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We propose a mid-infrared dual-rhombic air hole hexagonal lattice photonic crystal fiber with high birefringence and large nonlinearity based on Ge 20 Sb 15 Se 65 chalcogenide glass. The properties of birefringence, dispersion, nonlinearity, and confinement loss were investigated in the 3 µm~5 µm mid-infrared range by using the Finite Difference Time Domain (FDTD) method with perfectly matched layer (PML) absorption boundary conditions. The results indicate that for the optimized structural parameters of Λ = 2.0 µm, D = 1.932 µm, d = 0.8 µm, and H = 0.8 µm, an ultrahigh birefringence of 0.041, a very low confinement loss of 0.0013 dB/km (for x -polarization modes) and 0.0342 dB/km (for y -polarization modes), and the maximum nonlinearity coefficient of 4375 w −1 km −1 (for x -polarization modes) and 3960 w −1 km −1 (for y -polarization modes) were achieved, respectively. The proposed PCF has a lower confinement loss and higher birefringence than an elliptical-hole PCF with the same air-filling fraction. Thus, it will be an excellent candidate for mid-infrared optical fiber sensing, precision optical instruments and nonlinear optics. [ABSTRACT FROM AUTHOR]

A novel high birefringence As2Se3-based hexagonal lattice photonic crystal fiber (PCF) is proposed. In the structure, a central defect core and three kinds of elliptical air holes with different major axes length and ellipticity are introduced in the cladding. The finite difference time domain (FDTD) method with perfectly matched layer (PML) absorption boundary conditions are used to simulate the guided modes of the designed PCF. The properties of this PCF are investigated in detail including the birefringence, beat length, dispersion, nonlinearity and polarization mode dispersion in the 2-5 mid-infrared range. The results show that for the optimized structure parameters of , , , , , , , the high birefringence of 0.1192 and beat length of 41.93 are obtained. The maximum nonlinearity coefficient of 10,050 wkm and 15,200 wkm for x- and y-polarization modes are achieved. The distinctive dispersion is analyzed, which is all-normal in x-polarization direction while it has two zero dispersion points at 3.18 and 3.65 in y-polarization direction. The designed PCF with high birefringence, large nonlinearity and distinctive dispersion will be beneficial for mid-infrared fiber sensing, mid-infrared spectroscopy and nonlinear optics applications. [ABSTRACT FROM AUTHOR]