Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

The use of a semiconductor-metal phase transition for wavefront reversal of laser radiation was proposed. An investigation was made of nonlinear reflection of CO₂ laser radiation at a phase transition in VO₂. A three-wave interaction on a VO₂ surface was achieved using low-power cw and pulsed CO₂ lasers. In the first case, the intensity reflection coefficient was 0.5% for a reference wave intensity of 0.9 W/cm² and in the second case, it was 42% for a threshold reference wave energy density of 0.6–0.8 mJ/cm².