Nonresonance phase conjugation of light at the surface of GaN films upon high-power optical pumping

The possibility of the nonresonance phase conjugation of light in an excited semiconductor medium is shown theoretically and experimentally. In epitaxial GaN films pumped with a nitrogen laser at room temperature, the induced phase conjugation of light in the visible and infrared spectral regions is detected for the first time. The dependences of the phase-conjugation signal intensity on the photon energy and laser-pumping intensity are studied. An interpretation of the effect as a result of the absorption and refraction of light at laser-induced free charge carriers in the semiconductor medium is proposed.