Polarization singularities for shaping of vector flat-top beams in utilization for high-power laser micromachining of various materials

Abstract

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.