| As a new type of two-dimensional artificial electromagnetic material,metasurfaces can flexibly manipulate electromagnetic properties at sub-wavelength scales such as amplitude,phase,and polarization.Compared with traditional 3D metamaterials,metasurfaces retain excellent beam manipulation ability and have the characteristics of lightweight,low loss,easy integration,etc.,which is of critical importance for future applications in opto-electronics,ultrafast information technologies,microscopic imaging,and sensing.Many achievements have been made in the study of phase regulation of all-dielectric metasurface,such as beam deflection,optical beam splitter,focusing hyperlens,holographic imaging,etc.However,these functional devices still face a series of problems,such as low efficiency,small deflection angle,and narrow working band.To solve the above problems,we carried out research on beam manipulation based on an all-dielectric metasurface.The specific research contents are as follows:(1)We propose an all-dielectric Huygens’ metasurface for efficient beam manipulation at the visible region.All-dielectric Huygens’ metasurfaces are widely used in wavefront manipulation through multipole interactions.The all-dielectric Huygens’ metasurface uses the overlap between electric and magnetic dipole resonances to achieve transmission enhancement and phase change close to 2π.Benefiting from this unique property,we design and numerically investigate an all-dielectric Huygens’ metasurface exhibiting high-efficiency anomalous refraction.When the working wavelength is 692 nm,the diffraction angle is 30.84°,and the anomalous transmission efficiency is more than90.7%.The performance of this structure is much better than most existing phase gradient metasurface structures,which paves the way for des0 igning efficient beam deflector devices.(2)We propose an all-dielectric metasurface with high anomalous transmission intensity and a large anomalous transmission angle in the near-infrared region.The all-dielectric metasurface comprises discontinuous regular hexagonal nanorods supported by a silicon dioxide substrate.In the 1400-1600 nm wavelength range,the metasurface achieves high transmission efficiency and completely 2π phase change.Based on this structure,we first propose a six-element phase gradient metasurface.At the central wavelength of 1529 nm,the total transmission efficiency reaches 96.5%,the desired anomalous transmission efficiency reaches 96.2%,and the anomalous transmission angle reaches 30.64°.In order to obtain a larger anomalous transmission angle,the number of nanorods in the period was adjusted.We designed several groups of phase gradient metasurfaces with a different number of elements.When the anomalous transmission angle is extended to 68.58°,the anomalous transmission efficiency can still reach 69.6%.The excellent performance of this design can pave the way for its application in advanced wavefront control devices.(3)We numerically study a quasi-continuous beam splitter with highly efficient and wide bandwidth equal-power beam splitting that consists of rhombic aluminum antimonide nanorods standing on a silica substrate.We first designed a beam splitter based on a discrete structure.The results show that the beam splitter based on the discrete structure can only reach 42 nm when the beam splitter efficiency exceeds 80%.In order to further improve the performance of the splitter and obtain a structure that is easy to fabricate accurately,the splitter was optimized,and the proposed rhomboid quasi-continuous beam splitter was obtained.This equal-power beam splitter achieves a splitting efficiency of over80% in 111 nm bandwidth of 675-786 nm,where the splitting angle can vary in the range of 97.2-121.8°.In particular,the splitting efficiency reaches 93.4% when the wavelength is690 nm.Overall,the proposed beam splitter potentially paves the way for realizing broadband metasurfaces and high-performance quasi-continuous metasurface-based devices. |
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