Near-Field Metadevices for Wireless Power Transfer and Terahertz Wave Manipulation

Abstract

This thesis focuses on the design and implementation of low-complexity, high-performance near-field electromagnetic (EM) metadevices to address key challenges in wireless power transfer (WPT) and terahertz (THz) wavefront manipulation. The research encompasses three progressive stages:

First, to achieve efficient and robust wireless power transfer, a near-field WPT system integrating a Fabry-Pérot cavity (FPC) antenna and a rectifying metasurface (ReMS) was developed. By optimizing the metasurface unit cells and the rectifying network, the system achieves angle-insensitive radio frequency (RF) energy capture, with a peak RF-to- direct current (DC) harvesting efficiency of 94.5%. The highest measured end-to-end system efficiency reached 47.2%, providing stable DC power under varying distances and load conditions.

Second, to address the reliance on complex active components in conventional THz Airy beam generation, this work introduces an innovative proportional phase modulation approach. Three all-dielectric Airy metalenses, fabricated via high-resolution 3D printing, passively transform an incident plane wave into an Airy beam with a precisely controllable parabolic trajectory. The effectiveness of this passive strategy was validated through both simulations and near-field measurements.

Finally, building upon this passive control strategy, a compact composite metalens was developed for near-field THz imaging by integrating a gradient-index (GRIN) Mikaelian lens with an Airy beam generator. This device enables two-dimensional (2D), electronics-free beam scanning through simple mechanical movement and rotation. Coupled with an Airy beam-based imaging algorithm, the system successfully reconstructed object contours, opening a new avenue for developing low-cost, high-resolution passive THz imaging systems.

In summary, the findings of this thesis provide effective design paradigms and experimental validation for powerful and easily integrable EM metadevices.

Date of Award	8 Sept 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kwai Man LUK (Supervisor)