Numerical Investigation of Over One Octave High‐Coherence Supercontinuum Generation in Mid‐Infrared Based on As₂Se₃ Tapered Photonic Crystal Fiber

ABSTRACT The generation of high‐coherence mid‐infrared (MIR) supercontinuum (SC) spanning over one octave in As 2 Se 3 tapered photonic crystal fiber (As 2 Se 3 ‐TPCF) is investigated through numerical simulations. Combined with the photonic crystal fiber and tapered fiber's structural characteristics, six As 2 Se 3 ‐TPCFs with different tapered structures are designed. The tapered regions are the power function and cosine tapered structures, respectively, while the taper waist and the untapered region have the same structure. Moreover, the nonlinear coefficient of the taper waist is 2.23825 W −1 m −1 calculated by the finite element method (FEM), and the zero‐dispersion wavelength (ZDW) in the down‐taper moves with the increase of transmission distance, shifted from 5.2 to 2.4 μm. The temporal and spectral features of the MIR SC generated in As 2 Se 3 ‐TPCFs are numerically simulated by solving the generalized nonlinear Schrödinger equation (GNLSE), and the spectral broadening of As 2 Se 3 ‐TPCFs is mainly caused by self‐phase modulation, Raman soliton self‐frequency shift, and dispersive wave generation. Finally, six As 2 Se 3 ‐TPCFs with lengths of 0.1 m are pumped by short pulses with a center wavelength of 4.0 μm, pulse width of 40 fs, and pulse energy of 250 pJ, the results show that the linear tapered As 2 Se 3 ‐TPCF and the cosine tapered As 2 Se 3 ‐TPCF can achieve high‐coherence MIR spectra spanning 1.6 octaves, with spectral widths from 2.1 to 6.4 μm.