Theories of the Nonlinear Optical Properties of Composite Media: Applications toPhthalocyanine Dyes

摘要

This report describes the results of a theoretical investigation into thenonlinear optical response of granular composites. In particular, we have investigated the degree to which the cubic nonlinear response can be enhanced in such composites, relative to the same response in pure materials. Cubic nonlinear response is potentially of great practical importance in developing novel materials with a strongly intensity-dependent transmission coefficient, index of refraction, etc. We find that there are many types of composite geometries which give rise to such strong enhancements. These include composites near the percolation threshold, composites in which one of the components is arranged in the form of a fractal cluster, and nonlinear coatings (such as dyes) adsorbed onto the surface of particles which have a resonant optical response at an appropriate frequency. We have carried out this investigation using both analytical approximations and a variety of approximate numerical techniques, including large-scale computer simulations. Finally, we briefly describe some work in progress, in which a composite composed of materials with a purely guardratic response can exhibit an enhanced curbic response. (AN).