Ultrafast laser micromachining with a liquid film

A significant advantage of ultrafast laser processing is that very small feature sizes can be produced for a variety of materials, which makes them a powerful new tool for micromachining and microfabrication. However, one obstacle in producing high feature quality is material redeposition, which degrades the feature quality and repeatability. To avoid these effects, processing has traditionally been performed in a vacuum chamber, however this makes real-time processing on a large scale, e.g., an assembly line, impractical. This work presents a technique to reduce material redeposition during ultrafast laser processing by applying a confined liquid film with known thickness on top of the target surface. Experiments are performed using Ti:Sapphire femtosecond laser pulses to drill holes and machine grooves on a copper plate with and without a liquid film formed by distilled water. The results show that improved feature quality can be obtained for groove machining using a liquid film, with little material redeposition observed, though the material removal rate is reduced due to the presence of a water overcoat and the plasma shielding effect. This technique shows potential as a method to obtain high feature quality without the need of a vacuum chamber.