# Dynamic meta-atoms

## TL;DR

This paper develops a theoretical model to describe the electromagnetic response of time-variant meta-atoms, providing a foundational step for the study of linear time-varying metamaterials and metasurfaces, with validation through simulations.

## Contribution

It introduces a rigorous theoretical framework for analyzing the electric and magnetic responses of temporally-modulated meta-atoms, addressing a gap in the foundational understanding.

## Key findings

- Validated the model with full-wave simulations.
- Applicable to nanophotonics and nano-optics for dynamic control of optical properties.

## Abstract

Interaction of electromagnetic radiation with time-variant objects is a fundamental problem whose study involves foundational principles of classical electrodynamics. Such study is a necessary preliminary step for delineating the novel research field of linear time-varying metamaterials and metasurfaces. A closer look to the literature, however, reveals that this crucial step has not been addressed and important simplifying assumptions have been made. Before proceeding to studies of linear time-varying metamaterials and metasurfaces with their effective parameters, we need to rigorously describe the electric and magnetic responses of a temporally-modulated meta-atom. Here, we introduce a theoretical model which describes a time-variant meta-atom and its interaction with incident electromagnetic waves in time domain. The developed general approach is specialized for a dipole emitter/scatterer loaded with a time-varying reactive element. We confirm the validity of the theoretical model with full-wave simulations. Our study is of major significance also in the area of nanophotonics and nano-optics because the optical properties of all-dielectric and plasmonic nanoparticles can be varied in time in order to achieve intriguing scattering phenomena.