We provide a new physical interpretation of scattering from plasmonic nanoparticles on high-index substrates. We demonstrate the excitation of different types of resonant modes on disk-shaped, Ag nanoparticles. At short wavelengths, the resonances are localised at the top of the particle, while at longer wavelengths they are localised at the Ag/substrate interface. We attribute the long wavelength resonances to geometric resonances of surface plasmon polaritons (SPPs) at the Ag/substrate interface. We show that particles that support resonant SPP modes have enhanced scattering cross-sections when placed directly on a high-index substrate; up to 7.5 times larger than that of a dipole scatterer with an equivalent free-space resonance. This has implications for designing scattering nanostructures for light trapping solar cells.

Opt. Express
Photonic Materials

Beck, F. J., Verhagen, E., Mokkapati, S., Polman, A., & Catchpole, K. R. (2011). Resonant SPP modes supported by discrete metal nanoparticles on high-index substrates. Opt. Express, 19(S2), 146–156. doi:10.1364/OE.19.00A146