Analysis of coupling between two-dimensional photonic crystal waveguide and external waveguide

Coupling between conventional wire waveguide and two-dimensional photonic crystal waveguide was analyzed by means of a three-dimensional finite difference time domain method. We evaluated the transmittance corresponding to the coupling efficiency between two waveguides. By using SiO2 clad below the wire and setting the width of the wire to be an appropriate value, we obtained single mode guiding and a coupling efficiency over 80% for the wave length around 1.55 μm.