Conserving optical currents: angular momentum and spin

TL;DR

This paper introduces and analyzes the conservation of energy, momentum, angular momentum, and spin in electromagnetic fields within the first quantization framework, highlighting their additive nature for eigenmodes.

Contribution

It provides a quantum-level formulation of conserved optical quantities and clarifies their behavior during light propagation in vacuum.

Findings

Conservation of energy, momentum, angular momentum, and spin in vacuum

Additivity of these quantities only for electromagnetic eigenmodes

Framework based on first quantization of Maxwell's equations

Abstract

Within the first quantisation of Maxwell's equations, we introduce the dynamic energy, linear momentum, angular momentum and optical spin of the electromagnetic fields. We show that these different quantities are conserved during the propagation of light in vacuum and are additive only for eigenmodes of the electromagnetic field.