Second Harmonic Generation by Random Particle Systems.

We study the generation of second-harmonic radiation in the interaction of light with systems of two-dimensional particles in random positions. The medium composing the particles is assumed to be homogeneous and isotropic, and the numerical examples are calculated employing a free-electron model for the nonlinear polarization. We first present calculation for the differential scattering efficiencies of isolated particles. For symmetric particles illuminated along the axis of symmetry, we find that the second harmonic scattering amplitude is antisymmetric. The result has interesting implications on the reciprocity relations for second harmonic generation. We then present results for random systems of cylindrical particles. For the fundamental frequency, the results present a clear enhanced backscattering peak due to multiple scattering effects. In contrast, the second harmonic scattering patterns contain no clear indication of the presence of such coherent effects. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]