提出了一种基于双光弹调制差频调制和傅里叶 -贝塞尔 (Fourier-Bessel)变换的光谱偏振测量方法, 该方法将双光弹调制器 (Dual-photoelastic-modulator, Dual-PEM)分别工作在数值略有差异的频率上, 以对光进行差频调制, 并产生载有被测偏振信息的低频 (几十~几千赫兹)调制分量, 普通阵列探测器就可以实现低频分量的探测。通过对调制信号中的低频成分进行傅里叶 -贝塞尔变换, 可得到被测光对应的 Stokes矢量中 Q(σ)和 U(σ)的光谱。该方法降低了偏振光谱测量系统的复杂度。本文介绍了其原理并推导出了偏振光谱反演公式, 并通过仿真和实验验证其可行性。

A new differential frequency modulation method based on dual-photoelastic-modulator (dual-PEM) and Fourier-Bessel transform is proposed as an key component of dual-photoelastic-modulator-based spectropolarimeter. The dual-PEM are operated as an electro-optic circular retardance modulator. Operating the PEMs at slightly different resonant frequencies ω1and ω2 respectively, generates a differential signal at a much lower heterodyne frequency that modulates the incident light. This method retains the advantages of the existing PEM, and the frequency of modulated photocurrent is decreased by 2~3 orders of magnitude, which can be detected by common array detector. The incident light spectropolarimeter (Q(σ) and U(σ) of Stokes parameters) can be obtained by Fourier-Bessel transform of low frequency component in the modulated signal. The method reduces the complexity of spectropolarimeter measurement system. The basic principle is introduced, the basic equation is derived, and the feasibility is verified through the corresponding numerical simulation and experiment.