  We report the observations of spontaneous Raman scattering in silicon
photonic crystal waveguides. Continuous-wave measurements of Stokes emission
for both wavelength and power dependence is reported in single line-defect
waveguides in hexagonal lattice photonic crystal silicon membranes. By
utilizing the Bragg gap edge dispersion of the TM-like mode for pump
enhancement and the TE-like fundamental mode-onset for Stokes enhancement, the
Stokes emission was observed to increase by up to five times in the region of
slow group velocity. The results show explicit nonlinear enhancement in a
silicon photonic crystal slow-light waveguide device.
