Line Beam Research Articles

The next generation of light-based driver assistance systems

The headlamps are increasingly becoming an assistance system that supports drivers in avoiding dangerous situations when driving at night. A significant advancement in quality is offered by an adaptive cut-off line and glare-free high beam light that are made possible by the use of a camera system. Hella is continuing to develop further innovative solutions and is now working on adaptive lighting functions on the basis of LED headlamps.

A compact continuous-wave green laser with line beam for laser projection

An efficient and compact continuous-wave green laser with line beam using LBO crystal was developed. The maximum output power was 6.5 W. The optical-to-optical conversion efficiency was as high as 31%. The compact size of the line beam green laser was 2 cm×5 cm×8.8 cm. Reliability and stability of the green laser were evaluated.

Experimental and numerical study of phase mixing of an intense beam

We study, experimentally and numerically, the relaxation of an initially nonuniform intense beam in an alternating-gradient transport line. A nonlinear distribution consisting of five interacting beamlets is created and tracked for longer than seven plasma periods with the help of tomographic phase-space mapping. Emittance growth is initially rapid, but slows down as the nonuniform distribution homogenizes in a few plasma periods. Both growth rates are found to depend on the beam current.

Diffractive Line Beam Shaper

A diffractive laser beam shaper has been proposed as a lossless approach to transfer a Gaussian laser beam into a thin line beam with a uniform distribution along the line direction for scanning material processing or illumination application. With the consideration for the feasibility of fabrication, the optical performance of the diffractive beam shaper with its surface relief quantized at different levels has been analyzed with scalar diffraction theory, which shows that an 8 level solution is sufficient for keeping the uniformity in the line direction while the focusing function in the orthogonal dimension needs to be performed by an extra cylindrical lens.

Light Pipe Line Beam Shaper

A light pipe based laser beam shaper is proposed as a low loss approach to transfer a Gaussian laser beam into a long line beam with uniform distribution along the line direction for the applications of illumination or material processing. A telecentric relay optics has been used for solving the radiometric issues in the wide angle optics. In addition, the length of the light pipe is used as a parameter for manipulating irradiance distribution at the outlet to compensate for the non-uniformity resulting from the partial reflection at the optical interface in the relay optics, so as to achieve a highly uniform line beam at the target plane. The proposed scheme provides an economical and versatile solution for the wide angle beam shaping problem.

Precise control of phase transformation process in lead zirconate titanate thin films by focused line-beam scanning

Phase transformation and grain growth processes of lead zirconate titanate (PZT) thin films have been precisely controlled by using focused line-beam scanning. The authors promoted the lateral crystallization of PZT grains by controlling a nucleation process and increasing the size of single grains to be as large as 40μm in length. Focused line-beam scanning allows for the selective growth and crystallization of large PZT grains on predetermined nucleation sites. The high growth rate of the selected PZT grains was attributed to successive suppression of undesirable nucleation except at predetermined positions when pretreated PZT films were exposed to the focused line beam.

Femtosecond micromachining in transparent bulk materials using an anamorphic lens

A unique anamorphic lens design was applied to a circular 780nm femtosecond laser pulse to transform it into an elliptically shaped beam at focus. This lens was developed to give an alternative method of micromachining bulk transparent materials. The challenge for femtosecond laser processing is to control the nonlinear affect of self-focusing, which can occur when using a fast f-number lens. Once the focused spot is dominated by self-focusing the predicted focused beam becomes a filament inside the bulk, which is an undesirable effect. The anamorphic lens resolves this self-focusing by increasing the numerical aperture (NA) and employing an elliptical beam shape. The anamorphic lens was designed to furnish a 2.5mum by 190mum line at focus. Provided the pulse energy is high enough, transparent bulk material will be damaged with a single femtosecond laser pulse. Damage in this text refers to visual change in the index of refraction as observed under an optical microscope. Using this elliptical shape (or line), grating structures were micro-machined on the surface of SiC bulk transparent substrate. SiC was chosen because it is known for its micromachining difficulty and its crystalline structure. From the lack of self-focusing and using energy that is just above the damage threshold the focused line beam generated from the anamorphic lens grating structures produced a line shape nearly identical to the geometrical approximation. In this paper we discuss a new method of writing gratings (or other types of structures) in bulk transparent materials using a single femtosecond laser pulse. We will investigate the grating structures visually (inspected under an optical microscope) and also by use of an atomic force microscopy (AFM). In addition, we test the grating diffraction efficiency (DE) as a function of grating spacing, d.

Beam tracing description of non-Gaussian wave beams

In experiments involving electron-cyclotron waves, beams with a non-Gaussian amplitude profile can be generated by the launching system or during the propagation in the plasma. The propagation and absorption of non-Gaussian beams is formulated in terms of the beam tracing asymptotic technique. The proper sequence for tracing arbitrary beams has been established, which involves the formulation of the decomposition of arbitrary electric field profiles into Gaussian-Hermite modes, the generalization of the beam width parameter, and the damping of higher-order modes. The effect of the phase-shift of the modes (with respect to the beam axis) is analyzed within beam tracing and included in the description of the beam. As an application, we consider the propagation and absorption of multimode beams in a simplified plasma geometry, where a comparison with an exact solution is possible. Also, the properties of the propagation of a non-Gaussian beam in the transmission line of an EC launching system are analyzed.

Charge Coupled Device Camera–Scintillator System for Two Dimensional Proton Dose Measurements

A two-dimensional dosimeter composed of a charge coupled device (CCD) camera and a scintillating screen has been tested for measuring the dose distributions of therapeutic proton beams in situ. The dosimeter is the main component of the dosimetry system designed for the quality assurance of scanning beams in the course of patient treatments. A thin-wall parallel plate ionization chamber was built as part of the system to scale the beam currents, and a collimator and variable-thickness phantom being the other components. The system has been tested using a 40 MeV proton beam in a nontherapeutic beam line. The light output from the screen was linear within 0.1% at the typical dose rates of 1–2 Gy/min. The depth dose distributions were measured using the CCD camera system, and agreed well with the measurements by a calibrated ionization chamber. The CCD camera was also used to measure the beam intensity distributions produced with a Cu scatterer in the beam line. The comparison with the results of Monte Carlo simulations using MCNPX was useful for validating the code.

Investigation of the effects of nonconventional beam geometries in laser surface treatment of ceramics: Theoretical analysis

Laser surface treatment of ceramics by melting and resolidification generally leads to the formation of fully densified and homogeneous surfaces, with enhanced mechanical and physical properties. A common problem associated with the process is the formation of thermally induced cracks on solidification and cooling. This, however, can be eliminated by controlling the cooling rates and thermal gradients during processing. Such control can be achieved by applying pre- and postheating methods or by scanning the laser beam at relatively slow speeds to modify the thermal shock conditions to which the surface is subjected. The latter technique has been successfully applied to the development of crack-free surfaces in Al2O3-based refractory ceramics. The relatively slow speed, however, limits the practicability of the technique. This article presents a novel theoretical analysis of the effects of various nonconventional beam geometries on cooling rates and, hence, on interaction times and processing speeds, during laser surface treatment of ceramics. Initially, a commercial finite element analysis package was used to simulate the material-beam interaction conditions for various beam geometries, including rectangular, line, triangular, pi, and rhomboid. The cooling rates associated with these beam geometries were assessed and compared with those for the standard circular beam geometry. The model predicted that the rhomboid and pi beam geometries result in lower cooling rates, the line beam geometry in higher cooling rates, and the rectangular and the triangular beam geometries in similar cooling rates to those of the circular beam geometry. In particular, the model predicted that the processing speed for the rhomboid geometry had to be increased by a factor of about 5 and that for the pi geometry by a factor of about 2.5 compared to the standard circular beam geometry to produce similar cooling rates.

G31 ライン状レーザビームによる曲げ加工(G3 加工・生産システム3)

G31 ライン状レーザビームによる曲げ加工(G3 加工・生産システム3)

Double-Pulsed Green Laser Annealing Tbchnologies

The advanced lateral crystal growth (ALCG) process developed with the double-pulsed green laser annealing system enabled Si grains to be grown laterally and continuously through a step scan of a line beam in the same way as conventional excimer laser annealing (ELA). The field effect mobility of n-channel ALCG-SiTFTs for a current parallel to grain boundaries reaches a high level of 600 cm2/Vs and the strong temperature dependence of the mobility is close to that of single crystal MOS transistors. The 10μm-wide ultra fine beams up to 75 mm in length for the next generation p-SiTFT and up to 150 mm in length for OLED, applied to massproduction machines, were developed by using the beam delivery optics system in conjunction with the optical technique spatially combining multiple laser beams.

Particle-in-cell method for numerical simulation of beam and plasma dynamics

The finite particle methods are widely applied for the numerical simulation of a continuous medium including continuum electrodynamics and simulation of charged particle beams. This method allows studying the detailed beam and plasma characteristics, the distribution function of particles, the nonlinear self and external fields. The so-called “particle-in-cell” method is the most effective for simulations in the physics of plasma and charged particle beams. Two examples illustrate the application of the particle-in-cell method in beam dynamics and plasma physics. The first is a program library for numerical simulation and optimization of multi-component ion beam transportation from ion sources where RFQ accelerators are presented. The latest version of the library was applied for simulations of transverse dynamics of an argon ion beam in the beam line from the 18 GHz ECR Ion Source to the linear RFQ accelerator of the RIKEN Beam Factory. A partial neutralization of ion beam charge due to secondary electrons was assumed to realize the real experimental conditions in the beam line and was used in simulation. The second is a summary of recent development of physical and mathematical basements and the first version of a computer code library aimed for the three-dimensional (3D) simulation of the ECR plasma and ion production in the ECR ion source.

Advanced excimer-based crystallization systems for production solutions

Line beam excimer laser annealing (ELA) is a well-known technique for thin Si-film crystallization and established in LTPS mass production. With introduction of sequential lateral solidification (SLS) some aspects such as crystalline quality, throughput and flexibility regarding the substrate size could be improved, but for OLED manufacturing still further process development is necessary. This paper discusses line beam ELA and SLS-techniques that might enable process engineers to make polycrystalline-silicon (poly-Si) films with a high degree of uniformity and quality as required for system on glass (SOG) and active matrix organic light emitting displays (AMOLED). Equipment requirements are discussed and compared to previous standards. SEM-images of process examples are shown in order to demonstrate the viability.

The Effect Of Laser Deformation On FatigueProperties Of Automotive Dual Phase Steel

It became evident from previous research that the fatigue strength of wheel centre discs decreases as much as 83% during the manufacture (first production stage) of the automotive wheel [1, 2]. This information was the driving force in obtaining an alternative forming process in order to maintain the high fatigue strength of the metal. The laser forming/deforming process was chosen because of its ease of automation and reproducibility. It was found that it was possible to deform dual phase steel specimens, employing various laser parameters, to the same radius of curvature as that of the first production stage of wheel centre discs. Microstructural analysis indicated a change of the original microstructure due to the heat generated by the laser beam. The original martensite/ferrite microstructure transformed to various transformation phases of the steel, like bainite and ferrite/carbide aggregate. These microstructural changes are concentrated on the surface over which the laser beam radiated. Grain growth was also observed and is an important consideration as large grains are considered to embrittle a material. Fatigue testing of the laser formed specimens revealed that the process has potential to be used as a production stage, providing that line energy and beam diameter is carefully controlled. The laser formed specimens formed by employing a 1.5kW laser power showed results very similar to those obtained by specimens formed be means of a pure bend process. Although the results obtained indicated that laser forming has the possibility of being employed as a deformation process, the fatigue properties of the laser formed specimens were inferior compared to the original un-deformed material. It was also determined that the hardness profile along the length of the specimens showed a variation that could lead to a metallurgical notch. The hardness was at a maximum with the position corresponding to the centre of the laser beam with the lowest hardness obtained in the region between two consecutive laser heat lines.

Preliminary Study of Polymer Removal in 0.25, 0.3, and 0.5 µm Ruthenium Storage Nodes and 0.11 µm, 10.9:1 High-Aspect-Ratio Trenches by Laser-Induced Etching

The demands for new etching technology are increasing because of new materials, such as, ruthenium (Ru), platinum (Pt), and iridium (Ir), that are now being used, and the strict critical dimension (C/D) controls required in today's ultra large scale integrated (ULSI) circuit technology and dynamic random-access memory (DRAM) fabrication lines. Laser etching technology successfully etched organometallic polymers generated after reactive ion etching and ash processing in 0.25, 0.3, and 0.5 µm Ru storage nodes. In this study, the effects of the incident beam profile on the laser-induced etching of the polymers are investigated. Unevenness of the peak energy in the Gaussian beam profile creates unequal etching and heating effects on the polymer removal depending on the irradiating position of the line beam profile on the sample surface. This article discusses for the first time the preliminary results of laser-induced etching with a KrF laser to remove photoresist (PR) and polymer in 0.11 µm deep contact holes with a high-aspect-ratio 10.9:1 trench hole. How deep can the laser etching technology penetrate and strip the PR at a high aspect ratio (A/R) of 10.9:1 and a 0.11 µm hole size? The penetration depth for the PR removal was approximately 1 µm, which is about a 9.1:1 A/R in a 0.11 µm hole with a 1.2-µm-deep trench. Several promising points are discussed on the basis of laser etching in such a high A/R and small 0.11 µm contact hole. Laser-induced etching technology enabled a very uniform penetration depth without any fluctuations, and it also did not show any attack on the edge of the barrier material TiN.

Characterisation and corrosion performance of laser-melted 3CR12 steel

Dual-phase ferritic–martensitic 3CR12 steel, exhibiting an excellent corrosion resistance under ambient conditions, is a potential substitute for FeCrNi stainless steels in many applications. However, the steel suffers pitting corrosion in Cl −-containing environments, usually associated with the presence of non-metallic inclusions. The present work investigates the possibility of improvement of the pitting corrosion performance of hot-rolled and annealed 3CR12 steel using a laser surface melting (LSM) technique. The laser processing was carried out using a 3 kW CW Nd:YAG laser with 10 and 13 mm line beam profiles. Pitting resistance in de-aerated 3.5% NaCl solution was substantially increased by LSM. The degree of improvement is associated with the formation of ferrite and reduction of martensite in the melt region, the extent of which depends on the processing parameters. Observation of pitting morphologies of the laser-melted surfaces showed that corrosion was initiated at the ferrite grain boundaries, where the martensite or possibly impurities were located, compared with more random pitting in the banded microstructure of the initial steel.

Ultra-Shallow Junction Formation by a Non-Melting Process; Double-Pulsed Green Laser Annealing

AbstractIn order to investigate the possibility of nanosecond activation in the non-melting state, we adopted the method of double-pulsed green laser annealing (DPSS), controlling effectively the combined pulse width with two pulsed lasers (pulse duration: ˜100ns, frequency: 1kHz). We investigated the formation of ultra-shallow junctions (USJ) less than 10nm in spite of the deep penetration depth of the green wavelength in crystalline Si (˜1000nm). In order to limit the depth of B implant, a Ge pre-amorphization implant was performed at an energy of 3keV to a dose of 3E+14/cm2. After the pre-amorphization implant, a B implant was performed at 0.2kev and doses of 5E+14/cm2 and 1E+15/cm2. The implanted B dopants remain within the pre-amorphized Si layer. The double-pulsed laser irradiation was performed with a homogenized line beam of 0.1mm x 17mm, scanning a sample stage at a constant velocity of 10mm/s, that is, at an overlap ratio of 90%. The non-melting state was found to be in the pulse energy density range of E ≤ 780mJ/cm2 at a delay time of 300ns. Overcoming the issues of the short annealing time (˜<1μs) and the deep penetration depth (˜1000nm), we succeeded in the ultra-shallow junction formation beyond the 45nm CMOS node: maximum junction depth of 6nm, minimum sheet resistance of 0.65kohm/sq at a B dose of 1E+15/cm2, an abruptness of 1.4nm/dec.

The production of 9C beam in the secondary beam line of the HIMAC facility and its potential application in cancer therapy

The emitted particles from a β -delayed particle decay beam must enhance biological effects in the region of interest and such a radioactive ion beam may be useful in cancer treatment. To test this therapeutic purpose of β -delayed particle decay beams, 9 C beams were produced in the secondary beam line at HIMAC for the first time. The thickness of production target and degrader to yield a 9 C beam with higher production rate and purity was optimized and the momentum distribution of the produced 9 C beam under the optimal condition was measured. For upcoming radiobiological experiments, a uniform irradiation field for the produced 9 C beam was made by means of wobbling magnets.

The European answer to the integration issues of excimer laser annealing in MOS technology

Excimer laser annealing (ELA) of MOSFET devices is currently studied and evaluated within the frame of the IST project “Fundamentals and applications of laser processing for highly innovative MOS technology” (FLASH), funded by the European Commission. This European consortium aim to demonstrate that ELA can be industrialized in the context of semiconductor device fabrication. The technical achievement of homogeneous irradiation of entire wafers by industrial line beam system set up has been combined with device design solutions, in order to avoid the detrimental effects of the laser beam on device structures and tackle the integration issues, main obstacles for the use of ELA in the semiconductor industry. The launch of ELA, to open a new market segment in the semiconductor industry, implies also the availability of reliable process simulation tools. Therefore, a simulation program based on the phase-field method was produced, fully working and available.