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Showing papers in "Optics and Laser Technology in 2007"


Journal ArticleDOI
TL;DR: In this paper, the effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique.
Abstract: This paper presents an investigation of laser rapid manufacturing (LRM) for Inconel-625 components. LRM is an upcoming rapid manufacturing technology, it is similar to laser cladding at process level with different end applications. In general, laser-cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn out parts, while LRM is capable of near-net shaping the components by layer-by-layer deposition of the material directly from CAD model. In the present study, a high-power continuous wave (CW) CO 2 laser system, integrated with a co-axial powder-feeding system and a three-axis workstation were used. The effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique. Results indicated that the powder feed rate and the scan speed contributed about 56% and 26%, respectively to the deposition rate, while the influence of laser power was limited to 10% only. Fabricated components were subjected to non-destructive testing (like—ultrasonic testing, dye-penetrant testing), tensile testing, impact testing, metallographic examinations and micro-hardness measurement. The test results revealed defect-free material deposition with improved mechanical strength without sacrificing the ductility.

229 citations


Journal ArticleDOI
TL;DR: In this article, a statistical approach for an overlap assembly configuration using a filler wire composed of 85% Zn and 15% Al is presented, and the fracture mechanisms of the joints are analyzed by a detailed characterization of the seams.
Abstract: Joining steel with aluminum involving the fusion of one or both materials is possible by laser beam welding technique. This paper describes a method, called laser braze welding, which is a suitable process to realize this structure. The main problem with thermal joining of steel/aluminum assembly with processes such as TIG or MIG is the formation of fragile intermetallic phases, which are detrimental to the mechanical performances of such joints. Braze welding permits a localized fusion of the materials resulting in a limitation on the growth of fragile phases. This article presents the results of a statistical approach for an overlap assembly configuration using a filler wire composed of 85% Zn and 15% Al. Tensile tests carried on these assemblies demonstrate a good performance of the joints. The fracture mechanisms of the joints are analyzed by a detailed characterization of the seams.

205 citations


Journal ArticleDOI
TL;DR: Based on the theory of this technology, a promising rapid manufacturing system called "Laser Metal Deposition Shaping (LMDS)" has been constructed and developed successfully by Chinese Academy of Sciences, Shenyang Institute of Automation.
Abstract: Laser additive direct deposition of metals is a new rapid manufacturing technology, which combines with computer-aided design (CAD), laser cladding and rapid prototyping. The advanced technology can build fully dense metal components directly from CAD files with neither mould nor tool. Based on the theory of this technology, a promising rapid manufacturing system called “Laser Metal Deposition Shaping (LMDS)” has been constructed and developed successfully by Chinese Academy of Sciences, Shenyang Institute of Automation. Through the LMDS system, comprehensive experiments are carried out with nickel-based superalloy to systematically investigate the influences of the processing parameters on forming characteristics. By adjusting to the optimal processing parameters, fully dense and near-net-shaped metallic parts can be directly obtained through melting coaxially fed powder with a laser. Moreover, the microstructure and mechanical properties of as-formed samples are tested and analyzed synthetically. As a result, significant processing flexibility with the LMDS system over conventional processing capabilities is recognized, with potentially lower production cost, higher quality components, and shorter lead-time.

195 citations


Journal ArticleDOI
Jaegu Kim, Suck-Joo Na1
TL;DR: In this article, the morphology of thin metal films after machining with femtosecond laser ablation using about 1μm diameter laser beam is analyzed by comparing experimental images with data obtained using a two-temperature heat transfer model.
Abstract: Micromachining thin metal films coated on glass are widely used to repair semiconductor masks and to fabricate optoelectrical and MEMS devices. The interaction of lasers and materials must be understood in order to achieve efficient micromachining. This work investigates the morphology of thin metal films after machining with femtosecond laser ablation using about 1 μm diameter laser beam. The effect of the film thickness on the results is analyzed by comparing experimental images with data obtained using a two-temperature heat transfer model. The experiment was conducted using a high numerical aperture objective lens and a temporal pulse width of 220 fs on 200- and 500-nm-thick chromium films. The resulting surface morphology after machining was due to the thermal incubation effect, low thermal diffusivity of the glass substrate, and thermodynamic flow of the metal induced by volumetric evaporation. A Fraunhofer diffraction pattern was found in the 500-nm-thick film, and a ripple parallel to the direction of the laser light was observed after a few multiple laser shots. These results are useful for applications requiring micro- or nano-sized machining.

99 citations


Journal ArticleDOI
TL;DR: In this article, the optical absorption of thermally evaporated copper phthalocyanine (CuPc) was studied in the UV-VIS-NIR region and the spectral properties such as the molar extinction coefficient (e molar ), the oscillator strength ( f), the electric dipole strength ( q 2 ) and absorption half-bandwidth (Δ λ ) of the principle optical transitions were evaluated.
Abstract: The optical absorption of thermally evaporated copper phthalocyanine (CuPc) was studied in the UV-VIS-NIR region. The absorption spectra recorded in the UV-VIS region show two well-defined absorption bands of the phthalocyanine molecules, namely, the Soret ( B ) and the Q -band . The Q -band shows its characteristic splitting (Davydov splitting) of the main absorption peak in the metal phthalocyanine correlates with the relative tendencies of the metal to out-of-plane bonding. Some of the important spectral characteristics such as the molar extinction coefficient (e molar ), the oscillator strength ( f) , the electric dipole strength ( q 2 ) and absorption half-bandwidth (Δ λ ) of the principle optical transitions were evaluated. The analysis of the spectral behavior of the absorption coefficient α in the absorption region revealed two indirect allowed transitions with corresponding energies 2.95±0.03 and 1.55±0.02 eV. The spectra of the infrared absorption allow characterization of vibration modes for the powder, as-deposited material and thin films of CuPc annealed at 423 K for two hours. Discussion of the obtained results and their comparison with the previous published data are also given.

99 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of aged treatment on the microstructure and microhardness of the surface coating were studied, and the results showed that the prime phase (Co dendrite) and other phases, including Cr 23 C 6, Co 7 W 6, and CrNi existed in the coatings.
Abstract: Co-based alloy coating was deposited on tool steel by powder feeding laser cladding. Sections of such coatings were examined to reveal their microstructures and phases using scanning electron microscope (SEM) and X-ray diffractometer (XRD). The results showed that the prime phase ( γ -Co dendrite) and other phases, including Cr 23 C 6 , Co 7 W 6 , and CrNi existed in the coatings. Some different solidification morphologies, such as planar (at the interface), cellular and dendrite formed, varying from the interface to the surface. Fine microstructures of γ -Co dendrite and lamellar eutectic in dendritical regions strengthened the coatings. Besides, the effects of aged treatment on the microstructure and microhardness of the surface coating were studied. Aged treatment led to the precipitations of some carbide particles (Cr 7 C 3 and Co 3 C) and boride particles (Co 4 B) from the cladded coating, causing an increase in microhardness in the laser-cladded coating.

86 citations


Journal ArticleDOI
TL;DR: In this article, the principle of operation, design aspects, experimentation and performance of an extrinsic fiber optic displacement sensor for the measurement of amplitude and frequency of vibration is reported.
Abstract: This paper reports the principle of operation, design aspects, experimentation and performance of an extrinsic fibre optic displacement sensor for the measurement of amplitude and frequency of vibration. The device consists of fibre optic transmitter, fibre optic probe, mini-shaker, power amplifier, dynamic signal analyser and photodiode detector. The fibre optic probe consists of two well-polished PMMA (polymethyl methacrylate) fibres cemented together along some distance over the length. The sensor is capable of measuring vibration amplitudes ranging from 0.008 to 0.74 mm within a frequency range of 75 to 275 Hz. The sensitivity of the device is found to be 0.893 V/mm over 0.6 to 2.1 mm range and - 0.226 V / mm over 2.9 to 5.9 mm range. The simplicity of the design, high degree of sensitivity, dynamic range and the low cost of the fabrication make it suitable for real field applications. With the emerging fly-by-light concept, the fibre optic probe solves many sensing problems in aircrafts. Moreover, accuracy and reliability are the excellent pay-offs of this fibre optic sensor.

80 citations


Journal ArticleDOI
TL;DR: In this paper, a quantified mechanism was proposed for examining the laser cutting quality of a quad flat no-lead (QFN) package, and the influence of various factors such as laser current, laser frequency, and cutting speed on the laser-cutting quality was also examined.
Abstract: This paper reports the study of optimal laser parameters for cutting QFN (Quad Flat No-lead) packages by using a diode pumped solid-state laser system (DPSSL). The QFN cutting path includes two different materials, which are the encapsulated epoxy and a copper lead frame substrate. The Taguchi's experimental method with orthogonal array of L 9 (3 4 ) is employed to obtain optimal combinatorial parameters. A quantified mechanism was proposed for examining the laser cutting quality of a QFN package. The influences of the various factors such as laser current, laser frequency, and cutting speed on the laser cutting quality is also examined. From the experimental results, the factors on the cutting quality in the order of decreasing significance are found to be (a) laser frequency, (b) cutting speed, and (c) laser driving current. The optimal parameters were obtained at the laser frequency of 2 kHz, the cutting speed of 2 mm/s, and the driving current of 29 A. Besides identifying this sequence of dominance, matrix experiment also determines the best level for each control factor. The verification experiment confirms that the application of laser cutting technology to QFN is very successfully by using the optimal laser parameters predicted from matrix experiments.

70 citations


Journal ArticleDOI
TL;DR: In this article, the authors have fabricated Cr 3+ and Nd 3+ co-doped YAG (Cr;Nd:YAG) ceramics, and investigated their optical properties and laser characteristics.
Abstract: We have fabricated Cr 3+ and Nd 3+ co-doped YAG (Cr;Nd:YAG) ceramics, and investigated their optical properties and laser characteristics. The Cr;Nd:YAG has two broad absorption bands at around 440 nm ( 4 A 2 → 4 T 1 ) and 600 nm ( 4 A 2 → 4 T 2 ) respectively, caused by Cr 3+ ions. In the case of pumping at 440 nm, the maximum effective lifetime of the Cr;Nd:YAG was 737 μs with a 0.1 at% Cr 3+ and 1.0 at% Nd 3+ co-doped YAG sample. Cr 3+ ions take a role of an effective sensitizer to convert the UV light of flashlamp. For single-shot laser operation, a 10.4 J output energy at 1064 nm was obtained with 0.1 at% Cr 3+ and 1.0 at% Nd 3+ co-doped YAG ceramic rod with a laser efficiency of 4.9%. The laser efficiency was found to be more than twice that of a 1.0 at % Nd 3+ :YAG ceramic rod.

69 citations


Journal ArticleDOI
TL;DR: In this article, an analytical model estimate of the bending angle about the y-axis is constructed based on the theories of heat transfer and the mechanics of elastoplasticity.
Abstract: To obtain further insight into the deformation of a plate in the laser forming process, the temperature gradient mechanism (TGM) is studied. Through the investigation, it can be found that, under the processing conditions of TGM, the plate not only bends about the x -axis but also about the y -axis. An analytical model estimate of the bending angle about the y -axis is constructed based on the theories of heat transfer and the mechanics of elastoplasticity. Numerical simulations are carried out to investigate the deformation of the plate about the y -axis by choosing the different process parameters. The analytically based estimate is used to suggest suitable starting values for the simulation process of calculated results. The study of the bending about the y-axis may describe more fully the deformation of a plate, which is helpful in high-precision forming.

69 citations


Journal ArticleDOI
TL;DR: In this article, an experimental investigation of the influence of processing parameters on the clad angle in laser cladding by powder (LCP) is presented, which is determined from the mathematical expression relating to the clad height and clad width.
Abstract: Currently, laser cladding is an important process that allows the deposition of thick protective coatings on substrates. The article presents an experimental investigation of the influence of processing parameters on clad angle in laser cladding by powder (LCP). The clad angle is determined from the mathematical expression relating to the clad height and clad width. The cladding angle model was developed in terms of laser power, scanning speed, and powder mass flow rate by means of response surface methodology. A first-order equation covering a narrow range of the variables and a second-order equation covering a wide range of the variables are presented. An optimization technique, Scatter Search, is used to determine optimal processing parameters. The adequacy of the predictive model was tested by analysis of variance and found to be adequate.

Journal ArticleDOI
TL;DR: In order to ensure the measurement precision for shape recovery from a stereo vision system, a novel high precision calibration method is presented.
Abstract: In order to ensure the measurement precision for shape recovery from a stereo vision system, a novel high precision calibration method is presented. Some standard points acquired from the object of interest are used as standard world points. There are four rotation matrices and translation matrices that need to be calibrated, the first is between the left camera and the world coordinate, the second is between the right camera and the world coordinate, the third is between the left camera and the right camera, and the last is between the right camera and the left camera. The lens distortion parameters include radial and tangential distortion. The merits of the calibration method are its high precision, easy of operation, and high reliability.

Journal ArticleDOI
TL;DR: In this paper, a composite structured light pattern is formed by modulating two separate fringe patterns with a π phase difference along the orthogonal direction of the two distinct carrier frequencies.
Abstract: In Fourier transform profilometry (FTP), the zero frequency of the imaged patterns will influence the measurement range and precision. The π phase shifting technique is usually used to eliminate the zero order component, but this method requires the capture of two fringe patterns with a π phase difference between them, which will impede the real time application of the method. In this paper, a novel method is proposed, in which a composite structured light pattern is projected onto the object. The composite structured light pattern is formed by modulating two separate fringe patterns with a π phase difference along the orthogonal direction of the two distinct carrier frequencies. This method can eliminate the zero frequency by using only one fringe pattern. Experiments show that there is no decrease in the precision of this novel method compared with the traditional π phase shifting technique.

Journal ArticleDOI
TL;DR: In this paper, the effect of laser beam geometry and scanning direction on tube bending has been investigated, where axial scanning has been used for tube bending instead of commonly used circumferential scans.
Abstract: Laser forming has received considerable attention in recent years. Within laser forming, tube bending is an important industrial activity, with applications in critical engineering systems like micro-machines, heat exchangers, hydraulic systems, boilers, etc. Laser tube bending utilizes the thermal stresses generated during laser scanning to achieve the desired bends. The parameters to control the process are usually laser power, beam diameter, scanning velocity and number of scans. Recently axial scanning has been used for tube bending instead of commonly used circumferential scans. However the comparison between the scanning schemes has involved dissimilar laser beam geometries with circular beam used for circumferential scanning and a rectangular beam for the axial scan. Thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry and scanning direction and hence it is difficult to isolate the contribution made by these two variables. It has recently been established at the Corrosion and Protection Centre, University of Manchester, that corrosion properties of material during laser forming are affected by the number of laser passes. Depending on the material, the corrosion behaviour is either adversely or favourably affected by number of passes. Thus it is of great importance to know how different scanning schemes would affect laser tube bending. Moreover, any scanning scheme which results in greater bending angle would eliminate the need for higher number of passes, making the process faster. However, it is not only the bending angle which is critical, distortions in other planes are also extremely important. Depending on the use of the final product, unwanted distortions may be the final selection criteria. This paper investigates the effect of scanning direction on laser tube bending. Finite-element modelling has been used for the study of the process with some results also validated by experiments.

Journal ArticleDOI
TL;DR: In this article, index-guided triangular PCF with air-core is introduced which guides light by total internal reflection (TIR) when the air core is smaller than the air holes in cladding.
Abstract: In the paper, index-guided triangular PCF with air-core is introduced which guides light by total internal reflection (TIR) when the air-core is smaller than the air holes in cladding. Properties of dispersion and leakage loss are investigated using finite-element method. The total dispersion curve gets more flattened and leakage loss increases significantly as the air-core diameter increases. High birefringence PCF with elliptical air-core is put forward and the birefringence increases with the ellipticity of the air-core.

Journal ArticleDOI
TL;DR: In this article, a modified center position detection algorithm of the spot image for the Shack-Hartmann wavefront sensor was experimentally investigated, where the modified center of weight algorithm uses some power from the gray-level intensity of the spots instead of the gray level intensity itself.
Abstract: A modified center position detection algorithm of the spot image for the Shack–Hartmann wavefront sensor was experimentally investigated. The modified center of weight algorithm uses some power from the gray level intensity of the spot images instead of the gray level intensity itself. From the experiments, the repeatability and accuracy of the center position detection of the spot images which used the algorithm were improved when compared with those using the conventional center of weight algorithm. Applications of the algorithm to the measurement of the displacement of the spot images of the Shack–Hartmann wavefront sensor and the experimental results of the closed-loop wavefront correction are described in this paper.

Journal ArticleDOI
TL;DR: In this paper, the authors presented the results of the implementation of ion-chemical etching technology for generating a diffraction grating on the surface of a diamond film and the results on generating diamond diffractive optical elements and a sub-wavelength antireflection structure by plasma etching were also presented.
Abstract: The fabrication of diamond-based optical elements for high-power CO2 lasers is of particular interest because of low optical absorption, high thermal conductivity and weak temperature dependence of the refractive index of diamond. In earlier publications, we presented the results of the implementation of ion-chemical etching technology for generating a diffraction grating on the surface of a diamond film. The results on generating diamond diffractive optical elements and a sub-wavelength antireflection structure by plasma etching were also presented. In this paper, we study the generation of the grating on the diamond surface by ion-chemical etching. The choice of (Ar+O2) mixture as a working gas and use of niobium as a masking layer are substantiated. The results of studying a diffraction microrelief generated on the diamond-film surface through ion-chemical etching are discussed.

Journal ArticleDOI
TL;DR: In this paper, a CO 2 laser with a line-shape beam was used to cleave a soda-lime glass substrate at various beam-rotation angles to the cutting direction.
Abstract: A CO 2 laser with a line-shape beam was used to cleave a soda-lime glass substrate at various beam-rotation angles to the cutting direction. The stress distribution on the glass substrate cleaved by the laser beam has been analyzed in this study. An uncoupled thermal-elastic analysis was achieved by the ABAQUS software based on the finite element method. The numerical results show that the stress field of the fracture is caused by a complex stress state and the cleavages are significantly affected by the heat diffusion and beam rotation angle. At the rotation angle of zero degree to the cleaving direction, the phenomena of the chip formation have been found due to a large temperature gradient at the cleaving depth of the glass substrate.

Journal ArticleDOI
TL;DR: In this article, a ring tunable fiber laser based on Bragg gratings (TFBG) integrated with an optical circulator has been developed for the C-band with a side mode suppression ratio of 60 dB and power conversion efficiency of 25%.
Abstract: We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the oscillation of a single cavitation bubble near a solid boundary using a fiber-optic diagnostic technique based on optical beam deflection (OBD) and derived the maximum bubble radii and collapse time for each oscillation cycle from a sequence of bubble oscillations.
Abstract: The oscillation of a laser-generated single cavitation bubble near a solid boundary is investigated by a fiber-optic diagnostic technique based on optical beam deflection (OBD). The maximum bubble radii and collapse time for each oscillation cycle are determined from a sequence of bubble oscillations. Furthermore, by combining the revised Rayleigh theory, the prolongation factor κ at different dimensionless parameter γ ( γ = L / R max , where Rmax is the maximum bubble radius and L is the distance of a cavity inception point from a boundary) is obtained. In addition, the prolongation factor of the collapse time versus laser energy is also derived, which are valuable in the fields of hydraulic cavitation, laser lithotripsy and laser ophthalmology.

Journal ArticleDOI
Zhou. Xin1, Lai. Dong1, Yuan Sheng1, li da-hai1, Hu Jian-ping 
TL;DR: The quality of the reconstructed hidden image and of the composed image has been analyzed as thesuperposition weight varies, allowing the determination of the optimum superposition weight.
Abstract: A method for hiding information is proposed. Firstly, the image to be hidden is encoded by the doubled-random phase-encoding technique. Then, the real part of the encoded data, together with the imaginary part, is embedded into a sufficiently large host image, which has been enlarged according to some rules. The superposition weighting is adjusted to a proper value such that the composed image will not be subject to severe degradation compared to the original host image. When decryption is needed, the reconstructed hidden image can be extracted directly from the composed image without using original host image, with the result being quite satisfactory. The quality of the reconstructed hidden image and of the composed image has been analyzed as the superposition weight varies, allowing the determination of the optimum superposition weight. The optimum superposition weight is related to the average gray level value of the hiding image.

Journal ArticleDOI
Jichang Liu1, Lijun Li1
TL;DR: In this paper, the effects of process variables on wall thickness, powder primary efficiency and speed of forming a thin metallic wall in single-pass coaxial laser cladding are investigated, and some resolution models are established and testified experimentally.
Abstract: In this paper, effects of process variables on wall thickness, powder primary efficiency and speed of forming a thin metallic wall in single-pass coaxial laser cladding are investigated, and some resolution models are established and testified experimentally. With some assumptions, each of wall thickness, powder primary efficiency and formation speed can be defined as a function of the process variables. Wall thickness is equal to width of the molten pool created in single-pass laser cladding and determined by laser absorptivity, laser power, initial temperature, scanning speed and thermo-physical properties of clad material. Powder primary efficiency and formation speed are both dependent on an exponential function involving the ratio of melt pool width, which is decided by the process variables, to powder flow diameter. In addition, formation speed is influenced by powder feed rate. In present experiment, a 500 W continual-wave (CW) CO2 laser is used to produce thin-wall samples by single-pass coaxial laser cladding. The experimental results agree well with the calculation values despite some errors.

Journal ArticleDOI
TL;DR: In this article, an end-pumping with a fiber-coupled diode laser was demonstrated with room-temperature continuous-wave (cw) operation with the newly developed Yb:NaLa(WO 4 ) 2 disordered crystal.
Abstract: Room-temperature continuous-wave (cw) laser operation is demonstrated with the newly developed Yb:NaLa(WO 4 ) 2 disordered crystal by end-pumping with a fiber-coupled diode laser. A maximum output power of 330 mW is obtained with an optical efficiency of 4.9% and a slope efficiency of 6.3% with respect to the incident pump power. The efficiencies in terms of the absorbed pump power are roughly three times higher. Sellmeier dispersion curves for the ordinary and extraordinary refractive indices of the NaLa(WO 4 ) 2 host are reported along with crystallographic and spectroscopic properties related to the Yb 3+ -doping.

Journal ArticleDOI
TL;DR: In this article, a variety of near-field optical microscopy (SNOM)-based fabrication techniques have been developed for different applications, including material modification, addition, and removal, with emphasis on their abilities and reliability to make structures with resolutions at the nanometer level.
Abstract: In addition to its well-known capabilities in imaging and spectroscopy, scanning near-field optical microscopy (SNOM) has recently shown its great potentials for fabricating various structures at the nanoscale. A variety of SNOM-based fabrication techniques have been developed for different applications. In this paper, the SNOM-based techniques involving three major functions: material modification, addition, and removal, are examined with emphasis on their abilities and reliability to make structures with resolutions at the nanometer level. The principles and procedures underlying each technique are presented, and the differences and uniqueness among them are subsequently discussed. Finally, concluding remarks are provided to summarize the major techniques studied and to recommend the scopes for technology improvement and future research.

Journal ArticleDOI
TL;DR: In this article, a system that has been designed, the laser beam at selected wavelength and intensity was directed onto a selected textile surface and a computer-controlled laser beam source was used to change the colour substances on the textile surface.
Abstract: Developing new designs by using the computer and transferring the designs that are obtained to textile surfaces will not only increase and facilitate the production in a more practical manner, but also help you create identical designs. This means serial manufacturing of the products at standard quality and increasing their added values. Moreover, creating textile designs using the laser will also contribute to the value of the product as far as the consumer is concerned because it will not cause any wearing off and deformation in the texture of the fabric unlike the other methods. In the system that has been designed, the laser beam at selected wavelength and intensity was directed onto a selected textile surface and a computer-controlled laser beam source was used to change the colour substances on the textile surface. Pigment printing is also used for designing in textile and apparel sector. In this method, designs are transferred to the fabric manually by using dyestuff. In this study, the denim fabric used for the surfacing trial was 100% cotton, with a weft count per centimeter of 20 and a warp count per centimeter of 27, with fabric weight of 458 g/m 2 . The first step was to prepare 40 pieces of denim samples, half of which were prepared manually pigment printing and the other half by using the laser beam. After this, some test applications were done. The tensile strength, tensile extension and some fastness values of designed pieces with two methods were compared according to the international standards.

Journal ArticleDOI
TL;DR: Optical phase conjugation in gelatin film doped with basic green 1 has been measured using CW laser radiation ( λ = 632.8nm) generated by He-Ne laser of total power 35mW.
Abstract: Optical phase conjugation in gelatin film doped with basic green 1 has been measured using CW laser radiation ( λ =632.8 nm) generated by He–Ne laser of total power 35 mW. The degenerate four-wave mixing (DFWM) experiment allowed for measurement of phase conjugate reflectivity as a function of dye concentration, backward beam intensity, forward beam intensity, probe beam intensity, mean pumping beam intensity and angle between the forward pumping beam and probe beam. For 1 mM concentration of basic green 1-doped gelatin film, 0.1% phase conjugate reflectivity has been observed.

Journal ArticleDOI
TL;DR: In this paper, the beam combining of fiber array with hexagonal ring distribution is studied in detail and theoretical analysis and numerical calculation results are given to illustrate the propagation properties of the resulting beam through free space.
Abstract: Beam combining of fiber array with hexagonal ring distribution is studied in detail. The theoretical analysis and numerical calculation results are given to illustrate the propagation properties of the resulting beam through free space. A comparison between the coherent and the incoherent case shows that high peak irradiance and good beam quality for coherent combining can be obtained in the far field. The effect of phase errors and the beam quality M2 factor are also studied. Results indicate that the element numbers should be increased to achieve high power and the space between adjacent elements should be reduced to maintain good beam quality, which is basically the same for both coherent and incoherent beam combining.

Journal ArticleDOI
TL;DR: In this paper, the design and operation of a plastic optical fiber (POF) sensor based on the unconventional light leakage from one fiber to another one causing intensity modulation are presented, the dominant loss mechanism was found to be the evanescent loss and based on this phenomenon the optical fiber sensor was designed.
Abstract: In this article design and operation of a plastic optical fiber (POF) sensor based on the unconventional light leakage from one fiber to another one causing intensity modulation are presented. The dominant loss mechanism was found to be the evanescent loss and based on this phenomenon the optical fiber sensor was designed. The penetration depth of evanescent wave as a function of different refractive index of cladding was calculated. Operation of this sensor was tested as a liquid level sensor for different liquids and the experimental results are compared. The dry (air interface layer) and wet output (liquid interface layer) signals for this probe were measured for a series of measurements and important factors concerning sensor operation are described. The precision of measured values, reproducibility of the results (1.35% error), and the stability of sensing operation as a function of time at different launching powers are also reported (0.85% error). The reported results for this design are promising and verify the successful operation of such a device as a liquid level probe and also as an on/off level switch.

Journal ArticleDOI
TL;DR: It is shown that an advanced algorithm is able to achieve carrier removal with minimal manual intervention and significantly simplify the calibration process of a fringe projection system.
Abstract: This paper describes a comparison of several carrier-removal techniques normally used in fringe projection for surface shape measurement. The performance of various algorithms, including the necessity for manual intervention, the complexity in data recording, and the side effect on measurement accuracy, is evaluated. The applicability of nonlinear carrier removal and the restrictions on the direction of carrier fringe in various algorithms are also investigated in this paper. It is also shown that an advanced algorithm is able to achieve carrier removal with minimal manual intervention and significantly simplify the calibration process of a fringe projection system.

Journal ArticleDOI
TL;DR: In this paper, the authors report the fabrication of single mode SiC waveguides and the measurement of their propagation loss, which can be used as a benchmark for further development of SiC microphotonic components and circuit for sensor systems in harsh environment.
Abstract: We report the fabrication of single mode SiC (silicon carbide) waveguides and the measurement of their propagation loss. By studying the effect of sidewalls scattering loss due to surface roughness and by reducing it, minimal propagation loss of 2.3 dB/cm for the TM polarization is measured in the visible at 0.633 μm. This loss can be used as a benchmark for further development of SiC microphotonic components and circuit for sensor systems in harsh environment.