On the properties of materials for designing filters at optical frequencies

Frequency selective surfaces/volumes (FSS/Vs), periodic structures with frequency selective properties, have widely been used for millimeter and microwave applications. In recent years there has been an interest in using these structures at optical wavelengths. One of the applications is a thermo photovoltaic filter used to convert thermal energy into electricity. Numerical simulations of such filters are very limited in the literature. At optical frequencies, the usual material properties and perfect electric conductor (PEC) assumption is not applicable. Moreover, the conventional methods, such as using resistive sheets or lossy dielectrics to simulate metallic losses, are not accurate. The goal of this paper is to provide a new approach for modeling metallic losses more accurately at optical frequencies.