HOLOGRAPHIC WRITING AND ERASURE IN UNIPOLAR PHOTOREFRACTIVE MATERIALS WITH MULTIPLE ACTIVE-CENTERS - THEORETICAL-ANALYSIS

A general formalism based on the Kukhtarev equations is developed to describe the kinetics of holographic recording and erasure in unipolar photorefractive materials containing multiple active centers. One primary relevant result is that the exchange of charge among the various centers and the holographic grating dynamics, involving charge transport, are uncoupled after appropriate linearization of the equations. The formalism is then applied to the simple but physically meaningful case of two active centers, an optical donor and a thermally active trap. Detailed computer simulations have been carried out to investigate the influence of trap energy depth, trap concentration, temperature, and light intensity on the holographic behavior. The results qualitatively account for a number of unexpected features in the kinetics of grating recording and erasure observed in several photorefractive materials.