Generation and Annihilation of Topologically-Protected Bound States in the Continuum and Circularly-Polarized States by Symmetry Breaking

Abstract

We demonstrate by breaking the $C_6$ symmetry for higher-order at-$\Gamma$ bound states in the continuum (BICs) with topological charge $-2$ in photonic crystals, (i) deterministic generation of off-$\Gamma$ BICs from the at-$\Gamma$ BIC, and (ii) a variety of pair-creation and annihilation processes of circularly-polarized states with opposite topological charge and same handedness. These processes are well explained by the conservation of handedness-wise topological charges, showing topologically robustness of these phenomena. The results indicate a new control of topological aspect of far-field polarization vectors.

12 pages, 9 figures

References in corpus (7)

• Topological Photonics
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• Metasurface engineering through bound states in the continuum
• Singularities and Poincaré Indexes of Electromagnetic Multipoles
• Perfect Single-Sided Radiation and Absorption without Mirrors
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• Desktop laboratory of bound states in the continuum in metallic waveguide with dielectric cavities
• Parametric dependence of bound states in the continuum in periodic structures: vectorial cases
• Polariton Chern Bands in 2D Photonic Crystals Beyond Dirac Cones
• Topological photonics in nanoscaled systems with far field radiation and polarization singularities
• Optical Rashba effect in a monolithic light-emitting perovskite metasurface