Improved Femtosecond Laser Welding of Nonoptical Contact Glass by Pressure and a Water Intermediate Layer.

Ultrafast laser welding has emerged as a significant technology for the joining of transparent materials and has been extensively researched for the welding of glass materials in recent years. However, achieving a robust connection requires optical contact between the samples during laser processing, which complicates the welding process and increases its cost. To achieve high-strength welding of glass samples without optical contact, the samples are typically pressed together to minimize the gap, allowing the molten materials to completely fill it. In this study, two approaches are employed to facilitate high-strength welding of silica glasses: femtosecond (fs) laser welding with the assistance of pressure using a fixture and femtosecond laser welding aided by a water intermediate layer. The welding quality achieved by both methods is thoroughly examined and compared. The findings reveal that femtosecond laser welding with water assistance outperforms other methods in terms of welding uniformity and quality. Furthermore, the principle behind achieving high-quality welding is discussed to elucidate the success of this method.