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

Abstract

Measurements of non-steady-state photocurrents and of time-modulated conductivities for homogeneous illumination of varying intensity are performed with a photorefractive iron-doped barium–calcium titanate crystal of the congruently melting composition (Ba 0.77Ca 0.23TiO 3, BCT). The diffraction efficiency and the two-beam coupling gain are determined from conventional holographic experiments. Debye screening and diffusion lengths are found to be of the order of 0.1 μm. The response-time of the material is 2 s (light intensity 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, which are expected from the known electrooptic coefficients and space-charge fields.