Analysis of transmission characteristics and multiple resonances in plasmonic gratings coated with homogeneous dielectrics

We analyze the broadband transverse magnetic transmission characteristics of two very low aspect ratio plasmonic nanograting structures under normal incidence, using rigorous coupled wave analysis and full wave Maxwell's equations solver. A binary metallic grating with narrow fundamental surface plasmon resonance mode was obtained by systematic variation of geometrical parameters. The binary grating had an aspect ratio of 0.2 and exhibited a sensitivity of 560 nm/RIU. Our analysis of another structure consisting of a metallic grating with a very small aspect ratio of 0.1, patterned on a thin homogeneous metal interspacer layer on a dielectric substrate shows 50% reduction in full width at half maximum of fundamental surface plasmon resonance with a sensitivity of 590 nm/RIU. This plasmonic nanograting structure exhibits a strong potential to be used as refractive index sensor due to very high sensitivity, higher localization of the fields, possibly higher signal to noise ratio and very low aspect ratios that are needed to maintain laminar flow of analyte. Copyright © 2013 The Electromagnetics Academy.