Frequency dependence of the optical kerr effect and third-order electronic nonlinear-optical processes of organic liquids

An experimental study and a theoretical analysis of frequency-dependent optical Kerr effects in material media are presented. Through optimized pump-probe measurement techniques for the frequency dependence of the optical Kerr effect, individual resonant and nonresonant contributions to the third-order nonlinear-optical susceptibility X_ijkl⁽³⁾(-W₂; W₁ -W₁, w₂) can be obtained from the optical Kerr data. Third-order depolarization processes are reviewed to provide the optimum experimental conditions for measuring X_ijkl⁽³⁾(-W₂; W₁ -W₁, w₂) together with the corresponding formalism required for analyzing the frequency-dependent data. The experimental methods are demonstrated by dispersion measurements carried out for nonresonant and resonant optical Kerr effects in the organic Kerr liquids benzene and nitrobenzene. The results for benzene and nitrobenzene are discussed in terms of resonant 7r-electron excitations of each system.