Strong in-plane optical anisotropy in 2D van der Waals antiferromagnet VOCl

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.