Laser heating conditions for copper sphere implantation into borosilicate glass

•Laser absorption by glass and plasma formation enabled copper implantation.•Melted copper diffused into glass and precipitated as nanoparticles.•The sphere could not be implanted when the plasma propagation speed was > 50 mm/s. Implanting metals in glass can serve many different purposes, ranging from enhancing the electro-optical properties to modifying the mechanical properties of the substrate. One approach involves the use of continuous laser illumination to implant metal spheres by transferring particles from a metal foil in direct contact with one side of the glass substrate. The process, which occurs in a very short period time (in tens of milliseconds), is unidentified: due to the bright thermal emissions, it cannot be directly observed. In this study, the continuous laser heating conditions required for implanting copper spheres in borosilicate glass were investigated via spectroscopy and numerical calculations to estimate the temperature of the copper foil. Emission spectroscopy revealed that the temperature during implantation reached 5100 K, which largely exceeded the temperature threshold for laser absorption (∼2000 K). Under such conditions, the plasma forms and enables the migration of copper particles into the glass host. The plasma propagation speed increased with increasing laser power density. The copper sphere was implanted when the plasma propagation speed was 20–50 mm/s. The copper sphere could not be implanted, and fiber fuse occurred when the plasma propagation speed was higher than 50 mm/s.