Influence of Optical Condenser Type on Laser Micro Drilling

The effects of condensers on laser micro drilling in stainless steel foil were studied using second or fourth harmonic light of a nanosecond pulsed Nd: YAG laser, in order to clarify the features of an axially condensed beam. The through holes several ±m in diameter could be drilled by adjusting the work distance precisely, though a conventional convex lens was used. However, the diameters were doubled by only a 0.1 mm change in the work distance. When the drilling was performed by an axially condensed beam using an axicon, the through hole diameters of several ±m were not changed, even though the work distances were changed ± 5mm. The through holes with an aspect ratio of about 10 and a diameter of about 1 ±m could be drilled using the fourth harmonic light and a DOE axicon.