Tuning the Thickness and Orientation of Single Au Pyramids for Improved Refractive Index Sensitivities

Abstract

This paper describes three ways to tune the multipolar surface plasmon resonances of Au pyramidal particles: (1) by varying their thickness; (2) by controlling their relative orientation on a surface; and (3) by changing the refractive index of the surrounding media. We found that as the index of the medium was increased that the plasmon resonances red-shifted linearly from visible to near-infrared wavelengths. By screening the different geometric parameters, we found that 25-nm thick pyramids in a tip-up orientation produced the largest refractive index sensitivities.