A method for the design of waveguide-coupled microring resonators is described based on an improved coupled mode theory (CMT) approach. Characteristic parameters including coupling efficiency and Q factor are theoretically analyzed. The effects of variations in the refractive index, waveguide width, bus-to-ring gap spacing, and ring radius are investigated. The accuracy of this model is evaluated by comparing its predicted calculation results to those of the numerical beam propagation method (BP...