Coherent superposition of laser-driven soft-X-ray harmonics from successive sources

Seres, J.; Yakovlev, Vladislav S.; Seres, E.; Streli, Christina; Wobrauschek, P.; Spielmann, Christian; Krausz, Ferenc

doi:10.1038/nphys775

Cited by 208 publications

(117 citation statements)

References 37 publications

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“…It has been demonstrated that applications such as X-ray microscopy (Hertz et al 2009) or spectroscopy (Vogt et al 2004), which were restricted to synchrotron experiments could be realized. Apart from plasma sources, also other tabletop setups operating with high harmonic generation (Seres et al 2007;Zepf et al 2007) or X-ray lasers (Wang et al 2006) generate Xradiation of high brilliance. Laser plasmas are attractive compact X-ray sources due to their small size, high spatial stability and high brightness, and/or high flux.…”

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confidence: 99%

Characterization of refractory organic substances by NEXAFS using a compact X-ray source

et al. 2011

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Purpose We present the characterization of environmental samples using near-edge X-ray absorption fine structure (NEXAFS) spectra recorded with an in-house device. We want to point out the feasibility of such an easily accessed complementary technique, if not sometimes alternative to NEXAFS studies performed with synchrotron radiation, as the number of compact setups is increasing. Materials and methods The experiments were carried out using a laser-driven plasma source. We studied heterogeneous samples like refractory organic substances to demonstrate the potential of NEXAFS spectra, achieved by such an instrument, concerning specimens of high chemical complexity.Results and discussion From the respective resonance peaks in the spectra, the presence of certain functional groups, such as aromatic or carbonyl groups, is verified, and the elemental composition is estimated. The results of the reference samples are consistent with the literature. For the environmental samples, external influences of the extraction solvent or fertilizers can be determined from the spectra. Conclusions This could provide the possibility to perform test experiments with samples, which are later studied in more detail with synchrotron light and might as well give an impulse on the broader spread of the application of NEXAFS spectroscopy.

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confidence: 99%

Characterization of refractory organic substances by NEXAFS using a compact X-ray source

et al. 2011

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“…Either a modulation of the pump laser intensity in a modulated-diameter, hollow-core, gas-filled waveguide [14,15,16], or the use of a counter-propagating train of pulses [17,18] were used at this purpose. Recently, theoretical studies have predicted the possibility of achieving QPM by periodically modulating the density of the gas medium [19,20], and a proof-of-concept work has shown the coherent buildup of the harmonic field in two separated gas sources [21].…”

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confidence: 99%

Enhancing the yield of high-order harmonics with an array of gas jets

2008

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We report the experimental observation of an enhancement in the yield of high-order harmonics using an array of gas jets as the source medium. By comparing the experimental outcome for jet arrays of different spacings with the predicted harmonic intensity in the case of slit sources of equivalent lengths, we clearly show how the periodic modulation of the gas density can improve the harmonic yield. This behavior may attributed to a quasi-phase-matching effect which increases the length of coherent harmonic build-up during propagation by partially counteracting the dephasing induced by free electrons.PACS numbers: 32.80. Rm,42.65.Ky,32.80.Fb Keywords: Since its discovery in 1987 [1], the phenomenon of highorder harmonic generation (HHG) has become one of the most interesting topics in the field of highly nonlinear processes. Apart from its fundamental physics interest, HHG is now one of the most promising ways to obtain tunable, short-pulse, narrow-band radiation in the vacuum and extreme ultraviolet (VUV and XUV), and in the soft X-ray regions, where other coherent sources are scarcely available. However, the possibility of using high-order harmonics as a table-top VUV-XUV coherent source for applications is strongly connected to the optimization of the brightness of the source over the broadest spectral range.As in many other nonlinear processes, conversion efficiency in HHG depends on the interplay between the single-atom response [2] and the macroscopic response during propagation in the medium [3]. In particular, a constructive interference of the harmonic field emitted from different locations of the source length can only be obtained over the so-called coherence length L c . For media longer than L c , destructive interference soon depletes the generated field and dramatically limits the conversion efficiency. By an appropriate choice of the interaction parameters it is often possible to make the coherence length longer than the medium, thus reaching the so-called phase-matching conditions. However, when phase-matching is not achievable, one can still artificially beat the coherence length limits by properly modulating the interaction parameters along the field propagation direction. Examples of such quasi-phase-matching (QPM) techniques now abound for low-order nonlinear phenomena in structured crystals, and a few examples have been recently demonstrated in HHG. Many different phenomena contribute to limit the coherence length in HHG. Here, the atomic dispersion and the geometric Guoy phase [4,5], are always accompanied by the dispersion connected to free electrons in the partially ionized medium [6,7], and by the characteristic atomic dipole phase [8,9,10,11,12]. Depending on the gas type and density, and on the level of ionization, the coherence length in HHG is usually so short as to pose a serious limit to significant conversion efficiencies. Differently from QPM in periodically-poled nonlinear crystals [13], where the sign of the nonlinear coefficient is periodically flipped so as to always add c...

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“…In addition they examined the quality and divergence of the emitted HH beam. Systematic studies of HHG parameters in a single cell have also been reported by Ditmire et al [28] using thin cells (<1 mm) and Seres et al [35] using multiple cells.…”

Section: High Harmonic Generationmentioning

confidence: 67%

“…Pioneering time resolved studies using EUV carries an intensity dependent phase, making phase matching much more demanding [24][25][26]. Popular schemes to make use of some phase matching include gas jets [27][28][29], gas cells [16,[30][31][32][33][34] multiple gas cells in series [35] hollow core capillaries [36] and plasma plumes [37].…”

Section: Introductionmentioning

confidence: 99%

A Beamline for Time-Resolved Extreme Ultraviolet and Soft X-Ray Spectroscopy

Koch¹

2014

J Anal Bioanal Tech

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High harmonic generation is a convenient way to obtain extreme ultraviolet light from table-top laser systems and the experimental tools to exploit this simple and powerful light source for time-resolved spectroscopy are being developed by several groups. For these applications, brightness and stability of the high harmonic generation is a key feature. This article focuses on practical aspects in the generation of extreme ultraviolet pulses with ultrafast commercial lasers, namely generation parameters and online monitoring as well as analysis of generation yield and stability.

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Coherent superposition of laser-driven soft-X-ray harmonics from successive sources

Cited by 208 publications

References 37 publications

Characterization of refractory organic substances by NEXAFS using a compact X-ray source

Characterization of refractory organic substances by NEXAFS using a compact X-ray source

Enhancing the yield of high-order harmonics with an array of gas jets

A Beamline for Time-Resolved Extreme Ultraviolet and Soft X-Ray Spectroscopy

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