▎ 摘　　要

The multi-wavelength tunable plasmonically induced transparency (PIT) phenomena in two-ring and three-ring systems at infrared range were theoretically and numerically investigated. In the two-ring system, changing the bias voltage of graphene ring or the separation between graphene rings would induce an off-to-on PIT optical response. An asymmetry factor has been introduced to explain the corresponding transmission spectra. In the three-ring system, by bringing in a new asymmetry factor, multiple new PIT windows would arise at the left or right side of the original PIT windows. Numerical simulation by finite element method was conducted to verify our designs. Those proposed structures hence have potential in ultra-compact graphene optoelectronic devices at the infrared range. (C) 2015 AIP Publishing LLC.