Two-Dimensional Terahertz Beam Steering Based on Trajectory Deflection of Leaky-Mode

Free-space transmission of terahertz waves open great opportunities for wireless communication and sensing in the Beyond 5G/6G paradigm. Nevertheless, terahertz transmission suffers from severe diffraction losses due to the shorter wavelengths than the microwaves. To compensate for the diffraction losses, point-to-point transmission by directional beams is indispensable. However, implementing terahertz beam steering is still challenging due mainly to the lack of practical phase shifters. To circumvent this challenge, we demonstrate a novel strategy of two-dimensional (2-D) terahertz beam steering based on trajectory deflection of leaky-mode at around 300 GHz. We use a pair of metal plates with a mesh surface, in which the phase velocity exceeds the light speed in free-space. The leaky-mode can be steered vertically by a phase matching condition controllable with frequency sweep and horizontally by graded refractive index controllable with small tilt of the plate. The result confirms 2-D beam steering without relying on phase shifters.