UC Irvine

Surface plasmon polariton (SPP) modes on metallic films give rise to surface fields that can be used to enhance optical phenomena. Whereas SPP modes have been used to enhance the fluorescence and Raman response from molecules in the vicinity of the metallic surface, here we explore the use of SPP modes for detecting particles and structures that are non-fluorescent. In particular, we study the role of thin gold films in supporting SPP fields, which subsequently become distorted and confined by the presence of sub-micron-sized particles, resulting in nonlinear electron-hole pair generation in the gold followed by radiative recombination. This mechanism, in which the gold film is both the source of strong near-fields as well as the antenna for coupling radiation to the far-field, holds promise as a label-free sensing mechanism of small particles near the surface. In this work, the sensitivity and utility of this relatively unexplored property of thin gold films is investigated.