Spontaneous and stimulated Raman scattering in silica-cladded silicon photonic crystal waveguides

We report the observation of spontaneous and stimulated Raman scattering in a silica-cladded silicon photonic crystal (PhC) waveguide (WG) with modified holes. Spontaneous Raman scattering in the WG was enhanced when the Stokes wavelength was approached to the bandedge of a WG mode. A maximum enhancement up to similar to 5 times was obtained in the present work. At a Stokes wavelength in the lower group velocity region, nonlinear increase of the Stokes power as the pump power, a clear indication of the onset of stimulated Raman scattering, was observed. Moreover, Raman amplification with an external signal beam was also demonstrated. On-off gain becomes small as the Stokes wavelength gets away from the bandedge of the WG mode. These are the first observations of Raman scattering effects in silica-cladded silicon PhC structures. (C) 2015 The Japan Society of Applied Physics