Compact silicon-on-insulator asymmetric embedded dual microring resonators for sensing

A silicon microresonator consisting of an asymmetric embedded dual microring (EDMR) with a U-bend feedback coupled waveguide (FCW) is proposed and investigated for possible applications in sensing. A Fano resonance originates from the optical interference between the EDMR and racetrack-like resonator (RTR) in the proposed device. The interference between a high-Q EDMR cavity and a low-Q RTR cavity can increase the extinction ratio (ER) of Fano spectrum. The slope of Fano resonance can be well tuned by changing loss factor β of FCW. We can see the periodic spectrum transits from Lorentz profile to Fano profile by changing optical path length L of FCW. The maximum ER of Fano resonance is as high as −45 dB. Our sensor exhibits sensitivity of 1.2 × 104 dB / nm, and a minimum detection limit of 2 × 10 − 7 RIU. Moreover, for such a structure, the fabrication is simple and CMOS compatible. The sensor’s performance is simulated for ethylene glycol (C2H6O2) solution. The microcavity with optimized geometric structures presented provides the potential for ultracompact sensing applications.