Perfect Anomalous Absorption of TM Polarized Light in Metallic Grating Situated in Asymmetric Surroundings

In this paper, we predict an unexpected perfect optical absorption phenomenon of oblique-incident transverse magnetic polarized light in a metallic grating situated in asymmetric surroundings. Two physical processes result in the anomalous absorption: One is the total internal reflection at the grating's interface; another is the Fabry-Pérot-like resonance supported in the grating's slits. For small filling factor grating (f <; 0.9), the enhanced anomalous absorption only appears at grazing incidence with incident angle larger than 85°; however, if the filling factor is sufficiently large (f > 0.9), anomalous absorption is realizable only if the total internal reflection occurs. The influences of structural parameters, such as grating thickness, slits material on the anomalous absorption are investigated. Based on these properties, a plasmonic absorption device with a designed absorption line shape is proposed.