Features of radiation beam formation in resonators with perforated mirrors

The possibility of using perforated output mirrors in stable resonators of cw CO₂ lasers is discussed. The main factors responsible for the intracavity losses, including those connected with the diffraction of beams at the edges of holes in the mirrors are considered. The results of the experimental investigation of a 100-kW combustion product gas-dynamic CO₂ laser with stable and unstable resonators and output mirrors of various types are compared with the results of numerical simulation. The theoretical and experimental studies performed over a wide range of parameters explain some peculiarities of the beam formation process in resonators with perforated mirrors. Practical recommendations are offered for choosing the parameters of such mirrors.