通过主动相位控制实现了两路固体激光器的高光束质量相干合成输出, 总输出功率达到240 W。建立了两路120 W板条激光放大器, 通过光束整形获得了高光束质量方形光斑, 并实现了高占空比光束拼接, 填充因子高于92.4%。研制了光轴一致性探测与控制系统, 采用基于压电陶瓷的快反镜实现了光轴的高精度闭环控制, 两束激光光轴一致性优于2 μrad(RMS)。设计了基于现场可编程门阵列(FPGA)的相位探测与控制系统, 用随机并行梯度下降算法(SPGD)锁定了两束激光的活塞相位。相位闭环后, 远场光斑峰值提高到开环状态的1.7倍, 为理想值的84%。合成光束主瓣包含67%的激光总能量, 光束质量(BQ)为1.1。

We report a coherent combining of two 120 W solid state lasers with good beam quality. Laser beams from two slab laser amplifiers are reshaped into square beam. Up to 92.4% fill factor is achieved by splicing system with small gaps. A compact optical system with high sampling frequency is designed to detect the optical axis of slab lasers. A fast steering mirror (FSM) system driven by piezoelectric ceramics is applied to stabilizing the lasers. When the FSM system works, the root mean square error of the optical axis is significantly reduced to be less that 2 micro radians. The piston phase of two lasers is locked by a fast dithering system based on field programmable gate array (FPGA) using stochastic parallel gradient descent(SPGD) algorithm. After coherent beam combination, the peak intensity of the far-field spot is increased by a factor of 1.7, reaching 84% of the ideal case. When the beams are in phase, the BQ of the combined laser beam is 1.1, which means that more than 67% of the total energy is locked in the main lobe.