Generation of 100-MeV attosecond electron bunches with terawatt few-cycle laser pulses

Laser-wakefield acceleration has been demonstrated to be a promising technique for compact electron accelerators. However, it is still challenging to achieve high-quality 100-MeV electron bunches of sub-femtosecond duration with current techniques. Here, we present and numerically demonstrate an efficient scheme to produce such high-energy tunable ultrashort electron bunches, which is achieved by the use of a nonlinear wakefield driven by a terawatt few-cycle laser pulse in a new structure of plasma channel. With the driving laser pulse energy of 25mJ only, the resulting electron bunch can reach 101 MeV with 7.8 pC charge, ~4 mrad divergence, ~3% energy spread, energy efficiency above 3%, and a duration of hundreds of attoseconds. As such laser pulses may be obtained with a kilohertz repetition rate and high stability, our scheme could be interesting for ultrafast science and accelerator community.