Phase conjugation on the surface of optically excited ZnO

The feasibility of phase conjugation in excited semiconductor media is shown both theoretically and experimentally. For the first time, phase conjugation of a light wave (nitrogen laser) with a photon energy equal to half the exciton radiative recombination energy in the medium (ZnO epitaxial films) at room temperature is revealed. The spectral dependences of the phase conjugation signal are studied. The quadratic interaction between the electromagnetic and exciton waves in a semiconductor is suggested as a possible mechanism of this effect.