Numerical Liouville approach: intensity-dependent transient linear and nonlinear optical susceptibilities

An approach to handle nonstationary and intensity-dependent linear and nonlinear optical phenomena is presented based on the numerical Liouville approach, which is calculation method for nonlinear optical susceptibilities by solving the Liouville equation numerically. A three-state model system, which mimics the electronic states of t-octatetraene, in an intense pulsed laser is considered. Two types of pulse shapes are considered: rectangular and Gaussian. A new definition of time- and intensity-dependent transient optical susceptibility is proposed and the intensity-dependent behavior is examined in linear and THG third-order nonlinear optical processes.