Model of deep and shallow traps for the crystal Ba0.77Ca0.23TiO3

A model of deep and shallow traps has been applied in order to explain the temporal development of the signal wave amplification as well as the pump wave depletion in two-wave-mixing experiments in the crystal Ba_0.23Ca_0.77TiO₃ (BCT). The intensities of the outgoing waves have been studied at different intensities of the incident waves during the first 500 s before the beams have reached their stable states. On the basis of the obtained temporal dependences of the intensities, some material parameters of the crystal have been estimated, like excitation cross sections from the deep and shallow traps (valence levels) into the conduction band, recombination rates from the conduction band into the valence levels, absolute and redistributed charge densities of the deep and shallow traps, and modulations of the absorption and refractive indices. Received: 26 May 2000 / Revised version: 26 September 2000 / Published online: 21 February 2001