Radiation loss of coupled-resonator waveguides in photonic-crystal slabs

The authors characterize the intrinsic radiation loss of coupled-resonator optical waveguides by defining a waveguide-quality factor Q. They find that tuning an isolated resonator in a photonic-crystal slab to maximize its Q can also increase the waveguide Q. Due to interference between different resonators, the waveguide can have far lower loss than the isolated cavity; in other cases it can have far greater loss. They show that the dependence of waveguide Q on wave vector can largely be predicted by the shifting of the light cone within a tight-binding model.