新型中红外量子点级联激光器

Quantum cascade lasers are semiconductor laser sources based on intersubband transitions in multiple quantum well systems. Their unique operation principle and good performance have established themselves as the leading tunable coherent semiconductor source in the infrared and terahertz ranges of the electromagnetic spectrum. In principle, such lasers are restricted in broad tunability, surface emission, and high wallplug efficiency. Theoretical works have predicted that these issues can be raveled out in a quantum dot cascade laser (QDCL), in which quantum well active region is replaced by quantum-dot active region. This project puts forward a novel idea of realizing QDCL using self-assembled quantum dots layers replacing quantum well layers: with respect to active region design, for realizing population inversion utilizing “phonon bottleneck” effect, hybrid quantum dot/quantum well states are adopted as upper levels of electron transition in the coupled quantum-dot active region, and quantum dot states as lower levels; as to preparing quantum dots, we adopt a multi-strain-compensation technique to prepare InAs quantum dots embedded in tensile-strained InAlAs or GaAs layers effectively, i.e. quantum dots of InxAl(1-x)As/GaAs/InAs/InxAl(1-x)As composite structure, meanwhile, coupled-quantum-dot active region and coupled-quantum-well injection/relaxation region comprise one period of QDCL, and compensate the strain among one period totally. The aim is to realize our novel design of QDCL, validate the device, and reveal its inner operation mechanisms.

量子级联激光器是基于多量子阱系统子带跃迁的新颖半导体激光光源。其独特的工作原理和优异性能使它们成为在中红外和太赫兹领域主要的可调谐相干光源。原则上这些激光器还是受限于宽调谐性、面发射以及高功效等方面。理论上已经预测可以通过研究量子点级联激光器 (QDCL) 来得到克服。本项目提出一种应用应变自组织生长的量子点层取代有源区量子阱层研制QDCL的新思路：耦合量子点有源区中电子跃迁的上能态采用量子点/量子阱杂化态、下能态采用量子点态，从而利用“声子瓶颈”效应实现粒子数反转；采用多重应变补偿的技术实现张应变InAlAs或GaAs上InAs量子点的有效制备，即InxAl(1-x)As/GaAs/InAs/InxAl(1-x)As的复合结构量子点，另外耦合量子点区和耦合量子阱注入/抽运区构成一个完整的QDCL有源区周期，在一个周期内达到完全应变补偿。最终预期量子点级联激光器性能将得到很大提升。

量子级联激光器是基于强耦合多量子阱系统子带跃迁的新颖半导体激光光源。其独特的工作原理和优异性能使它们成为在中红外和太赫兹领域主要的可调谐相干光源。原理上这些激光器还是受限于宽调谐性、面发射以及高功效等方面。理论已经预测可以通过研究量子点级联激光器 (QDCL) 来得到克服。本项目提出并实施了一种应用应变自组织生长的量子点层取代有源区量子阱层研制QDCL的新思路：耦合量子点有源区中电子跃迁的上能态采用量子点/量子阱杂化态、下能态采用量子点态，从而利用“声子瓶颈”效应实现高效的粒子数反转；采用多重应变补偿的技术实现张应变InAlAs或GaAs上InAs量子点的有效制备，即InxAl(1-x)As/InAs/GaAs/InxAl(1-x)As的复合结构量子点，另外耦合量子点区和耦合量子阱注入/抽运区构成一个完整的QDCL有源区周期，在一个周期内达到完全应变补偿。结合创新的能带结构设计与材料制备技术，最终实现了国际首支7.2微米量子点级联激光器的室温连续波工作，器件具有垂直响应、光谱温度不敏感性与s偏振等典型量子点特征，特征温度可达1338 K，功率、阈值、动态范围等性能与常规量子阱级联激光器相当或更好，另外基于QDCL还开展了相干阵列器件、腔内差频太赫兹等特色研究，为量子级联激光器在宽调谐性、面发射、高功效、高功率以及室温太赫兹等方面的突破提供了一个新的可行方向。