Energy relations for space-charge waves in photorefractive materials

An energy balance equation is derived with the aid of a partial differential equation describing the space-charge field in photorefractive materials. Expressions are found for power flux, losses, and the power absorbed from an external source both for the low- and high-frequency branches of space-charge waves. The efficiency of energy conversion from the external source into the space-charge wave is calculated and compared for two different mechanisms of optical excitation: (i) by a moving interference pattern and (ii) by a combination of a stationary interference pattern and an external ac field. (C) 1996 American Institute of Physics.