研究目的
To develop compact devices that allow asymmetric response in wave propagation by engineering asymmetry in planar structures through unilateral excitation of evanescent waves.
研究成果
The study demonstrates that evanescent waves excited in subwavelength gratings can be exploited to achieve extreme electromagnetic effects in planar structures, such as angular-asymmetric absorption and reflection. This concept can be scaled to other frequencies and applied to wave processes of different nature, offering multiple practical outcomes including compact nonreciprocal devices and systems for one-side detection and sensing.
研究不足
The fabrication limitations and material dispersion prevent infinitely scaling down the structure dimensions to higher frequencies towards the visible range. The method requires a large number of small subcells for higher asymmetry, which complicates the fabrication process.
1：Experimental Design and Method Selection:
The study involves the design and experimental characterization of a metasurface for angular-asymmetric absorption, utilizing unilateral excitation of evanescent waves.
2：Sample Selection and Data Sources:
The metasurface is designed for operation at 75 GHz, with a metallic pattern supported by a metal-backed dielectric slab.
3：List of Experimental Equipment and Materials:
A thin aluminum film with a thickness of 25 nm and measured grid resistivity of 2 Ω/sq is used. The dielectric substrate has a relative permittivity of
4：3 - j015 and a thickness of 215 μm. Experimental Procedures and Operational Workflow:
The surface impedance is synthesized with 10 subelements over a period, ensuring the proper excitation of evanescent waves. The metasurface is fabricated using photolithography and lift-off process.
5：Data Analysis Methods:
The performance of the metasurface is analyzed through full-wave simulations and experimental measurements of backward and specular reflectance spectra.
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