Dynamics of a light induced self-written waveguide directional coupler in a photopolymer

We propose and study, using the variational approximation as well as numerical simulation, the evolution of a probe beam through a directional coupler formed in a photopolymer system. Both the results compare well. An analytical expression is derived for describing the dynamics of the coupler. The expression compares well with that of the standard linear coupler. The two waveguides are self-written in the photopolymerizable material as a result of the competition between diffraction and refractive index change due to photopolymerization. As a result the writing beam can be self-trapped along the propagation direction.