This work is devoted to the investigation of the laser-matter interaction during up to 20 kW ytterbium fiber laser welding of thick mild steel plates. The plume attenuation of a probe 1.3 µm wavelength diode laser beam as well as of continuous radiation in the 250-600 nm wavelength range was measured during welding with and without Ar shielding gas supply. The measured results allow the calculation of the average size and concentration of fine condensed metal particles in different plume areas using the multi-wavelength method and the Mie scattering theory. The plume temperature, which determines the condensation conditions, was measured by means of Fe I atom spectral line emission registration. The spatial distribution of the extinction coefficient in the welding plume was measured and the plume attenuation of the high-power fiber laser beam during the welding process was estimated.

Abstract:The results of an in-situ plume-laser interaction measurement during welding of mild steel with a 5 kW ytterbium fiber laser are reported. A measurement of the attenuation of probe laser beam passing through the plume has allowed to estimate the plume characteristics like the size of the extinction area and the spatial distribution of the extinction coefficient. The power loss of the fiber laser radiation propagating through the whole plume length was calculated. Together with a measured temporal characteristics of extinction the result indicates a significant decreasing of the laser radiation stability, which can lead to the formation of the macroscopic welding defects. Verification of the extinction coefficient distribution model with experimental data of the extinction signal depending on the plume height

Abstract:The mode competition in a double-mode diodepumped Nd:YAG laser is studied theoretically and experimentally. In particular, the influence of various laser parameters on the steady-state double-mode regime for parallel and orthogonal polarization of the modes is studied. It is shown that the establishment of steady-state double-mode lasing is accompanied by relaxation oscillations more complicated than for single-mode lasing. It is found that the scanning rate of the cavity modes influences the character of the relaxation oscillations. The value of the double-mode lasing range d as a function of ω 12

A diode-pumped continuous-wave Nd:YAG laser with two linear and mutually orthogonal polarized components of radiation at a wavelength 0.532 µm is studied theoretically and experimentally. The cavity configuration for the realization of generation in this region is suggested. Stable lasing with two mutually orthogonal polarized components is implemented within the range of the intercomponent separation practically from zero to approximately 10 GHz.