Macroscopic Quantum Electrodynamics with Gain: Modified Fluctuations and Their Consequences

TL;DR

This paper extends macroscopic quantum electrodynamics to include active media with gain, analyzing how gain modifies electromagnetic fluctuations and impacts phenomena like Casimir forces and Lamb shifts.

Contribution

It introduces a theoretical framework for MQED with gain, exploring how active media alter field correlations and fluctuation-induced forces.

Findings

Gain modifies electromagnetic field fluctuations.

Active media influence Casimir and van der Waals forces.

Framework unifies passive and active media in MQED.

Abstract

Macroscopic quantum electrodynamics (MQED) provides a unified framework to describe quantum electromagnetic fields in the presence of arbitrary macroscopic environments. Central to this theory is the field correlation, which governs both radiative (e.g., Lamb shifts and the Purcell effect) and mechanical phenomena, such as van der Waals and Casimir forces. In this tutorial, we provide an overview of MQED and its extension to active media, highlighting fluctuation-induced forces as manifestations of gain-modified field correlations.