Generation of isolated and polarized γ-ray pulse by few-cycle laser irradiating a nanofoil

Abstract

An isolated ultra-short γ-ray pulse is a unique tool for measuring ultrafast-physics process, such as imaging of intra-nuclear dynamics and inner-shell electron dynamics. Here, we propose an all-optical efficient scheme for generating isolated ultra-short γ-ray pulse from a laser-driven nanofoil. When a few-cycle circularly polarized laser pulse with an intensity of 10 22 W/cm 2 irradiates a nanofoil, the electrons in the nanofoil are pushed forward collectively, forming a single relativistic electron sheet (RES) with the charge of nC. The electrons are substantially accelerated to high energies by the super-ponderomotive force of the laser. Then a counter-propagating laser pulse with a peak intensity of 10 21 W/cm 2 collides with the RES, resulting in the generation of an isolated sub-femtosecond γ-ray pulse via nonlinear Compton scattering. The effects of laser polarization on the polarization degree of γ-rays is investigated by using a proof-of-principle calculation. It is shown that a highly-polarized isolated γ-ray pulse with the cut-off energy of 100 MeV can be eventually generated in a head-on colliding configuration when the scattering laser is a linearly polarized laser. Such an isolated ultra-short polarized γ-ray source would provide critical applications in high energy physics, laboratory astrophysics and nuclear physics.