Valley-Hall Photonic Topological Insulators with Dual-Band Kink States

Extensive researches have revealed that valley, a binary degree of freedom (DOF), can be an excellent candidate of information carrier. Recently, valley DOF is introduced into photonic systems, and several valley-Hall photonic topological insulators (PTIs) are experimentally demonstrated. However, in the previous valley-Hall PTIs, topological kink states only work at a single frequency band, which limits potential applications in multiband waveguides, filters, communications, and so on. To overcome this challenge, here a valley-Hall PTI, where the topological kink states exist at two separated frequency bands, is experimentally demonstrated in a microwave substrate-integrated circuitry. Both the simulated and experimental results demonstrate the dual-band valley-Hall topological kink states are robust against the sharp bends of the internal domain wall with negligible intervalley scattering. This work may pave the way for multichannel substrate-integrated photonic devices with high efficiency and high capacity for information communications and processing.