Fig. 6
Broken symmetry and quasi-BIC switching. a Left: Δε pattern on the slab surface in the unit cell at t = 300 fs and λprobe = 768.5 nm. Right: Δε at the same time delay and probe wavelength, cross-section on the central (z = 0) plane. b Downward far-field polarization in the perturbed (broken symmetry) case. The at-Γ BIC has split into two topological defects with charge q = −1. c Simulated transmission of the metasurface in the static (red curve) versus perturbed case (black curve). d Same as in panel c), for the additional simulation considering extra losses Δεadd = i0.01 and higher pump fluence, F = 500 μJ cm−2
