Complementary graphene metamaterial with independently tunable dual absorption bands at terahertz frequency

Implementation of Atomically Thick Graphene and Its Derivatives in Electromagnetic Absorbers

“…By combining the continuous graphene layer with patterned metallic unit cell structures, EM wave absorbers with reconfigurable operation frequency [20,29,31,124] or bandwidth [95,105] can be achieved. The devices with two independently-tunable resonant frequencies at THz [125,126] and mid-infrared [127] frequencies are also explored with full-wave simulations, demonstrating excellent stability on one resonant frequency while the other frequency is tuned. In addition, by varying the chemical potential of graphene, some metasurface absorbers also exhibit switching performance and operate as either fine absorbers or reflectors [104,113,114,128,129].…”

Design of a Broadband Tunable Terahertz Metamaterial Absorber Based on Complementary Structural Graphene

“…In our work, T is fixed at 300 K and τ is assumed to be 0.5 ps. Thus, the relative permittivity of graphene can be obtained by ε g = 1 + jσ g / ωε 0 t g [ 35 ].…”

“…However, most traditional MMAs have some drawbacks in that the absorption level and working frequency are uncontrolled apart from changing the geometrical parameters of the unit-cell structure, which will limit their practical applications [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Nowadays, to achieve tunable properties of the MMAs, some effective methods have been proposed and demonstrated, such as machine [ 23 ], laser [ 24 , 25 , 26 ], temperature [ 27 , 28 ], and voltage modulation [ 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. However, the realization of the broadband tunable and strong absorption of the MMA is still a great challenge.…”

“…Based on effective media theory, the complex permittivity ε ( ω ) and permeability μ ( ω ) of these MMAs can be changed when the conductivity of graphene sheet is effectively controlled by gate voltage or chemical doping [ 24 ]. Recently, some MMA-based-graphene have been proposed, which can achieve strong and tunable absorption by changing the chemical potential ( μ c ) [ 30 , 31 , 32 , 33 , 34 , 35 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. According to the well-known Kubo formula, the real part of permittivity of a graphene sheet is negative from THz to optical frequencies [ 30 ].…”

“…Nevertheless, the above mentioned multiband or broadband THz MMAs based on structural or patterned graphene are usually discontinuous or multilayer, which causes complexity of fabrication in practical applications. In addition, it is difficult to tune the conductivity of graphene via extra bias voltage [ 35 , 39 , 41 ].…”