The knowledge about the multidimensional features of laser-plasma interaction in the QED-dominated regime is still limited. In a non-QED regime, the laser ponderomotive force expels electrons off the high-intensity regions. An electron-free channel or a bubble is usually formed depending on the plasma density and pulse duration.Yet, in the QED regime, when the RR effect dominates, the collective electron response and laser propagation dynamics remain unclear.

The research group headed by Prof. Shen BaiFei at Shanghai Institute of Optics and Fines Mechanics , Chinese Academy of Sciences, have reported a new trapping effect of electrons inside the laser pulse in the near QED regime. The oscillation amplitude of electrons in the laser pulse strongly declines due to radiation reaction. Plenty of electrons gather around the propagating axis and form a dense bunch through the pinching effect. Radiation-reaction trapping leads to a collimated high-density plasma bulk inside the laser pulse such that γ-photon emission is greatly enhanced.

[Phys. Rev. Lett. 112, 145003; http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.112.145003]