THEORETICAL-ANALYSIS OF MECHANISM OF PHOTOREFRACTIVE ENHANCEMENT OF PHOTOCHROMIC GRATINGS IN BSO

We present the results of theoretical modelling of the increase in dif fraction efficiency in photorefractive BSO under conditions of photore fractive enhancement via permanent photochromic gratings. The results are modelled using coupled wave theory, including the anisotropic natu re of the secondary refractive index grating, optical activity and ele ctric field induced birefringence. The dependence of the enhancement o f the diffraction efficiency as a function of the input polarisation o f the diffracted beam, and of the applied electric field is presented for two different crystal geometries.