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太赫兹量子级联激光器中有源区上激发态电子向高能级泄漏的研究
引用本文:李金锋,万婷,王腾飞,周文辉,莘杰,陈长水.太赫兹量子级联激光器中有源区上激发态电子向高能级泄漏的研究[J].物理学报,2019,68(2):21101-021101.
作者姓名:李金锋  万婷  王腾飞  周文辉  莘杰  陈长水
作者单位:1. 华南师范大学信息光电子科技学院, 广东省微纳光子功能材料与器件重点实验室, 广州市特种光纤光子器件与应用重点实验室, 广州 510006; 2. 江门珠西激光智能科技有限公司, 江门 529000
基金项目:广东省自然科学基金(批准号:2015A030313383)资助的课题.
摘    要:利用热力学统计理论和激光器输出特性理论,建立了太赫兹量子级联激光器(THz QCL)有源区中上激发态电子往更高能级电子态泄漏的计算模型,以输出功率度量电子泄漏程度研究分析了晶格温度和量子阱势垒高度对电子泄漏的影响.数值仿真结果表明,晶格温度上升会加剧电子泄漏,并且电子从上激发态泄漏到束缚态的数量大于泄漏到阱外连续态,同时温度的上升也会降低激光输出功率.增加量子阱势垒高度能抑制电子泄漏,并且有源区量子阱结构中存在一个最优量子阱势垒高度. THz QCL经过最优量子阱势垒高度优化后,工作温度得到提升,其输出功率相比于以往的结果也有所提高.研究结果对优化THz QCL有源区结构、抑制电子泄漏和改善激光器输出特性有指导作用.

关 键 词:太赫兹  量子级联激光器  电子泄漏  有源区
收稿时间:2018-10-22

Electrons leakage from upper laser level to high energy levels in active regions of terahertz quantum cascade lasers
Li Jin-Feng,Wan Ting,Wang Teng-Fei,Zhou Wen-Hui,Xin Jie,Chen Chang-Shui.Electrons leakage from upper laser level to high energy levels in active regions of terahertz quantum cascade lasers[J].Acta Physica Sinica,2019,68(2):21101-021101.
Authors:Li Jin-Feng  Wan Ting  Wang Teng-Fei  Zhou Wen-Hui  Xin Jie  Chen Chang-Shui
Institution:1. Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, Guangzhou Key Laboratory for Special Fiber Photonic Devices, School of Information Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China; 2. Jiangmen Zhuxi Laser and Smart Co. Ltd., Jiangmen 529000, China
Abstract:Terahertz quantum cascade laser is a semiconductor laser that effectively obtains terahertz waves. It uses the semiconductor heterojunction to have a quantum cascade effect under an applied voltage, and then the phonon assists the electron resonance from the upper stage to the next stage, so that a single electron injected externally can emit multiple photons. However, some electrons will deviate from the transport path during transportation and these electrons are called leakage electrons. Electron leakage comes from three ways. The first way is the scattering of electrons from the upper laser level through the long longitudinal phonon to the low energy level; the second way is the scattering of electrons from the lower laser level to the high energy bound level and the continuous level; and the third way is the scattering of electrons from the upper laser level to high energy bound levels and continuous levels. These leakage electrons directly reduce the number of population inversions in the laser system, making the laser output power limited. At present, most of researchers explain the electron leakage through indirect measurements, and there are few studies in which the electron leakage is analyzed by establishing theoretical models. In this paper, the electron leakage model in THz QCL is established by using thermodynamic statistical theory and laser output characteristic theory. The degree of electron leakage is measured by output power. The influence of lattice temperature and quantum well barrier height on electron leakage are studied. It is found that when the lattice temperature rises and the electrons in the upper laser state leak to higher energy levels, the number of electrons leaking to the adjacent bound state and the continuous state increases, and the number of electrons leaking to the next near-bound level is relatively small. In the case of electron leakage, the utilization of electrons becomes lowered, and the laser output power is also lowered. The study also shows that an appropriate increase in the height of the quantum barrier can suppress the leakage of electrons. Using the established theoretical model to optimize the quantum well barrier height of the previously reported laser system, an 8 mW terahertz quantum cascade laser (THz QCL) laser output at 210 K is obtained. Compared with the reported experimental results, the temperature and output power are improved. These results provide a theoretical basis for studying the electron leakage temperature characteristics of THz QCL and also optimally designing the THz QCL active region structure.
Keywords:terahertz  quantum cascade laser  electron leakage  active region
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