  Wireless communications in the terahertz band (0.1-10 THz) is a promising and
key wireless technology enabling ultra-high data rate communication over
multi-gigahertz-wide bandwidths, thus fulfilling the demand for denser
networks. The complex propagation environment at such high frequencies
introduces several challenges, such as high spreading and molecular absorption
losses. As such, intelligent reflecting surfaces have been proposed as a
promising solution to enable communication in the presence of blockage or to
aid a resource-limited quasi-omnidirectional transmitter direct its radiated
power. In this paper, we present a metallic reflectarray design achieving
controlled non-specular reflection at true terahertz frequencies (i.e., 1-1.05
THz). We conduct extensive experiments to further characterize and validate its
working principle using terahertz time-domain spectroscopy and demonstrate its
effectiveness with information-carrying signals using a continuous-wave
terahertz testbed. Our results show that the reflectarray can help facilitate
robust communication links over non-specular paths and improve the reliability
of terahertz communications, thereby unleashing the true potential of the
terahertz band.
