Beam polarization effect on the surface quality during steel cutting by a CO2 laser

The beam polarization effect on the quality of oxygen-assisted laser cutting of low-carbon steel by a CO2 laser is studied experimentally and theoretically. The cut surface roughness is examined as a function of cutting parameters in the case with linear polarization of the laser beam. It is demonstrated that the minimum roughness level is reached if the electric field vector is aligned perpendicular to the cutting velocity vector. The distribution of the absorbed laser power inside a narrow cut channel is computed numerically. It is concluded that the absorbed power distribution exerts a significant effect on the surface quality and it is important to provide radiative heating of the side walls to ensure lower-level roughness. Based on the results obtained, a possible explanation is proposed for the worse quality of the cut surface of metal materials by a fiber laser as compared to a CO2 laser.