Fig. 3: Numerical simulation of resonances in periodic dielectric arrays.

a The Electric field (E), normalized to an incident field (E₀), was calculated for a silicon nitride photonic crystal slab. The top panel shows photonic crystal resonance (TM), and the bottom panel shows a symmetry-protected bound state in the continuum (BIC). Breaking the symmetry via a nonzero incidence angle (here 0.1°) results in a quasi-BIC (Q-BIC) mode with high Q and a ~ 10-fold higher enhancement in the electric field magnitude (compare the values inside red and blue ellipses). b Schematic representation of a biosensing configuration, illustrating the binding of target proteins (antigen active biolayer) to a functionalized surface (antibody fixed biolayer). c Calculated resonance spectra of the silicon nitride photonic crystal slab. Both TM and Q-BIC modes exhibit a redshift upon biolayer addition. The TM mode exhibits a more significant shift (i.e., higher sensitivity) compared to the Q-BIC mode, which is attributed to a greater field overlap with the analyte volume