CO2 laser with self-filtering unstable resonator applied for cutting

Abstract

Increasing of power with the retained high beam quality is one of the major directions of industrial cutting lasers improvement. CO2 lasers permit to produce the cut of perfect quality and are at the moment the most spread cutting lasers. The factor limiting the power of gas-flow CO2 lasers is the low mode volume of the stable resonator. Low order mode generation is necessary to guarantee that the BPP (beam parameter product) does not exceed the value needed for the qualitative cutting (about 6). We have optimized the self-filtering unstable resonator, SFUR applied to the gas-flow CO2 laser. It has been shown that the SFUR can provide the higher power (about 2…3 times) comparing to the stable resonator due to the bigger volume of the low order mode. The SFUR beam BPP value approaches to the low order mode of the stable resonator. Numerical calculations have been used to compare the aberration sensitivity of the SFUR and stable resonator.The SFUR beam spatial structure differs from TEM00 or TEM01* modes of the stable resonator. In the far field, the SFUR beam has weak diffraction rings, which can affect the cutting quality. The experiments on cutting were carried out with a transverse-flow laser with SFUR. The main experiments have been performed for mild steel up to 25 mm thick. Stainless steel and titanium have also been cut. The results have revealed that SFUR beam peculiarities do not affect the cutting quality. The kerf width and roughness of the cut samples approach to the values typical for the CO2 laser with the stable resonator. Titanium plates of 30 mm thick have been cut at the radiation power of 6 kW.Increasing of power with the retained high beam quality is one of the major directions of industrial cutting lasers improvement. CO2 lasers permit to produce the cut of perfect quality and are at the moment the most spread cutting lasers. The factor limiting the power of gas-flow CO2 lasers is the low mode volume of the stable resonator. Low order mode generation is necessary to guarantee that the BPP (beam parameter product) does not exceed the value needed for the qualitative cutting (about 6). We have optimized the self-filtering unstable resonator, SFUR applied to the gas-flow CO2 laser. It has been shown that the SFUR can provide the higher power (about 2…3 times) comparing to the stable resonator due to the bigger volume of the low order mode. The SFUR beam BPP value approaches to the low order mode of the stable resonator. Numerical calculations have been used to compare the aberration sensitivity of the SFUR and stable resonator.The SFUR beam spatial structure differs from TEM00 or TEM01* modes of...