Laser Beam Scanning Method Research Articles

A study on the removal of paint and oxide layer on the steel surface by laser beam scanning method

In this study, a laser cleaning method was developed in order to replace the existing manual work-based technologies. The experimental investigation analyzed the cleaning properties of the paint and the oxide layer on the steel surface according to the laser beam scanning method. Experiments showed that in the cleaning process, the line beam patterns with a moving stage showed differences in heat input depending on the area, and the square area beam patterns obtained with control of a Galvano scanner showed uniform cleaning performance. The results of this study demonstrated that through the prosed laser cleaning technique, oxide layers as well as paint on steel surfaces can be removed with excellent precision, which is expected to be useful in the development of eco-friendly surface cleaning techniques.

Measurement and investigation of mechanical properties of a partial oxide dispersion strengthened Zircaloy-4 tube via an instrumented indentation test

The formation of a partial oxide dispersion strengthened (here denoted as P-ODS) layer on the surface of a Zircaloy-4 (Zry-4) tube is regarded as one of the effective ways to increase the strength of the Zry-4 tube at a bulk scale. This consequently enhances the resistance to ballooning and rupture under accident conditions. In this study, the mechanical properties such as the yield strength of a P-ODS Zry-4 tube at local scale were investigated by micro instrumented indentation testing (IIT). The P-ODS layer was formed on the surface of the Zry-4 tube by a laser beam scanning (LBS) method that uses Y2O3 particles. The IIT was performed at a cross-sectional plane of the P-ODS Zry-4 tube using a spherical indenter. Several regions, including the base Zry-4 tube and P-ODS layer, were considered as indentation points. As a result, the mechanical properties of the P-ODS Zry-4 tube at the local scale were effectively obtained from the IIT. Considerable strength enhancement of the P-ODS layer was observed by comparing with the base Zry-4 tube. Furthermore, the strength enhancement was studied using microstructure-based strengthening models such as Orowan and Hall-Petch to predict the amount of strengthening theoretically. From the suggested strengthening models, the strengthening of the P-ODS layer was effectively investigated, and the results can be useful for both fabricating and simulating the P-ODS Zry-4 tube.

High performance thin-film transistors fabricated on a single crystal Si strip by micro-chevron laser beam scanning method

High performance and uniform thin-film transistors were fabricated on a grain-boundary (GB) free single crystal Si strip for the first time. Here sputter-SiO2 gate insulator was used. Electron mobility μ was 548 cm2 V−1 s−1, subthreshold swing ss was 0.279 V dec−1, and on/off ratio was 2.4 × 107. Variability of ss was only 9.4% but that of μ was 34.2%. Carrier scattering was known to be dominated by GB in conventional polycrystalline Si, but it was dominated by phonon scattering in the GB-free Si strip irrespective of μ value. The μ deviation was shown to be due to crystal orientation variation along channel direction.

Investigation of an interlaced laser beam scanning method for ultrashort pulse laser micromachining applications

Abstract This article investigates picosecond and sub-picosecond laser micromachining of Borofloat®33 glass and provides clear evidence that a simple modification of the laser beam scanning strategy can lead to significant improvement of machining efficiency and hence process throughput. Besides studying the impact of the fundamental laser machining parameters, such as laser fluence, pulse overlap, pulse repetition frequency (PRF), pulse duration and laser spot diameter, on the machined depth, surface roughness and material removal rate (MRR), it also compares the machining results for two different laser beam scanning strategies, called here sequential” method (SM) and “interlaced” method (IM). By changing the scanning strategy from SM to IM, the MRR can be significantly increased because IM allows high-quality machining of the glass at higher PRF values. The experimental results show that this simple, cost-free modification allows the MRR value to be increased by more than 4 times, i.e. from 0.12 mm3/s to 0.53 mm3/s. Moreover, by using a Phantom V2512 high-speed camera, the picosecond laser micromachining process using both SM and IM was filmed. The videos show that SM leads to the accumulation of glass particles within the laser-machined area, whereas in IM the glass material is removed layer by layer which leads to the generation of “cleaner” and deeper areas. The mechanisms associated with these machining improvements are discussed.

Lateral growth of a twin-free Si stripe longer than 1 mm as a result of rotation suppression

Rotation of the crystal orientation of a laterally grown grain in Si thin film was investigated with the micro-chevron laser beam scanning (μCLBS) method. The rate of orientation rotation Rθ was found to be inversely proportional to Si film thickness tSi, and a model to explain the orientation rotation was proposed. The rotation is caused by a 2.2% difference in expansion rate between the top and bottom surfaces of the Si film on solidification. An SiO2 capping film was used to suppress rotation, and as a result, a twin-free (100)-faced single-crystal Si stripe longer than 3 mm was formed. It was found that all sustainably grown grains had Rθ = 0, and all were (100) in the normal direction. This result shows that (100) is the only orientation for stable lateral crystal growth in thin film.

Progressive Micromodulation of Interlayer Coupling in Stacked WS2/WSe2 Heterobilayers Tailored by a Focused Laser Beam.

When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a focused laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The focused laser beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degrees of fluorescence quenching. Systematic studies are carried out to gain an insight into the mechanism involved in the onset of the interlayer coupling in the material. Our method is also successfully extended to a WS2/WS2 homobilayer structure.

Shape-dependent interaction of gold nanoparticles with cultured cells at laser exposure

Laser optoporation of cells by local heating of plasmonic gold nanoparticles (GNPs) was proven as a favorable delivery method of molecules into cells. The optoporation efficiency depends on the laser beam intensity and GNP properties. Here, we evaluate the membrane optoporation in vitro in terms of fluorescent dye permeability under treatment of a multi-pulsed nanosecond 1064 nm laser with a sharply-focused beam. Anisotropic GNPs, such as nanorods and nanostars, were fabricated to achieve the optimal GNP-cell interaction. Nanostars demonstrated highest optoporation efficacy with more than 80% of permeabilized cells within the illuminated area. By contrast to common laser techniques, the laser beam scanning method results in cell optoporation within a controllable programmed in advance irradiated area.

リン酸二水素カリウム単結晶の飽和水溶液中におけるレーザビーム走査による研磨

Potassium dihydrogen phosphate (KDP) is a non-linear optical and water-soluble crystal. However, since KDP is brittle material, it takes a large cost to obtain the surface roughness required in generating harmonics. Therefore, a new polishing method using YAG laser beam is developed and verified the method by experiments in our research work. The method developed in this paper is as follows. A YAG laser beam is focused at an edge of an end face of a single crystal in a saturated solution. The laser beam is scanned along the edge of the end surface. It is possible to polish the scanned surface by the solution of the crystal and the other portions are not removed in a saturated solution. In this paper, the surface of the crystal polished by our laser beam scanning method was compared with that polished by sandpapers. The surface polished by laser beam scanning is smoother than that polished by sandpapers when the both surface roughness were same. The crystallinity of both crystals after polishing were same degree by X-ray diffraction analysis. The second harmonic generation were performed using KDP crystals before polishing, after laser beam polishing and after sandpaper polishing. The intensity of the light from the crystal by the laser beam polishing was the best of these three crystals.

Microstructures of laser bonded SiC ceramics with Zr interlayers

SiC plates were bonded using a laser beam scanning method. As an interlayer material, a Zr sheet 0.4mm in thickness was used. Joining was performed at room temperature in air under atmospheric pressure. The interfacial microstructures along with their atomic compositions of the Zr/SiC reaction zone were analyzed. In the Zr side, diffused Si formed ZrSi2, Zr5Si3Cx, and Zr4Si phases. Carbide transformation was observed (Zr+C→ZrCx) near the Zr/SiC interface. No crystallographic orientation relationship was found in most of the grains; however, a boundary of ZrSi2 [100] parallel to Zr5Si3Cx[011¯1] was found in the observation. In the SiC side, penetrated Zr was found at up to 120μm from the Zr/SiC interface. The diffused Zr formed a silicon-rich metastable phase of ZrSiy (y>3.3).

Structure of Dental Resin-Based Adhesive Materials

This study aimed to show that the polymerization contraction of dental light cured resin-based materials, when it was used as adhesives on hard substrate, produces voids at the material/substrate interface. Two liner/base systems, one glass-ionomer, one restorative composite resins and two compomers were cured using mirror-like glass slide as a compliance-free reference substrate. The adhesive surface was analyzed by atomic force microscopy, and the polymerization contraction of bulk material was tested by laser beam scanning method. Nanoperiodic structure of 3D images, section analysis and roughness characteristics (Ra and Rz)) indicated that polymerization contraction produced voids at the interface. In visible light-cured (VLC) materials, the interface porosity decreased when an irradiation pause was carried out during gelation.

Adhesiveness of dental resin‐based restorative materials investigated with atomic force microscopy

This study aimed to show that the polymerization contraction of dental methacrylate-based materials, when used as adhesives on hard substrate, produces voids at the material-substrate interface. This phenomenology is closely related with the nanoleakage and the sealing ability of these materials. One prime/bond system, three restorative composite resins, and one orthodontic bonding system were cured by using mirror-like glass slides as a compliance-free reference substrate. The adhesive surface was analyzed by atomic force microscopy, and the polymerization contraction of bulk material was tested by laser beam-scanning method. Nanoperiodic structure of three-dimensional (3D) images, section analysis, and roughness characteristics (R(a) and R(z)) indicated that polymerization contraction produced voids at the interface. When the adhesive surface was exposed to oral simulating fluids (water, ethanol, and lactic acid solutions), hydrolytic degradation involved some hundreds of nanometers in depth. In visible light-cured (VLC) materials, the interface porosity decreased when an irradiation pause ( approximately 2 min) was carried out during gelation.

Vibrational Probing Technique for the Nano-CMM based on Optical Radiation Pressure Control

A microprobe system with a micrometer size probe sphere is required to establish the nano-CMM that is a three dimensional coordinate measuring machine with a measuring range of mm and accuracy of nm order. In this paper, the newly developed vibrational probing technique for the microprobe sytem is presented. The principle is based on the single-beam gradient-force optical trap and the forced vibration method. An optically trapped silica particle in air is vibrated using the laser beam scanning method. Frequency response is examined to estimate the radial spring constant of the microprobe system. Fundamental measurements of a micro-step specimen fabricated using a FIB (Focused Ion Beam) process are demonstrated to investigate the position detection sensitivity.

Quantitative Measurement of Liquid and Vapor Fuel Distribution Using a Two-Color Laser-Beam Scanning Method

Quantitative Measurement of Liquid and Vapor Fuel Distribution Using a Two-Color Laser-Beam Scanning Method

Polymerization of dental composite resins using plasma light

Five visible light-cured composite resins used as restoration or adhesive materials in dentistry, were irradiated with high energy plasma light (1300 mW/cm 2), and contraction, rate of contraction, irradiation-induced temperature were analysed. A comparison was carried out with the same materials irradiated with a conventional halogen light (400 mW/cm 2). The exposure to the photoactivating lights was either continuously or sequentially in three or more intervals with 10 min between intervals. Comparing the lengths of exposure of both lights, which induced the same contraction in a given material, it was found that the exposure length to the plasma light was greatly reduced, when compared with the exposure length of the halogen light (1 : 10). Frequently, the final contraction of plasma-irradiated materials was lower, whereas the rate of contraction, as indicated by the linear dimensional variation curves obtained by laser beam scanning method, did not show significant differences between the two lights. The temperature increase induced by plasma light on the material did not exceed the temperature induced by conventional light.

K-1344 ビームスキャニングによる高迎角物体はく離流れのPIV計測(S15-13 翼のはく離)(S15 噴流・はく離流れの計測と制御)

Two-color dual laser beam scanning PIV is applied to the measurements of the wake vortices behind an axisymmetric paraboloid to investigate the flows with separation over the body at high angles of attack. In order to record the image with the limited scattering efficiency of small tracer particles, laser beam scanning method was employed with a 3-CCD color digital video camera. The obtained single frame/multi-exposure color PIV image was decomposed into double frame/single exposure images according to the hue component of the pixel values. The developed technique is shown to provide sufficient velocity vectors in the plane normal to the symmetric axis of the body, with the exception in vortex cores. The agreement obtained between the PIV and flow visualization results is seen to be quite reasonable.

Twinning of a Quartz Plate at Low Temperature Using a Laser Beam

We have previously reported an artificial twinning (x-axis inversion) technique that involves the thermal treatment method and the laser beam scanning method for a rotated Y-cut (RY-cut) quartz plate. The heating temperature for twinning was about 520–540°C using the thermal treatment method. Furthermore, in the laser beam scanning method, a high preheating temperature of about 480°C was necessary to obtain a well-controlled twinning pattern. We present here twinning at low temperature (350°C ∼ room temperature) using the laser beam scanning method. This method can be used the potential to form an arbitrary fine twinning pattern at room temperature. High reproducibility of a fine twinning pattern was obtained at a preheating temperature of 350°C. A relatively good twinning pattern was also obtained by the laser beam scanning method without preheating. It was estimated that the shear strain caused by laser irradiation was of the order of 10-4, for the case there the twinning occurred. The large temperature gradient produced in the plate by laser beam irradiation drastically reduced the treatment temperature.

Analysis and Modeling of Surface Waviness Inspection with Light Reflection, Part 1: Laser Beam Scanning Method

The laser beam scanning method for inspecting a reflective surface has been studied with analytical derivations and numerical modeling. Specular reflection off the surface was assumed and mathematical relations consistent with analytic geometry were used to trace the laser beam and predict its screen projection. It was found that deviation of the screen projection is proportional to the surface slope along the projection direction at the reflecting point and the distance from the point to the screen. The 3-D modeling was validated with 2-D analytical relationship as a special case and was tested with a profiled SMC (sheet molding compound) panel. The screen projections of reflected laser scans off surfaces with typical features of interest are predicted and the effects of waviness orientation are investigated.

Control of twinning of a quartz plate by light beam scanning

We use a laser-beam scanning method to control the artificial twinning method of quartz plate with an arbitrary pattern. Thermal treatment of a quartz plate often causes x-axis inversion (twinning). If the x-axis inversion pattern is artificially controlled, it is possible to fabricate new piezoelectric and/or optical devices. A quartz plate is placed on a movable stage in a vacuum chamber. On the plate surface, a metal film is deposited and the plate is heated at around to 480°C, which is well below the α-β transition temperature of 573°C. A light beam is illuminated on the plate. The metal film on the quartz plate absorbs the light energy and the plate is locally heated. This causes strong mechanical stress and x-axis inversion (twinning) occurs around the illuminated area. As a result, an arbitrary twinning pattern can be fabricated by scanning the light beam.

9733323 Clarification of a three-dimensional diffusion spray mechanism using the multi-impingement-wall spray image analysis using the semiconductor laser beam scanning method Song Fei (Nippon Institute of Technology Graduate School), Kyoko Okamoto, Masaru Ogura (Nippon Institute of Technology), Noboru Tazima (Nippon Institute of Technology)

9733323 Clarification of a three-dimensional diffusion spray mechanism using the multi-impingement-wall spray image analysis using the semiconductor laser beam scanning method Song Fei (Nippon Institute of Technology Graduate School), Kyoko Okamoto, Masaru Ogura (Nippon Institute of Technology), Noboru Tazima (Nippon Institute of Technology)

Measurements of the Particle Size by the Laser-Beam Scanning Method

Measurements of the Particle Size by the Laser-Beam Scanning Method