Nonlinear optical phenomena in nanostructured fractal materials

The results of theoretical and experimental studies of nonlinear optical phenomena in fractal nanostructures are reviewed. Localization of optical excitations in fractal metal nanocomposites, such as colloidal aggregates, self-affine and semicontinuous films, results in strong enhancements of optical nonlinearities. The localized modes of fractals cover a broad spectral range, from the visible to the far-infrared. A number of optical processes are studied such as the Kerr-type nonlinearities, four-wave mixing, second and third harmonic generation and frequency-and polarization-selective photomodification.