High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated. The active polarization control technology based on the root-mean-square propagation (RMS-prop) algorithm is employed to guarantee a linearly polarized output from the system. A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio (PER) of > 11.4 dB. In addition, the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser. The M² factor of the laser beam at the highest output power is measured to be less than 1.15, indicating a diffraction-limited beam quality. Finally, the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W. This is the first time, to the best of our knowledge, that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.

Optical logic gates play important roles in all-optical logic circuits, which lie at the heart of the next-generation optical computing technology. However, the intrinsic contradiction between compactness and robustness hinders the development in this field. Here, we propose a simple design principle that can possess multiple-input-output states according to the incident circular polarization and direction based on the metasurface doublet, which enables controlled-NOT logic gates in infrared region. Therefore, the directional asymmetric electromagnetic transmission can be achieved. As a proof of concept, a spin-dependent Janus metasurface is designed and experimentally verified that four distinct images corresponding to four input states can be captured in the far-field. In addition, since the design method is derived from geometric optics, it can be easily applied to other spectra. We believe that the proposed metasurface doublet may empower many potential applications in chiral imaging, chiroptical spectroscopy and optical computing.

物体微振动信号测量在磁场、建筑、生物成像及航空航天等方面具有重要的应用价值。但是，物体微振动产生的弱反射光不仅极其微弱，易受到探测距离、雨雾气等环境因素的干扰，而且低频振动的振动形式多变，易受到经典噪声影响，难以实现极端微弱反射光条件下的振动信号测量。针对以上问题，文中采用光学偏振控制方法，对信号光与本振光的偏振性进行控制，以减少光学噪声的干扰；采用平衡外差探测，将低频直流信号转变为高频交流信号，避免信号被噪声湮没的同时，克服了光电流共模噪声的影响。在赫兹（~10 Hz）频段，探测器的噪声水平达到了散粒噪声极限，并实现了阿瓦量级反射光条件下的微振动信号测量，测得的物体微振动振幅为11.44 nm，A类标准不确定度为0.25 nm，合成不确定度为0.34 nm，测量精度为±0.75 nm。该方案不仅为微弱多普勒频率测量、振动检测等测量领域的研究提供了实验支持，在弱反光、长距离、雨雾天气等复杂测量环境也具有广阔的应用前景。

研究了表面光栅结构对垂直腔面发射激光器(VCSEL)的偏振控制作用。引入表面光栅后，对不同刻蚀深度下的偏振相关的镜面损耗进行了仿真，结果表明表面光栅刻蚀深度在44~130 nm范围内均可实现稳定偏振，具有较大的工艺容差。表面光栅VCSEL在基横模工作状态下偏振抑制比(Orthogonal Polarization Suppression Ratio, OPSR)超过20 dB，偏振光谱峰间偏振抑制比达到40 dB，且在多横模状态也实现了有效的偏振控制。为了进一步验证光栅对偏振控制的效果，制作了方向互相垂直的两种表面光栅，具有这两种方向光栅的VCSEL的OPSR均达20 dB以上。测试分析表明表面光栅是VCSEL实现稳定偏振的一种有效手段。