Mode coupling through a long period grating of χ

Long period grating provide a perturbation allowing the coupling of two asynchronous copropagating compound mode or supermodes. In a nonlinear directional coupler (NLDC), by varying the intensity, the output will change according to the relative phase between the two supermodes. By combining these effects, nonlinear grating assisted couplers have been suggested. In this paper we are proposing, to not only study the effect of a linear index grating but also the effect of a grating of the nonlinear refractive index (n₂). Recent experimental results with intermixed quantum wells and with photoexposed chalcogenide glasses have shown that variation in n₂ of more than 100% are possible leading to possible new devices