Slow light enhanced waveguide nonlinearity in ultrahigh-Q photonic crystal coupled resonator chain

We demonstrate highly enhanced optical nonlinearity in a coupled-resonator optical waveguide (CROW) in a four-wave mixing experiment. Using a CROW consisting of two-hundred coupled resonators of width-modulated photonic crystal nanocavities in a line defect, we obtained an effective nonlinear constant exceeding 10,000 /W/m.