Fig. 1. Schematic diagrams of H_x-BIC metasurfaces and band folding. (a) One unit cell of U-BIC lattice composed of DSRRs, where period p=73 μm and length l= 60 μm; (b) one unit cell of H_x-BIC lattice composed of dual DSRRs along x axis in a supercell, α=|l₁-l₂|/(l₁+l₂), represents asymmetry parameter, where l₁ and l₂ denote the total lengths of left and right metallic branches of DSRRs; (c)band folding of Brillouin zone, where the X-point of a single atomic lattice is folded into a diatomic superlattice BZ Γ point; (d) band structure diagrams and their folding relationships of U-BIC lattice (blue circles) and H_x-BIC lattice (orange dots), where gray dotted line represents light line. Perfect electric conductor and structures without substrate were used for DSRRs in simulations to calculate eigenvalues

Fig. 2. Experimental and simulated results of H_x-BIC metasurface. (a) Microscopic images of H_x-BIC metasurfaces; (b) amplitude transmission spectra of experimental (orange dotted line) and numerical simulations (gray solid line), and normalized scattering power of multipoles from simulations; (c) surface current distributions of three resonances with y-polarized incidence

Fig. 3. Numerical simulation results. (a) Relationship curve between the Q corresponding to resonance I (blue) and resonance II (orange) obtained from electromagnetic simulation and α; (b) relationship curve between the p_y and T_y components at the intrinsic frequencies of resonance I (blue) and resonance II (red) and α

Fig. 4. Simulation and experimental results of H_y-BIC metasurfaces. (a) H_y-BIC lattice composed of dual DSRRs along y axis, where period p=73 μm, length l= 60 μm, and d = 15 μm (α = 0.128), the inset depicts the band folding of H_y-BIC lattice from U-BIC lattice; (b) surface current distributions of three resonances in H_y-BIC metasurfaces with y-polarized incidence; (c) amplitude transmission spectra of experimental (orange dotted line) and numerical simulations (gray solid line) and the normalized scattering power of multipoles from simulations; (d) relationship curve between the Q corresponding to resonance I (blue) and resonance II (orange) and α; (e) relationship curve between the scattering intensity of p_y and T_x components at the intrinsic frequencies of resonance I (blue) and resonance II (red) and α