Ultrashort pulsed multibeam processing head for parallel ultrafast micromachining

Abstract

In recent years, one trend in surface processing can be ascertained in ultrashort pulsed lasers with high pulse repetition rates, e.g., nearly cold ablation for gravure printing. Short pulse width leads to very high peak power (on a megawatt scale). Such a high peak fluence results in multiphoton absorption and enables precise micro- and sub-micro-structuring of surfaces. Additionally, ultrafast processing is compatible with a wide range of materials: besides metals, functional surfaces can be provided to several high-bandgap materials such as glass and ceramics. One challenge of ultrafast micromachining is process velocity. The operational capacity of these processes can be maximized by increasing the scan rate or by increasing the number of beams—subject parallelism. This contribution focuses on parallelism using ultrashort pulsed lasers with a high repetition rate and an individually addressable acousto-optic beam deflector. The core of the multibeam generation is a smooth diffractive beam splitter component with high spot uniformity and negligible power loss and a prismatic array compressor to match the beam pitch according to the beamlet spot size. The optical design and the practical implementation of an eight-beam processing head in combination with a high average power single-mode ultrashort pulsed laser source are presented, as is promising laboratory research currently underway along with the shortly projected micromachining results. Finally, we assess the prospects for scaling the optical system to several tens of beamlets. This contribution will address challenges such as the power of available ultrashort pulsed lasers which can be overcome by beam combining, parallelism using optical modulation components, and optomechanical integration.