Fig. 1: At-Γ optical BIC in a photonic crystal slab.
From: Nonlinear polaritons in a monolayer semiconductor coupled to optical bound states in the continuum
a Schematic of a photonic crystal slab (PCS) sample, with Ta2O5 bars on a SiO2/Si substrate, illuminated with TE-polarized light near normal incidence. b SEM image of the PCS sample. c Calculated TE-mode electric field distribution at kx/k = 0.024. d Schematic of the photonic band structure for TE modes, with the at-Γ optical BIC position indicated with an x. e Experimental differential angle-resolved reflectance spectra showing one symmetric and two antisymmetric modes. f Wavevector-dependent peak position (black) and amplitude (red) extracted using Fano-like fits for the antisymmetric mode near the BIC location; blue squares show the peak positions shifted owing to a 9 nm hexagonal boron nitride (hBN) layer. g Extracted wavevector-dependent linewidth (black) and Q-factor (red), together with the corresponding simulation results (dashed lines) corrected for experimental resolution and scattering losses
