β因子用于被动相干组束系统光束质量评价的探讨

Discussion on Applying β Factor in the Evaluation of Beam Quality of the Passive Coherent Beam Combination System

利用二维4路光纤激光环形腔被动锁相相干组束实验平台,对被动相干组束系统的光束质量进行了研究。以衍射极限倍数β因子作为光束质量的评价方法,理论分析了光束占空比以及不同锁相模式对β因子的影响,实验测量了对应不同输出功率水平的β因子。结果表明,虽然β因子可以在一定程度上反映出不同实验条件下光束质量的差异,但是由于β因子的测量核心是确定出焦平面处83.8%环围能量(功率)比的桶尺寸,不能反映相干组束远场光斑的特点,不适合用于评价被动相干组束系统的光束质量。比较分析了β因子与光束质量,光束质量能更好地反映出相干组束的特点。

Beam quality of the passive coherent beam phase-locking experimental platform of four fiber lasers combination system is studied using the ring cavity passive in two-dimensional distribution. With the times-diffractionlimited factor βas the evaluation method, the impact of duty ratio of sub-beams and different phase-locked patterns on the β factor is analyzed theoretically; and the βfactor corresponding to different output power levels is measured in the experiment. The results show that although the β factor can reflect the difference in beam quality under different experimental conditions to some extent, it can not reflect the characteristics of coherent beam patterns in the far-field because the focus of the βfactor measurement is to determine the bucket size of 83.8% encircled energy （power） ratio at the focal plane, therefore it is not suitable for the evaluation of the beam quality of a passive coherent beam combination system. A comparative analysis of the βfactor and beam quality is done, beam quality can better reflect the characteristics of the coherent beam combination.