Mid-infrared broadband ultraflat-top supercontinuum generation in dispersion engineered Ge-Sb-Se chalcogenide photonic crystal fiber

Abstract

In this paper, we numerically demonstrate broadband, ultraflat-top and highly coherent mid-infrared Supercontinuum (SC) generation in an all-normal dispersion (ANDi) Ge15Sb15Se70 chalcogenide Circular Lattice Photonic Crystal Fiber (CL-PCF). The propagation properties of the fundamental mode are computed with the Finite Difference Method (FDM). Numerical results show that ANDi regime is obtained over the entire mid-infrared wavelength range with a cladding pitch and air holes diameter of Λ=2 μm and d=0.8 μm, respectively. Besides, the proposed CL-PCF exhibits small effective mode area and high Kerr nonlinearity up to 1.96 W−1 m−1 at 3 μm. Ultrashort pulse propagation inside the CL-PCF core is modelled by using the Generalized Non-Linear Schrodinger Equation (GNLSE). Simulation results show that by pumping at 3 μm laser pulses with a total energy of 0.6 nJ and duration of 50 fs, into 10 mm long of the CL-PCF, generates an ultrabroadband and highly coherent SC spanning the wavelength region from 1.86 μm to 5.35 μm within less than 3 dB spectral dynamics. By increasing the initial pulse energy to attain 1 nJ, the generated SC bandwidth increases too and reaches 4.53 μm in the spectral range extending from 1.67 μm to 6.2 μm at 4 dB spectral level. Moreover, the proposed CL-PCF based SC source is found promising for application in Optical Coherence Tomography (OCT) with an axial resolution of 0.87 μm, achieved when pumping 1 nJ energy and 50 fs duration optical pulses.