Interaction of near-field light with ordered polystyrene spheres: Experimental studies

We have experimentally observed the interaction of near-held light excited in a total internal reflection geometry with a periodic two-dimensional arr ay of polystyrene spheres. The angular- and frequency-scanned attenuated-to tal-reflection (ATR) method was employed to observe the interaction. ATR sp ectra indicate that there is an easy axis and a difficult axis for the ligh t propagation. When light is incident toward the easy axis, resonant dips a ppear in the ATR spectra. The experimental results were compared with those obtained by finite-difference time-domain analysis. The numerical results obtained by this method are able to explain a part of the experimental ones . Parts of the dips in the ATR spectra were considered to stem from propaga ting and whispering-gallery (WG) modes. That is, the propagation of the WG- modes over several spheres may enhance the coupling between the spheres and the incident light, and consequently may induce resonant structures in the ATR spectra.