Space – time structure of radiation from a high-power fast-flow CO2 laser

The space – time structure of radiation from an industrial electric-discharge, flowing CO₂ laser is studied experimentally. For the optimal design of the optical and gas-dynamic sections, a total suppression of high-frequency radiation fluctuations and a lowering of the amplitude of low-frequency fluctuations down to 6% – 10% were observed with increasing output power. At the same time, the intensity distribution in the near-field diffraction zone was complicated and unstable. 'Hot' spots and screw wave-front dislocations were observed in the laser-beam cross section. Numerical simulations showed that the properties of the near-field radiation structure are determined by random caustics and phase singularities formed due to the diffraction transformation of the initial wave-front perturbations.