Giant fluctuations of second harmonic generation on nanostructured surfaces

On the basis of spectral-expansion Green's function theory, we theoretically describe the fundamental harmonic (FH) and second harmonic (SH) local fields at nanorough surfaces of silver and gold. The numerical simulation of these fields in the model of random planar composites has shown that the SH local-field intensity possesses power-law (scaling) distribution for a wide range of system and excitation parameters, which is indicative of giant fluctuations of the SH local fields. Though these scaling phenomena are universal, the scaling index of the SH intensity distribution is not universal depending on the material, excitation frequency, and the fill factor of the nanosystem. The results obtained are in qualitative agreement with the existing experiments.