Steady-state energy exchange between writing beams controlled by an external electric field during hologram formation in $KNbO_3$

An investigation was made of the dependence of the steady-state energy exchange between writing beams on the period of a holographic grating in reduced $KNbO_3$ crystals and on an external electric field applied to these crystals. A modification in the energy exchange in an external field was observed for the first time. This effect was attributed to a drift mechanism of hologram recording when the quasineutrality condition was not obeyed. The experimental results were described using the theory of Kukhtarev and Vinetskil.