Extended Short-Wavelength Infrared (SWIR) Focal Plane Arrays (FPA) for Hyperspectral Imaging

Hyperspectral imaging at full short- and extended short-wavelength infrared spectral band (0.9 – 2.5 µm) has important military applications. When used for imaging, a SWIR camera can operate at night using light reflected off the subject in the scene, generating high resolution images with details such as shadows and surface roughness. Compared to thermal infrared imaging, SWIR images look more like visible images and thus scene interpretation is much easier. Even on moonless nights, natural background radiation from the sky, called nightglow, provides useful illumination for imaging. Additional advantages include imaging through glass windows, some types of camouflage, smokes, fires, and haze with less attenuation than visible light. Many objects of military interest, such as explosives and chemicals, disturbed earth, terrain, and vegetation, contain rich and unique spectral features in the SWIR band. The goal of this effort is to demonstrate high-performance extended short-wavelngth infrared photodetectors, focal plane arrays, and camera system based on Type-II superlattices. The photodetector performance goal is the following: quantum efficiency larger than 90% with anti-reflection coating, dark current density less than 7×10^-8 A/cm2 at an operating temperature 200K or higher.