Super-flat coherent supercontinuum source in AsSe chalcogenide photonic crystal fiber with all-normal dispersion engineering at a very low input energy.

We numerically report super-flat coherent mid-infrared supercontinuum (MIR-SC) generation in a chalcogenide AsSe photonic crystal fiber (PCF). The dispersion and nonlinear parameters of AsSe chalcogenide PCFs by varying the diameter of the air holes are engineered to obtain all-normal dispersion (ANDi) with high nonlinearities. We show that launching low-energy 50 fs optical pulses with 0.88 kW peak power (corresponding to pulse energy of 0.05 nJ) at a central wavelength of 3.7 μm into a 5 cm long ANDi-PCF generates a flat-top coherent MIR-SC spanning from 2900 to 4575 nm with a high spectral flatness of 3 dB. This ultra-wide and flattened spectrum has excellent stability and coherence properties that can be used for MIR applications such as medical diagnosis of diseases, atmospheric pollution monitoring, and drug detection.