氮化物增益开关超短脉冲垂直腔面发射激光器研究

Gain-switched semiconductor lasers have attracted considerable attention for their advantages of low cost, simple operation, compact size and tunable frequency, which are on demand in many applications such as optical communications, bio-medical, imaging, and micro-processing, etc. To further increase the range of such devices’ applications, the gain-switched pulses need to be shortened to several picoseconds or less. Nitride-based vertical-cavity surface-emitting laser (VCSEL), as a novel semiconductor laser, has both high optical gain and short cavity lifetime due to its short cavity length, making it favorable for the generation of ultra-short pulses via gain-switching. However, to date, only a few related studies have been reported in spite of its great value in practical applications. In this research, we aim to further study the gain-switching dynamics in nitride-based VCSELs systematically based on our previous theoretical and experimental investigations, and clarify the limiting factors and the physical mechanisms of the optical pulse-widths of the devices with different structural parameters. Additionally, we will then devise the ideal device structure to obtain the minimum limit of the optical pulse-width and make efforts to achieve femtosecond-pulse generation from the new-constructed gain-switched InGaN VCSELs. Undoubtedly, this research has profound scientific significance and is of great practical value since it not only provides a new way to obtain high performance gain-switched semiconductor lasers but also promotes the rapid development in this field.

基于增益开关技术的半导体脉冲激光器具有体积小、成本低、操作简单、频率可调等优点，在通讯、医疗、成像及微加工等领域有着广阔的应用前景。研究如何实现增益开关半导体激光器的超短激光脉冲输出一直是国际上的研究热点。氮化物垂直腔面发射激光器作为新型半导体激光器，同时满足“高材料增益”及“短光子寿命”这两个实现超短激光脉冲的必要条件，因此是理想的研究对象，但国内外对其研究和报道却寥寥无几。本项目基于前期的理论和实验研究，旨在更加深入系统地对氮化物VCSEL的增益开关特性进行研究，阐明不同结构参数对激光输出脉宽的限制规律及其物理机制，通过建立氮化物面发射激光器速率方程模型，对实验结果进行定量拟合与对比，探索产生极限脉宽的参数条件，进而研制出飞秒量级超短脉冲氮化物增益开关垂直腔面发射激光器。本项目为获得高性能增益开关半导体激光器提供了一种新途径，并有望推动该领域的快速发展，研究价值和应用潜力巨大。

由半导体激光器产生的皮秒光脉冲，在高比特速率光通信、高容量数据存储、超高速数据处理、光计算、光互联以及多光子生物成像等领域具有极大的吸引力和非常广阔的应用前景。半导体增益开关(Gain-Switch)技术和当前较为成熟的锁模(Mode-lock)和调Q(Q-Switch)技术并称为制备激光脉冲的三大技术。增益开关半导体激光器操作简单，具有频率任意可调、体积小、价格低及易于实现大规模生产等常规锁模和调Q激光器所无法比拟的诸多优点。因此，实现皮秒半导体激光器并阐明其物理机制，将极大地推动整个脉冲激光领域的发展，并可望广泛应用于工业、医疗、通信、国防等诸领域。本项目聚焦氮化物垂直腔面发射激光器(VCSEL)，引入ABC复合模型，构建了半导体激光器二维速率方程模型，分析了不同参数下半导体激光器的增益开关特性。模拟结果对半导体激光器材料生长控制以及有源区结构设计提供了重要的理论依据，对实现半导体增益开关超短脉冲的理论研究具有重要的意义。优化设计了InGaN非对称耦合多量子阱有源区结构，并详细研究了其载流子隧穿机制及光学特性。通过巧妙设计InGaN非对称量子阱结构，实现了波长可控的多波长GaN基VCSEL的室温光泵激射，并提出实现多波长GaN基VCSEL的通用策略，为获得GaN基多波长超短激光脉冲提供了理论及实验指导。搭建完成上转换超快光学瞬态测试系统，时间分辨率达到100飞秒。利用该超快光学测试系统，获得包括氮化物VCSEL在内的不同半导体激光器的增益开关激光特性，得到皮秒量级稳定激光脉冲输出。本项目为皮秒脉冲半导体激光器的实现及应用提供了重要的理论和实验支撑，具有重大的科学价值和应用价值，对促进国家产业技术升级和经济发展有着长远的战略意义。