Generation of nano or micro-scale structures on materials surface enables new functions and properties, such as super-hydrophobicity by lotus effect, surface blackening by light trapping, modification of surface tribological properties, etc. which are in high demand for a wide variety of industrial fields. Amongst the surface functionalization techniques, Ultra-Short Pulse lasers have been proven to be a reliable tool to create Laser Induced Periodic Surface Structures (LIPSS). Exploitation of LIPSS for industrial purposes poses some key problems like up scaling over large area with high repeatability and high throughput. Beam shaping could be a key element to overcome these issues. Specific shapes, such as top-hat line shape, could enable at once uniform processing over large surface with the consequence to reduce the processing time. Multi-Plane Light Conversion (MPLC) is an innovative technique of beam shaping which allows theoretically lossless complex beam shapes with a high control over amplitude and phase. The free-space reflective design allows for high beam shaping quality whilst maintaining the ultra-short property of the laser pulses, which is not usually achievable through other beam shaping methods. Here we show the results obtained over Stainless-Steel using an industrial femtosecond laser with a tophat line of 30μm × 594 μm intensity profile generated using MPLC technology. The beam has been delivered over the Stainless-Steel surface with a galvo scanner and focused through an f -theta lens of 100 mm. Surface morphology has been investigated via SEM and the processing time has been compared to conventional round Gaussian Beams
Ultra-short pulse laser (UPL) industry is counting on high power P sources (100W class) to increase the throughput of a wide variety of industrial fabrication process. Nevertheless, this poses the challenge to overcome heat accumulation phenomena observed when P exceeds few tens of Watts compromising the machining quality. Novel beam engineering strategies are required to tackle this issue and guarantee high throughput with the high, distinctive, UPL machining quality. Here a study is reported on a variety of laser processes carried out with 100W class femtosecond lasers following two possible beam engineering strategies i.e. beam scanning with high speed (both a 100 m/s polygon scanner head and a 2D, 20 m/s fast, galvo-head) and parallel processing with multiple beams (obtained with both a DOE and an SLM head). Results show that by increasing P from few to 100 W also the throughput increases by nearly a factor 10 for micro-cutting (with galvo head and DOE) and even higher for surface texturing (with polygon scanner) while the machining quality is kept unchanged. Furthermore, we optimised the use of an SLM head for precise micro drilling of matrix holes showing the benefit of this technological approach in term of throughput. A full characterisation of the results carried out via optic and electronic microscopy will be also reported. We believe that all these results further increase the USP laser technology effectiveness level which is primed for industrial applications.