A topological photonic crystal with ultra wide dual bandwidth

We demonstrated a sandwich topological photonic crystal (PC) structure with C6 honeycomb medium column, the background material of PC is E7 liquid crystal. The results show that the working bandwidth of the laminated PC with liquid crystal as the background material can be changed by voltage, i.e., 0.428-0.442(2zc/a)(without voltage) to 0.416-0.426(2zc/a)(with voltage), and the transmission efficiency of the laminated PC is over 90%. Besides, when the liquid crystal material is only added in the nontrivial layer structure, the working bandwidth of the PC has changed, which is 0.433-0.453(2zc/a) and 0.425-0.446(2zc/a), respectively, and it has a common bandwidth 0.433-0.446(2zc/a). The proposed topology photonic crystals are of great importance for their applications in optical communication devices and WDM optical networks.