Nonlinearities in silicon-on-insulator optical waveguides

Recent results on the nonlinear optical properties of silicon-on-insulator waveguides are reviewed. Interest on two photon absorption (TPA) in silicon has been raised by its potential applications for square law detection in autocorrelators for measuring pulsewidths and cross correlators for high speed all-optical clock recovery, high speed optical switches and optical wavelength conversion. The results reported by different groups on two photon absorption, optical Kerr effect, and Raman gain are compared and the range of possible values for the nonlinear figure of merit are calculated. The nonlinear figure of merit obtained from the average values of the various published experimental values suggests that silicon is suitable for all-optical nonlinear refractive switches which need only pi phase change but is not suitable for switches which need several pi of nonlinear phase change. The recent developments on obtaining optical gain using stimulated Raman scattering in silicon are also discussed.