Soliton-induced mid-infrared dispersive wave in horizontally-slotted Si₃N₄ waveguide

The flexibility of producing two dispersive waves (DWs) in silicon nitride (Si3N4) slot waveguide is demonstrated, by tailoring the slot features and the corresponding phase-matching condition. DWs are generated at visible and mid-infrared (mid-IR) wavelength regions, respectively. We obtain a broadband low normal dispersion region from 2 to 5.25 μm, which offers particular advantages for DW generation at mid-IR wavelength region. The long-wave dispersive wave (LWDW) can cover beyond 4 μm. This is the first time to illustrate the freedom of Si₃N₄ slot waveguide for DWs generation ever reported. A broadband spectrum can be extended from 0.5 to 4.5 μm at -30 dB level by launching a 1-kW 1550-nm hyperbolic secant input pump pulse to a 1-cm proposed waveguide. The newly formed spectrum has a high degree of coherence. This approach provides more flexibility for frequency conversion, and has the advantages for biophotonics, optical sensing, chip-integrated spectroscopy, health and environmental monitoring.