Dispersion-tuned TeO2 semi-elliptical rib waveguide for mid-IR supercontinuum generation: anomalous v/s normal pumping regions

Abstract

Mid-infrared supercontinuum generation (SCG) has gained significant interest among researchers due to its extensive applications, such as gas sensing, bioimaging, molecular fingerprinting, etc. However, effective dispersion tuning is crucial to balance spectral broadening and coherence. This paper presents a numerical simulation of mid-IR SC spectra in TeO₂ semi-elliptical rib waveguide structure, optimized for pumping in both anomalous and normal dispersion regions. We numerically present 3-octave broadband SC spectra spanning from 800 nm to 6500 nm (−30 dB), operating at 2000 nm in anomalous region (away from zero dispersion wavelength (ZDW) but with lower value of β₂) to maintain spectral coherence. 50 fs input laser pulse with 3 kW peak power was utilized in 3 mm long waveguide. For normal region pumping, we numerically generated 2.3-octave broad mid-IR SC spectra at 1550 nm, near the ZDW, resulting in a spectral range from 850 nm to 4100 nm (−50 dB) with high degree of coherence. In this case, 3.5 kW input laser pulse with 50 fs pulse width was employed in 5 mm long waveguide. A comparative analysis of coherence and spectral bandwidth provides valuable insights into trade-offs between stability and bandwidth. Moreover, semi-elliptical rib waveguide presents advantages over rectangular designs, including enhanced nonlinearity and simplified fabrication processes. These numerical findings clearly show that semi-elliptical TeO₂ rib waveguide structure is an excellent option for broadband mid-IR light sources. Furthermore, it underscores the importance of dispersion engineering, ZDW, optimizing pump parameters, waveguide geometry, and length, while directly linking pumping conditions to practical applications.