Berlin 2005 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
K: Kurzzeitphysik
K 1: Laserstrahlwechselwirkungen
K 1.3: Talk
Monday, March 7, 2005, 11:40–12:00, HU 3092
Dynamics of femtosecond laser ablation from dielectric surfaces — •Florenta Costache, Sebastian Eckert, and Jürgen Reif — Brandenburgische Technische Universität and JointLab IHP/BTU Cottbus, Konrad-Wachsmann-Allee 1, 03044 Cottbus, Germany
We report on time-resolved studies of the dynamics of femtosecond laser interaction with BaF2 and CaF2.
As demonstrated earlier by time-of-flight mass spectrometry, the ultra-short laser pulses induce intensity dependent non-equilibrium processes in the surface region of the dielectric target.
The initial laser-material coupling has been shown to be multi-photon ionization, the electron yield indicating a defect-state enhancement. To substantiate this, the induced defects and their lifetime were explored by laser induced fluorescence measurements. We found several fluorescence bands for the investigated materials, typically decaying within 1 µs and 50 ms.
The emission dynamics was studied by a pump-probe technique, measuring the particle yields as a function of time delay between two sub-threshold laser pulses.
In the desorption regime (low intensities), a strongly charged surface explodes on a femtosecond time scale. At higher laser intensity, a fraction of the particles appears to be emitted on a few-ps time scale possibly indicating a phase explosion of a superheated surface.