An exact property of the nonequilibrium photon Green function for bounded media

TL;DR

This paper analyzes the nonequilibrium photon Green function in bounded media, revealing how vacuum-induced fluctuations relate to classical wave propagation and generalizing previous steady-state results.

Contribution

It provides an exact analysis of the photon Green function components in bounded media, extending prior steady-state findings to more general nonequilibrium conditions.

Findings

Vacuum-induced fluctuations describe propagation of arbitrary light.

Components split into medium and vacuum contributions.

Generalizes previous steady-state results.

Abstract

The nonequilibrium photon Green function for a bounded medium surrounded by vacuum is analyzed on the basis of the Dyson equation. As its components, the field-field fluctuations as well as the spectral function split up into parts related to medium and vacuum. Particularly, it is shown that the vacuum-induced fluctuations describe propagation of arbitrary, even nonclassical light in terms of solutions of the classical wave propagation problem. The results generalize previously obtained ones for steadily excited media in slab geometry.