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Cutting Diamond Tools by Laser MicroJet

LMJ Process: In the Laser MicroJet system, a laser beam, passing through a pressurized water chamber, is focused into a nozzle. The low-pressure water jet emitted from the nozzle guides the laser beam by means of total internal reflection at the water/air interface.

By Sébastien Kurzen, Nitin Shankar

The water jet diameter is usually 50 microns and the laser power required is between 25 and 30 watts. While the principle looks simple, years of experimentation and optimization were required to fine-tune the process. The LMJ process works in two stages. The energy of the laser pulses vaporizes the workpiece material by heating while the water cools and cleans the surface in the interval between the pulses. Through a scanning process, a trench is formed that becomes deeper with each pass. As compared to traditional dry lasers, the LMJ "wet laser" technology has many advantages. The most important advantage is that Laser MicroJet cuts with a parallel beam and the cutting depth can extend up to several centimetres.This is not the case with conventional lasers where the focused laser beam has a limited working distance of just a few millimetres due to beam divergence. The beam converges at a focal point and then diverges. Therefore, a focus distance control is required and the working distance is short. The technology behind the Laser MicroJet is based on creating a laser beam that is completely reflected at the air-water interface, using the difference in the refractive indices of air and water. The laser is, therefore, entirely contained within the water jet as a cylindrical beam, similar in principle to an optical fibre. 

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