Measuring the parameters of photorefractive crystals by an electrooptical compensation method

A new compensation method, based on the longitudinal electrooptical effect in a modified Pockels cell accommodating two crystal plates instead of a si ngle plate, is proposed for measuring the parameters of photorefractive cry stals. The plates are oriented so that their surfaces are perpendicular to the optical axis and the long semiaxes of the electric-field-induced birefr ingence ellipsoids are rotated 90 degrees relative to one another around th is axis. The proposed method was used to measure the Maxwell relaxation tim e in the Bi12SiO20:Al crystal (0.2% Al) as a function of the photoexcitatio n intensity I-ex in the green-blue spectral region (lambda = 5145 Angstrom) . For I-ex = 10 mW/cm(2) , the Maxwell relaxation time decreases by 6 +/- 1 s as compared to the dark value (80 +/- 10 s). (C) 2001 MAIK "Nauka/Interp eriodica".