| Ultrafast pulses were used to probe molecular motion and intermolecular interactions on femtosecond and picosecond time scale. For a time resolved optical Kerr effect (TR-OKE) experiment, a robust sample with an effectively instantaneous response and high n2 (nonlinear refractive index) was needed to established the t = 0 point of pulse coincidence. Metal-doped oxide glasses (MDOG) were investigated for this purpose. The difficult nature of nonlinear optical measurements makes a predictive model of the magnitude of the nonlinear response based on material parameters very desirable. A semi-empirical equation for n2 for a wide variety of optical solids, the Boling, Glass, Owyoung (BGO) equation, predicts that n2 increases with increasing linear refractive index, n0, and decreasing Abbe number, nu d (a measure of dispersion). Lines derived a similar expression, based on a two-level bond-orbital approximation. The femtosecond TR-OKE was measured for a variety of metal-doped silicate glasses, including pairs of glasses with comparable refractive index and Abbe number but different dopant cations, particularly to test the BGO equation. The predictive ability of both models was reasonable only for glasses with a single dominant polarizable species, such as Pb in lead-oxide glasses. The Lines model was useful only for predicting general trends. For all tested glasses, the nonlinear response matched the measured autocorrelation function of the incident 130-fs laser pulses, and are therefore potentially useful in ultrafast photonic switching. The theory of Garetz and Newstein explains the absence of any detectable slow nuclear contributions through a detailed time-domain analysis of the contributions to an OKE measurement using ultrashort pulses. This analysis describes non-resonant vibrational contributions that are temporally indistinguishable from electronic contributions. Attempts were made to measure the time-resolved optical Kerr effect (TR-OKE) in carbon diselenide, CSe2. It was thought that comparison between CSe2 and CS2, which has been extensively studied, would yield some insight into the intermolecular interactions. Tests in the available high rep rate system (76 MHz) proved to be undoable, due to decomposition. An open aperture z-scan demonstrated significant two {09}photon absorption (TPA). A first-time estimate was made of the TPA coefficient of CSe2, 55 cm/GW. |
