Polarization Image Sensor for Highly Sensitive Polarization Modulation Imaging Based on Stacked Polarizers

In this article, We demonstrated an image sensor for detecting changes in polarization with high sensitivity. For this purpose, we constructed an optical system with a two-layer structure, comprising an external polarizer and polarizers on a pixel array. An external polarizer is used to enhance the polarization rotation while reducing the intensity to avoid pixel saturation of the image sensor. Using a two-layer structure, the two polarizers can be arranged under optimal conditions and the image sensor can achieve high polarization-change detection performance. We fabricated the polarization image sensor using a 0.35- \mu \text{m} CMOS process and, by averaging 50 {\times }\,\,50 pixels and 96 frames, achieved a polarization rotation detection limit of 5.2 {\times }\,\,10^{-4^{\circ}} at a wavelength of 625 nm. We also demonstrated the applicability of electric-field distribution imaging using an electrooptic crystal (ZnTe) for weak-polarization-change distribution measurements.