Conventional surface structuring processes often share two crucial disadvantages. First, after the structuring process itself, some kind of surface finishing is often needed, based on another technology, which means a substantial additional expense. Second, all conventional surface structuring processes are based on the removal of material, which is wasted without any further use during processing. A new approach of structuring metallic surface structuring by laser remelting (WaveShape). In this process, no material is removed but reallocated while molten. This structuring process is based on the new active principle of remelting. The surface structure and the microroughness result from a laser-controlled self-organization of the melt pool due to surface tension. Up to now, basic research has been focused on hot work steel 1.2343 (AISI: H11), and promising results have been achieved for this material. Current research and development are now seeking to expand the spectrum of processable materials. Since remelting is a thermally driven process, significant differences between metallic materials are expected due to their thermo physical properties such as thermal conductivity, absorption coefficient, viscosity, and heat capacity. The titanium alloy Ti6Al4V has a wide range of industrial applications, especially for aviation, aerospace, and medical engineering. The WaveShape process for this material will be investigated within this paper. The procedural principle of surface structuring by remelting is based upon a sinusoidal modulation of laser power while the laser beam is moved over the surface. The lower process limit of laser power is the power required to melt material and, therefore, create a melt pool. In this context, the upper process limit of laser power is the point just before substantial amounts of the molten material are evaporated. We used metallographic cross sections to measure the dimensions of melt pool depth and width as they depend on procedural parameters, such as laser beam diameter (125-500 lm), scanning velocity (25-200 mm/s), and laser power (20-400 W). We also investigated basic interdependencies between structural characteristics (e.g., height) and procedural parameters used, such as laser beam diameter, laser power, and wavelength of modulation. The results show that the WaveShape process is well suited to process titanium alloy Ti6Al4V since structures and process velocities achieved are significantly higher than for the previously investigated hot work steel. V C 2015 Laser Institute of America. [http://dx

Surface structuring by remelting with laser radiation is a new approach to shape metallic surfaces ("WaveShape"). In this structuring process, surface material is reallocated in its molten state instead of being removed, because the process is based on the new active principle of remelting. The surface structure and the microroughness result from a laser-controlled melt pool due to surface tension. Basic research has been conducted with promising results, especially for the hot work steel 1.2343. Since remelting is a thermally driven process, significant differences between metallic materials were expected due to their thermophysical properties such as thermal conductivity, absorption coefficient, viscosity, heat capacity, etc. Therefore, the presented research soughed to expand the spectrum of processable materials. Within the framework of our investigation, we compared the achieved structure height as well as melt pool dimensions for six different materials. Furthermo re, we successfully tested new structuring strategies such as not linearly shaped scanning vectors to create innovative surface structures on all materials investigated. The biggest structures were achieved on the titanium alloy Ti6Al4V and the nickel based super alloy IN718. Finally, an approach of reverse structuring was investigated in order to erase existing structures and achieve a smoothed rewriteable metallic surface. The results show that surface structuring by laser remelting is well suited to process a wide range of different metals and to achieve a broad variety of different structures as well as to effectively erase existing surface structures such as milling marks

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We present the design of a longitudinally diode-pumped Alexandrite laser in continuous-wave operation and resulting performance data. A laser power of 6.5 W in fundamental mode operation was measured, which is, to the best of our knowledge, the highest laser power in fundamental mode operation yet reported. The laser crystal was pumped by two diode modules emitting at 637 nm. The pump radiation was polarization-combined and spatially symmetrized. The laser operates at an output power of 6.5 W with an optical-to-optical efficiency of 26%, temporally stable output with stability of 8% on ms timescale, a beam quality of M2 = 1.1 in both spatial directions and emission of an output wavelength of 752 nm. Measurements of the thermal dioptric power at pumping intensities up to 9.5 kW/cm2 support the appropriate approach of the design. Based on our results, we estimate the potential and show our concept for future scaling of the output power.

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