{"title":"Speckle Theory for Arbitrary Wavefront Illumination in Free-Space Surface Scattering","authors":"Qiyong Xu;Janan Zhou;Yipeng Mo;Zichun Le","doi":"10.1109/JPHOT.2025.3580173","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3580173","url":null,"abstract":"Speckle has been shown to cause significant degradation to the imaging quality of laser imaging systems. However, in certain complex imaging environments, it can also act as an effective information carrier. Therefore, accurate characterization of speckle is imperative. In this study, a speckle characterization theoretical model, which describes the features of speckle at arbitrary wavefront illumination in a free-space surface scattering optical path, is developed and experimentally verified. The current study elucidates the combined effect of illumination wavefront and laser wavelength on speckle contrast, further refining the statistical theory of speckle. The findings have potential applications in the prediction of speckle characteristics or environmental parameters, and are primarily relevant to non-imaging optics-related fields.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-7"},"PeriodicalIF":2.1,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11037532","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144519429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yunke Sun;Yifei Xie;Xiaotong Yan;Xu Xing;Pengcheng Hu
{"title":"Phase Response Identification of Photodetectors in High-Speed Interferometry Using Photoelectric Pseudorandom Signals","authors":"Yunke Sun;Yifei Xie;Xiaotong Yan;Xu Xing;Pengcheng Hu","doi":"10.1109/JPHOT.2025.3579506","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3579506","url":null,"abstract":"Dynamic accuracy and synchronization of high-speed interferometry are crucial for advanced manufacturing, semiconductor fabrication, and dynamic metrology, where asynchronous errors introduced by the nonlinear phase responses of photodetectors can severely degrade the measurement performance. The complex cross-physical processes make the phase responses of photodetectors challenging. Owing to their bandwidth, resolution, and test deviation limitations, the existing methods are not applicable to interferometric photodetectors. In this study, we employ a commonly available small form-factor pluggable module to generate optical pseudorandom signals as a photodetector’s excitation signals. Through correlation operations and phase spectrum analysis, the phase response of a photodetector with a 10-MHz bandwidth is identified with a model reliability of 90% and an uncertainty of 0.50° (k = 2). In practical applications, the identified phase response can help an interferometer suppress asynchronous errors to the sub-nm level within a maximum speed of 1.58 m/s. Comparative experiments verify the accuracy of the identified results and highlight substantial improvements in test precision, frequency resolution, practicality, and universality over existing methods.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-10"},"PeriodicalIF":2.1,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11034693","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144536571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Advancing OAM-Based FSO Systems: Tackling Pointing Errors for Next-Generation Space and Terrestrial Links","authors":"Mohammad Taghi Dabiri;Meysam Ghanbari;Mazen Hasna","doi":"10.1109/JPHOT.2025.3575365","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3575365","url":null,"abstract":"Orbital Angular Momentum (OAM)-based Free-Space Optical (FSO) communication systems offer immense potential for high-capacity, secure links, but their performance is highly sensitive to pointing errors. This paper provides a comprehensive analysis of OAM systems under pointing inaccuracies for both short-range terrestrial links and long-range inter-satellite communications. For short links, we demonstrate the trade-offs between increasing modulation order and the number of OAM modes, highlighting the potential of low-complexity two-stage detectors to mitigate computational overhead while maintaining robust performance. For inter-satellite links, where severe pointing errors dominate, we propose an innovative asymmetric mode design and optimal beam waist adjustment to enhance robustness against angular misalignments. Simulation results reveal critical insights into the interplay between pointing error intensity, mode selection, and system performance, offering practical guidelines for OAM system design in diverse scenarios. This work bridges the gap between theoretical modeling and real-world implementation, paving the way for reliable OAM-based communication in next-generation terrestrial and space networks.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-14"},"PeriodicalIF":2.1,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11034716","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144646505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Micromachining Error Tolerance Analysis in EEG Sensing Nanostructure Arrays: Control of Fano Resonance for Enhanced Performance","authors":"Huicheng He;Zhanzhe Huang;Huazhen Shi;Ziying Wang;Hongxia Zhang;Dagong Jia","doi":"10.1109/JPHOT.2025.3578629","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3578629","url":null,"abstract":"The silicon-based electroencephalography (EEG) sensing technology encounters performance limitations due to spectral distortions caused by micromachining, which significantly degrade its effectiveness in Brain-Computer Interface (BCI) systems. To enhance the performance of EEG sensors, this study systematically investigates the tolerance of micromachining errors in silicon-based nanostructured arrays, specifically focusing on photonic crystal nanobeam cavities (PCNCs) used in optical EEG sensing systems. We propose a comprehensive error control methodology that integrates finite-difference time-domain (FDTD) simulations with multivariate linear regression (MLR) analysis to quantitatively assess the impact of lithographic and alignment errors on Fano resonance spectral characteristics. Our analysis establishes critical tolerance boundaries: horizontal displacement errors must be maintained within −4.56 nm to +26.31 nm, and angular deviations should be constrained between −0.068° and +0.083°. By establishing precise tolerance boundaries, our approach effectively mitigates spectral distortion while enhancing production yield, thereby ensuring manufacturing consistency. Notably, this study aligns with the fundamental objective of precision allocation in conventional silicon nanocomponents: achieving target performance metrics with cost efficiency.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-13"},"PeriodicalIF":2.1,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11030254","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144472547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yaohan Kang;Daizhong Liu;Xiuqing Jiang;Lei Gong;Xingqiang Lu;Mingying Sun
{"title":"Crystal’s Self-Alignment for High Power Laser Facility Based on Machine Learning","authors":"Yaohan Kang;Daizhong Liu;Xiuqing Jiang;Lei Gong;Xingqiang Lu;Mingying Sun","doi":"10.1109/JPHOT.2025.3578673","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3578673","url":null,"abstract":"Online alignment of harmonic conversion crystal in high-power laser facilities is a challenging and labor-intensive task. An automated technique for self-alignment of crystals on these facilities is proposed based on machine learning. The crystal alignment beam is sampled using grating diffraction. This method employs a machine learning algorithm running on a Raspberry Pi to automatically locate the reflective spot from the crystal’s back surface and adjust its position to achieve alignment. The proposed scheme comprises two modules: a rectangular spiral spot scanning search method module and an automatic spot aligning method module based on the open-source Machine-Learning Online Optimization Package (M-LOOP) algorithm. M-LOOP employs Bayesian optimization based on Gaussian process probabilistic agent model. The combination of these two modules enables automatic adjustment of the laser spot to align with the reference center, thus achieving crystal alignment. The hardware system comprises a crystal alignment optical setup, motors, a CCD camera and a Raspberry Pi. Multiplexed experiments conducted on the SG-II upgraded laser facility demonstrate that the method can complete automatic search and alignment of the crystal’s reflected spot within approximately 10 minutes. This solution addresses the limitations of traditional approaches that require manual search and adjustment of the crystal’s reflected spot for alignment.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-9"},"PeriodicalIF":2.1,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11030231","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Non-Uniformity Correction Method for Uncooled Infrared Polarization Imaging Systems","authors":"Cailing Zhao;Zhiguo Fan;Yunxiang Zhang","doi":"10.1109/JPHOT.2025.3578360","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3578360","url":null,"abstract":"Uncooled infrared polarization imaging systems integrate polarization components to acquire target polarization characteristics, thereby enhancing detection capabilities. However, due to the absence of a cold screen, such systems are susceptible to non-uniform internal thermal radiation exchange, which manifests as fixed pattern noise (FPN) independent of the scene during imaging. Previous non-uniformity correction (NUC) algorithms usually couple polarization information with FPN correction, resulting in the loss of polarization characteristics. To address this issue, a two-stage decoupled correction method is proposed in this paper. Firstly, a polarization response separation method (PRSM) is designed to extract the polarization response components associated with polarization channels through a blackbody radiation reference. Subsequently, a radial distance weighted fitting (RDWF) is proposed to process parametric model and compensate for FPN based on the spatial response characteristics of the optical system. Finally, the experimental results on real-world scene images demonstrate that the proposed method effectively eliminates FPN while preserving polarization information.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-8"},"PeriodicalIF":2.1,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11029575","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144472546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Generation of Dual-Frequency Microwave Pulse Based on Active Mode-Locked Optoelectronic Oscillator","authors":"Junfeng Ren;Ping Li;Chenyang Ma;Cheng Gu;Boxiong Cui;Huitong Yang;Zhengyang Xie;Xin Zhao;Zheng Zheng","doi":"10.1109/JPHOT.2025.3578499","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3578499","url":null,"abstract":"Active mode-locked optoelectronic oscillator(AML-OEO) is a high-quality pulsed microwave source that can be used to generate microwave pulse signals in various forms. We introduce a structure for an AML-OEO, which is intended to generate dual- frequency microwave pulses. In the context of a dual-band microwave pulse sequence, each sub-pulse incorporates signals having a pair of distinct center frequencies. Different filters can be selected for adjustment according to the band requirements of different scenarios. The generated dual-band microwave pulse signals exhibit excellent phase noise performance at both carrier frequencies, we can generate pulse signals with phase noise as low as −120.9 dBc/Hz@10 kHz at 6.55 GHz and −120.5 dBc/Hz@10 kHz at 10.79 GHz. This structure is simpler and more compact, and is expected to play a role in multi-band radar, communications and other fields in the future.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-6"},"PeriodicalIF":2.1,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11029582","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144519430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Dynamic Optical Amplifiers Enable Distributed Equalization in Optical Transmission Systems","authors":"Hongqiang Zou;Da Liu;Kai Zhang","doi":"10.1109/JPHOT.2025.3578614","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3578614","url":null,"abstract":"In this paper, we design and simulated a novel dynamic gain flattening filter (DGFF) module based on polarization-insensitive liquid crystal on silicon (PI-LCoS). The DGFF module measures 26*10.5 mm in size and integrates four DGFFs. Its compact design and minimal optical components reduce costs and enhance manufacturability. In our lab, we built a 6THz C-band transmission system and compared a novel distributed equalization scheme using DGFF in EDFAs with traditional centralized schemes. Results showed that this scheme effectively balanced OSNR across channels, reducing OSNR flatness from 3.5 dB to 0.5 dB. Additionally, it decreased ROADM station attenuation, leading to an average OSNR improvement of about 0.47 dB.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-5"},"PeriodicalIF":2.1,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11030253","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144536570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Mode Optimization and Polarization Control in VCSELs with Sub-Wavelength Gratings","authors":"Yongli Wang;Chuanchuan Li;Yang Zhang;Jian Li;Xin Wei","doi":"10.1109/JPHOT.2025.3578660","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3578660","url":null,"abstract":"We have demonstrated the integration of sub-wavelength gratings (SWG) into a 795 nm vertical cavity surface emitting laser (VCSEL) with inverse surface relief to achieve coordinated control of the mode and polarization. At a grating period of around 0.5 μm and an etching depth range of 60 nm to 100 nm, the reflectivity was higher than 91%. A high reflectivity difference was introduced between different modes, effectively suppressing high-order modes with a side mode suppression ratio (SMSR) of 38 dB. The SWG exhibited different refractive indices for the transverse electric (TE) and transverse magnetic (TM) components, increasing anisotropy and thus enhancing the orthogonal polarization suppression ratio (OPSR) to 26.7 dB. The predesign and relaxed fabrication tolerances of grating parameters may facilitate the mass production of high-performance VCSELs for applications in quantum sensing systems.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-6"},"PeriodicalIF":2.1,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11030241","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144597756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lorenzo Tunesi;Vittorio Curri;Andrea Carena;Paolo Bardella
{"title":"Enhanced Bandwidth Tunability in Thermally Controlled Multi-Pitch Contra-Directional Couplers","authors":"Lorenzo Tunesi;Vittorio Curri;Andrea Carena;Paolo Bardella","doi":"10.1109/JPHOT.2025.3576041","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3576041","url":null,"abstract":"Grating-Assisted Contra Directional Couplers (GACDCs) are versatile photonic devices which can implement free-spectral-range free add-drop flat-top responses, making them interesting solutions for Wavelength Division Multiplexing (WDM) systems and many other applications requiring spectral shaping. Their bandwidth can be dynamically changed through thermal means, granting an additional degree of freedom in their design and application. Design techniques involving the periodicity of the gratings (pitch chirping) can enhance the effect of this dynamic control, leading to wider bandwidth tunability in terms of both central channel wavelength and passband width, while leaving the control mechanism and power unchanged. In this work, we investigate the limits of these effects, highlighting the advantages through simulation of both the optical response and the thermal control.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"17 4","pages":"1-11"},"PeriodicalIF":2.1,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11024028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}