Stimulated Photon–Photon Scattering: Experimental Designs and Predicted Results for Multipetawatt Facilities

We present designs for an experiment using a multipetawatt facility to measure stimulated photon–photon scattering (SPPS), providing a first direct measurement of the nonlinearity of the quantum electrodynamic (QED) vacuum. SPPS is a prediction of strong-field QED for the response of the vacuum to intense electromagnetic fields, in which virtual electron–positron pairs mediate scattering between photons. The scattering is a fourth-order QED process and has never been directly observed due to its low cross section. The proposed experiments will test the hypothesis that the Euler–Heisenberg Lagrangian accurately predicts the nonlinear vacuum response to intense electromagnetic fields, and will begin to address the broader scientific question: how can we harness the nonlinearity of the quantum vacuum? Preliminary simulations using a realistically temporally and spatially shaped laser model predict a three-beam interaction using one 25-PW beam and two 10-PW beams will produce a detectable signal of >1000 scattered photons per shot. We present predicted results for proposed experimental configurations of the NSF OPAL facility, including realistic laser-focusing geometries with and without second-harmonic conversion of two input beams. From these predictions, we derive requirements for the laser facility, including experimental geometry, beam polarization, co-timing, and co-pointing. Requirements and potential technologies for the detector system are also discussed. By varying the relative power and, ultimately, focal geometry of the beams, we will rigorously assess the probability of SPPS and explore the scattering, frequency shifting, and birefringent properties of the nonlinear QED vacuum. This material is based upon work supported by the Department of Energy [National Nuclear Security Administration] University of Rochester “National Inertial Confinement Fusion Program” under Award Number DE-NA0004144 and Department of Energy under Award Number DE-SC0020431.