Sustained Continuous-Wave Lasing in Quantum Dot Microfluids

Sustained amplified stimulated emission (ASE) under continuous-wave (cw) excitation is a prerequisite for any new gain material being developed for lasing applications. Despite the great success achieved in colloidal quantum dot (QD) lasers, the cw light amplification is hampered by the high pump threshold and thermal effects of QD solids. Herein, the first-ever cw ASE and lasing from QDs relevant for practical implementations are realized by adopting the microfluidic dot-in-matrix design. Leveraging on the transient and steady-state gain spectroscopy, it is demonstrated that the high-concentration dispersed QDs with a gain feature customized for cw pumping render the low pump threshold (≈340 W cm^-2). Meanwhile, the QD micro-liquids effectively dissipate the heat arising from the nonradiative multi-carrier recombination. As such, the unprecedented two-band cw ASE and long-lasting cw lasing with coherent output beam are realized. The findings open the door to practical QD lasers and may unlock new possibilities in optofluidics and optoelectronics.