With the advent of sixth generation (6G) wireless technology, the future of wireless communication will take a big leap forward. A research team at City University of Hong Kong (CityU) has invented a pioneering tunable terahertz (THz) metadevice that can control the radiation direction and coverage of THz beams.

By rotating its meta surface, the device can instantly route a 6G signal only to the intended receiver, minimizing power leakage and increasing privacy. It is expected to provide highly regulated, versatile and secure tools for future 6G communication systems.

The potential of THz band technology is limitless because it has abundant spectral resources to support ultra-high data rates of 100 Gbps (gigabits per second) for wireless communication and even hundreds to thousands of Tbps (terabits per second). Many times faster than 5G data rates.

However, conventional THz systems use bulky, heavy dielectric lenses and reflectors that can only direct waves to a fixed transmitter or detector, or transmit them to a single receiver placed in a fixed location or covering a limited area. This hinders the development of future 6G applications that require precise positioning and concentrated signal strength.

Current bulky systems block 6G applications

With the joint efforts of two CityU research groups (SKLTMW), led by Professor Tsai Ding-Ping, Professor of the Department of Electrical Engineering, and Vice-Chancellor, and Director of Terahertz and Millimeter Waves State Key Laboratory, Professor Chang Chi-hou (SKLTMW), we have recently sought to overcome these challenges in terms of THz beam propagation direction and coverage. New adjustable meta-devices have been developed that can fully control the

“The advent of the tunable THz metadevice opens up exciting prospects for 6G communication systems,” said Professor Tsai, an expert in metasurfaces and photonics. “Our meta device allows the signal to be transmitted to specific users or detectors and has the flexibility to adjust the propagation direction as needed.”

Professor Chen, an expert in Terahertz technology research, added, “Our findings suggest a number of advantages for advanced THz communication systems, including security, flexibility, high directivity and signal concentration.”

A rotating metasurface containing thousands of micro-antennas

The meta device consists of two or three rotating meta surfaces (wavelength artificial thin sheet material) that work as efficient projectors to control the focal point of THz rays in a 2D or 3D plane. space. Each 30 mm diameter metasurface contains approximately 11,000 different microantennas measuring only 0.25 mm x 0.25 mm.

“The secret to the success of the metadevice lies in the careful calculation and design of each micro-antenna,” said Professor Tsai. By simply rotating the meta surfaces with no additional clearance, the focus of the THz beam can be adjusted and directed to the target’s given X, Y, and Z coordinates, respectively.

The research team conducted experiments with SKLTMW’s high-precision and advanced equipment and confirmed that the two types of varifocal metadevices they developed (binary and triple metadevices) can project the focal point of the THz wave to an arbitrary point. According to high precision in 2D plane and 3D space.

This innovative design demonstrated the meta-device’s ability to direct a 6G signal to a specific location in two- and three-dimensional space. Because only a user or detector at a particular point can receive a signal, and a highly concentrated signal can be flexibly passed to other users or detectors without wasting power or violating privacy at nearby receivers, metadevice versatility can increase security and flexibility. 6G communication of the future with lower energy consumption

It is easy to increase production at low costs

Metasurfaces are made using high-temperature resin and a 3D printing method developed by the team. They are light and small and can be easily produced on a large scale at low cost for practical applications.

The new tunable THz meta device is expected to have huge application potential for 6G communication systems, including wireless power transmission, image scaling and remote sensing. The research group plans to develop further applications of metadevices based on THz varifocal imaging.