Fig. 2: Merging BIC and Q enhancement.

Numerically simulated Q of the mechanical Bloch mode (colormaps) and far-field polarization map (blue, yellow and red streamlines) corresponding to before merging (a, a = 1198 nm), at merging (b, a = 1193 nm), and after merging (c, a = 1165 nm). The topological charge of the mechanical BICs is indicated. Simulated Q corresponding to k_y = 0 (d) and k_y = π/400 μm⁻¹ (e) before (blue), at (yellow), and after (red) BIC merging. f Simulated Q versus lattice constant for the grating length L = 400 μm (solid lines) and L = 120 μm (dashed lines) and different momentum k_x = 0.09π/a (green), k_x = 0.15π/a (purple), and k_x = 0.2π/a (gray). g Simulated Q of 1 × 4 supercells with σ = 1% random variations of the slot width for lattice constant a = 1193 nm (yellow), 1185 nm (blue), and 1165 nm (red). k_y = π/400 μm⁻¹.