Wood anomalies for s-polarized light incident on a one-dimensional metal grating and their coupling with channel plasmons

Angular spectra of reflectance of light from one-dimensional periodic gratings of V-shaped grooves in a metal film have been theoretically studied at a fixed wavelength. The exciting light wave was incident in the plane parallel to grooves. For the case of s-polarized incident wave there are two types of features (dips) in reflection spectra. The first type is associated with the excitation of channel plasmons in every single groove of a grating. Angular positions of features of the second type are determined by a period of a grating. We have shown that the features of the second type are Wood anomalies associated with the excitation of surface waves on a metal film by means of diffraction of the incident wave on a periodic grating. For certain periods of a grating and angles of incidence of the exciting wave the resonances of two types can be coupled.