Fig. 1
From: Experimental observation of photonic nodal line degeneracies in metacrystals
A single nodal line realized in cut-wire metacrystals. a Schematic of the metacrystal. The unit cell size is a = 4.5 mm, h = 2 mm. The size of the I-shaped copper cut-wire resonators is l = 1.1a, d = 0.5a. The widths of all wires are 0.1a, and the thicknesses are 35 μm. The substrate material is Teflon, whose permittivity is 2.1, with a loss tangent around 0.00028. The band structure of the metacrystal at zero and non zero k z are given in b and c, respectively. d Band structure of the metacrystal at high symmetry lines. Nodal line (NL) is formed between the second and third band at 16 GHz at crystal momentum U and Y. e The equi-frequency surface of the metacrystal exhibits a torus shape at 16.325 GHz, which is slightly above the NL frequency around 16 GHz. No other states are present in the Brillouin zone. f Polarization states on the NL calculated by an effective medium analysis. The area surrounded by the dashed line corresponds to the same area in e. Berry phase of the NL is well manifested by the nontrivial winding of polarization states
