MICROWAVE EXCITATION OF A DIFFUSION-COOLED CO2-LASER

A microwave-excited (2.45 GHz), diffusion-cooled CO2 laser, capable of operating in a quasi-cw mode, has been developed. By separating the discharge structure from the feeding RF waveguide and using distributed coupling, previous problems with local contracting discharges could be surmounted. For effective diffusion cooling a planar 1.9 mm high discharge channel was used, a structure which easily allows area scaling of laser output power. Two discharge channel designs (metal/glass and all ceramic) were investigated, differing mainly in thermal conductivity and waveguide losses for the 10.6 mum laser radiation. A conventional magnetron for microwave ovens was used as microwave source. System design and extensive measuring results are presented. With a first prototype non-optimized in gas mixture, optical resonator and waveguide surface quality laser output power above 20 W was obtained with an efficiency of about 10%.