Fig. 3
From: Experimental observation of photonic nodal line degeneracies in metacrystals
Band structure of the nodal line metacrystal. a–c Simulated and measured band structure of the 30-layers metacrystal along the (α) line. In a the NL is denoted by the magenta dots in the two valleys. Surface states (SSs) are colored in red and black according to the sign of their group velocities. b Band structure extracted from the E z field measured on the top surface. The cone-shaped valleys touch at around 16 GHz, indicating the bulk states of the NL. SSs are also excited (indicated by the white arrows) through scattering of bulk states at the sample’s edge. c SSs measured by placing a y-polarized source dipole close to the center of one edge of the top surface of the metacrystal. Note that only the red branch SSs in a are observed. Results within light cone are excluded for better visualization of the SSs. In a and b, the gray-colored bands correspond to extra waveguides modes in air which are not at present in the experiments. Results on (β), (γ), and (η) lines are given in d–f, g–i, and j–l
