The features of a quantum description of radiation in an optically dense medium

TL;DR

This paper develops a quantum theory of electromagnetic radiation in dense media, deriving self-consistent equations from first principles and revealing how photon energies include medium interactions and the concept of negative energy photons.

Contribution

It introduces a self-consistent quantum framework for radiation in dense media and derives a Bogoliubov-type transformation linking vacuum and collective excitations.

Findings

Transformation parameter equals the refractive index.

Photon energy includes medium and near-field interaction energies.

Negative energy photons concept is introduced.

Abstract

This paper is devoted to the theory of quantum electromagnetic field in an optically dense medium. Self-consistent equations describing interaction between a quantum field and a quantum dielectric medium are obtained from the first principles, i.e., outside a phenomenological description. Using these equations, we found a transformation (of the Bogoliubov transformation type) that converts the operators of the "vacuum" field into operators of collective perturbations of the field and an ensemble of atoms, that is, photons in the medium. Transformation parameter is the refractive index of the wave mode considered. It is shown that besides the energy of the collective electromagnetic field, the energy of photons in the medium includes the energy of the internal degrees of freedom of the substance and the energy of near-field dipole interaction between atoms in the polarized medium. The concept of negative energy photons is introduced on the basis of self-consistent equations.