The interaction of laser radiation with a material can excite coherent lattice vibration.
The observation of such periodic motion of the atoms in the lattice provides
information on the properties of the material. In the present work a femtosecond
pump-probe technique was applied for studies of acoustic vibrations in nanoparticles
and nanowires, and coherent optical phonons in thin films.
The elastic properties of spherical Ag nanoparticles and Ag and Bi nanowires
were studied in a dual-color femtosecond pump-probe experiment. The results of
the period determinations of the acoustic vibrations, obtained from the time-domain
measurements with low intensity pump pulses, together with the information about
the size of the particles, were used to determine the elastic constants of the materials.
Also changes in the measured acoustical response of the Ag nanowires under high
intensity laser excitation were studied.
In addition the coherent optical phonon excitation in a Bi film was studied in a
femtosecond pump-probe experiment. A red-shift of the phonon frequency at the high
photoexcitation density was observed. To separate the effect of the lattice softening
and the lattice anharmonicity the excitation with two pump pulses was employed.
Numerical simulations, which took into account the evolution of the spatial inhomogeneity
of the excitation density, were carried out and compared to the experimental
results.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1358 |
| Date | 15 May 2009 |
| Creators | Jerebtsov, Serguei Nikolaevich |
| Contributors | Schuessler, Hans A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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