Control of the supercontinuum spectrum bandwidth and emission efficiency for intense-isolated sub 40-as pulse generation by using a coherent superposition of states

Controlling the ionization and recombination rates of an electron in preexcited ions to generate an intense isolated sub-4-as pulse in a multicycle regime

“…1(a). Thus, it is not possible to obtain the intense higher-energy harmonics with He+ ions in a ground state alone [37,47] or with He+ ions in an excited state alone (i.e., when the initial state is prepared as the excited state). For comparison, we also present results when the initial state is the excited state [green dashed curve in Fig.…”

Isolated sub-30-attosecond pulse generation using a multicycle two-color chirped laser and a static electric field

“…Moreover, this approach also has the potential to select a short or long quantum path, which leads to the production of isolated short attosecond pulses, such as a 108-as pulse via an intense few-cycle chirped pulse, [25] a 10-as pulse with phase compensation using a chirped few-cycle laser and a static electric field, [26] a 37-as (57-as) pulse by an intense few-cycle chirped laser and a half cycle pulse (an ultraviolet attosecond pulse), [27,28] a 59-as pulse by a multicycle chirped pulse combined with a chirp-free pulse, [29] a 31-as (5-as) pulse without (with) phase compensation using a two-color laser pulse with the combined chirps, [30] a 102-as pulse with a multicycle chirped and chirp-free two-color field, [31] a sub-24-as pulse with phase compensation using multi-cycle chirped polarization gating pulses, [32] and an intense isolated sub-40-as pulse generation in pre-excited He-ionic medium with the use of a same-frequency laser field synthesis. [33] In our previous work, [34] by combining a 9-fs/800-nm fundamental chirped pulse and a 9-fs/1600-nm controlling chirped pulse, we realized a 1342-eV supercontinuum with a short path contribution and also obtained an isolated 28-as pulse with a bandwidth of 155 eV.…”

“…Our recent simulation calculation showed that a static electric field can not only modulate the quantum paths of the HHG, but also increase the ionization yield of electrons contributing to the continuous spectrum; as a result, the extension and enhancement of the HHG spectrum are achieved synchronously, which results in the production of an intense isolated 26-as pulse. [42] In this paper, the motivation of our simulation lies in the following considerations: first, though isolated attosecond pulse generations from the single chirped pulse, [25,43] the single chirped pulse or two-color laser in combination with a static electric field, [26,44] and two-color chirped pulse [28][29][30][31][32][33][34] have been investigated, few studies have been reported for the combination of the multicycle two-color chirped pulse and a static electric field; second, one of the current theoretical methods for producing single ultrashort attosecond pulses is by using the phase compensation for an achievable supercontinuum spectrum, which is not easy to achieve in an experiment; third, we intend to generate a single attosecond pulse with a duration below one atomic unit of time by straightforwardly filtering a large range of harmonics. Due to these ideas, in this paper we further investigate the HHG and isolated attosecond pulse generation of a model Ne atom in a multicycle two-color chirped laser and a static electric field.…”

Electron path control of high-order harmonic generation by a spatially inhomogeneous field

“…The production of isolated attosecond pulses can be experimentally achieved either with the technique of HHG in gas from a few-cycle driving pulse [10,11] or with the technique of temporal confinement of the HHG by polarization gating [12]. Moreover, theoretically, the two-colour control mechanisms [13][14][15][16], the coherent superposition state of the target technique [17][18][19] and the frequency-chirping method [20][21][22][23][24][25][26][27][28], have been introduced. To have easy way to create and control a focused wavepacket of the laser field, we employ the frequencychirping of driving laser pulse method this in article.…”