Multifocal Terahertz Lens with Adjustable Focal Points

TL;DR

This paper introduces a reconfigurable terahertz metasurface lens using VO2 that can dynamically adjust focal points and concentration width, enabling advanced applications in wireless communication and imaging.

Contribution

It presents a novel VO2-based phase-change metasurface capable of real-time reconfigurable focusing and power concentration control in the terahertz range.

Findings

The metasurface can dynamically focus on multiple points.

It achieves real-time control of concentration width.

Simulation results confirm the design's effectiveness.

Abstract

The conventional lens's tunability drawback always restricts their application compared to the metasurface lens (metalens). On the other side, reconfigurable metalenses offer the benefits of ultrathin thickness and capable of tunability. Therefore achieving reconfigurable functionalities in a single metasurface has attracted significant research interest for potential terahertz (THz) applications. In this paper, an adjustable metasurface is presented using Vanadium dioxide (VO2) to manipulate the electromagnetic waves and provide the full reflection phase. The phase-change metasurface is composed of a VO2 nanofilm, a silicon spacer, and a gold layer embedded in the structure's bottom. By employing the reconfigurable metasurface with the specific phase distribution, the incident beam can converge to determined points in any arbitrary manner, including the number of the focal points, focal points location, and power intensity ratio. Numerical simulations demonstrate that the proposed reconfigurable metasurface can concentrate power on one or more than one focal point in reflection modes as expected. Additionally, the VO2-based metasurface can control concentration width in a real-time manner using a novel proposed method. The simulation and theoretical results are in good agreement to verify the validity and feasibility of 2-bit metalens design, which has considerable potential in wireless high-speed communication and super-resolution imaging.