Rugate-filter-guided propagation of multiple Fano waves

Abstract

The canonical boundary-value problem of surface-wave propagation guided by the planar interface of a rugate filter and a homogeneous medium with negative permittivity was solved numerically. Multiple Fano waves with differing phase speed and linear polarization state are guided by the interface, even when the magnitude of the permittivity of the negative-permittivity partnering medium is less than the minimum value of the permittivity in the rugate filter. The concepts of Fano waves and Tamm waves can be unified.