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.

光纤激光是20世纪以来国内的研究热点。国防科技大学在光纤激光方向的研究始于“十一五”期间，至今已有约15年的历程，取得了一系列同行认可的研究成果。学校光纤激光的研究主体依托于光学工程学科。光学工程学是学校的优势学科之一，近几轮学科评估中得到了很好的成绩，为光纤激光方面的研究提供了高水平的科研平台和人才队伍等；另一方面，光纤激光的发展也受益于学校学科门类比较齐全的优势和在学科交叉方面的有益探索与实践。文中从学科交叉视角，梳理学校光纤激光学科方向与电子、材料、控制、智能、纳米等学科方向交叉取得的若干重要突破，从科研范式演进、学科主体驱动、应用需求牵引和科教融合发展等四个方面分析交叉科学研究和交叉学科建设面临的机遇。

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。

窄线宽光纤激光器在遥感探测、非线性频率转换和光束合成等领域具有重要的应用价值。介绍了窄线宽光纤激光振荡器的典型谐振腔结构及其工作原理，从实现更窄线宽的角度梳理了单频选模技术，从获得更高功率的角度梳理了功率提升技术，综述了窄线宽光纤激光振荡器的研究现状，并对窄线宽光纤激光技术的发展进行了展望。