Near-field plates and the near zone of metasurfaces

TL;DR

This paper discusses the distinct behaviors of near and far electromagnetic fields, focusing on near-field metasurfaces, their field decay patterns, and potential applications like near-field tweezers.

Contribution

It provides a detailed tutorial on near-field metasurfaces, highlighting their field decay characteristics and introducing designs for pseudo minima for advanced applications.

Findings

Near-field plates exhibit exponential or algebraic decay patterns.

Properly designed near-field plates can create pseudo minima.

Near-field metasurfaces have potential for tweezer-like applications.

Abstract

A brief, tutorial account is given of the differences between the near and far regions of the elec-tromagnetic field emphasizing the source-dependent behavior of the former and the universal properties of the latter. Field patterns of near-field plates, that is, metasurfaces used for sub-wavelength applications, are discussed in some detail. Examples are given of fields that decay away from the plates in an exponential manner, a ubiquitous feature of many interface problems, and metasurfaces for which the decay is not exponential, but algebraic. It is also shown that a properly designed system of two parallel near-field plates can produce fields that exhibit pseudo minima, which are potentially useful for near-field tweezer-like applications.