EFFECTS OF DIFFUSION ON THE SATURATION INTENSITY OF A CO2 LASER.

The power and gain capabilities of a CO2 laser are dependent upon the saturation intensity of the laser media. Saturation intensities reported in the literature range from 22 wattssq cm to 100 wattssq cm for seemingly similar laser discharge tube bores, currents, gas flow rates and gas mixtures. Measurements of saturation intensities between 7.5 and 57 wattssq cm in a CO2 laser amplifier indicate that this parameter is inversely related to the radius of the amplified beam. A significant increase in saturation intensity for small beam radii is attributed to diffusion of excited CO2 molecules into the beam. The experimental results are in qualitative agreement with a simplified derivation of a relation governing the saturation intensity which includes molecular diffusion. This effect can result in a serious overestimate of the capabilities of a large beam laser system designed with saturation intensities obtained from small diameter probe beams. Author