Chen Jinghan, Nasir Abdul, Abazi Adrian, Eich Alexander, Sánchez-Postigo Alejandro, Takeda Harunobu, Mikami Yuya, Tate Naoya, Oki Yuji, Yamamoto Yohei, Schuck Carsten, Yoshioka Hiroaki
Graduate School and Faculty of Information Science and Electrical Engineering, Kyushu University, 744 Motooka Nishi-ku, Fukuoka, 819-0395, Japan.
Department for Quantum Technology, University of Münster, Heisenbergstr. 11, Münster 48149, Germany.
ACS Photonics. 2024 Oct 8;11(12):5110-5117. doi: 10.1021/acsphotonics.4c00956. eCollection 2024 Dec 18.
Whispering-gallery mode (WGM) resonators, renowned for their high Q-factors and narrow line widths, are widely utilized in integrated photonics. Integrating diffraction gratings onto WGM cavities has gained significant attention because these gratings function as azimuthal refractive index modulators, enabling single-mode WGM emissions and supporting beams with orbital angular momentum (OAM). The introduction of curved grating structures facilitates guided mode resonances by coupling high-order diffracted waves with leaking modes from the waveguide. These gratings act as wavelength-selective mirrors and support concentric circular radial-guided modes. This study investigates the coexistence and interaction between OAM-carrying WGMs and radial-guided modes with Bessel beam characteristics in an active cladding grating-integrated microring laser. These phenomena are examined through both three-dimensional simulations and experiments. The active layer enhances the radial-guided modes at the microring's center, where cylindrical waves from the active cladding produce strong guided mode resonance at specific wavelengths corresponding to radial modes. Additionally, general WGMs are formed and confined within the microring. The effects of grating depth and microring size on radial-guided mode resonance are evaluated through two-dimensional simulations and experiments. These insights pave the way for integrating functional lasers into photonic circuits and advancing technologies for topological optical vortex emission and manipulation.
回音壁模式（WGM）谐振器以其高品质因数和窄线宽而闻名，在集成光子学中得到广泛应用。将衍射光栅集成到WGM腔上已引起广泛关注，因为这些光栅起到方位角折射率调制器的作用，能够实现单模WGM发射并支持具有轨道角动量（OAM）的光束。弯曲光栅结构的引入通过将高阶衍射波与来自波导的泄漏模式耦合来促进导模共振。这些光栅充当波长选择镜并支持同心圆形径向导模。本研究调查了在有源包层光栅集成微环激光器中，携带OAM的WGM与具有贝塞尔光束特性的径向导模之间的共存和相互作用。通过三维模拟和实验对这些现象进行了研究。有源层增强了微环中心的径向导模，有源包层的柱面波在对应于径向模式的特定波长处产生强烈的导模共振。此外，一般的WGM在微环内形成并被限制。通过二维模拟和实验评估了光栅深度和微环尺寸对径向导模共振的影响。这些见解为将功能激光器集成到光子电路以及推进拓扑光学涡旋发射和操纵技术铺平了道路。
