Beam manipulation for terahertz communications

The terahertz frequency band, ranging from 0.1 to 10 THz, offers extensive spectral resources for next-generation wireless communications systems. To compensate for the limited transmit power of terahertz transceivers and severe propagation losses, high-gain directional transmission is essential, making dynamic beam manipulation a key enabler for practical terahertz communications. The stringent gain requirements further extend the Fresnel region, necessitating efficient beam manipulation across both near-field and far-field conditions. The increasing reliance on beam manipulation reflects a paradigm shift in terahertz communications, where performance scaling is achieved through architecture-level innovation rather than solely through incremental hardware or algorithmic improvements. This article provides a comprehensive overview of terahertz beam manipulation techniques. It begins with an introduction of diffraction theory as the foundational propagation model for beam manipulation. Detailed examples tailored to specific communication scenarios are then presented. Experimental verifications using lenses and metasurfaces are included for three distinct beam manipulation cases. Alternative approaches for achieving beam manipulation, such as reconfigurable intelligent surfaces, are briefly discussed.