红外胶体量子点激光材料与器件研究

Colloidal quantum dots are emerging lasing materials with wide range wavelength tenability and great potentials in miniaturization and integration, promising their applications in information communication and processing. Even colloidal quantum dot lasers emitting visible light have been significantly improved during last two decades, there still lacks progresses in infrared range, which is actually of more importance in applications. The applicants have been working on visible colloidal quantum dot lasers during recent years and contributed several accomplishments to the field, including efforts in improving the cavity quality, decreasing the bandedge degeneracy and the lasing threshold. Given visible and infrared quantum dots have very similar electronic and crystal structures, they share common challenges to be good lasing materials. The applicants therefore propose to work on addressing the following key challenges to make better infrared colloidal quantum dot lasers. We will improve the cavity quality through exchanging the low index organic surface capping ligands with high index inorganic ones. We will grow thick shell quantum dots to decrease exciting power and epitaxially grow asymmetric colloidal quantum dots to decrease the bandedge degeneracy. We will optimize compositions of core-shell structure to delocalize electrons for decreasing Auger recombination and improving optical gain lifetime.

胶体量子点是一种新型的激光材料，由于其具有波长连续可调、可小型化和可集成化的特点，在信息通讯和处理等领域有重要的应用价值。近年来虽然可见光区胶体量子点激光器的研究取得了较大的进展，但是红外波段胶体量子点激光相关研究严重滞后，限制了其在通讯等领域的应用。申请人近四年来专注于研发可见光胶体量子点激光材料和器件，在提升谐振腔质量、降低简并度及激光阈值中积累了丰富的经验。鉴于可见和红外胶体量子点有非常相似的电子和晶体结构，其中关键科学问题相通。因此拟申请该项目开发高性能红外胶体量子点材料和器件。我们拟通过表面化学手段去除胶体量子点表面的低折射率有机配体以提升谐振腔的品质；外延生长高质量厚壳核-壳红外胶体量子点降低所需激发功率；外延生长非对称核-壳结构引入不对称应力，降低价带简并度以及激光阈值；优化设计核-壳组成实现电子适度离域以降低俄歇复合速率，延长光学增益寿命。

针对难以在近红外量子点中难以获得激光这一难题，我们在量子点材料以及激光器制备两个方面开展研究。在量子点材料制备方面，我们通过改变激发光偏振的方式降低纳米晶量子点能级简并度以降低激光阈值；同时我们发现空气中吸附的水分子能够钝化量子点表面的一些缺陷，进而降低激光阈值。在激光器件制备方面, 我们发展了一种胶体量子点液相自组装技术，该技术能够在1分钟之内将胶体量子点组装成衬底无依赖的球型激光超颗粒，实现低阈值激光。以上研究为为制备低阈值量子点激光器提供了重要的思路。此外，基于这些技术，我们开拓了量子点激光器在气体传感以及显示领域的应用。