Fast and slow light enhancement using cascaded microring resonators with the Sagnac reflector

A cascaded microring resonator based on silicon waveguides with an MMI (Multimode Interference) based Sagnac reflector is proposed in this study. By controlling the coupling coefficients with the used of the MMI based Sagnac reflector, the double of both pulse delay and advancement for the slow and fast light can be achieved. The new structure can produce the fast and slow light phenomenon on one chip with a double of the time delay and pulse advancement. By using the Sagnac reflector, the device is very compact. Transfer matrix method and FDTD (Finite Difference Time Domain) simulation are used to obtain the characteristics of the device. The transmission, phase, group delay and pulse propagation are analyzed in detail. Our FDTD simulations show a good agreement with the analytical theory.