Angular dependence of a narrowband reflection-and-transmission filter containing an ultrathin metallic film

The angular dependence of filtering properties for a novel narrowband reflection-and-transmission filter made of an ultrathin metallic film in front of a planar Fabry-Perot resonator is theoretically investigated. It is shown that the simultaneous peaks in reflection and transmission are strongly dependent on the polarization of the incident wave. The peak positions of the reflection and transmission are shifted to shorter wavelengths as the angle of incidence increases in both TM and TE polarization. Additionally, the reflection peak height is increased in TE polarization, whereas it is decreased in TM polarization. Two effective Brewster angles can be defined through the angle-dependent reflectance at the resonant wavelength for both polarizations. The first, for TE polarization, is found at 34°, and the second is 77° for TM polarization. The structure could thus be used as a polarizing device in addition to a filtering one.