Noninvasive Modulation of In-Plane Optical Anisotropy in ReSe2 via Etching-Induced Strain

The modulation of in-plane optical anisotropy in two-dimensional (2D) materials is of great significance for both fundamental research and optoelectronic device engineering. Here, we present a nondestructive and spatially tunable approach to control the anisotropic optical response of ReSe₂ through substrate etching–induced dielectric perturbations. Using a customized reflection difference spectroscopy (RDS) imaging system, we noninvasively characterized ReSe₂ flakes transferred onto both etched and pristine regions of patterned SiO₂ substrates. The etching process generates localized stress fields that weaken the intrinsic in-plane anisotropy of ReSe₂, enhance its overall reflectance, and induce a slight rotation of its optical principal axis. These effects are attributed to strain-driven modifications of the dielectric environment, which alter the optical response without compromising the structural integrity of the flakes. Our findings demonstrate that substrate-induced strain provides an effective means for controllable, localized, and nondestructive modulation of optical anisotropy in 2D semiconductors. This work establishes a practical strategy for tailoring the anisotropic optical properties of layered materials, offering potential implications for the design of strain-engineered optoelectronic devices and polarization-sensitive applications.