飞鸟撞击飞机与无人机黑飞是威胁航班起降安全的两大隐患，上述的飞鸟和无人机都属于“低慢小”飞行物。为保卫机场净空区的安全，需要研制具有反低慢小功能的预警系统。对此，设计并实现了一套低慢小飞行物实时检测系统，基于FPGA（field programmable gate array）驱动相机阵列实时采集大视场天空视频，将适于硬件操作的奇偶分流算法与帧间差分算法相结合进行运动目标检测，系统帧率达到17 帧/s@1 024×768 pixel，平均检测准确率为99.69%。采用千兆以太网、光纤和交换机将前端跑道视频传输至后端塔台指挥中心，支持3 km远距离传输。相比于传统基于软件串行处理的方式，该系统具有高实时性、低功耗与小体积的优势，适合部署在实际应用场景中。

Microresonator-based optical frequency combs are broadband light sources consisting of equally spaced and coherent narrow lines, which are extremely promising for applications in molecular spectroscopy and sensing in the mid-infrared (MIR) spectral region. There are still great challenges in exploring how to improve materials for microresonator fabrication, extend spectral bandwidth of parametric combs, and realize fully stabilized soliton MIR frequency combs. Here, we present an effective scheme for broadband MIR optical frequency comb generation in a MgF2 crystalline microresonator pumped by the quantum cascade laser. The spectral evolution dynamics of the MIR Kerr frequency comb is numerically investigated, revealing the formation mechanism of the microresonator soliton comb via scanning the pump-resonance detuning. We also experimentally implement the modulation instability state MIR frequency comb generation in MgF2 resonators covering from 3380 nm to 7760 nm. This work proceeds microresonator-based comb technology toward a miniaturization MIR spectroscopic device that provides potential opportunities in many fields such as fundamental physics and metrology.

为了在基于回音壁模式光学微腔的光学频率梳生成中优化微腔的性能和光频梳的质量，对氟化镁晶体微腔的色散调控进行研究。首先，理论仿真研究了MgF₂晶体微腔边缘形状对腔内模场和总色散的影响；接着根据仿真结果实际加工了两种面形的MgF₂晶体微腔，分别为边缘平面型和单边楔形；然后，搭建了微腔性能检测系统和晶体微腔光梳生成系统，实测加工出的MgF₂晶体微腔样品的品质因子（Q值）最高可达1.1×108；最后在加工的两种面形晶体腔中均有效激发了超过200 nm的宽光谱范围的克尔光频梳。实验结果验证了边缘楔形的微腔结构确实能够有效压缩模场并调控总色散，相比于边缘平面型的微腔能够产生更宽光谱范围的光梳。

We report a broadband two-dimensional (2D) Kerr and Raman–Kerr frequency comb generation in a silica bottle resonator accounting for azimuthal and axial degrees of freedom and pioneer a method that allows for controlled and reversible switching between a four wave mixing (FWM) state and a stimulated Raman scattering state. The repetition rate of the Raman–Kerr comb is not an integer number of the free spectral range, which spans more than 242 nm with hundreds of teeth. We show that, experimentally and numerically, multiple 2D comb regimes can be selectively accessed via dispersion engineering by exciting different orders of axial modes or modifying the curvature of the axial profile, involving cascaded FWM, Raman lasing, and Raman-assisted FWM. The effect of axial curvature on dispersion is associated with the axial mode number in bottle resonators. Our approach enables dispersion and spectral engineering flexibility in any resonator with localized axial modes.

为测量光线入射角度，设计了一种基于锥形透镜的新型光线入射角度测量系统。利用光阑、锥形透镜和图像接收装置，获取待测光线通过光阑射入锥形透镜后经过多次的折射和反射，在图像接收装置上得到的复杂光斑图像，通过图像处理得到光斑图像特征信息，进而求解光线入射角度。采用锥形透镜的测量方案，角度测量范围可达80°，精度最高可达 (1×10⁻⁴)″。该方案结构简单、体积小且不需要进行繁琐的安装调试。与现有的单光点测量等方法相比，该方案中锥形透镜具有角度放大作用，可大幅度提高测量精度且具有大视场；图像传感器像素分辨率对测量结果影响较小，系统光通量大，容易获得较高的信噪比。

In this Letter, we demonstrate high-quality (Q), millimeter-size, and V-shaped calcium fluoride crystalline resonators for modal modification. To manufacture such resonators, we develop a home-made machining system and explore a detailed process. With a dedicated polished container, three special polishing steps, including grinding, smoothing, and polishing, are employed to achieve the required surface smoothness, which is characterized by less than 3 nm. An ultra-high-Q factor exceeding 10⁸ is obtained by a coupled tapered fiber. In addition, a customized packaged structure for our disk resonator is achieved. The Q maintenance and stable spectrum are realized by sealing the coupling system in a hard disk. The simple, stable, portable, controlled, and integratable device would provide great potential in optical filters, sensors, nonlinear optics, cavity quantum electrodynamics, and especially some applications that require large resonators such as gyroscopes.