@article{GaalSchickHerzogetal.2012,
  author    = {Gaal, P. and Schick, Daniel and Herzog, Marc and Bojahr, Andre and Shayduk, Roman and Goldshteyn, J. and Navirian, Hengameh A. and Leitenberger, Wolfram and Vrejoiu, Ionela and Khakhulin, D. and Wulff, M. and Bargheer, Matias},
  title     = {Time-domain sampling of x-ray pulses using an ultrafast sample response},
  series = {Applied physics letters},
  volume    = {101},
  journal   = {Applied physics letters},
  number    = {24},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0003-6951},
  doi       = {10.1063/1.4769828},
  pages     = {4},
  year      = {2012},
  abstract  = {We employ the ultrafast response of a 15.4 nm thin SrRuO3 layer grown epitaxially on a SrTiO3 substrate to perform time-domain sampling of an x-ray pulse emitted from a synchrotron storage ring. Excitation of the sample with an ultrashort laser pulse triggers coherent expansion and compression waves in the thin layer, which turn the diffraction efficiency on and off at a fixed Bragg angle during 5 ps. This is significantly shorter than the duration of the synchrotron x-ray pulse of 100 ps. Cross-correlation measurements of the ultrafast sample response and the synchrotron x-ray pulse allow to reconstruct the x-ray pulse shape.},
  language  = {en}
}
@article{SchickBojahrHerzogetal.2012,
  author    = {Schick, Daniel and Bojahr, Andre and Herzog, Marc and von Korff Schmising, Clemens and Shayduk, Roman and Leitenberger, Wolfram and Gaa, P. and Bargheer, Matias},
  title     = {Normalization schemes for ultrafast x-ray diffraction using a table-top laser-driven plasma source},
  series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  volume    = {83},
  journal   = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques},
  number    = {2},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0034-6748},
  doi       = {10.1063/1.3681254},
  pages     = {7},
  year      = {2012},
  abstract  = {We present an experimental setup of a laser-driven x-ray plasma source for femtosecond x-ray diffraction. Different normalization schemes accounting for x-ray source intensity fluctuations are discussed in detail. We apply these schemes to measure the temporal evolution of Bragg peak intensities of perovskite superlattices after ultrafast laser excitation.},
  language  = {en}
}
@article{HerzogBojahrGoldshteynetal.2012,
  author    = {Herzog, Marc and Bojahr, Andre and Goldshteyn, J. and Leitenberger, Wolfram and Vrejoiu, I. and Khakhulin, D. and Wulff, M. and Shayduk, Roman and Gaal, P. and Bargheer, Matias},
  title     = {Detecting optically synthesized quasi-monochromatic sub-terahertz phonon wavepackets by ultrafast x-ray diffraction},
  series = {Applied physics letters},
  volume    = {100},
  journal   = {Applied physics letters},
  number    = {9},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0003-6951},
  doi       = {10.1063/1.3688492},
  pages     = {4},
  year      = {2012},
  abstract  = {We excite an epitaxial SrRuO3 thin film transducer by a pulse train of ultrashort laser pulses, launching coherent sound waves into the underlying SrTiO3 substrate. Synchrotron-based x-ray diffraction (XRD) data exhibiting separated sidebands to the substrate peak evidence the excitation of a quasi-monochromatic phonon wavepacket with sub-THz central frequency. The frequency and bandwidth of this sound pulse can be controlled by the optical pulse train. We compare the experimental data to combined lattice dynamics and dynamical XRD simulations to verify the coherent phonon dynamics. In addition, we observe a lifetime of 130 ps of such sub-THz phonons in accordance with the theory.},
  language  = {en}
}
@article{BojahrSchickMaertenetal.2012,
  author    = {Bojahr, Andre and Schick, Daniel and M{\"a}rten, Lena and Herzog, Marc and Vrejoiu, Ionela and von Korff Schmising, Clemens and Milne, Chris and Johnson, Steven Lee and Bargheer, Matias},
  title     = {Comparing the oscillation phase in optical pump-probe spectra to ultrafast x-ray diffraction in the metal-dielectric SrRuO3/SrTiO3 superlattice},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {85},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {22},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1098-0121},
  doi       = {10.1103/PhysRevB.85.224302},
  pages     = {6},
  year      = {2012},
  abstract  = {We measured the ultrafast optical response of metal-dielectric superlattices by broadband all-optical pump-probe spectroscopy. The observed phase of the superlattice mode depends on the probe wavelength, making assignments of the excitation mechanism difficult. Ultrafast x-ray diffraction data reveal the true oscillation phase of the lattice which changes as a function of the excitation fluence. This result is confirmed by the fluence dependence of optical transients. We set up a linear chain model of the lattice dynamics and successfully simulated the broadband optical reflection by unit-cell resolved calculation of the strain-dependent dielectric functions of the constituting materials.},
  language  = {en}
}
@article{BojahrHerzogSchicketal.2012,
  author    = {Bojahr, Andre and Herzog, Marc and Schick, Daniel and Vrejoiu, Ionela and Bargheer, Matias},
  title     = {Calibrated real-time detection of nonlinearly propagating strain waves},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {86},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {14},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1098-0121},
  doi       = {10.1103/PhysRevB.86.144306},
  pages     = {5},
  year      = {2012},
  abstract  = {Epitaxially grown metallic oxide transducers support the generation of ultrashort strain pulses in SrTiO3 (STO) with high amplitudes up to 0.5\%. The strain amplitudes are calibrated by real-time measurements of the lattice deformation using ultrafast x-ray diffraction. We determine the speed at which the strain fronts propagate by broadband picosecond ultrasonics and conclude that, above a strain level of approx. 0.2\%, the compressive and tensile strain components travel at considerably different sound velocities, indicating nonlinear wave behavior. Simulations based on an anharmonic linear-chain model are in excellent accord with the experimental findings and show how the spectrum of coherent phonon modes changes with time.},
  language  = {en}
}