Fig. 5

AlGaAs slab metasurface. a Unit cell of the hexagonal grating. The geometric parameters are d = 194 nm, l = 200 nm, t = 95 nm. The slab is free-standing and embedded in an air environment. b Normalized z-component of the magnetic eigenfield at Γ (cross-section taken at the central z = 0 plane). c (Downward) far-field polarization of the relevant photonic band. At Γ, the vortex centre corresponds to a BIC with q = −2