High quality drilling with Copper Vapor Lasers

High-quality materials processing on transparent substrates of BK7 glass, fused silica, corundum and ruby using a copper vapour laser (CVL) is described and discussed. The drilling process using the radiation emitted by a small diffraction-limited CVL is described and investigated by optical diagnostic methods allowed by the transparencyof the materials. In particular the hole making was entirely monitored in real time through a video camera. Images achieved in this way are reported to illustrate the morphology ofthe hole and of the ejected materials via the time-resolved fluorescence. Thisinvestigation provides the evaluation of the plume expansion speed, while the imaging supplies the quantitative evaluations of the drilling speed and threshold. The high quality of the hole in terms of wall smoothness and elevated aspect ratio is described in detail. We report according to our findings an interpretation of the peculiar combination of physical processes involved.