Giant optical responses in microcavity-fractal composites

Optical properties of fractal nanostructured composite materials are consid ered. The fractal geometry results in localization of plasmon excitations i n the "hot" spots, where the local field can exceed the applied field by se veral orders of magnitude. The high local fields of the localized fractal m odes result in dramatic enhancement of optical responses, making feasible t he surface-enhanced nonlinear spectroscopy of single molecules and nanocrys tals. The field enhancement becomes especially large when fractals are plac ed inside a microcavity. A theory for the enhanced Raman and hyper-Raman su rface-enhanced scattering in microcavity-fractal composites is developed.