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Super-oscillatory metalens at terahertz for enhanced focusing with reduced side lobes

Lookup NU author(s): Dr Victor Pacheco PenaORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

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.

Publication metadata

Author(s): Legaria S, Pacheo-Pena V, Beruete M

Publication type: Article

Publication status: Published

Journal: Photonics

Year: 2018

Volume: 5

Issue: 4

Online publication date: 05/12/2018

Acceptance date: 29/11/2018

Date deposited: 05/12/2018

ISSN (electronic): 2304-6732

Publisher: MDPI AG

URL: https://doi.org/10.3390/photonics5040056

DOI: 10.3390/photonics5040056

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