated. In the second step, which also takes place in the paraxial domain, additional geometric boundary conditions such as the radii, diameters and thicknesses of the lenses are taken into account. The results of this step serve as an input for the final optimization using optical design software, which derives practical solutions for minimum equivalent Abbe numbers with diffraction-limited image quality. As a significant result, the comparison with directly cemented lens doublets shows that the introduction of a distance between the elements allows for a much stronger chromatic decomposition for refractive, diffractive and also hybrid combinations. Quantitatively, the minimum equivalent Abbe number for refractive systems is reduced from 2.5 (without spacing) to 1.79 (with spacing). For hybrid combinations, a corresponding reduction from 0.4 to 0.29 is achieved. Full article

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

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7 pages, 1022 KiB

Open AccessCommunication

Two-Photon Absorption in Ca₃(VO₄)₂ and Ca_2.7Sr_0.3(VO₄)₂ Crystals

by Igor O. Kinyaevskiy, Valery I. Kovalev, Nikita S. Semin, Pavel A. Danilov, Sergey I. Kudryashov, Andrey V. Koribut and Elizaveta E. Dunaeva

Photonics 2023, 10(4), 466; https://doi.org/10.3390/photonics10040466 - 19 Apr 2023

Cited by 2 | Viewed by 1401

Abstract

Two-photon absorption has been systematically studied in Ca₃(VO₄)₂ and Ca_2.7Sr_0.3(VO₄)₂ crystals, both of which are prospective nonlinear optical and laser host materials. A strong dependence of the two-photon absorption coefficients on [...] Read more.

Two-photon absorption has been systematically studied in Ca₃(VO₄)₂ and Ca_2.7Sr_0.3(VO₄)₂ crystals, both of which are prospective nonlinear optical and laser host materials. A strong dependence of the two-photon absorption coefficients on the orientation of the laser beam polarization with respect to the optical c-axis of the crystals is revealed. The measured coefficients for perpendicular and parallel orientations were 50 ± 10 cm/TW and 19 ± 4 cm/TW in Ca₃(VO₄)₂, and 18 ± 3 cm/TW and 10 ± 2 cm/TW in Ca_2.7Sr_0.3(VO₄)₂, respectively. Thus, to minimize optical losses caused by two-photon absorption, an orientation of Ca_2.7Sr_0.3(VO₄)₂ crystals with the laser beam polarization parallel to the crystal optical c-axis is preferred. Full article

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

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18 pages, 8477 KiB

Open AccessArticle

Bifunctional Bicarbazole-Benzophenone-Based Twisted Donor–Acceptor–Donor Derivatives for Deep-Blue and Green OLEDs

by Prakalp Gautam, Shahnawaz, Iram Siddiqui, Dovydas Blazevicius, Gintare Krucaite, Daiva Tavgeniene, Jwo-Huei Jou and Saulius Grigalevicius

Nanomaterials 2023, 13(8), 1408; https://doi.org/10.3390/nano13081408 - 19 Apr 2023

Cited by 8 | Viewed by 3038

Abstract

Organic light-emitting diodes (OLEDs) have played a vital role in showing tremendous technological advancements for a better lifestyle, due to their display and lighting technologies in smartphones, tablets, television, and automotive industries. Undoubtedly, OLED is a mainstream technology and, inspired by its advancements, [...] Read more.

Organic light-emitting diodes (OLEDs) have played a vital role in showing tremendous technological advancements for a better lifestyle, due to their display and lighting technologies in smartphones, tablets, television, and automotive industries. Undoubtedly, OLED is a mainstream technology and, inspired by its advancements, we have designed and synthesized the bicarbazole-benzophenone-based twisted donor–acceptor–donor (D-A-D) derivatives, namely DB13, DB24, DB34, and DB43, as bi-functional materials. These materials possess high decomposition temperatures (>360 °C) and glass transition temperatures (~125 °C), a high photoluminescence quantum yield (>60%), wide bandgap (>3.2 eV), and short decay time. Owing to their properties, the materials were utilized as blue emitters as well as host materials for deep-blue and green OLEDs, respectively. In terms of the blue OLEDs, the emitter DB13-based device outperformed others by showing a maximum EQE of 4.0%, which is close to the theoretical limit of fluorescent materials for a deep-blue emission (CIE_y = 0.09). The same material also displayed a maximum power efficacy of 45 lm/W as a host material doped with a phosphorescent emitter Ir(ppy)₃. Furthermore, the materials were also utilized as hosts with a TADF green emitter (4CzIPN) and the device based on DB34 displayed a maximum EQE of 11%, which may be attributed to the high quantum yield (69%) of the host DB34. Therefore, the bi-functional materials that are easily synthesized, economical, and possess excellent characteristics are expected to be useful in various cost-effective and high-performance OLED applications, especially in displays. Full article

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

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16 pages, 4974 KiB

Open AccessArticle

Enhancing Spatial Debris Material Classifying through a Hierarchical Clustering-Fuzzy C-Means Integration Approach

by Fengqi Guo, Jingping Zhu, Liqing Huang, Haoxiang Li, Jinxin Deng, Huilin Jiang and Xun Hou

Appl. Sci. 2023, 13(8), 4754; https://doi.org/10.3390/app13084754 - 10 Apr 2023

Cited by 5 | Viewed by 1858

Abstract

This paper presents a novel approach for clustering spectral polarization data acquired from space debris using a fuzzy C-means (FCM) algorithm model based on hierarchical agglomerative clustering (HAC). The effectiveness of the proposed algorithm is verified using the Kosko subset measure formula. By [...] Read more.

This paper presents a novel approach for clustering spectral polarization data acquired from space debris using a fuzzy C-means (FCM) algorithm model based on hierarchical agglomerative clustering (HAC). The effectiveness of the proposed algorithm is verified using the Kosko subset measure formula. By extracting characteristic parameters representing spectral polarization from laboratory test data of space debris samples, a characteristic matrix for clustering is determined. The clustering algorithm’s parameters are determined through a random selection of points in the external field. The resulting algorithm is applied to pixel-level clustering processing of spectral polarization images, with the clustering results rendered in color. The experimental results on field spectral polarization images demonstrate a classification accuracy of 96.92% for six types of samples, highlighting the effectiveness of the proposed approach for space debris detection and identification. The innovation of this study lies in the combination of HAC and FCM algorithms, using the former for preliminary clustering, and providing a more stable initial state for the latter, thereby improving the effectiveness, adaptability, accuracy, and robustness of the algorithm. Overall, this work provides a promising foundation for space debris classification and other related applications. Full article

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

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11 pages, 3563 KiB

Open AccessArticle

Charge Injection and Energy Transfer of Surface-Engineered InP/ZnSe/ZnS Quantum Dots

by Jumi Park, Taehee Kim and Dongho Kim

Nanomaterials 2023, 13(7), 1159; https://doi.org/10.3390/nano13071159 - 24 Mar 2023

Cited by 2 | Viewed by 3131

Abstract

Surface passivation is a critical aspect of preventing surface oxidation and improving the emission properties of nanocrystal quantum dots (QDs). Recent studies have demonstrated the critical role of surface ligands in determining the performance of QD-based light-emitting diodes (QD-LEDs). Herein, the underlying mechanism [...] Read more.

Surface passivation is a critical aspect of preventing surface oxidation and improving the emission properties of nanocrystal quantum dots (QDs). Recent studies have demonstrated the critical role of surface ligands in determining the performance of QD-based light-emitting diodes (QD-LEDs). Herein, the underlying mechanism by which the capping ligands of InP/ZnSe/ZnS QDs influence the brightness and lifetime of the QD-LEDs is investigated. The electrochemical results demonstrate that highly luminescent InP/ZnSe/ZnS QDs exhibit modulated charge injection depending on the length of the surface ligand chains: short alkyl chains on the ligands are favorable for charge transport to the QDs. In addition, the correlation between the spectroscopic and XRD analyses suggests that the length of the ligand chain tunes the ligand–ligand coupling strength, thereby controlling the inter-QD energy transfer dynamics. The present findings shed new light on the crucial role of surface ligands for InP/ZnSe/ZnS QD-LED applications. Full article

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

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11 pages, 2529 KiB

Open AccessCommunication

Effect of Surface Nonlinearity Distribution on Second Harmonic Generation under Tightly Focused Beams

by Sergey Scherbak, Ilya Reshetov, Gennadiy Kan and Andrey Lipovskii

Photonics 2023, 10(4), 350; https://doi.org/10.3390/photonics10040350 - 23 Mar 2023

Viewed by 1864

Abstract

A thorough integral formulation describing the second harmonic generation under tightly focused linearly and radially polarized beams for an arbitrary distribution of the nonlinear susceptibility over the surface of isotropic media was presented. We numerically simulated effects caused by the straight edge of [...] Read more.

A thorough integral formulation describing the second harmonic generation under tightly focused linearly and radially polarized beams for an arbitrary distribution of the nonlinear susceptibility over the surface of isotropic media was presented. We numerically simulated effects caused by the straight edge of the nonlinear region. In particular, we demonstrated that the second harmonic radiation in the normal direction, which is forbidden in common cases of highly symmetrical nonlinear surfaces, is allowed in the presence of the edge. This is provided by χ⁽²⁾_xzx-component of the second-order susceptibility. Full article

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

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15 pages, 2857 KiB

Open AccessArticle

Facile Fabrication of Mixed–Cation FA_1−XCs_XPbI₃ Perovskites Thin Films for Photodetector Applications

by Fenyun Wang, Pachaiyappan Murugan, Shunhong Dong, Xiaolu Zheng, Jiaxiu Man, Zhiyong Liu, Weibin Zhang, Ting Zhu and Hong-En Wang

Photonics 2023, 10(3), 312; https://doi.org/10.3390/photonics10030312 - 14 Mar 2023

Cited by 4 | Viewed by 2204

Abstract

Formamidinium lead triiodide (FAPbI₃) perovskite has received great attention because of its distinct optoelectronic property, smaller band gap (~1.5 eV), and higher thermal stability than methylammonium lead triiodide (MAPbI₃). However, the efficient synthesis of such perovskite materials on a [...] Read more.

Formamidinium lead triiodide (FAPbI₃) perovskite has received great attention because of its distinct optoelectronic property, smaller band gap (~1.5 eV), and higher thermal stability than methylammonium lead triiodide (MAPbI₃). However, the efficient synthesis of such perovskite materials on a large scale at a low cost remains a challenge. In this work, mixed-cation FA_1−xCs_xPbI₃ thin films were directly prepared in an atmospheric environment with a high film formation rate, low material loss, low cost, and low requirements for experimental instruments and environment. The as-obtained FAPbI₃ films exhibited excellent optoelectronic properties, showing promising applications in the photodetection field. Full article

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

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19 pages, 8706 KiB

Open AccessArticle

Photophysical Properties of Bright Luminescent Polyethyleneimine@Carbon Nanodots and Their Application in White Light-Emitting Diodes

by Junming Zhang, Ailing Yang and Kang Zhang

Photonics 2023, 10(3), 262; https://doi.org/10.3390/photonics10030262 - 2 Mar 2023

Viewed by 2155

Abstract

Highly fluorescent carbon nanodots (CNDs) have broad application prospects in optoelectronics, energy, biological imaging, and other fields because of their good solubility in water, adjustable photoluminescence (PL), low toxicity, good biocompatibility, and stable chemical properties. In this paper, polyethyleneimine@CNDs (PEI@CNDs) with unique excitation- [...] Read more.

Highly fluorescent carbon nanodots (CNDs) have broad application prospects in optoelectronics, energy, biological imaging, and other fields because of their good solubility in water, adjustable photoluminescence (PL), low toxicity, good biocompatibility, and stable chemical properties. In this paper, polyethyleneimine@CNDs (PEI@CNDs) with unique excitation- and concentration-dependent PL properties were synthesized by a one-pot hydrothermal approach. The morphology, structure, surface chemistry, photophysical properties, and stability of the PEI@CNDs were well probed. The PEI@CNDs solution at low concentration displayed blue PL with a quantum yield of 50.6%. As the concentrations of the PEI@CNDs increase, the PL colors changed from blue, cyan, and green, to greenish-yellow. At low concentration, the excitation-independent and excitation-dependent PL property is mainly caused by carbon core and surface state emission. However, at higher concentration, the quenched blue emission and enhanced green emission were found. This is mainly attributed to the aggregate-related inner filter effect, electron transfer, and surface states. Mixing 10.0 mg/mL of PEI@CNDs with polyvinyl alcohol can be used to construct composite films, which were combined with the blue light-emitting diode to construct white light-emitting diodes with white and warm white emissions. Full article

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

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9 pages, 2364 KiB

Open AccessArticle

Spectroscopic Ellipsometry Studies on Solution-Processed OLED Devices: Optical Properties and Interfacial Layers

by Maria Gioti

Materials 2022, 15(24), 9077; https://doi.org/10.3390/ma15249077 - 19 Dec 2022

Cited by 3 | Viewed by 3158

Abstract

Τhe fabrication of organic light-emitting diodes (OLEDs) from solution involves the major problem of stack integrity, setting the determination of the composition and the characteristics of the resulting interfaces prerequisite for the optimization of the growth processes and the achievement of high devices’ [...] Read more.

Τhe fabrication of organic light-emitting diodes (OLEDs) from solution involves the major problem of stack integrity, setting the determination of the composition and the characteristics of the resulting interfaces prerequisite for the optimization of the growth processes and the achievement of high devices’ performance. In this work, a poly(9,9-dioctylfluorene) (F8) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) blend is used for the emissive layer (EML), poly-3,4-ethylene dioxythiophene; poly-styrene sulfonate (PEDOT:PSS) is used for a hole transport layer (HTL), and Poly(9,9-bis(3′-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluore-ne))dibromide (PFN-Br) for an electron transport layer (ETL) to produce the OLED device. All the layers are developed using the slot-die process, onto indium tin oxide (ITO)-coated polyethylene terephthalate (PET) flexible substrates, whereas Ag cathode was formed by ink-jet printing under ambient conditions. Spectroscopic ellipsometry measurements were performed upon completion of the successive films’ growth, in sequential steps, for the multilayer OLED development. Ellipsometry analysis using different models demonstrate the degree of intermixing within the layers and provide information about the interfaces. These interfacial properties are correlated with the emission characteristics as well as the final performance of the OLED devices. Full article

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

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8 pages, 3997 KiB

Open AccessCommunication

ZnCl₂-Enhanced Intrinsic Luminescence of Tin Chlorophosphate Glasses

by Ting Wu, Yiting Tao, Panting Wang, Mingjun Zhao and Danping Chen

Photonics 2022, 9(12), 973; https://doi.org/10.3390/photonics9120973 - 12 Dec 2022

Viewed by 1789

Abstract

This communication reports the intrinsic luminescence of tin chlorophosphate glasses. The glass maintains the low melting point characteristics of tin fluorophosphate glasses, and exhibits a red-shifted and broadened excitation wavelength peak. Tin chlorophosphate glasses can exhibit a broadband luminescence of 400–700 nm under [...] Read more.

This communication reports the intrinsic luminescence of tin chlorophosphate glasses. The glass maintains the low melting point characteristics of tin fluorophosphate glasses, and exhibits a red-shifted and broadened excitation wavelength peak. Tin chlorophosphate glasses can exhibit a broadband luminescence of 400–700 nm under an excitation of 380–430 nm. Furthermore, the introduction of ZnCl₂ into tin chlorophosphate glasses can considerably enhance the luminescence without affecting their low-melting characteristics. The luminescence intensity can be increased fourfold, with the enhancement attributed to the reduced visible absorption, improved dispersion of Sn²⁺ ions, and the energy exchange between Sn²⁺ and Zn²⁺ in the glasses owing to the addition of ZnCl₂. Full article

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

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