Generation principle for the robust comb-like resonant modes in photonic crystal ring resonator

Abstract Topological valley photonic crystal cavity supports the robust comb-like resonant modes, and thus is widely applied in chiral coupling of quantum dots, laser, nonlinear frequency conversion process, and photonic logical elements. So far, its robustness is mostly attributed to the different topological properties of the valley photonic crystals. In this work, we illustrate that the position of circular polarization topological singularity is the most important factor to generate comb-like resonant modes with robustness. We proposed a photonic crystal ring resonator purely by the linedefect waveguide, and simulation results demonstrate that the proposed cavity can generate robust comb-like resonant modes. This work can provide guidance to the design of high-quality and robust photonic crystal cavity.