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

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.