Magnetless Nonreciprocal Devices Based on Time Modulation and Nonlinearities

Reciprocity is a fundamental principle in electromagnetics, requiring that the response of a structure is symmetric when source and observation points are interchanged. It is of major significance for the analysis, design and operation of electromagnetic systems, but at the same time it poses fundamental limitations on the ways we handle and process signals. Nonreciprocal devices, which break this symmetry, are necessary for protection of sources from undesired reflections and the implementation of full-duplex systems. To date such devices are realized through magnetic materials, making their integration challenging. In this talk I will show how it is possible to address this problem and design magnetless nonreciprocal devices by using time modulation and optical nonlinearities. I will discuss how time modulation allows to impart an effective momentum to a structure and break reciprocity. I will show how this approach can be implemented at different frequency bands and over different platforms, including printed circuit boards, CMOS circuits, micromechanical resonators and silicon photonics. Then, I will present how we can remove the requirement of an external bias and realize all-passive nonreciprocal devices by introducing nonlinearities in asymmetric structures. I will discuss fundamental limitations of these devices, stemming from time-reversal symmetry, and show how they can be partially overcome. I will conclude my talk by providing an outlook for future opportunities in this rapidly advancing research field.
Professor Dimitrios Sounas is an assistant professor in the ECE Department at Wayne State University. Before that, he was a Postdoctoral Fellow and a Research Scientist at the University of Texas at Austin. He has received his Ph.D. and Bachelor's degrees in Electrical and Computer Engineering with highest honors from the Aristotle University of Thessaloniki, Thessaloniki, Greece, in 2009.
His major contributions can be found in the area of magnetless nonreciprocal components and have attracted significant interest from industry for inclusion in the next-generation wireless communication systems. He has contributed to the founding of Silicon Audio RF Circulator, Austin, TX, USA, specializing in the design of angular-momentum circulators for RF and acoustical systems. He has authored or co-authored 73 journal papers, 133 conference papers, 2 book chapters, and 6 patents, among which papers in highly selective journals, including Science, various Nature journals, various Physical Review journals, and IEEE transactions. His current research interests include smart and active electromagnetic and optical devices for various kinds of applications in communication, biomedical and sensing systems.
Dimitrios Sounas is a Senior Member of IEEE. He has chaired various sessions in international symposia and organized a special session about graphene devices during the EuCAP 2016 International Symposium. He is an Associate Editor for the IEEE Transactions on Antennas and Propagation and has been a regular reviewer for more than 20 engineering and physics journals.