A high-speed programmable and scalable terahertz holographic metasurface based on tiled CMOS chips

The integration of active electronic systems and meta-elements using commercial silicon fabrication techniques can be used to create scalable and dynamically programmable terahertz metasurfaces. Metasurfaces, which consist of arrays of subwavelength scatterers, can be used to precisely control incident electromagnetic fields, but are typically static once fabricated. A dynamically programmable array of terahertz meta-elements, in which each element can be individually reconfigured to allow controlled wavefront shaping, could be of value in terahertz applications such as wireless communication, sensing and imaging. Here, we show that large-scale programmable metasurfaces can be created using arrays of complementary metal-oxide-semiconductor (CMOS)-based chip tiles. We developed an aperture with a 2 x 2 array of tiled chips consisting of 576 meta-elements, each individually addressable and digitally programmable with 8 bits of control at GHz speed, and fabricated in a 65 nm industry-standard CMOS process. The active-circuit-coupled terahertz meta-element structure can be reconfigured, providing digitally programmable metasurfaces with amplitude and phase control, around 25 dB of amplitude modulation depth, dynamic beamforming across +/- 30 degrees, multibeam formation and programmable holographic projections at 0.3 THz.