Optical response of a self-standing monolayer of dielectric spheres

An analysis of the optical response of periodically arrayed monolayers composed of dielectric spheres with low refractive index is herein presented. The reflectance spectra of two-dimensional square and triangular lattices are obtained by means of the vector Korringa-Kohn-Rostoker method, both spectra showing very similar qualitative features for photon energies below the onset of diffraction spots. In this energy region, the same number of peaks of unitary amplitude in the reflectance spectra are predicted for both kinds of monolayers, suggesting that this must be a universal feature independent of the particular geometry of the lattice. The origin of these high reflectance peaks is investigated. It is found that the resonances of TM and TE modes due to dipolar, quadrupolar and octupolar interaction inside the monolayer are largely responsible for the peak structure observed in the reflectance spectra.