This work presents a novel hardware-efficient FPGA implementation of a real-time parallel loop-unrolled decision feedback equalizer (DFE) for PAM-4 IM/DD optical links. The proposed DSP architecture integrates timing recovery, a 5-tap FFE, and a novel single-tap parallel DFE leveraging an $8times 8$ loop-unrolled structure and a hardware-friendly error-based tap update mechanism thus effectively reduces processing complexity and clock delay. The implementation occupies only 4.2% LUTs, 2.75% FFs, and 6.8% DSP48E2 resources of a Xilinx XCVU13P chip. A successful 29.4912 Gb/s real-time PAM-4 signal transmission over a 10 km SSMF is demonstrated using a cost-effective directly modulated laser (DML) and achieving a BER below the 7% HD-FEC threshold, indicating a scalable and efficient solution for high-speed short reach optical data links.
{"title":"FPGA Implementation of a Real-Time Parallel Loop-Unrolled DFE for PAM-4 IM/DD Optical Links","authors":"Jianyu Wang;Jianwei Tang;Yaguang Hao;Yingying Zhou;Xiuquan Cui;Linsheng Fan;Zhongliang Sun;Junpeng Liang;Zhaopeng Xu;Weisheng Hu;Zhixue He;Yanfu Yang;Jinlong Wei","doi":"10.1109/LPT.2025.3636126","DOIUrl":"https://doi.org/10.1109/LPT.2025.3636126","url":null,"abstract":"This work presents a novel hardware-efficient FPGA implementation of a real-time parallel loop-unrolled decision feedback equalizer (DFE) for PAM-4 IM/DD optical links. The proposed DSP architecture integrates timing recovery, a 5-tap FFE, and a novel single-tap parallel DFE leveraging an <inline-formula> <tex-math>$8times 8$ </tex-math></inline-formula> loop-unrolled structure and a hardware-friendly error-based tap update mechanism thus effectively reduces processing complexity and clock delay. The implementation occupies only 4.2% LUTs, 2.75% FFs, and 6.8% DSP48E2 resources of a Xilinx XCVU13P chip. A successful 29.4912 Gb/s real-time PAM-4 signal transmission over a 10 km SSMF is demonstrated using a cost-effective directly modulated laser (DML) and achieving a BER below the 7% HD-FEC threshold, indicating a scalable and efficient solution for high-speed short reach optical data links.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 5","pages":"321-324"},"PeriodicalIF":2.5,"publicationDate":"2025-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729443","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}
Neural networks can be employed for chaotic synchronization and decryption at the receiver end of chaotic optical communication systems. Simple training methods and efficient networks are worthy of further exploration in this field. We propose a novel training method for application in electrooptic phase feedback (EOPF) chaotic communication systems. Specifically, it employs a gated recurrent unit neural network (GRU-NN) trained solely on datasets constructed from encrypted and plaintext data. Experimental validation confirms that the trained model achieves high-quality chaotic synchronization and supports decryption. This approach requires only partial plaintext data sharing between communication parties for training, offering a promising reference for remote training scenarios in chaotic optical communication.
{"title":"Chaos Synchronization and Decryption in Electro-Optic Chaotic Systems Using GRU Neural Networks","authors":"Hao Yang;Peng Hou;Xing Li;Jinyang Ye;Yuehua An;Anbang Wang;Yuncai Wang;Yuwen Qin;Zhensen Gao","doi":"10.1109/LPT.2025.3635654","DOIUrl":"https://doi.org/10.1109/LPT.2025.3635654","url":null,"abstract":"Neural networks can be employed for chaotic synchronization and decryption at the receiver end of chaotic optical communication systems. Simple training methods and efficient networks are worthy of further exploration in this field. We propose a novel training method for application in electrooptic phase feedback (EOPF) chaotic communication systems. Specifically, it employs a gated recurrent unit neural network (GRU-NN) trained solely on datasets constructed from encrypted and plaintext data. Experimental validation confirms that the trained model achieves high-quality chaotic synchronization and supports decryption. This approach requires only partial plaintext data sharing between communication parties for training, offering a promising reference for remote training scenarios in chaotic optical communication.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 5","pages":"301-304"},"PeriodicalIF":2.5,"publicationDate":"2025-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729442","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}
Pub Date : 2025-11-18DOI: 10.1109/LPT.2025.3634428
Mauro Biagi
This work investigates the impact of high-reflectivity wall coatings on the performance of NLOS VLC channels. We extend conventional models by incorporating measured Bidirectional Reflectance Distribution Function (BRDF) data to better represent real-world surface behaviors. A comprehensive analysis is conducted through simulations that assess key channel parameters, including received signal strength, delay spread, and achievable data rates. The results demonstrate that specialized coatings significantly enhance NLOS performance, improving signal coverage while moderately affecting multipath dispersion. Unlike prior BRDF-based studies focusing on single-surface cases, this letter provides a systematic, material-aware comparison ($rho =0.60$ –0.99) that jointly maps SNR, delay spread, and ISI-aware capacity, yielding quantitative design guidelines for NLOS VLC in real rooms.
{"title":"Impact of High-Reflectivity Wall Coatings on Non-Line-of-Sight Visible Light Communication Channels","authors":"Mauro Biagi","doi":"10.1109/LPT.2025.3634428","DOIUrl":"https://doi.org/10.1109/LPT.2025.3634428","url":null,"abstract":"This work investigates the impact of high-reflectivity wall coatings on the performance of NLOS VLC channels. We extend conventional models by incorporating measured Bidirectional Reflectance Distribution Function (BRDF) data to better represent real-world surface behaviors. A comprehensive analysis is conducted through simulations that assess key channel parameters, including received signal strength, delay spread, and achievable data rates. The results demonstrate that specialized coatings significantly enhance NLOS performance, improving signal coverage while moderately affecting multipath dispersion. Unlike prior BRDF-based studies focusing on single-surface cases, this letter provides a systematic, material-aware comparison (<inline-formula> <tex-math>$rho =0.60$ </tex-math></inline-formula>–0.99) that jointly maps SNR, delay spread, and ISI-aware capacity, yielding quantitative design guidelines for NLOS VLC in real rooms.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 5","pages":"337-340"},"PeriodicalIF":2.5,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830941","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}
Pub Date : 2025-11-17DOI: 10.1109/LPT.2025.3633564
Kawsar Ahmed;Md Mamun Ali;Md Aslam Mollah;Francis M. Bui;Li Chen
In this study, we present a deep-learning-assisted design of a photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) biosensor that enables simultaneous, label-free detection of multiple waterborne analytes. Using finite element analysis, a dual-channel PCF is modeled to generate more than 40,000 data points. A lightweight, fully connected regressor predicts the confinement loss (CL) and amplitude sensitivity (AS) from structural variables (hole sizes, gaps, metal/dielectric thicknesses) and operational variables (wavelength, refractive index (RI) of analytes in both channels), achieving $R^{2} approx 0.99$ with low error. The surrogate speeds up the process of exploring designs. Using SHAP analysis, it finds that wavelength and channel RIs are the main factors, while layer thicknesses mainly change channel-specific resonances. Parametric sweeps confirm stable, concurrent redshifts across channels with increasing RI, enabling multiplexed detection of bacterial pathogens and formaldehyde. The proposed model achieves maximum amplitude sensitivity (AS) of $512.87~RIU^{-1}$ , wavelength sensitivity (WS) of 10,$638.30~nm/RIU$ , and sensor resolution (SR) of $9.4times 10^{-5}$ . The resulting architecture combines high accuracy with computational efficiency, offering a compact route to rapid, real-time water quality monitoring and food safety screening, as well as a generalizable workflow for data-driven PCF-SPR design.
{"title":"Deep Learning Optimized SPR Multi-Analyte Biosensor for Simultaneous Detection of Water Pathogens","authors":"Kawsar Ahmed;Md Mamun Ali;Md Aslam Mollah;Francis M. Bui;Li Chen","doi":"10.1109/LPT.2025.3633564","DOIUrl":"https://doi.org/10.1109/LPT.2025.3633564","url":null,"abstract":"In this study, we present a deep-learning-assisted design of a photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) biosensor that enables simultaneous, label-free detection of multiple waterborne analytes. Using finite element analysis, a dual-channel PCF is modeled to generate more than 40,000 data points. A lightweight, fully connected regressor predicts the confinement loss (CL) and amplitude sensitivity (AS) from structural variables (hole sizes, gaps, metal/dielectric thicknesses) and operational variables (wavelength, refractive index (RI) of analytes in both channels), achieving <inline-formula> <tex-math>$R^{2} approx 0.99$ </tex-math></inline-formula> with low error. The surrogate speeds up the process of exploring designs. Using SHAP analysis, it finds that wavelength and channel RIs are the main factors, while layer thicknesses mainly change channel-specific resonances. Parametric sweeps confirm stable, concurrent redshifts across channels with increasing RI, enabling multiplexed detection of bacterial pathogens and formaldehyde. The proposed model achieves maximum amplitude sensitivity (AS) of <inline-formula> <tex-math>$512.87~RIU^{-1}$ </tex-math></inline-formula>, wavelength sensitivity (WS) of 10,<inline-formula> <tex-math>$638.30~nm/RIU$ </tex-math></inline-formula>, and sensor resolution (SR) of <inline-formula> <tex-math>$9.4times 10^{-5}$ </tex-math></inline-formula>. The resulting architecture combines high accuracy with computational efficiency, offering a compact route to rapid, real-time water quality monitoring and food safety screening, as well as a generalizable workflow for data-driven PCF-SPR design.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 4","pages":"283-286"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612216","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}
Pub Date : 2025-11-17DOI: 10.1109/LPT.2025.3633308
Yaoping Wu;Jincong Hu;Hui Yang;Lianshan Yan;Xihua Zou
A fully programmable digital optical frequency combs (DOFC)-assisted covert communication scheme is proposed and demonstrated, addressing the challenges associated with the high complexity of analog cloning and synchronization. In this scheme, flexible DOFC are cost-effectively cloned through meticulous design, while fast synchronization is achieved via cyclic shifting, leveraging the excellent reconfigurability and recoverability of digital binary sequences. In experiments, the narrow spectrum is replicated by unique DOFC and subsequently concealed within additive white Gaussian noise. Transmitted mixed signals, with different signal-to-noise ratios (SNRs), are efficiently recovered by cloned DOFC. For the 7% forward error correction limit, 201 comb lines achieve the maximal system processing gain of 21 dB from a low SNR (-15.49 dB @min.). The system tolerates high-order modulation formats and achieves $3times $ capacity enhancement. The proposed approach improves spectrum utilization and offers a simple, large-bandwidth, and high-security solution.
提出并演示了一种全可编程数字光频梳（DOFC）辅助隐蔽通信方案，解决了模拟克隆和同步的高复杂性带来的挑战。该方案通过精心设计，经济高效地克隆了灵活的DOFC，同时利用数字二进制序列优异的可重构性和可恢复性，通过循环移位实现了快速同步。在实验中，窄谱被唯一的DOFC复制，随后隐藏在加性高斯白噪声中。克隆DOFC可以有效地恢复传输的不同信噪比的混合信号。对于7%的前向纠错限制，201梳线在低信噪比（-15.49 dB @min）下实现了21 dB的最大系统处理增益。该系统支持高阶调制格式，并实现了3倍的容量增强。该方法提高了频谱利用率，提供了一种简单、大带宽、高安全性的解决方案。
{"title":"Programmable Digital Optical Frequency Combs Assisted Transceiver for Covert Communication","authors":"Yaoping Wu;Jincong Hu;Hui Yang;Lianshan Yan;Xihua Zou","doi":"10.1109/LPT.2025.3633308","DOIUrl":"https://doi.org/10.1109/LPT.2025.3633308","url":null,"abstract":"A fully programmable digital optical frequency combs (DOFC)-assisted covert communication scheme is proposed and demonstrated, addressing the challenges associated with the high complexity of analog cloning and synchronization. In this scheme, flexible DOFC are cost-effectively cloned through meticulous design, while fast synchronization is achieved via cyclic shifting, leveraging the excellent reconfigurability and recoverability of digital binary sequences. In experiments, the narrow spectrum is replicated by unique DOFC and subsequently concealed within additive white Gaussian noise. Transmitted mixed signals, with different signal-to-noise ratios (SNRs), are efficiently recovered by cloned DOFC. For the 7% forward error correction limit, 201 comb lines achieve the maximal system processing gain of 21 dB from a low SNR (-15.49 dB @min.). The system tolerates high-order modulation formats and achieves <inline-formula> <tex-math>$3times $ </tex-math></inline-formula> capacity enhancement. The proposed approach improves spectrum utilization and offers a simple, large-bandwidth, and high-security solution.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 5","pages":"313-316"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145712563","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}
We demonstrate an all-silicon local area network wavelength division multiplexing (LAN-WDM) transmitter with capacities of 1.6 Tbps and beyond, utilizing 8 traveling wave Mach-Zehnder modulators (TW-MZMs) with 3 dB EO bandwidths of 60 GHz and a lattice-filer-based Gaussian-like-passband $8times 1$ multiplexer. By using the joint linear and nonlinear equalization algorithm based on cascaded artificial neural network and maximum likelihood sequence estimation (ANN-MLSE), we demonstrate single-channel 250 Gbps four level pulse amplitude modulation (PAM4) with the corresponding bit error ratios (BER) below the 20% soft-decision forward error correction (SD-FEC) threshold of 2E-2. The aggregate bit rates of all 8 channels reach 2 Tbps and 1.6 Tbps for the PAM4 transmissions over 1 km and 10 km single mode fibers, respectively. The energy efficiency and the bandwidth density are as high as 0.18/0.143 pJ/bit and 28.9/36.2 Gbps/mm${}^{mathbf {2}}$ for 1.6/2 Tbps transmission.We believe the proposed SiPh transmitter has great potential in long-reach applications due to the outstanding performance and low-cost manufacturing.
{"title":"Beyond 1.6-Tb/s Silicon LAN-WDM Transmitter for High-Energy-Efficiency Transmission","authors":"Xinyu Wang;Shilan Zhou;Hui Yu;Jianyi Yang;Qiang Zhang;Penghui Xia","doi":"10.1109/LPT.2025.3633837","DOIUrl":"https://doi.org/10.1109/LPT.2025.3633837","url":null,"abstract":"We demonstrate an all-silicon local area network wavelength division multiplexing (LAN-WDM) transmitter with capacities of 1.6 Tbps and beyond, utilizing 8 traveling wave Mach-Zehnder modulators (TW-MZMs) with 3 dB EO bandwidths of 60 GHz and a lattice-filer-based Gaussian-like-passband <inline-formula> <tex-math>$8times 1$ </tex-math></inline-formula> multiplexer. By using the joint linear and nonlinear equalization algorithm based on cascaded artificial neural network and maximum likelihood sequence estimation (ANN-MLSE), we demonstrate single-channel 250 Gbps four level pulse amplitude modulation (PAM4) with the corresponding bit error ratios (BER) below the 20% soft-decision forward error correction (SD-FEC) threshold of 2E-2. The aggregate bit rates of all 8 channels reach 2 Tbps and 1.6 Tbps for the PAM4 transmissions over 1 km and 10 km single mode fibers, respectively. The energy efficiency and the bandwidth density are as high as 0.18/0.143 pJ/bit and 28.9/36.2 Gbps/mm<inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula> for 1.6/2 Tbps transmission.We believe the proposed SiPh transmitter has great potential in long-reach applications due to the outstanding performance and low-cost manufacturing.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 4","pages":"267-270"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612214","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}
We propose and experimentally demonstrate a 16-channel DFB laser array operating in the C-band, featuring high output power, narrow linewidth, low relatice intensity noise (RIN) and uniform wavelength spacing. The reconstruction equivalent chirp (REC) technique is used to introduce equivalent $pi $ phase shifts, simplify the grating process, and enhance the wavelength control accuracy. To maximize output efficiency, high-reflection (HR) and anti-reflection (AR) coatings are deposited on the rear and front facets, respectively. In addition, an asymmetric equivalent phase-shift configuration is incorporated into the cavity, which enhances the single-mode yield of the lasers and improves the precision of the wavelength spacing. A passive waveguide with light $n$ -type doping was introduced to suppress the overlap between the optical mode and both the $p$ -type cladding and the active region, thereby reducing carrier-induced absorption losses and significantly improving the slope efficiency of the laser. As a result, the proposed 16-channel DFB laser array operates with a channel spacing of 200 GHz and a maximum wavelength deviation of only 0.01 nm. Each laser delivers an output power exceeding 300 mW at a bias current of 1000 mA and $25~^{circ }$ C. The intrinsic Lorentzian linewidth is as narrow as 64 kHz, while the relative intensity noise (RIN) remains below −160 dB/Hz for bias currents above 500 mA. These results highlight the array’s strong potential for applications in optical I/O technology, free-space optical (FSO) communication, and light detection and ranging (LiDAR) systems.
{"title":"High-Power Narrow-Linewidth C-Band DFB Laser Array With High-Uniform Wavelength Spacing","authors":"Zhenxing Sun;Shenghong Xie;Yue Zhang;Yuechun Shi;Yunshan Zhang;Zhenzhen Xu;Xiangfei Chen","doi":"10.1109/LPT.2025.3633300","DOIUrl":"https://doi.org/10.1109/LPT.2025.3633300","url":null,"abstract":"We propose and experimentally demonstrate a 16-channel DFB laser array operating in the C-band, featuring high output power, narrow linewidth, low relatice intensity noise (RIN) and uniform wavelength spacing. The reconstruction equivalent chirp (REC) technique is used to introduce equivalent <inline-formula> <tex-math>$pi $ </tex-math></inline-formula> phase shifts, simplify the grating process, and enhance the wavelength control accuracy. To maximize output efficiency, high-reflection (HR) and anti-reflection (AR) coatings are deposited on the rear and front facets, respectively. In addition, an asymmetric equivalent phase-shift configuration is incorporated into the cavity, which enhances the single-mode yield of the lasers and improves the precision of the wavelength spacing. A passive waveguide with light <inline-formula> <tex-math>$n$ </tex-math></inline-formula>-type doping was introduced to suppress the overlap between the optical mode and both the <inline-formula> <tex-math>$p$ </tex-math></inline-formula>-type cladding and the active region, thereby reducing carrier-induced absorption losses and significantly improving the slope efficiency of the laser. As a result, the proposed 16-channel DFB laser array operates with a channel spacing of 200 GHz and a maximum wavelength deviation of only 0.01 nm. Each laser delivers an output power exceeding 300 mW at a bias current of 1000 mA and <inline-formula> <tex-math>$25~^{circ }$ </tex-math></inline-formula>C. The intrinsic Lorentzian linewidth is as narrow as 64 kHz, while the relative intensity noise (RIN) remains below −160 dB/Hz for bias currents above 500 mA. These results highlight the array’s strong potential for applications in optical I/O technology, free-space optical (FSO) communication, and light detection and ranging (LiDAR) systems.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 4","pages":"279-282"},"PeriodicalIF":2.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612215","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}
Pub Date : 2025-11-12DOI: 10.1109/LPT.2025.3631797
Xinying Tan;Hongyu Luo;Hanlin Peng;Jianfeng Li;Yong Liu
Mode-locked fluoride fiber oscillator provides a cost -effective and robust platform for generating mid-infrared (MIR) femtosecond pulses. Limited by the soliton area theorem, however, significantly scaling up the energy remains challenging. Although intra-cavity dispersion management has been proposed as a feasible way to overcome this limitation, the energies are clamped at <10> $sim 2.8~mu $ m based on the nonlinear polarization rotation mechanism, achieving a markedly scaled energy of >20 nJ. Specifically, an array of normal dispersion Ge rods is incorporated into a large-anomalous-dispersion cavity (i.e., −0.4 ps ${}^{mathbf {2}}$ ), primarily composed of a relatively long fluoride fiber, enabling precise dispersion management and thereby increasing the breathing ratio. Additionally, a backward pumping scheme is employed to reduce the round-trip-integrated nonlinear phase, thereby enhancing the maximum achievable energy before multi-pulsing or continuous-wave breakthrough occurs. As a result, the stretched pulses with a record energy of up to 20.9 nJ have been achieved, yielding a pulse width of 301 fs and a peak power of 65.2 kW under single-transverse-mode operation. To our knowledge, the energy represents, to date, the highest level of femtosecond fiber oscillators in the MIR. These results highlight the great potential of the mode-locked fluoride fiber oscillator for generating high-energy MIR femtosecond pulses in a compact configuration.
{"title":">20 nJ Femtosecond Pulses Generation From a 2.8 μm Mode-Locked Er3+-Doped Fluoride Fiber Oscillator","authors":"Xinying Tan;Hongyu Luo;Hanlin Peng;Jianfeng Li;Yong Liu","doi":"10.1109/LPT.2025.3631797","DOIUrl":"https://doi.org/10.1109/LPT.2025.3631797","url":null,"abstract":"Mode-locked fluoride fiber oscillator provides a cost -effective and robust platform for generating mid-infrared (MIR) femtosecond pulses. Limited by the soliton area theorem, however, significantly scaling up the energy remains challenging. Although intra-cavity dispersion management has been proposed as a feasible way to overcome this limitation, the energies are clamped at <10> <tex-math>$sim 2.8~mu $ </tex-math></inline-formula>m based on the nonlinear polarization rotation mechanism, achieving a markedly scaled energy of >20 nJ. Specifically, an array of normal dispersion Ge rods is incorporated into a large-anomalous-dispersion cavity (i.e., −0.4 ps <inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula>), primarily composed of a relatively long fluoride fiber, enabling precise dispersion management and thereby increasing the breathing ratio. Additionally, a backward pumping scheme is employed to reduce the round-trip-integrated nonlinear phase, thereby enhancing the maximum achievable energy before multi-pulsing or continuous-wave breakthrough occurs. As a result, the stretched pulses with a record energy of up to 20.9 nJ have been achieved, yielding a pulse width of 301 fs and a peak power of 65.2 kW under single-transverse-mode operation. To our knowledge, the energy represents, to date, the highest level of femtosecond fiber oscillators in the MIR. These results highlight the great potential of the mode-locked fluoride fiber oscillator for generating high-energy MIR femtosecond pulses in a compact configuration.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 5","pages":"329-332"},"PeriodicalIF":2.5,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729441","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}
Pub Date : 2025-11-12DOI: 10.1109/LPT.2025.3631796
Yunjing He;Dong Zhou;Weizong Xu;Feng Zhou;Fangfang Ren;Dunjun Chen;Rong Zhang;Youdou Zheng;Hai Lu
In this work, the reliability properties of Si photodetectors (PDs) and wide-bandgap semiconductor-based PDs, represented by SiC and GaN PDs, are compared upon high-dose ultra-violet (UV) irradiation. A high-power 275 nm UV light-emitting diode module with continuous-wave (CW) emission and a 266 nm nanosecond pulsed laser are selected as the aging light sources. It is found that after a cumulative 1 MJ/cm2 CW irradiation dose at 275 nm, the SiC and GaN PDs both exhibit a responsivity rise of ~3 %, while the Si PD exhibit a responsivity drop of more than 6 %. For the 266 nm pulsed laser irradiation with a peak power density of ~5 kW/cm ${}^{mathbf {2}}$ , when the cumulative dose reaches 0.1 MJ/cm ${}^{mathbf {2}}$ , the responsivity of the Si PD decreases by 6 %, while the SiC and GaN PDs show virtually no change in responsivity. Meanwhile, the dark current of the Si PD shows considerably larger increase than those of the SiC and GaN PDs upon pulsed UV laser irradiation.
{"title":"Reliability Performance Study of SiC, GaN, and Si Photodetectors Under High-Dose UV Irradiation","authors":"Yunjing He;Dong Zhou;Weizong Xu;Feng Zhou;Fangfang Ren;Dunjun Chen;Rong Zhang;Youdou Zheng;Hai Lu","doi":"10.1109/LPT.2025.3631796","DOIUrl":"https://doi.org/10.1109/LPT.2025.3631796","url":null,"abstract":"In this work, the reliability properties of Si photodetectors (PDs) and wide-bandgap semiconductor-based PDs, represented by SiC and GaN PDs, are compared upon high-dose ultra-violet (UV) irradiation. A high-power 275 nm UV light-emitting diode module with continuous-wave (CW) emission and a 266 nm nanosecond pulsed laser are selected as the aging light sources. It is found that after a cumulative 1 MJ/cm2 CW irradiation dose at 275 nm, the SiC and GaN PDs both exhibit a responsivity rise of ~3 %, while the Si PD exhibit a responsivity drop of more than 6 %. For the 266 nm pulsed laser irradiation with a peak power density of ~5 kW/cm <inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula>, when the cumulative dose reaches 0.1 MJ/cm <inline-formula> <tex-math>${}^{mathbf {2}}$ </tex-math></inline-formula>, the responsivity of the Si PD decreases by 6 %, while the SiC and GaN PDs show virtually no change in responsivity. Meanwhile, the dark current of the Si PD shows considerably larger increase than those of the SiC and GaN PDs upon pulsed UV laser irradiation.","PeriodicalId":13065,"journal":{"name":"IEEE Photonics Technology Letters","volume":"38 4","pages":"287-290"},"PeriodicalIF":2.5,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612161","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}
Pub Date : 2025-11-11DOI: 10.1109/LPT.2025.3631648
Xiangdong Xie;Chao Zhang
Laguerre–Gaussian (LG) modes, as vortex beams with well-defined OAM (orbital angular momentum), have been extensively studied. For applications, accurate identification of the radial and azimuthal indices of LG beams is essential. Various methods have been proposed to identify these indices. However, most of these approaches can only identify one of the two indices. In particular, by employing a $pi /2$ mode converter, LG modes can be transformed into the corresponding HG modes. In this case, the two indices of a single LG mode can then be indirectly determined from the number of intensity lobes of the transformed single HG mode. However, this method is limited to identifying beams with a single LG mode and is not applicable to beams with multiple LG modes. To overcome this limitation, we propose a method to decompose beams containing multiple LG modes based on the $pi /2$ mode converter. The proposed method can determine the mode composition and weight coefficients of beams with multiple LG modes. Crucially, this method requires only intensity measurements and no phase information, which significantly facilitates its applications. Moreover, the simulation results validate the proposed method and demonstrate its robustness under low signal-to-noise ratio conditions.
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