A comprehensive experimental and theoretical study of the optimization of a continuous-wave radiofrequency (rf) excited CO2 waveguide laser is presented. The numerical simulation includes the modelling of the gas-discharge plasma parameters like the plasma impedance and energy deposition, the laser kinetics and finally the influence of the resonator feedback on the lasing process. Along with this theoretical study, an extensive experimental research program enabled us to optimize the laser performance of the CO2 waveguide laser. As a result, a total output power of 42 W and a specific output power of 1.1 W/cm were obtained.

CFH5bump are 4.4 pm and 10 p" along its short and long axes, respectively. Fig. 1. Elliptical-shaped beam textured bump three-dimensional profile. The diameters of the CFHS Fig. 2. Micrograph of the textured bumps using the designed elliptical-shaped beam; the longer axes of bumps are all oriented along the head fly direction.It was recently shown' that the radiofrequency (RF) pumping of Xe-Ar-He gas at intermediate (-100 Torr) pressures leads to a dramatic (-io3 times) rise oflaser power in comparison with the well-known low-pressure directcurrent excited Xe laser. Continuous-wave power >5 W is demonstrated.' The physical reasons of such dramatic rise of laser parameters was not clear, however. Moreover, we observe specific space structures for the gain and output power of the RF-excited continuous Ar-He-Xe laser. The present contribution will treat this problem.We developed a model for the nonhomogeneous discharge of the active medium. From the solution of the Boltzmam equation, the production rates of the various species are obtained as a function ofthe position between the electrodes. In the electrode sheaths, there is a strong inhomogeneity of the plasma parameters like the electron density and the electricfield strength. The relatively low electron concentration and high electric field near the electrodes create favorable conditions for the laser level inversion. The main source of the high-energy electrons is the diffusion from the bulk plasma. The secondary emission from the electrodes is almost negligible. Further, it will be shown that at high input powers, the refractive-index gradient due to gas heating leads to light space configurations, which are essentially different from the well-known modes of empty waveguides. The effective recombination mechanism of electrons with excimer ions in the regions with enhanced electric field near the walls together with the emission-field concen tration provide favorable conditions for laser power production.

An analysis is presented of the effect of the RF frequency on the active media of CO2 waveguide lasers. It is found that the characteristics are improved with increasing RF frequency because the space charge sheath width decreases with increasing excitation frequency. We also found that the sheath width decreases with the discharge current; this fact was never discussed before. The higher the exciting frequency the higher is the maximum input power of the discharge in the stable low current mode. It is attractive to extend the input power while keeping the discharge in this mode. Finally, a stabilizing excitation technique is described for the inherent unstable region of the discharge.