Extension of harmonic cutoff in a multicycle chirped pulse combined with a chirp-free pulse

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

“…2(e)), there are also three main peaks but the maximum peak has been remarkably enhanced. According to the three-step model, the maximum energy-peak values (E max = I p + nU p , U p = E 2 /4ω 2 ) are decided by either the amplitude intensities (relating to the pulse intensities) or the widths of these processes (relating to the frequencies) [33,36,47]. By examining the laser profile in Fig.…”

Generation of 40-as few-cycle pulse through chirp manipulation

“…To obtain a regular and intense short attosecond pulse, some promising ways have been proposed to control quantum paths, such as the two-color schemes [9,10] and preparing ions in a coherent superposition of the states [11] . Recently, Xu et al [12] proved a combined same-color field scheme that can broaden the high-order harmonics plateau; they obtained an isolated 59-as pulse. In this letter, based on Ref.…”

“…In this letter, based on Ref. [12], we propose a method, in which the chirp of the laser pulse is controlled to generate a short and intense isolated broadband attosecond pulse. When the ratio of the chirp factors of the fundamental and controlling laser fields has a small value, the bandwidth of the harmonic plateau is broadened to 200 eV with some very slight modulations.…”

“…We first calculated the single-atom spectrum from He + ion for the case where the chirp parameters for the synthesized laser field are (β 1 = 6.25, β 2 = 0), i.e., the same chirp condition considered in Ref. [12]. The 2 pulses are equally intense and their peak intensities are chosen as 5 × 10 14 W/cm 2 .…”