Integrating Infrared (IR) Focal Plane Array (FPA) detectors with micropolarizer array achieves viable IR polarimeters. This work systematically studies the extinction ratio (ER) variation tendencies of the polarimeter associated with the assembling process. A 3D Finite-Different Time Domain (FDTD) model was established to characterize the electrical field distributions and extract the concerned parameters. The ER variation caused by the distance between the plane of grating wires and the focal plane is significant, while the one caused by the tilting is moderate. Hereby reasonable assembling strategies can be determined. What’s more, optimization methods have been proposed, which enables preferrable ERs with no additional process difficulties.
Polarization information is widely used in complex applications such as industrial detection, biomedicine, earth remote sensing, modern military, and aerospace. However, traditional polarization devices cannot adequately satisfy the requirements of increasingly complex environments. A subwavelength grating consisting of three types of materials, namely, aurum, platinum, and titanium, was designed to improve the performance of the polarimetric components of a midwavelength infrared polarization imaging system. The morphological structure parameters of the designed grating were optimized by analyzing the effects on the polarization performance through the rigorous coupled wave theory. The proposed Au–Pt–Ti composite grating could address the problem of grating peeling off from the substrate because of high temperature during preparation. The composite grating has some advantages such as high mechanical stability, lower oxidation, and great polarization properties. The diffraction can be reduced and the extinction ratio (ER) can be effectively enhanced in a midwave infrared (MWIR) focal plane array through appropriate reduction in the termination edge spacing and the addition of a gold frame between polarizer pixels. The grating with a period of 0.8 μm was designed for application in the MWIR band. The fill factor was 0.5 and the depths of Au–Pt–Ti in the grating region were 0.44 μm. Each pixel was separated by a 3.2-μm wide gold frame. Modeling results revealed that the ER of grating was higher than 28.68 and 32.77 above the incident wavelengths of 3.89 and 4.57 μm, respectively. Additionally, excellent polarization capability was observed over a wide MWIR spectrum. Furthermore, the current manufacturing process level may generate polarizers with the aforementioned structural specifications.
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