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Scaling of high-repetition-rate Q-switched CO2 lasers for industrial applications

: Fuß, W.; Märten, O.; Schmid, W.E.

Fotakis, C. ; Foundation of Research and Technology, Hellas; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
9th International Symposium on Gas Flow and Chemical Lasers 1992
Bellingham/Wash.: SPIE, 1993 (SPIE Proceedings Series 1810)
ISBN: 0-8194-1010-1
pp.79-83 : Abb.,Lit.
International Symposium on Gas Flow and Chemical Lasers <9, 1992, Crete>
Conference Paper
Fraunhofer ILT ()
chopper; conical mirror; insertion; pressure; pulse energy; resonator; wavefront deterioration; ZnSe-window

By insertion of a fast mechanical Q-switch into the resonator, continuous discharge CO2 lasers can yield high peak power pulses at multi-kHz repetition rate. First experiments have been done with diffusion-cooled low-pressure CO2 lasers. For this type of laser the pulse energy can only be increased by increasing the length of the active medium. A limit is given by the onset of uncontrolled self oscillation which prevents regular Q-switched operation. Single pulse energies can appearently not exceed 30 mJ at 250 ns pulse duration for this type of lasers. Fast gas-flow convection-cooled laser discharges allow to increase the stored energy by increasing diameter and pressure of the active medium as well as the electrical power density. We present the results of Q-switching of a 5 kW industrial laser. Our Q-switch is scalable in optical power. It is based on a fast chopper and a conical mirror. In some experiments we tuned the laser over a wide range by a diffraction grating. The influence of gas pressure and mixtures as well as discharge parameters has been studied. Single pulse energies of 100 mJ have been found, limited by the electrical input power density.