Modeling of nonlinear optical activity in propagation of ultrashort elliptically polarized laser pulses.

We propose a general model of third-order nonlinear optical susceptibility of isotropic gyrotropic medium with frequency and spatial dispersion. Our model allows for the description of the propagation of ultrashort (several oscillations) elliptically polarized laser pulses in such a medium and does not require smallness of the characteristic nonlocality dimension, unlike the conventional phenomenological model. We implemented our model numerically by means of a modified finite-difference time-domain method with an auxiliary differential equation. We have validated the correctness of our model by the comparison of the results obtained in our numerical simulations with generally known effects observed experimentally and described earlier theoretically for the monochromatic radiation or within the slowly varying envelope approach. We investigated effects accompanying the propagation of ultrashort (several oscillations) light pulses in nonlinear isotropic gyrotropic medium with frequency and spatial dispersion of cubic nonlinearity.