Boosting Quantum Vacuum Signatures by Coherent Harmonic Focusing

Abstract

We show that coherent harmonic focusing provides an efficient mechanism to boost all-optical signatures of quantum vacuum nonlinearity in the collision of high-intensity laser fields. Assuming two laser pulses of given parameters at our disposal, we demonstrate a substantial increase of the number of signal photons measurable in experiments where one of the pulses undergoes coherent harmonic focusing before it collides with the fundamental-frequency pulse. Imposing a quantitative criterion to discern the signal photons from the background of the driving laser photons as well as accounting for the finite purity of polarization filtering, the discernible signal photons are found to arise from manifestly inelastic interaction processes of the driving laser fields. Our results suggest that coherent harmonic focusing offers a promising new route to the first detection of signatures of quantum vacuum nonlinearities at the high-intensity frontier in the laboratory.

Probing Vacuum Polarization Effects with High-Intensity Lasers

“…(58) for the numbers of discernible signal photons in the quasielastic channel, it is plausible that -though very probably still not measurable with state-of-the-art technology -the full discernible signal will be dominated by inelastic contributions; cf. also the recent study [67].…”

“…A prominent nonlinear QED signature characterized by two signal photons in the final state is photon splitting [26][27][28][29][30][31][32][33][34]. On the other hand, prospective optical signatures such as vacuum birefringence [26,28,[35][36][37][38][39][40][41][42][43][44][45][46][47][48], quantum reflection [49,50], photon merging [51][52][53][54], generic photon scattering phenomena [55][56][57][58][59][60][61][62][63][64][65][66][67], and higher-harmonic generation [8,[68][69][70][71][7...…”

“…For completeness, let us emphasize here that it is nevertheless possible to come up with laser-pulse collision scenarios exclusively based on near-infrared high-intensity lasers and state-of-the-art detection technology, which give rise to several discernible signal photons per shot [58,59,[65][66][67]. These scenarios typically involve the collision of more than two focused high-intensity laser pulses at finite angles and heavily rely on the availability of different-color driving beams, as, e.g., accessible by sum-frequency generation techniques.…”

Photon emission in strong fields beyond the locally-constant field approximation

“…Accordingly, the leading contribution is determined by the diagram with four external legs, which can be approximately calculated within the LCFA approach developed in Refs. [6][7][8][9][10]. The leading term is proportional to…”

Detectable Optical Signatures of QED Vacuum Nonlinearities Using High-Intensity Laser Fields

“…To make the signal photons distinguishable from the background photons of the driving laser beams we use a special three dimensional geometry to interfere the pump lasers. Former studies of CHF only consider counter-propagating laser beams along one axis [37,45]. Here, we want to narrow down the volume of interaction by colliding pump lasers with different frequencies in a three dimensional geometry, see figure 1.…”