Controlling the diffraction efficiency in electrical fixing technique

An electrical fixing technique is used to permanently store holograms in a SBN:60 crystal. We have optimized the duration of the light illumination and applied electric field during the writing process. We have observed that the DE could be controlled by a write-reveal grating technique, where high-voltage pulses of opposite polarity are applied to the crystal. By varying the amplitude of electric field we obtained DE from 0 to 70%. The range of chosen applied electric fields depends on the coercive field of the crystal. An increase in the illumination time can also lead to a smaller DE, however, we have found that DE can be dramatically increased by exposing the crystal to several light pulses after the revealing phase. By varying the intensity and the duration of the exposure it is possible to control the DE of the grating.