Single attosecond pulse generation from asymmetric molecules with a multicycle laser pulse

A new scheme for single attosecond pulse generation from asymmetric molecules with a multicycle laser pulse is proposed. It is shown that both even and odd harmonics are generated from the asymmetric molecules, and the attosecond pulses are produced every full cycle of the driving laser field rather than each half-cycle. By filtering the harmonics in the cutoff of the spectrum, a single attosecond pulse can be obtained with a multicycle laser pulse with a duration of 2 times longer than the few-cycle pulse conventionally used.