Fig. 2: The band evolution and field distribution of transverse-magnetic (TM) polarized mode.

a–c The simulated band structures and field distributions of band edge states for the TM mode at θa = 60°, 71.57°, and 75°, respectively. Here, the yellow and blue areas in (a) and (c) denote the bandgaps while the blue numbers (1–4) mark the number of bandgaps. Dark green numbers (1–4) denote the numbers of the bulk bands. And purple labels (0, π) denote the Zak phase of each individual band. The parities of the field distribution of eigenmodes at band edges are marked with the blue (odd parity) and pink (even parity) dots, while the cross points marked with dark green dots.