Design of a mid-infrared ultra-broadband chalcogenide Ge20Sb15Se65 -based single-polarization single-mode photonic crystal fiber with large nonlinearity

This paper proposes a mid-infrared (mid-IR) Ge20Sb15Se65-based photonic crystal fiber (PCF) with hexagonally latticed dual-rhombic air holes to deliver single-polarization single-mode (SPSM) over a broad waveband. The properties of SPSM bandwidth, confinement loss, birefringence, effective mode area and nonlinear coefficient are investigated in 2μm-7μm region by utilizing the finite difference time domain method (FDTD) together with anisotropic perfectly matched layer (PML). The results reveal that for the optimized geometric parameters of Λ=2.6μm, D=2.4μm, d=1.2μm, D1=2.2μm, and d1=0.4μm, the proposed PCF is a low-loss SPSM-PCF within the wavelengths ranging from 4.0338μm to 7μm, where only the x-polarization mode exists with the highest nonlinearity coefficient of 1468 w-1km-1 (at 4.0338μm). It will become an outstanding candidate for mid-IR optical fiber sensing/detection/ imaging/monitoring and nonlinear fiber optics.