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Transient Diffraction Efficiency and the Role of the Deep Center Levels in BaTiO3 Crystal

Corresponding Author : Y. Haque (yasmeen@sust.edu)

Authors : M. H. Rashid , Y. Haque (yasmeen@sust.edu), S. K. Das , S. M. Sharafuddin

Keywords : photorefractive crystal, space charge field, modulation intensity

Abstract :

The charge transport model has been applied to the photorefractive crystal. Shallow & Deep levels have been accounted for in the formulation of the charge transport equations. It is assumed that the writing beams excite the shallow level charges where as the electrons from the deep level are the ones excited into the conduction band by the reading beam. An appreciable fraction of these electrons recombine with the deep level holes. The electron-hole recombination rate is dependent on the excitation rate of the electrons. This rate is a maximum when the number of electron in the shallow level is equal to the existing hole in the deep centers. The space charge field is directly dependent on the recombination rate. The space charge field is changed by the modulation intensity of the beams. In this study the analytical calculations used to obtain the space charge field is used in the expression of the gain coefficient. The theoretical result for the enhancement factor is seen to be in good agreement with the experimental data.  

Published on June 30th, 2010 in Volume 12, Issue1, Applied Sciences and Technology