Holographic and non-steady-state photocurrent characterization of photorefractive barium-calcium titanate

Measurements of non-steady-state photocurrents and of time-modulated conduc tivities for homogeneous illumination of varying intensity are performed wi th? a photorefractive iron-doped barium-calcium titanate crystal of the con gruently melting composition (Ba0.77Ca0.23TiO3, BCT). The diffraction effic iency and the two-beam coupling gain are determined fi-om conventional holo graphic experiments. Debye screening and diffusion lengths are found to be of the order of 0.1 mu m The response-time of the material is 2 s (light in tensity 0.2 W /cm(2), wavelength 514 nm) and the dark storage time is 6 s. The measured refractive index changes are only one third of the values, whi ch are expected from the known electrooptic coefficients and space-charge f ields. (C) 1999 Elsevier Science B.V. All rights reserved.