Analysis of the Third Harmonic of a Vacuum Response in a Subcritical Laser Field

TL;DR

This paper explores the nonlinear vacuum response, specifically the third harmonic generation, in a strong laser field using kinetic theory to compare quantum and semiclassical radiation mechanisms in electron-positron-photon plasma.

Contribution

It provides a nonperturbative kinetic analysis of vacuum excitation and photon emission channels in intense laser fields, highlighting the dominance of quantum radiation at high frequencies.

Findings

Quantum radiation dominates over semiclassical radiation at high frequencies.

The study models vacuum response using the Bogoliubov-Born-Green-Kirkwood-Yvon kinetic framework.

Comparison of quantum and semiclassical radiation mechanisms in strong laser fields.

Abstract

We investigate a nonlinear response of the physical vacuum by the example of the third harmonic in radiation of the electron-positron-photon plasma excited by a strong time dependent electric field at the focus spot of counterpropagating laser pulses. The investigation was developed within the framework of the Bogoliubov-Born-Green-Kirkwood-Yvon kinetic theory nonperturbatively describing vacuum creation of the quasiparticle electron-positron plasma (EPP) and different channels of its interaction with the photon subsystem in the single-photon approximation that are opened in the presence of a strong semiclassical field. We investigate the radiation of EPP in the annihilation channel on the basis of the well known approximations and compare the obtained result with the semiclassical radiation of the plasma oscillations. In the high-frequency range for large adiabaticity parameter the quantum radiation dominates in comparison with the semiclassical one.