Electromagnetic-Circuit Co-design approach towards Reconfigurable Terahertz Holographic CMOS Metasurface

In this article, we design and demonstrate a multi-functional, digitally programmable metasurface at 0.3 THz exploiting electromagnetic-circuit co-design approach. The metasurface is fabricated using industry standard 65-nm CMOS process. Each metasurface tile consists of $12 \times 12$ periodic array of unit cells. We also demonstrate the scalability of this approach by chip tiling and create a larger aperture of $2 \times 2$ array. Each unit cell in the metasurface is an individually addressable and programmable multi-split-ring resonator consisting of eight metaloxide-semiconductor field-effect transistors (MOSFET) at the capacitive gaps. Each unit cell can be programmed to control both amplitude and phase independently. We experimentally demonstrate multi-functional applications namely, high-speed beam modulation with switching ON/OFF ratio of $\sim 25$ dB at a maximum clock speed of 5 GHz, beamforming capability of ± 30° and spatial wavefront manipulation using binary-amplitude-only holography technique at 0.3 THz. The metasurface chip operates at near-zero DC power $(240 \mu \text{W})$ consumption.