Design and application of aspherical resonators for high-power CO2 lasers

Aspherical resonators were developed for an industrial high-power CO2 laser with a rated output power of 20 kW. The task of the aspherical resonators is to perform intra-cavity beam shaping in order to generate process-adapted laser beams for laser materials processing. To evaluate the capability of aspherical resonators for lasers materials processing their performance is compared to conventional spherical and unstable resonators. The times-diffraction-limit factor M2 obtained with an aspherical resonator has a value of 6.3 and is comparable to a spherical reference resonator. Compared to the spherical and the unstable resonator the electro-optical efficiency can be improved up to 50 per cent. In the far field a considerable enhancement of the peak intensity compared to the spherical resonator is obtained. Application of the aspherical resonator for welding demonstrates the essential importance of this resonator type for materials processing.