Stimulated photon emission from the vacuum

Abstract

We study the effect of stimulated photon emission from the vacuum in strong space-time dependent electromagnetic fields. We emphasize the viewpoint that the vacuum subjected to macroscopic electromagnetic fields with at least one nonzero electromagnetic field invariant, as, e.g., attainable by superimposing two laser beams, can represent a source term for outgoing photons. We believe that this view is particularly intuitive and allows for a straightforward and intuitive study of optical signatures of quantum vacuum nonlinearity in realistic experiments involving the collision of high-intensity laser pulses, and exemplify this view for the vacuum subjected to a strong standing electromagnetic wave as generated in the focal spot of two counter-propagating, linearly polarized high-intensity laser pulses. Focusing on a comparably simple electromagnetic field profile, which should nevertheless capture the essential features of the electromagnetic fields generated in the focal spots of real high-intensity laser beams, we provide estimates for emission characteristics and the numbers of emitted photons attainable with present and near future high-intensity laser facilities.

Photon polarization tensor in pulsed Hermite- and Laguerre-Gaussian beams

“…This approximate result for L HE differs from the -typically unknown -exact result in the considered inhomogeneous field by terms of O ( υ me ) 2 [33,35]. The effective action in inhomogeneous fields associated with the right-hand side of Eq.…”

“…3 For completeness, note that this definition of the photon polarization tensor differs from that of Ref. [33] by an overall minus sign.…”

“…It is straightforward to infer that this approximate result differs from the exact expression of the photon polarization tensor in the inhomogeneous field under consideration by [33]. In this article we use this approach to obtain analytical insights into the photon polarization tensor for low-energy (but not necessarily on-shell) probe photons a µ (k), with {ω, | k|} ≪ m e , in linearly polarized, pulsed Hermite-and Laguerre-Gaussian laser beams of frequency Ω ≪ m e and arbitrary mode composition.…”

“…The one-loop photon polarization tensor is known analytically for both homogeneous electromagnetic fields [8,[18][19][20][21][22][23][24][25][26][27], and generic plane wave backgrounds [28][29][30][31]. Besides, numerical results for inhomogeneous magnetic backgrounds are available from worldline Monte Carlo simulations [32], and analytical results for low-energy photons in slowly varying inhomogeneous electromagnetic fields were obtained in [33].…”

“…More specifically, the latter derivation makes use of the fact that for probe photons and background fields 2 with frequencies and momenta delimited from above by υ ≪ m e , the dominant contribution to the photon polarization tensor can be inferred straightforwardly from the constant-field result in two steps [4,33,34]: First, the Heisenberg-Euler Lagrangian in constant fields is adopted to inhomogeneous electromagnetic fields as…”