Silicon on Insulator Microring Resonators with Feedback Waveguides for Highly Sensitive Biomedical Sensors

Abstract

A novel sensing structure based on microring resonators with feedback using silicon waveguides is proposed in this paper. The proposed structure can produce a sharp asymmetric Fano resonance line shape, in which the slope between the zero and the unity transmission is greatly enhanced, comparing with that of the conventional microring resonators. As a result, biological sensors using this structure can provide a high sensitivity. In addition, multimode interference (MMI) couplers are employed as coupling elements instead of using directional couplers in the microring resonators. MMI couplers have shown to have relaxed fabrication requirements, simplicity, compactness and are less sensitive to the wavelength. The analytical description of output spectrum response of the proposed sensor is analyzed and derived. The transfer matrix method (TMM) and beam propagation method (BPM) are used to optimally design the sensor structure.