Abstract
Electromagnetic waves carrying an orbital angular momentum (OAM) are of great interest. However, most OAM antennas present disadvantages such as a complicated structure, low efficiency, and large divergence angle, which prevents their practical applications. So far, there are few papers and research focuses on the problem of the divergence angle. Herein, a metasurface antenna is proposed to obtain the OAM beams with a small divergence angle. The circular arrangement and phase gradient were used to simplify the structure of the metasurface and obtain the small divergence angle, respectively. The proposed metasurface antenna presents a high transmission coefficient and effectively decreases the divergence angle of the OAM beam. All the theoretical analyses and derivation calculations were validated by both simulations and experiments. This compact structure paves the way to generate OAM beams with a small divergence angle.
Highlights
Light beams carrying orbital angular momentum (OAM) have attracted extensive attention owing to their special electromagnetic properties [1,2,3,4]
We designed a simple metasurface antenna presenting the capacity in generating small-divergency-angle OAM beams
The circular arrangement of the unit cells was adopted in the design of the metasurface
Summary
Light beams carrying orbital angular momentum (OAM) have attracted extensive attention owing to their special electromagnetic properties [1,2,3,4]. Due to the orthogonality between different radio OAM modes, every OAM beam with different modes can be regarded as a communication channel. Infinite modes can provide infinite channels, which can infinitely expand the communication capacity without increasing the bandwidth [8, 9]. This characteristic of OAM beams may bring great advances in traditional wireless communication [10]. There are debates concerning the capability of OAMs to effectively increase the communication capacity of multiple-input-multiple-output wireless systems [11, 12], OAM beams exhibit distinct advantages in many fields such as particle trapping, optical imaging, and microscopic particle rotation [13,14,15,16]
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