An experiment for two-color photoionization using high intensity extreme-UV free electron and near-IR laser pulses

Radcliffe, P.; Düsterer, S.; Azima, Armin; Li, W.B.; Plönjes, Elke; Redlin, H.; Feldhaus, J.; Nicolosi, P.; Poletto, Luca; Dardis, J.; Gutiérrez, Joaquín M.; Hough, P.; Kavanagh, K.; Kennedy, E. T.; Luna, H.; Yeates, P.D.; Costello, J. T.; Delyseries, A.; Lewis, Ciaran; Glijer, D.; Cubaynes, D.; Meyer, Michael

doi:10.1016/j.nima.2007.09.014

Cited by 42 publications

(39 citation statements)

References 22 publications

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“…This laser is essentially a copy of the photocathode laser producing the electron pulses for the FEL and can thus provide the same pulse pattern as the FEL 21 . The actively mode-locked oscillator of the laser system allows a synchronization better than 1 ps jitter to the XUV pulses of the FEL 22 . This laser was focused to an approximately 30 mm FWHM spot on the sample and delivered approximately 25 mJ per pulse, producing fluences on the sample of between 2 and 6 J cm 22 .…”

Section: Methodsmentioning

confidence: 99%

“…The actively mode-locked oscillator of the laser system allows a synchronization better than 1 ps jitter to the XUV pulses of the FEL 22 . This laser was focused to an approximately 30 mm FWHM spot on the sample and delivered approximately 25 mJ per pulse, producing fluences on the sample of between 2 and 6 J cm 22 . The pulse length for the pump laser was 12.5 ps, giving peak intensities of about 2.2 Â 10 11 W cm 22 on the sample, adequate to fully destroy the sample in a single pulse.…”

Section: Methodsmentioning

confidence: 99%

“…A short-pulse linearly polarized laser (Nd:YLF operated at 523 nm) was used to initiate material ablation. The laser pulse length was 12.5 ps and delivered $25 mJ per pulse into a 30 mm FWHM focal spot on the sample, giving peak intensities of about 2.2 Â 10 11 W cm 22 . As incident from the left is focused onto the sample (iii) and acts as the excitation pulse.…”

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Ultrafast single-shot diffraction imaging of nanoscale dynamics

et al. 2008

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The transient nanoscale dynamics of materials on femtosecond to picosecond timescales is of great interest in the study of condensed phase dynamics such as crack formation, phase separation and nucleation, and rapid fluctuations in the liquid state or in biologically relevant environments. The ability to take images in a single shot is the key to studying non-repetitive behaviour mechanisms, a capability that is of great importance in many of these problems. Using coherent diffraction imaging with femtosecond X-ray free-electron-laser pulses we capture time-series snapshots of a solid as it evolves on the ultrafast timescale. Artificial structures imprinted on a Si 3 N 4 window are excited with an optical laser and undergo laser ablation, which is imaged with a spatial resolution of 50 nm and a temporal resolution of 10 ps. By using the shortest available free-electronlaser wavelengths 1 and proven synchronization methods 2 this technique could be extended to spatial resolutions of a few nanometres and temporal resolutions of a few tens of femtoseconds. This experiment opens the door to a new regime of time-resolved experiments in mesoscopic dynamics.To date, optical pulses have made it possible to resolve dynamics on the femtosecond timescale, but the spatial resolution of these studies has been limited to a few micrometres 3 . On the other hand, femtosecond X-ray pulses have been used to detect Å ngstrom-scale atomic motions in extended crystalline materials with long-range order through time-resolved diffraction experiments 4,5 . An entirely different methodology is needed to investigate the ultrafast dynamics of non-crystalline materials at nanometre length scales. Applications at these scales can be found in the study of fracture dynamics, shock formation, spallation, ablation, and plasma formation under extreme conditions. In the solid state it is desirable to directly image dynamic processes such as nucleation and phase growth, phase fluctuations and various forms of electronic or magnetic segregation.Electron microscopes can provide nanometre to atomic resolution, and have recently been demonstrated with ultrafast pulses 6 . However, they have limited penetrating power and struggle to obtain high-quality single-shot images due to space-charge issues 7 . Synchrotron beams from third-generation sources have comparatively long pulse lengths of 10-100 ps, as determined by the shortest electron bunch length possible in a given storage ring. Synchrotron sources can produce short-pulse ($100 fs) X-rays when operated as femtosecond slicing sources 8 , but produce comparatively weak X-ray beams of 1 Â 10 7 photons per second. Along with X-ray pulses from femtosecond laser plasma sources 9,10 and high-harmonic-generation sources 11 this limits their use to non-destructive phenomena where weak signals can be accumulated over many repeatable excitations of the sample.The intense femtosecond X-ray pulses from free-electron-laser (FEL) sources provide the penetrating power, spatial resolution and single-shot imaging c...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Ultrafast single-shot diffraction imaging of nanoscale dynamics

et al. 2008

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“…However, the measurement capabilities of FELs are currently limited to 100 fs by the timing stability of the electron beams and the synchronization capabilities between the electron beams and the optical lasers. Conventional microwave timing synchronization, which is based on coaxial cables, has difficulties in achieving even ps long-term stability as a result of the large timing drifts over the extent of a FEL [99]. As a remedy for this timing problem, it has been shown that the post-processing of X-ray pulse arrival time can be used to reduce the timing uncertainty to the 60-fs level [100].…”

Section: Large-scale Optical and Microwave Timing Synchronization Sysmentioning

confidence: 99%

Attosecond‐precision ultrafast photonics

Kim

Kärtner

2010

Laser & Photonics Reviews

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We review our recent progress toward attosecondprecision ultrafast photonics based on ultra-low timing jitter optical pulse trains from mode-locked lasers. In femtosecond mode-locked lasers, the concentration of a large number of photons in an extremely short pulse duration enables the scaling of timing jitter into the attosecond regime. To characterize such jitter levels, we developed new attosecond-resolution measurement techniques and show that standard fiber lasers can achieve sub-fs high-frequency jitter. By leveraging the ultralow jitter of free-running mode-locked lasers, we pursued highprecision optical-optical and optical-microwave synchronization techniques. Optical signals spanning 1.5 octaves were synthesized by attosecond-precision timing and phase synchronization of two independent mode-locked lasers. High-stability microwave signals were also synthesized from mode-locked lasers with drift-free sub-10-fs precision. We further demonstrated the attosecond-precision distribution of optical pulse trains to remote locations via timing-stabilized fiber links. Finally, the application of optical pulse trains for high-resolution sampling and analog-to-digital conversion is discussed.The ultra-low timing jitter of optical pulse trains from femtosecond mode-locked lasers can be used for the attosecond-precision generation, distribution, measurement, and synchronization of optical and microwave signals.

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“…The experiments were performed on beam line BL2 at FLASH using an experimental setup for electron spectroscopy similar to that described earlier [11]. The FEL was operated in single-bunch mode at a 5 Hz repetition rate and fundamental wavelengths of 26.9 nm (46 eV) with a mean pulse energy of 10-15 J as measured on line for each pulse using a gas-monitor detector [12].…”

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Two-Photon Excitation and Relaxation of the3d−4dResonance in Atomic Kr

et al. 2010

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Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes. DOI: 10.1103/PhysRevLett.104.213001 PACS numbers: 32.80.Rm, 32.80.Fb, 32.80.Hd, 42.50.Hz The chief manifestation of the coupling of electrons bound in atoms or molecules to electromagnetic radiation of high intensity is the onset of nonlinear processes, a feature that could in fact be viewed as the definition of a strong field. Phenomena such as multiphoton multiple ionization, above threshold ionization (ATI), and high order harmonic generation span the broad field of strong field physics that has until recently been restricted to interactions with infrared and optical radiation [1]. Because of the small photon energy, only the outermost electrons are ionized and multiple ionization is obtained via successive stripping of the outer subshell. In contrast, short-wavelength radiation couples predominantly to electrons in lower, more strongly bound shells, producing corehole states, which decay primarily by ultrafast Auger decay. The opportunity to study the underlying multiphoton dynamics arises only now with the availability of free electron lasers (FELs) in the extreme ultraviolet (XUV) to hard-x-ray wavelength regime [2,3].The investigation of nonlinear interactions using FELs started recently and has already highlighted several phenomena, such as, e.g., the formation of very high charged states [4,5] and two-photon double ionization [6,7], that could not be anticipated on the basis of the existing linear experience. A unique access to explore the interaction between matter and strong XUV fields is given by resonant two-photon inner-shell processes. Firstly, two-photon processes enable the study of a class of resonances, which are inaccessible in a single-photon process from the ground state. Secondly, inner-shell resonances are characterized by a dramatic increase of the photoionization cross section and provide, for example, chemical (i.e., atomic) selectivity in the photoionization process of molecules or clusters. The lifetime of a core hole of the order of several femtoseconds is determined by Auger processes, and the excitation in strong XUV fields of similar durations will inevitably result in the competition between sequential ionization and Auger decay. This new phenomenon, which will be present in all processes involving the interaction between intense XUV light and matter, can be addressed only due to the short pulse durations. It is the nonlinear behavior of such interactions that presents a new frontier, with multiphoton excitation and/or ionization o...

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An experiment for two-color photoionization using high intensity extreme-UV free electron and near-IR laser pulses

Abstract: We describe an experimental system designed for single-shot photoelectron spec-

Cited by 42 publications

References 22 publications

Ultrafast single-shot diffraction imaging of nanoscale dynamics

Ultrafast single-shot diffraction imaging of nanoscale dynamics

Attosecond‐precision ultrafast photonics

Two-Photon Excitation and Relaxation of the3d−4dResonance in Atomic Kr

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