Li Xueyang, Du Jun, Zhao Guohui, Zhang Boyu, Livache Clément, Ahn Namyoung, Jia Yuxi, Li Mingrun, Chen Ying, Zhu Jingyi, Guo Jingwei, Klimov Victor I, Wu Kaifeng
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China.
Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
Adv Mater. 2024 Feb;36(7):e2308979. doi: 10.1002/adma.202308979. Epub 2023 Dec 8.
Colloidal quantum-dot (QD) lasing is normally achieved in close-packed solid-state films, as a high QD volume fraction is required for stimulated emission to outcompete fast Auger decay of optical-gain-active multiexciton states. Here a new type of liquid optical-gain medium is demonstrated, in which compact compositionally-graded QDs (ccg-QDs) that feature strong suppression of Auger decay are liquefied using a small amount of solvent. Transient absorption measurements of ccg-QD liquid suspensions reveal broad-band optical gain spanning a wide spectral range from 560 (green) to 675 nm (red). The gain magnitude is sufficient to realize a two-color amplified spontaneous emission (ASE) at 637 and 594 nm due to the band-edge (1S) and the excited-state (1P) transition, respectively. Importantly, the ASE regime is achieved using quasicontinuous excitation with nanosecond pulses. Furthermore, the ASE is highly stable under prolonged excitation, which stands in contrast to traditional dyes that exhibit strong degradation under identical excitation conditions. These observations point toward a considerable potential of high-density ccg-QD suspensions as liquid, dye-like optical gain media that feature readily achievable spectral tunability and stable operation under intense photoexcitation.
胶体量子点（QD）激光通常在紧密堆积的固态薄膜中实现，因为受激发射要胜过光学增益活性多激子态的快速俄歇衰变，需要高量子点体积分数。本文展示了一种新型的液体光学增益介质，其中具有强俄歇衰变抑制特性的致密成分渐变量子点（ccg-QDs）使用少量溶剂进行液化。ccg-QD液体悬浮液的瞬态吸收测量揭示了从560（绿色）到675纳米（红色）的宽光谱范围内的宽带光学增益。由于分别为带边（1S）和激发态（1P）跃迁，增益幅度足以在637和594纳米处实现双色放大自发发射（ASE）。重要的是，ASE状态是使用纳秒脉冲准连续激发实现的。此外，ASE在长时间激发下高度稳定，这与传统染料在相同激发条件下表现出强烈降解形成对比。这些观察结果表明，高密度ccg-QD悬浮液作为液体、类似染料的光学增益介质具有巨大潜力，其具有易于实现的光谱可调性以及在强光激发下的稳定运行特性。
