Reflection and transmission in a heterostructured multilayer narrowband filtercontaining thin metallic films

A narrowband filter with two reflection peaks anda single transmission peak is proposed based on a multilayer heterostructure containing two different ultrathin metallic films. The heterostructure filter is formed by cascading two narrowband reflection-and-transmission filters. We use the transfer matrix method to calculate the optical reflectance, transmittance, and absorptance for this filter. Results show that the heterostructure has a pronounced effect on the reflectance,leading to two resonant peaks. The angular dependence of filtering properties is also investigated.This filter is of practical use in the optical signal processing.