New additional cooling effect of diffusion cooled sealed-off CO{sub}2 lasers excited by dielectric barrier discharges at about 1 MHz with an all-solid-state generator

摘要

Diffusion cooled sealed-off CO{sub}2 lasers excited by a dielectric barrier discharge with a developed all-solid-state gener- ator. A homogeneous discharge of hf excitation at average electri cal power density of up to 25 Wcm{sup}(-3) is obtained without applying any stabilization techniques on the discharge at a discharge gap of d =6 mm for the first time, A discharge gap of d = 6 mm is used to ensure a free propagation of the laser beam without any waveguide losses. A maximal output laser power of 70 W is attained with a laser efficiency of 8 % at an electrical power den sity of 20 Wcm{sup}(-3). A laser efficiency of 12.5 % is reached at an electrical input power of 10 Wcm{sup}(-3). Emission spectroscopy is used to measure the spatially resolved electron energy in the dis charge gap at excitation frequencies between 0.4 and 2.4 MHz, It shows, that the mean electron energy MBS in an efficient range to excite CO{sub}2 lasers. An optical-fibre thermometer is used to measure the gas temperature porfile inside the discharge gap. The measured gas temperature is 150 K below the theoretically calculated value. A additionally cooling effect is responsible for the low gas temperature.