Modulation of terahertz radiation from graphene surface plasmon polaritons via surface acoustic wave

Abstract

We present a theoretical study of terahertz (THz) radiation induced by surface plasmon polaritons (SPPs) on a graphene layer under modulation by a surface acoustic wave (SAW). In our gedanken experiment, SPPs are excited by an electron beam moving on a graphene layer situated on a piezoelectric MoS 2 flake. Under modulation by the SAW field, charge carriers are periodically distributed over the MoS 2 flake, and this causes periodically distributed permittivity. The periodic permittivity structure of the MoS 2 flake folds the SPP dispersion curve back into the center of the first Brillouin zone, in a manner analogous to a crystal, leading to THz radiation emission with conservation of the wavevectors between the SPPs and the electromagnetic waves. Both the frequency and the intensity of the THz radiation are tuned by adjusting the chemical potential of the graphene layer, the MoS 2 flake doping density, and the wavelength and period of the external SAW field. A maximum energy conversion efficiency as high as ninety percent was obtained from our model calculations. These results indicate an opportunity to develop highly tunable and integratable THz sources based on graphene devices.

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“…As the operating frequency of the proposed MA locates mainly in THz range and the MA works at room temperature (T=300K), the condition Ef ≫ћ and Ef ≫kBT is fulfilled. Consequently, the Kubo formula can be simplified to a Drude-like equation [29][30][31]:…”

Inversion Method Characterization of Graphene-Based Coordination Absorbers Incorporating Periodically Patterned Metal Ring Metasurfaces

“…As we only consider highly doped graphene, we should take into account that E f ≫ k B T and E f ≫ ℏ ω . Therefore, the Kubo equation can be simplified to a Drude-like equation [ 38 , 39 , 40 ]: where τ = μE f /( ), E f is set to 0.15 eV, the media carrier mobility μ is set to 1318 cm 2 V −1 s −1 [ 41 ], and the graphene Fermi velocity v F is set to 1 × 10 6 ms −1 . As shown in Figure 1 a, the periodic boundary conditions for the unit cell are along the X and Y axes.…”

“…As we only consider highly doped graphene, we should take into account that E f k B T and E f hω. Therefore, the Kubo equation can be simplified to a Drude-like equation [38][39][40]:…”