Giant high-order field moments in metal–dielectric composites

A scaling theory describing the local field distribution and high-order field moments in metal–dielectric percolating composites is developed. It is shown that the field distribution is extremely inhomogeneous and consists of small spatially separated clusters of very sharp peaks, “hot” spots, where the local fields are much greater than the applied field. The theory predicts that the high-order field moments that characterize the average enhancement of nonlinear optical processes are very large and frequency independent in a wide spectral range. The local nonlinear signals from the “hot” spots exceed the average surface-enhanced signal by many orders of magnitude, a fact that opens a fascinating possibility of the nonlinear spectroscopy of single molecules and nanoparticles.