Fig. 3: Mie modes and selective resonant pumping.

a, Experimental transmittance spectrum at the RSP-BIC condition with l₂ ≈ 226 nm for x- and y-polarized light, revealing two and one Mie modes, respectively (labelled Mie 1, Mie 2 and Mie 3). b, Normalized power loss density map for the unit cells (energy loss per time and unit volume) for the three Mie modes shows distinct mode profiles and dissimilar losses in both rods at a cutting plane of z = 30 nm. c, Comparison of average power loss density between the two rods for each Mie mode. Mie 1 exhibits the highest ratio between rods 1 and 2, indicating the strongest selective absorption. d, Sketch of the optical pumping principle. The above-bandgap excitation of carriers from the conduction band (CB) to the valence band (VB) generates free electrons and holes, which alters the polarizability and the refractive index. e, Pump–probe spectral time trace (720-nm pump with a fluence of 100 μJ cm⁻²) for a metasurface with l₂ = 236 nm. The pump pulse is y-polarized and the probe pulse is x-polarized, leading to a 9.2-nm spectral shift of the SP-BIC and an increase in the resonance amplitude. f, Corresponding γ_int and γ_rad obtained using TCMT fitting. A sharp increase of γ_int by approximately 100% upon pump arrival, followed by a rapid drop to approximately 14% above pre-pump values within 1 ps is visible. γ_rad increases by 250%, remaining at higher values before it returns back to pre-pump values within 20 ps. Inset, the quick decay of intrinsic losses within the first picoseconds after pump arrival. Scale bar, 100 nm (a).