Unstable resonator with spatial filtering of radiation in an industrial CO2-laser

An unstable resonator with spatial filtering of the radiation was used to generate a beam of power in excess of 1 kW and a small angular divergence in an industrial transverse-flow CO₂ laser. The measured divergence of the radiation was compared with the calculated value. The output beam was close in its quality to the TEM₀₀ mode emitted by a stable resonator. The resonator parameters were selected on the basis of numerical calculations carried out for an empty resonator. The dependence of the quality of the output beam on the geometric magnification of the resonator was calculated.