Generalized noise terms for the quantized fluctuational electrodynamics

TL;DR

This paper develops a comprehensive quantum electrodynamics framework that incorporates magnetic interactions and fluctuations in lossy, dispersive media, enabling detailed modeling of optical energy transfer and thermal phenomena in nanodevices.

Contribution

It introduces a general position-dependent quantized fluctuational electrodynamics formalism that includes magnetic field-matter interactions and additional noise operators, extending previous dielectric-only models.

Findings

Magnetic fluctuations add a new degree of freedom in field quantization.

The formalism allows modeling of optical energy transfer in magnetic and dielectric nanostructures.

Magnetic Purcell effect can enhance magnetic emitter emissivity beyond electric counterparts.

Abstract

The quantization of optical fields in vacuum has been known for decades, but extending the field quantization to lossy and dispersive media in nonequilibrium conditions has proven to be complicated due to the position-dependent electric and magnetic responses of the media. In fact, consistent position-dependent quantum models for the photon number in resonant structures have only been formulated very recently and only for dielectric media. Here we present a general position-dependent quantized fluctuational electrodynamics (QFED) formalism that extends the consistent field quantization to describe the photon number also in the presence of magnetic field-matter interactions. It is shown that the magnetic fluctuations provide an additional degree of freedom in media where the magnetic coupling to the field is prominent. Therefore, the field quantization requires an additional independent noise operator that is commuting with the conventional bosonic noise operator describing the polarization current fluctuations in dielectric media. In addition to allowing the detailed description of field fluctuations, our methods provide practical tools for modeling optical energy transfer and the formation of thermal balance in general dielectric and magnetic nanodevices. We use the QFED to investigate the magnetic properties of microcavity systems to demonstrate an example geometry in which it is possible to probe fields arising from the electric and magnetic source terms. We show that, as a consequence of the magnetic Purcell effect, the tuning of the position of an emitter layer placed inside a vacuum cavity can make the emissivity of a magnetic emitter to exceed the emissivity of a corresponding electric emitter.