Spatially resolved gain measurements of a slab type RF excited CO2 laser

Spatially resolved small signal gain in a slab type radio frequency (RF) discharge excited CO2 laser medium was analyzed in order to observe the effect of the plasma sheath region near the slab electrodes. Choosing four lines of 10.6 mu m transition such as P(14), P(20), P(26) and P(30), we measured each gain with a resolution of 0.1 mm using a digital beam profiling system based on a two-dimensional pyro-electric infrared detector array. As a result, the gain was found to have a peak value of 0.4%/cm at the center of the gap between the electrodes, which was reduced to approximately half in the sheath region. Gas temperature (rotation temperature of CO2) was calculated to be 400 K at the center and it increased to 600 K in the sheath region.