Circularly Polarized Lasing From Amplified Geometric Chirality of Twisted Nanoplatelet Assemblies

Circularly polarized lasers are essential for quantum information, biomedical science, and advanced 3D display. Directly generating such emission from semiconductor nanomaterials is attractive yet remains challenging, as most chiral nanostructures suffer from low optical gain or rely on external chiral sources. Here, we demonstrate a strategy that unlocks and amplifies latent structural chirality in achiral ligand‐capped CdSe/CdSeS core/crown nanoplatelets (NPLs) through nonequilibrium assembly. Post‐synthetic treatment with oleic acid imparts a weak but deterministic enantiomeric bias to the NPLs in solution, evidenced by a reproducible net negative circular dichroism. Fast evaporative self‐assembly then amplifies this nascent chirality, yielding a luminescence dissymmetry factor | g lum | of 0.61. Integrating the chiral films into a vertical‐cavity surface‐emitting laser (VCSEL) achieves low‐threshold circularly polarized lasing with | g lum | up to 1.57 and a cavity quality factor Q of ∼12 000. This combination of high g lum and Q is achieved without external chiral ligands, molecules, or structurally engineered chiral optical cavities, distinguishing this approach from existing strategies for circularly polarized lasing.