Anomalies of metallic diffraction gratings

Abstract

A detailed analysis of anomalies of metallic gratings is performed for a large interval of groove depths. Two types of zero of the zeroth diffraction order are distinguished: the Bragg type [ Alta Freq.38, 82 ( 1969)], exhibited in a Littrow mount for both TM and TE polarizations and localized for flat surfaces at negative imaginary infinity in the complex α plane of the sinus of angles of incidence, and a second type, connected with plasmon–polariton existence on a planar metal–air interface in TM polarization. The trajectories of these zeros are drawn in the α complex plane, revealing some new connections between them.