Study of Optical Third-Harmonic Generation in Reflection

This paper reports studies of optical third-harmonic generation reflected from the boundary of solids including metals, semiconductors, alkali halides, and glass. The harmonic wave generated in reflection was found to interfere with those generated in air and in various optical components along the path of the incident laser beam. By studying the interference pattern, reliable relative values for the third-harmonic coefficients were deduced for alkali halides and compared with previous measurements of the coefficients for nonresonant three-wave mixing. It is found that the optical anisotropy is small for these cubic crystals. Preliminary results for metals and semiconductors indicate that the coefficients for these materials are of the correct order of magnitude expected of the nonlinearities associated with the conduction and bound electrons.