The challenges of laser welding copper are related to two main physical properties of the material: low absorptivity to most high-power industrial lasers and high thermal conductivity during the process. We know that the absorption rate of copper increases with decreasing wavelength, which means that lasers in the visible band will yield significant advantages for copper welding.
Infrared lasers create absorption problems when dealing with solid materials. If the material melts or even evaporates by deep penetration welding, its absorption rate increases significantly. The absorption rate of solid copper is less than 4%, while the absorption rate of copper vapor (keyhole penetration welding) is higher than 60%. This absorption problem can be overcome by very high power densities, which greatly speed up the melting and evaporation of copper and thus increase its absorption.