High numerical aperture microwave metalens.
Opt Lett
; 45(22): 6262-6265, 2020 Nov 15.
Article
em En
| MEDLINE
| ID: mdl-33186965
ABSTRACT
The numerical aperture (NA) of a lens determines its focusing resolution capability and the maximum light collection or emission angle. In this Letter, an ultrathin high NA metalens operating in the microwave band is designed and demonstrated both numerically and experimentally. The proposed element is constructed by a multi-layer complementary split ring resonator, which can cover full 2π phase shift simultaneously with high transmission magnitude by varying its radius gradually. The numerical and experimental results reveal that the designed ultrathin (thickness is only â¼0.23λ) metalens can focus normal incident microwave efficiently to a spot of full width at half-maximum (FWHM) as small as â¼0.54λ with a corresponding high NA exceeding 0.9. Besides, the high NA metalens also possesses a relatively large focusing efficiency with a peak 48% within considered broad frequency range from 7.5 to 10 GHz. The performances of the presented metalens can be comparable or even superior to nowadays high-quality optical metalenses and represent an important step to develop a high-performance metalens in low spectrum. Besides, it can greatly facilitate the development of some novel miniaturized devices like a high-gain low profile scanning antenna, an ultra-compact retroreflector, and cloaks.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Opt Lett
Ano de publicação:
2020
Tipo de documento:
Article