9810183 Shalaev This proposal is concerned with nonlinear near field optical processes in fractal thin films, namely self-affine surfaces and 2d random metal-dielectric films. Nonlinear optical processes to be investigated include: Kerr-type nonlinear refraction and absorption, nearly-degenerate four wave mixing, and second and higher harmonic generation. Collective optical excitations of fractal thin films lead to "hot" spots which are separated in space by distances much larger than the spot size. These spatially localized "hot spots" represent the eigenmodes of a fractal film. Spatial distributions of the local (near-field) nonlinear spectra on a fractal thin film will be calculated. These spectra are experimentally accessible by parking a tip of a photon scanning tunneling microscope at different points on the surface and varying the wavelength. Important information are obtained about the local configurations of a fractal film and the resonance frequencies of these nm-scale random areas of the film. Phase and amplitude correlation properties of the nonlinear fields generated from different spots of a fractal film will be studied by analyzing the statistics of the nonlinear near-zone fields, e.g., through two-point correlation functions. %%% The PI's theoretical research contributes to the development of a nonlinear optical spectroscopy of single molecules and materials of dimensions on the scale of molecules. ***
