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ALT'23 The 30th International Conference on Advanced Laser Technologies
N-I-15
Drift-current-induced amplification and lasing of TE electromagnetic modes in graphene
I. Moiseenko1, D. Fateev1, V. Popov1
1-Kotelnikov Institute of Radio Engineering and Electronics (Saratov Branch) of the Russian Academy of Sciences,
Saratov, Russia
email address: popov_slava@yahoo.co.uk
The dispersion, excitation, and amplification of electromagnetic transverse electric (TE) modes at terahertz (THz) frequencies in graphene in the hydrodynamic (HD) regime, with a direct electric current flowing perpendicular to the TE mode wavevector, were theoretically investigated [1]. The expression for the nonlocal HD conductivity of graphene with a direct electric current (DC) flowing perpendicular to the TE mode wavevector was derived. The direct electric current in graphene leads to the capacitive nature of the graphene HD conductivity at THz frequencies, which makes TE modes exist in this frequency range [2]. The real part of graphene conductivity can be negative at THz frequencies due to DC in graphene which leads to amplification and lasing of THz radiation. The excitation of TE modes in graphene by an incident THz wave was modeled for the attenuated total reflection geometry. A new physical mechanism of TE mode amplification in graphene effective for a low value of carrier drift velocity was predicted. Terahertz lasing regimes with TE modes in graphene structure with direct electric current were found.
We study for the first time the interaction between the waveguide modes of graphene structure and freely propagating THz electromagnetic waves (this interaction takes place within the light cone) [3]. We revealed a new and rather unexpected physical phenomenon by showing that freely incident THz electromagnetic waves can resonate with the surface TE modes of the graphene waveguide in virtue of these modes having their dispersions in the vicinity of the light cone. The dispersion and amplification of surface TE modes in a dielectric waveguide covered with two graphene layers biased by DC, as well as the amplification and lasing of incident THz wave by excitation of TE mode resonances, are investigated. The results of this work can be used to create miniature technologically feasible sources and amplifiers of THz radiation. Such structure can be of great practical importance because an external THz wave can be amplified or generated in lasing process without using special coupling elements commonly needed for ensuring the interaction between external THz wave and surface waveguide modes. The use of a two-layer graphene structure makes it possible to reduce the charge-carrier drift velocity required for reaching the lasing threshold at those resonances, as compared to a structure with a single graphene layer.
This work was financially supported by the Russian Science Foundation (Project No. 22-19-00611).
[1] I.M. Moiseenko, V.V. Popov, D.V. Fateev, Terahertz transverse electric modes in graphene with DC current in hydrodynamic regime, J. Phys.: Condens. Matter, vol. 34, pp. 295301-1 - 295301-6, (2022).
[2] S.A. Mikhailov, K. Ziegler, New electromagnetic mode in graphene, Phys. Rev. Lett., vol. 99, pp. 016803-1 - 016803-4 (2007).
[3] I.M. Moiseenko, V.V. Popov, D.V. Fateev, Terahertz amplification and lasing by using transverse electric modes in a two-layer-graphene-dielectric waveguide structure with direct current, J. Phys.: Condens. Matter, vol. 35, pp. 255301-1 - 255301-6, (2023).
