The commercially available Synova Laser MicroJet® technology combines conventional laser capabilities with compressed water jet that precisely guide laser beam in a similar manner to optical fibers. Due to physical water breakdown, technology is typically focused on the nanosecond pulse duration range. A stable beam shaping setup with a diffusor and commercial fiber to couple into water jet, was developed allowing to test Laser MicroJet® at 100-300 ps pulse duration. The change to energy intensity profile with diffuser allowed to triple coupled energy without inducing the physical breakdown in water and could be further increased by implementing 2 and 3 pulse bursts into the setup. High quality scribing was achieved at Si wafer at high scanning speed. Preliminary results on multilayer Si-wafer have demonstrated that scribing quality is in this case more feedrate dependent, limited chipping occurring at speed of commercial interest. Cutting tests were performed on semiconductors as well as on metals. On both, it was possible to achieve high quality cuts with high feedrate up to 12 mm/s with Ra < 0,3 μm.
Glass-ceramic materials are increasingly becoming the material of choice in the field of dental prosthetics, as they can feature both high strength and very good aesthetics. It is believed that their color, microstructure and mechanical properties can be tuned such as to achieve an optimal lifelike performance. In order to reach that ultimate perfection a controlled arrangement of amorphous and crystalline phases in the material is required. A phase transformation from amorphous to crystalline is achieved by a heat treatment at defined temperature levels. The traditional approach is to perform the heat treatment in a furnace. This, however, only allows a homogeneous degree of crystallization over the whole volume of the parent glass material. Here a novel approach using a local heat treatment by laser irradiation is presented. To investigate the potential of this approach the crystallization process of SiO2-Li2O-Al2O3-based glass has been studied with laser systems (pulsed and continuous wave) operating at different wavelengths. Our results show the feasibility of gradual and partial crystallization of the base material using continuous laser irradiation. A dental prosthesis machined from an amorphous glassy state can be effectively treated with laser irradiation and crystallized within a confined region of a few millimeters starting from the body surface. Very good aesthetics have been achieved. Preliminary investigation with pulsed nanosecond lasers of a few hundreds nanoseconds pulse width has enabled more refinement of crystallization and possibility to place start of phase change within the material bulk.
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