Academic Appointments


2019-20 Courses


Stanford Advisees


All Publications


  • Time-dependent QED approach to x-ray nonlinear Compton scattering PHYSICAL REVIEW A Krebs, D., Reis, D. A., Santra, R. 2019; 99 (2)
  • Interferometry of dipole phase in high harmonics from solids NATURE PHOTONICS Lu, J., Cunningham, E. F., You, Y., Reis, D. A., Ghimire, S. 2019; 13 (2): 96-+
  • Characterization of high-harmonic emission from ZnO up to 11 eV pumped with a Cr:ZnS high-repetition-rate source OPTICS LETTERS Vampa, G., Vasilyev, S., Liu, H., Mirov, M., Bucksbaum, P. H., Reis, D. A. 2019; 44 (2): 259–62

    Abstract

    We report the measurement of high-order harmonics from a ZnO crystal with photon energies up to 11 eV generated by a high-repetition-rate femtosecond Cr:ZnS laser operating in the mid-infrared at 2-3 μm, delivering few-cycle pulses with multi-watt average power and multi-megawatt peak power. High-focus intensity is achieved in a single pass through the crystal without a buildup cavity or nanostructued pattern for field enhancement. We measure in excess of 108 high-harmonic photons/second.

    View details for DOI 10.1364/OL.44.000259

    View details for Web of Science ID 000455620100020

    View details for PubMedID 30644875

  • High-harmonic generation from solids NATURE PHYSICS Ghimire, S., Reis, D. A. 2019; 15 (1): 10–16
  • Theory of x-ray scattering from laser-driven electronic systems PHYSICAL REVIEW B Popova-Gorelova, D., Reis, D. A., Santra, R. 2018; 98 (22)
  • Frequency-selective excitation of high-wavevector phonons APPLIED PHYSICS LETTERS Teitelbaum, S. W., Henighan, T., Liu, H., Jiang, M. P., Kozina, M., Zhu, D., Chollet, M., Sato, T., Glownia, J. M., Trigo, M., Reis, D. A. 2018; 113 (17)

    View details for DOI 10.1063/1.5047447

    View details for Web of Science ID 000449145700017

  • Enhanced high-harmonic generation from an all-dielectric metasurface NATURE PHYSICS Liu, H., Guo, C., Vampa, G., Zhang, J., Sarmiento, T., Xiao, M., Bucksbaum, P. H., Vuckovic, J., Fan, S., Reis, D. A. 2018; 14 (10): 1006-+
  • Direct Measurement of Anharmonic Decay Channels of a Coherent Phonon PHYSICAL REVIEW LETTERS Teitelbaum, S. W., Henighan, T., Huang, Y., Liu, H., Jiang, M. P., Zhu, D., Chollet, M., Sato, T., Murray, E. D., Fahy, S., O'Mahony, S., Bailey, T. P., Uher, C., Trigo, M., Reis, D. A. 2018; 121 (12)
  • Probing periodic potential of crystals via strong-field re-scattering JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS You, Y., Cunningham, E., Reis, D. A., Ghimire, S. 2018; 51 (11)
  • Roadmap of ultrafast x-ray atomic and molecular physics JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Young, L., Ueda, K., Guehr, M., Bucksbaum, P. H., Simon, M., Mukamel, S., Rohringer, N., Prince, K. C., Masciovecchio, C., Meyer, M., Rudenko, A., Rolles, D., Bostedt, C., Fuchs, M., Reis, D. A., Santra, R., Kapteyn, H., Murnane, M., Ibrahim, H., Legare, F., Vrakking, M., Isinger, M., Kroon, D., Gisselbrecht, M., L'Huillier, A., Worner, H., Leone, S. R. 2018; 51 (3)
  • Ultrafast disordering of vanadium dimers in photoexcited VO2. Science (New York, N.Y.) Wall, S., Yang, S., Vidas, L., Chollet, M., Glownia, J. M., Kozina, M., Katayama, T., Henighan, T., Jiang, M., Miller, T. A., Reis, D. A., Boatner, L. A., Delaire, O., Trigo, M. 2018; 362 (6414): 572–76

    Abstract

    Many ultrafast solid phase transitions are treated as chemical reactions that transform the structures between two different unit cells along a reaction coordinate, but this neglects the role of disorder. Although ultrafast diffraction provides insights into atomic dynamics during such transformations, diffraction alone probes an averaged unit cell and is less sensitive to randomness in the transition pathway. Using total scattering of femtosecond x-ray pulses, we show that atomic disordering in photoexcited vanadium dioxide (VO2) is central to the transition mechanism and that, after photoexcitation, the system explores a large volume of phase space on a time scale comparable to that of a single phonon oscillation. These results overturn the current understanding of an archetypal ultrafast phase transition and provide new microscopic insights into rapid evolution toward equilibrium in photoexcited matter.

    View details for PubMedID 30385575

  • Orientation dependence of temporal and spectral properties of high-order harmonics in solids PHYSICAL REVIEW A Wu, M., You, Y., Ghimire, S., Reis, D. A., Browne, D. A., Schafer, K. J., Gaarde, M. B. 2017; 96 (6)
  • Anisotropic high-harmonic generation in bulk crystals NATURE PHYSICS You, Y. S., Reis, D. A., Ghimire, S. 2017; 13 (4): 345-349

    View details for DOI 10.1038/NPHYS3955

    View details for Web of Science ID 000398262900012

  • High-harmonic generation from an atomically thin semiconductor NATURE PHYSICS Liu, H., Li, Y., You, Y. S., Ghimire, S., Heinz, T. F., Reis, D. A. 2017; 13 (3): 262-?

    View details for DOI 10.1038/NPHYS3946

    View details for Web of Science ID 000395814000017

  • High-order harmonics from bulk and 2D crystals You, Y., Ndabashimiye, G., Liu, H., Li, Y., Heinz, T. F., Reis, D. A., Ghimire, S., IEEE IEEE. 2017
  • Visualization of Atomic-Scale Motions in Materials via Femtosecond X-Ray Scattering Techniques ANNUAL REVIEW OF MATERIALS RESEARCH, VOL 47 Lindenberg, A. M., Johnson, S. L., Reis, D. A., Clarke, D. R. 2017; 47: 425–49
  • Phase-coherence of high-order harmonics from bulk crystals using homodyne detection Cunningham, E., You, Y., Reis, D. A., Ghimire, S., IEEE IEEE. 2017
  • Nonsequential two-photon absorption from the K shell in solid zirconium PHYSICAL REVIEW A Ghimire, S., Fuchs, M., Hastings, J., Herrmann, S. C., Inubushi, Y., Pines, J., Shwartz, S., Yabashi, M., Reis, D. A. 2016; 94 (4)
  • Control of two-phonon correlations and the mechanism of high-wavevector phonon generation by ultrafast light pulses PHYSICAL REVIEW B Henighan, T., Trigo, M., Chollet, M., Clark, J. N., Fahy, S., Glownia, J. M., Jiang, M. P., Kozina, M., Liu, H., Song, S., Zhu, D., Reis, D. A. 2016; 94 (2)
  • Solid-state harmonics beyond the atomic limit NATURE Ndabashimiye, G., Ghimire, S., Wu, M., Browne, D. A., Schafer, K. J., Gaarde, M. B., Reis, D. A. 2016; 534 (7608): 520-?

    Abstract

    Strong-field laser excitation of solids can produce extremely nonlinear electronic and optical behaviour. As recently demonstrated, this includes the generation of high harmonics extending into the vacuum-ultraviolet and extreme-ultraviolet regions of the electromagnetic spectrum. High harmonic generation is shown to occur fundamentally differently in solids and in dilute atomic gases. How the microscopic mechanisms in the solid and the gas differ remains a topic of intense debate. Here we report a direct comparison of high harmonic generation in the solid and gas phases of argon and krypton. Owing to the weak van der Waals interaction, rare (noble)-gas solids are a near-ideal medium in which to study the role of high density and periodicity in the generation process. We find that the high harmonic generation spectra from the rare-gas solids exhibit multiple plateaus extending well beyond the atomic limit of the corresponding gas-phase harmonics measured under similar conditions. The appearance of multiple plateaus indicates strong interband couplings involving multiple single-particle bands. We also compare the dependence of the solid and gas harmonic yield on laser ellipticity and find that they are similar, suggesting the importance of electron-hole recollision in these solids. This implies that gas-phase methods such as polarization gating for attosecond pulse generation and orbital tomography could be realized in solids.

    View details for DOI 10.1038/nature17660

    View details for Web of Science ID 000378270300047

    View details for PubMedID 27281195

  • Generation mechanism of terahertz coherent acoustic phonons in Fe PHYSICAL REVIEW B Henighan, T., Trigo, M., Bonetti, S., Granitzka, P., Higley, D., Chen, Z., Jiang, M. P., Kukreja, R., Gray, A., Reid, A. H., JAL, E., Hoffmann, C., Kozina, M., Song, S., Chollet, M., Zhu, D., Xu, P. F., Jeong, J., Carva, K., Maldonado, P., Oppeneer, P. M., Samant, M. G., Parkin, S. S., Reis, D. A., Durr, H. A. 2016; 93 (22)
  • Resonant squeezing and the anharmonic decay of coherent phonons PHYSICAL REVIEW B Fahy, S., Murray, E. D., Reis, D. A. 2016; 93 (13)
  • Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films APPLIED PHYSICS LETTERS Chase, T., Trigo, M., Reid, A. H., Li, R., Vecchione, T., Shen, X., Weathersby, S., Coffee, R., Hartmann, N., Reis, D. A., Wang, X. J., Duerr, H. A. 2016; 108 (4)

    View details for DOI 10.1063/1.4940981

    View details for Web of Science ID 000375217200022

  • Ultrafast resonant soft x-ray diffraction dynamics of the charge density wave in TbTe3 PHYSICAL REVIEW B Moore, R. G., Lee, W. S., Kirchman, P. S., Chuang, Y. D., Kemper, A. F., Trigo, M., Patthey, L., Lu, D. H., Krupin, O., Yi, M., Reis, D. A., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Hays, G., Hering, P., Benson, T., Chu, J., Devereaux, T. P., Fisher, I. R., Hussain, Z., Shen, Z. 2016; 93 (2)
  • The origin of incipient ferroelectricity in lead telluride. Nature communications Jiang, M. P., Trigo, M., Savic, I., Fahy, S., Murray, É. D., Bray, C., Clark, J., Henighan, T., Kozina, M., Chollet, M., Glownia, J. M., Hoffmann, M. C., Zhu, D., Delaire, O., May, A. F., Sales, B. C., Lindenberg, A. M., Zalden, P., Sato, T., Merlin, R., Reis, D. A. 2016; 7: 12291-?

    Abstract

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV-VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.

    View details for DOI 10.1038/ncomms12291

    View details for PubMedID 27447688

    View details for PubMedCentralID PMC4961866

  • Anomalous nonlinear X-ray Compton scattering NATURE PHYSICS Fuchs, M., Trigo, M., Chen, J., Ghimire, S., Shwartz, S., Kozina, M., Jiang, M., Henighan, T., Bray, C., Ndabashimiye, G., Bucksbaum, P. H., Feng, Y., Herrmann, S., Carini, G. A., Pines, J., Hart, P., Kenney, C., Guillet, S., Boutee, S., Williams, G. J., Messerschmidt, M., Seibert, M. M., Moeller, S., Hastings, J. B., Reis, D. A. 2015; 11 (11): 964-970

    View details for DOI 10.1038/NPHYS3452

    View details for Web of Science ID 000364800600023

  • Phonon spectroscopy with sub-meV resolution by femtosecond x-ray diffuse scattering PHYSICAL REVIEW B Zhu, D., Robert, A., Henighan, T., Lemke, H. T., Chollet, M., Glownia, J. M., Reis, D. A., Trigo, M. 2015; 92 (5)
  • Imaging transient melting of a nanocrystal using an X-ray laser PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Clark, J. N., Beitra, L., Xiong, G., Fritz, D. M., Lemke, H. T., Zhu, D., Chollet, M., Williams, G. J., Messerschmidt, M. M., Abbey, B., Harder, R. J., Korsunsky, A. M., Wark, J. S., Reis, D. A., Robinson, I. K. 2015; 112 (24): 7444-7448

    Abstract

    There is a fundamental interest in studying photoinduced dynamics in nanoparticles and nanostructures as it provides insight into their mechanical and thermal properties out of equilibrium and during phase transitions. Nanoparticles can display significantly different properties from the bulk, which is due to the interplay between their size, morphology, crystallinity, defect concentration, and surface properties. Particularly interesting scenarios arise when nanoparticles undergo phase transitions, such as melting induced by an optical laser. Current theoretical evidence suggests that nanoparticles can undergo reversible nonhomogenous melting with the formation of a core-shell structure consisting of a liquid outer layer. To date, studies from ensembles of nanoparticles have tentatively suggested that such mechanisms are present. Here we demonstrate imaging transient melting and softening of the acoustic phonon modes of an individual gold nanocrystal, using an X-ray free electron laser. The results demonstrate that the transient melting is reversible and nonhomogenous, consistent with a core-shell model of melting. The results have implications for understanding transient processes in nanoparticles and determining their elastic properties as they undergo phase transitions.

    View details for DOI 10.1073/pnas.1417678112

    View details for Web of Science ID 000356251800042

    View details for PubMedID 26034277

    View details for PubMedCentralID PMC4475963

  • High-harmonic generation from Bloch electrons in solids PHYSICAL REVIEW A Wu, M., Ghimire, S., Reis, D. A., Schafer, K. J., Gaarde, M. B. 2015; 91 (4)
  • Strong-field and attosecond physics in solids JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Ghimire, S., Ndabashimiye, G., DiChiara, A. D., Sistrunk, E., Stockman, M. I., Agostini, P., DiMauro, L. F., Reis, D. A. 2014; 47 (20)
  • Below gap optical absorption in GaAs driven by intense, single-cycle coherent transition radiation OPTICS EXPRESS Goodfellow, J., Fuchs, M., Daranciang, D., Ghimire, S., Chen, F., Loos, H., Reis, D. A., Fisher, A. S., Lindenberg, A. M. 2014; 22 (14): 17423-17429

    Abstract

    Single-cycle terahertz fields generated by coherent transition radiation from a relativistic electron beam are used to study the high field optical response of single crystal GaAs. Large amplitude changes in the sub-band-gap optical absorption are induced and probed dynamically by measuring the absorption of a broad-band optical beam generated by transition radiation from the same electron bunch, providing an absolutely synchronized pump and probe geometry. This modification of the optical properties is consistent with strong-field-induced electroabsorption. These processes are pertinent to a wide range of nonlinear terahertz-driven light-matter interactions anticipated at accelerator-based sources.

    View details for DOI 10.1364/OE.22.017423

    View details for Web of Science ID 000340674700072

    View details for PubMedID 25090555

  • Measurement of transient atomic displacements in thin films with picosecond and femtometer resolution STRUCTURAL DYNAMICS-US Kozina, M., Hu, T., Wittenberg, J. S., Szilagyi, E., Trigo, M., Miller, T. A., Uher, C., Damodaran, A., Martin, L., Mehta, A., Corbett, J., Safranek, J., Reis, D. A., Lindenberg, A. M. 2014; 1 (3)

    View details for DOI 10.1063/1.4875347

    View details for Web of Science ID 000354989200001

  • X-ray second harmonic generation. Physical review letters Shwartz, S., Fuchs, M., Hastings, J. B., Inubushi, Y., Ishikawa, T., Katayama, T., Reis, D. A., Sato, T., Tono, K., Yabashi, M., Yudovich, S., Harris, S. E. 2014; 112 (16): 163901-?

    Abstract

    We report clear experimental evidence for second harmonic generation at hard x-ray wavelengths. Using a 1.7 Å pumping beam generated by a free electron laser, we observe second harmonic generation in diamond. The generated second harmonic is of order 10 times the background radiation, scales quadratically with pump pulse energy, and is generated over a narrow phase-matching condition. Of importance for future experiments, our results indicate that it is possible to observe nonlinear x-ray processes in crystals at pump intensities exceeding 1016  W/cm2.

    View details for PubMedID 24815649

  • X-Ray Second Harmonic Generation PHYSICAL REVIEW LETTERS Shwartz, S., Fuchs, M., Hastings, J. B., Inubushi, Y., Ishikawa, T., Katayama, T., Reis, D. A., Sato, T., Tono, K., Yabashi, M., Yudovich, S., Harris, S. E. 2014; 112 (16)
  • Evidence for photo-induced monoclinic metallic VO2 under high pressure APPLIED PHYSICS LETTERS Hsieh, W., Trigo, M., Reis, D. A., Artioli, G. A., Malavasi, L., Mao, W. L. 2014; 104 (2)

    View details for DOI 10.1063/1.4862197

    View details for Web of Science ID 000330431000045

  • Fourier-transform inelastic X-ray scattering from time- and momentum-dependent phonon-phonon correlations NATURE PHYSICS Trigo, M., Fuchs, M., Chen, J., Jiang, M. P., Cammarata, M., Fahy, S., Fritz, D. M., Gaffney, K., Ghimire, S., Higginbotham, A., Johnson, S. L., Kozina, M. E., Larsson, J., Lemke, H., Lindenberg, A. M., Ndabashimiye, G., QUIRIN, F., Sokolowski-Tinten, K., Uher, C., Wang, G., Wark, J. S., Zhu, D., Reis, D. A. 2013; 9 (12): 790-794

    View details for DOI 10.1038/NPHYS2788

    View details for Web of Science ID 000327944600017

  • Time- and momentum-resolved probe of heat transport in photo-excited bismuth APPLIED PHYSICS LETTERS Chen, J., Trigo, M., Fahy, S., Murray, E. D., Sheu, Y. M., Graber, T., Henning, R., Chien, Y. J., Uher, C., Reis, D. A. 2013; 102 (18)

    View details for DOI 10.1063/1.4804291

    View details for Web of Science ID 000320439900025

  • Real-Time Manifestation of Strongly Coupled Spin and Charge Order Parameters in Stripe-Ordered La_{1.75}Sr_{0.25}NiO_{4} Nickelate Crystals Using Time-Resolved Resonant X-Ray Diffraction. Physical review letters Chuang, Y. D., Lee, W. S., Kung, Y. F., Sorini, A. P., Moritz, B., Moore, R. G., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Yi, M., Krupin, O., Langner, M., Zhu, Y., Zhou, S. Y., Reis, D. A., Huse, N., ROBINSON, J. S., Kaindl, R. A., Schoenlein, R. W., Johnson, S. L., Först, M., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Sasagawa, T., Hussain, Z., Shen, Z. X., Devereaux, T. P. 2013; 110 (12): 127404-?

    Abstract

    We investigate the order parameter dynamics of the stripe-ordered nickelate, La_{1.75}Sr_{0.25}NiO_{4}, using time-resolved resonant x-ray diffraction. In spite of distinct spin and charge energy scales, the two order parameters' amplitude dynamics are found to be linked together due to strong coupling. Additionally, the vector nature of the spin sector introduces a longer reorientation time scale which is absent in the charge sector. These findings demonstrate that the correlation linking the symmetry-broken states does not unbind during the nonequilibrium process, and the time scales are not necessarily associated with the characteristic energy scales of individual degrees of freedom.

    View details for PubMedID 25166848

  • Real-Time Manifestation of Strongly Coupled Spin and Charge Order Parameters in Stripe-Ordered La1.75Sr0.25NiO4 Nickelate Crystals Using Time-Resolved Resonant X-Ray Diffraction PHYSICAL REVIEW LETTERS Chuang, Y. D., Lee, W. S., Kung, Y. F., Sorini, A. P., Moritz, B., Moore, R. G., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Yi, M., Krupin, O., Langner, M., Zhu, Y., Zhou, S. Y., Reis, D. A., Huse, N., ROBINSON, J. S., Kaindl, R. A., Schoenlein, R. W., Johnson, S. L., Foerst, M., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Sasagawa, T., Hussain, Z., Shen, Z. X., Devereaux, T. P. 2013; 110 (12)

    Abstract

    We investigate the order parameter dynamics of the stripe-ordered nickelate, La_{1.75}Sr_{0.25}NiO_{4}, using time-resolved resonant x-ray diffraction. In spite of distinct spin and charge energy scales, the two order parameters' amplitude dynamics are found to be linked together due to strong coupling. Additionally, the vector nature of the spin sector introduces a longer reorientation time scale which is absent in the charge sector. These findings demonstrate that the correlation linking the symmetry-broken states does not unbind during the nonequilibrium process, and the time scales are not necessarily associated with the characteristic energy scales of individual degrees of freedom.

    View details for DOI 10.1103/PhysRevLett.110.127404

    View details for Web of Science ID 000316411100019

  • Free-carrier relaxation and lattice heating in photoexcited bismuth PHYSICAL REVIEW B Sheu, Y. M., Chien, Y. J., Uher, C., Fahy, S., Reis, D. A. 2013; 87 (7)
  • Optical Probing of Ultrafast Electronic Decay in Bi and Sb with Slow Phonons PHYSICAL REVIEW LETTERS Li, J. J., Chen, J., Reis, D. A., Fahy, S., Merlin, R. 2013; 110 (4)
  • Photon-Counting Detectors for Pump-Probe Science 60th IEEE Nuclear Science Symposium (NSS) / Medical Imaging Conference (MIC) / 20th International Workshop on Room-Temperature Semiconductor X-ray and Gamma-ray Detectors Kenney, C. J., Dragone, A. B., Segal, J. D., Hasi, J., Mehta, A., Reis, D. A., Markovic, B., Caraguilo, P., Carini, G., Herrmann, S. C., Lindenberg, A. M., Haller, G. IEEE. 2013
  • X-ray and optical wave mixing NATURE Glover, T. E., Fritz, D. M., Cammarata, M., Allison, T. K., Coh, S., Feldkamp, J. M., Lemke, H., Zhu, D., Feng, Y., Coffee, R. N., Fuchs, M., Ghimire, S., Chen, J., Shwartz, S., Reis, D. A., Harris, S. E., Hastings, J. B. 2012; 488 (7413): 603-?

    Abstract

    Light-matter interactions are ubiquitous, and underpin a wide range of basic research fields and applied technologies. Although optical interactions have been intensively studied, their microscopic details are often poorly understood and have so far not been directly measurable. X-ray and optical wave mixing was proposed nearly half a century ago as an atomic-scale probe of optical interactions but has not yet been observed owing to a lack of sufficiently intense X-ray sources. Here we use an X-ray laser to demonstrate X-ray and optical sum-frequency generation. The underlying nonlinearity is a reciprocal-space probe of the optically induced charges and associated microscopic fields that arise in an illuminated material. To within the experimental errors, the measured efficiency is consistent with first-principles calculations of microscopic optical polarization in diamond. The ability to probe optical interactions on the atomic scale offers new opportunities in both basic and applied areas of science.

    View details for DOI 10.1038/nature11340

    View details for Web of Science ID 000308095100046

    View details for PubMedID 22932384

  • Temporal cross-correlation of x-ray free electron and optical lasers using soft x-ray pulse induced transient reflectivity OPTICS EXPRESS Krupin, O., Trigo, M., Schlotter, W. F., Beye, M., Sorgenfrei, F., Turner, J. J., Reis, D. A., Gerken, N., Lee, S., Lee, W. S., Hays, G., Acremann, Y., Abbey, B., Coffee, R., Messerschmidt, M., Hau-Riege, S. P., Lapertot, G., Luening, J., Heimann, P., Soufli, R., Fernandez-Perea, M., Rowen, M., Holmes, M., Molodtsov, S. L., Foehlisch, A., Wurth, W. 2012; 20 (10): 11396-11406

    Abstract

    The recent development of x-ray free electron lasers providing coherent, femtosecond-long pulses of high brilliance and variable energy opens new areas of scientific research in a variety of disciplines such as physics, chemistry, and biology. Pump-probe experimental techniques which observe the temporal evolution of systems after optical or x-ray pulse excitation are one of the main experimental schemes currently in use for ultrafast studies. The key challenge in these experiments is to reliably achieve temporal and spatial overlap of the x-ray and optical pulses. Here we present measurements of the x-ray pulse induced transient change of optical reflectivity from a variety of materials covering the soft x-ray photon energy range from 500eV to 2000eV and outline the use of this technique to establish and characterize temporal synchronization of the optical-laser and FEL x-ray pulses.

    View details for Web of Science ID 000303879700100

    View details for PubMedID 22565760

  • Phase fluctuations and the absence of topological defects in a photo-excited charge-ordered nickelate NATURE COMMUNICATIONS Lee, W. S., Chuang, Y. D., Moore, R. G., Zhu, Y., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Krupin, O., Yi, M., Langner, M., Huse, N., ROBINSON, J. S., Chen, Y., Zhou, S. Y., Coslovich, G., Huber, B., Reis, D. A., Kaindl, R. A., Schoenlein, R. W., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Johnson, S. L., Foerst, M., Sasagawa, T., Kung, Y. F., Sorini, A. P., Kemper, A. F., Moritz, B., Devereaux, T. P., Lee, D., Shen, Z. X., Hussain, Z. 2012; 3

    Abstract

    The dynamics of an order parameter's amplitude and phase determines the collective behaviour of novel states emerging in complex materials. Time- and momentum-resolved pump-probe spectroscopy, by virtue of measuring material properties at atomic and electronic time scales out of equilibrium, can decouple entangled degrees of freedom by visualizing their corresponding dynamics in the time domain. Here we combine time-resolved femotosecond optical and resonant X-ray diffraction measurements on charge ordered La(1.75)Sr(0.25)NiO(4) to reveal unforeseen photoinduced phase fluctuations of the charge order parameter. Such fluctuations preserve long-range order without creating topological defects, distinct from thermal phase fluctuations near the critical temperature in equilibrium. Importantly, relaxation of the phase fluctuations is found to be an order of magnitude slower than that of the order parameter's amplitude fluctuations, and thus limits charge order recovery. This new aspect of phase fluctuations provides a more holistic view of the phase's importance in ordering phenomena of quantum matter.

    View details for DOI 10.1038/ncomms1837

    View details for Web of Science ID 000304611400033

    View details for PubMedID 22588300

  • Generation and propagation of high-order harmonics in crystals PHYSICAL REVIEW A Ghimire, S., DiChiara, A. D., Sistrunk, E., Ndabashimiye, G., Szafruga, U. B., Mohammad, A., Agostini, P., DiMauro, L. F., Reis, D. A. 2012; 85 (4)
  • Molecular frame Auger electron energy spectrum from N-2 JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Cryan, J. P., Glownia, J. M., Andreasson, J., Belkacem, A., Berrah, N., Blaga, C. I., Bostedt, C., Bozek, J., Cherepkov, N. A., DiMauro, L. F., Fang, L., Gessner, O., Guehr, M., Hajdu, J., Hertlein, M. P., Hoener, M., Kornilov, O., Marangos, J. P., March, A. M., McFarland, B. K., Merdji, H., Messerschmidt, M., Petrovic, V. S., Raman, C., Ray, D., Reis, D. A., Semenov, S. K., Trigo, M., WHITE, J. L., White, W., Young, L., Bucksbaum, P. H., Coffee, R. N. 2012; 45 (5)
  • Ultrafast Photovoltaic Response in Ferroelectric Nanolayers PHYSICAL REVIEW LETTERS Daranciang, D., Highland, M. J., Wen, H., Young, S. M., Brandt, N. C., Hwang, H. Y., Vattilana, M., Nicoul, M., Quirin, F., Goodfellow, J., Qi, T., Grinberg, I., Fritz, D. M., Cammarata, M., Zhu, D., Lemke, H. T., Walko, D. A., Dufresne, E. M., Li, Y., Larsson, J., Reis, D. A., Sokolowski-Tinten, K., Nelson, K. A., Rappe, A. M., Fuoss, P. H., Stephenson, G. B., Lindenberg, A. M. 2012; 108 (8)

    Abstract

    We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond time scales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screening currents, associated with the displacement of electrons first antiparallel to and then parallel to the ferroelectric polarization direction.

    View details for DOI 10.1103/PhysRevLett.108.087601

    View details for Web of Science ID 000300669600033

    View details for PubMedID 22463572

  • Ultrafast pump-probe measurements of short small-polaron lifetimes in the mixed-valence perovskite Cs2Au2I6 under high pressures PHYSICAL REVIEW B Trigo, M., Chen, J., Jiang, M. P., Mao, W. L., Riggs, S. C., SHAPIRO, M. C., Fisher, I. R., Reis, D. A. 2012; 85 (8)
  • Strong-field Effects in Solids Conference on Lasers and Electro-Optics (CLEO) Ghimire, S., Ndabashimiye, G., DiChiara, A. D., Sistrunk, E., Szafruga, U., Agostini, P., DiMauro, L. F., Reis, D. A. IEEE. 2012
  • High-order harmonic generation in solid argon Conference on Lasers and Electro-Optics (CLEO) Ghimire, S., Ndabashimiye, G., Reis, D. A. IEEE. 2012
  • Scaling of High-Order Harmonic Generation in the Long Wavelength Limit of a Strong Laser Field IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS DiChiara, A. D., Ghimire, S., Blaga, C. I., Sistrunk, E., Power, E. P., March, A. M., Miller, T. A., Reis, D. A., Agostini, P., DiMauro, L. F. 2012; 18 (1): 419-433
  • Unveiling and Driving Hidden Resonances with High-Fluence, High-Intensity X-Ray Pulses PHYSICAL REVIEW LETTERS Kanter, E. P., Kraessig, B., Li, Y., March, A. M., Ho, P., Rohringer, N., Santra, R., Southworth, S. H., DiMauro, L. F., Doumy, G., Roedig, C. A., Berrah, N., Fang, L., Hoener, M., Bucksbaum, P. H., Ghimire, S., Reis, D. A., Bozek, J. D., Bostedt, C., Messerschmidt, M., Young, L. 2011; 107 (23)

    Abstract

    We show that high fluence, high-intensity x-ray pulses from the world's first hard x-ray free-electron laser produce nonlinear phenomena that differ dramatically from the linear x-ray-matter interaction processes that are encountered at synchrotron x-ray sources. We use intense x-ray pulses of sub-10-fs duration to first reveal and subsequently drive the 1s↔2p resonance in singly ionized neon. This photon-driven cycling of an inner-shell electron modifies the Auger decay process, as evidenced by line shape modification. Our work demonstrates the propensity of high-fluence, femtosecond x-ray pulses to alter the target within a single pulse, i.e., to unveil hidden resonances, by cracking open inner shells energetically inaccessible via single-photon absorption, and to consequently trigger damaging electron cascades at unexpectedly low photon energies.

    View details for DOI 10.1103/PhysRevLett.107.233001

    View details for Web of Science ID 000297501900007

    View details for PubMedID 22182083

  • Thermal transport in thin films measured by time-resolved, grazing incidence x-ray diffraction JOURNAL OF APPLIED PHYSICS Walko, D. A., Sheu, Y., Trigo, M., Reis, D. A. 2011; 110 (10)

    View details for DOI 10.1063/1.3661164

    View details for Web of Science ID 000297943700004

  • Redshift in the Optical Absorption of ZnO Single Crystals in the Presence of an Intense Midinfrared Laser Field PHYSICAL REVIEW LETTERS Ghimire, S., DiChiara, A. D., Sistrunk, E., Szafruga, U. B., Agostini, P., DiMauro, L. F., Reis, D. A. 2011; 107 (16)

    Abstract

    We report time-resolved electroabsorption of a weak probe in a 500 μm thick zinc-oxide crystal in the presence of a strong midinfrared pump in the tunneling limit. We observe a substantial redshift in the absorption edge that scales with the cube root of intensity up to 1 TW/cm(2) (0.38 eV cm(2/3) TW(-1/3)) after which it increases more slowly to 0.4 eV at a maximum applied intensity of 5 TW/cm(2). The maximum shift corresponds to more than 10% of the band gap. The change in scaling occurs in a regime of nonperturbative high-order harmonic generation where electrons undergo periodic Bragg scattering from the Brillouin zone boundaries. It also coincides with the limit where the electric field becomes comparable to the ratio of the band gap to the lattice spacing.

    View details for DOI 10.1103/PhysRevLett.107.167407

    View details for Web of Science ID 000296371800010

    View details for PubMedID 22107430

  • Single-cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation APPLIED PHYSICS LETTERS Daranciang, D., Goodfellow, J., Fuchs, M., Wen, H., Ghimire, S., Reis, D. A., Loos, H., Fisher, A. S., Lindenberg, A. M. 2011; 99 (14)

    View details for DOI 10.1063/1.3646399

    View details for Web of Science ID 000295625100017

  • Kapitza conductance of Bi/sapphire interface studied by depth- and time-resolved X-ray diffraction SOLID STATE COMMUNICATIONS Sheu, Y. M., Trigo, M., Chien, Y. J., Uher, C., Arms, D. A., Peterson, E. R., Walko, D. A., Landahl, E. C., Chen, J., Ghimire, S., Reis, D. A. 2011; 151 (11): 826-829
  • Nonlinear Atomic Response to Intense Ultrashort X Rays PHYSICAL REVIEW LETTERS Doumy, G., Roedig, C., Son, S., Blaga, C. I., DiChiara, A. D., Santra, R., Berrah, N., Bostedt, C., Bozek, J. D., Bucksbaum, P. H., Cryan, J. P., Fang, L., Ghimire, S., Glownia, J. M., Hoener, M., Kanter, E. P., Kraessig, B., Kuebel, M., Messerschmidt, M., Paulus, G. G., Reis, D. A., Rohringer, N., Young, L., Agostini, P., DiMauro, L. F. 2011; 106 (8)

    Abstract

    The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne(9+) is observed at x-ray frequencies below the Ne(8+), 1s(2) absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of Ne(8+) ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations.

    View details for DOI 10.1103/PhysRevLett.106.083002

    View details for Web of Science ID 000287714900007

    View details for PubMedID 21405568

  • Observation of high-order harmonic generation in a bulk crystal NATURE PHYSICS Ghimire, S., DiChiara, A. D., Sistrunk, E., Agostini, P., DiMauro, L. F., Reis, D. A. 2011; 7 (2): 138-141

    View details for DOI 10.1038/NPHYS1847

    View details for Web of Science ID 000286807000016

  • Strong-field Induced Optical Absorption in ZnO Crystal Conference on Lasers and Electro-Optics (CLEO) Ghimire, S., DiChiara, A. D., Sistrunk, E., DiMauro, L. F., Agostini, P., Reis, D. A. IEEE. 2011
  • Generation of > 100 mu J, Broadband THz Transients with > 10 MV/cm Fields via Coherent Transition Radiation at the Linac Coherent Light Source Conference on Lasers and Electro-Optics (CLEO) Daranciang, D., Goodfellow, J., Ghimire, S., Loos, H., Reis, D., Fisher, A. S., Lindenberg, A. M. IEEE. 2011
  • Imaging nonequilibrium atomic vibrations with x-ray diffuse scattering PHYSICAL REVIEW B Trigo, M., Chen, J., Vishwanath, V. H., Sheu, Y. M., Graber, T., Henning, R., Reis, D. A. 2010; 82 (23)
  • Auger Electron Angular Distribution of Double Core-Hole States in the Molecular Reference Frame PHYSICAL REVIEW LETTERS Cryan, J. P., Glownia, J. M., Andreasson, J., Belkacem, A., Berrah, N., Blaga, C. I., Bostedt, C., Bozek, J., Buth, C., DiMauro, L. F., Fang, L., Gessner, O., Guehr, M., Hajdu, J., Hertlein, M. P., Hoener, M., Kornilov, O., Marangos, J. P., March, A. M., McFarland, B. K., Merdji, H., Petrovic, V. S., Raman, C., Ray, D., Reis, D., Tarantelli, F., Trigo, M., WHITE, J. L., White, W., Young, L., Bucksbaum, P. H., Coffee, R. N. 2010; 105 (8)

    Abstract

    The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×10(11) photons in a ∼5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.

    View details for DOI 10.1103/PhysRevLett.105.083004

    View details for Web of Science ID 000281072100003

    View details for PubMedID 20868096

  • Time-resolved pump-probe experiments at the LCLS OPTICS EXPRESS Glownia, J. M., Cryan, J., Andreasson, J., Belkacem, A., Berrah, N., Blaga, C. I., Bostedt, C., Bozek, J., DiMauro, L. F., Fang, L., Frisch, J., Gessner, O., Guehr, M., Hajdu, J., Hertlein, M. P., Hoener, M., Huang, G., Kornilov, O., Marangos, J. P., March, A. M., McFarland, B. K., Merdji, H., Petrovic, V. S., Raman, C., Ray, D., Reis, D. A., Trigo, M., WHITE, J. L., White, W., Wilcox, R., Young, L., Coffee, R. N., Bucksbaum, P. H. 2010; 18 (17): 17620-17630

    Abstract

    The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.

    View details for Web of Science ID 000281054400005

    View details for PubMedID 20721148

  • Femtosecond electronic response of atoms to ultra-intense X-rays NATURE Young, L., Kanter, E. P., Kraessig, B., Li, Y., March, A. M., Pratt, S. T., Santra, R., Southworth, S. H., Rohringer, N., DiMauro, L. F., Doumy, G., Roedig, C. A., Berrah, N., Fang, L., Hoener, M., Bucksbaum, P. H., Cryan, J. P., Ghimire, S., Glownia, J. M., Reis, D. A., Bozek, J. D., Bostedt, C., Messerschmidt, M. 2010; 466 (7302): 56-U66

    Abstract

    An era of exploring the interactions of high-intensity, hard X-rays with matter has begun with the start-up of a hard-X-ray free-electron laser, the Linac Coherent Light Source (LCLS). Understanding how electrons in matter respond to ultra-intense X-ray radiation is essential for all applications. Here we reveal the nature of the electronic response in a free atom to unprecedented high-intensity, short-wavelength, high-fluence radiation (respectively 10(18) W cm(-2), 1.5-0.6 nm, approximately 10(5) X-ray photons per A(2)). At this fluence, the neon target inevitably changes during the course of a single femtosecond-duration X-ray pulse-by sequentially ejecting electrons-to produce fully-stripped neon through absorption of six photons. Rapid photoejection of inner-shell electrons produces 'hollow' atoms and an intensity-induced X-ray transparency. Such transparency, due to the presence of inner-shell vacancies, can be induced in all atomic, molecular and condensed matter systems at high intensity. Quantitative comparison with theory allows us to extract LCLS fluence and pulse duration. Our successful modelling of X-ray/atom interactions using a straightforward rate equation approach augurs favourably for extension to complex systems.

    View details for DOI 10.1038/nature09177

    View details for Web of Science ID 000279343800034

    View details for PubMedID 20596013

  • High-Harmonic Generation in Strongly Driven Bulk Periodic Solid Conference on Lasers and Electro-Optics (CLEO)/Quantum Electronics and Laser Science Conference (QELS) Ghimire, S., DiChiara, A., Sistrunk, E., DiMauro, L. F., Agostini, P., Reis, D. A. IEEE. 2010
  • Probing unfolded acoustic phonons with X rays PHYSICAL REVIEW LETTERS Trigo, M., Sheu, Y. M., Arms, D. A., Chen, J., Ghimire, S., GOLDMAN, R. S., Landahl, E., Merlin, R., Peterson, E., Reason, M., Reis, D. A. 2008; 101 (2)

    Abstract

    Ultrafast laser excitation of an InGaAs/InAlAs superlattice (SL) creates coherent folded acoustic phonons that subsequently leak into the bulk (InP) substrate. Upon transmission, the phonons become "unfolded" into bulk modes and acquire a wave vector much larger than that of the light. We show that time-resolved x-ray diffraction is sensitive to this large-wave vector excitation in the substrate. Comparison with dynamical diffraction simulations of propagating strain supports our interpretation.

    View details for DOI 10.1103/PhysRevLett.101.025505

    View details for Web of Science ID 000257553700035

    View details for PubMedID 18764197

  • Thermal transport in a semiconductor heterostructure measured by time-resolved x-ray diffraction PHYSICAL REVIEW B Sheu, Y. M., Lee, S. H., Wahlstrand, J. K., Walko, D. A., Landahl, E. C., Arms, D. A., Reason, M., GOLDMAN, R. S., Reis, D. A. 2008; 78 (4)
  • Carrier-induced disordering dynamics in InSb studied with density functional perturbation theory PHYSICAL REVIEW B Hillyard, P. B., Reis, D. A., Gaffney, K. J. 2008; 77 (19)
  • X-ray diffuse scattering measurements of nucleation dynamics at femtosecond resolution PHYSICAL REVIEW LETTERS Lindenberg, A. M., Engemann, S., Gaffney, K. J., Sokolowski-Tinten, K., Larsson, J., Hillyard, P. B., Reis, D. A., Fritz, D. M., ARTHUR, J., Akre, R. A., George, M. J., Deb, A., Bucksbaum, P. H., Hajdu, J., Meyer, D. A., Nicoul, M., Blome, C., Tschentscher, T., Cavalieri, A. L., Falcone, R. W., Lee, S. H., Pahl, R., Rudati, J., Fuoss, P. H., Nelson, A. J., Krejcik, P., Siddons, D. P., Lorazo, P., Hastings, J. B. 2008; 100 (13)

    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.

    View details for DOI 10.1103/PhysRevLett.100.135502

    View details for Web of Science ID 000254670300046

    View details for PubMedID 18517965

  • Wideband detection of transient solid-state dynamics using ultrafast fiber lasers and asynchronous optical sampling OPTICS EXPRESS Stoica, V. A., Sheu, Y., Reis, D. A., Clarke, R. 2008; 16 (4): 2322-2335

    Abstract

    We demonstrate optical time-domain spectroscopy from femtoseconds to nanoseconds using an ultrafast dual-fiber-laser system with kilohertz continuous scanning rates. Utilizing different wavelengths for the pump and probe beams, we exploit this system's broad range of timescales for quantitative studies of thermal transport and the detection of coherent spin and lattice excitations in epitaxial magnetic thin films. The extraordinary temporal dynamic range provides a way to connect the fast and slow timescales in the observation of dissipation and decoherence processes.

    View details for Web of Science ID 000253552100003

    View details for PubMedID 18542311

  • Femtosecond x-ray diffuse scattering measurements of semiconductor ablation dynamics Conference on High-Power Laser Ablation VII Lindenberg, A. M., Engemann, S., Gaffney, K. J., Sokolowski-Tinten, K., Larsson, J., Reis, D., Lorazo, P., Hastings, J. B. SPIE-INT SOC OPTICAL ENGINEERING. 2008

    View details for DOI 10.1117/12.784094

    View details for Web of Science ID 000258905800002

  • Asynchronous optical probing of coherent magnetic excitations from picoseconds to nanoseconds 2008 CONFERENCE ON LASERS AND ELECTRO-OPTICS & QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE, VOLS 1-9 Stoica, V. A., Sheu, Y., Reis, D. A., Clarke, R. 2008: 3333-3334
  • Phonon dispersion relations and softening in photoexcited bismuth from first principles PHYSICAL REVIEW B Murray, E. D., Fahy, S., Prendergast, D., Ogitsu, T., Fritz, D. M., Reis, D. A. 2007; 75 (18)
  • Carrier-density-dependent lattice stability in InSb PHYSICAL REVIEW LETTERS Hillyard, P. B., Gaffney, K. J., Lindenberg, A. M., Engemann, S., Akre, R. A., ARTHUR, J., Blome, C., Bucksbaum, P. H., Cavalieri, A. L., Deb, A., Falcone, R. W., Fritz, D. M., Fuoss, P. H., Hajdu, J., Krejcik, P., Larsson, J., Lee, S. H., Meyer, D. A., Nelson, A. J., Pahl, R., Reis, D. A., Rudati, J., Siddons, D. P., Sokolowski-Tinten, K., von der Linde, D., Hastings, J. B. 2007; 98 (12)

    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.

    View details for DOI 10.1103/PhysRevLett.98.125501

    View details for PubMedID 17501133

  • Ultrafast bond softening in bismuth: Mapping a solid's interatomic potential with X-rays SCIENCE Fritz, D. M., Reis, D. A., Adams, B., Akre, R. A., ARTHUR, J., Blome, C., Bucksbaum, P. H., Cavalieri, A. L., Engemann, S., Fahy, S., Falcone, R. W., Fuoss, P. H., Gaffney, K. J., George, M. J., Hajdu, J., Hertlein, M. P., Hillyard, P. B., Hoegen, M. H., Kammler, M., Kaspar, J., Kienberger, R., Krejcik, P., Lee, S. H., Lindenberg, A. M., McFarland, B., Meyer, D., Montagne, T., Murray, E. D., Nelson, A. J., Nicoul, M., Pahl, R., Rudati, J., Schlarb, H., Siddons, D. P., Sokolowski-Tinten, K., Tschentscher, T., von der Linde, D., Hastings, J. B. 2007; 315 (5812): 633-636

    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.

    View details for DOI 10.1126/science.1135009

    View details for Web of Science ID 000243909400039

    View details for PubMedID 17272718

  • Ultrafast X-ray scattering in solids LIGHT SCATTERING IN SOLIDS IX Reis, D. A., Lindenberg, A. M. 2007; 108: 371-422
  • Studies of ultrafast femtosecond-laser-generated strain fields with coherent X-rays SYNCHROTRON RADIATION INSTRUMENTATION, PTS 1 AND 2 Dufresne, E. M., Adams, B., Landahl, E. C., Khounsary, A. M., Reis, D., Fritz, D. M., Lee, S. 2007; 879: 1210-?
  • Picosecond time resolved x-ray diffraction measurements of coherent phonons and carrier dynamics at a buried interface 2007 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS, VOLS 1-4 Lee, S. H., Fritz, D. M., Sheu, Y., GOLDMAN, R. S., Walko, D., Landhal, E., Reis, D. A. 2007: 304-?
  • Simulations of time-resolved x-ray diffraction in Laue geometry JOURNAL OF PHYSICS-CONDENSED MATTER Lings, B., Wark, J. S., DeCamp, M. F., Reis, D. A., Fahy, S. 2006; 18 (40): 9231-9244
  • Ultrafast dynamics of laser-excited solids MRS BULLETIN Reis, D. A., Gaffney, K. J., Gilmer, G. H., Torralva, B. 2006; 31 (8): 601-606
  • Generation and propagation of a picosecond acoustic pulse at a buried interface: Time-resolved X-ray diffraction measurements PHYSICAL REVIEW LETTERS Lee, S. H., Cavalieri, A. L., Fritz, D. M., Swan, M. C., Hegde, R. S., Reason, M., GOLDMAN, R. S., Reis, D. A. 2005; 95 (24)

    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.

    View details for DOI 10.1103/PhysRevLett.95.246104

    View details for Web of Science ID 000233826100047

    View details for PubMedID 16384400

  • Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb PHYSICAL REVIEW LETTERS Gaffney, K. J., Lindenberg, A. M., Larsson, J., Sokolowski-Tinten, K., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A. G., Weinstein, D., Lowney, D. P., Allison, T., Matthews, T., Falcone, R. W., Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Macrander, A. T., Fuoss, P. H., Kao, C. C., Siddons, D. P., Pahl, R., Moffat, K., Als-Nielsen, J., Duesterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H. N., Lee, R. W., Hansen, T. N., Wark, J. S., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Krejcik, P., ARTHUR, J., Brennan, S., Luening, K., Hastings, J. B. 2005; 95 (12)

    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.

    View details for DOI 10.1103/PhysRevLett.95.125701

    View details for Web of Science ID 000231908200033

    View details for PubMedID 16197085

  • Effect of lattice anharmonicity on high-amplitude phonon dynamics in photoexcited bismuth PHYSICAL REVIEW B Murray, E. D., Fritz, D. M., Wahlstrand, J. K., Fahy, S., Reis, D. A. 2005; 72 (6)
  • Atomic-scale visualization of inertial dynamics SCIENCE Lindenberg, A. M., Larsson, J., Sokolowski-Tinten, K., Gaffney, K. J., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A. G., Weinstein, D., Lowney, D. P., Allison, T. K., Matthews, T., Falcone, R. W., Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Fuoss, P. H., Kao, C. C., Siddons, D. P., Pahl, R., Als-Nielsen, J., Duesterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Tschentscher, T., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H. N., Lee, R. W., Hansen, T. N., Techert, S., Wark, J. S., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Krejcik, P., ARTHUR, J., Brennan, S., Luening, K., Hastings, J. B. 2005; 308 (5720): 392-395

    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.

    View details for DOI 10.1126/science.1107996

    View details for Web of Science ID 000228492000046

    View details for PubMedID 15831753

  • Clocking femtosecond x rays PHYSICAL REVIEW LETTERS Cavalieri, A. L., Fritz, D. M., Lee, S. H., Bucksbaum, P. H., Reis, D. A., Rudati, J., Mills, D. M., Fuoss, P. H., Stephenson, G. B., Kao, C. C., Siddons, D. P., Lowney, D. P., MacPhee, A. G., Weinstein, D., Falcone, R. W., Pahl, R., Als-Nielsen, J., Blome, C., Dusterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Tschentscher, T., Schneider, J., Hignette, O., Sette, F., Sokolowski-Tinten, K., Chapman, H. N., Lee, R. W., Hansen, T. N., Synnergren, O., Larsson, J., Techert, S., Sheppard, J., Wark, J. S., Bergh, M., Caleman, C., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R. A., Bong, E., Emma, P., Krejcik, P., ARTHUR, J., Brennan, S., Gaffney, K. J., Lindenberg, A. M., Luening, K., Hastings, J. B. 2005; 94 (11)

    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.

    View details for DOI 10.1103/PhysRevLett.94.114801

    View details for Web of Science ID 000227923200034

    View details for PubMedID 15903864

  • X-ray synchrotron studies of ultrafast crystalline dynamics Symposium on Applications of Synchrotron Radiation to Materials DeCamp, M. F., Reis, D. A., Fritz, D. M., Bucksbaum, P. H., Dufresne, E. M., Clarke, R. WILEY-BLACKWELL. 2005: 177–192

    Abstract

    Ultrafast X-ray experiments at synchrotron sources hold tremendous promise for measuring the atomistic dynamics of materials under a wide variety of transient conditions. In particular, the marriage of synchrotron radiation and ultrafast laser technology is opening up a new frontier of materials research. Structural changes initiated by femtosecond laser pulses can be tracked in real time using time-resolved X-ray diffraction on picosecond time scales or shorter. Here, research at the Advanced Photon Source is described, illustrating the opportunities for ultrafast diffraction with some recent work on the generation of impulsive strain, coherent phonon generation and supersonic diffusion of electron-hole plasmas. The flexibility of time-resolved Bragg and Laue diffraction geometries are both utilized to illuminate the strain generation and evolution process. Time-resolved X-ray science will become increasingly important with the construction of linac-based ultrafast X-ray sources.

    View details for DOI 10.1107/S0909049504033679

    View details for Web of Science ID 000227377200008

    View details for PubMedID 15728970

  • Adaptive dispersion compensation for remote fiber delivery of near-infrared femtosecond pulses OPTICS LETTERS Lee, S. H., Cavalieri, A. L., Fritz, D. M., Myaing, M., Reis, D. A. 2004; 29 (22): 2602-2604

    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.

    View details for Web of Science ID 000224815400008

    View details for PubMedID 15552658

  • Ultrafast x-ray physics Indo/United States Workshop on Radiation Physics with Synchrotrons and Other New Sources Reis, D. A., Bucksbaum, P. H., DeCamp, M. F. PERGAMON-ELSEVIER SCIENCE LTD. 2004: 605–9
  • Ultrafast coherent control in x-ray scattering 227th National Meeting of the American-Chemical Society Bucksbaum, P. H., Reis, D. A. AMER CHEMICAL SOC. 2004: U270–U270
  • Ultrafast hard x-rays from electron accelerators 4th International Conference on Ultrafast Optics Bucksbaum, P. H., Reis, D. A., Hastings, J. SPRINGER. 2004: 333–340
  • Transient strain driven by a dense electron-hole plasma PHYSICAL REVIEW LETTERS DeCamp, M. F., Reis, D. A., Cavalieri, A., Bucksbaum, P. H., Clarke, R., Merlin, R., Dufresne, E. M., Arms, D. A., Lindenberg, A. M., MacPhee, A. G., Chang, Z., Lings, B., Wark, J. S., Fahy, S. 2003; 91 (16)

    Abstract

    We measure transient strain in ultrafast laser-excited Ge by time-resolved x-ray anomalous transmission. The development of the coherent strain pulse is dominated by rapid ambipolar diffusion. This pulse extends considerably longer than the laser penetration depth because the plasma initially propagates faster than the acoustic modes. X-ray diffraction simulations are in agreement with the observed dynamics.

    View details for DOI 10.1103/PhysRevLett.91.165502

    View details for Web of Science ID 000186068300026

    View details for PubMedID 14611411

  • Picosecond laser-pump, x-ray probe spectroscopy of GaAs REVIEW OF SCIENTIFIC INSTRUMENTS Adams, B. W., DeCamp, M. F., Dufresne, E. M., Reis, D. A. 2002; 73 (12): 4150-4156

    View details for DOI 10.1063/1.1516849

    View details for Web of Science ID 000179393200004

  • Picosecond X-ray diffraction studies of laser-excited acoustic phonons in InSb APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Larsson, J., Allen, A., Bucksbaum, P. H., Falcone, R. W., Lindenberg, A., Naylor, G., Missalla, T., Reis, D. A., Scheidt, K., Sjogren, A., Sondhauss, P., WULFF, M., Wark, J. S. 2002; 75 (4): 467-478
  • Picosecond time-resolved x-ray diffraction probe of coherent lattice dynamics (abstract) (invited) REVIEW OF SCIENTIFIC INSTRUMENTS Reis, D. A., DeCamp, M. F., Bucksbaum, P. H., Clarke, R., Dufresne, E., Merlin, R. 2002; 73 (3): 1361-?

    View details for DOI 10.1063/1.1448147

    View details for Web of Science ID 000174182800002

  • Coherent control of pulsed X-ray beams NATURE DeCamp, M. F., Reis, D. A., Bucksbaum, P. H., Adams, B., Caraher, J. M., Clarke, R., Conover, C. W., Dufresne, E. M., Merlin, R., Stoica, V., Wahlstrand, J. K. 2001; 413 (6858): 825-828

    Abstract

    Synchrotrons produce continuous trains of closely spaced X-ray pulses. Application of such sources to the study of atomic-scale motion requires efficient modulation of these beams on timescales ranging from nanoseconds to femtoseconds. However, ultrafast X-ray modulators are not generally available. Here we report efficient subnanosecond coherent switching of synchrotron beams by using acoustic pulses in a crystal to modulate the anomalous low-loss transmission of X-ray pulses. The acoustic excitation transfers energy between two X-ray beams in a time shorter than the synchrotron pulse width of about 100 ps. Gigahertz modulation of the diffracted X-rays is also observed. We report different geometric arrangements, such as a switch based on the collision of two counter-propagating acoustic pulses: this doubles the X-ray modulation frequency, and also provides a means of observing a localized transient strain inside an opaque material. We expect that these techniques could be scaled to produce subpicosecond pulses, through laser-generated coherent optical phonon modulation of X-ray diffraction in crystals. Such ultrafast capabilities have been demonstrated thus far only in laser-generated X-ray sources, or through the use of X-ray streak cameras.

    View details for Web of Science ID 000171750200040

    View details for PubMedID 11677601

  • Dynamics and coherent control of high-amplitude optical phonons in bismuth PHYSICAL REVIEW B DeCamp, M. F., Reis, D. A., Bucksbaum, P. H., Merlin, R. 2001; 64 (9)
  • Probing impulsive strain propagation with x-ray pulses PHYSICAL REVIEW LETTERS Reis, D. A., DeCamp, M. F., Bucksbaum, P. H., Clarke, R., Dufresne, E., Hertlein, M., Merlin, R., Falcone, R., Kapteyn, H., Murnane, M. M., Larsson, J., Missalla, T., Wark, J. S. 2001; 86 (14): 3072-3075

    Abstract

    Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation of a coherent acoustic pulse generated by ultrafast laser excitation. The surface and bulk components of the strain could be simultaneously measured due to the large x-ray penetration depth. Comparison of the experimental data with dynamical diffraction simulations suggests that the conventional model for impulsively generated strain underestimates the partitioning of energy into coherent modes.

    View details for Web of Science ID 000167866300040

    View details for PubMedID 11290110

  • Femtosecond X-ray diffraction: Experiments and limits Conference on X-Ray FEL Optics and Instrumentation Wark, J. S., Allen, A. M., Ansbro, P. C., Bucksbaum, P. H., Chang, Z., DeCamp, M., Falcone, R. W., Heimann, P. A., Johnson, S. L., Kang, I., Kapteyn, H. C., Larsson, J., Lee, R. W., Lindenberg, A. M., Merlin, R., Missalla, T., Naylor, G., Padmore, H. A., Reis, D. A., Scheidt, K., Sjoegren, A., Sondhauss, P. C., WULFF, M. SPIE-INT SOCIETY OPTICAL ENGINEERING. 2001: 26–37
  • Studies of nonlinear QED in collisions of 46.6 GeV electrons with intense laser pulses PHYSICAL REVIEW D Bamber, C., Boege, S. J., Koffas, T., Kotseroglou, T., Melissinos, A. C., Meyerhofer, D. D., Reis, D. A., Ragg, W., Bula, C., McDonald, K. T., Prebys, E. J., Burke, D. L., Field, R. C., Horton-Smith, G., Spencer, J. E., Walz, D., Berridge, S. C., Bugg, W. M., Shmakov, K., Weidemann, A. W. 1999; 60 (9)
  • Transverse emittance measurements from a photocathode RF gun with variable laser pulse length 20th International Free Electron Laser Conference 5th FEL User Workshop Reis, D. A., HERNANDEZ, M., Schmerge, J. F., Winick, H., Hogan, M. J. ELSEVIER SCIENCE BV. 1999: 341–46
  • Studies of nonlinear QED in high energy electron-laser collisions LASER PHYSICS Kotseroglou, T., Bamber, C., Berridge, S. C., Boege, S. J., Bugg, W. M., Bulal, C., Burke, D. L., Field, R. C., Horton-Smith, G., Koffas, T., McDonald, K. T., Melissinos, A. C., Meyerhofer, D. D., Prebys, E. J., Ragg, W., Reis, D. A., Shmakov, K., Spencer, J. E., Walz, D., Weidemann, A. W. 1998; 8 (1): 142-149
  • Emittance measurements for the SLAC gun test facility 17th Particle Accelerator Conference HERNANDEZ, M., Fisher, A., MEYERHOFER, D., Miller, R., Palmer, D. T., Park, S., Reis, D., Schmerge, J., Weaver, J., Wiedemann, H., Winick, H., Yeremian, D. IEEE. 1998: 2840–2842
  • Positron production in multiphoton light-by-light scattering PHYSICAL REVIEW LETTERS Burke, D. L., Field, R. C., HORTONSMITH, G., Spencer, J. E., Walz, D., Berridge, S. C., Bugg, W. M., Shmakov, K., Weidemann, A. W., Bula, C., McDonald, K. T., Prebys, E. J., Bamber, C., Boege, S. J., Koffas, T., Kotseroglou, T., Melissinos, A. C., Meyerhofer, D. D., Reis, D. A., Raggk, W. 1997; 79 (9): 1626-1629
  • SLAC RF photocathode gun test facility Conference on Free-Electron Laser Challenges Schmerge, J. F., Reis, D. A., HERNANDEZ, M., Meyerhofer, D. D., Miller, R. H., Palmer, D. T., Weaver, J. N., Winick, H., Yeremian, D. SPIE - INT SOC OPTICAL ENGINEERING. 1997: 90–96
  • 0.5-Hz, phase-stabilized terawatt laser system with a Nd:glass slab amplifier for nonlinear QED experiments International Workshop on Laser Physics (LPHYS 96) Bamber, C., Blalock, T., Boege, S., Kotseroglou, T., Melissinos, A. C., Ragg, W., Reis, D., Meyerhofer, D. D., Kelly, J., Shoup, M. INTERPERIODICA. 1997: 135–40