Coherence property of mid-infrared supercontinuum generation in tapered chalcogenide fibers with different structures

Abstract

We have numerically investigated the coherence property of mid-infrared supercontinuum generation in tapered step-index chalcogenide fibers with different structures. The pump source is a 4 μm laser with pulse width of 500 fs and peak power of 1 kW. The length ratio is the ratio of transition region length near the laser input to the other transition region length near the output. We calculate the bandwidth and the spectrally averaged coherence of the supercontinuum spectra generated in fibers with different length ratios under the same pumping condition. Numerical results show that as the length ratio increases, the bandwidth decreases from 4.84 μm to 4.11 μm while the spectrally averaged coherence increases from 0.53 to 0.9 and then jitters near the maximum. The length ratio within 1–1.5 is preferable to keep a balance between bandwidth and coherence.