Fig. 4: Experimental observation of topological interface state with the transverse-electric-transverse-magnetic (TE-TM) splitting effect.

a is the experimentally measured transmission spectra of the composite photonic crystals (PCs) as functions of the refracted angle θa for TE and TM polarization modes, respectively. b–e are the transmission spectra of TE (blue lines) and TM (red lines) waves at θa = 0°, 10°, 28°, and 36°, respectively.