Fig. 3: The angular response of guided-mode resonances.
From: Broadband infrared imaging governed by guided-mode resonance in dielectric metasurfaces

The measured (a, c) and simulated (b, d) transmission spectra under x-polarized (a, b) and y-polarized (c, d) optical illumination with the incident angle tuned along y-axis. The experimental transmission spectra are obtained by multiplying the measured transmission of the metasurface with the substrate reference and the measured transmission of the substrate with the air reference