Dumbbell-shaped metasurface for broadband terahertz multimode orbital angular momentum wave generation

Terahertz vortex beam communication is a core 6G technology that enables Terabit/s data transmission in high-frequency bands. This paper presents a metasurface-based terahertz vortex beam generator featuring a dumbbell-shaped unit cell structure. The metasurface has three layers: a dumbbell-shaped metallic top layer, a polyimide dielectric middle layer, and a metallic ground plane. Based on the Pancharatnam–Berry phase principle, the device incorporates a 16 × 16 unit cell array that successfully generates vortex beams with topological charges of ±1, ±2, ±3, and ±4 within the frequency range of 0.93–1.88 THz, achieving a reflectivity exceeding 95%. This design maintains a high reflectivity across an extensive bandwidth and exhibits exceptional broadband performance characteristics, extending the achievable vortex beam orders in the terahertz frequency band. The device demonstrates substantial application potential in various terahertz communication scenarios, including holographic communication, compact communication networks, and ultra-high-capacity data backhaul applications.