Photon merging and splitting in electromagnetic field inhomogeneities

TL;DR

This paper analyzes photon merging and splitting in inhomogeneous electromagnetic fields, providing analytical estimates for experimental detection using high-intensity lasers, and emphasizing deviations from constant field results.

Contribution

It introduces a detailed analysis of photon merging and splitting in inhomogeneous fields using the three-photon polarization tensor, highlighting deviations from constant field approximations.

Findings

Analytical expressions for merged/split photon numbers in laser focal spots.

Estimates for signal photon counts in petawatt and terawatt laser setups.

Photon merging as a signature for nonlinear quantum vacuum effects.

Abstract

We investigate photon merging and splitting processes in inhomogeneous, slowly varying electromagnetic fields. Our study is based on the three-photon polarization tensor following from the Heisenberg-Euler effective action. We put special emphasis on deviations from the well-known constant field results, also revisiting the selection rules for these processes. In the context of high-intensity laser facilities, we analytically determine compact expressions for the number of merged/split photons as obtained in the focal spots of intense laser beams. For the parameter range of a typical petawatt class laser system as pump and a terawatt class laser as probe, we provide estimates for the numbers of signal photons attainable in an actual experiment. The combination of frequency upshifting, polarization dependence and scattering off the inhomogeneities renders photon merging an ideal signature for the experimental exploration of nonlinear quantum vacuum properties.