Spiral modes supported by circular dielectric tubes and tube segments

Ebers, Lena; Hammer, Manfred; Förstner, Jens

doi:10.1007/s11082-017-1011-x

Cited by 5 publications

(5 citation statements)

References 11 publications

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“…Furthermore the considered structures are analysed in a 2-D environment by defining an out-ofplane wavenumber k z to simulate oblique incidence. To verify the program settings, 2-D structures, already analysed with semi-analytical methods [23,12,20,24], were investigated [19]. We observed an excellent agreement of our numerical solutions with the existing results.…”

Section: Oblique Wave Propagation Along Bent Slab Waveguide Cornerssupporting

confidence: 53%

“…Hence, we will focus on the parametrization from Figure 2. Here, the curved part, of constant thickness d, was already analysed for guided modes in [20] and similarities in field pattern could be observed [19]. We assume that the structures only guide the fundamental modes, the TE 0 and TM 0 modes with effective indices N TE 0 and N TM 0 .…”

Section: Oblique Wave Propagation Along Bent Slab Waveguide Cornersmentioning

confidence: 99%

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Oblique incidence of semi-guided planar waves on slab waveguide steps: effects of rounded edges

2018

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Oblique propagation of semi-guided waves across slab waveguide structures with bent corners is investigated. A critical angle can be defined beyond which all radiation losses are suppressed. Additionally an increase of the curvature radius of the bends also leads to low-loss configurations for incidence angles below that critical angle. A combination of two bent corner systems represents a step-like structure, behaving like a Fabry-Perot interferometer, with two partial reflectors separated by the vertical height between the horizontal slabs. We numerically analyse typical high-index-contrast Si/SiO structures for their reflectance and transmittance properties. When increasing the curvature radius the resonant effect becomes less relevant such that full transmittance is reached with less critical conditions on the vertical distance or the incidence angle. For practical interest 3-D problems are considered, where the structures are excited by the fundamental mode of a wide, shallow rib waveguide. High transmittance levels can be observed also for these 3-D configurations depending on the width of the rib.

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Section: Oblique Wave Propagation Along Bent Slab Waveguide Cornerssupporting

confidence: 53%

Section: Oblique Wave Propagation Along Bent Slab Waveguide Cornersmentioning

confidence: 99%

Oblique incidence of semi-guided planar waves on slab waveguide steps: effects of rounded edges

2018

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“…Alternatively, the finite-element (FE) solvers included in the COMSOL multiphysics suite [19] cover these parameterized 2-D problems as well. Our results on structures with rounded edges in [14,20] are based on those tools; for the following examples, the COMSOL suite has been used for the successful corroboration of the vQUEP results.…”

Section: Solversmentioning

confidence: 99%

Oblique evanescent excitation of a dielectric strip: A model resonator with an open optical cavity of unlimited Q

2019

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A rectangular dielectric strip at some distance above an optical slab waveguide is being considered, for evanescent excitation of the strip through the semi-guided waves supported by the slab, at specific oblique angles. The 2.5-D configuration shows resonant transmission properties with respect to variations of the angle of incidence, or of the excitation frequency, respectively. The strength of the interaction can be controlled by the gap between strip and slab. For increasing distance, our simulations predict resonant states with unit extremal reflectance of an angular or spectral width that tends to zero, i.e. resonances with a Q-factor that tends to infinity, while the resonance position approaches the level of the guided mode of the strip. This exceptionally simple system realizes what might be termed a "bound state coupled to the continuum".

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“…1 is defined by the permittivity function ̃ of the dielectric tube. Referring to the cylindrical coordinate system r, , y of the tube with its polar origin at the tube axis, ̃(r) is constant along the angular and axis coordinates , y, and piecewise constant along the radial coordinate r. Standard analysis procedures for the modes of cylindrical step-index optical fibers (Yeh 1987;Snyder and Love 1983;Brunet et al 2014;Ebers et al 2017; http://www.compu tatio nal-photo nics.eu/…”

Section: Guided Modes Of a Circular Dielectric Tube-shaped Fibermentioning

confidence: 99%

“…In both cases, adequate approximations can be obtained (Franchimon et al 2013;Hammer 2016). For our 2.5-D configurations with oblique incidence, the 2-D bend modes would have to be replaced by the spiral-modes of Ebers et al (2017). These are potentially lossy waves that propagate along spiral-shaped paths along the fiber surface; they are valid solutions for angular segments of the tube only.…”

Section: Guided Modes Of a Circular Dielectric Tube-shaped Fibermentioning

confidence: 99%

Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles

2020

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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.

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Spiral modes supported by circular dielectric tubes and tube segments

Cited by 5 publications

References 11 publications

Oblique incidence of semi-guided planar waves on slab waveguide steps: effects of rounded edges

Oblique incidence of semi-guided planar waves on slab waveguide steps: effects of rounded edges

Oblique evanescent excitation of a dielectric strip: A model resonator with an open optical cavity of unlimited Q

Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles

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