Modeling of dispersion engineered chalcogenide rib waveguide for ultraflat mid-infrared supercontinuum generation in all-normal dispersion regime

A rigorous numerical investigation has been carried out through dispersion engineering of chalcogenide rib waveguide for near-infrared to mid-infrared ultraflat broadband supercontinuum generation in all-normal group-velocity dispersion regime. We propose a novel design of a 1-cm-long air-clad rib waveguide which is made from Ge11.5As24Se64.5 chalcogenide glass as the core with either silica or Ge11.5As24S64.5 chalcogenide glass as a lower cladding separately. A broadband ultraflat supercontinuum spanning from 1300 to 1900 nm could be generated when pumped at 1.55 mu m with a low input peak power of 100 W. Shifting the pump to 2 mu m, the supercontinuum spectra extended in the mid-infrared region up to 3400 nm with a moderate-input peak power of 500 W. To achieve further extension in mid-infrared, we excite our optimized rib waveguide in both the anomalous and all-normal dispersion pumping regions at 3.1 mu m with a largest input peak power of 3 kW. In the case of anomalous dispersion region pumping, numerical analysis shows that supercontinuum spectrum can be extended in the mid-infrared up to 10 mu m, although this contains high spectral amplitude fluctuations over the entire bandwidth which limits the supercontinuum sources in the field of high precision measurement applications. On the other hand, by optimizing a rib waveguide geometry for pumping in all-normal dispersion region, we are able to generate a smooth and flat-top coherent supercontinuum spectrum with a moderate bandwidth spanning the wavelength range 2-5.5 mu m with less than 5 dB spectral fluctuation over the entire output bandwidth. Our proposed design is highly suitable for making on-chip SC light sources for a variety of applications such as biomedical imaging, and environmental and industrial sensing in the mid-infrared region.