Temperature Dependence of the Kerr Nonlinearity and Two-Photon Absorption in a Silicon Waveguide at 1.55 μm

We measure the temperature dependence of the two-photon absorption and optical Kerr nonlinearity of a silicon waveguide over a range of temperatures from 5.5 to 300 K. Measurements are taken at a wavelength of 1.55 mu m in the technologically important telecom C band. We observe a near halving (45% reduction) of the two-photon absorption coefficient at low temperature, whereas a smaller reduction in the Kerr nonlinearity of 25% is found. The increased ratio of Kerr to absorptive nonlinearity at low temperatures indicates an improved operation of integrated photonic devices that make use of a nonlinear phase shift, such as optical switches or parametric photon-pair sources. As an example, we examine how the heralding efficiency of a photon-pair source will change at low temperatures and predict a modest improvement in source performance. In addition, the modeling and experimental techniques developed can readily be extended to other wavelengths or materials of interest.