Author Affiliations
Abstract
1 State Key Laboratory of Energy Photon-Technology in Western China, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon-Technology, Northwest University, Xi’an 710127, China
2 Shaanxi Engineering Technology Research Center for Solid State Lasers and Application, Shaanxi Provincial Key Laboratory of Photo-electronic Technology, Northwest University, Xi’an 710127, China
We demonstrate a stable narrow linewidth single-frequency erbium-doped fiber laser (EDFL) operating at 1.6 µm. A Fabry–Perot fiber Bragg grating and two cascaded subrings are incorporated in the main ring cavity to achieve single-frequency operation. The experimentally measured optical signal-to-noise ratio is greater than 73 dB. Furthermore, the linewidth of the EDFL is measured to be about 480 Hz by the self-built short-delayed self-heterodyne interferometry device. The laser shows superior stability, with no mode-hopping during the 60-min observation period. The proposed EDFL provides a new experimental idea for realizing a single-frequency fiber laser in the L-band.
erbium-doped fiber laser two cascaded subrings single frequency Chinese Optics Letters
2024, 22(4): 041406
Author Affiliations
Abstract
1 Institute of Photonic Chips, University of Shanghai for Science and Technology, Shanghai 200093, China
2 Centre for Artificial-Intelligence Nanophotonics, School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
3 National Laboratory of Solid State Microstructures, and College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
Secret sharing is a promising technology for information encryption by splitting the secret information into different shares. However, the traditional scheme suffers from information leakage in decryption process since the amount of available information channels is limited. Herein, we propose and demonstrate an optical secret sharing framework based on the multi-dimensional multiplexing liquid crystal (LC) holograms. The LC holograms are used as spatially separated shares to carry secret images. The polarization of the incident light and the distance between different shares are served as secret keys, which can significantly improve the information security and capacity. Besides, the decryption condition is also restricted by the applied external voltage due to the variant diffraction efficiency, which further increases the information security. In implementation, an artificial neural network (ANN) model is developed to carefully design the phase distribution of each LC hologram. With the advantage of high security, high capacity and simple configuration, our optical secret sharing framework has great potentials in optical encryption and dynamic holographic display.
holographic encryption optical secret sharing cascaded liquid crystal hologram multi-dimensional multiplexing Opto-Electronic Advances
2024, 7(1): 230121
Author Affiliations
Abstract
1 Shandong University, Center for Optics Research and Engineering, Qingdao, China
2 Shandong University, Key Laboratory of Laser and Infrared System of the Ministry of Education, Qingdao, China
3 Shandong University, School of Information Science and Engineering, Qingdao, China
4 National Research Council Canada, Ottawa, Canada
5 University of Ottawa, Physics Department, Ottawa, Canada
The optical rogue wave (RW), known as a short-lived extraordinarily high amplitude dynamics phenomenon with small appearing probabilities, plays an important role in revealing and understanding the fundamental physics of nonlinear wave propagations in optical systems. The random fiber laser (RFL), featured with cavity-free and “modeless” structure, has opened up new avenues for fundamental physics research and potential practical applications combining nonlinear optics and laser physics. Here, the extreme event of optical RW induced by noise-driven modulation instability that interacts with the cascaded stimulated Brillouin scattering, the quasi-phase-matched four-wave mixing as well as the random mode resonance process is observed in a Brillouin random fiber laser comb (BRFLC). Temporal and statistical characteristics of the RWs concerning their emergence and evolution are experimentally explored and analyzed. Specifically, temporally localized structures with high intensities including chair-like pulses with a sharp leading edge followed by a trailing plateau appear frequently in the BRFLC output, which can evolve to chair-like RW pulses with adjustable pulse duration and amplitude under controlled conditions. This investigation provides a deep insight into the extreme event of RWs and paves the way for RW manipulation for its generation and elimination in RFLs through adapted laser configuration.
optical rogue wave modulation instability random fiber laser cascaded stimulated Brillouin scattering four-wave mixing temporally localized structure Advanced Photonics Nexus
2024, 3(2): 026008
1 南京邮电大学 集成电路科学与工程学院, 南京 210023
2 东南大学 毫米波国家重点实验室, 南京 210096
3 国防科技大学 计算机学院, 长沙 410073
采用 65 nm CMOS工艺, 设计了一种低相噪级联双锁相环毫米波频率综合器。该频率综合器采用两级锁相环级联的结构, 减轻了单级毫米波频率综合器带内和带外相位噪声受带宽的影响。时间数字转换器采用游标卡尺型结构, 改善了PVT变化下时间数字转换器的量化线性度。数字环路滤波器采用自动环路增益控制技术来自适应调节环路带宽, 以提高频率综合器的性能。振荡器采用噪声循环技术, 减小了注入到谐振腔的噪声, 进而改善了振荡器的相位噪声。后仿真结果表明, 在12 V电源电压下, 该频率综合器可输出的频率范围为22~26 GHz, 在输出频率为24 GHz时, 相位噪声为-1048 dBc/Hz @1 MHz, 功耗为468 mW。
全数字锁相环 噪声循环振荡器 亚采样锁相环 级联锁相环 相位噪声 all-digital phase-locked loop noise circulating oscillator sub-sampling phase-locked loop cascaded phase-locked loop phase noise
辽宁石油化工大学 信息与控制学院, 辽宁 抚顺 113001
视盘和视杯的精确分割是青光眼计算机辅助诊断的关键,考虑视盘的解剖学特征,提出基于超像素和级联SVM分类实现视盘的精确分割。首先对眼底图像超像素分割,基于视盘的解剖学结构特征,提取超像素的灰度、纹理、几何、位置分布等特征;然后采用基于SVM的监督聚类方法分类超像素区域,两级级联SVM分类器在分类过程中修正超像素位置信息,提升分割精度;最后基于Snake模型修复局部轮廓。在DRIONS和REFUGE数据库视盘分割精度分别为99.87%和99.52%,精度、灵敏度、特异性、AOL和DICE系数均高于该领域典型算法,实验证明所提方法能够精确分割视盘区域,且具有较强的鲁棒性;在青光眼诊断中具有一定的应用价值。
视盘分割 青光眼 超像素 级联SVM 鲁棒性 disc segmentation glaucoma super pixel cascaded SVM robustness
1 国防科技大学前沿交叉学科学院,湖南 长沙 410073
2 国防科技大学南湖之光实验室,湖南 长沙 410073
3 国防科技大学高能激光技术湖南省重点实验室,湖南 长沙 410073
由于自激振荡的限制,单级超荧光光纤光源的功率提升十分困难,目前仅达到百瓦量级。基于主振荡功率放大(MOPA)方案,使用1018 nm光纤激光级联泵浦1080 nm波段的超荧光,实现了6.2 kW高功率输出。最高功率下的光光转换效率为81.5%,没有出现横模不稳定(TMI),功率提升受限于受激拉曼散射(SRS)。
光纤光学 超荧光光源 高功率 级联泵浦 受激拉曼散射 横模不稳定 中国激光
2023, 50(22): 2215001
红外与激光工程
2023, 52(8): 20230420
战略支援部队信息工程大学信息系统工程学院,河南 郑州 450000
单光子雪崩二极管(SPAD)阵列探测器常被用作空间远距离目标的测距和三维成像。为快速获取光子数据,SPAD阵列探测系统一般选用高重复频率的探测体制。目前,主要采用随机序列对脉冲进行编码的方法来抑制高重复频率引起的距离模糊效应。为了在接收端对阵列像素实现有效区分,而且各周期内的编码波形不相互串扰,需要数量庞大且可保持相互正交的随机编码序列。本文提出了使用混沌序列对SPAD阵列进行编码的思路,并通过分析Lyapunov指数的值域变化,提出了复合型Logistic序列的优化编码方案。为确保阵元间的互扰不会影响最终的探测效果,提出了峰值旁瓣差(PSLD)的概念,并对阵列间互相关积累的影响进行了定量分析。依据峰值旁瓣差对生成的混沌序列进行了筛选,以保证其能够满足所需阵列规模的抗互扰要求。最后给出了具体的编码流程。
探测器 单光子探测阵列 混沌序列 峰值旁瓣差 级联编码 中国激光
2023, 50(19): 1906004
Author Affiliations
Abstract
School of Artificial Intelligence, Optics and Electronics (iOPEN), Northwestern Polytechnical University, Xi’an, Shaanxi 710072, P. R. China
The miniaturized femtosecond laser in near infrared-II region is the core equipment of three-photon microscopy. In this paper, we design a compact and robust illumination source that emits dual-color linearly polarized light for three-photon microscopy. Based on an all-polarization-maintaining passive mode-locked fiber laser, we shift the center wavelength of the pulses to the 1.7μm band utilizing cascade Raman effect, thereby generate dual-wavelength pulses. To enhance clarity, the two wavelengths are separated through the graded-index multimode fiber. Then we obtain the dual-pulse sequences with 1639.4nm and 1683.7nm wavelengths, 920fs pulse duration, and 23.75MHz pulse repetition rate. The average power of the signal is 53.64mW, corresponding to a single pulse energy of 2.25nJ. This illumination source can be further amplified and compressed for three-photon fluorescence imaging, especially dual-color three-photon fluorescence imaging, making it an ideal option for biomedical applications.
Three-photon fluorescence imaging illumination source dual-wavelength femtosecond pulse cascaded Raman effect graded-index multimode fiber Journal of Innovative Optical Health Sciences
2023, 16(5): 2241005