Abstract

In this paper, we design and numerically demonstrate an ultra-thin super-oscillatory metalens with a resolution below the diffraction limit. The zones of the lens are implemented using metasurface concepts with hexagonal unit cells. This way, the transparency and, hence, efficiency is optimized, compared to the conventional transparent–opaque zoning approach that introduces, inevitably, a high reflection in the opaque regions. Furthermore, a novel two-step optimization technique, based on evolutionary algorithms, is developed to reduce the side lobes and boost the intensity at the focus. After the design process, we demonstrate that the metalens is able to generate a focal spot of 0.46λ0 (1.4 times below the resolution limit) at the design focal length of 10λ0 with reduced side lobes (the side lobe level being approximately −11 dB). The metalens is optimized at 0.327 THz, and has been validated with numerical simulations.

Details

Title
Super-Oscillatory Metalens at Terahertz for Enhanced Focusing with Reduced Side Lobes
Author
Legaria, Santiago 1 ; Pacheco-Peña, Victor 2   VIAFID ORCID Logo  ; Beruete, Miguel 3   VIAFID ORCID Logo 

1  Antennas Group-TERALAB, Universidad Pública de Navarra, Campus Arrosadia, Pamplona 31006, Spain 
2  School of Engineering, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK 
3  Antennas Group-TERALAB, Universidad Pública de Navarra, Campus Arrosadia, Pamplona 31006, Spain; Institute of Smart Cities, Public University of Navarra, 31006 Pamplona, Spain 
First page
56
Publication year
2018
Publication date
2018
Publisher
MDPI AG
e-ISSN
23046732
Source type
Scholarly Journal
Language of publication
English
DOI
https://doi.org/10.3390/photonics5040056
ProQuest document ID
2582844036
Copyright
© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.