1 上海理工大学 光电信息与计算机工程学院，上海 200093
2 中国科学院上海光学精密机械研究所 高功率激光物理联合实验室，上海 201800
光学元件的损伤在高功率激光系统的终端光学组件中较为普遍且对激光系统的正常运行有重大影响。为提高元件的使用寿命和保证激光光路正常运行，首先要做的是检测和判断出损伤出现的位置、大小、类型。在线检测中终端光学损伤检测装置是一种重要的方法，它能够直接、实时地对元件的损伤情况进行成像并分析，另外还有一种间接获取损伤图像的方式，即用衍射环检测损伤，通过相关公式求出损伤点的大小和位置。针对更小的损伤的检测，深度学习这一工具能够处理大量数据，是目前研究该问题不可或缺的一类方法，它能够减少人工，并提高效率和准确率。修复损伤的主要方式是快速熔融缓解，即二氧化碳激光熔融损伤区，该方法是目前最常见、最有效的修复方式。对损伤问题处理的前提和关键在于精确定位更小的损伤点并分类不同类型的损伤，以便确定后续修复步骤。损伤的检测和修复是光学循环回路策略的重要部分，传统方法有一定的局限性。近些年，受到深度学习在图像处理和目标识别领域的优势的影响，未来会有越来越多深度学习的方法能够被用在与损伤检测相关的研究上。这对高功率激光系统长期稳定运行和正常发展有重要意义和作用。
元件损伤 在线检测 高功率激光系统 损伤修复 深度学习 Element damage On-line inspection High power laser system Damage repair Deep learning 光子学报
2022, 51(10): 1012002
1 中国科学院上海光学精密机械研究所信息光学与光电技术实验室, 上海 201800
2 中国科学院大学材料与光电研究中心, 北京 100049
3 上海理工大学光电信息与计算机工程学院, 上海 200093
磁悬浮热解石墨片的光驱转动提供了一种光能向动能转换的途径,对该现象的研究在能量转换领域中具有重要意义。使用等效磁荷法计算永磁体磁场的空间分布,接着对热解石墨片的受力、扭矩及势能分布进行了理论计算。基于此,对圆形热解石墨片在嵌套的圆柱形永磁体上的光驱转动现象进行计算分析和解释。研究发现,当嵌套的圆柱形永磁体严格同轴时,圆形热解石墨片在激光照射下不会发生光驱转动现象。但嵌套的永磁体在装配时不可避免地会产生一定的偏心量,导致磁场分布不对称,使得圆形热解石墨片的扭矩随着激光照射点呈周期性变化,因此产生了光驱转动现象。
物理光学 磁悬浮 热解石墨片 永磁体 光驱转动 激光与光电子学进展
2021, 58(1): 0126001
Author Affiliations
Abstract
1 National Key Laboratory on Solid-State Laser, Beijing 100015, China
2 University of Shanghai for Science and Technology, Shanghai 200093, China
3 Institute for Laser Science, University of Electro-Communications, Tokyo 182-8585, Japan
A rotating neodymium-doped yttrium aluminum garnet (Nd:YAG) disk laser resonator for efficiently generating vector beams with azimuthal and radial polarization is demonstrated. In the study, the laser crystal rotary for thermal alleviation and polarization discrimination uses c-cut ytterbium vanadate (YVO4). The laser output could be switched between azimuthal and radial polarizations by simply adjusting the cavity length. The laser power reached 4.38 W and 4.64 W for azimuthally and radially polarized beams at the slope efficiencies of 45.3% and 48.5%, respectively. Our study proved that an efficient, high-power vector rotary disk laser would be realistic.
cylindrical vector beam rotary disk polarization Chinese Optics Letters
2020, 18(12): 121401
Author Affiliations
Abstract
1 Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
The excitation of high-order Laguerre–Gaussian (LG) modes in a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser resonator was presented by applying the diffraction of a second-order circular Dammann grating (CDG) for annular pumping. In the study, the 808 nm pump light was shaped into a double-ring structure by the CDG and matched spatially with that of an ideal LG11 mode. As a result, the laser resonator generated an LG11 vortex mode, and the laser power reached 204 mW with 14.5% slope efficiency. Also, when the cavity mirror was tilted, the laser output could switch to the LG01 vortex mode. The results showed the convenience and versatility of CDG in an annular-pumped vortex laser.
140.3580 Lasers, solid-state 140.3480 Lasers, diode-pumped 050.1950 Diffraction gratings Chinese Optics Letters
2019, 17(5): 051402
1 中国科学院上海光学精密机械研究所信息光学与光电技术实验室, 上海 201800
2 中国科学院大学, 北京 100049
3 日本电气通信大学激光研究所, 东京 182-8585
径向偏振光聚焦后可以产生很强的纵向电场。以此为出发点, 首先依据基尔霍夫衍射理论, 计算得到了径向偏振光经锥面镜会聚后所形成的横截面呈现零阶贝塞尔函数分布的纵向电场, 分析了会聚区域光场的相干长度和横向宽度与入射光光斑尺寸、锥面镜的锥顶角以及锥面镜出射端半径的关系。在此基础上, 提出采用锥面镜和筒形反射镜的复合结构, 通过设计合适的锥面镜和筒形反射镜参数, 实现纵向电场的级联, 且电场呈周期性分布。分析了筒形反射镜的参数对所形成的级联纵向电场的横向宽度、周期和占空比等的影响。结果表明, 当所采用的锥面镜的锥顶角为60°时, 出射端半径和筒形反射镜的内径均为999.682λ(λ为波长), 可以实现周期长度为1154λ、占空比为1的纵向电场的级联; 当用于电子加速时, 加速区长度甚至可达到米级。这种级联纵向电场的设计将进一步使得电子的加速区长度得到显著增加, 为电子加速到更高能量提供了可能。
物理光学 径向偏振光 纵向电场 锥面镜 筒形反射镜 级联电子加速
中国科学院上海光学精密机械研究所, 上海 201800
研究了圆环达曼光栅（CDG）整形的环形光抽运的声光调Q Nd:YAG激光器。该激光器的腔体由激光晶体、声光调制器以及平面输出耦合镜组成。所用抽运源为光纤耦合808 nm半导体激光器，其发射光经过CDG发生一级衍射，产生的环形光场强度分布用于端面抽运Nd:YAG激光晶体。实验获得了高光束质量、线偏振、且具有螺旋相位的主动调Q脉冲光输出。当吸收抽运功率为5.6 W、声光调制器工作频率为5 kHz时，激光脉冲的平均功率为470 mW，峰值功率达到588 W，脉冲宽度为160 ns。
激光器 声光调Q 圆环达曼光栅 光束整形 涡旋光
中国科学院上海光学精密机械研究所, 上海 201800
实验利用YAG/Nd∶YAG/Cr4+∶YAG 键合晶体和光子晶体光栅镜获得高峰值功率和高光束质量的被动调Q径向脉冲激光输出，激光器的输出功率达到435 mW，斜率效率为14.7%。在吸收抽运功率为6.8 W 时，输出激光脉冲的峰值功率达到15.7 kW，脉冲能量达到50.1 mJ，脉冲宽度为3.2 ns，重复频率为8.1 kHz，径向偏振纯度为95.8%。实验中的晶体均采用<111>的切割方向，输出径向偏振光束的均匀性得到提高。
激光器 被动调Q 键合晶体 矢量光束 径向偏振
Author Affiliations
Abstract
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
We report a simple Nd:YAG laser that emits radially polarized beam with helical wavefront. The laser cavity consists of a piece of laser crystal and a plane output coupler, and there is no additional polarization component inside it. The pump light is converted into annular profile through de-focal coupling into a multi-mode fiber. For the continuous-wave (CW) operation, the laser emits radially polarized vortex beam, and it is observed that the helical wavefront of the laser beam is switched from right handedness to left handedness when the output coupler is tilted slightly. For the Q-switched operation under the insertion of a Cr4+:YAG saturable absorber inside the cavity, we obtain radially polarized outputs with left-handedness helical wavefront. By tilting the laser crystal slightly, the laser output switches to azimuthal polarization at pump power larger than 4.5 W and left-handedness helical wavefront of laser beam is preserved.
140.3580 Lasers, solid-state 140.3540 Lasers, Q-switched 140.3530 Lasers, neodymium 140.3480 Lasers, diode-pumped 140.3410 Laser resonators Chinese Optics Letters
2015, 13(3): 031405
Author Affiliations
Abstract
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
We propose and demonstrate a laser-diode-pumped, maglev rotating Nd:YAG disk laser. The disk of the laser crystal is attached to a maglev pyrolytic graphite disk and is rotated by compressed gas. In this rotating disk laser, the detrimental thermal effects are alleviated and the laser can be operated in the single transverse electromagnetic (TEM)00 mode with high brightness. In our proof-of-concept experiment, we achieve a 17.7 mW laser output at 447 mW of absorbed pump power and a ～4 Hz rotation frequency.
140.3580 Lasers, solid-state 140.3570 Lasers, single-mode 140.3480 Lasers, diode-pumped 140.6810 Thermal effects Chinese Optics Letters
2015, 13(12): 121403
中国科学院上海光学精密机械研究所, 上海 201800
径向偏振光束特有的偏振分布特性和聚焦特性使其在许多领域中都有重要应用前景，成为近年来的研究热点之一。采用偏振选择镜(光子晶体光栅镜)为选模器件是获得径向偏振激光的一项热门技术。介绍了以偏振选择镜为选模器件的径向偏振固体激光器的研究进展。针对微片径向偏振激光器热效应影响严重、强抽运作用下出现功率饱和的现象，总结了用键合结构增益介质来改善激光介质导热特性、提升径向偏振固体激光器性能的进展，包括基于键合结构晶体连续输出的瓦级径向偏振固体激光器、基于键合结构晶体的径向偏振主动调Q脉冲激光器和基于键合结构晶体的径向偏振被动调Q脉冲激光器。
激光器 径向偏振激光器 键合晶体 热透镜效应 光子晶体光栅 激光与光电子学进展
2013, 50(8): 080015
