Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi-linear electromagnetic mod
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Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi‑linear electromagnetic modeling Guennadi A. Kouzaev1 Received: 22 May 2020 / Accepted: 18 October 2020 © The Author(s) 2020
Abstract Novel rectangular waveguides with graphene inserts biased by light are proposed herein. The graphene films short the conductor plates of waveguides and support the localized transverse-electric modes. Their electric fields are parallel to the wide walls of these waveguides, and the eigenmodes have decreased conductor loss. The designs do not involve the conductor and graphene strips with their sharp edges, and the loss associated with the current crowding effect is excluded. The waveguides are treated in the quasi-linear regime using a rigorous field matching method, and the complex dispersion eigenmodal equation is solved using a validated iteration algorithm. At the terahertz frequencies of amplification, where the real part of graphene conductivity is negative, a gain increase is found with the eigenmodal number. This gain can be tuned by the waveguide geometry, dielectric filling, and the level of quasi-Fermi energy. The ideal waveguide theory is corrected using a perturbation approach and the Drude model of surface resistance of waveguide plates. Keywords Terahertz · Graphene · Waveguides · Amplification · Lasing · Semi-analytical modeling
1 Introduction Today, many efforts are being devoted to developing passive and active graphene devices [1–3]. These include interconnects, antennas, attenuators, transistors [4, 5], and nonlinear devices [6]. Many techniques are used to realize these and other prospective components, such as chemical doping [7], integration of graphene with other materials [3], and graphene nanoribbon or nanodot elements [8]. Some problems of active and passive components are solved by staking the graphene nanosheets or using the quantum–mechanical interaction of graphene layers [9]. An analysis of the current state of graphene and other one-atom materials is given in [3], where the industrial mass production of 2-D materials and components is predicted for the next 30 years of this century. The development of new components, with their analytical and semi-analytical models, will necessarily make these efforts easier. For instance, to avoid the lengthy ab initio * Guennadi A. Kouzaev [email protected] 1
Department of Electronic Systems, Norwegian University of Science and Technology-NTNU, No‑7491, Trondheim, Norway
computation of graphene components, the semiclassical scalar and dyadic models of conductivity of graphene are known based on the approach described by Kubo [10–13]. A theory based on a non-Kubo technique is discussed in Ref. [14]. In recent years, much attention has been paid to the experimental verification of conductivity models [15–17] and theories of guided plasmons in a multi-strip environment [18]. For instance, in Ref. [15], a difference between the results provided by a Kubo formula and the measurements is explained with the random m
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