Scaling laws for high-order-harmonic generation with midinfrared laser pulses

Frolov, M. V.; Manakov, N. L.; Xiong, Wei; Peng, Liang-You; Burgdörfer, Joachim; Starace, Anthony F.

doi:10.1103/physreva.92.023409

Cited by 22 publications

(22 citation statements)

References 40 publications

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“…For electron energies over the interval 25 eV E 50 eV, the β(E) results retrieved from the Ar HHG spectra are in excellent agreement with those of both accurate theoretical calculations [32] and experimental photoionization measurements [33]. The discrepancies for energies E < 25 eV may be attributed to (i) inaccuracies in the electronic wave packet used for retrieval (as only the shortest electron trajectory is taken into account, while the contributions of multiple return trajectories are known to be important for low-order harmonics [34,35]), and (ii) the parametrization (6) may fail for low-order harmonics. The discrepancies for energies E > 50 eV are most likely due to the low level of the experimental signal.…”

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confidence: 69%

Atomic photoionization experiment by harmonic-generation spectroscopy

et al. 2016

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Measurements of the high-order-harmonic generation yield of the argon (Ar) atom driven by a strong elliptically polarized laser field are shown to completely determine the field-free differential photoionization cross section of Ar, i.e., the energy dependence of both the angle-integrated photoionization cross section and the angular distribution asymmetry parameter. DOI: 10.1103/PhysRevA.93.031403 Advances in laser technologies have enabled measurements of atoms and molecules that provide detailed views of their structures as well as the ability to image ultrafast processes on attosecond (10 −18 s) time scales [1][2][3][4][5][6]. Nevertheless, the most common method for obtaining information on the electronic structure of atoms and molecules remains single-photon ionization (since the photoelectron angular and energy distributions are sensitive to both the initial target wave function and the final-state wave function of the ion and continuum electron [7][8][9]). Photoionization experiments nowadays are typically carried out at synchrotron or free-electron laser light source facilities. An appeal of laser spectroscopy for photoionization measurements is the tabletop size of the experimental setup. However, a main obstacle for laser spectroscopy measurements of energy-resolved photoionization spectra is the need for tunable laser sources. This remains a challenge in the important VUV and XUV photon energy regions. However, this problem can be overcome by high-order-harmonic generation (HHG) spectroscopy [10][11][12][13][14], which permits fully coherent, energyresolved photoionization measurements with a laser field whose frequency is much smaller than the ionization potentials of typical atomic or molecular targets. This connection of the nonlinear harmonic-generation process with the linear photoionization process is one of the key advances in our understanding of strong-field processes.HHG spectroscopy is based on the quasiclassical interpretation of HHG as a three-step process [3,15,16]: (i) tunnel ionization of an electron in an atomic or molecular target by a strong low-frequency laser field; (ii) propagation of the ionized electron in the laser-dressed continuum away from and back to the target ion by the oscillating field; and (iii) recombination of the returning electron back to the target ground state with emission of a harmonic photon. The intensity of the harmonic radiation carries information on the photorecombination cross section (PRCS), which is related (through the principle of detailed balance) to that for photoionization. The retrieval of the PRCS is based on the phenomenological parametrization of the HHG yield Y as the product of an electronic wave packet W (E) and the field-free PRCS σ (E) [17,18],where E is the energy of the recombining electron, E is the harmonic energy, and I p is the target binding energy. The parametrization (1) is valid in the tunneling regime and involves the exact PRCS for an electron having momentum directed along the polarization axis of the linearly polarized ...

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Atomic photoionization experiment by harmonic-generation spectroscopy

et al. 2016

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“…In order to understand the physics behind the differences in the spectra in the time-delay and no-time-delay cases, specifically the intensity enhancement and cutoff extension features, we have employed both a time-frequency analysis and a closed-form analytic description of HHG spectra produced by few-cycle pulses [38][39][40] to interpret the results of our TDSE calculations.…”

Section: Analysis and Interpretation Of The Resultsmentioning

confidence: 99%

“…For a more quantitative understanding of our results, we have employed an analytical description of HHG spectra produced by few-cycle pulses [38][39][40]. In this analytic description, the harmonic spectrum ρ( ) is obtained by coherently adding a handful of amplitudes corresponding to ionized electron trajectories (labeled by j and k) from different half cycles of the laser pulse:…”

Section: B Analytic Analysis Of the Hhg Spectramentioning

confidence: 99%

“…These TDSE numerical results, which show that the HHG spectra are highly sensitive to the introduction of a time delay between the two-color, few-cycle pulses, are analyzed and interpreted in Sec. IV by using both a time-frequency analysis and an analytic description of HHG driven by a short laser pulse [37][38][39][40]. These subcycle analyses of the electron dynamics reveal the underlying physics producing the different HHG spectra between the laser-pulse waveforms involving a time delay or not.…”

Section: Introductionmentioning

confidence: 99%

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Enhancing high-order-harmonic generation by time delays between two-color, few-cycle pulses

Peng

Frolov

et al. 2017

Phys. Rev. A

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Use of time delays in high-order-harmonic generation (HHG) driven by intense two-color, few-cycle pulses is investigated in order to determine means of optimizing HHG intensities and plateau cutoff energies. Based upon numerical solutions of the time-dependent Schrödinger equation for the H atom as well as analytical analyses, we show that introducing a time delay between the two-color, few-cycle pulses can result in an enhancement of the intensity of the HHG spectrum by an order of magnitude (or more) at the cost of a reduction in the HHG plateau cutoff energy. Results for both positive and negative time delays as well as various pulse carrier-envelope phases are investigated and discussed.

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“…1 [6]. An alternative approach is to use a high-intensity pulse together with highly-stripped ions containing bound electrons with a large ionization potential.…”

Section: Introductionmentioning

confidence: 99%

Two-color laser high-harmonic generation in cavitated plasma wakefields

Schroeder¹,

Benedetti²,

Esarey³

et al. 2017

AIP Conference Proceedings

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Abstract. A method is proposed for producing coherent x-rays via high-harmonic generation using a laser interacting with highlystripped ions in cavitated plasma wakefields. Two laser pulses of different colors are employed: a long-wavelength pulse for cavitation and a short-wavelength pulse for harmonic generation. This method enables efficient laser harmonic generation in the sub-nm wavelength regime.

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Scaling laws for high-order-harmonic generation with midinfrared laser pulses

Cited by 22 publications

References 40 publications

Atomic photoionization experiment by harmonic-generation spectroscopy

Atomic photoionization experiment by harmonic-generation spectroscopy

Enhancing high-order-harmonic generation by time delays between two-color, few-cycle pulses

Two-color laser high-harmonic generation in cavitated plasma wakefields

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