Localized Surface Plasmon Decay Pathways in Disordered Two-Dimensional Nanoparticle Arrays

The size and shape of a metal nanoparticle determine its optical properties. When placed in an array the single particle response is further modified by the scattered fields, which for a random array are unique to each scatterer. However, at the array level scattering and absorption retain single-particle-like spectra. Using T-Matrix calculations and an analytical model of intra-array coupling in amorphous arrays we show how the branching ratio of the localized plasmon decay depends on disorder and particle density. We calculate the effective polarizability and demonstrate its effects on scattering and absorption. The scattering-to-absorption ratio is a function of particle separation in the disordered array and can significantly deviate from the inherent single particle ratio. We trace the period of this oscillatory dependence of the ratio to the single particle plasmon resonance wavelength. This effect has implications for applications in which one of the decay channels has to be dominant, for example, absorption for hot electron hole pair generation in the metal particles or scattering into a nearby semiconductor