Laser-plasma interaction during visible-laser ablation of methods

Abstract

We have investigated the dynamics of high-radiance visible-laser interaction with a metal vapor plasma during laser ablation of aluminum and carbon steel. The experiment with a copper vapor laser reveals strong plasma-absorption induced ignition at laser intensities above 1–2 GW/cm2. Approximation based on hydrodynamic relations indicates that the vapor density at the end of the 40-ns laser pulse is 3×1020–1×1021 cm −3 with a pressure of a few thousand atmosphere at the target surface. This high-density vapor with a temperature exceeding 10 000 K leads to pronounced plasma absorption via photoionization. Plasma absorption via inverse bremsstrahlung is determined to be negligible because of a relatively low electron density, measured to be peaked at ∼5×1018 cm−3.

Energy Absorption and Propagation in Laser-Created Sparks

“…In the present studies, the absorption of the laser photons by the spark is mainly expected due to the inverse bremsstrahlung process. The inverse bremsstrahlung absorption via free electrons is approximated by: 39,40 ␣ ib ϭ 1.37 ϫ 10…”

Electron density and temperature measurements in a laser produced carbon plasma

“…It is noted that the absorption due to inverse bremsstrahlung is negligibly small at low irradiance levels and increases exponentially with increasing laser irradiance and saturates at higher irradiance levels. Absorption via photoionization can be estimated with Kramer's formula and absorption coefficient 37,38 …”

Internal structure and expansion dynamics of laser ablation plumes into ambient gases

“…[1][2][3][4][5][6][7] The different mechanisms involved during a laser ablation process, including laser absorption, evaporation, transient gas dynamics, radiation transport, condensation, ionization, and recombination, are rather complex and require further investigation.…”