Ultrafast dynamics in solids

We use ultrafast optical techniques to study highly non-equilibrium electron and lattice dynamics in semiconductors and metals � materials that are important for electronic and optoelectronic devices. Because of their miniaturization, electronic and optoelectronic devices operate increasingly in a regime of extremely high carrier density. We excite a very high number of electrons in a material by an intense optical pulse with a duration of less than a hundred femtoseconds. This allows us to create exotic states of matter that contain excited electronic populations 3 to 4 orders of magnitude larger compared to weak excitation studies.
Stopping time, at Perimeter Institute Public Lecture, Perimeter Institute (Waterloo, ON, Canada), Wednesday, December 1, 2010:
Time is of philosophical interest as well as the subject of mathematical and scientific research. Even though it is a concept familiar to most, the passage of time remains one of the greatest enigmas of the universe. The philosopher Augustine once said: "What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks me, I do not know." The concept time indeed cannot be explained in simple terms. Emotions, life, and death - all are related to our interpretation of the irreversible flow of time. After a discussion of the concept of time, we will review... Read more about Stopping time
Ultrafast broadband spectroscopic studies of GaAs under intense laser excitation, at OSA Annual Meeting 1996 (Rochester, NY), Tuesday, October 1, 1996
An ultrafast broadband spectroscopic technique (350 to 900 nm) is employed to measure the dielectric function of GaAs in response to a 70-fs laser pulse excitation. We observe drastic changes in the dielectric function within 1ps of the excitation, which we attribute to an ultrafast non-thermal structural transition. These broadband measurements provide extensive information on the initial electronic excitation and the dynamics of the subsequent phase transition.
Ultrafast Phase Transitions in Solids, at International School of Atomic and Molecular Spectroscopy (Erice, Sicily, Italy), Saturday, May 24, 2003:
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

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