Laser-parameter effects on the generation of ultrabroad harmonic and ultrashort attosecond pulse in a long-plus-short scheme

Abstract

By numerically solving the time-dependent Schrödinger equation for helium gas in a special two-color laser field, which is synthesized by a long (9 fs) driving pulse and a short (6 fs) controlling pulse, we discuss the influence of the carrier-envelope phase, frequency, and the intensity of the controlling pulse on the generation of harmonic spectra and isolated attosecond pluses. In the cutoff region, two or three plateaus can be controlled by optimizing these laser parameters, and an ultrabroad supercontinuum harmonic spectrum with a bandwidth of 800 eV can be produced, which can support an ultrashort isolated 4.5 as pulse generation by Fourier transformation. Furthermore, using classical ionizing and returning energy maps, time–frequency analyses are presented to explain the underlying physical mechanisms.

Keywords:

• high-order harmonic generation
• long-plus-short scheme
• isolated attosecond pulse
• laser parameter
• quantum wave packet

Acknowledgements

This work was supported by NUST Research Funding No. 2010ZYTS062, No. 2011ZDJH05, and NSF of China Grant No. 11004107.