We have discussed the recording of moving grating in photorefractive materials at large modulation depths using hopping model.The analytical expressions of the first three-order spatial charge field are presented which describe the nonstatic recording of the moving fringes.And the dependence of the space charge field on the veloctiy of the moving fringes is discussed for non diffusive field.We found that the higher-order harmonics of the space charge field for low diffusive field can be selectively enhanced with applied small dc field.Otherwise,they cannot be selectively enhanced if the diffusive field is large than the applied electric field.
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