First-order Freedericksz transition and front propagation in a liquid crystal light valve with feedback

Freedericksz transition can become subcritical in the presence of a feedback mechanism that leads to the dependence of the local electric field onto the liquid crystal re-orientation angle. We have characterized experimentally the first-order Freedericksz transition in a Liquid Crystal Light Valve with optical feedback. The bistability region is determined, together with the Freedericksz transition point and the Maxwell point. We show the propagation of fronts connecting the different metastable states and we estimate the front velocity. Theoretically, we derive an amplitude equation, valid close to the Freedericksz transition point, which accounts for the subcritical character of the bifurcation.