Thz four-beam steering using metagrating pair with angle insensitivity and tailored geometric symmetry

Dynamic multi-beam steering is highly desired in target tracking and networking, with faster speed and larger flexibility as compared to single-beam steering. Here, instead of actively controlling meta-atoms in phased array metasurfaces, four beams are simultaneously scanned by cascaded diffraction of a pair of rotating metagratings. By tailoring the rotation symmetry and azimuth-angle-insensitive diffraction of the metagratings, multiple tangential wave vectors in the two layers are one-to-one added vectorially in order to govern the output four-beam direction. By combining a four-beam splitter metagrating with a beam deflector, we experimentally demonstrate THz four-beam steering with symmetric or asymmetric trajectories. The asymmetric steering shows +/- 60 degrees field of view with average efficiency of 41 % by tuning the relative orientation of the two metagratings, and the symmetric steering shows +/- 22 degrees field of view with the potential for further increasing the coverage. The efficiency fluctuation of the four beams is less than 4 %. This dynamic multi-beam steering strategy shows great potential for flexible signal transmission and processing in the THz band.

Automated summary

The article introduces a dynamic multi-beam steering strategy that uses rotating metagratings and diffraction to scan and control the direction of four beams. Experimental results demonstrate that this strategy can achieve symmetric or asymmetric directional control of THz four beams, with a large field of view and high efficiency.