Dispersion tailoring of photonic crystal fibers for flat-top, coherent, and broadband supercontinuum generation

Abstract

A double-clad AsSe2-based photonic crystal fiber possessing ultra-flat near-zero dispersion has been introduced, here to achieve flat-top and coherent supercontinuum generation at Mid-IR range. Also, the required conditions to obtain flat-top, broadband, and coherent supercontinuum generation have been discussed based on the systematic study carried out here, by GNLSE regarding the input pump pulse characteristics and the dispersion regime. The proposed photonic crystal fiber in this study, presents nearly-zero all-normal dispersion of about D ∼ −3.4 ps(nm.km)−1 corresponding to minimum group velocity dispersion at 6.9 μm. For the pump pulse with λ = 6.9 μm, time duration of T = 50 fs, and low peak power of P = 1 kW, a coherent flat-top supercontinuum generation has been realized with the span of 4.14 μm and 4.97 μm at 8 dB and 20 dB levels, respectively. Moreover, a figure of merit covering the essential characteristics of supercontinuum generation spectra (bandwidth, coherency, and flatness) has been introduced to compare the performance of different structures. It has been shown that β 2 tailoring with near-zero and flat characteristic is essential to achieve higher figure of merit.