Beldarrain, O. (Oihane)
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- Efficient composite colorization of copper by spatially controlled oxidation with deep-UV ultrafast lasers(2023) Rodríguez-González, A. (Ainara); Groussin, B. (Baptiste); Martínez-Calderón, M. (Miguel); Granados, E. (Eduardo); Marsh, B.A. (Bruce A.); Olaizola-Izquierdo, S.M. (Santiago Miguel); Beldarrain, O. (Oihane)Colorizing metals using micrometer and nanometer scale surface modifications has been vastly investigated and presents many advantages for applications across scientific and technological fields. By tuning the surface chemical composition or controlling its morphology, it is possible to produce a wide range of chromatic effects. Ultrafast laser processing presents here an interesting asset, as it allows to simultaneously provide chemical and morphological modifications at the micro-scale in a single step. In this article, the composite colorization of copper surfaces with mW-class average power deep ultraviolet (DUV) femtosecond laser pulses is demonstrated. The advantages of this setup are twofold: first, thanks to the increased absorption of copper in the DUV, the technique allows scaling down the requirement for laser power. Second, under ultrafast short-wavelength illumination molecular oxygen bond-breaks occur, enhancing the oxidation rate of the copper. The technique allows for highly controllable and efficient copper oxidation with the irradiation parameters. Taking these two effects into account, the generation of a wide spectrum of colors-from dark blue to shiny red-is demonstrated, and the role of the surface oxidation rate, the laser fluence, and laser scanning strategies in the colorization of copper surfaces employing DUV lasers is discussed. Copper surface colorization with mW-class deep ultraviolet femtosecond laser pulses offers two key benefits: increased copper absorption in deep ultraviolet (DUV), reducing power needs, and spatially precise enhanced copper oxidation, resulting in a broad palette of colors with micron pixel resolution. Composite colorization of copper surfaces using DUV ultrafast pulsesimage
- Single-step fabrication of highly tunable blazed gratings using triangular-shaped femtosecond laser pulses(2024) Fantova-Sarasa, J. (Jorge); Olaizola, S.M. (Santiago Miguel); Rodríguez-González, A. (Ainara); Gómez-Aranzadi, M. (Mikel); Lens, J. (José); Beldarrain, O. (Oihane); Omeñaca-Segura, L. (Luís); Garcia-Mandayo, G. (Gemma)Blazed gratings are periodic surface structures of great interest for applications such as friction control, light trapping, and spectrometry. While different laser processing methods have been explored to produce these elements, they have not yet surpassed conventional surface manufacturing techniques, often based on lithography processes or mechanical ruling. This work introduces a new approach based on the combination of ultrashort pulses and triangular beam shaping, which enables the generation of asymmetrical grooves in a single step. The main advantage of this strategy is that by simply changing the laser processing direction we can induce a significant modification in the ratio of asymmetry between the sidewall angles of the machined channels. The paper includes a comprehensive study, which has been supported by statistical tools, of the effect of this and other experimental parameters on the morphology of grooves machined on stainless steel. As a result, we achieved a wide range of geometries, with asymmetry ratios spanning from 1 to 5 and channel depths between 3 and 15 mu m. Furthermore, we demonstrate the validity of the approach through the successful manufacture of blazed gratings of various slopes. The results reflect the versatility and cost-efficiency of the proposed fabrication strategy, and thus its potential to streamline the production of sawtooth gratings and other devices that are based on asymmetrical features.