Bragg reflection waveguide composite structures

The Bragg reflection waveguide directional coupler is analyzed rigorously in terms of the normal modes of the complete structure. A perturbation analysis leading to an explicit expression for the coupling constant in a general configuration with nearly degenerate modes is performed. The results are compared to those for a conventional directional coupler structure. It is shown that the bandlike dispersion diagram arising from the periodic lateral confining media is responsible for the unique features of the coupling constant and coupling length that are observed.>