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20 June 1989 Light-Material Interactions In Laser Material Processing
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Proceedings Volume 1031, 7th Intl Symp on Gas Flow and Chemical Lasers; (1989)
Event: 7th International Symposium on Gas Flow and Chemical Lasers, 1988, Vienna, Austria
Light interactions with materials in laser material processing operations occur by a variety of mechanisms depending on the material being processed, the wavelength of the laser light, the gaseous environment, and the physical state of the material surface. The high reflectivity of metals limits the fraction of the beam power absorbed by the solid metal surface. For metals in the solid state, reflectivity increases as the wavelength of the laser light and the electrical conductivity of the metal increase. The reflectivity of metals is reduced upon heating to the melting point, and further reduced upon melting. At high power densities the liquid metal surface is heated so quickly that very rapid vaporization occurs. The recoil force produced by the evaporation causes a depression in the liquid/vapor interface. The "keyhole" resulting from this depression allows for multiple reflections and thus increases beam absorption into the liquid. The vaporized metal above the liquid surface can cause attenuation of the beam. Both plasma absorption and fine particle scattering theory have been proposed to account for this beam attenuation. The attenuation is strongly affected by shielding gas type and pressure. In the laser cutting the beam interacts with the material through a high angle of incidence. Under these conditions the degree of beam polarization becomes important.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shichan Chiang and Charlies E. Albright "Light-Material Interactions In Laser Material Processing", Proc. SPIE 1031, 7th Intl Symp on Gas Flow and Chemical Lasers, (20 June 1989);


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