Terahertz Near‐Field Metasurfaces: Amplitude–Phase Combined Steering and Electromagnetostatic Dual‐Field Superfocusing,Advanced Optical Materials

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Terahertz Near‐Field Metasurfaces: Amplitude–Phase Combined Steering and Electromagnetostatic Dual‐Field Superfocusing
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2020-01-07 , DOI: 10.1002/adom.201901331
Feng‐Yuan Han ₁ , Pu‐Kun Liu ₁

Affiliation

Subwavelength resolution imaging entails a sharpened superfocusing to overcome the diffraction limit. However, conventional high‐numerical‐aperture superfocusing lenses are bulky and expensive. Relying on the abrupt amplitude and phase discontinuities, metasurfaces have been recently explored as an ultrathin platform to generate arbitrary wavefronts over subwavelength thicknesses. In this paper, a dual‐field superfocusing is demonstrated for terahertz wavelengths using a near‐field metasurface by simultaneously tailoring the amplitude and phase of the evanescent field, which satisfies both electrostatic and magnetostatic limits. A combined analytic theory is introduced to describe the physical mechanism and the entire design process of the near‐field metasurface. With three‐layer minuscule elements characterized by extremely small electric sizes, the metasurface can force both incident electric and magnetic fields to converge to a sharpened focus spot (0.066 and 0.045 wavelength focus spots at a distance of 0.073 wavelength) through radiationless electromagnetic interference. Practical implementations of these metasurfaces hold promise for near‐field terahertz beam steering, laser‐based microscopy, noncontact sensing, imaging, and lithography applications.

中文翻译：

太赫兹近场超表面：振幅-相位组合转向和电磁静态双场超聚焦

亚波长分辨率成像需要锐化的超聚焦以克服衍射极限。但是，传统的高数值孔径超聚焦镜头体积庞大且昂贵。依靠突然的幅度和相位不连续性，超表面最近被研究为超薄平台，可在亚波长厚度上产生任意波阵面。在本文中，通过同时调整the散场的幅度和相位，同时满足静电和静磁极限，证明了使用近场超表面对太赫兹波长进行双场超聚焦。引入了组合分析理论来描述近场超表面的物理机理和整个设计过程。采用三层微小元件，其电气尺寸极小，通过无辐射的电磁干扰，超颖表面可以迫使入射的电场和磁场都收敛到锐化的焦点（0.066和0.045波长的焦点，距离为0.073波长）。这些超表面的实际实现为近场太赫兹光束转向，基于激光的显微镜，非接触式传感，成像和光刻应用提供了希望。

更新日期：2020-03-20

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