  Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The
dispersion dependence of the idler conversion efficiency is measured and shown
to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB
increase in the conversion efficiency is observed. Concurrently, a decrease in
the conversion bandwidth is observed due to the increase in group velocity
dispersion in the slow-light regime. The experimentally observed conversion
efficiencies agree with the numerically modeled results.
