Transmissive metasurface with 3.5-μm-thick liquid crystals for subterahertz-wave dynamic beamforming

Propagation control is essential for the practical use of subterahertz waves. Liquid crystal (LC) metasurfaces, which can be easily fabricated using display manufacturing technologies, can achieve the large aperture required for controlling propagation channels. Here we propose a dual-linear polarization unit cell that incorporates an LC layer with a thickness that can be determined independently of cell scaling, and that can be designed over a broad frequency range from microwave to subterahertz. Our prototype transmissive metasurface includes a 3.5-μm-thick LC layer and comprises 47,524 cells with a cell size below λ/8, and exhibits an insertion loss of 2.5 dB with a 3-dB bandwidth of 10%. We experimentally demonstrate two-dimensional beam steering up to 30 degrees and variable focusing through amplitude modulation of the aperture in the 115-GHz band. We anticipate that the development of metasurfaces with display-grade LC thickness will promote the industrial use of subterahertz bands in next-generation mobile communications.