| 1. |
- Larsson, Jörgen, et al.
(author)
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Picosecond X-ray diffraction studies of laser-excited acoustic phonons in InSb
- 2002
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In: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630 .- 0947-8396. ; 75:4, s. 467-478
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Journal article (peer-reviewed)abstract
- We have employed time-resolved X-ray diffraction with picosecond temporal resolution to measure the time-dependent rocking curves of laser-irradiated asymmetrically cut single InSb crystals. Coherent acoustic phonons were excited in the crystals by irradiation with 800-nm, 100-fs laser pulses at irradiances between 0.25 and 12 mJ/cm(2). The induced time-dependent strain profiles (corresponding to the coherent phonons) were monitored by diffracting collimated, monochromatic pulses Of X-rays from the irradiated crystals. Recording of the diffracted radiation with a fast low-jitter X-ray streak camera resulted in an overall temporal resolution of better than 2 ps. The strain associated with the coherent phonons modifies the rocking curve of the crystal in a time-dependent manner, and the rocking curve is recorded by keeping the angle of incidence of the X-rays upon the crystal fixed, but varying the energy of the incident X-rays around a central energy of 8.453 keV (corresponding to the peak of the rocking curve of the unperturbed crystal). The observed time-dependent diffraction from the irradiated crystals is in reasonable agreement with simulations over a wide range of energies from the unperturbed rocking-curve peak.
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| 2. |
- Lindenberg, A. M, et al.
(author)
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Time-resolved X-ray diffraction from coherent phonons during a laser-induced phase transition
- 2000
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In: Physical Review Letters. - 1079-7114. ; 84:1, s. 111-114
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Journal article (peer-reviewed)abstract
- Time-resolved x-ray diffraction with picosecond temporal resolution is used to observe scattering from impulsively generated coherent acoustic phonons in laser-excited InSb crystals. The observed frequencies and damping rates are in agreement with a model based on dynamical diffraction theory coupled to analytic solutions for the laser-induced strain profile. The results are consistent with a 12 ps thermal electron-acoustic phonon coupling time together with an instantaneous component from the deformation-potential interaction. Above a critical laser fluence, we show that the first step in the transition to a disordered state is the excitation of large amplitude, coherent atomic motion.
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| 3. |
- Reis, D. A, et al.
(author)
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Probing impulsive strain propagation with x-ray pulses
- 2001
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In: Physical Review Letters. - 1079-7114. ; 86:14, s. 3072-3075
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Journal article (peer-reviewed)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.
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| 4. |
- Synnergren, Ola, et al.
(author)
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Projecting picosecond lattice dynamics through x-ray topography
- 2002
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:20, s. 3727-3729
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Journal article (peer-reviewed)abstract
- A method for time-resolved x-ray diffraction studies has been demonstrated. As a test case, coherent acoustic phonon propagation into crystalline InSb is observed using a laser plasma x-ray source. An extended x-ray topogram of the semiconductor's surface was projected onto a high spatial resolution x-ray detector and acoustic phonons were excited by rapidly heating the crystal's surface with a femtosecond laser pulse. A correlation between the spatial position on the x-ray detector and the time of arrival of the laser pulse was encoded into the experimental geometry by tilting the incident laser pulse with an optical grating. This approach enabled a temporal window of 200 ps to be sampled in a single topogram, thereby negating the disadvantages of pulse-to-pulse fluctuations in the intensity and spectrum of the laser-plasma source. (C) 2002 American Institute of Physics.
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