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Sample records for laser ablation caracterizacion

  1. Structural characterization of thin films of titanium nitride deposited by laser ablation; Caracterizacion estructural de peliculas delgadas de nitruro de titanio depositadas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Castro C, M.A.; Escobar A, L.; Camps C, E.; Mejia H, J.A. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2004-07-01

    Thin films of titanium nitride were deposited using the technique of laser ablation. It was studied the effect of the density of laser energy used for ablation the target as well as of the pressure of the work gas about the structure and the hardness of the deposited thin films. Depending on the pressure of the work gas films was obtained with preferential orientation in the directions (200) and (111). At a pressure of 1 x 10{sup -2} Torr only the direction (200) was observed. On the other hand to the pressure of 5 x 10{sup -3} Torr the deposited material this formed by a mixture of the orientation (200) and (111), being the direction (111) the predominant one. Thin films of Ti N were obtained with hardness of up to 24.0 GPa that makes to these attractive materials for mechanical applications. The hardness showed an approximately linear dependence with the energy density. (Author)

  2. Synthesis and characterization of nanoparticles of nickel obtained by laser ablation; Sintesis y caracterizacion de nanoparticulas de niquel obtenidas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Aviles, R.; Escobar A, L.; Camps, E.; Santiago, P. [ININ, A.P. 18-1027, 11801 Mexico D.F. (Mexico); Ascencio, J.A.; Von, H. [Instituto Mexicano del Petroleo, Mexico D.F. (Mexico)

    2002-07-01

    The result of the formation of nickel nanoparticles by the laser ablation technique with a size less or equal to 1.3 nm is reported, also the formation of agglomerates of tens of nanometers is shown. Under the experimental conditions used a high particle density (around 10{sup 5} particles/{mu}m{sup 2}) is obtained. The stability of the particles in function of its atom quantity, for less or equal sizes to 2 nm is studied, finding that the most stable structure is the icosahedron. (Author)

  3. Synthesis and characterization of titanium dioxide thin films deposited by laser ablation; Sintesis y caracterizacion de peliculas delgadas de TiO{sub 2} depositadas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Escobar A, L.; Camps C, E.; Falcon B, T.; Carapia M, L.; Haro P, E.; Camacho L, M.A. [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, C.P. 11801 Mexico D.F. (Mexico)

    2000-07-01

    In this work are presented the results obtained when TiO{sub 2} thin films were deposited using the laser ablation technique. Thin films were deposited at different substrate temperatures, and different oxygen pressures, with the purpose of studying the influence of this deposit parameters in the structural characteristics of the films obtained. The structural characterization was realized through Raman Spectroscopy and X-ray Diffraction (XRD), the surface morphology of the layers deposited was verified by Scanning Electron Microscopy (Sem). The results show that the films obtained are of TiO{sub 2} in rutile phase, getting this at low substrate temperatures, its morphology shows a soft surface with some spattered particles and good adherence. (Author)

  4. Synthesis and characterization of thin films of nitrided amorphous carbon deposited by laser ablation; Sintesis y caracterizacion de peliculas delgadas de carbono amorfo nitrurado, depositadas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Rebollo P, B

    2001-07-01

    The objective of this work is the synthesis and characterization of thin films of amorphous carbon (a-C) and thin films of nitrided amorphous carbon (a-C-N) using the laser ablation technique for their deposit. For this purpose, the physical properties of the obtained films were studied as function of diverse parameters of deposit such as: nitrogen pressure, power density, substrate temperature and substrate-target distance. For the characterization of the properties of the deposited thin films the following techniques were used: a) Raman spectroscopy which has demonstrated being a sensitive technique to the sp{sup 2} and sp{sup 3} bonds content, b) Energy Dispersive Spectroscopy which allows to know semi-quantitatively way the presence of the elements which make up the deposited films, c) Spectrophotometry, for obtaining the absorption spectra and subsequently the optical energy gap of the deposited material, d) Ellipsometry for determining the refraction index, e) Scanning Electron Microscopy for studying the surface morphology of thin films and, f) Profilemetry, which allows the determination the thickness of the deposited thin films. (Author)

  5. Laser ablation principles and applications

    CERN Document Server

    1994-01-01

    Laser Ablation provides a broad picture of the current understanding of laser ablation and its many applications, from the views of key contributors to the field. Discussed are in detail the electronic processes in laser ablation of semiconductors and insulators, the post-ionization of laser-desorbed biomolecules, Fourier-transform mass spectroscopy, the interaction of laser radiation with organic polymers, laser ablation and optical surface damage, laser desorption/ablation with laser detection, and laser ablation of superconducting thin films.

  6. Power Laser Ablation Symposia

    CERN Document Server

    Phipps, Claude

    2007-01-01

    Laser ablation describes the interaction of intense optical fields with matter, in which atoms are selectively driven off by thermal or nonthermal mechanisms. The field of laser ablation physics is advancing so rapidly that its principal results are seen only in specialized journals and conferences. This is the first book that combines the most recent results in this rapidly advancing field with authoritative treatment of laser ablation and its applications, including the physics of high-power laser-matter interaction. Many practical applications exist, ranging from inertial confinement fusion to propulsion of aerostats for pollution monitoring to laser ignition of hypersonic engines to laser cleaning nanoscale contaminants in high-volume computer hard drive manufacture to direct observation of the electronic or dissociative states in atoms and molecules, to studying the properties of materials during 200kbar shocks developed in 200fs. Selecting topics which are representative of such a broad field is difficu...

  7. femtosecond laser ablation

    OpenAIRE

    Margetic, Vanja

    2003-01-01

    Femtosecond laser ablation was investigated as a solid sampling method for elemental chemical analysis. In comparison to the sampling with longer laser pulses, two aspects could be improved by using ultrashort pulses: elimination of the elemental fractionation from the ablation crater, which is necessary for an accurate quantitative analysis, and better control of the material removal (especially for metals), which increases the spatial resolution of microanalysis. Basic aspects of ultrashort...

  8. Characterization by FTIR and nuclear analytical techniques of CN{sub x} films elaborated by laser ablation; Caracterizacion por FTIR y tecnicas analiticas nucleares de peliculas de CN{sub x} elaboradas por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Olea M, O.F

    2003-07-01

    At the present time the technique of deposit of laser ablation is used to produce different types of thin films. At the moment in the National Institute of Nuclear Research (ININ) it is carried out an investigation on the thermoluminescent response of thin films of CN{sub x} with possible application in dosimetry of electromagnetic radiation. Under this context, the present work is part of this investigation and has as objective to characterize thin films of CN{sub x} by means of Infrared spectrometry and nuclear analytical techniques. The deposits were elaborated by laser ablation under different such experimental conditions as: pressure of Nitrogen in the system (3 x 10{sup -3} and 7.5 X 10{sup -2} Torr), Distance target-substrate (3 and 5 cm) and density of incident energy in the target (from 17.5 up to 23.8 J/cm{sup 2}). Graphite of high purity was used like target and the deposits were made on their substrates of intrinsic silicon (100). By means of infrared spectrometry by Fourier Transform (Ftir) the type of bonds which are in the structure of the films of CN{sub x} were determined. The spectra of this type of samples present in general four characteristic bands related with different types of bonds among the elements C, O, H, N such as: C-C, C-N, C-H, N-H, O-H, C=N, C{identical_to}N, among others. It was carried out a semi quantitative study of the samples isolating each band of the total infrared spectra and making a comparison between their intensities and forms. This study allowed to observe that there is a dependence of the structure of the films with regard to the time, since mainly bonds of the type Sp{sup 3} between Hydrogen and Carbon (C-H) they presented a remarkable variation in intensity, increasing as it lapsed the time until reaching to a stabilization where the bonds already not varying. This increase probably is due to the absorption of water of the atmosphere, although one has seen in the literature that the incorporation of this compound in

  9. Field enhancement induced laser ablation

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob

    Sub-diffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures...

  10. Laser ablation in analytical chemistry.

    Science.gov (United States)

    Russo, Richard E; Mao, Xianglei; Gonzalez, Jhanis J; Zorba, Vassilia; Yoo, Jong

    2013-07-02

    In 2002, we wrote an Analytical Chemistry feature article describing the Physics of Laser Ablation in Microchemical Analysis. In line with the theme of the 2002 article, this manuscript discusses current issues in fundamental research, applications based on detecting photons at the ablation site (LIBS and LAMIS) and by collecting particles for excitation in a secondary source (ICP), and directions for the technology.

  11. Laser ablation studies of nanocomposites

    Directory of Open Access Journals (Sweden)

    Oleg V. Mkrtychev

    2015-03-01

    Full Text Available The first experimental measurements of the threshold energy density values for the laser ablation of glass nanocomposites with nanodimensional coatings have been carried out under the action of the YAG–Nd laser power pulse radiation. The coatings in question were of different compositions and had been created by the sol–gel technology. The procedure for determining the laser ablation threshold energy density values was worked out on the base of the breakdown probability level of 0.5. The statistical processing of the measurement data over all the samples allowed obtaining the dependence of the ablation destruction threshold energy parameters on the coating physical and chemical properties such as the sample transmission in the visible region of the spectrum, coating thickness, the chemical composition of the film-forming solution, and on the pulse duration of laser radiation.

  12. Laser ablation and optical surface damage

    Science.gov (United States)

    Chase, L. L.; Hamza, A. V.; Lee, H. W. H.

    Laser ablation usually accompanies optical surface damage to bare surfaces and coatings. Investigations of optical damage mechanisms by observation of ablation processes at laser fluences very close to the optical damage threshold are described. Several promising surface characterization methods for investigating damage mechanisms are also described. The possible role of laser ablation in initiating or promoting optical surface damage is discussed.

  13. Laser ablation mechanisms and optical surface damage

    Science.gov (United States)

    Chase, L. L.; Hamza, A. V.; Lee, H. W. H.

    1991-05-01

    Laser ablation usually accompanies optical surface damage to bare surfaces and coatings. Investigations of optical damage mechanisms by observation of ablation processes at laser fluences very close to the optical damage threshold are described. Several promising surface characterization methods for investigating damage mechanisms are also described. The possible role of laser ablation in initiating or promoting optical surface damage is discussed.

  14. Femtosecond laser ablation of enamel

    Science.gov (United States)

    Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

    2016-06-01

    The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

  15. Laser ablation at the hydrodynamic regime

    Directory of Open Access Journals (Sweden)

    Gojani Ardian B.

    2013-04-01

    Full Text Available Laser ablation of several metals and PVC polymer by high energy nanosecond laser pulses is investigated experimentaly. Visualization by shadowgraphy revealed the dynamics of the discontinuities in ambient air and ablation plume above the target surface, while surface profiling allowed for determination of the ablated mass.

  16. Laser ablation at the hydrodynamic regime

    OpenAIRE

    Gojani Ardian B.

    2013-01-01

    Laser ablation of several metals and PVC polymer by high energy nanosecond laser pulses is investigated experimentaly. Visualization by shadowgraphy revealed the dynamics of the discontinuities in ambient air and ablation plume above the target surface, while surface profiling allowed for determination of the ablated mass.

  17. Laser Ablation Propulsion A Study

    Science.gov (United States)

    Irfan, Sayed A.; Ugalatad, Akshata C.

    Laser Ablation Propulsion (LAP) will serve as an alternative propulsion system for development of microthrusters. The principle of LAP is that when a laser (pulsed or continuous wave) with sufficient energy (more than the vaporization threshold energy of material) is incident on material, ablation or vaporization takes place which leads to the generation of plasma. The generated plasma has the property to move away from the material hence pressure is generated which leads to the generation of thrust. Nowadays nano satellites are very common in different space and defence applications. It is important to build micro thruster which are useful for orienting and re-positioning small aircraft (like nano satellites) above the atmosphere. modelling of LAP using MATLAB and Mathematica. Schematic is made for the suitable optical configuration of LAP. Practical experiments with shadowgraphy and self emission techniques and the results obtained are analysed taking poly (vinyl-chloride) (PVC) as propellant to study the

  18. Effective temperatures of polymer laser ablation

    Science.gov (United States)

    Furzikov, Nickolay P.

    1991-09-01

    Effective temperatures of laser ablation of certain polymers are extracted from experimental dependences of ablation depths on laser fluences. Dependence of these temperatures on laser pulse durations is established. Comparison with the known thermodestruction data shows that the effective temperature corresponds to transient thermodestruction proceeding by the statistically most probable way.

  19. VUV laser ablation of polymers. Photochemical aspect

    Science.gov (United States)

    Castex, M. C.; Bityurin, N.; Olivero, C.; Muraviov, S.; Bronnikova, N.; Riedel, D.

    2000-12-01

    A photochemical theory of laser ablation owing to the direct chain scission process is considered in quite general form taking into account the modification of material. The formulas obtained can be used for estimating mechanisms of VUV laser ablation of polymers.

  20. Hydrodynamic modeling of ns-laser ablation

    Directory of Open Access Journals (Sweden)

    David Autrique

    2013-10-01

    Full Text Available Laser ablation is a versatile and widespread technique, applied in an increasing number of medical, industrial and analytical applications. A hydrodynamic multiphase model describing nanosecond-laser ablation (ns-LA is outlined. The model accounts for target heating and mass removal mechanisms as well as plume expansion and plasma formation. A copper target is placed in an ambient environment consisting of helium and irradiated by a nanosecond-laser pulse. The effect of variable laser settings on the ablation process is explored in 1-D numerical simulations.

  1. Fractional ablative erbium YAG laser

    DEFF Research Database (Denmark)

    Taudorf, Elisabeth H; Haak, Christina S; Erlendsson, Andrés M

    2014-01-01

    BACKGROUND AND OBJECTIVES: Treatment of a variety of skin disorders with ablative fractional lasers (AFXL) is driving the development of portable AFXLs. This study measures micropore dimensions produced by a small 2,940 nm AFXL using a variety of stacked pulses, and determines a model correlating...... laser parameters with tissue effects. MATERIALS AND METHODS: Ex vivo pig skin was exposed to a miniaturized 2,940 nm AFXL, spot size 225 µm, density 5%, power levels 1.15-2.22 W, pulse durations 50-225 microseconds, pulse repetition rates 100-500 Hz, and 2, 20, or 50 stacked pulses, resulting in pulse...... 190 to 347 µm. CONCLUSIONS: Pulse stacking with a small, low power 2,940 nm AFXL created reproducible shallow to deep micropores, and influenced micropore configuration. Mathematical modeling established relations between laser settings and micropore dimensions, which assists in choosing laser...

  2. Laser ablation in analytical chemistry - A review

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

    2001-10-10

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

  3. UV Laser Ablation of Electronically Conductive Polymers

    Science.gov (United States)

    1992-06-16

    deionized water. The polymerization solution for polyaniline was prepared by mixing equal volumes of a solution that was 0.25 M in ammonium persulfate with a...rum2,0 vvcsL) TbeUV.layer ablation of thin polypyrrole and polyaniline films coated on an insulating substrate is described. UV laser ablation is used to...11liiii929. 6 1 2:- A ABSTRACT The UV laser ablation of thin polypyrrole and polyaniline films coated on an insulating substrate is described. UV laser

  4. Nanosecond laser ablation of bulk Al, Bronze, and Cu: ablation rate saturation and laserinduced oxidation

    OpenAIRE

    R. Maisterrena-Epstein; S. Camacho-López; L. Escobar-Alarcón; M. A. Camacho-López

    2007-01-01

    In this work we report about the characteristics of nanosecond laser ablation, in atmospheric air, of bulk Al, Bronze, and Cu. Average per pulse laser ablation rate and its dependence on ablation depth is presented for these three metals. We will demonstrate and discuss some distinctive features of the ablation saturation effect of the above metals. We will also present results on laser-induced oxidation of the metals which results off the ablation event. We studied the laser-induced oxidatio...

  5. Ablation of solids by femtosecond lasers ablation mechanism and ablation thresholds for metals and dielectrics

    CERN Document Server

    Gamaly, E G; Tikhonchuk, V T; Luther-Davies, B

    2001-01-01

    The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The formulae for ablation thresholds and ablation rates for metals and dielectrics, combining the laser and target parameters, are derived and compared to experimental data. The calculated dependence of the ablation thresholds on the pulse duration is in agreement with the experimental data in a femtosecond range, and it is linked to the dependence for nanosecond pulses.

  6. Ablation of solids by femtosecond lasers: ablation mechanism and ablation thresholds for metals and dielectrics

    OpenAIRE

    Gamaly, E. G.; Rode, A. V.; Tikhonchuk, V. T.; Luther-Davies, B.

    2001-01-01

    The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The formulae ...

  7. Analysis of infrared laser tissue ablation

    Science.gov (United States)

    McKenzie, Gordon P.; Timmerman, Brenda H.; Bryanston-Cross, Peter J.

    2005-04-01

    The mechanisms involved in infrared laser tissue ablation are studied using a free electron laser (FELIX) in order to clarify whether the increased ablation efficiency reported in literature for certain infrared wavelengths is due to a wavelength effect or to the specific pulse structure of the lasers that are generally used in these studies. Investigations are presented of ablation of vitreous from pigs" eyes using several techniques including protein gel electrophoresis and ablation plume visualization. The ablation effects of three different infrared wavelengths are compared: 3 mm, which is currently in clinical surgical use, and the wavelengths associated with the amide I and amide II bands, i.e. 6.2 mm and 6.45mm, respectively. The results suggest a different ablation mechanism to be in operation for each studied wavelength, thus indicating that the generally reported increased ablation efficiency in the 6-6.5 micron range is due to the wavelength rather than the typical free electron laser pulse structure.

  8. Mechanism of Spatiotemporal Distribution of Laser Ablated Materials

    Institute of Scientific and Technical Information of China (English)

    XU Rong-Qing; CUI Yi-Ping; LU Jian; NI Xiao-Wu

    2009-01-01

    Interaction between subsequent laser and ablated materials in laser processing changes the laser spatiotemporal distribution and has influences on the efficiency and quality of laser processing. The theoretical and experimental researches on transportation behayiour of ablated materials are provided. It is shown that the velocity distribution of ablated materials is determined by ablation mechanism. The transportation behaviour of ablated materials is controlled by diffusion mechanism and light field force during laser pulse duration while it is only determined by diffusion mechanism when the laser pulse terminates. In addition, the spatiotemporal distribution of ablated materials is presented.

  9. Diagnostics of laser ablated plasma plumes

    DEFF Research Database (Denmark)

    Amoruso, S.; Toftmann, B.; Schou, Jørgen;

    2004-01-01

    The effect of an ambient gas on the expansion dynamics of laser ablated plasmas has been studied for two systems by exploiting different diagnostic techniques. First, the dynamics of a MgB2 laser produced plasma plume in an Ar atmosphere has been investigated by space-and time-resolved optical...

  10. Nanosecond laser ablation of silver nanoparticle film

    Science.gov (United States)

    Chung, Jaewon; Han, Sewoon; Lee, Daeho; Ahn, Sanghoon; Grigoropoulos, Costas P.; Moon, Jooho; Ko, Seung H.

    2013-02-01

    Nanosecond laser ablation of polyvinylpyrrolidone (PVP) protected silver nanoparticle (20 nm diameter) film is studied using a frequency doubled Nd:YAG nanosecond laser (532 nm wavelength, 6 ns full width half maximum pulse width). In the sintered silver nanoparticle film, absorbed light energy conducts well through the sintered porous structure, resulting in ablation craters of a porous dome shape or crown shape depending on the irradiation fluence due to the sudden vaporization of the PVP. In the unsintered silver nanoparticle film, the ablation crater with a clean edge profile is formed and many coalesced nanoparticles of 50 to 100 nm in size are observed inside the ablation crater. These results and an order of magnitude analysis indicate that the absorbed thermal energy is confined within the nanoparticles, causing melting of nanoparticles and their coalescence to larger agglomerates, which are removed following melting and subsequent partial vaporization.

  11. Laser ablation of a polysilane material

    Science.gov (United States)

    Hansen, S. G.; Robitaille, T. E.

    1987-08-01

    The laser ablation properties of a (50%)-isopropyl methyl-(50%)-n-propyl methyl silane copolymer are examined. Both 193- and 248-nm-pulsed excimer laser radiation cleanly and completely remove this material in vacuum above certain energy thresholds (30 and 50 mJ/cm2, respectively). Under these conditions the ablation properties are quite similar to those reported for typical organic polymers. Below threshold, ablation is less efficient and becomes increasingly inefficient as irradiation continues due to spectral bleaching. In the presence of air, material removal is incomplete even for high-energy densities and long exposures. The ablation rate is shown to be independent of substrate material both above and below threshold.

  12. UV laser ablation patterns in intraocular lenses

    Science.gov (United States)

    Lagiou, D. P.; Evangelatos, Ch.; Apostolopoulos, A.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-03-01

    The aim of this work is to investigate the effect of UV solid state laser radiation on intraocular lens (IOL) polymer surfaces as an alternative method to conventional surface shaping techniques for IOLs customization. Laser ablation experiments were performed on PMMA plates and commercially available hydrophobic and hydrophilic acrylic IOLs with the 5th harmonic of a Q-switched Nd:YAG laser (λ=213 nm). Circular arrays of holes were drilled on the polymer surface, covering the centre and the peripheries of the IOL. The morphology of the ablated IOL surface was examined with a conventional optical microscope (Leitz GMBH Wetzlar) and with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements of ablation rates were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variationsF in surface height. Laser interaction with IOLs depends on optical and mechanical material properties, in addition to laser radiation parameters. The exact ablation mechanism is discussed. Some polymer materials, depending on their properties, are more susceptible to the photothermal mechanism than the photochemical one or vice versa. In summary, every IOL polymer exhibits specific attributes in its interaction with the 5th harmonic of Nd:YAG laser.

  13. Effects of Confined Laser Ablation on Laser Plasma Propulsion

    Institute of Scientific and Technical Information of China (English)

    ZHENG Zhi-Yuan; ZHANG Jie; LU Xin; HAO Zuo-Qiang; XU Miao-Hua; WANG Zhao-Hua; WEI Zhi-Yi

    2005-01-01

    @@ We investigate the effects of confined laser ablation on laser plasma propulsion. Compared with planar ablation,the cavity ablation provides an effective way to obtain a large target momentum and a high coupling coefficient.When laser pukes are focused into a cavity with 1 mm diameter and 2mm depth, a high coupling coefficient is obtained. By using a glass layer to cover the cavity, the coupling coefficient is enhanced by 10 times. Meanwhile,it is found that with the increase of the target surface size, the target momentum presents a linear increase.

  14. Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Doggett, B.; Budtz-Jørgensen, C.

    2013-01-01

    The ablation plume dynamics arising from ablation of silver with a 500 fs, 248 nm laser at ~2 J cm-2 has been studied using angle-resolved Langmuir ion probe and thin film deposition techniques. For the same laser fluence, the time-of-flight ion signals from femtosecond and nanosecond laser ablat...

  15. Outpatient laser tonsillar ablation under local anaesthetic.

    Science.gov (United States)

    Andrews, Peter J; Latif, Abdul

    2004-11-01

    Outpatient laser ablation of the palatine tonsils under local anaesthetic is an alternative technique to capsular tonsillectomy for recurrent tonsillitis under general anaesthetic. Laser tonsillotomy ablates up to 70% of the tonsillar tissue and is performed when patients choose not to have a conventional tonsillectomy, or are unfit for a general anaesthetic. The technique described here is an adaptation of Krespis' laser-assisted serial tonsillectomy (LAST) whereby only one sitting is required. Krespis' technique effectively eliminates recurrent tonsillitis in 96% of the cases over a 4-year follow-up period and represents the only substantial study looking at treating recurrent tonsillitis with outpatient laser ablation. This study is a retrospective postal survey of 19 patients who underwent laser tonsillar ablation under local anaesthetic for recurrent chronic tonsillitis from 1997 to 2001 and was performed in liaison with the clinical audit department at Basildon Hospital. We had a response rate of 74% and an admission rate of 0%, which compares favourably with day case tonsillectomy surgery. Of the patients, 75% did not experience further episodes of tonsillitis 12 months after the procedure and 77% of the patients were glad they had the operation. Although this technique does not completely eliminate tonsillitis, it offers an alternative for those patients who prefer a procedure that is done quickly in an outpatient setting without the additional problems of general anaesthesia, overnight hospital admission and long waiting lists.

  16. Laser ablation of hepatocellular carcinoma-A review

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A wide range of local thermal ablative therapies have been developed in the treatment of non resectable hepatocellular carcinoma (HCC) in the last decade. Laser ablation (LA) and radiofrequency ablation (RFA) are the two most widely used of these. This article provides an up to date overview of the role of laser ablation in the local treatment of HCC. General principles, technique, image guidance and patient selection are discussed. A review of published data on treatment efficacy, long term outcome and complication rates of laser ablation is included and comparison with RFA made. The role of laser ablation in combination with transcatheter arterial chemoembolisation is also discussed.

  17. Physical processes of laser tissue ablation

    Science.gov (United States)

    Furzikov, Nickolay P.

    1991-05-01

    The revised ablation model applicable to homogeneous tissues is presented. It is based on the thermal mechanism and involves the instability of the laserinduced evaporation (thermodestruction) front the growth of the surface ripple structure the interference of the laser wave and of the surface wave arising by diffraction on the ripples Beer''s law violation the pulsed thermodestruction of the organic structural component the tissue water boiling and gas dynamic expansion of the resulting products into the surrounding medium which is followed by the shock wave formation. The UV and IR ablation schemes were implemented and compared to the corneal ablation experiments. The initial ablation pressure and temperature are given restored from the timeofflight measurements of the supersonic expansion of the product. 1.

  18. Laser Thermal Ablation of Thyroid Benign Nodules.

    Science.gov (United States)

    Shahrzad, Mohammad Karim

    2015-01-01

    Thermal ablation therapies for benign thyroid nodules have been introduced in recent years to avoid the complications of traditional methods such as surgery. Despite the little complications and the reportedly acceptable efficacy of thermal ablation methods, quite few medical centers have sought the potential benefits of employing them. This paper provides an introduction to the literature, principles and advances of Percutaneous Laser Ablation therapy of thyroid benign nodules, as well as a discussion on its efficacy, complications and future. Several clinical research papers evaluating the thermal effect of laser on the alleviation of thyroid nodules have been reviewed to illuminate the important points. The results of this research can help researchers to advance the approach and medical centers to decide on investing in these novel therapies.

  19. Bending diamonds by femtosecond laser ablation

    DEFF Research Database (Denmark)

    Balling, Peter; Esberg, Jakob; Kirsebom, Kim;

    2009-01-01

    We present a new method based on femtosecond laser ablation for the fabrication of statically bent diamond crystals. Using this method, curvature radii of 1 m can easily be achieved, and the curvature obtained is very uniform. Since diamond is extremely tolerant to high radiation doses, partly due...

  20. Barium Ferrite Films Grown by Laser Ablation

    NARCIS (Netherlands)

    Lisfi, A.; Lodder, J.C.; Haan, de P.; Smithers, M.A.; Roesthuis, F.J.G.

    1998-01-01

    Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al2O3 single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe12O19 phase, very well oriented with (001) texture, and exhibit a large perpendicular magnetic a

  1. Ablation of GaN Using a Femtosecond Laser

    Institute of Scientific and Technical Information of China (English)

    刘伟民; 朱荣毅; 钱土雄; 袁述; 张国义

    2002-01-01

    We study the pulsed laser ablation of wurtzite gallium nitride (GaN) films grown on sapphire, using the fem tosecond laser beam at a central wavelength of 800nm as the source for the high-speed ablation of GaN films. By measuring the backscattered Raman spectrum of ablated samples, the dependence of the ablation depth on laser fluence with one pulse was obtained. The threshold laser fluence for the ablation of GaN films was determined to be about 0.25J/cm2. Laser ablation depth increases with the increasing laser fluence until the amount of removed material is not further increased. The ablated surface was investigated by an optical surface interference profile meter.

  2. Ultrafast laser ablation of transparent materials

    Science.gov (United States)

    Bauer, Lara; Russ, Simone; Kaiser, Myriam; Kumkar, Malte; Faißt, Birgit; Weber, Rudolf; Graf, Thomas

    2016-03-01

    The present work investigates the influence of the pulse duration and the temporal spacing between pulses on the ablation of aluminosilicate glass by comparing the results obtained with pulse durations of 0.4 ps and 6 ps. We found that surface modifications occur already at fluences below the single pulse ablation threshold and that laser-induced periodic surface structures (LIPSS) emerge as a result of those surface modifications. For 0.4 ps the ablation threshold fluences is lower than for 6 ps. Scanning electron micrographs of LIPSS generated with 0.4 ps exhibit a more periodic and less coarse structure as compared to structures generated with 6 ps. Furthermore we report on the influence of temporal spacing between the pulses on the occurrence of LIPSS and the impact on the quality of the cutting edge. Keywords: LIPSS,

  3. Ultraviolet laser ablation of polyimide films

    Science.gov (United States)

    Srinivasan, R.; Braren, B.; Dreyfus, R. W.

    1987-01-01

    Pulsed laser radiation at 193, 248, or 308 nm can etch films of polyimide (DuPont KaptonTM). The mechanism of this process has been examined by the chemical analysis of the condensible products, by laser-induced fluorescence analysis of the diatomic products, and by the measurement of the etch depth per pulse over a range of fluences of the laser pulse. The most important product as well as the only one condensible at room temperature is carbon. Laser-induced fluorescence analysis showed that C2 and CN were present in the ablation plume. At 248 nm, even well below the fluence threshold of 0.08 J/cm2 for significant ablation, these diatomic species are readily detected and are measured to leave the polymer surface with translational energy of ˜5 eV. These results, when combined with the photoacoustic studies of Dyer and Srinivasan [Appl. Phys. Lett. 48, 445 (1986)], show that a simple photochemical mechanism in which one photon or less (on average) is absorbed per monomer is inadequate. The ablation process must involve many photons per monomer unit to account for the production of predominantly small (<4 atoms) products and the ejection of these fragments at supersonic velocities.

  4. Fundamental studies of pulsed laser ablation

    CERN Document Server

    Claeyssens, F

    2001-01-01

    dopant) have resulted in a coherent view of the resulting plume, which exhibits a multi-component structure correlated with different regimes of ablation, which are attributed to ejection from ZnO and ablation from a Zn melt. OES measurements show that the emitting Zn component within the plume accelerates during expansion in vacuum - an observation attributable to the presence of hot, fast electrons in the plume. The same acceleration behaviour is observed in the case of Al atomic emissions resulting from ablation of an Al target in vacuum. Deposition conditions, substrate temperature and background gas pressure were all varied in a quest for optimally aligned, high quality ZnO thin films. Initial ab initio calculations were performed also, to aid in understanding the stability of these c-axis aligned films. The pulsed ultraviolet (lambda = 193, 248 nm) laser ablation of graphite, polycrystalline diamond and ZnO targets has been investigated. Characteristics of the resulting plumes of ablated material have b...

  5. Femtosecond laser ablation of silicon in air and vacuum

    Institute of Scientific and Technical Information of China (English)

    Zehua Wu; Nan Zhang; Mingwei Wang; Xiaonong Zhu

    2011-01-01

    Femtosecond (fs) pulse laser ablation of silicon targets in air and in vacuum is investigated using a time-resolved shadowgraphic method. The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum. Similar to the ablation of metallic targets, while the shock wave front and a series of nearly concentric and semicircular stripes, as well as the contact front, are clearly identifiable in the process of ablation under 1 x 105 Pa, these phenomena are no longer observed when the ablation takes place in vacuum. Although the ambient air around the target strongly affects the evolution of the ablation plume, the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum. It is proven that the three rounds of material ejection are caused by different ablation mechanisms.%@@ Femtosecond(fs)pulse laser ablation of silicon targets in air and in vacuum is investigated using a timeresolved shadowgraphic method.The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum.Similar to the ablation of metallic targets,while the shock wave front and a series of nearly concentric and semicircular stripes,as well as the contact front,are clearly identifiable in the process of ablation under 1 x 105 Pa,these phenomena are no longer observed when the ablation takes place in vacuum.Although the ambient air around the target strongly affects the evolution of the ablation plume,the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum.It is proven that the three rounds of material ejection are caused by different ablation mechanisms.

  6. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    Science.gov (United States)

    Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

    2014-12-02

    In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

  7. Wavelength dependence of soft tissue ablation by using pulsed lasers

    Institute of Scientific and Technical Information of China (English)

    Xianzeng Zhang; Shusen Xie; Qing Ye; Zhenlin Zhan

    2007-01-01

    Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er:YAG laser produced the highest quality ablation with clear,sharp cuts following closely the patial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The blation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

  8. Numerical simulation of copper ablation by ultrashort laser pulses

    CERN Document Server

    Ding, PengJi; Li, YuHong

    2011-01-01

    Using a modified self-consistent one-dimensional hydrodynamic lagrangian fluid code, laser ablation of solid copper by ultrashort laser pulses in vacuum was simulated to study fundamental mechanisms and to provide a guide for drilling periodic microholes or microgratings on the metal surface. The simulated laser ablation threshold is a approximate constancy in femtosecond regime and increases as the square root of pulse duration in picosecond regime. The ablation depth as a function of pulse duration shows four different regimes and a minimum for a pulse duration of ~ 12ps for various laser fluences. The influence of laser-induced plasma shielding on ablation depth is also studied.

  9. Investigating Age Resolution in Laser Ablation Geochronology

    Science.gov (United States)

    Horstwood, Matt; Kosler, Jan; Jackson, Simon; Pearson, Norman; Sylvester, Paul

    2009-02-01

    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; Vancouver, British Columbia, Canada, 12-13 July 2008; Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) uranium-thorium-lead (U-Th-Pb) dating is an increasingly popular approach for determining the age of mineral grains and the timing of geological events. The spatial resolution offered by this technique allows detailed investigations of complex igneous and metamorphic processes, and the speed of data capture allows vast amounts of information to be gathered rapidly. Laser ablation U-Th-Pb dating is therefore becoming an increasingly influential technique to the geochronology community, providing cost-effective and ready access to age data for laboratories and end users worldwide. However, complications in acquiring, processing, and interpreting data can lead to inaccurate age information entering the literature. With the numbers of practitioners expanding rapidly, the need to standardize approaches and resolve difficulties (particularly involving the subjectivity in processing laser ablation U-Th-Pb data) is becoming important.

  10. Tissue tearing caused by pulsed laser-induced ablation pressure.

    Science.gov (United States)

    Cummings, J P; Walsh, J T

    1993-02-01

    Pressure induced by ablative pulses of laser radiation is shown to correlate with the mechanical disruption of tissue. The ablation pressure induced during Er:YSGG laser irradiation of skin, liver, and aorta was calculated from a ballistic pendulum-based measurement of recoil momentum. The ejected material and ablation crater were examined grossly and microscopically after ablation. A gas-dynamic model of laser-induced vaporization was used to understand the measured pressures. The results show that mechanical disruption of tissue occurs when the ablation pressure exceeds the strength of the irradiated tissue at sites of intrinsic weakness.

  11. Solar cell contact formation using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2015-07-21

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  12. Solar cell contact formation using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2014-07-22

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

  13. Solar cell contact formation using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Harley, Gabriel; Smith, David; Cousins, Peter

    2012-12-04

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  14. Ablation dynamics in laser sclerotomy ab externo

    Science.gov (United States)

    Brinkmann, Ralf; Droege, Gerit; Mohrenstecher, Dirk; Scheu, M.; Birngruber, Reginald

    1996-01-01

    Laser sclerostomy ab externo with flashlamp excited mid-IR laser systems emitting in the 2-3 micrometer spectral range is in phase II clinical trials. Although acutely high success rates were achieved, the restenosis rate after several months is about 40%. Laser pulses of several hundreds of microseconds, known to induce thermo-mechanical explosive evaporation were used for this procedure. We investigated the ablation dynamics in tissue and the cavitation bubble dynamics in water by means of an Er:YAG laser system to estimate the extent of mechanical damage zones in the sclera and in the anterior chamber, which may contribute to the clinical failure. We found substantial mechanical tissue deformation during the ablation process caused by the cavitation effects. Stress waves up to several bar generated by explosive evaporization were measured. The fast mechanical stretching and collapsing of the scleral tissue induced by cavitation resulted in tissue dissection as could be proved by flash photography and histology. The observed high restenosis might be a result of a subsequent enhanced wound healing process. Early fistula occlusions due to iris adherences, observed in about 20% of the clinical cases may be attributed to intraocular trauma induced by vapor bubble expansion through the anterior chamber after scleral perforation. An automatic feedback system minimizing adverse effects by steering and terminating the laser process during scleral fistulization is demonstrated. Moreover, a new approach in laser sclerostomy ab externo is presented using a cw-IR laser diode system emitting at the 1.94 micrometer mid-IR water absorption peak. This system was used in vitro and showed smaller damage zones compared to the pulsed laser radiation.

  15. Effects of laser ablation on cemented tungsten carbide surface quality

    Energy Technology Data Exchange (ETDEWEB)

    Tan, J.L.; Butler, D.L.; Sim, L.M.; Jarfors, A.E.W. [Singapore Institute of Manufacturing Technology, Singapore (Singapore)

    2010-11-15

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable. (orig.)

  16. Effects of laser ablation on cemented tungsten carbide surface quality

    Science.gov (United States)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  17. Laser ablation cell sorting in scanning cytometry

    Science.gov (United States)

    Shen, Feimo; Price, Jeffrey H.

    2001-05-01

    Flow cytometry has been an important tool for automated cells sorting. However, the lack of good sensitivity prevents it from being used for rare events sorting; furthermore, fragile cells, anchorage-dependent cells, and clump forming cells cannot be sorted this way. A fully automated, high-speed scanning cytometer with autofocus and image segmentation is capable of accurately locating contaminant cells in a monolayer cell population. A laser ablation system was incorporated into the cytometer to negatively sort out the unwanted cells by applying a focused, ultra-short laser pulse (sub-micron diameter, pulse duration = 4 nsec, wavelength - 500 nm) to each targeted cell. Due to the high power density (approximately 1010 W/cm2) that was present at the focal point, disruptive mechanical forces were generated and were responsible for the kill. Fluorescently stained NIH-3T3 fibroblast cells were used as a model contaminant target ells in an unstained NIH-3T3 population to determine the identification-kill effectiveness. The contaminant cells were stained with the fluorochrome CellTracker Blue CMAC, whereas the background cells were left intact. Ablation pulses were applied in frame-by-frame increment batches to the cell culture on the microscope. The negative sorting effectiveness was analyzed by automatically re-scanning the post-ablation cell culture in phase contrast and propidium iodide stained epi fluorescent fields to verify cell death.

  18. Pulsed laser ablation of solids basics, theory and applications

    CERN Document Server

    Stafe, Mihai; Puscas, Niculae N

    2014-01-01

    The book introduces ‘the state of the art' of pulsed laser ablation and its applications. It is based on recent theoretical and experimental studies. The book reaches from the basics to advanced topics of pulsed laser ablation. Theoretical and experimental fundamental phenomena involved in pulsed laser ablation are discussed with respect to material properties, laser wavelength, fluence and intensity regime of the light absorbed linearly or non-linearly in the target material. The energy absorbed by the electrons leads to atom/molecule excitation, ionization and/or direct chemical bond breaking and is also transferred to the lattice leading to material heating and phase transitions. Experimental  non-invasive optical methods for analyzing these phenomena in real time are described. Theoretical models for pulsed laser ablation and phase transitions induced by laser beams and laser-vapour/plasma interaction during the plume expansion above the target are also presented. Calculations of the ablation speed and...

  19. Superhydrophobic laser ablated PTFE substrates

    Energy Technology Data Exchange (ETDEWEB)

    Falah Toosi, Salma; Moradi, Sona [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC, V6T 1Z3 (Canada); Kamal, Saeid [Laboratory for Advanced Spectroscopy and Imaging research (LASIR) Chemistry Department, The University of British Columbia, Vancouver, BC, V6T 1Z3 (Canada); Hatzikiriakos, Savvas G., E-mail: savvas.hatzi@ubc.ca [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC, V6T 1Z3 (Canada)

    2015-09-15

    Highlights: • Uniaxial and biaxial patterns fabricated on PTFE surface are responsible for superhydrophobic behavior of the surface. • Biaxial scan artificially creates high level of dual scale roughness on the PTFE surface with high contact angles (CAs) and low contact angle hysteresis (CAH) similar in all directions. • Contact angle of biaxially scanned surfaces can be as high as 170° and their contact angle hysteresis can reach as low as 3°. - Abstract: The effect of femtosecond laser irradiation process parameters (fluence, scanning speed and beam overlap) on the wettability of the resulted micro/nano-patterned morphologies on polytetrafluoroethylene is studied in detail. Several distinctly different micro/nano-patterns were fabricated including uniaxial and biaxial patterns. In particular, using biaxial scanning well defined pillared morphology was fabricated. The wettability analysis of the biaxially scanned samples revealed enhanced superhydrophobicity exhibiting high contact angles and low contact angle hysteresis.

  20. Laser systems for ablative fractional resurfacing

    DEFF Research Database (Denmark)

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    of a variety of skin conditions, primarily chronically photodamaged skin, but also acne and burn scars. In addition, it is anticipated that AFR can be utilized in the laser-assisted delivery of topical drugs. Clinical efficacy coupled with minimal downtime has driven the development of various fractional...... ablative laser systems. Fractionated CO(2) (10,600-nm), erbium yttrium aluminum garnet, 2940-nm and yttrium scandium gallium garnet, 2790-nm lasers are available. In this article, we present an overview of AFR technology, devices and histopathology, and we summarize the current clinical possibilities...... with AFR incorporating our personal experience. AFR is still in the exploratory era, and systematic investigations of clinical outcomes related to various system settings are needed....

  1. Deflection of uncooperative targets using laser ablation

    Science.gov (United States)

    Thiry, Nicolas; Vasile, Massimiliano

    2015-09-01

    Owing to their ability to move a target in space without requiring propellant, laser-based deflection methods have gained attention among the research community in the recent years. With laser ablation, the vaporized material is used to push the target itself allowing for a significant reduction in the mass requirement for a space mission. Specifically, this paper addresses two important issues which are thought to limit seriously the potential efficiency of a laser-deflection method: the impact of the tumbling motion of the target as well as the impact of the finite thickness of the material ablated in the case of a space debris. In this paper, we developed a steady-state analytical model based on energetic considerations in order to predict the efficiency range theoretically allowed by a laser deflection system in absence of the two aforementioned issues. A numerical model was then implemented to solve the transient heat equation in presence of vaporization and melting and account for the tumbling rate of the target. This model was also translated to the case where the target is a space debris by considering material properties of an aluminium 6061-T6 alloy and adapting at every time-step the size of the computational domain along with the recession speed of the interface in order to account for the finite thickness of the debris component. The comparison between the numerical results and the analytical predictions allow us to draw interesting conclusions regarding the momentum coupling achievable by a given laser deflection system both for asteroids and space debris in function of the flux, the rotation rate of the target and its material properties. In the last section of this paper, we show how a reasonably small spacecraft could deflect a 56m asteroid with a laser system requiring less than 5kW of input power.

  2. CT Guided Laser Ablation of Osteoid Osteoma

    Directory of Open Access Journals (Sweden)

    Manohar Kachare

    2015-10-01

    Full Text Available To present our experience of Computed Tomography (CT guided laser ablation of radiologically proven osteoid osteoma in the inter trochantric region of the femur. A19 year old female presented with severe pain in left upper thigh region since 6-7 months, which was exaggerated during nights and was relived on taking oral Non Steroid Anti Inflammatory Drugs (NSAIDs. On CT scan hypodense lesion with surrounding dense sclerosis noted in intertrochanteric region in left femur. Magnetic Resonance Imaging (MRI revealed small focal predominantly cortical, oval lytic lesion in the intertrochanteric region which appeared hypointense on T1 Weighted Image (T1WI and hyperintense on T2 Weighted Image (T2WI and Short Tau Inversion Recovery (STIR image. Diffuse extensive sclerosis and hyperostosis of bone was noted surrounding the lesion appearing hypointense on T1W and T2W images. Under local anesthesia the laser fibre was inserted in the nidus under CT guidance through bone biopsy needle and 1800 joules energy delivered in the lesion continuous mode. Complete relief of pain noted after 24 hours after the treatment. CT guided LASER ablation is a safe, simple and effective method of treatment for osteoid osteoma.

  3. Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jung Hwan; Lee, Jeong Hyun [University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of); Valcavi, Roberto [Endocrinology Division and Thyroid Disease Center, Arcispedale Santa Maria Nuova, Reggio Emilia (Italy); Pacella, Claudio M. [Diagnostic Imaging and Interventional Radiology Department, Ospedale Regina Apostolorum, Albano Laziale-Rome (IT); Rhim, Hyun Chul [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Na, Dong Kyu [Human Medical Imaging and Intervention Center, Seoul (Korea, Republic of)

    2011-10-15

    Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation.

  4. Thermal character in organic polymers with nanojoule femtosecond laser ablation

    Institute of Scientific and Technical Information of China (English)

    Xiaochang Ni(倪晓昌); Ching-Yue Wang(王清月); Yanfeng Li(栗岩峰); Minglie Hu(胡明列); Zhuan Wang(王专); Lu Chai(柴路)

    2003-01-01

    Ablation experiments with femtosecond (fs) laser pulse (pulse duration 37 fs, wavelength 800 nm) on organic polymers have been performed in air. The ablation threshold is found to be only several nanojoules. The diameters of the dots ablated in the organic polymers are influenced by the laser fluence and the number of laser pulses. It is observed that heat is diffused in a threadlike manner in all directions around the central focus region. Explanations of the observed phenomena are presented. A one-dimensional waveguide is also ablated in the organic polymers.

  5. Nanosecond laser ablation and deposition of silicon

    Energy Technology Data Exchange (ETDEWEB)

    Siew, Wee Ong; Tou, Teck Yong [Multimedia University, Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Yap, Seong Shan; Reenaas, Turid Worren [Norwegian University of Science and Technology, Department of Physics, Trondheim (Norway); Ladam, Cecile; Dahl, Oeystein [SINTEF Materials and Chemistry, Trondheim (Norway)

    2011-09-15

    Nanosecond-pulsed KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) lasers were used to ablate a polycrystalline Si target in a background pressure of <10{sup -4} Pa. Si films were deposited on Si and GaAs substrates at room temperature. The surface morphology of the films was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Round droplets from 20 nm to 5 {mu}m were detected on the deposited films. Raman Spectroscopy indicated that the micron-sized droplets were crystalline and the films were amorphous. The dependence of the properties of the films on laser wavelengths and fluence is discussed. (orig.)

  6. Synthesis of Ag@Silica Nanoparticles by Assisted Laser Ablation

    Science.gov (United States)

    González-Castillo, Jr.; Rodriguez, E.; Jimenez-Villar, E.; Rodríguez, D.; Salomon-García, I.; de Sá, Gilberto F.; García-Fernández, T.; Almeida, DB; Cesar, CL; Johnes, R.; Ibarra, Juana C.

    2015-10-01

    This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon wafer immersed in water solution was laser ablated for several minutes. Subsequently, an AgNO3 aliquot was added to the aqueous solution. The redox reaction between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. The influence of the laser pulse energy, laser wavelength, ablation time, and Ag+ concentration on the size and optical properties of the Ag@Silica NPs was investigated. Furthermore, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, X-Ray diffraction, and high-resolution transmission electron microscopy (HRTEM).

  7. Ablation of steel using picosecond laser pulses in burst mode

    Science.gov (United States)

    Lickschat, Peter; Demba, Alexander; Weissmantel, Steffen

    2017-02-01

    Results obtained in picosecond laser processing of steel applying the burst mode are presented. Using the burst mode, pulse trains, i.e., bursts, consisting of a number of picosecond pulses with an inter-pulse delay of 12.5 ns and 10 ps pulse duration are applied for material processing. Small cavities with sizes in the range of the laser beam diameter made by single-burst ablation are compared to quadratic cavities of 0.5 × 0.5 mm² produced by multiburst ablation and simultaneous scanning of the laser beam across the steel sample surface. The ablated volume per pulse within the burst was calculated either from the ablated volume per burst or from the ablation depth of the quadratic cavities. With the second to fourth pulses in the bursts, a reduction of the ablated volume per pulse in comparison with the first pulse in the bursts (i.e., to the use of single pulses) was found for both single- and multiburst ablation, which is assumed to be due to plasma shielding. By contrast, the ablated volume per pulse within the bursts increases for the fifth to eighth pulses. Heat accumulation effect and the influence of the heated plasma can be assumed to be the reason for these higher ablation rates. SEM micrographs also show that there is a higher melt ejection out of the laser processed area. This is indicated by the formation of bulges about the ablated area.

  8. Laser Ablation for Cancer: Past, Present and Future

    Science.gov (United States)

    Schena, Emiliano; Saccomandi, Paola; Fong, Yuman

    2017-01-01

    Laser ablation (LA) is gaining acceptance for the treatment of tumors as an alternative to surgical resection. This paper reviews the use of lasers for ablative and surgical applications. Also reviewed are solutions aimed at improving LA outcomes: hyperthermal treatment planning tools and thermometric techniques during LA, used to guide the surgeon in the choice and adjustment of the optimal laser settings, and the potential use of nanoparticles to allow biologic selectivity of ablative treatments. Promising technical solutions and a better knowledge of laser-tissue interaction should allow LA to be used in a safe and effective manner as a cancer treatment. PMID:28613248

  9. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  10. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Science.gov (United States)

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  11. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Science.gov (United States)

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  12. Metal particles produced by laser ablation for ICP-MSmeasurements

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Jhanis J.; Liu, Chunyi; Wen, Sy-Bor; Mao, Xianglei; Russo, Richard E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm{sup -2}. Characterization of particles and correlation with Inductively Coupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of {approx} 50 and {approx} 12 for fs vs. ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the {sup 66}Zn transient signal by a factor of ten compared to nanosecond laser pulses.

  13. Excimer laser ablation of thin titanium oxide films on glass

    Energy Technology Data Exchange (ETDEWEB)

    Overschelde, O. van [Condensed Matter Physics Group, University of Mons-Hainaut, B-7000 Mons (Belgium); Dinu, S. [University of ' Valahia' , Targoviste (Romania); Guisbiers, G. [Condensed Matter Physics Group, University of Mons-Hainaut, B-7000 Mons (Belgium); Monteverde, F. [Materia Nova, Unit of Electronic Microscopy, B-7000 Mons (Belgium); Nouvellon, C. [Materia Nova, Inorganic and Analytical Chemistry, B-7000 Mons (Belgium); Wautelet, M. [Condensed Matter Physics Group, University of Mons-Hainaut, B-7000 Mons (Belgium)]. E-mail: michel.wautelet@umh.ac.be

    2006-04-30

    Thin titanium dioxide films are deposited on glass substrates by magnetron sputter deposition. They are irradiated in air, by means of a KrF excimer laser. The ablation rate is measured as a function of the laser fluence per pulse, F, and of the number of pulses, N. Above a fluence threshold, the films are partially ablated. The ablated thickness does not vary linearly with N. This is the signature of a negative feedback between the film thickness and the ablation rate. The origin of this negative feedback is shown to be due to either thermal or electronic effects, or both. At high F, the film detachs from the substrate.

  14. UV laser ablation of parylene films from gold substrates

    Energy Technology Data Exchange (ETDEWEB)

    O. R. Musaev, P. Scott, J. M. Wrobel, and M. B. Kruger

    2009-11-19

    Parylene films, coating gold substrates, were removed by laser ablation using 248 nm light from an excimer laser. Each sample was processed by a different number of pulses in one of three different environments: air at atmospheric pressure, nitrogen at atmospheric pressure, and vacuum. The laser-induced craters were analyzed by optical microscopy and x-ray photoelectron spectroscopy. Multi-pulse ablation thresholds of gold and parylene were estimated.

  15. Investigations on laser hard tissue ablation under various environments

    Energy Technology Data Exchange (ETDEWEB)

    Kang, H W [American Medical Systems-ICSV, San Jose, CA (United States); Oh, J [Division of Mechanical Engineering, Pukyong National University, Busan (Korea, Republic of); Welch, A J [Department of Biomedical Engineering, University of Texas at Austin, Austin, TX (United States)], E-mail: wook.kang@ammd.com

    2008-06-21

    The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 {mu}m wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

  16. Pulsed Tm:YAG laser ablation of knee joint tissues

    Science.gov (United States)

    Shi, Wei-Qiang; Vari, Sandor G.; Duffy, J. T.; Miller, J. M.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

    1992-06-01

    We investigated the effect of a free-running 2.01 micron pulsed Tm:YAG laser on bovine knee joint tissues. Ablation rates of fresh fibrocartilage, hyaline cartilage, and bone were measured in saline as a function of laser fluence (160 - 640 J/cm2) and fiber core size (400 and 600 microns). All tissues could be effectively ablated and the ablation rate increased linearly with the increasing fluence. Use of fibers of different core sizes, while maintaining constant energy fluence, did not result in significant difference in ablation rate. Histology analyses of the ablated tissue samples reveal average Tm:YAG radiation induced thermal damage (denatunalization) zones ranging between 130 and 540 microns, depending on the laser parameters and the tissue type.

  17. In situ Diagnostics During Carbon Nanotube Production by Laser Ablation

    Science.gov (United States)

    Arepalli, Sivaram

    1999-01-01

    The preliminary results of spectral analysis of the reaction zone during the carbon nanotube production by laser ablation method indicate synergetic dependence on dual laser setup. The emission spectra recorded from different regions of the laser ablated plume at different delay times from the laser pulses are used to map the temperatures of C2 and C3. These are compared with Laser Induced Fluorescence (LIF) spectra also obtained during production to model the growth mechanism of carbon nanotubes. Experiments conducted to correlate the spectral features with nanotube yields as a function of different production parameters will be discussed.

  18. [Moist ablation of the corneal surface with the Er:YAG laser. Results of optimizing ablation].

    Science.gov (United States)

    Bende, T; Jean, B; Matallana, M; Seiler, T; Steiner, R

    1994-10-01

    The Er:YAG laser, emitting light at 2.94 microns, may be an alternative to the 193 nm excimer laser for photorefractive keratectomy. Compared to the excimer laser, the ablation rate is very high. Surface roughness is also more pronounced than for the excimer laser. Using a precorneal liquid film, these two factors can be reduced, as shown in ablation experiments performed on porcine corneas. Thermal damage of the remaining corneal tissue is another side effect. There is no significant decrease in the amount of thermal damage with this new technique,--not even when the pulse length is reduced.

  19. Histological evaluation of vertical laser channels from ablative fractional resurfacing

    DEFF Research Database (Denmark)

    Skovbølling Haak, Christina; Illes, Monica; Paasch, Uwe

    2011-01-01

    Ablative fractional resurfacing (AFR) represents a new treatment potential for various skin conditions and new laser devices are being introduced. It is important to gain information about the impact of laser settings on the dimensions of the created laser channels for obtaining a safe and effici...

  20. Universal threshold for femtosecond laser ablation with oblique illumination

    Science.gov (United States)

    Liu, Xiao-Long; Cheng, Weibo; Petrarca, Massimo; Polynkin, Pavel

    2016-10-01

    We quantify the dependence of the single-shot ablation threshold on the angle of incidence and polarization of a femtosecond laser beam, for three dissimilar solid-state materials: a metal, a dielectric, and a semiconductor. Using the constant, linear value of the index of refraction, we calculate the laser fluence transmitted through the air-material interface at the point of ablation threshold. We show that, in spite of the highly nonlinear ionization dynamics involved in the ablation process, the so defined transmitted threshold fluence is universally independent of the angle of incidence and polarization of the laser beam for all three material types. We suggest that angular dependence of ablation threshold can be utilized for profiling fluence distributions in ultra-intense femtosecond laser beams.

  1. Morphology Characterization of Uranium Particles From Laser Ablated Uranium Materials

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In the study, metallic uranium and uranium dioxide material were ablated by laser beam in order to simulate the process of forming the uranium particles in pyrochemical process. The morphology characteristic of uranium particles and the surface of

  2. Laser ablation for the synthesis of carbon nanotubes

    Science.gov (United States)

    Holloway, Brian C; Eklund, Peter C; Smith, Michael W; Jordan, Kevin C; Shinn, Michelle

    2012-11-27

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  3. Laser ablation for the synthesis of carbon nanotubes

    Science.gov (United States)

    Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

    2012-01-01

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  4. Metal cathode patterning for OLED by nanosecond pulsed laser ablation

    Institute of Scientific and Technical Information of China (English)

    LIU Chen; ZHU Guang-xi; LIU De-ming

    2006-01-01

    In this paper,nanosecond pulsed laser is introduced to selectively ablate away indium tin oxide film and metal film without destroying the underlying layers for fabricating organic light-emitting diodes. By varying density of energy, pulse number and width of the laser, the influence on morphology of the laser trenches of indium tin oxide and metal films are investigated. It is presented that uniform ablation trench can be obtained with 16 laser pulses at 0.15 J/cm2 for aluminum film and 10 laser pulses at 0.65 J/cm2 for indium tin oxide film. It is found that the characteristics of the organic light-emitting diodes prepared with laser ablation are almost the same as those of that prepared with conventional patterning method.

  5. Enthalpy model for heating, melting, and vaporization in laser ablation

    OpenAIRE

    Vasilios Alexiades; David Autrique

    2010-01-01

    Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu) target in a helium (He) background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model th...

  6. Simulation of femtosecond pulsed laser ablation of metals

    Science.gov (United States)

    Davydov, R. V.; Antonov, V. I.

    2016-11-01

    In this paper a mathematical model for femtosecond laser ablation of metals is proposed, based on standard two-temperature model connected with 1D hydrodynamic equations. Wide-range equation of state has been developed. The simulation results are compared with experimental data for aluminium and copper. A good agreement for both metals with numerical results and experiment shows that this model can be employed for choosing laser parameters to better accuracy in nanoparticles production by ablation of metals.

  7. Development of laser ablation plasma by anisotropic self-radiation

    Directory of Open Access Journals (Sweden)

    Ohnishi Naofumi

    2013-11-01

    Full Text Available We have proposed a method for reproducing an accurate solution of low-density ablation plasma by properly treating anisotropic radiation. Monte-Carlo method is employed for estimating Eddington tensor with limited number of photon samples in each fluid time step. Radiation field from ablation plasma is significantly affected by the anisotropic Eddington tensor. Electron temperature around the ablation surface changes with the radiation field and is responsible for the observed emission. An accurate prediction of the light emission from the laser ablation plasma requires a careful estimation of the anisotropic radiation field.

  8. Dynamics of Laser Ablation in Superfluid ^4{He}

    Science.gov (United States)

    Buelna, X.; Popov, E.; Eloranta, J.

    2017-02-01

    Pulsed laser ablation of metal targets immersed in superfluid ^4{He} is visualized by time-resolved shadowgraph photography and the products are analyzed by post-experiment atomic force microscopy (AFM) measurements. The expansion dynamics of the gaseous ablation half-bubble on the target surface appears underdamped and follows the predicted behavior for the thermally induced bubble growth mechanism. An inherent instability of the ablation bubble appears near its maximum radius and no tightly focused cavity collapse or rebound events are observed. During the ablation bubble retreat phase, the presence of sharp edges in the target introduces flow patterns that lead to the creation of large classical vortex rings. Furthermore, on the nanometer scale, AFM data reveal that the metal nanoparticles created by laser ablation are trapped in spherical vortex tangles and quantized vortex rings present in the non-equilibrium liquid.

  9. Laser ablation with applied magnetic field for electric propulsion

    Science.gov (United States)

    Batishcheva, Alla; Batishchev, Oleg; Cambier, Jean-Luc

    2012-10-01

    Using ultrafast lasers with tera-watt-level power allows efficient ablation and ionization of solid-density materials [1], creating dense and hot (˜100eV) plasma. We propose ablating small droplets in the magnetic nozzle configurations similar to mini-helicon plasma source [2]. Such approach may improve the momentum coupling compared to ablation of solid surfaces and facilitate plasma detachment. Results of 2D modeling of solid wire ablation in the applied magnetic field are presented and discussed. [4pt] [1] O. Batishchev et al, Ultrafast Laser Ablation for Space Propulsion, AIAA technical paper 2008-5294, -16p, 44th JPC, Hartford, 2008.[0pt] [2] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

  10. Mechanisms of Carbon Nanotube Production by Laser Ablation Process

    Science.gov (United States)

    Scott, Carl D.; Arepalli, Sivaram; Nikolaev, Pavel; Smalley, Richard E.; Nocholson, Leonard S. (Technical Monitor)

    2000-01-01

    We will present possible mechanisms for nanotube production by laser oven process. Spectral emission of excited species during laser ablation of a composite graphite target is compared with that of laser irradiated C60 vapor. The similarities in the transient and spectral data suggest that fullerenes are intermediate precursors for nanotube formation. The confinement of the ablation products by means of a 25-mm diameter tube placed upstream of the target seems to improve the production and purity of nanotubes. Repeated laser pulses vaporize the amorphous/graphitic carbon and possibly catalyst particles, and dissociate fullerenes yielding additional feedstock for SWNT growth.

  11. Femtosecond laser ablation of Au film around single pulse threshold

    Institute of Scientific and Technical Information of China (English)

    Xiaochang Ni; Ching-Yue Wang; Yinzhong Wu; Li Yang; Wei Jia; Lu Chai

    2006-01-01

    @@ Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φo. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.

  12. Transient Newton rings in dielectrics upon fs laser ablation

    CERN Document Server

    Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Solis, Javier

    2014-01-01

    We report the appearance of transient Newton rings in dielectrics (sapphire and lead-oxide glass) during ablation with single fs laser pulses. Employing femtosecond microscopy with 800 nm excitation and 400 nm illumination, we observe a characteristic ring pattern that dynamically changes for increasing delay times between pump and probe pulse. Such transient Newton rings have been previously observed in metals and semiconductors at fluences above the ablation threshold and were related to optical interference of the probe beam reflected at the front surface of the ablating layer and at the interface of the non-ablating substrate. Yet, it had been generally assumed that this phenomenon cannot be (and has not been) observed in dielectrics due to the different ablation mechanism and optical properties of dielectrics. The fact that we are able to observe them has important consequences for the comprehension of the ablation mechanisms in dielectrics and provides a new method for investigating these mechanisms in ...

  13. Subpicosecond and picosecond laser ablation of dental enamel: comparative analysis

    Science.gov (United States)

    Rode, Andrei V.; Madsen, Nathan R.; Kolev, Vesselin Z.; Gamaly, Eugene G.; Luther-Davies, Barry; Dawes, Judith M.; Chan, A.

    2004-06-01

    We report the use of sub-picosecond near-IR and ps UV pulsed lasers for precision ablation of freshly extracted human teeth. The sub-picosecond laser wavelength was ~800nm, with pulsewidth 150 fs and pulse repetition rate of 1kHz; the UV laser produced 10 ps pulses at 266 nm with pulse rate of ~1.2x105 pulses/s; both lasers produced ~1 W of output energy, and the laser fluence was kept at the same level of 10-25 J/cm2. Laser radiation from both laser were effectively absorbed in the teeth enamel, but the mechanisms of absorption were radically different: the near-IR laser energy was absorbed in a plasma layer formed through the optical breakdown mechanism initiated by multiphoton absorption, while the UV-radiation was absorbed due to molecular photodissociation of the enamel and conventional thermal deposition. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain low with subpicosecond laser pulses, but risen up to 30°C, well above the 5°C pain level with the UV-laser. This study demonstrates the potential for ultra-short-pulsed lasers to precision and painless ablation of dental enamel, and indicated the optimal combination of laser parameters in terms of pulse energy, duration, intensity, and repetition rate, required for the laser ablation rates comparable to that of mechanical drill.

  14. Improving Consistency in Laser Ablation Geochronology

    Science.gov (United States)

    Horstwood, Matt; Gehrels, George; Bowring, James

    2010-07-01

    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; San Francisco, California, 12-13 December 2009; The use of uranium-thorium-lead (U-Th-Pb) laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) geochronology involves rapid analysis of U-and Th-rich accessory minerals. It routinely achieves 1-2% precision for U-Th-Pb dates constituting detrital mineral age spectra and for dating igneous and metamorphic events. The speed and low setup and analysis cost of LA-ICP-MS U-Th-Pb geochronology has led to a proliferation of active laboratories. Tens of thousands of analyses are produced per month, but there is little agreement on how to transform these data into accurate U-Th-Pb dates. Recent interlaboratory blind comparisons of zircon samples indicate that resolvable biases exist among laboratories and the sources of bias are not fully understood. Common protocols of data reduction and reporting are essential for scientists to be able to compare and interpret these data accurately.

  15. Ablation enhancement of silicon by ultrashort double-pulse laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin; Shin, Yung C. [Center for Laser-Based Manufacturing, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-09-15

    In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

  16. Laser Plasmas : Plasma dynamics from laser ablated solid lithium

    Indian Academy of Sciences (India)

    Debarati Bhattacharya

    2000-11-01

    Emission plasma plume generated by pulsed laser ablation of a lithium solid target by a ruby laser (694 nm, 20 ns, 3 J) was subjected to optical emission spectroscopy: time and space resolved optical emission was characterised as a function of distance from the target surface. Propagation of the plume was studied through ambient background of argon gas. Spectroscopic observations can, in general, be used to analyse plume structure with respect to an appropriate theoretical plasma model. The plume expansion dynamics in this case could be explained through a shock wave propagation model wherein, the experimental observations made were seen to fit well with the theoretical predictions. Spectral information derived from measurement of peak intensity and line width determined the parameters, electron temperature (e) and electron number density e, typically used to characterise laser produced plasma plume emission. These measurements were also used to validate the assumptions underlying the local thermodynamic equilibrium (LTE) model, invoked for the high density laser plasma under study. Some interesting results pertaining to the analysis of plume structure and spatio-temporal behaviour of e and e along the plume length will be presented and discussed.

  17. Observation of fs-laser spallative ablation using soft X-ray laser probe

    Science.gov (United States)

    Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro; Minami, Yasuo; Eyama, Takashi; Kakimoto, Naoya; Izutsu, Rui; Baba, Motoyoshi; Kawachi, Tetsuya; Suemoto, Tohru

    2017-03-01

    The initial stages of femtosecond laser ablation of gold were observed by single-shot soft X-ray laser interferometer and reflectometer. The ablation front surface and the spallation shell dome structure were observed from the results of the soft X-ray interferogram, reflective image, and shadowgraph. The formation and evolution of soft X-ray Newton's rings (NRs) were found by reflective imaging at the early stages of the ablation dynamics. The soft X-ray NRs are caused by the interference between the bulk ablated surface and nanometer-scale thin spallation layer. The spallation layer was kept at the late timing of the ablation dynamics, and the height of that reached over 100 μm. The temporal evolution of the bulk ablated surface was observed in the ablation dynamics. From these results, we have succeeded in obtaining the temporal evolution of the ablation front exfoliated from the gold surface.

  18. Wavelength scaling of silicon laser ablation in picosecond regime

    Science.gov (United States)

    Sikora, A.; Grojo, D.; Sentis, M.

    2017-07-01

    Single pulse laser ablation of silicon has been investigated at 343, 515, and 1030 nm using a laser pulse duration of 50 ps. In this large spectral range, ablation thresholds of silicon vary from 0.01 to 0.83 J/cm2, confirming a strong dependence on the wavelength. By solving the free-carrier density rate equation at threshold conditions, we show that band-to-band linear absorption dominates energy deposition at 343 and 515 nm, whereas at 1030 nm, the energy leading to ablation is primarily absorbed by the generated free-carriers. This allows us to determine the relevant criteria to derive a simple model predicting the wavelength dependence of the ablation threshold in this regime. We obtain an excellent agreement between experimental measurements and calculations by simply considering an averaged energy density required in the absorption depth for surface ablation and accounting for the laser-induced variations of the important thermophysical parameters. On the basis of this analysis, we discuss the optimal wavelength and fluence conditions for maximum removal rate, ablation efficiency, and accuracy. Despite the difference in mechanisms at the different wavelengths, we find that the maximal efficiency remains at around 7 times the ablation threshold fluence for all investigated wavelengths. This work provides guidelines for high-quality and efficient micromachining of silicon in the scarcely explored picosecond regime, while new picosecond sources offer numerous advantages for real throughput industrial applications.

  19. Single-shot femtosecond laser ablation on the nanoscale

    NARCIS (Netherlands)

    Zhang, H.

    2013-01-01

    The use of femtosecond lasers as a tool for precise machining of nano-structures in materials has been steadily growing in recent years. In particular, It has been demonstrated that direct femtosecond laser ablation can be used to rapidly prototype photonic waveguide devices operating at optical tel

  20. Direct laser interference ablating nanostructures on organic crystals

    NARCIS (Netherlands)

    Fang, Hong-Hua; Ding, Ran; Lu, Shi-Yang; Wang, Lei; Feng, Jing; Chen, Qi-Dai; Sun, Hong-Bo; Fang, Honghua

    2012-01-01

    Two-beam interference ablation of 1,4-Bis(4-methylstyryl) benzene organic crystal by short laser pulses (10 ns, 355 nm) is presented. The influence of laser fluence, interference period, and pulse number on the morphology have been studied. The morphology is closely associated with the molecular int

  1. Formation of nanostructures under femtosecond laser ablation of metals

    Energy Technology Data Exchange (ETDEWEB)

    Ashitkov, S I; Romashevskii, S A; Komarov, P S; Burmistrov, A A; Agranat, M B [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Zhakhovskii, V V [All-Russian Institute of Automatics, Moscow (Russian Federation); Inogamov, N A [Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Moscow region (Russian Federation)

    2015-06-30

    We present the results of studying the morphology of the modified surface of aluminium, nickel and tantalum after ablation of the surface layer by a femtosecond laser pulse. The sizes of characteristic elements of a cellular nanostructure are found to correlate with thermo-physical properties of the material and the intensity of laser radiation. (superstrong light fields)

  2. Single-shot femtosecond laser ablation on the nanoscale

    NARCIS (Netherlands)

    Zhang, H.

    2013-01-01

    The use of femtosecond lasers as a tool for precise machining of nano-structures in materials has been steadily growing in recent years. In particular, It has been demonstrated that direct femtosecond laser ablation can be used to rapidly prototype photonic waveguide devices operating at optical

  3. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Oraevsky, A.A. [Lawrence Livermore National Lab., CA (United States)]|[Rice Univ., Houston, TX (United States). Dept. of Electrical Engineering; DaSilva, L.B.; Feit, M.D. [Lawrence Livermore National Lab., CA (United States)] [and others

    1995-03-08

    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  4. UV solid state laser ablation of intraocular lenses

    Science.gov (United States)

    Apostolopoulos, A.; Lagiou, D. P.; Evangelatos, Ch.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-06-01

    Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (λ=355 nm and λ=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at λ=213 nm reveal a

  5. Heat effects of metals ablated with femtosecond laser pulses

    Science.gov (United States)

    Hirayama, Yoichi; Obara, Minoru

    2002-09-01

    Heat effects of metallic bulk crystals of Au, Ag, Cu, and Fe ablated with femtosecond Ti:sapphire laser pulses is experimentally studied. As a result of X-ray diffraction (XRD) measurements, the XRD peak signal of the area ablated with Ti:sapphire laser is much smaller than that of the crystalline metal sample. While the crystal form of the metal sample is crystalline before laser ablation, the crystal form in the ablated area is partially changed into the amorphous form. The residual pulse energy that did not contribute to the ablation process remains, which leads to the formation of thin layer of melted phase. The melted layer is abruptly cooled down not to be re-crystallized, but to transform into amorphous form. It is evident that the area ablated with femtosecond laser is changed into amorphous metals. This mechanism would be the same as the melt-quenching generally used as the fabrication method of amorphous metals. This experimental result is consistent with the theoretical result.

  6. Laser systems for ablative fractional resurfacing

    DEFF Research Database (Denmark)

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    Ablative fractional resurfacing (AFR) creates microscopic vertical ablated channels that are surrounded by a thin layer of coagulated tissue, constituting the microscopic treatment zones (MTZs). AFR induces epidermal and dermal remodeling, which raises new possibilities for the treatment of a var...

  7. Corneal surface morphology following excimer laser ablation with humidified gases.

    Science.gov (United States)

    Krueger, R R; Campos, M; Wang, X W; Lee, M; McDonnell, P J

    1993-08-01

    To compare the effects of blowing dry (nitrogen or helium) and humidified gases over the corneal surface during photorefractive keratectomy. Excimer laser myopic ablations were performed on porcine eyes (10 per group) using humidified and dry nitrogen and helium gas under ambient conditions. Surface smoothness was quantified with light and electron microscopy. Corneas that were ablated using humidified gas were smooth and equivalent to those ablated under ambient conditions. Dry nitrogen and helium blowing resulted in increased surface irregularity evident on light and electron microscopy (P excimer laser corneal ablation produces a smoother surface than does the blowing of dry gas and is comparable to that produced under ambient (no blowing) conditions. Maintaining corneal moisture is important in photorefractive keratectomy. If blowing gas is necessary to remove debris from the surface, the gas should be humidified.

  8. Thermal ablation of liver metastases from colorectal cancer: radiofrequency, microwave and laser ablation therapies.

    Science.gov (United States)

    Vogl, Thomas J; Farshid, Parviz; Naguib, Nagy N N; Darvishi, Abbas; Bazrafshan, Babak; Mbalisike, Emmanuel; Burkhard, Thorsten; Zangos, Stephan

    2014-07-01

    Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12-49 months follow-up, 2.7-12.5 % of MW ablated lesions at 5-19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4-33 % of patients treated with RF ablation, 0-19 % of patients treated with MW ablation and 0.1-3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases.

  9. Ablation from metals induced by visible and UV laser irradiation

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Schou, Jørgen; Thestrup Nielsen, Birgitte

    1996-01-01

    The deposition rate of laser-ablated silver has been determined for fluences between 0.5 and 15 J/cm2 at the wavelengths 532 and 355 nm for a beam spot area of around 0.01 cm2. The ablated metal was collected on a quartz crystal microbalance. The rate at 5 J/cm2 was about 4 × 1013 Ag/cm2 per puls...

  10. Pulsed laser ablation and deposition of niobium carbide

    Science.gov (United States)

    Sansone, M.; De Bonis, A.; Santagata, A.; Rau, J. V.; Galasso, A.; Teghil, R.

    2016-06-01

    NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation-deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  11. Langmuir probe study of plasma expansion in pulsed laser ablation

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1999-01-01

    Langmuir probes were used to monitor the asymptotic expansion of the plasma produced by the laser ablation of a silver target in a vacuum. The measured angular and temporal distributions of the ion flux and electron temperature were found to be in good agreement with the self-similar isentropic...... and adiabatic solution of the gas dynamics equations describing the expansion. The value of the adiabatic index gamma was about 1.25, consistent with the ablation plume being a low temperature plasma....

  12. Resonant holographic measurements of laser ablation plume expansion in vacuum and argon gas backgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Lindley, R.A. [Michigan Univ., Ann Arbor, MI (United States)

    1993-10-01

    This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Environments; Determining {lambda}{sub o}; resonant refraction effects; fringe shift interpretation; shot-to-shot consistency; laser ablation in vacuum and low pressure, inert, background gas; theoretically modeling plume expansion in vacuum and low pressure, inert, background gas; and laser ablation in higher pressure, inert, background gas.

  13. Pulsed laser ablation of dental calculus in the near ultraviolet.

    Science.gov (United States)

    Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

    2014-02-01

    Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ≤8  J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5  J/cm2 but has not been observed above this fluence.

  14. Influence of laser ablation parameters on trueness of imaging

    Energy Technology Data Exchange (ETDEWEB)

    Vaculovič, T.; Warchilová, T. [Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, Brno 61137 (Czech Republic); CEITEC, Masaryk University, Kamenice 5, Brno 62500 (Czech Republic); Čadková, Z.; Száková, J.; Tlustoš, P. [Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamýcka 129, Praha 16521 (Czech Republic); Otruba, V. [Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, Brno 61137 (Czech Republic); Kanický, V., E-mail: viktork@chemi.muni.cz [Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, Brno 61137 (Czech Republic); CEITEC, Masaryk University, Kamenice 5, Brno 62500 (Czech Republic)

    2015-10-01

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

  15. Two-Dimensional Fluorescence Spectroscopy for Measuring Uranium Isotopes in Femtosecond Laser Ablation

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Brumfield, Brian E.; Harilal, Sivanandan S.; Hartig, Kyle C.; Jovanovic, Igor

    2017-05-30

    We present the first two-dimensional fluorescence spectroscopy measurements of uranium isotopes in femtosecond laser ablation plasmas. A new method of signal normalization is presented to reduce noise in absorption-based measurements of laser ablation.

  16. Ablative fractional laser resurfacing helps treat restrictive pediatric scar contractures.

    Science.gov (United States)

    Krakowski, Andrew C; Goldenberg, Alina; Eichenfield, Lawrence F; Murray, Jill-Peck; Shumaker, Peter R

    2014-12-01

    Conventional management of debilitating pediatric scar contractures, including hand therapy and surgery, may often be beset by delayed treatment, suboptimal results, and additional surgical morbidity. Ablative fractional laser resurfacing is an emerging adjunctive procedural option for scar contractures because of its promising efficacy and safety profile. However, its use to improve function has not been studied in the pediatric population. Herein we report 2 pediatric patients with recalcitrant scar contractures, causing persistent functional deficits, treated with an ablative fractional laser protocol. Both patients experienced rapid and cumulative subjective and objective improvements in range of motion and function as measured by an independent occupational therapist without reported complications. We highlight ablative fractional laser resurfacing as a novel and promising tool in the management of function-limiting scar contractures in children and propose that the technique be incorporated into existing scar treatment paradigms, guided by future research.

  17. Near-field mapping by laser ablation of PMMA coatings

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kostiucenko, Oksana

    The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....... enhancements on and around the gold nanostructures. At the positions of the enhancements, the ablation threshold of the polymer coating is significantly lowered creating subdiffractional topographic modifications on the surface which are quantified via scanning electron microscopy and atomic force microscopy...

  18. Near-field mapping by laser ablation of PMMA coatings

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kostiucenko, Oksana

    The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....... enhancements on and around the gold nanostructures. At the positions of the enhancements, the ablation threshold of the polymer coating is significantly lowered creating sub-diffractional topographic modifications on the surface which are quantified via scanning electron microscopy and atomic force microscopy...

  19. Infrared Laser Ablation with Vacuum Capture for Fingermark Sampling

    Science.gov (United States)

    Donnarumma, Fabrizio; Camp, Eden E.; Cao, Fan; Murray, Kermit K.

    2017-09-01

    Infrared laser ablation coupled to vacuum capture was employed to collect material from fingermarks deposited on surfaces of different porosity and roughness. Laser ablation at 3 μm was performed in reflection mode with subsequent capture of the ejecta with a filter connected to vacuum. Ablation and capture of standards from fingermarks was demonstrated on glass, plastic, aluminum, and cardboard surfaces. Using matrix assisted laser desorption ionization (MALDI), it was possible to detect caffeine after spiking with amounts as low as 1 ng. MALDI detection of condom lubricants and detection of antibacterial peptides from an antiseptic cream was demonstrated. Detection of explosives from fingermarks left on plastic surfaces as well as from direct deposition on the same surface using gas chromatography mass spectrometry (GC-MS) was shown. [Figure not available: see fulltext.

  20. UV-laser ablation of sensory cells in living insects

    Science.gov (United States)

    Fuhr, G.; Ronacher, B.; Krahe, R.; Fest, S.; Shirley, S. G.; Rogaschewski, S.

    An experimental set-up for applying pulsed UV-laser ablation to the integument of insects and the high precision of ablation is demonstrated. In order to test for possible detrimental effects on physiological responses, this technique was applied to the ears of migratory locust (Locusta migratoria L.). The handling of living insects, the survival, and physiological response after treatment are described. We selectively interrupted the d-receptor of the tympanal organ, which is the receptor system responsible for the locust's sensitivity in the high-frequency range (>10 kHz). The effects of the laser treatment were tested by determining hearing thresholds in electrophysiological recordings from the tympanal nerves. In agreement with the literature, the interruption of the d-receptors led to a significant shift towards higher values of the thresholds in the high-frequency range. Future perspectives and biological applications of UV-laser ablation are discussed.

  1. Glass particles produced by laser ablation for ICP-MSmeasurements

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, J.; Liu, C.; Wen, S.; Mao, X.; Russo, R.E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate glass particles from two sets of standard reference materials using femtosecond (150fs) and nanosecond (4ns) laser pulses with identical fluences of 50 J cm{sup -2}. Scanning electron microscopy (SEM) images of the collected particles revealed that there are more and larger agglomerations of particles produced by nanosecond laser ablation. In contrast to the earlier findings for metal alloy samples, no correlation between the concentration of major elements and the median particle size was found. When the current data on glass were compared with the metal alloy data, there were clear differences in terms of particle size, crater depth, heat affected zone, and ICP-MS response. For example, glass particles were larger than metal alloy particles, the craters in glass were less deep than craters in metal alloys, and damage to the sample was less pronounced in glass compared to metal alloys samples. The femtosecond laser generated more intense ICP-MS signals compared to nanosecond laser ablation for both types of samples, although glass sample behavior was more similar between ns and fs-laser ablation than for metals alloys.

  2. Aerospace Laser Ignition/Ablation Variable High Precision Thruster

    Science.gov (United States)

    Campbell, Jonathan W. (Inventor); Edwards, David L. (Inventor); Campbell, Jason J. (Inventor)

    2015-01-01

    A laser ignition/ablation propulsion system that captures the advantages of both liquid and solid propulsion. A reel system is used to move a propellant tape containing a plurality of propellant material targets through an ignition chamber. When a propellant target is in the ignition chamber, a laser beam from a laser positioned above the ignition chamber strikes the propellant target, igniting the propellant material and resulting in a thrust impulse. The propellant tape is advanced, carrying another propellant target into the ignition chamber. The propellant tape and ignition chamber are designed to ensure that each ignition event is isolated from the remaining propellant targets. Thrust and specific impulse may by precisely controlled by varying the synchronized propellant tape/laser speed. The laser ignition/ablation propulsion system may be scaled for use in small and large applications.

  3. Pulsed laser ablation of polymers for display applications

    Science.gov (United States)

    Pedder, James E. A.; Holmes, Andrew S.; Booth, Heather J.

    2008-02-01

    Laser micromachining by ablation is a well established technique used for the production of 2.5D and 3D features in a wide variety of materials. The fabrication of stepped, multi-level, structures can be achieved using a number of binary mask projection techniques using excimer lasers. Alternatively, direct-writing of complex 2.5D features can easily be achieved with solid-state lasers. Excimer laser ablation using half-tone masks allows almost continuous surface relief and the generation of features with low surface roughness. We have developed techniques to create large arrays of repeating micro-optical structures on polymer substrates. Here, we show our recent developments in laser structuring with the combination of half-tone and binary mask techniques.

  4. Enthalpy model for heating, melting, and vaporization in laser ablation

    Directory of Open Access Journals (Sweden)

    Vasilios Alexiades

    2010-09-01

    Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.

  5. Femtosecond laser bone ablation with a high repetition rate fiber laser source.

    Science.gov (United States)

    Mortensen, Luke J; Alt, Clemens; Turcotte, Raphaël; Masek, Marissa; Liu, Tzu-Ming; Côté, Daniel C; Xu, Chris; Intini, Giuseppe; Lin, Charles P

    2015-01-01

    Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process.

  6. Thermal melting and ablation of silicon by femtosecond laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ionin, A. A.; Kudryashov, S. I., E-mail: sikudr@lebedev.ru; Seleznev, L. V.; Sinitsyn, D. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Bunkin, A. F.; Lednev, V. N.; Pershin, S. M. [Russian Academy of Sciences, General Physics Institute (Russian Federation)

    2013-03-15

    The space-time dynamics of thermal melting, subsurface cavitation, spallative ablation, and fragmentation ablation of the silicon surface excited by single IR femtosecond laser pulses is studied by timeresolved optical reflection microscopy. This dynamics is revealed by monitoring picosecond and (sub)nanosecond oscillations of probe pulse reflection, which is modulated by picosecond acoustic reverberations in the dynamically growing surface melt subjected to ablation and having another acoustic impedance, and by optical interference between the probe pulse replicas reflected by the spalled layer surface and the layer retained on the target surface. The acoustic reverberation periods change during the growth and ablation of the surface melt film, which makes it possible to quantitatively estimate the contributions of these processes to the thermal dynamics of the material surface. The results on the thermal dynamics of laser excitation are supported by dynamic measurements of the ablation parameters using noncontact ultrasonic diagnostics, scanning electron microscopy, atomic force microscopy, and optical interference microscopy of the modified regions appearing on the silicon surface after ablation.

  7. PbTe quantum dots grown by femtosecond laser ablation

    Science.gov (United States)

    Rodriguez, E.; Biggemann, D.; Moya, L.; Pippo, W. A.; Moreira, R. S.; Silva, D.; Cesar, C. L.; Barbosa, L. C.; Schrank, A.; Souza Filho, C. R.; de Oliveira, E. P.

    2008-02-01

    Laser ablation (LA) is a thin film fabrication technique which has generated a lot of interest in the past few years as one of the simplest and most versatile methods for the deposition of a wide variety of materials. With the rapid development experienced in the generation of ultra short laser pulses, new possibilities were opened for the laser ablation technique, using femtosecond lasers as ablation source. It is commonly believed that when the temporal length of the laser pulse became shorter than the several picoseconds required to couple the electronic energy to the lattice of the material, thermal effects could not play a significant role. Since the pulse width is too short for thermal effects to take place, with each laser pulse a few atom layers of material are direct vaporized away from the target surface and a better control in the quantum dots (QDs) fabrication could be achieved. In this work we report the fabrication of PbTe QDs by femtosecond laser ablation of a PbTe target in argon atmosphere. Experiments were carried out using a typical LA configuration comprising a deposition chamber and an ultra short pulsed laser (100 fs; 30 mJ) at a central wavelength of 800 nm. PbTe was chosen because its QDs absorption band can be controlled by its size to fall in the spectral window of interest for optical communications (1.3-1.5 μm). This, together with the QD high optical nonlinearity, makes this material an excellent candidate for development of photonic devices. It was investigated the influence of the number of laser pulses in the formation of the nanoparticles. The structural parameters and the surface density of the nanoparticles were studied by high resolution transmission electron microscopy (HRTEM).

  8. Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

    Science.gov (United States)

    Peña-Díaz, M.; Ponce, L.; Arronte, M.; Flores, T.

    2007-04-01

    Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

  9. Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Pena-Diaz, M; Ponce, L; Arronte, M; Flores, T [Laboratorio TecnologIa Laser, CICATA-IPN, Unidad Altamira, Carretera Tampico-Puerto Ind. Altamira, 89600, TAMPS (Mexico)

    2007-04-15

    Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

  10. Laser ablation dynamics and production of thin films of lysozyme

    DEFF Research Database (Denmark)

    Canulescu, Stela; Schou, Jørgen; Amoruso, S.;

    produced thin films of average thickness up to 300 nm, which not only contained a significant amount of intact molecules, but also maintained the bioactivity. These films were produced by a nanosecond laser in the UV regime at 355 nm with 2 J/cm2. The surprising fact that these molecules can be transferred....... This is the first time the ablation by fs-lasers of a protein has been recorded quantitatively. Films of lysozyme produced by fs-laser irradiation were analyzed by MALDI and a significant number of intact molecules in the films with fs-laser deposition was found as well....

  11. Production of nanoparticles from natural hydroxylapatite by laser ablation

    Directory of Open Access Journals (Sweden)

    Boutinguiza Mohamed

    2011-01-01

    Full Text Available Abstract Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW laser. Transmission electron microscopy (TEM measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism.

  12. Laser ablation dynamics and production of thin films of lysozyme

    DEFF Research Database (Denmark)

    Schou, Jørgen; Canulescu, Stela; Matei, Andreea;

    at the Technical University of Denmark (DTU) produced thin films of average thickness up to 300 nm, which not only contained a significant amount of intact molecules, but also maintained the bioactivity. These films were produced by a nanosecond laser in the UV regime at 355 nm with 2 J/cm2. The surprising fact......, there was a considerable ablation weight loss of lysozyme from each shot. This is the first time the ablation by fs-lasers of a protein has been recorded quantitatively. Films of lysozyme produced by fs-laser irradiation will be analysed by MALDI in order to explore if there also is a significant amount of intact...... molecules in the films for fs-laser deposition....

  13. Synthesis of selenium nanoparticles by pulsed laser ablation

    Science.gov (United States)

    Quintana, M.; Haro-Poniatowski, E.; Morales, J.; Batina, N.

    2002-07-01

    The synthesis of selenium nanoparticles by pulsed laser ablation using a YAG laser at 532 nm is reported. The nanoparticles were deposited on three different substrates: metallic gold films, silicon wafers and glass, and subsequently visualized and characterized by atomic force microscopy (AFM). It was found that the size, shape and population of the selenium nanoparticles are strongly dependent on the experimental conditions during the ablation process; in particular on the energy density, number of laser pulses and the nature of the substrate. Atomic force microscopy imaging allows recognition, quantitative and qualitative characterization of individual selenium nanoparticles and their aggregates as well. In most of the experiments just a few laser pulses (up to five), were sufficient to produce a noticeable amount of nanoparticles on the substrate surface.

  14. Setup for functional cell ablation with lasers: coupling of a laser to a microscope.

    Science.gov (United States)

    Sweeney, Sean T; Hidalgo, Alicia; de Belle, J Steven; Keshishian, Haig

    2012-06-01

    The selective removal of cells by ablation is a powerful tool in the study of eukaryotic developmental biology, providing much information about their origin, fate, or function in the developing organism. In Drosophila, three main methods have been used to ablate cells: chemical, genetic, and laser ablation. Each method has its own applicability with regard to developmental stage and the cells to be ablated, and its own limitations. The primary advantage of laser-based ablation is the flexibility provided by the method: The operations can be performed in any cell pattern and at any time in development. Laser-based techniques permit manipulation of structures within cells, even to the molecular level. They can also be used for gene activation. However, laser ablation can be expensive, labor-intensive, and time-consuming. Although live cells can be difficult to image in Drosophila embryos, the use of vital fluorescent imaging methods has made laser-mediated cell manipulation methods more appealing; the methods are relatively straightforward. This article provides the information necessary for setting up and using a laser microscope for lasesr ablation studies.

  15. Angular distributions and total yield of laser ablated silver

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Nordskov, A.; Schou, Jørgen;

    1997-01-01

    The angular distribution of laser ablated silver has been measured in situ with a newly constructed setup with an array of microbalances. The distribution is strongly peaked in the forward direction corresponding to cospθ, where p varies between 5 and 9 for laser fluences from 2 to 7 J/cm2 at 355...... nm for a beam spot of 0.015 cm2. The total deposited yield is of the order 1015 Ag-atoms per pulse....

  16. Fast photography of plasma formed by laser ablation of aluminum

    Science.gov (United States)

    Nedanovska, E.; Ivkovic, M.

    2008-07-01

    In this paper we present results of the temporal and spatial analysis of laser induced plasma performed by use of ICCD fast photography. The plasma is formed by excimer laser ablation of aluminum target in vacuum, air or different pressures of argon and helium. It is shown how the plasma luminous intensity and duration depends on gas pressure. The obtained time dependence of wave propagation distance is also compared with predictions given by the blast wave and drag-force theory also.

  17. Zinc nanoparticles in solution by laser ablation technique

    Indian Academy of Sciences (India)

    S C Singh; R Gopal

    2007-06-01

    Colloidal zinc metallic nanoparticles are synthesized using pulsed laser ablation of metal plate in an aqueous solution of suitable surfactant to prevent aggregation. UV-visible absorption, TEM, small angle X-ray diffraction and wide-angle X-ray diffraction are used for the characterization of colloidal zinc metallic nanoparticles. Colloidal nanoparticles are found highly stable for a long time.

  18. Laser ablation assisted adhesive bonding of automotive structural composites

    Energy Technology Data Exchange (ETDEWEB)

    Boeman, R.G.; Paulauskas, F.L.; Warren, C.D.

    1999-07-03

    Laser ablation has been evaluated as a surface pretreatment prior to adhesive bonding. In prior experimental work, it was observed that when adhesively bonded, composite, single lap shear samples fail, the fracture often occurs at either the adhesive/adherend interface or in the resin rich surface layer of the composite. These two areas represent the weakest portion of the joint. Laser ablation pretreatment generates areas where the resin on the composite surface is selectively removed leaving behind exposed reinforcing fibers which are the major load bearing members of the composite. In a subsequent adhesive bonding operation, this allows portions of the fibers to be encapsulated in the adhesive while other portions of the fiber remain in the composite resin. This type of pretreatment permits fibers to bridge and reinforce the interface between adhesive and adherend. A secondary benefit is the removal of surface contaminantes by pyrolysis. Microscopic observation of laser ablated surfaces indicates a prominent, fiber rich area. Results of the mechanical evaluation indicated that the lap shear strength for laser ablated samples was significantly higher than specimens with no pretreatment or with solvent cleaning only, but were slightly lower than specimens that were mechanically roughened and cleaned with solvents prior to bonding.

  19. Ins and outs of endovenous laser ablation: Afterthoughts

    NARCIS (Netherlands)

    H.A.M. Neumann (Martino); M.J.C. van Gemert (Martin)

    2014-01-01

    textabstractPhysicists and medical doctors "speak" different languages. Endovenous laser ablation (EVLA) is a good example in which technology is essential to guide the doctor to the final result: optimal treatment. However, for the doctor, it is by far insufficient just to turn on the knobs of the

  20. Ins and outs of endovenous laser ablation: Afterthoughts

    NARCIS (Netherlands)

    H.A.M. Neumann (Martino); M.J.C. van Gemert (Martin)

    2014-01-01

    textabstractPhysicists and medical doctors "speak" different languages. Endovenous laser ablation (EVLA) is a good example in which technology is essential to guide the doctor to the final result: optimal treatment. However, for the doctor, it is by far insufficient just to turn on the knobs of the

  1. Femtosecond laser ablation of gold interdigitated electrodes for electronic tongues

    Science.gov (United States)

    Manzoli, Alexandra; de Almeida, Gustavo F. B.; Filho, José A.; Mattoso, Luiz H. C.; Riul, Antonio; Mendonca, Cleber R.; Correa, Daniel S.

    2015-06-01

    Electronic tongue (e-tongue) sensors based on impedance spectroscopy have emerged as a potential technology to evaluate the quality and chemical composition of food, beverages, and pharmaceuticals. E-tongues usually employ transducers based on metal interdigitated electrodes (IDEs) coated with a thin layer of an active material, which is capable of interacting chemically with several types of analytes. IDEs are usually produced by photolithographic methods, which are time-consuming and costly, therefore, new fabrication technologies are required to make it more affordable. Here, we employed femtosecond laser ablation with pulse duration of 50 fs to microfabricate gold IDEs having finger width from 2.3 μm up to 3.2 μm. The parameters used in the laser ablation technique, such as light intensity, scan speed and beam spot size have been optimized to achieve uniform IDEs, which were characterized by optical and scanning electron microscopy. The electrical properties of gold IDEs fabricated by laser ablation were evaluated by impedance spectroscopy, and compared to those produced by conventional photolithography. The results show that femtosecond laser ablation is a promising alternative to conventional photolithography for fabricating metal IDEs for e-tongue systems.

  2. Superhydrophobic/superoleophilic magnetic elastomers by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Milionis, Athanasios, E-mail: am2vy@virginia.edu [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Fragouli, Despina; Brandi, Fernando; Liakos, Ioannis; Barroso, Suset [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Athanassiou, Athanassia, E-mail: athanassia.athanassiou@iit.it [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy)

    2015-10-01

    Highlights: • We report the development of magnetic nanocomposite sheets. • Laser irradiation of the nanocomposites induces chemical and structural changes to the surface. • The laser-patterned surfaces exhibit superhydrophobicity and superoleophilicity. • The particle contribution in altering the surface and bulk properties of the material is studied. - Abstract: We report the development of magnetic nanocomposite sheets with superhydrophobic and supeoleophilic surfaces generated by laser ablation. Polydimethylsiloxane elastomer free-standing films, loaded homogeneously with 2% wt. carbon coated iron nanoparticles, were ablated by UV (248 nm), nanosecond laser pulses. The laser irradiation induces chemical and structural changes (both in micro- and nano-scale) to the surfaces of the nanocomposites rendering them superhydrophobic. The use of nanoparticles increases the UV light absorption efficiency of the nanocomposite samples, and thus facilitates the ablation process, since the number of pulses and the laser fluence required are greatly reduced compared to the bare polymer. Additionally the magnetic nanoparticles enhance significantly the superhydrophobic and oleophilic properties of the PDMS sheets, and provide to PDMS magnetic properties making possible its actuation by a weak external magnetic field. These nanocomposite elastomers can be considered for applications requiring magnetic MEMS for the controlled separation of liquids.

  3. Pulsed laser deposition: metal versus oxide ablation

    NARCIS (Netherlands)

    Doeswijk, L.M.; Rijnders, G.; Blank, D.H.A.

    2004-01-01

    We present experimental results of pulsed laser interaction with metal (Ni, Fe, Nb) and oxide (TiO2, SrTiO3, BaTiO3) targets. The influence of the laser fluence and the number of laser pulses on the resulting target morphology are discussed. Although different responses for metal and oxide targets t

  4. Sand laser-ablation as source of elements laser isotope separation: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, N.A.S.; Destro, M.G.; Vasconcelos, G; Neri, J.W.; Silveira, C.A.B.; Riva, R. [Institute for Advanced Studies, Sao Jose dos Campos, SP (Brazil)]. E-mail: nicolau@ieav.cta.br

    2008-07-01

    This paper presents preliminary results of emission spectroscopy experiments, performed with the aim to verify the presence of monoatomic neutral material in the jet produced by laser ablation of simple and complex targets. All studied materials (copper, graphite, alumina and beach sand) showed emission of single atoms, indicating the presence of monoatomic material in the ablated plume. (author)

  5. Laser ablation of Al-Ni alloys and multilayers

    Science.gov (United States)

    Roth, Johannes; Trebin, Hans-Rainer; Kiselev, Alexander; Rapp, Dennis-Michael

    2016-05-01

    Laser ablation of Al-Ni alloys and multilayers has been studied by molecular dynamics simulations. The method was combined with a two-temperature model to describe the interaction between the laser beam, the electrons, and the atoms. As a first step, electronic parameters for the alloys had to be found and the model developed originally for pure metals had to be generalized to multilayers. The modifications were verified by computing melting depths and ablation thresholds for pure Al and Ni. Here known data could be reproduced. The improved model was applied to the alloys Al_3Ni, AlNi and AlNi_3. While melting depths and ablation thresholds for AlNi behave unspectacular, sharp drops at high fluences are observed for Al_3Ni and AlNi_3. In both cases, the reason is a change in ablation mechanism from phase explosion to vaporization. Furthermore, a phase transition occurs in Al_3Ni. Finally, Al layers of various thicknesses on a Ni substrate have been simulated. Above threshold, 8 nm Al films are ablated as a whole while 24 nm Al films are only partially removed. Below threshold, alloying with a mixture gradient has been observed in the thin layer system.

  6. Percutaneous laser ablation of unresectable primary and metastatic adrenocortical carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Pacella, Claudio M. [Regina Apostolorum Hospital, Department of Diagnostic Imaging and Interventional Radiology, Via San Francesco 50, Albano Laziale, Rome 00041 (Italy)], E-mail: claudiomaurizio.pacella@fastwebnet.it; Stasi, Roberto; Bizzarri, Giancarlo; Pacella, Sara; Graziano, Filomena Maria; Guglielmi, Rinaldo; Papini, Enrico [Regina Apostolorum Hospital, Department of Diagnostic Imaging and Interventional Radiology, Via San Francesco 50, Albano Laziale, Rome 00041 (Italy)

    2008-04-15

    Purpose: To evaluate the feasibility, safety, and clinical benefits of percutaneous laser ablation (PLA) in patients with unresectable primary and metastatic adrenocortical carcinoma (ACC). Patients and methods: Four patients with hepatic metastases from ACC and a Cushing's syndrome underwent ultrasound-guided PLA. In one case the procedure was performed also on the primary tumor. Results: After three sessions of PLA, the primary tumor of 15 cm was ablated by 75%. After 1-4 (median 1) sessions of PLA, five liver metastases ranging from 2 to 5 cm were completely ablated, while the sixth tumor of 12 cm was ablated by 75%. There were no major complications. Treatment resulted in an improvement of performance status and a reduction of the daily dosage of mitotane in all patients. The three patients with liver metastases presented a marked decrease of 24-h urine cortisol levels, an improved control of hypertension and a mean weight loss of 2.8 kg. After a median follow-up after PLA of 27.0 months (range, 9-48 months), two patients have died of tumor progression, while two other patients remain alive and free of disease. Conclusions: Percutaneous laser ablation is a feasible, safe and well tolerated procedure for the palliative treatment of unresectable primary and metastatic ACC. Further study is required to evaluate the impact of PLA on survival.

  7. 308-nm excimer laser ablation of human cartilage

    Science.gov (United States)

    Prodoehl, John A.; Rhodes, Anthony L.; Meller, Menachem M.; Sherk, Henry H.

    1993-07-01

    The XeCl excimer laser was investigated as an ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800 micrometers fiber with the laser delivering a range of fluences (40 to 190 mj/mm2) firing at a frequency of 5 Hz. To assess the effect of repetition rate on ablation rate, a set of measurements was made at a constant fluence of 60 mj/mm2, with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage at the maximum fluence tested. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10 - 70 micrometers ).

  8. Modeling of multi-burst mode pico-second laser ablation for improved material removal rate

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wenqian; Shin, Yung C.; King, Galen [Purdue University, Center for Laser-based Manufacturing, School of Mechanical Engineering, West Lafayette, IN (United States)

    2010-02-15

    This paper deals with the unique phenomena occurring during the multi-burst mode picosecond (ps) laser ablation of metals through modeling and experimental studies. The two-temperature model (TTM) is used and expanded to calculate the ablation depth in the multi-burst mode. A nonlinear increment of ablation volume is found during the multi-burst laser ablation. The deactivation of ablated material and the application of temperature-dependent electron-phonon coupling are demonstrated to be important to provide reliable results. The simulation results based on this expanded laser ablation model are experimentally validated. A significant increase of ablation rate is found in the multi-burst mode, compared with the single-pulse mode under the same total fluence. This numerical model provides a physical perspective into the energy transport process during multi-burst laser ablation and can be used to study the pulse-to-pulse separation time effect on the ablation rate. (orig.)

  9. Modeling of multi-burst mode pico-second laser ablation for improved material removal rate

    Science.gov (United States)

    Hu, Wenqian; Shin, Yung C.; King, Galen

    2010-02-01

    This paper deals with the unique phenomena occurring during the multi-burst mode picosecond (ps) laser ablation of metals through modeling and experimental studies. The two-temperature model (TTM) is used and expanded to calculate the ablation depth in the multi-burst mode. A nonlinear increment of ablation volume is found during the multi-burst laser ablation. The deactivation of ablated material and the application of temperature-dependent electron-phonon coupling are demonstrated to be important to provide reliable results. The simulation results based on this expanded laser ablation model are experimentally validated. A significant increase of ablation rate is found in the multi-burst mode, compared with the single-pulse mode under the same total fluence. This numerical model provides a physical perspective into the energy transport process during multi-burst laser ablation and can be used to study the pulse-to-pulse separation time effect on the ablation rate.

  10. Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses.

    Science.gov (United States)

    Sun, Mingying; Eppelt, Urs; Russ, Simone; Hartmann, Claudia; Siebert, Christof; Zhu, Jianqiang; Schulz, Wolfgang

    2013-04-08

    This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps.

  11. A unified model in the pulsed laser ablation process

    Institute of Scientific and Technical Information of China (English)

    HU De-zhi

    2008-01-01

    In this unified model, we introduce the electron-phonon coupling time (t) and laser pulse width (t). For long pulses, it can substitute for the traditional thermal conduction model; while for ultrashort pulses, it can substitute for the standard two-temperature model. As an example of the gold target, we get the dependence of the electron and ion temperature evolvement on the time and position by solving the thermal conduction equation using the finite-difference time-domain (FDTD) method.It is in good agreement with experimental data. We obtain the critical temperature of the onset of ablation using the Saha equation and then obtain the theoretical value of the laser ablation threshold when the laser pulse width ranges from nanosecond to femtosecond timescale, which consists well with the experimental data.

  12. Frequency mixing in boron carbide laser ablation plasmas

    Science.gov (United States)

    Oujja, M.; Benítez-Cañete, A.; Sanz, M.; Lopez-Quintas, I.; Martín, M.; de Nalda, R.; Castillejo, M.

    2015-05-01

    Nonlinear frequency mixing induced by a bichromatic field (1064 nm + 532 nm obtained from a Q-switched Nd:YAG laser) in a boron carbide (B4C) plasma generated through laser ablation under vacuum is explored. A UV beam at the frequency of the fourth harmonic of the fundamental frequency (266 nm) was generated. The dependence of the efficiency of the process as function of the intensities of the driving lasers differs from the expected behavior for four-wave mixing, and point toward a six-wave mixing process. The frequency mixing process was strongly favored for parallel polarizations of the two driving beams. Through spatiotemporal mapping, the conditions for maximum efficiency were found for a significant delay from the ablation event (200 ns), when the medium is expected to be a low-ionized plasma. No late components of the harmonic signal were detected, indicating a largely atomized medium.

  13. Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments

    Science.gov (United States)

    Brazolin, H.; Rodrigues, N. A. S.; Minucci, M. A. S.

    2008-04-01

    This paper describes a setup for thrust measurement in ablative laser propulsion experiments, based on a simple ballistic pendulum associated to an imaging system, which is being assembled at IEAv. A light aluminium pendulum holding samples is placed inside a 100 liters vacuum chamber with two optical windows: the first (in ZnSe) for the laser beam and the second (in fused quartz) for the pendulum visualization. A TEA-CO2 laser beam is focused to the samples providing ablation and transferring linear moment to the pendulum as a whole. A CCD video camera captures the oscillatory movement of the pendulum and the its trajectory is obtained by image processing. By fitting the trajectory of the pendulum to a dumped sinusoidal curve is possible to obtain the amplitude of the movement which is directly related to the momentum transfered to the sample.

  14. Laser ablation mass spectroscopy of nineteenth century daguerreotypes

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, Danel L. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6125 (United States); Golovlev, Valerie V. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6125 (United States); Gresalfi, Michael J. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6125 (United States); Chaney, John A. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6125 (United States); Feigerle, Charles S. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6125 (United States); Miller, John C. [Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6125 (United States); Romer, Grant [International Museum of Photography and Film, George Eastman House, 900 East Ave., Rochester, New York 14607-2298 (United States); Messier, Paul [Boston Art Conservation, 60 Oak Square Ave., Boston, Massachusetts 02135 (United States)

    1999-10-01

    Laser desorption mass spectroscopy has been used to characterize both modern and {approx}150-year-old daguerreotypes. Such investigations are a necessary prelude to attempts to clean them of tarnish and other contaminants by laser ablation of the surface layers. Both positive- and negative-ion time-of-flight spectra were obtained following YAG laser ablation/desorption at 1064, 532, and 355 nm. Major peaks obtained from several daguerreotypes reveal expected elements from the substrate (Ag, Cu) as well as the developing (Hg) and gilding (Au) processes. Silver clusters (Ag{sub n}) may reflect surface desorption of molecules or, alternatively, aggregates formed in the ejection process. Silver sulfide molecules observed from old daguerreotypes are the signature of the tarnishing process. (c) 2000 Society for Applied Spectroscopy.

  15. Laser ablation synthesis of indium oxide nanoparticles in water

    Energy Technology Data Exchange (ETDEWEB)

    Acacia, N. [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universita di Messina, Salita Sperone 31, I-98166 Messina (Italy); Barreca, F., E-mail: process@anmresearch.it [Advanced and Nano Materials Research s.r.l., Salita Sperone 31, I-98166 Messina (Italy); Barletta, E.; Spadaro, D.; Curro, G. [Advanced and Nano Materials Research s.r.l., Salita Sperone 31, I-98166 Messina (Italy); Neri, F. [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universita di Messina, Salita Sperone 31, I-98166 Messina (Italy)

    2010-09-01

    Colloidal solutions of Indium oxide nanoparticles have been produced by means of laser ablation in liquids (LALs) technique by simply irradiating with a second harmonic (532 nm) Nd:YAG laser beam a metallic indium target immersed in distilled water and varying the laser fluence up to 10 J cm{sup -2} and the ablation time up to 120 min. At all the investigated fluences the vaporization process of the indium target is the dominant one. It produces a majority (>80%) of small size (<6 nm) nanoparticles, with a very limited content of larger ones (size between 10 and 20 nm). The amount of particles increases regularly with the ablation time, supporting the scalability of the production technique. The deposited nanoparticles stoichiometry has been verified by both X-ray photoelectron spectroscopy (XPS) and Energy Dispersive X-ray (EDX) analysis. Optical bandgap values of 3.70 eV were determined by UV-vis absorption measurements. All these results confirm the complete oxidation of the ablated material.

  16. Ablation of Submicrometer Holes Using an Extreme-Ultraviolet Laser

    Science.gov (United States)

    Rossall, Andrew K.; Aslanyan, Valentin; Tallents, Greg J.; Kuznetsov, Ilya; Rocca, Jorge J.; Menoni, Carmen S.

    2015-06-01

    Simulations and experiments are used to study extreme-ultraviolet (EUV) laser drilling of submicrometer holes. The ablation process is studied with a 2D Eulerian hydrodynamic code that includes bound-free absorption processes relevant to the interaction of EUV lasers with a solid material. Good agreement is observed between the simulated and measured ablated depths for on-target irradiances of up to 1×10 10 W cm-2 . An increase in the irradiance to 1×10 12 W cm-2 is predicted to ablate material to a depth of 3.8 μ m from a single pulse with a hole diameter 3 to 4 times larger than the focal spot size. The model allows for the simulation of the interaction of a laser pulse with the crater created by a previous shot. Multiple-pulse lower-fluence irradiation configurations under optimized focusing conditions, i.e., approaching the diffraction limit, are shown to be advantageous for applications requiring mesoscale [(100 nm )- (1 μ m ) ] features and a high level of control over the ablation profile.

  17. Laser ablation of titanium in liquid in external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Serkov, A.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); The Federal State Educational Institution of Higher Professional Education, “Moscow Institute of Physics and Technology (State University)”, 9 Institutskiy per., 141700, Dolgoprudny, Moscow Region (Russian Federation); Barmina, E.V., E-mail: barminaev@gmail.com [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31, Kashirskoye Highway, 115409 Moscow (Russian Federation); Voronov, V.V. [A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow (Russian Federation)

    2015-09-01

    Highlights: • Ablation of a bulk Ti target by 10 ps laser pulses in liquid is experimentally studied in external DC electric field. • Applied cathodic bias leads to increase in average size of self-organized nanostructures formed upon ablation of titanium target. • Laser ablation of Ti target in external electric field results in generation of elongated titanium oxide nanoparticles. - Abstract: Ablation of a bulk Ti target by 10 ps laser pulses in water is experimentally studied in external DC electric field. It is demonstrated that both lateral size of nanostructures (NS) on Ti surface and their density depend on the electric field applied to the target. Scanning Electron Microscopy of NS reveals the shift of their size distribution function toward larger sizes with applied field (cathodic bias, 25 V DC). Density of mushroom-like NS with applied electric field amounts to 10{sup 10} cm{sup −2}. X-ray diffraction of generated nanoparticles (NPs) shows difference in the crystallographic structure of NPs of non-stoichiometric Ti oxides generated with and without electric field. This conclusion is corroborated with the optical absorption spectroscopy of obtained colloids. Transmission Electron Microscopy of NPs also shows difference in morphology of particles produced with and without cathodic bias. The results are interpreted on the basis of instability of the melt on Ti surface in the electric field.

  18. Thermal-mechanical modeling of laser ablation hybrid machining

    Science.gov (United States)

    Matin, Mohammad Kaiser

    2001-08-01

    Hard, brittle and wear-resistant materials like ceramics pose a problem when being machined using conventional machining processes. Machining ceramics even with a diamond cutting tool is very difficult and costly. Near net-shape processes, like laser evaporation, produce micro-cracks that require extra finishing. Thus it is anticipated that ceramic machining will have to continue to be explored with new-sprung techniques before ceramic materials become commonplace. This numerical investigation results from the numerical simulations of the thermal and mechanical modeling of simultaneous material removal from hard-to-machine materials using both laser ablation and conventional tool cutting utilizing the finite element method. The model is formulated using a two dimensional, planar, computational domain. The process simulation acronymed, LAHM (Laser Ablation Hybrid Machining), uses laser energy for two purposes. The first purpose is to remove the material by ablation. The second purpose is to heat the unremoved material that lies below the ablated material in order to ``soften'' it. The softened material is then simultaneously removed by conventional machining processes. The complete solution determines the temperature distribution and stress contours within the material and tracks the moving boundary that occurs due to material ablation. The temperature distribution is used to determine the distance below the phase change surface where sufficient ``softening'' has occurred, so that a cutting tool may be used to remove additional material. The model incorporated for tracking the ablative surface does not assume an isothermal melt phase (e.g. Stefan problem) for laser ablation. Both surface absorption and volume absorption of laser energy as function of depth have been considered in the models. LAHM, from the thermal and mechanical point of view is a complex machining process involving large deformations at high strain rates, thermal effects of the laser, removal of

  19. PREFACE AND CONFERENCE INFORMATION: Eighth International Conference on Laser Ablation

    Science.gov (United States)

    Hess, Wayne P.; Herman, Peter R.; Bäuerle, Dieter; Koinuma, Hideomi

    2007-04-01

    Laser ablation encompasses a wide range of delicate to extreme light interactions with matter that present considerably challenging problems for scientists to study and understand. At the same time, laser ablation also represents a basic process of significant commercial importance in laser material processing—defining a multi-billion dollar industry today. These topics were widely addressed at the 8th International Conference on Laser Ablation (COLA), held in Banff, Canada on 11-16 September 2005. The meeting took place amongst the majestic and natural beauty of the Canadian Rocky Mountains at The Banff Centre, where delegates enjoyed many inspiring presentations and discussions in a unique campus learning environment. The conference brought together world leading scientists, students and industry representatives to examine the basic science of laser ablation and improve our understanding of the many physical, chemical and/or biological processes driven by the laser. The multi-disciplinary research presented at the meeting underlies some of our most important trends at the forefront of science and technology today that are represented in the papers collected in this volume. Here you will find new processes that are producing novel types of nanostructures and nano-materials with unusual and promising properties. Laser processes are described for delicately manipulating living cells or modifying their internal structure with unprecedented degrees of control and precision. Learn about short-pulse lasers that are driving extreme physical processes on record-fast time scales and opening new directions from material processing applications. The conference papers further highlight forefront application areas in pulsed laser deposition, nanoscience, analytical methods, materials, and microprocessing applications. Laser ablation continues to grow and evolve, touching forefront areas in science and driving new technological trends in laser processing applications. Please

  20. Histological evaluation of vertical laser channels from ablative fractional resurfacing

    DEFF Research Database (Denmark)

    Skovbølling Haak, Christina; Illes, Monica; Paasch, Uwe

    2011-01-01

    Ablative fractional resurfacing (AFR) represents a new treatment potential for various skin conditions and new laser devices are being introduced. It is important to gain information about the impact of laser settings on the dimensions of the created laser channels for obtaining a safe...... and efficient treatment outcome. The aim of this study was to establish a standard model to document the histological tissue damage profiles after AFR and to test a new laser device at diverse settings. Ex vivo abdominal pig skin was treated with a MedArt 620, prototype fractional carbon dioxide (CO(2)) laser...... measurements for each laser setting (n¿=¿28). AFR created cone-shaped laser channels. Ablation depths varied from reaching the superficial dermis (2 mJ, median 41 µm) to approaching the subcutaneous fat (144 mJ, median 1,943 µm) and correlated to the applied energy levels in an approximate linear relation (r(2...

  1. Measurement of ablative Richtmyer-Meshkov evolution from laser imprint

    Science.gov (United States)

    Martinez, D. A.; Smalyuk, V. A.; Igumenshchev, I. V.; Delorme, B.; Casner, A.; Masse, L.; Park, H.-S.; Remington, B. A.; Olazabal-Loumé, M.

    2017-10-01

    Experiments were performed to investigate the ablative Richtmyer-Meshkov (RM) instability in plastic (CH2) foils. The two-dimensional (2-D) perturbations were created by laser imprinting using a special phase plate with a 2-D single mode, ˜70 μm wavelength sinusoidal intensity pattern on the plastic foil. The growth of imprinted perturbations was measured by face-on, X-ray radiography using Sm and Ta backlighters in 30-μm and 50-μm thick plastic foils, respectively. After the initial imprinting phase, the 2-D perturbations grew due to ablative RM instability before the onset of foil acceleration when they were further amplified by Rayleigh-Taylor instability. Experimental results agree reasonably well with 2-D hydrodynamic simulations and analytic models showing that the modulation growth in areal density is due to ablative RM instability.

  2. Ablation of silicon with bursts of femtosecond laser pulses

    Science.gov (United States)

    Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

    2016-03-01

    We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

  3. Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors

    Science.gov (United States)

    Chen, H.; Li, H.; Sun, Yc.; Wang, Y.; Lü, Pj.

    2016-02-01

    To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application.

  4. Frequency mixing in boron carbide laser ablation plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Oujja, M.; Benítez-Cañete, A.; Sanz, M.; Lopez-Quintas, I.; Martín, M.; Nalda, R. de, E-mail: r.nalda@iqfr.csic.es; Castillejo, M.

    2015-05-01

    Graphical abstract: - Highlights: • Two-color frequency mixing has been studied in a laser ablation boron carbide plasma. • A space- and time-resolved study mapped the nonlinear optical species in the plasma. • The nonlinear process maximizes when charge recombination is expected to be completed. • Neutral atoms and small molecules are the main nonlinear species in this medium. • Evidence points to six-wave mixing as the most likely process. - Abstract: Nonlinear frequency mixing induced by a bichromatic field (1064 nm + 532 nm obtained from a Q-switched Nd:YAG laser) in a boron carbide (B{sub 4}C) plasma generated through laser ablation under vacuum is explored. A UV beam at the frequency of the fourth harmonic of the fundamental frequency (266 nm) was generated. The dependence of the efficiency of the process as function of the intensities of the driving lasers differs from the expected behavior for four-wave mixing, and point toward a six-wave mixing process. The frequency mixing process was strongly favored for parallel polarizations of the two driving beams. Through spatiotemporal mapping, the conditions for maximum efficiency were found for a significant delay from the ablation event (200 ns), when the medium is expected to be a low-ionized plasma. No late components of the harmonic signal were detected, indicating a largely atomized medium.

  5. Renaissance of laser interstitial thermal ablation

    National Research Council Canada - National Science Library

    Missios, Symeon; Bekelis, Kimon; Barnett, Gene H

    2015-01-01

    .... The development of magnetic resonance thermography and its application to LITT have allowed for real-time thermal imaging and feedback control during laser energy delivery, allowing for precise...

  6. Laser wavelength effect on nanosecond laser light reflection in ablation of metals

    Science.gov (United States)

    Benavides, O.; de la Cruz May, L.; Mejia, E. B.; Ruz Hernandez, J. A.; Flores Gil, A.

    2016-12-01

    Reflection of nanosecond laser pulses with different wavelengths (1.06 and 0.69 µm) in ablation of titanium in air is studied experimentally. The laser wavelength effect on reflection is essential at low laser fluence values. However, it becomes negligible for laser fluence values by about an order of magnitude higher than the plasma ignition threshold. We speculate that the disappearance of the wavelength effect is explained by counter-acting processes of the laser light absorption in plasma, which increases with laser wavelength, and absorption in the surface layer, which decreases with increasing laser wavelength.

  7. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Science.gov (United States)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  8. Ablation of dentin by irradiation of violet diode laser

    Science.gov (United States)

    Hatayama, H.; Kato, J.; Akashi, G.; Hirai, Y.; Inoue, A.

    2006-02-01

    Several lasers have been used for clinical treatment in dentistry. Among them, diode lasers are attractive because of their compactness compared with other laser sources. Near-infrared diode lasers have been practically used for cutting soft tissues. Because they penetrate deep to soft tissues, they cause sufficiently thick coagulation layer. However, they aren't suitable for removal of carious dentin because absorption by components in dentin is low. Recently, a violet diode laser with a wavelength of 405nm has been developed. It will be effective for cavity preparation because dentin contains about 20% of collagen whose absorption coefficient at a violet wavelength is larger than that at a near-infrared wavelength. In this paper, we examined cutting performance of the violet diode laser for dentin. To our knowledge, there have been no previous reports on application of a violet laser to dentin ablation. Bovine teeth were irradiated by continuous wave violet diode laser with output powers in a range from 0.4W to 2.4W. The beam diameter on the sample was about 270μm and an irradiation time was one second. We obtained the crater ablated at more than an output power of 0.8W. The depth of crater ranged from 20μm at 0.8W to 90μm at 2.4W. Furthermore, the beam spot with an output power of 1.7W was scanned at a speed of 1mm/second corresponding to movement of a dentist's hand in clinical treatment. Grooves with the depth of more than 50μm were also obtained. From these findings, the violet diode laser has good potential for cavity preparation. Therefore, the violet diode laser may become an effective tool for cavity preparation.

  9. Analysis of fabric materials cut using ultraviolet laser ablation

    Science.gov (United States)

    Tsai, Hsin-Yi; Yang, Chih-Chung; Hsiao, Wen-Tse; Huang, Kuo-Cheng; Andrew Yeh, J.

    2016-04-01

    Laser ablation technology has widely been applied in the clothing industry in recent years. However, the laser mechanism would affect the quality of fabric contours and its components. Hence, this study examined carbonization and oxidation conditions and contour variation in nonwoven, cotton, and composite leather fabrics cut by using an ultraviolet laser at a wavelength of 355 nm. Processing parameters such as laser power, pulse frequency, scanning speed, and number of pulses per spot were adjusted to investigate component variation of the materials and to determine suitable cutting parameters for the fabrics. The experimental results showed that the weights of the component changed substantially by pulse frequency but slightly by laser power, so pulse frequency of 100 kHz and laser power of 14 W were the approximate parameters for three fabrics for the smaller carbonization and a sufficient energy for rapidly cutting, which the pulse duration of laser system was fixed at 300 μs and laser irradiance was 0.98 J/mm2 simultaneously. In addition, the etiolate phenomenon of nonwoven was reduced, and the component weight of cotton and composite leather was closed to the value of knife-cut fabric as the scanning speed increased. The approximate scanning speed for nonwoven and composite leather was 200 mm/s, and one for cotton was 150 mm/s, respectively. The sharper and firmer edge is obtained by laser ablation mechanism in comparison with traditional knife cutting. Experimental results can serve as the reference for laser cutting in the clothing industry, for rapidly providing smoother patterns with lower carbonization and oxidation edge in the fashion industry.

  10. Carbon nanotubes/laser ablation gold nanoparticles composites

    Energy Technology Data Exchange (ETDEWEB)

    Lascialfari, Luisa [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giusti 9, Firenze 50123 (Italy); Marsili, Paolo [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Caporali, Stefano [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giusti 9, Firenze 50123 (Italy); Muniz-Miranda, Maurizio [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Margheri, Giancarlo [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Serafini, Andrea; Brandi, Alberto [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Giorgetti, Emilia, E-mail: emilia.giorgetti@fi.isc.cnr.it [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Cicchi, Stefano, E-mail: stefano.cicchi@unifi.it [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giusti 9, Firenze 50123 (Italy)

    2014-10-31

    The production of nanohybrids formed by oxidized multiwalled carbon nanotubes (MWCNTs) and nanoparticles, produced by pulsed laser ablation in liquids process, is described. The use of linkers, obtained by transformation of pyrene-1-butanol, is mandatory to generate an efficient and stable interaction between the two components. Transmission electron microscopy and X-ray photoelectron spectroscopy analysis showed the obtainment of the efficient coverage of the MWCNTs by nanoparticles composed by metal gold and, partially, by oxides. - Highlights: • Laser ablation is a used for the production of gold nanoparticle colloids • An efficient decoration of carbon nanotubes with nanoparticles is obtained through the use of a linker • This method allows an efficient and tunable preparation of carbon nanotube hybrids.

  11. Nanostructured films of metal particles obtained by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Muniz-Miranda, M., E-mail: muniz@unifi.it [Dipartimento di Chimica “U. Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Gellini, C. [Dipartimento di Chimica “U. Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Giorgetti, E.; Margheri, G.; Marsili, P. [Istituto Sistemi Complessi (CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Lascialfari, L.; Becucci, L. [Dipartimento di Chimica “U. Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Trigari, S. [Istituto Sistemi Complessi (CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Giammanco, F. [Dipartimento di Fisica “E. Fermi”, Università di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy)

    2013-09-30

    Colloidal dispersions of silver and gold nanoparticles were obtained in pure water by ablation with nanosecond pulsed laser. Then, by filtration of the metal particles on alumina, we fabricated nanostructured films, whose surface morphology was examined by atomic force microscopy (AFM) and related to surface-enhanced Raman scattering (SERS) after adsorption of adenine. - Highlights: • Ag and Au colloidal nanoparticles were obtained by laser ablation. • Nanostructured Ag and Au films were fabricated by filtration of metal nanoparticles. • Surface morphology of metal films was investigated by atomic force microscopy. • Surface-enhanced Raman spectra (SERS) of adenine on metal films were obtained. • SERS enhancements were related to the surface roughness of the metal films.

  12. Ablation and nanostructuring of metals by femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ashitkov, S I; Komarov, P S; Ovchinnikov, A V; Struleva, E V; Agranat, M B [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Zhakhovskii, V V [All-Russian Institute of Automatics, Moscow (Russian Federation); Inogamov, N A [Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Moscow region (Russian Federation)

    2014-06-30

    Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ∼10{sup 9} s{sup -1}. (extreme light fields and their applications)

  13. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Energy Technology Data Exchange (ETDEWEB)

    See, Tian Long, E-mail: tianlong.see@postgrad.manchester.ac.uk [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Liu, Zhu [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Zhong, Xiang Li [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom)

    2016-02-28

    Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F{sub th} = 0.087 J/cm{sup 2}) than that for the femtosecond laser ablation of ABS (F{sub th} = 1.576 J/cm{sup 2}), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α{sup −1} = 223 nm) than that for femtosecond laser ablation (α{sup −1} = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas

  14. Laser ablation of the protein lysozyme

    DEFF Research Database (Denmark)

    Schou, Jørgen; Canulescu, Stela; Amoruso, Salvatore

    Lysozyme is a well-known protein, which is used in food processing because of its bactericidal properties. The mass (14307 amu) is in the range in which it easily can be monitored by mass spectrometric methods, for example by MALDI (Matrix assisted laser desorption ionization). We have recently...... produced thin films of average thickness up to 300 nm, which not only contained a significant amount of intact molecules, but also maintained the bioactivity. These films were produced by a nanosecond laser in the UV regime at 355 nm with 2 J/cm2. The surprising fact that these molecules can be transferred...... to a substrate as intact molecules by the violent laser impact ( up to 50 mJ/pulse) has not yet been understood. One issue is that up to 150 ng/pulse is removed by the laser, and much of the material is ejected from the target in relatively large chunks. We have explored as well the excitation mechanics by laser...

  15. Optical feedback signal for ultrashort laser pulse ablation of tissue

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

    1997-07-01

    An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

  16. Laser ablation method for production of surface acoustic wave sensors

    Science.gov (United States)

    Lukyanov, Dmitry; Shevchenko, Sergey; Kukaev, Alexander; Safronov, Daniil

    2016-10-01

    Nowadays surface acoustic wave (SAW) sensors are produced using a photolithography method. In case of inertial sensors it suffers several disadvantages, such as difficulty in matching topologies produced on opposite sides of the wafer, expensive in small series production, not allowing further topology correction. In this case a laser ablation method seems promising. Details of a proposed technique are described in the paper along with results of its experimental test and discussion.

  17. Laser ablation of molecular carbon nitride compounds

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, D., E-mail: d.fischer@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Schwinghammer, K. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany); Sondermann, C. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Lau, V.W.; Mannhart, J. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Lotsch, B.V. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany)

    2015-09-15

    We present a method for the preparation of thin films on sapphire substrates of the carbon nitride precursors dicyandiamide (C{sub 2}N{sub 4}H{sub 4}), melamine (C{sub 3}N{sub 6}H{sub 6}), and melem (C{sub 6}N{sub 10}H{sub 6}), using the femtosecond-pulsed laser deposition technique (femto-PLD) at different temperatures. The depositions were carried out under high vacuum with a femtosecond-pulsed laser. The focused laser beam is scanned on the surface of a rotating target consisting of the pelletized compounds. The resulting polycrystalline, opaque films were characterized by X-ray powder diffraction, infrared, Raman, and X-ray photoelectron spectroscopy, photoluminescence, SEM, and MALDI-TOF mass spectrometry measurements. The crystal structures and optical/spectroscopic results of the obtained rough films largely match those of the bulk materials.

  18. Negative ion production by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Motoi [Doshisha Univ., Tanabe, Kyoto (Japan). Faculty of Engineering; Sasao, Mamiko

    1997-02-01

    The status of the development of Li{sup -} production by generating a neutral Li flux with an intense radiation of a laser beam onto the surface of Li metal has been reported. The experimental apparatus was arranged to detect a mass separated Li{sup +} and Li{sup -} ion beams. A Li sputtering probe, immersed in the extraction region of a compact (6cm diam. 7cm long) magnetic multipole ion source was irradiated with a Nd-YAG laser of 0.4 J/pulse. The production of mass-separated positive ions of Li by laser irradiation has been confirmed, but the production of Li{sup -} has not been confirmed yet due to the noise caused by a temporal discharge. (author)

  19. Surface modulation of silicon surface by excimer laser at laser fluence below ablation threshold

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P. [Jawaharlal Nehru Centre for Advanced Scientific Research, Chemistry and Physics of Materials Unit (CPMU), Bangalore, Jakkur PO (India)

    2010-04-15

    Controlled single step fabrication of silicon conical surface modulations on [311] silicon surface is reported utilizing KrF excimer laser [{lambda}=248 nm] at laser fluence below ablation threshold laser fluence. When laser fluence was increased gradually from 0 to 0.2 J/cm{sup 2} for fixed 200 numbers of shots; first nanopores are observed to form at 0.1 J/cm{sup 2}, then very shallow nanocones evolve as a function of laser fluence. At 0.2 J/cm{sup 2}, nanoparticles are observed to form. Up to 0.15 J/cm{sup 2} the very shallow nanocone volume is smaller but increases at a fast rate with laser fluence thereafter. It is observed that the net material volume before and after the laser irradiation remains the same, a sign of the melting and resolidification without any ablation. (orig.)

  20. Precise femtosecond laser ablation of dental hard tissue: preliminary investigation on adequate laser parameters

    Science.gov (United States)

    Hikov, Todor; Pecheva, Emilia; Montgomery, Paul; Antoni, Frederic; Leong-Hoi, Audrey; Petrov, Todor

    2017-01-01

    This work aims at evaluating the possibility of introducing state-of-the-art commercial femtosecond laser system in restorative dentistry by maintaining well-known benefits of lasers for caries removal, but also in overcoming disadvantages such as thermal damage of irradiated substrate. Femtosecond ablation of dental hard tissue is investigated by changing the irradiation parameters (pulsed laser energy, scanning speed and pulse repetition rate), assessed for enamel and dentin. The femtosecond laser system used in this work may be suitable for cavity preparation in dentin and enamel, due to the expected effective ablation and low temperature increase when using ultra short laser pulses. If adequate laser parameters are selected, this system seems to be promising for promoting a laser-assisted, minimally invasive approach in restorative dentistry.

  1. Micropatterned polysaccharide surfaces via laser ablation for cell guidance

    Energy Technology Data Exchange (ETDEWEB)

    Barbucci, Rolando; Lamponi, Stefania; Pasqui, Daniela; Rossi, Antonella; Weber, Elisabetta

    2003-03-03

    Micropatterned materials were obtained by a controlled laser ablation of a photoimmobilised homogeneous layer of hyaluronic acid (Hyal) and its sulphated derivative (HyalS). The photoimmobilisation was performed by coating the polysaccharide, adequately functionalised with a photoreactive group, on aminosilanised glass substrate and immobilising it on the surface under UV light. Hyal or HyalS photoimmobilised samples were then subjected to laser ablation with wavelengths in the UV regions in order to drill the pattern. Four different patterns with stripes of 100, 50, 25 and 10 {mu}m were generated. A chemical characterisation by attenuated total reflection/Fourier transform infrared (ATR/FT-IR) and time of flight-secondary ions mass spectrometry (TOF-SIMS) confirmed the success of the laser ablation procedure and the presence of alternating stripes of polysaccharide and native glass. The exact dimensions of the stripes were determined by atomic force microscopy. The analysis of cell behaviour in terms of adhesion, proliferation and movement using mouse fibroblasts (3T3 line) and bovine aortic endothelial cells (BAEC) was also performed.

  2. Laser ablation loading of a radiofrequency ion trap

    CERN Document Server

    Zimmermann, K; Herrera-Sancho, O A; Peik, E

    2012-01-01

    The production of ions via laser ablation for the loading of radiofrequency (RF) ion traps is investigated using a nitrogen laser with a maximum pulse energy of 0.17 mJ and a peak intensity of about 250 MW/cm^2. A time-of-flight mass spectrometer is used to measure the ion yield and the distribution of the charge states. Singly charged ions of elements that are presently considered for the use in optical clocks or quantum logic applications could be produced from metallic samples at a rate of the order of magnitude 10^5 ions per pulse. A linear Paul trap was loaded with Th+ ions produced by laser ablation. An overall ion production and trapping efficiency of 10^-7 to 10^-6 was attained. For ions injected individually, a dependence of the capture probability on the phase of the RF field has been predicted. In the experiment this was not observed, presumably because of collective effects within the ablation plume.

  3. XUV-laser induced ablation of PMMA with nano-, pico-, and femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Juha, L. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic)]. E-mail: juha@fzu.cz; Bittner, M. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Chvostova, D. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic)] (and others)

    2005-06-15

    For conventional wavelength (UV-vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, etch (ablation) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various very short-wavelength ({lambda} < 100 nm) lasers, emitting pulses with durations ranging from {approx}10 fs to {approx}1 ns, have recently been placed into routine operation. This has facilitated the investigation of how ablation characteristics depend on the pulse duration in the XUV spectral region. Ablation of poly(methyl methacrylate) (PMMA) induced by three particular short-wavelength lasers emitting pulses of various durations, is reported in this contribution.

  4. Plasma Diagnostic in laser ablation plumes for isotope separation applications

    Energy Technology Data Exchange (ETDEWEB)

    Matos, Juliana B. de [Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, SP (Brazil)]. E-mail: juliana@ieav.cta.br; Rodrigues, Nicolau A.S.; Neri, Jose W.; Silveira, Carlos A.B. [Instituto de Estudos Avancados (IEAv/EFO), Sao Jose dos Campos, SP (Brazil). Div. de Fotonica

    2008-07-01

    The plasma plume produced in vacuum by ablation of copper, aluminum and tungsten samples, illuminated by copper laser pulses, was investigated. A Langmuir probe was used to study the macroscopic parameters electron number density (Ne) and electron temperature (Te). Plasma expansion velocity (Vp) was also investigated and it was studied the dependence of these parameters with the laser irradiance. Typical values are respectively N{sub e} {approx} 10{sup 8}-10{sup 9}/cm{sup 3}, T{sub e} {approx} 15 eV and Vp {approx} 10 km/s. (author)

  5. Tactile Sensing From Laser-Ablated Metallized PET Films

    KAUST Repository

    Nag, Anindya

    2016-10-17

    This paper reports the design, fabrication, and implementation of a novel sensor patch developed from commercial polyethylene terephthalate films metallized with aluminum on one side. The aluminum was ablated with laser to form interdigitated electrodes to make sensor prototypes. The interdigitated electrodes were patterned on the substrate with a laser cutter. Characterization of the prototypes was done to determine their operating frequency followed by experimentation. The prototypes have been used as a tactile sensor showing promising results for using these patches in applications with contact pressures considerably lesser than normal human contact pressure.

  6. Laser ablation deposition measurements from silver and nickel

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Ellegaard, Ole; Schou, Jørgen

    1996-01-01

    The deposition rate for laser ablated metals has been studied in a standard geometry for fluences up to 20 J/cm(2). The rate for silver and nickel is a few percent of a monolayer per pulse at the laser wavelengths 532 nm and 355 nm. The rate for nickel is significantly higher than that for silver...... at 532 nm, whereas the rate for the two metals is similar at 355 nm. This behaviour disagrees with calculations based on the thermal properties at low intensities as well as predictions based on formation of an absorbing plasma at high intensities. The deposition rate falls strongly with increasing...

  7. Laser ablation of hard tissue: correlation between the laser beam parameters and the post-ablative tissue characteristics

    Science.gov (United States)

    Serafetinides, Alexandros A.; Makropoulou, Mersini I.; Khabbaz, Maruan

    2003-11-01

    Hard dental tissue laser applications, such as preventive treatment, laser diagnosis of caries, laser etching of enamel, laser decay removal and cavity preparation, and more recently use of the laser light to enlarge the root canal during the endodontic therapy, have been investigated for in vitro and in vivo applications. Post-ablative surface characteristics, e.g. degree of charring, cracks and other surface deformation, can be evaluated using scanning electron microscopy. The experimental data are discussed in relevance with the laser beam characteristics, e.g. pulse duration, beam profile, and the beam delivery systems employed. Techniques based on the laser illumination of the dental tissues and the subsequent evaluation of the scattered fluorescent light will be a valuable tool in early diagnosis of tooth diseases, as carious dentin or enamel. The laser induced autofluorescence signal of healthy dentin is much stronger than that of the carious dentin. However, a better understanding of the transmission patterns of laser light in teeth, for both diagnosis and therapy is needed, before the laser procedures can be used in a clinical environment.

  8. Laser ablation and growth of Si and Ge

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Seong Shan, E-mail: seong.yap@ntnu.no [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Siew, Wee Ong; Nee, Chen Hon [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Reenaas, Turid Worren [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Tou, Teck Yong [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia)

    2012-02-01

    In this work, we investigated the laser ablation and deposition of Si and Ge at room temperature in vacuum by employing nanosecond lasers of 248 nm, 355 nm, 532 nm and 1064 nm. Time-integrated optical emission spectra were obtained for neutrals and ionized Ge and Si species in the plasma at laser fluences from 0.5 to 11 J/cm{sup 2}. The deposited films were characterized by using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Amorphous Si and Ge films, micron-sized crystalline droplets and nano-sized particles were deposited. The results suggested that ionized species in the plasma promote the process of subsurface implantation for both Si and Ge films while large droplets were produced from the superheated and melted layer of the target. The dependence of the properties of the materials on laser wavelength and fluence were discussed.

  9. Ablation of biological tissues by radiation of strontium vapor laser

    Energy Technology Data Exchange (ETDEWEB)

    Soldatov, A. N., E-mail: general@tic.tsu.ru; Vasilieva, A. V., E-mail: anita-tomsk@mail.ru [National Research Tomsk State University, Lenin ave., 36, 634050, Tomsk (Russian Federation)

    2015-11-17

    A two-stage laser system consisting of a master oscillator and a power amplifier based on sources of self- contained transitions in pairs SrI and SrII has been developed. The radiation spectrum contains 8 laser lines generating in the range of 1 – 6.45 μm, with a generation pulse length of 50 – 150 ns, and pulse energy of ∼ 2.5 mJ. The divergence of the output beam was close to the diffraction and did not exceed 0.5 mrad. The control range of the laser pulse repetition rate varied from 10 to 15 000 Hz. The given laser system has allowed to perform ablation of bone tissue samples without visible thermal damage.

  10. Periodic patterning of silicon by direct nanosecond laser interference ablation

    Energy Technology Data Exchange (ETDEWEB)

    Tavera, T. [CEIT and Tecnun (University of Navarra), Paseo Manuel Lardizabal, 15 20018, San Sebastian (Spain); Perez, N., E-mail: nperez@ceit.es [CEIT and Tecnun (University of Navarra), Paseo Manuel Lardizabal, 15 20018, San Sebastian (Spain); Rodriguez, A. [CIC Microgune Paseo Mikeletegi 48, 20009 San Sebastian (Spain); Yurrita, P.; Olaizola, S.M.; Castano, E. [CEIT and Tecnun (University of Navarra), Paseo Manuel Lardizabal, 15 20018, San Sebastian (Spain)

    2011-11-15

    The production of periodic structures in silicon wafers by four-beam is presented. Because laser interference ablation is a single-step and cost-effective process, there is a great technological interest in the fabrication of these structures for their use as antireflection surfaces. Three different laser fluences are used to modify the silicon surface (0.8 J cm{sup -2}, 1.3 J cm{sup -2}, 2.0 J cm{sup -2}) creating bumps in the rim of the irradiated area. Laser induced periodic surface structures (LIPSS), in particular micro and nano-ripples, are also observed. Measurements of the reflectivity show a decrease in the reflectance for the samples processed with a laser fluence of 2.0 J cm{sup -2}, probably caused by the appearance of the nano-ripples in the structured area, while bumps start to deteriorate.

  11. Femtosecond-laser ablation dynamics of dielectrics: basics and applications for thin films

    DEFF Research Database (Denmark)

    Balling, P.; Schou, Jørgen

    2013-01-01

    Laser ablation of dielectrics by ultrashort laser pulses is reviewed. The basic interaction between ultrashort light pulses and the dielectric material is described, and different approaches to the modeling of the femtosecond ablation dynamics are reviewed. Material excitation by ultrashort laser...

  12. Fabrication of CVD graphene-based devices via laser ablation for wafer-scale characterization

    DEFF Research Database (Denmark)

    Mackenzie, David; Buron, Jonas Christian Due; Whelan, Patrick Rebsdorf;

    2015-01-01

    Selective laser ablation of a wafer-scale graphene film is shown to provide flexible, high speed (1 wafer/hour) device fabrication while avoiding the degradation of electrical properties associated with traditional lithographic methods. Picosecond laser pulses with single pulse peak fluences of 140......-effect mobility, doping level, on–off ratio, and conductance minimum before and after laser ablation fabrication....

  13. Laser ablation of a platinum target in water. III. Laser-induced reactions

    Science.gov (United States)

    Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto

    2006-12-01

    This is the third paper in our series studying the laser-target-liquid interactions occurring in laser ablation in liquids (LAL). Here, laser ablation of a platinum target in pure water at 355nm wavelength is studied as a function of laser energy. We describe three distinct reaction regimes between the ablated target species and water at different laser focusing conditions. At low laser fluence (removal is caused by laser heating of the platinum surface and the primary products are small clusters with a large percentage of platinum atoms in a nonzero oxidation state. At intermediate fluences (10-70J/cm2), platinum nanoparticles are the primary products. Our previous studies demonstrated that in this fluence regime ablation occurs through both thermal vaporization and explosive ejection of molten droplets. In both cases reactivity is small due to the low reactivity of platinum with water. At high fluences (>70J/cm2), we find large, faceted particles that are attributed to the drying of PtOx gels formed by reactive plasma etching of the target. Taken together these results demonstrate that significant tunability in the target-liquid interaction is possible during nanomaterial synthesis by LAL.

  14. Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma

    Energy Technology Data Exchange (ETDEWEB)

    Tong Huifeng; Yuan Hong [Institute of Fluid Physics, Chinese Academy of Engineering Physics, P.O. Box 919-101, Mianyang, Sichuan 621900 (China); Tang Zhiping [CAS Key Laboratory for Mechanical Behavior and Design of Materials, Department of Mechanics and Mechanical Engineering, University of Science and Technology of China, Hefei 230026 (China)

    2013-01-28

    When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

  15. A study of particle generation during laser ablation with applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chunyi [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained in-line using a differential mobility analyzer (DMA) and a particle counter. The experimental results show that the particle size varies with laser energy, laser pulsewidth, ambient gas flow rate and sample properties. The results serve as a basis for controlling the size of nanoparticles generated by laser ablation. Laser shadowgraph imaging was used to study mass ejection processes and mechanisms. At higher laser irradiance, some particles were ejected in the liquid and even in the solid phase. Time-resolved images show the propagation of the shockwaves: external shockwaves propagate outward and decelerate, and internal shockwaves reflect back and forth between the gas contact surface and the sample surface. The internal shockwave is proposed to cause the ejection of liquid particles when the internal shockwave strikes the liquid molten layer. A simulation based on vapor plume expansion was carried out and provides satisfactory agreement with experimental results. Different material properties result in different particle ejection behavior:particle ejection for most materials including metals result in a conically shaped envelope for the ejected material while ejection for silicon resembles a liquid jet. The difference in density change when the materials melt was proposed to be an important factor in the different ejection behavior. The characteristics of particles generated by laser ablation have a strong influence on the chemical analysis of the irradiated sample. Large particles are more difficult to completely vaporize and ionize, and induced preferential vaporization causes fractionation (i.e. a detected chemical composition that differs from the sample material). Large particles also result in spikes in

  16. Laser ablative synthesis of carbon nanotubes

    Science.gov (United States)

    Smith, Michael W.; Jordan, Kevin; Park, Cheol

    2010-03-02

    An improved method for the production of single walled carbon nanotubes that utilizes an RF-induction heated side-pumped synthesis chamber for the production of such. Such a method, while capable of producing large volumes of carbon nanotubes, concurrently permits the use of a simplified apparatus that allows for greatly reduced heat up and cool down times and flexible flowpaths that can be readily modified for production efficiency optimization. The method of the present invention utilizes a free electron laser operating at high average and peak fluence to illuminate a rotating and translating graphite/catalyst target to obtain high yields of SWNTs without the use of a vacuum chamber.

  17. Laser ablation of borosilicate glass with high power shaped UV nanosecond laser pulses

    Science.gov (United States)

    von Witzendorff, Philipp; Bordin, Andrea; Suttmann, Oliver; Patel, Rajesh S.; Bovatsek, James; Overmeyer, Ludger

    2016-03-01

    The application of thin borosilicate glass as interposer material requires methods for separation and drilling of this material. Laser processing with short and ultra-short laser pulses have proven to enable high quality cuts by either direct ablation or internal glass modification and cleavage. A recently developed high power UV nanosecond laser source allows for pulse shaping of individual laser pulses. Thus, the pulse duration, pulse bursts and the repetition rate can be set individually at a maximum output power of up to 60 W. This opens a completely new process window, which could not be entered with conventional Q-switched pulsed laser sources. In this study, the novel pulsed UV laser system was used to study the laser ablation process on 400 μm thin borosilicate glass at different pulse durations ranging from 2 - 10 ns and a pulse burst with two 10 ns laser pulses with a separation of 10 ns. Single line scan experiments were performed to correlate the process parameters and the laser pulse shape with the ablation depth and cutting edge chipping. Increasing the pulse duration within the single pulse experiments from 2 ns to longer pulse durations led to a moderate increase in ablation depth and a significant increase in chipping. The highest material removal was achieved with the 2x10 ns pulse burst. Experimental data also suggest that chipping could be reduced, while maintaining a high ablation depth by selecting an adequate pulse overlap. We also demonstrate that real-time combination of different pulse patterns during drilling a thin borosilicate glass produced holes with low overall chipping at a high throughput rate.

  18. Investigation of excimer laser ablation threshold of polymers using a microphone

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, Joerg; Niino, Hiroyuki; Yabe, Akira

    2002-09-30

    KrF excimer laser ablation of polyethylene terephthalate (PET), polyimide (PI) and polycarbonate (PC) in air was studied by an in situ monitoring technique using a microphone. The microphone signal generated by a short acoustic pulse represented the etch rate of laser ablation depending on the laser fluence, i.e., the ablation 'strength'. From a linear relationship between the microphone output voltage and the laser fluence, the single-pulse ablation thresholds were found to be 30 mJ cm{sup -2} for PET, 37 mJ cm{sup -2} for PI and 51 mJ cm{sup -2} for PC (20-pulses threshold). The ablation thresholds of PET and PI were not influenced by the number of pulses per spot, while PC showed an incubation phenomenon. A microphone technique provides a simple method to determine the excimer laser ablation threshold of polymer films.

  19. Investigation of excimer laser ablation threshold of polymers using a microphone

    Science.gov (United States)

    Krüger, Jörg; Niino, Hiroyuki; Yabe, Akira

    2002-09-01

    KrF excimer laser ablation of polyethylene terephthalate (PET), polyimide (PI) and polycarbonate (PC) in air was studied by an in situ monitoring technique using a microphone. The microphone signal generated by a short acoustic pulse represented the etch rate of laser ablation depending on the laser fluence, i.e., the ablation "strength". From a linear relationship between the microphone output voltage and the laser fluence, the single-pulse ablation thresholds were found to be 30 mJ cm -2 for PET, 37 mJ cm -2 for PI and 51 mJ cm -2 for PC (20-pulses threshold). The ablation thresholds of PET and PI were not influenced by the number of pulses per spot, while PC showed an incubation phenomenon. A microphone technique provides a simple method to determine the excimer laser ablation threshold of polymer films.

  20. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    BULLOCK, A B

    1999-05-26

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  1. Laser ablation of lysozyme with UV, visible and infrared femto- and nanosecond pulses

    DEFF Research Database (Denmark)

    Schou, Jørgen; Canulescu, Stela; Matei, Andreea

    industry. Lysozyme molecules do not absorb energy for wavelengths above 310 nm, but nevertheless there is a strong mass loss by ablation for laser irradiation in the visible regime. The total ablation yield of lysozyme at 355 nm and at 2 J/cm2 is about 155 µg/pulse, possibly one of the highest ablation...

  2. Is the VUV laser ablation of polymers a pure photochemical process?

    Science.gov (United States)

    Castex, M. C.; Bityurin, N.

    2002-09-01

    Within the pure photochemical model of laser ablation of polymers, developed in our previous publications, we estimate the value of the surface temperature at the ablation front for several important examples. Derived formulas allow probing physical self-consistency of the pure photochemical ablation model.

  3. Double-pulse laser ablation coupled to laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Glaus, Reto, E-mail: reglaus@ufl.edu; Hahn, David W.

    2014-08-01

    Laser ablation coupled to laser-induced breakdown spectroscopy (LA-LIBS) is an analytical method, which minimizes sample matrix effects typically found in quantitative LIBS-based direct solid analyses. This paper reports the application of double-pulse laser ablation (DP-LA) to improve the analyte response and the achievable precisions of LA-LIBS. Two coaxial laser beams were applied at the ablation site and the analytical signals were then collected from a second free-standing LIBS plasma downstream of the ablation site. Signal improvements of up to one order of magnitude were observed compared to single-pulse LA-LIBS. The effect of the interpulse delay on the observed signal-to-noise ratios was studied and the quantification capabilities of the optimized DP-LA-LIBS setup were investigated for manganese and iron in a broad range of different alloy types. A linear response was observed for manganese across the different matrices, allowing for nonmatrix-matched calibrations. Matrix effects were observed when analyzing aluminum samples, which, however, could be compensated for by applying iron as internal standard. Size distributions of the ablated material and electron density measurements provide additional insight into the double-pulse process, with additional future work suggested. - Highlights: • Double-pulse laser ablation was coupled to laser-induced breakdown spectroscopy. • Nonmatrix-matched calibration of manganese in various alloys was performed. • Improved sensitivities and precisions compared to single-pulse LA were demonstrated. • Remaining matrix effects and internal standardization are discussed.

  4. Microfabrication of Fresnel zone plates by laser induced solid ablation

    Science.gov (United States)

    Rodrigues, Vanessa R. M.; Thomas, John; Santhosh, Chidangil; Ramachandran, Hema; Mathur, Deepak

    2016-07-01

    A novel and simple single-step method of inscribing optical elements on metal-coated transparent substrates is demonstrated. Laser induced solid ablation (LISA) demands very low laser energies (nJ), as can be amply provided by a femtosecond laser oscillator. Here, LISA is used to write Fresnel zone plates on indium and tungsten coated glass. With up to 100 zones, remarkable agreement is obtained between measured and expected values of the focal length. LISA has enabled attainment of focal spot sizes that are 38% smaller than what would be obtained using conventional lenses of the same numerical aperture. The simplicity with which a high degree of automation can readily be achieved using LISA makes this cost-effective method amenable to a wide variety of applications related to microfabrication of optical elements.

  5. Evaluation of the analytical capability of NIR femtosecond laser ablation-inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Hirata, Takafumi; Kon, Yoshiaki

    2008-03-01

    A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of (57)Fe, obtained from iron sulfide (FeS(2)), demonstrated that the resulting signal intensity of (57)Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm(2)). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the (206)Pb/(238)U (f(Pb/U)) and (238)U/(232)Th (f(U/Th)) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of (56)Fe and the isotopic ratios ((57)Fe/(54)Fe and (56)Fe/(54)Fe) have been measured on a natural pyrite (FeS(2)) sample. Repeatability in signal intensity of (56)Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in (57)Fe/(54)Fe and (56)Fe/(54)Fe ratio measurements could be improved by the fs-laser ablation system

  6. Fabrication of pillared PLGA microvessel scaffold using femtosecond laser ablation

    Directory of Open Access Journals (Sweden)

    Wang GJ

    2012-04-01

    Full Text Available Hsiao-Wei Wang1, Chung-Wei Cheng2, Ching-Wen Li3, Han-Wei Chang4, Ping-Han Wu2, Gou-Jen Wang 1Graduate Institute of Biomedical Engineering, National Chung Hsing University, Taichung, Taiwan, 2Laser Application Technology Center, Industrial Technology Research Institute, Tainan County, Taiwan, 3Department of Mechanical Engineering, 4Department of Chemical Engineering, National Chung Hsing University, Taichung, Taiwan, People’s Republic of ChinaAbstract: One of the persistent challenges confronting tissue engineering is the lack of intrinsic microvessels for the transportation of nutrients and metabolites. An artificial microvascular system could be a feasible solution to this problem. In this study, the femtosecond laser ablation technique was implemented for the fabrication of pillared microvessel scaffolds of polylactic-co-glycolic acid (PLGA. This novel scaffold facilitates implementation of the conventional cell seeding process. The progress of cell growth can be observed in vitro by optical microscopy. The problems of becoming milky or completely opaque with the conventional PLGA scaffold after cell seeding can be resolved. In this study, PLGA microvessel scaffolds consisting of 47 µm × 80 µm pillared branches were produced. Results of cell culturing of bovine endothelial cells demonstrate that the cells adhere well and grow to surround each branch of the proposed pillared microvessel networks.Keywords: femtosecond laser ablation, pillared microvessel scaffold, polylactic-co-glycolic acid, bovine endothelial cells

  7. Production of silver nanoparticles by laser ablation in open air

    Energy Technology Data Exchange (ETDEWEB)

    Boutinguiza, M., E-mail: mohamed@uvigo.es [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9. Vigo, 36310 (Spain); Comesaña, R. [Materials Engineering, Applied Mechanics and Construction Dpt., University of Vigo, EEI, Lagoas-Marcosende, Vigo, 36310 (Spain); Lusquiños, F.; Riveiro, A.; Val, J. del; Pou, J. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9. Vigo, 36310 (Spain)

    2015-05-01

    Highlights: • Silver nanoparticles have been obtained by laser ablation of metallic Ag in open air using nanosecond laser. • The continuous process enables increasing the production yield. • The obtained particles are rounded shape with narrow size distribution. - Abstract: Silver nanoparticles have attracted much attention as a subject of investigation due to their well-known properties, such as good conductivity, antibacterial and catalytic effects, etc. They are used in many different areas, such as medicine, industrial applications, scientific investigation, etc. There are different techniques for producing Ag nanoparticles, chemical, electrochemical, sonochemical, etc. These methods often lead to impurities together with nanoparticles or colloidal solutions. In this work, laser ablation of solids in open air conditions (LASOA) is used to produce silver nanoparticles and collect them on glass substrates. Production and deposition of silver nanoparticles are integrated in the same step to reduce the process. The obtained particles are analysed and the nanoparticles formation mechanism is discussed. The obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV/VIS absorption spectroscopy. The obtained nanoparticles consisted of Ag nanoparticles showing rounded shape with diameters ranging from few to 50 nm.

  8. Multidiagnostic analysis of ultrafast laser ablation of metals with pulse pair

    OpenAIRE

    LUNNEY, JAMES

    2010-01-01

    PUBLISHED Copper targets are irradiated in the ablation regime by pairs of equal, time-delayed collinear laser pulses separated on a timescale going from 2 ps to 2 ns. The ablation plume is characterized by ion probe diagnostic, fast imaging, and temporally and spatially resolved optical emission spectroscopy. The variation in the ablation efficiency with the delay between the pulses is analyzed by measuring the ablation crater profile with a contact profilometer. The second ...

  9. Laser ablative cutting of ceramics for electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Warner, B. E., LLNL

    1996-03-01

    Pulsed, high-beam quality lasers offer unique materials processing characteristics. In processing metals, copper vapor and pulsed Nd:YAG lasers have produced micron-scale cuts and holes with submicron heat-affected zones. Since the cost of laser photons is high and average material removal rates can be slow with ablation, high value-added applications are necessary to justify processing costs. Ceramics present a special challenge for manufacturing because of their high hardness, relatively low thermal conductivity, and brittle nature. Surface damage typically limits the strength of a ceramic part to a small fraction of its bulk strength. This work investigates the use of copper vapor and pulsed diode-pumped Nd:YAG lasers to cut precision features in ceramic substrates. Variations in laser wavelength and power, processing speed, ceramic type, and assist gas were investigated with the goal of producing <100-{mu}m wide by 600-{mu}m deep cuts through silicon-carbide and alumina/titanium-carbide substrates for potential use in electronics. Silicon-carbide bars 250-{mu}m wide by 600-{mu}m high by 2.5-cm long were laser cut from substrates without fracture.

  10. Measurements of Ablation Pressure and Mass Ablation Rate Using a Target Pendulum and a Thin Foil Target at 10 μm Laser Wavelength

    Science.gov (United States)

    Daido, Hiroyuki; Tateyama, Ryuzi; Ogura, Kazuki; Mima, Kunioki; Nakai, Sadao; Yamanaka, Chiyoe

    1983-04-01

    The ablation pressure and the mass ablation rate for a 10 μm CO2 laser were measured using two methods: a ballistic target pendulum and shifted X-ray emission images which are equivalent to X-ray back-lighting. The measured ablation pressure was 10 Mbar and the mass ablation rate was 106 g/cm2\\cdotsec at the absorbed laser intensity of 5× 1013 W/cm2. Comparing the ablation mass rate measured by the pendulum with that derived from the penetration depth of the hot electrons using K_α line emission, we could identify the hot electron driven ablation as the dominant process.

  11. Ins and outs of endovenous laser ablation: afterthoughts.

    Science.gov (United States)

    Neumann, H A Martino; van Gemert, Martin J C

    2014-03-01

    Physicists and medical doctors "speak" different languages. Endovenous laser ablation (EVLA) is a good example in which technology is essential to guide the doctor to the final result: optimal treatment. However, for the doctor, it is by far insufficient just to turn on the knobs of the laser. He should understand what is going on in the varicose vein. On the other hand, the physicist is usually not aware what problems the doctor finds on his road towards improving a new technique. We have tried to bring both languages together in the special on Ins and outs of endovenous laser ablation published in this issue of Lasers in Medical Science. The 13 articles include endovenous related clinical (de Roos 2014; Kockaert and Nijsten 2014; van den Bos and Proebstle 2014) and socioeconomical articles (Kelleher et al 2014), the first paper on the molecular pathophysiologic mechanisms (Heger et al 2014), fiber tips (Stokbroekx et al 2014), the future of EVLA (Rabe 2014), a review of EVLA with some important issues for debate (Malskat et al 2014), an excellent paper on transcutaneous laser therapies of spider and small varicose veins (Meesters et al 2014), as well as several scientific modeling articles, varying from a mathematical model of EVLA that includes the carbonized blood layer on the fiber tip (van Ruijven et al 2014) and its application to the simulation of clinical conditions (Poluektova et al 2014) via experimental measurements of temperature profiles in response to EVLA, radiofrequency waves, and steam injections (Malskat et al 2014) to a literature review and novel physics approach of the absorption and particularly scattering properties of whole blood also including the infrared wavelengths used by EVLA (Bosschaart et al 2014). The aim of our afterthoughts, the 14th article in this special, is to try to amalgamate the clinical and physical contents of these contributions, providing the reader with the bridge that overlaps these different backgrounds.

  12. Determining Optimum Propellants, Pulse Lengths, and Laser Intensity for Ablative Laser Propulsion Using the Pals Laser

    Science.gov (United States)

    Boody, Frederick P.

    2004-10-01

    Ablative Laser Propulsion (ALP) can potentially reduce the cost of launching payloads into near earth orbit by a factor of 100. Preliminary experiments have demonstrated high efficiency, coupling coefficient, and specific impulse that would be suitable for applications. These experiments, however, were performed at wavelengths not usable in the atmosphere and at pulse energies and spot sizes much smaller than will be required for application. The parameters of the Prague Asterix Laser System (PALS) high-energy iodine laser, other than wavelength: pulse energy, pulse length, and beam diameter, are equal to those required for application. While its wavelength is a little shorter than required, it is closer than any other laser available and, due to PALS' 2ω and 3ω capability, the wavelength dependence can be studied and the results extrapolated to application values. In fact, PALS is probably the only laser in the world with parameters suitable for definitive ALP studies. PALS also has a suitable infrastructure for measuring plasma parameters already and only an instrument for measuring momentum transfer, such as a ballistic pendulum, would have to be added.

  13. Process and structures for fabrication of solar cells with laser ablation steps to form contact holes

    Energy Technology Data Exchange (ETDEWEB)

    Harley, Gabriel; Smith, David D; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

    2013-11-19

    Contact holes of solar cells are formed by laser ablation to accomodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thickness.

  14. Endobronchial laser ablation in the management of epithelial-myoepithelial carcinoma of the trachea

    Directory of Open Access Journals (Sweden)

    David McCracken

    2015-01-01

    We present the first documented case to be treated with endobronchial laser ablation therapy with discussion of the incidence, presentation and characteristics of these tumours including the treatment options, as well as the use of laser ablation in the management of benign and malignant endobronchial lesions.

  15. Approximate theory of highly absorbing polymer ablation by nanosecond laser pulses

    Science.gov (United States)

    Furzikov, N. P.

    1990-04-01

    Surface interference, nonlinearly saturated instability of laser-induced thermodestruction, and subsequent oscillation of absorption mode permit the description of analytical ablation thresholds and depths per pulse of polymers having high absorption at laser wavelengths, e.g., polyimide and poly(ethylene terephtalate). Inverse problem solution for polycarbonate and ablation invariant designing are also realized.

  16. Effect of nanosecond pulse laser ablation on the surface morphology of Zr-based metallic glass

    Science.gov (United States)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-09-01

    In this study, we investigated the ripple patterns formation on the surface of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass using a nanosecond pulse laser ablation in air with a wavelength of 1064 nm. The strong thermal ablation phenomenon could be observed on vit1 BMG surface at laser energy of 200 mJ as a result of the adhibition of confining overlay. Many periodic ripples had formed on the edge of the ablated area at laser energy of 400 mJ because of the high intensity pulsed laser beam. The underlying mechanism of the periodic ripples formation could be explained by the K-H hydrodynamic instability theory. It had been shown that laser ablation with 600 mJ and 200 pulses results in the formation of many micro-cracks on the ablated area. Further analysis showed that the spatial occupation of the laser ablated area and the spacing between two adjacent ripples increased as the laser energy and the number of incident laser pulses increasing. The surface ripples feature on the edge of ablated area became more obvious with increasing laser pulses, but it was not correlated closely with the laser energies variation.

  17. Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, Rocio; Quintana, Iban; Etxarri, Jon [Manufacturing Processes Department, Fundacion TEKNIKER, Av. Otaola 20, 20600, Eibar, Guipuzcoa (Spain); Lejardi, Ainhoa; Sarasua, Jose-Ramon [Department of Mining and Metallurgy Engineering and Materials Science, School of Engineering, University of the Basque Country (EHU-UPV), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

    2011-11-01

    The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

  18. Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

    Directory of Open Access Journals (Sweden)

    Buxiang Zheng

    2014-02-01

    Full Text Available The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter, ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm2.

  19. Heat-affected zone of metals ablated with femtosecond laser pulses

    Science.gov (United States)

    Hirayama, Yoichi; Obara, Minoru

    2003-07-01

    The melted area is found on the surface ablated by nanosecond and picosecond laser pulses. However, the heat effect is little on the ablated surface in the case of femtosecond laser due to non-thermal ablation process. Heat-affected zone of metallic bulk crystal ablated with femtosecond Ti:sapphire laser pulses is experimentally studied. As a result of XRD (X-ray diffraction) measurements, the XRD peak signal of the area ablated with Ti:sapphire laser becomes smaller than that of the crystalline metal sample. While the crystallinity of the metal sample is crystalline before the laser ablation, the crystallinity in the ablated area is partially changed into the amorphous form. Because the residual pulse energy that is not used for the ablation process remains, leading to the formation of thin layer of melt phase. The melt layer is abruptly cooled down not to be re-crystallized, but to transform into the amorphous form. It is evident that the area ablated with femtosecond laser is changed into the amorphous metal. Additionally XRD measurements and AR+ etching are performed alternately to measure the thickness of the amorphous layer. In the case of iron, the thickness is measured to be 1 μm approximately, therefore heat-affected zone is quite small.

  20. MR guided percutaneous laser lumbar disk hernia ablation

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Takuo; Terao, Tohru; Ishibashi, Toshihiro; Yuhki, Ichiro; Harada, Junta; Tashima, Michiko [Jikei Univ., Chiba (Japan). Kashiwa Hospital; Abe, Toshiaki

    1998-03-01

    An MRI unit for interventional procedure is very useful for minimally invasive surgery of the brain and spine. Percutaneous laser disc decompression (PLDD) utilizing X-ray fluoroscopy is a relatively new less invasive procedure for treatment of lumbar disc herniation. MR guided laser surgery is applied to patients with disc herniation at our department. Approaching the target of the disc protrusion was easily conducted and vaporizing the disc hernia directly using a laser was possible under MR fluoroscopy. The purpose of the present study is to evaluate the usefulness of MR guided percutaneous laser disc hernia ablation (MR-guided PLDHA). As subjects, 36 patients with lumbar disc herniation, including 23 cases with L4/5 involvement and 13 cases with L5/S1 involvement were studied. Among these, 26 were males and 10 were females, age ranging from 24 to 62. We used an open type MR system (Hitachi, Airis 0.3T), a permanent, open configuration MR system. A YAG laser (LaserScope, USA) was used for PLDHA. An MR compatible 18G titanium needle 15 cm in length was used to puncture the herniated discs. The MR compatible needle was clearly visualized, and used to safely and accurately puncture the target herniated disc in each case with multidimensional guidance. Application of the laser was performed with MR guidance. The energy dose from the laser ranged from 800 to 2100 joules. In most cases, signs and symptoms improved in the patients immediately after disc vaporization. The overall success rate was 88.9%. The complication rate was 2.8%, including one case of discitis after PLDHA. MR fluoroscopy sequence permits near real time imaging and provides an easy approach to the therapeutic target of disc herniation. MR guided PLDHA is a minimally invasive procedure and is very useful for the treatment of lumbar disc protrusion. (author)

  1. EUV nanosecond laser ablation of silicon carbide, tungsten and molybdenum

    Science.gov (United States)

    Frolov, Oleksandr; Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Choukourov, Andrei; Kasuya, Koichi

    2015-09-01

    In this paper we present results of study interaction of nanosecond EUV laser pulses at wavelength of 46.9 nm with silicon carbide (SiC), tungsten (W) and molybdenum (Mo). As a source of laser radiation was used discharge-plasma driver CAPEX (CAPillary EXperiment) based on high current capillary discharge in argon. The laser beam is focused with a spherical Si/Sc multilayer-coated mirror on samples. Experimental study has been performed with 1, 5, 10, 20 and 50 laser pulses ablation of SiC, W and Mo at various fluence values. Firstly, sample surface modification in the nanosecond time scale have been registered by optical microscope. And the secondly, laser beam footprints on the samples have been analyzed by atomic-force microscope (AFM). This work supported by the Czech Science Foundation under Contract GA14-29772S and by the Grant Agency of the Ministry of Education, Youth and Sports of the Czech Republic under Contract LG13029.

  2. Picosecond laser ablation of nano-sized WTi thin film

    Science.gov (United States)

    Petrović, S.; Gaković, B.; Peruško, D.; Desai, T.; Batani, D.; Čekada, M.; Radak, B.; Trtica, M.

    2009-08-01

    Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm2 were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma.

  3. Oxidation of uranium nanoparticles produced via pulsed laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Trelenberg, T W; Glade, S C; Tobin, J G; Felter, T E; Hamza, A V

    2005-12-07

    An experimental apparatus designed for the synthesis, via pulsed laser deposition, and analysis of metallic nanoparticles and thin films of plutonium and other actinides was tested on depleted uranium samples. Five nanosecond pulses from a Nd:YAG laser produced films of {approx}1600 {angstrom} thickness that were deposited showing an angular distribution typical thermal ablation. The films remained contiguous for many months in vacuum but blistered due to induced tensile stresses several days after exposure to air. The films were allowed to oxidize from the residual water vapor within the chamber (2 x 10{sup -10} Torr base pressure). The oxidation was monitored by in-situ analysis techniques including x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) and followed Langmuir kinetics.

  4. Laser ablation initiated fast discharge for spectrochemical applications

    Directory of Open Access Journals (Sweden)

    Vinić Milica L.

    2014-01-01

    Full Text Available The results of an experimental study of the optical emission enhancement possibilities during the single pulse laser induced breakdown spectroscopy of the aluminum alloy are presented. This study is performed in air, argon and helium at different pressures with and without the additional fast electric discharge. The discharge was initiated by plasma plume created by laser ablation of target. The influences of various capacitors and discharge voltages on enhancement of the studied spectral line intensities were also studied. The application of the fast discharge through optical emission enhancement enables lowering of detection limits thus making this spectrochemical method comparable with the other analytical techniques. [Projekat Ministarstva nauke Republike Srbije, br. 171014

  5. Pulsed laser ablation and deposition of niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Sansone, M.; De Bonis, A. [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza (Italy); Santagata, A. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, UOS Tito Scalo, C.da Santa Loja, 85010 Tito, PZ (Italy); Rau, J.V. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100, 00133 Rome (Italy); Galasso, A. [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza (Italy); Teghil, R., E-mail: roberto.teghil@unibas.it [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza (Italy)

    2016-06-30

    Highlights: • We have deposited in vacuum niobium carbide films by fs and ns PLD. • We have compared PLD performed by ultra-short and short laser pulses. • The films deposited by fs PLD of NbC are formed by nanoparticles. • The structure of the films produced by fs PLD at 500 °C corresponds to NbC. - Abstract: NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation–deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  6. Dynamics of Molecular Emission Features from Nanosecond, Femtosecond Laser and Filament Ablation Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, Sivanandan S.; Yeak, J.; Brumfield, Brian E.; Suter, Jonathan D.; Phillips, Mark C.

    2016-06-15

    The evolutionary paths of molecular species and nanoparticles in laser ablation plumes are not well understood due to the complexity of numerous physical processes that occur simultaneously in a transient laser-plasma system. It is well known that the emission features of ions, atoms, molecules and nanoparticles in a laser ablation plume strongly depend on the laser irradiation conditions. In this letter we report the temporal emission features of AlO molecules in plasmas generated using a nanosecond laser, a femtosecond laser and filaments generated from a femtosecond laser. Our results show that, at a fixed laser energy, the persistence of AlO is found to be highest and lowest in ns and filament laser plasmas respectively while molecular species are formed at early times for both ultrashort pulse (fs and filament) generated plasmas. Analysis of the AlO emission band features show that the vibrational temperature of AlO decays rapidly in filament assisted laser ablation plumes.

  7. Endoscopic laser ablation of clival chordoma with magnetic resonance-guided laser induced thermal therapy

    Directory of Open Access Journals (Sweden)

    James Barrese

    2014-12-01

    Conclusion: The endoscopic endonasal approach to MRI-guided laser ablation is both technically feasible and safe. As a result, this therapy may be a useful alternative in hard-to-reach chordomas, or in recurrent cases that have failed other conventional treatment modalities.

  8. Noncontact Er:YAG laser ablation: clinical evaluation.

    Science.gov (United States)

    Dostálová, T; Jelínková, H; Kucerová, H; Krejsa, O; Hamal, K; Kubelka, J; Procházka, S

    1998-10-01

    The aim of this study is to evaluate the quality of laser ablation in comparison with the classical drilling preparation. For the experiment, the Er:YAG laser drilling machine was used. The system had a laser head, water cooler, and power supply with automatic control. Spot size of 300-350 microns was used for the preparation. Repetition rate of 1-4 Hz, and pulse energies of 100-400 mJ with water spray were chosen. Cavity shape in comparison with classical drill, time of preparation, and influence of cavity shape on filling materials retention in accordance with the U.S. Public Health Service System were used. The evaluation criteria for noncontact Er:YAG ablation were done. The cavity shape is irregular, but spot surface has larger area and microretentive appearance. Caries of enamel and dentin were treated with a noncontact preparation. It was possible to remove the old insufficient fillings, except for amalgam or metal alloys. The average number of pulses was 111.22 (SE 67.57). Vibrations of microexplosions during preparation were felt by patients on 14 cavities; however, nobody felt unpleasant pain. The qualities of filling materials in laser cavities were very stable; however, cavo surface margin discoloration of 82-86% of Alfa rating could be a problem. Changes of the color and anatomic form of the tooth were observed in 4-8%. In comparison with the classical treatment, it could be said that the retention and quality of filling materials is the same or very similar.

  9. Laser ablation of basal cell carcinomas guided by confocal microscopy

    Science.gov (United States)

    Sierra, Heidy; Cordova, Miguel; Nehal, Kishwer; Rossi, Anthony; Chen, Chih-Shan Jason; Rajadhyaksha, Milind

    2016-02-01

    Laser ablation offers precise and fast removal of superficial and early nodular types of basal cell carcinomas (BCCs). Nevertheless, the lack of histological confirmation has been a limitation. Reflectance confocal microscopy (RCM) imaging combined with a contrast agent can offer cellular-level histology-like feedback to detect the presence (or absence) of residual BCC directly on the patient. We conducted an ex vivo bench-top study to provide a set of effective ablation parameters (fluence, number of passes) to remove superficial BCCs while also controlling thermal coagulation post-ablation to allow uptake of contrast agent. The results for an Er:YAG laser (2.9 um and pulse duration 250us) show that with 6 passes of 25 J/cm2, thermal coagulation can be effectively controlled, to allow both the uptake of acetic acid (contrast agent) and detection of residual (or absence) BCCs. Confirmation was provided with histological examination. An initial in vivo study on 35 patients shows that the uptake of contrast agent aluminum chloride) and imaging quality is similar to that observed in the ex vivo study. The detection of the presence of residual tumor or complete clearance was confirmed in 10 wounds with (additional) histology and in 25 lesions with follow-up imaging. Our results indicate that resolution is sufficient but further development and use of appropriate contrast agent are necessary to improve sensitivity and specificity. Advances in RCM technology for imaging of lateral and deep margins directly on the patient may provide less invasive, faster and less expensive image-guided approaches for treatment of BCCs.

  10. Photonic Doppler velocimetry of laser-ablated ultrathin metals.

    Science.gov (United States)

    Valenzuela, A R; Rodriguez, G; Clarke, S A; Thomas, K A

    2007-01-01

    Obtaining velocity information from the interaction of a laser pulse on a metal layer provides insight into the rapid dynamics of material removal and plasma plume physics during ablation. A traditional approach involves using a velocity interferometer system for any reflector (VISAR) on a reflective metal surface. However, when the target is a thin metal layer, the cohesion of the surface is quickly lost resulting in a large spread of particle velocities that cannot be easily resolved by VISAR. This is due to material ejection"confusing" the VISAR measurement surface, effectively washing out the spatial fringe visibility in the VISAR interferometer. A new heterodyne-based optical velocimeter method is the photonic Doppler velocimeter (PDV). Because PDV tracks motion in a frequency encoded temporal electro-optical signal, velocity information is preserved and allows for multiple velocity components to be recorded simultaneously. The challenge lies in extracting PDV velocity information at short (nanosecond) laser ablation time scales with rapidly varying heterodyne beats by using electronic, optical, and analytical techniques to recover the velocity information from a fleeting signal. Here we show how we have been able to obtain velocity information on the nanosecond time scale and are able to compare it to hydrodynamic simulations. Also, we examine refinements to our PDV system by increasing the bandwidth, utilizing different probes, and sampling different analysis techniques.

  11. Hard tissue ablation with a spray-assisted mid-IR laser

    Energy Technology Data Exchange (ETDEWEB)

    Kang, H W [American Medical Systems, Minnetonka, MN (United States); Rizoiu, I [BioLase Technology, Irvine, CA (United States); Welch, A J [Department of Biomedical Engineering, University of Texas at Austin, Austin, TX (United States)

    2007-12-21

    The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a spray (dry ablation). In order to identify dominant ablation mechanisms, transient acoustic waves were compared to ablation thresholds and the volume of material removed. The ablation profile and depth were measured using optical coherence tomography (OCT). Irregular surface modification, charring and peripheral cracks were associated with dry ablation, whereas craters for spray samples were relatively clean without thermal damage. In spite of a 60% higher ablation threshold for spray associated irradiations owing to water absorption, acoustic peak pressures were six times higher and ablation volume was up to a factor of 2 larger compared to dry ablation. The enhanced pressure and ablation performance of the spray-assisted process was the result of rapid water vaporization, material ejection with recoil stress, interstitial water explosion and possibly liquid-jet formation. With water cooling and abrasive/disruptive mechanical effects, the spray ablation can be a safe and efficient modality for dental treatment.

  12. Particle Generation by Pulsed Excimer Laser Ablation in Liquid: Hollow Structures and Laser-Induced Reactions

    Science.gov (United States)

    Yan, Zijie

    2011-12-01

    Pulsed laser ablation of solid targets in liquid media is a powerful method to fabricate micro-/nanoparticles, which has attracted much interest in the past decade. It represents a combinatorial library of constituents and interactions, and one can explore disparate regions of parameter space with outcomes that are impossible to envision a priori. In this work, a pulsed excimer laser (wavelength 248 nm, pulse width 30 ns) has been used to ablate targets in liquid media with varying laser fluences, frequencies, ablation times and surfactants. It is observed that hollow particles could be fabricated by excimer laser ablation of Al, Pt, Zn, Mg, Ag, Si, TiO2, and Nb2O5 in water or aqueous solutions. The hollow particles, with sizes from tens of nanometers to micrometers, may have smooth and continuous shells or have morphologies demonstrating that they were assembled from nanoparticles. A new mechanism has been proposed to explain the formation of these novel particle geometries. They were formed on laser-produced bubbles through bubble interface pinning by laser-produced solid species. Considering the bubble dynamics, thermodynamic and kinetic requirements have been discussed in the mechanism that can explain some phenomena associated with the formation of hollow particles, especially (1) larger particles are more likely to be hollow particles; (2) Mg and Al targets have stronger tendency to generate hollow particles; and (3) the 248 nm excimer laser is more beneficial to fabricate hollow particles in water than other lasers with longer wavelengths. The work has also demonstrated the possiblities to fabricate novel nanostructures through laser-induced reactions. Zn(OH)2/dodecyl sulfate flower-like nanostructures, AgCl cubes, and Ag2O cubes, pyramids, triangular plates, pentagonal rods and bars have been obtained via reactions between laser-produced species with water, electrolyes, or surfactant molecules. The underlying mechanisms of forming these structures have been

  13. Laser Ablation Increases PEM/Catalyst Interfacial Area

    Science.gov (United States)

    Whitacre, Jay; Yalisove, Steve

    2009-01-01

    An investigational method of improving the performance of a fuel cell that contains a polymer-electrolyte membrane (PEM) is based on the concept of roughening the surface of the PEM, prior to deposition of a thin layer of catalyst, in order to increase the PEM/catalyst interfacial area and thereby increase the degree of utilization of the catalyst. The roughening is done by means of laser ablation under carefully controlled conditions. Next, the roughened membrane surface is coated with the thin layer of catalyst (which is typically platinum), then sandwiched between two electrode/catalyst structures to form a membrane/ele c t - rode assembly. The feasibility of the roughening technique was demonstrated in experiments in which proton-conducting membranes made of a perfluorosulfonic acid-based hydrophilic, protonconducting polymer were ablated by use of femtosecond laser pulses. It was found that when proper combinations of the pulse intensity, pulse-repetition rate, and number of repetitions was chosen, the initially flat, smooth membrane surfaces became roughened to such an extent as to be converted to networks of nodules interconnected by filaments (see Figure 1). In further experiments, electrochemical impedance spectroscopy (EIS) was performed on a pristine (smooth) membrane and on two laser-roughened membranes after the membranes were coated with platinum on both sides. Some preliminary EIS data were interpreted as showing that notwithstanding the potential for laser-induced damage, the bulk conductivities of the membranes were not diminished in the roughening process. Other preliminary EIS data (see Figure 2) were interpreted as signifying that the surface areas of the laser-roughened membranes were significantly greater than those of the smooth membrane. Moreover, elemental analyses showed that the sulfur-containing molecular groups necessary for proton conduction remained intact, even near the laser-roughened surfaces. These preliminary results can be taken

  14. Laser ablation of FOX-7: proposed mechanism of decomposition.

    Science.gov (United States)

    Civis, Martin; Civis, Svatopluk; Sovová, Kristýna; Dryahina, Kseniya; Spanel, Patrik; Kyncl, Martin

    2011-02-01

    A novel high-energy explosive material, FOX-7 (1,1-diamino-2,2-dinitroethylene), was studied using a combination of laser-induced breakdown spectroscopy (LIBS) and selected ion flow tube mass spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (an ArF excimer laser) as the energy source to convert small quantities of a sample into plasma and to induce the emission of its molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three reagent ions, with the ability to determine concentrations of trace gases and vapors of volatile organic compounds in real time. SIFT-MS was used to study the release of NO, NO(2), HCN, HONO, HCHO, CH(3)CH(2)OH, and C(2)H(2) after laser ablation of the explosive compound FOX-7 in solid crystalline form. The radiation emitted after excitation was analyzed using a time-resolved UV-vis spectrometer with an ICCD detector. The electronic bands of CN (388 nm), OH (308.4 nm), and NO (237.1 nm) radicals and the atomic lines of C, N, and H were identified.

  15. Femtosecond laser ablation of cemented carbides: properties and tribological applications

    Science.gov (United States)

    Dumitru, G.; Romano, V.; Weber, H. P.; Gerbig, Y.; Haefke, H.; Bruneau, S.; Hermann, J.; Sentis, M.

    Laser ablation with fs laser pulses was performed in air on cobalt cemented tungsten carbide by means of a Ti : sapphire laser (800 nm, 100 fs). Small and moderate fluences (2, 5, 10 J/cm2) and up to 5×104 pulses per irradiated spot were used to drill holes with aspect ratios up to 10. Cross-section cuts from laser-irradiated samples were produced and they were analysed with optical microscopy and SEM. EDX analyses were carried out on selected zones. Quasi-cylindrical holes were found for 2 J/cm2, whereas for 5 and 10 J/cm2 irregular shapes (lobes, bottoms wider than hole entrances) were found to occur after a given number of incident pulses. Layers with modified structure were evidenced at pore walls. SEM revealed a denser structure, while EDX analyses showed uniform and almost similar contents of W, C, and Co in these layers. As a direct application, patterning of coated WC-Co was carried out with 2 J/cm2 and 100 pulses per pore. The resulted surfaces were tribologically tested and these tests revealed an improved friction and wear behaviour.

  16. Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation.

    Directory of Open Access Journals (Sweden)

    Y Al-Hadeethi

    Full Text Available Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM. Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX. The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased.

  17. Morphological and spectroscopic characterization of laser-ablated tungsten at various laser irradiances

    Energy Technology Data Exchange (ETDEWEB)

    Akram, Mahreen; Bashir, Shazia; Hayat, Asma; Mahmood, Khaliq; Dawood, Asadullah [Government College University, Centre for Advanced Studies in Physics, Lahore (Pakistan); Rafique, Muhammad Shahid [University of Engineering and Technology, Department of Physics, Lahore (Pakistan); Bashir, M.F. [COMSATS Institute of Information Technology, Department of Physics, Lahore (Pakistan)

    2015-06-15

    The variation in surface morphology and plasma parameters of laser irradiated tungsten has been investigated as a function of irradiance. For this purpose, Nd:YAG laser (1064 nm, 10 ns, 10 Hz) is employed. Tungsten targets were exposed to various laser irradiances ranging from 6 to 50 GW/cm{sup 2} under ambient environment of argon at a pressure of 20 Torr. Scanning electron microscope analysis has been performed to analyze the surface modification of irradiated tungsten. It revealed the formation of micro- and nanoscale surface structures. In central ablated area, distinct grains and crack formation are observed, whereas peripheral ablated areas are dominated by cones and pinhole formation. It was observed that at irradiances exceeding a value of 13 GW/cm{sup 2}, the morphological trend of the observed structures has been changed from erosion to melting and re-deposition dominant phase. Ablation efficiency as a function of laser irradiance has also been investigated by measuring the crater depth using surface profilometry analysis. It is found to be maximum at an irradiance of 13 GW/cm{sup 2} and decreases at high laser irradiances. In order to correlate the accumulated effects of plasma parameters with the surface modification, laser-induced breakdown spectroscopy analysis has been performed. The electron temperature and number density of tungsten plasma have been evaluated at various laser irradiances. Initially with the increase of the laser irradiance up to 13 GW/cm{sup 2}, an increasing trend is observed for both plasma parameters due to enhanced energy deposition. Afterward, a decreasing trend is achieved which is attributed to the shielding effect. With further increase in irradiance, a saturation stage comes and insignificant changes are observed in plasma parameters. This saturation is explainable on the basis of the formation of a self-regulating regime near the target surface. Surface modifications of laser irradiated tungsten have been correlated with

  18. Corneal morphology after ex-vivo UV and mid-infrared laser ablation

    Science.gov (United States)

    Spyratou, E.; Voloudakis, G. E.; Moutsouris, K.; Asproudis, I.; Baltatzis, S.; Makropoulou, M.; Bacharis, C.; Serafetinides, A. A.

    2008-12-01

    In this work, ablation experiments of ex vivo porcine cornea tissue were conducted with two solid state lasers (an Er:YAG laser and the 4th harmonic of an Nd:YAG laser, both in the ns pulse width range) emitting in mid infrared and ultraviolet part of the spectrum respectively, at moderate laser fluences. The cornea epithelium of each porcine eye was manually removed before the ablation. Histology analysis of the specimens was performed, in order to examine the microscopic appearance of the ablated craters and the existence of any thermal or mechanical damage caused by the midinfrared and the UV laser irradiation. For a detailed and complete examination of the morphology of the laser ablated corneal tissue, the surface roughness was investigated by scanning electron microscopy.

  19. The study of laser plasma plume radiation produced by laser ablation of silicon

    Science.gov (United States)

    Huang, Qingju

    2014-12-01

    In order to study the laser plasma plume radiation mechanisms induced by the interaction between Nd: YAG plused laser and silicon, the radiation model of silicon laser plasma plume is established. Laser plasma plume radiation includes atom characteristic lines, ion lines and continuous background. It can reflect the characteristics of laser plasma plume radiation, reveal the mechanism of laser ablation on silicon. Time-resolved measurment of laser plasma plume radiation produced by pulsed Nd: YAG laser ablation of silicon in different ambient gas is thoroughly studied. The experimental ambient gas are N2 and O2.The pulse width of Nd: YAG plused laser adopted in the experiment is 20ns, the pulse energy is 60mJ, the laser pulsing frequency is 10Hz, and the emitted laser wavelength is 1064nm, The silicon target purity is 99.99%, The target is rotating at a speed of 240r/min. The focusing area of the laser on the Si target has a diameter of around 0.8mm.The pressure of ambient gas is tunable between 13Pa and 101.3kPa in the induced chamber, the number of points used in averaging is 15. The experimental results show that the ambient gas has obvious enhancement effect on the radiation intensity of silicon laser plasma plume. With the increase of the ambient gas pressure, the silicon laser plasma plume radiation intensity will first be increased and then be decreased, and the ambient gas has an obvious compression effect on the scope of silicon laser plasma plume radiation. For the two different ambient gases, the maximum silicon laser plasma plume radiation intensity and maximum pressure for they are different, for oxygen at 35kPa, for nitrogen at 50kPa. The silicon laser plasma plume radiation intensity in oxygen is bigger than that in nitrogen.The main excition mechanisms of laser plasma plume radiation induced by Nd:YAG plused laser induced silicon is analyzed, The plused laser can makes part molecules in the ambient gas and silicon atoms ionized at the surface of

  20. ["Skin rejuvenation" by non-ablative laser and light systems. Literature research and overview].

    Science.gov (United States)

    Grema, H; Raulin, C; Greve, B

    2002-06-01

    Currently, ablative laser therapy (with CO2/Er:YAG lasers) and deep chemical peeling are effective and promising methods of skin rejuvenation. The induction of collagen synthesis was observed after peelings with trichloroacetic acid or phenol as well as after treatments with the CO2 laser. In past years, the undesirable side effects and risks of these methods have led to intensified research in the fields of non-ablative facial rejuvenation and subsurfacing by means of ablative laser systems and intense pulsed light systems. The objective is to achieve selective, heat-induced denaturalisation of dermal collagen that leads to subsequent reactive synthesis but does not damage the epidermis. Recently, the results of numerous clinical and histological studies have indicated that these new technologies are successful. After critical review and assessment of current literature, we can say that in terms of their efficacy, non-ablative methods are not a comparable alternative to ablative skin resurfacing.

  1. Fabrication of gold nanoparticles in water by laser ablation technique and their characterization

    Energy Technology Data Exchange (ETDEWEB)

    Haider, A.F.M.Y.; Sengupta, S.; Abedin, K.M.; Talukder, Aminul I. [University of Dhaka, Physics Department and Non-linear Optics and Laser Spectroscopy Laboratory, Centre of Advanced Research in Sciences, Dhaka (Bangladesh)

    2011-11-15

    A colloidal solution of gold nanoparticles in deionized nanopure water was produced by laser ablation technique without the use of any chemical/surfactant. Spectral characterization and morphological studies of these nanoparticles were carried out by UV-Vis Spectroscopy and Scanning Electron Microscopy, respectively. A number of variables of the ablating laser pulse have been used to control the size of the fabricated nanoparticles. Excellent correlation between ablating laser pulse parameter and optical and morphological parameters of the gold colloids were obtained. The peak of the extinction spectra shows a monotonic blue shift for laser fluence of 410 J/cm{sup 2} and above. Below this the extinction peak remains fairly constant in wavelength. Blue shifts of the extinction spectra were also observed with increasing re-ablation time of previously ablated gold colloids. Possible explanations of all these observations are discussed. (orig.)

  2. Ultrafast properties of femtosecond-laser-ablated GaAs and its application to terahertz optoelectronics.

    Science.gov (United States)

    Madéo, Julien; Margiolakis, Athanasios; Zhao, Zhen-Yu; Hale, Peter J; Man, Michael K L; Zhao, Quan-Zhong; Peng, Wei; Shi, Wang-Zhou; Dani, Keshav M

    2015-07-15

    We report on the first terahertz (THz) emitter based on femtosecond-laser-ablated gallium arsenide (GaAs), demonstrating a 65% enhancement in THz emission at high optical power compared to the nonablated device. Counter-intuitively, the ablated device shows significantly lower photocurrent and carrier mobility. We understand this behavior in terms of n-doping, shorter carrier lifetime, and enhanced photoabsorption arising from the ablation process. Our results show that laser ablation allows for efficient and cost-effective optoelectronic THz devices via the manipulation of fundamental properties of materials.

  3. Characterization of laser ablation of copper in the irradiance regime of laser-induced breakdown spectroscopy analysis

    Energy Technology Data Exchange (ETDEWEB)

    Picard, J., E-mail: jessica.picard@cea.fr [Commissariat à l' Energie Atomique, DAM, Valduc, F-21120 Is-sur-Tille (France); Sirven, J.-B.; Lacour, J.-L. [Commissariat à l' Energie Atomique, DEN/DANS/DPC/SEARS/LANIE, Saclay, F-91191 Gif-sur-Yvette (France); Musset, O. [Université de Bourgogne, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS 5209, F-21000 Dijon (France); Cardona, D.; Hubinois, J.-C. [Commissariat à l' Energie Atomique, DAM, Valduc, F-21120 Is-sur-Tille (France); Mauchien, P. [Commissariat à l' Energie Atomique, DEN/DANS/DPC/SEARS/LANIE, Saclay, F-91191 Gif-sur-Yvette (France)

    2014-11-01

    The LIBS signal depends both on the ablated mass and on the plasma excitation temperature. These fundamental parameters depend in a complex manner on laser ablation and on laser–plasma coupling. As several works in the literature suggest that laser ablation processes play a predominant role compared to plasma heating phenomena in the LIBS signal variations, this paper focuses on the study of laser ablation. The objective was to determine an interaction regime enabling to maximally control the laser ablation. Nanosecond laser ablation of copper at 266 nm was characterized by scanning electron microscopy and optical profilometry analysis, in air at 1 bar and in the vacuum. The laser beam spatial profile at the sample surface was characterized in order to give realistic values of the irradiance. The effect of the number of accumulated laser shots on the crater volume was studied. Then, the ablation crater morphology, volume, depth and diameter were measured as a function of irradiance between 0.35 and 96 GW/cm². Results show that in the vacuum, a regular trend is observed over the whole irradiance range. In air at 1 bar, below a certain irradiance, laser ablation is very similar to the vacuum case, and the ablation efficiency of copper was estimated at 0.15 ± 0.03 atom/photon. Beyond this irradiance, the laser beam propagation is strongly disrupted by the expansion of the dense plasma, and plasma shielding appears. The fraction of laser energy used for laser ablation and for plasma heating is estimated in the different irradiance regimes. - Highlights: • The morphology of copper's craters was studied as a function of the pulse energy. • Correlation at low energy and two pressures between crater volume and pulse energy • The ablation efficiency of copper at 1 bar is equal to 0.15 atom/photon. • Ablation efficiency in the vacuum is not limited by laser–plasma interaction. • Physical mechanisms of laser ablation at both pressures are discussed.

  4. Measurements of erbium laser-ablation efficiency in hard dental tissues under different water cooling conditions.

    Science.gov (United States)

    Kuščer, Lovro; Diaci, Janez

    2013-10-01

    Laser triangulation measurements of Er:YAG and Er,Cr:YSGG laser-ablated volumes in hard dental tissues are made, in order to verify the possible existence of a "hydrokinetic" effect that has been proposed as an alternative to the "subsurface water expansion" mechanism for hard-tissue laser ablation. No evidence of the hydrokinetic effect could be observed under a broad range of tested laser parameters and water cooling conditions. On the contrary, the application of water spray during laser exposure of hard dental material is observed to diminish the laser-ablation efficiency (AE) in comparison with laser exposure under the absence of water spray. Our findings are in agreement with the generally accepted principle of action for erbium laser ablation, which is based on fast subsurface expansion of laser-heated water trapped within the interstitial structure of hard dental tissues. Our measurements also show that the well-known phenomenon of ablation stalling, during a series of consecutive laser pulses, can primarily be attributed to the blocking of laser light by the loosely bound and recondensed desiccated minerals that collect on the tooth surface during and following laser ablation. In addition to the prevention of tooth bulk temperature buildup, a positive function of the water spray that is typically used with erbium dental lasers is to rehydrate these minerals, and thus sustaining the subsurface expansion ablation process. A negative side effect of using a continuous water spray is that the AE gets reduced due to the laser light being partially absorbed in the water-spray particles above the tooth and in the collected water pool on the tooth surface. Finally, no evidence of the influence of the water absorption shift on the hypothesized increase in the AE of the Er,Cr:YSGG wavelength is observed.

  5. Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

    Science.gov (United States)

    Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

    2013-01-01

    This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

  6. Physical mechanisms of SiN{sub x} layer structuring with ultrafast lasers by direct and confined laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, S., E-mail: rapp@hm.edu [Faculty of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstraße 34, 80335 Munich (Germany); Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straße 6, 91052 Erlangen (Germany); Heinrich, G. [Technische Universität Ilmenau, Institut für Physik, Weimarer Straße 25., 98693 Ilmenau (Germany); CiS Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH, Konrad-Zuse-Straße 14, 99099 Erfurt (Germany); Wollgarten, M. [Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Huber, H. P. [Faculty of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstraße 34, 80335 Munich (Germany); Schmidt, M. [Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für Photonische Technologien, Konrad-Zuse-Straße 3-5, 91052 Erlangen (Germany)

    2015-03-14

    In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deeper understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN{sub x}) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm{sup 2} and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN{sub x} layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN{sub x} island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates.

  7. Co:MgF2 laser ablation of tissue: effect of wavelength on ablation threshold and thermal damage.

    Science.gov (United States)

    Schomacker, K T; Domankevitz, Y; Flotte, T J; Deutsch, T F

    1991-01-01

    The wavelength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical absorption length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 microns, a wavelength region in which the absorption length varies by a decade. For soft tissues the ablation threshold tracks the optical absorption length; for bone there is little wavelength dependence, consistent with the low water content of bone. Thermal damage vs. wavelength was also studied for cornea and bone. Thermal damage to cornea has a weak wavelength dependence, while that to bone shows little wavelength dependence. Framing-camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion.

  8. Water content contribution in calculus phantom ablation during Q-switched Tm:YAG laser lithotripsy.

    Science.gov (United States)

    Zhang, Jian J; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Wang, Hui; Chia, Ray W J; Hasenberg, Tom; Kang, Hyun Wook

    2015-01-01

    Q-switched (QS) Tm:YAG laser ablation mechanisms on urinary calculi are still unclear to researchers. Here, dependence of water content in calculus phantom on calculus ablation performance was investigated. White gypsum cement was used as a calculus phantom model. The calculus phantoms were ablated by a total 3-J laser pulse exposure (20 mJ, 100 Hz, 1.5 s) and contact mode with N=15 sample size. Ablation volume was obtained on average 0.079, 0.122, and 0.391  mm3 in dry calculus in air, wet calculus in air, and wet calculus in-water groups, respectively. There were three proposed ablation mechanisms that could explain the effect of water content in calculus phantom on calculus ablation performance, including shock wave due to laser pulse injection and bubble collapse, spallation, and microexplosion. Increased absorption coefficient of wet calculus can cause stronger spallation process compared with that caused by dry calculus; as a result, higher calculus ablation was observed in both wet calculus in air and wet calculus in water. The test result also indicates that the shock waves generated by short laser pulse under the in-water condition have great impact on the ablation volume by Tm:YAG QS laser.

  9. Laser-induced Breakdown Spectroscopy and ablation threshold analysis using a megahertz Yb fiber laser oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Parker, Gregory J.; Parker, Daniel E.; Nie, Bai; Lozovoy, Vadim [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Dantus, Marcos, E-mail: dantus@msu.edu [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2015-05-01

    A LIBS system is demonstrated using a 100 m cavity Yb fiber oscillator producing ~ 70 ps, 320 nJ clusters of 50–100 fs sub-pulses at 2 MHz. A new empirical model for femtosecond ablation is presented to explain the LIBS signal intensity's non-linear dependence on pulse fluence by accounting for the Gaussian beam's spatial distribution. This model is compared to experimental data and found to be superior to linear threshold fits. This model is then used to measure the ablation threshold of Cu using a typical amplified Ti:sapphire system, and found to reproduce previously reported values to within ~ 20%. The ablation threshold of Cu using the Yb fiber oscillator system was measured to be five times lower than on the amplified Ti:sapphire system. This effect is attributed to the formation of nanostructures on the surface, which have previously been shown to decrease the ablation threshold. The plasma lifetime is found to be ~ 1 ns, much shorter than that of nanosecond ablation, further indicating that the decreased threshold results from surface effects rather than laser–plasma interaction. The low threshold and high pulse energy of the Yb fiber oscillator allows the acquisition of LIBS spectra at megahertz repetition rates. This system could potentially be developed into a compact, fiber-based portable LIBS device taking advantage of the benefits of ultrafast pulses and high repetition rates. - Highlights: • We performed LIBS using a unique ultrafast fiber laser oscillator producing clusters of femtosecond pulses at 2 MHz. • We found the LIBS threshold to be lower than the ablation threshold for single femtosecond laser pulses. • We introduce a model for the LIBS threshold that leads to more accurate determination of threshold values. • We provide results for a number of different solid samples. • The new setup could lead to the design of very compact (portable) and femtosecond-LIBS setups.

  10. Spallative ablation of dielectrics by X-ray laser

    CERN Document Server

    Inogamov, N A; Faenov, A Ya; Khokhlov, V A; Shepelev, V V; Skobelev, I Yu; Kato, Y; Tanaka, M; Pikuz, T A; Kishimoto, M; Ishino, M; Nishikino, M; Fukuda, Y; Bulanov, S V; Kawachi, T; Petrov, Yu V; Anisimov, S I; Fortov, V E

    2009-01-01

    Short laser pulse in wide range of wavelengths, from infrared to X-ray, disturbs electron-ion equilibrium and rises pressure in a heated layer. The case where pulse duration $\\tau_L$ is shorter than acoustic relaxation time $t_s$ is considered in the paper. It is shown that this short pulse may cause thermomechanical phenomena such as spallative ablation regardless to wavelength. While the physics of electron-ion relaxation on wavelength and various electron spectra of substances: there are spectra with an energy gap in semiconductors and dielectrics opposed to gapless continuous spectra in metals. The paper describes entire sequence of thermomechanical processes from expansion, nucleation, foaming, and nanostructuring to spallation with particular attention to spallation by X-ray pulse.

  11. Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jikun; Stender, Dieter; Pichler, Markus; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas, E-mail: thomas.lippert@psi.ch [General Energy Research Department, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Döbeli, Max [Ion Beam Physics, ETH Zurich, CH-8093 Zurich (Switzerland)

    2015-10-28

    Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially {sup 18}O substituted La{sub 0.6}Sr{sub 0.4}MnO{sub 3} target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

  12. Reactions of Laser Ablation-magnesium Plasma with Methanol Clusters

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The laser ablation-molecular beam(LA-MB) method is useful for studying the reactions of metal ions with molecular clusters. Reactions of magnesium plasma with methanol clusters were studied by using this method. A specially designed reaction cell was used as a fast flow reactor operated under thermal conditions, and the reaction products were measured with a time-of-flight(TOF) mass spectrometer. Surprisingly, several series of cluster ions with complex sizes and intensity distributions were obtained when the laser ablating was applied to different parts of the molecular beam. In the front part of the molecular beam, strong Mg+ (CH3OH)n ( n = 0-5 ) and weak H+ (CH3OH)n (n = 0-5) cluster ions were observed with relatively small cluster sizes; in the middle part of the molecular beam,the main cluster ions were H+(CH3OH)n(n =6-17) and H+(H2O)2(CH3OH)n(n =6-17) with a relatively large cluster size and a weak intensity; in the back part of the molecular beam, two new series of cluster ions,MgO+ (H2O) (CH3OH) n ( n = 6-10) and MgOCH3+ (CH3OH)n ( n = 6-10), were obtained and accompanied by weak H+ (CH3OH)n(n = 4-7) and H+ (H2O)2 (CH3OH)n (n= 3-6). The formation mechanisms and speed characteristics of the cluster ions are discussed in this article.

  13. [A comparative analysis of tonsillectomy and ablation of the palatine tonsils with CO2 laser].

    Science.gov (United States)

    Zbyshko, Ia B

    2007-01-01

    Efficacy and toletance of two methods were compared: ablation of the palatine tonsils with CO2 laser and tonsillectomy. 270 case histories (118 after tonsillectomy and 152 after laser ablation of the palatine tonsils) have been analysed and 50 patients from each group have been examined. The comparison of the methods leads to conclusion that laser ablation of the palatine tonsils prevents intraoperative and postoperative complications; makes postoperative hemostatic therapy unnecessary; allows conduction of the operations in outpatient clinics or day hospitals; causes minimal pain in the postoperative period; shortens duration of disability.

  14. Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

    Science.gov (United States)

    Furukawa, Yuki; Sakata, Ryoichi; Konishi, Kazuki; Ono, Koki; Matsuoka, Shusaku; Watanabe, Kota; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji

    2016-06-01

    By pairing femtosecond laser pulses (duration ˜40 fs and central wavelength ˜810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm2 and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm2, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

  15. Percutaneous laser ablation of hepatocellular carcinoma in patients with liver cirrhosis awaiting liver transplantation

    Energy Technology Data Exchange (ETDEWEB)

    Pompili, Maurizio, E-mail: mpompili@rm.unicatt.i [Department of Internal Medicine, Universita Cattolica del Sacro Cuore, Largo A. Gemelli, 8, 00168 Roma (Italy); Pacella, Claudio Maurizio, E-mail: claudiomauriziopacella@gmail.co [Department of Diagnostic Imaging and Interventional Radiology, Ospedale Regina Apostolorum, Via S. Francesco D' Assisi, 50, 00041 Albano Laziale (RM) (Italy); Francica, Giampiero, E-mail: giampierofrancica@tin.i [Department of Interventional Ultrasound, Presidio Ospedaliero Camilliani, S. Maria della Pieta, Via S. Rocco, 9, 80026 Casoria (Namibia) (Italy); Angelico, Mario, E-mail: angelico@med.uniroma2.i [Hepatology Unit, Universita di Tor Vergata, Viale Oxford, 81, 00133 Rome (Italy); Tisone, Giuseppe, E-mail: tisone@med.uniroma2.i [Transplant and General Surgery Unit, Universita di Tor Vergata, Ospedale S. Eugenio, Piazzale dell' Umanesimo 10-00144 Rome (Italy); Craboledda, Paolo, E-mail: paolo.craboledda@virgilio.i [Department of Pathology, Ospedale S. Eugenio, Piazzale dell' Umanesimo, 10-00144 Rome (Italy); Nicolardi, Erica; Rapaccini, Gian Ludovico; Gasbarrini, Giovanni [Department of Internal Medicine, Universita Cattolica del Sacro Cuore, Largo A. Gemelli, 8, 00168 Roma (Italy)

    2010-06-15

    Objective: The aim of this study was to determine the effectiveness and safety of percutaneous laser ablation for the treatment of cirrhotic patients with hepatocellular carcinoma awaiting liver transplantation. Materials and methods: The data of 9 male cirrhotic patients (mean age 50 years, range 45-60 years) with 12 biopsy proven nodules of hepatocellular carcinoma (mean diameter 2.0 cm, range 1.0-3.0 cm) treated by laser ablation before liver transplantation between June 2000 and January 2006 were retrospectively reviewed. Laser ablation was carried out by inserting 300 nm optical fibers through 21-Gauge needles (from two to four) positioned under ultrasound guidance into the target lesions. A continuous wave Neodymium:Yttrium Aluminium Garnet laser was used. Transarterial chemoembolization prior to liver transplantation was performed in two incompletely ablated tumors. Results: No procedure-related major complications were recorded. During the waiting time to liver transplantation local tumor progression after ablation occurred in 3 nodules (25%). At histological examination of the explanted livers complete necrosis was found in 8 nodules (66.7%, all treated exclusively with laser ablation), partial necrosis >50% in 3 nodules (25%), and partial necrosis <50% in 1 nodule. Conclusion: In patients with cirrhotic livers awaiting liver transplantation, percutaneous laser ablation is safe and effective for the management of small hepatocellular carcinoma.

  16. Developing laser ablation in an electron cyclotron resonance ion source for actinide detection with AMS

    Energy Technology Data Exchange (ETDEWEB)

    Bauder, W. [Argonne National Laboratory, Physics Division, 9600 S. Cass Ave, Lemont, IL 60439 (United States); University of Notre Dame, Nuclear Science Laboratory, 124 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Pardo, R.C.; Kondev, F.G.; Kondrashev, S.; Nair, C.; Nusair, O. [Argonne National Laboratory, Physics Division, 9600 S. Cass Ave, Lemont, IL 60439 (United States); Palchan, T. [Hebrew University, Racah Institute of Physics, Jerusalem 91904 (Israel); Scott, R.; Seweryniak, D.; Vondrasek, R. [Argonne National Laboratory, Physics Division, 9600 S. Cass Ave, Lemont, IL 60439 (United States); Collon, P. [University of Notre Dame, Nuclear Science Laboratory, 124 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Paul, M. [Hebrew University, Racah Institute of Physics, Jerusalem 91904 (Israel)

    2015-10-15

    A laser ablation material injection system has been developed at the ATLAS electron cyclotron resonance (ECR) ion source for use in accelerator mass spectrometry experiments. Beam production with laser ablation initially suffered from instabilities due to fluctuations in laser energy and cratering on the sample surface by the laser. However, these instabilities were rectified by applying feedback correction for the laser energy and rastering the laser across the sample surface. An initial experiment successfully produced and accelerated low intensity actinide beams with up to 1000 counts per second. With continued development, laser ablation shows promise as an alternative material injection scheme for ECR ion sources and may help substantially reduce cross talk in the source.

  17. Endoscopic laser ablation of clival chordoma with magnetic resonance-guided laser induced thermal therapy

    OpenAIRE

    2014-01-01

    Background: Chordomas are rare malignant tumors that are difficult to treat and have high recurrence rates despite aggressive therapy. Objectives: We present the first case of a patient with a clival chordoma in which complete tumor ablation was achieved using Magnetic Resonance guided Laser Induced Thermal Therapy (LITT) delivered via an endoscopic endonasal approach. We analyzed the safety and feasibility of this approach and quantified the response of this pathology to thermal energy. T...

  18. Ablation characteristics of electrospun core-shell nanofiber by femtosecond laser.

    Science.gov (United States)

    Park, ChangKyoo; Xue, Ruipeng; Lannutti, John J; Farson, Dave F

    2016-08-01

    This study examined the femtosecond laser ablation properties of core and shell polymers their relationship to the ablation characteristics of core-shell nanofibers. The single-pulse ablation threshold of bulk polycaprolactone (PCL) was measured to be 2.12J/cm(2) and that of bulk polydimethylsiloxane (PDMS) was 4.07J/cm(2). The incubation coefficients were measured to be 0.82±0.02 for PCL and 0.53±0.03 for PDMS. PDMS-PCL core-shell and pure PCL nanofibers were fabricated by electrospinning. The energy/volume of pure PCL and PDMS-PCL core-shell nanofiber ablation was investigated by measuring linear ablation grooves made at different scanning speeds. At large scanning speed, higher energy/volume was required for machining PDMS-PCL nanofiber than for PCL nanofiber. However, at small scanning speed, comparable energy/volume was measured for PDMS-PCL and PCL nanofiber ablation. Additionally, in linear scanned ablation of PDMS-PCL fibers at small laser pulse energy and large scanning speed, there were partially ablated fibers where the shell was ablated but the core remained. This was attributed to the lower ablation threshold of the shell material.

  19. Energy distribution of ions produced by laser ablation of silver in vacuum

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Schou, Jørgen; Canulescu, Stela

    2013-01-01

    The ion energy in a silver ablation plume for fluence in the range of 0.6–2.4Jcm−2, typical for a pulsed laser deposition (PLD) experiment has been investigated. In this fluence range the ion fraction of the ablated particles becomes gradually dominant and can be utilized to characterize the abla...

  20. Molecular dynamics simulation of heat-affected zone of copper metal ablated with femtosecond laser

    Science.gov (United States)

    Hirayama, Yoichi; Obara, Minoru

    2005-03-01

    Femtosecond laser ablation of materials with high thermal conductivity is of paramount importance, because the chemical composition and properties of the area ablated with femtosecond laser are kept unchanged. The material processing by femtosecond laser can well control the heat-affected zone, compared to nanosecond laser ablation. We report on the heat-affected zone of crystalline copper (Cu) by use of femtosecond laser experimentally and theoretically. Laser ablation of Cu is investigated theoretically by two temperature model and molecular dynamics (MD) simulation. The MD simulation takes into account of electron temperature and thermal diffusion length calculated by two temperature model. The dependence of lattice temperature on time and depth is calculated by the MD simulation and two temperature model. The heat-affected zone estimated from the temperature is mainly studied and calculated to be 3 nm at 0.02 J/cm2 which is below the threshold fluence of 0.137 J/cm2. In addition, the thickness of heat-affected zone of copper crystal ablated with femtosecond Ti:sapphire laser is experimentally studied. As a result of X-ray diffraction (XRD) of the ablated surface, the surface crystallinity is partially changed into disordered structure from crystal form. The residual energy left in the metal, which is not used for ablation, will induce liquid phase, leading to the amorphous phase of the metal during resolidification. The thickness of heat-affected zone depends on laser fluence and is experimentally measured to be less than 1 μm at higher laser fluences than the ablation threshold.

  1. All-optical histology using two photon laser scanning microscopy and ablation with ultrashort pulses

    Science.gov (United States)

    Tsai, Philbert S.

    This dissertation discusses the use of ultrashort laser pulses to image and manipulate tissue for the purpose of three-dimensional histological reconstruction of extended brain structures. Two photon laser scanning microscopy (TPLSM) and ultrashort pulsed laser ablation are used to provide in situ three-dimensional imaging through thick preparations of fixed tissue. Surface regions of fixed tissue are first imaged using TPLSM. The imaged regions are then removed by ablation with amplified, ultrashort laser pulses, thereby exposing a previously underlying tissue region for imaging. This process of imaging and ablation proceeds iteratively until the desired tissue volume has been processed. First, the principles, design, and construction of a two photon laser scanning microscope are discussed, followed by a discussion of the physical mechanisms of tissue ablation with ultrashort laser pulses. The compatibility of tissue ablation using ultrashort pulses with subsequent histological analysis, particularly with fluorescent microscopy, is evaluated. Tissue ablation with ultrashort laser pulses is found to produce ablated tissue surfaces that are smooth to within a micrometer. Intrinsic fluorescence as well as immunoreactivity are found to be resilient to the ablation process. The all-optical histological technique is demonstrated on brain tissue from rats and mice, including tissue from embryonic mouse as early at E15. The ablation process is shown to preserve both macroscopic and microscopic structures within tissue. To facilitate the all-optical histological analysis of neuronal vasculature and its relative distribution to surrounding neuronal tissue, a fluorescent gel perfusion technique is developed that provides a temperature-stabilized fluorescent label of the neuronal vasculature. The use of immunohistochemistry to label specific cell populations throughout an 800 micrometer-thick tissue section is demonstrated. Additionally, the immersion of fixed tissue in high

  2. Laser ablation of powdered samples and analysis by means of laser-induced breakdown spectroscopy

    Science.gov (United States)

    Ctvrtnickova, T.; Cabalin, L.; Laserna, J.; Kanicky, V.; Nicolas, G.

    2009-03-01

    The presented work proves the capacities of laser-induced breakdown spectroscopy (LIBS) as a fast, universal, and versatile technique for analysis of complex materials as ceramics. This paper reports on the analysis of ceramic raw materials (brick clays and kaolin) submitted to laser ablation in the form of pressed pellets. Spectrographic study was provided by standard single-pulse LIBS technique and orthogonal reheating double-pulse LIBS. It was found that both methods are comparable in terms of analytical performance, if adequate experimental parameters and signal detection systems are used.

  3. High-Resolution Spectroscopy of Laser Ablation Plumes Using Laser-Induced Fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

    2017-02-06

    We used a CW laser as a narrow-band (~50kHz) tunable LIF excitation source to probe absorption from selected atomic transitions (Al, U etc. ) in a ns laser ablation plume. A comparison of fluorescence signal with respect to emission spectroscopy show significant increase in the magnitude and persistence from selected Al and U transitions in a LIBS plume. The high spectral resolution provided by the LIF measurement allows peaks to be easily separated even if they overlap in the emission spectra.

  4. Laser Ablation Plasma Injection into the Frankfurt 14 GHz ECRIS

    CERN Document Server

    Mironov, V; Runkel, S; Schmidt, L; Shirkov, G D; Stiebing, K E; Schmidt-Böcking, H; Schempp, A

    1999-01-01

    A Q-switched YAG:Nd3+ laser was used to evaporate a metal (Cd) target mounted close to a biased disk in the vacuum chamber of the 14 GHz Frankfurt ECRIS. The formation of the laser ablation plasma and the pulsed injection of neutral particles into ECR plasma resulting from the evaporation were studied in order to optimise the production of metal-ion beams and to perform diagnostics of the ECR plasma. The pulsed highly charged Cadmium ion beams were detected under the injection of neutral atoms of Cadmium into an Argon ECR discharge. The ionisation and confinements times for these ions were determined by using time-resolved spectroscopy of the charge state spectra. At the moment of the Cadmium injection, a pulsed increase of the Argon beam currents was detected, which is attributed to changes of the plasma potential. The amplitudes of these pulses are comparable with afterglow currents. Further investigations may provide a chance to use this effect for the injection of ion beams into the pulsed accelerators.

  5. A novel laser ablation plasma thruster with electromagnetic acceleration

    Science.gov (United States)

    Zhang, Yu; Zhang, Daixian; Wu, Jianjun; He, Zhen; Zhang, Hua

    2016-10-01

    A novel laser ablation plasma thruster accelerated by electromagnetic means was proposed and investigated. The discharge characteristics and thrust performance were tested with different charged energy, structural parameters and propellants. The thrust performance was proven to be improved by electromagnetic acceleration. In contrast with the pure laser propulsion mode, the thrust performance in electromagnetic acceleration modes was much better. The effects of electrodes distance and the off-axis distance between ceramic tube and cathode were tested, and it's found that there were optimal structural parameters for achieving optimal thrust performance. It's indicated that the impulse bit and specific impulse increased with increasing charged energy. In our experiments, the thrust performance of the thruster was optimal in large charged energy modes. With the charged energy 25 J and the use of metal aluminum, a maximal impulse bit of 600 μNs, a specific impulse of approximate 8000 s and thrust efficiency of about 90% were obtained. For the PTFE propellant, a maximal impulse bit of about 350 μNs, a specific impulse of about 2400 s, and thrust efficiency of about 16% were obtained. Besides, the metal aluminum was proven to be the better propellant than PTFE for the thruster.

  6. Nanometer thickness laser ablation for spatial control of cell attachment

    Science.gov (United States)

    Thissen, H.; Hayes, J. P.; Kingshott, P.; Johnson, G.; Harvey, E. C.; Griesser, H. J.

    2002-10-01

    We demonstrate here a new method to control the location of cells on surfaces in two dimensions, which can be applied to a number of biomedical applications including diagnostic tests and tissue engineered medical devices. Two-dimensional control over cell attachment is achieved by generation of a spatially controlled surface chemistry that allows control over protein adsorption, a process which mediates cell attachment. Here, we describe the deposition of thin allylamine plasma polymer coatings on silicon wafer and perfluorinated poly(ethylene-co-propylene) substrates, followed by grafting of a protein resistant layer of poly(ethylene oxide). Spatially controlled patterning of the surface chemistry was achieved in a fast, one-step procedure by nanometer thickness controlled laser ablation using a 248 nm excimer laser. X-ray photoelectron spectroscopy and atomic force microscopy were used to confirm the production of surface chemistry patterns with a resolution of approximately 1 µm, which is significantly below the dimensions of a single mammalian cell. Subsequent adsorption of the extracellular matrix proteins collagen I and fibronectin followed by cell culture experiments using bovine corneal epithelial cells confirmed that cell attachment is controlled by the surface chemistry pattern. The method is an effective tool for use in a number of in vitro and in vivo applications.

  7. Femtosecond laser ablation profile near an interface: Analysis based on the correlation with superficial properties of individual materials

    Energy Technology Data Exchange (ETDEWEB)

    Nicolodelli, Gustavo, E-mail: nicolodelli@ursa.ifsc.usp.br [Instituto de Fisica de Sao Carlos, University of Sao Paulo, Grupo de Optica, Av. Trabalhador Sancarlense 400, P.O. Box 369, CEP 13560-970, Sao Carlos, SP (Brazil); Kurachi, Cristina; Bagnato, Vanderlei Salvador [Instituto de Fisica de Sao Carlos, University of Sao Paulo, Grupo de Optica, Av. Trabalhador Sancarlense 400, P.O. Box 369, CEP 13560-970, Sao Carlos, SP (Brazil)

    2011-01-15

    Femtosecond laser ablation of materials is turning to be an important tool for micromachining as well as for selective removal of biological tissues. In a great number of applications, laser ablation has to process through interfaces separating media of different properties. The investigation of the ablation behavior within materials and passing through interfaces is the main aim of this study. Especially, the analysis of the discontinuity in the ablation profile close to interfaces between distinct materials can reveal some of the phenomena involved in the formation of an ablated microcavity geometry. We have used a method that correlates the ablation cross sectional area with the local laser intensity. The effective intensity ablation properties were obtained from surface ablation data of distinct materials. The application of this method allows the prediction of the occurrence of a size discontinuity in the ablation geometry at the interface of distinct media, a fact which becomes important when planning applications in different media.

  8. A Simple Method for Improving the Spatial Resolution in Infrared Laser Ablation Mass Spectrometry Imaging

    Science.gov (United States)

    Hieta, Juha-Pekka; Vaikkinen, Anu; Auno, Samuli; Räikkönen, Heikki; Haapala, Markus; Scotti, Gianmario; Kopra, Jaakko; Piepponen, Petteri; Kauppila, Tiina J.

    2017-01-01

    In mass spectrometry imaging of tissues, the size of structures that can be distinguished is determined by the spatial resolution of the imaging technique. Here, the spatial resolution of IR laser ablation is markedly improved by increasing the distance between the laser and the focusing lens. As the distance between the laser and the lens is increased from 1 to 18 m, the ablation spot size decreases from 440 to 44 μm. This way, only the collimated center of the divergent laser beam is directed on the focusing lens, which results in better focusing of the beam. Part of the laser energy is lost at longer distance, but this is compensated by focusing of the radiation to a smaller area on the sample surface. The long distance can also be achieved by a set of mirrors, between which the radiation travels before it is directed to the focusing lens and the sample. This method for improving the spatial resolution can be utilized in mass spectrometry imaging of tissues by techniques that utilize IR laser ablation, such as laser ablation electrospray ionization, laser ablation atmospheric pressure photoionization, and matrix-assisted laser desorption electrospray ionization.

  9. Precise ablation milling with ultrashort pulsed Nd:YAG lasers by optical and acoustical process control

    Science.gov (United States)

    Schulze, Volker; Weber, Patricia

    2010-02-01

    Laser ablation milling with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials like metals, ceramics and polymers. A precise machining result with high surface quality requires a defined ablation process. Problems arise through the scatter in the resulting ablation depth of the laser beam machining process where material is removed in layers. Since the ablated volume may change due to varying absorption properties in single layers and inhomogeneities in the material, the focal plane might deviate from the surface of the work piece when the next layer is machined. Thus the focal plane has to be adjusted after each layer. A newly developed optical and acoustical process control enables an in-process adjustment of the focal plane that leads to defined process conditions and thus to better ablation results. The optical process control is realized by assistance of a confocal white light sensor. It enables an automated work piece orientation before machining and an inline ablation depth monitoring. The optical device can be integrated for an online or offline process control. Both variants will be presented and discussed. A further approach for adjustment of the focal plane is the acoustical process control. Acoustic emissions are detected while laser beam machining. A signal analysis of the airborne sound spectrum emitted by the process enables conclusions about the focal position of the laser beam. Based on this correlation an acoustic focus positioning is built up. The focal plane can then be adjusted automatically before ablation.

  10. Laser ablation of polymer coatings allows for electromagnetic field enhancement mapping around nanostructures

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob

    2011-01-01

    Subdiffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures. The acc......Subdiffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures....... The accompanying field enhancement substantially lowers the ablation threshold of the polymer film and thus creates local ablation spots and corresponding topographic modifications of the polymer film. Such modifications are quantified straightforwardly via scanning electron microscopy and atomic force microscopy...

  11. Dendrimer-capped nanoparticles prepared by picosecond laser ablation in liquid environment

    National Research Council Canada - National Science Library

    Giorgetti, Emilia; Giusti, Anna; Giammanco, Francesco; Marsili, Paolo; Laza, Simona

    2009-01-01

    Fifth generation ethylendiamine-core poly(amidoamine) (PAMAM G5) is presented as an efficient capping agent for the preparation of metal and semiconductor nanoparticles by ps laser ablation in water...

  12. The theory study of Metal absorptivity in femtosecond pulsed laser ablation

    Institute of Scientific and Technical Information of China (English)

    LI Li; ZHANG Duan-ming; LI Zhi-hua; TAN Xin-yu; FANG Ran-ran

    2007-01-01

    In this paper,the effect of the absorptivity of metal on femtosecond pulsed laser ablation is investigated.The formulas for the absorptivity depending on target temperature are derived from Maxwell Equations and the Lambert-Beer's law.Based on this,a new two-temperature model is proposed to describe the femtosecond pulsed laser ablation with metal.Then,using Au as an example,a finite difference method is employed to simulate the space-dependent and time-dependent absorptivity and the target temperature.The temperature evolution of our model is compared with the result obtained form the heat conduction model taking the absorptivity as constant.It is shown that the absorptivity plays an important role in the femtosecond pulsed laser ablation.The results of this paper are helpful in choosing the best technical parameters in femtosecond pulsed laser ablation.

  13. PALS — The optimal laser for determining optimal ablative laser propulsion parameters?

    Science.gov (United States)

    Boody, Frederick P.

    2005-04-01

    Ablative laser propulsion (ALP) could revolutionize space travel by reducing the 30:1 propellant/payload ratio needed for near-earth orbit 50-fold. To date, experiments have demonstrated the necessary efficiency, coupling coefficient, and specific impulse for application, but were performed at pulse energies and spot sizes much smaller than required and at wavelengths not usable in the atmosphere. Also, most experiments have not simultaneously measured the properties of the ions produced or of the ablated surface, properties that would allow full understanding of the propulsion properties in terms of ion characteristics. Realistic measurement of laser propulsion parameters is proposed using PALS (Prague Asterix Laser System), whose parameters, except for pulse rate and wavelength — pulse energy (˜1kJ), pulse length (400ps), beam diameter (˜29cm), and flat beam profile — equal those required for application. PALS wavelength is a little short (1.3μm vs. >1.5μm) but is closer than any other laser available and, due to PALS 2ω / 3ω capability, wavelength dependence can be studied and results extrapolated to application values. PALS' proven infrastructure for measuring laser-driven ion properties means that only an instrument for measuring momentum transfer, such as a ballistic pendulum, will have to be added.

  14. Flow speed of the ablation vapors generated during laser drilling of CFRP with a continuous-wave laser beam

    Science.gov (United States)

    Faas, S.; Freitag, C.; Boley, S.; Berger, P.; Weber, R.; Graf, T.

    2017-03-01

    The hot plume of ablation products generated during the laser drilling process of carbon fiber reinforced plastics (CFRP) with a continuous-wave laser beam was analyzed by means of high-speed imaging. The formation of compression shocks was observed within the flow of the evaporated material, which is an indication of flow speeds well above the local speed of sound. The flow speed of the hot ablation products can be estimated by analyzing the position of these compression shocks. We investigated the temporal evolution of the flow speed during the drilling process and the influence of the average laser power on the flow speed. The flow speed increases with increasing average laser powers. The moment of drilling through the material changes the conditions for the drilling process and was confirmed to influence the flow speed of the ablated material. Compression shocks can also be observed during laser cutting of CFRP with a moving laser beam.

  15. Spin-offs from laser ablation in art conservation

    Science.gov (United States)

    Asmus, J.; Elford, J.; Parfenov, V.

    2013-05-01

    In 1973 The Center for Art Conservation Studies (CASS) was established at the University of California, San Diego (UCSD). This was in response to demonstrations that were conducted during January-March 1972 in Venice for UNESCO, Venice in Peril, International Fund for Monuments, and the Italian Petroleum Institute (ENI). The feasibility investigation explored in-situ pulsed holography, holographic interferometry, and laser ablation divestment for applications in art conservation practice. During subsequent decades scores of UCSD graduate and undergraduate students as well as conservators, conservation scientists, academics, and engineers who resided in CASS as "Visiting Scholars" contributed to advancing the understanding and performance of radiation technologies in the arts. Several technologies in addition to those involving optical wavelengths were also investigated to aid in art conservation and conservation science. Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) were employed to detect and map moisture within masonry. Lead isotopic analyses revealed authenticity and provenance of Benin bronzes. Inside-out x-ray radiography facilitated the detection of defects in stone. Ultrasonic imaging was introduced for the mapping of fresco strata. Photoacoustic Spectroscopy (PAS) was used to characterize varnish layers on paintings. Digital image processing was introduced in order to detect and visualize pentimenti within paintings as well as to perform virtual restoration and provide interactive museum displays. Holographic images were employed as imaginary theater sets. In the years that followed the graduation of students and the visits of professional collaborators, numerous other applications of radiation ablation began appearing in a wide variety of other fields such as aircraft maintenance, ship maintenance, toxic chemical remediation, biological sterilization, food processing, industrial fabrication, industrial maintenance, nuclear

  16. Experimental verification of the ablation pressure dependence upon the laser intensity at pulsed irradiation of metals

    Science.gov (United States)

    Krasyuk, I. K.; Semenov, A. Yu; Stuchebryukhov, I. A.; Khishchenko, K. V.

    2016-11-01

    Experiments for verification of a functional dependence of the ablation pressure on the irradiated surface of a target upon the laser intensity in a range from 1.2 to 350 TW/cm2 have been carried out. For that, at some intensities of the laser irradiation, time intervals between the laser pulse maximum and the moment of the shock-wave front arrival to the rear surface of the target were measured, which are dependent on the ablation pressure. Two schemes of the measurements were used. At the first scheme, at higher laser intensities, the front arrival moment is determined via an electron-optical camera when the rear surface begins glowing. At the second scheme, the front arrival moment is recorded when a probe laser pulse changes the character of the reflection by the rear surface of the irradiated target. Results of measurements are in agreement with the ablation pressure dependence upon the laser pulse intensity within 20%.

  17. Visualization of liquid-assisted hard tissue ablation with a pulsed CO2 laser

    Science.gov (United States)

    Li, X. W.; Chen, C. G.; Zhang, X. Z.; Zhan, Z. L.; Xie, S. S.

    2015-01-01

    To investigate the characteristics of liquid-mediated hard tissue ablation induced by a pulsed CO2 laser with a wavelength of 10.6 μm, a high speed camera was used to monitor the interaction between water, tissue and laser irradiation. The results showed that laser irradiation can directly impact on tissue through a vapor channel formed by the leading part of the laser pulse. The ablation debris plays a key role in liquid-assisted laser ablation, having the ability to keep the vapor channel open to extend actuation time. The runoff effect induced by vortex convection liquid flow can remove the tissue that obstructs the effect of the next laser pulse.

  18. Diamond nanospherulite: A novel material produced at carbon-water interface by pulsed-laser ablation

    Institute of Scientific and Technical Information of China (English)

    王育煌; 黄群健; 陈忠; 黄荣彬; 郑兰荪

    1997-01-01

    Formation of carbon nanoparticles with perfectly spherical.shape and diamond structure (diamond nanospherulite) by laser-ablating a variety of carbon samples in water is reported for the first time The studies reveal that molten carbon nanoparticles generated by laser ablation are quenched directly by water and end up as diamond nanospherulites,possibly due to the high pressure arising from surface tension and the high stability resulting from termination of dangling bonds with hydrogen atoms.

  19. Laser ablation production of Ba, Ca, Dy, Er, La, Lu, and Yb ions

    CERN Document Server

    Olmschenk, S

    2016-01-01

    We use a pulsed nitrogen laser to produce atomic ions by laser ablation, measuring the relative ion yield for several elements, including some that have only recently been proposed for use in cold trapped ion experiments. For barium, we monitor the ion yield as a function of the number of applied ablation pulses for different substrates. We also investigate the ion production as a function of the pulse energy, and the efficiency of loading an ion trap as a function of radiofrequency voltage.

  20. Ablation studies using a diode-pumped Nd:YVO4 micro-laser

    Science.gov (United States)

    Pervolaraki, M.; Dyer, P. E.; Monk, P.

    We report an investigation of ablating several materials using a nanosecond pulse duration Nd:YVO4 micro-laser operating at wavelengths of 1064 and 532 nm and high pulse-repetition rate (ballistic pendulum measurements and scanning electron microscopy are used to characterise the interaction. It is shown that good-quality micro-scale features can be produced in polyimide, gold foils and silicon targets by ablation using this laser.

  1. Non-thermal ablation of expanded polytetrafluoroethylene with an intense femtosecond-pulse laser

    OpenAIRE

    Hashida, M.; Mishima, H.; Tokita, S.; Sakabe, S.

    2009-01-01

    Ablation of expanded polytetrafluoroethylene without disruption of the fine porous structure is demonstrated using an intense femtosecond-pulse laser. As a result of laser-matter interactions near ablation threshold fluence, high-energy ions are emitted, which cannot be produced by thermal dissociation of the molecules. The ion energy is produced by Coulomb explosion of the elements of (-CF_{2}-CF_{2-})n and the energy spectra of the ions show contributions from the Coulomb explosions of the ...

  2. Characterization of the Morphology of RDX Particles Formed by Laser Ablation

    Science.gov (United States)

    2012-02-01

    laser-ablated particle sizes. ...................4 Figure 3. SEM images of laser-ablated M43 propellant grain at (a) 150× magnification and (b) 500...Experimental Method 2.1 Materials The energetic materials studied included an M43 propellant grain that consists of ~76% RDX, 12% cellulose acetate...butyrate (CAB), 8% plasticizer, and 4% nitrocellulose (NC) (26). Class-1 ( m) and class-5 (ឝ m) military-grade and research-grade (i.e

  3. Emission characteristics of laser ablation-hollow cathode glow discharge spectral source

    Directory of Open Access Journals (Sweden)

    Karatodorov Stefan

    2014-11-01

    Full Text Available The emission characteristics of a scheme combining laser ablation as sample introduction source and hollow cathode discharge as excitation source are presented. The spatial separation of the sample material introduction by laser ablation and hollow cathode excitation is achieved by optimizing the gas pressure and the sample-cathode gap length. At these conditions the discharge current is maximized to enhance the analytical lines intensity.

  4. Integration of multimode waveguides and micromirror couplers in printed circuit boards using laser ablation

    Science.gov (United States)

    Van Steenberge, Geert; Geerinck, Peter; Van Put, Steven; Van Daele, Peter

    2004-09-01

    Integration of optical interconnections on a Printed Circuit Board (PCB) is very challenging, as it should remain compatible with existing PCB manufacturing technology based on laminated FR4-substrates and making use of solder-reflow and well-known placement and assembly techniques. In this paper we will describe different technologies being used for integration of such optical interconnections in PCB's. As we will demonstrate, the use of laser ablation, already used in PCB manufacturing for microvia's, is a suitable technique for the fabrication of multimode waveguides and micromirrors to provide optical coupling. Laser ablation is a very flexible technology that is particularly well suited for structuring of polymers because of their excellent UV-absorption properties and highly non-thermal ablation behavior. One of the most critical problems on the integration of optical interconnections in PCB's is coupling the light in and out of the optical plane. Because in our set-up the excimer laser beam can be tilted, the 45 degrees micromirrors can be easily fabricated using laser ablation. The focus is on ablation of waveguides using a frequency tripled Nd-YAG laser and on ablation of 45 degrees facets using a KrF excimer laser. It is shown that these structures can be defined in one single processing step, resulting in a very accurate alignment.

  5. Preparation and Characterization of Alumina Nanoparticles in Deionized Water Using Laser Ablation Technique

    Directory of Open Access Journals (Sweden)

    Veeradate Piriyawong

    2012-01-01

    Full Text Available Al2O3 nanoparticles were synthesized using laser ablation of an aluminum (Al target in deionized water. Nd:YAG laser, emitted the light at a wavelength of 1064 nm, was used as a light source. The laser ablation was carried out at different energies of 1, 3, and 5 J. The structure of ablated Al particles suspended in deionized water was investigated using X-ray diffraction (XRD. The XRD patterns revealed that the ablated Al particles transformed into γ-Al2O3. The morphology of nanoparticles was investigated by field emission scanning electron microscopy (FE-SEM. The FE-SEM images showed that most of the nanoparticles obtained from all the ablated laser energies have spherical shape with a particle size of less than 100 nm. Furthermore, it was observed that the particle size increased with increasing the laser energy. The absorption spectra of Al2O3 nanoparticles suspended in deionized water were recorded at room temperature using UV-visible spectroscopy. The absorption spectra show a strong peak at 210 nmarising from the presence of Al2O3 nanoparticles. The results on absorption spectra are in good agreement with those investigated by XRD which confirmed the formation of Al2O3 nanoparticles during the laser ablation of Al target in deionized water.

  6. Laser Ablation with Vacuum Capture for MALDI Mass Spectrometry of Tissue

    Science.gov (United States)

    Donnarumma, Fabrizio; Cao, Fan; Murray, Kermit K.

    2016-01-01

    We have developed a laser ablation sampling technique for matrix-assisted laser desorption ionization (MALDI) mass spectrometry and tandem mass spectrometry (MS/MS) analyses of in-situ digested tissue proteins. Infrared laser ablation was used to remove biomolecules from tissue sections for collection by vacuum capture and analysis by MALDI. Ablation and transfer of compounds from tissue removes biomolecules from the tissue and allows further analysis of the collected material to facilitate their identification. Laser ablated material was captured in a vacuum aspirated pipette-tip packed with C18 stationary phase and the captured material was dissolved, eluted, and analyzed by MALDI. Rat brain and lung tissue sections 10 μm thick were processed by in-situ trypsin digestion after lipid and salt removal. The tryptic peptides were ablated with a focused mid-infrared laser, vacuum captured, and eluted with an acetonitrile/water mixture. Eluted components were deposited on a MALDI target and mixed with matrix for mass spectrometry analysis. Initial experiments were conducted with peptide and protein standards for evaluation of transfer efficiency: a transfer efficiency of 16% was obtained using seven different standards. Laser ablation vacuum capture was applied to freshly digested tissue sections and compared with sections processed with conventional MALDI imaging. A greater signal intensity and lower background was observed in comparison with the conventional MALDI analysis. Tandem time-of-flight MALDI mass spectrometry was used for compound identification in the tissue.

  7. Confocal Microscopy–Guided Laser Ablation for Superficial and Early Nodular Basal Cell Carcinoma

    Science.gov (United States)

    Chen, Chih-Shan Jason; Sierra, Heidy; Cordova, Miguel; Rajadhyaksha, Milind

    2014-01-01

    Importance Laser ablation is a rapid and minimally invasive approach for the treatment of superficial skin cancers, but efficacy and reliability vary owing to lack of histologic margin control. High-resolution reflectance confocal microscopy (RCM) may offer a means for examining margins directly on the patient. Observations We report successful elimination of superficial and early nodular basal cell carcinoma (BCC) in 2 cases-, using RCM imaging to guide Er-:YAG laser ablation. Three-dimensional (3-D) mapping is feasible with RCM-, to delineate the lateral border and thickness of the tumor. Thus, the surgeon may deliver laser fluence and passes with localized control—ie, by varying the ablation parameters in sub-lesional areas with specificity that is governed by the 3-D topography of the BCC. We further demonstrate intra-operative detection of residual BCC after initial laser ablation and complete removal of remaining tumor by additional passes. Both RCM imaging and histologic sections confirm the final clearance of BCC. Conclusions and Relevance Confocal microscopy may enhance the efficacy and reliability of laser tumor ablation. This report represents a new translational application for RCM imaging, which, when combined with an ablative laser, may one day provide an efficient and cost-effective treatment for BCC. PMID:24827701

  8. A method for rapid measurement of laser ablation rate of hard dental tissue

    Science.gov (United States)

    Perhavec, T.; Gorkič, A.; Bračun, D.; Diaci, J.

    2009-06-01

    The aim of the study reported here is the development of a new method which allows rapid and accurate in-vitro measurements of three-dimensional (3D) shape of laser ablated craters in hard dental tissues and the determination of crater volume, ablation rate and speed. The method is based on the optical triangulation principle. A laser sheet projector illuminates the surface of a tooth, mounted on a linear translation stage. As the tooth is moved by the translation stage a fast digital video camera captures series of images of the illuminated surface. The images are analyzed to determine a 3D model of the surface. Custom software is employed to analyze the 3D model and to determine the volume of the ablated craters. Key characteristics of the method are discussed as well as some practical aspects pertinent to its use. The method has been employed in an in-vitro study to examine the ablation rates and speeds of the two main laser types currently employed in dentistry, Er:YAG and Er,Cr:YSGG. Ten samples of extracted human molar teeth were irradiated with laser pulse energies from 80 mJ to the maximum available energy (970 mJ with the Er:YAG, and 260 mJ with the Er,Cr:YSGG). About 2000 images of each ablated tooth surface have been acquired along a translation range of 10 mm, taking about 10 s and providing close to 1 million surface measurement points. Volumes of 170 ablated craters (half of them in dentine and the other half in enamel) were determined from this data and used to examine the ablated volume per pulse energy and ablation speed. The results show that, under the same conditions, the ablated volume per pulse energy achieved by the Er:YAG laser exceeds that of the Er,Cr:YSGG laser in almost all regimes for dentine and enamel. The maximum Er:YAG laser ablation speeds (1.2 mm 3/s in dentine and 0.7 mm 3/s in enamel) exceed those obtained by the Er,Cr:YSGG laser (0.39 mm 3/s in dentine and 0.12 mm 3/s in enamel). Since the presented method proves to be easy to

  9. High-resolution monitoring of the hole depth during ultrafast laser ablation drilling by diode laser self-mixing interferometry.

    Science.gov (United States)

    Mezzapesa, Francesco P; Ancona, Antonio; Sibillano, Teresa; De Lucia, Francesco; Dabbicco, Maurizio; Lugarà, Pietro Mario; Scamarcio, Gaetano

    2011-03-15

    We demonstrate that diode laser self-mixing interferometry can be exploited to instantaneously measure the ablation front displacement and the laser ablation rate during ultrafast microdrilling of metals. The proof of concept was obtained using a 50-μm-thick stainless steel plate as the target, a 120 ps/110 kHz microchip fiber laser as the machining source, and an 823 nm diode laser with an integrated photodiode as the probe. The time dependence of the hole penetration depth was measured with a 0.41 µm resolution.

  10. Human cornea wound healing in organ culture after Er:YAG laser ablation

    Science.gov (United States)

    Shen, Jin-Hui; Joos, Karen M.; Robinson, Richard D.; Shetlar, Debra J.; O'Day, Denis M.

    1998-06-01

    Purpose: To study the healing process in cultured human corneas after Er:YAG laser ablation. Methods: Human cadaver corneas within 24 hours post mortem were ablated with a Q- switched Er:YAG laser at 2.94 micrometer wavelength. The radiant exposure was 500 mJ/cm2. The cornea was cultured on a tissue supporting frame immediately after the ablation. Culture media consisted of 92% minimum essential media, 8% fetal bovine serum, 0.125% HEPES buffer solution, 0.125% gentamicin, and 0.05% fungizone. The entire tissue frame and media container were kept in an incubator at 37 degrees Celsius and 5% CO2. Serial macroscopic photographs of the cultured corneas were taken during the healing process. Histology was performed after 30 days of culture. Results: A clear ablated crater into the stroma was observed immediately after the ablation. The thickness of thermal damage ranges between 1 and 25 micrometer. Haze development within the crater varies from the third day to the fourteenth day according to the depth and the roughness of the crater. Histologic sections of the cultured cornea showed complete re- epithelization of the lased area. Loose fibrous tissue is observed filling the ablated space beneath the epithelium. The endothelium appeared unaffected. Conclusions: The intensity and time of haze development appears dependent upon the depth of the ablation. Cultured human corneas may provide useful information regarding the healing process following laser ablation.

  11. Selective Ablation of thin Nickel-chromium-alloy Films Using Ultrashort Pulsed Laser

    Science.gov (United States)

    Pabst, Linda; Ebert, Robby; Exner, Horst

    The selective ablation of 100nm thin Nickel-Chromium-alloy films on glass substrate was investigated using femtosecond laser pulses (λ=1030nm, τp=170 fs, Ep,max=7μJ). The influence of the processing parameters such as fluence, pulse number and pulse repetition rate on the ablation process was examined. Single and multiple pulses ablation thresholds of the Nickel-Chromium-alloy film were determined and the incubation coefficient calculated. Optical and electron microscopy were employed to characterize the patterned area. As a result, different irradiation morphologies were observed, dependent from the processing parameters. A processing window for film side ablation of the Nickel-Chromium-alloy film without damaging the underlying glass substrate was found, however, the edge of the ablation craters were covered with laser induced periodic surface structures (LIPSS).

  12. Ablation plasma transport using multicusp magnetic field for laser ion source

    Science.gov (United States)

    Takahashi, K.; Umezawa, M.; Uchino, T.; Ikegami, K.; Sasaki, T.; Kikuchi, T.; Harada, N.

    2016-05-01

    We propose a plasma guiding method using multicusp magnetic field to transport the ablation plasma keeping the density for developing laser ion sources. To investigate the effect of guiding using the magnetic field on the ablation plasma, we demonstrated the transport of the laser ablation plasma in the multicusp magnetic field. The magnetic field was formed with eight permanent magnets and arranged to limit the plasma expansion in the radial direction. We investigated the variation of the plasma ion current density and charge distribution during transport in the magnetic field. The results indicate that the plasma is confined in the radial direction during the transport in the multicusp magnetic field.

  13. Ablation and ultrafast dynamics of zinc selenide under femtosecond laser irradiation

    Institute of Scientific and Technical Information of China (English)

    Xiaofeng Wang; Tianqing Jia; Xiaoxi Li; Chengbin Li; Donghai Feng; Haiyi Sun; Shizhen Xu; Zhizhan Xu

    2005-01-01

    The ablation in zinc selenide (ZnSe) crystal is studied by using 150-fs, 800-nm laser system. The images of the ablation pit measured by scanning electronic microscope (SEM) show no thermal stress and melting dynamics. The threshold fluence is measured to be 0.7 J/cm2. The ultrafast ablation dynamics is studied by using pump and probe method. The result suggests that optical breakdown and ultrafast melting take place in ZnSe irradiated under femtosecond laser pulses.

  14. Ultrafast laser ablation and machining large-size structures on porcine bone.

    Science.gov (United States)

    An, Ran; Khadar, Ghadeer W; Wilk, Emilia I; Emigh, Brent; Haugen, Harold K; Wohl, Gregory R; Dunlop, Brett; Anvari, Mehran; Hayward, Joseph E; Fang, Qiyin

    2013-07-01

    When using ultrafast laser ablation in some orthopedic applications where precise cutting/drilling is required with minimal damage to collateral tissue, it is challenging to produce large-sized and deep holes using a tightly focused laser beam. The feasibility of producing deep, millimeter-size structures under different ablation strategies is investigated. X-ray computed microtomography was employed to analyze the morphology of these structures. Our results demonstrated the feasibility of producing holes with sizes required in clinical applications using concentric and helical ablation protocols.

  15. Deviation from threshold model in ultrafast laser ablation of graphene at sub-micron scale

    Energy Technology Data Exchange (ETDEWEB)

    Gil-Villalba, A.; Xie, C.; Salut, R.; Furfaro, L.; Giust, R.; Jacquot, M.; Lacourt, P. A.; Dudley, J. M.; Courvoisier, F., E-mail: francois.courvoisier@femto-st.fr [Institut FEMTO-ST, UMR 6174 CNRS, Universite de Bourgogne Franche-Comte, 25030 Besançon Cedex (France)

    2015-08-10

    We investigate a method to measure ultrafast laser ablation threshold with respect to spot size. We use structured complex beams to generate a pattern of craters in CVD graphene with a single laser pulse. A direct comparison between beam profile and SEM characterization allows us to determine the dependence of ablation probability on spot-size, for crater diameters ranging between 700 nm and 2.5 μm. We report a drastic decrease of ablation probability when the crater diameter is below 1 μm which we interpret in terms of free-carrier diffusion.

  16. Effect of oblique force source induced by laser ablation on ultrasonic generation.

    Science.gov (United States)

    Guo, Yuning; Yang, Dexing; Chang, Ying; Gao, Wei

    2014-01-13

    The effect of asymmetry caused by oblique line-shaped laser ablation on the generation of ultrasonic waves in metal, especially the effect of transverse component of the ablation force source on the ultrasonic waves is analyzed. Due to the oblique force source, the displacements of shear wave increase obviously by the enhanced shear force, the energy concentration area of longitudinal wave deflects to the small range centered on the incident direction while that of shear wave is approximately perpendicular to incident direction. In addition, surface wave enhances in the direction of transverse power flow. Furthermore, some ultrasonic characteristics under vortex laser ablation condition are inferred.

  17. Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

    Science.gov (United States)

    Bauer, Franziska; Michalowski, Andreas; Kiedrowski, Thomas; Nolte, Stefan

    2015-01-26

    High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

  18. Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas

    Science.gov (United States)

    Ding, Xuecheng; Zhang, Zicai; Liang, Weihua; Chu, Lizhi; Deng, Zechao; Wang, Yinglong

    2016-06-01

    A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles. supported by the Natural Science Foundation of Hebei Province, China (No. A2015201166) and the Natural Science Foundation of Hebei University, China (No. 2013-252)

  19. Research on ablation process of constant elastic alloy with femtosecond laser in solution medium

    Science.gov (United States)

    Deng, Guilin; Su, Wenyi; Duan, Ji'an; Fan, Nannan; Sun, Xiaoyan; Zhou, Jianying; Wang, Cong; Yin, Kai; Dong, Xinran; Hu, Youwang

    2016-09-01

    Constant elastic alloy is widely used material with high applied performance. In order to develop the application of constant elastic alloy, laser ablation of constant elastic alloy in different ablation mediums was investigated with different femtosecond lasers. Constant elastic alloy was ablated in solution with different ethanol contents and different thicknesses of the liquid layer above the target material and for comparison, in air. Also, the effects of laser energy and laser pulses of femtosecond laser on the morphology are studied. The effects of the position of the laser focus relative to the target surface were also discussed. The experimental results indicate that larger laser-induced area and smaller depth of craters tend to be obtained in solution than in air. The laser-induced area firstly increases and then decreases, and depths of craters decrease at first and increase later with the increase in ethanol content. Furthermore, the larger were energy of laser pulses, the larger were laser-induced area and deeper craters made in all different ablation solutions.

  20. Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty.

    Science.gov (United States)

    Cepek, Jeremy; Lindner, Uri; Davidson, Sean R H; Haider, Masoom A; Ghai, Sangeet; Trachtenberg, John; Fenster, Aaron

    2014-01-01

    To study the effect of needle placement uncertainty on the expected probability of achieving complete focal target destruction in focal laser ablation (FLA) of prostate cancer. Using a simplified model of prostate cancer focal target, and focal laser ablation region shapes, Monte Carlo simulations of needle placement error were performed to estimate the probability of completely ablating a region of target tissue. Graphs of the probability of complete focal target ablation are presented over clinically relevant ranges of focal target sizes and shapes, ablation region sizes, and levels of needle placement uncertainty. In addition, a table is provided for estimating the maximum target size that is treatable. The results predict that targets whose length is at least 5 mm smaller than the diameter of each ablation region can be confidently ablated using, at most, four laser fibers if the standard deviation in each component of needle placement error is less than 3 mm. However, targets larger than this (i.e., near to or exceeding the diameter of each ablation region) require more careful planning. This process is facilitated by using the table provided. The probability of completely ablating a focal target using FLA is sensitive to the level of needle placement uncertainty, especially as the target length approaches and becomes greater than the diameter of ablated tissue that each individual laser fiber can achieve. The results of this work can be used to help determine individual patient eligibility for prostate FLA, to guide the planning of prostate FLA, and to quantify the clinical benefit of using advanced systems for accurate needle delivery for this treatment modality.

  1. Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Cepek, Jeremy, E-mail: jcepek@robarts.ca; Fenster, Aaron [Robarts Research Institute, London, Ontario N6A 5K8, Canada and Biomedical Engineering, The University of Western Ontario, London, Ontario N6A 5B9 (Canada); Lindner, Uri; Trachtenberg, John [Department of Surgical Oncology, Division of Urology, University Health Network, Toronto, Ontario M5G 2C4 (Canada); Davidson, Sean R. H. [Ontario Cancer Institute, University Health Network, Toronto, Ontario M5G 2M9 (Canada); Haider, Masoom A. [Department of Medical Imaging, Sunnybrook Health Sciences Center, Toronto, Ontario M4N 3M5, Canada and Department of Medical Imaging, University of Toronto, Toronto, Ontario M5S 2J7 (Canada); Ghai, Sangeet [Department of Medical Imaging, University Health Network, Toronto, Ontario M5G 2M9 (Canada)

    2014-01-15

    Purpose: To study the effect of needle placement uncertainty on the expected probability of achieving complete focal target destruction in focal laser ablation (FLA) of prostate cancer. Methods: Using a simplified model of prostate cancer focal target, and focal laser ablation region shapes, Monte Carlo simulations of needle placement error were performed to estimate the probability of completely ablating a region of target tissue. Results: Graphs of the probability of complete focal target ablation are presented over clinically relevant ranges of focal target sizes and shapes, ablation region sizes, and levels of needle placement uncertainty. In addition, a table is provided for estimating the maximum target size that is treatable. The results predict that targets whose length is at least 5 mm smaller than the diameter of each ablation region can be confidently ablated using, at most, four laser fibers if the standard deviation in each component of needle placement error is less than 3 mm. However, targets larger than this (i.e., near to or exceeding the diameter of each ablation region) require more careful planning. This process is facilitated by using the table provided. Conclusions: The probability of completely ablating a focal target using FLA is sensitive to the level of needle placement uncertainty, especially as the target length approaches and becomes greater than the diameter of ablated tissue that each individual laser fiber can achieve. The results of this work can be used to help determine individual patient eligibility for prostate FLA, to guide the planning of prostate FLA, and to quantify the clinical benefit of using advanced systems for accurate needle delivery for this treatment modality.

  2. Increasing the penetration depth for ultrafast laser tissue ablation using glycerol based optical clearing

    Science.gov (United States)

    Gabay, Ilan; Subramanian, Kaushik G.; Martin, Chris; Yildirim, Murat; Tuchin, Valery V.; Ben-Yakar, Adela

    2016-03-01

    Background: Deep tissue ablation is the next challenge in ultrafast laser microsurgery. By focusing ultrafast pulses below the tissue surface one can create an ablation void confined to the focal volume. However, as the ablation depth increases in a scattering tissue, increase in the required power can trigger undesired nonlinear phenomena out of focus that restricts our ability to ablate beyond a maximum ablation depth of few scattering lengths. Optical clearing (OC) might reduce the intensity and increase the maximal ablation depth by lowering the refractive index mismatch, and therefore reducing scattering. Some efforts to ablate deeper showed out of focus damage, while others used brutal mechanical methods for clearing. Our clinical goal is to create voids in the scarred vocal folds and inject a biomaterial to bring back the tissue elasticity and restore phonation. Materials and methods: Fresh porcine vocal folds were excised and applied a biocompatible OC agent (75% glycerol). Collimated transmittance was monitored. The tissue was optically cleared and put under the microscope for ablation threshold measurements at different depths. Results: The time after which the tissue was optically cleared was roughly two hours. Fitting the threshold measurements to an exponential decay graph indicated that the scattering length of the tissue increased to 83+/-16 μm, which is more than doubling the known scattering length for normal tissue. Conclusion: Optical clearing with Glycerol increases the tissue scattering length and therefore reduces the energy for ablation and increases the maximal ablation depth. This technique can potentially improve clinical microsurgery.

  3. Metal nanoparticles and IR laser applications in medicine for biotissue ablation and welding

    Science.gov (United States)

    Lalayan, A. A.; Israelyan, S. S.

    2016-05-01

    We report the possibility of laser welding and ablation of biotissue by using metal and hybrid metal nanoparticles (NPs) and infrared laser irradiation spectrally located far from plasmon resonances. A nanosecond YAG:Nd laser of wavelength 1064 nm has been used for synthesis of metal NPs. The Ag, Au, Cu, Ti and Ni, as well as Au-Ag and Au-Cu hybrid metal colloidal NPs were formed in a liquid medium. The diagnostic technique of second harmonic generation (SHG) has been applied to determine the biotissue ablation area after IR laser irradiation. The effectiveness of biotissue ablation was 4-5 times larger in the case of a tissue sample colored with metal NPs than for an uncolored sample. IR laser welding has been demonstrated for deep-located biotissue layers colored by metal NPs.

  4. Ablation and analysis of small cell populations and single cells by consecutive laser pulses

    Science.gov (United States)

    Shrestha, Bindesh; Nemes, Peter; Vertes, Akos

    2010-10-01

    Laser ablation of single cells through a sharpened optical fiber is used for the detection of metabolites by laser ablation electrospray ionization (LAESI) mass spectrometry (MS). Ablation of the same Allium cepa epidermal cell by consecutive pulses indicates the rupture of the cell wall by the second shot. Intracellular sucrose heterogeneity is detected by subsequent laser pulses pointing to rupturing the vacuolar membrane by the third exposure. Ion production by bursts of laser pulses shows that the drying of ruptured A. cepa cells occurs in ˜50 s at low pulse rates (10 pulses/s bursts) and significantly faster at high pulse rates (100 pulses/s bursts). These results point to the competing role of cytoplasm ejection and evaporative drying in diminishing the LAESI-MS signal in ˜50 s or 100 laser pulses, whichever occurs first.

  5. Wavelength effect on hole shapes and morphology evolution during ablation by picosecond laser pulses

    Science.gov (United States)

    Zhao, Wanqin; Wang, Wenjun; Li, Ben Q.; Jiang, Gedong; Mei, Xuesong

    2016-10-01

    An experimental study is presented of the effect of wavelength on the shape and morphology evolution of micro holes ablated on stainless steel surface by a 10 ps Q-switched Nd:VAN pulsed laser. Two routes of hole development are associated with the visible (532 nm) and near-infrared (1064 nm) laser beams, respectively. The evolution of various geometric shapes and morphological characteristics of the micro holes ablated with the two different wavelengths is comparatively studied for other given processing conditions such as a laser power levels and the number of pulses applied. Plausible explanations, based on the light-materials interaction associated with laser micromachining, are also provided for the discernable paths of geometric and morphological development of holes under laser ablation.

  6. Laser-assisted fabrication and size distribution modification of colloidal gold nanostructures by nanosecond laser ablation in different liquids

    Science.gov (United States)

    Nikov, R. G.; Nedyalkov, N. N.; Atanasov, P. A.; Karashanova, D. B.

    2017-07-01

    This study presents results on pulsed laser ablation of gold target immersed in different liquids. In the experiments chloroform, toluene and ethanol are used as liquid media for the laser ablation. Two different wavelengths: the fundamental (1064 nm) and second harmonic (532 nm) of a Nd:YAG laser, are utilized to produce various colloids. The optical properties of the colloids were evaluated by optical transmittance measurements in the UV-Vis spectral range. The morphology of the colloidal nanoparticles created and the evaluation of their size distribution are investigated by transmission electron microscopy. The selected area electron diffraction is employed for chemical phase identification of the created nanostructures. Ablation in chloroform resulted in formation of spherical and spheroidal gold nanoparticles with the similar mean size at both laser wavelengths used—11.5 nm at 1064 and 9.3 nm at 532 nm. Nanoparticles with smaller mean size (below 5 nm) in the case of ablation in toluene were observed. Spherical nanoparticles with mean diameter of 7.7 nm produced by 1064 nm and thin elongated nanostructures with thickness of about 5 nm using 532 nm are observed in the case of ablation in ethanol. An additional laser irradiation of the colloids demonstrated the changing of the optical properties and size distribution of the nanostructures produced by ablation in ethanol and chloroform. The irradiation of toluene-based colloid does not induce observable change of the colloid properties.

  7. Comparison of transcatheter laser and direct-current shock ablation of endocardium near tricuspid anulus

    Science.gov (United States)

    Zhang, Yu-Zhen; Wang, Shi-Wen; Li, Junheng

    1993-03-01

    Forty to eighty percent of the patients with accessory pathways (APs) manifest themselves by tachyarrhythmias. Many of these patients needed either life-long medical therapy or surgery. In order to avoid the discomfort and expenses in surgical procedures, closed chest percutaneous catheter ablation of APs became a potentially desirable therapeutic approach. Many investigations indicated that ablation of right APs by transcatheter direct current (dc) shock could cause life-threatening arrhythmias, right coronary arterical (RCA) spasm, etc. With the development of transcatheter laser technique, it has been used in drug-incurable arrhythmias. The results show that laser ablation is much safer than surgery and electric shock therapy. The purpose of this study is to explore the effectiveness, advantages, and complications with transcatheter Nd:YAG laser and dc shock in the ablation of right atrioventricular accessory pathways in the atrium near the tricuspid annulus (TA) in 20 dogs.

  8. Nanograting formation in air through plasmonic near-field ablation induced by femtosecond laser pulses

    Science.gov (United States)

    Miyaji, Godai; Miyazaki, Kenzo

    2017-02-01

    Superimposed multiple shots of low-fluence femtosecond (fs) laser pulses form a periodic nanostructure on solid surfaces through ablation. We have demonstrated that the self-organization process of nanostructuring can be regulated to fabricate a homogeneous nanograting on the target surface in air. A simple two-step ablation process and an ablation technique using interfering fs laser beams were developed to control plasmonic near-fields generated by fs laser pulses. The results have shown the nature of a single spatial standing wave mode of surface plasmon polaritons of which periodically enhanced near-fields ablate the target surface, to fabricate the nanograting on gallium nitride (GaN) and metals such as stainless steel (SUS) and titanium (Ti).

  9. Evaluation of explosive sublimation as the mechanism of nanosecond laser ablation of tungsten under vacuum conditions

    Science.gov (United States)

    Oderji, Hassan Yousefi; Farid, Nazar; Sun, Liying; Fu, Cailong; Ding, Hongbin

    2016-08-01

    A non-equilibrium mechanism for nanosecond laser ablation is suggested herein, and its predictions are compared to the results of W experiments performed under vacuum conditions. A mechanism of particle formation is explained via this model, with partial sublimation of the superheated irradiated zone of the target considered to be the mechanism of laser ablation. In this study, a mixture of vapor and particles was explosively generated and subsequently prevented the rest of a laser pulse from reaching its intended target. This mechanism was found to play an essential role in the ablation of W under vacuum conditions, and it provides a theoretical justification for particle formation. Moreover, special considerations were taken into account for the expansion of plasma into a vacuum. The model was evaluated by measuring the mass of ablated particles using a quartz crystal deposition monitor and time-resolved optical emission spectroscopy. The results of this model were found to be in good agreement with experimental values.

  10. Real-time near IR (1310 nm) imaging of CO2 laser ablation of enamel.

    Science.gov (United States)

    Darling, Cynthia L; Fried, Daniel

    2008-02-18

    The high-transparency of dental enamel in the near-IR (NIR) can be exploited for real-time imaging of ablation crater formation during drilling with lasers. NIR images were acquired with an InGaAs focal plane array and a NIR zoom microscope during drilling incisions in human enamel samples with a lambda=9.3-microm CO(2) laser operating at repetition rates of 50-300-Hz with and without a water spray. Crack formation, dehydration and thermal changes were observed during ablation. These initial images demonstrate the potential of NIR imaging to monitor laser-ablation events in real-time to provide information about the mechanism of ablation and to evaluate the potential for peripheral thermal and mechanical damage.

  11. Fully Automated Laser Ablation Liquid Capture Sample Analysis using NanoElectrospray Ionization Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, Matthias [ORNL; Ovchinnikova, Olga S [ORNL; Van Berkel, Gary J [ORNL

    2014-01-01

    RATIONALE: Laser ablation provides for the possibility of sampling a large variety of surfaces with high spatial resolution. This type of sampling when employed in conjunction with liquid capture followed by nanoelectrospray ionization provides the opportunity for sensitive and prolonged interrogation of samples by mass spectrometry as well as the ability to analyze surfaces not amenable to direct liquid extraction. METHODS: A fully automated, reflection geometry, laser ablation liquid capture spot sampling system was achieved by incorporating appropriate laser fiber optics and a focusing lens into a commercially available, liquid extraction surface analysis (LESA ) ready Advion TriVersa NanoMate system. RESULTS: Under optimized conditions about 10% of laser ablated material could be captured in a droplet positioned vertically over the ablation region using the NanoMate robot controlled pipette. The sampling spot size area with this laser ablation liquid capture surface analysis (LA/LCSA) mode of operation (typically about 120 m x 160 m) was approximately 50 times smaller than that achievable by direct liquid extraction using LESA (ca. 1 mm diameter liquid extraction spot). The set-up was successfully applied for the analysis of ink on glass and paper as well as the endogenous components in Alstroemeria Yellow King flower petals. In a second mode of operation with a comparable sampling spot size, termed laser ablation/LESA , the laser system was used to drill through, penetrate, or otherwise expose material beneath a solvent resistant surface. Once drilled, LESA was effective in sampling soluble material exposed at that location on the surface. CONCLUSIONS: Incorporating the capability for different laser ablation liquid capture spot sampling modes of operation into a LESA ready Advion TriVersa NanoMate enhanced the spot sampling spatial resolution of this device and broadened the surface types amenable to analysis to include absorbent and solvent resistant

  12. Effects of picosecond laser repetition rate on ablation of Cr12MoV cold work mold steel

    Science.gov (United States)

    Wu, Baoye; Deng, Leimin; Liu, Peng; Zhang, Fei; Duan, Jun; Zeng, Xiaoyan

    2017-07-01

    In this paper, the effects of pulse repetition rate on ablation efficiency and quality of Cr12MoV cold work mold steel have been studied using a picosecond (ps) pulse Nd:YVO4 laser system at λ= 1064 nm. The experimental results of area ablation on target surface reveal that laser repetition rate plays a significant role in controlling ablation efficiency and quality. Increasing the laser repetition rate, while keeping a constant mean power improves the ablation efficiency and quality. For each laser mean power, there is an optimal repetition rate to achieve a higher laser ablation efficiency with low surface roughness. A high ablation efficiency of 42.29, 44.11 and 47.52 μm3/mJ, with surface roughness of 0.476, 0.463 and 0.706 μm could be achieved at laser repetition rate of 10 MHz, for laser mean power of 15, 17 and 19 W, respectively. Scanning electron microcopy images revels that the surface morphology evolves from rough with numerous craters, to flat without pores when we increased the laser repetition rate. The effects of laser repetition rate on the heat accumulation, plasma shield and ablation threshold were analyzed by numerical simulation, spectral analysis and multi-laser shot, respectively. The synergetic effects of laser repetition rate on laser ablation rate and machining quality were analyzed and discussed systemically in this paper.

  13. Optimization of silver nanoparticles production by laser ablation in water using a 150-ps laser

    Science.gov (United States)

    Stašić, J.; Živković, Lj.; Trtica, M.

    2016-12-01

    Silver nanoparticles were synthesized by laser ablation in liquid (water) using a 150-ps Nd:YAG laser. Due to their extraordinary characteristics, especially when obtained by this method providing high purity and high stability of colloids, silver NPs are nowadays highly important in various applications. The objective of this study was to optimize the process parameters in order to achieve the highest possible yield while retaining small particle size. Yield/mass concentration of the obtained particles was measured depending on different parameters: time of irradiation, pulse energy, position regarding the focus, and number of irradiation locations. The conditions providing relatively high yield, small particle size, highest production rate, and highest efficiency are 7 mJ, 15-min irradiation time (9000 pulses), and target position ˜4 mm in front of the lens focus. The results are compared with the results obtained by the longer nanosecond as well as the ultrashort pulsed lasers. A possible physical explanation is given.

  14. Colloidal Metal Nanoparticles Prepared by Laser Ablation and their Applications.

    Science.gov (United States)

    Zhang, Jianming; Claverie, Jerome; Chaker, Mohamed; Ma, Dongling

    2017-05-05

    This review article highlights the recent advances of the synthesis and application of metal nanoparticles (NPs) fabricated via pulsed laser ablation in liquid (PLAL) phase and also introduces relevant NP formation mechanisms. Although wet-chemical approaches have been well established to synthesize colloidal metal NPs with various components and structures, some inherent drawbacks, such as reaction residuals and/or contaminations, largely limit some of their applications. The PLAL method has recently been developed as an alternative approach and received increasing attention for colloidal NP preparation, without involving complicated chemical reactions. In certain cases, by using PLAL, ligand-free and surface-clean NPs can be obtained and well dispersed in liquid, leading to the formation of a "surface-clean" NP dispersion. This unique feature renders PLAL-synthesised metal NPs attractive candidates for many interesting applications in catalysis, biology, sensing, and clean energy generation and storage. We conclude this review by proposing several interesting research directions and future challenges, from PLAL fabrication to applications. We hope this review can serve as a good reference and help with the further development of PLAL-NPs and their diverse applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Antibacterial effect of bismuth subsalicylate nanoparticles synthesized by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Castañeda, Mariela [Instituto Nacional de Investigaciones Nucleares (Mexico); Vega-Jiménez, Alejandro L., E-mail: argelia.almaguer@mac.com; Almaguer-Flores, Argelia [Universidad Nacional Autónoma de México, Facultad de Odontología, DEPeI, I (Mexico); Camps, Enrique; Pérez, Mario [Instituto Nacional de Investigaciones Nucleares (Mexico); Silva-Bermudez, Phaedra [Instituto Nacional de Rehabilitación, Unidad de Ingeniería de Tejidos, Terapia Celular y Medicina Regenerativa (Mexico); Berea, Edgardo [FarmaQuimia SA de CV. (Mexico); Rodil, Sandra E. [Universidad Nacional Autónoma de México, Instituto de Investigaciones en Materiales (Mexico)

    2015-11-15

    The antimicrobial properties of bismuth subsalicylate (BSS) nanoparticles against four opportunistic pathogens; E. coli, P. aeruginosa, S. aureus, and S. epidermidis were determined. BSS nanoparticles were synthesized by pulse laser ablation of a solid target in distilled water under different conditions. The nanoparticles were characterized using high-resolution transmission electron microscopy and absorption spectra and small angle X-ray scattering. The analysis shows that the colloids maintained the BSS structure and presented average particle size between 20 and 60 nm, while the concentration ranges from 95 to 195 mg/L. The antibacterial effect was reported as the inhibition ratio of the bacterial growth after 24 h and the cell viability was measured using the XTT assay. The results showed that the inhibition ratio of E. coli and S. epidermidis was dependant on the NPs size and/or concentration, meanwhile P. aeruginosa and S. aureus were more sensitive to the BSS nanoparticles independently of both the size and the concentration. In general, the BSS colloids with average particle size of 20 nm were the most effective, attaining inhibition ratios >80 %, similar or larger than those obtained with the antibiotic used as control. The results suggest that the BSS colloids could be used as effective antibacterial agents with potential applications in the medical area.

  16. Laser ablation ICP-MS: Application in biomedical research.

    Science.gov (United States)

    Sussulini, Alessandra; Becker, Julia Susanne; Becker, Johanna Sabine

    2017-01-01

    In the last decade, the development of diverse bioanalytical methodologies based on mass spectrometry imaging has increased, as has their application in biomedical questions. The distribution analysis of elements (metals, semimetals, and non-metals) in biological samples is a point of interest in life sciences, especially within the context of metallomics, which is the scientific field that encompasses the global analysis of the entirety of elemental species inside a cell or tissue. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been efficiently employed to generate qualitative and quantitative maps of elemental distribution in thin tissue sections of a variety of biological samples, for example, brain, cartilage, spinal cord, etc. The combination of elemental with molecular mass spectrometry allows obtaining information about the elements bound to proteins, when they are previously separated by gel electrophoresis (metalloproteomics), and also adding a new dimension to molecular mass spectrometry imaging by the correlation of molecular and elemental distribution maps in definite regions in a biological tissue. In the present review, recent biomedical applications in LA-ICP-MS imaging as a stand-alone technique and in combination with molecular mass spectrometry imaging techniques are discussed. Applications of LA-ICP-MS in the study of neurodegenerative diseases, distribution of contrast agents and metallodrugs, and metalloproteomics will be focused in this review. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:47-57, 2017. © 2015 Wiley Periodicals, Inc.

  17. Anaesthesia for foetoscopic Laser ablation- a retrospective study

    Directory of Open Access Journals (Sweden)

    Vaishali Kumbhar

    2016-01-01

    Full Text Available Background and Aims: Twin pregnancy with monochorionic placenta may be associated with arteriovenous vascular anastomosis of the placental vessels resulting in twin-to-twin transfusion syndrome (TTTS and twin reversed arterial perfusion syndrome (TRAP. Foetoscopic LASER ablation (FLA is the treatment of choice in reducing foetal mortality related to this. Methods: A retrospective review of medical records of 41 FLA procedures for TTTS and TRAP were analysed for anaesthetic management. Thirty-four patients received subarachnoid block, three combined spinal-epidural block, three general anaesthesia and one local anaesthesia with sedation. Nitroglycerine 5 mg patch was used for tocolysis 1 h before the procedure and continued for 24-48 h postoperatively. Results: Bupivacaine was used in 34 patients, and ropivacaine in three patients. Mean dose of bupivacaine 0.5% was 2.43 ± 0.32 ml and ropivacaine 0.75% was 2.85 ± 0.19 ml. The mean duration of surgery was 117.07 ± 28 min. Mild hypotension occurred in all patients under spinal anaesthesia and was treated with vasopressors. The foetal outcome among all 41 patients were 13 delivered live twins, 15 had a single live baby with intrauterine death of other twin baby. In 12 patients, both babies were intrauterine death. One patient was lost for follow-up. Conclusion: Foetoscopic procedures can be done under central neuraxial block, however occasionally general anaesthesia may be required.

  18. Anaesthesia for foetoscopic Laser ablation- a retrospective study

    Science.gov (United States)

    Kumbhar, Vaishali; Radhika, M; Gundappa, Parameswara; Simha, Jayashree; Radhakrishnan, Prathima

    2016-01-01

    Background and Aims: Twin pregnancy with monochorionic placenta may be associated with arteriovenous vascular anastomosis of the placental vessels resulting in twin-to-twin transfusion syndrome (TTTS) and twin reversed arterial perfusion syndrome (TRAP). Foetoscopic LASER ablation (FLA) is the treatment of choice in reducing foetal mortality related to this. Methods: A retrospective review of medical records of 41 FLA procedures for TTTS and TRAP were analysed for anaesthetic management. Thirty-four patients received subarachnoid block, three combined spinal-epidural block, three general anaesthesia and one local anaesthesia with sedation. Nitroglycerine 5 mg patch was used for tocolysis 1 h before the procedure and continued for 24–48 h postoperatively. Results: Bupivacaine was used in 34 patients, and ropivacaine in three patients. Mean dose of bupivacaine 0.5% was 2.43 ± 0.32 ml and ropivacaine 0.75% was 2.85 ± 0.19 ml. The mean duration of surgery was 117.07 ± 28 min. Mild hypotension occurred in all patients under spinal anaesthesia and was treated with vasopressors. The foetal outcome among all 41 patients were 13 delivered live twins, 15 had a single live baby with intrauterine death of other twin baby. In 12 patients, both babies were intrauterine death. One patient was lost for follow-up. Conclusion: Foetoscopic procedures can be done under central neuraxial block, however occasionally general anaesthesia may be required. PMID:28003695

  19. Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Shaheen, M.E., E-mail: mshaheen73@science.tanta.edu.eg [Department of Physics, Faculty of Sciences, Tanta University, Tanta (Egypt); Gagnon, J.E.; Fryer, B.J. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Earth and Environmental Sciences, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

    2015-05-01

    Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using {sup 66}Zn/{sup 63}Cu, {sup 208}Pb/{sup 238}U, {sup 232}Th/{sup 238}U, {sup 66}Zn/{sup 232}Th and {sup 66}Zn/{sup 208}Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%). - Highlights: • Fractionation and ICP-MS signal response were investigated for two different pulse widths using NIST 610 and Naval Brass. • Dependence of fractionation indices on repetition rate and pulse width. • Higher ablation rate was observed in picosecond compared to

  20. Human dermis separation via ultra-short pulsed laser plasma-mediated ablation

    Energy Technology Data Exchange (ETDEWEB)

    Huang Huan; Guo Zhixiong, E-mail: guo@jove.rutgers.ed [Department of Mechanical and Aerospace Engineering, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States)

    2009-08-21

    In vitro layer separation of human dermal tissues via laser plasma-mediated ablation was successfully conducted for the first time. The ablation of wet dermis was generated using a 900 fs ultra-short pulsed laser with the wavelength centred at 1552 nm. The ablation and separation results were imaged and measured by scanning electron microscopy. The dermis ablation threshold was determined as 9.65 {+-} 1.21 J cm{sup -2} and the incubation factor was found as 0.46 {+-} 0.03. Histological examinations were performed to find proper laser parameters for dermis ablation and separation with minimal thermal damage. No thermal damage was found in the single line ablation results when the pulse overlap rate was not over 5 pulses {mu}m{sup -1}. Even in the multi-line ablation, thermal damage was insignificant and the lateral damage zone was generally within 5 {mu}m in the results with 100 continuously repeated line scans. The separation of a whole piece of wet dermal tissue into two thin layers was presented. Several separation tests with different layer thicknesses from 200 to 600 {mu}m were completed. The unevenness of the separated layers was generally under 10%. The cohesion and morphology of the separated tissue layers were not altered.

  1. Reactive laser-induced ablation as approach to titanium oxycarbide films

    Energy Technology Data Exchange (ETDEWEB)

    Jandova, V., E-mail: jandova@icpf.cas.cz; Fajgar, R.; Dytrych, P.; Kostejn, M.; Drinek, V.; Kupcik, J.

    2015-09-01

    The IR laser-induced reactive ablation of frozen titanium ethoxide target was studied. The method involves the laser ablation of titanium ethoxide at − 140 °C in gaseous methane (4–50 Pa) atmosphere. This process leads to reactions of the ablative species with hydrocarbon in the gaseous phase. During the ablation of the frozen target excited species interact with methane molecules. The reactive ablation process leads to the formation of a smooth thin film. The thickness of prepared films depends on the number of IR pulses and their composition depends on the pressure of gaseous methane. This reactive IR ablation proceeds as a carbidation process providing nanostructured films with good adhesion to various substrates (glass, metals, KBr) depending on the carbon content in prepared films. Particles are also stabilized by layer preventing their surface oxidation in the atmosphere. The described results are important in the general context for the synthesis of reactive particles in the gas phase. The final products are characterized by spectroscopic, microscopic and diffraction techniques: SEM/EDX, HRTEM, electron diffraction, Raman spectroscopy and XPS. - Highlights: • IR laser ablation of frozen target of titanium ethoxide leads to a reduction in the gaseous methane (4-50 Pa). • Films deposited in methane have Ti/O/C stoichiometry and are oxidized in the atmosphere. • Layers deposited in methane are reduced and have less O in the topmost layers.

  2. Myocardium tissue ablation with hollow-waveguide-delivered near-infrared nanosecond laser pulses

    Science.gov (United States)

    Sato, Shunichi; Arai, Tsunenori; Shi, Yi-Wei; Matsuura, Yuji; Miyagi, Mitsunobu; Ashida, Hiroshi

    2001-06-01

    With 1064-nm, nanosecond laser pulses delivered from hollow waveguide, ablation characteristics of porcine myocardium tissue have been investigated in vitro. For the hollow waveguide a vacuum-cored scheme was introduced to suppress the laser-induced air breakdown that limited the available transmitted laser energy/power. The delivered laser pulse beam was focused with a collimation lens and a focusing lens, and it was shown that higher efficiency ablation was obtained when a focusing lens with a shorter focal length was used. Waveguide bending (bending angle 90 degree(s)C, bending radius approximately 50 cm) caused no deteriorating effect on the ablation characteristics for ablation energies up to approximately 60 mJ/pulse. It was demonstrated that deep and sharp ablated holes with aspect ratios > 8 was obtained with the hollow-waveguide-delivered laser pulses. It may be a realistic option to aim at using the present hollow waveguide system for trocar-based applications or replacing articulated mirror-based laser delivery systems. It is an important part of the future works to downsize the waveguide output unit for catheter-based applications.

  3. Obtention of Ti nanoparticles by laser ablation; Obtencion de nanoparticulas de Ti por ablacion laser

    Energy Technology Data Exchange (ETDEWEB)

    Diaz E, J.R.; Escobar A, L.; Camps, E.; Santiago, P.; Ascencio, J. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    2002-07-01

    The obtention of Ti nanoparticles around 5-30 nm diameter through the laser ablation technique is reported. The formation of nanoparticles is carried out in He atmosphere to different pressures, placing directly in Si substrates (100) and in Cu grids. The results show that the work pressure is an important parameter that allows to control the nanoparticles size. Also the plasma characterization results are presented where the Ti II is the predominant specie with an average kinetic energy of 1824 eV. (Author)

  4. Rapid revelation of radiocarbon records with laser ablation Accelerator Mass Spectrometry.

    Science.gov (United States)

    Münsterer, Caroline; Wacker, Lukas; Hattendorf, Bodo; Christl, Marcus; Koch, Joachim; Dietiker, Rolf; Synal, Hans-Arno; Günther, Detlef

    2014-01-01

    By focusing high-intensity laser pulses on carbonate samples carbon dioxide is generated and can be directly introduced into the gas ion source (GIS) of an Accelerator Mass Spectrometer (AMS). This new technique allows rapid radiocarbon analyses at high spatial resolution. The design of the deignated laser ablation cell as well as first results on a stalagmite sample are presented.

  5. Analysis and removal of ITER relevant materials and deposits by laser ablation

    Science.gov (United States)

    Xiao, Qingmei; Huber, Alexander; Philipps, Volker; Sergienko, Gennady; Gierse, Niels; Mertens, Philippe; Hai, Ran; Ding, Hongbin

    2014-12-01

    The analysis of the deposition of eroded wall material on the plasma-facing materials in fusion devices is one of the crucial issues to maintain the plasma performance and to fulfill safety requirements with respect to tritium retention by co-deposition. Laser ablation with minimal damage to the plasma facing material is a promising method for in situ monitoring and removal of the deposition, especially for plasma-shadowed areas which are difficult to reach by other cleaning methods like plasma discharge. It requires the information of ablation process and the ablation threshold for quantitative analysis and effective removal of the different deposits. This paper presents systemic laboratory experimental analysis of the behavior of the ITER relevant materials, graphite, tungsten, aluminum (as a substitution of beryllium) and mixed deposits ablated by a Nd:YAG laser (1064 nm) with different energy densities (1-27 J/cm2, power density 0.3-3.9 GW/cm2). The mixed deposits consisted of W-Al-C layer were deposited on W substrate by magnetron sputtering and arc plasma deposition. The aim was to select the proper parameters for the quantitative analysis and for laser removal of the deposits by investigating the ablation efficiency and ablation threshold for the bulk materials and deposits. The comparison of the ablation and saturation energy thresholds for pure and mixed materials shows that the ablation threshold of the mixed layer depends on the concentration of the components. We propose laser induced breakdown spectroscopy for determination of the elemental composition of deposits and then we select the laser parameters for the layer removal. Comparison of quantitative analysis results from laboratory to that from TEXTOR shows reasonable agreements. The dependence of the spectra on plasma parameters and ambient gas pressure is investigated.

  6. Doping He droplets by laser ablation with a pulsed supersonic jet source

    Energy Technology Data Exchange (ETDEWEB)

    Katzy, R.; Singer, M.; Izadnia, S.; LaForge, A. C., E-mail: aaron.laforge@physik.uni-freiburg.de; Stienkemeier, F. [Physikalisches Institut, Universität Freiburg, 79104 Freiburg (Germany)

    2016-01-15

    Laser ablation offers the possibility to study a rich number of atoms, molecules, and clusters in the gas phase. By attaching laser ablated materials to helium nanodroplets, one can gain highly resolved spectra of isolated species in a cold, weakly perturbed system. Here, we present a new setup for doping pulsed helium nanodroplet beams by means of laser ablation. In comparison to more well-established techniques using a continuous nozzle, pulsed nozzles show significant differences in the doping efficiency depending on certain experimental parameters (e.g., position of the ablation plume with respect to the droplet formation, nozzle design, and expansion conditions). In particular, we demonstrate that when the ablation region overlaps with the droplet formation region, one also creates a supersonic beam of helium atoms seeded with the sample material. The processes are characterized using a surface ionization detector. The overall doping signal is compared to that of conventional oven cell doping showing very similar dependence on helium stagnation conditions, indicating a comparable doping process. Finally, the ablated material was spectroscopically studied via laser induced fluorescence.

  7. Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

    Science.gov (United States)

    Freitas, A. Z.; Freschi, L. R.; Samad, R. E.; Zezell, D. M.; Gouw-Soares, S. C.; Vieira, N. D., Jr.

    2010-03-01

    The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm2 for the composite resins Z-100 and Z-350, and 0.25 J/cm2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed.

  8. Nanosecond laser ablation processes in aluminum-doped zinc-oxide for photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Canteli, D., E-mail: david.canteli@ciemat.es [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Fernandez, S. [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Molpeceres, C. [Centro Laser, Universidad Politecnica de Madrid, Ctra. de Valencia Km 7.3, 28031 Madrid (Spain); Torres, I.; Gandia, J.J. [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer A study of the ablation of AZO thin films deposited at different temperature conditions with nanosecond UV laser light for photovoltaic devices has been performed. Black-Right-Pointing-Pointer The ablation threshold of AZO thin films was measured and related with the absorption coefficient of the films at the laser wavelength, showing a direct correspondence. Black-Right-Pointing-Pointer A change in the material structure in the areas closest to the edges of laser grooves made in samples deposited at temperatures below 100 Degree-Sign C was observed and studied. - Abstract: Aiming to a future use in thin film solar modules, the processing of aluminum doped zinc oxide thin films with good optoelectronic properties with a nanosecond-pulsed ultraviolet laser has been studied. The ablation threshold fluence of the films has been determined and associated with the material properties. The ablation process has been optimized and grooves with good properties for photovoltaic devices have been obtained. The morphology of the ablated surfaces has been observed by confocal microscopy and its structure has been characterized by Raman spectroscopy. The influence of ablation parameters like focus distance, pulse energy and repetition frequency in the groove morphology has been studied with special attention to the thermal effects on the material structure.

  9. Fabrication of uniform nanogrooves on 6H-SiC by femtosecond laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Hoon; Jeong, Sungho [Gwangju Institute of Science and Technology, Department of Mechatronics, Gwangju (Korea, Republic of); Sohn, Ik-Bu [Gwangju Institute of Science and Technology, Advanced Photonics Research Institute, Gwangju (Korea, Republic of)

    2011-01-15

    The fabrication of parallel deep nanogrooves on 6H-SiC by femtosecond laser ablation ({lambda}=785 nm) is reported. The periodicity of the nanogrooves was measured to be about 200{+-}20 nm and the depth exceeded 15 {mu}m. The nanogrooves have high uniformity in size and pattern over the entire depth. Laser fluence is found to be the critical parameter to obtain these deep and regular nanogrooves. The feasibility for large area fabrication of nanogrooves by femtosecond laser ablation is demonstrated. (orig.)

  10. Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.; Harilal, Sivanandan S.; Hartig, Kyle C.; Jovanovic, Igor

    2017-06-19

    We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.

  11. Production of fullerene ions by combining of plasma sputtering with laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, K., E-mail: yamada.keisuke@jaea.go.jp; Saitoh, Y.; Yokota, W. [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2014-02-15

    We have produced C{sub 60} ion beams by combining plasma sputtering and laser ablation. A C{sub 60} sample was placed in an electron cyclotron resonance type ion source, negatively biased and sputtered by argon plasma. The beam current of C{sub 60}{sup +} decreased rapidly, but it was transiently recovered by a single laser shot that ablates the thin sample surface on the sputtered area. Temporal variations in beam current are reported in response to laser shots repeated at intervals of a few minutes.

  12. Dentin ablation-rate measurements in endodontics witj HF and CO2 laser radiation

    Science.gov (United States)

    Makropoulou, Mersini I.; Serafetinides, Alexander A.; Khabbaz, Marouan; Sykaras, Sotirios; Tsikrikas, G. N.

    1996-01-01

    Recent studies focused on the ability of the laser light to enlarge the root canal during the endodontic therapy. The aim of this research is the experimental and theoretical study of the ablation rate of two infrared laser wavelengths on dentin. Thirty freshly extracted human teeth were longitudinally sectioned at thicknesses ranged from 0.5 to 2 mm, and irradiated on the root canal dentin. The measured ablation rates in dentinal wall of the root canal showed that the HF laser at 2.9 micrometer can more effectively penetrate into the tissue, whereas the carbon dioxide laser at 10.6 micrometer leads to high thermal damage of the ablation crater surroundings.

  13. Mechanisms of nanoparticle formation by ultra-short laser ablation of metals in liquid environment.

    Science.gov (United States)

    Povarnitsyn, Mikhail E; Itina, Tatiana E; Levashov, Pavel R; Khishchenko, Konstantin V

    2013-03-07

    Laser ablation in liquids is now commonly used to produce colloidal nanoparticles (NPs) that have found numerous applications in different areas. In experiments, NPs of different materials can be rather easily obtained by using laser systems with various pulse durations, shapes, wavelengths, and fluences. In this paper, we focus our attention on metal (gold) NPs produced by ultra-short laser pulses. To better understand the mechanisms of the NPs formation, we perform modeling of femtosecond laser interactions with a gold target in the presence of liquid (water). Simulation of the ablation process over several nanoseconds shows that most of the primary NPs originate from the ablated metastable liquid layer, whereas only a minority is formed by condensation inside the cavitation bubble. These particles will further grow/evaporate, and coagulate during a much longer collision stage in the liquid colloid.

  14. Comparative study of excimer and erbium:YAG lasers for ablation of structural components of the knee

    Science.gov (United States)

    Vari, Sandor G.; Shi, Wei-Qiang; van der Veen, Maurits J.; Fishbein, Michael C.; Miller, J. M.; Papaioannou, Thanassis; Grundfest, Warren S.

    1991-05-01

    This study was designed to compare the efficiency and thermal effect of a 135 ns pulsed-stretched XeCl excimer laser (308 nm) and a free-running Erbium:YAG laser (2940 nm) with 200 microsecond(s) pulse duration for ablation of knee joint structures (hyaline and fibrous cartilage, tendon and bone). The radiant exposure used for tissue ablation ranged from 2 to 15 J/cm2 for the XeCl excimer and from 33 to 120 J/cm2 for Er:YAG. The excimer and Er:YAG lasers were operated at 4 and 5 Hz respectively. The ablative laser energy was delivered to tissue through fibers. Ablation rates of soft tissues (hyaline and fibrous cartilage, tendon) varied from 8.5 to 203 micrometers /pulse for excimer and from 8.2 to 273 micrometers /pulse for Er:YAG lasers. Ablation rates of soft tissues are linearly dependent on the radiant exposure. Within the range of parameters tested all the tissues except the bone could be rapidly ablated by both lasers. Bone ablation was much less efficient, requiring 15 J/cm2 and 110 J/cm2 radiant exposure for excimer and Er:YAG lasers to ablate 9.5 and 8.2 micrometers tissue per pulse. However, excimer laser ablation produced less thermal damage in the tissues studied compared to Er:YAG at the same laser parameters. The authors conclude that both lasers are capable of efficient knee joint tissue ablation. XeCl excimer laser requires an order of magnitude less energy than Er:YAG laser for comparable tissue ablation.

  15. Femtosecond laser ablation of dielectric materials in the optical breakdown regime: Expansion of a transparent shell

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Lechuga, M.; Siegel, J., E-mail: j.siegel@io.cfmac.csic.es; Hernandez-Rueda, J.; Solis, J. [Laser Processing Group, Instituto de Optica, Serrano 121, 28006 Madrid (Spain)

    2014-09-15

    Phase transition pathways of matter upon ablation with ultrashort laser pulses have been considered to be understood long-since for metals and semiconductors. We provide evidence that also certain dielectrics follow the same pathway, even at high pulse energies triggering optical breakdown. Employing femtosecond microscopy, we observe a characteristic ring pattern within the ablating region that dynamically changes for increasing time delays between pump and probe pulse. These transient Newton rings are related to optical interference of the probe beam reflected at the front surface of the ablating layer with the reflection at the interface of the non-ablating substrate. Analysis of the ring structure shows that the ablation mechanism is initiated by a rarefaction wave leading within a few tens of picoseconds to the formation of a transparent thin shell of reduced density and refractive index, featuring optically sharp interfaces. The shell expands and eventually detaches from the solid material at delays of the order of 100 ps.

  16. Integrated polymer polarization rotator based on tilted laser ablation

    Science.gov (United States)

    Poulopoulos, Giannis; Kalavrouziotis, Dimitrios; Missinne, Jeroen; Bosman, Erwin; Van Steenberge, Geert; Apostolopoulos, Dimitrios; Avramopoulos, Hercules

    2017-02-01

    sidewalls, employing the tilted laser ablation technology, currently available at CMST. Therefore, the aforementioned simulation steps adhere fully to the respective design rules, taking into account the anticipated fabrication variations

  17. SOLID BODY ABLATION UNDER EXPOSURE TO ULTRA SHORT LASER PULSES: STUDY BY MOLECULAR DYNAMICS METHODS

    Directory of Open Access Journals (Sweden)

    D. S. Ivanov

    2014-09-01

    Full Text Available The process of laser ablation under the influence of ultra short laser pulses on metals is investigated by methods of molecular dynamics. The validity and applicability of the hybrid atomistic-continuous model for the estimation of optimum modes of ultra short laser pulses processing are explored. Combination of atomistic model of laser-induced non-equilibrium process of a phase transition at the atomic level with continuous two-temperature model for describing the dynamics of photo-excitation of free media is proposed. Applicability of laser ablation model on the example of aluminum films and gold under exposure to pulses with different energy density and duration is shown. It is indicated that, depending on the ratio of the laser pulse duration and the characteristic time of electron-phonon material interaction, photothermal and photomechanical modes of destruction are implemented that determine the quality and performance of the laser processing. It is established that at the duration of laser pulse less than the time of electron-phonon interaction high-performance photomechanical type of destruction is implemented by internal stresses arising in the area of exposure. This is confirmed by a linear dependence of the ablation rate from the absorbed energy. At the duration of laser pulse greater than the time of electron-phonon interaction inefficient photothermal mode of destruction is implemented. The results may be useful for specialists engaged in the development of laser technologies

  18. Synthesis and characterization of a novel laser ablation sensitive triazene incorporated epoxy resin

    KAUST Repository

    Patole, Archana S.

    2014-01-01

    New triazene monomer was synthesized and further employed as a crosslinking agent partner with epoxy matrix using ethyl methyl imidazole as a curing agent in order to investigate the effect of triazene moieties on polymeric properties for laser ablation application. The synthesized triazene monomer was characterized by analytical and spectroscopic methods, while the surface morphology of resist after laser ablation was visualized by optical laser scanning images and scanning electron microscopy. Thermogravimetrical investigations indicate the loss of nitrogen being the initial thermal decomposition step and exhibit sufficient stabilities for the requirements for laser ablation application. Fourier transform infra-red, nuclear magnetic resonance, and gas chromatography analyses showed the successful synthesis of triazene. The ablation results from the optical laser scanning images revealed that the etching depth could be controlled by varying the concentration of triazene monomer in the formulation of epoxy. The shear strength analysis revealed that that the shear strength increased with increasing the amount of triazene in the formulation of direct ablation sensitive resist. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

  19. Material morphological characteristics in laser ablation of alpha case from titanium alloy

    Science.gov (United States)

    Yue, Liyang; Wang, Zengbo; Li, Lin

    2012-08-01

    Alpha case (an oxygen enriched alloy layer) is commonly formed in forged titanium alloys during the manufacturing process and it reduces the service life of the materials. This layer is normally removed mechanically or chemically. This paper reports the feasibility and characteristics of using a short pulsed laser to remove oxygen-enriched alpha case layer from a titanium alloy (Ti6Al4V) substrate. The material removal rate, i.e., ablation rate, and ablation threshold of the alpha case titanium were experimentally determined, and compared with those for the removal of bulk Ti6Al4V. Surface morphologies of laser processed alpha case titanium layer, especially that of cracks at different ablated depths, were carefully examined, and also compared with those for Ti6Al4V. It has been shown that in the alpha case layer, laser ablation has always resulted in crack formation while for laser ablation of alpha case free Ti6Al4V layers, cracking was not present. In addition, the surface is rougher within the alpha case layer and becomes smoother (Ra - 110 nm) once the substrate Ti-alloy is reached. The work has demonstrated that laser is a feasible processing tool for removing alpha case titanium, and could also be used for the rapid detection of the presence of alpha case titanium on Ti6Al4V surfaces in aerospace applications.

  20. Absorption-Ablation-Excitation Mechanisms of Laser-Cluster Interactions in a Nanoaerosol System

    CERN Document Server

    Ren, Yihua; Zhang, Yiyang; Tse, Stephen D; Long, Marshall B

    2014-01-01

    The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy (PS-LIBS). As the excitation laser intensity is increased beyond 0.16GW/cm2, the scattering cross-section of TiO_2 clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensities, the cross-sections of clusters decrease during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by non-dimensionalizing the Fokker-Planck equation, with analogous Strouhal Sl_E, Peclet Pe_E, and Damkohler Da_E n...

  1. Ultra-short laser pulse ablation using shear-force feedback: Femtosecond laser induced breakdown spectroscopy feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Samek, Ota [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany)]. E-mail: samek@ansci.de; Kurowski, Andre [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany); Kittel, Silke [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany); Kukhlevsky, Sergei [Institute of Physics, University of Pecs, Ifjusag u. 6, Pecs 7624 (Hungary); Hergenroeder, Roland [ISAS-Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund (Germany)

    2005-08-31

    This work reports on a feasibility study of proximity ablation using femtosecond pulses. Ultra-short pulses were launched to a bare tapered optical fiber and delivered to the sample. The tip-sample distance was controlled by means of shear-force feedback. Consequently, ablation craters with submicrometer dimensions were obtained. Potential analytical applications for Laser Induced Breakdown Spectroscopy (LIBS) technique, such as e.g. inclusions in steel or bio cells, are suggested.

  2. Edge isolation of transparent conductive polymer (TCP) thin films on flexible substrates using UV laser ablation.

    Science.gov (United States)

    Hsiao, Wen-Tse; Tseng, Shih-Feng; Huang, Kuo-Cheng; Chiang, Donyau; Chen, Ming-Fei

    2012-06-01

    The purpose of this study was to directly use the writing techniques for the complex electrode edge isolation of transparent conductive polymer (TCP) thin films by a nanosecond pulsed UV laser processing system. The processing parameters including the laser pulse energy, the pulse repetition frequency, and the scan speed of galvanometers were examined to ablate the TCP films deposited on polyethylene terephtalate substrates of 188 microm thick. The thickness of TCP films was approximately 20 nm. The laser pulse repetition frequency and the scan speed of galvanometers were applied to calculate the overlapping rate of laser spots and to discuss the patterning region quality. Surface morphology, edge quality, and width and depth of edge isolated patterning structures after laser ablation process were measured by a three-dimensional confocal laser scanning microscope. In addition, the electrical conductivity of ablated TCP films was measured by a four-point probes instrument. After isolated line patterning was formed, the ablated TCP films with a better edge quality were obtained directly when the overlapping rate of laser spots, the scan speed, and the pulse repetition rate were 83.3%, 200 mm/s, and 40 kHz, respectively. The better surface morphology of electrode pattern structures was also obtained when the scan speed and the pulse repetition rate were 500 mm/s and 40 kHz, respectively.

  3. LASER ABLATION OF MONOCRYSTALLINE SILICON UNDER PULSED-FREQUENCY FIBER LASER

    Directory of Open Access Journals (Sweden)

    V. P. Veiko

    2015-05-01

    Full Text Available Subject of research. The paper deals with research of the surface ablation for single-crystal silicon wafers and properties of materials obtained in response to silicon ablation while scanning beam radiation of pulse fiber ytterbium laser with a wavelenght λ = 1062 nm in view of variation of radiation power and scanning modes. Method. Wafers of commercial p-type conductivity silicon doped with boron (111, n-type conductivity silicon doped with phosphorus (100 have been under research with a layer of intrinsical silicon oxide having the thickness equal to several 10 s of nanometers and SiO2 layer thickness from 120 to 300 nm grown by thermal oxidation method. The learning system comprises pulse fiber ytterbium laser with a wavelenght λ = 1062 nm. The laser rated-power output is equal to 20 W, pulse length is 100 ns. Pulses frequency is in the range from 20 kHz to 100 kHz. Rated energy in the pulse is equal to 1.0 mJ. Scanning has been carried out by means of two axial scanning device driven by VM2500+ and controlled by personal computer with «SinMarkТМ» software package. Scanning velocity is in the range from 10 mm/s to 4000 mm/s, the covering varies from 100 lines per mm to 3000 lines per mm. Control of samples has been carried out by means of Axio Imager A1m optical microscope Carl Zeiss production with a high definition digital video camera. All experiments have been carried out in the mode of focused laser beam with a radiation spot diameter at the substrate equal to 50 μm. The change of temperature and its distribution along the surface have been evaluated by FLIR IR imager of SC7000 series. Main results. It is shown that ablation occurs without silicon melting and with plasma torch origination. The particles of ejected silicon take part in formation of silicon ions plasma and atmosphere gases supporting the plasmo-chemical growth of SiO2. The range of beam scanning modes is determined where the growth of SiO2 layer is observed

  4. Laser ablation-laser induced breakdown spectroscopy for the measurement of total elemental concentration in soils.

    Science.gov (United States)

    Pareja, Jhon; López, Sebastian; Jaramillo, Daniel; Hahn, David W; Molina, Alejandro

    2013-04-10

    The performances of traditional laser-induced breakdown spectroscopy (LIBS) and laser ablation-LIBS (LA-LIBS) were compared by quantifying the total elemental concentration of potassium in highly heterogeneous solid samples, namely soils. Calibration curves for a set of fifteen samples with a wide range of potassium concentrations were generated. The LA-LIBS approach produced a superior linear response different than the traditional LIBS scheme. The analytical response of LA-LIBS was tested with a large set of different soil samples for the quantification of the total concentration of Fe, Mn, Mg, Ca, Na, and K. Results showed an acceptable linear response for Ca, Fe, Mg, and K while poor signal responses were found for Na and Mn. Signs of remaining matrix effects for the LA-LIBS approach in the case of soil analysis were found and discussed. Finally, some improvements and possibilities for future studies toward quantitative soil analysis with the LA-LIBS technique are suggested.

  5. Femtosecond-laser ablation dynamics of dielectrics: basics and applications for thin films

    DEFF Research Database (Denmark)

    Balling, P.; Schou, Jørgen

    2013-01-01

    -field excitation makes it possible to produce films of materials that are transparent to the laser light. Second, the highly localized excitation reduces the emission of larger material particulates. Third, lasers with ultrashort pulses are shown to be particularly useful tools for the production of nanocluster......Laser ablation of dielectrics by ultrashort laser pulses is reviewed. The basic interaction between ultrashort light pulses and the dielectric material is described, and different approaches to the modeling of the femtosecond ablation dynamics are reviewed. Material excitation by ultrashort laser...... can be described by various rate-equation models in combination with different descriptions of the excited electrons. The optical properties of the highly excited dielectric undergo a rapid change during the laser pulse, which must be included in a detailed modeling of the excitations. The material...

  6. Translational medicine in the field of ablative fractional laser (AFXL)-assisted drug delivery

    DEFF Research Database (Denmark)

    Haedersdal, Merete; Erlendsson, Andrés M; Paasch, Uwe

    2016-01-01

    enhanced topical drug uptake into skin after ablative fractional laser treatment. Clinical evidence encompassed 18 studies, of which 9 were randomized controlled trials and 2 were controlled trials, examining neoplastic lesions, photodamaged skin, scars, onychomycosis, and topical anesthetics. The highest......Ablative fractional lasers enhance uptake of topical therapeutics and the concept of fractional laser-assisted drug delivery has now been taken into clinical practice. Objectives We systematically reviewed preclinical data and clinical evidence for fractional lasers to enhance drug uptake...... laser-assisted drug delivery implies risks of systemic drug absorption, especially when performed over large skin areas. Conclusions Fractional laser-assisted drug delivery is beneficial in enhancing preclinical and clinical outcomes for certain skin conditions....

  7. XPS investigations on the UV-laser ablation mechanism of poly(ether imide)

    Energy Technology Data Exchange (ETDEWEB)

    Wambach, J.; Kunz, T.; Schnyder, B.; Koetz, R.; Wokaun, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    UV-Laser ablated samples of poly(ether imide) [Kapton{sup TM}] were studied with small-spot XPS. Applying fluences above the threshold level (0.167 J/cm{sup 2}) resulted in the expected behaviour of a decline of both nitrogen and oxygen. Below the threshold level a hint for an altered ablation mechanism was found. (author) 1 fig., 5 refs.

  8. Imaging gold nanoparticles in mouse liver by laser ablation inductively coupled plasma mass spectrometry

    OpenAIRE

    Li, Qing; Wang, Zheng; Mo, Jiamei; Zhang, Guoxia; Chen, Yirui; Huang, Chuchu

    2017-01-01

    Imaging the size distribution of metal nanoparticles (NPs) in a tissue has important implications in terms of evaluating NP toxicity. Microscopy techniques used to image tissue NPs are limited by complicated sample preparation or poor resolution. In this study, we developed a laser ablation (LA) system coupled to single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) for quantitative imaging of gold (G)NPs in tissue samples. In this system, GNPs were ablated but did not disi...

  9. A study of photothermal laser ablation of various polymers on microsecond time scales.

    Science.gov (United States)

    Kappes, Ralf S; Schönfeld, Friedhelm; Li, Chen; Golriz, Ali A; Nagel, Matthias; Lippert, Thomas; Butt, Hans-Jürgen; Gutmann, Jochen S

    2014-01-01

    To analyze the photothermal ablation of polymers, we designed a temperature measurement setup based on spectral pyrometry. The setup allows to acquire 2D temperature distributions with 1 μm size and 1 μs time resolution and therefore the determination of the center temperature of a laser heating process. Finite element simulations were used to verify and understand the heat conversion and heat flow in the process. With this setup, the photothermal ablation of polystyrene, poly(α-methylstyrene), a polyimide and a triazene polymer was investigated. The thermal stability, the glass transition temperature Tg and the viscosity above Tg were governing the ablation process. Thermal decomposition for the applied laser pulse of about 10 μs started at temperatures similar to the start of decomposition in thermogravimetry. Furthermore, for polystyrene and poly(α-methylstyrene), both with a Tg in the range between room and decomposition temperature, ablation already occurred at temperatures well below the decomposition temperature, only at 30-40 K above Tg. The mechanism was photomechanical, i.e. a stress due to the thermal expansion of the polymer was responsible for ablation. Low molecular weight polymers showed differences in photomechanical ablation, corresponding to their lower Tg and lower viscosity above the glass transition. However, the difference in ablated volume was only significant at higher temperatures in the temperature regime for thermal decomposition at quasi-equilibrium time scales.

  10. Numerical simulation of the ablation of thin molybdenum films under laser irradiation

    Science.gov (United States)

    Kazanskiy, N. L.; Poletayev, S. D.

    2016-09-01

    Laser irradiation of a molybdenum film on a quartz substrate is numerically studied. The simulated results prove the experimental effect lying in a threefold decrease in the size of the ablation region in comparison with the focal spot. The numerical experiment proves the hypothesis on the two-stage ablation of metal film with the primary formation of oxide phase. It is demonstrated that oxidation leads to a selective decrease in the thermal resistance of the film along the vertical direction, so that the anisotropic character of the ablation is enhanced.

  11. Femtosecond laser ablation of a metal, a dielectric and a semiconductor illuminated at oblique angles of incidence

    CERN Document Server

    Liu, Xiao-Long; Petrarca, Massimo; Polynkin, Pavel

    2016-01-01

    We report the measurements of fluence thresholds for single-shot femtosecond laser ablation, as functions of the angle of incidence and at different polarizations of the laser beam, for a metal, a dielectric and a semiconductor. We use the linear index of refraction, unperturbed by the ablating laser pulse, to compute the values of the laser fluence transmitted into the material, corresponding to the measured values of the ablation threshold fluence in the incident beam. Our data show that, in spite of the complex nonlinear ionization dynamics involved in the ablation process, thus computed transmitted threshold fluence is remarkably independent of the angle of incidence and polarization of the laser beam, for all three material types. We suggest that the angular dependence of ablation threshold can be utilized for profiling fluence distributions in ultra-intense femtosecond laser beams.

  12. Analysis of surface damage produced by pulsed laser ablation on metal Al and semiconductor Si

    Institute of Scientific and Technical Information of China (English)

    ManBao-Yuan; LiuAi-Hua; 等

    1998-01-01

    The suraface morphological changesd produced by Nd:YAG pulsed laser ablation of metal Al and semiconductor Si were carefully examined and analyzed by using scanning elkectron microscope.The formation mechanism of the droplets was discussed.and the reasons for formation of the microcracks on the laser irradiated area of the target surface were analyzed by calculating the thermal stress,the vapor pressure and the shock pressure induced by the laser supported detonation.

  13. Laser-induced surface ablation as a probe of optical surface damage mechanisms

    Science.gov (United States)

    Chase, L. L.

    1990-02-01

    The phenomenon of laser surface damage is briefly reviewed, with an emphasis on the fundamental physical mechanisms of the interaction of laser light with the surface. Recent measurements of laser ablation of charged and neutral surface constituents and impurities are described, and it is shown that these experiments can he used to investigate optical damage mechanisms. Crystalline ZnS is used as the primary example of this work.

  14. Enhancement of muonium emission rate from silica aerogel with a laser ablated surface

    CERN Document Server

    Beer, G A; Hirota, S; Ishida, K; Iwasaki, M; Kanda, S; Kawai, H; Kawamura, N; Kitamura, R; Lee, S; Marshall, W Lee G M; Mibe, T; Miyake, Y; Okada, S; Olchanski, K; Olin, A; Oishi, Y; Onishi, H; Otani, M; Saito, N; Shimomura, K; Strasser, P; Tabata, M; Tomono, D; Ueno, K; Yokoyama, K; Won, E

    2014-01-01

    Emission of muonium ($\\mu^+e^-$) atoms from a laser-processed aerogel surface into vacuum was studied for the first time. Laser ablation was used to create hole-like regions with diameter of about 270$~\\mu$m in a triangular pattern with hole separation in the range of 300--500$~\\mu$m. The emission probability for the laser-processed aerogel sample is at least eight times higher than for a uniform one.

  15. Filamentation due to the Weibel Instability in two counterstreaming laser ablated plasmas

    Science.gov (United States)

    Dong, Quan-Li; Yuan, Dawei; Gao, Lan; Liu, Xun; Chen, Yangao; Jia, Qing; Hua, Neng; Qiao, Zhanfeng; Chen, Ming; Zhu, Baoqiang; Zhu, Jianqiang; Zhao, Gang; Ji, Hantao; Sheng, Zheng-Ming; Zhang, Jie

    2016-05-01

    Weibel-type filamentation instability was observed in the interaction of two counter streaming laser ablated plasma flows, which were supersonic, collisionless, and closely relevant to astrophysical conditions. The plasma flows were created by irradiating a pair of oppositely standing plastic (CH) foils with 1ns-pulsed laser beams of total energy of 1.7 kJ in two laser spots. With characteristics diagnosed in experiments, the calculated features of Weibel-type filaments are in good agreement with measurements.

  16. Studying ultrafast laser parameters to deter self-focusing for deep tissue ablation

    Science.gov (United States)

    Martin, Chris; Ben-Yakar, Adela

    2016-03-01

    Ultrafast pulsed lasers are a promising tool for precise and noninvasive tissue surgery. The high peak intensity of the pulses allows nonlinear interaction with tissue, causing three-dimensional confined ablation without thermal damage. However, deep tissue ablation has been limited to a few scattering lengths due to laser beam extinction. As pulse energies are increased to overcome attenuation, unwanted side effects can occur such as self-focusing, where the highly intense pulse alters the refractive index of the material, causing a lensing effect and long filaments of damage or complete beam collapse before the focus. Here, we examine laser parameters to overcome self-focusing for deep tissue ablation. Through imaging ablation voids with third harmonic generation, we show that increasing the pulse width from 200-fs to 2-ps reduces self-focusing induced focal plane shifting and avoids multiple filamentation altogether, resulting in deeper ablation without extended axial damage. Additionally, we simulate beam propagation for pulses of different central wavelengths, and show that longer wavelengths can ablate deeper because of decreased scattering in tissue and a subsequent reduction in self-focusing.

  17. Nd:YAG 1.44 laser ablation of human cartilage

    Science.gov (United States)

    Cummings, Robert S.; Prodoehl, John A.; Rhodes, Anthony L.; Black, Johnathan D.; Sherk, Henry H.

    1993-07-01

    This study determined the effectiveness of a Neodymium:YAG 1.44 micrometers wavelength laser on human cartilage. This wavelength is strongly absorbed by water. Cadaveric meniscal fibrocartilage and articular hyaline cartilage were harvested and placed in normal saline during the study. A 600 micrometers quartz fiber was applied perpendicularly to the tissues with a force of 0.098 N. Quantitative measurements were then made of the ablation rate as a function of fluence. The laser energy was delivered at a constant repetition rate of 5 Hz., 650 microsecond(s) pulsewidth, and energy levels ranging from 0.5 joules to 2.0 joules. Following the ablation of the tissue, the specimens were fixed in formalin for histologic evaluation. The results of the study indicate that the ablation rate is 0.03 mm/mj/mm2 for hyaline cartilage and fibrocartilage. Fibrocartilage was cut at approximately the same rate as hyaline cartilage. There was a threshold fluence projected to be 987 mj/mm2 for hyaline cartilage and fibrocartilage. Our results indicate that the pulsed Nd:YAG laser operating at 1.44 micrometers has a threshold fluence above which it will ablate human cartilage, and that its ablation rate is directly proportional to fluence over the range of parameters tested. Fibrocartilage and hyaline cartilage demonstrated similar threshold fluence and ablation rates which is related to the high water content of these tissues.

  18. Optical feedback-induced light modulation for fiber-based laser ablation.

    Science.gov (United States)

    Kang, Hyun Wook

    2014-11-01

    Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30% in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation.

  19. Synergistic skin heat shock protein expression in response to combined laser treatment with a diode laser and ablative fractional lasers.

    Science.gov (United States)

    Paasch, Uwe; Sonja, Grunewald; Haedersdal, Merete

    2014-06-01

    Diode laser-based skin heating has been shown to minimise scars by interfering with wound healing responses through the induction of heat shock proteins (HSP). HSP are also induced after ablative fractional laser (AFXL) wound healing. AFXL itself is highly recommended for scar treatment. Therefore, the sequential combination of both modalities may produce superior outcomes. The aim of this study was to examine the pretreatment effects of a diode laser before AFXL on wound healing responses in terms of HSP up-regulation in an in vitro model. Immediate responses and responses on days 1, 3 or 6 post-procedure were studied in an in vitro porcine skin model (n = 240). Untreated samples served as control. Immunohistochemical investigation (Hsp70) was performed in all untreated controls, diode laser-, AFXL-, and in diode laser + AFXL-treated samples. Hsp70 was shown to be up-regulated by all interventions between days 1 and 6 after interventions. The largest effect was caused by the combination of a diode laser and an AFXL procedure. Diode laser exposure induces a skin HSP response that can be further enhanced by sequential AFXL treatment. Clinical studies are necessary to investigate the dose response of HSP on scar formation and refine suitable laser exposure settings.

  20. Preparation of starch stabilized silver nanoparticles with spatial self-phase modulation properties by laser ablation technique

    Energy Technology Data Exchange (ETDEWEB)

    Zamiri, Reza; Azmi, B.Z.; Sadrolhosseini, Amir R.; Husin, M.S.; Zaidan, A.W. [Universiti Putra Malaysia, Department of Physics, Faculty of Science, UPM Serdang, Selangor (Malaysia); Darroudi, Majid [Universiti Putra Malaysia, Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, UPM Serdang, Selangor (Malaysia); Mahdi, M.A. [Universiti Putra Malaysia, Wireless and Photonics Networks Research Center, Faculty of Engineering, UPM Serdang, Selangor (Malaysia)

    2011-01-15

    Silver nanoparticles inside the starch solution have been successfully fabricated by laser ablation of a silver plate immersed in starch solution. The ablation has been done using a Q-switched Nd:YAG laser at 10 Hz repetition rate. The starch solution allows for the formation of silver nanoparticles with uniform particle diameters and well dispersed. The ablation was performed at different time durations to study the influence of the laser ablation time on efficiency of particle formation and sizes. The Spatial Self-phase modulation phenomena which can determine the nonlinear optical property of the samples were also investigated for starch solutions containing silver nanoparticles. (orig.)

  1. Femtosecond Laser Ablation Multicollector ICPMS Analysis of Uranium Isotopes in NIST Glass

    Energy Technology Data Exchange (ETDEWEB)

    Duffin, Andrew M.; Springer, Kellen WE; Ward, Jesse D.; Jarman, Kenneth D.; Robinson, John W.; Endres, Mackenzie C.; Hart, Garret L.; Gonzalez, Jhanis J.; Oropeza, Dayana; Russo, Richard; Willingham, David G.; Naes, Benjamin E.; Fahey, Albert J.; Eiden, Gregory C.

    2015-02-06

    We have utilized femtosecond laser ablation coupled to multi-collector inductively couple plasma mass spectrometry to measure the uranium isotopic content of NIST 61x (x=0,2,4,6) glasses. The uranium content of these glasses is a linear two-component mixing between isotopically natural uranium and the isotopically depleted spike used in preparing the glasses. Laser ablation results match extremely well, generally within a few ppm, with solution analysis following sample dissolution and chemical separation. In addition to isotopic data, sample utilization efficiency measurements indicate that over 1% of ablated uranium atoms reach a mass spectrometer detector, making this technique extremely efficient. Laser sampling also allows for spatial analysis and our data indicate that rare uranium concentration inhomogeneities exist in NIST 616 glass.

  2. Promotion of protein crystal growth by actively switching crystal growth mode via femtosecond laser ablation

    Science.gov (United States)

    Tominaga, Yusuke; Maruyama, Mihoko; Yoshimura, Masashi; Koizumi, Haruhiko; Tachibana, Masaru; Sugiyama, Shigeru; Adachi, Hiroaki; Tsukamoto, Katsuo; Matsumura, Hiroyoshi; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Yoshikawa, Hiroshi Y.; Mori, Yusuke

    2016-11-01

    Large single crystals with desirable shapes are essential for various scientific and industrial fields, such as X-ray/neutron crystallography and crystalline devices. However, in the case of proteins the production of such crystals is particularly challenging, despite the efforts devoted to optimization of the environmental, chemical and physical parameters. Here we report an innovative approach for promoting the growth of protein crystals by directly modifying the local crystal structure via femtosecond laser ablation. We demonstrate that protein crystals with surfaces that are locally etched (several micrometers in diameter) by femtosecond laser ablation show enhanced growth rates without losing crystal quality. Optical phase-sensitive microscopy and X-ray topography imaging techniques reveal that the local etching induces spiral growth, which is energetically advantageous compared with the spontaneous two-dimensional nucleation growth mode. These findings prove that femtosecond laser ablation can actively switch the crystal growth mode, offering flexible control over the size and shape of protein crystals.

  3. Hyperthermal Pulsed-Laser Ablation Beams for Film Deposition and Surface Microstructural Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Lowndes, D.H.

    1999-11-08

    This paper presents an overview of pulsed-laser ablation for film deposition and surface microstructure formation. By changing the ambient gas pressure from high vacuum to several Torr (several hundred Pa) and by selecting the pulsed-laser wavelength, the kinetic energy of ablated atoms/ions can be varied from several hundred eV down to {approximately}0.1 eV and films ranging from superhard to nanocrystalline may be deposited. Furthermore, cumulative (multi-pulse) irradiation of a semiconductor surface (e.g. silicon) in an oxidizing gas (0{sub 2}, SF{sub 6}) et atmospheric pressure can produce dense, self-organized arrays of high-aspect-ratio microcolumns or microcones. Thus, a wide range of materials synthesis and processing opportunities result from the hyperthermal flux and reactive growth conditions provided by pulsed-laser ablation.

  4. Modification of narrow ablating capillaries under the influence of multiple femtosecond laser pulses

    CERN Document Server

    Gubin, K V; Trunov, V I; Pestryakov, E V

    2016-01-01

    Powerful femtosecond laser pulses that propagate through narrow ablating capillaries cause modification of capillary walls, which is studied experimentally and theoretically. At low intensities, laser-induced periodic surface structures (LIPSS) and porous coating composed of sub-micron particles appear on the walls. At higher intensities, the surface is covered by deposited droplets of the size up to 10 $\\mu$m. In both cases, the ablated material forms a solid plug that completely blocks the capillary after several hundreds or thousands of pulses. The suggested theoretical model indicates that plug formation is a universal effect. It must take place in any narrow tube subject to ablation under the action of short laser pulses.

  5. The characteristics of confined ablation in laser propulsion

    Institute of Scientific and Technical Information of China (English)

    Zheng Zhi-Yuan; Zhang Jie; Hao Zuo-Qiang; Yuan Xiao-Hui; Zhang Zhe; Lu Xin; Wang Zhao-Hua; Wei Zhi-Yi

    2006-01-01

    Compared with direct ablation, confined ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. By using a transparent glass layer to cover the target surface, the coupling coefficient is enhanced by an order of magnitude. With the increase of the gap width between the target surface and the cover layer, the coupling coefficient exponentially decreases. It is found that the coupling coefficient is also related to the thickness of the cover layer.

  6. Theoretical and experimental study of energy transportation and accumulation in femtosecond laser ablation on metals

    Institute of Scientific and Technical Information of China (English)

    TAN Xin-yu; ZHANG Duan-ming; MAO Feng; LI Zhi-hua; YI DI; ZHANG Xiao-zhong

    2009-01-01

    The energy transportation and accumulation effect for femtosecond (fs) laser ablation on metal targets were studied using both theoretical and experimental methods.Using finite difference method,numerical simulation of energy transportation characteristics on copper target ablated by femtosecond laser was performed.Energy accumulation effects on metals of silver and copper ablated by an amplified Ti: sapphire femtosecond laser system were then studied experimentally.The simulated results show that the electrons and lattices have different temperature evolvement characteristics in the ablation stage.The electron temperature increases sharply and reaches the maximum in several femtoseconds while it needs thousands of femtoseconds for lattice to reach the maximum temperature.The experimental results show that uniform laser-induced periodic surface structures (PSS) can be formed with the appropriate pulsed numbers and laser energy density.Electron-phonon coupling coefficient plays an important role in PSS formation in different metals.Surface ripples of Cu are more pronounced than those of Au under the same laser energy density.

  7. Stainless steel surface wettability control via laser ablation in external electric field

    Science.gov (United States)

    Serkov, A. A.; Shafeev, G. A.; Barmina, E. V.; Loufardaki, A.; Stratakis, E.

    2016-12-01

    Laser ablation of stainless steel in external electric field (up to 10 kV/cm) is experimentally studied. The dependencies of both morphology and chemical properties of surface structures on laser parameters and electric field strength are investigated. Surface wettability properties of the laser-treated samples are considered by means of contact angle measurement. It is shown that under certain conditions laser irradiation in external electric field can render the surface superhydrophobic. Influence of electric field on the laser surface treatment is discussed on basis of its impact on melt solidification and oxidation processes.

  8. Investigations of morphological features of picosecond dual-wavelength laser ablation of stainless steel

    Science.gov (United States)

    Zhao, Wanqin; Wang, Wenjun; Mei, Xuesong; Jiang, Gedong; Liu, Bin

    2014-06-01

    Investigations on the morphological features of holes and grooves ablated on the surface of stainless steel using the picosecond dual-wavelength laser system with different powers combinations are presented based on the scarce researches on morphology of dual-wavelength laser ablation. The experimental results show the profiles of holes ablated by the visible beam appear V-shaped while those for the near-infrared have large openings and display U-shaped, which are independent of the ablation mechanism of ultrafast laser. For the dual-wavelength beam (a combination of visible beam and near-infrared), the holes resemble sunflower-like structures and have smoother ring patterns on the bottom. In general, the holes ablated by the dual-wavelength beam appear to have much flatter bottoms, linearly sloped side-walls and spinodal structures between the bottoms of the holes and the side-walls. Furthermore, through judiciously combining the powers of the dual-wavelength beam, high-quality grooves could be obtained with a flat worm-like structure at the bottom surface and less resolidified melt ejection edges. This study provides insight into optimizing ultrafast laser micromachining in order to obtain desired morphology.

  9. Thermal characteristics of double-layer thin film target ablated by femtosecond laser pulses

    Institute of Scientific and Technical Information of China (English)

    Gao Xun; Song Xiao-Wei; Lin Jing-Quan

    2011-01-01

    Thermal characteristics of tightly-contacted copper-gold double-layer thin film target under ablation of femtosecond laser pulses are investigated by using a two-temperature theoretical model. Numerical simulation shows that electron heat flux varies significantly on the boundary of copper-gold film with different maximal electron temperature of 1.15 × 103 K at 5 ps after ablating laser pulse in gold and copper films, which can reach a balance around 12.6 ps and 8.2 ps for a single and double pulse ablation, respectively, and in the meantime, the lattice temperature difference crossing the gold-copper interface is only about 0.04 × 103 K at the same time scale. It is also found that electron-lattice heat relaxation time increases linearly with laser fluence in both single and double pulse ablation, and a sudden change of the relaxation time appears after the laser energy density exceeds the ablation threshold.

  10. Real-time near-IR imaging of laser-ablation crater evolution in dental enamel

    Science.gov (United States)

    Darling, Cynthia L.; Fried, Daniel

    2007-02-01

    We have shown that the enamel of the tooth is almost completely transparent near 1310-nm in the near-infrared and that near-IR (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue and for observing defects in the interior of the tooth. Lasers are now routinely used for many applications in dentistry including the ablation of dental caries. The objective of this study was to test the hypothesis that real-time NIR imaging can be used to monitor laser-ablation under varying conditions to assess peripheral thermal and transient-stress induced damage and to measure the rate and efficiency of ablation. Moreover, NIR imaging may have considerable potential for monitoring the removal of demineralized areas of the tooth during cavity preparations. Sound human tooth sections of approximately 3-mm thickness were irradiated by a CO II laser under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with band-pass filter centered at 131--nm combined with an InGaAs focal plane array with a NIR zoom microscope in transillumination. Due to the high transparency of enamel at 1310-nm, laser-incisions were clearly visible to the dentin-enamel junction and crack formation, dehydration and irreversible thermal changes were observed during ablation. This study showed that there is great potential for near-IR imaging to monitor laser-ablation events in real-time to: assess safe laser operating parameters by imaging thermal and stress-induced damage, elaborate the mechanisms involved in ablation such as dehydration, and monitor the removal of demineralized enamel.

  11. Influence of external cooling on the femtosecond laser ablation of dentin.

    Science.gov (United States)

    Le, Q T; Vilar, R; Bertrand, C

    2017-07-11

    In the present work, the influence of external cooling on the temperature rise in the tooth pulpal chamber during femtosecond laser ablation was investigated. The influence of the cooling method on the morphology and constitution of the laser-treated surfaces was studied as well. The ablation experiments were performed on dentin specimens using an Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs, 1030 nm). Cavities were created by scanning the specimens at a velocity of 5 mm/s while pulsing the stationary laser beam at 1 kHz and with fluences in the range of 2-14 J/cm(2). The experiments were performed in air and with surface cooling by a lateral air jet and by a combination of an air jet and water irrigation. The temperature in the pulpal chamber of the tooth was measured during the laser experiments. The ablation surfaces were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The temperature rise reached 17.5 °C for the treatments performed with 14 J/cm(2) and without cooling, which was reduced to 10.8 ± 1.0 and 6.6 ± 2.3 °C with forced air cooling and water cooling, respectively, without significant reduction of the ablation rate. The ablation surfaces were covered by ablation debris and resolidified droplets containing mainly amorphous calcium phosphate, but the amount of redeposited debris was much lower for the water-cooled specimens. The redeposited debris could be removed by ultrasonication, revealing that the structure and constitution of the tissue remained essentially unaltered. The present results show that water cooling is mandatory for the femtosecond laser treatment of dentin, in particular, when high fluences and high pulse repetition rates are used to achieve high material removal rates.

  12. Phase II Evaluation of Magnetic Resonance Imaging Guided Focal Laser Ablation of Prostate Cancer.

    Science.gov (United States)

    Eggener, Scott E; Yousuf, Ambereen; Watson, Sydeaka; Wang, Shiyang; Oto, Aytekin

    2016-12-01

    Magnetic resonance imaging guided focal laser ablation is an investigational strategy for the treatment of prostate cancer. This phase II evaluation of focal laser ablation included men with stage T1c-T2a, prostate specific antigen less than 15 ng/ml or prostate specific antigen density less than 0.15 ng/ml(3), Gleason 7 or less in 25% or less of biopsies and magnetic resonance imaging with 1 or 2 lesions concordant with biopsy detected cancer. At 3 months all patients underwent magnetic resonance imaging with biopsy of ablation zone(s). At 12 months all underwent magnetic resonance imaging and systematic biopsy. I-PSS (International Prostate Symptom Score) and SHIM (Sexual Health Inventory for Men) scores were collected before focal laser ablation, and at 1, 3 and 12 months. The primary end point was no cancer on the 3-month ablation zone biopsy. Secondary end points were safety, 12-month biopsy, and urinary and sexual function. In the 27 men median age was 62 years and mean prostate specific antigen was 4.4 ng/ml. Biopsy Gleason score was 6 in 23 patients (85%) and Gleason 7 in 4 (15%). Seven men (26%) had low volume Gleason 6 disease outside the intended ablation zone(s). At 3 months 26 patients (96%) had no evidence of cancer on magnetic resonance imaging guided biopsy of the ablation zone. No significant I-PSS changes were observed (each p >0.05). SHIM was lower at 1 month (p = 0.03), marginally lower at 3 months (p = 0.05) and without a significant difference at 12 months (p = 0.38). At 12-month biopsy cancer was identified in 10 patients (37%), including in the ablation zone(s) in 3 (11%) and outside the ablation zone(s) in 8 (30%) with cancer in and outside the ablation zone in 1. In select men with localized prostate cancer and visible magnetic resonance imaging lesions focal laser ablation has an acceptable morbidity profile and is associated with encouraging short-term oncologic outcomes. Significantly longer followup is mandatory to fully assess this

  13. The influence of laser ablation plume at different laser incidence angle on the impulse coupling coefficient with metal target

    Science.gov (United States)

    Zhao, Xiong-Tao; Tang, Feng; Han, Bing; Ni, Xiao-Wu

    2016-12-01

    A calibrated pendulum measuring device and a dimensionless analysis method were used to measure the impulse coupling coefficient at different laser intensities with aluminum, steel, and iron targets. The experiment was performed with a pulsed laser with the wavelength of 1.06 μm and the pulse duration of 7 ns. The experimental measurements of the variation of the impulse coupling coefficient versus the laser energy density agree with the theoretical prediction, and the optimum laser energy density correlated with the maximum impulse coupling coefficient corresponding to the theoretical predictions. The impulse coupling coefficients with laser incidence angles of 0 ° and 45 ° are compared for understanding of the effects of the ablation plume on the impulse coupling effect, and the experimental result shows that the impulse coupling effect grows as the incidence angle changes from 0 ° to 45 ° . Furthermore, the transmittance of the incident laser through the ablation plume in front of the target is deduced from the impulse measurements, and the effect of the ablation plume on the impulse coupling at high laser intensity is discussed. In order to investigate the weak impulse coupling effect, which is difficult to obtain from the experiments, the impulse coupling coefficient at low laser energy density was calculated by the finite element simulation.

  14. IR-Laser Welding and Ablation of Biotissue Stained with Metal Nanoparticles

    CERN Document Server

    Lalayan, A A

    2015-01-01

    In the present work we have studied the possibility of laser welding and ablation of biological tissue by the using of spherical metal nanoparticles (NPs) and infrared laser irradiation which spectrally located far from plasmon resonances. YAG:Nd laser with 1064 nm wavelength, 8 ns pulse duration, and operating in transverse electromagnetic modes TEM$_{00}$ was used for the synthesis of metal NPs. The Au,Ti Ni and Cu as well as Au-Ag and Au-Cu hybrid metal NPs were formed in the liquid medium. Effectiveness of laser ablation in the case of the biotissue sample that stained with the metal NPs was approximately on 4-5 times larger than for the native sample. Also the scheme of a laser point welding for the deep-located biotissue layer selectively stained by the metal NPs has been demonstrated.

  15. Mass spectroscopic analysis of a plume induced by laser ablation of pyrolytic boron nitride

    CERN Document Server

    Chae, H B; Lee, I H; Park, S M

    1998-01-01

    The laser ablation of a pyrolytic boron nitride (pBN) target was investigated by time-of- flight quadrupole mass spectroscopy. According to the laser-correlated ion mass spectra, B sup + and B sub 2 sup + ions were produced, but neither N sup + , N sub 2 sup + , or BN sup + ions were observed at laser fluences below 1 J/cm sup 2. Instead, neutral N sub 2 molecules were found to be formed. The mean velocities and kinetic energies of the B sup + ions were obtained by time-of-flight analysis. Also, reactive laser ablation under a N sub 2 atmosphere was attempted by using a pulsed valve synchronized with the laser pulse.

  16. Effect of air breakdown with a focusing lens on ultrashort laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Hu Wenqian; Shin, Yung C.; King, Galen [School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2011-12-05

    The effect of air breakdown on ultrashort laser ablation is investigated in this letter using an integrated simulation method on atomistic level. The generation of air breakdown with different laser peak power densities in the range from 10{sup 13} to 10{sup 16} W/cm{sup 2} and various focusing conditions is analyzed. Air breakdown is generated directly from laser energy absorption through avalanche ionization at a high power density (over 10{sup 14} W/cm{sup 2}), while at a lower power density, air breakdown is assisted by a metal target near the focal region. The laser energy loss due to air breakdown and its effect on laser ablation are studied.

  17. In-Situ Apatite Laser Ablation U-Th-Sm/He Dating, Methods and Challenges

    Science.gov (United States)

    Pickering, J. E.; Matthews, W.; Guest, B.; Hamilton, B.; Sykes, C.

    2015-12-01

    In-situ, laser ablation U-Th-Sm/He dating is an emerging technique in thermochronology that has been proven as a means to date zircon and monzonite1-5. In-situ U-Th-Sm/He thermochronology eliminates many of the problems and inconveniences associated with traditional, whole grain methods, including; reducing bias in grain selection based on size, shape and clarity; allowing for the use of broken grains and grains with inclusions; avoiding bad neighbour effects; and eliminating safety hazards associated with dissolution. In-situ apatite laser ablation is challenging due to low concentrations of U and Th and thus a low abundance of radiogenic He. For apatite laser ablation to be effective the ultra-high-vacuum (UHV) line must have very low and consistent background levels of He. To reduce He background, samples are mounted in a UHV stable medium. Our mounting process uses a MicroHePP (Microscope Mounted Heated Platen Press) to press samples into FEP (fluorinated ethylene propylene) bonded to an aluminum backing plate. Samples are ablated using a Resonetics 193 nm excimer laser and liberated He is measured using a quadrupole mass spectrometer on the ASI Alphachron noble gas line; collectively this system is known as the Resochron. The ablated sites are imaged using a Zygo Zescope optical profilometer and ablated pit volume measured using PitVol, a custom MatLab algorithm developed to enable precise and unbiased measurement of the ablated pit geometry. We use the well-characterized Durango apatite to demonstrate the accuracy and precision of the method. He liberated from forty-two pits, having volumes between 1700 and 9000 um3, were measured using the Resochron. The ablated sites were imaged using a Zygo Zescope optical profilometer and ablated pit volume measured using PitVol. U, Th and Sm concentrations were measured by laser ablation and the U-Th-Sm/He age calculated by standard age equation. An age of 33.8±0.31 Ma was determined and compares well with conventional

  18. a Chirped-Pulse Fourier Transform Microwave Spectrometer Combined with a Laser Ablation Source

    Science.gov (United States)

    Mata, S.; Pena, I.; Cabezas, C.; López, J. C.; Alonso, J. L.; Pate, B. H.

    2011-06-01

    The design of a chirped-pulse Fourier transform microwave spectrometer CP-FTMW combined with a laser ablation LA source is presented. The spectrometer is capable of measuring the 6.5-18 GHz region. Rotational spectra of solid samples of proline (m.p. 228° C) and alanine (m.p. 290° C) vaporized by laser ablation has been recorded. Four low-energy conformers of proline and two in alanine have been detected. 13C species of alanine in their natural abundance have been also observed. The performance of this spectrometer is compared to a LA-MB-FTMW spectrometer.

  19. Density bump formation in a collisionless electrostatic shock wave in a laser-ablated plasma

    CERN Document Server

    Garasev, M A; Kocharovsky, V V; Malkov, Yu A; Murzanev, A A; Nechaev, A A; Stepanov, A N

    2016-01-01

    The emergence of a density bump at the front of a collisionless electrostatic shock wave have been observed experimentally during the ablation of an aluminium foil by a femtosecond laser pulse. We have performed numerical simulations of the dynamics of this phenomena developing alongside the generation of a package of ion-acoustic waves, exposed to a continual flow of energetic electrons, in a collisionless plasma. We present the physical interpretation of the observed effects and show that the bump consists of transit particles, namely, the accelerated ions from the dense plasma layer, and the ions from the diluted background plasma, formed by a nanosecond laser prepulse during the ablation.

  20. Experimental and Analytical Investigation of Cemented Tungsten Carbide Ultra-Short Pulse Laser Ablation

    Science.gov (United States)

    Urbina, J. P. Calderón; Daniel, C.; Emmelmann, C.

    Ultra-short pulse laser processing of hard materials, such as cemented tungsten carbide, requires an accurate and agile experimental and analytical investigation to obtain adequate information and setting parameters to maximize ablation rate. Therefore, this study presents a systematic approach which, first, experimentally searches for the variables with the most significant influence on the objective using a design of experiments method; and second, analyzes by means of existing ablation theory the interaction of the material and laser taking into account the Beer-Lambert law and incubation effect.Therefore, this places a basis for future analytical-experimental validation of the examined material.

  1. Angular distributions of emitted particles by laser ablation of silver at 355 nm

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Schou, Jørgen; Hansen, T.;

    1998-01-01

    The angular distribution of laser ablated silver in vacuum has been measured in situ with an array of quartz-crystal microbalances. The silver surface was irradiated by ns pulses from a Nd:YAG laser operating at 355 nm for fluences ranging from 0.7 J/cm2 to 8 J/cm2. The distribution is strongly p...... peaked in the forward direction corresponding to cosp/, where p varies from 5 to 12 for the largest beam spot, but is less peaked for the smallest beam spots. The total collected yield of ablated atoms is about 221015 Ag atoms per pulse for the highest pulse energies....

  2. Target-plane deposition of diamond-like carbon in pulsed laser ablation of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Yap, S.S. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Tou, T.Y. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia)], E-mail: tytou@mmu.edu.my

    2007-10-15

    In pulsed Nd:YAG laser ablation of highly oriented pyrolytic graphite (HOPG) at 10{sup -6} Torr, diamond-like carbon (DLC) are deposited at laser wavelengths of 1064, 532, and 355 nm on substrates placed in the target-plane. These target-plane samples are found to contain varying sp{sup 3} content and composed of nanostructures of 40-200 nm in size depending on the laser wavelength and laser fluence. The material and origin of sp{sup 3} in the target-plane samples is closely correlated to that in the laser-modified HOPG surface layer, and hardly from the backward deposition of ablated carbon plume. The surface morphology of the target-plane samples shows the columnar growth and with a tendency for agglomeration between nanograins, in particular for long laser wavelength at 1064 nm. It is also proposed that DLC formation mechanism at the laser-ablated HOPG is possibly via the laser-induced subsurface melting and resolidification.

  3. Fiber-delivered mid-infrared (6-7) laser ablation of retinal tissue under perfluorodecalin

    Science.gov (United States)

    Mackanos, Mark A.; Joos, Karen M.; Jansen, E. Duco

    2003-07-01

    The Er:YAG laser (l=2.94mm) is an effective tool in vitreo-retinal surgery. Pulsed mid-infrared (l=6.45 mm) radiation from the Free Electron Laser has been touted as a potentially superior cutting tool. To date, use of this laser has been limited to applications in an air environment. The goal of this study was: 1) determine feasibility of fiberoptic delivery of 6.45mm using silverhalide fibers (d=700mm); 2) use infrared transparent vitreous substitute (perfluorodecalin) to allow non-contact ablation of the retina at 6.45mm. Fiber damage threshold=7.8J/cm2 (0.54GW/cm2) while transmission loss=0.54dB/m, allowing supra-ablative radiant exposures to the target. FTIR measurements of perfluorodecalin at 6.45mm yielded ma=3mm-1. Pump-probe imaging of ablation of a tissue-phantom through perfluorodecalin showed feasibility of non-contact ablation at l=6.45mm. Ablation of the retinal membranes of enucleated pig eyes was carried out under perfluorodecalin (5 Hz, 1.3 J/cm2). Each eye was cut along its equator to expose the retina. Vitreous was replaced by perfluorodecalin and laser radiation was delivered to the retina via the silverhalide fiber. The eye was rotated (at 2 rpm) using a stepper motor (0.9o/step) to create an ablation circle around the central axis of the retina (50% spot-to-spot overlap). Histological analysis of ablation yield and collateral damage will be presented. We have shown that using l=6.45mm delivered via silver halide fibers through perfluorodecalin allowed non-contact laser ablation. Remote structures are shielded, as the radiant exposure falls below the ablation threshold owing non-negligible absorption of perfluorodecalin at 6.45mm. This may optimize efficacy and safety of laser-based vitreoretinal surgery.

  4. In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-12-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

  5. Laser ablation for small hepatocellular carcinoma: State of the art and future perspectives

    Institute of Scientific and Technical Information of China (English)

    Giovan; Giuseppe; Di; Costanzo; Giampiero; Francica; Claudio; Maurizio; Pacella

    2014-01-01

    During the last two decades, various local thermal ablative techniques for the treatment of unresectable hepatocellular carcinoma(HCC) have been developed. According to internationally endorsed guidelines, percutaneous thermal ablation is the mainstay of treatment in patients with small HCC who are not candidates for surgical resection or transplantation. Laser ablation(LA) represents one of currently available loco-ablative techniques. In this article, the general principles, technique, image guidance, and patient selection are reported. Primary effectiveness, long-term outcome, and complications are also discussed. A review of published data suggests that LA is equivalent to the more popular and widespread radiofrequency ablation in both local tumor control and long-term outcome in the percutaneous treatment of early HCC. In addition, the LA technique using multiple thin laser fibres allows improved ablative effectiveness in HCCs greater than 3 cm. Reference centres should be equipped with all the available techniques so as to be able to use the best and the most suitable procedure for each type of lesion for each patient.

  6. Optical design and laser ablation of surface textures: demonstrating total internal reflection

    Science.gov (United States)

    Gommans, Hans; Booij, Silvia; Pijlman, Fetze; Krijn, Marcel; de Zwart, Siebe; Sepkhanov, Ruslan; Beaumont, Dave; van der Schaft, Hans; Sanders, Rene

    2015-09-01

    In lighting applications key drivers for optical design of surface textures are integration of optical elements, the disentanglement of optical functionality and appearance and late stage configuration. We investigated excimer laser ablation as a mastering technology for micro textured surfaces, where we targeted an increase in correspondence between surface design and ablated surface for high aspect ratio structures. To achieve this we have improved the photo mask design using a heuristic algorithm that corrects for the angular dependence of the ablation process and the loss of image resolution at ablation depths that exceed the depth of field. Using this approach we have been able to demonstrate close correspondence between designed and ablated facet structures up to 75° inclination at 75 μm depth. These facet design parameters allow for total internal reflection (TIR) as a means of beam deflection which is demonstrated in a range of mono shaped cone arrays in hexagonal tessellation. BSDF analysis was used to characterize the narrow TIR deflection beams that matched the peak positions of the design down to 28° apex. In addition, a single surface TIR-Fresnel lens design with focal distance 5 mm has been manufactured using this photo mask design algorithm and beam collimation up to 12° beam angle and 32° field angle is shown. These outcomes demonstrate that the laser ablation process intrinsically yields sufficient small dispersion in structure and fillet radii for lighting applications.

  7. Characterization of laser-induced damage in silicon solar cells during selective ablation processes

    Energy Technology Data Exchange (ETDEWEB)

    Poulain, G. [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France); Agence de l’environnement et de la Maîtrise de l’Energie, 20, avenue du Grésillé, BP 90406 49004 Angers Cedex 01 (France); Blanc, D., E-mail: daniele.blanc@insa-lyon.fr [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France); Focsa, A.; De Vita, M.; Fraser, K. [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France); Sayad, Y. [Institut de Sciences et Technologies, Centre Universitaire de Souk Ahras, Route de Annaba, Souk Ahras (Algeria); Lemiti, M. [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France)

    2013-05-15

    Selective laser ablation of silicon nitride layers on crystalline silicon wafers was investigated for solar cell fabrication. Laser processing was performed with a nanosecond UV laser at various energy densities ranging from 0.2 to 1.5 J cm{sup −2}. Optical microscopy was used as a simple mean to assess the ablation threshold that was correlated to the temperature at the interface between the silicon nitride coating and the silicon substrate. Minority carrier lifetime measurements were performed using a microwave photo-conductance decay technique. Band to band photoluminescence spectroscopy proved to be a sensitive technique to qualify the laser-induced damage to the silicon substrate. The crystalline structure of silicon seemed to be maintained after silicon nitride ablation as shown by UV reflectivity measurements. Laser parameters corresponding to fluences of around 0.4 J cm{sup −2} were found to achieve selective ablation of SiN{sub x} without causing detrimental damage to the surrounding material.

  8. Tungsten trioxide (WO{sub 3-x}) nanoparticles prepared by pulsed laser ablation in water

    Energy Technology Data Exchange (ETDEWEB)

    Barreca, F., E-mail: process@anmresearch.it [Advanced, Nano Materials Research s.r.l, Viale F. Stagno d' Alcontres 31, I-98166, Messina (Italy); Acacia, N. [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universita di Messina, Viale F. Stagno d' Alcontres 31, I-98166, Messina (Italy); Spadaro, S.; Curro, G. [Advanced, Nano Materials Research s.r.l, Viale F. Stagno d' Alcontres 31, I-98166, Messina (Italy); Neri, F. [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universita di Messina, Viale F. Stagno d' Alcontres 31, I-98166, Messina (Italy)

    2011-05-16

    Research highlights: {yields} First time prepared, by laser ablation in water, WO{sub x} nanoparticles (NPs). {yields} Nearly 60% of almost stoichiometric (x = 2.9), small size (2-6 nm) NPs plus 80-100 nm aggregates. {yields} A plasma shielding effect occurs at high laser fluence. {yields} Modulation of optical gap with the NPs size. {yields} Potential scalability of the production technique. - Abstract: Tungsten trioxide (WO{sub 2.9}) nanoparticles were prepared, to our knowledge for the first time, by pulsed laser ablation in distilled water. The experiments were performed irradiating a tungsten target with a second harmonic (532 nm) Nd:YAG laser beam varying the operative fluence between 1 and 7 J cm{sup -2} and the ablation time up to 120 min. As evidenced by means of transmission electron microscopy (TEM), at all investigated fluences, small nanostructures of 2-6 nm were accompanied by larger particles with a diameter of about 10-20 nm and aggregates of about 80-100 nm. A plasma shielding effect was evidenced upon increasing the laser fluence, while if the ablation time is increased the amount of particles increases as well, supporting the scalability of the production technique. The deposited nanoparticles stoichiometry has been verified by X-ray photoelectron spectroscopy (XPS), while the optical bandgap values were determined by UV-vis optical absorption measurements.

  9. Laser Ablation Surface Preparation of Ti-6A1-4V for Adhesive Bonding

    Science.gov (United States)

    Palmieri, Frank L.; Watson, Kent A.; Morales, Guillermo; Williams, Thomas; Hicks, Robert; Wohl, Christopher J.; Hopkins, John W.; Connell, John W.

    2012-01-01

    Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable bonds. Laser ablation imparts both topographical and chemical changes to a surface which can lead to increased bond durability. A laser based process provides an alternative to chemical-dip, manual abrasion and grit blast treatments which are expensive, hazardous, polluting, and less precise. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Failure mode, surface roughness, and chemical makeup were analyzed using fluorescence enhanced visualization, microscopy, and X-ray photoelectron spectroscopy, respectively. Single lap shear tests were conducted on bonded and aged specimens to observe bond strength retention and failure mode. Some promising results showed increasing strength and durability of lap shear specimens as laser ablation coverage area and beam intensity increased. Chemical analyses showed trends for surface chemical species which correlated with improved bond strength and durability. Combined, these results suggest that laser ablation is a viable process for inclusion with or/and replacement of one or more currently used titanium surface treatments. On-going work will focus on additional mechanical tests to further demonstrate improved bond durability.

  10. Controlled Contamination of Epoxy Composites with PDMS and Removal by Laser Ablation

    Science.gov (United States)

    Palmieri, Frank; Ledesma, Rodolfo; Cataldo, Daniel; Lin, Yi; Wohl, Christopher; Gupta, Mool; Connell, John

    2016-01-01

    Surface preparation is critical to the performance of adhesively bonded composites. During manufacturing, minute quantities of mold release compounds are inevitably deposited on faying surfaces and may compromise bond performance. To ensure safety, mechanical fasteners and other crack arrest features must be installed in the bondlines of primary structures, which negates some advantages of adhesively bonded construction. Laser ablation is an automated, repeatable, and scalable process with high potential for the surface preparation of metals and composites in critical applications such as primary airframe structures. In this study, laser ablation is evaluated on composite surfaces for the removal of polydimethylsiloxane (PDMS), a common mold release material. Composite panels were contaminated uniformly with PDMS film thicknesses as low as 6.0 nm as measured by variable angle spectroscopic ellipsometry. Bond performance was assessed by mechanical testing using a 250 F cure, epoxy adhesive and compared with pre-bond surface inspection results. Water contact angle, optically stimulated electron emission, and laser induced breakdown spectroscopy were used to characterize contaminated and laser ablated surfaces. The failure mode obtained from double cantilever beam tests correlated well with surface characterization data. The test results indicated that even low levels of PDMS were not completely removed by laser ablation.

  11. Treatment of osteoid osteoma using CT-guided radiofrequency ablation versus MR-guided laser ablation: A cost comparison

    Energy Technology Data Exchange (ETDEWEB)

    Maurer, M.H., E-mail: martin.maurer@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Gebauer, B., E-mail: bernhard.gebauer@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Wieners, G., E-mail: gero.wieners@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); De Bucourt, M., E-mail: maximilian.de-bucourt@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Renz, D.M., E-mail: diane.renz@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Hamm, B., E-mail: bernd.hamm@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Streitparth, F., E-mail: florian.streitparth@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany)

    2012-11-15

    Objective: To compare the costs of CT-guided radiofrequency ablation (RFA) and MR-guided laser ablation (LA) for minimally invasive percutaneous treatment of osteoid osteoma. Materials and methods: Between November 2005 and October 2011, 20 patients (14 males, 6 females, mean age 20.3 {+-} 9.1 years) underwent CT-guided RFA and 24 patients (18 males, 6 females; mean age, 23.8 {+-} 13.8 years) MR-guided LA (open 1.0 Tesla, Panorama HFO, Philips, Best, Netherlands) for osteoid osteoma diagnosed on the basis of clinical presentation and imaging findings. Prorated costs of equipment use (purchase, depreciation, and maintenance), staff costs, and expenditure for disposables were identified for CT-guided RFA and MR-guided LA procedures. Results: The average total costs per patient were EUR 1762 for CT-guided RFA and EUR 1417 for MR-guided LA. These were (RFA/LA) EUR 92/260 for equipment use, EUR 149/208 for staff, and EUR 870/300 for disposables. Conclusion: MR-guided LA is less expensive than CT-guided RFA for minimally invasive percutaneous ablation of osteoid osteoma. The higher costs of RFA are primarily due to the higher price of the disposable RFA probes.

  12. Femtosecond laser ablation properties of transparent materials: impact of the laser process parameters on the machining throughput

    Science.gov (United States)

    Matylitsky, V. V.; Hendricks, F.; Aus der Au, J.

    2013-03-01

    High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives for industrial applications [1]. The unique advantage of material processing with subpicosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid materials. The study on the impact of the laser processing parameters on the removal rate for transparent substrate using femtosecond laser pulses will be presented. In particular, examples of micro-processing of poly-L-lactic acid (PLLA) - bio-degradable polyester and XensationTM glass (Schott) machined with SpiritTM ultrafast laser will be shown.

  13. Laser ablation laser induced fluorescence for sensitive detection of heavy metals in water

    Science.gov (United States)

    Godwal, Yogesh

    Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the first pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (≤ 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy single-pulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 muJ and an excitation laser pulse energy of 8 muJ. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the effect of detector gain, the gate delay and the gate width were studied. In

  14. Estimation of Al2O3 critical temperature using a Langmuir probe in laser ablation

    Science.gov (United States)

    Yahiaoui, K.; Abdelli-Messaci, S.; Messaoud Aberkane, S.; Kellou, A.

    2016-11-01

    Pulsed laser deposition (PLD) has demonstrated its capacity in thin films growing under the moderate laser intensity. But when the laser intensity increases, the presence of droplets on the thin film limits the PLD efficiency such that the process needs an optimization study. In this way, an experimental study has been conducted in order to correlate between the appearance of those droplets and the laser fluence. The comprehension of the physical mechanism during ablation and the control of the deposition parameters allowed to get a safe process. Our experiment consists in measuring the amount of ejected matter from polycrystalline alumina target as a function of the laser fluence when irradiated by a KrF laser. According to laser fluence, several kinds of ablation regimes have been identified. Below a threshold value found as 12 J/cm2, the mechanism of ablation was assigned to normal evaporation, desorption and nonthermal processes. While above this threshold value, the mechanism of ablation was assigned to phase explosion phenomenon which is responsible of droplets formation when the surface temperature approaches the critical temperature T tc. A negative charge collector was used to collect the positive ions in the plume. Their times of flight (TOF) signal were used to estimate the appropriate T tc for alumina target. Ions yield, current as well as kinetic energy were deduced from the TOF signal. Their evolutions show the occurrence of an optical breakdown in the vapor plume which is well correlated with the onset of the phase explosion phenomenon. At 10 J/cm2, the ions velocities collected by the probe have been compared to those obtained from optical emission spectroscopy diagnostic and were discussed. To prove the occurrence of phase explosion by the appearance of droplets, several thin films were elaborated on Si (100) substrate at different laser fluence into vacuum. They have been characterized by scanning electron microscope. The results were well

  15. Laser ablation synthesis of zinc oxide clusters: a new family of fullerenes?

    CERN Document Server

    Bulgakov, A V; Bulgakov, Alexander V.; Ozerov, Igor; Proxy, Wladimir Marine; ccsd-00000864, ccsd

    2003-01-01

    Positively charged zinc oxide clusters ZnnOm (up to n = 16, m <= n) of various stoichiometry were synthesized in the gas phase by excimer ArF laser ablation of a ZnO target and investigated using time-of-flight mass spectrometry. Depending on ablation conditions, either metal rich or stoichiometric clusters dominate in the mass spectrum. When the irradiated target surface is fairly fresh, the most abundant clusters are metal rich with Zn(n+1)On and Zn(n+3)On being the major series. The stoichiometric clusters are observed with an etched ablated surface. The magic numbers at n = 9, 11 and 15 in mass spectra of (ZnO)n clusters indicate that the clusters have hollow spheroid structures related to fullerenes. A local abundance minimum at n = 13 provides an additional evidence for the presence in the ablation plume of fullerene-like (ZnO)n clusters.

  16. Laser ablation - inductively coupled plasma mass spectrometry (LA-ICP-MS): Novel applications for coal research

    Energy Technology Data Exchange (ETDEWEB)

    Booth, C.A.; Spears, D.A.

    1999-07-01

    Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) has enormous potential in coal research. Element concentrations are determined with limits of detection currently in the parts per billion range, whilst spatial resolution as low as 10 microns can be achieved using the CETAC Technologies LSX-100 laser ablation system. Calibration of the LA-ICP-MS systems is notoriously difficult but in this paper the authors review two different techniques used in Sheffield, which allow trace element concentrations of whole coals (bituminous) and minerals and macerals within the coal to be determined. The first technique involves calibrating the system with PF grade coal samples in order that trace element concentrations can directly be determined after ablation of a solid coal or pressed coal sample. Using this technique, potentially hazardous trace elements such as As, Cd, Pb and Hg can be detected and measured even in the low parts per billion concentration (mg/Kg) range. The second application utilizes the spatial resolution of the laser to measure element concentrations in individual coal components. In this paper the results from ablating pyrite framboids in polished sections of the coal are discussed. Elemental information is obtained throughout the ablation procedure and this is then calibrated against the Fe content in order to establish the concentration of an element per 1% pyritic iron.

  17. Graphene patterning by nanosecond laser ablation: the effect of the substrate interaction with graphene

    Science.gov (United States)

    Pérez-Mas, Ana M.; Álvarez, Patricia; Campos, Nuria; Gómez, David; Menéndez, Rosa

    2016-08-01

    This paper focuses on the development of patterned graphene/substrate by means of green nanosecond pulse laser irradiation. Monolayer graphene samples supported on a Si/SiO2 substrate were patterned using 532 nm laser irradiation under fluence conditions ranging from 31 mJ cm-2 to 4240 mJ cm-2. Raman spectroscopy was used to investigate the effect of laser irradiation on the graphene. It was found that at 356 mJ cm-2 selective ablation of the graphene occurs. However, at fluence values above 1030 mJ cm-2 (when damage to the substrate is observed) no ablation of the graphene takes place. In contrast, its graphenic structure was found to have been modified. Only at fluence values where the ablation of the substrate occurs, is graphene eliminated in an area almost equivalent to that of the ablated substrate. In this case, additional damage to the graphene sheet edges is produced. The increment in the number of oxygenated functional groups in these regions, as measured by x-ray photoelectron spectroscopy (XPS), suggests that this damage is probably caused by thermal phenomena during the ablation of the substrate.

  18. An improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jinping; Chen, Yuping, E-mail: ypchen@sjtu.edu.cn; Hu, Mengning; Chen, Xianfeng [State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-02-14

    In this paper, an improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum was proposed and proved in our experiment. Aiming to achieve hole-drilling with a high ratio of depth/entrance diameter in vacuum, this model can predict the depth and radius of the drilled holes precisely when employing different laser parameters. Additionally, for multi-pulse laser ablation, we found that the laser fluence and number of pulses are the dominant parameters and the multi-pulse ablation threshold is much lower than the single-pulse one, which will help to obtain high-quality holes.

  19. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    Science.gov (United States)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  20. Photothermal ablation is the primary mechanism in holmium:YAG laser lithotripsy of urinary calculi

    Science.gov (United States)

    Glickman, Randolph D.; Teichman, Joel M. H.; Corbin, Nicole S.; Vassar, George J.; Weintraub, Susan T.; Chan, Kin Foong; Welch, Ashley J.

    1999-09-01

    Because of the >= 250 microsecond(s) pulsewidth emitted by the Ho:YAG laser used in clinical lithotripsy, it is unlikely that stress confinement occurs within the irradiated stones. Experimental data supports a thermal mechanism for Ho:YAG laser stone ablation. Previous work has shown that stone fragmentation occurs soon after the onset of the laser pulse, is uncorrelated to cavitation bubble formation or collapse, and is associated with low pressures. Moreover, lithotripsy proceeds fastest with desiccated stones in air (data based on laser ablation of calcium oxalate monohydrate stones), indicating that direct absorption of the laser radiation by the stone material is required for the most efficient ablation. Lowering the initial temperature of calculi reduces the stone mass-loss following 20 J of delivered laser energy: 2.2 +/- 1.1 mg vs 5.2 +/- 1.6 mg for calcium oxalate monohydrate (COM) stones (-80 vs 23 degree(s)C), and 0.8 +/- 0.4 mg vs 2.2 +/- 1.1 mg for cystine stones (-80 vs 23 degree(s)C), p cystine; Ca2O7P2 from calcium hydrogen phosphate dihydrate, and cyanide and alloxan from uric acid. All of these observations are most consistent with a photothermal breakdown process induced by Ho:YAG laser lithotripsy.

  1. Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces

    Directory of Open Access Journals (Sweden)

    Nadezhda M. Bulgakova

    2014-12-01

    Full Text Available In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular features, including influence of the laser-excited plasma re-radiation, back flux of energetic plasma species, and massive material redeposition, on the surface quality and processing efficiency. In this paper, we analyze different plasma aspects, which go beyond a simple consideration of the well-known effect of plasma shielding of laser radiation. The following effects are considered: ambient gas ionization above the target on material processing with formation of a “plasma pipe”; back heating of the target by both laser-driven ambient and ablation plasmas through conductive and radiative heat transfer; plasma chemical effects on surface processing including microstructure growth on liquid metals; complicated dynamics of the ablation plasma flow interacting with an ambient gas that can result in substantial redeposition of material around the ablation spot. Together with a review summarizing our main to-date achievements and outlining research directions, we present new results underlining importance of laser plasma dynamics and photoionization of the gas environment upon laser processing of materials.

  2. Post ablation recanalization of varicose veins of the limbs: Comparison ablation method of mechanochemical and laser procedure

    Science.gov (United States)

    Suhartono, R.; Irfan, W.; Wangge, G.; Moenadjat, Y.; Destanto, W. I.

    2017-08-01

    Endovenous ablation has been performed for varicose veins of the limbs in Indonesia since 2010. Endovenous laser ablation (EVLA) therapy has been performed in Cipto Mangunkusumo Hospital (RSCM) in Jakarta, and mechanochemical ablation (MOCA) has been conducted in Fatmawati Hospital. This was a descriptive analytical study, with a cross-sectional design to analyze post-ablation recanalization after MOCA and EVLA procedures. Patients who had undergone MOCA or EVLA treatment were interviewed 3-18 months after the procedures. All the patients underwent vascular ultrasonography (USG) of the operated limb to assess recanalization. Secondary presurgery data were obtained from the patients’ from patients’ medical records. The clinical characteristics of the subjects were recorded to compare the potential correlation between these characteristics and recanalization post-MOCA and EVLA procedures. All the data were analyzed using SPSS ver. 20.0. The study consisted of 43 limbs: 24 treated by MOCA and 19 treated by EVLA. Most subjects in the MOCA group were 7 mm in 13/19 extremities. In the MOCA group, total recanalization occurred in 2/24 extremities, and partial recanalization occurred in 8/24 extremities. In the EVLA group, total recanalization occurred in 1/19 extremities, and partial recanalization occurred in 3/19 extremities. The association between the clinical characteristics of the patients and recanalization was not statistically significant (p > 0.05). The recanalization tendency was higher in the MOCA group than in the EVLA group. Although there was no statistically significant association between the clinical characteristics of the patients and recanalization, the largest diameter of the VSM presurgery (>7 mm) was higher in 3/4 extremities in the MOCA group, as compared to 3/13 extremities in the EVLA group.

  3. Selective photothermal ablation of tissue with a fiber-delivered Er:YAG laser

    Science.gov (United States)

    Pierce, Mark C.; Dickinson, Mark R.; Devlin, Hugh

    1999-06-01

    The feasibility of using laser-induced photoemission signals to distinguish between hard and soft biological tissues during photothermal ablation with a pulsed Er:YAG laser has been investigated. Time-resolved emission spectroscopy indicated a threshold fluence of approximately 35 J/cm2 to regularly initiate photoemission from dental enamel, while no emission was detected from porcine muscle tissue with incident laser fluences of up to approximately 140 J/cm2. The delay time of an emission signal with respect to the incident, ablative Er:YAG laser pulse was found to decrease from approximately 150 microseconds near the emission threshold fluence to approximately 60 microseconds at the highest fluence level used. Optical multichannel analyzer spectroscopy of Er:YAG irradiated enamel demonstrated that photoemissions typically consisted of a broad, continuous background in the visible region, with superimposed peaks arising from the presence of elements including calcium, characteristic of plasma emission either from the sample surface or emission plume.

  4. Photoluminescent zinc oxide polymer nanocomposites fabricated using picosecond laser ablation in an organic solvent

    Science.gov (United States)

    Wagener, Philipp; Faramarzi, Shamsolzaman; Schwenke, Andreas; Rosenfeld, Rupert; Barcikowski, Stephan

    2011-06-01

    Nanocomposites made of ZnO nanoparticles dispersed in thermoplastic polyurethane were synthesized using picosecond laser ablation of zinc in a polymer-doped solution of tetrahydrofuran. The pre-added polymer stabilizes the ZnO nanoparticles in situ during laser ablation by forming a polymer shell around the nanoparticles. This close-contact polymer shell has a layer thickness up to 30 nm. Analysis of ZnO polyurethane nanocomposites using optical spectroscopy, high resolution transmission electron microscopy and X-ray diffraction revealed that oxidized and crystalline ZnO nanoparticles were produced. Those nanocomposites showed a green photoluminescence emission centred at 538 nm after excitation at 350 nm, which should be attributed to oxygen defects generated during the laser formation mechanism of the monocrystalline nanoparticles. Further, the influence of pulse energy and polymer concentration on the production rate, laser fluence and energy-specific mass productivity was investigated.

  5. Optical transmission and laser ablation of pathologically changed eye lens capsule

    Energy Technology Data Exchange (ETDEWEB)

    Gamidov, A A; Bolshunov, A V [Research Institute of Eye Diseases, Russian Academy of Medical Sciences, Moscow (Russian Federation); Yuzhakov, A V; Shcherbakov, E M; Baum, O I; Sobol, E N [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation)

    2015-02-28

    Optical transmission and ablation mechanisms in the secondary cataract films under the impact of 1.06-mm laser radiation are studied. The comparison of incident and transmitted (paraxial) radiation power at different values of the power density is carried out for two types of the eye lens capsule tissue (hard and soft) possessing different optical and mechanical properties. It is found that the effective attenuation coefficient for soft films is almost five times as large as that for the hard ones. The obtained measurement data on the transparency variation in the process of laser action allow the temperature evaluation and the determination of dominant mechanism of laser ablation, as well as the development of recommendations, providing the prevention or reduction of possible side effects. The obtained results can be used to optimise the regimes of laser impact in the process of the opacified lens capsule removal.

  6. 3D transient model to predict temperature and ablated areas during laser processing of metallic surfaces

    Science.gov (United States)

    Naghshine, Babak. B.; Kiani, Amirkianoosh

    2017-02-01

    Laser processing is one of the most popular small-scale patterning methods and has many applications in semiconductor device fabrication and biomedical engineering. Numerical modelling of this process can be used for better understanding of the process, optimization, and predicting the quality of the final product. An accurate 3D model is presented here for short laser pulses that can predict the ablation depth and temperature distribution on any section of the material in a minimal amount of time. In this transient model, variations of thermal properties, plasma shielding, and phase change are considered. Ablation depth was measured using a 3D optical profiler. Calculated depths are in good agreement with measured values on laser treated titanium surfaces. The proposed model can be applied to a wide range of materials and laser systems.

  7. Microsecond enamel ablation with 10.6μm CO2 laser radiation

    Science.gov (United States)

    Góra, W. S.; McDonald, A.; Hand, D. P.; Shephard, J. D.

    2016-02-01

    Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold

  8. Contribution of material’s surface layer on charge state distribution in laser ablation plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kumaki, Masafumi, E-mail: rogus@asagi.waseda.jp [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198 (Japan); Steski, Dannie; Kanesue, Takeshi [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Ikeda, Shunsuke [Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198 (Japan); Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Kanagawa 226-8503 (Japan); Okamura, Masahiro [Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198 (Japan); Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Washio, Masakazu [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)

    2016-02-15

    To generate laser ablation plasma, a pulse laser is focused onto a solid target making a crater on the surface. However, not all the evaporated material is efficiently converted to hot plasma. Some portion of the evaporated material could be turned to low temperature plasma or just vapor. To investigate the mechanism, we prepared an aluminum target coated by thin carbon layers. Then, we measured the ablation plasma properties with different carbon thicknesses on the aluminum plate. The results showed that C{sup 6+} ions were generated only from the surface layer. The deep layers (over 250 nm from the surface) did not provide high charge state ions. On the other hand, low charge state ions were mainly produced by the deeper layers of the target. Atoms deeper than 1000 nm did not contribute to the ablation plasma formation.

  9. Production of microscale particles from fish bone by gas flow assisted laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Boutinguiza, M.; Lusquinos, F.; Comesana, R.; Riveiro, A.; Quintero, F. [Dpto. Fisica Aplicada, Universidad de Vigo, ETSI Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain); Pou, J. [Dpto. Fisica Aplicada, Universidad de Vigo, ETSI Industriales, Lagoas-Marcosende 9, 36310 Vigo (Spain)], E-mail: jpou@uvigo.es

    2007-12-15

    Recycled wastes from fish and seafood can constitute a source of precursor material for different applications in the biomedical field such as bone fillers or precursor material for bioceramic coatings to improve the osteointegration of metallic implants. In this work, fish bones have been used directly as target in a laser ablation system. A pulsed Nd:YAG laser was used to ablate the fish bone material and a transverse air flow was used to extract the ablated material out of the interaction zone. The particles collected at a filter were in the micro and nanoscale range. The morphology as well as the composition of the obtained particles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results reveal that the composition of the analyzed particles is similar to that of the inorganic part of the fish bone.

  10. Preparation of silver nanoparticles in virgin coconut oil using laser ablation

    Science.gov (United States)

    Zamiri, Reza; Azmi, B Z; Sadrolhosseini, Amir Reza; Ahangar, Hossein Abbastabar; Zaidan, A W; Mahdi, M A

    2011-01-01

    Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10−8, 1.6 × 10−8, 2.4 × 10−8, respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method. PMID:21289983

  11. Plasmonic angular tunability of gold nanoparticles generated by fs laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Pace, M.L.; Guarnaccio, A.; Ranù, F. [CNR, ISM UOS Tito Scalo, Zona Industriale, Tito Scalo (PZ) 85050 (Italy); Trucchi, D. [CNR, ISM UOS Montelibretti, Via Salaria km 29.300, Monterotondo Scalo, (RM) 00015 (Italy); Orlando, S., E-mail: stefano.orlando@ism.cnr.it [CNR, ISM UOS Tito Scalo, Zona Industriale, Tito Scalo (PZ) 85050 (Italy); Mollica, D.; Parisi, G.P. [CNR, ISM UOS Tito Scalo, Zona Industriale, Tito Scalo (PZ) 85050 (Italy); Medici, L.; Lettino, A. [CNR, IMAA, Area della Ricerca di Potenza -Zona Industriale, Tito Scalo, (PZ) 85050 (Italy); De Bonis, A.; Teghil, R. [Dipart. di Scienze,Università della Basilicata, Viale dell’Ateneo Lucano 10, Potenza, 85100 (Italy); Santagata, A. [CNR, ISM UOS Tito Scalo, Zona Industriale, Tito Scalo (PZ) 85050 (Italy)

    2016-06-30

    Highlights: • fs pulsed laser ablation as a technique to produce nanoparticles. • Nanoparticle distribution as an evidence for plasmonic tunable resonances. • Correlation between angular distribution of deposited nanoparticles and specific plasmonic resonances. - Abstract: With the aim to study the influence of deposition parameters on the plasmonic properties of gold (Au) nanoparticles (NPs) deposited by ultra-short ablation, we have focused our attention in evaluating how their size distribution can be varied. In this work, the role played by the NPs’ angular distribution, agglomeration and growth is related to the resulting optical properties. UV–vis-NIR absorption spectra together with Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray microdiffraction observations are presented in order to show how the angular distribution of fs laser ablation and deposition of Au NPs provides different plasmonic properties which can be beneficial for several aims, from optoelectronic to biosensor applications.

  12. Single-shot and single-spot measurement of laser ablation threshold for carbon nanotubes

    CERN Document Server

    Lednev, Vasily N; Obraztsova, Elena D; Kudryashov, Sergey I; Bunkin, Alexey F

    2013-01-01

    A simple and convenient procedure for single-shot, single-spot ablation threshold measurement has been developed. It is based on the employment of cylindrical lens to obtain elliptical Gaussian laser spot. The ablated spot chords which are parallel to the minor axis were measured across the spot major axis which is proportional to the fluence cross-section thus providing wide range dependence of damaged spot size versus fluence in one spot measurement. For both conventional and new-developed procedures the ablation threshold for typical Nd:YAG laser parameters (1064 nm, 10 ns) has been measured as 50 mJ/cm2 which is one order of magnitude lower than that for a bulk graphite.

  13. Femtosecond pulsed laser ablation of molybdenum carbide: Nanoparticles and thin film characteristics

    Science.gov (United States)

    De Bonis, A.; Santagata, A.; Sansone, M.; Rau, J. V.; Mori, T.; Teghil, R.

    2013-08-01

    In this paper we have used pulsed laser deposition (PLD) technique to ablate a Mo2C target in vacuum by using an ultra-short pulse laser, with a 250 fs pulse duration, carrying out the study of both plasma and film characteristics. The aim of the work is to connect the film structure and morphology to the characteristics of the nanoparticles found in the plasma produced by the target ablation. To analyze the plasma we have used ICCD fast imaging and optical emission spectroscopy while the films have been characterized by X-ray diffraction, scanning electron microscopy and atomic force spectroscopy. The obtained results have been interpreted considering an ablation model which justifies the emission of molten nanoparticles directly from the target.

  14. Preparation of silver nanoparticles in virgin coconut oil using laser ablation.

    Science.gov (United States)

    Zamiri, Reza; Azmi, B Z; Sadrolhosseini, Amir Reza; Ahangar, Hossein Abbastabar; Zaidan, A W; Mahdi, M A

    2011-01-07

    Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10(-8), 1.6 × 10(-8), 2.4 × 10(-8), respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method.

  15. Effects of femtosecond laser ablation on the surface morphology and microstructure of a bulk TiCuPdZr glass alloy

    Institute of Scientific and Technical Information of China (English)

    WANG Hongshui; LIANG Chunyong; CHEN Xueguang; WANG Lei; YANG Yang; YANG Jianjun; ZHU Shengli; LI Changyi

    2009-01-01

    The effects of femtosecond laser ablation on the surface characteristics and microstructure of a bulk TiCuPdZr glass alloy were investigated. The heat influence zone of femtosecond laser ablated with a laser energy of 100 μJ exhibits a ripple-like feather, while a porous structure appears on the surface of the specimen ablated by a 200 μJ femtosecond laser. The contents of Ti, Zr, and Pd on the ablated surface decrease and that of Cu increases with increasing laser energy. The crystallization process occurs on the glass alloy specimens during femtosecond laser ablation, and the crystallinity of a 100 μJ femtosecond laser-ablated specimen is greater than that of a 200 μJ femtosecond laser-ablated one.

  16. Laser-induced breakdown spectroscopy for on-line control of selective removal of cobalt binder from tungsten carbide hardmetal by pulsed UV laser surface ablation

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-09-01

    Laser-induced breakdown spectroscopy (LIBS) was successfully used in on-line control of selective removal of cobalt from tungsten carbide hardmetal by pulsed UV laser surface ablation. The dependence of LIBS on number of laser shots was investigated at different laser fluences. The optimal laser fluence of 2.5 J/cm 2 suited for selective removal of cobalt from surface layer of hardmetal was confirmed. The result sample was also subject to different post-examinations to evaluate the feasibility of the application of LIBS in this laser ablation process. It was demonstrated that, monitoring of the emission intensity of cobalt lines could be used as a control parameter for selective removal of cobalt from surface layer of hardmetal by pulsed UV laser. The on-line implementation of the spectroscopic technique LIBS to the surface-ablation process provided important information about the optimal-ablation parameters.

  17. Ablation from artificial or laser-induced crater surfaces of silver by laser irradiation at 355 nm

    DEFF Research Database (Denmark)

    Toftmann, B.; Schou, Jørgen; Larsen, N.B.

    1999-01-01

    The angular distribution of laser ablated particles from silver irradiated at 355 nm has been studied. The angular distribution from craters prepared by more than 10(4) shots exhibits only minor changes compared with that from a nonirradiated target. The distribution from artificial cylindrical...

  18. Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

    2016-06-01

    Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1–10 Hz) at various laser fluences ranging from 0.2 to 11 J cm{sup −2} is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He–Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm{sup −2} and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm{sup −2}. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

  19. Femtosecond Laser Ablation of Solid Targets using Gaussian and Vortex Beams

    OpenAIRE

    Kiliyanamkandy, Anoop

    2015-01-01

    This thesis presents a detailed investigation of laser ablation of solid targets with femtosecond (fs) pulses, focusing on three prominent aspects: 1) spatial and temporal evolution of the laser produced plume, in high vacuum condition; 2) nanoparticles generation in high vacuum and applications of nanostructured films in material science; 3) surface micro/nanostructure formation, in ambient condition. Most of the experiments were carried out on pure copper and silicon targets, and some of th...

  20. Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

    Science.gov (United States)

    Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

    2016-06-01

    Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1-10 Hz) at various laser fluences ranging from 0.2 to 11 J cm-2 is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He-Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm-2 and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm-2. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

  1. Investigation of pulsed laser ablation process of Hg0.8Cd0.2Te

    Institute of Scientific and Technical Information of China (English)

    Xinling Zhou; Chuansong Chen; Baoyuan Man; Juan Guo

    2007-01-01

    The vaporization threshold was measured under the irradiation of 1.064-μm, 10-ns pulsed laser. Then we calculated the vaporization temperature based on the conservation law of energy and analyzed the vaporization time based on our established model. These results coincided well with the information from the micrograph of scanning electron microscope (SEM) and the spectra of the plasma. Besides, the laser ablation rate was also computed and discussed theoretically.

  2. Tuning Optical Nonlinearity of Laser-Ablation-Synthesized Silicon Nanoparticles via Doping Concentration

    Directory of Open Access Journals (Sweden)

    Lianwei Chen

    2014-01-01

    Full Text Available Silicon nanoparticles at different doping concentrations are investigated for tuning their optical nonlinear performance. The silicon nanoparticles are synthesized from doped silicon wafers by pulsed laser ablation. Their dispersions in water are studied for both nonlinear absorption and nonlinear refraction properties. It is found that the optical nonlinear performance can be modified by the doping concentration. Nanoparticles at a higher doping concentration exhibit better saturable absorption performance for femtosecond laser pulse, which is ascribed to the free carrier absorption mechanism.

  3. MRI-guided percutaneous laser ablation of small renal cell carcinoma: Initial clinical experience

    Energy Technology Data Exchange (ETDEWEB)

    Kariniemi, Juho; Ojala, Risto; Hellstroem, Pekka; Sequeiros, Roberto Blanco (Dept. of Radiology, Dept. of Surgery, Oulu Univ. Hospital, Oulu (Finland)), e-mail: juho.kariniemi@oulu.fi

    2010-05-15

    Background: The number of detected small renal cell carcinomas (RCCs) has been rising, largely due to advances in imaging. Open surgical resection is the standard management of small RCCs; however, imaging-guided percutaneous ablative therapies have emerged as a minimally invasive treatment alternative, especially for patients who are poor candidates for surgery. Purpose: To evaluate the initial clinical experience of magnetic resonance imaging (MRI)-guided percutaneous laser ablation of small RCCs. Material and Methods: Eight patients with 10 tumors were treated with percutaneous MRI-guided laser ablation. All tumors (diameter range 1.5-3.8 cm, mean 2.7 cm) were biopsy-proven RCCs. By using a 0.23 T open MRI system and general anesthesia in patients, one to four (mean 2.6) laser fibers were placed and the tumors were ablated under near real-time MRI control by observing the signal void caused by the temperature change in the heated tissue. The treatment was considered successful if the tumor showed no contrast enhancement at follow-up imaging. Results: All except one tumor were successfully ablated in one session. The first patient treated showed enhancing residual tumor in post-procedural MRI; she has thus far declined retreatment. One complication, a myocardial infarction, occurred; all other patients tolerated the procedure well. No local recurrence was discovered during the follow-up (range 12-30 months, mean 20 months). Conclusion: In this small group of patients with relatively short follow-up period, MRI-guided percutaneous laser ablation proved to be a promising treatment option for small RCCs

  4. The impact of laser ablation on optical soft tissue differentiation for tissue specific laser surgery-an experimental ex vivo study

    Directory of Open Access Journals (Sweden)

    Stelzle Florian

    2012-06-01

    Full Text Available Abstract Background Optical diffuse reflectance can remotely differentiate various bio tissues. To implement this technique in an optical feedback system to guide laser surgery in a tissue-specific way, the alteration of optical tissue properties by laser ablation has to be taken into account. It was the aim of this study to evaluate the general feasibility of optical soft tissue differentiation by diffuse reflectance spectroscopy under the influence of laser ablation, comparing the tissue differentiation results before and after laser intervention. Methods A total of 70 ex vivo tissue samples (5 tissue types were taken from 14 bisected pig heads. Diffuse reflectance spectra were recorded before and after Er:YAG-laser ablation. The spectra were analyzed and differentiated using principal component analysis (PCA, followed by linear discriminant analysis (LDA. To assess the potential of tissue differentiation, area under the curve (AUC, sensitivity and specificity was computed for each pair of tissue types before and after laser ablation, and compared to each other. Results Optical tissue differentiation showed good results before laser exposure (total classification error 13.51%. However, the tissue pair nerve and fat yielded lower AUC results of only 0.75. After laser ablation slightly reduced differentiation results were found with a total classification error of 16.83%. The tissue pair nerve and fat showed enhanced differentiation (AUC: 0.85. Laser ablation reduced the sensitivity in 50% and specificity in 80% of the cases of tissue pair comparison. The sensitivity of nerve–fat differentiation was enhanced by 35%. Conclusions The observed results show the general feasibility of tissue differentiation by diffuse reflectance spectroscopy even under conditions of tissue alteration by laser ablation. The contrast enhancement for the differentiation between nerve and fat tissue after ablation is assumed to be due to laser removal of the

  5. Spatial and Temporal Investigations of Laser Ablation Plasma Plume Density and Composition

    Science.gov (United States)

    Iratcabal, Jeremy; Bach, Bernhard; Beatty, Cuyler; Dutra, Eric; Darling, Timothy; Wiewior, Piotr; Covington, Aaron

    2016-10-01

    Laser ablation of solid targets with laser intensities of the order of 108-1011 W/cm2 provides a rich platform for investigating the density and composition of coexisting molecular, atomic, and ion species in the resulting plasma plume. Experiments measuring the spatial- and temporal-evolution of laser ablation plumes have been performed to simultaneously characterize the multiple parameters related to the energy and momentum partitioning of the incident laser energy as the ablation process occurs. The temperature, density, and relative populations of different molecular, atomic, and ion species can be determined by the simultaneous measurement of optical and charged particle spectroscopy, fast imaging cameras, and optical interferometric diagnostics. Additionally, background gas pressure, density, and species were carefully varied. A comparison of density measurements obtained with multiple interferometric, spectroscopic, and fast imaging diagnostics for a carbon ablation plume expanding into vacuum and into background gases with different Reynolds numbers will be presented. Atomic, molecular, and ion species population evolution will be presented as measured with optical and charged particle spectroscopy. This work was supported by the U.S. DOE NNSA Cooperative Agreement No. DE-NA0002075 and National Securities Technologies, LLC under Contract No. DE-AC52-06NA25946/subcontract No. 165819.

  6. Influence of the atomic mass of the background gas on laser ablation plume propagation

    DEFF Research Database (Denmark)

    Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

    2008-01-01

    A combination of time-of-flight ion probe measurements and gas dynamical modeling has been used to investigate the propagation of a laser ablation plume in gases of different atomic/molecular weight. The pressure variation of the ion time-of-flight was found to be well described by the gas dynami...

  7. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation

    NARCIS (Netherlands)

    C.W.M. van der Geld (Cees); R.R. van den Bos (Renate); P.W.M. van Ruijven (Peter); T.E.C. Nijsten (Tamar); H.A.M. Neumann (Martino); M.J.C. van Gemert (Martin)

    2010-01-01

    textabstractEndovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport mai

  8. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation

    NARCIS (Netherlands)

    van der Geld, C.W.M.; van den Bos, R.R.; van Ruijven, P.W.M.; Nijsten, T.; Neumann, H.A.M.; van Gemert, M.J.C.

    2010-01-01

    Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a con

  9. Fabrication of fluorescent nanoparticles of dendronized perylenediimide by laser ablation in water

    NARCIS (Netherlands)

    Yasukuni, R.; Asahi, T.; Sugiyama, T.; Masuhara, H.; Sliwa, M.; Hofkens, J.; De Schryver, F. C.; Van der Auweraer, M.; Herrmann, A.; Mueller, K.; Müllen, K.

    2008-01-01

    Highly fluorescent organic nanoparticles with size of about 300 nm were prepared by nanosecond laser ablation of micrometer-sized powder of dendronized perylenediimide dispersed in water. The nanoparticle colloidal solution provided a fluorescence quantum yield of 0.58. The absorption and emission s

  10. Angle-resolved energy distributions of laser ablated silver ions in vacuum

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1998-01-01

    The energy distributions of ions ablated from silver in vacuum have been measured in situ for pulsed laser irradiation at 355 nm. We have determined the energy spectra for directions ranging from 5 degrees to 75 degrees with respect to the normal in the intensity range from 100 to 400 MW/cm(2...

  11. Magnetic trapping of superconducting submicron particles produced by laser ablation in superfluid helium

    Science.gov (United States)

    Takahashi, Yuta; Suzuki, Junpei; Yoneyama, Naoya; Tokawa, Yurina; Suzuki, Nobuaki; Matsushima, Fusakazu; Kumakura, Mitsutaka; Ashida, Masaaki; Moriwaki, Yoshiki

    2017-02-01

    We produced spherical superconducting submicron particles by laser ablation of their base metal tips in superfluid helium, and trapped them using a quadrupole magnetic field owing to the diamagnetism caused by the Meissner effect. We also measured their critical temperatures of superconductivity, by observing the threshold temperatures for the confinement of superconducting submicron particles in the trap.

  12. Femtosecond pulse laser ablation of chromium: experimental results and two-temperature model simulations

    Science.gov (United States)

    Saghebfar, M.; Tehrani, M. K.; Darbani, S. M. R.; Majd, A. E.

    2017-01-01

    In this work, the results of experimental and computational single- and multi-shot ablation threshold and the incubation effect of chromium metal sample, irradiated by ultrashort laser pulses, are presented. The experimental value of the ablation threshold is determined based on D2 method by measuring the outer ablation crater diameters as a function of incident laser pulse energy using 800 nm, 30 fs, laser pulses. The value of 0.19 ± 0.04 (J/cm2 ), is obtained for the single-shot ablation threshold fluence. The experimental results are compared with time-dependent heat flow calculations based on the two-temperature model and the effect of number and separation time of two consecutive laser pulses with the same total fluence is studied for the Cr target. Moreover, the role of pulse width and absorbed fluence in thermal equilibrium time between electrons and lattice is investigated in two-temperature model. The thermal equilibrium between electron and lattice is established after a few picoseconds for low fluences and after a few tens of picoseconds at higher fluences.

  13. Atomistic simulation of laser ablation of gold : Effect of pressure relaxation

    NARCIS (Netherlands)

    Norman, G. E.; Starikov, S. V.; Stegailov, V. V.

    2012-01-01

    The process of ablation of a gold target by femto- and picosecond laser radiation pulses has been studied by numerical simulations using an atomistic model with allowance for the electron subsystem and the dependence of the ion-ion interaction potential on the electron temperature. Using this potent

  14. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation

    NARCIS (Netherlands)

    van der Geld, C.W.M.; van den Bos, R.R.; van Ruijven, P.W.M.; Nijsten, T.; Neumann, H.A.M.; van Gemert, M.J.C.

    2010-01-01

    Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a con

  15. Endovenous laser ablation (EVLA): a review of mechanisms, modeling outcomes, and issues for debate

    NARCIS (Netherlands)

    W.S.J. Malskat (Wendy S.); A.A. Poluektova (Anna); C.W.M. van der Geld (Cees); H.A.M. Neumann (Martino); R.A. Weiss (Robert); C.M.A. Bruijninckx; M.J.C. van Gemert (Martin)

    2013-01-01

    textabstractEndovenous laser ablation (EVLA) is a commonly used and very effective minimally invasive therapy to manage leg varicosities. Yet, and despite a clinical history of 16 years, no international consensus on a best treatment protocol has been reached so far. Evidence presented in this paper

  16. Towards nanopatterning by femtosecond laser ablation of pre-stretched elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Surdo, Salvatore; Piazza, Simonluca; Ceseracciu, Luca; Diaspro, Alberto; Duocastella, Martí, E-mail: marti.duocastella@iit.it

    2016-06-30

    Graphical abstract: - Highlights: • We present a new approach to increase the focusing capabilities of optical systems. • Laser patterning is performed over a stretched elastomeric membrane. • After releasing stress, patterns shrink according to the applied strain. • Minimum feature size is controlled by strain, enabling sub-diffraction patterning. - Abstract: Diffraction limits the focusing capabilities of an optical system seriously constraining the use of lasers for nanopatterning. In this work, we present a novel and simple approach to reduce the minimum feature size of a laser-direct write system by ablating a pre-stretched material. In particular, by focusing and scanning a femtosecond laser beam on the surface of a uniaxially pre-stretched elastomeric membrane we are able to obtain microstructures according to a desired pattern. After removing the stress applied to the elastomer, the membrane relaxes to its original size and the ablated patterns shrink while preserving their shape. In this way, the minimum feature size that is typically determined by the optical properties of the focusing system can be now controlled by the strain applied to the elastomer during the ablation process. We demonstrate this approach by ablating lines on a stretchable polymeric membrane at different strain conditions. Experimental results are in good agreement with theoretical predictions. The proposed method opens up new interesting possibilities for the rapid prototyping of micro- and nano-structures suitable for a wide range of applications such as soft-lithography, micro-/nano-fluidics and lab-on-chip.

  17. Transparent conducting AZO and ITO films produced by pulsed laser ablation at 355 nm

    DEFF Research Database (Denmark)

    Thestrup, B.; Schou, Jørgen

    1999-01-01

    Thin films of aluminium-doped zinc oxide (AZO) and indium tin oxide (ITO) were deposited on glass substrates by laser ablation in an oxygen environment. The electrical and optical properties of films grown at various oxygen pressures were compared. With no substrate heating, highly transparent...

  18. Photodynamic therapy using upconversion nanoparticles prepared by laser ablation in liquid

    Energy Technology Data Exchange (ETDEWEB)

    Ikehata, Tomohiro; Onodera, Yuji; Nunokawa, Takashi [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Hirano, Tomohisa; Ogura, Shun-ichiro; Kamachi, Toshiaki [Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Odawara, Osamu [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Wada, Hiroyuki, E-mail: wada.h.ac@m.titech.ac.jp [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan)

    2015-09-01

    Highlights: • Highly crystalline upconversion nanoparticles were prepared by laser ablation in liquid. • Highly transparent near-IR irradiation generated singlet oxygen. • Viability of cancer cells was significantly decreased by near-IR irradiation. - Abstract: Upconversion nanoparticles were prepared by laser ablation in liquid, and the potential use of the nanoparticles for cancer treatment was investigated. A Nd:YAG/SHG laser (532 nm, 13 ns, 10 Hz) was used for ablation, and the cancer treatment studied was photodynamic therapy (PDT). Morphology and crystallinity of prepared nanoparticles were examined by transmission electron microscopy and X-ray diffraction. Red and green emissions resulting from near-infrared excitation were observed by a fluorescence spectrophotometer. Generation of singlet oxygen was confirmed by a photochemical method using 1,3-diphenylisobenzofuran (DPBF). In vitro experiments using cultivated cancer cells were conducted to investigate PDT effects. Uptake of the photosensitizer by cancer cells and cytotoxicities of cancer cells were also examined. We conclude that the combination of PDT and highly crystalline nanoparticles, which were prepared by laser ablation in liquid, is an effective cancer treatment.

  19. Evolution of the plasma parameters in the expanding laser ablation plume of silver

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Schou, Jørgen; Hansen, T.N.;

    2002-01-01

    The angular and radial variation of the ion density and electron temperature in the plasma plume produced by laser ablation of silver at fluences of 0.8-1.3 J cm(-2) at 355 nm have been studied using a time-resolving Langmuir probe. The angular dependence of the electron temperature and the magni...

  20. The use of ablative lasers in the treatment of facial melasma*

    Science.gov (United States)

    de Morais, Orlando Oliveira; Lemos, Érica Freitas Lima; Sousa, Márcia Carolline dos Santos; Gomes, Ciro Martins; Costa, Izelda Maria Carvalho; de Paula, Carmen Déa Ribeiro

    2013-01-01

    Melasma represents a pigmentary disorder that is difficult to treat. This study aims to broadly review the use of ablative lasers (Er:YAG and CO2) in the treatment of melasma, presenting the level of evidence of studies published to date. A total of 75 patients were enrolled in four case series studies (n=39), one controlled clinical trial (n=6) and one randomized controlled clinical trial (n=30). Studies on the Er:YAG laser showed better results with the use of short square-shaped pulses, which determined low rates of post-inflammatory hyperpigmentation and long-lasting maintenance of results. Likewise, studies on the CO2 laser proved the benefits of short pulse duration along with low-density energy. Post-treatment maintenance with the use of antipigmenting creams was necessary and effective to sustain long-term results. Ablative lasers may represent another useful and effective tool against melasma. Postinflammatory hyperpigmentation and difficulty in sustaining long-term results still represent the main limitations to a broader use of ablative lasers. Based on actual evidence, the use of this technology should be restricted to patients with recalcitrant disease. Further studies will help establish optimal laser parameters and treatment regimens. PMID:23739704

  1. A comparison of the DPSS UV laser ablation characteristic of 1024 and H10F WC-Co

    Science.gov (United States)

    See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

    2017-07-01

    An investigation on ablation characteristics of 1024 and H10F cobalt cemented tungsten carbide (WC-Co) with a DPSS nanosecond UV laser (50 ns pulse width, 355 nm wavelength, 90 W average power and 10 kHz repetition rate) is presented. The ablation characteristic parameters such as ablation threshold, incubation effect and optical penetration depth were evaluated based on the spot ablation diameter and depth. It was observed that the ablation threshold is significantly influenced by the number of pulses (NOP) and it decreases with increase NOP which is attributed to the incubation effect. Only one ablation region is observed at low laser fluence and an additional molten ablation region is observed at high laser fluence accompanied with cracks. The cracks formation is due to the thermal induced stress and changes in WC microstructure during laser beam irradiation. The crack depth is proportional to the thickness of the molten WC region. The ablation threshold of 1024 WC-Co and H10F WC-Co were found to be Fth1 =4.32 J/cm2 and Fth1 =4.26 J/cm2 respectively. The difference in chemical composition has insignificant effect on the ablation threshold value of the material. The incubation factor and optical penetration depth values of 1024 WC-Co and H10F WC-Co were found to be ξ=0.73, α-1 =411 nm and ξ=0.75, α-1 =397 nm respectively.

  2. In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer

    Science.gov (United States)

    Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

    2012-01-01

    A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

  3. Study of fractional ablative laser in surgical and post traumatic scar

    Directory of Open Access Journals (Sweden)

    Nagat Sobhy

    2012-07-01

    Full Text Available Introduction: Ablative, fractional lasers generate microscopic columns of coagulated tissue through the epidermis and dermis to evoke a wound healing response. In this study, we examined the efficacy and safety of fractional ablative 2940nm erbium: YAG laser in the treatment of surgical and post-traumatic scars. Fractional laser photothermolysis is the latest in the broad range of Er: YAG laser technique. This technique promises a novel means of providing treatments that would be as effective as traditional Er: YAG, while further reducing their down time and risk.Aim of the Work: The aim of this work is to assess the efficacy and safety of variable square pulse (VSP fractional Er: YAG laser for the treatment of surgical and post-traumatic scars; both clinically and histopathologically.Methods: Clinical studies were conducted on a range of surgical and post-traumatic scars with a 2940nm erbium: YAG fractional ablative laser varying energy, pulse widths, treatment passes, and number of treatments: twenty subjects, with Fitzpatrick skin types III-IV, received two to five treatments at one month interval and a follow up period for 3 months. Clinical and histopathological evaluation of the results was performed.Results: Almost all patients improved both clinically and histopathologically. Clinical improvement in scars according to investigator assessment: 40% of patients had excellent improvement of 76-100% (grade 3, 50% of patients had good improvement of 50-75% (grade 2, 10% had fair improvement of 26-49% (grade 1 at three month follow up. Histologic findings demonstrated remodeling of scar tissue with renewal and reorganization of collagen fibers in the dermis was noted two weeks post-treatment.Conclusion: These data illustrate the safety and efficacy of the 2940nm erbium:YAG fractional ablative laser in the treatment of surgical and post-traumatic scars with short down time period, and almost no incidence of complication.

  4. Ablation of polymers and composites when exposed to CO2 laser radiation (review)

    Science.gov (United States)

    Said-Galiev, É. E.; Nikitin, L. N.

    1992-03-01

    As can be seen from the data presented in this review, ablation of polymers has been studied extensively and is being used commercially as manufacturing operation. The convenience of laser technology, and in some cases its irreplacability, are not doubted in the slightest by specialists in this area. The use of CO2 lasers for dimensional working of composites based on phenyl-formaldehyde resin and various fillers is a matter of extreme interest at the present time [75]. The search for new types of polymeric binders and their application in industry make it necessary for research workers to investigate features of their behavior in a laser beam. If we consider specific manufacturing operations in which it is particularly convenient to use lasers, we may note the cutting of sheet materials [4, 69, 76], scribing, piercing holes with fine or ultrafine diameter, processing fibers, etc. [4, 76, 77], By using lasers, it is possible to avoid such undesirable effects as cracking and scaling of particularly brittle thermosetting polymers [69]. In predicting the behavior of new types of polymers in a laser beam, it is first necessary to establish their classification group (A, B, or C), their flammability, their tendency to form secondary polymeric structures, etc. The mechanism of ablation of various groups has certain features that need detailed study and refinement. At present, description of the ablation process in polymers is largely borrowed from the theory of vaporization of metals when exposed to laser radiation. The development of a specific theory of ablation of polymeric materials is a matter for the immediate future.

  5. Fabrication of CVD graphene-based devices via laser ablation for wafer-scale characterization

    DEFF Research Database (Denmark)

    Mackenzie, David; Buron, Jonas Christian Due; Whelan, Patrick Rebsdorf

    2015-01-01

    mJ cm−2 for 1064 nm, 40 mJ cm−2 for 532 nm, and 30 mJ cm−2 for 355 nmare sufficient to ablate the graphene film, while the ablation onset for Si/SiO2 (thicknesses 500 μm/302 nm) did not occur until 240 mJ cm−2, 150 mJ cm−2, and 135 mJ cm−2, respectively, allowing all wavelengths to be used...... for graphene ablation without detectable substrate damage. Optical microscopy and Raman Spectroscopy were used to assess the ablation of graphene, while stylus profilometery indicated that the SiO2 substrate was undamaged. CVDgraphene devices were electrically characterized and showed comparable field......Selective laser ablation of a wafer-scale graphene film is shown to provide flexible, high speed (1 wafer/hour) device fabrication while avoiding the degradation of electrical properties associated with traditional lithographic methods. Picosecond laser pulses with single pulse peak fluences of 140...

  6. Ultrafast laser ablation in liquids for nanomaterials and applications.

    Science.gov (United States)

    Rao, S Venugopal; Podagatlapalli, G Krishna; Hamad, Syed

    2014-02-01

    We present an inclusive overview of the ultrafast ablation technique performed in liquids. Being a comparatively new method, we bring out the recent progress achieved, present the challenges ahead, and outline the future prospects for this technique. The review is conveniently divided into five parts: (a) a succinct preamble to the technique of ultrafast ablation in liquids (ULAL) is provided. A brief introduction to the conventional ns ablation is also presented for the sake of completeness (b) fundamental physical processes involved in this technique are elaborated (c) specific advantages of the technique compared to other physical and chemical methodologies are enumerated (d) applications of this technique in photonics; biomedical and explosives detection [using surface-enhanced Raman scattering (SERS)] is updated (e) future prospects describing the potential of this technique for creating unique nanoparticles (NPs) and nanostructures (NSs) for niche applications. We also discuss some of the recently reported significant results achieved in a variety of materials, especially metals, using this technique. Furthermore, we present some of our own experimental data obtained from ULAL of Ag, Cu, and Zn in a variety of liquids such as acetone, water, acetonitrile etc. The generated NPs (colloidal solutions) and NSs (on substrates) have been successfully utilized for nonlinear optical, SERS, and biomedical applications.

  7. Dependence of ablation threshold and LIPSS formation on copper thin films by accumulative UV picosecond laser shots

    Science.gov (United States)

    Huynh, Thi Trang Dai; Semmar, Nadjib

    2014-09-01

    The ablation threshold and Laser-induced periodic surface structure (LIPSS) formation on copper thin film were investigated using a picosecond laser (Nd:YAG laser: 266 nm, 42 ps, 10 Hz). We show that the ablation threshold varies with respect to the number of laser shots ( N) on two different substrates. The single-shot ablation threshold was estimated to be close to 170 ± 20 mJ/cm2. The incubation coefficient was estimated to be 0.68 ± 0.03 for copper thin films on silicon and glass substrates. In addition, morphology changes of the ablated regions, in the same spot area, were studied as a function of fluence and number of laser shots. An intermediate structure occurred with a mix of low spatial frequency LIPSS (LSFL), high spatial frequency LIPSS (HSFL) and regular spikes at a fluence F LIPSS formation was established in the form of a 2D map.

  8. Ablation plume structure and dynamics in ambient gas observed by laser-induced fluorescence imaging spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Khumaeni, A.; Kato, M.; Wakaida, I.

    2015-08-01

    The dynamic behavior of an ablation plume in ambient gas has been investigated by laser-induced fluorescence imaging spectroscopy. The second harmonic beam from an Nd:YAG laser (0.5–6 J/cm{sup 2}) was focused on a sintered oxide pellet or a metal chip of gadolinium. The produced plume was subsequently intersected with a sheet-shaped UV beam from a dye laser so that time-resolved fluorescence images were acquired with an intensified CCD camera at various delay times. The obtained cross-sectional images of the plume indicate that the ablated ground state atoms and ions of gadolinium accumulate in a hemispherical contact layer between the plume and the ambient gas, and a cavity containing a smaller density of ablated species is formed near the center of the plume. At earlier expansion stage, another luminous component also expands in the cavity so that it coalesces into the hemispherical layer. The splitting and coalescence for atomic plume occur later than those for ionic plume. Furthermore, the hemispherical layer of neutral atoms appears later than that of ions; however, the locations of the layers are nearly identical. This coincidence of the appearance locations of the layers strongly suggests that the neutral atoms in the hemispherical layer are produced as a consequence of three-body recombination of ions through collisions with gas atoms. The obtained knowledge regarding plume expansion dynamics and detailed plume structure is useful for optimizing the experimental conditions for ablation-based spectroscopic analysis. - Highlights: • Ablated ground-state species accumulated in a thin hemispherical boundary layer • Inside the layer, a cavity containing a small density of ablated species was formed. • The hemispherical layers of atoms and ions appeared at a nearly identical location. • The measured intensity peak variation was in good agreement with a model prediction. • We ascribed the dominant process for forming the layer to a three

  9. Pulsed erbium laser ablation of hard dental tissue: the effects of atomized water spray versus water surface film

    Science.gov (United States)

    Freiberg, Robert J.; Cozean, Colette D.

    2002-06-01

    It has been established that the ability of erbium lasers to ablate hard dental tissue is due primarily to the laser- initiated subsurface expansion of the interstitial water trapped within the enamel and that by maintaining a thin film of water on the surface of the tooth, the efficiency of the laser ablation is enhanced. It has recently been suggested that a more aggressive ablative mechanism, designated as a hydrokinetic effect, occurs when atomized water droplets, introduced between the erbium laser and the surface of the tooth, are accelerated in the laser's field and impact the tooth's surface. It is the objective of this study to determine if the proposed hydrokinetic effect exists and to establish its contribution to the dental hard tissue ablation process. Two commercially available dental laser systems were employed in the hard tissue ablation studies. One system employed a water irrigation system in which the water was applied directly to the tooth, forming a thin film of water on the tooth's surface. The other system employed pressurized air and water to create an atomized mist of water droplets between the laser hand piece and the tooth. The ablative properties of the two lasers were studied upon hard inorganic materials, which were void of any water content, as well as dental enamel, which contained interstitial water within its crystalline structure. In each case the erbium laser beam was moved across the surface of the target material at a constant velocity. When exposing material void of any water content, no ablation of the surfaces was observed with either laser system. In contrast, when the irrigated dental enamel was exposed to the laser radiation, a linear groove was formed in the enamel surface. The volume of ablated dental tissue associated with each irrigation method was measured and plotted as a function of the energy within the laser pulse. Both dental laser systems exhibited similar enamel ablation rates and comparable ablated surface

  10. Detection of the Single-Session Complete Ablation Rate by Contrast-Enhanced Ultrasound during Ultrasound-Guided Laser Ablation for Benign Thyroid Nodules: A Prospective Study

    Directory of Open Access Journals (Sweden)

    Shuhua Ma

    2016-01-01

    Full Text Available This study aimed to investigate the single-session complete ablation rate of ultrasound-guided percutaneous laser ablation (LA for benign thyroid nodules. LA was performed in 90 patients with 118 benign thyroid nodules. Contrast-enhanced ultrasound (CEUS was used to evaluate complete nodule ablation one day after ablation. Thyroid nodule volumes, thyroid functions, clinical symptoms and complications were evaluated 1, 3, 6, 12, and 18 months after ablation. Results showed that all benign thyroid nodules successfully underwent LA. The single-session complete ablation rates for nodules with maximum diameters ≤2 cm, 2-3 cm and ≥3 cm were 93.4%, 70.3% and 61.1%, respectively. All nodule volumes significantly decreased than that one day after ablation (P0.05. Three patients had obvious pain during ablation; one (1.1% had recurrent laryngeal nerve injury, but the voice returned to normal within 6 months after treatment. Thus, ultrasound-guided LA can effectively inactivate benign thyroid nodules. LA is a potentially viable minimally invasive treatment that offers good cosmetic effects.

  11. Femtosecond laser ablation: Experimental study of the repetition rate influence on inductively coupled plasma mass spectrometry performance

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Jhanis J. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Fernandez, Alberto [Centro de Fisicoquimica. Escuela de Quimica, Universidad Central de Venezuela, Caracas 1020-A (Venezuela); Oropeza, Dayana; Mao Xianglei [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Russo, Richard E. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)], E-mail: RERusso@lbl.gov

    2008-02-15

    This paper demonstrates the feasibility of performing bulk chemical analysis based on laser ablation for good lateral resolution with only nominal mass ablated per pulse. The influence of repetition rate (1-1000 Hz) and scan speed (1-200 {mu}m/s) using a low energy (30 {mu}J) and a small spot size ({approx} 10 {mu}m) UV-femtosecond laser beam was evaluated for chemical analysis of silica glass samples, based on laser ablation sampling and inductively coupled plasma mass spectrometry (ICP-MS). Accuracy to approximately 14% and precision of 6% relative standard deviation (RSD) were measured.

  12. Femtosecond laser surface ablation of transparent solids: understanding the bulk filamentation damage

    Science.gov (United States)

    Kudryashov, Sergey I.; Joglekar, A.; Mourou, G.; Ionin, A. A.; Zvorykin, V. D.; Hunt, A. J.

    2007-06-01

    Direct SEM examination reveals a complex nanoscale structure of deep narrow central channels within shallow wide external craters produced by single-shot high-intensity femtosecond laser radiation on Corning 0211 glass and sapphire surfaces. These internal narrow channels are not expected from ordinary surface melt spallation and expulsion processes characteristic of the external surface nanocraters, but exhibit nearly the same appearance threshold. Surprisingly, the nanochannel radiuses rapidly saturate versus incident laser intensity indicating bulk rather than surface character of laser energy deposition, in contrast to the external craters extending versus laser intensity in a regular manner. These facts may be explained by channeling of electromagnetic radiation by near-surface ablative filamentary propagation of intense femtosecond laser pulses in the highly electronically excited dielectrics, by spherical aberrations in the surface layer, or deep drilling of the samples by short-wavelength Bremsstrahlung radiation of relatively hot surface electron-hole or electron-ion plasma. The double structure of ablated surface nano-features is consistent with similar structures observed for bulk damage features fabricated by femtosecond laser pulses at supercritical laser powers, but much lower laser intensities.

  13. Synthesis of silver nanoparticles by laser ablation in ethanol: A pulsed photoacoustic study

    Energy Technology Data Exchange (ETDEWEB)

    Valverde-Alva, M.A., E-mail: azbmiguel@gmail.com [Posgrado en Ciencia e Ingeniería de Materiales, Universidad Nacional Autónoma de México (UNAM), México D.F., C.P. 04510, México (Mexico); García-Fernández, T. [Universidad Autónoma de la Ciudad de México (UACM), Prolongación San Isidro 151, Col. San Lorenzo Tezonco, México D.F., C.P. 09790, México (Mexico); Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R. [CCADET Universidad Nacional Autónoma de México (UNAM), México D.F., C.P. 04510, México (Mexico); Esparza-Alegría, E. [Facultad de Ciencias, Universidad Nacional Autónoma de México (UNAM), México D.F., C.P. 04510, México (Mexico); Sánchez-Valdés, C.F. [Instituto Potosino de Investigación Científica y Tecnológica A.C., Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P., C.P. 78216, México (Mexico); and others

    2015-11-15

    Graphical abstract: - Highlights: • Pulsed photoacoustic technique allowed to determine the production rate of NPs. • Pulsed photoacoustic technique allows to determine the Ag concentration in colloids. • The nanoparticles production rate drops quickly during the first laser pulses. • Nanoparticles production rate is almost constant after few hundreds of laser shots. • Photoacoustic signal amplitude was proportional to fluence on the target surface. - Abstract: The pulsed photoacoustic (PA) technique was used to study the synthesis by laser ablation of silver nanoparticles (Ag-NPs) in ethanol. PA technique allowed to determine the production rate per laser pulse and concentration of synthesized Ag-NPs. The samples were produced by using a pulsed Nd:YAG laser with 1064 nm of wavelength and 7 ns of pulse duration. The laser pulse energy varied from 10 to 100 mJ. Transmission electron microscopy micrographs demonstrated that the obtained nanoparticles were spherical with an average size close to 10 nm. The absorption spectra of the colloids showed a plasmon absorption peak around 400 nm. The PA analyses showed a significant reduction of the production rate of Ag-NPs during the first hundreds of laser pulses. For a higher number of pulses this rate was kept almost constant. Finally, we found that the root mean square (RMS) value of the PA signal was proportional to the laser pulse fluence on the target surface. Thus PA technique was useful to monitor the ablation process.

  14. Study of Laser Ablation Plumes in 1-MA Z-Pinch Experiments

    Science.gov (United States)

    Anderson, Austin; Dutra, Eric; McKee, Erik; Beatty, Cuyler; Darling, Timothy; Ivanov, Vladimir; Wiewior, Piotr; Chalyy, Oleksandr; Asttanovitskiy, Alexey; Nalajala, Vidya; Dmitriev, Oleg; Covington, Aaron

    2016-10-01

    Laser ablation plumes have been explored as a vehicle for pinch experiments and pulsed neutron production at the NTF research facility. The laser ablation plume is generated by striking a target with a 20J, 0.8ns laser pulse from the Leopard laser. The plume is allowed to expand and then pinched by a 1 MA current generated by the Zebra pulsed power machine. The plume is compact and pre-ionized, offering an advantage over neutral gas puffs and wire arrays. When used with deuterated-polyethylene targets, pinched ablation plumes can generate a pulse of 1011 neutrons with a 35 ns pulse width. A laser-based 532 nm Mach-Zender interferometer and 16 frame imaging with 5 ns temporal resolution are used to characterize plasma density and observe implosion dynamics. Cathode activation was also measured post shot and has been used to determine the deuteron currents produced in the shots. Results and discussion are presented. This work was supported by the U.S. DOE NNSA Cooperative Agreement No. DE-NA0002075 and National Securities Technologies, LLC under Contract No. DE-AC52-06NA25946/subcontract No. 165819.

  15. Effect of carbon dioxide laser ablation followed by intralesional steroids on keloids

    Directory of Open Access Journals (Sweden)

    Gaurav A Garg

    2011-01-01

    Full Text Available Abstract : Keloid is a difficult-to-treat condition and an ideal treatment modality is not available. Carbon dioxide (CO 2 laser is one of the modalities to treat keloids. Aim : To evaluate the effect of CO 2 laser ablation followed by intralesional steroids on keloids. Settings and Design : This was a prospective, single-center, uncontrolled, open study. Materials and Methods : Twenty-eight patients having 35 keloids were included in the study. Keloids were ablated or excised with CO 2 laser followed by intralesional steroid 3-4 weeks apart for 6 months. Results were evaluated after 6 months of stopping of intralesional steroids. Statistical Analysis : Fisher′s exact test was applied for obtaining difference in recurrence rate of regular and irregular patients. Results : Thirteen patients followed up regularly for intralesional steroids. During 6 months of follow-up after stoppage of steroids, only two patients showed recurrence. Ten patients were irregular for intralesional steroids and seven of them showed recurrence. Difference in recurrence rate of regular and irregular patients was significant. Conclusion : Only CO 2 laser ablation is not sufficient for halting the pathogenesis of keloid formation.We therefore conclude that CO 2 laser followed by intralesional steroid is a useful therapeutic approach for the treatment of keloids; however, patients need to be observed for recurrence over the next 1 year.

  16. Maximum available flux of charged particles from the laser ablation plasma

    Science.gov (United States)

    Sakai, Yasuo; Itagaki, Tomonobu; Horioka, Kazuhiko

    2016-12-01

    The laser ablation plasma was characterized for high-flux sources of ion and electron beams. An ablation plasma was biased to a positive or a negative high voltage, and the fluxes of charged particles through a pair of extraction electrodes were measured as a function of the laser intensity IL. Maximum available fluxes and the ratios of electron and ion beam currents Je/Ji were evaluated as a function of the laser irradiance. The ion and the electron fluxes increased with a laser intensity and the current ratio was around 40 at IL = 1.3 × 108 W/cm2 which monotonically decreased with an increase of the laser intensity. The current ratios Je/Ji were correlated to the parameters of ablation plasma measured by the electrostatic probes. The results showed that the ion fluxes are basically enhanced by super-sonically drifting ions in the plasma and the electron fluxes are also enhanced by the drift motion together with a reduction of the sheath potential due to the enhanced ion flux to the surrounding wall.

  17. Er:YAG laser ablation: 5-11 years prospective study

    Science.gov (United States)

    Dostalova, Tatjana; Jelinkova, Helena; Nemec, Michal; Sulc, Jan; Miyagi, Mitsunobu

    2005-03-01

    The Er:YAG laser at 2940 nm has been proposed for use in dental cavity preparation and removal of carious enamel and dentin. The purpose of the present study was to determine the effect of the Er:YAG laser ablation in treating dental caries after a period from 5 to 11 years. For this study, 133 cavities were chosen, and for their reparation of it the three restorative materials were used. Baseline examination was made in the following intervals: one week, 1 year, and from 5 to 11 years after cavity preparation and placement of filling material. Clinical assessments were carried out in accordance with the US Public Health Service System. The follow-up included: the marginal ridge, marginal adaptation, anatomic form, caries, color match, cavo surface margin discoloration, surface smoothness, and postoperative sensitivity. Er:YAG laser ablation is an excellent method for treating frontal teeth, i.e., incisors, canines, premolars, and initial occlusal caries of molars. However, visual control of non-contact therapy is necessary. Er:YAG laser ablation is safe, and it strongly reduces pain. The laser treatment markedly decreases the unpleasant sound and vibration.

  18. Nanoparticle formation in the expansion process of a laser ablated plume

    Energy Technology Data Exchange (ETDEWEB)

    Takiya, T [Hitachi Zosen Corporation, Taisho-ku, Osaka 551-0022 (Japan); Umezu, I [Konan University, Higashinada-ku, Kobe 658-8501 (Japan); Yaga, M [University of the Ryukyus, Nishihara, Okinawa 903-0213 (Japan); Han, M [Nanjing University, Nanjing 210093 (China)

    2007-04-15

    In the present article, we describe the process of nanoparticle formation during pulsed laser ablation in an inert gas atmosphere. We investigated the interaction between laser ablated plumes and shock waves using one dimensional Eulerian fluid dynamics equations combined with a rate equation relating to a classical nucleation model of supersaturated vapors. The initial values for the plume immediately after laser irradiation onto a silicon target were calculated based on stochastic thermodynamics, which was first used by Houle et al. We found a certain case wherein the rate of nanoparticle formation becomes higher when a reflected shock wave passes through the plume. In that particular case, mono-dispersed nanoparticles can be generated by carrying out nucleation and nanoparticle growth as separate processes.

  19. Hydrodynamic size distribution of gold nanoparticles controlled by repetition rate during pulsed laser ablation in water

    Science.gov (United States)

    Menéndez-Manjón, Ana; Barcikowski, Stephan

    2011-02-01

    Most investigations on the laser generation and fragmentation of nanoparticles focus on Feret particle size, although the hydrodynamic size of nanoparticles is of great importance, for example in biotechnology for diffusion in living cells, or in engineering, for a tuned rheology of suspensions. In this sense, the formation and fragmentation of gold colloidal nanoparticles using femtosecond laser ablation at variable pulse repetition rates (100-5000 Hz) in deionized water were investigated through their plasmon resonance and hydrodynamic diameter, measured by Dynamic Light Scattering. The increment of the repetition rate does not influence the ablation efficiency, but produces a decrease of the hydrodynamic diameter and blue-shift of the plasmon resonance of the generated gold nanoparticles. Fragmentation, induced by inter-pulse irradiation of the colloids was measured online, showing to be more effective low repetition rates. The pulse repetition rate is shown to be an appropriate laser parameter for hydrodynamic size control of nanoparticles without further influence on the production efficiency.

  20. Dynamics of the plume produced by nanosecond ultraviolet laser ablation of metals

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Schou, Jørgen; Lunney, J.G.

    2003-01-01

    The dynamics of the ablation plume of a partially ionized plasma produced by a nanosecond UV laser with different irradiation spot geometries has been explored. We have used an ensemble of quartz crystal microbalances to make the first systematic and quantitative study of how the shape of the plume...... varies as the aspect ratio (b/a) of the elliptical laser spot is varied by about a factor of ten. The flip-over effect can be described by the adiabatic expansion model of Anisimov using a value of the adiabatic constant of about gamma = 1.4. We have also studied the forward peaking of the ablation plume...... for a large number of metals at the same laser fluence. Contrary to earlier reports, we find that the more refractory metals have the broader angular distributions....

  1. Single and double long pulse laser ablation of aluminum induced in air and water ambient

    Science.gov (United States)

    Akbari Jafarabadi, Marzieh; Mahdieh, Mohammad Hossein

    2017-02-01

    In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water.

  2. Non-ablative fractional laser provides long-term improvement of mature burn scars

    DEFF Research Database (Denmark)

    Taudorf, Elisabeth H; Danielsen, Patricia L; Paulsen, Ida F

    2015-01-01

    BACKGROUND AND OBJECTIVES: Non-ablative fractional laser-treatment is evolving for burn scars. The objective of this study was to evaluate clinical and histological long-term outcome of 1,540 nm fractional Erbium: Glass laser, targeting superficial, and deep components of mature burn scars......-Patient-and-Observer-Scar-Assessment-Scale (mPOSAS, 1 = "normal skin", 10 = "worst imaginable scar"). Secondary outcomes included histology, patient satisfaction (0-10), patient-assessed improvement, and safety. RESULTS: Study was completed by 17 of 20 randomized patients with normotrophic (n = 11), hypertrophic (n = 5) or atrophic (n = 1...... of scar-appearance. CONCLUSIONS: Combined superficial and deep non-ablative fractional laser-treatments induce long-term clinical and histological improvement of mature burn scars....

  3. Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

    Directory of Open Access Journals (Sweden)

    M. Vinod

    2014-12-01

    Full Text Available Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

  4. Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

    Institute of Scientific and Technical Information of China (English)

    M. Vinod; K.G.Gopchandran

    2014-01-01

    Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

  5. Femtosecond laser ablation of polymeric substrates for the fabrication of microfluidic channels

    Energy Technology Data Exchange (ETDEWEB)

    Suriano, Raffaella, E-mail: raffaella.suriano@chem.polimi.it [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Kuznetsov, Arseniy [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Eaton, Shane M. [Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Kiyan, Roman [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Cerullo, Giulio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Osellame, Roberto [Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Chichkov, Boris N. [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Levi, Marinella; Turri, Stefano [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)

    2011-05-01

    This manuscript presents a study of physical and chemical properties of microchannels fabricated by femtosecond laser processing technology in thermoplastic polymeric materials, including poly(methyl methacrylate) (PMMA), polystyrene (PS) and cyclic olefin polymer (COP). By surface electron microscopy and optical profilometry, the dimensions of microchannels in the polymers were found to be easily tunable, with surface roughness values comparable to those obtained by standard prototyping techniques such as micromilling. Through colorimetric analysis and optical microscopy, PMMA was found to remain nearly transparent after ablation while COP and PS darkened significantly. Using infrared spectroscopy, the darkening in PS and COP was attributed to significant oxidation and dehydrogenation during laser ablation, unlike PMMA, which was found to degrade by a thermal depolymerization process. The more stable molecular structure of PMMA makes it the most viable thermoplastic polymer for femtosecond laser fabrication of microfluidic channels.

  6. Shock wave mediated plume chemistry for molecular formation in laser ablation plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, Sivanandan S.; Brumfield, Brian E.; Cannon, Bret D.; Phillips, Mark C.

    2016-02-16

    Laser ablation is used in a variety of applications albeit formation mechanisms of molecules and nanoclusters are not well understood. We investigated the formation mechanisms of AlO molecules during complex interactions between an Al laser plume expanding into ambient air at atmospheric pressure levels. To produce the plasma a high-purity Al target was ablated using 1064 nm, 6 ns laser pulses. Our results show that the plasma chemistry leading to the formation of AlO is mediated by shock waves. During the early times of plasma expansion, the generated shock waves at the plume edges act as a barrier for the combustion process and the molecular formation is prevalent after the shockwave collapse. The temporally and spatially resolved contour mapping of Al and AlO highlight the formation routes and persistence of species in the plasma and its relation to plume hydrodynamics.

  7. Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water

    Science.gov (United States)

    Vaccaro, L.; Popescu, R.; Messina, F.; Camarda, P.; Schneider, R.; Gerthsen, D.; Gelardi, F. M.; Cannas, M.

    2016-07-01

    Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a sub-nanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO2 and amorphous fully oxidized SiO2, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescence bands agrees with the two structural typologies: Si nanocrystals emit a μs-decaying red band; defects of SiO2 give rise to a ns-decaying UV band and two overlapping blue bands with lifetime in the ns and ms timescale.

  8. Inductively Coupled Plasma: Fundamental Particle Investigations with Laser Ablation and Applications in Magnetic Sector Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Saetveit, Nathan Joe [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    Particle size effects and elemental fractionation in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are investigated with nanosecond and femtosecond laser ablation, differential mobility analysis, and magnetic sector ICP-MS. Laser pulse width was found to have a significant influence on the LA particle size distribution and the elemental composition of the aerosol and thus fractionation. Emission from individual particles from solution nebulization, glass, and a pressed powder pellet are observed with high speed digital photography. The presence of intact particles in an ICP is shown to be a likely source of fractionation. A technique for the online detection of stimulated elemental release from neural tissue using magnetic sector ICP-MS is described. Detection limits of 1 μg L-1 or better were found for P, Mn, Fe, Cu, and Zn in a 60 μL injection in a physiological saline matrix.

  9. Laser ablation process for single-walled carbon nanotube production

    Science.gov (United States)

    Arepalli, Sivaram

    2004-01-01

    Different types of lasers are now routinely used to prepare single-walled carbon nanotubes. The original method developed by researchers at Rice University used a "double-pulse laser oven" process. Several researchers have used variations of the lasers to include one-laser pulse (green or infrared), different pulse widths (ns to micros as well as continuous wave), and different laser wavelengths (e.g., CO2, or free electron lasers in the near to far infrared). Some of these variations are tried with different combinations and concentrations of metal catalysts, buffer gases (e.g., helium), oven temperatures, flow conditions, and even different porosities of the graphite targets. This article is an attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

  10. Preparation of silver nanoparticles in virgin coconut oil using laser ablation

    Directory of Open Access Journals (Sweden)

    Reza Zamiri,B Z Azmi. Amir Reza Sadrolhosseini

    2011-01-01

    Full Text Available Reza Zamiri1, B Z Azmi1,2, Amir Reza Sadrolhosseini1, Hossein Abbastabar Ahangar3, A W Zaidan1, M A Mahdi41Department of Physics, 2Advanced Materials and Nanotechnology Laboratory, 3Department of Chemistry, 4Wireless and Photonics Networks Research Center, Universiti Putra Malaysia, Serdang, Selangor, MalaysiaAbstract: Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10-8, 1.6 × 10-8, 2.4 × 10-8, respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method.Keywords: silver nanoparticles, laser ablation, virgin coconut oil

  11. Towards nanopatterning by femtosecond laser ablation of pre-stretched elastomers

    Science.gov (United States)

    Surdo, Salvatore; Piazza, Simonluca; Ceseracciu, Luca; Diaspro, Alberto; Duocastella, Martí

    2016-06-01

    Diffraction limits the focusing capabilities of an optical system seriously constraining the use of lasers for nanopatterning. In this work, we present a novel and simple approach to reduce the minimum feature size of a laser-direct write system by ablating a pre-stretched material. In particular, by focusing and scanning a femtosecond laser beam on the surface of a uniaxially pre-stretched elastomeric membrane we are able to obtain microstructures according to a desired pattern. After removing the stress applied to the elastomer, the membrane relaxes to its original size and the ablated patterns shrink while preserving their shape. In this way, the minimum feature size that is typically determined by the optical properties of the focusing system can be now controlled by the strain applied to the elastomer during the ablation process. We demonstrate this approach by ablating lines on a stretchable polymeric membrane at different strain conditions. Experimental results are in good agreement with theoretical predictions. The proposed method opens up new interesting possibilities for the rapid prototyping of micro- and nano-structures suitable for a wide range of applications such as soft-lithography, micro-/nano-fluidics and lab-on-chip.

  12. Role of Confocal Laser Endomicroscopy in Detection of Residual Barrett's Esophagus after Radiofrequency Ablation

    Directory of Open Access Journals (Sweden)

    Giorgio Diamantis

    2011-01-01

    Full Text Available Endoscopic endoluminal radiofrequency ablation (RFA is a novel and promising modality for Barrett's esophagus (BE treatment. Actually the only surveillance method after the ablation treatment is random biopsies throughout the whole treated area. Confocal laser endomicroscopy (CLE is a new endoscopic imaging tool that permits high-resolution microscopic examination of the gastrointestinal tract. The technology has garnered increasing attention because of its ability to provide real-time “optical” biopsy specimens, with a very high sensitivity and specificity. This paper summarize the potential application of CLE in the surveillance of the reepithelialization of BE, after endoscopic RFA.

  13. Monitoring of the morphologic reconstruction of deposited ablation products in laser irradiation of silicon

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2008-01-01

    Full Text Available Using electron microscopy, atomic force microscopy, X-ray microanalysis, and IR spectroscopy, it was established that, in the regime of continuous laser irradiation of silicon at P = 170 W in different gaseous atmospheres with an oxygen impurity, SiOx composite films with a complex morphology form. The main components of ablation products are clusters that form during flight of ablation products and as a result of separation of SiOx-clusters from the zone of the irradiation channel. The roughness and density of the films depend on the heating temperature of the target surface and the type of deposited clusters.

  14. Ion time-of-flight study of laser ablation of silver in low pressure gases

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1999-01-01

    The dynamics of ions from a laser-ablated silver target in low pressure background atmospheres have been investigated in a simple geometry using an electrical probe. A simple scattering picture for the first transmitted peak of the observed plume splitting has been used to calculate cross section...... of the ablated silver ions in oxygen (sigma{O(2)} = 4.8 x 10(-16) cm(2)) and in argon (sigma{Ar} = 6.7 x 10(-16) cm(2)). The dynamics of the blast wave is well described by blast wave theory. (C) 1999 Elsevier Science B.V. All rights reserved....

  15. Osteoid Osteoma with a Multicentric Nidus: Interstitial Laser Ablation under MRI Guidance

    Directory of Open Access Journals (Sweden)

    David Kaul

    2013-01-01

    Full Text Available Osteoid osteoma (OO is a common benign tumor of the bone and is typically treated by thermal ablation with computed tomography (CT guidance. Only a few cases of multicentric OO have been described. We here report the case of an 11-year-old boy with multicentric OO of the right femur treated with laser ablation under open high-field MRI guidance. The steps of the interventional MRI procedure are described, discussing the benefits and disadvantages of MRI versus CT guidance especially with regard to younger patients.

  16. Numerical Simulation and Analysis on 3D Temperature Field of the Metal Ablated with Femtosecond Pulse Laser

    Energy Technology Data Exchange (ETDEWEB)

    Yang Li; Yang Wei [Science College, Civil Aviation University of China, Tianjin 300300 (China); Wang Chingyue, E-mail: y_lyang@yahoo.com.cn [Key Laboratory of Opto-electronic Information Science and Technology, Ministry of Education, Tianjin University, Tianjin 300072 (China)

    2011-02-01

    To describe femtosecond laser ablation on the metal, numerical simulation on the basis of the double-temperature equation for three-dimension temperature field of the copper ablated with femtosecond pulse laser was performed by finite-difference method. Based on imbalance of the electronic and lattice's temperatures, the calefactive process of the electron and the lattice was obtained, respectively. The dependence of the electron-lattice coupling time on irradiated laser fluence was studied. The ablation depth and the ablation radius of the copper for single pulse fluence were calculated. The dependence of the start ablation (phase explosion arises) time of the copper on irradiated laser fluence was studied. The results indicate that the material jet due to phase explosion is earlier and the duration of ablation is longer with the increase of the laser fluence. When the laser fluence is higher than 1.5 J/cm{sup 2} the ablation start time is about 2-3 ps.

  17. Selective ablation of photovoltaic materials with UV laser sources for monolithic interconnection of devices based on a-Si:H

    Energy Technology Data Exchange (ETDEWEB)

    Molpeceres, C. [Centro Laser UPM, Univ. Politecnica de Madrid, Crta. de Valencia Km 7.3, 28031 Madrid (Spain)], E-mail: carlos.molpeceres@upm.es; Lauzurica, S.; Garcia-Ballesteros, J.J.; Morales, M.; Guadano, G.; Ocana, J.L. [Centro Laser UPM, Univ. Politecnica de Madrid, Crta. de Valencia Km 7.3, 28031 Madrid (Spain); Fernandez, S.; Gandia, J.J. [Dept. de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda, Complutense 22, 28040 Madrid (Spain); Villar, F.; Nos, O.; Bertomeu, J. [CeRMAE Dept. Fisica Aplicada i Optica, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain)

    2009-03-15

    Lasers are essential tools for cell isolation and monolithic interconnection in thin-film-silicon photovoltaic technologies. Laser ablation of transparent conductive oxides (TCOs), amorphous silicon structures and back contact removal are standard processes in industry for monolithic device interconnection. However, material ablation with minimum debris and small heat affected zone is one of the main difficulty is to achieve, to reduce costs and to improve device efficiency. In this paper we present recent results in laser ablation of photovoltaic materials using excimer and UV wavelengths of diode-pumped solid-state (DPSS) laser sources. We discuss results concerning UV ablation of different TCO and thin-film silicon (a-Si:H and nc-Si:H), focussing our study on ablation threshold measurements and process-quality assessment using advanced optical microscopy techniques. In that way we show the advantages of using UV wavelengths for minimizing the characteristic material thermal affection of laser irradiation in the ns regime at higher wavelengths. Additionally we include preliminary results of selective ablation of film on film structures irradiating from the film side (direct writing configuration) including the problem of selective ablation of ZnO films on a-Si:H layers. In that way we demonstrate the potential use of UV wavelengths of fully commercial laser sources as an alternative to standard backscribing process in device fabrication.

  18. Analysis of the laser ablation processes for thin-film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Haas, Stefan; Schoepe, Gunnar; Zahren, Christoph [Research Centre Juelich (Germany). Institute of Energy Research 5 - Photovoltaic; Stiebig, Helmut [Malibu GmbH and Co. KG, Bielefeld (Germany)

    2008-09-15

    A detailed analysis of the monolithical series connection of thin-film silicon modules with ZnO/Ag back contact is presented. In this study, pulsed lasers with wavelengths of 1064 nm and 532 nm were used. The influence of various laser parameters like laser power, pulse overlap, etc., on the different patterning steps is discussed. The focus of this study was on the back contact patterning process. Here (i) the flake formation process during the ablation and (ii) the influence of a NIR-laser source as an alternative approach to the green laser were investigated in detail. The latter would reduce system costs if only one NIR-laser source could be used for all patterning steps. (orig.)

  19. Picosecond pulsed laser ablation and micromachining of 4H-SiC wafers

    Energy Technology Data Exchange (ETDEWEB)

    Molian, Pal, E-mail: molian@iastate.edu [Laboratory for Lasers, MEMS and Nanotechnology, Department of Mechanical Engineering, Iowa State University, 301 Black, Ames, IA 50011 (United States); Pecholt, Ben; Gupta, Saurabh [Laboratory for Lasers, MEMS and Nanotechnology, Department of Mechanical Engineering, Iowa State University, 301 Black, Ames, IA 50011 (United States)

    2009-02-01

    Ultra-short pulsed laser ablation and micromachining of n-type, 4H-SiC wafer was performed using a 1552 nm wavelength, 2 ps pulse, 5 {mu}J pulse energy erbium-doped fiber laser with an objective of rapid etching of diaphragms for pressure sensors. Ablation rate, studied as a function of energy fluence, reached a maximum of 20 nm per pulse at 10 mJ/cm{sup 2}, which is much higher than that achievable by the femtosecond laser for the equivalent energy fluence. Ablation threshold was determined as 2 mJ/cm{sup 2}. Scanning electron microscope images supported the Coulomb explosion (CE) mechanism by revealing very fine particulates, smooth surfaces and absence of thermal effects including melt layer formation. It is hypothesized that defect-activated absorption and multiphoton absorption mechanisms gave rise to a charge density in the surface layers required for CE and enabled material expulsion in the form of nanoparticles. Trenches and holes micromachined by the picosecond laser exhibited clean and smooth edges and non-thermal ablation mode for pulse repetition rates less than 250 kHz. However carbonaceous material and recast layer were noted in the machined region when the pulse repetition rate was increased 500 kHz that could be attributed to the interaction between air plasma and micro/nanoparticles. A comparison with femtosecond pulsed lasers shows the promise that picosecond lasers are more efficient and cost effective tools for creating sensor diaphragms and via holes in 4H-SiC.

  20. IR-Laser Welding and Ablation of Biotissue Stained with Metal Nanoparticles

    OpenAIRE

    Lalayan, A. A.; Israelyan, S. S.

    2015-01-01

    In the present work we have studied the possibility of laser welding and ablation of biological tissue by the using of spherical metal nanoparticles (NPs) and infrared laser irradiation which spectrally located far from plasmon resonances. YAG:Nd laser with 1064 nm wavelength, 8 ns pulse duration, and operating in transverse electromagnetic modes TEM$_{00}$ was used for the synthesis of metal NPs. The Au,Ti Ni and Cu as well as Au-Ag and Au-Cu hybrid metal NPs were formed in the liquid medium...

  1. On the growth mechanism of nanoparticles in plasma during pulsed laser ablation in liquids

    Science.gov (United States)

    Taccogna, F.; Dell’Aglio, M.; Rutigliano, M.; Valenza, G.; De Giacomo, A.

    2017-04-01

    Particle-in-cell methodology is applied to study the simultaneous charging and coagulation of a nanoparticle, taking into account the self-consistent dynamics of surrounding plasma induced by laser ablation in liquid. The model uses, as an input, plasma temperature and electron number density which are experimentally obtained by high temporally resolved optical emission spectroscopy of the laser-induced plasma in water. Results show the important role of ions in the growth process and of the atom-induced evaporation process for the final nanoparticle size. The competition between different mechanisms of nanoparticle formation in the laser-induced plasma is finally discussed.

  2. Dendrimer-Capped Nanoparticles Prepared by Picosecond Laser Ablation in Liquid Environment

    Directory of Open Access Journals (Sweden)

    Paolo Marsili

    2009-09-01

    Full Text Available Fifth generation ethylendiamine-core poly(amidoamine (PAMAM G5 is presented as an efficient capping agent for the preparation of metal and semiconductor nanoparticles by ps laser ablation in water. In particular, we describe results obtained with the fundamental, second and third harmonic of a ps Nd:YAG laser and the influence of laser wavelength and pulse energy on gold particle production and subsequent photofragmentation. In this framework, the role of the dendrimer and, in particular, its interactions with gold clusters and cations are accounted.

  3. Laser ablation of toluene liquid for surface micro-structuring of silica glass

    Energy Technology Data Exchange (ETDEWEB)

    Niino, H. [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)]. E-mail: niino.hiro@aist.go.jp; Kawaguchi, Y. [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Sato, T. [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Narazaki, A. [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Gumpenberger, T. [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Kurosaki, R. [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2006-04-30

    Microstructures with well-defined micropatterns were fabricated on the surfaces of silica glass using a laser-induced backside wet etching (LIBWE) method by diode-pumped solid state (DPSS) UV laser at the repetition rate of 10 kHz. For a demonstration of flexible rapid prototyping as mask-less exposure system, the focused laser beam was directed to the sample by galvanometer-based point scanning system. Additionally, a diagnostics study of plume propagation in the ablated products of toluene solid film was carried out with an intensified CCD (ICCD) camera.

  4. Modelling the formation of nanostructures on metal surface induced by femtosecond laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Djouder, M. [Laboratoire de Physique et Chimie Quantique, Universite Mouloud Mammeri de Tizi-ouzou, BP 17 RP, 15000 Tizi-Ouzou (Algeria); Itina, T.E. [Laboratoire Hubert Curien, UMR CNRS 5516/Universite Jean Monnet, 18 rue de Professeur Benoit Lauras, 42000 Saint-Etienne (France); Deghiche, D. [Laboratoire de Physique et Chimie Quantique, Universite Mouloud Mammeri de Tizi-ouzou, BP 17 RP, 15000 Tizi-Ouzou (Algeria); Lamrous, O., E-mail: omarlamrous@mail.ummto.dz [Laboratoire de Physique et Chimie Quantique, Universite Mouloud Mammeri de Tizi-ouzou, BP 17 RP, 15000 Tizi-Ouzou (Algeria)

    2012-01-15

    We employ the particle-in-cell method to simulate the mechanisms of femtosecond (fs) laser interactions with a metallic target. The theoretical approach considers the solid as a gas of free electrons in a lattice of immobile ions and the laser fluences close to the ablation threshold. At first moments of the interaction, our simulations mapped out different nanostructures. We carefully characterized the rippling phase and found that its morphology is dependent on the distribution of the electron density and the period of the ripples depends on the laser intensity. The simulation method provides new insights into the mechanisms that are responsible for surface grating formation.

  5. On the influence of surface plasmon-polariton waves on pattern formation upon laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Gurevich, E.L., E-mail: gurevich@lat.rub.de [Ruhr-Universität Bochum, Chair of Applied Laser Technology, Universitätsstraße 150, 44801 Bochum (Germany)

    2013-08-01

    Here we analyze whether the laser-induced periodic surface structures (LIPSS), which appear on solid surfaces exposed to single-pulse femtosecond laser radiation, can be explained by excitation of surface plasmon-polariton waves. We demonstrate that excitation of the surface plasmons is impossible in the laser-ablation experiments, since the excitation conditions are not fulfilled. Moreover, properties and morphology of the observed periodic patterns contradict to the theory of the plasmonic nature of the LIPSS. The results are illustrated with experimental examples.

  6. A parametric study of laser induced ablation-oxidation on porous silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    De Stefano, Luca; Rea, Ilaria; Nigro, M Arcangela; Della Corte, Francesco G; Rendina, Ivo [National Council of Research-Institute for Microelectronic and Microsystems-Department of Naples, Via P Castellino 111, 80131 Naples (Italy)], E-mail: luca.destefano@na.imm.cnr.it

    2008-07-02

    We have investigated the laser induced ablation-oxidation process on porous silicon layers having different porosities and thicknesses by non-destructive optical techniques. In particular, the interaction between a low power blue light laser and the porous silicon surfaces has been characterized by variable angle spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The oxidation profiles etched on the porous samples can be tuned as functions of the layer porosity and laser fluence. Oxide stripes of width less than 2 {mu}m and with thicknesses between 100 nm and 5 {mu}m have been produced, depending on the porosity of the porous silicon, by using a 40 x focusing objective.

  7. Evaluation of an ablative and non-ablative laser procedure in the treatment of striae distensae

    Directory of Open Access Journals (Sweden)

    Sule Gungor

    2014-01-01

    Full Text Available Background: Striae distensae or stretch marks are atrophic linear dermal scars with epidermal atrophy. There are many therapeutic options for management, but no consistently effective modality is available yet. Objective: We compared the efficacy of 1064 nm long pulse (LP Nd: YAG laser and 2940 nm variable square pulse (VSP erbium: YAG laser in the treatment of striae distensae. Methods: Twenty female volunteers (Fitzpatrick skin types II-V aged between 20 and 40 years with striae (3 patients with the rubra type and 17 with the alba type were enrolled in the study. The duration of striae ranged from 4 months to 12 years. Lesions were located on the abdomen in all patients except one patient who had striae on the arms and two patients with striae in the lumbar region. Treatments were randomly allocated to both sides of the body in each patient, one side being treated with VSP erbium: YAG laser and the opposite side with LP Nd: YAG laser. All subjects were treated monthly for a total of three treatments. Two 3-mm punch biopsies were obtained from six subjects, both of the same striae, one before the first treatment and one 4 weeks after the last session. Results: Response was evaluated clinically by photographic comparison and was found to be poor in 17 subjects, both on the LP Nd: YAG laser treated side and VSP erbium YAG laser treated side. All these patients had mature lesions (striae distensae alba. Three subjects had a moderate response on both sides; these patients′ striae were immature (striae distensae rubra. Histologically, elastic fibers were slightly increased in post-treatment samples compared with pretreatment skin biopsies. Conclusion: We observed no satisfactory clinical improvement in striae distensae alba lesions although histopathological changes were seen. We suggest that variable square pulse Er: YAG and long pulse Nd: YAG lasers are not useful in the treatment of striae distensae alba.

  8. Bubble dynamics in metal nanoparticle formation by laser ablation in liquid studied through high-speed laser stroboscopic videography

    Energy Technology Data Exchange (ETDEWEB)

    Tanabe, Rie; Nguyen, Thao T.P.; Sugiura, Takahiro; Ito, Yoshiro, E-mail: itoy@vos.nagaokaut.ac.jp

    2015-10-01

    Highlights: • Observations at 1 μs interval were carried out for laser ablation in water. • Laser-induced shock wave and cavitation bubble are dynamically observed. • Jet-like shadows are observed during LAL in water after multiple-pulse irradiation. • Cloudlike-shadow moving away from the irradiated copper surface was observed. - Abstract: Laser ablation in liquid (LAL) is utilized in many applications, such as the fabrication of nanoparticles, laser cleaning and laser peening. We have developed a high-speed laser stroboscopic videography system that enables observations at intervals of 1 μs. Using this imaging system, we investigated the dynamics of cavitation bubbles induced by LAL to elucidate the timing and location of nanoparticle formation and dispersion into the surrounding liquid. The initial bubble demonstrated a well-defined, smooth boundary during its growth and shrinkage. Although previous studies have reported the ejection of particles at the boundary of the bubble, this was not observed in our images. Intermixing between the gas phase of the bubble and the surrounding liquid occurred when the first bubble collapsed. Jet-like shadows were recorded during LAL in water after multiple-pulse irradiation, but were not observed in freshly filled water that had not yet been irradiated. These shadows disappeared within 10 μs and are postulated to be micro-bubbles induced by interactions between nanoparticles suspended in the water and the incoming laser beam.

  9. Properties of the ablation process for excimer laser ablation of Y sub 1 Ba sub 2 Cu sub 3 O sub 7

    Energy Technology Data Exchange (ETDEWEB)

    Neifeld, R.A.; Potenziani, E. (United States Army, Electronics Technology and Devices Laboratory, Fort Monmouth, New Jersey 07703-5000 (US)); Sinclair, W.R. (Martin Goffman Associates, 3 Dellview Drive, Edison, New Jersey 08820-2545 (US)); Hill III, W.T.; Turner, B.; Pinkas, A. (Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (US))

    1991-01-15

    The process of excimer laser ablation has been studied while varying the laser fluence from 0.237 to 19.1 J/cm{sup 2}. Ion time-of-flight, total charge, target etch depth per pulse, and etch volume per pulse have been measured. Results indicate a maximum ablation volume and minimum ionization fraction occur near 5 J/cm{sup 2}. Several of the parameters measured vary rapidly in the 1--5 J/cm{sup 2} range. Variation in these parameters strongly influences the properties of films grown by this technique.

  10. Laser Guidance in C-Arm Cone-Beam CT-Guided Radiofrequency Ablation of Osteoid Osteoma Reduces Fluoroscopy Time

    NARCIS (Netherlands)

    Kroes, M.W.; Busser, W.M.H.; Hoogeveen, Y.L.; Lange, F. de; Schultze Kool, L.J.

    2017-01-01

    PURPOSE: To assess whether laser guidance can reduce fluoroscopy and procedure time of cone-beam computed tomography (CBCT)-guided radiofrequency (RF) ablations of osteoid osteoma compared to freehand CBCT guidance. MATERIALS AND METHODS: 32 RF ablations were retrospectively analyzed, 17

  11. Laser machining of special designed photopolymers-photochemical ablation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Lippert, T. [Los Alamos National Lab., NM (United States); Dickinson, J.T.; Langford, S.C. [Washington State University, Dept. of Physics, Pullman, WA (United States); Furutani, H.; Fukumura, H.; Masuhara, H. [Osaka University, Dept. of Applied Physics, Osaka, (Japan); Kunz, T.; Wokaun, A. [Paul Scherrer Institute, Villigen, (Switzerland)

    1997-08-01

    Photopolymers based on the triazeno chromophore group (-N=N-N{lt}) have been developed. The absorption properties can be tailored for a specific irradiation wavelength. The photochemical exothermic decomposition yields high energetic gaseous products which are not contaminating the surface. The polymer can be structured with high resolution. No debris has been found around the etched corners. Maximum ablation rates of about 3 micrometer/pulse were achieved due to the dynamic absorption behavior (bleaching during the pulse). No physical or chemical modifications of the polymer surface could be detected after irradiation at the tailored absorption wavelength, whereas irradiation at different wavelengths resulted in modified (physical and chemical) surfaces.

  12. Characterization of Ag and Au nanoparticles created by nanosecond pulsed laser ablation in double distilled water

    Energy Technology Data Exchange (ETDEWEB)

    Nikolov, A.S., E-mail: anastas_nikolov@abv.bg [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Nedyalkov, N.N.; Nikov, R.G.; Atanasov, P.A. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Alexandrov, M.T. [Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, G. Bonchev Street, bl. 25, Sofia 1113 (Bulgaria)

    2011-04-01

    Pulsed laser ablation of Ag and Au targets, immersed in double-distilled water is used to synthesize metallic nanoparticles (NPs). The targets are irradiated for 20 min by laser pulses at different wavelengths-the fundamental and the second harmonic (SHG) ({lambda} = 1064 and 532 nm, respectively) of a Nd:YAG laser system. The ablation process is performed at a repetition rate of 10 Hz and with pulse duration of 15 ns. Two boundary values of the laser fluence for each wavelength under the experimental conditions chosen were used-it varied from several J/cm{sup 2} to tens of J/cm{sup 2}. Only as-prepared samples were measured not later than two hours after fabrication. The NPs shape and size distribution were evaluated from transmission electron microscopy (TEM) images. The suspensions obtained were investigated by optical transmission spectroscopy in the near UV and in the visible region in order to get information about these parameters. Spherical shape of the NPs at the low laser fluence and appearance of aggregation and building of nanowires at the SHG and high laser fluence was seen. Dependence of the mean particle size at the SHG on the laser fluence was established. Comments on the results obtained have been also presented.

  13. Excimer laser ablation lithography applied to the fabrication of reflective diffractive optics

    Science.gov (United States)

    Flury, M.; Benatmane, A.; Gérard, P.; Montgomery, P. C.; Fontaine, J.; Engel, T.; Schunck, J. P.; Fogarassy, E.

    2003-03-01

    We propose a low cost technique for the production of diffractive optical elements (DOE). These elements are devoted to high power lasers beam shaping in the mid-infrared wavelengths. This process called laser ablation lithography (LAL), may seem similar to laser beam writing (LBW) in the way the whole DOE's design is reproduced pixel by pixel on the substrate placed on a computer controlled XY translation stage. A first difference is that the photoresist is not exposed with UV light but is directly ablated with short excimer laser pulses. Furthermore, with LAL technique the size of the smallest pixel ( 5 μm×5 μm) is more than 10 times greater than those produced by LBW. We discuss in details the experimental set-up for LAL and demonstrate that it gives a resolution up to 10 times greater than photolithography with flexible masks. This makes LAL a promising solution for the production of DOE for use with Nd:YAG lasers. New applications of DOEs are finally introduced with high power lasers sources, such as laser marking or multi-point brazing.

  14. Fast femtosecond laser ablation for efficient cutting of sintered alumina substrates

    Science.gov (United States)

    Oosterbeek, Reece N.; Ward, Thomas; Ashforth, Simon; Bodley, Owen; Rodda, Andrew E.; Simpson, M. Cather

    2016-09-01

    Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0 J/cm2 (±0.3) and Fth,∞=2.5 J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500 mW power, 100 mm focal length, 2000 μm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143 μm/s - more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users.

  15. Transendoscopic laser ablation of upper respiratory cysts in 12 horses, 1993-2003

    Science.gov (United States)

    Tate, Lloyd P., Jr.

    2004-07-01

    Laser logs and hopstial medical records were examined to determine the number of horses presented for transendoscopic laser ablation of upper respiratory cysts. The two most common lesions were subepiglottic cysts and dorsal pharyngeal cysts. The majority of the horses presenting with these two cystic lesions were under four years of age. Two horses, six and eight years of age, were presented with maxillary sinus cyst of less than 2 cm diameter as demonstrated by radiography. The two horses which presented for nasal cyst were significantly older than any others, being eighteen and twenty-five years of age. Cysts located in the nasal passage and pharynx were visible endoscopically via either of the nasal passages. In the case of the maxillary sinus cyst, trephination allowed for a visual examination and treatment. All horses were treated by transendoscopic laser ablation using either the Nd:YAG laser or the 50-watt 980 nm diode laser using standing sedation. The twelve-year-old horse with the subepiglottic cyst returned, after receiving laser photoablation, for surgical resection of the deflated cyst as portions of it could still be observed on endoscopic examination. For the remainder of the horses, transendoscopic laser photoablation of the respiratory cyst proved to be a satisfactory means of treating the lesion with minimal complications.

  16. Ablative fractional laser enhances MAL-induced PpIX accumulation

    DEFF Research Database (Denmark)

    Haak, C S; Christiansen, K; Erlendsson, Andrés M

    2016-01-01

    BACKGROUND AND OBJECTIVES: Pretreatment of skin with ablative fractional laser enhances accumulation of topical provided photosensitizer, but essential information is lacking on the interaction between laser channel densities and pharmacokinetics. Hence our objectives were to investigate how prot...... by enhancing AFL densities up to 5%. Further, this model indicates that incubation time as well as drug concentration of MAL may be reduced with laser pretreatment....... protoporphyrin accumulation was affected by laser densities, incubation time and drug concentration. METHODS: We conducted the study on the back of healthy male volunteers (n=11). Test areas were pretreated with 2940nm ablative fractional Er:YAG laser, 11.2mJ per laser channel using densities of 1, 2, 5, 10...... incubation. The individual fluorescence intensity reached from the highest density (15%) and longest MAL 160mg/g incubation time (180min) was selected as reference (100%) for other interventional measurements. RESULTS: A low laser density of 1% markedly enhanced fluorescence intensities from 34% to 75% (no...

  17. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, Seisuke, E-mail: seisuke@riken.jp [RIKEN-Advanced Science Institute, Wako, Saitama 351-0198 (Japan); Sugioka, Koji; Midorikawa, Katsumi [RIKEN-Advanced Science Institute, Wako, Saitama 351-0198 (Japan)

    2009-09-30

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  18. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    Science.gov (United States)

    Nakashima, Seisuke; Sugioka, Koji; Midorikawa, Katsumi

    2009-09-01

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  19. Ablation properties of inorganic filler modified benzoxazine composite coating irradiated by high-intensity continuous laser

    Science.gov (United States)

    Xu, Feng; Ma, Zhuang; Li, Hezhang; Gao, Lihong; Wang, Fuchi

    2017-05-01

    Benzoxazine resin with good heat resistance, low combustion heat release and high char yield is a promising thermosetting resin. Meanwhile, research shows that the inorganic filler can effectively improve the thermodynamic property of the resin. It makes that the inorganic filler modified benzoxazine may have a potential application in laser ablation. The benzoxazine coating with and without inorganic filler ammonium polyphosphate, melamine and pentaerythritol (P-BOZ and BOZ) were prepared by brush and thermal curing method. The ablation properties of these coatings irradiated by high-intensity laser were investigated. The scanning electron microscope, Raman spectroscopy and thermal gravimetric analysis were used to characterize the micrographs, carbon layer structure and thermodynamic property of the sample. Results show that the composite coating has excellent thermal protective properties. The back temperature of 20 wt% P-BOZ coating under different parameter laser power (1000W/cm2, 5s; 1000W/cm2, 10s) are 40% lower than these of the BOZ coating and the 20 wt% P-BOZ has higher mass ablation rate. In the surface layer of the irradiated area, dense carbon layer is produced which reduces the absorb of the laser energy of the interior. In the interior of the sample, a large number of closed bell shaped holes are generated which are beneficial to obstruct the heat conduction.

  20. Processing condition influence on the characteristics of gold nanoparticles produced by pulsed laser ablation in liquids

    Energy Technology Data Exchange (ETDEWEB)

    Nikov, R.G., E-mail: rosen_nikov@abv.bg [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Nikolov, A.S.; Nedyalkov, N.N.; Atanasov, P.A. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Alexandrov, M.T. [Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, G. Bonchev Street, Building 25, Sofia 1113 (Bulgaria); Karashanova, D.B. [Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, G. Bonchev Street, Building 109, Sofia 1113 (Bulgaria)

    2013-06-01

    A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental (λ = 1064 nm), second (λ{sub SHG} = 532) and third (λ{sub THG} = 355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532 nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λ{sub irrad} = 532 nm (laser energy 40 mJ) at different times up to 25 min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.