An optimum multimode interference coupler as an all-optical switch based on nonlinear modal propagation analysis

This paper proposes the modal propagation analysis (MPA) as a desirable way to study the all-optical switch based on small dimension MMI coupler in nonlinear regime. The finite difference method as a rigorous numerical method applies to solve the nonlinear modal equations and measure the modal propagation constant. The contrast ratio between ON and OFF outputs that is called switching performance gain (SPG) is used to optimize the switch via output width. The results show good efficiency in few micrometer of MMI length and sensitivity of SPG to output width as well as input intensity.