Mediating Fano losses in plasmonic scatterers by tuning the dielectric environment

Abstract

Scattering from metal nanoparticles above a high index substrate has the potential to significantly enhance light trapping in thin film devices with minimal additional cost. However, the benefits of this approach are currently limited by short wavelength losses from Fano resonances arising due to interference between the plasmon modes in a nanoparticle. In this paper, the effect of particle-substrate interactions on the observed Fano behaviour is explored in detail, using finite-difference time-domain simulations and an analytical model. Several approaches to mitigate the Fano loss are explored, and it is found that overcoating the particle with a thin dielectric film represents by far the most effective way to remove Fano losses whilst keeping broadband forward scattering high.