Quantum Theory of the Effect of Increasing Weak Electromagnetic Wave by a Strong Laser Radiation in 2D Graphene

Abstract

Analytic expressions for the absorption coefficient (AC) of a weak electromagnetic wave (EMW) in 2D Graphene under influence of strong laser radiation are calculated using the quantum kinetic equation (QKE) in the case of electron-optical phonon scattering in both the absence and presence of a magnetic field perpendicular to the graphene sheet. The dependence of the AC on the intensity E₀₂ and the frequency Ω₂ of a weak EMW, on the intensity E₀₁ and the frequency Ω₁ of a strong laser radiation, on the temperature T of the system is obtained. These results are investigated from low temperature to high temperature. These results are obtained from the QKE method, which broke the limit of the Boltzmann kinetic equations (only investigated in the high-temperature domain). Besides, the numerical results show that the AC of a weak EMW in 2D Graphene can have negative values. This demonstrates the possibility of increasing weak EMW by strong laser radiation in 2D Graphene. This is different from a similar problem in bulk semiconductors and the case without strong laser radiation. In the case of the presence of an external magnetic field, the numerical calculation results also show the appearance of the peak spectral lines that obey the magneto-phonon resonance conditions. The appearance of these resonance peaks provides a model illustrating the dependence of the Half-Width at Half Maximum (HWHM) on the external magnetic field. This is an important criterion for the fabrication of graphene-related electronic components and orientation for future experiments.

Fig. 7 The dependence of the Half-Width at Half Maximum (HWHM) on the magnetic field at T = 4.2 K for the transition n = 0 and n′ = 1. The squares, triangles and circles respectively are our calculations in the case of the system without or under the influence of the laser radiation field and the experimental data taken from Ref. [23].