Efficient high-order harmonic generation boosted by below-threshold harmonics

Brizuela, F.; Heyl, Christoph M.; Rudawski, Piotr; Kroon, David; Rading, Linnea; Dahlström, Jan Marcus; Mauritsson, Johan; Johnsson, Per; Arnold, Cord L.; L’Huillier, Anne

doi:10.1038/srep01410

Cited by 109 publications

(90 citation statements)

References 30 publications

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“…The enhancement of high harmonics generation boosted by below-threshold harmonics 23 has not been seen in this experiment. This enhancement was seen when the low harmonics (3-7eV) of the first gas target were optimised, with the high harmonics (>20eV) not produced efficiently.…”

Section: Methodscontrasting

confidence: 55%

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Synchronized pulses generated at 20 eV and 90 eV for attosecond pump–probe experiments

et al. 2015

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The development of attosecond pulses across different photon energies is an essential precursor to performing pump-probe attosecond experiments in complex systems, where the potential of attosecond science 1 can be further developed 2,3 . We report the generation and characterization of synchronised XUV (90 eV) and VUV (20 eV) pulses generated simultaneously via high harmonic generation. The VUV pulses are well suited for pump-probe experiments that exploit the high photoionisation cross-section of many molecules in this spectral region 4 , and the higher photon flux due to the higher conversion efficiency of the high harmonics generation process at these energies 5 . We temporally characterised all pulses using the attosecond streaking technique 6 and the FROG-CRAB retrieval method 7 . We report 57616 as pulses at 20 eV and 25721 as pulses at 90 eV. Our demonstration of synchronised attosecond pulses at different photon energies, and inherently jitter-free due to the common-path geometry implemented, offers unprecedented possibilities for pump-probe studies.The production of isolated attosecond pulses (IAP) in the extreme ultraviolet (XUV) region (30-150 eV) with an intense near-infrared (NIR) femtosecond laser is nowadays a robust process. The generation of IAP via high harmonic generation 1 (HHG) requires temporally gating the high harmonics emission to a single burst by using one of several techniques. Most common are polarization gating 8 , double optical gating 9 , ionization gating 10 and amplitude gating 11 . However, the

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Section: Methodscontrasting

confidence: 55%

“…We employed in-line interaction regions in a pair of pulsed gas targets 22,23 to simultaneously generate XUV and VUV pulses with a single NIR pulse. Such implementation provides a convenient spatial and temporal superposition of the generated pulses and minimizes the time jitter of the two pulses due to the common-path geometry.…”

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confidence: 99%

Synchronized pulses generated at 20 eV and 90 eV for attosecond pump–probe experiments

et al. 2015

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“…Similarly, enhancement of HHG has been predicted in many theoretical simulations (Supplementary Discussion). More recently, advancement in optical parametric amplification (OPA) and optical parametric chirped-pulse amplification (OPCPA) technology has made it possible to perform coherent wavelength multiplexing of ultra-broadband (over two or more octaves) pulses with full phase and amplitude control, thus allowing the generation of any optical waveform [8][9][10][11][12][13][14][15][16][17][18] . With so many 'knobs' accessible, it is of critical importance to develop a general algorithm for optimal waveform control for the efficient enhancement of high-harmonic generation and for other strong field phenomena.…”

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confidence: 99%

Waveforms for optimal sub-keV high-order harmonics with synthesized two- or three-colour laser fields

et al. 2014

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High-order harmonics extending to the X-ray region generated in a gas medium by intense lasers offer the potential for providing tabletop broadband light sources but so far are limited by their low conversion efficiency. Here we show that harmonics can be enhanced by one to two orders of magnitude without an increase in the total laser power if the laser's waveform is optimized by synthesizing two-or three-colour fields. The harmonics thus generated are also favourably phase-matched so that radiation is efficiently built up in the gas medium. Our results, combined with the emerging intense high-repetition MHz lasers, promise to increase harmonic yields by several orders to make harmonics feasible in the near future as general bright tabletop light sources, including intense attosecond pulses.

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“…To overcome low up-conversion efficiency of HHG, it has been proposed to modify the subcycle laser waveform by optimally synthesizing multicolor laser pulses [31][32][33][34][35][36][37] (see review in Ref. [38]).…”

Section: Introductionmentioning

confidence: 99%

Macroscopic scaling of high-order harmonics generated by two-color optimized waveforms in a hollow waveguide

2017

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We present the macroscopic scaling of high harmonics generated by two-color laser pulses interacting with Ne gas in a hollow waveguide. We demonstrate that the divergence of harmonics is inversely proportional to the waveguide radius and harmonic yields are proportional to the square of the waveguide radius when the gas pressure and waveguide length are chosen to meet the phase-matching condition. We also show that harmonic yields are inversely proportional to the ionization level of the optimized two-color waveform with proper gas pressure if waveguide radius and length are fixed. These scaling relations would help experimentalists find phase-matching conditions to efficiently generate tabletop high-flux coherent soft x rays for applications.

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Efficient high-order harmonic generation boosted by below-threshold harmonics

Cited by 109 publications

References 30 publications

Synchronized pulses generated at 20 eV and 90 eV for attosecond pump–probe experiments

Synchronized pulses generated at 20 eV and 90 eV for attosecond pump–probe experiments

Waveforms for optimal sub-keV high-order harmonics with synthesized two- or three-colour laser fields

Macroscopic scaling of high-order harmonics generated by two-color optimized waveforms in a hollow waveguide

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