Third-order nonlinearity in silicon beyond 2350 nm

Measurement of the Kerr nonlinearity in silicon is reported in the 2350 nm to 2750 nm wavelength range, where three-photon absorption effect is present. The measurements confirm that the Kerr interaction strength is comparable to that in the near-infrared. The measured dispersion trend for the Kerr coefficient is consistent with that obtained using Kramers-Krönig relations. Three-photon absorption was measured, and its effect on the nonlinear figure of merit in silicon appears not to be as restrictive as that of two-photon absorption. The results identify silicon as a promising platform for parametric processes in mid-infrared spectral region.