激光线宽对光学锁相环锁相效果的影响

Influence of Laser Linewidth on Phase-Lockingof Optical Phase Locked Loop

为了获得利于相干合成的具有高相干性的单元光束,可利用光学锁相环(OPLL)来实现本振激光的相位锁定。推导了锁相后激光复振幅的互相关函数表达式,并以此评价锁相后光束间的相干性。具体计算了参考光线宽、时间常数和本振激光线宽差对互相关函数值的影响。定义与本振激光线宽差相关的评价参数M,以此表征当其他参数一定时本振激光线宽差对锁相后激光相干性的影响。进一步针对本振激光线宽不一致对锁相效果的影响进行详细分析,得到相关参数合理值范围的计算公式。结果表明对于不同的本振激光线宽差范围需要设计不同的OPLL系统时间常数来实现有效锁相。

Herein,we use an optical phase locked loop(OPLL)for locking the local laser′s phase to achieve better laser phase-lock and obtain highly coherent unit beams.First,the cross-correlation function of the phase-locked laser′s complex amplitude is determined,and the coherence between different phase-locked lasers is evaluated with a cross-correlation function.The influences of several key parameters,such as the linewidth of the reference light,time constant of the OPLL system,and the difference values of the local laser′s linewidth on the function′s value are analyzed.The evaluation parameter Mis used to characterize the influence of the difference values of the local laser′s linewidth on the coherence of the phase-locked laser keeping other parameters constant.Furthermore,the influence of the difference values of the local laser′s linewidth on the phase-locking effect is analyzed in detail,and the related formula for calculating a reasonable value range of the related parameter is obtained.Our results indicate that the time constant of the OPLL system must be designed on the basis of the linewidth interval of a local laser to achieve effective phase-locking.