Ultra-compact graphene plasmonic filter integrated in a waveguide*

Project supported by the National Basic Key Research Program of China (Grant No. 2015CB932400), the National Key Research and Development Program of China (Grant No. 2016YFA0201600), the National Natural Science Foundation of China (Grant Nos. 51372045, 11504063, and 11674073), the Key Program of the Bureau of Frontier Sciences and Education, Chinese Academy of Sciences (Grant No. QYZDBSSW- SLH021), and the Science and Technology Projects of Beijing City, China (Grant No. Z161100002116016).
Liao Baoxin1, 2, Guo Xiangdong1, 2, Hu Hai1, 2, Liu Ning1, 2, Chen Ke1, 2, Yang Xiaoxia1, 2, ‡, Dai Qing1, 2, †
       

(color online) (a) Schematic of the graphene plasmonic waveguide filter. A rectangular hole in the nanoribbon acts as a filter. Gate voltage V is used to tune the Fermi level of the graphene. We set SiO2 as the substrate with the dielectric εsub = 4. The width, length, and thickness of SiO2 substrate are 300 nm, 470 nm, and 100 nm, respectively. The dielectric of air on the top of graphene is εair = 1. (b) Top view of the plasmonic waveguide filter. The length and width of the cavity are l and d, respectively. Width of the waveguide is W. Ports 1 and 2 are source port and transmission port, respectively. The distance between these two ports was L = 450 nm. (c) Effective refractive index (neff) of the modes supported by graphene ribbons with different widths. The Fermi level of graphene is EF = 0.35 eV. The mode frequency is 20 THz. Inset shows the EZ profile of the two modes supported by the graphene ribbon with W = 150 nm. The cut-off width of mode #2 is 118 nm. (d) Effective refractive index (orange) and corresponding loss (blue) of mode #1 as a function of incident frequency. The width of ribbon is 50 nm.