It has been shown that during the propagation of an initially elliptically polarized light pulse through a nematic liquid crystal in the isotropic phase, at a temperature close to the phase transition temperature, spatio-temporal optical vortices are formed in its circularly polarized components. This occurs due to the large, compared to the pulse duration, temporal inertia of the medium’s nonlinear optical response, which stabilizes the nonlinear collapse.
Grigoriev et al. (Mon,) studied this question.