  A design of all optical diode in $L$-shaped photonic crystal waveguide is
proposed that uses the multistability of single nonlinear Kerr microcavity with
two dipole modes. Asymmetry of the waveguide is achieved by difference in
coupling of the dipole modes with the left and right legs of waveguide. By use
of coupled mode theory we present domains in axis of light frequency and
amplitude where an extremely high transmission contrast can be achieved. The
direction of optical diode transmission can be governed by power and frequency
of injecting light. The theory agrees with numerical solution of the Maxwell
equations.
