Study on the Effect of Focusing Parameters of Ultrashort Pulses on the Process of Laser Welding of Transparent Materials with Metals

We study the effect of optical focusing parameters of picosecond laser pulses (1–3 ps) on the process of forming a welded joint between transparent materials and metals. It is found that when use is made of lenses with a numerical aperture NA = 0.25, there is no stable formation of welded joints, in contrast to the use of an F-Theta lens with a focal length of 100 mm (NA = 0.05). Welds are tested for shear; the average values of the strength of welded joints are in the range from 5 to 15 MPa. Thermal cycling tests of welded samples are performed in the temperature range from –10 to 60°C. A study of welded joints using a scanning electron microscope reveals that the glass–metal interaction region is 250 nm. For the first time, a T-joint welding of a quartz mirror element to an invar substrate is performed, which significantly increases the application of this technology in industry, especially for instrument-making and optics.