Linear Dichroism Conversion in Quasi‐1D Weyl Semimetal (TaSe₄)₂I Crystal with Giant Optical Anisotropy

Abstract The LD conversion offers great potential in providing an additional degree of freedom that may be beneficial to novel polarization‐wavelength‐selective detectors and optical switching. However, conventional crystals with optical anisotropy typically show unidirectional LD over a broad wavelength range and the materials with LD conversion behavior remain scarce. Here, by combining angle‐resolved polarized optical absorption measurements and theoretical calculations, this study demonstrates that quasi‐1D Weyl semimetal (TaSe₄)₂I single crystal shows unique LD conversion phenomenon at the wavelength of 1064 nm. Meanwhile, (TaSe₄)₂I persists giant linear optical anisotropy due to the intrinsic feature of 1D [TaSe₄] chains along the c‐axis. Additionally, the (TaSe₄)₂I nanoribbon exhibits anisotropic second harmonic generation (SHG). These results hold significant importance to facilitate the development of topological photonics and novel photonic devices applications based on topological semimetals.