Rodríguez, A. (Ainara)
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- Femtosecond laser fabrication of monolithic double volume phase-gratings in glass(2020) Azkona, J.J. (J. J.); Olaizola, S.M. (Santiago Miguel); de-la-Peña, J.L. (J.L.); Gómez-Aranzadi, M. (Mikel); Rodríguez, A. (Ainara); Morlanes, T. (T.)A diffractive optical element was fabricated by monolithically integrating two volume phase-gratings (VPGs) in the bulk of a single-piece transparent material. A computer model of the diffraction generated by the double volume phase-grating (DVPG) was made with a rigorous coupled wave analysis simulator. Simulations and experiments show that the diffractive behavior of a DVPG can be controlled by arranging the relative displacement and the distance between the VPGs according to Talbot self-imaging planes. In order to diffract the total incident light, the phase accumulation in the VPGs has to be π/2, which was achieved by single-scan femtosecond laser processing of a nanocrystal doped glass as the substrate material. Ex situ microscope images of the cross-sections are presented for laser processed lines in the form of VPGs and DVPGs. The far-field diffraction of DVPGs formed by selectively located VPGs was characterized with a monochromatic 633 nm and a supercontinuum white light. Functional designs of high diffraction efficiency with potential applications in photonics were successfully fabricated in a one-step and free of chemicals process.
- LIPSS manufacturing with regularity control through laser wavefront curvature(Elsevier, 2021) Olaizola, S.M. (Santiago Miguel); San-Blas, A. (Alejandro); Martínez-Calderón, M. (Miguel); Gómez-Aranzadi, M. (Mikel); Rodríguez, A. (Ainara); Granados-Mateo, E. (Eduardo)Laser-Induced Periodic Surface Structures (LIPSS) manufacturing is a convenient laser direct-writing technique for the fabrication of nanostructures with adaptable characteristics on the surface of virtually any material. In this paper, we study the influence of 1D laser wavefront curvature on nanoripples spatial regularity, by irradiating stainless steel with a line-focused ultrafast laser beam emitting 120 fs pulses at a wavelength of 800 nm and with 1 kHz repetition rate. We find high correlation between the spatial regularity of the fabricated nanostructures and the wavefront characteristics of the laser beam, with higher regularity being found with quasi-plane-wave illumination. Our results provide insight regarding the control of LIPSS regularity, which is essential for industrial applications involving the LIPSS generation technique.
- Polarization conversion on nanostructured metallic surfaces fabricated by LIPSS(SPIE, 2019) Olaizola, S.M. (Santiago Miguel); Perez-Hernandez, N. (Noemí); Casquero, N. (Noemí); Martínez-Calderón, M. (Miguel); Rodríguez, A. (Ainara); Granados-Mateo, E. (Eduardo)Waveplates modify polarization by generating a phase change. Laser Induced Periodic Surface Structures (LIPSS) have recently started to be studied as waveplates due to the birefringence in-duced by the nanoripples, easily fabricated in a one-step process by laser, where LIPSS morphology is defined by the characteristics of the laser process parameters and the substrate material. The optical properties of these waveplates are defined by LIPSS parameters such as period, depth or width of the ripples. In this work we have deposited thin film coatings on stainless steel samples containing LIPSS for different coating thickness and composition. Results show that thin film coatings are a good candidate for the tunability of LIPSS birefringence since the coating modifies the induced polarization change and reflectivity of the sample depending on coating thickness and composition, as expected from numerical simulations.
- Study of the processing conditions for stainless steel additive manufacturing using femtosecond laser(Elsevier, 2023) Olaizola, S.M. (Santiago Miguel); Ramón-Conde, I. (Iñigo); Gómez-Aranzadi, M. (Mikel); Rodríguez, A. (Ainara)The use of ultrashort-pulsed (USP) lasers in Additive Manufacturing (AM) enables the processing of different materials and has the potential to reduce the sizes and shapes manufactured with this technology. This work confirms that USP lasers are a viable alternative for Laser Powder Bed Fusion (LPBF) when higher precision is required to manufacture certain critical parts. Promising results were obtained using tailored and own-produced stainless steel powder particles, manufacturing consistent square layers with a series of optimized processing parameters. The critical role of processing parameters is confirmed when using this type of lasers, as a slight deviation of any of them results in an absence of melting. For the first time, melting has been achieved at low pulse repetition (500 kHz) and using low average laser power values (0.5–1 W), by generating heat accumulation at reduced scanning speeds. This opens up the possibility of further reducing the minimum size of parts when using USP lasers for AM.
- Femtosecond laser fabrication of LIPSS-based waveplates on metallic surfaces(2020) Olaizola, S.M. (Santiago Miguel); Buencuerpo, J. (Jerónimo); San-Blas, A. (Alejandro); Martínez-Calderón, M. (Miguel); Gómez-Aranzadi, M. (Mikel); Del-Hoyo, J. (Jesús); Sanchez-Brea, L.M. (Luis M.); Rodríguez, A. (Ainara)A fast and reliable method for the fabrication of polarization modifying devices using femtosecond laser is reported. A setup based on line focusing is used for the generation of LIPSS on stainless steel, processing at different speeds between 0.8 and 2.4 mm/s with constant energy per pulse of 1.4 mJ. SEM and AFM characterizations of the LIPSS show a progressive increase in period as the processing speed increases, while height remains approximately constant in the studied range. Optical characterization of the devices shows an induced change in the polarization of the reflected beam that varies with the processing speed, which allows a controlled fabrication of these devices.