The joint project GROTESK investigates the application of additive manufacturing for the generation of optical, thermal and structural components using the example of a laser system. This includes multi-material connections of metallic and non-metallic materials with laser metal deposition, e.g. mountings for solid-state laser materials like neodymium-doped yttrium aluminum garnet (Nd:YAG), and the related material development for wire-based as well as powder-based processing. The contrary material groups require an exact consideration of the thermal and physical properties. In particular, the melting point of the alloy must be as low as possible, preventing thermal destruction of the Nd:YAG. Furthermore, this reduces the thermal gradient in the crystalline structure of the YAG and improves thermal shock resistance. Besides, a sufficient thermal conductivity is important to ensure a targeted heat dissipation. Another crucial aspect is the induced stress due to different thermal expansions of the connected materials leading to structural damage. Therefore, the thermal expansion coefficient of the alloy has to match the coefficient of the optical component. The recent approach is the application of copper-molybdenum pseudoalloys. The idea is to combine the low thermal expansion of molybdenum with the high thermal conductivity of copper. State-of-the-art are sintered molybdenum powders that are infiltrated with molten copper resulting in promising physical properties exceeding the requirements of the intended purpose and allowing the application in high-power laser systems. During first practical experiments with these powders, promising results have been achieved with a 680-Watt diode laser by solely melting the copper. The structure of the generated object contained unaffected molybdenum grains embedded into a copper matrix and therefore successfully forming a pseudoalloy. Effects of the adjusted powder composition, the laser parameters and the resulting thermomechanical properties are investigated. With the help of microsections, the additive manufactured pseudoalloys are evaluated and characterized.
The use of additive manufacturing methods in research and industry has led to the possibility of designing more compact, light and low-cost assemblies. In the field of laser development, new opportunities resulting from additive manufacturing have rarely been considered so far. We present a compact, lightweight solid-state amplifier system for low-power applications where the optomechanical components are manufactured completely additive via Fused Filament Fabrication (FFF). The amplifier system is based on a Nd:YVO4-crystal pumped with an external, fiber-coupled diode at a wavelength of 808nm and a maximum output power of 3 W. The seed source is a Nd:YVO4-crystal based solid-state laser with an emission wavelength of 1064 nm. The commercial optical components, such as lenses and crystal, are firmly imprinted via FFF in the optomechanics and thus secured against misalignment. Additionally, sensor technology for temperature measurement is implemented into the devices. The use of FFF, in which the components are printed from polymers, results in a lightweight yet stable construction. We have shown, that optical components can be imprinted without adding mechanical stress. To increase the mechanical and thermal robustness of the system different types of polymers as well as post process treatments are tested and the use of Laser Metal Deposition for this application is investigated. The thermal stability of the printed structures is evaluated to determine the maximum power level of the system without damaging the polymer-optomechanics. Furthermore, output power, optical-to-optical efficiency, beam pointing, and beam shape are measured for several on- and off-switching processes as well as long-term operation.