Decoupling efficiency of multiple coupled photonic crystal waveguides

We investigate decoupling characteristics and efficiency of multiple coupled photonic crystal waveguides (M-CPCWs) using coupled mode theory on the basis of self-imaging principle. The three-, four- and eight-CPCWs are selected as the typical structures to discuss the general characteristics of the M-CPCWs. It is found that around the frequency where the multiple guided modes are almost degenerate, which leads to that the power transfer in the M-CPCWs is eliminated for any entrance. The frequency region for decoupling is insensitive to the number of coupled waveguides with the extinction ratios higher than −15dB. An optimization way by introducing a defect mode is utilized to enhance the decoupling efficiency. The simulation results are based on the finite-difference time-domain method. The decoupling of the M-CPCWs exhibit many advantages and may have practical applications in photonic integrated circuits.