Ultralow-Threshold NIR AgAuSe Colloidal Quantum Dot Laser

Abstract Solution-processable quantum dot (QD) lasers are essential for next-generation integrated photonic circuits, ranging, and optical sensing. However, their practical deployment remains hampered by high lasing thresholds. Here, we report AgAuSe QD lasing with a record-low threshold of 0.01 μJ cm–2 at 900 nm, representing a reduction of more than 4 orders of magnitude compared to those of previous near-infrared (NIR) QD lasing reports. This achievement is enabled by a well-designed twisted-lattice photonic crystal (PhC) nanocavity delivering extreme light confinement with an ultrahigh quality (Q) factor. The extended photon lifetime reduces the required gain volume, enabling lasing from a single-layer self-assembled QD superlattice (SL), which minimizes scattering losses. Crucially, the robust system allows us to push the operational regime to quasi-continuous-wave (q-CW) lasing at room temperature. These results establish a new benchmark for solution-processed NIR QD sources and provide a technologically viable pathway for sustained CW operation.