Spectrally-Resolved Polarization Anisotropy of Single Plasmonic Nanoparticles Excited by Total Internal Reflection

Abstract

Polarization-resolved optical studies of individual plasmonic nanoparticles are valuable for providing orientation information about anisotropic plasmonic nanostructures, such as nanorods and nanoparticle dimers, but are less useful for structures such as nanoprisms. In this study, the anisotropic polarization-dependent excitation field generated by through-the-objective total internal reflection (TIR) is used to probe the orientation of single gold nanorods and single silver triangular nanoprisms with spectral and polarization resolution. By correlating localized surface plasmon resonance (LSPR) and polarization-resolved spectra with scanning electron microscopy (SEM) imaging, we show that both nanorods and nanoprisms show anisotropic polarization-sensitive scattering. While the polarization response of the nanorods is consistent with previous reports, the nanoprisms show an unexpected anisotropy that is related to their orientation in the x–y plane. Exploiting the anisotropic polarization-dependent excitation field offered by TIR allows us to access orientational information about a variety of nanostructures through a nonperturbative optical technique.