Abstract
Silicon based nonlinear photonics has been extensively researched at telecom wavelengths in recent years. However, studies of Kerr nonlinearity in silicon at mid-infrared wavelengths still remain limited. Here, we report the wavelength dependency of third-order nonlinearity in the spectral range from 1.6 mu m to 6 mu m, as well as multi-photon absorption coefficients in the same range. The third-order nonlinear coefficient n(2) was measured with a peak value of 1.65 x 10(-13) cm(2)/W at a wavelength of 2.1 mu m followed by the decay of nonlinear refractive index n(2) up to 2.6 mu m. Our latest measurements extend the wavelength towards 6 mu m, which show a sharp decrement of n(2) beyond 2.1 mu m and steadily retains above 3 mu m. In addition, the analysis of three-photon absorption and four-photon absorption processes are simultaneously performed over the wavelength range from 2.3 mu m to 4.4 mu m. Furthermore, the effect of multi-photon absorption on nonlinear figure of merit in silicon is discussed in detail. (C) 2013 Optical Society of America