Photon-photon scattering at the high-intensity frontier

The tremendous progress in high-intensity laser technology and the establishment of dedicated high-field laboratories in recent years have paved the way towards a first observation of quantum vacuum nonlinearities at the high-intensity frontier. We advocate a particularly prospective scenario, where three synchronized high-intensity laser pulses are brought into collision, giving rise to signal photons, whose frequency and propagation direction differ from the driving laser pulses, thus providing various means to achieve an excellent signal to background separation. Based on the theoretical concept of vacuum emission, we employ an efficient numerical algorithm which allows us to model the collision of focused high-intensity laser pulses in unprecedented detail. We provide accurate predictions for the numbers of signal photons accessible in experiment. Our study is the first to predict the precise angular spread of the signal photons, and paves the way for a first verification of quantum vacuum nonlinearity in a well-controlled laboratory experiment at one of the many high-intensity laser facilities currently coming online.

Figure 1

Illustration of a three dimensional collision geometry, displaying the propagation directions ${\widehat{\overrightarrow{e}}}_{{\kappa }_b}$ and polarization vectors ${\widehat{\overrightarrow{e}}}_{E_b}$ of the high-intensity laser beams. The dominant emission direction (${\phi }_{*}$, ${\vartheta }_{*}$) of the signal photons ${\gamma }_{*}$ is highlighted by an arrow.

Figure 2

Directional emission characteristics of signal photons for the scenario featured in the last line of Table 2 using the Mollweide projection. The signal photons of energy ${\omega }_{*}\approx 3\omega =4.65\mathrm{eV}$ are emitted predominantly in directions outside the forward cones of the high-intensity lasers, delimited by ${\theta }_b\approx 18.24°$ and depicted as light (dark) gray circles for the beams of frequency $2\omega$ ($\omega$). The dominant emission direction lies in the collision plane and is marked by a cross. The signal falls off asymmetrically: Its radial divergence is well-approximated by an ellipsis (black) with minor and major radial divergences ${\theta }_{*}^{\text{minor}}\approx 11.1°$ and ${\theta }_{*}^{\text{major}}\approx 28.7°$ in and perpendicular to the collision plane, respectively.