Influence of Shallow Levels in Charge Transport Process on Enhancement of Transient Diffraction Efficiency in BaTiO₃ Crystal

A unique enhancement of the transient diffraction efficiency in an undoped BaTiO3 crystal is experimentally observed. The enhancement is a strong function of the switched-off time (or dark time) of the pulsed reading beam incident to a steady-state grating, formed in advance, in the crystal. This enhancement can be maximized for an optimum dark time, which reveals the presence of two shallow levels in the charge transport process at room temperature.