Abstract
In this paper we grew the LiNbO3:Cu:Ce crystals with the size of phi 25 mm x 65 mm along the Z axis by the vertical Bridgman method. The UV-visible absorption spectra and OH- absorption spectra of 2-mm thick crystal samples cut from the bottom, middle and top parts of the as-grown crystal were measured with a Shimadzu spectrophotometer. It was found that the absorption edge at the absorption coefficient of 20 cm(-1) increased along the growth axis. The oxidized samples exhibited a difference in the absorbance of OH- peaks at 3480 cm(-1), while the reduced samples showed almost the same absorbance. These optical inhomogeneities were explained in terms of the nonunity segregations of Cu and Ce ions in the LiNbO3 crystal. The light-induced scattering effects of the poled crystal samples were also studied and compared using a green laser at the wavelength of 532 nm. Both oxidized and reduced X-cut samples with e-light showed stronger scattering as compared with the Z-cut samples. The reduced samples exhibited faster scattering effects than the oxidized ones. It was also found that the Z-cut sample with the light incident onto its + Z face had almost no scattering. In the case of low incident power density, the reduced samples exhibited stronger scattering than the oxidized ones at the same power density. (c) 2004 Elsevier B.V. All rights reserved.