Abstract
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- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process and, by averaging 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\times }\,\,50$ </tex-math></inline-formula> pixels and 96 frames, achieved a polarization rotation detection limit of 5.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\times }\,\,10^{-4^{\circ}} $ </tex-math></inline-formula> 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.
Highlights
O PTICAL polarization detection can provide information that cannot be obtained by ordinary light intensity detection, such as the angle of the incident surface [1], differences in materials [2], distortions in a transparent material [3], and separation of reflected and transmitted components in transparent media
We demonstrated the feasibility of electric-field imaging using the proposed sensor and a (100)-ZnTe crystal
Application to High-Frequency Electric-Field Imaging In this study, we demonstrated visualizing the electric field on a microstrip line via a fabricated polarization image sensor
Summary
O PTICAL polarization detection can provide information that cannot be obtained by ordinary light intensity detection, such as the angle of the incident surface [1], differences in materials [2], distortions in a transparent material [3], and separation of reflected and transmitted components in transparent media. The first layer is an external polarizer, which can achieve a high extinction ratio of 10−3 or higher, even with a polarizing beam splitter or a relatively inexpensive film polarizer This polarizer is placed at an angle that blocks incident polarized light. With this method, the polarization rotation angle can be enhanced while the light intensity is reduced. The polarization rotation angle can be enhanced while the light intensity is reduced This effect enables the image sensor to detect weak polarization with higher sensitivity, despite its limited light-receiving capacity. SASAGAWA et al.: POLARIZATION IMAGE SENSOR FOR HIGHLY SENSITIVE POLARIZATION MODULATION IMAGING the ON-pixel polarizing element at ±π/4 rad with respect to the incident polarized light, the polarization rotation is efficiently converted into intensity. If the light source intensity can be sufficiently high, a higher polarization detection sensitivity is expected using a polarizer with a higher extinction ratio
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