Analysis of infrared scattering from a dielectric-mounted frequency selective surface

Abstract

Periodic frequency selective surfaces (FSSs) have been used extensively as filters, output couplers, diplexers, and interferometers in the far-IR and millimeter wavebands for a number of years. Microlithographic advances now make it possible to fabricate these devices for use in the mid-IR (4-12 μm). The analysis of IR scattering from a dielectric-mounted FSS involves the solution of an electric field integral equation obtained using the standard Green's function techniques relating the induced current distribution on the FSS to the incident excitation field. The method we describe represents a generalization of the method for scattering from a freestanding FSS.1 The dielectric mounting generally includes dielectric layers and/ or substrate on either side of the FSS. The Green’s function in the presence of the dielectric layers is derived using the spectral domain technique. 2 Comparison to experimental results obtained for resonant metal dipole arrays is presented. Our analysis takes into consideration the lossy nature of metals in the IR. The treatment of stacked FSSs and/or multiple dielectric layers is also discussed. The method involves cascading the scattering matrices of the individual elements, which for an FSS includes the immediately adjacent dielectric layers.