Impact of core cladding boundary shape on the waveguide properties of   hollow core microstructured fibers
  In this paper we consider an interaction between the air core modes of hollow core waveguide microstructures and core cladding boundary walls in various shapes. The analysis is based on well established models such as the 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 as dependant on the type of its discrete rotational symmetry. Based on our findings we analyze the mechanisms of light localization in the core cladding boundary walls of negative curvature hollow core microstructured fibers. 
A.D. Pryamikov, G.K. Alagashev, A.S. Biriukov
physics.optics