Dynamic focus metalens for adaptive beam power control in terahertz wireless communication and sensing

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Abstract
Terahertz waves from 0.1 to 0.5 THz are promising candidates for high-speed, high-capacity wireless communication networks and high-resolution sensing applications; however, with the increase in operating frequency, atmospheric attenuation and free-space losses are significant issues to overcome. Commonly used dielectric and metasurface lenses have attracted considerable attention for the enhancement of beam power characteristics, but these solutions still lack the adjustability necessary for dynamic operation, which is necessary for the development of high-efficiency systems. Here, we present a 0.3 THz band adjustable focus lens that allows for dynamic control of the focal length and beam width in response to the operating conditions. The dynamic focus lens is based on a polarization-independent 3-layer ABA-type Jerusalem cross geometry, which allows for thinner, lightweight, and more efficient devices. In the experimental verification, we have confirmed that dynamic tuning of focus can provide over 10 dB (900%) power increase and a focal length tuning ratio of 1:22 (f=0.05−1.1m). We also confirmed that the lens can operate in a wide 40 GHz (0.28–0.32 THz) frequency range, which allowed for transmission data rates of over 123 Gbps, the highest ever achieved for metasurface devices in communication. This work will have a significant impact on the development of stable communication in future high-speed wireless networks operating in terahertz bands to adjust performance in response to environmental conditions. It will also support the further development of high-resolution imaging and sensing applications.

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