Transparent laser welding using femtosecond pulses offers a promising solution for precise joining of glass materials. In this study, we demonstrate the successful assembly of large-diameter (20 mm), crack-free fused silica using femtosecond laser welding, without the requirement of chemical pre-treatment or adhesives. A microscope objective, with a numerical aperture of 0.26, was used to focus the laser at the interface, generating a highly localized and intense spot for precise melting of the material. Using a femtosecond laser with a pulse energy of 60 µJ, a repetition rate of 200 kHz, and a scanning speed of 10 mm/s, the spiral pattern minimizes overprocessing and reduces stop-start points, ensuring uniform energy deposition. This approach produced defect-free welds, contributing to improved mechanical resistance, as demonstrated by tensile testing. These results demonstrate the potential for transparent laser welding to be adopted for industrial applications in optics, photonics, and high-precision manufacturing.

Glass welding using femto-second lasers conveys numerous advantages compared to the usual glass joining technics such as better resistance to high temperature and no requirement for an extra intermediate material. However, it requires an optical contact between the two glass plates to weld. This poses constraints on the flatness and rugosity of the glass plates. We demonstrated that using the burst mode of the laser combined with a long focal lens can help to overcome this restriction by allowing a welding despite the gap with high speed (up to several meters per second). We’ve been able to weld two glass plates with a gap of 3 µm with a scanning speed of 2 m/s. The mechanical resistance of the welding will also be discussed.

Ultrashort pulsed laser welding is of significant interest for manufacturing precision optical systems. Typically, the process employs a high numerical aperture (NA) lens to focus the laser near the interface, providing a sufficiently high energy density to confine thermal energy and reduce unwanted non-linear effects (e.g., damage) above the desired focal region. However, high NA focusing cannot be readily combined with high-speed scanning, resulting in slow process rates with typical translation speeds of a few mm/s.

In this presentation, we demonstrate that welding is possible at higher speeds using a 167 mm focal length telecentric lens (providing an NA of 0.03). This lens, in combination with a galvanometer scanhead, enables much higher process rates. However, material cracking can be an issue, depending on the material combination and processing parameters. We present results of successful welding of Silicon-BK7 and AlSi-BK7, including measurement and analysis of stress-induced birefringence.

The GHz-burst mode, a relatively new regime in femtosecond laser processing, offers a novel solution for joining dissimilar materials. Its unique way of energy deposition within materials makes it an excellent candidate for the transparent welding of metal and glass. This study investigates the feasibility of this approach, addressing the challenges posed by the differing physical and chemical properties of the materials. Experimental results reveal the formation of strong, defect-free interfaces between silica and copper or steel assemblies, attributed to precise energy deposition and minimal thermal impact. This innovative approach to dissimilar material assembly combines the best characteristics of each material, offering promising potential for advanced applications in the fields of electronics, optics, and photonics.

The production of practical, miniaturized pipelines that allow liquids to flow smoothly presents numerous challenges. Coatings are usually applied to the inner walls of the pipes. An innovative approach involves the use of high-precision laser processing. The utilization of USP laser processing is used both to create functional surfaces and to produce miniaturized pipes through overlap welding process. In the context of the conducted investigations, results on overlap welding with two non-transparent thin foils with USP lasers are presented here. In this study, we conducted overlap welding on two 20 µm thin 1.4301 stainless steel foils using a ps-burst laser. We present insights into the optimal process parameters and the influence of sample preparation. The parameters are evaluated in terms of power density, weld quality, reduced heat-affected zone (HAZ), and reproducibility of the welding results.

Ultrashort pulsed laser welding presents an attractive alternative to the adhesive bonding currently used for bonding metal to optical components in the manufacture of precision optical systems. However, this process has lacked a standardized surface preparation methodology to ensure high yield and high-quality bonding. To address this, we have developed a multi-stage preparation process for stainless steel SS316 and tested its general applicability with three related metals: the controlled expansion alloys Invar, Kovar, and Inconel.

In this presentation, we showcase the welding results achieved using this preparation methodology. Each alloy was bonded to an optical material with closely matched thermal expansion: Invar to fused silica, Kovar to BK7, and Inconel to quartz. These material combinations are crucial for optical applications operating over a broad temperature range to minimize stress-induced birefringence.