Bound states in the continuum (BIC) holds significant promise in manipulating electromagnetic fields and reducing losses in optical structures, leading to advancements in both fundamental research and practical applications. Despite their observation in various optical systems, the behavior of BIC in whispering-gallery-modes (WGMs) optical microcavities, essential components of photonic integrated chips, has yet to be thoroughly explored. In this study, we propose and experimentally identify a robust mechanism for generating quasi-BIC in a single deformed microcavity. By introducing boundary deformations, we construct stable unidirectional radiation channels as leaking continuum shared by different resonant modes and experimentally verify their external strong mode coupling. This results in drastically suppressed leaking loss of one originally long-lived resonance, manifested as more than a 3-fold enhancement of its quality (Q) factor, while the other short-lived resonance becomes more lossy, demonstrating the formation of Friedrich-Wintgen quasi-BICs as corroborated by both the theoretical model and the experimental data. This research will provide a practical approach to enhance the Q factor of optical microcavities, opening up potential applications in the area of deformed microcavities, nonlinear optics, quantum optics, and integrated photonics.
Decomposed entropy and estimation of output power in deformed microcavity lasers
Park等人[Phys. Rev. A 106，L031504（2022）]表明，变形微腔激光器中远场分布（FFP）的单个随机变量的概率分布的香农熵可以有效地测量变形微腔激光器的方向性。在这项研究中，我们而是考虑两个随机变量的FFP与联合概率分布，并介绍了分解（香农）熵的峰值强度的方向性排放。这提供了一个新的基础，使得分解的熵可以估计在给定的FFP的输出功率的程度没有任何进一步的信息。
Reconfigurable and Recyclable Low-Threshold Quasi-BIC Lasers via a Tunable polymer Coating
Key Laboratory of Multiscale Spin Physics (Ministry of Education), Applied Optics Beijing Area Major Laboratory, School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院，多尺度自旋物理教育部重点实验室，应用光学北京地区重大实验室）
Dynamically Switchable Polarization Lasing between q-BIC and Bragg Resonance Modes
Key Laboratory of Multiscale Spin Physics (Ministry of Education), Applied Optics Beijing Area Major Laboratory, School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院，多尺度自旋物理教育部重点实验室，应用光学北京地区 major 实验室）
