40 MHz femtosecond laser single burst to weld glass

We investigate the combination of a 40 MHz burst-mode ultrashort-pulse laser with a negative interburst overlap strategy to achieve high-speed welding of glass plates, both with and without optical contact, and for air gaps up to 3 µm. The laser source is a commercial 50W femtosecond laser (Amplitude) operating at a wavelength of 1030 nm with a pulse duration of 400 fs. Negative overlap between successive bursts is realized using a low repetition rate on the order of tens of kilohertz and a high scanning speed of 1 m/s. This strategy allows to make a discrete welding, for which each welding spot is caused by a single burst. Focusing is achieved using an f-theta lens with a 50 mm focal length, leading to a 30 µm spot size. The proposed approach demonstrates that only 40 µJ per burst is necessary to achieve the welding, what would be not enough to weld with a single pulse. This method has potential for a significant scalability, and with the use of industrial grade laser with higher average powers, welding speeds approaching 100 m/s could be possible.