Symmetry Breaking in One Dimensional Directional Phtonic Crystal Wave Guide

We have studied symmetry breaking in the one dimensional directional crystal wave guide that holds a single nonlinear defect positioned on the centre line of the waveguide. When only the monopole eigen mode of the defect cavity belongs to the propagation band of photonic crystal waveguide. There are varieties of nonlinear optical processes mostly related to a bistability of light transmission. Two dipole resonant modes of the single non-linear defect made from a Kerr medium. The degenerated dipole modes have opposite parities relative to injected even light mode propagating in the waveguide. For the linear cavity the light would be coupled with the even dipole mode only to give rise to Breit-Wigner resonant peak at the eigen frequency of the cavity. Nonlinear coupling between the dipole modes may cause excitation of both dipole modes. For equal phases, the symmetry is broken by the light intensity relative to mirror reflection.