Quasi-static electric-field-enhanced degenerate four-wave mixing in a nematic liquid-crystal film.

Degenerate four-wave mixing can be induced or enhanced dramatically when two weak overlapping laser beams are incident upon a nematic liquid-crystal film that is biased by a quasi-static electric field. This phenomenon is shown to be the result of the critical behavior at the Freedericksz transition. The experimental results show that the diffracted intensity is proportional to the third power of the laser intensity, as expected for a four-wave mixing process, despite the strength of the electric-field bias voltage above threshold.