Characterization of a Compact Wideband Microwave Metasurface Lens for Cryogenic Applications

In this paper, we present characterization of a compact flat microwave lens operating between 6 GHz and 14 GHz using a near field scanning system. An X-band horn antenna and open-end rectangular waveguide were used as an illumination source and probe, respectively. |S21| is measured as the probe antenna moves on a plane orthogonal to the optical axis vertically and horizontally. The lens is made of a metasurface layer that is sandwiched by two layers of cross-oriented gratings. The overall dimension of the lens is 10 cm in diameter and 0.57 cm in thickness. The measurement results show that the lens's focal length is 8 cm, and the beamwidth (full width at half maximum (FWHM)) is 3.5 cm, A transmission efficiency of over 90% and a cross-polarization gain of 25 dB were achieved over the entire bandwidth. The measurement results at room temperature are in good agreement with numerical simulations. The proposed lens will be used in a cryogenic environment e.g. dilution refrigerators for quantum computing systems. More results at cryogenic temperature e.g, below 30 K will be shown at the conference.