-
M. Trigo,
M. Fuchs,
J. Chen,
M. P. Jiang,
M. E. Kozina,
G. Ndabashimiye,
M. Cammarata,
G. Chien,
S. Fahy, D. M. Fritz, [......],
S. L. Johnson,
J. Larsson,
H. Lemke,
A. M. Lindenberg,
F. Quirin,
K. Sokolowski-Tinten,
C. Uher,
J. S. Wark,
D. Zhu,
D. A. Reis
[show abstract]
[hide abstract]
ABSTRACT: The macroscopic characteristics of a solid, such as its thermal, optical or
transport properties are determined by the available microscopic states above
its lowest energy level. These slightly higher quantum states are described by
elementary excitations and dictate the response of the system under external
stimuli. The spectrum of these excitations, obtained typically from inelastic
neutron and x-ray scattering, is the spatial and temporal Fourier transform of
the density-density correlation function of the system, which dictates how a
perturbation propagates in space and time. As frequency-domain measurements do
not generally contain phase information, time-domain measurements of these
fluctuations could yield a more direct method for investigating the excitations
of solids and their interactions both in equilibrium and far-from equilibrium.
Here we show that the diffuse scattering of femtosecond x-ray pulses produced
by a free electron laser (FEL) can directly measure these density-density
correlations due to lattice vibrations in the time domain. We obtain
spectroscopic information of the lattice excitations with unprecedented
momentum- and frequency- resolution, without resolving the energy of the
outgoing photon. Correlations are created via an acoustic analog of the
dynamical Casimir effect, where a femtosecond laser pulse slightly quenches the
phonon frequencies, producing pairs of squeezed phonons at momenta +q and -q.
These pairs of phonons manifest as macroscopic, time-dependent coherences in
the displacement correlations that are then probed directly by x-ray
scattering. Since the time-dependent correlations are preferentially created in
regions of strong electron-phonon coupling, the time-resolved approach is
natural as a spectroscopic tool of low energy collective excitations in solids,
and their microscopic interactions, both in linear response and beyond.
01/2013;
-
A M Lindenberg,
S Engemann,
K J Gaffney,
K Sokolowski-Tinten,
J Larsson,
P B Hillyard,
D A Reis, D M Fritz,
J Arthur,
R A Akre, [......],
R W Falcone,
S H Lee,
R Pahl,
J Rudati,
P H Fuoss,
A J Nelson,
P Krejcik,
D P Siddons,
P Lorazo,
J B Hastings
[show abstract]
[hide abstract]
ABSTRACT: Femtosecond time-resolved small and wide angle x-ray diffuse scattering techniques are applied to investigate the ultrafast nucleation processes that occur during the ablation process in semiconducting materials. Following intense optical excitation, a transient liquid state of high compressibility characterized by large-amplitude density fluctuations is observed and the buildup of these fluctuations is measured in real time. Small-angle scattering measurements reveal snapshots of the spontaneous nucleation of nanoscale voids within a metastable liquid and support theoretical predictions of the ablation process.
Physical Review Letters 04/2008; 100(13):135502. · 7.37 Impact Factor
-
J. Arthur,
S. Boutet,
J-C. Castagna,
H. Chapman,
Y. Feng,
W. Foyt, D.M. Fritz,
K.J. Gaffney,
G. Gr|bel,
J. Hajdu, [......],
N. Kurita,
J. Larsson,
K. Ludwig,
M. Messerschmidt,
J. Miao,
D.A. Reis,
A. Robert,
G.B. Stephenson,
Th. Tschentscher,
N. van Bakel
[show abstract]
[hide abstract]
ABSTRACT: The Stanford Linear Accelerator Center (SLAC), along with Argonne National Laboratory (ANL), Lawrence Livermore National Laboratory (LLNL), and the University of California at Los Angeles (UCLA), is constructing a Free-Electron Laser (FEL) facility, which will operate in the wavelength range 1.5 nm - 0.15 nm. This FEL, the Linac Coherent Light Source (LCLS), utilizes the SLAC linac and will produce sub-picosecond pulses of short wavelength X-rays with very high peak brightness and almost complete transverse coherence. The final one-third of the SLAC linac will be used as the source of electrons for the LCLS. The high energy electrons will be transported across the SLAC Research Yard, into a tunnel which will house a long undulator. In passing through the undulator, the electrons will be bunched by the force of their own synchrotron radiation and produce an intense, monochromatic, spatially coherent beam of X-rays. By varying the electron energy, the FEL X-ray wavelength will be tunable from 1.5 nm to 0.15 nm. The LCLS will include two experimental halls as well as X-ray optics and infrastructure necessary to create a facility that can be developed for research in a variety of disciplines such as atomic physics, materials science, plasma physics and biosciences. This Conceptual Design Report, the authors believe, confirms the feasibility of designing and constructing three X-ray instruments in order to exploit the unique scientific capability of this new LCLS facility. The technical objective of the LCLS Ultrafast Science Instruments (LUSI) project is to design, build, and install at the LCLS three hard X-ray instruments that will complement the initial instrument included in the LCLS construction. As the science programs advance and new technological challenges appear, instrumentation needs to be developed and ready to conquer these new opportunities. The LCLS instrument concepts have been developed in close consultation with the scientific community through a series of workshops team meetings and focused reviews. In particular, the LUSI project instruments have been identified as meeting the most urgent needs of the scientific community based on the advice of the LCLS Scientific Advisory Committee (SAC) in response to an open call for letters of intent (LOI) from the breadth of the scientific community.
10/2007;
-
P B Hillyard,
K J Gaffney,
A M Lindenberg,
S Engemann,
R A Akre,
J Arthur,
C Blome,
P H Bucksbaum,
A L Cavalieri,
A Deb, [......],
S H Lee,
D A Meyer,
A J Nelson,
R Pahl,
D A Reis,
J Rudati,
D P Siddons,
K Sokolowski-Tinten,
D von der Linde,
J B Hastings
[show abstract]
[hide abstract]
ABSTRACT: The ultrafast decay of the x-ray diffraction intensity following laser excitation of an InSb crystal has been utilized to observe carrier dependent changes in the potential energy surface. For the first time, an abrupt carrier dependent onset for potential energy surface softening and the appearance of accelerated atomic disordering for a very high average carrier density have been observed. Inertial dynamics dominate the early stages of crystal disordering for a wide range of carrier densities between the onset of crystal softening and the appearance of accelerated atomic disordering.
Physical Review Letters 04/2007; 98(12):125501. · 7.37 Impact Factor
-
D M Fritz,
D A Reis,
B Adams,
R A Akre,
J Arthur,
C Blome,
P H Bucksbaum,
A L Cavalieri,
S Engemann,
S Fahy, [......],
A J Nelson,
M Nicoul,
R Pahl,
J Rudati,
H Schlarb,
D P Siddons,
K Sokolowski-Tinten,
Th Tschentscher,
D von der Linde,
J B Hastings
[show abstract]
[hide abstract]
ABSTRACT: Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.
Science 03/2007; 315(5812):633-6. · 31.20 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The phonon dispersion relations for equilibrium and photoexcited bismuth are calculated from first-principles density-functional perturbation theory, with constrained occupation of excited electronic states. The dependence of phonon frequency on photoexcited electron-hole plasma density is found for modes throughout the Brillouin zone. The resulting phonon dispersion curves are in good agreement with available neutron-scattering data for the equilibrium occupation of electronic bands. We find the effect of phonon softening by the electron-hole plasma to be substantially larger in the optical modes than in the acoustic modes throughout the Brillouin zone.
Physical Review B. 01/2007; 75(18):-.
-
D.M. Fritz,
B. Adams,
C. Blome,
P.H. Bucksbaum,
A. Cavalieri,
S. Engemann,
S. Fahy,
P.H. Fuoss,
K.J. Gaffney,
P. Hillyard, [......],
D. Meyer,
E. Murray,
M. Nicoul,
R. Pahl,
J. Rudati,
D.P. Siddons,
K. Sokolowski-Tinten,
J.K. Wahlstrand,
J.B. Hastings,
D.A. Reis
[show abstract]
[hide abstract]
ABSTRACT: We investigate high amplitude coherent optical phonon dynamics in bismuth through femtosecond X-ray and optical scattering. From these experiments, we present the first detailed measurements of changes in the interatomic potential following high-density photoexcitation.
Lasers and Electro-Optics, 2006 and 2006 Quantum Electronics and Laser Science Conference. CLEO/QELS 2006. Conference on; 06/2006
-
[show abstract]
[hide abstract]
ABSTRACT: We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al0.3Ga0.7As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.
Physical Review Letters 01/2006; 95(24):246104. · 7.37 Impact Factor
-
K J Gaffney,
A M Lindenberg,
J Larsson,
K Sokolowski-Tinten,
C Blome,
O Synnergren,
J Sheppard,
C Caleman,
A G MacPhee,
D Weinstein, [......],
D van der Spoel,
N Timneanu,
J Hajdu,
R A Akre,
E Bong,
P Krejcik,
J Arthur,
S Brennan,
K Luening,
J B Hastings
[show abstract]
[hide abstract]
ABSTRACT: The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.
Physical Review Letters 10/2005; 95(12):125701. · 7.37 Impact Factor
-
A M Lindenberg,
J Larsson,
K Sokolowski-Tinten,
K J Gaffney,
C Blome,
O Synnergren,
J Sheppard,
C Caleman,
A G Macphee,
D Weinstein, [......],
D van der Spoel,
N Timneanu,
J Hajdu,
R A Akre,
E Bong,
P Krejcik,
J Arthur,
S Brennan,
K Luening,
J B Hastings
[show abstract]
[hide abstract]
ABSTRACT: The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.
Science 05/2005; 308(5720):392-5. · 31.20 Impact Factor
-
A L Cavalieri, D M Fritz,
S H Lee,
P H Bucksbaum,
D A Reis,
J Rudati,
D M Mills,
P H Fuoss,
G B Stephenson,
C C Kao, [......],
R A Akre,
E Bong,
P Emma,
P Krejcik,
J Arthur,
S Brennan,
K J Gaffney,
A M Lindenberg,
K Luening,
J B Hastings
[show abstract]
[hide abstract]
ABSTRACT: Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.
Physical Review Letters 04/2005; 94(11):114801. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We report on remote delivery of 25-pJ broadband near-infrared femtosecond light pulses from a Ti:sapphire laser through 150 m of single-mode optical fiber. Pulse distortion caused by dispersion is overcome with precompensation by adaptive pulse shaping techniques, while nonlinearities are mitigated by use of an SF10 glass rod for the final stage of pulse compression. A near-transform-limited pulse duration of 130 fs was measured after the final compression.
Optics Letters 12/2004; 29(22):2602-4. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We report on remote delivery of 25 pJ broadband near-infrared femtosecond light pulses from a Ti:sapphire laser through 150 meters of single-mode optical fiber. Pulse distortion due to dispersion is overcome with pre-compensation using adaptive pulse shaping techniques, while nonlinearities are mitigated using an SF10 rod for the final stage of pulse compression. Near transform limited pulse duration of 130 fs is measured after the final compression. Comment: 3 pages, 4 figures
06/2004;
-
[show abstract]
[hide abstract]
ABSTRACT: Electro-optic sampling (EOS) is used to temporally characterize compressed ultra-relativistic electron bunches at the Stanford linear accelerator center (SLAC). These electron bunches are used to produce ultrafast X-rays at the sub-picosecond pulse source experiment (SPPS).
Lasers and Electro-Optics, 2004. (CLEO). Conference on; 06/2004
-
[show abstract]
[hide abstract]
ABSTRACT: Separate theoretical and experimental investigations of the effect of lattice anharmonicity on the A1g phonon dynamics in photoexcited bismuth are presented. First-principles density functional calculations show that the anharmonic contribution to the phonon period is negligible for an excitation of 1.25% or less of the valence electrons, corresponding to electronic frequency softening from 2.9 to 2.3 THz. Experiments using optical double-pump-probe excitation of coherent phonon motion clearly separate the role of lattice anharmonicity from electron-hole plasma and other dynamics, confirming that the effect of anharmonicity on the phonon period is much smaller than the observed softening.
Phys. Rev. B. 72(6).
-
F Van Den Berghe,
S Düsterer,
J Feldhaus,
R Ischebeck,
K Ludwig,
J Hauschildt,
H Schlarb,
B Schmidt,
P Schmüser,
S Simrock,
B Steffen,
A Winter,
P H Bucksbaum,
A L Cavalieri, D M Fritz,
S.-H Lee,
D A Reis,
F Ludwig
[show abstract]
[hide abstract]
ABSTRACT: For pump-probe experiments at the VUV-Free Electron Laser (FEL) at DESY, an external optical laser system will be installed, capable of delivering ultra-short pulses of high intensity. The laser pulses with a central wavelength of 800 nm are correlated with the VUV-FEL beam which op-erates in the wavelength regime between 6 nm and 80 nm. The expected duration of the FEL pulses is in the 100 fs range. For pump-probe experiments a precise timing of the FEL and Ti:Sa pulses is mandatory. In this paper we describe the layout of a high-resolution electron bunch ar-rival time monitor based on an electro-optic technique. We present numerical simulations for a specifically designed optical system that allows the transport of an ultra-short laser pulse through a 170 m long optical fibre without pulse stretching. Furthermore, the electro-optical effect in a non-linear crystal is simulated for various thicknesses of the crystal.
-
A M Lindenberg,
S Engemann,
K J Gaffney,
K. Sokolowski-Tinten,
J Larsson,
P B Hillyard,
D A Reis, D M Fritz,
J. Arthur,
R A Akre, [......],
R W Falcone,
S H Lee,
R Pahl,
J. Rudati,
P H Fuoss,
A.J. Nelson,
P. Krejcik,
D P Siddons,
P. Lorazo,
J.B. Hastings
Phys. Rev. Lett. 100(2008),135502.
-
D M Fritz,
D A Reis,
B Adams,
R A Akre,
J. Arthur,
C. Blome,
P H Bucksbaum,
A L Cavalieri,
S Engemann,
S Fahy, [......],
A.J. Nelson,
M Nicoul,
R Pahl,
J. Rudati,
H. Schlarb,
D P Siddons,
K. Sokolowski-Tinten,
Th. Tschentscher,
D von der Linde,
J.B. Hastings
Science 315(2007)5812,633-636.
-
K J Gaffney,
A M Lindenberg,
J Larsson,
K Sokolowski-Tinten,
C Blome,
O Synnergren,
J Sheppard,
C Caleman,
A G MacPhee,
D Weinstein, [......],
D Spoel,
N Timneanu,
J Hajdu,
R A Akre,
E Bong,
P Krejcik,
J Arthur,
S Brennan,
K Luening,
J B Hastings
Physical Review Letters. 95(12):125701.
-
A M Lindenberg,
J Larsson,
K Sokolowski-Tinten,
K Gaffney,
C Blome,
O Synnergren,
J Sheppard,
C Caleman,
A G MacPhee,
D Weinstein, [......],
J Hajdu,
D Linde,
R A Akre,
E Bong,
P Emma,
P Krejcik,
J Arthur,
S Brennan,
K Luening,
J B Hastings
Science. 308:392-395.
