Design of integrated silicon waveguides for Raman-enhanced four-wave mixing in the telecom band

Silicon planar waveguides are designed to maximize the wavelength conversion efficiency via the use of Raman-enhanced four-wave mixing in the telecom band. By investigating the dispersion properties of various rib waveguide structures, the optimum etch depth and width are selected to obtain efficient phase-matching for a continuous-wave pump at 1545 nm. The design benefits from good fabrication tolerance in the structural parameters, which are well within the precision of standard lithography and etching processes. Using the optimized waveguides, simulations show that it is possible to reach conversion efficiencies as high as ∼45 dB for waveguide lengths as short as 4.6 cm, with a pump power of only 130 mW. This enhancement in the conversion efficiency is about 50 dB higher than conventional values for FWM in integrated silicon photonic systems, highlighting the benefits of exploiting the coupling between the two nonlinear processes.