Abstract
Metasurfaces allow the rapid development of compact and flat electromagnetic devices owing to their capability in manipulating the wavefront of electromagnetic waves. Particularly, with respect to the metasurface lenses, wide operational bandwidth and wide incident angle behavior are critically required for practical applications. Herein, a single-layer phase gradient metasurface lens is presented to achieve millimeter-wave focusing at a focal point of 13 mm regardless of the incident angle. The proposed metasurface lens is fabricated by constructing subwavelength-thick (< λ/10) phase elements composed of two metallic layers separated by a single dielectric substrate that exhibits low-Q resonance properties and a wide phase modulation range with satisfactory transmissivity. By controlling the spatial phase distribution, the proposed metasurface lens successfully realises effective wavefront manipulation properties and high-performance electromagnetic-wave-focusing characteristics over a wide operating frequency range from 35 to 40 GHz with incident angle independency up to 30°.
Highlights
With the advent of metamaterials, artificially engineered materials that enable the manipulation of electromagnetic waves, i.e., two-dimensional planar metamaterials referred to as metasurfaces, are garnering significant attention[1,2,3,4,5]
It is critical for the lenses to maintain the focusing features, including focal point, focal length, and focused field intensity over a wide range of incident angles
We propose a single-layer phase-gradient metasurface lens with a subwavelength thickness that is capable of effectively controlling the spatial phase and transmission distribution with low-Q resonance properties, 1Department of Information Communication Convergence Technology, Soongsil University, Seoul 0678, South Korea. 2School of Electronic Engineering, Soongsil University, Seoul 0678, South Korea. *email: hojinl@ssu.ac.kr
Summary
With the advent of metamaterials, artificially engineered materials that enable the manipulation of electromagnetic waves, i.e., two-dimensional planar metamaterials referred to as metasurfaces, are garnering significant attention[1,2,3,4,5] Owing to their capability in manipulating the phase, amplitude, and polarisation of electromagnetic waves, metasurfaces allow the rapid development of compact and flat electromagnetic devices for recent integration-optics applications[6,7,8,9]. The stacking of multiple metasurface layers has been suggested to achieve high-performance metasurface lenses[30,31], phase-shifting s urfaces[32], and transmitarray antennas[33,34] recently Despite their favourable characteristics, multilayer stacking methodologies are not an optimal solution for developing compact and lightweight microwave devices for mobile applications. We confirm that the proposed metasurface exhibits electromagnetic-wave-focusing characteristics from 35 to 40 GHz and maintains a spatially fixed focal point at 13 mm for incident angles from − 30° to 30°
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