Ultraviolet Chiral Lasing in In-Plane Photonic Crystal via Quasi-Bound State in the Continuum

Chiral lasers with circularly polarized emissions are crucial for applications in quantum optics, display technologies, and biosensing. UV chiral lasers, in particular, enable highly sensitive detection of biomolecules with circular dichroism. However, achieving compact and highly chiral UV lasers remains challenging due to fabrication complexities and material constraints. Here, we demonstrate a UV chiral laser based on quasi-bound states in the continuum (quasi-BIC), achieving strong intrinsic chirality without requiring slanted structures. Our design utilizes a GaN nanopillar array with in-plane asymmetry introduced via semielliptical notches and out-of-plane asymmetry achieved by removing the index-matching superstrate. This simple yet effective approach enables highly circularly polarized lasing with a degree of circular polarization (DOCP) of 0.95, a linewidth of 0.18 nm, and a beam divergence of 1.80°. This work provides a scalable and material-compatible platform for chiral laser sources, paving the way for advancements in quantum optics, photonic devices, and enantioselective sensing.