Plasmon-Induced Nearly Null Transmission of Light Through Gratings in Very Thin Metal Films

Abstract

Based on numerical simulations, we show that a very thin metal (Ag) film, otherwise transmissive partially, becomes opaque for transverse magnetic-polarized light in a certain spectrum band when perforated with grating-like slits. Positions of the nearly null transmission band are dependent on the various structure dimensions, particularly on the ridge width for gratings with relatively narrow slit width. Our analyses show that the nearly null transmission is related to resonant excitation of anti-symmetric bound surface plasmon waves at the ridges of the thin metal film gratings and further resulted from destructive interference of waves evolved from the fields at the ridges and slits that are in opposite phase. It is also found that for 2D gratings, the nearly null transmission band appears only for disk array-type gratings and not for the hole array-type gratings. This structure may be applied in novel photonic devices to enhance their performances and functionalities.