<title>Microablation of pure metals: laser plasma and crater investigations</title>

Abstract

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.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.