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

Graphene/Graphitized Polydopamine/Carbon Nanotube All-Carbon Ternary Composite Films with Improved Mechanical Properties and Through-Plane Thermal Conductivity

Graphene films (GFs) are promising ultrathin thermally conductive materials for portable electronic devices because of their excellent thermally conductive property, light weight, high flexibility, and low cost. However, the application of GFs is limited due to their poor mechanical properties and through-plane thermal conductivity. Here, a graphene-(graphitized polydopamine)-(carbon nanotube) (G-gPDA-CNT) all-carbon ternary composite film was fabricated by chemical reduction, carbonization, graphitization, and mechanical compaction of the evaporation-assembled (graphene oxide)-PDA@CNT film. The G-gPDA-CNT film exhibited a uniform all-carbon composite structure in which the components of the graphene, gPDA layers, and CNTs were cross-linked by strong covalent bonds. This unique structure promoted the load transfer and energy dissipation between the components by which the mechanical properties of the G-gPDA-CNT film were substantially improved. Furthermore, electron and phonon transfers were also promoted, greatly improving the electrical and thermal conductivities, especially the through-plane thermal conductivity of the G-gPDA-CNT film. The G-gPDA-CNT film showed a tensile strength of 67.5 MPa, 15.1% ultimate tensile strain, toughness of 6.07 MJ/m3, electrical conductivity of 6.7 × 105 S·m-1, in-plane thermal conductivity of 1597 W·m-1·K-1, and through-plane thermal conductivity of 2.65 W·m-1·K-1, which were 2.24, 1.44, 3.16, 1.46, 1.15, and 3.90 times that of the pure GFs, respectively.</p