Effects of the surrounding medium on the optical properties of a subwavelength aperture.

Influence of the refractive index of the surrounding material on the performance of a C-shaped subwavelength aperture is investigated. The changes in the spectral response (0.6 microm to 6 microm wavelength range) and power throughput of the aperture in an optically opaque silver (Ag) film are described for two configurations: one where the film with the aperture is immersed in an infinite dielectric slab and the other where the metallic layer is immediately adjacent to a semi-infinite dielectric substrate. It is shown that, while the resonant wavelengths increase monotonically with refractive index for both cases, the rates of these increases, as well as the behavior of the power throughput, depend not only on the configuration, but also strongly on the transmission mode. These findings have important implications for the design of subwavelength aperture-enhanced devices.