Fig. 3. Gap dependence and dispersion for h¹⁰BN.

a The reflection spectra for g = 3, 8, and 20 nm given the periodicity of 150 nm. The spatial distribution of the electric fields for b the symmetric mode and c antisymmetric mode. The white arrows represent Poynting vectors. d Reflection spectra measured from the devices whose resonance wavelengths for the symmetric mode are almost aligned at the wavenumber of 1522 cm⁻¹. e The gap dependence of the magnitude of a resonance as a function of the gap sizes for the symmetric and anti-symmetric mode at around the frequency of 1522 and 1416 cm⁻¹, respectively. The solid lines denote the numerical results with constant scaling factors of 0.75 and 0.2 for the symmetric and antisymmetric case. f The in-plane momenta extracted from the measured spectra for different gap sizes of g = 3 (red circle), 8 (blue triangle), and 20 nm (black square) together with the analytical dispersions. For each gap size, the dispersion is calculated for t = 20 and 30 nm (the shaded area between two solid lines) to account for hBN thickness (t) variation in the fabricated samples.