Theoretical study of single attosecond pulse generation with a three-colour laser field

We present a method of producing single attosecond pulses by using a few-cycle (5 fs) driving pulse with two additional weak control pulses. We discuss how single attosecond pulses produced from high-order harmonic generation processes in a synthesized three-colour laser field are similar to those processes in a much shorter single-colour laser field. Based on the high-order harmonic spectrum, classical ionizing and returning energy maps, time-frequency maps and time profiles of the attosecond pulses, the actions of the synthesized three-colour laser field are analogous to a 3 fs field although some differences still exist, and our method is proved to be a potential way to reduce the attosecond pulse duration from high-order harmonic generation with a currently available ultrafast laser source instead of a shorter pulse.