Papers by Keyword: Laser Materials Processing

Abstract: Here, we showed formation of chiral nanoprotrusions upon direct laser ablation of bulk crystalline silicon (c-Si) wafer with single femtosecond (fs) pulses having asymmetric donut-shaped intensity profile. Breaking circular symmetry of the irradiating donut-shaped fs-pulse beam was demonstrated to switch the geometry of formed surface nanoprotrusions from regular to chiral, while the chirality of the obtained Si nanostructures was found to promote with a degree of asymmetry of the laser beam. The obtained experimental results explain, for the first time, the formation of previously reported chiral c-Si nanostructures produced via donut-shaped beam ablation in terms of uneven helical flow of laser-melted Si material caused by asymmetry of initial intensity and temperature pattern on laser-irradiated Si surface. Our findings open a pathway towards easy-to-implement inexpensive fabrication of chiral all-dielectric nanostructures for advanced nanophotonic applications.

Abstract: We report on the results of intense third party evaluation of the COLD SPLIT technology. In total nine different SiC manufactures supplied test material. The results confirm the tremendous potential of the technology with total kerf losses per wafer of less than 100μm. Furthermore, our general approach led to comparable results for all vendors. The vendor specific difference like lateral doping level were addressed via control loops in our lasering process. These loops take crystal properties into account and adjust the applied laser energy and the depth of the laser process accordingly. Even the current best case results of sub 80μm split loss per wafer are dominated by systematic effects, which are addressed by continuous improvement efforts.

Abstract: Formation of a chiral nanorelief appearing on the surface of plasmonic-active metals upon their ablation with vortex and spiral-shape beam was recently found to be mainly driven by the helical-shape temperature and corresponding surface tension gradients rather than optical angular momentum transfer from the incident beam. Meanwhile, optimization of the laser intensity pattern driving the rotational movement of transiently molten metal allowing fabrication of surface structures with controlled chirality is still an actual task for various practical applications in nanophotonics and biosensing. Here, we show that by properly designing the intensity distribution in the spiral-shape beam used for direct laser ablation, the chirality of produced nanostructures can be controlled in a wide range of parameter.

Abstract: The interest in laser material processing of Carbon Fibre Reinforced Plastic (CFRP) over the past few years has increased, especially in the aerospace industry. A number of different laser groups around the world are investigating different laser sources for the express reason of developing a laser material processing centre for machining CFRP for the aerospace and automotive industry. This paper reports on the work of two such groups, in the UK and Germany, who are using fibre laser technology and a diode pumped solid state laser system. The initial results from the two studies are reported and show that these two very different laser systems offer processing capability with respect to machining CFRP.

Abstract: The micromachining technique for the fabrication of Fe-36%Ni (Invar®) microgrooves using a novel laser-induced wet etching system with an optical fiber as the light waveguide and machining tool is investigated. Microgrooves fabricated at the optimal process conditions with the proposed etching system have good surface morphology and dimensional accuracy. It is shown that the variation of etch profiles such as etch width and depth depends significantly upon the process parameters. Fiber damage, which is attributed to macrobubbles, can be dramatically reduced by adjusting the distance between the workpiece surface and the fiber terminal. The effects of process parameters such as laser power, scan speed, and threshold distance on etch width, depth, and crosssectional profiles are reported and the optimal process conditions to fabricate Invar® microgrooves with excellent shape and size are provided. Also, the applicability of the Invar® microgrooves for the manufacturing of shadow mask for an organic light emitting diode (OLED) is demonstrated.