Abstract

Conducting films with periodic sub-wavelength perforations feature high resonant optical and THz transmission peaks [1]. In this paper we analyze with both analytical calculations and numerical techniques the properties of the resonant features of such metal gratings sandwiched between thin dielectric films. The induced frequency shifts of the transmission resonances can allow the determination of the permittivity of the films. Further, we investigate for the first time how the sensitivity of the gratings (sensors) can be improved by different grating geometries. For analysis, the normal incidence of a plane wave is considered, as illustrated in Fig. la. To calculate the transmission spectrum of the grating, we extended the modal expansion approach pursued for the bare grating in [2] to include the thin dielectric films sandwiching the grating.

© 2007 IEEE