SCATTERING OF 2ND-HARMONIC LIGHT FROM SMALL SPHERICAL-PARTICLES ORDERED IN A CRYSTALLINE LATTICE

Experimental evidence of scattering of second-harmonic light from the surface of spherical particles of optical dimensions is presented. Thi s mechanism for second-harmonic generation is observed in a suspension of monodisperse spherical colloidal particles, ordered in a centrosym metric crystalline lattice. In this periodic structure the mechanism o f phase matching is provided by the bending of the photon dispersion c urve near the Bragg reflection band. A simple theoretical analysis bas ed on the Rayleigh-Gans scattering approximation shows that constructi ve interference of the second-harmonic light scattered from different portions of a single sphere surface leads to a nonvanishing field with a quadrupolar distribution intensity pattern.