Anisotropic Light–Matter Interaction in α-In₂Se₃: Wavelength-Dependent Study

The anisotropic light-matter interactions in 2D materials have garnered significant attention for their potential to develop futuristic polarization-based optoelectronic devices such as photodetectors and photoactuators. In this study, we investigate the polarization-dependent interactions in ferroelectric 3R α-In₂Se₃ using Angle-Resolved Polarized Raman Spectroscopy with different excitation lasers. Our experimental findings supported by complementary Density Functional Theory calculations demonstrate that the light-matter interactions depend not only on the crystallographic orientation but also on the excitation energy. Highly anisotropic 3R crystal structure, confirmed by scanning transmission electron microscopy, facilitates significant optical anisotropy, driven by a complex interplay of electron-photon and electron-phonon interactions, which is reflected in the complex nature of the Raman tensor elements. Additionally, this anisotropy is reflected in the material's electrical response under light illumination. Remarkably, the anisotropic photoresponse can be tuned by both polarization and the wavelength of the incident light, making In₂Se₃ a promising material for advanced polarization-sensitive photodetection applications.