Error analysis of the dispersion-compensated wide-band polarization sagnac interferometer

Imaging polarimetry can obtain two-dimensional intensity distribution information and its corresponding states of polarization from the target simultaneously. Sagnac polarization imaging interferometer is one of the typical channeled polarimetry technologies. By splitting the incident light through the triangular optical structure, the polarization information of the target is modulated into the interference fringes and can be obtained by the demodulation algorithm. The non-ideal optical elements in the system will cause reconstruction errors. This article analyses several factors that affect the measurement accuracy, including the splitting ratio of polarization beam splitter and the diffraction efficiency of the blazed grating. We derive the modified intensity formula and obtain interference patterns through numerical simulations. By calculating the modulation degree of interference fringes and reconstruction error under different non-ideal parameters, we have come to the conclusion that to meet the requirement of modulation degree > 0.5 and reconstruction error < 10%, the beam splitting ratio of the PBS should be α < 1.22. The diffraction efficiency ratio of s-polarization to p-polarization of the blazed grating should be ηs/ηp > 0.83, and the first-order diffraction efficiency should be η1 > 79%.