The high-power mode-programmable orbital angular momentum (OAM) beam has attracted significant attention in a wide range of applications, such as long-distance optical communication, nonlinear frequency conversion, and beam shaping. Coherent beam combining (CBC) of an optical phased array (OPA) can offer a promising solution for both generating the high-power OAM beam and rapidly switching the OAM modes. However, achieving real-time phase noise locking and formation of desired phase structures in a high-power CBC system faces significant challenges. Here, an internal phase-sensing technique was utilized to generate the high-power OAM beam, which effectively mitigated thermal effects and eliminated the need for large optical devices. An OPA with six elements was employed for experimental demonstration. The first effective generation of over 1.5 kW mode-programmable OAM beam in a continuous-wave domain was presented. Moreover, the results demonstrated that the generated OAM beam could be modulated with multiple dimensions. The topological charge can be switched in real time from -1 to -2. Notably, this OAM beam emitter could function as an OAM beam copier by easily transforming a single OAM beam into an OAM beam array. More importantly, a comprehensive analysis was conducted on power scaling, mode switching speed, and expansion of OAM modes. Additionally, the system’s compact design enabled it to function as a packageable OAM beam emitter. Owing to the advantages of having high power and programmable modes with multiple dimension modulation in phase structures and intensity distribution, this work can pave the way for producing high-power structured light beams and advancing their applications.

We experimentally demonstrated a cascaded internal phase control technique. A laser array with 12 channels was divided into three sub-arrays and a stage array, and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent (SPGD) algorithm, respectively. In this way, the phases of the whole array were locked, and the visibility of the interference pattern of the whole emitted laser array in the far field was ∼93%. In addition, the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination (CBC) system due to its compact spatial structure.

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。

全光纤激光阵列主动相位控制利用全光纤网络实现阵列激光的活塞相位内部探测与控制，具有结构紧凑、无需外部反馈光学器件和易于扩展等优点，是大阵元规模光纤激光相干合成重要发展方向之一。采用全光纤相位探测结构，介绍了全光纤激光阵列主动相位控制技术的系统原理和利用光纤耦合器实现相位锁定的过程，总结了全光纤激光阵列主动相位控制关键技术，通过优化算法实现全光纤激光阵列主动相位控制验证实验。探讨了在全光纤结构主动相位控制中π相位模糊问题及解决方法，给出了利用双波长探测实现消除π相位模糊问题的仿真结果。最后梳理了全光纤激光阵列主动相位控制研究现状，并从路数扩展、功率提升和应用等方面进行了展望。

介绍了本课题组近年来在基于空间结构内部锁相的光纤激光相干合成方面的研究工作，给出了空间结构内部锁相相干合成的基本原理,搭建了七路低功率光纤激光阵列实验系统，结果表明在内部相位噪声校正基础之上，可以稳定补偿外部相位差进而实现激光阵列同相位输出，验证了内部锁相方法的可行性。进一步介绍了空间结构内部锁相技术在目标在回路相干合成、阵列光束光场调控等方面的拓展应用，通过实验论证了空间结构内部锁相技术能够有效提升目标在回路相干合成系统的相位控制带宽，并在远场有效生成轨道角动量光束阵列，其拓扑荷数可从−1到+1切换。