Dispersion engineering of suspended silicon photonic waveguides for broadband mid-infrared wavelength conversion

Abstract

Silicon photonics has much potential in the mid-infrared (MIR) band due to the broad low-loss window of silicon. The performance of wavelength conversion based on degenerate four-wave mixing is theoretically evaluated in suspended silicon waveguides, which are adopted to eliminate the strong absorption of silica in the MIR region. A theoretical model is formed for MIR wavelength conversion by taking the nonlinear loss into account, where three-photon absorption and related free-carrier absorption play dominant roles. The relationship of the dispersion and the waveguide dimensions is analyzed, and the dispersion is manipulated by tuning the cross section of the waveguide. The phase mismatch is effectively reduced, and a MIR band conversion bandwidth as broad as 706 nm is obtained with a conversion efficiency of −20.5  dB in an 8 mm long suspended silicon waveguide pumped by a light intensity as low as 0.1  GW/cm2.