  Laser wakefield acceleration offers the promise of a compact electron
accelerator for generating a multi-GeV electron beam using the huge field
gradient induced by an intense laser pulse, compared to conventional rf
accelerators. However, the energy and quality of the electron beam from the
laser wakefield accelerator have been limited by the power of the driving laser
pulses and interaction properties in the target medium. Recent progress in
laser technology has resulted in the realization of a petawatt (PW) femtosecond
laser, which offers new capabilities for research on laser wakefield
acceleration. Here, we present a significant increase in laser-driven electron
energy to the multi-GeV level by utilizing a 30-fs, 1-PW laser system. In
particular, a dual-stage laser wakefield acceleration scheme (injector and
accelerator scheme) was applied to boost electron energies to over 3 GeV with a
single PW laser pulse. Three-dimensional particle-in-cell simulations
corroborate the multi-GeV electron generation from the dual-stage laser
wakefield accelerator driven by PW laser pulses.
