Nonreciprocal guided waves in the presence of swift electron beams

Breaking the reciprocity of electromagnetic interactions is of paramount importance in photonic and microwave technologies, as it enables unidirectional power flows and other unique electromagnetic phenomena. Here we explore a method to break the reciprocity of electromagnetic guided waves utilizing...

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Bibliographic Details
Published in:Physical review. B 2021-06, Vol.103 (21), Article 214303
Main Authors: Fallah, Asma, Kiasat, Yasaman, Silveirinha, Mário G., Engheta, Nader
Format: Article
Language:English
Subjects:
Accelerators
Broadband
Electromagnetic interactions
Electromagnetic properties
Electromagnetic radiation
Electron accelerators
Electron beams
Frequency ranges
Microwave photonics
Optoelectronics
Power flow
Reciprocity
Traveling wave tubes
Traveling waves
Wave propagation
Waveguides
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Summary:Breaking the reciprocity of electromagnetic interactions is of paramount importance in photonic and microwave technologies, as it enables unidirectional power flows and other unique electromagnetic phenomena. Here we explore a method to break the reciprocity of electromagnetic guided waves utilizing an electron beam with a constant velocity. By introducing an effective dynamic conductivity for the beam, we theoretically demonstrate how nonreciprocal guided waves and a one-way propagating regime can be achieved through the interaction of swift electrons with electromagnetic waves in two-dimensional (2D) parallel-plate and three-dimensional (3D) circular-cylindrical waveguides. Unlike the conventional electron beam structures such as traveling wave tubes and electron accelerators, here the goal is neither to generate and/or amplify the wave nor to accelerate electrons. Instead, we study the salient features of nonreciprocity and unidirectionality of guided waves in such structures. The relevant electromagnetic properties such as the modal dispersion, the field distributions, the operating frequency range, and the nonreciprocity strength and its dependence on the electron velocity and number density are presented and discussed. Moreover, we compare the dispersion characteristics of waves in such structures with some electric-current-based scenarios in materials reported earlier. This broadband tunable magnet-free method offers a unique opportunity to have a switchable strong nonreciprocal response in optoelectronics, nanophotonics, and THz systems.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.103.214303