Grating-Vector-Assisted Plasmonic Coupling in a Hexagonally Arranged Silver Island Array

We experimentally and numerically investigated the attenuated total reflection (ATR) spectra of hexagonally periodic structures of discrete silver nano islands array (NIA) and that of continuous silver film with nanohole array (NHA). Some peculiar reflection fine dips in the ATR spectra of the NIA structures were observed. In comparison with the ATR results between NHA and NIA structures as well as carefully analyzing the multiwavelengths numerical ATR spectra of the NIA, we found out the mechanisms leading to the ATR fine dips. They are resulted from the effects of surface plasmon resonances (SPR) and Wood’s anomalies that occur at the silver/air or silver/prism interface with the assistance of two-dimensional reciprocal grating-vectors provided by the NIA. Particularly, our results demonstrated that there are continuous-film-like SPR modes existing in the NIA structures, which can be excited through the coupling between the incident light and the two-dimensional grating-vectors of the NIA.