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The interaction between a linear electron beam and a guided electromagnetic wave is studied in the contest of exceptional points of degeneracy (EPD) supported by such an interactive system. The study focuses on the case of a linear beam…

Abstract An exceptional point of degeneracy (EPD) is induced in a system made of an electron beam interacting with an electromagnetic (EM) guided mode. This enables a degenerate synchronous regime in backward wave oscillators (BWOs) where…

Applied Physics · Physics 2021-06-16 Tarek Mealy , Ahmed F. Abdelshafy , Filippo Capolino

We show how an exceptional point of degeneracy (EPD) is formed in a system composed of an electron beam interacting with an electromagnetic mode guided in a slow wave structure (SWS) with distributed power extraction from the interaction…

Applied Physics · Physics 2020-07-29 Tarek Mealy , Ahmed F. Abdelshafy , Filippo Capolino

We analyze wavepacket propagation in traveling wave tubes (TWTs) analytically and numerically. TWT design in essence comprises a pencil-like electron beam in vacuum interacting with an electromagnetic wave guided by a slow-wave structure…

Plasma Physics · Physics 2025-04-22 Kasra Rouhi , Filippo Capolino , Alexander Figotin

We present a novel paradigm for dispersion engineering in coupled transmission lines (CTLs) based on exceptional points of degeneracy (EPDs). We develop a theory for fourth-order EPDs consisting of four Floquet-Bloch eigenmodes coalescing…

We present a transmission line theory of exceptional points of degeneracy (EPD) in coupled-mode guiding structures, i.e., a theory that illustrates the characteristics of coupled electromagnetic modes under a special dispersion degeneracy…

Optics · Physics 2017-09-15 Mohamed A. K. Othman , Filippo Capolino

The traveling tube (TWT) design in a nutshell comprises of a pencil-like electron beam (e-beam) in vacuum interacting with guiding it slow-wave structure (SWS). In our prior studies the e-beam was represented by one-dimensional electron…

Accelerator Physics · Physics 2023-11-28 Alexander Figotin

We demonstrate that a periodic waveguide comprising of uniform lossless segments together with discrete gain and radiating elements supports exceptional points of degeneracy (EPDs). We provide analytical expressions for all possible…

Applied Physics · Physics 2021-06-16 Ahmed F. Abdelshafy , Tarek Mealy , Ehsan Hafezi , Alireza Nikzamir , Filippo Capolino

We demonstrate how exceptional points of degeneracy (EPDs) are induced in a single transmission line (TL) directly by applying periodic space-time modulation to the per-unit-length distributed capacitance. In such space-time modulated…

Applied Physics · Physics 2020-12-30 Kasra Rouhi , Hamidreza Kazemi , Alexander Figotin , Filippo Capolino

Transmission peak degeneracies (TPDs) have emerged as a promising alternative to exceptional points (EPs) for non-Hermitian sensing, providing square-root frequency splitting without the eigenbasis collapse and associated noise…

We demonstrate several new aspects of exceptional points of degeneracy (EPD) pertaining to propagation in two uniform coupled transmission-line structures. We describe an EPD using two different approaches - by solving an eigenvalue problem…

Applied Physics · Physics 2018-04-11 George W. Hanson , Alexander B. Yakovlev , Mohamed Othman , Filippo Capolino

We investigate the interaction of electromagnetic waves and electron beams in a 4 meters long traveling wave tube (TWT). The device is specially designed to simulate beam-plasma experiments without appreciable noise. This TWT presents an…

Plasma Physics · Physics 2020-10-19 M. C. de Sousa , F. Doveil , Y. Elskens , I. L. Caldas

We present the theory of a new amplification regime in Travelling Wave Tubes (TWTs) composed of a slow-wave periodic structure that supports multiple electromagnetic modes that can all be synchronized with the electron beam. The interaction…

Optics · Physics 2016-04-19 Mohamed Othman , Venkata Ananth Tamma , Filippo Capolino

We present the experimental demonstration of the occurrence of exceptional points of degeneracy (EPDs) in a single resonator by introducing a linear time-periodic variation of one of its components, in contrast to EPDs in parity time…

The dispersion of a three-way waveguide is engineered to exhibit exceptional modal characteristics. Two coupled waveguides with Parity-Time (PT) symmetry have been previously demonstrated to exhibit second order exceptional points of…

Applied Physics · Physics 2022-06-08 Farshad Yazdi , Tarek Mealy , Alireza Nikzamir , Robert Marosi , Filippo Capolino

In our prior studies we synthesized special circuits possessing evolution matrices that involve nontrivial Jordan blocks and the corresponding degenerate eigenfrequencies. The degeneracy of this type is sometimes referred to as exceptional…

Classical Physics · Physics 2021-05-05 Alexander Figotin

The concept of exceptional point of degeneracy (EPD) is used to conceive a degenerate synchronization regime that is able to enhance the level of output power and power conversion efficiency for backward wave oscillators (BWOs) operating at…

Applied Physics · Physics 2021-07-07 Tarek Mealy , Ahmed F. Abdelshafy , Filippo Capolino

We demonstrate that exceptional points of degeneracy (EPDs) are obtained in two coupled waveguides without resorting to gain and loss. We show the general concept that modes resulting from a proper coupling of forward and backward waves…

Optics · Physics 2023-02-01 Tarek Mealy , Filippo Capolino

Robust transfer efficiency against the various operating conditions in a wireless power transfer system remains a fundamentally important challenge. This challenge becomes even more critical when transferring power to groups of inductively…

Applied Physics · Physics 2025-05-19 Fatemeh Mohseni , Amin Hakimi , Alireza Nikzamir , Hung Cao , Filippo Capolino

The past few years have witnessed growing interests in exceptional points (EPs) in various domains, including photonics, acoustics and electronics. However, EPs have mainly been realized based on the degeneracy of resonances of physical…

Optics · Physics 2021-09-20 Changqing Wang , William R. Sweeney , A. Douglas Stone , Lan Yang
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