Fig. 1. Planar interfaces formed by two semi-infinite biaxial media. (a) Interface along y direction; (b) interface along x direction

Fig. 2. Two types of photonic crystals. (a) Schematic diagrams of photonic crystal 1 (PC1) and photonic crystal 2 (PC2); (b) band structures of PC1 and PC2; (c)(d) calculated effective electromagnetic parameters of PC1 and PC2

Fig. 3. Impedance of photonic crystal 1 (dash line) and photonic crystal 2 (solid line) obtained by effective medium theory, and impedance of photonic crystal 1 (dot dash line) and photonic crystal 2 (dot line) obtained by numerical simulation

Fig. 4. Interface states at different interfaces. (a) Interface between photonic crystal 1 and photonic crystal 2 along y direction; (b) interface between photonic crystal 1 and photonic crystal 2 along x direction; (c) interface state after replacing photonic crystal 1 with corresponding biaxial medium; (d) interface state after replacing photonic crystal 1 with isotropic medium with same impedance