HOME / PRESENTATIONS /

Maria Kandyla

Ultrafast Frequency Dynamics of Coherent Phonons in Te Under High Density Photoexcitation, at Photonics West 2006 (San Jose, CA), Wednesday, January 25, 2006:
talk_1178.pdf
We report on the ultrafast dynamics of large amplitude A1 coherent optical phonons in Te after excitation with femtosecond laser pulses. Using time-resolved pump-probe dielectric tensor measurements on a single crystal Te sample we can monitor the excitation of the A1 phonon mode due to photoexcited carrier density redistribution. By performing a short-term Fourier transform of the observed dielectric tensor oscillations we can track the evolution of their local frequency and determine the time-resolved frequency response of the photoexcited A1 phonon mode.

The purpose of the experiment...

Read more about Ultrafast Frequency Dynamics of Coherent Phonons in Te Under High Density Photoexcitation
Ultrafast dynamics in highly excited semiconductors, at Seminar in the Institute of Electronic Structure and Laser (IESL), Foundation for Reaserch and Technology - Hellas (FORTH) (Heraklion, Crete, Greece), Friday, January 7, 2005:
talk_1130.pdf
A pump-probe technique measuring the dielectric function is presented and applied in a series of experiments. An ultrafast semiconductor-to-metal phase transition is observed in highly excited GaAs. High amplitude coherent phonon dynamics in Te are resolved suggesting a THz-driven semiconductor-semimetal transition. Coherent control including both enhancement and cancellation of the lattice vibrations in Te is demonstrated revealing a departure from the low-excitation behavior of similar materials.
Ultrafast Phase Transitions in Solids, at International School of Atomic and Molecular Spectroscopy (Erice, Sicily, Italy), Saturday, May 24, 2003:
talk_513.pdf
In this talk we present the coherent excitation and coherent control of the A1 phonon mode in Te. First, the underlying theory about the excitation of the A1 phonon mode, and only this, in a certain class of materials is discussed. The theory, called Displacive Excitation of Coherent Phonons (DECP), predicts the excitation of the A1 phonon mode as a result of electronic excitation following absorption of an ultrashort laser pulse by the material. Since there is no symmetry breaking mechanism in the electronic excitation through absorption the effect can only take place in materials which... Read more about Ultrafast Phase Transitions in Solids