用于量化残余晶体各向异性的极端交叉偏振消光方法
Extreme Cross-polarization Extinction Method for Quantification of Residual Crystal Anisotropy
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中文总结 AI 辅助
本研究提出极端交叉偏振消光（EXE）方法，利用光自旋-轨道相互作用产生的暗中心十字图案，可高精度量化光学晶体的残余椭圆双折射，适用于表征单层等材料的各向异性。
中文摘要 AI 辅助
近轴激光束的高消光交叉偏振测量会产生类厄米-高斯（HG₁₁）的四瓣暗中心十字图案。这种方位角自旋分离的模式图案被认为源于光的自旋-轨道相互作用。由于极端交叉偏振消光（EXE），光束中心存在完美暗区，此处被用于精确测定激光束的轴上残余偏振，并以此确定光学晶体的残余椭圆双折射。通过让激光束沿光轴平行或垂直于光束传播方向切割的单轴光学晶体传播并进行EXE测量，我们展示了一种简单方法，可精确量化原本被认为不存在的晶体残余椭圆双折射，达到10⁻⁸分之一的高消光程度。实验结果通过基于琼斯矩阵的近轴激光束及其在光学晶体中传播的计算进行解释。EXE技术的高灵敏度和高精度使其非常适合测量和表征单层、超薄膜及二维材料的各向异性及其色散。
英文摘要
The high-extinction cross-polarization measurement of a paraxial laser beam results in a Hermite-Gaussian ($\text{HG}_{11}$)-like four-lobes with a dark-centered cross pattern. The azimuthally spin-separated mode pattern is understood to result from the spin-orbit interaction of light. The perfect dark region at the beam center, due to extreme cross-polarization extinction (EXE), is used here to accurately determine the on-axis residual polarization of the laser beam and, using it, the residual elliptical birefringence of optical crystals. By propagating the laser beam through uniaxial optical crystals with their optic axis cut either parallel or perpendicular to the beam propagation direction and performing the EXE measurement, we demonstrate a simple approach to precisely quantify the residual elliptical birefringence of crystals, which are otherwise assumed to be absent, to a high degree of extinction of 1 part in $10^{-8}$. The experimental results are interpreted using Jones-matrix-based calculations for a paraxial laser beam and upon its propagation through the optical crystals. The high sensitivity and high accuracy of the EXE technique make it well-suited for measuring and characterizing anisotropy and its dispersion of monolayers, ultrathin films, and 2D materials.
