Photonics

38 pages, 10775 KiB

Open AccessReview

Comparison of Thin-Film Lithium Niobate, SOH, and POH for Silicon Photonic Modulators

by Tai-Cheng Yu, An-Chen Liu, Wei-Ta Huang, Chang-Chin Wu, Chung-Hsun Li, Tsung-Sheng Kao, Shu-Wei Chang, Chin-Wei Sher, Huang-Yu Lin, Chi-Wai Chow and Hao-Chung Kuo

Photonics 2025, 12(5), 429; https://doi.org/10.3390/photonics12050429 - 29 Apr 2025

Abstract

Optical modulators are indispensable components in optical communication systems and must be designed to minimize insertion loss, reduce driving voltage, and enhance linearity. State-of-the-art silicon modulator technology has limitations in terms of power, performance, and spatial size. The addition of materials such as [...] Read more.

Optical modulators are indispensable components in optical communication systems and must be designed to minimize insertion loss, reduce driving voltage, and enhance linearity. State-of-the-art silicon modulator technology has limitations in terms of power, performance, and spatial size. The addition of materials such as thin-film lithium niobate (TFLN), silicon–organic hybrids (SOH), and plasma–organic hybrids (POH) has improved the modulation performance in silicon photonics. An evaluation of the differences among these modulators and their respective performance characteristics is conducted. Full article

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19 pages, 5431 KiB

Open AccessArticle

Polarization-Insensitive Silicon Grating Couplers via Subwavelength Metamaterials and Metaheuristic Optimization

by Jorge Parra

Photonics 2025, 12(5), 428; https://doi.org/10.3390/photonics12050428 - 29 Apr 2025

Abstract

Silicon photonics is the leading platform in photonic integrated circuits (PICs), enabling dense integration and low-cost manufacturing for applications such as data communications, artificial intelligence, and quantum processing, to name a few. However, efficient and polarization-insensitive fiber-to-PIC coupling for multipoint wafer characterization remains [...] Read more.

Silicon photonics is the leading platform in photonic integrated circuits (PICs), enabling dense integration and low-cost manufacturing for applications such as data communications, artificial intelligence, and quantum processing, to name a few. However, efficient and polarization-insensitive fiber-to-PIC coupling for multipoint wafer characterization remains a challenge due to the birefringence of silicon waveguides. Here, we address this issue by proposing polarization-insensitive grating couplers based on subwavelength dielectric metamaterials and metaheuristic optimization. Subwavelength periodic structures were engineered to act as uniaxial homogeneous linear (UHL) materials, enabling tailored anisotropy. On the other hand, particle swarm optimization (PSO) was employed to optimize the coupling efficiency, bandwidth, and polarization-dependent loss (PDL). Numerical simulations demonstrated that a pitch of 100 nm ensures UHL behavior while minimizing leaky waves. Optimized grating couplers achieved coupling efficiencies higher than −3 dB and a PDL of below 1 dB across the telecom C-band (1530–1565 nm). Three optimization strategies were explored, balancing efficiency, the bandwidth, and the PDL while considering the Pareto front. This work establishes a robust framework combining metamaterial engineering with computational optimization, paving the way for high-performance polarization-insensitive grating couplers with potential uses in advanced photonic applications. Full article

(This article belongs to the Special Issue Photonics Metamaterials: Processing and Applications)

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16 pages, 3126 KiB

Open AccessArticle

Waveguide Coupled Full-Color Quantum Dot Light-Emitting Diodes Modulated by Microcavities

by Yilan Zhang, Wenhao Wang, Fankai Zheng, Jiajun Zhu, Guanding Mei, Yuxuan Ye, Jieyu Tan, Hechun Zhang, Qiang Jing, Bin He, Kai Wang and Dan Wu

Photonics 2025, 12(5), 427; https://doi.org/10.3390/photonics12050427 - 29 Apr 2025

Abstract

Integrated light-emitting diodes (LEDs) with waveguides play an important role in applications such as augmented reality (AR) displays, particularly regarding coupling efficiency optimization. Quantum dot light-emitting diodes (QLEDs), an emerging high-performance optoelectronic device, demonstrate substantial potential for next-generation display technologies. This study investigates [...] Read more.

Integrated light-emitting diodes (LEDs) with waveguides play an important role in applications such as augmented reality (AR) displays, particularly regarding coupling efficiency optimization. Quantum dot light-emitting diodes (QLEDs), an emerging high-performance optoelectronic device, demonstrate substantial potential for next-generation display technologies. This study investigates the influence of microcavity modulation on the output of QLEDs coupled with a silicon nitride (SiNx) waveguide by simulating a white light QLED (W-QLED) with a broad spectrum and mixed RGB QDs (RGB-QLED) with a comparatively narrower spectrum. The microcavity converts both W-QLED and RGB-QLED emissions from broadband white-light emissions into narrowband single-wavelength outputs. Specifically, both of them have demonstrated wavelength tuning and full-width at half-maximum (FWHM) narrowing across the visible spectrum from 400 nm to 750 nm due to the microcavity modulation. The resulting RGB-QLED achieves a FWHM of 11.24 nm and reaches 110.76% of the National Television System Committee 1953 (NTSC 1953) standard color gamut, which is a 20.95% improvement over W-QLED. Meanwhile, due to the Purcell effect of the microcavity, the output efficiency of the QLED coupled with a SiNx waveguide is also significantly improved by optimizing the thickness of the Ag anode and introducing a tilted reflective mirror into the SiNx waveguide. Moreover, the optimal output efficiency of RGB-QLED with the tilted Ag mirror is 10.13%, representing a tenfold increase compared to the sample without the tilted Ag mirror. This design demonstrates an efficient and compact approach for the near-eye full-color display technology. Full article

(This article belongs to the Special Issue Quantum Dot Light-Emitting Diodes: Innovations and Applications)

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16 pages, 3746 KiB

Open AccessArticle

Theoretical Research on Large Field-of-View Polarization Imaging Based on Dynamic Vision Sensors

by Xiaotian Lu, Kunpeng Xing, Siran Li, Ziyu Gu and Lei Xin

Photonics 2025, 12(5), 426; https://doi.org/10.3390/photonics12050426 - 29 Apr 2025

Abstract

The combination of dynamic vision sensors (DVSs) and polarization can overcome the limitation of DVSs whereby they can only detect dynamic scenes, and it also has the ability to detect artificial targets and camouflaged targets, and is thus expected to become a new [...] Read more.

The combination of dynamic vision sensors (DVSs) and polarization can overcome the limitation of DVSs whereby they can only detect dynamic scenes, and it also has the ability to detect artificial targets and camouflaged targets, and is thus expected to become a new means of remote sensing detection. Remote sensing detection often requires the field-of-view (FOV) and width to be large enough to improve detection efficiency, but when large FOV polarization imaging is performed, the polarization state in the edge FOV and the center FOV will not be consistent, which does not meet the paraxial approximation condition, and the inconsistency increases as the angle between the incident light and the optical axis increases. This affects the accuracy of target detection, so in this paper, based on the characteristics of polarization imaging using a DVS, factors such as the polarizer rotation step, incident light polarization state, and incident angle are considered to establish a theoretical model of large FOV polarization imaging using DVSs. And the influence of the detection ability is analyzed for three types of incident conditions, namely linearly polarized light, natural light, and partially polarized light. The results show that when the rotation step is 5°, the highest false alarm rate for natural light incident in the edge FOV will be nearly 53%, and the highest false alarm rate for linearly polarized light incident will be nearly 32%. Full article

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15 pages, 8047 KiB

Open AccessArticle

Compact Four-Channel Optical Emission Module with High Gain

by Xiying Dang, Linyi Li, Man Chen, Zijian Hu, Tianyu Yang, Zeping Zhao and Zhike Zhang

Photonics 2025, 12(5), 425; https://doi.org/10.3390/photonics12050425 - 28 Apr 2025

Abstract

In this paper, a four-channel optical emission module is developed using hybrid integration technology that integrates directly modulated laser (DML) chips, low-noise amplifier (LNA) chips, and control circuits, with dimensions of 24.4 mm × 21 mm × 5.9 mm. This module enables high-gain [...] Read more.

In this paper, a four-channel optical emission module is developed using hybrid integration technology that integrates directly modulated laser (DML) chips, low-noise amplifier (LNA) chips, and control circuits, with dimensions of 24.4 mm × 21 mm × 5.9 mm. This module enables high-gain signal output and minimizes crosstalk between neighboring channels while improving integration. An equivalent circuit model of radio frequency (RF) signal transmission is established, and the accuracy of the model and the effectiveness of the approach to improve signal gain are verified using simulations and experiments. With optimized thermal management, the module has the ability to operate at stable temperatures across an ambient range of −55 °C to 75 °C. The module has a channel wavelength spacing of approximately 1 nm, and the −3 dB bandwidth of each channel exceeds 20 GHz. The crosstalk between neighboring channels is less than −65 dB. In the range of 0.8~25 GHz, the four-channel gain is approximately 15 dB through the integration of the LNA chip. The module achieves a noise figure (NF) of less than 30 dB. Full article

(This article belongs to the Special Issue Microwave Photonics: Science and Applications)

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20 pages, 2763 KiB

Open AccessReview

Recent Advances of Guided Mode Resonant Sensors Applied to Cancer Biomarker Detection

by Pankaj K. Sahoo, Arshad Ahmad Bhat, Mandeep Singh and Kezheng Li

Photonics 2025, 12(5), 424; https://doi.org/10.3390/photonics12050424 - 28 Apr 2025

Abstract

Guided mode resonance (GMR)-based sensors have emerged as a promising technology for the early screening of cancer, offering advantages such as sensitivity, specificity, low cost, non-invasiveness, and portability. This review article provides a comprehensive overview of the latest advancements in GMR technology and [...] Read more.

Guided mode resonance (GMR)-based sensors have emerged as a promising technology for the early screening of cancer, offering advantages such as sensitivity, specificity, low cost, non-invasiveness, and portability. This review article provides a comprehensive overview of the latest advancements in GMR technology and its applications in biosensing, with a specific focus on cancer. The current state of cancer diagnosis and the critical need for point-of-care (POC) devices to address these challenges are discussed in detail. Furthermore, the review systematically explores various strategies employed in GMR-based cancer detection including design principles and the integration of advanced technologies. Additionally, it aims to provide researchers valuable insights for developing GMR sensors capable of detecting cancer biomarkers outside the laboratory environment. Full article

(This article belongs to the Section Biophotonics and Biomedical Optics)

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10 pages, 3231 KiB

Open AccessArticle

A Flexible Photonic Method for Angle-of-Arrival and Frequency Measurements

by Yunkun Luo, Yang Jiang, Jing Xu, Xiaohong Lan, Jinjian Feng, Jiancheng Yu, Qianyou Long, Tingyi Jiang, Hui Zhang and Yu Wu

Photonics 2025, 12(5), 423; https://doi.org/10.3390/photonics12050423 - 28 Apr 2025

Abstract

A microwave photonic approach for measuring the angle of arrival (AOA) and frequency is proposed and experimentally demonstrated. The AOA-dependent phase difference and frequency of two received signals were mapped to intensity information through subtractive and differential operations, which were achieved by a [...] Read more.

A microwave photonic approach for measuring the angle of arrival (AOA) and frequency is proposed and experimentally demonstrated. The AOA-dependent phase difference and frequency of two received signals were mapped to intensity information through subtractive and differential operations, which were achieved by a delayed superposition structure with phase inversion. By measuring the output signal powers, both the phase difference and frequency of the two signals could be determined. The theoretical analysis results are given in detail. In this proof-of-concept experiment, the system had a phase difference measurement range of 340 degrees, with a maximum error of 2.9 degrees. The frequency measurement covered 1–10 GHz, with a maximum error of 2.2%. The proposed approach offers a straightforward method for measuring the AOA and frequency under the same configuration, which provides new insight into AOA- and frequency-measurement techniques. Full article

(This article belongs to the Section New Applications Enabled by Photonics Technologies and Systems)

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17 pages, 4106 KiB

Open AccessReview

Molecular Alignment Under Strong Laser Pulses: Progress and Applications

by Ming Wang, Enliang Zhang, Qingqing Liang and Yi Liu

Photonics 2025, 12(5), 422; https://doi.org/10.3390/photonics12050422 - 28 Apr 2025

Abstract

Molecular alignment under strong laser pulses is an important tool for manipulating quantum states and investigating ultrafast phenomena. This review summarizes two decades of advancement in laser-driven alignment techniques, such as cross-polarized double pulses, optical centrifuges, and elliptically truncated fields. Given the prominent [...] Read more.

Molecular alignment under strong laser pulses is an important tool for manipulating quantum states and investigating ultrafast phenomena. This review summarizes two decades of advancement in laser-driven alignment techniques, such as cross-polarized double pulses, optical centrifuges, and elliptically truncated fields. Given the prominent emphasis on transformational applications in current alignment research, we outline its importance in cutting-edge applications under strong laser pulses, such as chiral discrimination, high-harmonic generation (HHG), photoelectron angular distributions (PADs) and ionization yields in photoionization, and Terahertz (THz) manipulation. These interdisciplinary developments provide fundamental insights into ultrafast molecular dynamics. They also establish frameworks for advanced light–matter interaction control. Full article

(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)

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16 pages, 3858 KiB

Open AccessArticle

Feasibility and Safety of Endoscopic Balloon-Assisted Laser Treatment (EBLT) for Gastroesophageal Reflux Disease: Functional, Structural, and Gene Expression Analysis in Preclinical Model

by Boram Cha, Hyejin Kim, Van Gia Truong, Sun-Ju Oh, Seok Jeong and Hyun Wook Kang

Photonics 2025, 12(5), 421; https://doi.org/10.3390/photonics12050421 - 28 Apr 2025

Abstract

Gastroesophageal reflux disease (GERD) is a prevalent disorder caused by lower esophageal sphincter (LES) dysfunction, often requiring long-term treatment. This study assessed the feasibility of endoscopic balloon-assisted laser treatment (EBLT) using a porcine GERD model. One week after GERD induction, EBLT was performed [...] Read more.

Gastroesophageal reflux disease (GERD) is a prevalent disorder caused by lower esophageal sphincter (LES) dysfunction, often requiring long-term treatment. This study assessed the feasibility of endoscopic balloon-assisted laser treatment (EBLT) using a porcine GERD model. One week after GERD induction, EBLT was performed on three animals, while one served as a control. A 980 nm continuous-wave laser was delivered at 30 W for 90 s (energy = 2700 J and power density = 2.17 W/cm²) in a circumferential, non-contact manner using a balloon-assisted catheter. Real-time mucosal temperature monitoring was achieved using a fiber Bragg grating (FBG) sensor integrated with the balloon, maintaining temperatures below 40 °C. Endoscopic ultrasound and manometry were used to evaluate LES thickness and pressure before and after treatment. After a 12-week observation period, esophageal tissues were harvested for histological and gene expression analysis. Compared to the control, the treated group showed an increase in LES thickness (3.6 ± 0.2 mm vs. 1.5 mm) and relative LES pressure changes (2.9 ± 1.6 vs. 0.6). Upregulation of fibrosis- and hypertrophy-related genes suggested structural remodeling of the LES. No adverse effects or mucosal injury were observed. These findings support EBLT as a promising and minimally invasive strategy for GERD treatment. Full article

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10 pages, 5727 KiB

Open AccessArticle

Dual-Band Topological Valley Cavity in Mid-Infrared Range

by Chen Kang, Jinling Yu, Can Chen, Yunfeng Lai, Shuying Cheng, Yonghai Chen, Yuan Li, Shuman Liu, Jinchuan Zhang and Fengqi Liu

Photonics 2025, 12(5), 420; https://doi.org/10.3390/photonics12050420 - 28 Apr 2025

Abstract

Topological edge states, emerging at boundaries between regions with distinct topological properties, enable unidirectional transmission with robustness against defects and disorder. However, achieving dual-band operation with high performance remains challenging. Here, we integrate dual-band topological edge states into a valley photonic crystal cavity [...] Read more.

Topological edge states, emerging at boundaries between regions with distinct topological properties, enable unidirectional transmission with robustness against defects and disorder. However, achieving dual-band operation with high performance remains challenging. Here, we integrate dual-band topological edge states into a valley photonic crystal cavity operating in the mid-infrared region, leveraging triangular scatterers. A key contribution of this work is the simultaneous realization of ultra-high Q-factors (up to 6.1593 × 10⁹) and uniform mode distribution (inverse participation ratio < 2) across both bands. Moreover, the dual-band cavity exhibits exceptional defect tolerance. These findings provide a promising platform for mid-infrared photonic integration, paving the way for high-performance optical cavities in multifunctional photonic systems. Full article

(This article belongs to the Section Lasers, Light Sources and Sensors)

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18 pages, 5158 KiB

Open AccessArticle

Research on Maximum Likelihood Decoding Algorithm and Channel Characteristics Optimization for 4FSK Ultraviolet Communication System Based on Poisson Distribution

by Li Kuang, Yingkai Zhao, Kangjian Li, Xingfa Wang, Linyi Li, Huishi Zhu, Weijie Zhang and Jianguo Liu

Photonics 2025, 12(5), 419; https://doi.org/10.3390/photonics12050419 - 27 Apr 2025

Abstract

This study focuses on a 4FSK-modulated ultraviolet (UV) communication system, introducing an innovative symbol-level maximum likelihood decoding approach based on Poisson statistics. A forward error correction (FEC) coding mechanism is integrated to enhance system robustness. Through Monte Carlo simulations, the proposed decoding scheme [...] Read more.

This study focuses on a 4FSK-modulated ultraviolet (UV) communication system, introducing an innovative symbol-level maximum likelihood decoding approach based on Poisson statistics. A forward error correction (FEC) coding mechanism is integrated to enhance system robustness. Through Monte Carlo simulations, the proposed decoding scheme and the error correction performances of Reed–Solomon (RS) and Low-Density Parity-Check (LDPC) codes are evaluated in UV channels. Both RS and LDPC codes significantly improve the Bit Error Rate (BER), with LDPC codes achieving superior gains under low SNR conditions. Hardware implementation and field tests validate the decoding algorithm and LDPC-optimized 4FSK system. Under non-line-of-sight (NLOS) conditions (10–45° transmit elevation angle), stable 60 m communication with BER < 10⁻³ is achieved. In line-of-sight (LOS) scenarios, the system demonstrates 900 m range with BER < 10⁻³, highlighting practical applicability in challenging atmospheric environments. Full article

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14 pages, 2088 KiB

Open AccessReview

Optical Link Design for Quantum Key Distribution-Integrated Optical Access Networks

by Sunghyun Bae and Seok-Tae Koh

Photonics 2025, 12(5), 418; https://doi.org/10.3390/photonics12050418 - 27 Apr 2025

Abstract

To achieve commercial scalability, fiber-based quantum key distribution (QKD) systems must be integrated into existing optical communication infrastructures, rather than deployed exclusively on dedicated dark fibers. Integrating QKD into optical access networks (OANs) would be particularly advantageous, as these networks provide direct connectivity [...] Read more.

To achieve commercial scalability, fiber-based quantum key distribution (QKD) systems must be integrated into existing optical communication infrastructures, rather than deployed exclusively on dedicated dark fibers. Integrating QKD into optical access networks (OANs) would be particularly advantageous, as these networks provide direct connectivity to end users for whom security is critical. Such integration can address the inherent security vulnerabilities in current OANs, which are primarily based on time-division multiplexing passive optical networks (TDM-PONs). However, integrating QKD into PONs poses significant challenges due to Raman noise and other detrimental effects induced by PON signals, which intensify as the launched power of PONs increases to support higher transmission speeds. In this study, we review recent advancements in both QKD and access network technologies, evaluate the technical feasibility of QKD-OAN integration, and propose cost-effective strategies to facilitate the widespread deployment of QKD in future access networks. Full article

(This article belongs to the Special Issue Optical Signal Processing for Advanced Communication Systems)

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15 pages, 371 KiB

Open AccessArticle

Circuit-QED for Multi-Loop Fluxonium-Type Qubits

by Larisa-Milena Pioraş-Ţimbolmaş, Levente Máthé and Liviu P. Zârbo

Photonics 2025, 12(5), 417; https://doi.org/10.3390/photonics12050417 - 25 Apr 2025

Abstract

Fluxonium qubits, designed to mitigate charge noise and enhance anharmonicity, are among the most promising superconducting platforms for quantum computing. To understand and exploit their quantum properties and design novel fluxonium-based architectures with improved functionalities, these systems require an accurate Hamiltonian formulation to [...] Read more.

Fluxonium qubits, designed to mitigate charge noise and enhance anharmonicity, are among the most promising superconducting platforms for quantum computing. To understand and exploit their quantum properties and design novel fluxonium-based architectures with improved functionalities, these systems require an accurate Hamiltonian formulation to capture their energy level structure and quantum dynamics. This work presents a systematic method for constructing the Hamiltonian for multi-loop circuits that partitions the system into a set of uncoupled harmonic oscillators and a coupled anharmonic part originating from the Josephson circuit elements, allowing clear identification of independent modes and isolating the nonlinearity in the Josephson terms. While demonstrated for fluxonium-type multi-loop circuits, this method can be generalized to other superconducting qubit architectures within the broader context of circuit QED, making it a versatile tool for exploring different circuit configurations. Our systematic and flexible modeling approach forms the theoretical basis for the qubit measurement and control experiments validating multi-loop fluxonium architectures. Full article

(This article belongs to the Special Issue Quantum Dot Light-Emitting Diodes: Innovations and Applications)

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11 pages, 4986 KiB

Open AccessArticle

Improved Optical Signal Processing with On-Chip Programmable Filter

by Tiantian Li, Yumeng Liu, Luwen Xing, Shuo Lang, Zhangfeng Ge, Dongdong Han, Zhanqiang Hui, Huimin Du and Haowen Shu

Photonics 2025, 12(5), 416; https://doi.org/10.3390/photonics12050416 - 25 Apr 2025

Abstract

Bandwidth-limited transmitters have become a severe issue with the rapid growth of bandwidth-hungry services. We investigate the impact of an on-chip optical pre-emphasizer on a bandwidth-limited transmitter and quantitatively analyze the results of bandwidth extension. Improvements in eye diagram performance are discussed. The [...] Read more.

Bandwidth-limited transmitters have become a severe issue with the rapid growth of bandwidth-hungry services. We investigate the impact of an on-chip optical pre-emphasizer on a bandwidth-limited transmitter and quantitatively analyze the results of bandwidth extension. Improvements in eye diagram performance are discussed. The 3 dB electro-optical bandwidth of the transmission system is effectively extended from 18 GHz to 40 GHz. The extinction ratio of the on–off keying (OOK) signal at data rates of 20 to 50 Gbps is improved by 0.64–3.2 dB. Additionally, the Q factor of the eye diagram increases by 0.78–4.36 at data rates ranging from 20 to 50 Gbps. Full article

(This article belongs to the Special Issue Advanced Fiber Laser Technology and Its Application)

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15 pages, 2584 KiB

Open AccessArticle

Measurement of Coherence Time in Cold Atom-Generated Tunable Photon Wave Packets Using an Unbalanced Fiber Interferometer

by Ya Li, Wanru Wang, Qizhou Wu, Youxing Chen, Can Sun, Hai Wang and Weizhe Qiao

Photonics 2025, 12(5), 415; https://doi.org/10.3390/photonics12050415 - 25 Apr 2025

Abstract

In the realm of quantum communication and photonic technologies, the extension of coherence time for photon wave packets is essential for improving system efficacy. This research introduces a methodology for measuring coherence time utilizing an unbalanced fiber interferometer, specifically designed for tunable pulse-width [...] Read more.

In the realm of quantum communication and photonic technologies, the extension of coherence time for photon wave packets is essential for improving system efficacy. This research introduces a methodology for measuring coherence time utilizing an unbalanced fiber interferometer, specifically designed for tunable pulse-width photon wave packets produced by cold atoms. By synchronously generating write pulses, signal light, and frequency-locking light from a single laser source, the study effectively mitigated frequency discrepancies that typically arise from the use of multiple light sources. The implementation of frequency-resolved photon counting under phase-locked conditions was accomplished through the application of polarization filtering and cascaded filtering techniques. The experimental results indicated that the periodicity of frequency shifts in interference fringe patterns diminishes as the differences in delay arm lengths increase, while fluctuations in fiber length and high-frequency laser jitter adversely affect interference visibility. Through an analysis of the correlation between delay and photon counts, the coherence time of the write laser was determined to be 2.56 µs, whereas the Stokes photons produced through interactions with cold atoms exhibited a reduced coherence time of 1.23 µs. The findings suggest that enhancements in laser bandwidth compression and fiber phase stability could further prolong the coherence time of photon wave packets generated by cold atoms, thereby providing valuable technical support for high-fidelity quantum information processing. Full article

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21 pages, 10397 KiB

Open AccessArticle

Design and Analysis of High-Precision Workbench with Large Stroke and Heavy Load for Fabricating Large-Area Grating

by Guangdong Yu, Heshig Bayan, Qi Chen, Hao Chen, Xin He and Xuefeng Yao

Photonics 2025, 12(5), 414; https://doi.org/10.3390/photonics12050414 - 24 Apr 2025

Abstract

When scanning beam interference lithography (SBIL) technology is used for grating fabrication, the stroke, bearing capacity, and accuracy of the workbench determine the size and accuracy of the grating. For large-area gratings with dimensions exceeding the meter level, the existing workbench cannot fully [...] Read more.

When scanning beam interference lithography (SBIL) technology is used for grating fabrication, the stroke, bearing capacity, and accuracy of the workbench determine the size and accuracy of the grating. For large-area gratings with dimensions exceeding the meter level, the existing workbench cannot fully meet the requirements. Therefore, the structure design, drive type, and assembly technology of the workbench were studied in this research, and a two-dimensional workbench with a large stroke, heavy load, and high precision was developed. The performance of this workbench was tested. The stroke of the workbench can reach 1800 mm × 700 mm; the straightness is better than 1.5 μm for the whole stroke range. The load can be up to 2.5 t and the positioning accuracy can achieve the nanometer level. A scanning exposure experiment was carried out with this workbench and a grating of 1400 mm × 420 mm was made. The performance index of the grating was outstanding, achieving the intended goals of the experiment. Full article

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23 pages, 4596 KiB

Open AccessReview

Multimodal Imaging in Stem Cell Therapy for Retinal Disease

by Mi Zheng and Yannis M. Paulus

Photonics 2025, 12(5), 413; https://doi.org/10.3390/photonics12050413 - 24 Apr 2025

Abstract

Stem cell therapy has emerged as a promising approach for treating various retinal diseases, particularly degenerative retinal diseases such as geographic atrophy in age-related macular degeneration (AMD), retinitis pigmentosa (RP), and Stargardt disease. A wide variety of imaging techniques have been employed in [...] Read more.

Stem cell therapy has emerged as a promising approach for treating various retinal diseases, particularly degenerative retinal diseases such as geographic atrophy in age-related macular degeneration (AMD), retinitis pigmentosa (RP), and Stargardt disease. A wide variety of imaging techniques have been employed in both preclinical and clinical settings to assess the efficacy and safety of stem cell therapy for retinal diseases. These techniques can be classified into two categories: methods for imaging stem cells and those for the overall morphology and function of the retina. The techniques employed for stem cell imaging include optical imaging, magnetic resonance imaging (MRI), and radionuclide imaging. Additional imaging techniques include fundus photography, fluorescein angiography, and fundus autofluorescence. Each technique has its own advantages and disadvantages, and thus, the use of multimodal imaging can help to overcome the shortcomings and achieve a more comprehensive evaluation of stem cell therapy in retinal disease. This review discusses the characteristics of the main techniques and cell-labeling techniques applied in stem cell therapy, with a particular focus on the applications of multimodal imaging. Furthermore, this review discusses the challenges and prospects of multimodal imaging in stem cell therapy for retinal disease. Full article

(This article belongs to the Special Issue Exploring Cutting-Edge Technologies and Applications of Optics and Photonics)

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9 pages, 8350 KiB

Open AccessCommunication

Asymmetry Analysis of the Autler–Townes Doublet in the Trap-Loss Fluorescence Spectroscopy of Cesium MOT with Single-Step Rydberg Excitation

by Xiaokai Hou, Yuewei Wang, Jun He and Junmin Wang

Photonics 2025, 12(5), 412; https://doi.org/10.3390/photonics12050412 - 24 Apr 2025

Abstract

The Autler–Townes (AT) doublet, a fundamental manifestation of quantum interference effects, serves as a critical tool for studying the dynamic behavior of Rydberg atoms. Here, we investigate the asymmetry of the Autler–Townes (AT) doublet in the trap-loss fluorescence spectroscopy (TLFS) of cesium (Cs) [...] Read more.

The Autler–Townes (AT) doublet, a fundamental manifestation of quantum interference effects, serves as a critical tool for studying the dynamic behavior of Rydberg atoms. Here, we investigate the asymmetry of the Autler–Townes (AT) doublet in the trap-loss fluorescence spectroscopy (TLFS) of cesium (Cs) atoms confined in a magneto-optical trap (MOT) with single-step Rydberg excitation using a 319-nm ultraviolet (UV) laser. A V-type three-level system involving the ground state

6 S_{1 / 2}

(F = 4), excited state

6 P_{3 / 2}

(

F^{'}

= 5), and Rydberg state (

n P_{3 / 2}

(

m_{J}

= +3/2)) is theoretically modeled to analyze the nonlinear dependence of the AT doublet’s asymmetry and interval on the cooling laser’s detuning. Experiments reveal that as the cooling laser detuning

Δ_{1}

decreases from −15 MHz to −10 MHz, the AT doublet exhibits increasing symmetry, while its interval shows a nonlinear decrease. Theoretical simulations based on the density matrix equation and Lindblad master equation align closely with experimental data, confirming the model’s validity. This study provides insights into quantum interference dynamics in multi-level systems and offers a systematic approach for optimizing precision measurements in cold atom spectroscopy. Full article

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13 pages, 3166 KiB

Open AccessArticle

Dynamic Measurement of Flowing Microparticles in Microfluidics Using Pulsed Modulated Digital Holographic Microscopy

by Yunze Lei, Yuge Li, Xiaofang Wang, Kequn Zhuo, Ying Ma, Sha An, Juanjuan Zheng, Kai Wen, Lihe Yan and Peng Gao

Photonics 2025, 12(5), 411; https://doi.org/10.3390/photonics12050411 - 24 Apr 2025

Abstract

We propose a pulsed modulated digital holographic microscopy (PM-DHM) technique for the dynamic measurement of flowing microparticles in microfluidic systems. By digitally tuning the pulse width and the repetition rate of a laser source within a single-frame exposure, this method enables the recording [...] Read more.

We propose a pulsed modulated digital holographic microscopy (PM-DHM) technique for the dynamic measurement of flowing microparticles in microfluidic systems. By digitally tuning the pulse width and the repetition rate of a laser source within a single-frame exposure, this method enables the recording of multiple images of flowing microparticles at different time points within a single hologram, allowing the quantification of velocity and acceleration. We demonstrate the feasibility of PM-DHM by measuring the velocity, acceleration, and forces exerted on PMMA microspheres and red blood cells flowing in microfluidic chips. Compared to traditional frame-sampling-based imaging methods, this technique has a much higher time resolution (in a range of microseconds) that is limited only by the pulse duration. This method demonstrates significant potential for high-throughput label-free flow cytometry detection and offers promising applications in drug development and cell analysis. Full article

(This article belongs to the Special Issue Advanced Quantitative Phase Microscopy: Techniques and Applications)

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