Nd:YAG激光器退偏率测量实验研究

Experimental Investigation of Depolarization Rate of Nd∶YAG Laser

固体激光腔内放置薄膜偏振片对P偏振光存在4％～5％反射，当激光器输出P偏振光时，退偏损耗光束中包含较强P偏振光，无法测得腔内光束真实退偏率。实验研究Nd：YAG固体激光在输出P偏振光时，薄膜偏振片对P偏振光反射对腔内光束退偏率测量的影响。结果表明，当损耗光束中所包含P偏振光不被剔除时，不同透射率所对应退偏率曲线间存在较大差异；而当剔除这些P偏振光时，不同透射率所对应退偏率测量曲线趋于一致，测量结果可反映腔内光束的实际退偏率；在激光器输出s偏振光时，其退偏率测量值与当剔除损耗光束中P偏振成分后，输出P偏振光Nd：YAG谐振腔腔内光束退偏率测量值趋于一致。

Thin film polarizer reflects about 4%~5% p-polarized light, when the laser beam is incident on the thin film polarizer at Brewster＇s angle, which makes the laser beam reflected by intra-cavity thin film polarizer contain depolarized light （s-polarized light）and unignorable p-polarized light. This will result in intra-cavity depolarization rate measurement inaccurate. Intra-cavity depolarization rate measuring inaccuracy caused by intra-cavity thin film polarizer reflecting p-polarized light in an outputting p-polarized Nd ： YAG resonator is experimentally investigated. The results show that, for different output mirror transmission in a outputting p-polarized light Nd ： YAG resonator, there is obvious difference between the measured depolarization rate plots, when the p-polarized light caused by reflecting effect of thin film polarizer is not filtered from the depolarized light. And that tends to be consistent, if the p-polarized light are filtered from light reflected by the thin film polarizer. The investigation also shows that, for a outputting s-polarized Nd ： YAG, the the depolarization rate can be directly measured, because the depolarization light, which is s-polarized light, contains little p-polarized light.