Taghipour Nima, Dalmases Mariona, Whitworth Guy L, Dosil Miguel, Othonos Andreas, Christodoulou Sotirios, Liga Shanti Maria, Konstantatos Gerasimos
ICFO, Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain.
Laboratory of Ultrafast Science, Department of Physics, University of Cyprus, Nicosia, 1678, Cyprus.
Adv Mater. 2023 Jan;35(1):e2207678. doi: 10.1002/adma.202207678. Epub 2022 Nov 21.
The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485 ps, lowering the amplified spontaneous emission (ASE) threshold down to 300 µJ cm , and showing a record high net modal gain coefficient of 2180 cm . By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot 〈N 〉 of 0.45 due to bleaching of the ground state absorption. This in turn have led to a fivefold reduction in ASE threshold at 〈N 〉 = 0.70 excitons-per-dot, associated with a gain lifetime of 280 ps. Finally, these heterostructured QDs are used to achieve near-infrared lasing at 1670 nm at a pump fluences corresponding to sub-single-exciton-per-dot threshold (〈N 〉 = 0.87). This work brings infrared CQD lasing thresholds on par to their visible counterparts, and paves the way toward solution-processed infrared laser diodes.
在红外激光器件中使用胶体量子点（CQD）作为增益介质，是由于需要高泵浦强度、极短的增益寿命和低增益系数。在此，PbS/PbSSe核/合金壳CQD被用作红外增益介质，其俄歇复合得到高度抑制，寿命为485皮秒，将放大自发辐射（ASE）阈值降低至300微焦/平方厘米，并显示出创纪录的2180厘米的高净模态增益系数。通过对这些设计的核/壳CQD进行掺杂，使其几乎填满第一激发态，通过瞬态吸收测量表明，由于基态吸收的漂白，光学增益阈值显著降低，平均每个量子点的激子数〈N〉为0.45。这反过来又导致在〈N〉=0.70个激子/量子点时ASE阈值降低了五倍，增益寿命为280皮秒。最后，这些异质结构量子点被用于在对应于每个量子点亚单激子阈值（〈N〉=0.87）的泵浦通量下实现1670纳米的近红外激光发射。这项工作使红外CQD激光发射阈值与可见同类器件相当，并为溶液处理的红外激光二极管铺平了道路。
