Abstract
In this study, the high-efficiency phase control Si metasurfaces are investigated based on aperiodic nanoarrays unlike widely-used period structures, the aperiodicity of which providing additional freedom to improve metasurfaces’ performance. Firstly, the phase control mechanism of Huygens nanoblocks is demonstrated, particularly the internal electromagnetic resonances and the manipulation of effective electrical/magnetic polarizabilities. Then, a group of high-transmission Si nanoblocks with 2π phase control is sought by sweeping the geometrical parameters. Finally, several metasurfaces, such as grating and parabolic lens, are numerically realized by the nanostructures with high efficiency. The conversion efficiency of the grating reaches 80%, and the focusing conversion efficiency of the metalens is 99.3%. The results show that the high-efficiency phase control metasurfaces can be realized based on aperiodic nanoarrays, i.e., additional design freedom.
Highlights
Due to the restricted permittivity and permeability, natural materials cannot manipulate electromagnetic waves arbitrarily and wilfully
It is shown that the simultaneous manipulation of electric and magnetic dipoles can achieve 2π phase control in a single-layer dielectric nanoarray
Some reports have demonstrated that Huygens metasurface [29,31,34], using Si and TiO2 [35] as low-loss semiconductor materials, can realize high efficiency in 2π phase wavefront control
Summary
Due to the restricted permittivity and permeability, natural materials cannot manipulate electromagnetic waves arbitrarily and wilfully. The disadvantages of high loss, fabrication challenges and strong dispersion [6] limit the possible applications of 3D metamaterial, resulting in the appearance of metasurfaces, i.e., sub-wavelength nanostructure (meta-atom) arrays. Metasurfaces can compress the thickness of traditional optical elements [7] to the sub-wavelength level, performing an arbitrary manipulation of amplitude [8,9,10,11], phase [12,13,14,15,16], and polarization [17,18,19].
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