Nonlinear absorption and refraction in crystalline silicon in the mid-infrared

The wavelength dependence of the nonlinear absorption and the third order nonlinear refraction of crystalline silicon between 2.75μm and 5.5μm as well as at 1.55μm have been measured. It was found that at all wavelengths multi-photon and free carrier absorption can be significant. In particular nonlinear absorption can affect silicon devices designed for the mid-infrared that require strong nonlinear response, such as for the generation of a supercontinuum. The wavelength dependence of the nonlinear absorption and the third order nonlinear refraction of crystalline silicon between 2.75 μm and 5.5 μm as well as at 1.55 μm have been measured. It was found that at all wavelengths multi-photon and free carrier absorption can be significant. In particular nonlinear absorption can affect silicon devices designed for the mid-infrared that require strong nonlinear response, such as for the generation of a supercontinuum.