@article{20189,
  abstract     = {{A dielectric step-index optical fiber with tube-like profile is considered, being positioned with a small gap on top of a dielectric slab waveguide. We propose a 2.5-D hybrid analytical/numerical coupled mode model for the evanescent excitation of the tube through semi-guided waves propagating in the slab at oblique angles. The model combines the directional polarized modes supported by the slab with analytic solutions for the TE-, TM-, and orbital-angular-momentum (OAM) modes of the tube-shaped fiber. Implementational details of the scheme are discussed, complemented by finite-element simulations for verification purposes. Our results include configurations with resonant in-fiber excitation of OAM modes with large orbital angular momentum and strong field enhancement.}},
  author       = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}},
  issn         = {{0306-8919}},
  journal      = {{Optical and Quantum Electronics}},
  keywords     = {{tet_topic_waveguides}},
  title        = {{{Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles}}},
  doi          = {{10.1007/s11082-020-02595-z}},
  volume       = {{52}},
  year         = {{2020}},
}

@article{3830,
  abstract     = {{The modal properties of curved dielectric slab waveguides are investigated. We
consider quasi-confined, attenuated modes that propagate at oblique angles with respect to
the axis through the center of curvature. Our analytical model describes the transition from
scalar 2-D TE/TM bend modes to lossless spiral waves at near-axis propagation angles,
with a continuum of vectorial attenuated spiral modes in between. Modal solutions are
characterized in terms of directional wavenumbers and attenuation constants. Examples for
vectorial mode profiles illustrate the effects of oblique wave propagation along the curved
slab segments. For the regime of lossless spiral waves, the relation with the guided modes
of corresponding dielectric tubes is demonstrated.}},
  author       = {{Ebers, Lena and Hammer, Manfred and Förstner, Jens}},
  issn         = {{0306-8919}},
  journal      = {{Optical and Quantum Electronics}},
  keywords     = {{tet_topic_waveguide}},
  number       = {{4}},
  pages        = {{49:176}},
  publisher    = {{Springer Nature}},
  title        = {{{Spiral modes supported by circular dielectric tubes and tube segments}}},
  doi          = {{10.1007/s11082-017-1011-x}},
  volume       = {{49}},
  year         = {{2017}},
}