Alexandre Semerok

Laser ablation efficiency of pure metals with femtosecond, picosecond, and nanosecond pulses

Laser ablation of pure metals by femtosecond, picosecond and nanosecond pulses is studied experimentally in air at atmospheric pressure. Craters created by interaction of visible and UV laser pulses with the targets are investigated. The dependence of the ablation efficiency in terms of ablated volume per unit of energy on the pulse duration and wavelength is discussed.

Microablation of pure metals: laser plasma and crater investigations

Crater shapes and plasma plume expansion in the interaction of femtosecond, picosecond and nanosecond laser pulses with various pure metal in air and noble gases at atmospheric pressure were studied. The craters formed at the surfaces were measured by an optical microscope profilometer with 0.01 micrometers depth and 0.5 micrometers lateral resolutions. The measurements of laser plasma expansion were carried out with ICCD camera with 3 micrometers spatial and 1 ns temporal resolutions. These measurements were made in 0-100 ns time delay range and at different wavelengths in 200-850 nm optical spectral range. Laser ablation efficiencies, crater profiles, plasma plume shapes at different time delays, rates of plasma expansion in both longitudinal and transversal directions to the laser beam were obtained. Experimental results were analyzed from the point of view of different theoretical models of laser beam interaction with plasma and metals. The laser pulse duration range used in our study was of particular interest, as it includes the characteristic time of electron-phonon relaxation in solids, that is, of the order off one picosecond. Thus, we could study the different regimes of laser ablation without and with laser beam/plasma plume interaction. It was found that for nanosecond pluses the laser beam absorption, as well as its scattering and reflection in plasma, were the limiting factors for efficient laser ablation and precise material processing with sharply focused laser beams.

Development of a tip enhanced near-field laser ablation system for the sub-micrometric analysis of solid samples

A near-field laser ablation system was developed for the analysis of inorganic solid samples in the nanometer resolution range. The instrument is based on the coupling of a nanosecond Nd:YAG laser with an atomic force microscope. The technique uses a tip enhancement effect obtained by the interaction of laser radiation with the conductive tip of the AFM maintained at a few nanometers above the sample surface. By applying this technique to conducting gold and semiconducting silicon samples, a lateral resolution of 100 nm was demonstrated. With a single laser pulse, craters of about 100 nm in diameter and a few nanometers in depth were obtained. A multi-parametric study was carried out in order to understand the effect of different experimental parameters (laser fluence, tip-to-sample distance, sample and tip nature) on the near-field laser ablation efficiency, crater dimensions and amount of ablated material. Numerical simulations of the localized heating with a home-made 3-D code presented a good explanation for the nanometer-sized crater diameters obtained in our experiments.

Experimental investigation of laser ablation efficiency of metals

We have investigated the craters created after high intensity visible and UV-laser pulse interaction with the metal surfaces in air. The experiments were performed on different pure metal samples in the intensity range typical for laser plasma analytical application experiments with nanosecond laser pulses. The craters were characterized by their depth, diameter and volume. The analysis and discussion of the obtained results are presented.

Influence of laser pulse duration on the ablation efficiency of metals

Laser ablation of pure metals by femtosecond, picosecond and nanosecond pulses is studied in air at atmospheric pressure. Craters created after interaction of visible and UV laser pulses with the targets are investigated. The dependence of the ablation efficiency in terms of ablated volume per unit of energy on the pulse duration is discussed.

Laser plasma limiting effects at nanosecond laser microablation

Plasma plume expansion and crater formation in the interaction of Nd-YAG laser beam (TEMoo-mode, 532 nm, 6 ns pulse duration and 10 micrometers waist at FWHM) with various metal targets in air were investigated. The craters formed at the surfaces were measured with 0.1 micrometers longitudinal and 0.5 micrometers transversal resolutions. Laser plasma expansion during laser pulse/surface interaction was measured by ICCD camera with 3 micrometers spatial and 1 ns temporal resolutions. These measurements were performed with different optical filters in the following spectral ranges (250< (lambda) <400 nm, 300<(lambda) <600 nm, 600< (lambda) <800 nm).