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Photonic Materials and Devices

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Optical and Photonic Materials".

Deadline for manuscript submissions: closed (31 October 2020) | Viewed by 56132

Special Issue Editor

Dr. Maciej Dems

E-Mail Website
Guest Editor
Institute of Physics, Lodz University of Technology, 90-924 Lodz, Poland
Interests: semiconductor lasers; VCSELs; subwavelength structures; gratings; photonic crystals; numerical simulations; modal methods

Special Issue Information

Dear Colleagues,

Photonics has become one of the fundamentals of science and technology in the 21st century. Optical communication, gas sensing, metrology, optical computing, lighting, imaging, and many more applications rely on efficient light emission, processing, and detection. For this reason, photonic materials and devices are a continuous hot topic in today’s science and are rapidly advancing into new areas of discovery.

It is my pleasure to invite you to submit a manuscript to the Materials Special Issue on Photonic Materials and Devices. We are particularly interested in original research on natural and artificial materials with a broadly understood application in photonics on the modern photonic devices. Potential specific topics include but are not limited to the following:

  • Novel materials used in optical and photonic systems;
  • Optical fibers;
  • Meta-materials and left-handed materials;
  • Photonic crystals and gratings;
  • Novel photonic devices;
  • Lasers and gain;
  • Passive and active optical elements;
  • Ultra-fast photonics;
  • Characterization of optical properties of materials;
  • Optical sensing technologies.

Dr. Maciej Dems
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • optical elements
  • fibers
  • meta-materials
  • lasers
  • photonic crystals
  • gratings

Published Papers (22 papers)

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17 pages, 5512 KiB  
Article
Electrically Parallel Three-Element 980 nm VCSEL Arrays with Ternary and Binary Bottom DBR Mirror Layers
by Nasibeh Haghighi and James A. Lott
Materials 2021, 14(2), 397; https://doi.org/10.3390/ma14020397 - 14 Jan 2021
Cited by 7 | Viewed by 3249
Abstract
To meet the performance goals of fifth generation (5G) and future sixth generation (6G) optical wireless communication (OWC) and sensing systems, we seek to develop low-cost, reliable, compact lasers capable of sourcing 5–20 Gb/s (ideally up to 100 Gb/s by the 2030s) infrared [...] Read more.
To meet the performance goals of fifth generation (5G) and future sixth generation (6G) optical wireless communication (OWC) and sensing systems, we seek to develop low-cost, reliable, compact lasers capable of sourcing 5–20 Gb/s (ideally up to 100 Gb/s by the 2030s) infrared beams across free-space line-of-sight distances of meters to kilometers. Toward this end, we develop small arrays of electrically parallel vertical cavity surface emitting lasers (VCSELs) for possible future use in short-distance (tens of meters) free-space optical communication and sensing applications in, for example, homes, data centers, manufacturing spaces, and backhaul (pole-to-pole or pole-to-building) optical links. As a starting point, we design, grow by metal–organic vapor phase epitaxy, fabricate, test, and analyze 980 nm top-emitting triple VCSEL arrays. Via on-wafer high-frequency probe testing, our arrays exhibit record bandwidths of 20–25 GHz, optical output powers of 20–50 mW, and error-free data transmission at up to 40 Gb/s—all extremely well suited for the intended 5G short-reach OWC and sensing applications. We employ novel p-metal and top mesa inter-VCSEL connectors to form electrically parallel but optically uncoupled (to reduce speckle) arrays with performance exceeding that of single VCSELs with equal total emitting areas. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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10 pages, 1879 KiB  
Article
Novel Aggregation-Induced Emission Materials/Cadmium Sulfide Composite Photocatalyst for Efficient Hydrogen Evolution in Absence of Sacrificial Reagent
by Xi Ke, Kunqiang Wang, Chen Tu, Runda Huang, Dongxiang Luo and Menglong Zhang
Materials 2020, 13(22), 5287; https://doi.org/10.3390/ma13225287 - 22 Nov 2020
Cited by 3 | Viewed by 1993
Abstract
This work focuses on the development of a novel organic–inorganic photoactive material composited by aggregation-induced emission luminogens (AIE) and CdS. Tetraphenylethene-based AIE (TPE-Ca) is synthesized on CdS to form CdS/TPE-Ca electrode, due to its suitable band structure and potential capability of renewable energy [...] Read more.
This work focuses on the development of a novel organic–inorganic photoactive material composited by aggregation-induced emission luminogens (AIE) and CdS. Tetraphenylethene-based AIE (TPE-Ca) is synthesized on CdS to form CdS/TPE-Ca electrode, due to its suitable band structure and potential capability of renewable energy production. The CdS/TPE-Ca electrode presents over three-fold improved photocurrent density and dramatically reduced interfacial resistance, compared with the pure CdS electrode. In addition, the engineering of the band alignment allows the holes to accumulate on the valance band of TPE-Ca, which would partially prevent the CdS from photo-corrosion, thus improving the stability of the sacrificial-free electrolyte photoelectrochemical cell. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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14 pages, 6888 KiB  
Article
Challenges in a Hybrid Fabrication Process to Generate Metallic Polarization Elements with Sub-Wavelength Dimensions
by Stefan Belle, Babette Goetzendorfer and Ralf Hellmann
Materials 2020, 13(22), 5279; https://doi.org/10.3390/ma13225279 - 22 Nov 2020
Cited by 2 | Viewed by 1874
Abstract
We report on the challenges in a hybrid sub-micrometer fabrication process while using three dimensional femtosecond direct laser writing and electroplating. With this hybrid subtractive and additive fabrication process, it is possible to generate metallic polarization elements with sub-wavelength dimensions of less than [...] Read more.
We report on the challenges in a hybrid sub-micrometer fabrication process while using three dimensional femtosecond direct laser writing and electroplating. With this hybrid subtractive and additive fabrication process, it is possible to generate metallic polarization elements with sub-wavelength dimensions of less than 400 nm in the cladding area. We show approaches for improving the adhesion of freestanding photoresist pillars as well as of the metallic cladding area, and we also demonstrate the avoidance of an inhibition layer and sticking of the freestanding pillars. Three-dimensional direct laser writing in a positive tone photoresist is used as a subtractive process to fabricate free-standing non-metallic photoresist pillars with an area of about 850 nm × 1400 nm, a height of 3000 nm, and a distance between the pillars of less than 400 nm. In a subsequent additive fabrication process, these channels are filled with gold by electrochemical deposition up to a final height of 2200 nm. Finally, the polarization elements are characterized by measuring the degree of polarization in order to show their behavior as quarter- and half-wave plates. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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10 pages, 2309 KiB  
Article
Precise Method for Measuring the Quadratic Electro-Optic Effect in Noncentrosymmetric Crystals in the Presence of Natural Birefringence
by Marek Izdebski, Rafał Ledzion and Włodzimierz Kucharczyk
Materials 2020, 13(18), 3942; https://doi.org/10.3390/ma13183942 - 06 Sep 2020
Cited by 1 | Viewed by 1627
Abstract
The application of the improved dynamic polarimetric method for the measurement of the quadratic electro-optic effect in NH4H2PO4 (ADP) crystal with the light beam propagating perpendicularly to its optical axis is presented. This technique can be applied in [...] Read more.
The application of the improved dynamic polarimetric method for the measurement of the quadratic electro-optic effect in NH4H2PO4 (ADP) crystal with the light beam propagating perpendicularly to its optical axis is presented. This technique can be applied in noncetrosymmetric crystals in the presence of natural birefringence even when the fast and slow rays diverge slightly, causing them to only partially interfere. The method allows for minor errors in cutting and orientation of the crystal samples, resulting in deviations from configurations in which the crystal symmetry vetoes the linear electro-optic effect. The occurring contribution of the linear effect, if it is not too large, not only does not exclude the measurement of the quadratic effect, but increases its accuracy. The method does not require any prior compensation for the natural birefringence. Its sensitivity allows for quadratic electro-optic effect measurements in ferroelectrics in temperatures significantly different from the phase transition temperature or in paraelectric crystals, for which this effect is relatively small. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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11 pages, 2712 KiB  
Article
Double Electromagnetically Induced Transparency and Its Slow Light Application Based on a Guided-Mode Resonance Grating Cascade Structure
by Guofeng Li, Junbo Yang, Zhaojian Zhang, Yuyu Tao, Lingjun Zhou, Huimin Huang, Zhenrong Zhang and Yunxin Han
Materials 2020, 13(17), 3710; https://doi.org/10.3390/ma13173710 - 21 Aug 2020
Cited by 11 | Viewed by 2146
Abstract
In recent years, the achievement of the electromagnetically induced transparency (EIT) effect based on the guided-mode resonance (GMR) effect has attracted extensive attention. However, few works have achieved a double EIT-like effect using this method. In this paper, we numerically achieve a double [...] Read more.
In recent years, the achievement of the electromagnetically induced transparency (EIT) effect based on the guided-mode resonance (GMR) effect has attracted extensive attention. However, few works have achieved a double EIT-like effect using this method. In this paper, we numerically achieve a double EIT-like effect in a GMR system with a three-layer silicon nitride waveguide grating structure (WGS), using the multi-level atomic system model for theoretical explanation. In terms of slow light performance, the corresponding two delay times reach 22.59 ps and 8.43 ps, respectively. We also investigate the influence of wavelength detuning of different GMR modes on the transparent window and slow light performance. Furthermore, a wide-band flat-top transparent window was also achieved by appropriately adjusting the wavelength detuning between GMR modes. These results indicate that the EIT-like effect in the WGS has potential application prospects in low-loss slow optical devices, optical sensing, and optical communications. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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11 pages, 1810 KiB  
Article
Realization of Deep UV Plasmonic Enhancement to Photo Response through Al Mesh
by Gaoming Li, Jingwen Zhang, Yaoting Hu and Yongning He
Materials 2020, 13(15), 3252; https://doi.org/10.3390/ma13153252 - 22 Jul 2020
Cited by 1 | Viewed by 1627
Abstract
High-performance UV detectors are of great significance for various applications. Plasmonic structures enable great improvement of the performance of detectors. However, to push the plasmonic enhancement to photo response into the deep-UV region presents some challenges. In this work, we found that the [...] Read more.
High-performance UV detectors are of great significance for various applications. Plasmonic structures enable great improvement of the performance of detectors. However, to push the plasmonic enhancement to photo response into the deep-UV region presents some challenges. In this work, we found that the optical properties of the supporting layer play important roles in achieving the optimal plasmonic enhancement. Therefore, we fully considered the dependence of the optical constants of the MgZnO supporting layer, which is a promising material to realize deep-UV photodetectors, on microstructure and crystalline quality, which are related to the fabrication method. Based on the optical constants, we designed an Al mesh plasmonic structure and fabricated it with a polystyrene monolayer as a mask. Finally, we demonstrated a three-times enhancement to photo response with UV radiation at 254 nm. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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17 pages, 6168 KiB  
Article
A Four Green TM/Red TE Demultiplexer Based on Multi Slot-Waveguide Structures
by Dror Malka
Materials 2020, 13(14), 3219; https://doi.org/10.3390/ma13143219 - 20 Jul 2020
Cited by 20 | Viewed by 2251
Abstract
A four green transverse magnetic (TM)/red transverse electric (TE) light wavelength demultiplexer device, based on multi slot-waveguide (SW) structures is demonstrated. The device aims to demultiplex wavelengths in the green/red light range with wavelengths of 530, 540, 550, and 560 nm; 630, 640, [...] Read more.
A four green transverse magnetic (TM)/red transverse electric (TE) light wavelength demultiplexer device, based on multi slot-waveguide (SW) structures is demonstrated. The device aims to demultiplex wavelengths in the green/red light range with wavelengths of 530, 540, 550, and 560 nm; 630, 640, 650, and 660 nm. This means that the device functions as a 1 × 4 demultiplexer for each polarization mode (TE/TM). The controlling of the light switching between two closer segment SWs under the TM/TE polarization mode was studied by designing a suitable SW structure and setting the right segment length to fit the coupling lengths of the operating wavelengths. The device is composed of six-segment SW units and six S-bends (SB) SW. The key SW and SB parameters were optimized and determined by a full vectorial beam propagation method (FV-BPM). Results show power losses better than 0.138 dB, crosstalk better than −21.14 dB, and an optical spectrum smaller than 9.39 nm, with an overall compact size of 104.5 µm. The device can be integrated in wavelength division multiplexing (WDM) for increasing data bit rate in a visible light communication (VLC) system. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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13 pages, 1060 KiB  
Article
Impact of an Antiresonant Oxide Island on the Lasing of Lateral Modes in VCSELs
by Marta Więckowska, Robert P. Sarzała, Rafał Ledzion and Maciej Dems
Materials 2020, 13(9), 2195; https://doi.org/10.3390/ma13092195 - 11 May 2020
Cited by 2 | Viewed by 2188
Abstract
Use of antiresonant structures is a proven, efficient method of improving lateral mode selectivity in VCSELs. In this paper, we analyze the impact of a low-refractive antiresonant oxide island buried in a top VCSEL mirror on the lasing conditions of lateral modes of [...] Read more.
Use of antiresonant structures is a proven, efficient method of improving lateral mode selectivity in VCSELs. In this paper, we analyze the impact of a low-refractive antiresonant oxide island buried in a top VCSEL mirror on the lasing conditions of lateral modes of different orders. By performing comprehensive thermal, electrical, and optical numerical analysis of the VCSEL device, we show the impact of the size and location of the oxide island on the current-crowding effect and compute threshold currents for various lateral modes. If the island is placed close to the cavity, the threshold shows strong oscillations, which for moderate island distances can be tuned to increase the side mode discrimination. We are therefore able to pinpoint the most important factors influencing mode discrimination and to identify oxide island parameters capable of providing single-lateral-mode emission. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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16 pages, 4637 KiB  
Article
Numerical Investigation of the Impact of ITO, AlInN, Plasmonic GaN and Top Gold Metalization on Semipolar Green EELs
by Maciej Kuc, Łukasz Piskorski, Maciej Dems, Michał Wasiak, Adam K. Sokół, Robert P. Sarzała and Tomasz Czyszanowski
Materials 2020, 13(6), 1444; https://doi.org/10.3390/ma13061444 - 22 Mar 2020
Cited by 7 | Viewed by 2064
Abstract
In this paper, we present the results of a computational analysis of continuous-wave (CW) room-temperature (RT) semipolar InGaN/GaN edge-emitting lasers (EELs) operating in the green spectral region. In our calculations, we focused on the most promising materials and design solutions for the cladding [...] Read more.
In this paper, we present the results of a computational analysis of continuous-wave (CW) room-temperature (RT) semipolar InGaN/GaN edge-emitting lasers (EELs) operating in the green spectral region. In our calculations, we focused on the most promising materials and design solutions for the cladding layers, in terms of enhancing optical mode confinement. The structural modifications included optimization of top gold metalization, partial replacement of p-type GaN cladding layers with ITO and introducing low refractive index lattice-matched AlInN or plasmonic GaN regions. Based on our numerical findings, we show that by employing new material modifications to green EELs operating at around 540 nm it is possible to decrease their CW RT threshold current densities from over 11 kA/cm2 to less than 7 kA/cm2. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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11 pages, 2306 KiB  
Article
Nanowire Ring Embedded in a Flexible Substrate for Local Strain Detection
by Shengkun Li, Yue Qin, Xin Li and Yuejin Zhao
Materials 2020, 13(2), 347; https://doi.org/10.3390/ma13020347 - 12 Jan 2020
Viewed by 2123
Abstract
Optical sensing has attracted more and more attention in recent years with the advance in planar waveguide fabrication processes. The photon, as a carrier of information in sensing areas, could have a better performance than electrons. We propose a novel end-to-end ring cavity [...] Read more.
Optical sensing has attracted more and more attention in recent years with the advance in planar waveguide fabrication processes. The photon, as a carrier of information in sensing areas, could have a better performance than electrons. We propose a novel end-to-end ring cavity to fabricate sensitive units of a strain sensor. We then propose a method of combining a flexible substrate with an end-to-end semiconductor nanowire ring cavity to fabricate novel strain sensors. We used a tuning resonant wavelength detected by a homebuilt excitation and detection system to measure applied strain. The resonant wavelength of the strain gauge was red-shift and linear tuned with increasing strain. The gauge factor was about 50, calculated through experiments and theory, and Q was 1938, with structural parameters L = 70 µm and d = 1 µm. The high sensitivity makes it possible to measure micro deformation more accurately. End-to-end coupling active nanowire waveguides eliminate the shortcomings of side by side coupling structures, which have the phasing shift with no minor optical density loss. This resonator in flexible substrates could be used not only as on-chip strain sensors for micro or nano deformation detecting but also as tunable light sources for photonic integrated circuits. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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16 pages, 3788 KiB  
Article
Random Voids Generation and Effect of Thermal Shock Load on Mechanical Reliability of Light-Emitting Diode Flip Chip Solder Joints
by Jiajie Fan, Jie Wu, Changzhen Jiang, Hao Zhang, Mesfin Ibrahim and Liang Deng
Materials 2020, 13(1), 94; https://doi.org/10.3390/ma13010094 - 23 Dec 2019
Cited by 7 | Viewed by 2873
Abstract
To make the light-emitting diode (LED) more compact and effective, the flip chip solder joint is recommended in LED chip-scale packaging (CSP) with critical functions in mechanical support, heat dissipation, and electrical conductivity. However, the generation of voids always challenges the mechanical strength, [...] Read more.
To make the light-emitting diode (LED) more compact and effective, the flip chip solder joint is recommended in LED chip-scale packaging (CSP) with critical functions in mechanical support, heat dissipation, and electrical conductivity. However, the generation of voids always challenges the mechanical strength, thermal stability, and reliability of solder joints. This paper models the 3D random voids generation in the LED flip chip Sn96.5–Ag3.0–Cu0.5 (SAC305) solder joint, and investigates the effect of thermal shock load on its mechanical reliability with both simulations and experiments referring to the JEDEC thermal shock test standard (JESD22-A106B). The results reveal the following: (1) the void rate of the solder joint increases after thermal shock ageing, and its shear strength exponentially degrades; (2) the first principal stress of the solder joint is not obviously increased, however, if the through-hole voids emerged in the corner of solder joints, it will dramatically increase; (3) modelling of the fatigue failure of solder joint with randomly distributed voids utilizes the approximate model to estimate the lifetime, and the experimental results confirm that the absolute prediction error can be controlled around 2.84%. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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9 pages, 2599 KiB  
Article
Linear Tuning of Phase-Matching Temperature in LiNbO3:Zr Crystals by MgO Co-Doping
by Tengfei Kong, Hongde Liu, Liyun Xue, Weiwei Wang, Shahzad Saeed, Dahuai Zheng, Shiguo Liu, Shaolin Chen, Ling Zhang, Yongfa Kong and Jingjun Xu
Materials 2019, 12(24), 4155; https://doi.org/10.3390/ma12244155 - 11 Dec 2019
Viewed by 1787
Abstract
We grew a series of co-doped LiNbO3 crystals with fixed 1.5 mol % ZrO2 and various MgO concentrations (1.0, 3.0, 4.0, 6.0 mol %), and investigated their optical properties and defect structures. By 3.0 mol % MgO co-doping, the optical damage [...] Read more.
We grew a series of co-doped LiNbO3 crystals with fixed 1.5 mol % ZrO2 and various MgO concentrations (1.0, 3.0, 4.0, 6.0 mol %), and investigated their optical properties and defect structures. By 3.0 mol % MgO co-doping, the optical damage resistance at 532 nm reached 6.5 × 106 W/cm2, while the phase-matching temperature for doubling 1064 nm was only 29.3 °C—close to room temperature—which was conducive to realizing the 90° phase matching at room temperature by slightly modulating the incident angle of the fundamental beam. Notably, we found that the phase-matching temperature increased linearly with the increase of MgO doping, and this linear dependence helped us to grow the high-quality crystal for room temperature 90° phase matching. Moreover, the defect analysis indicated that the linear tuning of phase-matching temperature might be attributed to Mg Li + + Zr Nb − neutral pairs in crystals. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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8 pages, 912 KiB  
Article
Highly Deep Ultraviolet–Transparent h-BN Film Deposited on an Al0.7Ga0.3N Template by Low-Temperature Radio-Frequency Sputtering
by Guo-Dong Hao, Manabu Taniguchi and Shin-ichiro Inoue
Materials 2019, 12(24), 4046; https://doi.org/10.3390/ma12244046 - 05 Dec 2019
Cited by 5 | Viewed by 2634
Abstract
Hexagonal boron nitride (h-BN) is an attractive wide-bandgap material for application to emitters and detectors operating in the deep ultraviolet (DUV) spectral region. The optical transmittance of h-BN in the DUV region is particularly important for these devices. We report on the deposition [...] Read more.
Hexagonal boron nitride (h-BN) is an attractive wide-bandgap material for application to emitters and detectors operating in the deep ultraviolet (DUV) spectral region. The optical transmittance of h-BN in the DUV region is particularly important for these devices. We report on the deposition of thick h-BN films (>200 nm) on Al0.7Ga0.3N templates via radio-frequency sputtering, along with the realization of ultrahigh transmittance in the DUV region. The fraction of the gas mixture (Ar/N2) was varied to investigate its effects on the optical transmittance of BN. DUV light transmittance of as high as 94% was achieved at 265 nm. This value could be further enhanced to exceed 98% by a post-annealing treatment at 800 °C in a N2 ambient for 20 min. The phase of the highly DUV–transparent BN film was determined to be a purely hexagonal structure via Raman spectra measurements. More importantly, these deposition processes were performed at a low temperature (300 °C), which can provide protection from device performance degradation when applied to actual devices. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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13 pages, 916 KiB  
Article
Influence of Various Bottom DBR Designs on the Thermal Properties of Blue Semiconductor-Metal Subwavelength-Grating VCSELs
by Robert P. Sarzała, Łukasz Piskorski, Tomasz Czyszanowski and Maciej Dems
Materials 2019, 12(19), 3235; https://doi.org/10.3390/ma12193235 - 02 Oct 2019
Cited by 6 | Viewed by 2612
Abstract
In this paper, we consider several designs for nitride-based vertical-cavity surface-emitting lasers (VCSELs) with a top semiconductor-metal subwavelength grating (SMSG) as the facet mirror. The constructions of the bottom distributed Bragg reflectors (DBRs) used in the VCSEL designs were inspired by devices demonstrated [...] Read more.
In this paper, we consider several designs for nitride-based vertical-cavity surface-emitting lasers (VCSELs) with a top semiconductor-metal subwavelength grating (SMSG) as the facet mirror. The constructions of the bottom distributed Bragg reflectors (DBRs) used in the VCSEL designs were inspired by devices demonstrated recently by several research groups. A multiparameter numerical analysis was performed, based on self-consistent thermal and electrical simulations. The results show that, in the case of small aperture VCSEL designs, dielectric-based DBRs with metallic or GaN channels enable equally efficient heat dissipation to designs with monolithically integrated DBRs. In the case of broad aperture designs enabled by SMSGs, monolithically integrated DBRs provide much more efficient heat dissipation in comparison to all other considered designs. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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17 pages, 3246 KiB  
Article
Delay-Differential-Equation Modeling of Mode-Locked Vertical-External-Cavity Surface-Emitting Lasers in Different Cavity Configurations
by Eugene A. Avrutin and Krassimir Panajotov
Materials 2019, 12(19), 3224; https://doi.org/10.3390/ma12193224 - 01 Oct 2019
Cited by 10 | Viewed by 2238
Abstract
A simple, versatile model for the dynamics of electrically and optically pumped vertical-external-cavity surface-emitting lasers, which are mode locked by a semiconductor saturable-absorber mirror, is presented. The difference between the laser operation in the linear and folded cavity, as well as the potential [...] Read more.
A simple, versatile model for the dynamics of electrically and optically pumped vertical-external-cavity surface-emitting lasers, which are mode locked by a semiconductor saturable-absorber mirror, is presented. The difference between the laser operation in the linear and folded cavity, as well as the potential for a colliding pulse operation, are studied. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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15 pages, 7350 KiB  
Article
A Terahertz (THz) Single-Polarization-Single-Mode (SPSM) Photonic Crystal Fiber (PCF)
by Tianyu Yang, Can Ding, Richard W. Ziolkowski and Y. Jay Guo
Materials 2019, 12(15), 2442; https://doi.org/10.3390/ma12152442 - 31 Jul 2019
Cited by 30 | Viewed by 3297
Abstract
This paper presents a novel approach to attain a single-polarization-single-mode (SPSM) photonic crystal fiber (PCF) in the terahertz (THz) regime. An initial circular hole PCF design is modified by introducing asymmetry in the first ring of six air holes in the cladding, i.e., [...] Read more.
This paper presents a novel approach to attain a single-polarization-single-mode (SPSM) photonic crystal fiber (PCF) in the terahertz (THz) regime. An initial circular hole PCF design is modified by introducing asymmetry in the first ring of six air holes in the cladding, i.e., epsilon-near-zero (ENZ) material is introduced into only four of those air holes and the other two remain air-filled but have different diameters. The resulting fundamental X-polarized (XP) and Y-polarized (YP) modes have distinctly different electric field distributions. The asymmetry is arranged so that the YP mode has a much larger amount of the field distributed in the ENZ material than the XP mode. Since the ENZ material is very lossy, the YP mode suffers a much higher loss than the XP mode. Consequently, after a short propagation distance, the loss difference (LD) between the XP and YP modes will be large enough that only the XP mode still realistically exists in the PCF. To further enhance the outcome, gain material is introduced into the core area to increase the LDs between the wanted XP mode and any unwanted higher order (HO) modes, as well as to compensate for the XP mode loss without affecting the LD between the XP and YP modes. The optimized PCF exhibits LDs between the desired XP mode and all other modes greater than 8.0 dB/cm across a wide frequency range of 0.312 THz. Consequently, the reported PCF only needs a length of 2.5 cm to attain an SPSM result, with the unwanted modes being more than 20 dB smaller than the wanted mode over the entire operational band. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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14 pages, 3782 KiB  
Article
Multicolor and Warm White Emissions with a High Color Rendering Index in a Tb3+/Eu3+-Codoped Phosphor Ceramic Plate
by Haggeo Desirena, Jorge Molina-González, Octavio Meza, Priscilla Castillo and Juan Bujdud-Pérez
Materials 2019, 12(14), 2240; https://doi.org/10.3390/ma12142240 - 11 Jul 2019
Cited by 2 | Viewed by 2574
Abstract
A series of Tb3+/Eu3+-codoped phosphor ceramic plates with a high color rendering index (CRI) for a near-ultraviolet light emitting diode (LED) were fabricated. Color emission can be tuned from green to reddish as a function of Eu3+ concentration. [...] Read more.
A series of Tb3+/Eu3+-codoped phosphor ceramic plates with a high color rendering index (CRI) for a near-ultraviolet light emitting diode (LED) were fabricated. Color emission can be tuned from green to reddish as a function of Eu3+ concentration. By doping only 0.15 mol% of Eu3+ concentration, a comfortable warm white emission is promoted as a result of simultaneous emissions of Tb3+ and Eu3+ ions. A theoretical model is proposed to calculate the contributions of the emitted color of the donor (Tb3+) and acceptor (Eu3+) ions in terms of europium concentration. The energy transfer from Tb3+ to Eu3+ ions is corroborated by the luminescence spectra and decay time of Tb3+, with a maximum energy transfer efficiency of 76% for 28 mol% of Tb3+ and 14 mol% of Eu3+. Warm white LEDs were constructed using a 380 nm UV chip and showed a CRI of 82.5, which was one of highest values reported for Tb3+/Eu3+-codoped samples. Color-correlated temperature (CCT), color coordinate (CC), and luminous efficacy (LE) were utilized to know the potentials as a phosphor converter in solid-state lighting. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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13 pages, 4667 KiB  
Article
Efficient 1 µm Laser Emission of Czochralski-Grown Nd:LGSB Single Crystal
by Catalina-Alice Brandus, Stefania Hau, Alin Broasca, Madalin Greculeasa, Flavius-Marian Voicu, Cristina Gheorghe, Lucian Gheorghe and Traian Dascalu
Materials 2019, 12(12), 2005; https://doi.org/10.3390/ma12122005 - 22 Jun 2019
Cited by 8 | Viewed by 4242
Abstract
A 5.0-at.% Nd-doped La0.64Gd0.41Sc2.95(BO3)4 (Nd:LGSB) borate laser crystal was successfully grown by the Czochralski method, for the first time to our knowledge. The spectroscopic properties of the grown crystal are discussed and 1 µm [...] Read more.
A 5.0-at.% Nd-doped La0.64Gd0.41Sc2.95(BO3)4 (Nd:LGSB) borate laser crystal was successfully grown by the Czochralski method, for the first time to our knowledge. The spectroscopic properties of the grown crystal are discussed and 1 µm laser emission, under end-pumping with a fiber-coupled diode laser at 807 nm, is reported. A c-cut Nd:LGSB medium yielded 1.35 W continuous-wave output power at 0.63 overall optical-to-optical efficiency, with respect to the absorbed pump power, together with the high 0.68 slope efficiency. With an a-cut Nd:LGSB sample, 0.81 W output power at 0.52 optical-to-optical efficiency was obtained. The laser emission performances under quasi-continuous wave pumping are presented as well, for both c-cut and a-cut crystals. Passive Q-switching was investigated with a semiconductor saturable absorber mirror (SESAM). Laser pulses with 2.2 µJ energy and 32.8 ns durations were recorded from a-cut Nd:LGSB. The average output power reached 0.36 W at 1.55 W absorbed pump power. Passive mode-locking with SESAM was achieved in a long Z-type resonator. Ultrashort pulses with 0.19 W average power, 1.63 nJ energy, and 1.43 ps pulse duration, at 118 MHz repetition rate, are demonstrated for the a-cut Nd:LGSB medium. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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12 pages, 25446 KiB  
Article
Design of a 2 × 4 Hybrid MMI-MZI Configuration with MMI Phase-Shifters
by Boris B. Niraula and Conrad Rizal
Materials 2019, 12(9), 1555; https://doi.org/10.3390/ma12091555 - 12 May 2019
Cited by 2 | Viewed by 3756
Abstract
This paper reports design of a 2 × 4 hybrid multimode interferometer-Mach-zehnder interferometer (MMI-MZI) configuration consiting of compact thermo-optical switches on the silicon-on-insulator (SOI) platform. The device consists of two identical MMI slab waveguides as power splitters and couplers that are connected with [...] Read more.
This paper reports design of a 2 × 4 hybrid multimode interferometer-Mach-zehnder interferometer (MMI-MZI) configuration consiting of compact thermo-optical switches on the silicon-on-insulator (SOI) platform. The device consists of two identical MMI slab waveguides as power splitters and couplers that are connected with two identical MMI-based phase shifters, and linear tapers at both ends of the MMIs to minimize the power coupling loss. A thin Al pad is used as a heating element and a trench is created around this pad to prevent heat from spreading, and to minimize loss. The calculated average thermo-optical switching power consumption, excess loss, and power imbalance are 1.4 mW, 0.9 dB, and 0.1 dB, respectively. The overall footprint of the device is 6 × 304 μ m 2 . The new heating method has advantages of compact size, ease of fabrication on SOI platform with the current CMOS technology, and offers low excess loss and power consumption as demanded by devices based on SOI technology. The device can act as two independent optical switches in one device. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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16 pages, 8781 KiB  
Article
Applications of Copolymers Consisting of 2,6-di(9H-carbazol-9-yl)pyridine and 3,6-di(2-thienyl)carbazole Units as Electrodes in Electrochromic Devices
by Chung-Wen Kuo, Jui-Cheng Chang, Yu-Ting Huang, Jeng-Kuei Chang, Li-Ting Lee and Tzi-Yi Wu
Materials 2019, 12(8), 1251; https://doi.org/10.3390/ma12081251 - 16 Apr 2019
Cited by 10 | Viewed by 2429
Abstract
A series of carbazole-based polymers (PdCz, P(dCz2-co-dTC1), P(dCz2-co-dTC2), P(dCz1-co-dTC2), and PdTC) were deposited on indium tin oxide (ITO) conductive electrodes using electrochemical polymerization. The as-prepared P(dCz2-co-dTC2) displayed a high ΔT (57.0%) and multichromic behaviors [...] Read more.
A series of carbazole-based polymers (PdCz, P(dCz2-co-dTC1), P(dCz2-co-dTC2), P(dCz1-co-dTC2), and PdTC) were deposited on indium tin oxide (ITO) conductive electrodes using electrochemical polymerization. The as-prepared P(dCz2-co-dTC2) displayed a high ΔT (57.0%) and multichromic behaviors ranging from yellowish green, greenish gray, gray to purplish gray in different redox states. Five organic electrochromic devices (ECDs) were built using dCz- and dTC-containing homopolymers and copolymers as anodic materials, and poly(3,4-(2,2-dimethylpropylenedioxy)thiophene) (PProdot-Me2) as the cathodic material. The P(dCz2-co-dTC2)/PProdot-Me2 ECD presented remarkable electrochromic behaviors from the bleached to colored states. Moreover, P(dCz2-co-dTC2)/PProdot-Me2 ECD displayed a high optical contrast (ΔT, 45.8%), short switching time (ca. 0.3 s), high coloration efficiency (528.8 cm2 C−1) at 580 nm, and high redox cycling stability. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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Review

Jump to: Research, Other

15 pages, 938 KiB  
Review
A Review of Polarization-Sensitive Materials for Polarization Holography
by Yueyang Zhai, Li Cao, Ying Liu and Xiaodi Tan
Materials 2020, 13(23), 5562; https://doi.org/10.3390/ma13235562 - 06 Dec 2020
Cited by 24 | Viewed by 3058
Abstract
Polarization holography has the unique capacity to record and retrieve the amplitude, phase, and polarization of light simultaneously in a polarization-sensitive recording material and has attracted widespread attention. Polarization holography is a noteworthy technology with potential applications in the fields of high-capacity data [...] Read more.
Polarization holography has the unique capacity to record and retrieve the amplitude, phase, and polarization of light simultaneously in a polarization-sensitive recording material and has attracted widespread attention. Polarization holography is a noteworthy technology with potential applications in the fields of high-capacity data storage, polarization-controlled optical elements, and other related fields. The choice of its high-performance materials is particularly important. To further develop polarization holography applications and improve the quality of the information recorded (i.e., material sensitivity and resolution), a deeper understanding of such materials is needed. We present an overview of the polarization-sensitive materials, which introduced polarization holographic technology and the development of polarization holographic materials. The three main types of polarization holographic materials are described, including azopolymer materials, photopolymer material, and photorefractive polymer material. We examine the key contributions of each work and present many of the suggestions that have been made to improve the different polarization-sensitive photopolymer materials. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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Other

Jump to: Research, Review

7 pages, 1367 KiB  
Letter
A 33.2 W High Beam Quality Chirped-Pulse Amplification-Based Femtosecond Laser for Industrial Processing
by Zhenao Bai, Zhenxu Bai, Xiaolong Sun, Yong Liang, Kun Wang, Duo Jin and Zhongwei Fan
Materials 2020, 13(12), 2841; https://doi.org/10.3390/ma13122841 - 24 Jun 2020
Cited by 9 | Viewed by 2406
Abstract
A photonic crystal fiber-based chirped pulse amplification delivering 272 fs pulses of 66.4 µJ energy at a repetition rate of 500 kHz is presented, resulting in an average/peak power of 33.2 W/244 MW. A single grating is adopted for the pulse width stretching [...] Read more.
A photonic crystal fiber-based chirped pulse amplification delivering 272 fs pulses of 66.4 µJ energy at a repetition rate of 500 kHz is presented, resulting in an average/peak power of 33.2 W/244 MW. A single grating is adopted for the pulse width stretching and compression, which leads to high-compactness and low cost of the system. The output beam is near-diffraction-limited (M2 = 1.1 ± 0.05) with a power stability better than 0.5%. The cutting of alumina ceramic substrate and flexible printed circuit are demonstrated by using the laser system. The results indicate that the laser is competent for industrial applications. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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