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介绍了随机并行梯度下降(SPGD)算法用于相干合成的基本理论,利用数值模拟的方法对实际相干合成实验中涉及到的算法评价函数、扰动电压分布等参数进行优化选取,确定了实验中应选择的最佳评价函数、扰动电压分布和扰动方式。利用数字信号处理器(DSP)执行SPGD算法,实时控制各路光束的相位,实现了三路瓦量级保偏光纤放大器输出光束的相干合成。实验结果表明,SPGD算法能够有效控制各路光纤激光的相位,系统闭环将合成光束目标圆孔内的能量提高了2.62倍,合成效率达到了理想情形的87%,远场光斑对比度为85%。
This paper introduces the basic theory of Stochastic Parallel Gradient Degradation (SPGD) algorithm for coherent synthesis, and uses the numerical simulation method to optimize the algorithm evaluation function, perturbation voltage distribution and other parameters involved in the actual coherent synthesis experiment, Choose the best evaluation function, perturbation voltage distribution and disturbance mode. The implementation of SPGD algorithm by digital signal processor (DSP) realizes real-time control of the phase of each beam and realizes the coherent synthesis of the output beam of a three-way watt-order PM fiber amplifier. Experimental results show that the SPGD algorithm can effectively control the phase of each fiber laser. The closed loop of the system increases the energy in the target circular aperture of the composite beam by 2.62 times, and the synthesis efficiency achieves 87% of the ideal case and the far-field spot contrast is 85%.