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arXiv 2006.06394physics.app-phphysics.optics
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空间离散化的时空调制元表面：自由空间N路系统

Space-Time Modulated Metasurfaces with Spatial Discretization: Free-Space N-path Systems

Zhanni Wu, Cody Scarborough, Anthony Grbic

发表信息：
Phys. Rev. Applied 14, 064060 (2020)
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摘要：

本文从理论和实验上研究了具有空间离散行波调制（SD-TWM）的超颖表面。代表性的超颖表面被认为是由时间调制的亚波长单位单元（称为stixel）的列组成。SD-TWM是通过在施加到相邻列的时间波形之间施加时间延迟来实现的。与通常在时空元表面研究中假设的连续行波调制相反，这里的调制是空间离散的。为了考虑离散化的空间调制，一个修改后的Floquet分析介绍了一个新的边界条件，已推导出SD-TWM结构的基础上。改进的Floquet分析将散射场分为宏观和微观变化。理论和实验结果表明，SD-TWM超颖表面的电磁行为可以分为三个区域。对于电大空间调制周期，可以忽略每个stixel上的微观场变化。在这种情况下，时空超颖表面允许同时进行频率平移和角偏转。当超颖表面上的空间调制周期在电学上很小时，微观变化导致新的超颖表面能力，例如次谐波混合。当超颖表面的空间调制周期是波长尺度时，超颖表面允许同时实现次谐波混合和角偏转。为了验证我们的分析，一个双极化，时空调制的超颖表面，开发和测量在X波段的频率。

英文摘要：

This work theoretically and experimentally studies metasurfaces with spatially-discrete, traveling-wave modulation (SD-TWM). A representative metasurface is considered consisting of columns of time-modulated subwavelength unit cells, referred to as stixels. SD-TWM is achieved by enforcing a time delay between temporal waveforms applied to adjacent columns. In contrast to the continuous traveling-wave modulation commonly assumed in studies of space-time metasurfaces, here the modulation is spatially discretized. In order to account for the discretized spatial modulation, a modified Floquet analysis is introduced based on a new boundary condition that has been derived for SD-TWM structures. The modified Floquet analysis separates the scattered field into its macroscopic and microscopic variations. The reported theoretical and experimental results reveal that the electromagnetic behavior of an SD-TWM metasurface can be categorized into three regimes. For electrically-large spatial modulation periods, the microscopic field variation across each stixel can be neglected. In this regime, the space-time metasurface allows simultaneous frequency translation and angular deflection. When the spatial modulation period on the metasurface is electrically small, the microscopic variation results in new metasurface capabilities such as subharmonic mixing. When the spatial modulation period of the metasurface is wavelength-scale, the metasurface allows both subharmonic mixing and angular deflection to be achieved simultaneously. To verify our analysis, a dual-polarized, spatio-temporally modulated metasurface, is developed and measured at X-band frequencies.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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