Metrology of high-order harmonics for free-electron laser seeding

Erny, Christian; Mansten, Erik; Gisselbrecht, Mathieu; Schwenke, Jörg; Rakowski, Rafał; He, Xinkui; Gaarde, Mette B.; Werin, Sverker; L’Huillier, Anne

doi:10.1088/1367-2630/13/7/073035

Cited by 19 publications

(19 citation statements)

References 37 publications

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“…Our calculations26 confirm the experimental observation that HHG in Ar peaks at a certain pressure (~10 mbar) which corresponds to optimized phase matching27, while below-threshold harmonics continue to increase up to pressures as high as 100 mbar. We also investigated the propagation of the fundamental and TH fields in a high pressure cell28 (see Methods).…”

Section: Resultssupporting

confidence: 86%

“…We performed calculations which combine the solution of the time-dependent Schrödinger equation in a single-active electron approximation and propagation in a partially ionized medium265 using a slowly-varying envelope approximation. Our main goal was to examine the influence of the pressure both for low-order and high-order harmonic generation in conditions mimicking the experiment.…”

Section: Methodsmentioning

confidence: 99%

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

Brizuela

Heyl

Rudawski

et al. 2013

Sci Rep

104

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High-order harmonic generation (HHG) in gases has been established as an important technique for the generation of coherent extreme ultraviolet (XUV) pulses at ultrashort time scales. Its main drawback, however, is the low conversion efficiency, setting limits for many applications, such as ultrafast coherent imaging, nonlinear processes in the XUV range, or seeded free electron lasers. Here we introduce a novel scheme based on using below-threshold harmonics, generated in a “seeding cell”, to boost the HHG process in a “generation cell”, placed further downstream in the focused laser beam. By modifying the fundamental driving field, these low-order harmonics alter the ionization step of the nonlinear HHG process. Our dual-cell scheme enhances the conversion efficiency of HHG, opening the path for the realization of robust intense attosecond XUV sources.

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Section: Resultssupporting

confidence: 86%

Section: Methodsmentioning

confidence: 99%

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

Brizuela

Heyl

Rudawski

et al. 2013

Sci Rep

104

View full text Add to dashboard Cite

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“…Due to the high sensitivity of the XUV camera to the infrared radiation, the harmonic beam energy is measured within the aluminum filter's transmission window, i.e., between 14 eV and 71 eV, corresponding to harmonic orders between 11 and 45. The measurement procedure, similar to the one described by Erny et al, 31 is based on XUV-CCD recorded backgroundsubtracted images. The images are integrated to obtain the total number of counts.…”

Section: Resultsmentioning

confidence: 99%

A high-flux high-order harmonic source

Rudawski

Heyl

Brizuela

et al. 2013

Review of Scientific Instruments

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We develop and implement an experimental strategy for the generation of high-energy high-order harmonics (HHG) in gases for studies of nonlinear processes in the soft x-ray region. We generate high-order harmonics by focusing a high energy Ti:Sapphire laser into a gas cell filled with argon or neon. The energy per pulse is optimized by an automated control of the multiple parameters that influence the generation process. This optimization procedure allows us to obtain energies per pulse and harmonic order as high as 200 nJ in argon and 20 nJ in neon, with good spatial properties, using a loose focusing geometry (\documentclass[12pt]{minimal}\begin{document}$f_\# \approx 400$\end{document}f#≈400) and a 20 mm long medium. We also theoretically examine the macroscopic conditions for absorption-limited conversion efficiency and optimization of the HHG pulse energy for high-energy laser systems.

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“…An HHG light source provides temporally and spatially coherent radiation in the EUV and soft X-ray region, and its well-defined phase properties even allow the formation of single attosecond pulses or pulse trains [15,16]. Several HHG sources for seeding a free-electron laser (FEL) are discussed in the literature [17][18][19]. First seeding of an FEL using an HHG source has been demonstrated at the SPring-8 compact SASE source at 160 nm [20].…”

Section: Introductionmentioning

confidence: 99%

A high-harmonic generation source for seeding a free-electron laser at 38 nm

et al. 2013

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Direct seeding with a high-harmonic generation (HHG) source can improve the spectral, temporal, and coherence properties of a free-electron laser (FEL) and shall reduce intensity and arrival-time fluctuations. In the seeding experiment sFLASH at the extreme ultraviolet FEL in Hamburg FLASH, which operates in the selfamplified spontaneous emission mode (SASE), the 21st harmonic of an 800 nm laser is refocused into a dedicated seeding undulator. For seeding, the external light field has to overcome the noise level of SASE; therefore, an efficient coupling between seed pulse and electron bunch is mandatory. Thus, an HHG beam with a proper divergence, width, beam quality, Rayleigh length, pointing stability, single-shot pulse energy, and stability in the 21st harmonic is needed. Here, we present the setup of the HHG source that seeds sFLASH at 38.1 nm, the optimization procedures, and the necessary diagnostics.

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Metrology of high-order harmonics for free-electron laser seeding

Cited by 19 publications

References 37 publications

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

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

A high-flux high-order harmonic source

A high-harmonic generation source for seeding a free-electron laser at 38 nm

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