高功率光纤激光的时间部分相干性对相干合成的影响

Effect of partially coherence of high power fiber laser on coherent combination

将多个光纤激光器的输出光束进行相干合成是获得高功率、高光束质量激光的有效途径。利用准部分相干光(PPCB)模型,计算了高功率光纤激光器阵列发出的部分相干光在远场的能量分布,分析了激光的时间部分相干性对相干合成的影响。计算结果表明,随着单根激光器输出光束线宽的增大,远场光斑的图样基本保持不变,但峰值功率和Strehl比随之减小。对于采用的算例,要保证远场光斑的Strehl比大于0.8,单根光纤激光器的线宽不能超过5 nm。

Coherent combination of multiple fiber laser is an effective method to get high power laser with excellent beam quality. However, recently developed high power fiber lasers have relatively long linewidths, which means degradation of coherence and disaduentage of coherent combination. The far-field energy distribution of coherent combining high power fiber laser beam array was calculated using pseudo-partially coherent beam（PPCB） model. The results show that when the linewidths of single fiber laser beam get larger, the far-field pattern hardly changes, but the peak power and Strehl value of far-field spot reduce, which means the degradation of the combined beam. The linewidth of single fiber laser should be no more than 5 nm to keep the Strehl ratio larger than 0.8.