电光与磁光效应的互补特性及其传感应用

研究了兼有电光效应和磁光效应的晶体内电光与磁光效应的互补特性及其传感应用. 在光强度调制条件下, 晶体中偏振光波的电光调制与磁光调制具有互相补偿的效果, 从而能够使输出光强度保持为一个固定值. 基于这种互补特性, 提出了一种利用单块闪烁锗酸铋(Bi₄Ge₃O₁₂, BGO)晶体的电光补偿型光学电流(磁场)传感器, 其光学传感单元由两个偏振器和一块平行四边形BGO晶体组成. 该晶体自身能够产生π/2的光学相位偏置, 同时兼用作电流传感和电光补偿元件, 通过控制BGO晶体的外加电压, 能够实时补偿被测电流(磁场)变化引起的磁光旋转角和输出光强度的变化, 从而实现电流(磁场)的闭环光学测量. 实验测量了5.0 A范围内的工频交流电流, 所需要的电光补偿电压约为21.2 V/A, 补偿电压与被测电流之间具有良好的线性关系, 其非线性误差低于1.7%.

Mutual compensation property of electrooptic and magnetooptic effects and its application to sensor

Mutual compensation property between electrooptic and magnetooptic modulations in a crystal with electrooptic and magnetooptic effects and its application to magnetooptic sensor are investigated theoretically and experimentally. Under the condition of light intensity modulation, electrooptic and magnetooptic modulation effects can compensate for each other, so that the transmitted light intensity through the crystal can be kept at a certain fixed value. Based on this mutual compensation property, a novel optical current (or magnetic field) sensor is proposed and demonstrated experimentally by use of a single bismuth germanate (Bi₄Ge₃O₁₂, BGO) crystal. The optical sensing unit is composed mainly of two polarizers and a block of BGO crystal with the shape of parallelogram. The BGO crystal itself can produce an optical phase bias of π/2, and it can be used as both a current sensing element and an electrooptic compensator. The change of magnetooptic rotation angle through the crystal can be compensated in real time by the change of electrooptic phase retardation caused by the applied voltage, thus the closed-loop optical measurement of current (or magnetic field) can be achieved. The 50 Hz ac current within 5 A is measured experimentally. The required compensating ac voltage is about 21.2 V/A in root-mean-square value. Experimental data show a good linear relationship between measured current and compensating voltage, and the nonlinear error is less than 1.7%.