All-Optical Switch With Cascaded Two-Stage Mach–Zehnder Interferometers Using Saturable Absorption Accompanied by Refractive-Index Change in Graphene

An all-optical switch using saturable absorption that accompanies refractive-index change such as in graphene films is proposed. The switching conditions are theoretically derived for arbitrary values of absorption and refractive-index change. It is found that switching can be performed by weaker control light when the refractive-index change is accompanied in saturable absorption. Switching conditions for various combinations of absorption and refractive-index change are confirmed by FD-BPM simulation. The saturable absorption and refractive-index change in multilayered graphene sheets are also discussed based on reported experimental results.