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Showing papers in "Optics and Laser Technology in 2009"


Journal ArticleDOI
TL;DR: In this paper, a hybrid approach of Taguchi methodology and grey relational analysis has been applied to achieve better cut qualities within existing resources, which minimized the kerf width, kerf taper, and kerf deviation together during pulsed Nd:YAG laser cutting of a thin sheet of nickel-based superalloy SUPERNI 718.
Abstract: This paper presents a hybrid optimization approach for the determination of the optimum laser cutting process parameters which minimize the kerf width, kerf taper, and kerf deviation together during pulsed Nd:YAG laser cutting of a thin sheet of nickel-based superalloy SUPERNI 718 (an equivalent grade to Inconel 718). A hybrid approach of Taguchi methodology and grey relational analysis has been applied to achieve better cut qualities within existing resources. The input process parameters considered are oxygen pressure, pulse width, pulse frequency, and cutting speed. A higher resolution based L27 orthogonal array has been used for conducting the experiments for both straight and curved cut profiles. The designed experimental results are used in grey relational analysis and the weights of the quality characteristics are determined by employing the entropy measurement method. The significant parameters were obtained by performing analysis of variance (ANOVA). The optimized parameters for straight and curved laser cut profiles have been compared. On the basis of optimization results it has been found that the optimal parameter level suggested for straight cut profiles are not valid for curved cut profiles. The application of the hybrid approach for straight cuts has reduced Kt and Kd by 52.37% and 17%, respectively. For curved cuts the approach has reduced Kw and Kt by 8.45% and 44.44%, respectively. The results have also been verified by running confirmation tests.

149 citations


Journal ArticleDOI
TL;DR: In this paper, a study was made to investigate the effects of process parameters, namely, laser power, welding speed, size of the laser beam and clamp pressure, on the lap-shear strength and weld-seam width for laser transmission welding of acrylic (polymethyl methacrylate), using a diode laser system.
Abstract: In the present work, a study is made to investigate the effects of process parameters, namely, laser power, welding speed, size of the laser beam and clamp pressure, on the lap-shear strength and weld-seam width for laser transmission welding of acrylic (polymethyl methacrylate), using a diode laser system. Response surface methodology (RSM) is employed to develop mathematical relationships between the welding process parameters and the output variables of the weld joint to determine the welding input parameters that lead to the desired weld quality. In addition, using response surface plots, the interaction effects of process parameters on the responses are analyzed and discussed. The statistical software Design-Expert v7 is used to establish the design matrix and to obtain the regression equations. The developed mathematical models are tested by analysis-of-variance (ANOVA) method to check their adequacy. Finally, a comparison is made between measured and calculated results, which are in good agreement. This indicates that the developed models can predict the responses adequately within the limits of welding parameters being used.

124 citations


Journal ArticleDOI
TL;DR: In this article, the precision of the LIBS measurements for the coal sample can be improved by using the optimum experimental parameters, including sample preparation parameters, lens-to-sample distance, sample operation mode, and ambient gas.
Abstract: The purpose of this work is to improve the precision of the elemental analysis of coal using laser-induced breakdown spectroscopy (LIBS). The LIBS technique has the ability to allow simultaneous elemental analysis and on-line determination, so it could be used in the elemental analysis of coal. Organic components such as C, H, O, N and inorganic components such as Ca, Mg, Fe, Al, Si, Ti, Na, and K of coal have been identified. The precision of the LIBS technique depends strongly on the experimental conditions, and the choice of experimental parameters should be aimed at optimizing the repeatability of the measurements. The dependences of the relative standard deviation (RSD) of the LIBS measurements on the experimental parameters including the sample preparation parameters, lens-to-sample distance, sample operation mode, and ambient gas have been investigated. The results indicate that the precision of LIBS measurements for the coal sample can be improved by using the optimum experimental parameters.

78 citations


Journal ArticleDOI
TL;DR: In this paper, a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems is proposed, which can obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10 −4 ǫdB/m in the entire S+C+L telecommunication band.
Abstract: This paper reveals a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems. The finite-difference method with an anisotropic perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed novel DC-PCF shows that it is possible to obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10 −4 dB/m in the entire S+C+L telecommunication band by using a modest number of design parameters. The proposed module can be used in 40 Gb/s dense wavelength division multiplexing (DWDM) systems in optical fiber communication networks.

71 citations


Journal ArticleDOI
TL;DR: In this paper, a cylindrically polarized vortex beam is decomposed into radial and azimuthal polarization, and the total intensity distribution in the focal region is dependent not only on the numerical aperture maximal angle and the polarization rotation angle but also on the topological charge.
Abstract: The focus-shaping technique of a cylindrically polarized vortex beam by a high numerical-aperture lens is reported. Such a polarized vortex beam is decomposed into radial and azimuthal polarization. It is shown that the total intensity distribution in the focal region is dependent not only on the numerical-aperture maximal angle and the polarization rotation angle but also on the topological charge. By choosing the proper combination of parameters, the adjustably confined flat-topped focus and focal hole can be obtained. The focus-shaping technique may find wide applications, such as optical tweezers, laser printing and material processing.

68 citations


Journal ArticleDOI
TL;DR: In this article, the double-pulse was used for percussion drilling in stainless steel samples with different laser fluences, sample's thickness, repetition rates and ambient pressures, and the experimental results show that the drilling rates of doublepulse drilling are more than one order of magnitude higher than that of conventional single-pulses in air.
Abstract: Nanosecond double-pulse laser drilling is reported in this paper. The double-pulse herein represents two closely conjoint pulses with 21 ns pulse duration and about 52 ns interpulse separation, which are acquired by temporal pulse shaping. Percussion drilling with such double-pulse is performed in stainless steel samples with different laser fluences, sample's thickness, repetition rates and ambient pressures. The experimental results show that the drilling rates of double-pulse drilling are more than one order of magnitude higher than that of conventional single-pulse drilling in air. Differences in the processing results between single-pulse and double-pulse with various processing parameters are investigated. In addition the ablation mechanisms of the double-pulse drilling are discussed.

67 citations


Journal ArticleDOI
TL;DR: In this paper, a metallic cardiovascular stent cutting system based on fiber laser was designed in order to achieve the cutting of stent, the main modules and the key technologies were analyzed and achieved then with the cutting system, the kerf width size was studied for different cutting parameters including laser output power, pulse length, repeat frequency, cutting speed and assisting gas pressure.
Abstract: A metallic cardiovascular stent cutting system based on fiber laser was designed in this study In order to achieve the cutting of stent, the main modules and the key technologies were analyzed and achieved Then with the cutting system, the kerf width size was studied for different cutting parameters including laser output power, pulse length, repeat frequency, cutting speed and assisting gas pressure Finally, a high quality of cutting of 316L stainless steel cardiovascular stent was achieved

63 citations


Journal ArticleDOI
TL;DR: In this article, a Gaussian model is established to quantitatively predict the powder stream concentration in order to facilitate coaxial nozzle design optimizations, and an experimental setup is designed to measure the powder concentration for this process.
Abstract: The structure below the coaxial nozzle is critical since the spatial distribution of metal powder particles determines the laser attenuation as well as catchment efficiency. It is difficult to simulate the powder concentration distribution, because the complex phenomena involved in the two-phase turbulence flow. In this paper, the air-powder flow is studied along with powder properties, nozzle geometries and shielding gas setting. A Gaussian model is established to quantitatively predict the powder stream concentration in order to facilitate coaxial nozzle design optimizations. An experimental setup is design to measure the powder concentration for this process. The simulated results are compared with the experimental results. This study shows that the powder concentration mode is influenced significantly by powder properties, nozzle geometries and shielding gas setting.

63 citations


Journal ArticleDOI
TL;DR: In this article, the effect of initial sample temperature on spectral emission of laser-induced plasma has been investigated and the results suggest that increasing the sample temperature can improve the limits of detection (LOD).
Abstract: The effect of initial sample temperature on spectral emission of laser-induced plasma has been investigated. The plasma has been produced on aluminum alloy surface at ambient air pressure. The sample has been uniformly heated by a heating element up to 150 °C. The spectral emission of aluminum at different initial sample temperature and gate delay times has been measured. A simple model has been improved in order to compare the analytical and experimental results. An increase in sample temperature leads to an increase in the area under spectral line profiles. The results suggest that increasing the sample temperature can improve the limits of detection (LOD).

59 citations


Journal ArticleDOI
TL;DR: In this paper, a glass sheet is stressed thermally using a 808-940 nm diode laser radiation and the problem of cut deviation at the leading and the trailing edges of the glass sheet was analyzed.
Abstract: In laser cleaving of brittle materials using controlled fracture technique, thermal stresses are used to induce a crack and the material is separated along the cutting path by extending this crack. In this study, a glass sheet is stressed thermally using a 808–940 nm diode laser radiation. One of the problems in laser cutting of glass with controlled fracture technique is the cut deviation at the leading and the trailing edges of the glass sheet. In order to avoid this damage it is necessary to understand the stress distributions which control crack propagation. A study is conducted here to analyse the cut deviation problem of glass by examining the stress fields during diode laser cutting of soda-lime glass sheets. Optical microscope photographs of the breaking surface are obtained to examine the surface quality and cut path deviation while the latter is explained from the results of the stress fields which are obtained from a finite element simulation.

59 citations


Journal ArticleDOI
TL;DR: In this paper, a 2D axisymmetric model of a molten pool created by a laser heat source has been developed, which solves the coupled equations of a laminar fluid flow and heat transfer to demonstrate the flow behavior in the pool.
Abstract: A pulse laser (Nd:YAG) interaction with an AZ91 magnesium alloy has been experimentally and numerically studied. A two-dimensional (2D) axisymmetric model of a molten pool created by a laser heat source has been developed. The elaborated model solves the coupled equations of a laminar fluid flow and heat transfer to demonstrate the flow behavior in the pool. This model takes into account the coupled effects of buoyancy and Marangoni forces, the thermophysic variation properties with temperature, and the radiation and convection heat losses. Concerning numerical results, the molten temperature distribution, velocity field and molten shape were discussed. It was noted that the Marangoni flow significantly alters the characteristics of the thawing and solidifying processes, and makes the molten pool wider and shallower. On the other hand, the experimental results showed that the material thermal properties have significant effects on the transport phenomena which takes place in the molten pool, and consequently on the formation as well as the shape of the pool. Finally, a comparison between the numerical and experimental results exhibited a good agreement.

Journal ArticleDOI
TL;DR: In this article, the effect of temperature on structural and optical properties of ZnO thin films was investigated systematically by XRD, SEM, FTIR and PL spectra, and it was shown that the best structural properties can be achieved for Zn oxide thin film fabricated at 700 and 400°C using powder target and ceramic target, respectively.
Abstract: Zinc oxide thin films have been obtained in O 2 ambient at a pressure of 1.3 Pa by pulsed laser deposition (PLD) using ZnO powder target and ceramic target. The effect of temperature on structural and optical properties of ZnO thin films was investigated systematically by XRD, SEM, FTIR and PL spectra. The results show that the best structural and optical properties can be achieved for ZnO thin film fabricated at 700 °C using powder target and at 400 °C using ceramic target, respectively. The PL spectrum reveals that the efficiency of UV emission of ZnO thin film fabricated by using powder target is low, and the defect emission of ZnO thin film derived from Zn i and O i is high.

Journal ArticleDOI
TL;DR: Analysis of the grey relational grade indicates that parameter significance and the optimal parameter combination for the laser cutting process are identified and confirm that laser cutting technology can be effectively applied to cut substrates into special shapes.
Abstract: This paper presents a novel effective method for optimizing laser cutting of specially shaped electronic printed circuit board (PCB) carrier substrates of advanced integrated circuit (IC) back-end packages that have multiple performance characteristics identified using grey relational analysis (GRA) Laser cutting parameters, including laser beam parameters (average laser power and Q-switch frequency), focusing parameters (laser beam focusing spot size), and machine parameters (laser cutting speed), were optimized based on multiple performance characteristics Some characteristics of the specially shaped flash memory module for IC packages, such as smart disk (SD) cards are verified The characteristics of interest are the average surface roughness on a PCB substrate cross-section, and the maximum width of the heat-affected zone (HAZ) Eight experiments were conducted using GRA to optimize the settings for laser beam cutting parameters to generate various quality characteristics Analysis of the grey relational grade indicates that parameter significance and the optimal parameter combination for the laser cutting process are identified The analytical results from two confirmation experiments using the optimal parameters confirm that laser cutting technology can be effectively applied to cut substrates into special shapes

Journal ArticleDOI
TL;DR: In this paper, the effects of Sn and Sb dopants on structural and optical properties of ZnO thin films were investigated and the starting material was zinc acetate dihydrate, 2methoxyethanol was used as solvent and monoethanolamine (MEA) as stabilizer.
Abstract: Undoped and doped ZnO thin films were prepared by sol–gel method and deposited on tin-doped indium oxides (ITO) substrate using spin coating technique. The effects of Sn and Sb dopants on structural and optical properties were investigated. The starting material was zinc acetate dihydrate, 2-methoxyethanol was used as solvent and monoethanolamine (MEA) as stabilizer. ZnO films were doped with 2% and 7% Sn and Sb concentrations. Optical measurements show an important effect of Sn and Sb dopants on optical band gap.

Journal ArticleDOI
TL;DR: This paper proposes an alternative method for direct tension measurement, which utilizes a washer with a white light speckle pattern on its face as an optical force transducer, which enables real-time monitoring of clamping force during fastening and has a potential of being used for mass measurement of clamped force in a production environment.
Abstract: Bolts are widely used in industry for joining members together. The behavior and service life of bolted joints depend on several factors including bolt material, dimensions, surface finish, surface coating and thread tolerances. However, the uppermost factor affecting the reliability and durability is the correctness of the clamping force exerted by the bolt. Thus it is very important to monitor the bolt clamping force to ensure a proper preload during assembly process. Each of the available monitoring techniques including torque control, torque-angle control, strain gauged bolt and ultrasound suffers one or more limitations which affect the reliability of measurement. In this paper, we propose an alternative method for direct tension measurement, which utilizes a washer with a white light speckle pattern on its face as an optical force transducer. By measuring the strain of the washer using automatic digital image correlation, the clamping force can be determined. This method, which enables real-time monitoring of clamping force during fastening, has a potential of being used for mass measurement of clamping force in a production environment. Experiments conducted on bolted structures with washers of different sizes have demonstrated the reliability and usefulness of this new approach.

Journal ArticleDOI
TL;DR: In this paper, the laser beam weldability of acrylonitrile/butadiene/styrene (ABS) plates is determined by combining both experimental and theoretical aspects.
Abstract: The laser beam weldability of acrylonitrile/butadiene/styrene (ABS) plates is determined by combining both experimental and theoretical aspects. In modeling the process, an optical model is used to determine how the laser beam is attenuated by the first material and to obtain the laser beam profile at the interface. Using this information as the input data to a thermal model, the evolution of the temperature field within the two components can be estimated. The thermal model is based on the first principles of heat transfer and utilizes the temperature variation laws of material properties. Corroborating the numerical results with the experimental results, some important insights concerning the fundamental phenomena that govern the process could be extracted. This approach proved to be an efficient tool in determining the weldability of polimeric materials and assures a significant reduction of time and costs with the experimental exploration.

Journal ArticleDOI
TL;DR: In this article, a nonlinear directional coupler in the presence of intermodal dispersion, cross-phase modulation (CPM), third-order dispersion and self-steepening effect is reported.
Abstract: Dark soliton switching in a nonlinear directional coupler in the presence of intermodal dispersion, cross-phase modulation (CPM), third-order dispersion, Raman effect, and self-steepening effect is reported for the first time. It is shown that, with the exception of CPM, all of the other perturbative effects have almost no effect on the switching characteristics of the dark soliton switch, which is an improvement over the corresponding bright soliton switch. Although the CPM increases the critical power of dark soliton switching, the soliton pulse remains stable inside the coupler during its propagation.

Journal ArticleDOI
TL;DR: Here the fast switching action of SOA with reliable frequency encoded control input signals, it is possible to achieve a faithful MUX/DEMUX service at tera-Hz operational speed.
Abstract: Multiplexing and demultiplexing are the essential parts of any communication network In case of optical multiplexing and demultiplexing the coding of the data as well as the coding of control signals are most important issues Many encoding/decoding mechanisms have already been developed in optical communication technology Recently frequency encoding technique has drawn some special interest to the scientific communities The advantage of frequency encoding technique over any other techniques is that as the frequency is fundamental character of any signal so it remains unaltered in reflection, refraction, absorption, etc during transmission of the signal and therefore the system will execute the operation with reliability On the other hand, the switching speed of semiconductor optical amplifiers (SOA) is sufficiently high with property of best on/off contrast ratio In our present communication we propose a method of implementing a ‘4-to-1’ multiplexer (MUX) and a ‘1-to-4’ demultiplexer (DEMUX) exploiting the switching character of nonlinear SOA with the use of frequency encoded control signals To implement the ‘4-to-1’ MUX and ‘1-to-4’ DEMUX system, the frequency selection by multiquantum well (MQW)-grating filter-based SOA has been used for frequency routing purpose At the same time, the polarization rotation character of SOA has also been exploited to get the desired purpose Here the fast switching action of SOA with reliable frequency encoded control input signals, it is possible to achieve a faithful MUX/DEMUX service at tera-Hz operational speed

Journal ArticleDOI
TL;DR: In this article, a method for full-field measurement of temperature of a fluid flow by using the schlieren technique was developed, where the intensity level of each pixel in a Schlieren image was compared to the corresponding knife-edge position measured at the exit focal plane of the system.
Abstract: In this work, we have developed a procedure for full-field measurement of temperature of a fluid flow by using the schlieren technique. The basic idea is to relate the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the system. The method is applied in the measurement of temperature fields of the air convection caused by a heated rectangular metal plate (7.3 cm×12 cm). Our tests are carried out at plate temperatures of 50 °C and 80 °C. To validate the proposed method, the schlieren temperature results are compared to those obtained by a thermocouple. Thermocouple data are obtained along two mutually perpendicular directions (one direction along the optical axis, z-direction, and other direction along the x-axis, which is perpendicular to the optical axis) at points located on a 9×9 grid with a variable spacing. The thermocouple measurements were integrated along the z-axis in order to be compared with the measurements obtained by the schlieren technique. The results from the two methods show good agreement between them.

Journal ArticleDOI
TL;DR: In this paper, the grey relational analysis (GRA) was used to directly optimize laser cutting of a quad flat non-lead (QFN) strip using six performance characteristics.
Abstract: This paper reports an application of the grey relational analysis (GRA) to directly optimize laser cutting of a quad flat non-lead (QFN) strip using six performance characteristics. The most important performance characteristics include the cutting depth, the width of heat affected zone (HAZ), and the width of cutting line for both epoxy and Cu+epoxy materials along the cutting path. During the GRA, higher grades are obtained from any of the deeper (more complete) cutting depth, reduced widths of the HAZ and reduced widths of the cutting line. From nine experiments based on the orthogonal array of L9(34), a current of 29 A, a frequency of 2 kHz, and a cutting speed of 2 mm/s were found to be the best parameters for laser cutting of a QFN strip with a thickness of 0.9 mm. Moreover, the analysis of variance (ANOVA) is also employed to determine the contribution of each control parameter on the cutting quality characteristics. The three largest measured contributions on the cutting quality in decreasing order are the frequency, the current, and the cutting speed. Compared with the Taguchi optimization method, the GRA approach is significantly simpler because it directly assigns appropriate weighting factors to the required qualities. Finally, confirmation experiments are performed to ensure the robustness of the GRA predicted optimal configuration for laser cutting a QFN strip.

Journal ArticleDOI
Jitae Kim1, Suck-Joo Na1
TL;DR: In this paper, a new method for 3D laser forming of sheet metal is proposed, which uses geometrical information rather than a complicated stress-strain analysis, and two different target shapes were formed by laser irradiation with the proposed procedure to validate the algorithm.
Abstract: Forming sheet metal by laser-induced thermal stress (laser forming) is considered to offer great potential for rapid prototyping and flexible manufacturing. Accordingly, many studies have been carried out in different areas of laser forming. However, in order to apply the laser-forming process to real 3D products, a method that encompasses the whole process planning is required, including the laser irradiation patterns, laser power, and travel speed, when the target shape is given. In this work, a new method for 3D laser forming of sheet metal is proposed. This method uses geometrical information rather than a complicated stress–strain analysis. Using this new method the total calculation time is reduced considerably while affording strong potential for enhanced accuracy. Two different target shapes were formed by laser irradiation with the proposed procedure to validate the algorithm.

Journal ArticleDOI
TL;DR: In this article, rare-earth ions coactivated red phosphors Gd 0.2 RE 1.8 (WO 4 ) 3 (RE=Eu 3+ and Sm 3+ ) were synthesized by conventional solid-state reaction using boric acid as a flux agent.
Abstract: Rare-earth ions coactivated red phosphors Gd 0.2 RE 1.8 (WO 4 ) 3 (RE=Eu 3+ and Sm 3+ ) were synthesized by conventional solid-state reaction using boric acid as a flux agent. The samples were characterized by X-ray diffractometer (XRD), energy-dispersive X-ray spectrometer (EDS) and luminescence spectrometer (LS). The results showed that the Eu–Sm system exhibits higher emission intensity than those of the Eu single-doped system and Sm separate-doped system under ultraviolet (UV) radiation. Samarium(III) ions are effective in broadening and strengthened absorptions around 400 nm. Furthermore, it exhibits enhanced luminescence emission. when the mole ratio of boric acid is about 0.16, the luminescence capability is optimum. Two strongest lines at ultraviolet (394 nm) and blue (465 nm) in excitation spectra of these phosphors match well with the output wavelengths of UV and blue GaN-based light-emitting diodes (LEDs) chips.

Journal ArticleDOI
TL;DR: Based on the second-order moments, the beam propagation factors and the kurtosis parameters of a Lorentz beam have been investigated in this article, where the M2 value of the beam is verified to be 2.
Abstract: Based on the second-order moments, the beam propagation factors and the kurtosis parameters of a Lorentz beam have been investigated. The M2 value of a Lorentz beam is verified to be 2 . The analytical expressions of the kurtosis parameters have been derived. The kurtosis parameter varies upon the propagation, and it is decided by two ratios z/zrx and z/zry. The kurtosis parameter versus the two ratios z/zrx and z/zry is plotted and discussed in detail. This work is of benefit to the practical application of laser sources that produce highly divergent beams.

PatentDOI
TL;DR: An octagonal structure of photodiodes using standard CMOS technology has been developed to serve as a de-multiplexer for spatially multiplexed fiber optic communication systems as mentioned in this paper.
Abstract: An octagonal structure of photodiodes using standard CMOS technology has been developed to serve as a de-multiplexer for spatially multiplexed fiber optic communication systems.

Journal ArticleDOI
TL;DR: In this paper, a switchable erbium-doped fiber-ring laser providing dual-wavelength outputs with orthogonal polarizations when operating at room temperature is proposed.
Abstract: A switchable erbium-doped fiber-ring laser providing dual-wavelength outputs with orthogonal polarizations when operating at room temperature is proposed. One polarization-maintaining fiber Bragg grating (PMFBG) in a Sagnac loop interferometer is used as the wavelength-selective filter. Due to the enhancement of the polarization hole burning (PHB) by the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The optical signal-to-noise ratio (OSNR) is over 42 dB. The amplitude variation over 90 min is less than 0.6 dB for both wavelengths.

Journal ArticleDOI
TL;DR: In this paper, the feasibility of a microstructured optical fiber (MOF) amplifier, made of a novel Er3+-doped chalcogenide glass, has been demonstrated via accurate simulations performed by employing an oppositely implemented computer code.
Abstract: The feasibility of a microstructured optical fiber (MOF) amplifier, made of a novel Er3+-doped chalcogenide glass, has been demonstrated via accurate simulations performed by employing an oppositely implemented computer code. The optical and geometrical parameters measured on the first MOF sample together with other physical constants from literature have been taken into account in the simulations. The calculated optical gain of the optimized MOF amplifier, 2.79 m long, is close to 23 dB at the signal wavelength of 1.538 μm, by using a pump power of 200 mW and a signal power of 0.1 μW.

Journal ArticleDOI
TL;DR: This procedure, while using only laser-coplanar points, is oriented towards laser line detection and allows the matching of two images on the laser projection plane without the use of a rigid motion equation.
Abstract: In order to ensure the precision of the measurement of complex 3D object surfaces using non-contact laser scanning systems, a novel stereo vision calibration procedure based on a laser line projection plane is presented. This calibration procedure can also be used in measurement systems based on a single camera and a laser line projection. This procedure, while using only laser-coplanar points, is oriented towards laser line detection and allows the matching of two images on the laser projection plane without the use of a rigid motion equation. These features make this procedure very precise, simple and, consequently, easier to implement.

Journal ArticleDOI
Yong Zhao1, Hua-Wei Zhao1, Xinyuan Zhang1, Bo Yuan1, Shuo Zhang1 
TL;DR: In this article, some important theoretical and technical developments of slow light technology that occurred over the last decade are discussed and their primary applications are introduced in detail, as well as the future developing trends and its potential applications, especially in optical fiber sensors, are also forecasted and proposed.
Abstract: The last decade has been of great significance for the development of slow light technology. Electromagnetically induced transparency (EIT), coherent population oscillation (CPO), stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), soliton collision, and photonic crystal waveguides have been used to slow down the velocity of light. In this paper, some important theoretical and technical developments of slow light technology that occurred over the last decade are discussed. Novel technologies for slowing down the velocity of light and their primary applications are introduced in detail. In addition, the future developing trends of slow light and its potential applications, especially in optical fiber sensors, are also forecasted and proposed in this paper.

Journal ArticleDOI
TL;DR: In this paper, the influence of substrate temperature on the structural and morphological properties of thin films was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy(SEM).
Abstract: Tin oxide (SnO 2 ) thin films were grown on Si (1 0 0) substrates using pulsed laser deposition (PLD) in O 2 gas ambient (10 Pa) and at different substrate temperatures (RT, 150, 300 and 400 °C). The influence of the substrate temperature on the structural and morphological properties of the films was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). XRD measurements showed that the almost amorphous microstructure transformed into a polycrystalline SnO 2 phase. The film deposited at 400 °C has the best crystalline properties, i.e. optimum growth conditions. However, the film grown at 300 °C has minimum average root mean square (RMS) roughness of 3.1 nm with average grain size of 6.958 nm. The thickness of the thin films determined by the ellipsometer data is also presented and discussed.

Journal ArticleDOI
TL;DR: In this paper, the effect of laser fluence on the crystallization of amorphous silicon irradiated by a frequency-doubled Nd:YAG laser is studied both theoretically and experimentally.
Abstract: The effect of laser fluence on the crystallization of amorphous silicon irradiated by a frequency-doubled Nd:YAG laser is studied both theoretically and experimentally. An effective numerical model is set up to predict the melting threshold and the optimized laser fluence for the crystallization of 200-nm-thick amorphous silicon. The variation of the temperature distribution with time and the melt depth is analyzed. Besides the model, the Raman spectra of thin films treated with different fluences are measured to confirm the phase transition and to determine the optimized fluence. The calculating results accord well with those obtained from the experimental data in this research.