Dynamics of laser processing in transparent media

High-quality laser processing for industrial production requires, in addition to a suitable beam source, an appropriate adaption of the laser emission to the processing material. Therefore the interaction of the high-intensity laser beam with solid transparent matter was investigated. The kinetics of heating and evaporation by laser pulses was studied. The experiments showed that transparent materials can be vaporized by laser light in spite of their small absorption. The first initial spike (peak intensity
\sim10^{8}
W/cm
²
) turns the absorption coefficient of a surface layer in a very short time (
\sim10^{-7}
s) from 10
^-2
to 10
³
cm
^-1
. The further emission is absorbed completely in the heated layer and vaporizes the material at an approximately constant rate. A model explaining the heating of transparent materials by laser beams is demonstrated and accounts for the experimental observations. The shape of the resulting holes is discussed.