Probing the semi-macroscopic vacuum by higher-harmonic generation under focused intense laser fields

TL;DR

This paper proposes using focused intense laser fields to generate higher harmonics in vacuum, enabling the detection of weakly coupled, low-mass fields and probing nonlinear photon interactions over macroscopic scales.

Contribution

It introduces a novel method for probing photon interactions in vacuum via higher-harmonic generation, extending sensitivity to weaker couplings and lower masses than previous techniques.

Findings

Potential to detect fields weaker than gravity

Enhanced sensitivity to low-mass, weakly coupled fields

New experimental parameter regimes for photon-field interactions

Abstract

The invention of the laser immediately enabled the detection of nonlinear photon-matter interactions, as manifested for example by Franken et al.'s detection of second-harmonic generation. With the recent advancement in high-power, high-energy lasers and the examples of nonlinearity studies of the laser-matter interaction by virtue of properly arranging lasers and detectors, we envision the possibility of probing nonlinearities of the photon interaction in vacuum over substantial space-time scales, compared to the microscopic scale provided by high-energy accelerators. Specifically, we introduce the photon-photon interaction in a quasi-parallel colliding system and the detection of higher harmonics in that system. The method proposed should realize a far greater sensitivity of probing possible low-mass and weakly coupling fields that have been postulated. With the availability of a large number of coherent photons, we suggest a scheme for the detection of higher harmonics via the averaged resonant production and decay of these postulated fields within the uncertainty of the center-of-mass energy between incoming laser photons. The method carves out a substantial swath of new experimental parameter regimes on the coupling of these fields to photons, under appropriate laser technologies, even weaker than that of gravity in the mass range well below 1 eV.