太赫兹偏振测量系统及其应用

Polarization sensitive terahertz measurements and applications

麦克斯韦方程中的介质响应特性一般由本构关系中的介电函数ε(ω)和磁导率μ(ω)来描述,对于介质中传播的电磁场,通常存在两个独立的本征传播模式,它们是齐次麦克斯韦方程组的特解,各自具有特定的色散关系和偏振态。如果介质中传播的电磁场为两个本征模分量的线性迭加,其偏振态将会随着传播的过程而改变。常见的现象有各向异性晶体中的双折射、超材料中的偏振调制效应、自然界中手性材料的旋光响应以及外磁场作用下产生的Faraday效应等。本文从测量方法、数据处理、测量精度等方面介绍太赫兹时域偏振检测系统及其发展状况,特别是利用线栅、超材料以及光学手段调制太赫兹电场偏振态的方法。对近几年太赫兹偏振检测系统在分析手性超材料、太赫兹圆二色谱以及Faraday效应等实验中的应用进行了总结和讨论。最后展望了太赫兹偏振检测系统未来进一步的发展空间及应用前景。

In Maxwell equations, the electromagnetic response of a medium is usually described by permittivity ε（ω） and permeabilityμ（ω） in constitutive relations. For an electromagnetic field propagating in a medium, there exist two independent eigen modes in general, each of which is a special particular solution of Maxwell equations, satisfies a unique dispersion relation and keeps its own polarization during propagation. If a traveling electromagnetic field is a linear superposition of the two eigen modes, its polarization will constantly change as propagating in medium, such as birefringence in anisotropic crystals, polarization modulation in rnetamateri- als, optical activity in natural chiral materials and external magnetic field induced Faraday effects, etc. In this review, terahertz time-domain polarization measurement system is introduced, including principle, data pro- cessing and measurement accuracy. Polarization modulation using wire grid polarizer, metamaterial and other optical methods are discussed in detail. The applications of the polarization measurement system are reviewed in analyzing properties of chiral metamaterials, terahertz circular dichroism spectroscopy and Faraday effects. Finally, we give a brief comment on the future development and prospect of the polarization sensitive terahertz measurement technique.