Zhang Shengnan, Li Yufeng, Hu Peng, Li Aixing, Zhang Ye, Du Wei, Du Mengqi, Li Qiang, Yun Feng
Opt Express. 2020 Mar 2;28(5):6443-6451. doi: 10.1364/OE.386453.
To reduce the threshold and achieve unidirectional lasing emission in a whispering gallery mode microcavity, we propose and demonstrate a GaN-based eccentric microring with an inner hole located off the center. Compared to microdisk with the same outer diameter, the eccentric microring structure exhibits a remarkable reduction of lasing threshold by up to 53%. The introduction of the hole disturbs and eventually suppresses the field distribution of the higher order modes. Laser emission with high unidirectionality with a far-field divergence angle of about 40° has been achieved, meanwhile the Q factor of the whispering gallery modesis remains high as 6388. Finite-difference time-domain numerical simulation is carried out to prove that the far-field profile of the eccentric microring structure can be controlled by the position and the size of the hole. The properties of the whispering gallery mode microcavities are improved greatly through a simple structure and process, which has an important guiding significance to the research and development of the microcavity lasers.
为了降低阈值并在回音壁模式微腔中实现单向激光发射，我们提出并展示了一种基于氮化镓的偏心微环，其内部孔洞偏离中心位置。与具有相同外径的微盘相比，偏心微环结构的激光阈值显著降低，降幅高达53%。孔洞的引入扰乱并最终抑制了高阶模式的场分布。已实现具有约40°远场发散角的高单向性激光发射，同时回音壁模式的品质因数仍高达6388。进行了时域有限差分数值模拟，以证明偏心微环结构的远场分布可通过孔洞的位置和尺寸来控制。通过简单的结构和工艺极大地改善了回音壁模式微腔的性能，这对微腔激光器的研发具有重要的指导意义。
