We report on numerical and experimental studies showing the influence of arc curvature on the confinement loss in hypocycloid-core Kagome hollow-core photonic crystal fiber. The results prove that with such a design the optical performances are strongly driven by the contour negative curvature of the core-cladding interface. They show that the increase in arc curvature results in a strong decrease in both the confinement loss and the optical power overlap between the core mode and the silica core-surround, including a modal content approaching true single-mode guidance. Fibers with enhanced negative curvature were then fabricated with a record loss-level of 17 dB/km at 1064 nm.
Debord, B., Alharbi, M., Bradley, T., Fourcade-dutin, C., Wang, Y. Y., Vincetti, L., Gérôme, F., & Benabid, A. (2013). Hypocycloid-shaped hollow-core photonic crystal fiber Part I: Arc curvature effect on confinement loss. Optics Express, 21(23), 28597-28608. https://doi.org/10.1364/OE.21.028597