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Structured light is desired in the micromachining of various materials. As the latest ultrashort laser sources increase the average power by increasing the repetition rate, the efficiency of the process becomes crucial in laser micromachining. The standard Gaussian beam shape, because of its slow ascending/descending slope, is not the most efficient beam, neither in precise energy deposition nor in heat management. Flat-top beams are required for precise and even energy distribution and are used in laser ablation or thin-film removal. We look at a rather abstract concept of polarization singularities and investigate them to create a vector flat-top beam. For this purpose, we devise a beam-shaping method based on the volumetric birefringent nano gratings which allow the generation of high-energy polarization singularities. By tuning the input beam waist, we have generated three most common laser micromachining beam profiles (Gaussian, Flat-top, and ring- or doughnut-shaped). The resulting high-quality and high-energy polarization singularities allow us to systematically demonstrate their use in transparent and opaque material micromachining, as well as the usual application for flat-top beams of thin-film removal. • Vector beams with polarization singularities applied in laser micro processing. • Dynamical shaping of a laser beam in focal zone using a single optical element. • Employment of geometric phase elements for high >92% transmission laser beam shaping. • Generation of flat-top beams without pre- of post-intensity peaks in the focal zone. [ABSTRACT FROM AUTHOR]

The ultrashort pulsed laser micromachining of transparent and opaque materials has become a mature technology providing microscale accuracy. While the ultrashort laser sources are being constantly developed with growing average power or more complex pulse temporal control, studies in the spatial domain can also lead to improving the performance i.e., higher process speed, better fabrication quality, etc. By purposely transforming the Gaussian beam of the laser output to a custom beam shape we are able to improve speed and quality in many laser micromachining tasks, where micro-welding of various materials is one of them. In this work, we apply custom hollow spatially variable waveplates based on nanograting technology (manufactured by Workshop of Photonics) that help to form curved or flat intensity distribution beams. Using numerical modeling and experimental research we will demonstrate beam transformations that could have an impact on enhancing the micro-welding process in terms of reduced stress or better heat dissipation. [ABSTRACT FROM AUTHOR]