Mapping the Effective Stimulated Raman Nonlinearity in Submicrometer Silicon Waveguides

Stimulated Raman scattering (SRS) with the effect of large longitudinal electric field (E_z) that appears in submicrometer waveguide (SMWG) is studied. Because of the existence of large E_z, SRS is allowed even its pump-Stokes polarization combination seems to be forbidden by the Raman selection rules. It also suggests that SRS is quite weak in extremely small SMWG because the mode distributes a large part outside the waveguide core region which has no contribution to SRS. Based on its stronger Raman gain and better performance in single mode property and free carrier lifetime reduction, the ridge waveguide is a better candidate than wire one to realize SRS lasing in extremely small SMWG.