Static-to-dynamic field conversion with time-varying media

TL;DR

This paper demonstrates that a static electric field can be partially converted into radiation when the permittivity of a medium changes over time, offering a new method for generating electromagnetic radiation.

Contribution

Theoretical analysis of how time-varying permittivity in a dielectric medium can convert static fields into radiated electromagnetic waves, with analytical expressions derived.

Findings

Partial conversion of static fields to radiation via temporal permittivity change

Analytical expressions for radiated fields in a waveguide setup

Discussion on energy exchange and boundary conditions in time-varying media

Abstract

In this Letter, we theoretically demonstrate that a uniform static electric field distribution can be partially converted to radiation fields when a portion of the medium undergoes a temporal change of its permittivity. An in-depth theoretical investigation of this phenomenon is developed for a dielectric block with a step-like temporal change located inside a waveguide charged with a DC voltage source. Closed analytical expressions are derived for the radiated electric and magnetic fields. The exchange of energy between the electrostatic and electromagnetic fields is discussed. The reconciliation between the seemingly contradictory temporal and spatial boundary conditions for the electric and magnetic fields at the interface of the time-varying dielectric block is analyzed and elucidated. Our findings may provide an alternative solution for generating electromagnetic radiation based on time-varying media.