ELECTRONIC EXCITATION OF SPACE-CHARGE WAVES IN PHOTOREFRACTIVE MATERIALS

The excitation of a space charge wave in a uniformly illuminated photo refractive crystal by an applied ac voltage is studied theoretically. A spatial differential equation for the ac component of the space char ge held is derived and boundary conditions applicable both to Ohmic an d rectifying junctions are obtained leading to an analytical solution for the space charge wave amplitude. It is shown that the low frequenc y space charge wave associated with the recharge of impurities can be efficiently excited with an amplitude approximately equal to the appli ed ac field. For the parameters of a BSO crystal, the space charge wav e region declines within a few grating spacings near the cathode. The possibility of experimental observation of the effect is discussed. (C ) 1996 American Institute of Physics.