Fig. 4: RSE analysis of the change in refractive index near the RSP-BIC.
From: Optical control of resonances in temporally symmetry-broken metasurfaces
a, Unit cell in which the refractive index of rod 1 (nrod1) is reduced by Δn with respect to the constant index of rod 2 (nrod2). b, Simulation results (dots) compared with RSE theory (solid lines). γrad is plotted versus l2 for Δn = 0 (grey) and for the experimentally estimated Δn = 0.13 (blue). Increasing Δn shifts the RSP-BIC to smaller l2, so depending on l2, moving from the grey to the blue curve either increases (green-shaded region) or decreases (red-shaded region) γrad. c, Four representative metasurfaces (1–4) and their corresponding γrad are shown as a function of Δn for: (1) mode broadening (γrad increases), (2) dark-to-bright creation (γrad increases from zero to a finite value), (3) annihilation (γrad decreases approaching zero) and (4) sharpening of a bright mode (γrad decreases).
