Generation of Intense Vortex Gamma Rays via Spin-to-Orbital Conversion of Angular Momentum in Relativistic Laser-Plasma Interactions

Vortex gamma-ray beams with large orbital angular momentum (OAM) have significant potential applications in material science, nuclear detection, and astrophysics. An all-optical scheme for production of intense vortex gamma-ray beams using relativistic laser-plasma interactions is proposed, where the OAM of gamma-photons is converted from the spin angular momentum of circularly polarized (CP) lasers. The spin-to-orbital angular momentum conversion is achieved by two processes: resonant acceleration of electrons in CP laser-plasma interactions and nonlinear Compton scattering (NCS) of another linearly polarized laser from the former. Three-dimensional particle-in-cell simulations show that vortex gamma-ray beams with a large and controllable OAM of 2.5 x 10(18)(h) over bar and energy up to hundreds of MeV can be obtained by using two lasers at intensities of approximately 10(22)W/cm(2), which is much more practical and more efficient than previously proposed NCS of a Laguerre-Gaussian beam.