In the Laser MicroJet method developed by the Swiss company Synova, the laser beam is focused in a nozzle and guided within an ultra-thin water jet at low pressure, allowing it to carry out precise machining operations such as cutting, edge grinding, drilling or scoring (Figure 1). The water jet emitted from the nozzle at low pressure guides the laser beam by total internal reflection at the water/air interface and acts in a similar way to a conventional optical fibre. This produces a »cold and clean« laser that avoids all well-known problems such as heat damage, distortion and lack of precision (Figure 2).
In addition to the beam shaping optical system, the optical head also contains a camera to adjust the nozzle opening for the laser beam and a light source. There is also a camera for positioning the part to be machined. The laser beam is first collimated in the optical head and then focused in the nozzle opening through a quartz window. This window separates the optical system in the machining head from the water-filled nozzle chamber. In this section, water is fed into the nozzle through several channels perpendicular to the laser beam with rotational symmetry, so that an ultra-fine water jet emerges from the nozzle.