Nematic kink states in a laser field

We have investigated the nonlinear optical interaction of uniform and kink states of a nematic and a ferrofluid-doped nematic (ferronematic) liquid crystal with an incident laser field. We find that the transition between the permitted uniform oreintational states of these systems is of first order in the case of nematics, and of second order in the case of ferronematics. In the latter case we also find the phenomenon of reentrance. We find new kink states in a magnetic field with topological winding different from $\pi$ in the case of nematics, and $2\pi$ in the case of ferronematics. In ferronematics, due to grain segregation the phase diagrams for uniform and kink states are entirely different. In these systems we find a first or second order structural transformation from a single kink into a pair of kinks. Further, we obtain a rich variety of kink states as the intensity of the laser field is varied.