Modelling of all-chalcogenide all-normal dispersion photonic crystal fiber for ultraflat mid-infrared supercontinuum generation

We design an all-solid Photonic Crystal Fiber (PCF) with all-normal dispersion profile to achieve broadband, ultraflat-top and coherent supercontinuum generation in the mid-infrared spectral region, by using sub-nanojoule laser pulses. Two environment friendly and thermally compatible chalcogenide glasses, namely Ge15Sb15Se70\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm {Ge}}_{15} {\mathrm {Sb}}_{15}{\mathrm {Se}}_{70}$$\end{document} and Ge20Se80\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm {Ge}}_{20}{\mathrm {Se}}_{80}$$\end{document}, are used as background material and for solid rods, respectively. To the best of our knowledge, this is the first report of an all-solid PCF made of non-toxic ChG glasses for MIR SC generation. The finite difference method is employed to investigate and optimize the guiding linear and nonlinear properties. Simulations results indicate that high Kerr nonlinearity up to 2.21W-1m-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.21 ~{\mathrm {~W}}^{-1} {\mathrm {~m}}^{-1}$$\end{document} at 3μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3 ~\upmu {\mathrm {m}}$$\end{document} and all-normal dispersion profile over the entire wavelength range are successfully achieved for a structure design with cladding pitch Λ=3μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Lambda =3 ~\upmu {\mathrm {m}}$$\end{document} and solid rods diameter d=1.4μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d=1.4 ~\upmu {\mathrm {m}}$$\end{document}. Furthermore, by pumping at 3μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3 ~\upmu {\mathrm {m}}$$\end{document} a 50fs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$50 ~{\mathrm {fs}}$$\end{document} duration optical pulses with a total energy of 900pJ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$900 ~{\mathrm {pJ}}$$\end{document} into 10mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10 {\mathrm {~mm}}$$\end{document} PCF long, a bright, broadband and perfectly coherent supercontinuum spectrum with -5dB\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-5 {\mathrm {~dB}}$$\end{document} bandwidth covering the wavelength range from 1.6μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.6 ~\upmu {\mathrm {m}}$$\end{document} to 7μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$7 ~\upmu {\mathrm {m}}$$\end{document}, is generated. The proposed all-solid PCF based SC laser source is found promising for various potential mid-infrared applications, covering the molecular fingerprint region, such as high resolution imaging of biological tissues, monitoring of greenhouse gases and materials characterization.