Simulation study on supercontinuum broadening based on the BIC model

Bound states in the continuum (BIC) refers to waves that are entirely confined within the continuous spectrum of radiation waves without interacting with them. In our study, we attempted to construct a waveguide satisfying BIC conditions by forming a polymer layer on a 4H-SiC substrate, positioned on an <i>S</i> <i>i</i> <i>O</i> ₂ insulator. By fine-tuning the waveguide parameters, we minimized losses to the substrate continuum and determined that the lowest loss meeting BIC conditions occurs when the HSQ width is 1.82 µm and the 4H-SiC thickness is 440 nm. Subsequently, we investigated the supercontinuum generation (SCG) in this waveguide. First, we analyzed the primary linear and nonlinear effects in the SCG process, introducing well-established theoretical frameworks such as the generalized nonlinear Schrödinger equation (GNLSE) for pulse propagation in nonlinear media. We then studied the influence of waveguide parameters on SCG, observing the variations in SCG with different HSQ widths and 4H-SiC thicknesses. Our results indicate that optimal spectral broadening and conversion efficiency are achieved with an HSQ width of 1.82 µm and a 4H-SiC thickness of 440 nm. In our simulations, the waveguide length was set to 1 cm, and the pump pulse was modeled as a Gaussian pulse with a width of 100 fs and a peak power of 8 W.