All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam, which can provide a promising way to overcome the power limitation of a single-fiber laser. One of the key points is combining efficiency, which is determined by various mismatches during fabrication. A theoretical model has been built, and the mismatch error is analyzed numerically for the first time. The mismatch errors have been numerically studied with the beam quality and combining efficiency being chosen as the evaluation criteria. The tolerance of each mismatch error for causing 1% loss is calculated to guide the design of the beam combiners. The simulation results are consistent with the experimental results, which show that the mismatch error of the square-core fiber is the main cause of the efficiency loss. The results can provide useful guidance for the fabrication of all-fiber coherent beam combiners.

超快光纤激光相干合成技术是突破飞秒激光单根光纤功率提升受限的有效技术手段。基于光纤拉伸器锁相，并结合随机并行梯度下降（SPGD）算法，成功实现了两路超快激光相干偏振合成。该锁相方案不仅避免了采用常规电光相位调制器对脉冲信号造成的光谱调制，而且可有效降低系统的插入损耗，提高相位调制范围、耐受功率以及前级光源系统的紧凑性与鲁棒性。合成的最高功率为10.9 W，最高功率下合成效率为90.1%，闭环状态下锁相残差为λ/31。实验结果表明，采用光纤拉伸器和SPGD算法组成的相位控制系统，在超快激光相干合成领域具有较强的发展潜力。合成的脉冲在最高功率下可压缩至494 fs，压缩效率为73.3%，对应的单脉冲能量为3.99 μJ。

主要介绍了近年来光纤激光相控阵相干合成技术的发展现状，总结了中国科学院光电技术研究所在这方面的最新研究成果，包括基于振幅调制的光纤激光相控阵相干合成能力优化、光纤激光相控阵实现收发一体相干合成、光纤激光相控阵的目标在回路相干合成、光纤激光相控阵在大气湍流下实现耦合接收光束的共相合束、基于多孔径波前探测的相干合成方法、基于自适应光纤准直器和微透镜阵列的光束大角度高精度连续寻址扫描等。以上研究工作将促进光纤激光相控阵技术朝向更多单元、更高功率、更远距离等方向演进，并推动其与激光大气传输、空间激光通信、自适应光学等理论和应用的结合与发展。

介绍了目前研究中相干合成多采用空间结构的研究现状，分析了空间结构的相干合成方案需要复杂的光路调节且长时间工作稳定性欠缺，肯定了基于光纤合束器件的全光纤激光相干合成在相干合成光源中的稳定性与实用性，梳理了近年来基于光纤合束器件的全光纤激光相干合成方案，分别介绍了基于光纤耦合器、光子灯笼、相干信号合束器以及基于自成像效应实现全光纤合束的技术方案及研究现状，分析了不同光纤器件目前的主要限制因素和发展瓶颈，并展望了未来的发展方向。

分析了多抖动算法的工作原理，通过波动光学原理以2-11路相干合成系统作为数学模型进行仿真模拟，引入了动态噪声模型，以总合成光束的均方根相位误差作为评价函数，分析了不同阵列规模下的相干合成系统中噪声频率以及噪声振幅对系统相位锁定效果的影响，当噪声频率或噪声振幅过大，超出算法补偿相位噪声的能力时，便会锁相失败。证明了增益系数与调制振幅存在一个最优区间且只有处于该区间内时，才能快速完成锁相。引入有效控制带宽概念，用以直观评价多抖动算法的锁相性能，研究表明，有效控制带宽与采样频率、第一路调制频率成正比例，与噪声振幅成反比例，且随着阵列规模增大，有效控制带宽降低。

截至目前，光学相控阵技术已经发展了70多年，针对不同的应用方向，发展出了液晶、MEMS、光波导、相干合成等多种器件和技术方案，在激光雷达、空间光通信、高亮度激光产生、合成孔径探测等应用领域获得了初步应用。光学相控阵技术通过对光束阵列中单元光束相位的控制，从而实现阵列光束等相面的重构或精密调控，具有系统体积质量小、响应速度快、光束质量好等优点。首先介绍了光学相控阵的工作原理，然后从激光发射和远距离成像两方面对几种主流相控阵技术的发展现状、应用方向及发展趋势进行了综述，最后给出了笔者的一些思考与建议。

High-power orbital angular momentum (OAM) beams have distinct advantages in improving capacity and data receiving for free-space optical communication systems at long distances. Utilizing the coherent combination of a beam array technique and helical phase approximation by a piston phase array, we have proposed a generating system for a novel high-power beam carrying OAM, which could overcome the power limitations of a common vortex phase modulator and a single beam. The characteristics of this generating method and the orthogonality of the generated OAM beams with different eigenstates have been theoretically analyzed and verified. Also a high-power OAM beam produced by coherent beam combination (CBC) of a six-element hexagonal fiber amplifier array has been experimentally implemented. Results show that the CBC technique utilized to control the piston phase differences among the array beams has a high efficiency of 96.3%. On the premise of CBC, we have obtained novel vortex beams carrying OAM of $\pm 1$ by applying an additional piston phase array modulation on the corresponding beam array. The experimental results agree approximately with the theoretical analysis. This work could be beneficial to areas that need high-power OAM beams, such as ultra-long distance free-space optical communications, biomedical treatments, and powerful trapping and manipulation under deep potential wells.