Low threshold and tunable all-optical switch using two-photon absorption in array of nonlinear ring resonators coupled to MZI

In this paper a novel structure based on Mach–Zehnder Interferometer (MZI) and an array of nonlinear ring resonators for all-optical switching including very low threshold, fast and all-optically tunable is presented. In this proposal, an array including N   ring resonators is coupled to one arm of MZI to introduce the required nonlinear phase shift to switching. Also, two-photon absorption phenomenon is used and will be proposed as another alternative for manipulation of optical switching properties. The proposed idea needs small chip area (∝1/N∝1/Ntraditional cases) for implementation. We show that the switching threshold intensity can be decreased with increase of N  , decrease of the coupling coefficient and increase of the two-photon absorption coefficient. In this structure with traditional optical fibers with the low nonlinear index of refractions (10-18m2/W) and using an array including 15 ring resonators with 6 mm diameter for each rings only 3 mW for the switching threshold power is required. Also, using erbium-doped fiber for implementation of the rings with the high nonlinear index of refractions (10-15m2/W) and five ring resonators including 0.3 mm diameter, the switching threshold power can be reduced to μWμW level. If the nonzero two-photon absorption coefficient is considered, the switching threshold will be very smaller than the above-mentioned values. We show that with changing the optical amplifier gain the switching threshold can be tuned. So, the proposal can be used as a functional block for the integrated optical switch with very small and tunable threshold.