Electrical activating of the “nonradiative” terahertz plasmon modes in a periodic grating-gate graphene structure with asymmetrical gating

Electrical tuning the radiative damping of “nonradiative” (weak) terahertz plasmon mode in a periodic dual-grating-gate graphene structure is studied theoretically. Tuning the dc voltage value applied to one of the gate subgratings can change the radiative damping of the weak plasmon mode from zero to the dissipative damping of the plasmons in high-quality graphene allowing for maximum energy conversion from the incident wave to “nonradiative” plasmon mode. Radiative damping increases due to the increase of the dipole moment of this mode by virtue of its asymmetrical gating. Using the weak plasmon modes is important for effective excitation of the plasmon resonances in high-quality graphene as well as for realizing the concept of low-threshold terahertz lasers based on graphene plasmonic structures.