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The power conversion of a terahertz wave normally incident on a periodic graphene structure to propagating-plasmon power is theoretically studied. The conditions of the maximum conversion of the incident radiation power to the propagating-plasmon power and excitation condition of unidirectional traveling plasmon are determined. It is found that up to 15% of the incident wave power can be converted to propagating-plasmon power.

The rectification of terahertz radiation in a periodically almost-depleted graphene structures with dual grating gate is studied. Plasmonic electron-hole ratchet based rectified current grows with decreasing the Fermi energy of charge carriers in the gated parts of graphene. It is shown that the charge carriers accumulated at boundaries of depleted parts of graphene enhance the magnitude and inhomogeneity of oscillating electric field of the plasmon, which leads to significant growth in the rectification efficiency. Interaction of plasmon modes in different gated parts of graphene can increase the rectification efficiency due to excitation of the hybrid plasmon modes.

The achievement of the laser regime upon the excitation of weak plasmon modes in structures based on active graphene has been theoretically investigated. The weak ``acoustic'' plasmon modes in two-layer structures and weak ``nonradiative'' gated modes in noncentrosymmetric grating-gated structures are investigated. The radiative damping and gain rate of strong and weak plasmon modes in graphene structures are calculated. The possibilities of changing the radiative damping of plasmon modes by changing the geometry of the structure are considered. It is proposed to use weak plasmon modes with low radiative damping for decreasing the threshold for the laser plasmon regime in periodic graphene structures.

We demonstrate that the periodic graphene structure with asymmetric unit cell can effectively transform the incident electromagnetic wave into propagating plasmon. Periodic graphene structure with asymmetric unit cell and active graphene transforms the incident electromagnetic wave into amplifying propagating plasmon.

Weak plasmon modes in periodic structures with a two-dimensional electron gas without an inversion center are studied theoretically. The asymmetry of the electric field and Fourier harmonics of weak plasmon modes can lead to the excitation of a travelling plasmon by an electromagnetic wave normally incident on the structure and to the appearance of nonlinear effects leading to the rectification of the incident radiation. The low radiation damping of weak plasmon modes can be used to increase the efficiency of terahertz plasmon amplifiers.

The rectification of terahertz radiation due to plasmonic nonlinearities in a periodic graphene structure with a dual-grating gate and an asymmetric unit cell is considered. The influence of unit-cell asymmetry on the plasmonic rectification of the terahertz radiation near higher plasmonic resonances is considered for the cases of electron and hole conduction in parts of the graphene unit cell. The current responsivity of the rectification of terahertz radiation due to the plasmonic effects of differential charge-carrier drag and electron–hole ratchet is calculated.

The amplification of the unidirectionally propagating plasmon modes excited by the incident terahertz wave in a periodical structure with an active graphene is studied theoretically. The amplification of propagating plasmon modes is due to radiative recombination in inverted graphene.

Plasmonic transport is considered as a replacement for electronic transport in low-dimensional systems like field-effect transistors, as plasmons are faster than electrons. Plasmons in graphene are promising for use at THz frequencies, but this research is held back by the primitive state of circuitry for plasmonic devices. This study employs an asymmetric periodic grating to solve the problem of effective excitation of propagating plasmons in graphene. The important role of ``dark'' (weakly radiative) plasmon modes in efficient excitation is revealed. The approach outlined here could help to fill the need for THz plasmon sources, for tomorrow's devices.

The transformation of normally incident electromagnetic wave into propagating plasmon in periodical graphene structure with double grating gate is theoretically investigated. The most effective transformation appears in case of excitation plasmon modes with the wavevectors quantized with structure period. Blocking the reflection and the transmission of electromagnetic wave through the graphene structure by metal back gate and Fabry-Perot resonator are used. We found the 72% transformation of the incident wave radiation power into the power of unidirectionally-travelling plasmon for 1 ps momentum relaxation time in graphene.

The amplification of the unidirectionally propagating plasmon modes excited by the incident terahertz wave in a periodical structure with an active graphene is studied theoretically. The effective excitation of propagating plasmon mode occurs due to the simultaneous excitation of “radiative” and “nonradiative” plasmon modes at the same frequency. The amplification of propagating plasmon modes is due to radiative recombination in inverted graphene.

The problem of the rectification of terahertz radiation due to plasmonic nonlinearities in a periodic two-dimensional electron system upon the excitation of plasma oscillations by the attenuated total reflection method is solved. This model allows the independent study of different plasmonic rectification mechanisms, i.e., plasmonic electron drag and plasmonic ratchet effects.

Rectification of terahertz radiation in a spatially periodic graphene structure with dual grating gate is theoretically studied. The calculated current responsivity is an order of magnitude greater than the responsivity of conventional plasmonic detector based on the field-effect-transistor array.

The plasmonic terahertz detection in a dual grating-gate graphene structure with an asymmetric unit cell is studied theoretically using a hydrodynamic approach. Two plasmonic effects of rectification of terahertz radiation—the differential plasmonic drag of charge carriers and the plasmonic electron-hole ratchet—are introduced and investigated. The plasmonic electron-hole ratchet effect appears only if the carriers of opposite signs are there in graphene under different subgratings of the dual grating gate. We demonstrate that the electron-hole ratchet effect dominates in the terahertz frequency range.