Reflectivity changes of Ge due to illumination by beams of unequal frequency

Reflectivity changes of Ge have been measured as a function of the intensity of the stronger of two optical beams having different frequencies, the frequency difference being produced through stimulated Rayleigh and Brillouin scattering. The observed nonlinear components of the weak beam reflectivity is smaller, and the diffracted beam generated by the surface grating arising from the interference of the incident beams is drastically reduced, compared to results with equal frequency input beams. The experimental results are compared with theoretical predictions, and, while limited qualitative agreement was obtained, substantial discrepancies remain which have not yet been explained.