Experimental and Theoretical Studies of the Nonlinear Optical Response of Certain Fullerenes, Polymers and Glasses.

The third-order nonlinear optical properties of three classes of materials are discussed in this dissertation. They are fullerenes, organic materials, and glasses. The experimental techniques used include degenerate-four-wave-mixing (DFWM), degenerate-four-wave-mixing interferometry, two-color wave mixing, and transient transmission. Of these techniques, the degenerate-four-wave-mixing interferometry is our innovation. In terms of physical process, this dissertation investigates the interactions between optical photons and the following constituents of solutions and solids: bound electrons, molecular vibrations, phonons, thermal changes, polarons, and bipolarons. The non-resonant third-order nonlinearity of C60 and C70 is studied by DFWM in C60/benzene and C70/benzene solutions. The upper limit of the nonlinearity is determined. We also determine the ratio in the nonlinearity of two common organic solvents, benzene and carbon-disulfide, to the best accuracy to date. We study the resonant nonlinearity involving excited solute molecules in solution. This is complicated by the hydrodynamic contribution to the nonlinear signal. A theory including bot contributions is formulated. The imaginary part of the excited-state polarizability of C60 molecule is experimentally determined while only an upper limit can be placed on the real part because of the hydrodynamic signals. We study the thermal and acoustic properties of benzene, and discover the frequency (~ 1GHz) above which the low-frequency limit of viscosity fails to describe damping. Theoretical background of the DFWM interferometry is described and the procedure for data reduction is illustrated. The phase of the transient third-order nonlinearity X ^{(3)} in a semiconductor doped glass is studied as it makes the transition from one dominant mechanism to another. Investigations of linear bis-thienyl polyenes and two-dimensional bis-benzothiazole are described. Agreement between experimental values for resonant X^ {(3)} and predictions of a two-level model is shown for the bipolaronic state of bis-thienyl polyenes. The two-dimensional chromophore, protonic doped bis-benzothiazole, exhibits optical limiting effect. The mechanism of the effect is studied by two different methods and a model is proposed which correlates the results of both methods. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089-0182.).