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A model of drilling by high radiance pulsed lasers is described. The model involves a one-dimensional description of heat transport below the bottom of the hole, hydrodynamic expansion of the vapor and compressed air, and light propagation through the vapor. The pressure and energy of the vapor are taken from a separate Saha equilibrium code. The boundary conditions at the vaporization surface include the formation of a transition layer within which macroscopic fluid conditions are reached. The absorption mechanisms are photoionization and inverse bremsstrahlung. The model has been applied to the case of drilling in stainless steel with green copper laser light, for peak input intensities ranging from 108 to 4 × 1010 W/cm2. Below 3 × 108 W/cm2, there is negligible absorption in the vapor and ablation increases rapidly with intensity. After decreasing for a short interval beyond this point, the ablation rate then increases steadily with power because of a growing electron thermal conduction to the surface. The experimental ablation rate exhibits a somewhat faster overall growth. It appears comparable to the model at low power but is about five times greater at the highest power.A model of drilling by high radiance pulsed lasers is described. The model involves a one-dimensional description of heat transport below the bottom of the hole, hydrodynamic expansion of the vapor and compressed air, and light propagation through the vapor. The pressure and energy of the vapor are taken from a separate Saha equilibrium code. The boundary conditions at the vaporization surface include the formation of a transition layer within which macroscopic fluid conditions are reached. The absorption mechanisms are photoionization and inverse bremsstrahlung. The model has been applied to the case of drilling in stainless steel with green copper laser light, for peak input intensities ranging from 108 to 4 × 1010 W/cm2. Below 3 × 108 W/cm2, there is negligible absorption in the vapor and ablation increases rapidly with intensity. After decreasing for a short interval beyond this point, the ablation rate then increases steadily with power because of a growing electron thermal conduction to the surface....

Computational model of drilling with high radiance pulsed lasers