Resonantly-enhanced harmonic generation in Argon

Ackermann, Patric; Münch, Holger; Halfmann, Thomas

doi:10.1364/oe.20.013824

Cited by 24 publications

(15 citation statements)

References 10 publications

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“…We do this by first solving the time-dependent Schrödinger equation (TDSE) in the single active electron (SAE) approximation for wavelengths between 425 − 500 nm and for intensities up to 140 TW/cm 2 . We have chosen the intensity and wavelength regime such that the Keldysh parameter, of approximately 2, is in line with previous studies [11,15,21]. We identify resonant enhancement of harmonics 7, 9, and 11 (H7, H9, H11) due to Stark-shifted resonances between the ground state and the 1s2p, 1s3p, and 1s4p states.…”

Section: Introductionmentioning

confidence: 78%

Interplay between resonant enhancement and quantum path dynamics in harmonic generation in helium

2015

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We present a theoretical study of the influence of resonant enhancement on quantum path dynamics in the generation of harmonics above and below the ionization threshold in helium. By varying the wavelength and intensity of the driving field from 425 to 500 nm and from 30 to 140 TW/cm 2 , respectively, we identify enhancements of harmonics 7, 9, and 11 that correspond to multiphoton resonances between the ground state and the Stark-shifted 1s2p, 1s3p, and 1s4p excited states. A time-frequency analysis of the emission shows that both the short and the long quantum path contributions to the harmonic yield are enhanced through these bound-state resonances. We analyze the subcycle time structure of the ninth harmonic yield in the vicinity of the resonances and find that on resonance the long trajectory contribution is phase shifted by approximately π/4. Finally, we compare the single atom and the macroscopic response of a helium gas and find that while the subcycle time profiles are slightly distorted by propagation effects, the phase shift of the long-trajectory contribution is still recognizable.

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Section: Introductionmentioning

confidence: 78%

Interplay between resonant enhancement and quantum path dynamics in harmonic generation in helium

2015

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“…Resonant HHG may increase the harmonic yield through a number of different mechanisms35363738394041. For H21 with photon energy of 25.2 eV, the closest resonance is the 3s 2 3p 6 → 3s 1 3p 6 4p 1 transition (26.6 eV), which is a window resonance4243.…”

Section: Resonant Hhgmentioning

confidence: 99%

Sub-cycle ionization dynamics revealed by trajectory resolved, elliptically-driven high-order harmonic generation

Larsen

Carlström

Lorek

et al. 2016

Sci Rep

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The sub-cycle dynamics of electrons driven by strong laser fields is central to the emerging field of attosecond science. We demonstrate how the dynamics can be probed through high-order harmonic generation, where different trajectories leading to the same harmonic order are initiated at different times, thereby probing different field strengths. We find large differences between the trajectories with respect to both their sensitivity to driving field ellipticity and resonant enhancement. To accurately describe the ellipticity dependence of the long trajectory harmonics we must include a sub-cycle change of the initial velocity distribution of the electron and its excursion time. The resonant enhancement is observed only for the long trajectory contribution of a particular harmonic when a window resonance in argon, which is off-resonant in the field-free case, is shifted into resonance due to a large dynamic Stark shift.

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“…These studies comprise both the theoretical treatment and the first attempts to achieve the resonance conditions in gas HHG experiments. While theoretical estimates testify the possibility of efficient enhancement of individual harmonics and groups of harmonics, experiments in gases revealed the difficulties encountered in the observation of resonantly enhanced single harmonic [20]. Further developments have revealed that the use of laser ablation plasma media could largely facilitate the resonance enhancement of harmonics.…”

Section: Introductionmentioning

confidence: 99%

Comparative studies of resonance enhancement of harmonic radiation in indium plasma using multicycle and few-cycle pulses

et al. 2013

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Enhanced single harmonic generation is analyzed in indium laser ablation plasmas at excitation conditions of multicycle (30 fs) and few-cycle (3.5 fs) pulses. We demonstrate the strong influence of pulse duration, on the emission spectra from the indium plasma. For few-cycle pulses, the enhanced emissions do not coincide with the expected harmonic wavelengths, which is the case for multicycle pulses. We test the coherent properties of an enhanced emission around 20 eV using polarization and double-slit interference techniques. We also characterize the dynamics of the emissions from the indium plasma by tuning the laser pulse duration. A theoretical analysis is presented to describe the indium plasma emission upon excitation by few-cycle pulses.

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Resonantly-enhanced harmonic generation in Argon

Cited by 24 publications

References 10 publications

Interplay between resonant enhancement and quantum path dynamics in harmonic generation in helium

Interplay between resonant enhancement and quantum path dynamics in harmonic generation in helium

Sub-cycle ionization dynamics revealed by trajectory resolved, elliptically-driven high-order harmonic generation

Comparative studies of resonance enhancement of harmonic radiation in indium plasma using multicycle and few-cycle pulses

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