Chalcogenide Ge₂₀Sb₅Se₇₅ photonic crystal fiber with seven air-hole rings for ultraflat mid-infrared supercontinuum generation

Supercontinuum (SC) generation in solid-core circular photonic crystal fibers (PCFs) made of Ge 20 Sb 5 Se 75 is numerically analyzed. A large core is projected to increase light coupling efficiency into selected PCFs as well as raise coupling to standard silica fibers. High nonlinear coefficient and near-zero flat dispersion allow ultraflat SC spanning 1.5–4.6 μ m in an all-normal dispersion regime. This requires 3 kW of peak power with 180 fs of pulse duration. The fiber with one zero-dispersion wavelength (ZDW) generates SC bandwidth in the range of 1.54–7.39 μ m at 3.5 μ m using peak power of 10 kW. For the same input power, the SC spectral covers from 1.39 to 7.36 μ m in 10 cm of fiber with two ZDWs. These are wider SC bandwidths than those of previous chalcogenide fibers reached with lower peak powers. Therefore, the proposed Ge 20 Sb 5 Se 75 PCFs are excellent candidates for the broadband ultraflat mid-infrared SC spectra used in high-speed nonlinear imaging and frequency measurement.