光腔衰荡法的单波长反射率测量实验研究

分析了反射率光腔衰荡法测量原理的近似条件,讨论了共焦腔的失调特性,计算了腔镜反射率对衰荡信号的影响。在此基础上,为减少OPO激光束的衍射损耗引入的测量误差,选择He-Ne激光作导引光,建立以共焦腔为衰荡腔的单波长反射率测量装置。利用直腔和折叠腔对腔镜和插入镜片的反射率进行了实验测量。直腔方式下测量的均方差小于6×10-6。分析表明,光腔衰荡法只适用于高反镜反射率的测量;在光路调节中采用具有对数变换功能的示波器,可以提高测量精度。

Experimental study of reflectivity measurement of single wavelength by cavity ring-down method

Approximate condition of reflectivity measurement with cavity ring-down method is analyzed,misadjustment characteristic of confocal cavity is discussed and influence of cavity mirror's reflectivity on ring-down signal is calculated.In order to lessen metrical precision from diffraction losses of OPO laser,based on the above analyses,a reflectivity measuring system for single wavelength is set up with cavity ring-down method,whose ring-down cavity is confocal cavity.Experimental measurement of reflectivity of cavity mirror and inserted mirror is carried out.The measurement RMS in linear cavity is less than 6×10^-6.Results show that cavity ring-down method is only for higher reflectivity,and metrical precision can be improved by using logarithm transform of oscillograph in adjustment of the optical cavity.