Low Threshold RF and Optical Oscillators Using Exceptional Points of Degeneracy


Jacobs Hall, Room 4309, Jacobs School of Engineering, 9500 Gilman Dr, La Jolla, San Diego, California 92093

Sponsored By:
Professor Gabriel Rebeiz

Filippo Capolino, Ph.D.
University of Florence, Italy
Filippo Capolino


We present a unified theory of exceptional points of degeneracy (EPD) in coupled-mode guiding structures, i.e., a theory that illustrates electromagnetic mode characteristics under the special dispersion degeneracy condition of state eigenvectors. This concept finds a variety of applications in both optics and microwave regimes.

In particular, we investigate degeneracies of second, third and fourth order in electromagnetic systems. We also show the concept of Parity-Time (PT)-symmetry in coupled uniform transmission lines with balanced and symmetric gain-loss and how this condition is associated with various order EPDs. Fourth order degeneracies in periodic couple waveguides are also demonstrated, namely the degenerate band edge (DBE) in both lossless and gain-loss balanced structures. We also show how such fourth order EPD is perturbed due to tolerances and losses using full-wave simulation and demonstrate that experimentally as well in a metallic waveguide with DBE.

These special degeneracy conditions are promising to enhance the performance of a variety of microwave and optical resonators and devices such as oscillators, including lasers, amplifiers and sensors. In particular we will show how to use the DBE in a pulse compression application: when operating at the DBE, the waveguide system excited by an external generator accumulates energy over a length of time. By breaking the DBE (i.e., by using varactors) the energy is no longer trapped, enabling very short (in time) output pulse with high power pulse compression ratio. We will show also how the DBE leads to oscillators with low threshold and possibly high efficiency. We have use this concept in various kind of oscillators, with lumped elements, microwave circuits, and lasers. We are currently exploring other applications like wide band high power amplifiers in slow-wave structures with an electron beam using a third order degeneracy.


Speaker Bio:
Filippo Capolino received the Ph.D. degree in electrical engineering from the University of Florence, Italy, in 1997. He is currently an Associate 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).
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.

Travis Spackman (tspackman@eng.ucsd.edu)