High-efficiency four-wave mixing in low-loss silicon photonic spiral waveguides beyond the singlemode regime

Low-loss optical waveguides are highly desired for nonlinear photonics such as fourwave mixing (FWM), optical parametric amplification, and pulse shaping. In this work, low-loss silicon photonic spiral waveguides beyond the single-mode regime are proposed and demonstrated for realizing an enhanced FWM process. In particular, the designed 2-mu m-wide silicon photonic waveguides are fabricated with standard foundry processes and have a propagation loss as low as similar to 0.28 dB/cm due to the reduced light-matter interaction at the waveguide sidewalls. In the experiments, strong FWM effect is achieved with a high conversion efficiency of -8.52 dB in a 2-mu m-wide and 20-cm-long silicon photonic waveguide spiral, and eight new wavelengths are generated with the pump power of similar to 80 mW (corresponding to a low power density of similar to 195 mW/mu m(2)). In contrast, the FWM efficiency for the 0.45-mu m-wide waveguide spiral is around -15.4 dB, which is much lower than that for the 2-mu m-wide waveguide spiral. It can be seen that silicon photonics beyond the singlemode regime opens a new avenue for on-chip nonlinear photonics and will bring new opportunities for nonlinear photonic applications. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement