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Proceedings Paper

Closed-loop power-control system for CO2-lasers
Author(s): Manfred Geiger; Guenter Deinzer
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Paper Abstract

The working quality in laser material processing is influenced by a number of parameters as to laser source, beam guiding system and material. Although the reliability of the lasers and the stability of the system components have been improved there are still some weak points. In the following a closed-loop control system is presented which will help to meet the requirements. The output power of a rf-excited CO2 laser is fluctuating in various frequencies, which influences the working quality in laser material processing. In order to avoid these effects, a closed-loop control system for stabilization of the output power of the laser has been developed. This system consists of a beam diagnostic device positioned at the rear outcoupling window of the laser resonator, a signal transformer and a modified PID controller. With the combination of two pyroelectric detectors--one of them having a chopper wheel in order to detect the signal portion of the laser running in continuous wave operating mode--the actual output power of the laser can be measured very quickly. An 11% decrease of the output power in a time range of 30 seconds and fluctuations of +/- 4% with a frequency of about 300 Hz have been measured. The closed-loop control is tested with the laser running in a cw- mode. The amplitude of the rf-exciting signal is used as correcting variable. Referring to basic investigations on the dynamic behavior of the output power of a laser, a strategy for a PI- controller has been derived and the optimal parameters have been found experimentally. Using this closed-loop control, the fast fluctuations can be reduced to +/- 1%. The above- mentioned decrease of the output power is completely avoided.

Paper Details

Date Published: 31 March 1995
PDF: 7 pages
Proc. SPIE 2502, Gas Flow and Chemical Lasers: Tenth International Symposium, (31 March 1995); doi: 10.1117/12.204982
Show Author Affiliations
Manfred Geiger, Univ. Erlangen-Nuernberg (Germany)
Guenter Deinzer, Univ. Erlangen-Nuernberg (Germany)


Published in SPIE Proceedings Vol. 2502:
Gas Flow and Chemical Lasers: Tenth International Symposium
Willy L. Bohn; Helmut Huegel, Editor(s)

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