@article{HerzogSchickLeitenbergeretal.2012,
  author    = {Herzog, Marc and Schick, Daniel and Leitenberger, Wolfram and Shayduk, Roman and van der Veen, Renske M. and Milne, Christopher J. and Johnson, Steven Lee and Vrejoiu, Ionela and Bargheer, Matias},
  title     = {Tailoring interference and nonlinear manipulation of femtosecond x-rays},
  series = {New journal of physics : the open-access journal for physics},
  volume    = {14},
  journal   = {New journal of physics : the open-access journal for physics},
  number    = {1},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/14/1/013004},
  pages     = {9},
  year      = {2012},
  abstract  = {We present ultrafast x-ray diffraction (UXRD) experiments on different photoexcited oxide superlattices. All data are successfully simulated by dynamical x-ray diffraction calculations based on a microscopic model, that accounts for the linear response of phonons to the excitation laser pulse. Some Bragg reflections display a highly nonlinear strain dependence. The origin of linear and two distinct nonlinear response phenomena is discussed in a conceptually simpler model using the interference of envelope functions that describe the diffraction efficiency of the average constituent nanolayers. The combination of both models facilitates rapid and accurate simulations of UXRD experiments.},
  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{HerzogSchickGaaletal.2012,
  author    = {Herzog, Marc and Schick, Daniel and Gaal, P. and Shayduk, Roman and von Korff Schmising, Clemens and Bargheer, Matias},
  title     = {Analysis of ultrafast X-ray diffraction data in a linear-chain model of the lattice dynamics},
  series = {Applied physics : A, Materials science \& processing},
  volume    = {106},
  journal   = {Applied physics : A, Materials science \& processing},
  number    = {3},
  publisher = {Springer},
  address   = {New York},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-011-6719-z},
  pages     = {489 -- 499},
  year      = {2012},
  abstract  = {We present ultrafast X-ray diffraction (UXRD) experiments which sensitively probe impulsively excited acoustic phonons propagating in a SrRuO3/SrTiO3 superlattice and further into the substrate. These findings are discussed together with previous UXRD results (Herzog et al. in Appl. Phys. Lett. 96, 161906, 2010; Woerner et al. in Appl. Phys. A 96, 83, 2009; v. Korff Schmising in Phys. Rev. B 78, 060404(R), 2008 and in Appl. Phys. B 88, 1, 2007) using a normal-mode analysis of a linear-chain model of masses and springs, thus identifying them as linear-response phenomena. We point out the direct correspondence of calculated observables with X-ray signals. In this framework the complex lattice motion turns out to result from an interference of vibrational eigenmodes of the coupled system of nanolayers and substrate. UXRD in principle selectively measures the lattice motion occurring with a specific wavevector, however, each Bragg reflection only measures the amplitude of a delocalized phonon mode in a spatially localized region, determined by the nanocomposition of the sample or the extinction depth of X-rays. This leads to a decay of experimental signals although the excited modes survive.},
  language  = {en}
}
@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}
}