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 MachZehnder 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 / N traditional 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 - 18 m 2 / W ) and using an array including 15 ring resonators with 6mm diameter for each rings only 3mW 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 - 15 m 2 / W ) and five ring resonators including 0.3mm diameter, the switching threshold power can be reduced to ?W ? W 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.
tunable all-optical switch two-photon absorption nonlinear ring resonators mzi switching threshold fast optical switch