Wideband Mid-Infrared Supercontinuum Generation Using Inverse Tapered Silicon Nitride Waveguide

In this paper, we have proposed a novel supercontinuum (SC) light source which can emit a broadband spectrum in the mid-infrared (MIR) region ranging from 760 nm to 6675 nm. The proposed 3-mm-long inversely tapered shaped waveguide is optimized numerically adopting the parabolic tapering approach. Structurally, the waveguide is comprised of silicon nitride (Si3N4) as core material and silica (SiO2) for upper and lower claddings. The proposed structure is tuned for pumping only in the anomalous group-velocity dispersion regime through varying waveguide width along the pulse propagation direction. The predicted SC spectra between the proposed design with the designs which have no tapering at all (typical uniform waveguide) in terms of MIR expansion and spectral flatness is compared. Simulation results show a good spectral flatness throughout the spectral region covered apart from broadband spectral bandwidth predicted in the MIR. All geometries considered here are excited at 1.55 μm wavelength with an ultrashort pulse of 50-fs duration and a moderate peak power of 10 kW.