Terahertz Plasmon Excitation by Nonlinear Mixing of Two Laser Beams in Graphene Sheet
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Terahertz Plasmon Excitation by Nonlinear Mixing of Two Laser Beams in Graphene Sheet Neha Verma1 · Anil Govindan1 · Pawan Kumar2 Received: 13 July 2020 / Accepted: 13 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Graphene is a promising material for terahertz radiation generation and has unique properties. In graphene, surface plasmon resonance (SPR) can be tuned in THz range in graphene by doping. Here we proposed a scheme of THz graphene plasmon (GP) excitation at difference frequency in graphene sheet by nonlinear mixing of two laser beams. Two laser beams that are obliquely incident, from the free space on the graphene sheet, are deposited on a dielectric substrate. These laser beams impart oscillatory velocities to electrons and exert a difference frequency ponderomotive force on the free electrons of the graphene film, the latter beats with the carrier density to produce a nonlinear current that excite THz SPs at difference frequency. The amplitude of THz graphene SPs falls monotonically because at higher frequency the coupling of SPs is weak. Keywords Plasmonics · Graphene · Terahertz plasmonics
Introduction Graphene has become the most fascinating research area in science and technology in present days because of its several unique properties [1–3] and potential applications [4–7]. One important property of graphene is that all its Dirac electrons, irrespective of their energy, have same speed, as energy versus momentum relation is linear. Graphene localizes electron motion in a plane with very small electron effective mass giving rise to high in-plane conductivity. The special spectrum of the charge carriers leads to a number of interesting transport properties. In many cases it is desirable to tightly confine the probing radiation like as surface plasmons (SPs). SPs are guided electromagnetic modes, propagate along the surface between a conductor and a dielectric or conductor and air with their field amplitude peaking at the interface and falling off exponentially away from it in either medium [8–11]. It also has
* Pawan Kumar [email protected] 1
Department of Physics, MMH College Ghaziabad, UP, Ghaziabad, India
Department of Physics, Research Centre for Compact Radiation Sources, Raj Kumar Goel Institute of Technology, Ghaziabad, UP 201003, India
2
been shown that in a noble metal film, SPs can be used to generate light radiation [12]. Moreover, graphene surface plasmons (GPs) have many advantages over metal film SPPs because the conductivity and permittivity of graphene can be controlled by adjusting external gate voltage, chemical doping, etc. The graphene GPs have the properties of extremely high confinement and low Ohmic loss because of their high carrier mobility at room temperature [13–15]. The 2D nature of graphene also gives rise to plasmons with wavelengths that are substantially smaller than free-space electromagnetic radiation of the same frequency by approximately two orders of magnitude, generating large non-local effects.
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