Photorefractive gratings in sillenite crystals in a square-wave field

The space-charge-field harmonics in the refractive-index grating generated in a bismuth silicate crystal to which a square-wave external electric fiel d is applied were examined theoretically and experimentally at high interfe rence-pattern contrasts. The model taking into account three spatial harmon ics ensures good agreement with experimental data for the fundamental- and second-harmonic gratings. By fitting the experimental data with theoretical curves, the acceptor concentration and the product of the carrier mobility and recombination time in the crystal were evaluated.