Sustained Lasing Using Colloidal Quantum Dots

Abstract

Colloidal Quantum dots (CQDs) are solution synthesized nanocrystals that exhibit bright emission and narrow bandwidth, making them promising for light emission applications such as down-conversion luminescence, light amplification, and lasing. The emission wavelength of CQDs can also be controlled by the size of the nanocrystals potentially leading to tunable color light emission. In this work, CdSe-CdS-ZnS core-shell-shell quantum dots were synthesized and incorporated into a distributed feedback optical cavity to demonstrate sustained lasing. We show that the duration of lasing is limited by thermal runaway and that thermal management in the form of engineering the CQDs to form ultra-compact films and using a thermally conductive substrate can lead to efficient heat dissipation and therefore sustained lasing. The ultra-compact films were achieved by replacing long-chained organic ligands with inorganic-halide passivation. The new CQD films exhibited high modal gain (1,200 cm-1) and a low amplified spontaneous emission threshold of 50kw/cm2 (average peak power). Sustained lasing was first demonstrated for a microsecond, followed by fully continuous wave operation.