Fig. 4: Experimental results of the vortex-centered hyperbolic photonic topological insulator.

a The microscopy image of the fabricated vortex-centered hyperbolic sample. Because the microscope field of view is relatively small, the whole microscope picture is taken by twice independent photographing. And then we joint them together. b, c Measured transmission spectra with the CPS and APS being excited. Red and blue lines correspond to transmission spectra related to clockwise and counterclockwise output ports, respectively. d, e Measured field distributions of topological edge states with the excited pseudo-spins being CPS and APS in the vortex-centered hyperbolic photonic topological insulator. f Measured field distributions of trivial bulk states in the vortex-centered hyperbolic photonic topological insulator.