Optical voltage sensor using bismuth silicate crystal grown by hydrothermal method

An optical voltage sensor is proposed which uses one single bismuth silicate (Bi₁₂SiO₂₀, BSO) crystal grown by hydrothermal method. The voltage sensing unit is only composed of one block of BSO crystal and two prism polarizers. Experimental results demonstrate that the used BSO crystal sample exhibits obvious linear electro-optic Pockels effect, and can be used for the measurement of alternating voltage. By use of the inherent natural optical activity in the BSO crystal, monotonous and linear voltage measurement ranges of the proposed voltage sensor are larger than those of the conventional voltage sensors using electro-optic crystals without optical activity. The size of the used BSO crystal sample is 6.0 mm×4.0 mm×2.9 mm³. The angle, through which the plane-of-vibration rotates in the BSO crystal due to its optical activity, is about 132° for light wavelength of 633 nm. The measurand voltage is the alternating voltage with industrial frequency of 50 Hz, and is monotonously and nonlinearly measured in the range of 108-1 300 V (root-mean-square amplitude). The output voltage of the sensor is still monotonously changed with measured voltage when the corresponding electro-optic phase retardation reaches 2π. In addition, under the application of a proper stress-induced birefringence in the BSO crystal, the output voltage is linearly changed with measured voltage in a certain voltage range, e. g., 900 V, corresponding voltage measurement sensitivity is 0.027 6 mV/V and nonlinear error is less than 3.1%.