DATE:

Friday, October 14, 2022

TIME:

3:30 PM

LOCATION:

GMCS 314

SPEAKER:

Dr. Filippo Capolino, Electrical Engineering and Computer Science, UC Irvine

ABSTRACT:

There are various kinds of degeneracies in systems and we discuss an important class of them: the case when two or more eigenstates of a system coalesce. Such degeneracies can happen in any kind of system: we will present a general theory but focus on cases of circuits, resonators (i.e., coupled LC resonators, electromagnetic cavities, optical ring resonators, etc.), multimode waveguides and other optical systems. This kind of exceptional degeneracy that involves also the polarization states, can happen in a surprisingly large number of systems. Such degeneracies occur in systems that can be fully passive or in systems that include gain elements; we discuss the common aspects of these two classes. The number of coalescing eigenmodes determines the order of the degeneracy. We will discuss the role of symmetries in the occurrence of exceptional points of degeneracy (EPDs) in waveguides.

For example, we explore the concept of array of antennas arranged periodically and sequentially fed by two coupled transmission lines. We investigate different radiating array structures capable of exhibiting EPDs in their dispersion diagram. We will explore a few kinds of EPDs called, the regular band edge, the stationary inflection point, and the degenerate band edge, etc.

We will also provide various experimental verifications of the occurrence of EPDs in resonators and waveguides. We will discuss possible applications in oscillators, antenna arrays, amplifiers, delay lines, etc.

In the second part of the talk we will discuss how the concept of EPD is useful to conceive very high sensitive systems that can pave the way to a new scheme of highly-sensitive sensors. Indeed, it has been apparent that resonant frequencies in a system with EPD are extremely sensitive to a perturbation. Therefore, the detection of a frequency shift in a resonator or in an oscillator based on EPD is an indicator of an applied physical, chemical or biological perturbation. Systems of EPDs can be realized using gain and loss (usually referred as EPDs induced in PT symmetric systems), time modulation of a component, etc. We will provide the experimental demonstration of such extremely sensitive systems.

Bio: Filippo Capolino received the Ph.D. degree in electrical engineering from the University of Florence, Italy, in 1997. He is currently a Professor with the Department of Electrical Engineering and Computer Science at the University of California, Irvine, CA, USA. Previously he has been an Assistant Professor at the Department of Information Engineering at the University of Siena, Italy. From 1997 to 1999, he was a Fulbright Scholar and Postdoctoral Fellow with the Department of Aerospace and Mechanical Engineering, Boston University, MA, USA. From 2000 to 2001, part of 2005 and in 2006, he was a Research Assistant Visiting Professor with the Department of Electrical and Computer Engineering, University of Houston, TX, USA. He has been a short term Visiting Professor at the Fresnel Institute, Marseille, France (2003) and at the Centre de Recherche Paul Pascal, Bordeaux, France (2010). From Jan. to Jun. 2022 he hold a Cathedra of Excellence at the University of Carlos III, Madrid, Spain.

His research interests include applied electromagnetics in general, sensors in both microwave and optical ranges, photonics, microscopy, metamaterials and their applications, traveling wave tubes, antennas, propagation, wireless systems, chip-integrated systems, etc. He is an IEEE Fellow, and he is the editor of the two volume “Metamaterials Handbook”.

HOST:

Jose Castillo

VIDEO: