State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

We demonstrate both theoretically and numerically that slow light can enhance the parametric process of silicon in photonic crystal line-defect waveguides. Specifically, to get the desired gain, the pump power for a given gain medium length or the gain medium length for given pump power can be reduced by (c/v_gn)² when slow light waveguides are used, where n is the material index of conventional waveguide, vg is the group velocity of the slow light waveguide and c is the light velocity in vacuum.