Outstanding slow-light effect for graphene metasurface in terahertz

So as to realize good slow-light effects in a simple graphene-based nano-structure, a n-shaped graphene metasurface is proposed in this paper. Through the detailed studies, plasmon induced transparency (PIT) can be observed in the proposed metasurface, and the bright-dark mode is used to explain the physical mechanism of this phenomenon. Especially, a convenient modulation for PIT can be realized through Fermi level and carrier mobility. In addition, a developed coupled mode theory (CMT) is established for demonstrating the optical responses of the n-shaped graphene metasurface, and the theoretical results are in well agreement with the numerical results. At last, an excellent slow-light effect with ultra-high group index of 2510 can be achieved in the proposed simple graphene-based metasurface. The outstanding performance of slow-light effect may play important roles for designing the plasmonic slow-light devices in terahertz.