{"title":"Active Intracavity Rotation Angle Sensor Based on a Simple Balloon-Shaped Fiber Ring","authors":"Zhiyu Zhang;Xiaolei Bai;Si Cheng;Chuan Tian","doi":"10.1109/LPT.2025.3609795","DOIUrl":"https://doi.org/10.1109/LPT.2025.3609795","url":null,"abstract":"An intensity-modulated active intracavity rotation angle sensor was demonstrated based on a simple balloon-type fiber. The sensor leverages macrobending-induced loss, modulated by torsional deformation, where changes in the rotation angle are converted into variations in laser output power. Through geometric optimization, the passive structure achieves <inline-formula> <tex-math>$7.34~mu $ </tex-math></inline-formula>W/° sensitivity in a limited linear range (30°–120°). By integrating the sensor into a ring fiber laser cavity, the active configuration significantly suppresses high bending loss and enhances sensitivity to 0.4719 mW/° with a 50-dB signal-to-noise ratio (SNR) improvement. The linear measurement range expands to 40°–150° (full range: 0°–180°), outperforming passive designs by two orders of magnitude in sensitivity. This work presents a compact and cost-effective solution for high-dynamic-range angular sensing.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1433-1436"},"PeriodicalIF":2.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Reconfigurable Nonlinear Activation Functions by Add-Drop Resonator Mach–Zehnder Interferometers","authors":"Weiwei Pan;Ruoyun Yao;Yu Cheng;Chen Ji","doi":"10.1109/LPT.2025.3609873","DOIUrl":"https://doi.org/10.1109/LPT.2025.3609873","url":null,"abstract":"We propose and experimentally demonstrate a reconfigurable nonlinear activation function (NAF) unit based on add-drop resonator Mach-Zehnder interferometers (ADRMZIs) for photonic neural networks. By incorporating a tunable Mach-Zehnder interferometer (MZI) as the coupler within the ADRMZI, we successfully realized four distinct nonlinear activation functions: sigmoid, leaky ReLU, sinusoidal, and Gaussian functions, utilizing chips fabricated on a silicon photonic platform. We also assessed the performance of the NAF in an artificial neural network (ANN) trained for the MNIST handwritten digit classification task. Numerical calculations based on the measured leaky ReLU function demonstrated a prediction accuracy exceeding 97.49%, significantly surpassing the 92.41% accuracy achieved using linear operations alone. Our proposed ADRMZI-based NAF unit provides a versatile and reconfigurable solution for implementing diverse NAFs, thereby enhancing the computational capacity and flexibility of photonic neural networks for machine learning tasks.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1437-1440"},"PeriodicalIF":2.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Low-Threshold GaSb-Based Interband Cascade Lasers Emitting at 4.5 μm","authors":"Wenxiang Huang;Shiyu Hu;Junjie Tu;Peng Wang;Wenquan Ma;Yanhua Zhang;Jianliang Huang","doi":"10.1109/LPT.2025.3609298","DOIUrl":"https://doi.org/10.1109/LPT.2025.3609298","url":null,"abstract":"We present low-threshold high-performance interband cascade lasers (ICLs) emitting at <inline-formula> <tex-math>$4.5~mu$ </tex-math></inline-formula>m at room temperature (RT). The broad-area ICL device had a RT threshold input power density of 782 W/cm<inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula> and a threshold current density of 163 A/cm<inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula> that is substantially lower than the previous record of 220 A/cm<inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula> for ICLs with emitting wavelengths beyond <inline-formula> <tex-math>$4mu$ </tex-math></inline-formula>m. For continuous-wave (CW) operation, the narrow-ridge device with epi-down mounting and a high-reflection coating on the back facet, exhibited threshold current and power densities of only 220 A/cm<inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula> and 1056 W/cm<inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula> at <inline-formula> <tex-math>$20~^{circ }$ </tex-math></inline-formula>C, respectively, and delivered a maximum power of 33 mW at the same temperature. The same narrow-ridge device also operated in CW mode at temperatures up to <inline-formula> <tex-math>$78~^{circ }$ </tex-math></inline-formula>C, which is <inline-formula> <tex-math>$12~^{circ }$ </tex-math></inline-formula>C higher than the previously reported maximum operating temperature for ICLs in the wavelength region beyond <inline-formula> <tex-math>$4~mu$ </tex-math></inline-formula>m.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1429-1432"},"PeriodicalIF":2.5,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145073179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bin Ni;Tianhao Gu;Guanghu Chu;Qizhen Zhang;Xuefeng Liu;Jichuan Xiong
{"title":"High-Q Polarization-Independent Dual-BIC Metasurface via Weak Perturbation","authors":"Bin Ni;Tianhao Gu;Guanghu Chu;Qizhen Zhang;Xuefeng Liu;Jichuan Xiong","doi":"10.1109/LPT.2025.3605310","DOIUrl":"https://doi.org/10.1109/LPT.2025.3605310","url":null,"abstract":"Quasi-bound state in the continuum (BIC) with ultra-high quality factor (Q) is of paramount significance for promoting the development of photonic devices. However, the design strategies of introducing small dimensional asymmetry or perturbation pose great challenge for its actual realization. Here, we propose a totally symmetric metasurface with relatively large perturbation parameters that supports two high-Q quasi-BICs induced by Brillouin zone folding (BZF), which can avoid tiny structural asymmetry or positional change. The BZF is triggered by periodically introducing circular nanorods (i.e., perturbations) into the weak eigenfield regions of the lattice, enabling two high-Q quasi-BICs at <inline-formula> <tex-math>$Gamma $ </tex-math></inline-formula> point even when the radius of the circular nanorods is relatively large. Moreover, the C4 symmetry of the unit cell remains undisturbed, making it insensitive to the incident polarization. The BICs also exhibit inconspicuous dependence on the shape of the lattice, further enhancing the manufacturing tolerances. Numerical simulations show that an ultra-high Q of up to 16,390 can be accessible even when the circular nanorods has a 60-nm radius. Such design will help facilitate the implementation of high-performance photonic devices in a variety of application fields such as optical sensing and nonlinearity.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1409-1412"},"PeriodicalIF":2.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145073180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fiber-Optic Temperature Sensor Using Differential LP-Mode Delay Measurement in Weakly-Coupled FMFs","authors":"Jiarui Zhang;Gang Qiao;Tianliang Lv;Yiran Wang;Lei Shen;Chengbin Long;Baolong Zhu;Wei Chen;Jie Luo;Zhangyuan Chen;Yongqi He;Juhao Li","doi":"10.1109/LPT.2025.3605275","DOIUrl":"https://doi.org/10.1109/LPT.2025.3605275","url":null,"abstract":"In recent years, different kinds of fiber-optic temperature sensors have been widely applied in various areas such as power systems and environmental monitoring, which are typically built based on temperature-induced influences to interferometers, grating structures or back-scattered light propagation in traditional single-mode fibers (SMF). In this letter, we propose a novel temperature sensing mechanism based on weakly-coupled few-mode fibers (FMF), in which signals in different linearly-polarized (LP) modes could propagate independently through the fiber, and the influence of temperature to differential mode delay (DMD) between LP modes are utilized for the sensing. The simulation model is established and the simulative results show a linearly-increased relation between DMD and temperature variations, which are then experimentally verified based on the DMD measurement for different mode pairs in a 4-LP-mode FMF utilizing white-light interferometry scheme. The proposed sensing mechanism could achieve flexible systematic structures and find high potential in various applications.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1413-1416"},"PeriodicalIF":2.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145073331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Ultra-High-Order Laguerre-Gaussian Mode Output Based on Annular Pumping and Intra-Cavity Lens","authors":"Zhaokun Lu;Feifan Wang;Aodong Ni;Bo Zhang;Kang Li;Fuqiang Jia","doi":"10.1109/LPT.2025.3607389","DOIUrl":"https://doi.org/10.1109/LPT.2025.3607389","url":null,"abstract":"This letter presents an experimental study on generating ultra-high-order Laguerre-Gaussian (LG) modes in an Nd:YAG solid-state laser using annular pumping and an intra-cavity lens. The hollow structure of the annular pump beam effectively suppresses low-order modes, creating optimal conditions for high-order modes excitation. The intra-cavity convex lens enhances single-mode selection, enabling stable ultra-high-order petal-like <inline-formula> <tex-math>${mathrm {LG}}_{{0,pm }{l}}$ </tex-math></inline-formula> mode output. By adjusting the pump beam size and lens position, the highest angular indices l reached 375th order was achieved. This approach provides a novel method for high-order <inline-formula> <tex-math>${mathrm {LG}}_{{0,pm }{l}}$ </tex-math></inline-formula> mode generation in solid-state lasers, with potential applications in optical manipulation, optical communication, and related fields.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1441-1444"},"PeriodicalIF":2.5,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145223676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xudong Wang;Yongxin Xu;Xiaokai Guan;Wenqing Jiang;Mengyue Shi;Weisheng Hu;Lilin Yi
{"title":"A Low-Complexity ONU Activation Scheme for TFDMA Coherent PON Systems","authors":"Xudong Wang;Yongxin Xu;Xiaokai Guan;Wenqing Jiang;Mengyue Shi;Weisheng Hu;Lilin Yi","doi":"10.1109/LPT.2025.3607514","DOIUrl":"https://doi.org/10.1109/LPT.2025.3607514","url":null,"abstract":"The emergence and development of new communication services have prompted optical access systems to evolve toward higher speed rates. Coherent passive optical network (PON) based on digital subcarrier multiplexing (DSCM) has become one of the key technologies driving the evolution of optical access networks, owing to its flexible spectrum resource allocation and support for time-frequency division multiple access (TFDMA). In PON systems, a new joining optical network unit (ONU) must achieve upstream synchronization through an activation process. The activation scheme should meet the requirements of future communication services for high capacity and low latency, while imposing minimal impact on the data signal. For the TFDMA-based coherent PON architecture, we propose an innovative low-complexity and low-latency ONU activation scheme without a quiet window, which supports both ranging and frequency offset calibration. To validate the proposed scheme, experiments are conducted in a TFDMA coherent PON system with <inline-formula> <tex-math>$6times 10$ </tex-math></inline-formula> GHz subcarriers. The experimental results show that the scheme can achieve a time delay estimation accuracy of 2.5 ns, while the impact of the registration signal on upstream data transmission performance is less than 0.2 dB.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1421-1424"},"PeriodicalIF":2.5,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145073307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Temperature-Stabilized 850 nm High-Speed VCSEL With Modulation Bandwidth Over 30 GHz","authors":"Zhenhuan Qiu;Jian Feng;Wei Miao;Shupeng Deng;Chuyu Zhong;Shihao Ding;Jinlong Lu;Nannan Li;Wu Wang;Hui Li","doi":"10.1109/LPT.2025.3607402","DOIUrl":"https://doi.org/10.1109/LPT.2025.3607402","url":null,"abstract":"We present an 850 nm vertical-cavity surface- emitting laser (VCSEL) featuring enhanced thermal stability and >30 GHz modulation bandwidth. The device maintains stable performance with bandwidths of 30.30 GHz at 25°C and 30.54 GHz at 55°C under 5 mA bias, showing minimal change. Notably, the bandwidth remains nearly constant across a wide current range (3-7 mA). The VCSEL exhibits excellent signal integrity, with relative intensity noise (RIN) consistently below −140 dB/Hz even at elevated temperatures. Advanced thermal management techniques, including polyimide integration and a double-mesa structure, effectively mitigate thermal impedance increase and carrier dynamics degradation. Furthermore, the device successfully achieves 106 Gbit/s PAM4 transmission, as evidenced by clear eye diagrams. These results demonstrate that our co-optimized thermal and carrier design represents a promising approach for developing robust optoelectronic devices capable of reliable high-temperature operation.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"37 24","pages":"1417-1420"},"PeriodicalIF":2.5,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145073308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}