Reconfigurable traveling-wave radiation in valley topological photonic crystals

Valley photonic topological insulators have recently attracted much attention, in which the valley degree of freedom provides a promising solution to manipulate light waves. Currently, most studies of valley photonic topological insulators focus on designing valley-dependent transport behavior, but few studies on its radiation properties. In developing functional communication devices for practical applications, studying traveling-wave radiation and its reconfigurable properties in valley photonic topological insulators deserve more attention. In this paper, by adding nematic liquid crystals with tunable refractive index into waveguide channels of valley topological photonic crystals, we propose a reconfigurable traveling-wave radiation system that can dynamically manipulate radiation beams and their coverage regions. Via tuning dispersion of valley-locked waveguide modes controlled by the phase states of liquid crystals, we demonstrate that radiation beams have some unique tunable capabilities in the THz regime, such as single-beam, dual-beam, and multi-beam reconfigurabilities. Moreover, leveraging the idea of digitally encoding waveguide channels, we provide a solution for dynamically steerable traveling-wave radiation in the valley topological photonic platform. The proposed configurations provide more freedom to manipulate traveling-wave radiation and open a pathway for developing reconfigurable traveling-wave antennas in THz multi-link wireless communication system.