Spectral and spatial investigation of midinfrared surface waves on a plasmonic grating

摘要

A patterned metal film with a periodic array of subwavelength apertures, fabricated upon a semiconductor substrate and designed to possess transmission resonances in the midinfrared is interrogated with a wavelength-tunable external cavity quantum cascade laser. The interaction of the coherent light with this plasmonic structure is studied using a spatially resolved transmission experiment, allowing for the far-field imaging of propagating waves on the surface of the metal film. Spatial and spectral transmission is investigated for a range of near-normal incidence angles. For nonzero angles of incidence, coupling of laser light, at distinct frequencies, to surface waves propagating in opposite directions is demonstrated.