Surface Microprocessing AISI-O1 by Pulsed Nd: YAG Laser

Due to tedious and time-consuming work put into the conventional mold/die microprocessing (about 37% of the total time of the entire mold/die production). Therefore, to improve or enhance the quality of mold/dies at the final step with a less number of trained and skilled operators or decrease the processing time to cut the overall cost dramatically, AISI-O1 cold work steel was micro-processed by Pulsed Nd: YAG laser. The influence of laser processing parameters on the evolution of the correlated surface morphology was investigated by a 3D profilometer, scanning electron microscopy (SEM), and optical microscopy (OM). The results show that when AISI-O1 specimens were irradiated with various parameters, the morphology of AISI-O1 cold work steel was changed correspondingly. It also demonstrates that the different kinds of micro-processed surface morphology could be established successfully to satisfy the later practical requirements for a given laser. Meanwhile, the effect of laser processing parameters on the relevant temperature was described, and the laser microprocessing temperature field was also proposed. It reveals that the influence of laser pulse feed rate was more prominent than that of other parameters on the relevant micro-processed surface morphology

VLSI top-down design based on the separation of hierarchies

Despite the presence of structure, interactions between the three views on VLSI design still lead to lengthy iterations. By separating the hierarchies for the respective views, the interactions are reduced. This separated hierarchy allows top-down design with functional abstractions as exemplified by an experimental self-timed CMOS RISC computer design

Microprocesado de dieléctricos transparentes con pulsos ultracortos. Nuevos esquemas de fabricación de dispositivos fotónicos

[ES]El microprocesado de materiales transparentes con pulsos láser ultracortos ha atraído un creciente interés en la investigación debido a las propiedades únicas de la interacción lásermateria a escalas de tiempo ultracortas. En particular, la posibilidad de producir modificaciones locales controladas del índice de refracción en dieléctricos abrió la puerta a la microfabricación 3D de circuitos fotónicos integrados. En este trabajo se presentan nuevas estrategias para la optimización de las técnicas para la fabricación de guías de ondas ópticas en materiales cristalinos, así como para su caracterización. El uso de estas estrategias es una contribución al desarrollo tecnológico para la fabricación de dispositivos fotónicos complejos. Las estructuras fotónicas fabricadas están basadas en modificaciones Tipo II en cristales, en este contexto distintas técnicas tales como Guías con estrés inducido y Guías depressed cladding fueron utilizadas. En el caso de las guías de onda con estrés inducido, se utilizó un nuevo esquema de fabricación en el que se utilizó un interferómetro para generar dos haces láser de femtosegundos que, enfocados con cierta separación lateral dentro del cristal, producen simultáneamente dos tracks de da con un solo barrido. Por otra parte, se presenta la fabricación de arreglos de guías de onda basados en guías depressed cladding. Los arreglos consisten en guías de ondas hexagonales divergentes entre sí y con distintas separaciones entre ellas a la salida del cristal. Los resultados muestran un rendimiento óptimo de las estructuras fabricadas y sugieren un uso potencial en aplicaciones fotónicas tales como linternas fotónicas, las cuales pueden ser f當ilmente implementadas en otros materiales transparentes. También se presenta un nuevo tipo de estructuras llamadas guías con estructura fotónicas que emulan en forma, a las fibras de cristal fotónico. Estas estructuras presentan características atractivas tales como el hecho de poder manipular su sección transversal a lo largo de la guía de onda introduciendo defectos axiales que permitan la manipulación del haz de una manera controlada y reproducible. Esta importante característica ofrece la posibilidad de fabricar estructuras monolíticas. También se presenta un estudio de las modificaciones inducidas por pulsos de femtosegundos en la cerámica nanoestructurada YSZ, un material prometedor para aplicaciones biomédicas, así como el estudio y la integración de guías de ondas ópticas en este material. Además se caracterizaron propiedades tales como el umbral de ablación y las propiedades ópticas no lineales. Finalmente, se presenta un estudio preliminar de las características temporales pulsos ultracortos al propagarse en distintos tipos de guías de onda.[EN]Ultrafast laser microprocessing of transparent materials has attracted an increasing research interest due to the unique properties of laser-matter interaction at ultrashort time scales. In particular, the possibility to produce controlled local modifications of the refractive index in dielectrics opened the door to the microfabrication of 3D integrated photonic circuits. In this work, new strategies for the optimization of the techniques for the fabrication of optical waveguides in crystalline materials as well as as for their characterization are presented. The use of these strategies is a contribution to the technological development for the fabrication of integrated complex photonic devices. The fabricated photonic structures are based on Type II modifications in crystals and different techniques were used such as Stressed induced waveguides and Depressed cladding waveguides. In the case of stressed induced waveguides a new approach in which an interferometer was used to generate two femtosecond laser beams that, focused with certain lateral separation inside the crystal, produced two simultaneous parallel damage tracks with a single scan. On the other hand, the fabrication of waveguides arrays based on depressed cladding waveguides is presented. The arrays consist of divergent hexagonal waveguides with different separations between the waveguides at the exit of the crystal. The results show a good performance of the fabricated structures and suggest a promising potential use in photonic applications such as photonic lanterns, which can be easily implemented in other transparent materials. It is also presented a novel kind of structures called photonic lattice-like structures which emulates in shape, the photonic crystal fibers. These structures present attractive characteristics such the fact of being able to manipulate the cross section along the waveguide by introducing axial defects which allows beam manipulation in a controlled and reproducible manner. This important characteristic offers the possibility of fabricate monolithic structures. A study of the ultrafast laser-induced modifications of femtoseconds pulses in the nanostructured polycrystalline YSZ ceramic, a very promising material for bio-medical applications, as well as the study and the integration of optical waveguides in this material is also presented. In addition, properties such as the ablation threshold and the nonlinear optical properties were characterized. Finally, a preliminary study of the temporal features of ultrashort pulses propagating to different types of waveguides is presented

A model of a generalized chip structure

Three distinct levels can be distinguished in the design of digital systems: architecture, implementation and realization. Description methods are available at each level assuming that at the realization level components such as nands and nors are used. The introduction of programmable components, such as microprocessors and programmable input/output chips, which now form the basis elements at the realization level, forces to reconsider these description methods

Lasers in the manufacturing of cardiovascular metallic stents: Subtractive and additive processes with a digital tool

Laser beams can be manipulated to achieve different types of interaction mechanisms with metals allowing them to heat, melt, vaporize, or ablate them. Today's laser sources are robust, fast-addressable optoelectronic devices, easily integrated into automation systems along with sophisticated CAD/CAM solutions. Being a photonic digital tool, the laser beam is a fundamental tool for Industry 4.0 and is already widely exploited in the manufacturing of metallic stents. The conventional manufacturing method of laser cutting employs a subtractive method to cut the stent mesh on tubular feedstock. On the other hand, laser beams can be exploited to melt metallic powders to produce stent geometries in a layer-by-layer fashion. The present work provides a short state of the art review concerning the works focusing on the two laser-based manufacturing processes underlining the evolution of the laser source types and used materials. The work provides insights into the future opportunities and challenges that should be faced by the manufacturing research communities in the light of improving the biomedical device performance by exploiting the possibilities provided by the digital tool

Excimer lasers - a novel tool for material fine and microprocessing of glasses

Over the last 15 years, the laser has evolved to become a key technology because of quality, flexibility and cost effectiveness that it can provide. There is scarcely another technology which is more suited for material fme and microprocessing. Industrial laser applications include cutting, drilling, welding, soldering, marking, trimming, coating, alloying, annealing, hardening, lithography, etc. Each year thousands of laser Systems for material processing are installed worldwide. Also into glass industry the laser has found access. Standard laser applications in this field are: cutting quartz tubes; scribing quartz tubes and plates; scribing (drinking) glasses with subsequent thermal blast-off of the upper part; sealing glass casings containing electronic circuits (transponders); marking quartz glasses, bulbs and flasks, dyed or coated drinking glasses, cups, etc.; marking, cutting and drilling diamonds. Despite these examples the number of actual laser applicaüons in the glass industry is limited, and behind each of these applications there are only a few producing Systems. The manufacturers of lasers for material processing do not even accomplish 1 % of their turnover with the glass industry Reasons for the minor role of the laser in this industry can be found in the features of CO₂ and N d : YAG lasers, which are the lasers mainly applied up to now

Local Quantum Dot Tuning on Photonic Crystal Chips

Quantum networks based on InGaAs quantum dots embedded in photonic crystal devices rely on QDs being in resonance with each other and with the cavities they are embedded in. We developed a new technique based on temperature tuning to spectrally align different quantum dots located on the same chip. The technique allows for up to 1.8nm reversible on-chip quantum dot tuning

Parallel laser micromachining based on diffractive optical elements with dispersion compensated femtosecond pulses

We experimentally demonstrate multi-beam high spatial resolution laser micromachining with femtosecond pulses. The effects of chromatic aberrations as well as pulse stretching on the material processed due to diffraction were significantly mitigated by using a suited dispersion compensated module (DCM). This permits to increase the area of processing in a factor 3 in comparison with a conventional setup. Specifically, 52 blind holes have been drilled simultaneously onto a stainless steel sample with a 30 fs laser pulse in a parallel processing configuration

Selective cell response on natural polymer bio-interfaces textured by femtosecond laser

This study reports on the evaluation of laser processed natural polymer-chitosan, which is under consideration as a biointerface used for temporary applications as skin and cartilage substitutes. It is employed for tissue engineering purposes, since it possesses a significant degree of biocompatibility and biodegradability. Chitosan-based thin films were processed by femtosecond laser radiation to enhance the surface properties of the material. Various geometry patterns were produced on polymer surfaces and employed to examine cellular adhesion and orientation. The topography of the modified zones was observed using scanning electron microscopy and confocal microscopy. Test of the material cytotoxicity was performed by evaluating the life/dead cell correlation. The obtained results showed that texturing with femtosecond laser pulses is appropriate method to initiate a predefined cellular response. Formation of surface modifications in the form of foams with an expansion of the material was created under laser irradiation with a number of applied laser pulses from N = 1-5. It is shown that irradiation with N > 5 results in disturbance of microfoam. Material characterization reveals a decrease in water contact angle values after laser irradiation of chitosan films. Consequently, changes in surface roughness of chitosan thin-film surface result in its functionalization. Cultivation of MC3T3 and ATMSC cells show cell orientational migration concerning different surface patterning. The influence of various pulse durations (varying from tau = 30-500 fs) over biofilms surface was examined regarding the evolution of surface morphology. The goal of this study was to define the optimal laser conditions (laser energy, number of applied pulses, and pulse duration) to alter surface wettability properties and porosity to improve material performance. The acquired set of results indicate the way to tune the surface properties to optimize cell-interface interaction