Generation of nondiffraction beams by using graphene-based metasurface in terahertz regime

摘要

In this article, a graphene-based reflective metasurface which can generate Bessel beams at arbitrary directions is proposed at 1.52 THz. It chooses the classical cross structure as the unit cell and extends the coverage of the reflection phase to 360 degrees by adjusting two key parameters while maintaining a relatively high-reflection amplitude. Combined with the excellent impedance characteristics of graphene in the terahertz regime and the long energy transmission distance of the nondiffraction beam, the reflective metasurface finally realize the pseudo-Bessel beam with a maximum propagation distance of about 3358.85 um and a deflection of about 15 degrees in yoz-plane as expected. Two forms of efficiency are proposed for the metasurface, one is the focusing efficiency, the other is the conventional radiation efficiency. The simulation results show that the former shows a trend of increasing first and then decreasing, which conforms to the beam-forming property of Bessel beam; the latter can be basically maintained at high value of 70% within the nondiffraction propagation distance, which conforms to the energy transmission characteristic of the nondiffraction beam. All the studies show that the graphene-based metasurface combined with the nondiffraction theory has the advantages of highly controllable beam deflection, long focusing distance, and high-energy transfer efficiency in the terahertz regime, so it will have a broad application prospect in terahertz telecommunication, wireless energy transmission, near-field detecting, imaging and many other fields.