Coupling between a high-Q photonic crystal cavity and a dielectric waveguide embedded in a photonic crystal slab

A theoretical investigation is made of the coupling between a photonic crystal cavity and a dielectric waveguide embedded in a photonic crystal slab. The quadrupole and the hexapole modes with high-Q factors are excited in the photonic crystal cavity and are coupled to a waveguide mode. The coupling efficiency is computed as a function of the distance between the cavity and the waveguide by using a three-dimensional finite-difference time-domain simulation. A large coupling efficiency of >83 % is obtained. The ability to efficiently couple and waveguide light offers new opportunities for all-optical devices in integrated nanoscale photonic systems.