偏振分光镜传输系数不等对非线性误差的影响

为了减小激光外差干涉非线性误差，必须考虑偏振分光镜透过率和反射率不等对非线性误差的影响。通过分析两臂透过率与反射率不等对测量信号的影响，推导出两臂反射率与透过率不等对激光外差干涉非线性误差一次谐波和二次谐波影响的理论模型。仿真结果表明，透过率与反射率不等将严重的影响非线性误差一次谐波的大小，当反射率为1而透射率由1变为0．85时，其非线性误差由0、56nm增加到2．03nm，同时非线性误差只是一次谐波和二次谐波的简单叠加。仿真结果表明调整偏振分光镜的旋转角度误差能够有效的消除两臂透过率与反射率不等对非线性误差的影响。为进一步指导调整减小或消除非线性误差提供了理论依据。

Nonlinearity from difference between transmission coefficients of PBS in laser heterodyne interferometer

Different transmission coefficients of polarized beam splitter(PBS) in different directions seriously affect the nonlinearity in laser heterodyne interferometer.Nonlinearity resulting from difference between transmission coefficients in theory is analyzed,and the models of nonlinearity resulting from different transmission coefficients with elliptical polarized and rotation angels of PBS are proposed.The simulation results show different transmission coefficients only affect the first-harmonic nonlinearity.With a constant rotation angle of PBS,when the reflectivity is 1 and the transmissivity reduce from 1 to 0.85,the nonlinearity increase from 0.56nm to 2.03nm,and the nonlinearity is simple superposing of first harmonic and second-harmonic.When reduce the error of rotation angle of PBS,the nonlinearity resulting from different transmission coefficients can be effectively eliminated.