Scattering in Time-Varying Drude-Lorentz Models

TL;DR

This paper investigates how wave scattering in time-varying Drude-Lorentz models depends on the microscopic dispersion details, revealing unique effects and limitations of abrupt plasma frequency changes.

Contribution

It compares four different time-varying Drude-Lorentz models to understand their distinct scattering behaviors and verifies results with a custom FDTD algorithm.

Findings

Scattering coefficients vary significantly between models due to dispersion details.

Abrupt plasma frequency changes lead to unique forward and backward wave splitting.

Model limitations are discussed in the context of abrupt temporal changes.

Abstract

Motivated by recent experiments, the theoretical study of wave propagation in time varying materials is of current interest. Although significant in nearly all such experiments, material dispersion is commonly neglected in theoretical studies. Yet, as we show here, understanding the precise microscopic model for the material dispersion is crucial for predicting experimental outcomes. Here we study the temporal scattering coefficients of four different time-varying Drude-Lorentz models, exploring how an incident continuous wave splits into forward and backward waves due to an abrupt change in plasma frequency. The differences in the predicted scattering are unique to time-varying media, and arise from the exact way in which the time variation appears in the various model parameters. We verify our results using a custom finite difference time domain algorithm, concluding with a discussion of the limitations that arise from using these models with an abrupt change in plasma frequency.