INVESTIGATION OF THE INTERNAL FIELD IN PHOTOREFRACTIVE MATERIALS AND MEASUREMENT OF THE EFFECTIVE ELECTROOPTIC COEFFICIENT

An experimental investigation of the electric field in the bulk of a B i12SiO20 crystal is carried out, and a two-region model is developed t hat can account for the buildup of screening charges near the electrod es. In light of our results, a simple method is proposed for the deter mination of the effective electro-optic coefficients based on applying a sufficiently high-frequency square-wave voltage to prevent screenin g charge buildup. A demonstration of this method for Bi12SiO20 leads t o a value of 4.4 pm/V for the stress-free (unclamped) coefficient, and a subsequent consideration of piezoelastic contributions allows the s train-free (clamped) coefficient to be estimated at 3.7 pm/V.