Revealing Resonant Mode Properties in Asymmetric Photonic Crystal Microrings through Diverse Excitation Methods

The photonic crystal (PhC)-modulated microring resonator enables engineered dispersion, the formation of photonic bandgap, enhanced slow light effects, making it attractive platform for nonlinear optics, optical sensing, or quantum photonics. Recently, symmetry-breaking PhC microrings have shown promise for realizing miniature bound states in the continuum (BICs), but challenges remain, including limited <i>Q</i>-factor and an incomplete understanding of the radiated mode patterns. Here, we present a comprehensive investigation of the resonant modes in asymmetric PhC microrings by employing various excitation methods. Our results show that the radiation from the dielectric band modes carries orbital angular momentum, with its characteristics strongly influenced by asymmetric parameters. Moreover, the quasi-BIC mode achieves a <i>Q</i>-factor exceeding 3 × 10³, allowing temperature detection with a sensitivity of up to 32.2 pm/°C. This work advances the understanding of light confinement and radiation control in PhC microring, with implications for on-chip optical sensing and structured beam generation.