研究目的
To design and test a large aperture metal-mesh graded index Fresnel lens for THz astronomy applications, matching the performance of traditional polyethylene lenses.
研究成果
Initial results show that the focusing properties of the large metamaterial lens match that of an ideal lens. Further results detailing the precise chromatic behavior, cross polarisation levels, and insertion loss of the lens will be presented in a full paper.
研究不足
The increase in thickness required for scaling up the lens design means that over 60 mesh grids are required, which is not practical to build. The design had to be adjusted to a Fresnel graded index profile to address this issue.
1：Experimental Design and Method Selection:
The lens was designed based on a Fresnel graded index profile to compress the overall index range, allowing for more favorable index values. The variation in index was achieved by applying a radial profile to the size of square copper patches.
2：Sample Selection and Data Sources:
A 300mm diameter Fresnel lens with a focal length of 1050mm, optimized for 150GHz, was fabricated using a hot press technique.
3：List of Experimental Equipment and Materials:
The lens consisted of 20 identical mesh layers separated by 100μm polypropylene, yielding a total thickness of 2mm. A new testing facility was developed for measurement.
4：Experimental Procedures and Operational Workflow:
The lens was placed in a collimated beam fully illuminating the lens surface. The receiver was mounted on an XYZ stage for sub-millimeter positioning capability. The system was controlled by LabVIEW.
5：Data Analysis Methods:
Beam scans were performed at two frequency bands, 75-110 GHz and 160–260 GHz, and compared to the predicted airy function of an ideal lens.
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