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 that in molecules and atoms, etc. However, so far the achievable photon energy remains at the keV level, thereby limiting their range of applications. For instance, probing intranuclear dynamics requires photon energies in the gamma-ray regime. We propose here a scheme for generating intense attosecond gamma-ray pulses by irradiating a thin solid-density foil with 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 can efficiently (with ∼ 30 % energy conversion efficiency) radiate ultrashort ( ∼ 400 as), high-flux ( > 10 10 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 rays. 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. [ABSTRACT FROM AUTHOR]