<title>Q-switched and mode-locked solid state laser for precision machining of transparent materials</title>

Abstract

A cw-pumped and mode-locked solid state laser emits an endless pulse sequence with pulse duration of about 50-100 ps and pulse intervals of about 10 ns. A pulse sequence of 300 ns is formed by the optional use of Q-switching. The largest pulse of this pulse sequence reaches a peak power of 2 MW. Power densities in the range of 1010.1012 W/cm2 are available by suitable focusing. Such a laser system has been first used for precision machining.Because of the high power density non-linear effects allow the machining of transparent materials. The temporal and spatial formation of a laser induced plasma in the case of surface and sub-surface focusing has been investigated by a special high speed framing microscope. It consists of four electronic high speed cameras coupled with a long distance microscope via image splitter.The sub-surface focusing regime has been applied to anti-counterfeiting or decorative 2d and 3d-marking. The surface focusing regime (micro laser plasma sputtering) has been applied to pixel based micro marking of glass surfaces, creating of special scattering surfaces and non-slip finishing of glass flooring. Repetition rates up to 500 Hz guarantee a efficient production because of with processing time.