Improving the Impedance Matching in Photonic Crystal Waveguides

Summary form only given: We demonstrate that the dispersion of guided propagating modes in certain photonic crystal waveguides (PCWGs) can be kept constant when the waveguide's structure changes with distance. This suggests that the principle of constant group velocity may be utilized to improve impedance matching between different types of PCWGs while at the same time providing significant design flexibility. We illustrate this principle through the design of several efficient coupling structures between two different PCWGs via a local density of state (LDOS) and Fourier transform analysis of the associate electromagnetic fields. The couplers consist of heterostructures whose individual sections exhibit rather distinct structural parameters. Furthermore, we compare these structures to an adiabatic coupler