Fig. 4. Merging accidental BICs and split BICs at arbitrary k points.

a The unit cell with elliptic cylindrical etched holes. Calculated distribution of polarization vectors with Q factors as background for b isolated BICs with θ = 10° and t = 338 nm, c merging BIC at $\left(\mp 0.025\pi /a,\pm 0.085\pi /a\right)$ with θ = 10° and t = 334.7 nm, and d merging BIC at $\left(\mp 0.045\pi /a,\pm 0.07\pi /a\right)$ with θ = 35° and t = 335.6 nm. In b-d, the lattice constant, semi-major axis and semi-minor are kept at a = 336 nm, r₁ = 110 nm and r₂ = 80 nm, respectively. The materials used are the same as before