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We analyze the impact of geometrical parameters on such important optical characteristics of negative curvature hollow-core fibers (NCHCFs) as waveguide dispersion, waveguide losses and the structure of transmission bands. We consider both theoretically and experimentally the resonance effects and formation of band edges under bending in NCHCFs.

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In hydrodynamics, vortex generation upon the transition from smooth laminar flows to turbulence is generally accompanied by increased dissipation. However, plane vortices can provide transport barriers and decrease losses, as it happens in numerous geophysical, astrophysical flows and in tokamaks. Photon interactions with matter can affectlight transportin waveguides in unexpected and somewhat counterintuitive ways resembling fluid dynamics. Here, we demonstrate dramatic impact of light vortex formation in micro-structured optical fibres on the energy dissipation. We show possibility of vortices formation in both solid core and hollow core fibres on the zero flow lines in the cladding. We find that vortices reduce light leakage by three orders of magnitude, effectively improving wave guiding. A strong light localization based on the same principle can also be achieved in the negative curvature hollow core fibres.

In this paper we consider an interaction between the air core modes (ACMs) of hollow core waveguide microstructuresandcore -cladding boundary walls in various shapes. The analysis is based on well -established models such as the ARROW (anti-resonant reflecting optical waveguide) model and on the models proposed for the first time. In particular, we consider the dynamics of light localization in the polygonalcore cladding boundary wall asdependant on the type of its discrete rotational symmetry. Based on ourfindingsweanalyzethe mechanisms of light localization in the corecladding boundary walls of negative curvature hollow core microstructured fibers (NC HCMFs).