【作者】 王贞福；

【导师】 宁永强；

【作者基本信息】 中国科学院研究生院（长春光学精密机械与物理研究所） ， 凝聚态物理， 2011， 博士

【摘要】 垂直腔面发射激光器(VCSELs)作为一种结构紧凑,性能优良的新型光源被广泛应用于光通信、光互联、光存储等领域。与传统的边发射激光器(EELs)相比垂直腔面发射激光器有如下优点:有源区体积小,具有很小的阈值电流;圆形对称光斑,发散角小,容易与光纤高效耦合,有利于进行光束整形;出光窗口面积大,不易发生光学灾变损伤;谐振腔腔长短,极易实现动态单纵模工作;可以二维集成,制作高功率二维面阵;焊接封装容易,适合大批量生产。特别是单模VCSELs对于许多领域有着重要的应用,像自由空间的光互联、激光读写、医疗诊断、机载光探测和激光测距系统等都需要VCSELs光束具有高功率单模、低的远场发散角等特点。然而垂直腔面发射激光器的有源区和出光窗口具有一定的横向宽度,因此会有一些横模被激发出来。有源区载流子和多种横模的光子的相互作用导致的空间烧孔效应,是产生多横模的主要原因,因而通常的大口径垂直腔面发射激光器多为多横模单纵模出射。本论文采用在垂直腔面发射激光器窗口表面直接制作GaAs微透镜的技术,来提高器件的光束质量,压缩发散角。首先理论上分析和计算了微透镜耦合垂直腔面发射激光器的基本原理,对影响器件性能的几个主要参数进行了分析,包括有效反射率,阈值电流,微分量子效率,电光转换效率,模式特性,光谱特性等,通过深入研究氧化限制型VCSELs的结构,合理安排了微透镜集成底发射VCSELs的工艺流程,并且优化了器件制作过程中的几个关键技术,然后采用限制扩散湿法刻蚀法直接在GaAs衬底上制作出不同直径的微透镜和微透镜阵列,得到了较好的表面形貌。通过对微透镜集成VCSELs器件进行测试表明,在出光窗口表面制作微透镜,可以明显的改善光束质量,压缩发散角。对于400μm的单管器件,室温下当工作电流为4A时,最高输出功率200mW,激射波长为978.1nm,光谱半高宽0.8nm,器件的远场发散角为8.4°和8.7°,而没有微透镜的器件远场发散角为18.9°和19.8°,并对有无微透镜的器件的光束质量因子进行了测试。对于6×6微透镜集成垂直腔面发射激光器列阵进行了测试,列阵共有36个发光单元,单元圆心间距为120μm,有源区直径为90μm ,出光口径为100μm ,室温下最高连续输出功率大于1W,相应的功率密度为0.44KW/cm2,斜率效率0.36W/A,微透镜的耦合效率为85%。当驱动电流1A到4A变化时,有微透镜器件的远场发散角小于6.6°,实验测试结果与理论预期计算的结果基本一致。更多还原

【Abstract】 Vertical cavity surface emitting lasers (VCSELs) as a compact structure, excellent performance of novel light sources are widely applied for optical interconnection communication, optical communication, optical storage and other fields. Compared to the conventional edge-emitting lasers (EELs), VCSELs have the following advantages: lower threshold current; circular output beam, small divergence angle, efficiently fiber coupling and easy beam shaping; not prone to catastrophic optical damage due to large emitting windows; operating on dynamic single longitudinal mode; highly integrated two-dimensional area array with high power; easy welding and package; easy mass production. Particularly for single-mode VCSELs have important applications in many fields, such as free space optical interconnection, laser written, medical diagnostics, airborne light detection and laser ranging system, and so high power single-mode VCSELs with excellent beam quality and low divergence far-field angle are necessary. However, because vertical-cavity surface-emitting laser’s active region has a transverse width, so there will be some high order transverse modes are emitted. Thus, vertical cavity surface emitting lasers with large emitting windows usually operated on multi-transverse-mode and single longitudinal mode.In this paper, the main parts include directly fabricating microlens on the emitting windows of vertical cavity surface emitting laser in order to improve the beam quality of the device and compress far-field divergence angle. Firstly, the basic principle of the microlens coupling vertical-cavity surface-emitting lasers is theoretically analysised and calculated. The important parameters such as the effective reflectivety, threshold current, differential quantum efficiency, electro-optical conversion efficiency and spectral characteristics are demonstrated. We also optimize the structure of the device wafer and the key to the device manufacturing process technology. And then GaAs microlens and microlens array with different diameter are directly fabricated by using limited-diffusion wet etching technique on the substrate. The maximum continuous output power of microlens-integrated single device with an emitting windows of 400μm at room temperature is more than 200mW at a current of 4A, and the far field divergence angles of that are 8.4°and 8.7°, respectively. However, the far-field divergence angle of the same structure without microlens devices is 18.9°and 19.8°. For the 6×6 microlens-integrated vertical-cavity surface-emitting laser array, the maximum continuous output power at room temperature is more than 1W, and the far field divergence angle is less than 6.6°. Yet, the far-field divergence angle of the same structure without microlens devices is more than 15°. The results of experiment are basically consistent with the results of theoretical simulation.更多还原