Light transmission through metallic channels much smaller than the wavelength

A resonant cavity-enhanced light transmission mechanism in metallic grating s with subwavelength apertures is theoretically interpreted for operation w ith visible light. It is shown that under appropriate boundary conditions, the apertures behave as open Fabry-Perot resonant cavities delivering a hig h photon flux, and that the coupling between the incident light and the fun damental mode supported by the aperture is strongly controlled by surface w aves. Compared to the well-known perfect metallic case, we show that the ef fective index of the fundamental mode strongly depends on the aperture dime nsion, especially when aperture widths much smaller than the wavelength are considered. Consequently, it is predicted that small variations of apertur e shape or dimensions have a huge effect on the transmission properties of real metallic gratings. (C) 2000 Published by Elsevier Science B.V. All rig hts reserved.