Spin-Orbit-Locking Chiral Bound States in the Continuum

Abstract

Bound states in the continuum (BICs), which are confined optical modes exhibiting infinite quality factors and carrying topological polarization configurations in momentum space, have recently sparked significant interest across both fundamental and applied physics.} Here we show that breaking time-reversal symmetry by external magnetic field enables a new form of chiral BICs with spin-orbit locking. Applying a magnetic field to a magneto-optical photonic crystal slab lifts doubly degenerate BICs into a pair of chiral BICs carrying opposite pseudo-spins and orbital angular momenta. Multipole analysis verifies the non-zero angular momenta and reveals the spin-orbital-locking behaviors. In momentum space, we observe ultrahigh quality factors and near-circular polarization surrounding chiral BICs, enabling potential applications in spin-selective nanophotonics. Compared to conventional BICs, the magnetically-induced chiral BICs revealed here exhibit distinct properties and origins, significantly advancing the topological photonics of BICs by incorporating broken time-reversal symmetry.

References in corpus (5)

• Topological nature of bound states in the radiation continuum
• Metasurfaces with maximum chirality empowered by bound states in the continuum
• Generation and Annihilation of Topologically-Protected Bound States in the Continuum and Circularly-Polarized States by Symmetry Breaking
• Singular points of polarizations in the momentum space of photonic crystal slabs
• Singularities and Poincaré Indexes of Electromagnetic Multipoles

Cited by in corpus (1)

• Magnetically Tunable Chiral Phonon Polaritons with Magneto-optical Bound States in the Continuum