Analysis of scattering from frequency-selective surfaces in the infrared

A comparative theoretical and experimental analysis of scattering from a doubly periodic dielectric-mounted frequency-selective surface (FSS) in the mid-infrared (4–12 μm) is presented. The theoretical analysis involves the solution of an electric-field integral equation relating the induced current on the FSS in the presence of the dielectric mounting to the incident excitation field. The Green’s function in the presence of the dielectric layers is derived by using a simple spectral-domain technique. In modeling the FSS, the structure is assumed to be infinitesimally thin and is described by complex sheet resistance. Fabrication of FSS’s for use in the mid-infrared is possible by using photolithographic techniques. Experimental and theoretical results are presented for metallic (aluminum) rectangular patch arrays fabricated by reactive ion etching and lift-off processing, respectively, and a resistive (bismuth) patch array fabricated by lift-off processing. These structures exhibit a spectral band-stop characteristic in transmittance.