Polarization-dependent wavelength-selective structures for multispectral polarimetric infrared imaging

Abstract

The need for compact, rugged, low-cost multispectral-polarimetric filtering technology exists in both the civilian and defense communities. Such technology can be used for object detection, object recognition, and image contrast enhancement. Mosaicked multispectral-polarimetric filter technology, using CMOS-type metallo-dielectric grating structures, is presented as a potential solution in which the spectral filtering and polarization filtering functions are performed in a single component. In this work, single-layer and double-layer metallic-grating structures, embedded in uniform dielectric are investigated. Spectral tunability using only transverse grating properties in a two-layer metallic-grating structure is demonstrated. Additionally, one-layer and two-layer slotted-grid rectangular-aperture two-dimensional metallic gratings for infrared imaging are also studied. To complement the simulations, thirty-nine separate infrared optical polarization and spectral filters were fabricated in silicon using the AMI 0.5pm / MOSIS foundry service, and they were characterized using polarized FTIR analysis. Polarized transmission spectra from these CMOS-based filters compare favorably with simulation results for four of the most promising filter types. An external-cavity-coupled single-layer metallic-grating structure, compatible with CMOS microbolometer detector technology is also offered as an application example.