Attosecond γ-ray vortex generation in near-critical-density plasma driven by twisted laser pulses

Ultra-short brilliant γ-rays have many potential applications in astrophysics, nuclear physics, and ultra-fast science. However, attosecond γ-ray beams with energy above 100 MeV are still very challenging. Here, we propose and numerically demonstrate an all-optical scheme to produce sub-GeV attosecond γ-rays in near-critical-density (NCD) plasma. When a left-hand circularly polarized Laguerre–Gaussian (LG) laser pulse irradiates the NCD plasma, dense attosecond electron bunches are produced, trapped by the LG laser, and accelerated to GeV energies. Subsequently, these electrons oscillate in the LG laser electric fields and emit a string of hundreds MeV attosecond (367 as) γ-ray pulses. Three-dimensional particle-in-cell simulations indicate that, at a laser intensity of 1022 W/cm2, the yield of γ-ray pulses with photon energies above 1 MeV is as high as 1013 with a peak angular momentum of 10 − 15 kg m 2 / s. This results in γ-ray vortex beams with an unprecedented peak brilliance of 1024 photons s−1 mm−2 mrad−2 per 0.1% bandwith at 1 MeV, which may offer a unique opportunity for diverse applications.