The light field uniformity (LFU) in lithography system is a key factor in defining the resolution across the entire micro/nano structures. In this work, a cost-effective and straightforward method ...based on the focused laser marking on heat-mode resist is proposed for measuring and optimizing the LFU. The factors affecting the LFU are analyzed from the perspectives of optical system aberrations and mechanical assembly error. Subsequently, marking patterns with special structures are designed based on the properties of the heat-mode resist. By analyzing the marked patterns, the LFU of the system is obtained with uniformity coefficient is 42.24%. After optimization achieved by dynamic laser power adjustment, the uniformity coefficient was notably enhanced to 96.11%. This work provides an effective method for measuring and optimizing the LFU in dual-galvanometer laser scanning lithography system.
•Propose a cost-effective method to measure light field uniformity of dual-galvanometer laser scanning lithography.•The factors influencing light field uniformity are analyzed: mainly optical aberrations and mechanical assembly error.•Optimization enhanced light field uniformity from 42.24% to 96.11% and significantly reduced feature size error to 35 nm.
Laser marking has the characteristics of a dry process and has been widely used in many industries. Making more colors on the material would be more applicable; however, it is challenging to ...fabricate green colors through laser heating on titanium (Ti). In this study, a CW (continuous wave) laser with a wavelength of 1064 nm was used to make various colors on the Ti surface. CIE (Commission Internationale de l’Eclairage) color measurement shows that almost green color was achieved. Furthermore, the relationship between laser process parameters and surface temperature is established with an infrared (IR) camera.
•The CIE spectrometer analysis validating colors close to green is available.•Green color has been achieved on Ti by CW laser.•The surface temperature was close to the heating threshold.
Laser marking is one of the main industrial applications of lasers. To mark many materials or to obtain patterns of small dimensions, triggered pulsed solid laser sources are increasingly used ...emitting in the fundamental in the infrared and to which two nonlinear (NL) stages are added to obtain an emission in the UV. The conversion efficiency as well as that of the marking then depends mainly on the peak power of the UV pulses generated. One of the solutions for obtaining a higher peak power is to reduce the duration of the laser pulses. To do this, it is possible to change the architecture of the laser cavity by switching from a Q-Switch operating mode (QS) to a cavity dumped mode (CD). With this architecture it is thus possible to reduce the duration of the pulses by an order of magnitude. This peak power gain is unfortunately achieved at the cost of a very long transient regime, up to a few tens of milliseconds, compared to the classic QS which generally only occurs for the first laser pulse. Unfortunately, laser marking is by nature based on chopped operation for the laser, which corresponds to working permanently in a transient state. Marking with a CD architecture laser is then often full of defects and therefore unacceptable in terms of quality. After a study of the problem specific to the use of a UV source with CD architecture in the context of marking, we propose an original solution to dissociate the chopped regime, specific to marking, from the transient regime of the laser. This solution is based on the use of an RTP (Rubidium Titanyle Phosphate RTiOPO4) electro-optical crystal placed between the laser output and the NL stages. This crystal is driven like a half-wave plate by high voltage square pulses of a duration corresponding to the duration of the marking laser pulse trains. This thus makes it possible to obtain laser operation in a stabilized regime, therefore outside the transient regime, and simultaneously chopped operation characteristic of laser marking. The new operating mode obtained is characterized in detail with the new marking performances which prove to be optimal and compatible with the requirements of a quality marking. In addition to making the CD architecture compatible with laser marking, this solution also makes it possible to adjust the average power, and therefore the energy of the laser pulses to adapt it according to the materials and this without changing the thermal behavior of the laser. Last advantage, by adjusting the extinction voltage applied to the RTP outside the cavity, it is also possible to keep a few milliwatts of the marking laser beam as the aiming beam, with the certainty of perfect alignment with the full power beam.
•Cavity dumped laser have longer transient time than conventional Q-switch laser.•Cavity dumped architecture laser can't be easily used in chopped mode.•Use of an external polarization control allows to decorrelate transient mode with transient time of the laser source.•New possibilities for cavity dumped laser in marking applications.
Abstract Laser marking is a critical production process step in most automated production systems. However, some materials such as polyoxymethylene (POM) can be quite challenging to laser to 80 ...kHz.mark, hence the need to develop new laser marking methods. By employing a wide range of marking parameters (marking speed 15–2000 mm/s, laser power from 10 to 100% of 30 W maximum, and frequencies mainly from 1 to 400 kHz) and characterization techniques, and with the use of marker inks as masking agents successful laser marking POM is demonstrated irrespective of its presentation (white or black coloured) using a new method akin to Laser Polymer Tattooing (LPT), and without prior modification of polymer composition (by addition of laser marking additives). Results indicate laser marking of acceptable quality can be obtained with black POM at marking speeds up to 2000 mm/s. For white POM, markings of acceptable quality were obtained at markings speeds up to 100 mm/s, with laser power ≥ 80% (of 30 W maximum), and with frequencies in the range of 20 kHz with the help of a masking agent. The effects of the laser marking parameters on marking quality and the changes induced in the material are presented and discussed. The wide range of marking parameters employed enabled the determination of feasible marking parameters for the development of a lean manufacturing-based automatic and self-evaluating and improving laser marking system with minimal human intervention.
•A color stability evaluation method for all parameter spaces without proposing reference points is proposed.•Direct laser color marking of barcodes colorized on Ti6Al4V and SS 304 surfaces are ...carried out.•The mechanism of color stability of laser color marking is investigated.
The main problems of laser color marking are the reproducibility and stability. For this issue, the color stability of laser marking is investigated by experiments and simulations. A color stability evaluation model is established and turns out to be valid with mean squared error (MSE) of 0.67 and goodness of fit (R2) of 0.88. The direct laser color marking of barcodes on the Ti6Al4V and stainless steel (SS) 304 surfaces are marked by a nanosecond laser, and hence the color stability evaluations are carried out by the MATLAB software. The influence of cell edge, cell area, and scanning speed on the color stability of laser marking is analyzed. The temperature distribution of the laser heating SS surface process is simulated. The results show that the comprehensive effect of the temperature and time makes the color stability fluctuate periodically with the scanning speed. The color with a large relative temperature difference has a low stability, while the color with a small relative temperature difference has a high stability.
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Counterfeiting of the products for healing is as old as trading, and it is difficult to quantify the magnitude of the problem. It is known that substandard and/or falsified (SF) ...medicines are a growing global threat to health, and they cause serious social and economic damage. The EU has a strong legal framework for medicines, it is mandatory to meet the requirements of Directive 2011/62/EU. Serialisation prevents SF medicinal products from entering the legal distribution chain. The present study is an extension of the original idea and aims to develop a laser technology-based method to mark an individual traceable code on the surface of the tablet, which technology can also be used for marking personalized medicines. The method is based on the ablation of the upper layer of a double-layer, differently coloured coating. The 2D code should be formed without harming the functional layer, and anyone with a smartphone integrated with a camera should be able to authenticate these drugs with a suitable application. The present findings confirmed that KrF excimer laser and Ti:sapphire femtosecond laser are efficient and reliable for marking. These should be promising candidates for pharmaceutical companies that would like to have additional protection against drug counterfeiters.
•Mechanical interlocking is the main mechanism for successfully connecting metals and plastics.•The number of burrs in the height range of 10–20 μm is main factor controlling the shear strength.•The ...threshold of the process parameters for the maximum shear strength of the joint is obtained.
The circular array structure is fabricated on the 304 stainless steel surface by fiber laser, and it is connected with the plastic under the condition of heating and pressurizing. The effects of heating temperature, connection pressure and coverage rate on the interfacial strength of the 304 stainless steel and plastics were studied, and the optimum process parameters of heating temperature and bonding pressure are obtained. The results show that the shear force of 304 stainless steel and plastic is the strongest when the heating temperature is 400 C. The strength of the connection joint is enhanced with the increase of the connection pressure, and the shear force of the 304 stainless steel and plastic connection joint is the strongest when the pressure is 70 kN. After laser treatment, the height and quantity of burr in the circular array structure have an important influence on the connection strength between stainless steel and plastic. The number of burrs in the height range of 10–20 μm is defined as Hm, which is main factor controlling the shear strength. When the Hm value corresponding to the burr height of 10–20 μm is less than 14.82%, the metal and plastic damage from the connection joint, and the connection strength increases with the increase of Hm. When the Hm is greater than 14.82%, the connection strength between stainless steel and plastic is more than that fracture strength of the plastic. And the shear force floats between 893N and 962 N, this is consistent with the average shear fracture force of plastics 946 N. The coverage rate of laser processing area has influences on the connection strength and machining efficiency. The results show that the corresponding minimum coverage rate is 38.5% when the stainless steel and plastic connection joint is damaged at the plastic, at which time the shear force is 901 ± 14.18 N.
Laser marking of polymer materials is a technology that is increasingly used in industry. Polypropylene (PP) shows a low ability to absorb electromagnetic radiation in the near-infrared range (λ = ...1064 nm). The paper presents the influence of the surface condition of white-colored polypropylene moldings on the efficiency of their marking with a laser beam. In addition, the operation of the commercial laser marking additive (LMA) Lifolas M 117009 UN, intended to support the process of laser marking of polyolefin surfaces, was verified. The study is an attempt to combine laser operating parameters, material, and geometric properties of PP moldings to obtain the expected quality of graphic symbols. The test samples were made by injection molding method with the use of a specially designed modular injection mold. The molding cavities were prepared with various methods of metal processing, thanks to which obtained moldings differed in surface condition. The marking effects were assessed based on colorimetric tests and digital image analysis. The 0.5 wt% LMA content resulted in obtaining a graphic sign with high contrast in comparison to the background. The gradual increase in the modifier content resulted in a further increase in contrast. These values depended on the degree of surface finish of the samples, and therefore on the roughness parameters. Samples with a rough surface finish showed higher contrast compared to surfaces with a high surface finish. It was also found that for the analyzed moldings, the laser-marking process should be performed with the use of a low head velocity (450-750 mm/s) and a high concentration of the laser beam (0.03-0.05 mm).
In this work, we studied a method of laser-induced coloration of metals, where small-scale spatially periodic structures play a key role in the process of color formation. The formation of such ...structures on a surface of AISI 304 stainless steel was demonstrated for the 1.06µm fiber laser with nanosecond duration of pulses and random (elliptical) polarization. The color of the surface depends on the period, height and orientation of periodic surface structures. Adjustment of the polarization of the laser radiation or change of laser incidence angle can be used to control the orientation of the structures. The formation of markings that change their color under the different viewing angles becomes possible. The potential application of the method is metal product protection against falsification.
•Steel surface coloration was made by small-scale spatially periodic structures.•AFM, SEM and Raman scattering measurements of obtained structures were done.•The surface color depends on the period, height and orientation of structures.•Structures orientation is a function of laser polarization or incident angle.•Formed markings change their color under the different viewing angles.
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