光反馈光腔衰荡技术同时测量高反膜S和P偏振反射率

摘要

提出采用光反馈光腔衰荡技术同时测量高反膜的S(垂直于入射平面)和P(在入射平面内)偏振反射率的方法,通过将一束具有一定偏振比、光强方波调制的偏振光入射到衰荡腔中,在调制方波下降沿记录从衰荡腔腔镜透射的光腔衰荡信号,通过双指数拟合得到S、P相应的衰荡时间,从而计算得到高反膜S、P偏振光的反射率.与采用纯S(P)光测量得到的偏振反射率相比,S和P偏振反射率偏差分别仅为1 ppm和15 ppm,证明了同时测量结果的正确性.与传统光腔衰荡测量高反膜偏振反射率方法相比,该测量方法装置简单,操作方便,测量更快速.%An optical feedback cavity ring down (OF-CRD) technique for simultaneously measuring the S-(perpendicular to the plane of incidence) and P-(in the plane of incidence) polarization reflectivity of highly reflective coatings is developed. Polarized light with a certain ratio of S- and P-polarization power and with square-wave modulated intensity is coupled into a ring-down cavity. The ring-down signal that leaks out from a cavity mirror is recorded at the negative edge of the modulation and fitted to a bi-exponential function to determine simultaneously the ring-down time for S and P polarizations. The reflection coefficients of highly reflective coatings for the S and P polarizations are therefore calculated from the determined ring-down time. Compared to the results obtained with purely S or P polarization, the differences for both S and P polarizations are respectively 1 ppm and 15 ppm, indicating the correctness of the simultaneous measurements. Compared to the conventional CRD approach, this simultaneous measurement method has the advantages of simpler configuration, easier operation, and higher speed.