Modes Trimming and Clustering in a Weakly Perturbed High-Q Whispering Gallery Microresonator

Authors：Fu, Botao; Gao, Renhong; Lin, Jintian; Yao, Ni^*; Zhang, Haisu; Wang, Min; Qiao, Lingling; Fang, Wei; Cheng, Ya^*

Source：Laser & Photonics Reviews, 2023.

DOI：10.1002/lpor.202300116

• lithium niobate
• mode trimming and clustering
• weak perturbation
• whispering gallery mode microcavity

In general, a high-quality (Q) microresonator can accommodate abundant whispering gallery modes (WGMs) with the mode number increasing with the dimensional sizes of the microresonator. Removing the unnecessary modes while reorganizing the remaining modes is of vital importance, which, however, has been proved challenging and usually results in a tradeoff with the Q of the microresonator. Here, an effective and controllable mode trimming and clustering mechanism is revealed underlying the generation of polygon and star modes in weakly perturbed tapered fiber-coupled lithium niobate whispering gallery microresonators. Experimentally, various polygon and star modes are observed in sequence within a single microresonator by tuning the excitation wavelength or varying the coupling position between a tapered fiber and the circular microresonator, which can be well reproduced with the theoretical model. The finding offers a ubiquitous solution for a broad range of applications requiring elaborate selection and organization of the high-Q WGMs. @@@ An effective and controllable mode trimming and clustering mechanism underlying the generation of polygon and star modes is demonstrated in a weakly perturbed lithium niobate microcavity. The various polygon and star mode signals are observed in sequence in a microcavity without the need for some external deformations, agreeing well with the theoretical model.image

• Institution
  浙江大学; 中国科学院; y; 中国科学院研究生院