Unveiling spin-orbital angular momentum locking in photonic Dirac vortex cavities

Abstract

Dirac vortices, originally studied in quantum field theories to predict localized zero-energy modes, were recently realized in photonics, leading to Dirac vortex cavities. With topological protection, Dirac vortex cavities offer robust single-mode large-area localized modes appealing for high-performance micro-lasers and other applications. As a spectrally-isolated single mode, the radiation of a Dirac vortex cavity mode was believed as having vanishing orbital angular momentum due to time-reversal symmetry. Here, we report the direct observation of orbital angular momentum radiation of a Dirac vortex cavity through spin-resolved measurements. Remarkably, we confirm the spin-orbital angular momentum locking in such radiation due to the spin-valley locking and inter-valley couplings. We demonstrate that the spin-orbital angular momentum locking is controlled by the chirality of the Kekulé modulation and propose design schemes for arbitrary-order single-mode OAM radiation.

References in corpus (13)

• Topological Photonics
• Asymmetric metasurfaces with high-$Q$ resonances governed by bound states in the continuum
• Valley Vortex States in Sonic Crystals
• Valley-protected backscattering suppression in silicon photonic graphene
• Valley-contrasting orbital angular momentum in photonic valley crystals
• Majorana-like zero modes in Kekulé distorted sonic lattices
• Valley engineering by strain in Kekulé-distorted graphene
• Dirac-vortex topological photonic crystal fibre
• Quasi 1D topological nodal vortex line phase in doped superconducting 3D Dirac Semimetals
• Topological Majorana and Dirac zero modes in superconducting vortex cores
• Vortex end Majorana zero modes in superconducting Dirac and Weyl semimetals
• A topological Dirac-vortex parametric phonon laser
• Photo-induced Multiply Quantized Vortex States in Dirac-like Materials