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arXiv · 1909.08570

Topological properties of bound-states-in-the-continuum in geometries with broken anisotropy-symmetry

Samyobrata Mukherjee·Jordi Gomis-Bresco·Pilar Pujol-Closa·David Artigas·Lluis Torner
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Abstract

Waveguiding structures made of anisotropic media support bound states in the continuum (BICs) that arise when the radiation channel of otherwise semi-leaky modes is suppressed. Hitherto, only structures with optical axes aligned in symmetric orientations inside the waveguide plane, where BICs appear as lines in the momentum-frequency dispersion diagram, have been considered. Here we address settings where such symmetry is broken and unveil a number of fundamental new features. Weak and strong symmetry-breaking regimes are identified, corresponding to azimuthal and polar optical axes orientation asymmetries, respectively. The azimuthal symmetry-breaking is found to still preserve the existence loci of BICs in the momentum-frequency dispersion diagram as lines. However, all possible BICs become interferometric, while the polarization separable states that occur in symmetric settings cease to exist. The polar symmetry-breaking has stronger effects and transforms the BICs' existence loci from lines to points, which correspond to full-vector states that exist at discrete values of the optical axis orientation for a given wavelength. Such transformation results in fundamental changes in the topological properties of the radiated field around the BICs.

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Samyobrata Mukherjee, Jordi Gomis-Bresco, Pilar Pujol-Closa, David Artigas, Lluis Torner. 2019-09-18. Topological properties of bound-states-in-the-continuum in geometries with broken anisotropy-symmetry. https://doi.org/10.1103/physreva.98.063826

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