480 GHz metamaterial flat lens design and characterization

Cassandra N. Whitton; Sven van Berkel; Daniel Lu; Adhitya B. Sriram; Philip D. Mauskopf; Christopher E. Groppi; Paul F. Goldsmith; Georgios Trichopoulos; Jose V. Siles

doi:10.1117/12.3017836

26 August 2024 480 GHz metamaterial flat lens design and characterization

Cassandra N. Whitton, Sven van Berkel, Daniel Lu, Adhitya B. Sriram, Philip D. Mauskopf, Christopher E. Groppi, Paul F. Goldsmith, Georgios Trichopoulos, Jose V. Siles

Author Affiliations +

Proceedings Volume 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI; 131003T (2024) https://doi.org/10.1117/12.3017836
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

Flat, Lightweight optics have the potential to significantly reduce the cost of space-based observing by allowing for reduced vehicle sizes and launch costs. We have designed, manufactured, and tested a metamaterial flat lens which operates at 480GHz. 480GHz was chosen as an intermediate step to designing a 557GHz lens, which is a frequency that has scientific importance as it is a ground-state water transition line, but nearly impossible to observe from the ground or from a balloon due to water in the atmosphere. The lens is constructed from polyimide (generic Kapton) and aluminum. The metamaterial design consists of ten layers of sub-wavelengthsized aluminum squares, sized via optimization to achieve the ideal phase transformation to create a 150mm focal distance at 480GHz. This optimization process also creates an effective anti-reflection quality. The lens has an aperture size of 124mm and an f-number of f/1.2. It weighs approximately three grams and is 110 microns thick. We have demonstrated the lens has near diffraction-limited beam performance with roughly 2.5dB of loss. The loss was measured using a radiometric y-factor method, using a room-temperature absorber as the hot load and an absorber submersed in liquid nitrogen as the cold load. The beam performance was measured using a near-field scan of the lens with a waveguide probe at the focus to illuminate the lens and a second probe to measure the phase and magnitude of the near-field collimated output. The loss was roughly 1.5 dB higher than expected in our design simulations.

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Cassandra N. Whitton, Sven van Berkel, Daniel Lu, Adhitya B. Sriram, Philip D. Mauskopf, Christopher E. Groppi, Paul F. Goldsmith, Georgios Trichopoulos, and Jose V. Siles "480 GHz metamaterial flat lens design and characterization", Proc. SPIE 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI, 131003T (26 August 2024); https://doi.org/10.1117/12.3017836

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