Dispersion-engineered Si3N4–Al2O3 dual-core waveguide for ultra-compact mid-infrared supercontinuum generation

On-chip mid-infrared supercontinuum sources are fundamentally constrained by limited spectral bandwidth, insufficient dispersion control, and long interaction lengths that restrict scalable photonic integration. Current silicon nitride and hybrid waveguide platforms cannot simultaneously deliver octave-spanning mid-infrared coverage and millimeter-scale device footprints when pumped at telecommunication wavelengths. In this work, we overcome these limitations by introducing a dispersion-engineered hybrid dual-core waveguide that couples a high-index Si 3 N 4 core with a lower-index Al 2 O 3 core, enabling strong modal coupling and broadband supermode anti-crossing. The resulting dispersion profile provides wide anomalous group-velocity dispersion from the near-infrared to the mid-infrared, which is inaccessible in conventional single-core designs. Using a 50 fs pump pulse at 1550 nm with a peak power of 10 kW, the selected waveguide geometry produces a calculated supercontinuum spanning 0.81–6.71 μ m, within a propagation length of only 2 mm, corresponding to more than three octaves of spectral broadening. Compared with state-of-the-art Si 3 N 4 -based and hybrid waveguides, this approach combines multi-octave numerical bandwidth with a 2 mm interaction length. These results establish the proposed Si 3 N 4 –Al 2 O 3 dual-core platform as a CMOS-compatible solution for ultra-compact broadband mid-infrared light sources, enabling scalable on-chip spectroscopy, sensing, and integrated nonlinear photonic systems.