Abstract

The optimization of the material properties for photorefractive uses requires information on the centers which supply carriers and information on the trapping centers responsible for the optical excitation and transport process. Particularly interesting are the generation of space charge fields, photovoltaic effects, and photoconductivity data which are correlated to the impurity centers in the photorefractive crystal. To characterize and optimize KNbO₃ crystals, we measured optical absorption within the 250-2400-nm wavelength range at room temperature, dark and photoconductivity for different laser intensities, diffraction efficiency, and beam coupling efficiency as a function of the grating spacing for two laser wavelengths of 488 and 515 nm. In differently treated Fe-doped crystals, information related to the concentration of empty traps, the sign of the dominant photocarrier, beam coupling gain, and effective electrooptic coefficient have been obtained in these experiments.

© 1988 Optical Society of America