Elliptical cladding elements in negative curvature hollow-core fiber for low-loss terahertz guidance

Optical losses of ellipse-nested elliptical negative curvature hollow-core fibers are numerically presented for the terahertz region. Primary design parameters of all fibers were iteratively optimized and confinement and total losses as low as $2.79 \times 10^{-5} \mathrm{~dB} / \mathrm{m}$ and $0.015 \mathrm{~dB} / \mathrm{m}$ were achieved at 0.55 THz, respectively. Single-mode light guidance of the proposed design was investigated and a higher-order mode extinction ratio of around 3000 was calculated.