22 citations · 138 across the 22 of their papers we have counts for
23 papers
Lasing at a Stationary Inflection Point: erratum
Albert Herrero-Parareda, Nathaniel Furman, Tarek Mealy +4
This erratum provides an updated fitting function for the lasing threshold of finite-length cavities operating at a stationary inflection point (SIP) or regular band edge (RBE) res…
Small-Signal Model for Inhomogeneous Helix Traveling-Wave Tubes using Transfer Matrices
Robert Marosi, Kasra Rouhi, Tarek Mealy +2
Abstract We introduce a practical method for modeling the small-signal behavior of frequency-dispersive and inhomogeneous helix-type traveling-wave tube (TWT) amplifiers based on a…
Parametric Modeling of Serpentine Waveguide Traveling Wave Tubes
Kasra Rouhi, Robert Marosi, Tarek Mealy +2
A simple and fast model for numerically calculating small-signal gain in serpentine waveguide traveling-wave tubes (TWTs) is described. In the framework of the Pierce model, we con…
Frozen Mode Regime in an Optical Waveguide With Distributed Bragg Reflector
Nathaniel Furman, Tarek Mealy, Md Shafiqul Islam +5
We introduce a glide symmetric optical waveguide exhibiting a stationary inflection point (SIP) in the Bloch wavenumber dispersion relation. An SIP is a third order exceptional poi…
Lasing at a Stationary Inflection Point
Albert Herrero-Parareda, Nathaniel Furman, Tarek Mealy +4
The concept of lasers based on the frozen mode regime in active periodic optical waveguides with a 3rd-order exceptional point of degeneracy (EPD) is advanced. The frozen mode regi…
Design of a Modified Coupled Resonators Optical Waveguide Supporting a Frozen Mode
Mohamed Y. Nada, Tarek Mealy, Md Shafiqul Islam +5
We design a three-way silicon optical waveguide with the Bloch dispersion relation supporting a stationary inflection point (SIP). The SIP is a third order exceptional point of deg…
Analytical Solution for Space-Charge Waves in a Two-Stream Cylindrical Electron Beam
Tarek Mealy, Robert Marosi, Kasra Rouhi +1
We present an analytical method to compute the wavenumbers and electric fields of the space-charge-wave eigenmodes supported by a two-stream electron beam, consisting of a solid in…
Exceptional Points of Degeneracy with Indirect Bandgap Induced By Mixing Forward and Backward Propagating Waves
Tarek Mealy, 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 result…
Reduced Plasma Frequency Calculation Based on Particle-In-Cell Simulations
Tarek Mealy, Robert Marosi, Filippo Capolino
We propose a scheme to calculate the reduced plasma frequency of a cylindrical-shaped electron beam flowing inside of a cylindrical tunnel, based on results obtained from Particle-…
Degenerate Distributed Feedback Photonic Structure with Double Grating Exhibiting Degenerate Band Edge
Tarek Mealy, Filippo Capolino
We propose a degenerate version of the Bragg condition, associated to a degenerate band edge (DBE). A standard Bragg condition can be implemented using a periodic grating that oper…
Three-Way Serpentine Slow-Wave Structures with Stationary Inflection Point and Enhanced Interaction Impedance
Robert Marosi, Tarek Mealy, Alexander Figotin +1
We introduce two novel variants of the serpentine waveguide slow-wave structure (SWS), often utilized in millimeter-wave traveling-wave tubes (TWTs), with an enhanced interaction i…
Third Order Modal Exceptional Degeneracy in Waveguides with Glide-Time Symmetry
Farshad Yazdi, Tarek Mealy, Alireza Nikzamir +2
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 demon…
Triple Ladder Lumped Circuit with Sixth Order Modal Exceptional Degeneracy
Farshad Yazdi, Alireza Nikzamir, Tarek Mealy +2
We introduce a circuit topology based on a simple triple-ladder circuit realized with lumped reactive components that provides a sixth order degenerate band-edge (6DBE). The 6DBE i…
Exceptional Degeneracy in a Waveguide Periodically Loaded with Discrete Gain and Radiation Loss Elements
Ahmed F. Abdelshafy, Tarek Mealy, Ehsan Hafezi +2
We demonstrate that a periodic waveguide comprising of uniform lossless segments together with discrete gain and radiating elements supports exceptional points of degeneracy (EPDs)…
High Power Backward Wave Oscillator using Folded Waveguide with Distributed Power Extraction Operating at an Exceptional Point
Tarek Mealy, Ahmed F. Abdelshafy, Filippo Capolino
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…
Exceptional Degeneracies in Traveling Wave Tubes with Dispersive Slow-Wave Structure Including Space-Charge Effect
Kasra Rouhi, Robert Marosi, Tarek Mealy +3
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 interactiv…
Traveling Wave Tube Eigenmode Solver for Interacting Hot Slow Wave Structure Based on Particle-In-Cell Simulations
Tarek Mealy, Filippo Capolino
A scheme to characterize the dynamics of the electron beam-electromagnetic power exchange along a traveling wave tube (TWT) is proposed. The method is based on defining a state vec…
Frozen Mode in Three-Way Periodic Microstrip Coupled Waveguide
Mohamed Y. Nada, Tarek Mealy, Filippo Capolino
We demonstrate theoretically and experimentally that a periodic three-way microstrip coupled waveguide exhibits a stationary inflection point (SIP). The SIP is a third order except…
Exceptional Point of Degeneracy in Linear-Beam Tubes for High Power Backward-Wave Oscillators
Tarek Mealy, Ahmed F. Abdelshafy, Filippo Capolino
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 sy…
General Conditions to Realize Exceptional Points of Degeneracy in Two Uniform Coupled Transmission Lines
Tarek Mealy, Filippo Capolino
We present the general conditions to realize a fourth order exceptional point of degeneracy (EPD) in two uniform (i.e., invariant along z) lossless and gainless coupled transmissio…
Experimental Demonstration of Sixth Order Degenerate Band Edge in Coupled Microstrip Waveguides
Farshad Yazdi, Dmitry Oshmarin, Tarek Mealy +3
We show the physical realization and experimental demonstration of an exceptional point of 6th order degeneracy in a triple ladder (or three-way) microwave waveguide realized using…
Exceptional Point of Degeneracy in Backward-Wave Oscillator with Distributed Power Extraction
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 (SW…
Exceptional Points of Degeneracy Induced by Linear Time-Periodic Variation Hamidreza
Hamidreza Kazemi, Mohamed Y. Nada, Tarek Mealy +2
We present a general theory of exceptional points of degeneracy (EPD) in periodically time-variant systems that do not necessarily require the presence of loss or gain, and we show…