Fast uniform micro structuring of DLC surfaces using multiple ultrashort laser spots through spatial beam shaping

Femtosecond laser surface micro-machining is an expanding technique for applications where ablation is required with restricted side-effect on the micro-nano-scale. To face the cost demands, spatial beam shaping enables to parallelize the machining process by generating multiple laser spots in the processing plane and is associated with a fast scanning head. Spatial beam shaping is usually achieved through wavefront modulation with possible modulations errors due to the optical set-up. Thus, there is a challenge in producing an homogeneous array of laser spots to ensure a uniform micro-structuring of the substrate. We study the influence of the target array characteristics (number of spots, size) on the success of beam shaping. By optimization of the desired laser spot array and beam scanning strategy, a uniform network of micro-dimples of sub-micrometric depth (below 7% standard deviation) on a DLC surface is reported.