Laser Shock Microforming of Thin Metal Sheets

Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the applicability of such type of lasers is limited by the long-relaxation-time of the thermal fields responsible for the forming phenomena. As a consequence of such slow relaxation, the final sheet deformation state is attained only after a certain time, what makes the generated internal residual stress fields more dependent on ambient conditions and might make difficult the subsequent assembly process from the point of view of residual stresses due to adjustment. The use of ns laser pulses provides a suitable parameter matching for the laser forming of an important range of sheet components used in MEMS that, preserving the short interaction time scale required for the predominantly mechanic (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization, particularly important according to its frequent use in such systems. In the present paper, a discussion is presented on the physics of laser shock microforming and the influence of the different effects on the net bending angle. The experimental setup used for the experiments, sample fabrication and experimental results of influence of number of laser pulses on the net bending angle are also presented

Laser ablation modelling of aluminium, silver and crystalline silicon for applications in photovoltaic technologies

Laser material processing is being extensively used in photovoltaic applications for both the fabrication of thin film modules and the enhancement of the crystalline silicon solar cells. The two temperature model for thermal diffusion was numerically solved in this paper. Laser pulses of 1064, 532 or 248 nm with duration of 35, 26 or 10 ns were considered as the thermal source leading to the material ablation. Considering high irradiance levels (108–109 W cm−2), a total absorption of the energy during the ablation process was assumed in the model. The materials analysed in the simulation were aluminium (Al) and silver (Ag), which are commonly used as metallic electrodes in photovoltaic devices. Moreover, thermal diffusion was also simulated for crystalline silicon (c-Si). A similar trend of temperature as a function of depth and time was found for both metals and c-Si regardless of the employed wavelength. For each material, the ablation depth dependence on laser pulse parameters was determined by means of an ablation criterion. Thus, after the laser pulse, the maximum depth for which the total energy stored in the material is equal to the vaporisation enthalpy was considered as the ablation depth. For all cases, the ablation depth increased with the laser pulse fluence and did not exhibit a clear correlation with the radiation wavelength. Finally, the experimental validation of the simulation results was carried out and the ability of the model with the initial hypothesis of total energy absorption to closely fit experimental results was confirmed

OPTICAL CONSTANTS AND BAND STRENGTHS OF CH4:C2H6 ICES IN THE NEAR- AND MID-INFRARED

[EN] We present a spectroscopic study of methane-ethane ice mixtures. We have grown CH4:C2H6 mixtures with ratios 3:1, 1:1, and 1:3 at 18 and 30 K, plus pure methane and ethane ices, and have studied them in the near-infrared (NIR) and mid-infrared (MIR) ranges. We have determined densities of all species mentioned above. For amorphous ethane grown at 18 and 30 K we have obtained a density of 0.41 and 0.54 g cm(-3), respectively, lower than a previous measurement of the density of the crystalline species, 0.719 g cm(-3). As far as we know this is the first determination of the density of amorphous ethane ice. We have measured band shifts of the main NIR methane and ethane features in the mixtures with respect to the corresponding values in the pure ices. We have estimated band strengths of these bands in the NIR and MIR ranges. In general, intensity decay in methane modes was detected in the mixtures, whereas for ethane no clear tendency was observed. Optical constants of the mixtures at 30 and 18 K have also been evaluated. These values can be used to trace the presence of these species in the surface of trans-Neptunian objects. Furthermore, we have carried out a theoretical calculation of these ice mixtures. Simulation cells for the amorphous solids have been constructed using a Metropolis Monte Carlo procedure. Relaxation of the cells and prediction of infrared spectra have been carried out at density functional theory level.Funds have been provided for this research from the Spanish MINECO, Project FIS2013-48087-C2-1-P and FIS2013-48087-C2-2-P. G.M. acknowledges MINECO PhD grant BES-2014-069355. We are grateful to M. A. Moreno, J. Rodriguez, and I. Tanarro for technical help and to V. J. Herrero and I. Tanarro for discussions and manuscript preparation.Molpeceres, G.; Satorre, MÁ.; Ortigoso, J.; Millán Verdú, C.; Escribano, R.; Mate, B. (2016). OPTICAL CONSTANTS AND BAND STRENGTHS OF CH4:C2H6 ICES IN THE NEAR- AND MID-INFRARED. The Astrophysical Journal. 825(2). https://doi.org/10.3847/0004-637X/825/2/156S825

Electronic control of the spin-wave damping in a magnetic insulator

It is demonstrated that the decay time of spin-wave modes existing in a magnetic insulator can be reduced or enhanced by injecting an in-plane dc current, $I_\text{dc}$, in an adjacent normal metal with strong spin-orbit interaction. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of $I_\text{dc}$ in a 5~$\mu$m diameter YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope (MRFM). Complete compensation of the damping of the fundamental mode is obtained for a current density of $\sim 3 \cdot 10^{11}\text{A.m}^{-2}$, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime.Comment: 6 pages 4 figure

Densities, infrared band strengths, and optical constants of solid methanol

[EN] Contact. The increasing capabilities of space missions like the James Webb Space Telescope or ground-based observatories like the European Extremely Large Telescope demand high quality laboratory data of species in astrophysical conditions for the interpretation of their findings. Aims. We provide new physical and spectroscopic data of solid methanol that will help to identify this species in astronomical environments. Methods. Ices were grown by vapour deposition in high vacuum chambers. Densities were measured via a cryogenic quartz crystal microbalance and laser interferometry. Absorbance infrared spectra of methanol ices of different thickness were recorded to obtain optical constants using an iterative minimization procedure. Infrared band strengths were determined from infrared spectra and ice densities. Results. Solid methanol densities measured at eight temperatures vary between 0.64 g cm(-3) at 20 K and 0.84 g cm(-3 )at 130 K. The visible refractive index at 633 nm grows from 1.26 to 1.35 in that temperature range. New infrared optical constants and band strengths are given from 650 to 5000 cm(-1) (15.4-2.0 mu m) at the same eight temperatures. The study was made on ices directly grown at the indicated temperatures, and amorphous and crystalline phases have been recognized. Our optical constants differ from those previously reported in the literature for an ice grown at 10 K and subsequently warmed. The disagreement is due to different ice morphologies. The new infrared band strengths agree with previous literature data when the correct densities are considered.Funds have been provided for this research by the Spanish MINECO, Project FIS2016-77726-C3-1-P and FIS2016-77726-C3-3-P. German Molpeceres acknowledges MINECO PhD grant BES-2014-069355. We are grateful to R. Escribano for helpful discussions. Our skillful technicians C. Santonja, M. A. Moreno, and J. Rodriguez are also gratefully acknowledged.Luna Molina, R.; Molpeceres, G.; Ortigoso, J.; Satorre, MÁ.; Domingo Beltran, M.; Maté, B. (2018). Densities, infrared band strengths, and optical constants of solid methanol. Astronomy and Astrophysics. 617:1-9. https://doi.org/10.1051/0004-6361/201833463S19617Boogert, A. C. A., Pontoppidan, K. M., Knez, C., Lahuis, F., Kessler‐Silacci, J., van Dishoeck, E. F., … Stapelfeldt, K. R. (2008). The c2dSpitzerSpectroscopic Survey of Ices around Low‐Mass Young Stellar Objects. I. H2O and the 5–8 μm Bands1,2. The Astrophysical Journal, 678(2), 985-1004. doi:10.1086/533425Boogert, A. C. A., Gerakines, P. A., & Whittet, D. C. B. (2015). Observations of the Icy Universe. Annual Review of Astronomy and Astrophysics, 53(1), 541-581. doi:10.1146/annurev-astro-082214-122348Bossa, J.-B., Maté, B., Fransen, C., Cazaux, S., Pilling, S., Rocha, W. R. M., … Linnartz, H. (2015). POROSITY AND BAND-STRENGTH MEASUREMENTS OF MULTI-PHASE COMPOSITE ICES. The Astrophysical Journal, 814(1), 47. doi:10.1088/0004-637x/814/1/47Bottinelli, S., Boogert, A. C. A., Bouwman, J., Beckwith, M., van Dishoeck, E. F., Öberg, K. I., … Lahuis, F. (2010). THE c2dSPITZERSPECTROSCOPIC SURVEY OF ICES AROUND LOW-MASS YOUNG STELLAR OBJECTS. IV. NH3AND CH3OH. The Astrophysical Journal, 718(2), 1100-1117. doi:10.1088/0004-637x/718/2/1100Bouilloud, M., Fray, N., Bénilan, Y., Cottin, H., Gazeau, M.-C., & Jolly, A. (2015). Bibliographic review and new measurements of the infrared band strengths of pure molecules at 25 K: H2O, CO2, CO, CH4, NH3, CH3OH, HCOOH and H2CO. Monthly Notices of the Royal Astronomical Society, 451(2), 2145-2160. doi:10.1093/mnras/stv1021Cazaux, S., Bossa, J.-B., Linnartz, H., & Tielens, A. G. G. M. (2014). Pore evolution in interstellar ice analogues. Astronomy & Astrophysics, 573, A16. doi:10.1051/0004-6361/201424466Dohnálek, Z., Kimmel, G. A., Ayotte, P., Smith, R. S., & Kay, B. D. (2003). The deposition angle-dependent density of amorphous solid water films. The Journal of Chemical Physics, 118(1), 364-372. doi:10.1063/1.1525805Drabek-Maunder E., Greaves J., Fraser H. J., Clements D. L., & Alconcel L. N. 2017, Int. J. Astrobiol., DOI: 10.1017/S1473550417000428Gálvez, O., Maté, B., Martín-Llorente, B., Herrero, V. J., & Escribano, R. (2009). Phases of Solid Methanol. The Journal of Physical Chemistry A, 113(14), 3321-3329. doi:10.1021/jp810239rGerakines, P. A., Bray, J. J., Davis, A., & Richey, C. R. (2005). The Strengths of Near‐Infrared Absorption Features Relevant to Interstellar and Planetary Ices. The Astrophysical Journal, 620(2), 1140-1150. doi:10.1086/427166Hodyss, R., Parkinson, C. D., Johnson, P. V., Stern, J. V., Goguen, J. D., Yung, Y. L., & Kanik, I. (2009). Methanol on Enceladus. Geophysical Research Letters, 36(17). doi:10.1029/2009gl039336Hudgins, D. M., Sandford, S. A., Allamandola, L. J., & Tielens, A. G. G. M. (1993). Mid- and far-infrared spectroscopy of ices - Optical constants and integrated absorbances. The Astrophysical Journal Supplement Series, 86, 713. doi:10.1086/191796Hudson, R. L., Ferrante, R. F., & Moore, M. H. (2014). Infrared spectra and optical constants of astronomical ices: I. Amorphous and crystalline acetylene. Icarus, 228, 276-287. doi:10.1016/j.icarus.2013.08.029Ioppolo, S., van Boheemen, Y., Cuppen, H. M., van Dishoeck, E. F., & Linnartz, H. (2011). Surface formation of CO2 ice at low temperatures. Monthly Notices of the Royal Astronomical Society, 413(3), 2281-2287. doi:10.1111/j.1365-2966.2011.18306.xIsokoski, K., Bossa, J.-B., Triemstra, T., & Linnartz, H. (2014). Porosity and thermal collapse measurements of H2O, CH3OH, CO2, and H2O:CO2 ices. Physical Chemistry Chemical Physics, 16(8), 3456. doi:10.1039/c3cp54481hMaté, B., Gálvez, Ó., Herrero, V. J., & Escribano, R. (2008). INFRARED SPECTRA AND THERMODYNAMIC PROPERTIES OF CO2/METHANOL ICES. The Astrophysical Journal, 690(1), 486-495. doi:10.1088/0004-637x/690/1/486Merlin, F., Quirico, E., Barucci, M. A., & de Bergh, C. (2012). Methanol ice on the surface of minor bodies in the solar system. Astronomy & Astrophysics, 544, A20. doi:10.1051/0004-6361/201219181Molpeceres, G., Satorre, M. A., Ortigoso, J., Millán, C., Escribano, R., & Maté, B. (2016). OPTICAL CONSTANTS AND BAND STRENGTHS OF CH4:C2H6ICES IN THE NEAR- AND MID-INFRARED. The Astrophysical Journal, 825(2), 156. doi:10.3847/0004-637x/825/2/156Öberg, K. I. (2016). Photochemistry and Astrochemistry: Photochemical Pathways to Interstellar Complex Organic Molecules. Chemical Reviews, 116(17), 9631-9663. doi:10.1021/acs.chemrev.5b00694Pontoppidan, K. M., Dartois, E., van Dishoeck, E. F., Thi, W.-F., & d’ Hendecourt, L. (2003). Detection of abundant solid methanol toward young low mass stars. Astronomy & Astrophysics, 404(1), L17-L20. doi:10.1051/0004-6361:20030617Sandford, S. A., & Allamandola, L. J. (1993). Condensation and vaporization studies of CH3OH and NH3 ices: Major implications for astrochemistry. The Astrophysical Journal, 417, 815. doi:10.1086/173362Satorre, M. Á., Domingo, M., Millán, C., Luna, R., Vilaplana, R., & Santonja, C. (2008). Density of , and ices at different temperatures of deposition. Planetary and Space Science, 56(13), 1748-1752. doi:10.1016/j.pss.2008.07.015Satorre, M. Á., Leliwa-Kopystynski, J., Santonja, C., & Luna, R. (2013). Refractive index and density of ammonia ice at different temperatures of deposition. Icarus, 225(1), 703-708. doi:10.1016/j.icarus.2013.04.023Satorre, M. Á., Millán, C., Molpeceres, G., Luna, R., Maté, B., Domingo, M., … Santonja, C. (2017). Densities and refractive indices of ethane and ethylene at astrophysically relevant temperatures. Icarus, 296, 179-182. doi:10.1016/j.icarus.2017.05.005Sauerbrey, G. (1959). Verwendung von Schwingquarzen zur W�gung d�nner Schichten und zur Mikrow�gung. 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Soda-lime glass as biocompatible material to fabricate capillary-model devices by laser technologies

Microfluidic devices have been widely developed in the last decades because of the huge number of fields where they can be applied. Among all the different fabrication techniques available, laser direct writing stands out since it is a fast, accurate, versatile and non-contact method. It is particularly well-suited when working with glass, a robust and cost-efficient material. These laser advantages allow the direct fabrication of not only high quality single microchannel devices but also complex and bifurcated structures. This work establishes a roadmap for manufacturing capillary-model devices with good biocompability in soda-lime glass substrates with pulsed lasers operating in the nanosecond, picosecond and femtosecond temporal range. We determine the optimal laser parameters required for fabricating channels with a diameter:depth rate of 2:1, keeping a semi-circular section. The presence of tin doping (∼2%) in the soda-lime glass is shown to enable the fabrication with nanosecond pulses, and to improve the quality of the channels, reducing the cracking at the sides, when picosecond or femtosecond pulses were used. On the other hand, two regimes of surface roughness are found: a low roughness regime for channels fabricated with nanosecond lasers and a high roughness regime for those fabricated with pico and femtosecond lasers. Human umbilical vein endothelial cells (HUVEC) are employed for cell culturing for evaluating the biocompatibility of the channels. Structures manufactured with the nanosecond laser resulted more suitable in terms of cell adhesion than those fabricated with the picosecond and femtosecond lasers, due to the different surface roughness regimes obtained. In order to increase the biocompatibility of the channels fabricated with pico and femtosecond lasers and to improve the cell growth, a controlled post-thermal treatment is carried out for smoothing the surface

Análisis de Tensiones Residuales Inducidas en Aleaciones Metálicas por Tratamientos Superficiales mediante Ondas de Choque Generadas por Láser

En el presente artículo se plantea un estudio sobre la medida de tensiones residuales mediante el método del taladro en banda extensométrica (o agujero ciego) aplicado en probetas de aluminio 2024-T351, previamente tratadas superficialmente mediante laser shock processing (método de tratamiento superficial por ondas de choque generadas por láser, conocido como LSP). Finalmente, se realiza una comparación entre los resultados experimentales obtenidos al medir las tensiones residuales obtenidas en probetas tratadas mediante LSP y los valores obtenidos mediante un modelo de simulación

Analysis by Finite Element Calculations of Light Scattering in Laser-textured AZO Films for PV thin-film Solar Cells

In the thin-film photovoltaic industry, to achieve a high light scattering in one or more of the cell interfaces is one of the strategies that allow an enhancement of light absorption inside the cell and, therefore, a better device behavior and efficiency. Although chemical etching is the standard method to texture surfaces for that scattering improvement, laser light has shown as a new way for texturizing different materials, maintaining a good control of the final topography with a unique, clean, and quite precise process. In this work AZO films with different texture parameters are fabricated. The typical parameters used to characterize them, as the root mean square roughness or the haze factor, are discussed and, for deeper understanding of the scattering mechanisms, the light behavior in the films is simulated using a finite element method code. This method gives information about the light intensity in each point of the system, allowing the precise characterization of the scattering behavior near the film surface, and it can be used as well to calculate a simulated haze factor that can be compared with experimental measurements. A discussion of the validation of the numerical code, based in a comprehensive comparison with experimental data is include

UV laser-induced high resolution cleaving of Si wafers for micro-nano devices and polymeric waveguide characterization

In this work we propose a method for cleaving silicon-based photonic chips by using a laser based micromachining system, consisting of a ND:YVO4laser emitting at 355 nm in nanosecond pulse regime and a micropositioning system. The laser makes grooved marks placed at the desired locations and directions where cleaves have to be initiated, and after several processing steps, a crack appears and propagate along the crystallographic planes of the silicon wafer. This allows cleavage of the chips automatically and with high positioning accuracy, and provides polished vertical facets with better quality than the obtained with other cleaving process, which eases the optical characterization of photonic devices. This method has been found to be particularly useful when cleaving small-sized chips, where manual cleaving is hard to perform; and also for polymeric waveguides, whose facets get damaged or even destroyed with polishing or manual cleaving processing. Influence of length of the grooved line and speed of processing is studied for a variety of silicon chips. An application for cleaving and characterizing sol–gel waveguides is presented. The total amount of light coupled is higher than when using any other procedure