• Open Access

Parity-Time Symmetric Nonlocal Metasurfaces: All-Angle Negative Refraction and Volumetric Imaging

Francesco Monticone, Constantinos A. Valagiannopoulos, and Andrea Alù
Phys. Rev. X 6, 041018 – Published 25 October 2016
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Abstract

Lens design for focusing and imaging has been optimized through centuries of developments; however, conventional lenses, even in their most ideal realizations, still suffer from fundamental limitations, such as limits in resolution and the presence of optical aberrations, which are inherent to the laws of refraction. In addition, volume-to-volume imaging of three-dimensional regions of space is not possible with systems based on conventional refractive optics, which are inherently limited to plane-to-plane imaging. Although some of these limitations have been at least theoretically relaxed with the advent of metamaterials, several challenges still stand in the way of ideal imaging of three-dimensional regions of space. Here, we show that the concept of parity-time symmetry, combined with tailored nonlocal responses, enables overcoming some of these challenges, and we propose the design of a loss-immune, linear, transversely invariant, planarized metamaterial lens, with reduced aberrations and the potential to realize volume-to-volume imaging.

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  • Received 23 October 2015

DOI:https://doi.org/10.1103/PhysRevX.6.041018

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Francesco Monticone1, Constantinos A. Valagiannopoulos2, and Andrea Alù1,3,*

  • 1Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA
  • 2Department of Physics, School of Science and Technology, Nazarbayev University, KZ-010000 Astana, Kazakhstan
  • 3Center for Nanophotonics, FOM Institute for Atomic and Molecular Physics, Science Park 104, 1098 XG Amsterdam, The Netherlands

  • *alu@mail.utexas.edu

Popular Summary

Focusing and imaging are common operations, typically performed with lenses whose designs have been optimized for centuries. Conventional lenses suffer from fundamental limitations, however, such as limits in resolution and the inherent presence of optical aberrations, which stem from the well-established laws of reflection and refraction. In addition, systems based on conventional refractive optics are inherently limited to plane-to-plane imaging, and they cannot realize volume-to-volume imaging of three-dimensional regions of space. Recent advances in the area of metamaterials have shown potential ways to relax some of these limitations, yet several challenges still stand in the way of ideal imaging systems.

Here, we introduce an imaging platform based on parity-time symmetric surfaces composed of a suitable combination of absorbing and emitting elements, time-reversed of each other, which enables enticing possibilities for focusing and imaging. We first derive a general recipe to obtain aberration-free volumetric imaging, showing the potential offered by parity-time symmetric systems in this context. A key aspect of this goal is the realization of an appropriate nonlocal parity-time symmetric response, which we achieve using multilayered metamaterials. Based on this scheme, we design a flat, transversely invariant lens based on a pair of parity-time symmetric, spatially dispersive metasurfaces that realizes robust all-angle negative refraction and volumetric imaging with reduced reflections and aberrations.

Our findings offer interesting opportunities in the application of active electromagnetic systems, shed light on the practical implementation challenges of nonlocal active metamaterials, and open uncharted territory in the centuries-old field of imaging.

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Vol. 6, Iss. 4 — October - December 2016

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