Diffractively Structured Multi-Spectral GaAs EO Seeker Windows for Kill Vehicles

摘要

The goal of this effort was to design, develop, and demonstrate diffractive anti-reflection structures (DARS) on gallium arsenide (GaAs). Structures were designed and fabricated in GaAs intended to reduce the reflectance to infrared radiation from 1-10 microns wavelength. Design trade studies were performed to determine the optimum overall depth and period of the structure. The wafers were coated with UV sensitive photoresist and exposed in our interferometric stepper and our reduction stepper. Patterned areas were approximately 1cm x 1cm square. The wafers were then developed and measured to determine that the appropriate size and shape had been achieved prior to etching the pattern into the substrate. The wafer was etched in a-plasma reactor to transfer the developed pattern into the GaAs. The depth and period of the surface was characterized using an atomic force microscope and a Scanning Electron Microscope. Reflectance spectra were measured for several angles of incidence.