Measurement of the spatial distribution of the gain in infrared lasers

A description is given of a method for recording the transverse distribution of the gain in an active medium by illumination with a wide collimated beam. A probing laser beam is formed by using a small part of the cross section of the investigated active medium and an auxiliary resonator. A report is given of the experimental results obtained in an investigation of a transverse-discharge continuous-flow CO₂ laser.