A fractional phase-coding strategy for terahertz beam patterning on digital metasurfaces.
A fractional phase-coding strategy for terahertz beam patterning on digital metasurfaces.
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DOI：
10.1364/oe.385691
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发表时间：
2020-03
期刊：
影响因子：
3.8
通讯作者：
Luyang Wang;F. Lan;Yaxin Zhang;S. Liang;Wenxin Liu;Ziqiang Yang;L. Meng;Zongjun Shi;Jing Yin;Tianyang Song;Hongxin Zeng;P. Mazumder
中科院分区：
文献类型：
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作者：
Luyang Wang;F. Lan;Yaxin Zhang;S. Liang;Wenxin Liu;Ziqiang Yang;L. Meng;Zongjun Shi;Jing Yin;Tianyang Song;Hongxin Zeng;P. Mazumder
近十年来，编码超表面因其在深亚波长尺度的数字波操纵而受到广泛关注，越来越迫切需要适合太赫兹波前操纵的更复杂、更灵活的编码策略。由于其在相位梯度划分上的刚性，相位梯度超表面和传统的相位编码技术都缺乏在大视场和精确瞄准中扩展应用的灵活性。该研究提出了一种基于相控阵理论和超表面概念的精确重构阵列因子的广义编码方法，可应用于反常散射和超细辐射图案。根据对偏转角与超胞间距关系的定量分析，通过对超胞间距尺度进行逻辑离散，得到了一种任意相位梯度分布的分数编码方法。通过切换不同的编码序列或入射频率，可以在分数相位编码超表面上以最小的步长实现扩展角度范围内的单光束到多光束扫描。作为概念验证，由四个分数编码序列排列的 2 位编码超表面已被制造和测量，展示了 0.34-0.5 THz 范围内 22° 至 74° 的连续单光束转向模式。通过数值预测、仿真和实验之间的良好一致性进行了交叉验证，所提出的编码策略为高分辨率成像和检测的精细光束调节铺平了道路。
Coding metasurfaces have drawn great attention for its digital wave manipulation in deep subwavelength-scale in the last decade, more sophisticated and flexible coding strategies suitable for terahertz wavefront manipulations are becoming more urgently demanded. Due to its rigidity in phase gradient division, both phase gradient metasurfaces and conventional phase coding technique lack the flexibility to expand applications in a large field of view and accurate targeting. This study presents a generalized coding method by precisely reconfiguring the array factor based on the phased array theory and metasurface concept, which can be applied for anomalous scattering and ultrafine radiation patterning. According to our quantitative analysis on the relationship between the deflected angles and the supercell spacing, a fractional coding method for arbitrary phase gradient distribution has been attained by logically discretizing the spacing scale of supercells. By switching on different coding sequences or incident frequencies, a single beam to multiple beam scanning in an expanded angular range with minimal step can be achieved on the fractional phase-coding metasurfaces. As a proof of concept, the 2-bit coding metasurfaces arranged by four fractional coding sequences have been fabricated and measured, demonstrating a consecutive single-beam steering pattern ranging from 22° to 74° in 0.34-0.5 THz. Crosswise verified by the good accordance among numerical prediction, simulation and experiment, the proposed coding strategy paves a path to delicate beam regulation for high-resolution imaging and detection.