We analyze the propagation of self-trapped optical beams close to the Fréedericksz threshold in nematic liquid crystals. Accounting for power-dependent changes in walk-off due to the all-optical response, we demonstrate that light beams can switch from positive to negative refraction according to the excitation.
Alberucci, A., Jisha, C.P., Assanto, G. (2015). Nonlinear negative refraction in reorientational soft matter. PHYSICAL REVIEW A, 92(3) [10.1103/PhysRevA.92.033835].