Mutual-Coupling in High-Q Silicon Dual-Concentric Micro-Ring/Racetrack Resonator

Micro-ring resonator (MRR) is a key element in integrated optics. The mutual-coupling in dual-concentric MRR has great influence on the resonance output. In this work, high-Q silicon dual-concentric MRR and racetrack resonator have been investigated by the coupled mode theory. The theoretical model is built to explain and alleviate the phenomenon of resonance splitting. CMOS fabrication is adopted for the preparation of dual-concentric MRR and racetrack resonators. The highest Q-factors of dual-concentric MRR and racetrack resonator are measured to be ∼9.00 × 10
⁴
at 1530.783 nm and ∼7.32 × 10
⁴
at 1536.596 nm, respectively. The notch depth improvement over 20 dB has been demonstrated on the 5-μm-radius double-ring structure. The experimental results prove that the asymmetry of resonance splitting can be tuned by adjusting the distance between the inner-ring and outer-ring, as well as the waveguide width. The proposed work has potentials in the design and optimization of dual-concentric ring resonators.