Limitation of the output power of cw electric-discharge CO2 lasers

The output power of a sealed-off tunable cw CO₂ laser was optimised. The dependences of the small-signal gain for the 10P(20) line and of the output powers for different transmittances of the cavity on the discharge current were determined. The distributed loss coefficient and the saturation parameter were measured. The saturation parameter increased continuously with increase in the discharge current, leading to a mismatch between the output power and gain maxima. It was established that the principal factor limiting the output power of cw electric-discharge CO₂ lasers is not an increase in the temperature of the active medium but the dissociation of CO₂ molecules. When the latter is minimised in order to achieve the maximum laser power, low gas temperatures are not required.