Analytical study of nonlinear directional coupler

In recent years, there has been great interest in using all-optical devices with Kerr-like nonlinear media for ultra-high-speed optical signal processing. Among those devices, nonlinear directional couplers have been investigated extensively owing to their potential applications in optical signal processing, computing, switching and amplification. So far various theoretical reports have, however, not considered the residual coupling in the input and output taper regions which critically affects the overall performance of the couplers. But proper fabrication of such couplers requires through understanding of the design characteristics needed to produce optimum coupling lengths as well as switching intensities. Consequently, the purpose of this paper is to improve the previous studies and extensively explore the coupling effect of the tapered input and output transition regions on the nonlinear directional coupler system