Notes on the Electrodynamics of Time-Varying Systems

Carlos Molero Jiménez

Universidad de Sevilla, Departamento de Electrónica y Electromagnetismo, Grupo de Microondas

Resumen/Abstract

Time-varying electromagnetic devices have emerged as promising alternatives for RF and photonic systems. By introducing time as an additional degree of freedom, these structures enable the breaking of conventional physical symmetries, opening new opportunities for fast and efficient communication technologies. Time-varying materials are characterized by a refractive index that changes with time. Their analysis generally requires solving Maxwell’s equations, a task that can become mathematically demanding and computationally intensive. Frequency-domain techniques may be employed when the problem is periodic in time; however, their applicability is limited to such scenarios. Non-periodic phenomena, in contrast, must typically be addressed using time-domain approaches. In this context, matrix-based techniques arise as efficient and accurate alternatives, allowing the solution to be constructed through the concatenation of steady-state responses across temporal interfaces.

Curriculum ponente

Carlos Molero (Member, IEEE) was born in Seville, Spain, in April 1987. He received the Licenciado and Ph.D. degrees in Physics from Universidad de Sevilla in 2011 and 2017, respectively. From March 2017 to July 2020, he held a postdoctoral position at INSA Rennes, France. From 2020 to 2025, he worked at the University of Granada as a postdoctoral researcher. He currently holds a position at Universidad de Sevilla under an Emergia grant. Dr. Molero is the author or co-author of more than 90 publications, including journal papers and contributions to national and international conferences. He has received several awards, including the Best Engineer Prize at the European Microwave Conference 2015 held in Paris. He has taught courses in electromagnetics, electronics, and advanced signal processing, and has supervised four Ph.D. theses. In addition, he has participated in more than 15 research projects, serving as principal investigator in three of them. He has also been involved in technology-transfer activities and is currently active in science communication. In this context, he directs the podcast Pasiensia. His research interests focus on the study of periodic structures, both planar and three-dimensional, for the design of single- and multi-band polarizing devices. He is also an expert in the development of circuit models applied to 1-D, 2-D and 3-D metasurfaces. In addition, he has worked on the design and fabrication of fully metallic and fully dielectric devices using additive manufacturing techniques. More recently, his research has focused on time-modulated systems, both from the circuit-engineering perspective and in applications to spatially modulated metasurfaces.