PARAMETRIC PHASE-CONJUGATION OF LASER-BEA MS IN A NEMATIC LIQUID-CRYSTAL LAYER WITH NONRECIPROCAL FEEDBACK

A study is reported of parametric oscillation in the course of concurr ent stimulated scattering of a beam from a quasi-cw YAG:Nd laser in a layer of a nematic liquid crystal without an absorbing dye but in the presence of a nonreciprocal feedback loop. The phase nonreciprocity of this loop is realised by a polarisation rotator and a phase plate. A significant reduction in the threshold of generation of a phase-conjug ated wave is reported for the case of a pi/2 phase shift between the o ptical pump and scattering waves travelling in opposite directions alo ng the feedback loop.