Fig. 1. Cross section and finite element mesh structure of hollow core fiber with negative curvature. (a) Cross section of fiber; (b) finite element meshing of quarter fiber structure

Fig. 2. Measured refractive indices and the fitted curve of As₄₀S₆₀ chalcogenide glass

Fig. 3. Loss of x-polarization FM, y-polarization FM, and LP₁₁ mode and the change of HOMER under different wall thicknesses, and electric field maps of the three modes at t1=0.43 µm and λ=4 µm

Fig. 4. Variation in mode loss, PER, and HOMER with capillary radius r₁. (a) x-polarization FM loss, y-polarization FM loss, and PER; (b) x-polarization FM loss, LP₁₁ mode loss, and HOMER

Fig. 5. x-polarization FM loss, HOMER, and PER under different core diameters at 4 µm

Fig. 6. x-polarization FM loss, HOMER, and PER change with wavelength after optimizing the fiber structure parameter

Fig. 7. Relationship between the critical bending radius, loss, PER, HOMER, and effective refractive index of fiber mode and bending angle. (a) Critical bending radius of x-polarization FM at different bending angles and the loss at corresponding bending radii; (b) PER and HOMER of fiber mode under different bending radii; (c) effective refractive index of fiber FM under different bending radii; (d) effective refractive index of fiber mode under different bending radii

Fig. 8. Loss and effective mode field area of x-polarization FM under different bending radii

Fig. 9. Normalized output power under different fiber length