Analysis of isolated attosecond pulse generation from a multi-cycle two-color pulse

Abstract

We theoretically investigate the high-order harmonic and attosecond pulse generation by numerically solving the one-dimensional time-dependent Schrodinger equation for a hydrogen atom in a two-color laser field that is synthesized by adding a suitable multi-cycle infrared pulse to a multicycle 800-nm fundamental pulse. Our result clearly shows that with the addition of a suitable second optical field, the electric field profile of the synthesized pulse presents multi-segments and that in the first and the last segments, the amplitudes of the electric field are dramatically suppressed. If this synthesized pulse is adopted as an incident driving pulse, only the amplitude of the electric field in the middle segment makes a major contribution to the plateau and to the cutoff region of the harmonic spectrum. This will cause a wide quasicontinuous spectrum around the cutoff position. Thus, an isolated attosecond pulse can be obtained even if we adopt the synthesized pulse with a multi-cycle pulse duration.