Optical alignment of Cu2+ axial centers in KTaO3: Spectral dependence of the effect

The Cu _Ta ²⁺ -V_O axial centers in crystalline KTaO₃ were found to undergo alignment under the action of polarized light. The sign of the effect is shown to change depending on the wavelength of the aligning light. A parallel study of the spectral response of photoconductivity of the same samples led to the conclusion that the alignment of the copper centers is driven not by reorientation but rather by an anisotropic recharging of the centers, which involves both the conduction and valence bands of the crystal. This interpretation was supported by a study of the kinetics of thermal destruction of the copper center alignment.