The CuTa2+–VO axial centers in crystalline KTaO3 were found to undergo alignment under the action of polarized light. The sign of the effect was shown to change depending upon 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 Cu centers was 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 Cu center alignment.

Optical Alignment of Cu2+ Axial Centers in KTaO3 - Spectral Dependence of the Effect. S.A.Basun, A.G.Razdobarin, L.S.Sochava, D.R.Evans: Physics of the Solid State, 2004, 46[2], 258-64