Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles
M. Hammer, L. Ebers, J. Förstner, Optical and Quantum Electronics 52 (2020).

Spiral modes supported by circular dielectric tubes and tube segments
L. Ebers, M. Hammer, J. Förstner, Optical and Quantum Electronics 49 (2017) 49:176.