Efficient photonic crystal cavity-waveguide couplers

Coupling of photonic crystal (PC) linear three-hole defect cavities to PC waveguides is theoretically and experimentally investigated. The systems are designed to increase the overlap between the evanescent cavity field and the waveguide mode and to operate in the linear dispersion region of the waveguide. The simulations indicate increased coupling when the cavity is tilted by 60° with respect to the waveguide axis, which was also confirmed by experiments. Up to 90% coupling efficiency into the waveguide was obtained.