Laser Spot Scanning Research Articles

Influence of laser spot scanning speed on micro-polishing of metallic surface using UV nanosecond pulse laser

During laser micro-polishing of the metallic surface, it is very important to choose the optimal laser energy density. The optimal laser energy density is merely related to the laser spot scanning speed while the spot size and the irradiated laser energy are rated. In this paper, during micro-polishing on the metallic surface by using UV nanosecond pulse laser, the influence of laser spot scanning speed on the polishing effect was investigated in terms of the relationship with the laser energy density. The experimental and analytical considerations were shown that there is the optimal scanning speed of laser spot for the best laser micro-polishing effect when the laser energy density on the workpiece surface was rated. In addition, the optimal process parameters for the laser micro-polishing of Ti and Ni metallic surfaces were obtained and the laser micro-polishing experiments on those metallic surfaces were conducted. For Ti and Ni metallic surfaces, the surface roughness improvements of up to 56% and 52% were, respectively, obtained.

Laser direct-writing electrode for rapid customization of a photodetector.

The interdigital Ag electrode is fabricated via a simple and fast approach called laser direct writing (LDW). The morphology and conductivity of electrode fingers are investigated systematically under different experimental parameters, including the laser spot size, laser power, and scanning speed. "Dose" describes the combined influence of these experimental parameters. It is found that overdose results in net-shape and dot-shape hollows in the middle of an Ag line due to the sintering degree and complex flow dynamics, which reduced the conductivity of the Ag lines. Based on the printed Ag electrodes with the best conductivity, a photodetector is customized further, which can detect the offset of the line-shape laser easily. Moreover, to the best of our knowledge, this is the first time the printed Ag electrodes are applied to photodetectors, which can be highly valuable for developing all-printed electronic devices by LDW in the future.

Laser induced nano-patterning with atomic-scale thickness on an InAs/GaAs surface

Nano-patterned substrates fabricated by different techniques have been widely applied in high performance semiconductor devices. For the influence of surface morphology on semiconductor electronic properties and epitaxy growth, there is an increasing interest to realize atomic-scale surface modification by a simple and effective method. In this study, laser induced nano-patterning with atomic-scale thickness on an InAs/GaAs surface was studied in both atmosphere and vacuum environments. Periodic nano-grooves with an average depth of 1 to 2 atomic layers were fabricated by focused laser spot scanning in the air. The depth and width of nano-grooves increase with the laser energy intensity. The result of nano-patterning is attributed to atom desorption stimulated by photon-induced electronic excitation. To explore the situation in the vacuum, in situ two-beam laser interference was applied during InAs/GaAs sample MBE growth. Periodic InGaAs nano-islands were fabricated, which show significant influence on subsequent crystal growth. The formation of ordered InAs quantum dots agreeing with the atomic layer nano-pattern demonstrates the potential application of the technique in site-controlled quantum dot growth.

A New Method for Production of Double-Curvature Dome-Shaped Part: Statistical Analysis of the Effects of Process Parameters on the Radius of Curvature of Obtained Dome Shape

A New Method for Production of Double-Curvature Dome-Shaped Part: Statistical Analysis of the Effects of Process Parameters on the Radius of Curvature of Obtained Dome Shape

Simple and Fast Patterning Process by Laser Direct Writing for Perovskite Quantum Dots

AbstractFor the application of quantum dots (QDs) on next‐generation displays, it is of significant importance to improve QDs patterning technology. Here, this paper reports a simple and fast approach of perovskite QDs patterning based on laser direct writing (LDW). It is a mask‐free and programmable method, including three steps: spin‐coating perovskite QDs, laser writing, and solvent washing. The LDW patterning on QDs relies on the removal of surfactant around the QDs by laser scanning. Macroscopic QD patterns are composed of many microscale QD lines formed via laser scanning. The width and morphology of QD lines can be controlled by varying LDW parameters, including the laser spot size, scanning speed, and laser energy, which also leads to the variation of QDs brightness. Moreover, a large‐scale (100 mm × 100 mm) patterning is demonstrated by LDW, which implies its great potential for large area display application.

Parameters influence of laser forming on shaped surface by soft computing technique

Shaped surface modeling by laser forming process needs many irradiations along surface paths with different parameters of heating. This surface requires thickening and bending in order to get required shapes. In this study was attempted to analyze the process parameters influence on the bending and thickening of the shaped surface by laser. The used inputs were circular and radial laser scan, laser spot diameter, laser power and scan speed. Adaptive neuro-fuzzy inference system (ANFIS) and variable selection procedure was used in order to determine the parameters influence on the bending and thickening of the shaped surface. The selection procedure was done to obtain the found the process parameters which has the highest influence on the bending and thickening of the shaped surface. The method can produce results to simplify the shaped surface forming.

Effect of laser scanning speed on geometrical features of Nd:YAG laser machined holes in thin silicon nitride substrate

0.5mm thick Silicon nitride (Si3N4) substrates with MgO-Y2O3 additives were employed for hole machining study with a Nd:YAG two-dimensional laser machining (cutting) system. The effects of laser scanning speed on features of the machined holes such as hole diameter, hole circularity, taper angle, heat affected zone (HAZ), recast layer, and micro-cracks were studied. The results show that the diameters at the front side are larger than the back side for all holes machined at different spot scanning speed. The taper angle of the machined holes decreases, while the hole circularity increases with the increase of the spot scanning speed. In addition, the heat-affected-zone (HAZ) was observed clearly around the back side of drilled holes, whose area decreases with the increase of the laser spot scanning speed. The result shows that the HAZ is the largest when the laser scanning speed is 20mm/min. Nevertheless, the machined hole did not completely cross through the thickness of the substrate when the laser scanning speed was 60mm/min. To obtain holes with relatively good quality, laser scanning speed should be controlled between 30mm/min and 50mm/min.

In situ Analysis of Mg Isotopic Compositions of Basalt Glasses by Femtosecond Laser Ablation Multi-collector Inductively Coupled Plasma Mass Spectrometry

Abstract A method was developed for the in situ analysis of magnesium isotopes by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (fsLA-MC-ICP-MS). Concentration matching experiment revealed that the Mg isotopic composition could be measured accurately when Mg concentration difference between sample and standard were in the range of 0.4–3.0. The Mg isotopic composition was affected by the femtosecond laser conditions, including laser spot size and scanning speed, due to mass discrimination changing which was caused by different mass loading into mass spectrometer. The amount of ablated aerosol was correlated with laser frequency, laser ablation spot size, and scanning speed. However, the laser energy density showed negligible effect on the accuracy of Mg isotope measurement due to the high energy output of femtosecond laser which was higher than the ablation threshold. To obtain reliable Mg isotopic compositions, the laser ablation spot size, laser frequency and scanning speed should be consistent during one analytical section and the difference of Mg concentration between standard and samples should be in 3 times. The results of two reference materials agreed well with the published values within 2 s analytical uncertainties. The developed method is simple, reliable and accurate, and can be used for the Mg isotope analysis of volcanic glasses and silicate minerals.

Influence of laser ablation parameters on trueness of imaging

Influence of laser ablation conditions on limit of detection, spatial resolution and time of analysis was studied for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) applied to elemental mapping. Laser repetition rate and laser fluence were investigated in tapeworm thin section to attain optimum ablation rate, yielding appropriately low detection limit which complies with elemental contents in the tissue. Effect of combinations of laser spot size and scan speed on relative broadening (Δwrel) of image of the ablated pattern (line) was investigated with the aim to quantify the trueness of imaging. Ink lines printed on paper were employed for the study of influence of spot size and scan speed on limit of detection, relative broadening of elemental image and duration of elemental mapping. An uneven distribution of copper in a printed line (coffee stain effect) was observed. The Δwrel is strongly reduced (down to 2%) at low scan speed (10μms−1) and laser spot diameter of 10μm but resulting in unacceptably long time of mapping (up to 3000min). Finally, tapeworm thin-section elemental maps (4mm×5mm) were obtained at the laser spot diameter of 65μm and the scan speed of 65μms−1 within 100min. A dissimilar lateral distribution of Pb was observed in comparison with that of Cu or Zn due to different pathways of element uptake.

Study on an actuator with giant magnetostrictive materials for driving galvanometer in selective laser sintering precisely

As a non-traditional machining in advanced manufacturing technology, selective laser sintering technology can quickly realise manufacturing of the workpiece which shape is very complicated without mechanical processing equipment. However, this technology has gradually shown some problems such as moulding parts with higher surface roughness and lower accuracy which limit its application in the field of precise machining. To solve these problems, in this paper, it makes full use of the excellent performance of giant magnetostrictive materials and proposes that using giant magnetostrictive actuator in driving galvanometer for selective laser sintering. Based on the analysis of magnetostrictive effect mechanism of giant magnetostrictive materials, according to the operating features of galvanometer, a giant magnetostrictive actuator used to drive galvanometer precisely is designed. Its working theory model which can describe the relationship between elongation and working current is established. In addition, working performances of the giant magnetostrictive actuator are studied through a series of experiment. The experiment results show that linear range of the actuator is 4.26 KA/m14.2 KA/m approximately and the first resonance frequency is about 380 HZ. The research results may provide a new method to realise high precision scanning of laser spot and open up a new application field for giant magnetostrictive materials.

Lateral resolution improvement of laser-scanning imaging for nano defects detection

Abstract Demand for higher efficiency in the semiconductor manufacturing industry is continually increasing. In particular, nano defects measurement on patterned or bare Si semiconductor wafer surfaces is an important quality control factor for realizing high productivity and reliability of semiconductor device fabrication. Optical methods and electron beam methods are conventionally used for the inspection of semiconductor wafers. Because they are nondestructive and suitable for high-throughput inspection, optical methods are preferable to electron beam methods such as scanning electron microscopy, transmission electron microscopy, and so on. However, optical methods generally have an essential disadvantage about lateral spatial resolution than electron beam methods, because of the diffraction limit depending on the optical wavelength. In this research, we aim to develop a novel laser-scanning imaging method that can be applied to nano-/micro manufacturing processes such as semiconductor wafer surface inspection to allow lateral spatial super-resolution imaging with resolution beyond the diffraction limit. In our proposed method, instead of detecting the light intensity value from the beam spot on the inspection surface, the light intensity distribution, which is formed with infinity corrected optical system, coming from the beam spot on the inspection surface is detected. In addition, nano scale shifts in the beam spot are applied for laser spot scanning using a conventional laser-scanning method in which the spots are shifted at about a 100 nm pitch. By detecting multiple light intensity distributions due to the nano scale shifts, a super-resolution image reconstruction with resolution beyond the diffraction limit can be expected. In order to verify the feasibility of the proposed method, several numerical simulations were carried out.

Four-Channel Current-Biased Kinetic Inductance Detectors Using MgB $$_2$$ 2 Nanowires for Sensing Pulsed Laser Irradiation

We recently proposed the idea of a novel sort of superconducting detector, i.e., a current-biased kinetic inductance detector (CB-KID). This detector is different from a current-biased transition edge detector studied previously, and is able to sense a change in kinetic inductance $$L_k$$ given by $$L_{k} = \Lambda _{k}l/S = m_{s}l/n_{s}{q_{s}}^{2}S$$ ( $$\Lambda _{k}$$ ; kinetic inductivity, $$m_s$$ ; mass of Cooper pair, $$n_s$$ ; density of Cooper pairs, $$q_s$$ ; charge of Cooper pair, $$l$$ ; length of device, $$S$$ ; cross sectional area) under a constant dc bias current $$I_b$$ . In the present work, we first extend this idea to construct a multi-channel CB-KIDs array made of 200-nm-thick MgB $$_2$$ thin-film meanderline with 3- $$\upmu $$ m thin wire. We succeeded in observing clear signals for imaging from the four-channel CB-KIDs at 4 K by irradiating focused pulsed laser. A scanning laser spot can be achieved by an XYZ piezo-driven stage and an optical fiber with an aspheric focused lens. We can see typical signals from all 4 channels at 4 K, and obtain the positional dependence of the signal as the contour in XY plane. Our CB-KIDs can be used as neutron detectors by utilizing energy released from a nuclear reaction between $$^{10}$$ B and cold neutron.

Current-Biased Kinetic Inductance Detector Using $ \hbox{MgB}_{2}$ Nanowires for Detecting Neutrons

We propose a current-biased kinetic inductance detector (CB-KID). This detector senses a change in kinetic inductance under a dc bias current, in contrast to a current-biased transition edge detector, reported previously, which probes the transient change in the bias current at the transition edge. Our CB-KID consists of a 200-nm-thick thin-film meander line with 3- wire. It is operated at 4 K. A scanning laser spot can be achieved by an XYZ piezo-driven stage and an optical fiber with an aspheric focused lens. We succeeded in observing a signal image in the contour at 4 K. The magnitude of the signal should be proportional to the number of quasi-particles excited by the laser. Because our CB-KID has a typical signal of 3-ns pulse width and can operate at 4 K, it will be possible to assemble a large-scale array of neutron detectors with single flux quantum readout circuits.

Lasersonic® LIFT Process for Large Area Digital Printing

The currently used digital printing methods e.g. Inkjet or Xerography are very costly on an industrial scale, because they use expensive consumables, specific inks and specially-coated substrates for the printing process. The laser-induced forward transfer of inks from a donor ribbon or roller to substrates allows for the use of inexpensive inks and paper as they are commonly used in today’s industrial rotogravure or offset printing. The challenge of this approach is to develop a fast direct laser writing unit which can cover an area of more than 1 m/min with a screen resolution of 300 dpi to 600 dpi and which allows for laser spot pointing accuracy of less than 4 μm and for a fine (8 bit) reproduction of each grey tone value of the printed image pixels. Due to the large area and the desired high printing speed, the laser power (mean) needs to be within a range of a few hundred Watts. At 20 to 25 MHz modulation rate of the high power laser beam and at a laser spot scanning speed of 800 to 2116 m/s over a scan field length of 530 mm, we demonstrated reproducible printing of commonly used, water-based environment-friendly and inexpensive inks.

Influence of Process Parameters on Temperature Field in Laser Remelting Coating Prepared by Plasma Spraying on Titanium Alloy Surface

In order to research the effect of process parameters on temperature field evolution in laser remelting coating prepared by plasma spraying on titanium alloy surface，the finite element model of laser multi-tracks remelting temperature field was established based on ANSYS, and remelting temperature field was analyzed. The analysis results show that: under certain scanning velocity and laser spot diameter, too small laser power can't achieve metallurgical combination between coating and substrate; the effect on temperature field of scanning velocity was smaller than laser power; the influence on molten pool center temperature and remelting width of spot diameter is bigger; preheating coating and substrate can be effectively balance remelting process temperature field, thereby reducing the thermal stress and coating cracks appear chance.Through the calculation model can master the evolution of the temperature of lasre remelting process and can provide the theory basis for process parameter selection and optimization.

Parametric study on bending and thickening in laser forming of a bowl shaped surface

Shaping a circular sheet into a bowl requires in-plane thickening as well as out-of-plane bending. Combinations of radial and circular laser scan paths can make that. In this work, the effects of various process parameters, viz. laser spot diameter, laser power and scan speed, on the in-plane and out-of-plane forming of stainless steel circular blanks were studied for various circular and radial scan schemes. Taguchi method was used to plan the experimental runs. Both bending angle and thickness increment for circular and radial scan schemes, respectively, were found to increase with reducing laser beam diameter and scan speed, and increasing laser power. The experimental results were corroborated with the predictions by simplified analytical models. Further, the bending angle was found to increase with increasing radius of the circular scan path. Increase in the number or in the length of radial scan lines increased the thickness increment and the bending angle, induced due to the resultant shrinkage in the periphery of the blanks. It was found that the combination of radial and circular scan schemes works better for achieving higher bending angle with smaller coefficient of variation, which gives a measure of wrinkling in the formed blanks.

Observation of meander pattern in signals from superconducting MgB2 detector by scanning pulsed laser imaging

Superconducting MgB2 meander detector has been imaged by scanning a spot of 1.5-μm focused pulsed laser. The superconducting detector using high-quality 10B-enriched MgB2 thin films at higher operating temperatures has been fabricated to utilize a resistance change induced by the nuclear energy of 10B and neutron. The MgB2 detector consists of a 200-nm-thick MgB2 thin-film meander line, a 300-nm-thick SiO protective layer, and 150-nm-thick Nb electrodes with 1-μm MgB2 wires. The devices were placed in a 4K refrigerator to control at a certain temperature below Tc. A scanning laser spot can be used by the combination of the XYZ piezo-drive stage and an optical fibre with an aspheric focused lens. The measurement system is fully controlled by LabVIEW based software. We succeeded in observing a line-and-space image of a meandering pattern by analysing response signals.

A two-step nanosecond laser surface texturing process with smooth surface finish

Surface texturing (for example, producing micro dimples on the surface) of mechanical parts has a great potential to improve the surface tribological properties. Surface texturing through nanosecond laser ablation has many associated advantages and hence has drawn lots of attentions. However, the produced micro dimple bottom (if through laser spot scanning) is often very rough, which may harm the surface tribological properties. In this paper, a two-step laser surface texturing process is proposed and studied, where a relatively high-fluence laser ablation step (which is to create dimples) is followed by a low-fluence laser-induced melting, melted material flow and re-solidification step (which is to smooth the ablated dimple bottom surface). The study shows that the two-step laser surface texturing process can produce dimples with very smooth bottom surfaces. The effects of laser pulse duration and scan speed in Step 2 on the dimple bottom surface morphology and roughness have also been investigated, and some very interesting physical phenomena have been found, which have been rarely reported before in literature. Some hypothesized explanations are given for the observed effects, which require future work to completely understand their underlying mechanisms.

A 2D optomechanical focused laser spot scanner: analysis and experimental results for microstereolithography

This paper proposes and analyzes a 2D optomechanical-focused laser spot scanning system (patent pending) which allows uniform intensity focused spot scanning with high speed and high resolution over a large range of scan. Such scanning is useful where variation of focused spot characteristics affects the performance of applications such as micro-/nano-stereolithography, laser micro-machining, scanning optical tweezers, optical scanning microscopy, and so on. Proposed scanning is achieved by using linear movement of mirrors and lens maintaining the alignment of motion and optical axis of laser. Higher speed and high resolution at the same time are achieved by use of two serial double parallelogram flexural mechanisms with mechatronics developed around them. Optical analysis is carried out to demonstrate effectiveness of the proposed system numerically and is further supported by the experimental results. Additional analysis is carried out to demonstrate robustness of the scanner in the case of small misalignment errors incurred in actual practice. Although the proposed scanner is useful in general in several applications mentioned above, discussion in this paper is focused on microstereolithography.

Temperature field computation for a rotating cylindrical workpiece under laser quenching

Laser quenching is usually performed on a localized area of workpiece surfaces through a certain thermal cycle. As a result, the treated area possesses improved mechanical properties. The quality of the treatment results depends on the selection of laser process parameters, which relies on the knowledge of the temperature field caused by laser heating. This paper reports a model for the evaluation of the laser-induced thermal field. This model assumes a laser beam of uniform intensity and considers the effect of the base temperature on the total temperature. Surface temperatures were computed and compared for different scanning velocities and laser spot sizes. The analyses indicate that the temperature in later-heated areas is much higher than that in earlier-heated areas.