Sponsored by the National Science Foundation and the Sandia National Laboratory
This study employs an ultrafast laser pump-and-probe experimental facility to investigate energy transfer from photons to electrons to lattice heating. Our current interest is to investigate ultrafast energy transfer process through coherent phonon excitation and diagnostics. Coherent phonon refers to collective excitation of phonon vibration. It is being used to understand ultrafast interactions among energy carriers (electron-phonon scattering, phonon-phonon scattering, and scattering of phonons with interfaces and grain boundaries). These studies provide a fundamental understanding of energy transfer process in nanomaterials, and the resulting macroscopic energy transfer properties.
Coherent phonon excitation in bismuth. In the experiment, two fs pulses,with variable separation times are used to irradiate a Bi sample. The separation time of the two pulses were adjusted so that to enhance phonon vibration; (red line) or completely cancel phonon vibration (blueline) after the second pulse.
Additionally, electron-phonon coupling time, phonon-phonon coupling time,and phonon dephasing time can all be obtained from the experimental data,allowing investigations of fundamental energy transfer process at the ultrafast time scale.
See publication list for papers in this area.
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