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 array of polystyrene spheres. The angular- and frequency-scanned attenuated-total-reflection (ATR) method was employed to observe the interaction. ATR spectra indicate that there is an easy axis and a difficult axis for the light propagation. When light is incident toward the easy axis, resonant dips appear 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 propagating 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.