Single Isolated attosecond pulse from multicycle lasers

We propose a new experimental scheme to produce clean isolated pulses lasting a few hundreds of attoseconds. It is based on high harmonics generation and uses the polarization gating technique combined with the ionization dynamics and the spatial filtering provided by the three-dimensional field propagation. The proposed method is easy to implement, robust against laser parameter fluctuations, and shows to be effective up to a 25 fs pulse duration.