Two-wave and four-wave mixing experiments are performed on semiconductor with DX centers, CdF<sub>2</sub>:Ga,Y. The crystal is known to exhibit strong modification of optical constants when exposed to light as a result of optically induced transformation of DX-centers. Our experimental results reveal strong χ<sup>(3)</sup> nonlinearity of this crystal and remarkable dynamic photorefractive effect at ambient temperature. With the z-scan technique we found that the 10 μW green light beam induces the negative change of refractive index of 10<sup>-5</sup>. The diffraction efficiency reaches 50%. The grating decays in a few seconds at room temperature but the decay time decreases with temperature. The phase conjugate wave is generated with nearly 40% reflectivity, and the coherent oscillation is observed in semilinear cavity with two counter-propagating pump beams. Centro-symmetric and optically isotropic CdF<sub>2</sub>:Ga,Y is equivalent to or surpasses in some properties the well-known polar photorefractive crystals.

© 2003 Optical Society of America

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