Trench-assisted silicon–germanium photonic rib waveguide for enhanced supercontinuum generation in mid-infrared regime

In this paper, we theoretically demonstrate enhanced supercontinuum generation in a trench-assisted silicon–germanium (Si–Ge) rib waveguide on a sapphire substrate. The computational analysis of the proposed design is done by solving the nonlinear Schrödinger equation using the Split-Step Fourier Method (SSFM) in MATLAB and finite element method (FEM) simulations. By incorporating sidewall trenches, the waveguide exhibits a 30.07% reduction in the effective mode area of the fundamental mode at a pump wavelength of 3.5[Formula: see text][Formula: see text]m, leading to a 42.98% increase in the nonlinear coefficient. These enhancements intensify nonlinear interactions such as self-phase modulation and soliton dynamics, resulting in a broader and more intense supercontinuum spectrum. Using the SSFM with secant hyperbolic pump pulses centered at 3.5[Formula: see text][Formula: see text]m having a pulse width of 45[Formula: see text]fs and a peak power of 5[Formula: see text]kW, we simulate supercontinuum generation and compare the results with those of a conventional rib waveguide. While the standard design yields a coherent spectrum spanning 1.7–6.2[Formula: see text][Formula: see text]m, the trench-assisted configuration extends the bandwidth to 1.6–7.4[Formula: see text][Formula: see text]m. The suggested waveguide design can serve as a potential candidate for mid-infrared supercontinuum sources, with strong potential for applications in spectroscopy, environmental sensing, biomedical diagnostics, and free-space optical communication.