CProfessor Duncan Hand
Title: Picosecond laser microwelding: a novel technique for hermetic joining of transparent materials
We have developed a laser welding process for bonding optical materials to other (optical and non-optical) materials using ultra-short laser pulses of only a few picoseconds duration. This process creates very small weld volumes and hence there is minimal total heat input. These ultra-short pulses of laser light have an extremely high peak power which leads to absorption even in a transparent material, but only at the focus of the laser beam where the power density exceeds a few TW/cm2. This means that a plasma volume only a few microns across can be created at focus, and the associated heat creates a melt volume only a few tens of microns across, without affecting the surrounding material. This allows very thin transparent materials to be welded, for example thin flex glass.
We report application of this process to a wide range of materials, demonstrating the welding of glasses and optical crystals to metals, semiconductors and glasses. In particular, we focus on the welding of thin flex glass to thin flex glass (both 100 µm thick) for hermetic encapsulation of OLEDs in conformable packages. The welding can be combined with conventional laser material removal processes such as laser micro-machining/thin film ablation for more complex packaging challenges.
This work is being carried out as part of an Innovate UK project called UltraWELD, and a prototype commercial laser welding machine is being developed for this process
Duncan Hand is Professor Applied Photonics at Heriot-Watt University and leads research into applications of high power lasers in manufacturing, working closely with a range of industrial partners. His main focus is on high precision micro-scale applications, including bonding, micro-machining, cutting, and surface structuring. Applications range from packaging of electronics, manufacturing of microfluidics, through to generation of high friction surfaces for ship engine parts. He also is involved in fibre optic delivery of short pulse, high peak power laser light for applications in both manufacturing and surgery.