Revistas
Revista:
OPTICS AND LASER TECHNOLOGY
ISSN:
0030-3992
Año:
2023
Vol.:
161
Págs.:
109232
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.
Autores:
San-Blas, A. (Autor de correspondencia); Martínez, Miguel; Granados, E.; et al.
Revista:
SURFACES AND INTERFACES
ISSN:
2468-0230
Año:
2021
Vol.:
25
Págs.:
101205
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 quasiplane-wave illumination. Our results provide insight regarding the control of LIPSS regularity, which is essential for industrial applications involving the LIPSS generation technique.
Revista:
PHYSICAL REVIEW MATERIALS
ISSN:
2475-9953
The control of the interaction between materials and biological tissues is a key factor to optimize the overall performance of implants and prostheses integrated into the body. With this objective in mind, biomimetic hierarchical one- and two-dimensional surface patterns textured at the micro and nano scales were fabricated on titanium alloys using femtosecond laser processing. The experimental results show that laser irradiation promotes surface oxidation together with a polarization-dependent nano-ripple formation. Human mesenchymal stem cells were subsequently cultured on different surface patterns aiming at determining their response to the underlying micro and nano structures. The ripple topography was demonstrated to induce a nonfouling behavior, which could be exploited in the fabrication of biomimetic hierarchical surface patterns to develop cell-trapping modules.
Autores:
San-Blas, A. (Autor de correspondencia); Martínez, Miguel; Buencuerpo, J.; et al.
Revista:
APPLIED SURFACE SCIENCE
ISSN:
0169-4332
Revista:
OPTICS EXPRESS
ISSN:
1094-4087
Año:
2020
Vol.:
28
N°:
20
Págs.:
29054 - 29063
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 pi/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.
Revista:
APPLIED OPTICS
ISSN:
1559-128X
Año:
2019
Vol.:
58
N°:
16
Págs.:
4220 - 4226
Volume-phase gratings (VPGs) were fabricated in CdSxSe1-x quantum-dot-doped borosilicate glass at a low repetition rate (800 nm, 140 fs, 1 kHz). The VPGs were designed based on rigorous coupled wave analysis simulations. Results indicate that the inscribed thickness (L) is the key parameter to maximize the diffraction efficiency at order 1. Microscope images of the cross sections and diffraction efficiency measurements were taken in order to characterize the modification of the material at different laser-inscription parameters. A maximum VPG diffraction efficiency of 67% (at order 1) was achieved. Also, a refractive index change of Delta n = 2.25.10(-3) is estimated from these VPG diffraction efficiency measurements. The measurements regarding polarization-insensitive diffraction efficiency showed that the birefringence produced in the substrate is negligible. (C) 2019 Optical Society of America
Revista:
SCIENTIFIC REPORTS
ISSN:
2045-2322
Año:
2018
Vol.:
8
N°:
14262
We demonstrate a rapid, accurate, and convenient method for tailoring the optical properties of diamond surfaces by employing laser induced periodic surface structuring (LIPSSs). The characteristics of the fabricated photonic surfaces were adjusted by tuning the laser wavelength, number of impinging pulses, angle of incidence and polarization state. Using Finite Difference Time Domain (FDTD) modeling, the optical transmissivity and bandwidth was calculated for each fabricated LIPSSs morphology. The highest transmission of similar to 99.5% was obtained in the near-IR for LIPSSs structures with aspect ratios of the order of similar to 0.65. The present technique enabled us to identify the main laser parameters involved in the machining process, and to control it with a high degree of accuracy in terms of structure periodicity, morphology and aspect ratio. We also demonstrate and study the conditions for fabricating spatially coherent nanostructures over large areas maintaining a high degree of nanostructure repeatability and optical performance. While our experimental demonstrations have been mainly focused on diamond anti-reflection coatings and gratings, the technique can be easily extended to other materials and applications, such as integrated photonic devices, high power diamond optics, or the construction of photonic surfaces with tailored characteristics in general.
Revista:
OPTICAL MATERIALS EXPRESS
ISSN:
2159-3930
Año:
2017
Vol.:
7
N°:
9
Págs.:
3389 - 3396
We demonstrate the formation of laser-induced periodic surface structures (LIPSS) in boron-doped diamond (BDD) by irradiation with femtosecond near-IR laser pulses. The results show that the obtained LIPSS are perpendicular to the laser polarization, and the ripple periodicity is on the order of half of the irradiation wavelength. The surface structures and their electrochemical properties were characterized using Raman micro-spectroscopy, in combination with scanning electron and atomic force microscopies. The textured BDD surface showed a dense and large surface area with no change in its structural characteristics. The effective surface area of the textured BDD electrode was approximately 50% larger than that of a planar substrate, while wetting tests showed that the irradiated area becomes highly hydrophilic. Our results indicate that LIPSS texturing of BDD is a straightforward and simple technique for enhancing the surface area and wettability properties of the BDD electrodes, which could enable higher current efficiency and lower energy consumption in the electrochemical oxidation of toxic organics. (C) 2017 Optical Society of America
Revista:
OPTICS EXPRESS
ISSN:
1094-4087
Año:
2017
Vol.:
25
N°:
13
Págs.:
15330 - 15335
We study the fabrication of photonic surface structures in single crystal diamond by means of highly controllable direct femtosecond UV laser induced periodic surface structuring. By appropriately selecting the excitation wavelength, intensity, number of impinging pulses and their polarization state, we demonstrate emerging high quality and fidelity diamond grating structures with surface roughness below 1.4 nm. We characterize their optical properties and study their potential for the fabrication of photonic structure antireflection coatings for diamond Raman lasers in the near-IR. (C) 2017 Optical Society of America
Revista:
APPLIED SURFACE SCIENCE
ISSN:
0169-4332
Año:
2016
Vol.:
374
Págs.:
81 - 89
In this work we have developed hierarchical structures that consist of micro-patterned surfaces covered by nanostructures with a femtosecond laser. The first part of this work is a study to determine the microscale modifications produced on a stainless steel alloy (AISI304) surface at high pulse energy, different velocities, and number of overscans in order to obtain microstructures with a selected depth of around 10 mu m and line widths of 20 mu m. The second part of the work is focused on finding the optimal irradiation parameters to obtain the nanostructure pattern. Nanostructures have been defined by means of Laser Induced Periodical Surface Structures (LIPSS) around 250 nm high and a period of 580 nm, which constitute the nanostructure pattern. Finally, dual scale gratings of 50 mm(2) were fabricated with different geometries and their effect on the measured contact angle. Combining the micro-pattern with the LIPSS nano-pattern, highly hydrophobic surfaces have been developed with measured static contact angles higher than 150 degrees on a stainless steel alloy. (C) 2015 Elsevier B.V. All rights reserved.
Revista:
SCIENTIFIC REPORTS
ISSN:
2045-2322
Año:
2016
Vol.:
6
N°:
36296
Págs.:
81 - 89
The precise control over the interaction between cells and the surface of materials plays a crucial role in optimizing the integration of implanted biomaterials. In this regard, material surface with controlled topographic features at the micro- and nano-scales has been proved to affect the overall cell behavior and therefore the final osseointegration of implants. Within this context, femtosecond (fs) laser micro/nano machining technology was used in this work to modify the surface structure of stainless steel aiming at controlling cell adhesion and migration. The experimental results show that cells tend to attach and preferentially align to the laser-induced nanopatterns oriented in a specific direction. Accordingly, the laser-based fabrication method here described constitutes a simple, clean, and scalable technique which allows a precise control of the surface nano-patterning process and, subsequently, enables the control of cell adhesion, migration, and polarization. Moreover, since our surface-patterning approach does not involve any chemical treatments and is performed in a single step process, it could in principle be applied to most metallic materials.
Revista:
APPLIED SURFACE SCIENCE
ISSN:
0169-4332
Año:
2015
Vol.:
351
Págs.:
135 - 139
In this work, submicro and nanostructures self-formed on the surface of Platinum thin films under femtosecond laser-pulse irradiation are investigated. A Ti:Sapphire laser system was used to linearly scan 15 mm lines with 100 fs pulses at a central wavelength of 800 nm with a 1 kHz repetition rate. The resulting structures were characterized by scanning electron microscopy (SEM) and 2D-Fast Fourier Transform (2D-FFT) analysis. This analysis of images revealed different types of structures depending on the laser irradiation parameters: random nanostructures, low spatial frequency LIPSS (LSFL) with a periodicity from about 450 to 600 nm, and high spatial frequency LIPSS (HSFL) with a periodicity from about 80 to 200 nm. Two different modifications regimes have been established for the formation of nanostructures: (a) a high-fluence regime in which random nanostructures and LSFL are obtained and (b) a low-fluence regime in which HSFL and LSFL are obtained. (C) 2015 Elsevier B.V. All rights reserved.
Revista:
IEEE SENSORS JOURNAL
ISSN:
1530-437X
Año:
2015
Vol.:
15
N°:
2
Págs.:
1216 - 1223
The integration of 3D microfluidic structures to enhance surface-sample interaction with microfluidic enclosed biosensors is reported. The method was tested in a device with a microfluidic network made from polydimethylsiloxane ( PDMS), fabricated using a double layer mold technique. As an intermediate step before the tests, a self-assembled monolayer (SAM), which acted as a ligand for 252-nm amine-coated fluorescent polystyrene particles, was formed on top of a gold layer. The results showed that the microstructures produced an increase of coverage of the sensing areas up to 67% which, combined with the property of the SAM of binding with different biological molecules, provide a potential method to enhance the sensitivity of a wide range of multipurpose microfluidic biosensors.
Revista:
OPTICS EXPRESS
ISSN:
1094-4087
Año:
2015
Vol.:
23
N°:
20
Págs.:
26683 - 26688
Ultrafast laser inscription of volume phase gratings with low index contrast and self-images with visibility of 0.96 is demonstrated. It is also demonstrated that phase differences of p/2 for visible light are achievable with only one layer of structures induced in bulk borosilicate glass by direct laser writing. The fabrication method avoids the stitching of several layers of structures and significantly reduces the time of process. The increment of visibility with the induced phase difference is proved and results are compared with the expected for planar phase gratings. (C) 2015 Optical Society of America
Revista:
JOURNAL OF APPLIED PHYSICS
ISSN:
0021-8979
Año:
2014
Vol.:
115
N°:
17
The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced. (C) 2014 AIP Publishing LLC.