Measurements of the small-signal gain and saturation intensity for a cw CO2 laser using an intracavity loss element

A new scheme with an intra-cavity loss element for small-signal gain measurement at two main wavelengths of a tunable gas flow longitudinally excited CO₂ laser is presented. By inserting a ZnSe stack polariser into the cavity, the critical condition for the laser is obtained. The small-signal gain and saturation intensity are calculated using the Rigrod formula. The small-signal gain measurement was performed for different gas pressures and different input electric powers. Under the same experimental conditions, the values of the saturation intensities were calculated from the output power and the measured small-signal gains. The advantage of this method is that no probe laser system is required. The results agree with experimental data obtained earlier by the conventional oscillator–amplifier method.