Wavelength-selective infrared Salisbury screen absorber

Abstract

Experimental long wavelength infrared spectral response characterization of a narrowband Salisbury screen absorber suitable for use in microbolometer focal plane arrays is presented. We have demonstrated a microfabricated germanium dielectric support structure layer that replaces the usual silicon nitride structural layer in microbolometers. The fabricated Salisbury screen absorber consists of a chromium resistive sheet as an absorber layer above a germanium dielectric/air-gap/interference structure. In order to produce wavelength-selective narrowband absorption, the general design rules for the germanium dielectric supported Salisbury screen show that the thickness of the air gap should be a half wavelength thick and the optical thickness of the germanium layer a quarter dielectric wavelength thick.