Visualization of interaction between laser beam and YAG-laser-induced plume

This study was performed to obtain a fundamental knowledge of the effect of a laser-induced plume on the absorption or attenuation, refraction and defocusing of the incident laser beam during welding. The interaction of the near-infrared laser beams such as a YAG laser and a fiber laser with the YAG laser-induced plume was investigated by measuring the passing-through power and by visualizing the beam behavior in terms of the attenuation and the refraction of the laser beam. The attenuation of the probe laser was confirmed to increase with a decrease in the wavelength, and the maximum attenuation of the fiber laser was about 5 %. Such attenuation was attributed to Rayleigh scattering. On the other hand, the laser beam was bent only about 0.6 mrad by the refraction. The refraction was further evaluated by observing the behavior of a fiber laser beam through the plume. The visualization of the spot behavior revealed that the interaction between the near-infrared laser beam and the YAG laser-induced plume was considerably small. It was consequently concluded that the fiber and YAG lasers were recognized to deliver a desirable wavelength with the slight interaction against the laser-induced plume.