Ultrabright attosecond gamma ray from irradiating solid foil with tailored vortex laser pulse

Intense attosecond light sources are required for investigating ultrafast electron dynamics, such as in molecules and atoms, etc. However, so far their achievable photon energy remains at the keV level, thus limiting their range of applications. For instance, probing intranuclear dynamics requires photon energies in the gamma-ray regime. Here we propose a scheme for generating intense attosecond gamma-ray pulses by irradiating a thin solid-density foil with tailored intense vortex laser. In the interaction, the laser driven foil electrons are differentially accelerated within a quarter-wave field and become highly bunched. Three-dimensional particle-in-cell simulations show that they efficiently (at ∼ 30% conversion efficiency) radiate ultrashort (∼ 400as), high-flux (> 1010 photons per pulse), and ultrabrilliant (up to 1027 photons s−1 mm−2 mrad−2 per 0.1% BW at 1 MeV photon energy) gamma ray. With an X-ray driving laser, the scheme can even produce isolated bright sub-attosecond gamma-ray pulses that are useful for time-resolved nuclear spectroscopy and many other areas.