284 citations · 2.2k across the 91 of their papers we have counts for
33 papers · 1 filter
Time Modulation to Manage and Increase the Power Harvested From External Vibrations
Alireza Nikzamir, Kasra Rouhi, Alexander Figotin +1
We investigate how a single resonator with a time-modulated component extracts power from an external ambient source. However, the collected power is largely dependent on the preci…
Pulse Generation Based on a Microstrip Circuit with Fourth Order Degenerate Band Edge
Dmitry Oshmarin, Alireza Nikzamir, Michael M. Green +1
A pulse generation scheme is proposed based on a structured resonance in a cavity where the non-conventional energy distribution is concentrated in its middle part. The cavity is f…
Highly Sensitive Coupled Oscillator Based on an Exceptional Point of Degeneracy and Nonlinearity
Alireza Nikzamir, Filippo Capolino
We propose a scheme for obtaining highly-sensitive oscillators in a coupled-resonator system with an exceptional point of degeneracy (EPD) and a small instability. The oscillator w…
One-transmitter Multiple-receiver Wireless Power Transfer System Using an Exceptional Point of Degeneracy
Fatemeh Mohseni, Amin Hakimi, Alireza Nikzamir +2
Robust transfer efficiency against the various operating conditions in a wireless power transfer system remains a fundamentally important challenge. This challenge becomes even mor…
An Accurate Analytic Model for Traveling Wave Tube Dispersion Relation
Ahmed F. Abdelshafy, Filippo Capolino, Alexander Figotin
Abstract -- We construct an analytical model for the dispersion of the hot modes in a traveling wave tube (TWT) based on the Lagrangian field theory, upgrading its constants to be…
Enhanced Sensitivity of Degenerate System Made of Two Unstable Resonators Coupled by Gyrator Operating at an Exceptional Point
Kasra Rouhi, Alireza Nikzamir, Alexander Figotin +1
We demonstrate that a circuit comprising two unstable LC resonators coupled via a gyrator supports an exceptional point of degeneracy (EPD) with purely real eigenfrequency. Each of…
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…
Experimental Demonstration of a New Oscillator Concept Based on Degenerate Band Edge in Microstrip Circuit
Dmitry Oshmarin, Ahmed F. Abdelshafy, Alireza Nikzamir +2
The first experimental demonstration of an oscillator based on a periodic, resonant microstrip circuit with a degenerate band edge (DBE) is presented. The DBE is a fourth-order exc…
Exceptional Points in Gyrator-Based Circuit and Nonlinear High-Sensitivity Oscillator
Alireza Nikzamir, Kasra Rouhi, Alexander Figotin +1
We present a scheme for high-sensitive oscillators based on an exceptional point of degeneracy (EPD) in a circuit made of two LC resonators coupled by a gyrator. The frequency of o…
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…
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…
Exceptional Points of Degeneracy Directly Induced by Space-Time Modulation of a Single Transmission Line
Kasra Rouhi, Hamidreza Kazemi, Alexander Figotin +1
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…
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…
Distributed Degenerate Band Edge Oscillator
Ahmed F. Abdelshafy, Dmitry Oshmarin, Mohamed A. K. Othman +2
We propose a new class of oscillators by engineering the dispersion of two-coupled periodic waveguides to exhibit a degenerate band edge (DBE). The DBE is an exceptional point of d…
Ultra-Sensitive Radio Frequency Biosensor at an Exceptional Point of Degeneracy induced by Time Modulation
Hamidreza Kazemi, Amirhossein Hajiaghajani, Mohamed Y. Nada +4
We exploit the premises of exceptional points of degeneracy (EPDs) induced in linear time-periodic (LTP) systems to achieve extremely sensitive biosensors. The EPD is formed in a s…
Experimental Demonstration of Exceptional Points of Degeneracy in Linear Time Periodic Systems and Exceptional Sensitivity
Hamidreza Kazemi, Mohamed Y. Nada, Alireza Nikzamir +2
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…
Helicity Maximization Below the Diffraction Limit
Mina Hanifeh, Mohammad Albooyeh, Filippo Capolino
Optimally-chiral electromagnetic fields with maximized helicity density, recently introduced in [1], enable chirality characterization of optically small nanoparticles. Here, we de…
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…
Illusion Mechanisms with Cylindrical Metasurfaces: A General Synthesis Approach
Mahdi Safari, Hamidreza Kazemi, Ali Abdolali +2
We explore the use of cylindrical metasurfaces in providing several illusion mechanisms including scattering cancellation and creating fictitious line sources. We present the gener…
Simultaneous Perfect Bending and Polarization Rotation of Electromagnetic Wavefront using Chiral Gradient Metasurfaces
Hamidreza Kazemi, Mohammad Albooyeh, Filippo Capolino
We introduce chiral gradient metasurfaces that allow perfect transmission of all the incident wave into a desired direction and simultaneous perfect rotation of the polarization of…