Process monitoring based on plasma emission for power-modulated glass welding with bursts of subpicosecond laser pulses.

Defects and process irregularities influence the bonding strength and thus the stability and lifetime of welded glass components. The present paper proposes to monitor the laser-based glass welding process by means of a single photodetector that records the radiation emitted from the laser-induced plasma. It is shown that the plasma emission provides information about irregularities of the welded seam height, gap bridging, process interruptions, and the position of the seam.

Reproducible process regimes during glass welding by bursts of subpicosecond laser pulses.

During welding of glass with ultrafast lasers, an irregular formation of weld seams was prevented by modulation of the average laser power and spatial beam shaping. The formation of individual molten volumes in regular intervals was achieved by means of power modulation, resulting in a predictable and reproducible weld seam with a regular structure. At constant average power, a homogeneous weld seam without a periodic signature was alternatively achieved by means of a shaped beam generating an elongated interaction volume and resulting in a continuous melting of the material.

Process regimes during welding of glass by femtosecond laser pulse bursts.

Various process regimes were observed during microwelding of glass with bursts of ultrashort laser pulses. Two major welding regimes and various subregimes were identified for two different materials. The radiation emitted by the laser-induced plasma was used to monitor different regimes that characterize glass microwelding.