Robustness of electric field vector sensing of electromagnetic waves by analyzing crystal angle dependence of the electro-optic effect
Robustness of electric field vector sensing of electromagnetic waves by analyzing crystal angle dependence of the electro-optic effect
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DOI：
10.1364/josab.30.002940
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发表时间：
2013-11
影响因子：
1.9
通讯作者：
N. Yasumatsu;S. Watanabe
中科院分区：
文献类型：
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作者：
N. Yasumatsu;S. Watanabe
我们从理论上和实验上研究了利用晶体角度依赖于电光效应来确定电磁波电场矢量的大小和方向的准确性。本文的数学处理是我们以前用自旋EO传感器方法确定太赫兹电磁波电磁场方向的工作的一个很大的扩展[Rev. Sci.]。仪器仪表，83,023104(2012)]。这里我们考虑了实验装置中波片和偏振器的误差，以及由于均匀应变和局部应变引起的EO晶体残余双折射的影响。主要结果如下：(1)当光晶体中不存在残余双折射时，波片和偏光镜的误差不影响实验确定的电场矢量方向。这是正确的，甚至当与EO信号的电场大小的平方成比例的项变得重要时。(2)残差双折射误差可以通过信号减法算法有效消除，其大致为波片失调角与残差双折射度的乘积，且误差很小。(3)误差与电场大小无关；因此，我们可以在电场较弱的情况下应用该技术，并且由EO效应引起的探针脉冲的偏振旋转远小于剩余双折射引起的偏振旋转。这些结果为旋转EO传感器方法的精度和可靠性提供了数学基础，该方法具有鲁棒性，可用于远红外至中红外超宽带电磁场矢量传感。
We theoretically and experimentally investigate the accuracy with which the magnitude and direction of the electric field (E-field) vector of electromagnetic waves can be determined using the crystal angle dependence of the electro-optic (EO) effect. The mathematical treatment in this paper is a large extension of our previous work to determine the E-field direction of terahertz electromagnetic waves by the spinning EO sensor method [Rev. Sci. Instrum.83, 023104 (2012)]. Here we include misadjustments of the wave plate and polarizer in the experimental setup as well as the effect of the residual birefringence of the EO crystal due to uniform and local strains. The main results are as follows: (1) When there is no residual birefringence in the EO crystal, misadjustments of the wave plate and polarizer do not affect the experimentally determined direction of the E-field vector. This is true even when the term proportional to the square of the E-field magnitude of the EO signal becomes important. (2) The error due to residual birefringence can be effectively eliminated by a signal subtraction algorithm and it is roughly the product of the misadjustment angle of the wave plate and the degree of residual birefringence, which is very small. (3) The error does not depend on the magnitude of the E-field; thus, we can apply the technique when the E-field is weak and the polarization rotation of the probe pulse caused by the EO effect is much smaller than that induced by residual birefringence. These results give a mathematical basis for the accuracy and reliability of the spinning EO sensor method, which is robust, and will be useful for ultrabroadband E-field vector sensing at far-infrared to mid-infrared frequencies.