Surface plasmon coupling enhanced dielectric environment sensitivity in a quasi-three-dimensional metallic nanohole array

An enhanced dielectric environment response is observed in a kind of metallic nanohole arrays which are prepared by metal deposition on a sacrificial two dimensional colloidal crystal template. The periodic metallic structures are composed of interlinked metallic half-shells supported on a planar dielectric substrate. When putting in dielectric matrix of different refractive index, the measured sensitivity of the quasi-three-dimensional metallic nanohole array can reach a value of 1192 nm per refractive index unit which shows a five-fold increase as compared with the metallic structures supported on the template. The observed boost in sensitivity is found to originate from a substantially reduced substrate effect, resulting in a pronounced surface plasmon coupling of which its strength is independent of the dielectric environment, a characteristics absent in conventional planar metallic subwavelength hole arrays. These findings are analyzed theoretically and confirmed by numerical simulations.