Plasma vs. rf interactions in fast-flow CO2 high-power lasers

Although the plasma properties of CO 2 gas lasers have been extensively investigated there seems to be remaining uncertainties concerning the achievement of an optimized plasma state giving the best possible laser efficiency. Such optimization would be especially for high power lasers where a loss of some percents in efficiency can mean a considerable decrease for the laser output. To investigate the effects of plasma vs. rf interactions in longitudinal fast-flow CO 2 lasers a sufficient adequate plasma theory is used, based on the cross-sections of all involved processes. The main interest lies in the determination of all relevant parameters such as the electric field and current density along the electrodes which have pronounced dependencies on gas temperature and pressure. Although these variables change enormously in downstream direction the model reveals plasma coefficients which stay as unchangeable constants. Moreover, as is common for longitudinal fast-flow CO 2 lasers the electrodes are slightly inclined to obtain an increased laser performance, independent of the rf matching. By a rather simple consideration of plasma and rf interactions this effect can be basically explained so that an optimization for the best attainable efficiency is possible. The calculations are compared to measurements of different authors and are applied to a 6 kW fast flow coaxial system.