Analysis of a laser beam controlled nonlinear directional coupler for optical signal processing

One of the most promising devices for high speed optical signal processing is the Nonlinear Directional Coupler (NLDC). In this paper an asymmetric nonlinear directional coupler controlled by an external laser beam focused on the surface of the coupler has been analyzed. The analysis is based on couple-mode theory using rigorous perturbation technique and enables one to obtain asymptotically correct coupled-mode equations. The effects of various parameters such as plasma density, waveguide width, laser beam frequency and laser spot position on the coupling of power have been investigated and presented.