Fig. 2: Experimental demonstration of a 3D magnetic Weyl photonic crystal.

a Photograph of the fabricated 3D gyromagnetic photonic crystal that consists of 30 layers in the z direction and \(30\times 10\) unit cells in the x-y plane. Left upper inset: schematic of the experimental setup for measuring the bulk band structure. Right lower inset: 3D bulk BZ and projected surface BZ with two pairs of WPs. b, c Enlarged photographs of the perforated copper plates and dielectric foams, respectively. Red and blue disks denote the magnetized directions of gyromagnetic rods at different sublattice sites. d Magnified image of a gyromagnetic rod (black color) sandwiched between two permanent magnets (silver color). e Gyromagnetic rods sandwiched between permanent magnets are inserted into the dielectric foam to fix their positions. f Measured (background color) and calculated (white solid lines) projected bulk band structures along high-symmetry lines of the projected surface BZ. Orange and purple spheres represent WPs with opposite topological charges of +1 and −1, respectively.