面向近红外激光器的Ag2Se/AgZnSe核壳量子点的光增益特性研究

受益于量子限域效应，胶体半导体量子点作为光增益材料展现出了多种优越的性能。然而，俄歇复合严重阻碍了胶体量子点激光器的发展。本项目提出利用低毒的最低量子态2重简并的Ag2Se量子点替代最低量子态8重简并的铅盐量子点来实现低阈值的近红外光增益。并通过在Ag2Se表面包覆组分渐变的AgZnSe合金壳，来构建平缓的界面势垒和钝化Ag2Se的表面，进一步抑制俄歇复合从而提高光增益性能。拟采用超快瞬态吸收研究Ag2Se量子点和Ag2Se/AgZnSe核壳量子点的光增益动力学，评估合金壳对俄歇复合的抑制以及光增益性能的促进。以实验结果为指导，优化合金壳的结构，研制出具有优异的光增益性能的Ag2Se/AgZnSe量子点，并利用该量子点制备垂直腔面发射的近红外量子点激光器。该研究既有助于建立基于Ag2Se的核壳量子点的光增益动力学的相关理论，又能够促进近红外发射的胶体量子点激光器向实用型激光器发展。

Owing to the quantum confinement effect, colloidal semiconductor quantum dots (QDs) exhibit various advantageous properties as optical gain media. However, the development of colloidal QD lasers is blocked by Auger recombination (AR). This project proposes that low toxic Ag2Se QDs whose lowest quantized states are 2-fold degeneracy could substitute for lead-salt QDs whose lowest quantized states are 8-fold degeneracy to achieve low-threshold near-infrared optical gain. Depositing AgZnSe alloyed shell with gradient composition on the surface of Ag2Se can build “smoothing” interfacial potential and passivate the surface of Ag2Se, which further suppresses AR and boosts optical gain performance. Moreover, ultrafast transient absorption spectroscopy will be employed to study the optical gain dynamics of the Ag2Se QDs and Ag2Se/AgZnSe core/shell QDs, to evaluate the influence of alloy shell on the suppression of AR and the facilitation of optical gain properties. Guided by experimental results, Ag2Se/AgZnSe QDs with excellent optical gain properties would be developed, which also could be used to fabricate vertical-cavity surface-emitting near-infrared QD lasers. This studies can not only contribute to establish relative theory of optical gain dynamics of the core/shell QDs based on Ag2Se, but also promote the development of near-infrared colloidal QD lasers to practical lasers.