Characterization of Band-Edge Photorefractive Effect in Compound Semiconductors

We have recently shown that at optical wavelengths near the band-edge, non-electrooptic gratings can be used for two beam coupling energy transfer [1]. By combining these gratings with conventional electrooptic gratings, very large gain coefficients can be achieved. We will present measurements of the wavelength dependence of the two-beam-coupling gain in compound semiconductors. A large increase in the amount of energy transfer is observed near the band edge, as compared with values at longer wavelengths. We will discuss the relative magnitude and origins of the mechanisms involved and compare the beam coupling results with direct measurements of the nonlinearities. We will discuss possible applications.