Generation of an Extreme Ultraviolet Supercontinuum in a Two-Color Laser Field

Abstract

We theoretically investigate the high-order harmonic generation in a helium atom with a two-color optical field synthesized by an intense 6 fs pulse at 800 nm and a relatively weak 21.3 fs pulse at 400 nm. When the frequency-doubled pulse is properly time shifted with respect to the fundamental pulse, an ultrabroad extreme ultraviolet supercontinuum spectrum with a 148 eV spectral width can be generated which directly creates an isolated 65 as pulse even without phase compensation. We explain this extraordinary phenomenon by analyzing maximum electron kinetic energies at different return times.

High-order harmonic generation spectra and isolated attosecond pulse generation with a two-color time delayed pulse

“…Therefore, recently, these two issues have been addressed by using the two or multi-color laser field scheme [24][25][26][27]. Within this framework, Zeng et al [28] theoretically obtain an isolated 65as pulse through the combination of an 800 nm fundamental field and a 400 nm controlling field. Chen et al [29] theoretically obtained an isolated 38as pulse by using an 800 nm fundamental field combined with a 1600 nm controlling field.…”

Quantum path control on the harmonic emission in the presence of a terahertz field

“…However, for the practical application, an isolated attosecond pulse obtained from the continuum HHG spectrum is more useful to trace the ultrafast electronic dynamics process. In order to produce an isolated attosecond pulse from a continuum harmonic spectrum, many methods aiming to control the movement of the emitted electron have been proposed, such as the few-cycle driving pulse scheme [12,13], the polarization gate scheme [14,15], the chirp pulse scheme [16,17], and the two-color or multi-color pulses scheme [18][19][20] etc. The shortest pulse duration achieved by these methods are about 80 as [12] and sub-10 as [20] from the experimental and the theoretical sides, respectively.…”

Single quantum path control by a fundamental chirped pulse combined with a subharmonic control pulse

“…However, the use of a single-color scheme in few-cycle regime has limited the extension of the supercontinuum bandwidth, thus making it difficult to obtain a shorter isolated attosecond pulse. By using a two-color or three-color scheme [15,16], the limitation can be overcome, just as shown in, for example, Zeng's study [17] where an isolated 65 as pulse is theoretically produced through the combination of an intense 800 nm fundamental field and a weak 400 nm control field, Zhai's work [18] theoretically reporting an isolated 45 as pulse in the two-color field of an intense 800 nm laser pulse and a weak 1600 nm laser pulse, and Feng's study [19] where an isolated 7 as pulse is theoretically predicted by using the three-color field, consisting of a 800 nm fundamental field, a 400 nm control field and a 1600 nm control field. In addition, recent investigations show that the macroscopic propagation effect (depending on the experimental setup) also plays an important role in the generation of the isolated attosecond pulse [20][21][22].…”