High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion (ICF) and optical communication. However, traditional optical vortices featuring nonuniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam (PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm (GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve a flat-top PVB with dramatically reduced beam speckle contrast. The GAFA-based flat-top PVB generation method can pave the way for high-intensity vortex beam generation, which is crucial for potential applications in ICF, laser processing, optical communication and optical trapping.

鉴于通过测量高精度的位移数据可以获得高精度的微重力加速度数据，进而服务于多种空间科学载荷的研究任务，提出了一种基于三组正交对称角锥棱镜的双频光路，利用外差干涉测量技术实现空间惯性质量块的六自由度位移和角度测量的方法。通过光路矢量分析建立了实际角锥棱镜的光路模型，考虑质量块在运动过程中带来的附加光程差，推导了各测量光路的光程变化与质量块六自由度位姿的函数关系。为了克服小角度近似法精度不高的缺陷，提出了利用数值计算法解耦姿态角进而获得相对位移的位姿解算算法。利用空间在轨位姿数据和随机位姿数据进行系统仿真。仿真结果表明：数值计算的位移误差小于0.02 fm，且该方法的计算误差不会随着飞行器振动的增大而变大，算法具有更高的精度和更好的适应性。最后，分析了系统的误差来源，在保证角度安装误差小于5 mrad、距离安装误差小于10 μm且平行度小于2 mrad时，系统的姿态角测量误差小于0.017°，位移测量误差小于10 nm。本文提出的六自由度测量及解算方法也可以服务于其他精密加工与检测领域。

Nonlinear frequency conversion of wavelength agile and high-power random fiber lasers can provide a promising way to generate continuous-wave (CW) visible and mid-infrared (MIR) light with unique properties such as the continuous modeless spectrum, low temporal/spatial coherence, and high temporal stability. Here, we report a dual-wavelength switchable and tunable random Raman fiber laser (RRFL) based on a phosphosilicate fiber that has two Raman gain peaks for the first time and demonstrate its superior capability to generate widely tunable CW visible and mid-infrared light via nonlinear frequency conversions. By using the combination of a tunable pump and two tunable gratings in Littrow configuration that can provide separated point feedback for the two Stokes wavelengths corresponding to silica- and phosphorus-related Raman peaks, the spectrum of an RRFL can be flexibly manipulated for the aim of nonlinear frequency conversions, including single-wavelength tunable emission at the 1.1 μm or 1.2 μm band for second-harmonic generation (SHG), dual-wavelength simultaneously tunable emission at the 1.1 μm and 1.2 μm bands for the sum-frequency generation (SFG), and dual-wavelength separation tunable emission for difference-frequency generation (DFG). As a result, with the combination of SHG and SFG in a periodically poled lithium niobate crystal array, we experimentally demonstrate the broadest tuning range (560–630 nm) of visible light generated from an RRFL, to the best of our knowledge. The tunable MIR light in the range of 10.7–12.3 μm is also demonstrated through DFG of an RRFL operating in separation tunable dual-wavelength emission mode in a BaGa4Se7 (BGSe) crystal, which is the first realization of >10μm CW DFG in the BGSe crystal. We believe the developed dual-wavelength switchable and tunable RRFL can provide a new compact, robust, and cost-effective platform to realize broadly tunable light in both the visible and MIR regions, which can also find potential applications in imaging, sensing, and temporal ghost imaging in various spectral bands.

单光子探测器具有最高的光探测灵敏度，在激光雷达系统中使用单光子探测器可以极大提升系统的综合性能。近红外二区（1.0~1.7 μm）激光具有大气透过率高、散射弱、太阳背景辐射弱等优势，是大气遥感、三维成像等激光雷达系统的理想工作波段。研制了一种基于InGaAs/InP负反馈雪崩光电二极管的微型化自由运行单光子探测器。该探测器长宽高为116 mm×107.5 mm×80 mm，在1.5 μm最大探测效率超过35%，时间抖动（半高宽）低至80 ps。为满足激光雷达系统对光子飞行时间测量的需求，探测器内部集成时间数字转换（TDC ）功能，时间精度100 ps。同时，探测器集成一套后脉冲修正及计数率修正算法，可以有效降低探测器所引起的雷达信号畸变。