矩形光斑阵列合束的锁相闭环分析

Coherent Combination Analyses of Rectangle Spot Beams Array with Phase-Locked Closing-Loop

光束合成是高功率固体激光器进一步发展的重要途径,其中各子束的相位锁定是实现相干合成的关键。分析了4束矩形光斑在光束合成中子束相位探测方法,建立阵列光束在锁相闭环下的光束合成模型。采用外差法探测子束与参考光束形成的拍频信号,通过异或电路及滤波电路得到直流信号,计算出该子束的相对相位差;将相位差转换为相位调制控制器的驱动电压,从而实现子束的相位闭环控制。利用模型研究了锁相开环、闭环下,不同子束间相位差、随机像差对合成光束远场强度分布的影响。模拟结果显示,锁相闭环下可以实现各子束与参考光束相位一致。另外讨论了影响闭环控制下相位残差的因素。

Beams combination is an important way for development of high power solid state lasers,and the phase control electronics contributes greatly to the success of the coherent combining.The method of phase detection for beamlets in a 4 rectangle spot beams array is analyzed,and its mathematical model of coherent combination under phase-locked condition is established.A high-speed wavefront sensor is used to sample the wavefront of one beamlet in laser array,and phase difference between the beamlet and reference beam is detected by the way of heterodyne method from the beat frequency signal,which results from the interference of the reference beam with each beamlet.The phase difference is used to actively control the phase modulator of the beamlet,and then all of the output phases are exactly aligned.Some simulated waveform signals changing versus time are presented during the locking loop is closed,and it is also simulated that the intensity distribution of combined far-field spots changes with phase difference and random aberration among these beamlets,which is compared with that when the locking loop is opened.It is concluded from the simulated results that all output phases of each beamlets can be exactly aligned when the locking loop is closed.The control precision and condition of closing-loop are also analyzed.