Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

K: Kurzzeitphysik

K 1: Laserstrahlwechselwirkungen

K 1.3: Vortrag

Montag, 7. März 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.