用于微米尺度晶体对称性实时监测的矢量光束
Vector beams for real-time monitoring of crystalline symmetry on μm length scale
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中文总结 AI 辅助
本研究利用矢量光束实现非旋转斜入射装置，实时监测微米尺度晶体对称性，显著降低反馈延迟和焦斑尺寸，简化非线性光学各向异性测量，推动结构光场在凝聚态研究中的应用。
中文摘要 AI 辅助
对称性约束并决定了晶体固体的物理性质。确定晶体对称性通常需要大型衍射设施和先进的分析软件，因此无法实现实时反馈。或者，光学各向异性也被用于在较小的台式装置上阐明固体的旋转、镜像和反演对称性。特别是二次谐波产生，在相变过程中对这些对称性的细微变化表现出显著的敏感性。为了在低温或真空环境中获取晶体的完整非线性磁化率，需要逐角度旋转斜入射和出射光束的散射平面，并协调其偏振态。这通常导致装置庞大且不稳定，反馈延迟显著，且焦斑尺寸大于20微米，不适用于如少层二维材料等微观样品。在本工作中，我们利用矢量光束实现非旋转斜入射装置，展示了在直径约2微米的样品区域上实时（>10帧每秒）的晶体对称性可视化。反馈延迟和焦斑尺寸均比先前基于高斯光束和机械旋转台的设计改善了一个数量级以上。这里，矢量光束的使用极大地简化并降低了非线性光学各向异性测量的成本，预示着该方法在研究和工业领域的广泛应用，例如应变监测和晶体对准。我们的工作也可能促进未来结构光场在固态和凝聚态物质研究中的更广泛整合。
英文摘要
Symmetry constrains and determines the physical properties of crystalline solids. Determining crystalline symmetry often requires large-scale diffraction facility and advanced analysis software and therefore cannot be realized with real-time feedback. Alternatively, optical anisotropy has also been exploited for elucidating the rotation, mirror and inversion symmetries of solids on smaller tabletop setups. Second harmonic generation, in particular, has demonstrated a remarkable sensitivity to subtle changes in these symmetries during phase transitions. To access the full nonlinear susceptibility of a crystal in a cryogenic or vacuum environment, angle-by-angle rotation of the scattering plane of an obliquely incident and outgoing beam in co-ordination with their polarization states is required. This typically results in a bulky and wobbly setup, significant feedback latency, and a focal spot size > 20 μm unsuitable for microscopic samples such as few-layer 2D materials. In this work, we make use of vector beams to realize a non-rotating oblique-incidence setup, demonstrating a real-time (> 10 fps) visualization of crystalline symmetry on a sample area of ~ 2 μm in diameter. Both the feedback latency and focal spot size represent more than an order of magnitude improvement over previous designs based on a Gaussian beam and mechanically-rotating stages. Here, the use of a vector beam greatly simplifies and reduces the cost of nonlinear optical anisotropy measurements, heralding widespread applications of this approach in both research and industrial settings, for example, for strain monitoring and crystal alignment. Our work may also promote broader integration of structured optical field into solid state and condensed matter research in the future.
发表机构
- Shanghai Jiao Tong University（上海交通大学）
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