Design and analysis of equiangular spiral photonic crystal fiber for mid-infrared supercontinuum generation

A design of equiangular spiral photonic crystal fiber (PCF) in As₂Se₃ chalcogenide glass is reported for mid-infrared supercontinuum generation. Supercontinuum covering the 1.2-15 μm molecular fingerprint region is achieved using only 8 mm long designed PCF pumped with 50 fs laser pulses of 500 W peak power. The structural parameters have been tailored for all-normal dispersion characteristic. Proposed structure has high nonlinearity (γ = 12474 W^-1 km^-1) at 3.5 μm with very low and flat dispersion -2.9 [ps/(nm × km)]. Supercontinuum with such broadening and high coherence degree is applicable for mid-infrared spectroscopy, gas sensing, early cancer diagnostics and free space communication.