Finite-element modeling of nonlinear Mach-Zehnder interferometers based on photonic-crystal waveguides for all-optical signal processing

A nonlinear Mach-Zehnder interferometer based on photonic-crystal waveguides is proposed and modeled by using rigorous finite-element-based numerical scheme. Guided modes of nonlinear photonic-crystal waveguides are investigated to determine a length of nonlinear arm and a switching power, and further, intensity-dependent switching characteristics of the nonlinear Mach-Zehnder interferometer, for the first time, as far as the authors know, are demonstrated. Effects of saturable nonlinearity and two-photon absorption (TPA) on switching characteristics are also taken into account.