In this paper, the realization and design of a novel waveguide microring resonator for
biological and chemical sensing are presented. The structure of the proposed sensor uses a 3x3
multimode interference (MMI) coupler based on silicon waveguides for highly sensitivity,
compactness and CMOS compatibility. The Fano resonances based on this structure can be
achieved. As a result, sensors based on the proposed device can provide high sensitivity. In
addition, many useful optical functions such as all-optical switches, filters and single-mode
lasers can be realized using the proposed Fano-type transmission device. The transfer matrix
method (TMM) and beam propagation method (BPM) are used to optimally design the sensor
structure.