Transient States to Control the Electromagnetic Response of Space-time Dispersive Media

TL;DR

This paper investigates how transient electromagnetic states form when a dispersive slab's properties change abruptly in time, revealing their potential for frequency conversion and field control.

Contribution

It introduces a combined analytical approach for modeling transient responses in time-varying dispersive media and validates it with FDTD simulations.

Findings

Transient states can be harnessed for frequency conversion.

Abrupt property changes induce controllable transient electromagnetic responses.

Transient effects can be used to amplify or attenuate fields.

Abstract

In this paper, we study the dynamic formation of transients when plane waves impinge on a dispersive slab that abruptly changes its electrical properties in time. The time-varying slab alternates between air and metal-like states, whose frequency dispersion is described by the Drude model. It is shown how the physics of this complex system can be well described with the joint combination of two terms: one associated with temporal refractions and the other associated with spatial refractions. To test the validity of the approach, some analytical results are compared with a self-implemented finite-difference time-domain (FDTD) method. Results show how the transients that occurred after the abrupt temporal changes can shape the overall steady-state response of the space-time system. In fact, far from always being detrimental, these transient states can be conveniently used to perform frequency conversion or to amplify/attenuate the electromagnetic fields.