Optically induced nonlinearities in fullerenes and fullerene doped polymer composites

We describe the results of the investigations of optical nonlinearities in fullerenes in various forms, ranging from solutions to composites devised in device-oriented forms. Two types of optically-induced nonlinearities are of great interest here: third-order nonlinearity and photorefractivity. The third-order nonlinearity has been investigated by a combination of photoinduced transient absorption and optical Kerr gate, using femtosecond pulses at 61 5 nm and 796 nm. Specially useful is here the new technique of femtosecond phase-tuned optically heterodyned Kerr gate by which we have measured both the signs and the magnitudes of the real and the imaginary components of χ⁽³⁾. This information is very useful in understanding the roles of one- and two-photon resonances. Another application of fullerenes is in polymeric photorefractivity which is derived from a combination of optically induced space-charge field and the electro-optic effect. Exceptionally rapid progress has been recently witnessed in the development of polymeric photorefractive materials which now exhibit parameters of merit comparable or surpassing best inorganic photorefractives. We have devised polymer composite with C as the photosensitizer to produce highly efficient photorefractive materials. The dynamic and the kinetic aspects of the photorefractive process in the polymer composite have been investigated.