A femtosecond X-ray/optical cross-correlator

Gahl, Cornelius; Azima, Armin; Beye, Martin; Deppe, Martin H.; Döbrich, K. M.; Hasslinger, Urs; Hennies, Franz; Melnikov, A.V.; Nagasono, Mitsuru; Pietzsch, Annette; Wolf, Martin; Würth, W.; Föhlisch, Alexander

doi:10.1038/nphoton.2007.298

Cited by 151 publications

(115 citation statements)

References 38 publications

(29 reference statements)

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“…13 If the photon frequency exceeds the plasmon frequency ω p , the dielectric function becomes positive and the incident light can propagate into the material. The dielectric function then is dominated by band structure absorption processes similar to that in Equation (5). This also applies to insulators and semiconductors where x-ray absorption has produced a significant density of excited electrons in the conduction band.…”

confidence: 95%

“…3,4 The increase in conduction electrons and valence holes causes an abrupt change in optical reflectivity, which makes the x-ray pump optical probe technique a valuable tool for characterizing the dynamical response of the material as well as the temporal characteristics of the incident x-ray pulse. 5,6 Optical pump optical probe studies have long been used to observe dynamical responses in a variety of materials, especially with the advent of high power femtosecond lasers. 7,8 For semiconductors and insulators, changes in optical reflectivity are directly dependent on changes in absorption: when absorption increases at the optical probe energy, for example, fewer photons can be reflected.…”

mentioning

confidence: 99%

“…9 Below we analyze the basic response seen in x-ray pump optical probe reflectivity measurements of insulating silicon nitride (Si 3 N 4 ), semiconducting gallium arsenide (GaAs), and metallic gold (Au). 5,10 This analysis assumes that the band structure is not drastically changed, i.e. that the deposited power is not driving the material into a new metastable phase or creating irreversible damage.…”

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confidence: 99%

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X-ray induced optical reflectivity

Durbin

2012

AIP Advances

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The change in optical reflectivity induced by intense x-ray pulses can now be used to study ultrafast many body responses in solids in the femtosecond time domain. X-ray absorption creates photoelectrons and core level holes subsequently filled by Auger or fluorescence processes, and these excitations ultimately add conduction and valence band carriers that perturb optical reflectivity. Optical absorption associated with band filling and band gap narrowing is shown to explain the basic features found in recent measurements on an insulator (silicon nitride, Si3N4), a semiconductor (gallium arsenide, GaAs), and a metal (gold, Au), obtained with ∼100 fs x-ray pulses at 500-2000 eV and probed with 800 nm laser pulses. In particular GaAs exhibits an abrupt drop in reflectivity, persisting only for a time comparable to the x-ray excitation pulse duration, consistent with prompt band gap narrowing

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confidence: 95%

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confidence: 99%

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confidence: 99%

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X-ray induced optical reflectivity

Durbin

2012

AIP Advances

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“…This is a single-shot method with a best resolution reported to date of about 10 fs (refs 17,18). Multi-shot methods such as those based on spectral analysis 19,20 or correlation techniques 12,[21][22][23][24] have also been explored; these typically yield the pulse duration but not the temporal distribution.…”

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confidence: 99%

Few-femtosecond time-resolved measurements of X-ray free-electron lasers

et al. 2014

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X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1 fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100 GW.

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“…5,6 For the hard x-ray regime strong field ionization of atomic targets opening resonant absorption channels has been proposed as x-ray-optical cross correlation technique. 7 Alternative approaches to twocolor ionization of atomic targets are to measure ultrafast x-ray induced changes in surface reflectivity 8 or transient changes in the optical transmission of a membrane via spectral encoding. 9 Based on the tilted wavefront technique, 10 the reflectivity method has been further developed into a single-shot measurement of the relative timing between short wavelength pulses from the FLASH free electron and an external optical laser.…”

mentioning

confidence: 99%

X-ray–optical cross-correlator for gas-phase experiments at the Linac Coherent Light Source free-electron laser

Schorb

Gorkhover

Cryan

et al. 2012

Applied Physics Letters

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X-ray–optical pump–probe experiments at the Linac Coherent Light Source (LCLS) have so far been limited to a time resolution of 280 fs fwhm due to timing jitter between the accelerator-based free-electron laser (FEL) and optical lasers. We have implemented a single-shot cross-correlator for femtosecond x-ray and infrared pulses. A reference experiment relying only on the pulse arrival time information from the cross-correlator shows a time resolution better than 50 fs fwhm (22 fs rms) and also yields a direct measurement of the maximal x-ray pulse length. The improved time resolution enables ultrafast pump–probe experiments with x-ray pulses from LCLS and other FEL sources.

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A femtosecond X-ray/optical cross-correlator

Cited by 151 publications

References 38 publications

X-ray induced optical reflectivity

X-ray induced optical reflectivity

Few-femtosecond time-resolved measurements of X-ray free-electron lasers

X-ray–optical cross-correlator for gas-phase experiments at the Linac Coherent Light Source free-electron laser

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