Electro-Optical Effect of Bi₄Ge₃O₁₂ Crystals for Optical Voltage Sensors

Abstract

The electro-optical coefficient r 41 of Bi 4 Ge 3 O 12 , corresponding to the sensitivity of the optical voltage sensor, and the temperature dependence of response characteristics to applied step voltage are studied. From these measurements, two kinds of dc drift are found to exist in Bi 4 Ge 3 O 12 crystals. One is found to be due to the relaxation of the piezoelectric polarization (type (a)), and the other is explained as the deduction phenomenon by the thermally induced space-charge field (type (b)). By correcting for dc drift of type (a), the accurate value of r 41 =1.09×10 -12 m/V is obtained at 855 nm wavelength.