Radiation pressure and electrostriction induced enhancement for Kerr-like nonlinearities in a nanoscale silicon pedestal waveguide

We report an enhancement of effective nonlinear-index coefficient from the combination of radiation pressure and electrostriction in an air-cladding silicon pedestal waveguide. The effective nonlinear-index coefficient was experimentally measured by characterizing spectral broadening with incident pulses in the pedestal waveguide. Larger spectral broadening was observed in the pedestal waveguide compared to a conventional silicon waveguide. Theoretically, the primary enhancement of the effective nonlinear-index coefficient can be calculated by using Kramers–Kronig relations, which is associated with the change in absorption from stimulated Brillouin scattering in the pedestal waveguide. The calculations were consistent with experimental results. By tailoring the pillar width of the pedestal waveguide, about 27.6% enhancement in the effective nonlinear-index coefficient of the pedestal waveguide was possible at the center wavelength of 1555 nm. (paper)