Ultra-High-Quality Factor Micro-Ring Resonator Based on Silicon Nitride

On-chip micro-ring resonators (MRRs) with low propagation loss have the potential to revolutionize numerous fields, including microwave photonic filters, optoelectronic oscillators, on-chip soliton micro combs, and Brillouin lasers [1–2]. Silicon nitride (Si 3 N 4 ) is an excellent photonic platform due to its wide transparency range, relatively high refractive index, compatibility in large-scale semiconductor manufacturing, and ultra-low loss [3–4]. Although high-quality factor (Q) resonators have been demonstrated in low confinement Si 3 N 4 waveguides, they rely on a large mode volume, weak constraints, and millimeter-scale bending radii [5]. For the high confinement Si 3 N 4 waveguides, such as the photonic Damascene reflow process, which needs “preform reflow” and substrate annealing to reduce waveguide sidewall roughness and absorption loss [6].