Reconfigurable Circularly Polarized Terahertz Emission from vdW Ferroelectric NbOI ₂

ABSTRACT Chiral light plays a pivotal role in probing, distinguishing, and even controlling the behavior of chiral materials, such as biological molecules, chiral phonons, and spin‐textured quantum materials. However, in frequency ranges where efficient waveplates are not available, such as the terahertz (THz) range or Ultraviolet (UV), a highly efficient, compact, and flexible light source is in great demand. In this work, we propose a dual‐flake‐based chiral THz emitter with large tunability. We experimentally realize this concept and demonstrate the active manipulation of both chirality and ellipticity using a van der Waals ferroelectric material, NbOI 2 . The application of this approach is not restricted to the THz range and can be extended to other spectral domains. This concept offers new opportunities for the generation of chiral light and provides a platform for exploring previously inaccessible regimes of light‐matter interaction, particularly in cases where conventional methods of polarization control are ineffective.