Chang Qi, Hou Tianyue, Chang Hongxiang, Ma Pengfei, Su Rongtao, Ma Yanxing, Zhou Pu
Opt Express. 2021 Oct 11;29(21):34863-34879. doi: 10.1364/OE.442313.
Coherent beam combination (CBC) holds promise for scaling the output power of the laser system while maintaining good beam quality. Owing to the thermal effect and mechanics instability, piston and tilt distortions always exist and affect the performance of the combined beam. To ensure the constructive interference in the far-field, dynamic correction of the distortions is highly required. Here, we propose an approach for the simultaneous correction of piston and tilt distortions in CBC systems. Based on the position and interval information of the near-field interference fringes, the theoretical expressions for the relative piston phase and tilt errors of each array element are derived, indicating that dynamic distortions in CBC systems can be directly calculated and then corrected by employing phase control servos. To demonstrate the feasibility of the proposed approach, Monte-Carlo Simulations have been carried out for different perturbative environments. Our results indicate that both piston phase and tilt errors can be calculated and compensated accurately (λ/25 and 0.11μrad) by the proposed approach even in 169 beamlets, which also has high tolerance for defocus errors. This work could provide valuable reference on the practical implementation of high-power, phase-locked fiber laser array systems.
相干光束合成（CBC）有望在保持良好光束质量的同时提高激光系统的输出功率。由于热效应和机械不稳定性，活塞和倾斜畸变总是存在并影响合成光束的性能。为确保远场中的相长干涉，对畸变进行动态校正非常必要。在此，我们提出一种在CBC系统中同时校正活塞和倾斜畸变的方法。基于近场干涉条纹的位置和间隔信息，推导了每个阵列元件的相对活塞相位和倾斜误差的理论表达式，表明CBC系统中的动态畸变可以直接计算，然后通过采用相位控制伺服器进行校正。为证明所提方法的可行性，针对不同的微扰环境进行了蒙特卡洛模拟。我们的结果表明，即使在169个小光束的情况下，所提方法也能准确计算并补偿活塞相位和倾斜误差（λ/25和0.11μrad），并且对离焦误差具有高容忍度。这项工作可为高功率锁相光纤激光阵列系统的实际实现提供有价值的参考。
