The invention relates to an arrangement for the generation of CO.sub.2 laser pulses of high power which, on the one hand, permit material processing tasks to be carried out that require the high power densities at the processing site, such as cutting, welding and engraving or defined material removal, especially in the case of metals with a high degree of reflection for the laser radiation, such as aluminum and copper, and, on the other, make possible the use of relatively small, compact CO.sub.2 lasers in applications, such as scribing and defined material removal in electronic and microelectronic technology.
Numerous applications of CO.sub.2 laser radiation require power densities which, even with optimal focussing, can only be realized by radiated power far in the kW range. To achieve these powers, the CO.sub.2 lasers generally are operated in the pulsed mode in such cases. Aside from generating adequate peak powers, the maximum conversion of the potentially available average power into radiation pulses is aimed for.
Various technical solutions are known for generating high-power CO.sub.2 laser pulses.
One possibility of generating CO.sub.2 laser radiation pulses is represented by the principle of the transversely excited high-pressure CO.sub.2 laser (TEA laser) which, because of the high pressure of the laser gas, permits the realization of exceptionally high pulsed peak powers. Achieving the frequently required high pulse repetition frequencies is, however, very problematical. Frequencies of even a few hundred hertz require an enormous technical effort.
The electrical excitation of pulses of the CO.sub.2 laser discharge is the method primarily used industrially to generate intensive radiation pulses for processing materials. This mechanism permits pulse repetition frequencies up to 2.5 kHz with low-pressure CO.sub.2 lasers. However, with electrically pulsed gas discharges, the achievable magnification of the peak pulse power relative to the cw (continuous-wave) power is limited to a factor of about 10, since the processes of the build-up of the population inversion by the gas discharge and the decay of the inversion by the oscillation build-up of the laser overlap in time.
This disadvantage is largely avoided by the various methods of Q-switching CO.sub.2 lasers, since with these methods a population inversion of maximum amplitude can develop to begin with, which is then converted by the sudden increase in the quality of the laser resonator into a radiation pulse of greatly magnified power. All conventional methods of Q-switching, however, have significant deficiencies with respect to material processing tasks. The main deficiencies are
an unfavorable duty ratio of laser on to laser off and thus a considerable loss of average power during active revolving-mirror Q-switching (cf. Flynn, IEEE Journal of Quantum Electronics, vol. QE-2, 378 (1966));
a limitation to periodic pulse sequences or to a fixed pulse repetition frequency, for example, in the case of passive Q-switching (see, for example, Appl. Phys. Lett. 11, 88 (1967);
high costs, for example, when actively switching by means of electro-optical crystals (see, for example, IEE Journal of Quantum Electronics, vol. QE-2, 243 (1966)).
The arrangements, described in the German Offenlegungsschrift 2,610,652 and the German Offenlegungsschrift 2,913,270, represent attempts to combine the advantages of the pulsed supply of pumping energy with the active Q-switching of the laser. Both arrangements are, however, usable only on optically pumped lasers in the visible or near infrared region of the spectrum, where there is the possibility of using the advantageous properties of electrooptical crystals (in contrast to the CO.sub.2 laser spectral range of wavelengths between 9 .mu.m and 11 .mu.m). By synchronizing the pumped light pulses with the operation of the electro-optical Q-switch, it was possible to achieve advantageous parameters of the laser pulses generated.