Three Dimensional Subwavelength focus by a near-field plate lens

TL;DR

This paper presents a near-field plate lens designed via inverse methods that achieves subwavelength focusing, surpassing the diffraction limit, with potential applications in imaging and wireless power transfer.

Contribution

The authors designed and fabricated a flat near-field lens using inverse design and artificial impedance surfaces to achieve subwavelength focus.

Findings

Achieved a focus nearly three times smaller than the diffraction limit.

Successfully fabricated the lens with lumped reactive elements.

Demonstrated potential for applications in imaging and wireless power transfer.

Abstract

We implemented the inverse design method to build a thin near-field lens that could produce a desired subwavelength focus by manipulating the near fields of a magnetic dipole source. The flat near-field lens represented by an artificial impedance surface was fabricated by lumped reactive elements (capacitor and inductor) with spatially varying values. In the experiment a desired annular focusing spot with a characteristic size nearly three times smaller than that allowed by the diffraction limit was obtained. Besides high-resolution imaging, the proposed near-field plate could be extended for other interesting applications, such as wireless power transfer or complex wavefront/beam shaper.