Giant high-order field moments in metal-dielectric composites

A scaling theory describing the local field distribution and high-order fie ld moments in metal-dielectric percolating composites is developed. It is s hown 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 predi cts that the high-order field moments that characterize the average enhance ment of nonlinear optical processes are very large and frequency independen t in a wide spectral range. The local nonlinear signals from the "hot" spot s 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. (C) 1999 Published by Elsevier Science B.V. All rights reserved.