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.

Recently, besides investigating the transmission characteristics of topological edge states, researchers have also explored their localization and trapping behaviors. However, the scenario where topological edge states are localized and confined at specific interfaces in a frequency-dependent manner remains unexplored and unreported. In this work, by leveraging the coupling effects of different interface stacking types, we systematically investigate valley Hall edge states at distinct interfaces of valley photonic crystals (VPCs), including bearded and armchair interfaces. Subsequently, we construct a U-shaped topological waveguide composed of these interfaces. Both numerically and experimentally, we demonstrate that valley Hall topological states in this U-shaped waveguide can be localized and confined at a designated interface in a frequency-dependent manner. Compared with conventional topological rainbow systems — where edge states of different frequencies are separated and trapped at distinct spatial positions — our proposed waveguide avoids complex techniques such as modulating external magnetic fields or designing structures with gradually varying parameters, thereby greatly facilitating photonic integration. These results provide a practical and feasible platform for nanoscale electromagnetic wave manipulation using the interface as a valley degree of freedom (DOF), with promising applications in integrated photonic devices such as multi-frequency routers and ultra-compact topological rainbow nanolasers.