Low-Divergence Wave-Chaotic Microlasers From Fiber-Hybridized Colloidal Quantum Dots

Abstract

Colloidal quantum dot (QD) lasers have attracted intense interest by virtue of their cost-effective solution-processibility and broadband spectral tunability. However, the present QD lasers generally exhibit poor directionality and divergence, which hinders their implementations in fiber optics and photonic circuits. Here, a novel kind of QD laser utilizing a fused silica fiber platform is designed and fabricated, which features directional and low-divergence output in combination with the high Q-factors. Based on the comprehensive numerical simulation and spectroscopic characterizations, the merits of the laser are attributed to the presence of a new kind of resonance mode termed waveguide-multiple islands in the QD-fiber hybrid resonator. The low divergence is well explained by the converging effect of the high-refractive curved boundary on the outgoing light. Furthermore, the output angle and the far-field distribution can be modulated on-demand by breaking the resonance symmetry through adjusting the diameter of constituted fibers. The laser design is general for QD gain media, such that the low-divergence red, green, and blue coherent emission is obtained. These findings represent significant progress toward the integration application of QD lasers.