Highly sensitive silicon microring sensor with sharp asymmetrical resonance.

We analyze the resonance spectrum in silicon microring resonators taking into account the end-facet reflection from a coupled waveguide, which can provide a dense set of Fabry-Perot resonances. Based on the simple configuration of a microring coupled with a waveguide, the resulting asymmetric Fano-like non-Lorentzian resonance is obtained by scattering theory and experiment. Enhanced sensing performance with steeper slope to the resonance is theoretically predicted and experimentally demonstrated for a 10-microm racetrack silicon microring resonator. A high sensitivity of approximately 10(-8) RIU in terms of the detection limit is obtained in a 30-dB signal-to-noise ratio (SNR) system.