EFFECTS OF DIFFUSION ON 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 to 100 W/cm2 for seemingly similar laser discharge tube bores, currents, gas flow rates, and gas mixtures. Measurements of saturation intensities between 7.5 and 57 W/cm2 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 CO 2 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. © 1969 The American Institute of Physics.