Modelling laser machining of nickel with spatially shaped three pulse sequences using deep learning

• Published in: Optics express Vol. 28; no. 10; pp. 14627 - 14637
• Main Authors: McDonnell, M D T, Grant-Jacob, J A, Xie, Y, Praeger, M, Mackay, B S, Eason, R W, Mills, B
• Format: Journal Article
• Language: English
• Published: United States 11.05.2020
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.381421

Femtosecond laser machining is a complex process, owing to the high peak intensities involved. Modelling approaches for the prediction of final sample quality based on photon-atom interactions are therefore challenging to extrapolate up to the microscale and beyond. The problem is compounded when multiple exposures are used to produce a final structure, where surface modifications from previous exposures must be taken into consideration. Neural network approaches allow for the automatic creation of a model that accounts for these challenging processes, without any physical knowledge of the processes being programmed by a specialist. We present such a network for the prediction of surface quality for multi-exposure femtosecond machining on a 5µm electroless nickel layer deposited on copper, where each pulse is uniquely spatially shaped using a spatial light modulator. This neural network modelling method accurately predicts the surface profile after three, sequential, overlapping exposures of dissimilar intensity patterns. It successfully reproduces such effects as the sub-diffraction limit machining feasible with multiple exposures, and the smoothing effect on edge-burr from previous exposures expected in multi-exposure laser machining.