Intrapulse x-ray parametric amplification in high-order-harmonic generation

Abstract

We demonstrate strong-field-driven impulsive XUV-x-ray parametric amplification (IXPA) processes in high-order harmonic generation at the single-atom level by using ab initio calculations. We consider the example of Li + ions exposed simultaneously to an intense IR pulse and a weak 200-as XUV-x-ray pulse with central photon energies varying from 90 to 400 eV. We determine optimal parameter ranges and the precise delays between the IR and the XUV-x-ray pulses for IXPA to occur. The present results might be a guide to achieve exponential growth of the XUV-x-ray signal in tabletop XUV-x-ray lasers.

Strong-field assisted extreme-ultraviolet lasing in atoms and molecules

“…The follow-up experiments [14][15][16] and the joint theoretical and experimental study [17] also report parametric amplification of x-ray radiation up to 1 keV [14]. Furthermore, the theoretical studies [18][19][20][21] and the joint theoretical and experimental work [17] support the interpretation of the experiments [13][14][15][16][17] as parametric amplification.…”

“…Specifically, using a Maxwell-Schrödinger model, [22,23] argue that the superquadratic growth of the HHG signal with gas pressure under tight focusing conditions reported experimentally in [13] can be completely accounted for by the phase matching in the standard (coherent parametric) HHG. Moreover, [24] shows that the gain (amplification) reported theoretically at the single atom level in [17,[19][20][21], is indeed the opposite, i.e. XUV loss.…”

“…As such, the simulations separate the facts from the fictions in the physics of stimulated HHG processes at the single atom level: any faithful theory must rigorously account for the loss channels in the medium, which, in our case, is one-photon XUV absorption from the ground state into the continuum (figure 1), see also [24]. This has not been accounted for at all previously [17][18][19][20][21].…”

Extreme-ultraviolet coherent pulse amplification in argon

“…This improvement is key for the use of table-top coherent XUV and x-ray sources in many applications [1,2]. In particular, simultaneous excitation of atoms with an intense infrared (IR) driving pulse and a weak XUV pulse or train of pulses conveniently synchronized has been extensively investigated both theoretically and experimentally as a method to amplify the signal from the single-atom level interaction and also considering the effects of propagation [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…The fundamental physics behind the involved scattering mechanisms, however, lack a detailed explanation which is certainly very necessary for the possibility of amplifying XUV and x-ray coherent pulses at any desired photon energies. Different theoretical * carles.serrat-jurado@upc.edu approaches [9,10,12,14,15,17] have described the amplification in terms of extended electron trajectories in the HHG process together with parametric interactions, such as x-ray parametric amplification (XPA) and intra-XUV-pulse parametric amplification (IXPA), although only qualitative agreement with the measurements has been reported so far [8,9,12,13]. Some of these studies have been performed in the frame of the solution of the time-dependent Schrödinger equation (TDSE) both in the strong-field (SFA) and in the single-activeelectron (SAE) approximations.…”