Laser-driven amplification of soft X-rays by parametric stimulated emission in neutral gases

Seres, J.; Seres, E.; Hochhaus, D. C.; Ecker, B.; Zimmer, Daniel; Bagnoud, V.; Kuehl, Thomas J.; Spielmann, Christian

doi:10.1038/nphys1638

Cited by 58 publications

(96 citation statements)

References 43 publications

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“…From the study above we can conclude that the enhancement effect observed in the harmonics spectrum is due to XUV forward scattering from the nonstationary electronic wave packet promoted by the intense IR driving field, which dominates as compared with the normal weak scattering from bound or stationary free electrons. Forward scattering by the nonstationary electron wave function may include several processes between virtual states, such as Raman scattering, high-order parametric processes, or stimulated bremsstrahlung, with a relative contribution that highly depends on the laser parameters and the particular conditions [6].…”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

Coherent Extreme Ultraviolet Light Amplification by Strong-Field-Enhanced Forward Scattering

Serrat

2013

Phys. Rev. Lett.

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We theoretically study the response of He atoms exposed simultaneously to an intense IR pulse and a weak extreme ultraviolet (XUV) pulse with photon energies far from the principal atomic He resonances. We find that XUV forward scattering from the nonstationary electronic wave packet promoted by the intense IR driving field is strongly enhanced as compared with the normal weak scattering from bound or free electrons. Based on this effect, we predict that large amplification of XUV radiation can be achieved in the cutoff spectral region of high-harmonic generation in He gas. DOI: 10.1103/PhysRevLett.111.133902 PACS numbers: 42.65.Ky, 32.80.Fb, 42.55.Vc The availability of tabletop coherent extreme ultraviolet (XUV) radiation sources with high photon energies has been largely pursued over the last two decades [1]. In this Letter we consider the amplification of the XUV yield generated in high-harmonic generation (HHG) processes by considering the simultaneous excitation of He atoms with an intense IR driving pulse and an XUV pulse. It is known that synchronization of one or several low-order harmonics of high peak intensities with the driving IR laser pulse can produce a large yield enhancement [2,3]. The target medium is in this case strongly ionized due to the XUV photon energies that are considered and due to their high intensity, so that the influence of the combined fields on the HHG spectrum is at spectral regions of higher photon energies than the added XUV pulse. The present research is crucially different from these previous approaches in that we consider weak intensity XUV pulses with photon energies that are far from the principal atomic resonances, with negligible XUV ionization [4]. In our approach, the only affect on the HHG spectrum is at about the same spectral region as the added XUV pulse. Specifically, we address the influence of the high-intensity IR driving pulse on the scattering of XUV radiation from He atoms in HHG processes. We find that forward scattering is largely enhanced when an XUV pulse is synchronized with the amplitude maxima of the IR laser pulse. It is shown numerically that this effect can be used for the amplification of coherent XUV radiation in the HHG cutoff spectral region to power levels that might be useful for most applications.We resolve the interaction of a He atom with the combined IR laser and XUV pulse by numerically solving the time-dependent Schrödinger equation in the singleatom strong-field approximation [5]. The strong-field approximation describes the interaction with laser light of arbitrary frequency content, accounts for most important quantum effects-such as quantum diffusion of wave packets and quantum interferences, and allows our study to be computationally efficient. The present results apply for low-pressure HHG processes, propagation effects in a higher-pressure gas will be discussed in a future paper. Resonant absorption from He atoms will be evaluated in the last part of the study.In the following we consider a 5 fs (FWHM) laser pulse with Gau...

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Section: Fig 1 (Color Online)mentioning

confidence: 99%

Coherent Extreme Ultraviolet Light Amplification by Strong-Field-Enhanced Forward Scattering

Serrat

2013

Phys. Rev. Lett.

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“…Our electron trajectory analysis suggests that multiple scattered electrons returning after about two optical cycles produce soft X-ray radiation in the spectral range above 200 eV up to a few keV. When the conditions for X-ray parametric amplification (XPA) [22] are fulfilled, the harmonics can be efficiently generated, and the quantum-path interference of two dominating trajectories explains the uncommon harmonic line structure very well.…”

Section: Introductionmentioning

confidence: 87%

“…In Equation (1), the possibility of the parametric amplification contribution [22,[24][25][26] and the absorption are also considered by the second term, which describes the amplification with stimulated emission cross-section σeq and "excited" atomic density 1 n and the absorption with the cross-section of σaq, Solving Equation (1), we get the electric field of the q-th harmonic at the output of the gas medium with length L: …”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…The gas backing pressure was set to 250 mbar, and the gas jet was moved approximately 1 mm after the focus. This position allows the exploitation of further phase matching contributions [10,20] and the enhancement effect of X-ray parametric amplification [22]. The lower order harmonics and the residual laser light are blocked with a 100 nm-thick Ti foil.…”

Section: Experiments 3: Improving Phase Matching With a Double-pulse Ementioning

confidence: 99%

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Quantum Path Interference and Multiple Electron Scattering in Soft X-Ray High-Order Harmonic Generation

Seres

Landgraf

et al. 2015

Photonics

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High-order harmonic generation is an important mechanism to generate coherent radiation in the few-100-eV spectral range with ultrashort laser pulses. Moreover, a closer inspection of the measured spectra provides unique information about the underlying physics and allows deriving guidelines for improvements. The long-range modulation of the spectral envelope is linked to phase matching, and we will show how to improve it with a double-pulse excitation scheme. Additionally, the spectrum contains only every fourth harmonic, which can be well explained by the quantum interference of multiple scattered electrons, and two dominant electron trajectories were selected by X-ray parametric interaction.

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“…High repetition rate and high average power laser systems are now very attractive to push further this field and are a promising tool for new understanding of HHG physics [1,2]. The moderate energy and long duration of the pulses delivered by to these systems require tight focusing geometry leading to a reduced harmonic efficiency.…”

Section: Introductionmentioning

confidence: 99%

Optimized XUV source at 100 kHz repetition rate

Cabasse

Machinet

Hazera

et al. 2013

EPJ Web of Conferences

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Abstract. Fiber based laser systems at high repetition rate are becoming very attractive for high-order harmonics generation as they allow to reach high intensities. Their characteristics (central wavelength, energy and pulse duration) require specific optimizing conditions. We analyse how the harmonic efficiency with such a system is influenced by several parameters (atomic gas media, pressure, interaction geometry (a jet or a cell)). This study allows us to define optimal conditions for HHG appropriate to this new type of laser and experimentally, a photon flux higher than 10 12 photons/s is measured.

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Laser-driven amplification of soft X-rays by parametric stimulated emission in neutral gases

Cited by 58 publications

References 43 publications

Coherent Extreme Ultraviolet Light Amplification by Strong-Field-Enhanced Forward Scattering

Coherent Extreme Ultraviolet Light Amplification by Strong-Field-Enhanced Forward Scattering

Quantum Path Interference and Multiple Electron Scattering in Soft X-Ray High-Order Harmonic Generation

Optimized XUV source at 100 kHz repetition rate

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