Andrea Cavalleri

Abstract:

Using time-resolved x-ray diffraction the ultafast strain dynamics in fs-laserexcited Ge/Si-heterostructures has been studied. A fluence dependent, anharmonic damping of the impulsively generated acoustic phonons and vibrational transport across the buried Ge/Si-interface are observed.

Abstract:

Using ultrafast X-ray, line radiation generated with a 20-fs multi-terawatt laser system, femtosecond induced lattice dynamics was observed in bulk semiconductors with milliangstrom spatial and picosecond resolution via time resolved X-ray diffraction. Coherent phonon generation and propagation, ultrafast melting of thin films and buried interface lattice coupling were observed.

Abstract:

Using ultrafast, time-resolved, 1.54 angstrom x-ray diffraction, thermal and ultrafast nonthermal melting of germanium, involving passage through nonequilibrium extreme states of matter, was observed. Such ultrafast, optical-pump, x-ray diffraction probe measurements provide a way to study many other transient processes in physics, chemistry, and biology, including direct observation of the atomic motion by which many solid-state processes and chemical and biochemical reactions take place.

Abstract:

Femtosecond laser ablation of semiconductors was studied with a number of techniques, including time resolved microscopy and time-of-flight mass spectroscopy. The laser pulse excites a very dense electron-hole plasma in the semiconductor, leading to nonthermal melting on a sub-picosecond timescale. The liquid is left in a state of high temperature and high pressure.