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Industry has growing interest in lasers with high output power of high beam quality. Therefore, laser developers have to concentrate their efforts on the optimization of every component involved in the beam generation, e.g. the rf-power incoupling and the gas flow generation. At present CO2 lasers of very high output power are developed by increasing the dimensions of the whole system. Inevitably, a more or less pronounced reduction of beam quality and efficiency will occur, if scaling laws are not considered. In order to reach the goal of a well designed system with high performance data the knowledge of homogeneity and stability of the discharge as a function of the various parameters involved is essential. The evolution of filaments for example increases with the rf-input power. This filamentation, however, is a complex mechanism that also depends on gas temperature, gas turbulence and contamination as well as on the excitation frequency of rf-discharges. In this work, diagnostic methods for determining the degree of filamentation are presented. The results achieved are used to determine the frequency-dependency and scaling laws of rf-excited CO2 discharges. The range of parameters favorable for a stable discharge is generally not the same compared to the parameters yielding high values of small signal gain and saturation intensity. The optimal discharge geometry (length and diameter) depends on various quantities. The values for mass flow and of rf-input power are given by the gas circulating system and the rf- generator. The maximum rf-input power density depends on the limit of stable operation, which itself is a function of gas pressure and velocity and various other parameters. Taking into account the gain saturation of the medium, the optimal gas pressure itself depends on the input power. Measurement data of small signal gain and saturation intensity spatially resolved parallel to the gas flow direction as well as electro-optical efficiency will be given. Based on these measurements, scaling laws are derived and will be presented.
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