Fig. 2

Broken optical symmetry. a Scheme of permittivity modulation. b Far-field polarization (in transmission) in the broken symmetry case. Red (blue) point represents a circularly polarized resonance with positive (negative) helicity, corresponding to a vortex centre for the polarization with topological charge −1/2. c Transmission of the metasurface in static (solid trace) versus perturbed conditions (corresponding to broken symmetry, dashed trace). The spectral resolution of the simulations is 0.1 nm