Critical Power in Three-Core Photonic Crystal Fibers

When a photonic crystal fiber has more than one core, the switching capacity loss among the cores as of a given power, called critical power, becomes a relevant effect for switching applications. In this paper, we study the critical power obtained when ultrashort pulses are propagated in a nonlinear directional coupler. Here, we consider the specific example of a three-core photonic crystal fiber in two possible arrangements: one-dimensional and triangular array. In each core, the pulses propagate in the anomalous dispersion regime, in which an input pulse in the form of a hyperbolic secant is injected into one of the cores, considering different input peak powers. By relating the group velocity dispersion and the coupling coefficient with the temporal width of the input pulse, we can observe some relations between the fiber parameters and the critical power. In addition, we show that when self-phase modulation is combined with other effects, the critical power can be increased or decreased depending on the combination of these effects.