Super-oscillatory metalens at terahertz for enhanced focusing with reduced side lobes
Fecha
2018Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión publicada / Argitaratu den bertsioa
Impacto
|
10.3390/photonics5040056
Resumen
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 re ...
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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. [--]
Materias
Super-oscillatory lens,
Metalens,
Metamaterials,
Metasurfaces,
Terahertz,
Evolutionary algorithm,
Subwavelength focusing
Editor
MDPI
Publicado en
Photonics, 2018, 5, 56
Departamento
Universidad Pública de Navarra/Nafarroako Unibertsitate Publikoa. Institute of Smart Cities - ISC
Versión del editor
Entidades Financiadoras
This research was funded by the Spanish Ministerio de Economía y Competitividad with European
Union Fondo Europeo de Desarrollo Regional (FEDER) funds, grant number TEC2014-51902-C2-2-R.