Temperature dependence of the Kerr nonlinearity and two-photon absorption in a silicon waveguide at 1.55{\mu}m

TL;DR

This study investigates how temperature affects two-photon absorption and Kerr nonlinearity in silicon waveguides at 1.55 μm, revealing significant reductions at low temperatures that enhance nonlinear device performance.

Contribution

It provides the first detailed measurement of temperature-dependent Kerr and two-photon absorption in silicon waveguides at 1.55 μm, with implications for low-temperature nonlinear photonic devices.

Findings

Two-photon absorption decreases nearly two-fold from 300K to 5.5K.

Kerr nonlinearity reduces slightly at low temperatures.

Improved ratio of Kerr to absorptive nonlinearity at low temperatures.

Abstract

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 at a wavelength of 1.55 {\mu}m. The two-photon absorption coefficient is calculated from the power dependent transmission of a 4.9 ps pulse. We observed a nearly two-fold decrease in the two-photon absorption coefficient from 0.76 cm/GW at 300K to 0.42 cm/GW at 5.5 K. The Kerr nonlinearity is inferred from the self-phase modulation induced spectral broadening of the transmitted pulse. A smaller reduction in Kerr nonlinearity from 5.2E-18 m^2/W at 300 K to 3.9E-18 m^2/W at 5.5 K is found. The increased ratio of Kerr to absorptive nonlinearity at low temperatures indicates an improved operation of devices that make use of a nonlinear phase shift, such as optical switches or parametric photon-pair sources. We examine how the heralding efficiency of a photon-pair source will change at low temperature. In addition, the modelling and experimental techniques developed can readily be extended to other wavelengths or materials of interest.