Fundamental and higher-order Bloch surface plasmons in planar bimetallic gratings on silicon and glass substrates

摘要

We study fundamental and higher-order (HO) localized Bloch surface plasmons (BSPs) in a 1D subwavelength-periodic thin metal film with silicon and glass claddings. The film is a lamellar bimetallic grating where the real part of permittivity of the slit is also negative. We show that transmission enhancement due to HO BSPs is much weaker compared with the case when the first-order or fundamental BSP (FBSP) mediates resonant transmission. We also identify parameters of the structure corresponding to the mixed-order double resonance, i.e., a resonance between the FBSP on one surface of the film and a HO BSP on the other surface. We show that, unlike the double resonance between two FBSPs, this condition does not affect the transmission enhancement. Finally, we observe strong suppression of transmittance for a structure with a silicon superstrate and glass substrate. This effect occurs only when all higher-order harmonics in the substrate are evanescent. In the regime of transmission suppression, the propagating zero-order diffracted wave and evanescent first-order diffracted harmonic at the metal-glass interface are phase shifted by pi. (C) 2008 Optical Society of America.