Reduction of the pump power threshold in the nonlinear all-optical photonic crystal directional coupler switches

In this paper, the cross-phase modulation Kerr nonlinear effect is utilized to induce nonlinearity and a change in the coupling length by a high-intensity pump signal in the nonlinear photonic crystal directional coupler. We have analyzed and modified the nonlinear square-lattice directional couplers for the first time, to the best of our knowledge, and have improved the power consumption for inducing the nonlinear switching. We have shown that according to the slower group velocity and the increased confinement of the TM modes with lower frequency in the region with a higher dielectric constant in a square lattice, the required switching pump power of the structure is less than that of the same triangular structure.