Two-dimensional (2D) van der Waals (vdW) magnetic materials with strong in-plane anisotropy can make possible novel applications such as optospintronics and strain sensors. In this work, the strong in-plane optical anisotropy in 2D vdW antiferromagnet VOCl has been systematically investigated. The optical brightness and absorption coefficient exhibit evident periodic variation with the change of incident polarization, unveiling the strong in-plane anisotropic optical absorption. The Raman intensity in this material shows obvious dependence on the polarization angle of incident laser, demonstrating that the phonon properties possess strong in-plane anisotropy. Besides, we have also realized in-situ visualization of in-plane optical reflection anisotropy in this material. Moreover, the strong second harmonic generation (SHG) signal can only be detected when the incident polarization is along specific in-plane crystal orientations, illustrating the presence of strong in-plane nonlinear optical anisotropy. These findings will benefit the applications of VOCl in the field of polarization-dependent electronics and spintronics.

具有强面内各向异性的二维 (2D) 范德瓦尔斯 (vdW) 磁性材料可以使光自旋电子学和应变传感器等新应用成为可能。在这项工作中，系统地研究了 2D vdW 反铁磁体 VOCl 中强的面内光学各向异性。随着入射偏振的变化，光学亮度和吸收系数表现出明显的周期性变化，揭示了强烈的面内各向异性光学吸收。该材料的拉曼强度明显依赖于入射激光的偏振角，表明声子特性具有很强的面内各向异性。此外，我们还实现了原位该材料中面内光学反射各向异性的可视化。此外，只有当入射偏振沿着特定的面内晶体方向时才能检测到强二次谐波生成 (SHG) 信号，说明存在强面内非线性光学各向异性。这些发现将有利于 VOCl 在偏振相关电子学和自旋电子学领域的应用。