单向光输出低发散角量子级联微腔激光器研究

Micro-cavity quantum cascade lasers have been investigated widely due to its extremely high quality factor lasing modes,low lasing threshold and mid-infrared laser applications. However,traditional devices have the drawbacks that the emission direction is isotropic and the emission intensity is low, which confine its applications. In this project, a novel elliptical micro-cavity structure with a small notch is proposed.This micro-cavity structure can support high Q lasing mode with an unidirectional optical emission, and the in-plane divergence angle is suppressed down to 3 degree. At the same time, the circular shaped contact is employed to suppress high order radial mode and improve carrier injection efficiency. For the material structure design, we present InGaAs/InAlAs quantum cascade active region with a large optical waveguide structure design. Due to the advantage of the large optical waveguide structue in vertical directional beam quality, the vertical divergence angle is expected to 30 degree. Low threshold and high optical power will be also achieved due to the improved optical confinement factor. Furthermore, adopting the advantage of directional emission and low divergence angle of the micro-cavity laser, a novel micro-cavity quantum cascade laser on-chip array design is finally presented in this project in order to improve the total light output power level, and to push forward the quantum cascade micro-cavity laser applications, such as the trace-gas sensing, biological testing and sensing,air pollution monitoring, and photonic integrations. And this project will also provide a novel scientific concept for the micro-cavity laser research in our country.

量子级联微腔激光器以高品质因子、低激射阈值的特点和中远红外激光应用优势一直备受关注，然而传统器件结构的光输出方向性差和输出功率低是制约其发展的瓶颈问题。本项目提出一种新型带切口椭圆微腔结构，在保证高品质因子的同时，能够实现单向光输出，并将实现水平方向发散角3度 ,同时提出采用环形电极结构实现对高阶径向模的抑制及载流子注入效率的提高；在材料结构设计方面，引入大光波导结构InGaAs/InAlAs量子级联为增益介质，提高垂直方向光束质量，将实现垂直方向发散角30度 ，并通过改善光限制因子、降低激射阈值、提高光输出功率；发挥激光器单向光输出、低发散角的优势，提出单片集成微腔激光器阵列的新设计理念，进一步提高激光器的光功率输出水平。本研究将使量子级联微腔激光的应用前景变得光明，在痕量气体探测、生物探测传感、大气污染检测、光子集成等领域得到快速发展，也为我国微腔激光的研究提供新的科学理念。

本项目针对半导体微腔激光器光输出方向性差、光输出功率低以及量子级联激光器激射阈值较高等科学问题按计划完成了相应的研究工作,工作中提出了新型带切口椭圆微腔半导体激光设计结构，实现了微腔激光器单一方向输出，通过优化设计,器件水平远场发散角在3度以内，为器件制备提供了工艺参数。对InGaAs/InAlAs量子级联增益波导结构分析研究,并对材料体系进行特性表征，增益介质中引入多级InGaAs/InAlAs量子级联结构，在提高器件光增益的同时有利于改善垂直方向光束质量,发散角在30度；提出了新型图形化电极下的非均匀激励InGaAs/InAlAs量子级联微腔激光器的电流注入结构，器件电流注入效率得到显著提高，有效改善了器件的阈值特性，也提高了激光器的工作稳定性。实验研制出单向光输出低发散角椭圆微腔激光器单管器件，在制备技术研究工作中对关键技术问题，特别是微腔腔体光刻、掩模对准技术精度以及感应耦合等离子体（ICP）刻蚀技术和器件热稳定性等进行了研究；单管器件实现了室温峰值光功率13mW以上的光输出，器件的实验结果表明椭圆形微腔激光器在0°方向呈现出显著的单一出射模瓣，出射膜瓣半高全宽为6.5°；激光器的激射波长为10微米；实验制备了图形化电极结构InGaAs/InAlAs量子级联微腔激光器件，器件激射阈值电流降低10%以上。对微腔激光器阵列集成进行了设计及制备研究，研究阵列器件热源组成、温场分布、单元器件之间的热相互作用，以及器件实际制备工艺中的关键技术问题；通过工艺技术首次研制出单一方向光输出低发散角半导体微腔激光器阵列器件，阵列激光器件实现了室温脉冲工作，阵列整体激光功率水平获得大幅提升,展现出中远红外波段量子级联微腔激光在痕量气体探测、生物探测传感、大气污染检测、光子集成等领域应用技术发展的广阔前景。授权国家发明专利1项，国家发明专利申请4项；发表学术论文13篇，其中SCI、EI收录10篇，中文核心3篇 ，毕业博士、硕士研究生3名。