Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies.

Ren Wang,Zhi-Shuang Gong,Xiao Ding,Bing-Zhong Wang

doi:10.1038/srep11131

Ren Wang, Zhi-Shuang Gong + Show 2 more

Open Access

https://doi.org/10.1038/srep11131

Copy DOI

Abstract

A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green’s function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments.

Highlights

The SRR cell has a switch in the middle of the metal split ring, which is printed on a dielectric substrate
The proposed imaging method includes two key points: (1) the metalens cell with localized mode resonance can convert evanescent waves into propagating waves and can limit the surface field within a small scope, (2) the near-field scanning is realized by switching the SRR cell in this study
The near-field scanning is realized by changing the switch status of each SRR cell, producing an electrical or an optical scanning process when the switch is a micro-electromechanical system (MEMS) or a photoconductive semiconductor switch (PCSS)

Summary

Introduction

The resonant metalens composed of switchable SRRs can be used for far-field subwavelength imaging by setting the switch status of each cell. A metalens composed of 4 × 4 switchable SRRs (Fig. 1(a)) is used to demonstrate the far-field subwavelength imaging.

Results

Conclusion