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Photonics
Volume 13
Issue 1
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Photonics, Volume 13, Issue 1 (January 2026) – 103 articles

Cover Story (view full-size image): The rapid growth of AI workloads is driving urgent demand for ultra-high-speed, energy-efficient optical interconnects inside AI data centers. This work introduces an optical triple-band multiplexing scheme that enables beyond-600 Gb/s transmission using single-photodiode direct detection and low-bandwidth DACs. By replacing electronic RF mixers and local oscillators with photonic multiplexing, three independently modulated optical bands are generated and coherently combined in the optical domain. The proposed architecture breaks the conjugate-symmetry constraint in direct detection systems, significantly enhancing dispersion tolerance. Experimental results achieve a line rate of 686.6 Gb/s over 200 m standard single-mode fiber, providing a scalable and energy-efficient solution for next-generation 1.6T AI data-center interconnects. View this paper
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20 pages, 2413 KB  
Article
Modeling and Optimization of NLOS Underwater Optical Channels Using QAM-OFDM Technique
by Noor Abdulqader Hamdullah, Mesut Çevik, Hameed Mutlag Farhan and İzzet Paruğ Duru
Photonics 2026, 13(1), 99; https://doi.org/10.3390/photonics13010099 - 22 Jan 2026
Viewed by 125
Abstract
Due to increasing human activities underwater, there is a growing demand for high-speed underwater optical communication (UOWC) data links for security surveillance, environmental monitoring, pipeline inspection, and other applications. Line-of-sight communication is impossible under certain conditions due to misalignment, physical obstructions, irregular usage, [...] Read more.
Due to increasing human activities underwater, there is a growing demand for high-speed underwater optical communication (UOWC) data links for security surveillance, environmental monitoring, pipeline inspection, and other applications. Line-of-sight communication is impossible under certain conditions due to misalignment, physical obstructions, irregular usage, and difficulty adjusting the receiver orientation, especially when used in environments with mobile users or submerged sensor networks. Therefore, non-line-of-sight (NLOS) optical communication is used in this study. Advanced modulation schemes—quadrature amplitude modulation and orthogonal frequency-division multiplexing (QAM-OFDM)—were used to transmit the signal underwater between two network nodes. QAM increases the data transfer rate, while OFDM reduces dispersion and inter-symbol interference (ISI). The proposed UOWC system is investigated using a 532 nm green laser diode (LD). Reliable high-speed data transmission of up to 15 Gbps is achieved over horizontal distances of 134 m, 43 m, 21 m, and 5 m in four different aquatic environments—pure water (PW), clear ocean (CLO), coastal ocean (COO), and harbor II (HarII), respectively. The system achieves effectively error-free performance within the simulation duration (BER < 10−9), with a received optical signal power of approximately −41.5 dBm. Clear constellation patterns and low BER values are observed, confirming the robustness of the proposed architecture. Despite the limitations imposed by non-line-of-sight (NLOS) communication and the diversity aquatic environments, our proposed architecture excels at underwater long-distance data transmission at high speeds. Full article
(This article belongs to the Section Optical Communication and Network)
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10 pages, 1864 KB  
Article
Application of Phycocyanin Extracted from Cyanidioschyzon merolae in Luminescent Solar Concentrators
by Shang-Ping Ying, Han-Yi Fu, Bing-Mau Chen, You-Wei Liang and Yu-Kang Chang
Photonics 2026, 13(1), 103; https://doi.org/10.3390/photonics13010103 - 22 Jan 2026
Viewed by 203
Abstract
Building-integrated photovoltaics (BIPVs) enable the seamless incorporation of solar energy systems into architectural structures. Luminescent solar concentrators (LSCs) represent a technology that offers a promising route for semitransparent solar harvesting. In this study, phycocyanin, a bio-derived luminescent material extracted from the extremophilic red [...] Read more.
Building-integrated photovoltaics (BIPVs) enable the seamless incorporation of solar energy systems into architectural structures. Luminescent solar concentrators (LSCs) represent a technology that offers a promising route for semitransparent solar harvesting. In this study, phycocyanin, a bio-derived luminescent material extracted from the extremophilic red alga Cyanidioschyzon merolae, was used as the emissive layer in thin-film LSCs to achieve a sustainable BIPV system. This material exhibited high transparency, strong red fluorescence, and notable stability under illumination conditions, primarily attributable to its unique pigment–protein structure. Thin-film LSCs incorporating phycocyanin at various weight ratios were fabricated and evaluated under simulated sunlight conditions. These concentrators demonstrated efficient photon collection and maintained stable optical performance during solar exposure. Overall, these findings underscore the potential of phycocyanin derived from C. merolae as an eco-friendly and renewable alternative to conventional organic or synthetic luminophores, which can advance the development of sustainable and efficient LSC systems for next-generation BIPV applications. Full article
(This article belongs to the Special Issue Next-Generation Solar Energy Harvesting, Lighting, and Photovoltaic Innovations)
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12 pages, 1240 KB  
Article
Conditions for a Rotationally Symmetric Spectral Degree of Coherence Produced by Electromagnetic Scattering on an Anisotropic Random Medium
by Xin Xia and Yi Ding
Photonics 2026, 13(1), 102; https://doi.org/10.3390/photonics13010102 - 22 Jan 2026
Viewed by 96
Abstract
The problem was recently reported that the far-zone electromagnetic momentum of light produced by scattering on a spatially anisotropic random medium can be the same at every azimuthal angle of scattering. Here, we extend the analysis to focus on the possibility of producing [...] Read more.
The problem was recently reported that the far-zone electromagnetic momentum of light produced by scattering on a spatially anisotropic random medium can be the same at every azimuthal angle of scattering. Here, we extend the analysis to focus on the possibility of producing a rotationally symmetric spectral degree of coherence (SDOC) generated by scattering by an anisotropic process. The necessary and sufficient conditions for producing such a SDOC in the far zone are derived when a polychromatic electromagnetic plane wave is scattered by an anisotropic Gaussian Schell-model medium. We find that, unlike the generation of a rotationally symmetric momentum flow, it is not enough to simply restrict the structural characteristics of the medium and the incident light source to achieve a SDOC with rotational symmetry. An additional and essential requirement is that the azimuthal angles of scattering corresponding to the two observation points of the SDOC must be constrained to be equal. Only when all these constraints are satisfied simultaneously can a rotationally symmetric electromagnetic SDOC generated by scattering by an anisotropic process be realized. In addition, we find that although the medium parameter conditions for generating a rotationally symmetric SDOC and a rotationally symmetric momentum flow are completely different, it remains possible that the SDOC and the momentum flow produced by a spatially anisotropic medium can still simultaneously exhibit rotational symmetry, provided that the distribution of the correlation function of the scattering potential of the medium is isotropic in the plane perpendicular to the incident direction. Our results not only contribute to a deeper understanding of the far-field distribution of light scattering on an anisotropic scatterer, but also have potential applications in light-field manipulation and in the inverse scattering problem. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
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11 pages, 3060 KB  
Communication
Design and Implementation of a Ku Band Waveguide Energy-Selective Device
by Tongxin Liu, Chenxi Liu, Yanqing Cheng and Yanlin Xu
Photonics 2026, 13(1), 101; https://doi.org/10.3390/photonics13010101 - 22 Jan 2026
Viewed by 162
Abstract
This paper presents a waveguide energy-selective device operating in the Ku band. By utilizing the nonlinear characteristics of PIN diodes, the device can autonomously switch its operating state according to the power level of incident signals inside the waveguide, achieving an adaptive transmission [...] Read more.
This paper presents a waveguide energy-selective device operating in the Ku band. By utilizing the nonlinear characteristics of PIN diodes, the device can autonomously switch its operating state according to the power level of incident signals inside the waveguide, achieving an adaptive transmission response. Concurrently, through a dual-layer structural design and optimized inter-layer coupling, it enables the device to deliver broadband-protective performance within the Ku band. To validate its feasibility, the device was designed and implemented based on the waveguide WR62. The results indicate that during the transmission of a −10 dBm signal, the device exhibits insertion loss fluctuating around 1 dB within the 13–17 GHz band, whereas under 45 dBm signal incidence, the shielding effectiveness exceeds 10 dB across this frequency range. The device can be integrated into waveguides to provide adaptive high-power protection, thus demonstrating significant application potential in the field of electromagnetic protection for sensitive electronic equipment. Full article
(This article belongs to the Special Issue Advances in Terahertz and Microwave Electromagnetic Manipulation)
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14 pages, 9894 KB  
Article
Low-Loss, Multi-Reticle-Stitched SiN Waveguides for 300 mm Wafer-Level Optical Interconnects
by Pengfei Xu, Chiara Marchese, Guy Lepage, Negin Golshani, Ruben Van Eenaeme, Andrea Mingardi, Joost Van Ongeval, Rafal Magdziak, Luc Halipre, Darko Trivkovic, Peter Verheyen, Maumita Chakrabarti, Dimitrios Velenis, Andy Miller, Filippo Ferraro, Yoojin Ban and Joris Van Campenhout
Photonics 2026, 13(1), 100; https://doi.org/10.3390/photonics13010100 - 22 Jan 2026
Viewed by 157
Abstract
With the rapid development of artificial intelligence (AI) and machine learning (ML) applications, wafer-level optical I/O is becoming increasingly attractive for massive and efficient data interconnects in future wafer-scale multi-processor-units (multi-XPU) compute clusters with unparalleled data bandwidth, energy efficiency, and low latency. In [...] Read more.
With the rapid development of artificial intelligence (AI) and machine learning (ML) applications, wafer-level optical I/O is becoming increasingly attractive for massive and efficient data interconnects in future wafer-scale multi-processor-units (multi-XPU) compute clusters with unparalleled data bandwidth, energy efficiency, and low latency. In this paper, we present a 300 mm sized wafer reticle-stitched low-pressure chemical vapor deposition (LPCVD) silicon nitride (SiN) waveguide technology and demonstrate a multi-reticle-stitched ~56 cm long waveguides across 20 reticles with propagation loss of 0.13~0.15 dB/cm at 1310 nm wavelength, and <0.001~0.002 dB SiN waveguide stitch loss, which is because of <5 nm high-precision reticle lithography offset. These advantageous features of low-loss reticle-stitched SiN waveguides have the potential to significantly enhance future optically interconnected wafer-scale multi-chip compute systems. Full article
(This article belongs to the Special Issue Recent Progress in Silicon Photonics)
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15 pages, 3041 KB  
Article
A Novel Scanning and Acquisition Method of Optical Phased Array for Space Laser Communication
by Ye Gu, Xiaonan Yu, Rui Weng, Guosheng Fan, Penglang Wang, Quanhan Wang, Naiyuan Liang, Dewang Liu, Shuai Chang, Dongxu Jiang and Shoufeng Tong
Photonics 2026, 13(1), 98; https://doi.org/10.3390/photonics13010098 - 21 Jan 2026
Viewed by 155
Abstract
To meet the requirements of non-mechanical beam scanning and acquisition in space laser communication, this study proposes a two-dimensional scanning and acquisition method based on a silicon-based optical phased array (OPA). The OPA utilizes thermo-optic phase modulation to achieve horizontal beam pointing, while [...] Read more.
To meet the requirements of non-mechanical beam scanning and acquisition in space laser communication, this study proposes a two-dimensional scanning and acquisition method based on a silicon-based optical phased array (OPA). The OPA utilizes thermo-optic phase modulation to achieve horizontal beam pointing, while vertical beam pointing is controlled by wavelength tuning. By combining the OPA with a rectangular spiral scanning strategy, non-mechanical scanning is realized and beam acquisition experiments are carried out. Experimental results demonstrate that for an 8° step signal, the horizontal and vertical rise times are 156.8 μs and 214.76 ms, respectively. A full scan of 440 points covering a ±4° field of view is completed in 8.119 s. Acquisition experiments were conducted assuming a Gaussian-distributed uncertainty region (standard deviation σ=1°). Out of 106 independent trials, a success rate of 97.17% was achieved with an average acquisition time of 0.41 s. This work experimentally applies a rectangular spiral scanning strategy to an OPA-based acquisition system, addressing a capability that has been largely missing in previous studies. These results verify that the OPA technology has good scanning efficiency and acquisition robustness in space laser communication applications. Full article
(This article belongs to the Special Issue Advances and Challenges in Free-Space Optics)
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8 pages, 1605 KB  
Communication
Saturation of Optical Gain in Green Laser Diode Structures as Functions of Excitation Density and Excitation Length
by Young Sun Jo, Seung Ryul Lee, Sung-Nam Lee and Yoon Seok Kim
Photonics 2026, 13(1), 97; https://doi.org/10.3390/photonics13010097 - 21 Jan 2026
Viewed by 104
Abstract
In this study, the optical gain characteristics of a green laser sample based on a III-Nitride InGaN single-quantum-well structure were investigated. The Green gap phenomenon, caused by bandgap fluctuations due to inhomogeneous indium composition and the quantum-confined Stark effect (QCSE), has been a [...] Read more.
In this study, the optical gain characteristics of a green laser sample based on a III-Nitride InGaN single-quantum-well structure were investigated. The Green gap phenomenon, caused by bandgap fluctuations due to inhomogeneous indium composition and the quantum-confined Stark effect (QCSE), has been a major obstacle in achieving high efficiency and high output in green-light-emitting devices. To address these issues, a sample grown on a (0001)-oriented GaN substrate with a single-quantum-well active layer was fabricated to suppress In composition non-uniformity and enhance the overlap of electron and hole wavefunctions. The optical gain behavior was analyzed using the Variable Stripe Length Method (VSLM) under various excitation densities and stripe lengths (Lcav). The results showed that as the stripe length increased, the spectral linewidth decreased and stimulated emission occurred at lower excitation densities. However, excessive cavity length led to gain saturation and a red shift in the peak wavelength due to Joule heating effects. These findings provide essential insights for determining the optimal cavity length in laser diode fabrication and are expected to serve as fundamental guidelines for improving the efficiency and output power of III-Nitride-based green laser diodes. Full article
(This article belongs to the Special Issue Development and Optimization of High-Power Semiconductor Laser Diodes and Photodetectors)
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22 pages, 566 KB  
Article
Interference-Induced Bound States in the Continuum in Optical Giant Atoms
by Vassilios Yannopapas
Photonics 2026, 13(1), 96; https://doi.org/10.3390/photonics13010096 - 21 Jan 2026
Viewed by 161
Abstract
The giant atom paradigm, where a single quantum emitter couples to a continuum at multiple discrete points, has enabled unprecedented control over light-matter interactions, including decoherence-free subspaces and chiral emission. However, realizing these non-local effects beyond the microwave regime remains a significant challenge [...] Read more.
The giant atom paradigm, where a single quantum emitter couples to a continuum at multiple discrete points, has enabled unprecedented control over light-matter interactions, including decoherence-free subspaces and chiral emission. However, realizing these non-local effects beyond the microwave regime remains a significant challenge due to the diffraction limit. Here, we theoretically propose a photonic analog of giant atoms operating at optical frequencies, utilizing a quantum emitter resonantly coupled to a pair of spatially separated single-mode cavities interacting with a common 1D photonic continuum. By rigorously deriving the effective non-Hermitian Hamiltonian and integrating out the bath degrees of freedom, we demonstrate that the interference between cavity-mediated emission pathways leads to the formation of robust Bound States in the Continuum (BICs). These interference-induced dark states allow for the infinite trapping of excitation within the emitter-cavity subsystem, effectively shielding it from radiative decay. Our results extend the giant atom toolbox to the optical domain, offering a scalable architecture for integrated quantum photonics and quantum interconnects. Full article
(This article belongs to the Special Issue Bound States in the Continuum in Photonics, Plasmonics, and Terahertz Technology)
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17 pages, 12498 KB  
Article
Wavefront Fitting over Arbitrary Freeform Apertures via CSF-Guided Progressive Quasi-Conformal Mapping
by Tong Yang, Chengxiang Guo, Lei Yang and Hongbo Xie
Photonics 2026, 13(1), 95; https://doi.org/10.3390/photonics13010095 - 21 Jan 2026
Viewed by 164
Abstract
In freeform optical metrology, wavefront fitting over non-circular apertures is hindered by the loss of Zernike polynomial orthogonality and severe sampling grid distortion inherent in standard conformal mappings. To address the resulting numerical instability and fitting bias, we propose a unified framework curve-shortening [...] Read more.
In freeform optical metrology, wavefront fitting over non-circular apertures is hindered by the loss of Zernike polynomial orthogonality and severe sampling grid distortion inherent in standard conformal mappings. To address the resulting numerical instability and fitting bias, we propose a unified framework curve-shortening flow (CSF)-guided progressive quasi-conformal mapping (CSF-QCM), which integrates geometric boundary evolution with topology-aware parameterization. CSF-QCM first smooths complex boundaries via curve-shortening flow, then solves a sparse Laplacian system for harmonic interior coordinates, thereby establishing a stable diffeomorphism between physical and canonical domains. For doubly connected apertures, it preserves topology by computing the conformal modulus via Dirichlet energy minimization and simultaneously mapping both boundaries. Benchmarked against state-of-the-art methods (e.g., Fornberg, Schwarz–Christoffel, and Ricci flow) on representative irregular apertures, CSF-QCM suppresses area distortion and restores discrete orthogonality of the Zernike basis, reducing the Gram matrix condition number from >900 to <8. This enables high-precision reconstruction with RMS residuals as low as 3×10−3λ and up to 92% lower fitting errors than baselines. The framework provides a unified, computationally efficient, and numerically stable solution for wavefront reconstruction in complex off-axis and freeform optical systems. Full article
(This article belongs to the Special Issue Freeform Optical Systems: Design and Applications)
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17 pages, 2008 KB  
Article
Generative Adversarial Optical Networks Using Diffractive Layers for Digit and Action Generation
by Pei Hu, Tengyu Cui, Yuanyuan Zhang and Shuai Feng
Photonics 2026, 13(1), 94; https://doi.org/10.3390/photonics13010094 - 21 Jan 2026
Viewed by 175
Abstract
Within the traditional electronic neural network framework, Generative Adversarial Networks (GANs) have achieved extensive applications across multiple domains, including image synthesis, style transfer and data augmentation. Recently, several studies have explored the use of optical neural networks represented by the diffractive deep neural [...] Read more.
Within the traditional electronic neural network framework, Generative Adversarial Networks (GANs) have achieved extensive applications across multiple domains, including image synthesis, style transfer and data augmentation. Recently, several studies have explored the use of optical neural networks represented by the diffractive deep neural network (D2NN) for GANs. However, most of these focus on applications of the generative network, and there is currently no well-established D2NN architecture that simultaneously implements generative adversarial functionality. Here, we propose a novel implementation scheme for generative adversarial networks based on all-optical diffraction layers, demonstrating a complete all-optical adversarial architecture that simultaneously realizes both the generative network and the adversarial network (D2NN-GAN). We validated this method on the MNIST handwritten digit dataset, achieving Nash equilibrium convergence with the discriminator accuracy stabilizing around 50%. Concurrently, the average SSIM parameter of generated images reached 0.9573, indicating that the generated samples possess high quality and closely resemble real samples. Furthermore, we extended the framework to the KTH human action dataset, successfully reconstructing the “running” action with a discriminator accuracy of approximately 75%. The D2NN-GAN architecture introduces a fully optical generative adversarial model, providing a practical path for future optical modeling methods, such as image generation and video synthesis. Full article
(This article belongs to the Section New Applications Enabled by Photonics Technologies and Systems)
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19 pages, 1108 KB  
Article
Quantitative Analysis of Fission-Product Surrogates in Molten Salt Chloride Aerosols
by Garrett LeCroy, Rachelle Austin, Ruchi Gakhar and Ammon Williams
Photonics 2026, 13(1), 93; https://doi.org/10.3390/photonics13010093 - 20 Jan 2026
Viewed by 164
Abstract
This work demonstrates laser-induced breakdown spectroscopy (LIBS) applied to a stream of aerosolized salt from molten eutectic LiCl-KCl. We demonstrate analytical capabilities to track fission-product surrogates of Cs, Sr, Pr, and Nd simultaneously, with application to monitor salts in pyroprocessing schemes and molten [...] Read more.
This work demonstrates laser-induced breakdown spectroscopy (LIBS) applied to a stream of aerosolized salt from molten eutectic LiCl-KCl. We demonstrate analytical capabilities to track fission-product surrogates of Cs, Sr, Pr, and Nd simultaneously, with application to monitor salts in pyroprocessing schemes and molten salt reactors. This work demonstrates limits of detection using LIBS on the order of 100 μg/g, which proves potentially applicable to monitoring fission-product concentrations in pyroprocessing applications. Additionally, this work explores fundamental aspects of plasma temperature and plasma electron density of the aerosolized species during LIBS with a specific focus on potential non-uniform plasma conditions in the aerosol. Full article
(This article belongs to the Special Issue Fundamentals and Applications of Aerosol Analysis with Laser-Induced Breakdown Spectroscopy)
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14 pages, 3272 KB  
Article
High-Precision Endoscopic Shape Sensing Using Two Calibrated Outer Cores of MC-FBG Array
by Bo Xia, Chujie Tu, Weiliang Zhao, Xiangpeng Xiao, Jialei Zuo, Yan He and Zhijun Yan
Photonics 2026, 13(1), 92; https://doi.org/10.3390/photonics13010092 - 20 Jan 2026
Viewed by 172
Abstract
We present a high-precision endoscopic shape-sensing method using only two calibrated outer cores of a multicore fiber Bragg grating (MC-FBG) array. By leveraging the geometric relationship among two non-collinear outer cores and the central core, the method estimates curvature and bending angle without [...] Read more.
We present a high-precision endoscopic shape-sensing method using only two calibrated outer cores of a multicore fiber Bragg grating (MC-FBG) array. By leveraging the geometric relationship among two non-collinear outer cores and the central core, the method estimates curvature and bending angle without relying on multiple outer-core channels, thereby reducing complexity and error propagation. On canonical shapes, the proposed method achieves maximum relative reconstruction errors of 1.62% for a 2D circular arc and 2.81% for a 3D helix, with the corresponding RMSE values reported for completeness. In addition, representative endoscope-relevant configurations including the α-loop, reversed α-loop, and N-loop are accurately reconstructed, and temperature tests over 25–81 °C further verify stable reconstruction performance under thermal disturbances. This work provides a resource-efficient and high-fidelity solution for endoscopic shape sensing with strong potential for integration into next-generation image-guided and robot-assisted surgical systems. Full article
(This article belongs to the Special Issue Emerging Technologies and Applications in Fiber Optic Sensing)
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16 pages, 2333 KB  
Article
On-Chip Volume Refractometry and Optical Binding of Nanoplastics Colloids in a Stable Optofluidic Fabry–Pérot Microresonator
by Noha Gaber, Frédéric Marty, Elodie Richalot and Tarik Bourouina
Photonics 2026, 13(1), 91; https://doi.org/10.3390/photonics13010091 - 20 Jan 2026
Viewed by 181
Abstract
Plastic pollution raises concerns for health and the environment. Plastics are not biodegradable but gradually erode to microplastic and nanoplastic particles spreading almost everywhere. Nanoplastics exhibit colloidal behavior. Thereby, their analysis can be accomplished by refractometry, preferably by an on-chip tool. We present [...] Read more.
Plastic pollution raises concerns for health and the environment. Plastics are not biodegradable but gradually erode to microplastic and nanoplastic particles spreading almost everywhere. Nanoplastics exhibit colloidal behavior. Thereby, their analysis can be accomplished by refractometry, preferably by an on-chip tool. We present a study of such colloids using a microfabricated Fabry–Pérot cavity with curved mirrors, which holds a capillary micro-tube used both for fluid handling and light collimation, resulting in an optically stable microresonator. Despite the numerous scatterers within the sample, the sub-millimeter scale cavity provides the advantages of reduced interaction length while maintaining light confinement. This significantly reduces optical loss and hence keeps resonance modes with quality factors (resonant frequency/bandwidth) above 1100. Therefore, small quantities of colloids can be measured by the interference spectral response through the shift in resonant wavelengths. The particles’ Brownian motion potentially causing perturbations in the spectra can be overcome either by post-measurement cross-correlation analysis or by avoiding it entirely by taking the measurements at once by a wideband source and a spectrum analyzer. The effective refractive index of solutions with solid contents down to 0.34% could be determined with good agreement with theoretical predictions. Even lower detection capabilities might be attained by slightly altering the technique to cause particle aggregation achieved solely by light. Full article
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12 pages, 2542 KB  
Article
200G VCSEL Development and Proposal of Using VCSELs for Near-Package-Optics Scale-Up Application
by Tzu Hao Chow, Jingyi Wang, Sizhu Jiang, M. V. Ramana Murty, Laura M. Giovane, Chee Parng Chua, Lip Min Chong, Lowell Bacus, Xiaoyong Shan, Salvatore Sabbatino, Zixing Xue and I-Hsing Tan
Photonics 2026, 13(1), 90; https://doi.org/10.3390/photonics13010090 - 20 Jan 2026
Viewed by 457
Abstract
The connectivity demands of high-performance computing (HPC), artificial intelligence (AI) and data centers are driving the development of a new generation of multimode optical components. This paper discusses the vertical cavity surface emitting laser (VCSEL) bandwidth and noise performance needed to support 106 [...] Read more.
The connectivity demands of high-performance computing (HPC), artificial intelligence (AI) and data centers are driving the development of a new generation of multimode optical components. This paper discusses the vertical cavity surface emitting laser (VCSEL) bandwidth and noise performance needed to support 106 Gbd line rates with PAM4 modulation for 200 Gbps per lane multimode optical links. A −3 dB bandwidth greater than 35 GHz and a RIN of less than −152 dB/Hz are demonstrated. No uncorrectable errors were observed over 50 m of OM4 fiber, demonstrating good link stability. VCSEL device performance and the associated wear-out life are presented. Leveraging good device reliability and low power consumption of VCSEL-based links, a novel VCSEL near-packaged optics (NPO) concept is proposed for optical interconnects in AI scale-up network applications. Optical interconnects allow for longer reaches, compared to copper interconnects, which facilitate larger AI clusters with network disaggregation. The proposed VCSEL NPO can achieve an energy efficiency of ~1 pJ/bit, which is the highest among optical interconnects. Full article
(This article belongs to the Special Issue Advances in Multimode Optical Fibers and Related Technologies)
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9 pages, 1364 KB  
Communication
Multiband Infrared Photodetection Based on Colloidal Quantum Dot
by Yingying Xu, Xiaomeng Xue, Lixiong Wu, Zhikai Gan, Menglu Chen and Qun Hao
Photonics 2026, 13(1), 89; https://doi.org/10.3390/photonics13010089 - 20 Jan 2026
Viewed by 273
Abstract
Multispectral infrared detection plays a crucial role in advanced applications spanning environmental monitoring, military surveillance, and biomedical diagnostics, offering superior target identification accuracy compared to single-band imaging techniques. In this work, we synthesized four distinct bands of colloidal quantum dots (CQDs)—specifically, a cut-off [...] Read more.
Multispectral infrared detection plays a crucial role in advanced applications spanning environmental monitoring, military surveillance, and biomedical diagnostics, offering superior target identification accuracy compared to single-band imaging techniques. In this work, we synthesized four distinct bands of colloidal quantum dots (CQDs)—specifically, a cut-off of 1.3 µm with PbS CQDs and 1.8 µm, 2.6 µm, and 3.5 µm with HgTe CQDs—and employed them to construct planar multiband infrared photodetectors. The device exhibited a clear photoresponse at room temperature from 0.8 µm to 3.5 µm, with responsivity of 5.39 A/W and specific detectivity of 2.01 × 1011 Jones at 1.8 µm. This materials–device co-design strategy integrates wavelength-selective CQD synthesis with planar pixel-level patterning, providing a versatile pathway for developing low-cost, solution-processed, multiband infrared photodetectors. Full article
(This article belongs to the Special Issue New Perspectives in Micro-Nano Optical Design and Manufacturing)
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12 pages, 1899 KB  
Article
Packaging of 128-Channel Optical Phased Array for LiDAR
by Abu Sied, Eun-Su Lee, Kwon-Wook Chun, Jinung Jin and Min-Cheol Oh
Photonics 2026, 13(1), 88; https://doi.org/10.3390/photonics13010088 - 20 Jan 2026
Viewed by 286
Abstract
We developed a complete packaging strategy for a 128-channel optical phased array (OPA) for Light Detection and Ranging (LiDAR) applications operating at a 1550 nm wavelength. The process comprised three major steps: waveguide end-facet polishing, fiber-to-optical waveguide pigtailing, and electrical wire bonding. Sequential [...] Read more.
We developed a complete packaging strategy for a 128-channel optical phased array (OPA) for Light Detection and Ranging (LiDAR) applications operating at a 1550 nm wavelength. The process comprised three major steps: waveguide end-facet polishing, fiber-to-optical waveguide pigtailing, and electrical wire bonding. Sequential polishing with silicon carbide paper followed by colloidal silica reduced coupling losses to 0.74 dB per facet. An automated fiber alignment setup was used to perform edge coupling. The electrical connections, formed under optimized wire-bonding conditions (18 mW ultrasonic power), achieved a bond strength of 4.66 gf while maintaining electrode-pad integrity. The final packaged device demonstrated uniform optical throughput, with a throughput power variation maintained below 0.2 dB following the packaging process, and a uniform electrical resistance of 0.48% across all 128 channels, verifying the process stability and packaging integrity. These results confirmed that the proposed packaging scheme offers a dependable route for photonic integration in LiDAR applications. Full article
(This article belongs to the Special Issue Recent Progress in Integrated Photonics and Future Prospects)
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14 pages, 3259 KB  
Article
Design of Circularly Polarized VCSEL Based on Cascaded Chiral GaAs Metasurface
by Xiaoming Wang, Bo Cheng, Yuxiao Zou, Guofeng Song, Kunpeng Zhai and Fuchun Sun
Photonics 2026, 13(1), 87; https://doi.org/10.3390/photonics13010087 - 19 Jan 2026
Viewed by 186
Abstract
Vertical cavity surface emitting lasers (VCSELs) have shown great potential in high-speed communication, quantum information processing, and 3D sensing due to their excellent beam quality and low power consumption. However, generating high-purity and controllable circularly polarized light usually requires external optical components such [...] Read more.
Vertical cavity surface emitting lasers (VCSELs) have shown great potential in high-speed communication, quantum information processing, and 3D sensing due to their excellent beam quality and low power consumption. However, generating high-purity and controllable circularly polarized light usually requires external optical components such as quarter-wave plates, which undoubtedly increases system complexity and volume, hindering chip-level integration. To address this issue, we propose a monolithic integration scheme that directly integrates a custom-designed double-layer asymmetric metasurface onto the upper distributed Bragg reflector of a chiral VCSEL. This metasurface consists of a rotated GaAs elliptical nanocolumn array and an anisotropic grating above it. By precisely controlling the relative orientation between the two, the in-plane symmetry of the structure is effectively broken, introducing a significant optical chirality response at a wavelength of 1550 nm. Numerical simulations show that this structure can achieve a near 100% high reflectivity for the left circularly polarized light (LCP), while suppressing the reflectivity of the right circularly polarized light (RCP) to approximately 33%, thereby obtaining an efficient in-cavity circular polarization selection function. Based on this, the proposed VCSEL can directly emit high-purity RCP without any external polarization control components. This compact circularly polarized laser source provides a key solution for achieving the next generation of highly integrated photonic chips and will have a profound impact on frontier fields such as spin optics, secure communication, and chip-level quantum light sources. Full article
(This article belongs to the Special Issue Vertical-Cavity Surface-Emitting Laser Technology: Innovations and Future Trends)
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19 pages, 2581 KB  
Article
Effect of Mo Layer Thickness on Bandwidth Tunability and Absorption Properties of Planar Ultra-Wideband Optical Absorbers
by Kao-Peng Min, Yu-Ting Gao, Cheng-Fu Yang, Walter Water and Chi-Ting Ho
Photonics 2026, 13(1), 86; https://doi.org/10.3390/photonics13010086 - 19 Jan 2026
Viewed by 184
Abstract
This study utilizes COMSOL Multiphysics (version 6.0) to design a planar ultra-broadband optical absorber with a multilayer configuration. The proposed structure consists of seven stacked layers arranged from bottom to top: W (h1, acting as a reflective substrate and transmission blocker), [...] Read more.
This study utilizes COMSOL Multiphysics (version 6.0) to design a planar ultra-broadband optical absorber with a multilayer configuration. The proposed structure consists of seven stacked layers arranged from bottom to top: W (h1, acting as a reflective substrate and transmission blocker), WSe2 (h2), SiO2 (h3), Ni (h4), SiO2 (h5), Mo (h6), and SiO2 (h7). One key finding of this study is that, when all other layer thicknesses are fixed, variations in the Mo layer thickness systematically induce a redshift in both the short- and long-wavelength cutoff edges. Notably, the long-wavelength cutoff exhibits a larger shift than the short-wavelength edge, resulting in an increased absorption bandwidth where absorptivity remains above 0.900. The second contribution is the demonstration that this planar structure can be readily engineered to achieve ultra-broadband absorption, spanning from the near-ultraviolet and visible region (360 nm) to the mid-infrared (6300 nm). An important characteristic of the proposed design is that the thickness of the h7 SiO2 layer influences the cutoff wavelength at the short-wavelength edge, while the thickness of the h6 Mo layer governs the cutoff position at the long-wavelength edge. This dual modulation capability allows the proposed optical absorber to flexibly tune both the spectral range and the bandwidth in which absorptivity exceeds 0.900, thereby enabling the realization of a wavelength- and bandwidth-tunable optical absorber. Full article
(This article belongs to the Special Issue Photonics Metamaterials: Processing and Applications)
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15 pages, 4559 KB  
Article
Simulation Study on Parameter Optimization of Laser Acupuncture Based on a Human Acupoint Skin Model
by Zhike Zhao, Shuai Han, Shihao Xie, Wenhao Xue, Husheng Dong, Ruihao Xue and Peng Li
Photonics 2026, 13(1), 85; https://doi.org/10.3390/photonics13010085 - 19 Jan 2026
Viewed by 263
Abstract
To achieve precise and safe laser acupuncture treatment, a computational model of the skin acupoint was constructed utilizing COMSOL Multiphysics (Version 6.1). This model incorporates its multilayer anatomical structure: the epidermis, papillary dermis, reticular dermis, hypodermis, and muscle layer. A coupled multiphysics approach [...] Read more.
To achieve precise and safe laser acupuncture treatment, a computational model of the skin acupoint was constructed utilizing COMSOL Multiphysics (Version 6.1). This model incorporates its multilayer anatomical structure: the epidermis, papillary dermis, reticular dermis, hypodermis, and muscle layer. A coupled multiphysics approach integrating geometric optics, radiation beams, and bioheat transfer was employed to investigate the effects of light source parameters and cooling layers on the photothermal response and thermal damage of acupoints. Under optimized parameters (808 nm, 3 mm beam waist, 50 mW) with a 0.5 mm glycerol layer, 600 s irradiation achieved a stable dermal temperature (40.86–42.04 °C) and a negligible epidermal thermal damage factor (0.0063), significantly below the subclinical injury threshold of 0.15; under identical parameters, the dermal temperature for the Gaussian periodic pulsed source was maintained between 38.85 and 40.35 °C, with a corresponding epidermal thermal damage factor of merely 0.0010. The model exhibited good robustness, tolerating variations of ±5% in laser power and ±40% in glycerol layer thickness. The resultant temperature deviations in the epidermis and dermis were well within the safe range, and the thermal damage factor remained below the injury threshold. This work serves as a guideline for selecting laser acupuncture parameters according to acupoint depth. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
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13 pages, 3196 KB  
Article
Enhancing Temperature Sensing in Fiber Specklegram Sensors Using Multi-Dataset Deep Learning Models: Data Scaling Analysis
by Francisco J. Vélez Hoyos, Juan D. Arango, Víctor H. Aristizábal, Carlos Trujillo and Jorge A. Herrera-Ramírez
Photonics 2026, 13(1), 84; https://doi.org/10.3390/photonics13010084 - 19 Jan 2026
Viewed by 162
Abstract
This study presents a robust deep learning-based approach for temperature sensing using Fiber Specklegram Sensors (FSS), leveraging an extended experimental framework to evaluate model generalization. A convolutional neural network (CNN), specifically a customized MobileNet architecture (MNet-reg), was trained on multiple experimental datasets to [...] Read more.
This study presents a robust deep learning-based approach for temperature sensing using Fiber Specklegram Sensors (FSS), leveraging an extended experimental framework to evaluate model generalization. A convolutional neural network (CNN), specifically a customized MobileNet architecture (MNet-reg), was trained on multiple experimental datasets to assess the impact of increasing data availability on sensing accuracy. Generalization is evaluated as cross-dataset performance under unseen experimental realizations, rather than under controlled intra-dataset splits. The experimental setup utilized a multi-mode optical fiber (MMF) (core diameter 62.5 µm) subjected to controlled thermal cycles via a PID-regulated heating system. The curated dataset comprises 24,528 specklegram images captured over a temperature range of 25.00 °C to 200.00 °C with increments of ~0.20 °C. The experimental results demonstrate that models trained with an increasing number of datasets (from 1 to 13) significantly improve accuracy, reducing Mean Absolute Error (MAE) from 13.39 to 0.69 °C, and achieving a Root Mean Square Error (RMSE) of 0.90 °C with an R2 score of 0.99. Our systematic analysis establishes that scaling experimental data diversity—through training on multiple independent realizations—is the foundational strategy to overcome domain shift and enable robust cross-dataset generalization. Full article
(This article belongs to the Special Issue Optical Fiber Sensors: Recent Progress and Future Prospects)
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17 pages, 4065 KB  
Article
Inverse Electromagnetic Parameter Design of Single-Layer P-Band Radar Absorbing Materials
by Guoxu Feng, Jie Huang, Jinwang Wang, Kaiqiang Wen, Quancheng Gu and Han Wang
Photonics 2026, 13(1), 83; https://doi.org/10.3390/photonics13010083 - 19 Jan 2026
Viewed by 173
Abstract
In response to the significant threat posed by low-frequency P-band anti-stealth radar to aircraft stealth capabilities, this paper examines the inverse design of electromagnetic parameters for a single-layer, thin P-band radar absorbing material. An efficient computational model is constructed by integrating impedance boundary [...] Read more.
In response to the significant threat posed by low-frequency P-band anti-stealth radar to aircraft stealth capabilities, this paper examines the inverse design of electromagnetic parameters for a single-layer, thin P-band radar absorbing material. An efficient computational model is constructed by integrating impedance boundary conditions with the characteristic basis function method. The NSGA-II genetic algorithm is employed to accomplish multi-objective co-optimization of electromagnetic parameters and material thickness. Results demonstrate that the optimized single-layer RAM, with a relative permittivity of μr = 3.3078 + j3.9018 and permeability of εr = 2.3522 + j6.9519, exhibits outstanding P-band absorption characteristics within a thickness constraint of only 1 mm. Applying this RAM to aircraft wing components’ leading/trailing edges, intake duct cavities, and lip areas effectively suppresses edge diffraction and cavity scattering. The target achieves a maximum forward average RCS reduction of −13.97 dB and a maximum rearward average RCS reduction of −5.03 dB, maintaining stable performance within a pitch angle range of 0° ± 5°. Full article
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20 pages, 4237 KB  
Article
Systematic Measurement and Analysis of Beam Degree of Polarization Under Diverse Atmospheric Turbulence Conditions
by Chenghu Ke, Yan Shu, Meimiao Han and Xizheng Ke
Photonics 2026, 13(1), 82; https://doi.org/10.3390/photonics13010082 - 18 Jan 2026
Viewed by 118
Abstract
Atmospheric turbulence-induced random fluctuations in the refractive index can lead to the degradation of the polarization of polarized light. In accordance with the unified theory of coherent polarization, a comprehensive investigation was undertaken to explore the variation in the degree of polarization (DOP) [...] Read more.
Atmospheric turbulence-induced random fluctuations in the refractive index can lead to the degradation of the polarization of polarized light. In accordance with the unified theory of coherent polarization, a comprehensive investigation was undertaken to explore the variation in the degree of polarization (DOP) of laser beams propagating through atmospheric turbulence channels under diverse weather conditions. This investigation involved both theoretical analyses and experimental validations, providing a multifaceted approach to understanding the dynamics of laser beam propagation in atmospheric turbulence. To this end, numerical simulations were performed to analyze the polarization-maintaining characteristics of laser beams with varying wavelengths, turbulence intensities, and initial DOP values. To validate the simulation results for various weather scenarios, three experimental links with different propagation distances were constructed. The experimental results demonstrated that as the turbulence intensity increased, the average DOP of the beam continuously decreased until it reached a threshold value. Furthermore, the polarization fluctuations exhibited a distance-threshold effect, wherein the polarization parameters tended to saturate beyond a critical propagation distance. Full article
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11 pages, 1174 KB  
Article
Distillation of Multipartite Gaussian EPR Steering Based on Measurement-Based Noiseless Linear Amplification
by Yang Liu
Photonics 2026, 13(1), 81; https://doi.org/10.3390/photonics13010081 - 18 Jan 2026
Viewed by 151
Abstract
Multipartite Gaussian Einstein–Podolsky–Rosen (EPR) steering is a key resource for quantum networks, but in practice it is strongly degraded by channel loss and excess noise. This motivates the need to distill multipartite Gaussian EPR steering across all relevant mode partitions. Here we propose [...] Read more.
Multipartite Gaussian Einstein–Podolsky–Rosen (EPR) steering is a key resource for quantum networks, but in practice it is strongly degraded by channel loss and excess noise. This motivates the need to distill multipartite Gaussian EPR steering across all relevant mode partitions. Here we propose and analyze a measurement-based noiseless linear amplification (NLA) protocol that distills Gaussian EPR steering in a four-mode square cluster state transmitted through lossy and noisy channels. Starting from a CV cluster shared by a transmitted node A and three local nodes (B, C, and D), we reconstruct the covariance matrix of the Gaussian cluster state and evaluate Gaussian steering monotones for all (1+1), (1+2), and (1+3) bipartitions before and after applying measurement-based NLA. We show that appropriate conditioning on the noisy mode or on selected relay nodes systematically restores and enhances directional steering, extends both one-way and two-way steerable regions, and preserves the monogamy constraints characteristic of Gaussian graph states. Taken together, these results show that measurement-based NLA provides a practical route to distributing robust multipartite steering in CV cluster architectures, thereby strengthening the foundations for continuous-variable quantum information processing. Full article
(This article belongs to the Special Issue Recent Progress in Optical Quantum Information and Communication)
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12 pages, 1599 KB  
Article
Simulation Analysis of Atmospheric Transmission Performance for Different Beam Types in Laser Energy Transfer
by Le Zhang, Jing Wang, Fengjie Xi and Xiaojun Xu
Photonics 2026, 13(1), 80; https://doi.org/10.3390/photonics13010080 - 16 Jan 2026
Viewed by 182
Abstract
Laser Wireless Power Transmission (LWPT), as a revolutionary energy supply technology, holds broad application prospects in areas such as drone endurance, space solar energy transmission, and power supply in remote regions. The core efficiency of this technology primarily depends on the energy concentration [...] Read more.
Laser Wireless Power Transmission (LWPT), as a revolutionary energy supply technology, holds broad application prospects in areas such as drone endurance, space solar energy transmission, and power supply in remote regions. The core efficiency of this technology primarily depends on the energy concentration and uniformity of the light spot at the receiving end. Through systematic simulation analysis, this paper studies the spot uniformity and energy transmission efficiency of Gaussian beams, vortex beams, and flat-topped beams under different atmospheric conditions (turbulence intensity, visibility) and transmission distances. By quantitatively analyzing key indicators such as light spot non-uniformity and power density within the bucket, the advantages and disadvantages of the three beam types are comprehensively evaluated. The results indicate that the flat-topped beam is the optimal choice for short-distance laser energy transfer under favorable atmospheric conditions, while the vortex beam exhibits the best overall performance and robustness in medium and strong turbulence transmission environments. This study provides a theoretical basis for beam selection in different application scenarios. Full article
(This article belongs to the Special Issue Challenges and Future Directions in Adaptive Optics Technology, 2nd Edition)
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10 pages, 2513 KB  
Article
Near-Infrared Absorption Enhancement of GaAs Photocathode Through “Sandwich” Micro-Nano Structure
by Ziyang Xiao, Miao Dong, Yonggang Huang, Jinhui Yang, Peng Jiao, Pan Shi, Yajie Du, Ying He, Jing Cheng and Yinsheng Xu
Photonics 2026, 13(1), 79; https://doi.org/10.3390/photonics13010079 - 16 Jan 2026
Viewed by 166
Abstract
In this paper, a nano-layered transmission GaAs photocathode structure is proposed. The near-infrared absorption of the photocathode is enhanced by inserting a “sandwich” structure of nano-SiO2 layer + Si3N4 nanopillar array + nano-SiO2 layer between the cathode optical [...] Read more.
In this paper, a nano-layered transmission GaAs photocathode structure is proposed. The near-infrared absorption of the photocathode is enhanced by inserting a “sandwich” structure of nano-SiO2 layer + Si3N4 nanopillar array + nano-SiO2 layer between the cathode optical window and the photocathode. Compared with the flat film structure GaAs photocathode used in the current third-generations image intensifiers, the optical absorption of the optimized “sandwich” structure GaAs photocathode in the near-infrared band has been significantly improved: when the wavelength λ is 868 nm and 896 nm, the optical absorption is increased by 41.69%, 55.08%, respectively. The effects of structural parameters including film thickness and grating filling medium on the light absorption of photocathode are investigated. The results show that the near-infrared light absorption enhancement is the most obvious when Si3N4 is selected as the grating filling medium for the current design, and the deposition of SiO2 film with 10 nm thickness could effectively prevent the damage of Si3N4 during bonding with the photocathode. The theoretical analyses offer important guidance in material selection and structural optimization in the grating cathode optical window used in the third-generation image intensifier for improving performance. Full article
(This article belongs to the Special Issue New Perspectives in Micro-Nano Optical Design and Manufacturing)
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11 pages, 5921 KB  
Article
MWIR Meanderline Reflective Quarter-Wave Plate
by Bhanu Ghimire and Glenn D. Boreman
Photonics 2026, 13(1), 78; https://doi.org/10.3390/photonics13010078 - 16 Jan 2026
Viewed by 182
Abstract
We present, for the first time, a design and measured data for a meanderline reflective quarter-wave plate suitable for operation in the 3- to 5-micron MWIR band. Across this spectral range, the reflection coefficient is around 80%, the axial ratio is less than [...] Read more.
We present, for the first time, a design and measured data for a meanderline reflective quarter-wave plate suitable for operation in the 3- to 5-micron MWIR band. Across this spectral range, the reflection coefficient is around 80%, the axial ratio is less than 2, and the polarization conversion ratio is above 75%. We also demonstrate experimentally that the meanderline structure has stable performance as a reflective quarter-wave plate over a 20-degree angular bandwidth centered around incident angles between 35 and 55 degrees. One notable difference as compared to LWIR meanderline waveplates is that the vertical height of the grid lines is necessarily larger, to keep the relative phase between TE and TM near 90°. Full article
(This article belongs to the Special Issue Optical Metasurfaces: Applications and Trends)
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14 pages, 2941 KB  
Article
High-Sensitivity Optical Sensor Driven by the High-Q Quasi-Bound States in the Continuum of an Asymmetric Bow-Tie Metasurface
by Zanhui Chen, Jiandao Huang, Qinghao Tan, Gongli Xiao, Tangyou Sun, Fabi Zhang, Ahmad Syahrin Idris, Qiping Zou, Haiou Li and Guowei Lu
Photonics 2026, 13(1), 77; https://doi.org/10.3390/photonics13010077 - 16 Jan 2026
Viewed by 251
Abstract
All-dielectric metasurfaces based on quasi-bound states in the continuum (quasi-BICs) have emerged as a powerful platform for nanophotonic sensing, as they support high-Q resonances and strong near-field enhancements. Herein, we propose and numerically investigate an asymmetric bow-tie metasurface composed of two silicon semi-cylinders [...] Read more.
All-dielectric metasurfaces based on quasi-bound states in the continuum (quasi-BICs) have emerged as a powerful platform for nanophotonic sensing, as they support high-Q resonances and strong near-field enhancements. Herein, we propose and numerically investigate an asymmetric bow-tie metasurface composed of two silicon semi-cylinders with unequal radii and a central bar to achieve a quasi-BIC resonance with a Q-factor of 11,000. The transition mechanism of the BIC modes in the asymmetric bow-tie metasurface is analyzed. Additionally, the spectral features of the asymmetric bow-tie metasurface as a function of the refractive index and temperature of the local environment are also investigated. The proposed structure exhibits a refractive index sensitivity of 454 nm/RIU and a temperature sensitivity of 134 pm/°C. Furthermore, a high figure of merit (FOM) of 3159 RIU−1 is achieved, and the nearly 100% modulation depth maintained across three distinct resonance dips. Our study suggests that the proposed asymmetric bow-tie metasurface offers a promising approach for the development of high-sensitivity biosensing platforms. Full article
(This article belongs to the Special Issue Photonics for Emerging Applications in Communication and Sensing, 2nd Edition)
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21 pages, 28550 KB  
Article
Design, Calibration, and On-Site Validation of an LCVR-Driven Fast-Tunable Lyot Filter for the YOGIS Coronagraph
by Tengfei Song, Yu Liu, Xuefei Zhang, Mingyu Zhao and Zhen Li
Photonics 2026, 13(1), 76; https://doi.org/10.3390/photonics13010076 - 16 Jan 2026
Viewed by 186
Abstract
The Lyot filter, a fundamental element of the Yunnan Observatories Coronagraph Green-line Imaging System (YOGIS) at Lijiang Observatory, utilizes a Liquid Crystal Variable Retarder (LCVR) for swift electrical modulation. This filter allows for precise observations of the coronal green line (Fe XIV, central [...] Read more.
The Lyot filter, a fundamental element of the Yunnan Observatories Coronagraph Green-line Imaging System (YOGIS) at Lijiang Observatory, utilizes a Liquid Crystal Variable Retarder (LCVR) for swift electrical modulation. This filter allows for precise observations of the coronal green line (Fe XIV, central wavelength 5303 Å) with a narrow full-width at half-maximum (FWHM) of 1 Å and enables rapid adjustment of the transmission band wavelength. This feature aids in capturing the sky background intensity around the green line and images of two line wings (offset by ±0.45 Å from the central wavelength), crucial for determining the green line’s Doppler shift. By employing sky background subtraction and processing line wing images, an improved signal-to-noise ratio (SNR) in coronal green line images is achieved. The YOGIS Lyot filter, an enhancement of the NOrikura Green-line Imaging System (NOGIS) filter, operates at a wavelength of 5303 Å, offers a wavelength tuning range of ±2 Å, and tunes within <60 ms. This study elucidates the filter’s design principles, outlines essential calibration procedures, and validates its performance through on-site observations using the YOGIS. Full article
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15 pages, 5058 KB  
Article
Optimizing the Focusing Performance of Diffractive Optical Elements by Integrated Structure Techniques and Laser Lithography
by Hieu Tran Doan Trung, Young-Sik Ghim and Hyug-Gyo Rhee
Photonics 2026, 13(1), 75; https://doi.org/10.3390/photonics13010075 - 15 Jan 2026
Viewed by 349
Abstract
Diffractive optical elements (DOEs) offer significant advantages over conventional refractive optics, particularly in non-visible spectral regions such as ultraviolet, gamma rays, and X-rays, where material limitations restrict traditional optical components. Owing to their design flexibility, DOEs enable the generation of complex beam profiles—including [...] Read more.
Diffractive optical elements (DOEs) offer significant advantages over conventional refractive optics, particularly in non-visible spectral regions such as ultraviolet, gamma rays, and X-rays, where material limitations restrict traditional optical components. Owing to their design flexibility, DOEs enable the generation of complex beam profiles—including circular, vortex, and Airy beams—across a wide range of wavelengths. Despite their structural simplicity and compatibility with micro- and nanoscale fabrication, conventional DOEs often suffer from limited focusing efficiency, frequently requiring additional refractive lenses that introduce optical aberrations, increased system complexity, and higher cost. In this work, we present an integrated design and fabrication approach for micro-scale diffractive optical elements capable of achieving high focusing performance without reliance on supplementary optical components. A machine learning-based decision tree method is employed to generate optimized writing paths, which are subsequently fabricated using direct laser lithography. The proposed integrated DOE structures enable efficient focusing of multiple customized beam profiles within a compact and standalone optical element. This approach improves optical efficiency while maintaining low fabrication cost and system simplicity. The demonstrated integrated micro-DOEs provide a scalable and versatile platform for advanced beam shaping and focusing applications in photonics, particularly where compactness and performance are critical. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
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5 pages, 147 KB  
Editorial
Editorial Review: Group IV Photonics—Advances and Applications
by Alex Yasha Yi
Photonics 2026, 13(1), 74; https://doi.org/10.3390/photonics13010074 - 14 Jan 2026
Viewed by 204
Abstract
n/a n/a n/a Full article
(This article belongs to the Special Issue Group IV Photonics: Advances and Applications)
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