In recent years, laser welding of copper using visible wavelengths with high absorption rates has gained attention. In this study, to achieve high-efficiency welding using a blue laser by understanding the changes in the optical absorption properties of copper during laser welding, we observed the irradiation spot and measured the reflected light during the copper welding with the blue laser. Additionally, we observed the post-weld surface and evaluated the changes in the optical absorption properties due to surface morphology, oxidation, and phase transitions from solid to liquid.
