Modelling of octagonal Ga₈Sb₃₂S₆₀-photonic crystal fiber for LWIR broadband supercontinuum generation

In this paper, the supercontinuum generation with all-normal and anomalous dispersion based on Ga₈Sb₃₂S₆₀-photonic crystal fibers with an octagonal lattice is investigated in detail. We propose two types of photonic crystal fibers with the same lattice structure but different numbers of air holes in the cladding (O-PCF₁ with eight rings of air holes arranged parallel to the axis of the core and O-PCF₂ with the air holes in the innermost layer near the core removed) to evaluate the supercontinuum generation performance. By adjusting the structural parameters, the characteristic quantities such as dispersion, effective mode area, nonlinear coefficients, confinement loss can be optimized. The O-PCF₂s exhibits flatter and near-zero dispersion, higher nonlinear coefficients with values of 1197.526 W⁻¹ km⁻¹ and 695.739 W⁻¹ km⁻¹, low confinement losses of about 10⁻⁶ dB/m at a pump wavelength of 4.5 µm enabling spectra spanning from 1.262 to 9.531 µm and from 1.863 to 18.0 µm corresponding to bandwidths of 6.82 µm and 12.41 µm at 30 dB in the long-wave infrared region with peak powers of 12 kW and 20 kW using all-normal and anomalous dispersions profiles, respectively. Supercontinuum laser sources using the proposed fibers are promising for many potential infrared applications involving optical coherence tomography, fingerprinting, and molecular spectroscopy.