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1

Double pulse laser ablation and plasma: Laser induced breakdown spectroscopy signal enhancement  

Microsoft Academic Search

A review of recent results of the studies of double laser pulse plasma and ablation for laser induced breakdown spectroscopy applications is presented. The double pulse laser induced breakdown spectroscopy configuration was suggested with the aim of overcoming the sensitivity shortcomings of the conventional single pulse laser induced breakdown spectroscopy technique. Several configurations have been suggested for the realization of

V. I. Babushok; F DELUCIAJR; J. L. Gottfried; C. A. Munson; A. W. Miziolek

2006-01-01

2

Determination of ablation threshold of copper alloy with orthogonal dual-pulse laser-ablation laser-induced breakdown spectroscopy.  

PubMed

Orthogonal dual-pulse laser-ablation laser-induced breakdown spectroscopy was first used to determine the laser-ablation threshold of samples. In this technique, the first laser pulse was used to ablate samples and the second time-delayed laser pulse was used to break down the ablated samples. Orthogonal geometric arrangement was adopted in this technique to ensure both high spatial resolution and high detection sensitivity. By monitoring the intensities of the atomic emission of the plasma under different pulse energies of the ablation laser and using an extrapolation method, the minimum pulse energy needed for the ablation of copper alloy under the tightly focused condition with a nanosecond 532 nm ablation laser was determined to be 1.9±0.1 ?J. After experimentally determining the beam spot size on the focal plan, the fluence threshold of the studied sample was determined to be 0.64±0.06 J/cm². This technique is able to realize direct and sensitive determination of a laser-ablation threshold of solid samples, and it is possible to find some important applications in different fields. PMID:23938407

Zhou, Qi; Chen, Yuqi; Peng, Feifei; Yang, Xuejiao; Li, Runhua

2013-08-10

3

Excimer-laser-induced fluorescence spectroscopy of human arteries during laser ablation  

NASA Astrophysics Data System (ADS)

The autofluorescence of human arterial tissue with varying degrees of atherosclerosis was studied in vitro to develop a diagnostic tool for tissue differentiation simultaneously to tissue ablation induced by a XeCl-excimer laser (wavelength 308 nm). Healthy vessel walls and artery segments containing lipid-rich or calcified areas were investigated in air, saline solution (0.9% NaCl), and in blood. The fluorescence spectra in the wavelength range from 320 nm to 650 nm were recorded with an optical multichannel analyzer, and they allowed for a clear discrimination between plaque and healthy vessel wall even in blood. For each single laser shot with an energy density of about 4-5 J/cm2, well above the ablation threshold, a complete spectrum was recorded. The fluorescence spectra were analyzed in terms of their contributions from normal arterial tissue, lipid-rich and calcified plaques. The results clearly show the feasibility of controlling the ablation process by fluorescence spectroscopy in order to avoid vessel-wall perforation which is one of the main drawbacks in laser angioplasty.

Abel, B.; Hippler, Horst; Koerber, B.; Morguet, A.; Neu, Walter

1991-11-01

4

Optical emission spectroscopy and modeling of plasma produced by laser ablation of titanium oxides  

Microsoft Academic Search

In the present study, the time evolution of electron number density, of electron, atom and ion temperatures, of plasma produced by KrF excimer laser ablation of titanium dioxide and monoxide targets, are investigated by temporally and spatially resolved optical emission spectroscopy over a wide range of laser fluence from 1.7 to 6 J cm?2, oxygen pressures of 10?2–10?1 torr and

A. De Giacomo; V. A. Shakhatov; O. De Pascale

2001-01-01

5

Analysis of gas-phase reactions during pulsed laser ablation using laser-induced fluorescence, absorption, and emission spectroscopy  

Microsoft Academic Search

The role of gas-phase reactions during pulsed-laser ablation in low-pressure atmospheres has been investigated by time- and space- resolved spectroscopic measurements. Thus, excited species have been detected by optical emission spectroscopy. The population densities were determined in an absolute scale after calibration of the spectroscopic apparatus. Complementary information was obtained by detecting ground-state species using laser-induced fluorescence (LIF) spectroscopy. Therefore,

Joerg Hermann; Christophe Dutouquet

2002-01-01

6

Laser ablated Sr2FeMoO6 plasma studied by optical emission spectroscopy  

NASA Astrophysics Data System (ADS)

The pulsed laser ablation and deposition of Sr2FeMoO6 films having good magnetic performances is strongly affected by the adopted deposition parameters, which require precise choices. Among them, the laser energy density seems to be the basic factor governing the achievement of the correct material phase during film growth. Optical emission spectroscopy of the plasma plume, produced by the laser interaction with stoichiometric targets, in different ablation and ambient conditions, can outline the plasma dynamics and consequently sustain hypothesis about the film formation mechanism. In order to follow the plasma dynamics during Nd:Yag laser (2=532 nm) ablation of Sr2FeMoO6 targets, time- and space-resolved optical emission spectroscopy measurements in the range 350 -500 nm have been performed. The integral intensities of spectral lines were measured as a function of distance from the target surface and laser power density in the presence of 02 partial pressure. The intensity ratio of ionic and atomic Strontium emission spectral line and their time-of-flights were measured as a function of laser energy density. On the basis of the obtained results it is shown how different plasma species kinetics can play a key role in determining the magnetic film properties.

Santagata, A.; Di Trolio, A.; Parisi, G. P.; Larciprete, R.

2005-06-01

7

Laser-ablated active doping technique for visible spectroscopy measurements on Z.  

SciTech Connect

Visible spectroscopy is a powerful diagnostic, allowing plasma parameters ranging from temperature and density to electric and magnetic fields to be measured. Spectroscopic dopants are commonly introduced to make these measurements. On Z, dopants are introduced passively (i.e. a salt deposited on a current-carrying surface); however, in some cases, passive doping can limit the times and locations at which measurements can be made. Active doping utilizes an auxiliary energy source to disperse the dopant independently from the rest of the experiment. The objective of this LDRD project was to explore laser ablation as a method of actively introducing spectroscopic dopants. Ideally, the laser energy would be delivered to the dopant via fiber optic, which would eliminate the need for time-intensive laser alignments in the Z chamber. Experiments conducted in a light lab to assess the feasibility of fibercoupled and open-beam laser-ablated doping are discussed.

Gomez, Matthew Robert

2013-09-01

8

Two-dimensional space-resolved emission spectroscopy of laser ablation plasma in water  

SciTech Connect

We developed a method for two-dimensional space-resolved emission spectroscopy of laser-induced plasma in water to investigate the spatial distribution of atomic species involved in the plasma. Using this method, the laser ablation plasma produced on a Cu target in 5 mM NaCl aqueous solution was examined. The emission spectrum varied considerably depending on the detecting position. The temperature and the atomic density ratio N{sub Na}/N{sub Cu} at various detecting positions were evaluated by fitting emission spectra to a theoretical model based on the Boltzmann distribution. We are successful in observing even a small difference between the distributions of the plasma parameters along the directions vertical and horizontal to the surface. The present approach gives direct information for sound understanding of the behavior of laser ablation plasma produced on a solid surface in water.

Matsumoto, Ayumu; Tamura, Ayaka; Fukami, Kazuhiro; Ogata, Yukio H. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Sakka, Tetsuo [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan)

2013-02-07

9

Progress of laser ablation for accelerator mass spectroscopy at ATLAS utilizing an ECRIS.  

PubMed

Beams of ions from the laser ablation method of solid materials into an electron cyclotron resonance ion source (ECRIS) plasma have been used for the first time in experiments at ATLAS. Initial accelerator mass spectroscopy experiments using laser ablation for actinides and samarium have been performed. Initial results of coupling the laser system to the ECR source have guided us in making a number of changes to the original design. The point of laser impact has been moved off axis from the center of the ECR injection side. Motor control of the laser positioning mirror has been replaced with a faster and more reliable piezo-electric system, and different raster scan patterns have been tested. The use of the laser system in conjunction with a multi-sample changer has been implemented. Two major problems that are being confronted at this time are beam stability and total beam intensity. The status of the development will be presented and ideas for further improvements will be discussed. PMID:24593480

Scott, R; Palchan, T; Pardo, R; Vondrasek, R; Kondev, F; Nusair, O; Peters, C; Paul, M; Bauder, W; Collon, P

2014-02-01

10

Two-tracer spectroscopy diagnostics of temperature profile in the conduction layer of a laser-ablated plastic foil  

SciTech Connect

A technique that combines the diagnostics of electron temperature history and the measurements of ablation velocity with two-tracer x-ray spectroscopy has been developed for diagnosing the temperature profiles in the thermal conduction layers of laser-ablated plastic foils. The electron temperature in the plastic ablator was diagnosed using the isoelectronic line ratios of Al Ly{alpha} line to Mg Ly{alpha} line, emitted from a tracer layer of Al/Mg mixture buried under the ablator. The ablation velocity was inferred from the time delay between the onset time of x-ray line emissions from Al and Mg tracer layers buried at two depths in the ablator, respectively. From the measured electron temperatures and ablation velocity, the electron temperature profile in the conduction layer was inferred. The measured temperature profile was compared with the simulated one and reasonable agreement was found.

Zhang Jiyan; Yang Guohong; Hu Xin; Yang Jiamin; Ding Yaonan; Ding Yongkun; Zhang Baohan; Zheng Zhijian [Research Center of Laser Fusion, P. O. Box 919-986, Mianyang 621900 (China); Xu Yan; Yan Jun; Pei Wenbin [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2010-11-15

11

Hook spectroscopy as an atomic number density diagnostic applied to laser-ablated copper plasmas  

SciTech Connect

Hook spectroscopy has been used to determine the absolute number density of ground state copper atoms in laser-ablated plasma plumes. An ablation laser power flux of {approximately} 1.5 GW/cm{sup 2} is applied to a solid copper target in a background gas, producing a plasma plume suitable for studying homogeneous copper vapor condensation. Density is measured at post-ablation time delays ranging from 10 {mu}s to 3 ms with 25 torr of argon as the background gas. Planar laser-induced fluorescence (PLEF) images containing relative density information are used in conjunction with the hook spectra to resolve spatially the absolute density within the plume. Copper atom densities thus measured ranged from 1.9 {times} 10{sup 15} cm{sup {minus}3} at a delay of 10 {mu}s to 2.7 {times} 10{sup 13} cm{sup {minus}3} at 3 ms delay in 25 torr of argon The decrease in density is due to the condensation of copper vapor to form fine particulate. As a combustion diagnostic, the hook method may prove extremely useful for the determination of metal impurity density in coal fired flames as well as a single -- shot OH density and temperature diagnostic.

Zerkle, D.K.; Sappey, A.D.; Gamble, T.K.

1993-11-01

12

Characterization of hydrocarbon and mixed layers in TEXTOR by laser induced ablation spectroscopy  

NASA Astrophysics Data System (ADS)

Laser-based methods are investigated for the development of an in situ diagnostic for spatially and temporally resolved characterization of the first wall in fusion devices. Here we report on the first systematic laser-induced ablation spectroscopy (LIAS) measurements carried out on various surface layers in the TEXTOR tokamak. These materials include a-C:D, mixed W/C/Al/D2, Oerlikon Balzers 'Balinit' diamond-like carbon layers and EK98 fine-grain graphite. In LIAS, the bulk or deposited material is evaporated during the plasma discharge by intense laser radiation. The light emitted by particles entering the edge of the ionizing tokamak plasma is then observed by optical spectroscopy. In the measurements taken, it was found that the studied layers can be identified by their characteristic line emission. A good correlation between the observed line intensity and layer thickness is found. The observed plumes show target material dependence. To analyze layers formed during tokamak operation, further investigation of the ablation process and reference materials for cross calibration is required.

Gierse, N.; Brezinsek, S.; Giesen, T. F.; Huber, A.; Laengner, M.; Leyte-Gonzales, R.; Marot, L.; Meyer, E.; Möller, S.; Naiim-Habib, M.; Philipps, V.; Pospieszczyk, A.; Schweer, B.; Sergienko, G.; Zlobinski, M.; Samm, U.; TEXTOR Team

2011-12-01

13

Laser ablation: LIBS and ICPMS  

SciTech Connect

Laser ablation has become a dominant technology for directsolid sampling chemical analysis. Commonly used detection modalitiesinclude LIBS (laser induced breakdown spectroscopy) for directspectroscopic analysis from the laser-induced plasma at the samplesurface,and ICPMS (inductively coupled plasma mass spectroscopy) in whichthe ablated aerosol is transported and excited in a secondary source.Each measurement approach dictates the laser parameters required foroptimum performance. Fundamental and experimental research studies haveled to significant improvements in performance metrics for laser ablationsolid sampling chemical analysis using both LIBS and ICPMS.

Russo, Richard E.; Gonzalez, Jhanis; Liu, Chunyi

2006-08-29

14

Dynamics of femto- and nanosecond laser ablation plumes investigated using optical emission spectroscopy  

SciTech Connect

We investigated the spatial and temporal evolution of temperature and electron density associated with femto- and nanosecond laser-produced plasmas (LPP) from brass under similar laser fluence conditions. For producing plasmas, brass targets were ablated in vacuum employing pulses either from a Ti:Sapphire ultrafast laser (40 fs, 800 nm) or from a Nd:YAG laser (6 ns, 1064 nm). Optical emission spectroscopy is used to infer the density and temperature of the plasmas. The electron density (n{sub e}) was estimated using Stark broadened profiles of isolated lines while the excitation temperature (T{sub exc}) was estimated using the Boltzmann plot method. At similar fluence levels, continuum and ion emission are dominant in ns LPP at early times (<50 ns) followed by atomic emission, while the fs LPP provided an atomic plume throughout its visible emission lifetime. Though both ns and fs laser-plasmas showed similar temperatures ({approx}1 eV), the fs LPP is found to be significantly denser at shorter distances from the target surface as well as at early phases of its evolution compared to ns LPP. Moreover, the spatial extension of the plume emission in the visible region along the target normal is larger for fs LPP in comparison with ns LPP.

Verhoff, B.; Harilal, S. S.; Freeman, J. R.; Diwakar, P. K.; Hassanein, A. [Center for Materials Under Extreme Environment and School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2012-11-01

15

Applications of ultra-short pulsed laser ablation: thin films deposition and fs\\/ns dual-pulse laser-induced breakdown spectroscopy  

Microsoft Academic Search

In this paper, we report a survey of two of the large number of possible practical applications of the laser ablation performed by an ultra-short pulse laser, namely pulsed laser deposition (PLD) and fs\\/ns dual-pulse laser-induced breakdown spectroscopy (DP-LIBS). These applications differ from those using just longer pulsed lasers as a consequence of the distinctive characteristics of the plasma produced

R. Teghil; A. Santagata; A. DeBonis; G. Albano; P. Villani; D. Spera; G. P. Parisi; A. Galasso

2008-01-01

16

Calcium detection of human hair and nail by the nanosecond time-gated spectroscopy of laser-ablation plume  

NASA Astrophysics Data System (ADS)

We demonstrate the nanosecond time-gated spectroscopy of plume in laser ablation of biological tissue, which allows us to detect calcium (Ca) with high sensitivity by the use of either a UV or a near-IR laser pulse. Clear and sharp peaks of Ca+ appear in the luminescence spectrum of laser-ablation plume although the Ca content is only 0.1 percent in human hair and nail. Luminescence peaks of sodium atom (Na) and ionized carbon are also detectable. This specific spectroscopy is low invasive because a single low-energy laser pulse illuminates the tissue sample, and it does not require any poisonous sensititizers like fluorescence dye. This method, therefore, is a promising candidate for optical biopsy in the near future. In particular, Ca detection of human hair may lead to new diagnosis, including monitor of daily intake of Ca and a screening diagnosis of osteoporosis.

Haruna, Masamitsu; Ohmi, Masato; Nakamura, Mitsuo; Morimoto, Shigeto

2000-04-01

17

[Delivery of megawatts high energy laser pulse with large core diameter silica fiber and its application in dual-wavelength laser-ablation laser-induced breakdown spectroscopy].  

PubMed

To resolve the contradiction between spatial resolution and analysis sensitivity in single pulse laser-induced breakdown spectroscopy (LIBS), a study on dual-wavelength laser-ablation laser-induced breakdown spectroscopy (LA-LIBS) was carried out by using one Nd : YAG laser which was capable of two laser beam outputs with different wavelengths, where, the second harmonic output, 532 nm laser beam, was used as laser-ablation source, and the fundamental output, 1064 nm laser beam, was delivered with a large core diameter silica fiber to realize nanoseconds time-delay and then used to breakdown the ablated samples. Two laser beams were orthogonally arranged to realize element analysis with high spatial resolution and high sensitivity. Some key techniques on the coupling of 1064 nm laser beam into fiber, the collimation of laser at the fiber end and re-focusing of the laser beam were studied. The energy delivery capabilities of four fibers of different types were studied and the maximum values were determined experimentally. A Q-switched laser pulse with 15 mJ pulse energy was successfully delivered by selecting a 50 meter long silica fiber with 800 microm core diameter and 0. 39 numerical aperture. And 250 ns time-delay was realized. A copper alloy was analyzed by spectra with current established LA-LIBS system and the possibility of realizing dual-wavelength LA-LIBS analysis based on one Nd : YAG laser was demonstrated experimentally. In this technique, only one Nd: YAG laser was required to carry out spectral analysis. It has a few advantages, such as simple equipment structure, and being convenient to miniaturize the whole system etc. This dual-wavelength LA-LIBS technique was suitable for in-situ elements microanalysis for different samples with both high spatial resolution and high sensitivity. PMID:24611409

Zhou, Qi; Peng, Fei-Fei; Li, Run-Hua; Chen, Yu-Qi; Yang, Xue-Jiao

2013-12-01

18

Multielemental analysis of prehistoric animal teeth by laser-induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry  

SciTech Connect

Laser-induced breakdown spectroscopy (LIBS) and laser ablation (LA) inductively coupled plasma (ICP) mass spectrometry (MS) were utilized for microspatial analyses of a prehistoric bear (Ursus arctos) tooth dentine. The distribution of selected trace elements (Sr, Ba, Fe) was measured on a 26 mmx15 mm large and 3 mm thick transverse cross section of a canine tooth. The Na and Mg content together with the distribution of matrix elements (Ca, P) was also monitored within this area. The depth of the LIBS craters was measured with an optical profilometer. As shown, both LIBS and LA-ICP-MS can be successfully used for the fast, spatially resolved analysis of prehistoric teeth samples. In addition to microchemical analysis, the sample hardness was calculated using LIBS plasma ionic-to-atomic line intensity ratios of Mg (or Ca). To validate the sample hardness calculations, the hardness was also measured with a Vickers microhardness tester.

Galiova, Michaela; Kaiser, Jozef; Fortes, Francisco J.; Novotny, Karel; Malina, Radomir; Prokes, Lubomir; Hrdlicka, Ales; Vaculovic, Tomas; Nyvltova Fisakova, Miriam; Svoboda, Jiri; Kanicky, Viktor; Laserna, Javier J.

2010-05-01

19

Laser-ablation processes.  

National Technical Information Service (NTIS)

The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10(sup 13) W/cm(sup ...

R. S. Dingus

1992-01-01

20

Mapping of lead, magnesium and copper accumulation in plant tissues by laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were utilized for mapping the accumulation of Pb, Mg and Cu with a resolution up to 200 ?m in a up to cm × cm area of sunflower ( Helianthus annuus L.) leaves. The results obtained by LIBS and LA-ICP-MS are compared with the outcomes from Atomic Absorption Spectrometry (AAS) and Thin-Layer Chromatography (TLC). It is shown that laser-ablation based analytical methods can substitute or supplement these techniques mainly in the cases when a fast multi-elemental mapping of a large sample area is needed.

Kaiser, J.; Galiová, M.; Novotný, K.; ?ervenka, R.; Reale, L.; Novotný, J.; Liška, M.; Samek, O.; Kanický, V.; Hrdli?ka, A.; Stejskal, K.; Adam, V.; Kizek, R.

2009-01-01

21

Infrared laser bone ablation  

Microsoft Academic Search

The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and COâ, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig

Roger C. Nuss; Richard L. Fabian; Rajabrata Sarkar; Carmen A. Puliafito

1988-01-01

22

In situ deuterium inventory measurements of a-C:D layers on tungsten in TEXTOR by laser induced ablation spectroscopy  

NASA Astrophysics Data System (ADS)

Laser induced ablation spectroscopy (LIAS) is a diagnostic to provide temporally and spatially resolved in situ measurements of tritium retention and material migration in order to characterize the status of the first wall in future fusion devices. In LIAS, a ns-laser pulse ablates the first nanometres of the first wall plasma-facing components into the plasma edge. The resulting line radiation by plasma excitation is observed by spectroscopy. In the case of the full ionizing plasma and with knowledge of appropriate photon efficiencies for the corresponding line emission the amount of ablated material can be measured in situ. We present the photon efficiency for the deuterium Balmer ?-line resulting from ablation in TEXTOR by performing LIAS on amorphous hydrocarbon (a-C:D) layers deposited on tungsten substrate of thicknesses between 0.1 and 1.1 ?m. An experimental inverse photon efficiency of [ {\\frac{{D}}{{{XB}}}} ]_{{D}_\\alpha({EXP})}^{{a {- C:D}}\\mathop {\\mathop \\to \\limits_{{LIAS}} } D}= 75.9 +/- 23.4 was determined. This value is a factor 5 larger than predicted values from the ADAS database for atomic injection of deuterium under TEXTOR plasma edge conditions and about twice as high, assuming normal wall recycling and release of molecular deuterium and break-up of D2 via the molecular ion which is usually observed at the high temperature tokamak edge (Te > 30 eV).

Gierse, N.; Brezinsek, S.; Coenen, J. W.; Giesen, T. F.; Huber, A.; Laengner, M.; Möller, S.; Nonhoff, M.; Philipps, V.; Pospieszczyk, A.; Schweer, B.; Sergienko, G.; Xiao, Q.; Zlobinski, M.; Samm, U.; the TEXTOR Team

2014-04-01

23

Optical emission spectroscopy of molecular species in plasma induced by laser ablation of carbon in nitrogen  

Microsoft Academic Search

The results obtained from the study of time-integrated molecular spectra emitted by a plasma induced by excimer laser (XeCl, ?=308 nm, ?=30 ns) ablation of a graphite target in nitrogen atmospheres are presented. The dominant molecular species are found to be CN and C2. The intensities of CN and C2 bands have been studied for laser fluences in the range

G. Dinescu; E Aldea; M. L De Giorgi; A Luches; A Perrone; A Zocco

1998-01-01

24

Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy: Effect of nanoparticles deposited on sample surface on laser ablation and plasma emission  

NASA Astrophysics Data System (ADS)

In this paper the use of metallic nanoparticles (NPs) for improving Laser Induced Breakdown Spectroscopy (LIBS) is discussed. In the case of conductors an emission signal enhancement up to 1-2 orders of magnitude was obtained depositing NPs on the sample surface by drying a micro-drop of colloidal solution. The basic mechanisms of Nanoparticle Enhanced LIBS (NELIBS) were studied and the main causes of this significantly large enhancement were found to be related to the effect of NPs on the laser ablation process, in terms of a faster and more efficient production of seed electrons with respect to conventional LIBS. The characteristics of NELIBS-produced plasma were investigated by emission spectroscopy and spectrally resolved images. In spite of similar plasma parameters, the NELIBS plasma was found to have larger emission volume and longer persistence than the LIBS one. A method to determine NP concentration and size was also proposed, which involved depositing NPs on non-interacting substrates, and proved the feasibility of LIBS as a fast detection tool for a preliminary characterization of NPs.

De Giacomo, A.; Gaudiuso, R.; Koral, C.; Dell'Aglio, M.; De Pascale, O.

2014-08-01

25

Evolutions in time and space of laser ablated species by dual-laser photoabsorption spectroscopy  

SciTech Connect

An atmospheric aluminum laser induced plasma is investigated by means of absorption and emission spectroscopies in the near ultraviolet range. The absorbed radiation is produced by a second aluminum laser induced plasma, which is generated at adjustable time delay. The measurements of both ground and resonant state number densities are derived from the fitting of the experimental 308.21 nm ({sup 2}P{sub 1/2}{sup 0}-{sup 2}D{sub 3/2}) and 396.15 nm ({sup 2}P{sub 3/2}{sup 0}-{sup 2}S{sub 1/2}) line absorption profiles on the numerical solution of the radiative transfer equation. Owing to the dominant role played by the Stark effect in the line broadening and shifting, the calculation also provides the evolution in time and in space of the free electron density along the line of sight. More classically, the same method is applied to the emission profiles which exhibit strong self-absorbed shapes. The reliability of the results derived from both absorption and emission experiments is analyzed and the origin of the asymmetric shape of the absorption lines is discussed.

Ribiere, M.; Mees, L.; Allano, D.; Cheron, B. G. [Technopole du Madrillet, UMR 6614 CNRS (CORIA), BP 12, 76801 Saint Etienne du Rouvray (France)

2008-08-15

26

Mapping of lead, magnesium and copper accumulation in plant tissues by laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were utilized for mapping the accumulation of Pb, Mg and Cu with a resolution up to 200 ?m in a up to cm×cm area of sunflower (Helianthus annuus L.) leaves. The results obtained by LIBS and LA-ICP-MS are compared with the outcomes from Atomic Absorption Spectrometry (AAS) and

J. Kaiser; M. Galiová; K. Novotný; R. ?ervenka; L. Reale; J. Novotný; M. Liska; O. Samek; V. Kanický; A. Hrdlicka; K. Stejskal; V. Adam; R. Kizek

2009-01-01

27

Pb distribution in bones from the Franklin expedition: synchrotron X-ray fluorescence and laser ablation/mass spectroscopy  

NASA Astrophysics Data System (ADS)

Synchrotron micro-X-ray Fluorescence has been used to map the metal distribution in selected bone fragments representative of remains associated with the Franklin expedition. In addition, laser ablation mass spectroscopy using a 25 ?m diameter circular spot was employed to compare the Pb isotope distributions in small regions within the bone fragments. The X-ray Fluorescence mapping shows Pb to be widely distributed in the bone while the Pb isotope ratios obtained by laser ablation within small areas representative of bone with different Pb exchange rates do not show statistically significant differences. These results are inconsistent with the hypothesis that faulty solder seals in tinned meat were the principle source of Pb in the remains of the expedition personnel.

Martin, Ronald Richard; Naftel, Steven; Macfie, Sheila; Jones, Keith; Nelson, Andrew

2013-04-01

28

Laser ablation of dyes  

NASA Astrophysics Data System (ADS)

High density 50 ?s pulses of the UV dyes PPF, POPOP and BBO and of two dyes in the visible region, Xanthen N92 and Fluorol 7GA were generated by laser ablation. Dye powders were pressed with 7800 kp/cm 2 in round pellets which were ablated by exposure to KrF excimer laser radiation (248 nm) at a fluence of 100 mJ/cm 2. The ablation cloud was optically activated with a XeCl excimer laser. Its fluorescence spectrum was measured and was identified as a dye vapour fluorescence spectrum by comparison to conventional dye solution and dye vapour spectra. The dye cloud is not deflected in an electric field (10 6 V/m). By changing the delay time between the ablation laser and the focused activation laser, the velocity distribution of the ablated dye was measured. Its maximum is at 600 m/s for PPF. Knowing the thickness of the ablated dye layer per shot (300 Å) and the size of the ablation cloud (pictures of a video camera), one can estimate the maximum density of the dye in the gas pulse to be 10 -5 mol/ l in the range of concentration of lasing dyes. However, no lasing was observed up to now.

Späth, M.; Stuke, M.

1992-01-01

29

Laser ablation studies of concrete  

SciTech Connect

Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. The authors present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied using cement and high density concrete as targets. Ablation efficiency and material removal rates were determined as functions of irradiance and pulse overlap. Doped samples were also ablated to determine the efficiency with which surface contaminants were removed and captured in the effluent. The results show that the cement phase of the material melts and vaporizes, but the aggregate portion (sand and rock) fragments. The effluent consists of both micron-size aerosol particles and chunks of fragmented aggregate material. Laser-induced optical emission spectroscopy was used to analyze the surface during ablation. Analysis of the effluent showed that contaminants such as cesium and strontium were strongly segregated into different regions of the particle size distribution of the aerosol.

Savina, M.; Xu, Z.; Wang, Y.; Reed, C.; Pellin, M.

1999-10-20

30

Rubidium isotope measurements in solid samples by laser ablation-laser atomic absorption spectroscopy  

Microsoft Academic Search

Laser atomic absorption was used to measure the rubidium isotopes in a laser-induced plasma. An 85Rb\\/87Rb isotope ratio of 2.7±0.2 was determined in solid calcium carbonate samples. A Nd:YAG laser was used to produce the plasma on the surface of solid samples placed inside a low pressure chamber with a controlled atmosphere of 150 mtorr to 10 torr. The plasma

L. A King; I. B Gornushkin; D Pappas; B. W Smith; J. D Winefordner

1999-01-01

31

Investigation of heavy-metal accumulation in selected plant samples using laser induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Single-pulse Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass-Spectrometry (LA-ICP-MS)\\u000a were applied for mapping the silver and copper distribution in Helianthus Annuus L. samples treated with contaminant in controlled conditions. For Ag and Cu detection the 328.07 nm Ag(I) and 324.75 nm Cu(I)\\u000a lines were used, respectively. The LIBS experimental conditions (mainly the laser energy and the observation

M. Galiová; J. Kaiser; K. Novotný; J. Novotný; T. Vaculovic; M. Liska; R. Malina; K. Stejskal; V. Adam; R. Kizek

2008-01-01

32

Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy  

NASA Technical Reports Server (NTRS)

Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal atoms survive for several milliseconds while the gaseous carbon atoms and small molecules nucleate more rapidly. Additional experiments and the development of in situ methods for carbon nanotube detection would allow these results to be interpreted from the perspective of carbon nanotube formation.

deBoer, Gary; Scott, Carl

2003-01-01

33

Nanoparticles by Laser Ablation  

Microsoft Academic Search

This review concerns nanoparticles collected in the form of nanopowder or a colloidal solution by laser ablating a solid target that lies in a gaseous or a liquid environment. The paper discusses the advantages of the method as compared with other methods for nanoparticle synthesis, outlines the factors on which the properties of the produced nanoparticles depend, explains the mechanisms

N. G. Semaltianos

2010-01-01

34

OCDR guided laser ablation device  

DOEpatents

A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

Dasilva, Luiz B. (Danville, CA); Colston, Jr., Bill W. (Livermore, CA); James, Dale L. (Tracy, CA)

2002-01-01

35

Optical emission spectroscopy of thin film fabrication by pulsed laser ablation under high-gravity  

NASA Astrophysics Data System (ADS)

We carried out the thin film deposition of iron silicide by pulsed laser ablation (PLA) on a sapphire substrate, which was placed on a high-speed rotating titanium disk. The deposited thin film exhibited a continuous composition gradient. We investigated how the continuous composition gradient was attained, because the strength of the gravity field in our experiment was far below that in the experiment on bulk crystalline compounds. In the present study, we obtain the spatial distribution of several species in the PLA plume of FeSi2 by using an intensified charge-coupled device (ICCD) camera. We obtained the distribution of each species through high-speed imaging using narrow bandpass filters, whose wavelengths corresponded to the emission wavelengths of Fe2+, Fe+, Si2+, Si+, and neutral Fe. From the observed images, we could identify the particle species as well as determine the average velocity and the relative number density of each species. The Fe2+ ions, Fe+ ions, and Fe atoms had quite different average velocities as a result of which they formed separate groups while moving toward the substrate. Species with the same valence value moves with the same velocity. We believe that the compositional gradient of FeSi2 attained under an appropriate gravity field may be explained by the movement of both the components driven by the acceleration field and the effect of selective etching.

Kajiwara, Takashi; Nishiyama, Takashi; Morinaga, Sachi; Nagayama, Kunihito

2010-12-01

36

Femtosecond-laser-induced Ablation of an Aluminum Target Probed by Space- and Time-resolved Soft X-ray Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

Laser ablation involves phase transitions that produce an ablation plume consisting of various states of matter, namely solid, liquid, vapor, and plasma. This plume plays an important role in the deposition of thin films [1], the formation of nanoparticles [2], and other processes. It is important to investigate this ablation plume at the atomic level not only for a basic study of laser ablation dynamics but also to provide a better understanding of such processes. Because the plume evolves spatially over time, space- and time-resolved measurements are also required. One atomic-level diagnostic method is X-ray absorption spectroscopy (XAS). This involves an element-specific probe of the local structure in a material and provides information about its electronic and atomic structure. An important advantage of this technique is that a wide variety of solid, liquid, and gaseous samples can be examined directly and nondestructively. Furthermore, we can combine this technique with an ultrafast X-ray probe generated by femtosecond-laser-induced plasma [3]-[6], and this makes time-resolved XAS suitable for the study of laser ablation processes.

Okano, Yasuaki; Oguri, Katsuya; Nishikawa, Tadashi; Nakano, Hidetoshi

37

CO2 laser ablation of biological tissue  

Microsoft Academic Search

This paper presents a comprehensive review of the CO2 laser ablation of biological tissue. Based on energy balance for modeling laser ablation, the thermal relaxation time and the ablation threshold are determined. Laser ablation of biological tissue is related to the spatial coherence of laser beams, so that the propagation of laser beams, the beam quality and the focusability of

Dan C. Dumitras; Doru C. Dutu; Consuela-Elena Matei

1998-01-01

38

Complementary analysis of historical glass by scanning electron microscopy with energy dispersive X-ray spectroscopy and laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

.  Laser ablation inductively coupled plasma mass spectrometry (LA ICP MS) was used as a supporting method for elemental analysis\\u000a of historical glass investigated by means of scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM\\/EDS).\\u000a Investigated objects represent mainly late- and post-medieval glass objects (mostly Façon-de-Venise vessels and nuppenbechers), window glass and chandeliers from excavation in Elbl?g, Pozna? and Wroc?aw

Barbara Wagner; Anna Nowak; Ewa Bulska; Jerzy Kunicki-Goldfinger; Olivier Schalm; Koen Janssens

2008-01-01

39

Femtosecond laser ablation of bovine cortical bone.  

PubMed

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma. PMID:23208295

Cangueiro, Liliana T; Vilar, Rui; Botelho do Rego, Ana M; Muralha, Vania S F

2012-12-01

40

Femtosecond laser ablation of bovine cortical bone  

NASA Astrophysics Data System (ADS)

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

Cangueiro, Liliana T.; Vilar, Rui; Botelho do Rego, Ana M.; Muralha, Vania S. F.

2012-12-01

41

High spatial resolution mapping of deposition layers on plasma facing materials by laser ablation microprobe time-of-flight mass spectroscopy  

NASA Astrophysics Data System (ADS)

A laser ablation microprobe time-of-flight mass spectroscopy (LAM-TOF-MS) system with high spatial resolution, ˜20 nm in depth and ˜500 ?m or better on the surface, is developed to analyze the composition distributions of deposition layers on the first wall materials or first mirrors in tokamak. The LAM-TOF-MS system consists of a laser ablation microprobe combined with a TOF-MS and a data acquisition system based on a LabVIEW program software package. Laser induced ablation combined with TOF-MS is an attractive method to analyze the depth profile of deposited layer with successive laser shots, therefore, it can provide information for composition reconstruction of the plasma wall interaction process. In this work, we demonstrate that the LAM-TOF-MS system is capable of characterizing the depth profile as well as mapping 2D composition of deposited film on the molybdenum first mirror retrieved from HL-2A tokamak, with particular emphasis on some of the species produced during the ablation process. The presented LAM-TOF-MS system provides not only the 3D characterization of deposition but also the removal efficiency of species of concern.

Xiao, Qingmei; Li, Cong; Hai, Ran; Zhang, Lei; Feng, Chunlei; Zhou, Yan; Yan, Longwen; Duan, Xuru; Ding, Hongbin

2014-05-01

42

High spatial resolution mapping of deposition layers on plasma facing materials by laser ablation microprobe time-of-flight mass spectroscopy.  

PubMed

A laser ablation microprobe time-of-flight mass spectroscopy (LAM-TOF-MS) system with high spatial resolution, ?20 nm in depth and ?500 ?m or better on the surface, is developed to analyze the composition distributions of deposition layers on the first wall materials or first mirrors in tokamak. The LAM-TOF-MS system consists of a laser ablation microprobe combined with a TOF-MS and a data acquisition system based on a LabVIEW program software package. Laser induced ablation combined with TOF-MS is an attractive method to analyze the depth profile of deposited layer with successive laser shots, therefore, it can provide information for composition reconstruction of the plasma wall interaction process. In this work, we demonstrate that the LAM-TOF-MS system is capable of characterizing the depth profile as well as mapping 2D composition of deposited film on the molybdenum first mirror retrieved from HL-2A tokamak, with particular emphasis on some of the species produced during the ablation process. The presented LAM-TOF-MS system provides not only the 3D characterization of deposition but also the removal efficiency of species of concern. PMID:24880373

Xiao, Qingmei; Li, Cong; Hai, Ran; Zhang, Lei; Feng, Chunlei; Zhou, Yan; Yan, Longwen; Duan, Xuru; Ding, Hongbin

2014-05-01

43

Femtosecond laser ablation of solid materials  

NASA Astrophysics Data System (ADS)

In this dissertation, femtosecond laser materials processing is studied. A time-of-flight mass spectrometer has been designed, constructed and utilized to measure the time-of-flight spectra of the ions ablated by femtosecond laser pulses. The velocities and kinetic energies of the ions are determined. Emission spectroscopy and imaging have been carried out to analyze the laser-induced plume. Craters ablated in vacuum and under ambient pressure are measured by a scanning electron microscope (SEM) and a light interferometric microscope. Numerical methods in microscale energy transfer are first reviewed. Subsequently, a numerical model based on the two-temperature concept is utilized to account for the non-equilibrium energy transfer processes dominating the ultrashort laser pulse excitation of materials. Time-of-flight measurements reveal the presence of extremely energetic ions in femtosecond laser-induced plumes, with kinetic energies more than one order of magnitude higher than those of nanosecond laser-induced ions. Two different ablation regimes, exhibiting different laser fluence dependence of the total ion yields, and the corresponding percentage of energetic ions and the crater depths, are discovered for femtosecond laser ablation of titanium. Numerical modeling shows that the laser fluences associated with the second ablation regime can raise the lattice system to the range of the thermodynamic critical point and hence may cause explosive evaporation leading to the observed higher ablation rates. The first regime, however, occurs at lower laser fluences, when the laser energy is mainly deposited in the shallow region defined by the optical penetration depth. The more localized energy deposition is believed to lead to higher percentage of energetic ions, albeit to less total ablation volume. Femtosecond laser-induced plumes have been found to be much smaller in spatial dimensions and weaker in intensity than those induced by nanosecond laser pulses. The ambient pressure is found to restrain the expansion of the plumes. The non-equilibrium microscopic energy transfer between the electron and lattice subsystems needs to be considered to model femtosecond laser materials processing. The two-temperature approach is capable of at least semi-quantitatively modeling real engineering problems. Due to the large temperature range encountered in typical laser ablation applications, the temperature dependence of the materials thermal properties is found to be very important for accurate modeling. (Abstract shortened by UMI.)

Ye, Mengqi

44

Kilohertz laser ablation for doping helium nanodroplets  

SciTech Connect

A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the nonvolatile DNA basis guanine is found to be efficient and a number of oligomers are detected.

Mudrich, M.; Forkl, B.; Mueller, S.; Dvorak, M.; Buenermann, O.; Stienkemeier, F. [Physikalisches Institut, Universitaet Freiburg, D-79104 Freiburg (Germany)

2007-10-15

45

Multiple target laser ablation system  

DOEpatents

A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film. 3 figs.

Mashburn, D.N.

1996-01-09

46

Multiple target laser ablation system  

DOEpatents

A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film.

Mashburn, Douglas N. (Knoxville, TN)

1996-01-01

47

Plasma chemistry in laser ablation processes  

Microsoft Academic Search

Based on the results of quantitative spectroscopic diagnostics (LIF in combination with time resolved emission spectroscopy) chemical dynamics in laser-produced plasmas of metallic (Ti, Al,), and graphite samples have been examined. The Nd-YAG (1064 nm, 10 ns, 100 mJ) and excimer XeCl (308 nm, 10 ns, 10 mJ) lasers were employed for ablation. The main attention was focused on the

V. S. Burakov; N. V. Tarasenko; N. A. Savastenko

2001-01-01

48

Influence of ambient gas and its pressure on the laser-induced breakdown spectroscopy and the surface morphology of laser-ablated Cd  

NASA Astrophysics Data System (ADS)

The ablation of Cd has been performed by employing Q-switched Nd: YAG 10 ns laser pulses with a central wavelength of 1064 nm for a pulsed energy of 200 mJ under various ambient environments of argon, air and helium. The optical emission spectroscopy of Cd plasma has been studied under different filling pressures of shield gases ranging from 5 torr to 760 torr using LIBS spectrometer system. The effect of different gases and their pressures on the intensity of spectral emission, electron temperature and density of the laser-produced plasma has been investigated. SEM analysis has been performed to investigate the dependence of surface morphological changes of an irradiated target on the nature and pressure of an ambient gas. A strong correlation has revealed the vital role of electron temperature and density of laser-induced plasma for the surface modification of Cd. These results strongly indicate that the nature and pressure of the ambient atmosphere is one of the controlling factors of the plasma characteristics, as well as the factors related to the laser energy absorption for surface modification.

Bashir, Shazia; Farid, Nazar; Mahmood, Khaliq; Shahid Rafique, M.

2012-04-01

49

Diagnostics Techniques of Plasmas Produced by Laser Ablation  

SciTech Connect

Laser ablation in addition for thin film growing is also used for analytical techniques as Laser Induced Breakdown Spectroscopy and for applications as simulation of natural lightning. In this work we present several diagnostic techniques such as probe beam deflection, shadowgraphy, interferometry, pulsed laser photoacoustic and the electrical perturbation induced by laser ablation plasmas that's gives essential information of the plasma, hot core air and shock wave expansion.

Villagran Muniz, M.; Sobral, H.; Sanchez Ake, C.; Sangines de Castro, R.; Sterling, E. [Laboratorio de Fotofisica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-186, Mexico D.F. 04510 (Mexico); Bredice, F. [Centro de Investigaciones Opticas, P.O.Box 124, C.P.1900, La Plata (Argentina)

2005-04-21

50

Laser-Ablated Active Doping Technique for Visible Spectroscopy Measurements on Z.  

National Technical Information Service (NTIS)

Visible spectroscopy is a powerful diagnostic, allowing plasma parameters ranging from temperature and density to electric and magnetic fields to be measured. Spectroscopic dopants are commonly introduced to make these measurements. On Z, dopants are intr...

M. R. Gomez

2013-01-01

51

Species-resolved imaging and gated photon counting spectroscopy of laser ablation plume dynamics during KrF- and ArF-laser PLD of amorphous diamond films  

SciTech Connect

Gated photon counting spectroscopy and species-resolved ICCD photography were used to study the weak plasma luminescence following the propagation of the initial ablation plume in vacuum and during the rebound of the plume with a substrate during pulsed laser deposition of amorphous diamond. These methods techniques were required in order to investigate notable differences between amorphous diamond-like carbon films formed by pulsed laser deposition from ArF (193 nm) and KrF (248 nm) irradiation of pyrolytic graphite in vacuum. Three principal regions of plume emission were found: (1) a bright luminescent ball (v {approximately}3--5 cm/{mu}s) displaying nearly entirely C{sup +} emission which appears to result from laser interaction with the initial ejecta, (2) a spherical ball of emission (v {approximately} 1 cm/{mu}s) displaying neutral carbon atomic emission lines and, at early times, jets of excited C{sub 2}, and (3) a well-defined region of broadband emission (v {approximately} 0.3 cm/{mu}s) near the target surface first containing emission bands from C{sub 2}, then weak, continuum emission thought to result from C{sub 3} and higher clusters and/or blackbody emission from hot clusters or nanoparticles.

Geohegan, D.B. [Oak Ridge National Lab., TN (United States); Puretzky, A.A. [Russian Academy of Sciences, Troitsk (Russian Federation). Inst. of Spectroscopy

1995-12-01

52

Laser Ablation of Biological Tissue Using Pulsed CO2 Laser  

Microsoft Academic Search

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and

Yuichi Hashishin; Shu Sano; Takeyoshi Nakayama

2010-01-01

53

UV laser ablation of parylene films from gold substrates  

SciTech Connect

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.

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

2009-11-19

54

UV Laser Ablation of Electronically Conductive Polymers.  

National Technical Information Service (NTIS)

The UV laser ablation of thin polypyrrole and polyaniline films coated on an insulating substrate is described. UV laser ablation is used to pattern the conductive polymer coating; patterns with submillimeter features are easily obtained with edge resolut...

L. S. Van Dyke C. J. Brumlik Z. Yu G. J. Collins C. R. Martin

1992-01-01

55

LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM  

SciTech Connect

This report describes the installation, testing, and acceptance of the Waste Treatment and Immobilization Plant (WTP) procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste (HLW) samples in a hot cell environment. The work was completed by the Analytical Process Development (APD) group in accordance with Task Order 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S Laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

SEIDEL CM; JAIN J; OWENS JW

2009-02-23

56

LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM  

SciTech Connect

This report describes the installation, testing and acceptance of the Waste Treatment and Immobilization Plant procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste samples in a hot cell environment. The 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

LOCKREM LL; OWENS JW; SEIDEL CM

2009-03-26

57

Laser surface ablation cleaning of nuclear facilities  

NASA Astrophysics Data System (ADS)

High power Nd:YAG laser beam with wavelength 1064nm, pulsewidth 10 picosecond regime was focused onto the scanning targets of SUS304 stainless steel with Zn coating of thickness 21 micrometers , and delivered via a step index fused silica optical fiber of length 3m and core diameter 1mm. Irradiation ablation effect and some basic aspects of high power laser beam transporting in optical fiber were studied. Ablation rate was defined as ablated volume to laser fluence and used as a description of ablation cleaning ability which was investigated by means of ablated profile measurement, ablation rate calculation, chemical composition analysis of ablated area.

Zhou, Xianglin; Imasaki, Kazuo; Umino, Hideo; Sakagishi, Kohji; Nakai, Sadao; Yamanaka, Chiyoe

2000-01-01

58

Size dependent Cu dielectric function for plasmon spectroscopy: Characterization of colloidal suspension generated by fs laser ablation  

NASA Astrophysics Data System (ADS)

Copper metal nanoparticles (Nps) have received increasing interest during the last years due to their potential applications in several fields of science and technology. Their optical properties depend on the characteristics of the dielectric function of the metal, their size, and the type of environment. The contribution of free and bound electrons on the dielectric function of copper Nps is analyzed as well as their influence on its plasmonic properties. The contribution of free electrons is corrected for particle size under 10 nm, introducing a term inversely proportional to the particle's radius in the damping constant. For bound electron contribution, interband transitions from the d-band to the conduction band are considered. For particles with sizes below 2 nm, the larger spacing between electronic energy levels must be taken into account by making the electronic density of states in the conduction band size-dependent. Considering these specific modifications, optical parameters and band energy values could be determined by fitting the bulk complex dielectric function. The obtained values were coefficient for bound electron contribution Kbulk = 2 × 1024, gap energy Eg = 1.95 eV, Fermi energy EF = 2.15 eV, and bound electrons damping constant ?b = 1.15 × 1014 Hz. Based on the dielectric function determined in this way, experimental extinction spectra of colloid suspensions generated by ultrafast laser ablation of a solid copper target in liquids was fitted using the Drude-interband model and Mie's theory. Depending on the experimental conditions and liquid medium, the particles in the suspension may have nanometric or subnanometric core size and may be capped with a shell of oxide. From the fitting, it was possible to determine the structure and size distribution of spherical bare core and core-shell copper Nps in the nanometer-subnanometer size range. These results were compared with those obtained by standard microscopy techniques such as AFM and HRTEM. There is a very good agreement between the three techniques, showing that optical extinction spectroscopy (OES) is a good complementary technique to standard high resolution electron microscopy and AFM for sizing spherical nanometric-subnanometric Nps. OES has also the advantage of a very good measurement statistics, due to the large number of probed particles across the sample cell. Besides, it avoids coalescence effects since the measurement is made directly on the colloidal suspension.

Santillán, J. M. J.; Videla, F. A.; Fernández van Raap, M. B.; Schinca, D. C.; Scaffardi, L. B.

2012-09-01

59

Debris of potassium–magnesium silicate glass generated by femtosecond laser-induced ablation in air: An analysis by near edge X-ray absorption spectroscopy, micro Raman and energy dispersive X-ray spectroscopy  

NASA Astrophysics Data System (ADS)

The redeposited material (debris) resulting from ablation of a potassium-magnesium silicate glass upon scanning femtosecond laser pulse irradiation (130 fs, 800 nm) in air environment is investigated by means of three complementary surface analytical methods. Changes in the electronic band structure of the glass constituent Magnesium (Mg) were identified by X-ray Absorption Near Edge Structure spectroscopy (XANES) using synchrotron radiation. An up-shift of ?0.8 eV of a specific Magnesium K-edge absorption peak in the spectrum of the redeposited material along with a significant change in its leading edge position was detected. In contrast, the surface left after laser ablation exhibits a downshift of the peak position by ?0.9 eV. Both observations may be related to a change of the Mg coordinative state of the laser modified/redeposited glass material. The presence of carbon in the debris is revealed by micro Raman spectroscopy (?-RS) and was confirmed by energy dispersive X-ray spectroscopy (EDX). These observations are attributed to structural changes and chemical reactions taking place during the ablation process.

Grehn, M.; Seuthe, T.; Reinhardt, F.; Höfner, M.; Griga, N.; Eberstein, M.; Bonse, J.

2014-05-01

60

Information recording by laser ablation  

Microsoft Academic Search

Information recording by laser ablation involves energy absorption by an active layer followed by heating at the focal point and in the immediately adjacent area. We have used various organic dyes as recording media and characterized their properties. The substrates employed were made of polymethyl methacrylate (PMMA) or polycarbonate (PC). The influence of defect in the substrate and the birefringence

Maria Bardosova; A. V. Irlin; G. Cik; Volodymir G. Tsukanov

1995-01-01

61

Nanoparticle Formation by Laser Ablation  

Microsoft Academic Search

The properties of nanoparticle aerosols of size ranging from 4.9?nm to 13?nm, generated by laser ablation of solid surfaces are described. The experimental system consisted of a pulsed excimer laser, which irradiated a rotating target mounted in a cylindrical chamber 4?cm in diameter and 18-cm long. Aerosols of oxides of aluminum, titanium, iron, niobium, tungsten and silicon were generated in

Marc Ullmann; Sheldon K. Friedlander; Andreas Schmidt-Ott

2002-01-01

62

Analysis of metallic fuels by laser ablation  

NASA Astrophysics Data System (ADS)

A hot cell-based solid sampling system has been developed for application to the analyses of irradiated materials such as metallic reactor fuel from a nuclear reactor, and radioactive waste forms. This system employs one of two sampling techniques, glow discharge or laser ablation, for introduction of material into one of two instruments for analysis, either a time of flight mass spectrometer or an inductively coupled argon plasma-atomic emission spectrometer (ICP-AES). This paper will discuss using ICP-AES for the analysis of major, minor and trace constituents in an unirradiated U-10 wt % Zr metallic reactor fuel. The behavior of highly refractory elements, such as Zr, in the laser ablation process will be examined in detail. Additional corroborative data provided via scanning electron microscopy-energy dispersive x-ray fluorescence spectroscopy (SEM-EDS) will be presented.

Johnson, Stephen G.; Goodall, Phillip S.; Kimbrell, Sandra M.; Wood, Elon L.

1995-04-01

63

Real-Time Analysis of Individual Airborne Microparticles Using Laser Ablation Mass Spectroscopy and Genetically Trained Neural Networks  

SciTech Connect

We are developing a method for analysis of airborne microparticles based on laser ablation of individual molecules in an ion trap mass spectrometer. Airborne particles enter the spectrometer through a differentially-pumped inlet, are detected by light scattered from two CW laser beams, and sampled by a pulsed excimer laser as they pass through the center of the ion trap electrodes. After the laser pulse, the stored ions are separated by conventional ion trap methods. The mass spectra are then analyzed using genetically-trained neural networks (NNs). A number of mass spectra are averaged to obtain training cases which contain a recognizable spectral signature. Averaged spectra for a bacteria and a non-bacteria are shown to the NNs, the response evaluated, and the weights of the connections between neurodes adjusted by a Genetic Algorithm (GA) such that the output from the NN ranges from 0 for non-bacteria to 1 for bacteria. This process is iterated until the population of the GA converges or satisfies predetermined stopping criteria. Using this type of bipolar training we have obtained generalizing NNs able to distinguish five new bacteria from five new non-bacteria, none of which were used in training the NN.

Parker, E.P.; Rosenthal, S.E.; Trahan, M.W.; Wagner, J.S.

1999-01-22

64

[Characteristic study of plasma plume produced by nanosecond pulsed laser ablation of silicon using optical emission spectroscopy].  

PubMed

The 355 nm laser pulse from THG (Third Harmonic Generation) of a Qswitched Nd3+ : YAG laser was used to ablate silicon mounted in air. The time-and space-resolved optical emission spectra were measured for different pulse energy in the wavelength range of 380-420 nm, the emission spectra of N+ was found for impact ionization of air near target surface on the early stage of plasma plume expansion. Under the model of local thermodynamic equilibrium, the electronic temperature of plasma was deduced to be in the range of 18 000-40 000 K using the Saha equation by the relative line intensities, and the electron density was deduced to be in the 10(17) cm(-3) scale by FWHM (the full width at half maximum) of Si spectral lines, the temporal and spatial evolution of the electronic temperature and electron density was given, showing that the electronic temperature and electron density exhibited second order exponential decreasing with laser delay time and a Lorentz distribution in space. The reason for the spatial position deviation of the maximum electron density from the maximum spectral intensity was analyzed. The relationship between the plasma plume parameters and laser pulse energy was discussed. PMID:20707170

Gao, Xun; Jin, Ming-Xing; Ding, Da-Jun; Lin, Jing-Quan

2010-06-01

65

Laser ablation at the hydrodynamic regime  

NASA Astrophysics Data System (ADS)

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.

Gojani, Ardian B.

2013-04-01

66

Precise laser ablation with ultrashort pulses  

Microsoft Academic Search

Laser ablation of solid targets by Ti:sapphire laser radiation is studied. The targets are irradiated by 150 fs–5 ns laser pulses with a fluence in the range of several J\\/cm2. Measurements on the ablation depth yield an effective penetration depth higher than the optical penetration depth. Advantages and potentials of sub-picosecond laser radiation for the ablation and for the microstructuring

C. Momma; S Nolte; B N. Chichkov; F v. Alvensleben; A Tünnermann

1997-01-01

67

Optical transient absorption spectroscopy of LaO produced by pulsed laser ablation of La2O3.  

PubMed

Temporally and spatially resolved absorption spectrometry has been used to study molecular LaO absorption in laser ablated plume from an La2O3 target The absorption time-of-flight (TOF) spectra of ground-state LaO molecules were measured The TOF spectra indicate that only one component is observed in vacuum and in an Ar ambient, while there are two component, a fast and a broad slow component, observed at higher O2 pressure. The absorbance of LaO molecules decreases gradually with increasing ambient gas pressure. The dependence of the absorbance of LaO on the detection distance can be fitted by an exponential decay equation. The shock wave model is used to describe the behavior of ground state LaO molecules in high O2 pressure region. PMID:10728868

Tang, Y; Yang, X; Liu, X; Qin, Q

2000-01-01

68

Heterodyne laser spectroscopy system  

DOEpatents

A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency, and provides spectral analysis of a laser beam.

Wyeth, Richard W. (Livermore, CA); Paisner, Jeffrey A. (San Ramon, CA); Story, Thomas (Antioch, CA)

1990-01-01

69

Heterodyne laser spectroscopy system  

DOEpatents

A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency and the like, and provides spectral analysis of a laser beam.

Wyeth, Richard W. (Livermore, CA); Paisner, Jeffrey A. (San Ramon, CA); Story, Thomas (Antioch, CA)

1989-01-01

70

Laser-induced modification of metal nanoparticles formed by laser ablation technique in liquids  

Microsoft Academic Search

The effects of laser irradiation of silver colloids prepared by laser ablation technique in acetone have been studied. The laser irradiation was performed using laser radiation at different wavelengths (532, 266, 400 and 800nm). Additional irradiation of colloids resulted in the changes of particles morphology, which were monitored by absorption spectroscopy and transmission electron microscopy methods. The experimental conditions favoring

N. V. Tarasenko; A. V. Butsen; E. A. Nevar

2005-01-01

71

Analysis of geological samples by atomic emission spectroscopy of plasmas induced by laser ablation at low pressures  

NASA Astrophysics Data System (ADS)

Elemental analysis of geologic samples based on atomic emission spectroscopy is currently considered for several future space lander missions to planets, moons and asteroids in solar system. The spectroscopic techniques, called laser-induced plasma (breakdown) spectroscopy (LIBS), provides quantitatively the microscopic in-situ abundances of all major and many trace elements of surfaces of solar system bodies. Excitation and evolution of the plasmas induced by lasers depend on the properties of the investigated material and on environmental conditions. This study focuses on the feasibility of spectroscopy of plasmas induced by low-energy laser (below 1 mJ per pulse) for the exploration of solar system bodies with thin atmospheres (pressures below 1 mPa). At such low pressures the excited plasmas have small plumes and expand very rapidly, which limits both the LIBS signal intensity and the available acquisition time. This, in turn, requires usually relatively powerful laser sources to create a detectable LIBS plasma. The low pressure conditions are simulated in a dedicated chamber at the DLR-Berlin Institute of Planetary Research, that can hold the Martian-like atmosphere or high vacuum conditions. Two infrared Q-switched lasers are used for comparative investigation of atomic emission spectra: Firstly, a Nd:YAG laser (Inlite, Continuum) operating at 1064 nm and at 10 Hz, pulse energy up to 230 mJ at 8-10 ns pulse duration and, secondly, developed for future planetary missions Nd:YLF laser (NeoLASE) operating at 1053 nm and at 10-50 Hz, pulse energy up to 3 mJ at 3-5 ns pulse duration. The emitted light of the laser-induced plasma is analysed by an echelle spectrometer (LTB Aryelle Butterfly) covering the wavelength range of 280-900 nm with a spectral resolution of around 104. Identification of atomic transitions is performed using the LTB built-in spectrometer software by comparison with the NIST spectral database. Several basaltic rock and sediment standards were crushed to powder and pressed into pellets. Reduction of both pressure and laser excitation energy results in a significant decrease of the signal-to-noise ratio for most atomic lines (an exception are the widely broadened lines of H). However, the detection of atomic emission lines of elements with relative abundances above 10-3 (0.1 wt%) - Al, Ca, Cr, H, K, Mg, Mn, Na, Ni, O, Si, Ti, - is possible down to a laser excitation energy of 0.9 mJ (laser irradiance on the sample surface 46 MW/mm2). Additionally, the detection of carbon and sulphur, having strong atomic transitions in ultraviolet range, can be expected by extension of the spectral range of the LIBS spectrometer to 190 nm. Atomic doublet and triplet transitions, broadened by atomic collisions at ambient pressures (100 kPa), become spectrally resolved and are identified below 1 mPa. This demonstrates the feasibility of miniaturized laser-induced breakdown spectrometry for space missions to solar bodies with absent or thin atmospheres.

Pavlov, S.; Schröder, S.; Jessberger, E.; Hübers, H.

2011-12-01

72

Observation of femtosecond-laser-induced ablation plumes of aluminum using space- and time-resolved soft x-ray absorption spectroscopy  

SciTech Connect

The dynamics of the laser ablation plume expansion of aluminum was investigated by using space- and time-resolved soft x-ray absorption spectroscopy. Blueshifts of the Al L-shell photoabsorption edge indicating the state of aluminum were observed in the plumes, which were generated by irradiating an aluminum target with 120 fs near-infrared pulses at an intensity of 10{sup 14} W/cm{sup 2}. The spatiotemporal evolution of the plumes exhibited a multilayer structure consisting of vaporized aluminum and condensed aluminum particles, following the expansion of plasma, with expansion velocities of 10{sup 4} m/s for the atomic state and 10{sup 3} m/s for the condensed state.

Okano, Yasuaki; Oguri, Katsuya; Nishikawa, Tadashi; Nakano, Hidetoshi [NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

2006-11-27

73

Dynamics of Laser Driven, Ablatively Accelerated Targets.  

National Technical Information Service (NTIS)

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, < 10 to the 14th power w/sq cm), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics inclu...

J. Grun

1981-01-01

74

Characterization of products of excimer laser ablation of collagen  

NASA Astrophysics Data System (ADS)

The presence of hydroxyl radicals in the ArF excimer ablation sites in bovine corneal tissue has been investigated by laser-induced fluorescence and Raman spectroscopy. Raman spectroscopy has also been applied to examine the time-resolved temperature of the water component of the ablation site as well as the spatially selective measurement of surface desiccation. Results indicate that the hydroxyl radical is not generate in abundance during the ablation process. Also, Raman monitoring of the ablation site demonstrates no detectable heating during ArF irradiation, while elevated temperatures are observed following exposure of the corneal surface to a Er:YAG laser. Finally, comparison of C-H and O-H Raman bands shows potential utility as a spatially selective means for monitoring tissue hydration.

Ediger, Marwood N.; Hahn, D. W.; Pettit, George H.

1995-05-01

75

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

Microsoft Academic Search

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

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

2002-01-01

76

Photopolymers designed for laser ablation - photochemical ablation mechanism  

NASA Astrophysics Data System (ADS)

We have designed photopolymers based on a photolabile chromophore with absorption properties tailored for a specific irradiation wavelength. The introduction of the two photolabile groups (-N?N-N?) into one repetition unit of the main polymer chain results in a well-defined decomposition pathway. The exothermic decomposition mechanism yields high energetic, gaseous products, which are not contaminating the polymer surface. The products of laser ablation were studied with time-of-flight mass spectroscopy (TOF-MS). All products are totally compatible with a photochemical decomposition mechanism and their high energies can be explained by a laser induced microexplosion. Time resolved techniques, such as transmission, reflectivity or surface interferometry, revealed a `dynamic' behavior. Ns-interferometry showed that etching of the polymer nearly starts and ends with the laser pulse. During the initial stages of the irradiation, darkening of the surface was detected, which corresponds to a decrease of reflectivity and an increase of transmission. This is due to a decrease of the refractive index and absorption coefficient, caused by the photodecompostion of the polymer starting with the irradiation pulse.

Lippert, Thomas; Dickinson, J. T.; Langford, S. C.; Furutani, H.; Fukumura, H.; Masuhara, H.; Kunz, T.; Wokaun, A.

1998-05-01

77

Effect of Laser Pulse Energy on the Gold Nanoparticles Produced by Laser Ablation Method  

NASA Astrophysics Data System (ADS)

Laser pulse energy is shown to influence characteristics of Au nanoparticles (NPs) produced by laser ablation. Au NPs were formed with spherical shape and different size depending on the laser pulse energy. UV-Vis-NIR spectroscopy revealed the changes of surface plasmon resonance features with respect to size and number of NPs.

Dorranian, D.; Ghamkhari, S. M.; Mirghasemzadeh, N.

2013-05-01

78

Permalloy nanoparticles generated by laser ablation  

Microsoft Academic Search

We describe a new method for producing ultrafine magnetic particles that employs pulsed-laser particle ablation. Pulsed-laser radiation with wavelength of 248 nm was used to ablate 1 to 10 ?m diameter Permalloy microparticles under normal atmospheric conditions. The ejected nanoparticles were collected on silicon substrates for further analysis. Scanning electron micrographs of the samples were analyzed by computer aided image

Jaemyoung Lee; M. F. Becker; J. R. Brock; J. W. Keto; R. M. Walser

1996-01-01

79

PULSED LASER ABLATION OF CEMENT AND CONCRETE  

EPA Science Inventory

Laser ablation was investigated as a means of removing radioactive contaminants from the surface and near-surface regions of concrete from nuclear facilities. We present the results of ablation tests on cement and concrete samples using a pulsed Nd:YAG laser with fiber optic beam...

80

Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

Degenerate gases. Probing vortex pair sizes in the Berezinskii-Kosterlitz-Thouless regime on a two-dimensional lattice of Bose-Einstein condensates / V. Schweikhard ... [et al.]. Interacting Bose-Einstein condensates in random potentials / P. Bouyer ... [et al.]. Towards quantum magnetism with ultracold atoms in optical lattices / I. Bloch -- Precision measurement and fundamental physics. T-violation and the search for a permanent electric dipole moment of the mercury atom / E. N. Fortson -- Quantum information and control I. Quantum information processing and ramsey spectroscopy with trapped ions / C. F. Roos ... [et al.]. Quantum non-demolition counting of photons in a cavity / S. Haroche ... [et al.] -- Ultra-fast control and spectroscopy. Frequency-Comb- assisted mid-infrared spectroscopy / P. de Natale ... [et al.] -- Precision measurement and applications. Precision gravity tests by atom interferometry / G. M. Tino ... [et al.] -- Novel spectroscopic applications. On a variation of the proton-electron mass ratio / W. Ubachs ... [et al.] -- Quantum information and control II. Quantum interface between light and atomic ensembles / H. Krauter ... [et al.] -- Degenerate Fermi gases. An atomic Fermi gas near a P-wave Feshbach resonance / D. S. Jin, J. P. Gaebler and J. T. Stewart. Bragg scattering of correlated atoms from a degenerate Fermi gas / R. J. Ballagh, K. J. Challis and C. W. Gardiner -- Spectroscopy and control of atoms and molecules. Stark and Zeeman deceleration of neutral atoms and molecules / S. D. Hogan ... [et al.]. Generation of coherent, broadband and tunable soft x-ray continuum at the leading edge of the driver laser pulse / A. Jullien ... [et al.]. Controlling neural atoms and photons with optical conveyor belts and ultrathin optical fibers / D. Meschede. W. Alt and A. Rauschenbeutel -- Spectroscopy on the small scale. Wide-field cars-microscopy / C. Heinrich ... [et al.]. Atom nano-optics and nano-lithography / V. I. Balykin ... [et al.] -- Pinhead town talk, public lecture and mountainfilm. The quantum revolution - towards a new generation of supercomputers / R. Blatt -- Cold atoms and molecules I. Ultracold & ultrafast: making and manipulating ultracold molecules with time-dependent laser fields / C. P. Koch ... [et al.]. Bose-Einstein condensates on magnetic film microstructures / M. Singh ... [et al.] -- Cold atoms and molecules II. Ultracold metastable Helium-4 and Helium-3 gases / W. Vassen ... [et al.] -- Single atoms and quantum optics I. Recent progress on the manipulation of single atoms in optical tweezers for quantum computing / A. Browaeys ... [et al.]. Progress in atom chips and the integration of optical microcavities / E. A. Hinds ... [et al.] -- Single atoms and quantum optics II. Quantum optics with single atoms and photons / H. J. Kimble -- Optical atomic clocks. Frequency comparison of Al[symbol] and Hg[symbol] optical standards / T. Rosenband ... [et al.]. Sr optical clock with high stability and accuracy / A. Ludlow ... [et al.].

Hollberg, Leo; Bergquist, James Charles; Kasevich, Mark A.

2008-04-01

81

Laser ablation-induced spectral plasma characteristics in optical far- and near fields  

Microsoft Academic Search

The aim of this work is to elucidate the ablation-induced plasma physics for chemical species analysis by laser-induced breakdown spectroscopy at higher spatial resolution. To accomplish this, the effect of the laser spot size on the laser ablation-induced plasma characteristics is experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of ~200 nm thickness

David J. Hwang; Hojeong Jeon; Costas P. Grigoropoulos; Jong Yoo; Richard E. Russo

2008-01-01

82

Laser ablation-induced spectral plasma characteristics in optical far- and near fields  

Microsoft Academic Search

The aim of this work is to elucidate the ablation-induced plasma physics for chemical species analysis by laser-induced breakdown spectroscopy at higher spatial resolution. To accomplish this, the effect of the laser spot size on the laser ablation-induced plasma characteristics is experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of ?200 nm thickness

David J. Hwang; Hojeong Jeon; Costas P. Grigoropoulos; Jong Yoo; Richard E. Russo

2008-01-01

83

Preparation of planar multilayered targets for laser ablation studies  

Microsoft Academic Search

A method is described for the reliable production of reproducible multilayered targets for laser ablation rate studies using time-resolved x-ray spectroscopy. The targets consist of alternating layers of plastic and evaporated metals whose thickness and uniformity were examined by weighing and by SEM micrography to be suitable for experiments. The plastic layers are deposited by a dipping technique using various

R. Popil; A. Haromy; R. Fedosejevs; A. A. Offenberger

1986-01-01

84

Deep ablation and depth profiling by laser-induced breakdown spectroscopy (LIBS) employing multi-pulse laser excitation: application to galvanized steel.  

PubMed

The potential of a multi-pulse (MP) laser excitation scheme for deep stratigraphy of electrolytically galvanized steel using laser-induced breakdown spectrometry (LIBS) has been evaluated. For this purpose, a commercial electro-optically (EO) Q-switched Nd:YAG laser was employed, where by reducing the delay between the Q-switch opening and the flash lamp, a train of pulses (up to 11) separated by approximately 7.40 ?s was generated during one lamp flashing. Plasma emission after each individual laser pulse of the MP sequence was detected by a spectrograph equipped with an intensified charge-coupled device (iCCD) detector. With MP excitation, the ablation efficiency was increased ten-fold on iron sample and 22.5-fold on zinc material with respect to dual-pulse or single-pulse excitation. The LIBS signal generated by MP excitation shows an analogous enhancement. Although the total energy per shot delivered to samples was only 60 mJ, it was possible using LIBS to measure the sample stratigraphy up to depths of 90 ?m on zinc-coated steel sheets. A satisfactory agreement between the Zn thickness determined by the MP-LIBS system and data from the manufacturer has also been obtained. PMID:21740642

Cabalín, Luisa María; González, Alina; Lazic, Violeta; Laserna, Javier

2011-07-01

85

Characterization of toners and inkjets by laser ablation spectrochemical methods and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy  

NASA Astrophysics Data System (ADS)

Detection and sourcing of counterfeit currency, examination of counterfeit security documents and determination of authenticity of medical records are examples of common forensic document investigations. In these cases, the physical and chemical composition of the ink entries can provide important information for the assessment of the authenticity of the document or for making inferences about common source. Previous results reported by our group have demonstrated that elemental analysis, using either Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) or Laser Ablation Induced Breakdown Spectroscopy (LIBS), provides an effective, practical and robust technique for the discrimination of document substrates and writing inks with minimal damage to the document. In this study, laser-based methods and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) methods were developed, optimized and validated for the forensic analysis of more complex inks such as toners and inkjets, to determine if their elemental composition can differentiate documents printed from different sources and to associate documents that originated from the same printing source. Comparison of the performance of each of these methods is presented, including the analytical figures of merit, discrimination capability and error rates. Different calibration strategies resulting in semi-quantitative and qualitative analysis, comparison methods (match criteria) and data analysis and interpretation tools were also developed. A total of 27 black laser toners originating from different manufacturing sources and/or batches were examined to evaluate the discrimination capability of each method. The results suggest that SEM-EDS offers relatively poor discrimination capability for this set (~ 70.7% discrimination of all the possible comparison pairs or a 29.3% type II error rate). Nonetheless, SEM-EDS can still be used as a complementary method of analysis since it has the advantage of being non-destructive to the sample in addition to providing imaging capabilities to further characterize toner samples by their particle morphology. Laser sampling methods resulted in an improvement of the discrimination between different sources with LIBS producing 89% discrimination and LA-ICP-MS resulting in 100% discrimination. In addition, a set of 21 black inkjet samples was examined by each method. The results show that SEM-EDS is not appropriate for inkjet examinations since their elemental composition is typically below the detection capabilities with only sulfur detected in this set, providing only 47.4% discrimination between possible comparison pairs. Laser sampling methods were shown to provide discrimination greater than 94% for this same inkjet set with false exclusion and false inclusion rates lower than 4.1% and 5.7%, for LA-ICP-MS and LIBS respectively. Overall these results confirmed the utility of the examination of printed documents by laser-based micro-spectrochemical methods. SEM-EDS analysis of toners produced a limited utility for discrimination within sources but was not an effective tool for inkjet ink discrimination. Both LA-ICP-MS and LIBS can be used in forensic laboratories to chemically characterize inks on documents and to complement the information obtained by conventional methods and enhance their evidential value.

Trejos, Tatiana; Corzo, Ruthmara; Subedi, Kiran; Almirall, José

2014-02-01

86

Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion  

SciTech Connect

Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

2004-03-23

87

Ultraviolet femtosecond and nanosecond laser ablation of silicon: ablation efficiency and laser-induced plasma expansion  

NASA Astrophysics Data System (ADS)

Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

Zeng, Xianzhong J.; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

2004-09-01

88

Femtosecond laser ablation ICP-MS  

SciTech Connect

Femtosecond laser ablation was investigated for direct solid sample chemical analysis. The phonon relaxation time in a solid is of the order of 100 fs, which is the same as the laser pulse duration. For such excitation, there should be little time for the matrix to experience a ''temperature'' during the laser pulse. If the surface explodes before the photon energy is dissipated as heat in the lattice, the ablation process should produce stoichiometric vapor (elemental fractionation should be negligible). Based on this hypothesis, NIST glasses were ablated using 100 fs laser pulses at 800 nm, with subsequent elemental analysis using the ICP-MS. Pb and U intensities, and Pb/U ratios in the ICP, were measured during repetitively femtosecond-pulsed ablation. These data show that fluence (laser energy/spot area) has a significant influence on the amount of mass ablated and on the degree of fractionation. An optimal fluence was found at which the fractionation index approached unity; negligible fractionation. Infrared femtosecond laser ablation produced similar characteristics to UV nanosecond laser ablation.

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

2002-02-15

89

Pulsed Laser Ablation Synthesis of Diamond Molecules in Supercritical Fluids  

NASA Astrophysics Data System (ADS)

Nanocarbon materials have been synthesized by pulsed laser ablation (532 nm; 52 J/cm2; 7 ns; 10 Hz) of highly oriented pyrolytic graphite in adamantane-dissolved supercritical xenon at a temperature T = 290.2 K and pressure p = 5.86 MPa. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3 hybridized bonds also found in diamond structures. The synthesis of diamantane was confirmed by gas chromatography-mass spectrometry. The same measurements also indicate the possible synthesis of other diamondoids up to octamantane. Thus, laser ablation in supercritical fluids is proposed as one practical method of synthesizing diamondoids.

Nakahara, Sho; Stauss, Sven; Miyazoe, Hiroyuki; Shizuno, Tomoki; Suzuki, Minoru; Kataoka, Hiroshi; Sasaki, Takehiko; Terashima, Kazuo

2010-09-01

90

IR laser ablation of dental enamel  

NASA Astrophysics Data System (ADS)

An overview of the basic mechanisms of IR laser ablation of dental enamel is presented. Enamel is a highly structured tissue consisting of an heterogeneous distribution of water, mineral, protein and lipid. Absorption bands of water and carbonated hydroxyapatite can be selectively targeted from 2.7 to 11-micrometer via several laser wavelengths. Mechanistic differences in the nature of ablation and the varying surface morphology produced can be explained by the microstructure of the tissue. Suggested criteria for the choice of the optimum laser parameters for clinical use, the influence of plasma shielding and the role of exogenous water on the mechanism of ablation are discussed.

Fried, Daniel

2000-03-01

91

Laser ablation of a B 4C–polysiloxane composite  

Microsoft Academic Search

Composite materials, specifically ceramic–polymer composites and metal–polymer composites have received increased interest in a number of engineering applications, from impact protection, microelectronics to tribology. The characteristics of Nd:YAG laser ablation of a B4C:polysiloxane mixture have been studied with the use of time-integrated spectroscopy, laser surface profiling and microscopic analysis. The removal process for a variety of pulse widths and pulse

M. J. J. Schmidt; D. K. Y. Low; L. Li

2002-01-01

92

Femtosecond laser ablation of the stapes.  

PubMed

A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations. PMID:19405768

McCaughey, Ryan G; Sun, Hui; Rothholtz, Vanessa S; Juhasz, Tibor; Wong, Brian J F

2009-01-01

93

Femtosecond laser ablation of the stapes  

NASA Astrophysics Data System (ADS)

A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations.

McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

2009-03-01

94

Modern physical principles of laser ablation  

NASA Astrophysics Data System (ADS)

Physical principles of ablation, that is a phenomenon of fast superficial evaporation of the solid or liquid due to energy deposition into a thin layer near a surface of the specimen, are discussed. The opportunity of studying ablation at a laboratory is directly related to invention of a laser, which is very intensive source of radiation energy. For the first time, the laser ablation was demonstrated by Maiman in 1960 just by using his ruby laser for perforation of a razor blade. Since then there has been demonstrated, that the laser ablation has very complicated physics and can be used for a lot of applications. This fact results from a tremendous variety of laser parameters. Variations of laser intensity in time, radiation spectrum, geometry of specimen irradiation, its chemical composition, etc., result in unique possibility of changing physical parameters of ablation and, hence, its physical features, which allow us to use laser radiation both in science and technology beginning from laser material processing up to high-temperature plasma formation for laser fusion.

Krokhin, Oleg N.

2000-08-01

95

Laser Ablation of Alumina in Water  

SciTech Connect

Bulk {alpha}-alumina immersed in distilled water was ablated by pulsed UV laser radiation. The resulting colloidal solution contained micron and submicron size particles. X-ray diffraction and Raman spectra of the ablated and original material are similar. Hence, most of the ablated material is {alpha}-alumina. From transmission electron microscope images, most of the submicron and all of the micron-sized particles have sharp edges and do not have spherical shapes, indicating that the dominant ablation mechanism is due to crack propagation. Some spherical particles of diameter less than 100 nm are observed, indicating that they were formed from the liquid state.

Musaev, O.; Midgley, A; Wrobel, J; Kruger, M

2010-01-01

96

Dynamics of mid-infrared femtosecond laser resonant ablation  

NASA Astrophysics Data System (ADS)

Resonant ablation is beneficial to avoiding uncontrollable subsurface damages in the laser ablation of polymers. In this paper the dynamics of mid-infrared laser resonant ablation of polylactic acid and toluene was calculated by using fluid dynamic equations. The merits and drawbacks of mid-infrared femtosecond laser resonant ablation of high molecular weight polymers have been discussed.

Pang, Dongqing; Li, Yunxuan; Wang, Qingyue

2013-11-01

97

Dynamics of mid-infrared femtosecond laser resonant ablation  

NASA Astrophysics Data System (ADS)

Resonant ablation is beneficial to avoiding uncontrollable subsurface damages in the laser ablation of polymers. In this paper the dynamics of mid-infrared laser resonant ablation of polylactic acid and toluene was calculated by using fluid dynamic equations. The merits and drawbacks of mid-infrared femtosecond laser resonant ablation of high molecular weight polymers have been discussed.

Pang, Dongqing; Li, Yunxuan; Wang, Qingyue

2014-06-01

98

Estimation of Laser Ablation Surface Cleaning Efficiency  

Microsoft Academic Search

Based on the properties of a high-power short–pulsed Nd:YAG laser and its ablation effect investigated using a 21 ?m-thick\\u000a Zn-coated steel plate as a target, the surface cleaning efficiency of laser ablation processing was discussed through theoretical\\u000a analysis and experimental data. Cleaning efficiency was derived and a 2-fibre structure was used to examine whether calculations\\u000a agreed with experimental results. The

X. Zhou; K. Imasaki; H. Furukawa; S. Nakai; C. Yamanaka

2002-01-01

99

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

A new laser ablation technique combined with a chemical evaporation reaction has been developed for elemental ratio analysis of solid samples using an inductively coupled plasma mass spectrometer (ICPMS). Using a chemically assisted laser ablation (CIA) technique developed in this study, analytical repeatability of the elemental ratio measurement was successively improved. To evaluate the reliability of the CLA-ICPMS technique, Pb/U isotopic ratios were determined for zircon samples that have previously been analyzed by other techniques. Conventional laser ablation for Pb/U shows a serious elemental fractionation during ablation mainly due to the large difference in elemental volatility between Pb and U. In the case of Pb/U ratio measurement, a Freon R-134a gas (1,1,1,2-tetrafluoroethane) was introduced into the laser cell as a fluorination reactant. The Freon gas introduced into the laser cell reacts with the ablated sample U, and refractory U compounds are converted to a volatile U fluoride compound (UF6) under the high-temperature condition at the ablation site. This avoids the redeposition of U around the ablation pits. Although not all the U is reacted with Freon, formation of volatile UF compounds improves the transmission efficiency of U. Typical precision of the 206Pb/238U ratio measurement is 3-5% (2sigma) for NIST SRM 610 and Nancy 91500 zircon standard, and the U-Pb age data obtained here show good agreement within analytical uncertainties with the previously reported values. Since the observed Pb/U ratio for solid samples is relatively insensitive to laser power and ablation time, optimization of ablation conditions or acquisition parameters no longer needs to be performed on a sample-to-sample basis. PMID:12553756

Hirata, Takafumi

2003-01-15

100

Pulse laser ablation of ground glass  

NASA Astrophysics Data System (ADS)

We have studied pulse laser ablation of ground glass surface. Ablation process in air and in vacuum has been observed by high speed framing camera. Burst of small fragments of glass has been observed in the present experiment, when ground glass surface is laser ablated through glass plate from rear side. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of ablation of other transparent materials. By using ns-duration Nd:YAG laser of 100 400 mJ/pulse, observed maximum particle velocity ranges from 0.5 to 1.5 km/s. In order to understand the particle generation process, scanning electron micrograph observation of the ground surface in the region of no laser irradiation and also in the damaged region, has been made. Cleavage surface structure has been evidenced in the damaged surface area, which stems from plenty of micro cracks covering the virgin glass surface. Effects of surface roughness on the particle generation were studied by using ground glass of quartz with different surface roughness. Produced glass particles were captured in vacuum by a polymethylmetacrylate (PMMA) plate. Size distribution was obtained by analysing the trapped particles on the PMMA plate and revealed that most probable particles size has almost no dependence on the initial surface roughness. Finally, we applied the phenomena to ignite pentaerithritoltetranitrate (PETN) powder explosive, and succeeded in igniting (PETN) powder only by laser ablation of ground glass.

Nagayama, K.; Kotsuka, Y.; Kajiwara, T.; Nishiyama, T.; Kubota, S.; Nakahara, M.

2007-11-01

101

Nanosecond laser ablation of gold nanoparticle films  

SciTech Connect

Ablation of self-assembled monolayer protected gold nanoparticle films on polyimide was explored using a nanosecond laser. When the nanoparticle film was ablated and subsequently thermally sintered to a continuous film, the elevated rim structure by the expulsion of molten pool could be avoided and the ablation threshold fluence was reduced to a value at least ten times lower than the reported threshold for the gold film. This could be explained by the unusual properties of nanoparticle film such as low melting temperature, weak bonding between nanoparticles, efficient laser energy deposition, and reduced heat loss. Finally, submicron lines were demonstrated.

Ko, Seung H.; Choi, Yeonho; Hwang, David J.; Grigoropoulos, Costas P.; Chung, Jaewon; Poulikakos, Dimos [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Department of Mechanical Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich (Switzerland)

2006-10-02

102

Analysis of infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

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.

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

2005-04-01

103

Highspeed laser ablation cutting of metal  

NASA Astrophysics Data System (ADS)

In laser ablation cutting, irradiation of high-intense laser beams causes ejection of molten and evaporated material out of the cutting zone as a result of high pressure gradients, induced by expanding plasma plumes. This paper investigates highspeed laser ablation cutting of industrial grade metal sheets using high-brilliant continuous wave fiber lasers with output powers up to 5 kW. The laser beam was deflected with scan speeds up to 2700 m/min utilizing both a fast galvanometer scan system and a polygon scan system. By sharp laser beam focusing using different objectives with focal lengths ranging between 160 mm and 500 mm, small laser spot diameters between 16.5 ?m and 60 ?m were obtained, respectively. As a result high peak intensities between 3*108 W/cm² and 2.5*109 W/cm² were irradiated on the sample surface, and cutting kerfs with a maximum depth of 1.4 mm have been produced. In this study the impact of the processing parameters laser power, laser spot diameter, cutting speed, and number of scans on both the achievable cutting depth and the cutting edge quality was investigated. The ablation depths, the heights of the cutting burr, as well as the removed material volumes were evaluated by means of optical microscope images and cross section photographs. Finally highspeed laser ablation cutting was studied using an intensified ultra highspeed camera in order to get useful insights into the cutting process.

Ullmann, F.; Loeschner, U.; Hartwig, L.; Szczepanski, D.; Schille, J.; Gronau, S.; Knebel, T.; Drechsel, J.; Ebert, R.; Exner, H.

2013-02-01

104

Laser Ablation of Biological Tissue Using Pulsed CO2 Laser  

NASA Astrophysics Data System (ADS)

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO2 laser (wavelength: 10.6 ?m pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

2010-10-01

105

Ultraviolet-laser ablation of skin  

Microsoft Academic Search

The authors report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding

R. Linsker; J. J. Wynne; A. Torres; R. G. Geronemus

1985-01-01

106

Laser ablation threshold of cultural heritage metals  

Microsoft Academic Search

The present work has the purpose to evaluate experimentally the ablation threshold fluences of copper, silver, and their alloys in order to induce a safety laser cleaning of the metal artifacts avoiding damages to the bulkE We used two different pulsed lasers: a KrF excimer laser operating at 248 nm, 23 ns pulse duration and a Nd:YAG laser operating at

A. Lorusso; V. Nassisi; A. Buccolieri; G. Buccolieri; A. Castellano; L. S. Leo; M. di Giulio; L. Torrisi; F. Caridi; A. Borrielli

2008-01-01

107

Basic Physics of Femtosecond Laser Ablation  

Microsoft Academic Search

Laser ablation being the basic process for many prominent applications of lasers in present day high technology, medicine,\\u000a and other fields, its basic physics is reviewed in this chapter. In order to distinguish the fundamental, laser–material interaction\\u000a from the secondary effects, we concentrate on ultrashort laser pulses (???100?fs duration) at comparably low intensities,\\u000a below the commonly indicated threshold for massive

Juergen Reif

108

Femtosecond laser ablation induced plasma characteristics from submicron craters in thin metal film  

SciTech Connect

The ablation-induced plasma physics at reduced ablation crater dimensions is experimentally investigated. Frequency doubled femtosecond laser pulses are tightly focused through objective lenses onto a Cr thin film coated on quartz wafer in order to obtain ablation craters of submicron lateral dimensions. Side-view time-resolved emission images and the corresponding spectra depict the detailed plasma evolution at the fluence range near the ablation threshold. Collected emission spectra at the laser fluence level of around two to three times of ablation threshold display characteristic atomic transition peaks of the ablated Cr material from submicron ablation craters. This finding confirms that improved spatial resolution for laser-induced breakdown spectroscopy can be achieved.

Hwang, David J.; Jeon, Hojeong; Grigoropoulos, Costas P.; Yoo, Jong; Russo, Richard E. [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California 94720-1740 (United States); Applied Spectra, 48834 Kato Rd, Suite 109A, Fremont, California 94538 (United States)

2007-12-17

109

Optical properties of tin oxide nanoparticles prepared by laser ablation in water: Influence of laser ablation time duration and laser fluence  

SciTech Connect

Colloidal tin oxide nanoparticles are prepared by laser (having a wavelength of 1064 nm) ablation of tin metallic target immersed in pure deionized water. The influences of laser ablation time and laser fluence on the size and optical properties of the synthesized nanoparticles are studied. Prepared tin oxide nanoparticles are characterized by transmission electron microscope, selected area electron diffraction and UV-Visible absorption spectroscopy. The morphology of prepared tin oxide nanoparticles is found to be mostly spherical and with sizes in the nanometric range (mean radius of 3.2 to 7.3 nm). The measured UV-Visible absorption spectra show the presence of absorption peaks in the ultraviolet region. The band gap energy of samples prepared with different laser ablation time duration is calculated and is found to be increased with decrease in size (radius) of the prepared nanoparticles. Photoluminescence emission measurements at room temperature show that all the samples exhibit photoluminescence in the visible region. The peak photoluminescence emission intensity in the sample prepared with 50 min of laser ablation time is 3.5 times larger than that obtained in the sample prepared with 10 min of laser ablation time. - Highlights: Black-Right-Pointing-Pointer SnO{sub 2} nanoparticles (6.4-14.6 nm) are prepared by laser ablation in liquid technique. Black-Right-Pointing-Pointer The influences of laser ablation time and laser fluence are studied. Black-Right-Pointing-Pointer Samples are characterized by TEM and UV-Visible absorption spectroscopy. Black-Right-Pointing-Pointer UV-Visible absorption spectra exhibit quantum confinement effect. Black-Right-Pointing-Pointer Samples exhibit enhanced photoluminescence emissions in the visible region.

Desarkar, Himadri Sankar; Kumbhakar, P., E-mail: nitdgpkumbhakar@yahoo.com; Mitra, A.K.

2012-11-15

110

Laser ablation in analytical chemistry—a review  

Microsoft Academic Search

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,

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

2002-01-01

111

Laser ablation-induced spectral plasma characteristics in optical far- and near fields  

SciTech Connect

The aim of this work is to elucidate the ablation-induced plasma physics for chemical species analysis by laser-induced breakdown spectroscopy at higher spatial resolution. To accomplish this, the effect of the laser spot size on the laser ablation-induced plasma characteristics is experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of {approx}200 nm thickness on quartz substrate as a target. The far-field ablation is affected under tight focusing conditions, wherein nanosecond laser pulses of 532 nm wavelength are focused to laser focal spot diameters of {approx}7 and 1.5 {mu}m. The measured results show that the ablation-induced plasma from sub-10 {mu}m ablation craters exhibits complex three-dimensional behavior, leading to greatly reduced laser-plasma interaction and an order of magnitude shorter plasma lifetime. Nanosecond laser pulses of 532 nm wavelength are also coupled to a pulled fiber based near-field scanning optical microscopy probe. Due to the sharp tip presence in close proximity of the ablation craters, entirely different plasma evolution behavior is observed, highlighted by orders of magnitude shorter plasma lifetime and strongly directional material ejection. The ablation-induced plasma from reduced lateral crater dimensions both in far- and near-field shows improved contrast of atomic transition signals with respect to the wide-spectrum background, hence confirming the potential for laser-induced breakdown spectroscopy with high spatial resolution.

Hwang, David J.; Jeon, Hojeong; Grigoropoulos, Costas P. [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Yoo, Jong; Russo, Richard E

2008-07-01

112

Ablation de matériaux par laser femtoseconde  

NASA Astrophysics Data System (ADS)

L'ablation de métaux par laser impulsionnel ultrabref (femtoseconde) est étudiée en analysant les cratères par microscopie optique. La profondeur du cratère a été mesurée en fonction du nombre d'impulsions et de la fluence. Les résultats sont comparés à un modèle analytique décrivant l'interaction laser-matière en régime femtoseconde.

Bruneau, S.; Hermann, J.; Itina, T.; Sentis, M.; Semerok, A.; Marine, W.

2003-06-01

113

Resonant laser ablation: Mechanisms and applications  

SciTech Connect

Ever since the first report of laser action, it has been recognized that laser ablation (evaporation/volatilization) may provide a useful sampling mechanism for chemical analysis. In particular, laser ablation is rapidly gaining popularity as a method of sample introduction for mass spectrometry. While most laser ablation/mass spectrometry has been performed with fixed frequency lasers operating at relatively high intensities/fluences ({ge}10{sup 8} W/cm{sup 2}, {ge}1 J/cm{sup 2}), there has been some recent interest in the use of tunable lasers to enhance the ionization yield of selected components in an analytical sample. This process has been termed resonant laser ablation (RLA), and typically relies on irradiation of a sample in a mass spectrometer with modest intensity laser pulses tuned to a one- or two-photon resonant transition in the analyte of interest. Potential advantages of RLA include: (1) simplification of the mass spectrum, by enhancement of signal from the analyte of interest; (2) improvement of the absolute detection limits by improving the ionization efficiency, and (3) improvement in relative sensitivity. The sensitivity enhancement results from reduction of spurious signal, and accompanying noise, in the detection channel. This spurious signal may be due to bleed through from adjacent mass channels, or from isobaric interferences. RLA tends to produce higher mass resolution because of minimal spatial spread in the ion source and small space charge effects. In this manuscript we present a survey of RLA attributes and applications.

Anderson, J.E.; Bodla, R.; Eiden, G.C.; Nogar, N.S.; Smith, C.H.

1994-06-01

114

Pulsed Laser Deposition — Ablation Mechanism and Applications  

NASA Astrophysics Data System (ADS)

Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough. In general, the method of pulsed laser deposition (PLD) is simple. Only few parameters need to be controlled during the process. Targets used in PLD are small compared with other targets used in other sputtering techniques. It is quite easy to produce multi-layer film composed of two or more materials. Besides, by controlling the number of pulses, a fine control of film thickness can be achieved. Pulsed-laser deposition has been used to deposit an extraordinarily wide range of materials. Historically, the most significant application of PLD has been in the area of high temperature superconducting thin films. The demonstration that PLD could be used to deposit YBa2Cu3O7-x (YBCO) films with zero resistivity at nearly 85 K sparked a significant amount of high temperature superconductivity research over the past decade and has stimulated research in PLD in general. The most striking limitations of PLD are the generation of particulates during the deposition process and the non uniform coating thickness, when substrates of large area are deposited.

Rao, M. C.

115

Nanosecond laser ablation of silver nanoparticle film  

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

116

Resonant laser ablation: mechanisms and applications  

SciTech Connect

We report on aspects of resonant laser ablation (RLA) behavior for a number of sample types: metals, alloys, thin films, zeolites and soil. The versatility of RLA is demonstrated, with results on a variety of samples and in several mass spectrometers. In addition, the application to depth profiling of thin films is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation is presented.

Anderson, J.E. [Los Alamos National Lab., NM (United States); Allen, T.M. [California Univ., Davis, CA (United States). Dept. of Chemistry; Garrett, A.W.; Gill, C.G.; Hemberger, P.H. [Los Alamos National Lab., NM (United States); Kelly, P.B. [California Univ., Davis, CA (United States). Dept. of Chemistry; Nogar, N.S. [Los Alamos National Lab., NM (United States)

1996-10-01

117

Laser ablation of phenylazide in an argon matrix: direct observation and chemical reactivity of ablated fragments  

NASA Astrophysics Data System (ADS)

Ablation of pentafluorophenylazide (FPA) in an Ar matrix at 8-10 K was carried out upon irradiation with ns-pulsed UV lasers in a vacuum. The plume of ablated products was monitored by a time-resolved imaging/spectroscopic technique using a gated and intensified CCD camera system. A large amount of pentafluorophenylnitrene (FPN) having a high kinetic energy ( 6 eV) was ejected as fragments from the matrix film during ablation. A quantitative formation of triplet FPN from the photolysis of the FPA was observed by spectroscopic measurements in the IR and UV-visible regions, and was confirmed by a theoretical IR spectrum calculated according to density functional theory. A FPN beam is useful for chemical surface modification of organic materials, such as aromatic polyester and alkylthiol. A surface analysis of these materials by X-ray photoelectron spectroscopy and Fourier transform infrared reflection absorption spectroscopy showed that the FPN was immobilized onto the surface through chemical bonds. This technique for the chemical surface modification of materials is made possible by a pulsed beam of reactive fragments with a high density in the laser ablation process.

Niino, H.; Sato, T.; Yabe, A.

118

Ultrafast microscopy of laser ablation of refractory materials: ultra low threshold stress-induced ablation  

Microsoft Academic Search

The fundamental mechanisms of photothermal laser ablation of thin films of refractory materials on glass are investigated, using time-resolved microscopy with variable duration ablation pulses (1ns–10?s). A fundamental understanding of ablation mechanisms can be used to develop designer materials with ultra efficient ablation, i.e. materials that can be ablated using economical low power laser sources. Refractory Ti and TiN thin

Serguei G. Koulikov; Dana D. Dlott

2001-01-01

119

Femtosecond laser lithotripsy: feasibility and ablation mechanism  

NASA Astrophysics Data System (ADS)

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (?=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 ?m, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 ?m, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

Qiu, Jinze; Teichman, Joel M. H.; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D.; Chan, Kin Foong; Milner, Thomas E.

2010-03-01

120

[The deposition of elements in the process of laser ablation of silicon].  

PubMed

Laser processing in the semiconductor industry (especially silicon material) has broad application prospects. The interaction between the laser and silicon is complex, and the present paper mainly studied the silicon morphology in UV laser ablation and the influence law of ambient gas. Studies have shown that the laser plasma ionization effect of silicon in the UV laser ablation has a decisive impact: the removal of the material becomes possible because of generating gasification and ionization, laser plasma shock wave can make phase transition material discharge effectively, and laser plasma spectroscopy ionization effect can make the oxygen elements in the air ionize and deposit effectively. PMID:23697147

Wang, Shao-Peng; Feng, Guo-Ying; Duan, Tao; Han, Jing-Hua

2013-02-01

121

Quantifying the quality of femtosecond laser ablation of graphene  

NASA Astrophysics Data System (ADS)

The influence of beam intensity on laser ablation quality and ablation size is experimentally studied on graphene-coated silicon/silicon dioxide substrates. With an amplified femtosecond-pulsed laser system, by systematically decreasing the average power, periodic stripes with decreasing widths are ablated. Histogram analyses of the untouched and ablated regions of scanning electron microscope images of the fabricated structures make it possible to quantify the ablation quality. These analyses reveal that submicron ablation can be achieved while maintaining 75 % ablation accuracy by adjusting the beam intensity around the ablation threshold.

Sahin, Ramazan; Akturk, Selcuk; Simsek, Ergun

2014-06-01

122

Laser ablated hard coating for microtools  

DOEpatents

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

McLean, II, William (Oakland, CA); Balooch, Mehdi (Berkeley, CA); Siekhaus, Wigbert J. (Berkeley, CA)

1998-05-05

123

Laser ablated hard coating for microtools  

DOEpatents

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

McLean, W. II; Balooch, M.; Siekhaus, W.J.

1998-05-05

124

Plasma study in laser ablation process for deposition  

NASA Astrophysics Data System (ADS)

In order to get a better inside in the reactive Pulsed Laser Deposition of nitride thin films, we performed time- and space-resolved plasma diagnostics during ablation of Ti, Al and C targets in low pressure nitrogen containing atmospheres using pulsed nanosecond UV lasers. In the case of carbon, thin films of CxNy were deposited on silicon substrates and characterized by Rutherford Backscattering Spectroscopy and Nuclear Reaction Analysis. With respect to irradiation of metal targets, during which a dense and highly ionized plasma was induced for laser intensities >= 100 MWcm-2, much higher values >= 1 GWcm-2 were necessary to induce significant plasma ionization on carbon. To increase the plasma reactivity in the case of carbon ablation, a radiofrequency discharge was added to excite and preionize the ambient gas. From correlation between the plasma characteristics and thin film analyses, conclusions could be made about the CxNy deposition process.

Vivien, C.; Hermann, Jorg; Boulmer-Leborgne, C.

1998-05-01

125

Ultrashort Pulse Laser Ablation for Depth Profiling of Bacterial Biofilms  

PubMed Central

Sample ablation by pulsed lasers is one option for removing material from a sample surface for in situ depth profiling during imaging mass spectrometry, but ablation is often limited by laser-induced damage of the remaining material. A preliminary evaluation was performed of sub-100 fs, 800 nm pulsed laser ablation for depth profiling of bacterial biofilms grown on glass by the drip flow method. Electron and optical microscopy were combined with laser desorption vacuum ultraviolet postionization mass spectrometry to analyze biofilms before and after ablation. Ultrashort laser pulses can ablate 10 – 100 µm thick sections of bacterial biofilms, leaving behind a layer of lysed cells. However, mass spectra from intact and ablated biofilms doped with antibiotic are almost identical, indicating little chemical degradation by ablation. These results are consistent with prior observations from laser surgery and support the use of ultrashort pulse laser ablation for minimally disruptive depth profiling of bacterial biofilms and intact biological samples.

Milasinovic, Slobodan; Liu, Yaoming; Gasper, Gerald L.; Zhao, Youbo; Johnston, Joanna L.; Gordon, Robert J.; Hanley, Luke

2010-01-01

126

Laser ablation of gall bladder stones  

NASA Astrophysics Data System (ADS)

Study of laser interaction with calculi is presented. A system of Nd-Yag and Ho-Yag pulsed lasers were used to produce fluorescence and plasma signals at the stone surface surrounded by saline and bile fluids. Fourth harmonic from Nd-Yag laser was transmitted to the samples by graded UV optical fibres. Gall bladder stones of various compositions were subjected to the high power Ho-Yag laser. Temporal transients and spectral evolution of plasma and fluorescence signals were monitored by a streak camera. A profile of acoustic pressures generated by shock waves was recorded with sensitive hydrophones placed in the surrounding fluids. Ablation threshold, cavitation process and fluorescence dependence on the laser parameters were studied in detail. Potential of stone identification by fluorescence and possible hydrodynamic model for ablation of biological samples is discussed.

Marafi, M.; Makdisi, Y.; Bhatia, K. S.; Abdulah, A. H.; Kokaj, Y.; Mathew, K.; Quinn, F.; Qabazard, A.

1999-06-01

127

Laser Ablation for Small Hepatocellular Carcinoma  

PubMed Central

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is increasingly detected at small size (<5?cm) owing to surveillance programmes in high-risk patients. For these cases, curative therapies such as resection, liver transplantation, or percutaneous ablation have been proposed. When surgical options are precluded, image-guided tumor ablation is recommended as the most appropriate therapeutic choice in terms of tumor local control, safety, and improvement in survival. Laser ablation (LA) represents one of currently available loco-ablative techniques: light is delivered via flexible quartz fibers of diameter from 300 to 600??m inserted into tumor lesion through either fine needles (21g Chiba needles) or large-bore catheters. The thermal destruction of tissue is achieved through conversion of absorbed light (usually infrared) into heat. A range of different imaging modalities have been used to guide percutaneous laser ablation, but ultrasound and magnetic resonance imaging are most widely employed, according to local experience and resource availability. Available clinical data suggest that LA is highly effective in terms of tumoricidal capability with an excellent safety profile; the best results in terms of long-term survival are obtained in early HCC so that LA can be proposed not only in unresectable cases but, not differently from radiofrequency ablation, also as the first-line treatment.

Pacella, Claudio Maurizio; Francica, Giampiero; Di Costanzo, Giovanni Giuseppe

2011-01-01

128

Mapping of different structures on large area of granite sample using laser-ablation based analytical techniques, an exploratory study  

Microsoft Academic Search

Laser-ablation based analytical techniques represent a simple way for fast chemical analysis of different materials. In this work, an exploratory study of multi-element (Ca, Al, Fe, Mn) mappings of a granite sample surface was performed by laser-induced breakdown spectroscopy (LIBS) and subsequently by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. The operating parameters (e.g. pulse energy, ablation-crater size)

K. Novotny; J. Kaiser; M. Galiova; V. Kone?ná; J. Novotny; R. Malina; M. Liska; V. Kanický; V. Otruba

2008-01-01

129

Hydroxyapatite coatings deposited by laser-assisted laser ablation method  

Microsoft Academic Search

Application of a new hydroxyapatite coating method called the laser-assisted laser ablation method improves adhesion due to irradiation by an assist laser beam for optical annealing. In this study, substrate immersion in a simulated body fluid was performed to confirm the biocompatibility of the technique. The coatings contained a significant quantity of amorphous calcium phosphates. The amorphous phase was dissolved

Masahito Katto; Masahiro Nakamura; Toshiharu Tanaka; Takeyoshi Nakayama

2002-01-01

130

Laser ablation of silver and gold in liquid ammonia  

NASA Astrophysics Data System (ADS)

Laser ablation of a silver (Ag) and/or gold (Au) target was performed in liquid ammonia (l-NH3) at 233 K using nanosecond laser pulses of 1064, 532 and 355 nm wavelengths. An “in situ” monitoring of the ablation process by UV/vis/NIR spectroscopy has shown the evolution of the surface plasmon extinction band of silver or gold nanoparticles and thus confirmed their formation. While sols of Au nanoparticles in l-NH3 are quite stable in air, those of Ag nanoparticles undergo oxidation to Ag(I) complexes with NH3 ligands. On the other hand, formation of solvated electrons, namely of the (e-)NH3 solvates, has not been unequivocally confirmed under the conditions of our laser ablation/nanoparticle fragmentation experiment, since only very weak vis/NIR spectral features of these solvates were observed with a low reproducibility. Reference experiments have shown that the well-known chemical production of these solvates is hindered by the presence of Ag and Au plates. Ag and Au targets can thus possibly act as electron scavengers in our ablation experiments.

Šmejkal, Petr; Pfleger, Ji?í; Vl?ková, Blanka

2010-10-01

131

Laser Ablation and Thin Film Deposition  

NASA Astrophysics Data System (ADS)

One of the most versatile deposition techniques in solid-state physics and analytical chemistry is the vaporization of condensed matter using photons. A short-pulsed high-power laser beam is focused onto a sample surface thereby converting a finite volume of a solid instantaneously into its vapor phase constituents such as ions and neutrals. Subsequently, the vapor moves away from the target at a high velocity and can be sampled either to grow a film or being analyzed by various spectroscopic techniques. In this chapter, the focus is on general properties of pulsed laser ablation relevant for solid-state physics like the initial ablation processes, plume formation, and plume properties. Next, oxide thin film growth will be discussed and the growth of LaAlO3/SrTiO3 heterostructures is presented as one example of tailoring oxide interfaces with surprising properties. The final discussion is on the topic of polymer ablation.

Schneider, Christof W.; Lippert, Thomas

132

Picosecond laser ablation of transparent materials  

NASA Astrophysics Data System (ADS)

Processing of thin and ultra-thin glass displays is becoming more important in the fast increasing market of display manufacturing. As conventional technologies such as mechanical scribing followed by manual breaking mostly lead to bad edge quality and thus to a huge amount of reject, other processes like ablation processes [1] with picosecond lasers are getting more and more interesting. However processing with ultrashort pulsed lasers partially leads to unwanted effects which should be understood in a better way by means of intensive basic research. Therefore the ablation mechanism of ultrashort pulses on transparent materials was investigated in this research project. On the one hand the ablation mechanism was analyzed in a simulative way by means of rate equations on the other hand by laboratory experiments.

Russ, Simone; Siebert, Christof; Eppelt, Urs; Hartmann, Claudia; Faißt, Birgit; Schulz, Wolfgang

2013-03-01

133

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition  

SciTech Connect

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

Geohegan, D.B.

1994-09-01

134

Experimental studies on plasma emission spectroscopy of laser ablation of hexahydro-l,3,5-trinitro-l,3,5-triazine  

NASA Astrophysics Data System (ADS)

A Q-switched Nd: YAG laser (with a wavelength of 532 nm and a pulse width of 15 ns) was used to ablate hexahydrol, 3,5-trinitro-l,3,5-triazine (RDX) in the air. The plasma emission spectra were recorded by an intensified charge-coupled device (ICCD) camera. The results showed that the plasma existed in the process of laser ablation of RDX. In the ultraviolet area, the main spectral lines were C I (187.46 nm and 223.01 nm), C II (323.1 nm) and N II (243.72 nm and 332.9 nm), while the dominating emission lines in the visible area were N II (393.9 nm and 454.7 nm), O II (490.75 nm) and O III (401.2 nm). Under experimental conditions, the intensities of the main peaks grew obviously with the increasing of the pulse delay, but laser energy didn't have so much effect on the spectra. The ionization of the air almost did not influence plasma emission lines of RDX.

Zhang, Wei; Shen, Ruiqi; Wu, Lizhi; Ye, Yinghua; Hu, Yan

2013-05-01

135

Dynamical modeling of laser ablation processes  

SciTech Connect

Several physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume; plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms; gas dynamic, hydrodynamic, and collisional descriptions of plume transport; and molecular dynamics models of the interaction of plume particles with the deposition substrate. The complexity of the phenomena involved in the laser ablation process is matched by the diversity of the modeling task, which combines materials science, atomic physics, and plasma physics.

Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

1995-09-01

136

Surface properties of femtosecond laser ablated PMMA.  

PubMed

The effects of femtosecond laser ablation on the physical and chemical properties at the surface of poly methylmethacrylate (PMMA) were studied. Femtosecond laser microfabrication caused the initially wetting behavior of PMMA to become nonwetting, mainly because of the laser-induced surface porosity at the submicroscale. Static and dynamic contact angle measurements along with morphological characterization revealed that after the laser irradiation, the system lies in an intermediate regime between those theorized by Wenzel and Cassie-Baxter. Spectroscopic analysis did not evidence any significant variation in the chemical properties of the processed polymeric surfaces. PMID:20735111

Marco, Carmela De; Eaton, Shane M; Suriano, Raffaella; Turri, Stefano; Levi, Marinella; Ramponi, Roberta; Cerullo, Giulio; Osellame, Roberto

2010-08-01

137

Reactions of Laser-Ablated Metal Atoms.  

National Technical Information Service (NTIS)

Laser-ablated boron atoms react with methyl fluoride in an argon stream to form two major products, CH2BF and CHBF. In similar reactions of boron with methyl chloride and methyl bromide, both CH2BX and CHBX are also observed, as well as the primary insert...

L. Andrews

2000-01-01

138

NOVEL LASER ABLATION TECHNOLOGY FOR SURFACE DECONTAMINATION  

EPA Science Inventory

The objective of this project is to develop a novel Laser Ablation Decontamination in Liquid (LADIL) technology for surface decontamination and safe removal of radioactive and/or toxic contaminants. It aims to achieve more efficient surface decontamination without secondary conta...

139

Laser ablation investigations for future microthrusters  

NASA Astrophysics Data System (ADS)

Low thrust engines with high specific impulse and long lifetime that allow for precise distance control in satellite formation flight and compensation of small disturbing forces become increasingly important in missions for geodetic purposes or astronomic science. Currently available microthrusters cannot yet meet these demands. Laser ablative micropropulsion is a relatively new concept that has already proven its potential for providing very small impulse bits and high specific impulses. Additionally, by using electro-optic beam control even the most stringent conditions like "no moving parts" could be met. An overview of the experimental facilities for characterization of the ablation process and future plans for the experimental setups are presented. In a first step, laser ablation of metal targets in a vacuum vessel using short pulse solid state laser sources is investigated. In this paper we present first results on Faraday cup and profilometry measurements and discuss their impact on further investigations of plume characteristics. Future experimental goals as well as DLR's research strategy for the development of precise and reliable laser ablation microthrusters are addressed.

Karg, Stephanie; Scharring, Stefan; Eckel, Hans-Albert

2012-07-01

140

Laser ablation and cryotherapy of melanoma metastases.  

PubMed

Both laser therapy and cryotherapy have been used with good results in the ablation of cutaneous melanoma metastases. There is less literature evidence in support of cryotherapy. Carbon dioxide laser therapy is a simple, low cost, patient-friendly technique, effective for palliation of individual lesions. There is evidence of a more profound regional effect, with unexplained absences of recurrence at treated sites and reported complete remissions, which demands further investigation. PMID:24249157

John, Hannah E; Mahaffey, Peter J

2014-03-01

141

Laser surface ablation cleaning of nuclear facilities  

Microsoft Academic Search

High power Nd:YAG laser beam with wavelength 1064nm, pulsewidth 10 picosecond regime was focused onto the scanning targets of SUS304 stainless steel with Zn coating of thickness 21 micrometers , and delivered via a step index fused silica optical fiber of length 3m and core diameter 1mm. Irradiation ablation effect and some basic aspects of high power laser beam transporting

Xianglin Zhou; Kazuo Imasaki; Hideo Umino; Kohji Sakagishi; Sadao Nakai; Chiyoe Yamanaka

2000-01-01

142

Confined laser ablation for single-shot nanoparticle deposition of silver  

NASA Astrophysics Data System (ADS)

Spatially confined laser ablation of silver was used to form long-lived dense plasma for single-shot deposition of a nanoparticle film. The expansion of the ablation plume was restricted by placing a glass substrate at 50 ?m from the silver target surface. Time-resolved optical emission spectroscopy showed that the confined plasma is sustained for longer time than for free ablation. A single laser shot is sufficient to produce a layer of silver nanoparticles on the substrate. In absorption the nanoparticle layer displays a surface plasmon resonance which is comparable to films made by conventional pulsed laser deposition in vacuum.

Donnelly, T.; Lunney, J. G.

2013-10-01

143

Free electron laser ablation of urinary calculi: an experimental study  

Microsoft Academic Search

Infrared laser ablation of urinary calculi was investigated as a function of wavelength to determine the relation of ablation threshold fluences, ablation depths, and optical absorption. A simple photothermal ablation model was employed to examine this relationship. Human urinary calculi composed of >95% uric acid, >95% cystine, >95% calcium oxalate monohydrate (COM), and >90% magnesium ammonium phosphate hexahydrate (MAPH) were

Kin Foong Chan; Bernard Choi; Gracie Vargas; Daniel X. Hammer; Brian Sorg; T. Joshua Pfefer; Joel M. H. Teichman; Ashley J. Welch; E. Duco Jansen

2001-01-01

144

Laser ablation mechanism of transparent dielectrics with picosecond laser pulses  

NASA Astrophysics Data System (ADS)

Thin glass sheets (thickness <1 mm) have a great potential in OLED and LCD displays. While the conventional manufacturing methods, such as mechanical scribing and breaking, result in poor edge strength, ultra-short-pulsed laser processing could be a promising solution, offering high-quality cutting edges. However laser precision glass cutting suffers from unwanted material modification and even severe damage (e.g. cracks and chipping). Therefore it is essential to have a deep understanding of the ultra-short-pulsed laser ablation mechanism of transparent dielectrics in order to remedy those drawbacks. In this work, the ablation mechanism of transparent dielectrics irradiated by picosecond laser pulses has been studied. Ultrafast dynamics of free-electrons is analyzed using a rate equation for free-electron density including multi-photon ionization, avalanche ionization and loss terms. Two maps of free-electron density in parameter space are given to discuss the dependence of ablation threshold intensity/fluence on pulse duration. The laser ablation model describing laser beam propagation and energy deposition in transparent dielectrics is presented. Based on our model, simulations and experiments have been performed to study the ablation dynamics. Both simulation and experimental results show good agreement, offering great potential for optimization of laser processing in transparent dielectrics. The effects of recombination coefficient and electron-collision time on our model are investigated.

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

2012-11-01

145

Wavelength dependence of soft tissue ablation by using pulsed lasers  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-micron 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 spatial 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 ablation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

Zhang, Xianzeng; Xie, Shusen; Ye, Qing; Zhan, Zhenlin

2007-04-01

146

A Review of Laser Ablation Propulsion  

NASA Astrophysics Data System (ADS)

Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Sänger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing ``Lightcraft'' and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important rôle in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

Phipps, Claude; Bohn, Willy; Lippert, Thomas; Sasoh, Akihiro; Schall, Wolfgang; Sinko, John

2010-10-01

147

A Review of Laser Ablation Propulsion  

SciTech Connect

Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Saenger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing 'Lightcraft' and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important role in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

Phipps, Claude [Photonic Associates, LLC, 200A Ojo de la Vaca Road, Santa Fe NM 87508 (United States); Bohn, Willy [Bohn Laser Consult, Weinberg Weg 43, Stuttgart (Germany); Lippert, Thomas [Paul Scherrer Institut, CH5232 Villigen PSI (Switzerland); Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Chikusa-ku, Nagoya (Japan); Schall, Wolfgang [DLR Institute of Technical Physics, Stuttgart (Germany); Sinko, John [Micro-Nano GCOE, Nagoya University, Furo-cho, Nagoya, Aichi (Japan)

2010-10-08

148

Laser plasma interaction at an early stage of laser ablation  

Microsoft Academic Search

Laser scattering and its interaction with plasma during KrF excimer laser ablation of silicon are investigated by ultrafast phototube detection. There are two peaks in an optical signal with the first peak attributed to laser scattering and the second one to plasma generation. For laser fluence above 5.8 J\\/cm2, the second peak rises earlier to overlap with the first one.

Y. F. Lu; M. H. Hong; T. S. Low

1999-01-01

149

The production of sub-micron sodium nitrate particles by laser ablation  

Microsoft Academic Search

Laser ablation is a useful source of particles for chemical analysis by inductively coupled mass spectroscopy in many applications. Optimum particle transport and ionization requires particles with sizes in the range 0.1-2 7m. Significant questions remain as to the mechanisms behind particle production by laser ablation. In this work, we collect and observe particles produced from single-crystal sodium nitrate during

S. C. Langford; J. T. Dickinson; M. L. Alexander

1999-01-01

150

The production of sub-micron sodium nitrate particles by laser ablation  

Microsoft Academic Search

Laser ablation is a useful source of particles for chemical analysis by inductively coupled mass spectroscopy in many applications. Optimum particle transport and ionization requires particles with sizes in the range 0.1-2 mum. Significant questions remain as to the mechanisms behind particle production by laser ablation. In this work, we collect and observe particles produced from single-crystal sodium nitrate during

S. C. Langford; J. T. Dickinson; M. L. Alexander

1999-01-01

151

Small glass particle cloud generation induced by laser ablation  

Microsoft Academic Search

Burst of small fragments of glass has been evidenced in the present study, when ground glass surface is laser ablated. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of metal or polymer ablation. In this case, no additional metal coating has been made to further

Kunihito Nagayama; Yuriko Kotsuka; Motonao Nakahara; Shiro Kubota

2005-01-01

152

Specific Impulse Definition for Ablative Laser Propulsion  

NASA Technical Reports Server (NTRS)

The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

Herren, Kenneth A.; Gregory, Don A.

2004-01-01

153

Simulation of Double-Pulse Laser Ablation  

SciTech Connect

We investigate the physical reasons of a strange decrease in the ablation depth observed in femtosecond double-pulse experiments with increasing delay between the pulses. Two ultrashort pulses of the same energy produce the crater which is less than that created by a single pulse. Hydrodynamic simulation shows that the ablation mechanism is suppressed when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The modeling of the double-pulse ablation for different delays between pulses confirms this explanation.

Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R. [Joint Institute for High Temperatures of RAS, Izhorskaya 13 Bldg 2, Moscow, 125412 (Russian Federation); Itina, Tatian E. [Laboratoire Hubert Curien, UMR CNRS 5516, 18 rue Benoit Lauras, Bat. F, 42000, St-Etienne (France)

2010-10-08

154

[Laser ablation. Do we still need it?].  

PubMed

Laser ablation (LA) is momentarily the only invasive ablation procedure besides radiofrequency ablation (RFA) which can be performed entirely under magnetic resonance imaging (MRI) guidance. The long-term outcome and morbidity profiles are broadly identical for both modalities, excluding the RFA-specific prevalence for skin burns. The technical and logistic disadvantages of LA have been overcome since the introduction of miniaturized two-component applicators. The main advantage of LA is its superior MRI compatibility. Interference-free imaging during LA allows MR thermometric real-time therapy control without the need for RF filters. High-resolution thermometry in the target zone only makes sense without the extinction artifact of a metal probe and this condition is met only by the glass fibers of LA. An independent therapy monitoring is crucial in modern scenarios of oncologic quality management. PMID:22249697

Rosenberg, C; Hoffmann, C O M; Mensel, B; Puls, R; Hosten, N

2012-01-01

155

Status of the Ablative Laser Propulsion Studies  

NASA Technical Reports Server (NTRS)

We present a short review of our laser-propulsion research as well as some of the current results of the Ablative Laser Propulsion (ALP) studies currently underway at the University of Alabama in Huntsville. It has been shown that direct surface ablation of a solid material produces high specific impulse (Isp) at relatively high energy conversion efficiency (20 - 40%). We detail measurements of specific impulse, thrust and coupling coefficients for elemental target materials both with single and with double pulse laser shots. We also present measurements taken using three independent methods for determination of Isp. The three methods produce consistent values from ion time-of-flight technique, impulse measurements and imaging of the expansion front of plasma plume. We present a demonstration of our ALP lightcraft, a small free-flying micro-vehicle that is propelled by ablation. For ALP lightcraft we use a subscale thin shell of nickel replicated over a diamond turned mandrel that produces a highly polished self-focusing, truncated at the focus parabolic mirror. The mass of the lightcraft is 54 mg and it is driven by 100-ps wide, 35-mJ laser pulses at 532 nm wavelength. This is an ongoing research. We also present the latest work on laserdriven micro-thrusters and detail some the near term goals of our program.

Herren, Kenneth A.; Lin, Jun; Cohen, Tinothy; Pakhomov, Andrew V.; Thompson, M. Shane

2004-01-01

156

Surface cleaning by laser ablation.  

National Technical Information Service (NTIS)

Nd:YAG laser cleaning of metal oxides from 304L stainless steel surfaces has been characterized. Thin chromium oxide films can be completely removed from the surface using a single 10 nsec pulse of laser radiation with an average surface irradiance greate...

H. C. Peebles N. A. Creager D. E. Peebles

1991-01-01

157

Experimental research of two-wavelength laser ablation biological tissue  

NASA Astrophysics Data System (ADS)

Laser ablation biologic tissue is an important performance of laser application. Based on the combination function of two-wavelength laser to biologic tissue ablation, the semi-continuous two-wavelength laser at 532nm and 1064nm ablating blood tissue was investigated by experiment. The fresh pork and pig liver specimens were ablated at different laser power density and different laser power proportion in water conditions and ablation depth and thermo-damage thickness were measured. The experiment results indicate that there is no effective ablation but deeper thermo-damage of the 1064 nm laser to biologic tissue in water conditions when the 532nm laser power is little but the ablation efficiency sharp inc- reases and the thermo-damage sharp decreases when the 532nm laser power arrives to a threshold. The combination function of two wavelength laser to tissue ablation is appeared here. It indicates that the ablation efficiency and hemostatic function in laser surgery can be adjusted by the two-wavelength laser power proportion.

Yao, Yucheng; Huang, Chuyun; He, Yanyan; Chen, Xia

2009-08-01

158

Modeling CO{sub 2} Laser Ablative Impulse with Polymers  

SciTech Connect

Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO{sub 2} laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO{sub 2} laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

Sinko, John E. [Micro-Nano Global Center of Excellence (GCOE), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan 464-8603 (Japan); Phipps, Claude R. [Photonic Associates, LLC, 200A Ojo de la Vaca Rd., Santa Fe, NM 87508 (United States); Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan, 464-8603 (Japan)

2010-10-08

159

Modeling CO2 Laser Ablative Impulse with Polymers  

NASA Astrophysics Data System (ADS)

Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO2 laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO2 laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

Sinko, John E.; Phipps, Claude R.; Sasoh, Akihiro

2010-10-01

160

Femtosecond, picosecond and nanosecond laser ablation of solids  

Microsoft Academic Search

Laser ablation of solid targets by 0.2-5000rps Ti : Sapphire laser pulses is studied. Theoretical models and qualitative explanations of experimental results are presented. Advantages of femtosecond lasers for precise material processing are discussed and demonstrated.

B. N. Chichkov; C. Momma; S. Nolte; F. von Alvensleben; A. Tünnermann

1996-01-01

161

Characterization of laser ablation plasmas by laser beam deflection  

Microsoft Academic Search

Laser probe beam and multiple-pass deflection techniques were used for real time and in situ monitoring of laser ablation plasma plumes in the mTorr pressure regime. Intensity and transit time of shock wave fronts were studied as functions of focal lens position, laser energy and pressure. The velocity of the shock wave was determined to be up to 30kms?1 for

C. Sánchez Aké; H. Sobral; M. Villagrán Muniz; L. Escobar-Alarcon; E. Camps

2003-01-01

162

Deposition of diamond-like carbon films via excimer laser ablation of polybutadiene  

Microsoft Academic Search

The process of depositing diamond-like carbon films on fused quartz substrates via the plume generated by the excimer laser ablation of polybutadiene is reported in this paper. The deposited films were characterized and investigated using Raman spectroscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. Microhardness and thickness of the deposited films were measured, and influence of experimental factors such as substrate

Meng Ouyang; Hiroyuki Hiraoka

1996-01-01

163

Applications and mechanisms of laser ablation for elemental analysis of nuclear wastes and contaminated soils  

Microsoft Academic Search

Survey methods for compositional analysis of nuclear wastes and contaminated soils are under development to support characterization prior to treatment and continued monitoring during remediation. Laser ablation in conjunction with optical spectroscopy and mass spectroscopy are attractive because of the safety and convenience of minimal sample handling and very small sampling volume. However, the signal intensities in analytic applications depend

Steven C. Langford; Tom Dickinson

1996-01-01

164

Internal structure and expansion dynamics of laser ablation plumes into ambient gases  

Microsoft Academic Search

The effect of ambient gas on the expansion dynamics of the plasma generated by laser ablation of an aluminum target has been investigated using frequency doubled radiation from a Q-switched Nd:YAG laser. The diagnostic tools include fast photography of overall visible plume emission using a 2 ns gated intensified CCD camera and space and time resolved emission spectroscopy using a

S. S. Harilal; C. V. Bindhu; M. S. Tillack; F. Najmabadi; A. C. Gaeris

2003-01-01

165

Measurement and analysis of the pure rotational spectra of tin monochloride, SnCl, using laser ablation equipped chirped pulse and cavity Fourier transform microwave spectroscopy  

NASA Astrophysics Data System (ADS)

The pure rotational spectrum of tin monochloride, SnCl, has been measured and analyzed using chirped pulse and cavity Fourier transform microwave spectrometers equipped with a laser ablation source. SnCl, in its X2? electronic state, has been measured in the 8-17 GHz region. Rotational constants, centrifugal distortion constants, ?-doubling constants, magnetic hyperfine constants, and nuclear electric quadrupole coupling constants for multiple isotopologues have been determined and are reported. The bond length, nuclear magnetic and quadrupole constants have been analyzed and compared against the family of tetral halides. Analysis of the bond length and hyperfine interactions point to a Sn-Cl single bond which is largely ionic in nature.

Grubbs, G. S.; Frohman, Daniel J.; Novick, Stewart E.; Cooke, S. A.

2012-10-01

166

KTP-532 laser ablation of urethral strictures  

NASA Astrophysics Data System (ADS)

In 1988, the KTP-532 laser was used to ablate a series of benign urethral strictures. Rather than using a single incision, as in urethrotomy, strictures were treated with a 360$DEG contact photoradiation. Thirty-one males, average age 53.2 years, received 37 treatments. Six patients underwent a second laser treatment. Stricture etiology was commonly iatrogenic (32%), traumatic (16%), and post-gonococcal (10%). Stricture location included mainly bulbar (49%), membranous (20%), and penile (12%) areas. The surgical technique consisted of a circumferential ablation followed by foley catheter placement (mean 10 days). Follow-up on 29 of 31 patients ranged from 1 to 16 months (mean 9.7) Complete success occurred in 17 patients (59%) who had no further symptoms or instrumentation. Partial success was seen in 6 patients (20.5%) with symptoms but no stricture recurrence. Six patients (20.5%) failed therapy requiring additional surgery or regular dilatations. No complications were encountered. Although longer assessment is required, KTP-532 laser ablation of urethral strictures appears efficacious.

Malloy, Terrence P.

1991-07-01

167

Solar cell contact formation using laser ablation  

SciTech Connect

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.

Harley, Gabriel; Smith, David; Cousins, Peter

2012-12-04

168

CO2 Laser Absorption in Ablation Plasmas  

SciTech Connect

The impulse formation by laser ablation is limited by the premature absorption of the incident laser radiation in the initially produced cloud of ablation products. The power fraction of a CO2 laser pulse transmitted through a small hole in a POM sample for pulse energies of 35 to 150 J focused on a spot of 2 cm2 has been compared with the incident power. The plasma formation in vacuum and in air of 3500 Pa and the spread of the shock wave with velocities of 1.6 to 2.4 km/s in the low pressure air was observed by Schlieren photography. A sharp edged dark zone with a maximum extension of 10 to 12 mm away from the target surface develops within 5 {mu}s independently of the pressure and is assumed to be a plasma. In order to find out, if this is also the zone where the majority of the incident laser radiation is absorbed, a CO2 probe laser beam was directed through the expansion cloud parallel to and at various distances from the sample surface. The time behavior of the absorption signal of the probe beam has been measured and an absorption wave could be observed.

Eckel, Hans-Albert; Tegel, Jochen; Schall, Wolfgang O. [DLR-Institute of Technical Physics, D-70503 Stuttgart, Postfach 80 03 20 (Germany)

2006-05-02

169

Nanosecond and femtosecond excimer laser ablation of fused silica  

Microsoft Academic Search

Ablation of fused silica using standard excimer lasers (20–30 ns pulse duration at 193, 248, and 308 nm) and a short pulse laser system (500 fs at 248 nm) is reported. Ablation rates range from several hundred nm\\/pulse (193 nm or fs-laser) up to about 6 µm\\/pulse (308 nm). The performance of the ablation is found to depend not only

J. Ihlemann; B. Wolff; P. Simon

1992-01-01

170

Spectroscopic characterization of laser ablation brass plasma  

SciTech Connect

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated.

Shaikh, Nek M. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Institute of Physics, University of Sindh, 76080 Jamshoro (Pakistan); Hafeez, Sarwat; Kalyar, M. A.; Ali, R.; Baig, M. A. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan)

2008-11-15

171

Ablation dynamics in laser sclerotomy ab externo  

NASA Astrophysics Data System (ADS)

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.

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

1996-01-01

172

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

National Technical Information Service (NTIS)

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 inte...

R. A. Lindley

1993-01-01

173

Nanosecond laser ablation for pulsed laser deposition of yttria  

NASA Astrophysics Data System (ADS)

A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

Sinha, Sucharita

2013-09-01

174

Dynamics of Laser-Driven, Ablatively Accelerated Targets.  

National Technical Information Service (NTIS)

The characteristics of ablation plasma from planar targets, driven by long Nd:glass laser pulses (4 nsec, < 10 exp 14 W/cm exp 2 ), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arra...

J. Grun

1981-01-01

175

Elemental fractionation and stoichiometric sampling in femtosecond laser ablation  

Microsoft Academic Search

Elemental fractionation in femtosecond laser ablation is studied by ICP-MS by applying successive single laser shots to binary metallic and semiconductor samples as well as to multi-component glasses. Fractionation can be observed in the first laser shots in particular if the laser fluence is near the ablation threshold of the sample. However, the element ratio in the laser-sampled masses changes

Carmen C. Garcia; Helmut Lindner; Alex von Bohlen; Cedomil Vadla; Kay Niemax

2008-01-01

176

Spectroscopic characterization of laser ablated silicon plasma  

NASA Astrophysics Data System (ADS)

We report plasma parameters of laser ablated silicon plasma using the fundamental (1064 nm) and second harmonics (532 nm) of a Nd?:?YAG laser. The electron temperature and electron number density are evaluated using the Boltzmann plot method and Stark broadened line profile, respectively. The electron temperature and electron number density are deduced using the same laser irradiance 2–16 GW cm?2 for 1064 nm and 532 nm as 6350–7000 K and (3.42–4.44) × 1016 cm?3 and 6000–6400 K and (4.20–5.72) × 1016 cm?3, respectively. The spatial distribution of plasma parameters shows a decreasing trend of 8200–6300 K and (4.00–3.60) × 1016 cm?3 for 1064 nm and 6400–5500 K and (5.10–4.50) × 1016 cm?3 for 532 nm laser ablation. Furthermore, plasma parameters are also investigated at low pressure from 45 to 550 mbar, yielding the electron temperature as 4580–5535 K and electron number density as (1.51–2.12) × 1016 cm?3. The trend of the above-mentioned results is in good agreement with previous investigations. However, wavelength-dependent studies and the spatial evolution of plasma parameters have been reported for the first time.

Shakeel, Hira; Mumtaz, M.; Shahzada, S.; Nadeem, A.; Haq, S. U.

2014-06-01

177

Preparation of nanofluids using laser ablation in liquid technique  

SciTech Connect

In this work we report some results on thermal and transport properties of Ag-di water and Al-di water nanofluids that were prepared using Nd:yag laser to ablate Ag and Al in deionized water. The produced nanofluids were characterized using UV-VIS spectroscopy and TEM analysis. Our results on the UV-VIS spectra of the generated nanofluids demonstrated that using laser ablation in liquid we could generate stable colloids containing well-dispersed nanosized particles without use of any dispersants or surface reactive reagents. For Ag-di water nanofluids, the particles were spherical and the majority of the particles were in the 9 – 21 nm range with some big ones 23 - 26nm in size. The results on Al showed that the amplitude of the UV-VIS absorption spectra of Al-di water changed with time indicating that the ablated Al species reacts with water to yield an amorphous gel that transforms to the crystallized aluminum hydroxides with different shapes and sizes. The shapes were fibrous, triangular, rectangular, spherical shapes and joining of two pieces of triangles. In fact, these triangular and rectangular shapes were indeed pyramidal structures and hexagonal prisms, respectively.

Tran, P.X.; Soong, Yee

2007-06-01

178

Fabricating atom chips with femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We report on the microfabrication of atom chips using a femtosecond laser ablation technique to arbitrarily sculpture both thin conductive metal films and permanent magnetic materials. We have measured the threshold fluences for a variety of materials relevant to atom chip development (Au, Ag, Cu, Cr, Ni, TbGdFeCo, SmCo, CoCr). The quality of the ablation process is investigated by extracting the power spectral density of the edge roughness from composite scanning electron microscope images and through the use of a magnetoresistance microscope to measure the associated magnetic field noise. Finally, we present results from a sculptured wire which produces an array of tunable double wells designed for near-surface force sensing with Bose-Einstein condensates.

Wolff, C. H.; Whitlock, S.; Lowe, R. M.; Sidorov, A. I.; Hall, B. V.

2009-04-01

179

Pulsed holmium laser ablation of cardiac valves  

SciTech Connect

Ablation efficiency and residual thermal damage produced by pulsed holmium laser radiation were investigated in vitro for bovine mitral valves and human calcified and noncalcified cardiac valves. Low-OH quartz fibers (200 and 600 microns core diameter) were used in direct contact perpendicular to the specimen under saline or blood. Etch rate was measured with a linear motion transducer. Radiant exposure was varied from 0 to 3 kJ/cm{sup 2}. For 200-microns fibers, the energy of ablation was approximately 5 kJ/cm{sup 3} in noncalcified and 15 kJ/cm{sup 3} in calcified valves. Etch rates were dependent on mechanical tissue properties. Maximum etch rate at 1,000 J/cm{sup 2} was 1-2 mm/pulse at 3 Hz repetition rate. Microscopic examination revealed a zone of thermal damage extending 300 microns lateral into adjacent tissue. Thermal damage was independent of radiant exposure beyond twice threshold.

Lilge, L.; Radtke, W.; Nishioka, N.S. (Massachusetts General Hospital, Boston (USA))

1989-01-01

180

Effects of pressure rise on cw laser ablation of tissue  

NASA Astrophysics Data System (ADS)

The objectives of this research were to identify mechanisms responsible for the initiation of continuous wave (cw) laser ablation of tissue and investigate the role of pressure in the ablation process. Porcine aorta samples were irradiated in a chamber pressurized from 1 X 10-4 to 12 atmospheres absolute pressure. Acrylic and Zn-Se windows in the experimental pressure chamber allowed video and infrared cameras to simultaneously record mechanical and thermal events associated with cw argon laser ablation of these samples. Video and thermal images of tissue slabs documented the explosive nature of cw laser ablation of soft biological media and revealed similar ablation threshold temperatures and ablation onset times under different environmental pressures; however, more violent initiation explosions with decreasing environmental pressures were observed. These results suggest that ablation initiates with thermal alterations in the mechanical strength of the tissue and proceeds with an explosion induced by the presence superheated liquid within the tissue.

LeCarpentier, Gerald L.; Motamedi, Massoud; Welch, Ashley J.

1991-06-01

181

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser  

PubMed Central

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.

Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

2011-01-01

182

Experimental investigation of ablation efficiency and plasma expansion during femtosecond and nanosecond laser ablation of silicon  

NASA Astrophysics Data System (ADS)

Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-induced plasmas decreased faster than ns-induced plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions were compared.

Zeng, X.; Mao, X. L.; Greif, R.; Russo, R. E.

2005-02-01

183

Numerical study on propulsion properties of laser ablated polymer target  

NASA Astrophysics Data System (ADS)

Laser propulsion as a new concept propulsion technology, it is paid more and more extensive concern. Laser ablation micro thruster is one of the focus with its high specific impulse, wide dynamic range of impulse, small minimum impulse bit, low power etc, laser ablation micro thruster has wide application prospects on high-precision task of satellite attitudeadjustment, orbit maintain and networking formation control. Due to low thermal conduction, low ablation threshold, polymer material was easily ablated to generate thrust. A computational model of laser ablated polymer was established to simulated the micro-thruster working in vacuum environment. The polymer don't have fixed fusion point, so build the ablation criterion based on threshold energy, which has observed in many experiments. Put forward the polymer ablation criterion in the numerical model, the target ablation phenomenon happens when inner deposited energy achieve the threshold value. Established the energy distribution equation to describes the ablation process of temperature rise, phase change and the influence of chemical exothermic process. When ablation phenomenon happened the ablation products would ejected, and the target gained recoil impulse from ejection process. According to energy distribution equations we can get the ejection energy, and then get the recoil momentum of target based on momentum conservation law. The propulsion properties of laser ablated polymer was studied through the numerical analysis model. Revealed the relationship between the propulsion capability and laser parameters. Analyzed influence of different propellants to propulsion performance. The numerical analysis model can reflect the propulsion capability of different polymer propellant, revealed the law of propulsion parameters in laser ablation process.

Li, Nanlei; Hong, Yanji; Wu, Jie; Zhou, Weijing; Ye, Jifei

2013-05-01

184

Parametric study on femtosecond laser pulse ablation of Au films  

NASA Astrophysics Data System (ADS)

Ablation process of 1 kHz rate femtosecond lasers (pulse duration 148 fs, wavelength 775 nm) with Au films on silica substrates has been systemically studied. The single-pulse threshold can be obtained directly. For the multiple pulses the ablation threshold varies with the number of pulses applied to the surface due to the incubation effect. From the plot of accumulated laser fluence N × ?th( N) and the number of laser pulses N, incubation coefficient of Au film can be obtained ( s = 0.765). As the pulse energy is increased, the single pulse ablation rate is increasing following two ablation logarithmic regimes, which can be explained by previous research.

Ni, Xiaochang; Wang, Ching-yue; Yang, Li; Li, Jianping; Chai, Lu; Jia, Wei; Zhang, Ruobing; Zhang, Zhigang

2006-11-01

185

Focal laser ablation for localized prostate cancer.  

PubMed

Throughout history, medicine has witnessed paradigm shifts that significantly change patient treatment. In surgical oncology, the introduction of lumpectomy revolutionized breast cancer treatment while partial nephrectomy has altered the management of kidney cancer. In both cases, organ preservation is combined with efficacious management of the cancer via a less invasive approach. Within urology, prostate cancer (PCa) may be the next to benefit from such a treatment paradigm. Current management of PCa involves either whole organ treatment, with the inherent side effects, while selected patients are eligible for active surveillance. Focal therapy offers a middle ground for low-risk patients with PCa, again using the principles of a minimally invasive treatment of the cancer, in this case using an energy source with few side effects, combined with maximal organ preservation. Because focal therapy for PCa is still in evolution, there is no consensus on the ideal energy source that should be used to ablate the PCa, imaging to monitor the tissue destruction in real time, how many treatments may be offered, and the ideal follow-up regimen. Long-term follow-up of patients is needed before it is recommended as a first-line treatment. Nevertheless, evidence is accumulating that radically treating PCa holds survival benefit for patients; however, the number of men needed to treat is considerable, with significant side effects; thus, more centers are investigating focal therapy as an option. This review focuses on the use of the laser as the energy source for focal ablation, while bringing historically relevant information regarding laser energy and highlighting the perceived advantageous of focal laser ablation. PMID:20477544

Lindner, Uri; Lawrentschuk, Nathan; Trachtenberg, John

2010-05-01

186

Structure and Scaling Laws of Laser-Driven Ablative Implosions.  

National Technical Information Service (NTIS)

A stationary, spherical flow model gives the form of laser-driven ablation fronts and scaling laws for the dependence of implosion parameters on laser wavelength, pusher atomic number, and other input quantities.

S. J. Gitomer R. L. Morse B. S. Newberger

1975-01-01

187

Germanium dioxide whiskers synthesized by laser ablation  

NASA Astrophysics Data System (ADS)

We obtained germanium dioxide (GeO2) whiskers in bulk quantity by ablating a germanium target at 820 °C with a pulsed KrF excimer laser in an argon atmosphere. Most of the GeO2 whiskers were smooth and straight with hexagonal or triangular, or quadrilateral cross sections while some of them had a bamboo-shoot-shaped form. Results of scanning electron microscopy, transmission electron microscopy, and x-ray diffraction showed that the whiskers are hexagonal crystalline GeO2.

Tang, Y. H.; Zhang, Y. F.; Wang, N.; Bello, I.; Lee, C. S.; Lee, S. T.

1999-06-01

188

Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation  

SciTech Connect

The ablation plume dynamics arising from ablation of silver with a 500 fs, 248 nm laser at {approx}2 J cm{sup -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 ablation are similar; both show a singly peaked time-of-flight distribution. The angular distribution of ion emission and the deposition are well described by the adiabatic and isentropic model of plume expansion, though distributions for femtosecond ablation are significantly narrower. In this laser fluence regime, the energy efficiency of mass ablation is higher for femtosecond pulses than for nanosecond pulses, but the ion production efficiency is lower.

Toftmann, B.; Schou, J. [DTU Fotonik, Riso Campus, DK-4000 Roskilde (Denmark); Doggett, B.; Budtz-Jorgensen, C.; Lunney, J. G. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland)

2013-02-28

189

Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation  

NASA Astrophysics Data System (ADS)

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 ablation are similar; both show a singly peaked time-of-flight distribution. The angular distribution of ion emission and the deposition are well described by the adiabatic and isentropic model of plume expansion, though distributions for femtosecond ablation are significantly narrower. In this laser fluence regime, the energy efficiency of mass ablation is higher for femtosecond pulses than for nanosecond pulses, but the ion production efficiency is lower.

Toftmann, B.; Doggett, B.; Budtz-Jørgensen, C.; Schou, J.; Lunney, J. G.

2013-02-01

190

Microlens fabrication in PMMA with scanning excimer laser ablation techniques  

Microsoft Academic Search

Laser ablation is a versatile technique for fabricating microstructures on polymer surfaces. Due to the nature of the process, the fabrication of the microstructure can take place in a very late stage of a heterogeneous assembly. This makes laser ablation very attractive for fabricating micro-optical components on opto-electronic assemblies in comparison to other fabrication techniques like injection molding and embossing.

Kris Naessens; Peter Van Daele

191

Direct optimization of femtosecond laser ablation using adaptive wavefront shaping  

Microsoft Academic Search

We introduce an approach based on using an iterative simulated annealing algorithm to drive the outcome of femtosecond laser ablation towards a specific target shape by using a two-dimensional deformable mirror. Unlike previous work combining adaptive optics and laser machining we use the machining outcome itself as the fitness parameter for the optimization procedure. Single-pulse ablation features with programmable aspect

S Campbell; S M F Triphan; R El-Agmy; A H Greenaway; D T Reid

2007-01-01

192

Acceleration of solid macro-particles by laser produced ablation  

Microsoft Academic Search

The feasibility of accelerating a macroparticle (BB) with laser light is studied. One and two dimensional Lagrangian hydrodynamic calculations are performed using the LASNEX magnetohydrodynamic computer code. The results of these calculations are then used to infer laser intensity, scaling laws for ablation pressure, and mass flow rate. In order to optimize the BB kinetic energy production efficiency, the ablation

T. E. McCann

1978-01-01

193

Investigation of plasma produced by laser and electron pulse ablation  

Microsoft Academic Search

Short laser pulses with high energy are a very promising tool for controlled ablation of materials, both for structurization and for deposition. They are especially suited for the ablation of non-conducting and of complex materials. The plasmas induced by the laser irradiation are distinguished by their high degree of ionization and excitation. A new source with comparable pulse properties is

Th. Witke; A. Lenk; B. Schultrich; C. Schultheiss

1995-01-01

194

Elemental fractionation of glass using laser ablation inductively coupled plasma mass spectrometry  

SciTech Connect

Three laser wavelengths (1064, 532, and 266 nm) were employed for laser ablation at varied laser pulse energies to study the effect of irradiance and wavelength upon analytical results for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Two important results were observed and are reported here: (1) the intensity of the MS signal came to a local minimum when the laser focal point was on the sample surface, and (2) elemental fractionation based upon laser wavelength and laser pulse energy was observed. For the waste glass simulant studied, ablation with 1064-nm (IR) and 532-nm (green) radiation produced elemental fractionation that relates to the melting point of the elemental oxide, whereas with 266-nm (UV) ablation the response was independent of the elemental oxide melting point. At high laser powers, ablation at 266 nm produced an elemental bias based upon the mass of the elements. These observations suggest the use of ultraviolet radiation at low pulse energies to obtain improved analytical results. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

Figg, D. [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States)] [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States); Kahr, M.S. [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States)] [CST-9, Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos New Mexico, 87545 (United States); [Orbital Sciences Corporation, 2771 North Garey Ave., Pomona, California 91767 (United States)

1997-08-01

195

Determination of femtosecond ablation thresholds by using laser ablation induced photoacoustics (LAIP)  

NASA Astrophysics Data System (ADS)

Femtosecond laser material processing as micromachining and nanoparticles fabrication require a careful control of the fluences deposited on the samples. In many cases, best results are obtained by using fluences slightly above the Laser Ablation Threshold (LAT), therefore its accurate determination is an important requirement. LAT can be obtained by measuring the intensity of the acoustic signal generated during the ablation process as a function of the laser fluence. In this work femtosecond laser ablation thresholds of commercially polished stainless steel plates, white high impact polystyrene, frosted glass, antique rag papers and silicon oxynitride thin films were determined by using laser ablation induced photoacoustics (LAIP). Results were compared with similar data previously obtained by using a nanosecond Nd:YAG laser.

Orzi, Daniel J. O.; Alvira, Fernando C.; Bilmes, Gabriel M.

2013-03-01

196

Mechanism study of skin tissue ablation by nanosecond laser pulses  

NASA Astrophysics Data System (ADS)

Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed. A laser-induced and localized thermal ionization pathway has been investigated and it was found to have significant influence on the initial free electron density during plasma formation due to the combination of strong light absorption by chromophores and confined temperature rise in the chromophores. Good agreements have been found between the new plasma-mediated ablation model and experimental results. The implications of this dissertation research to the future improvement of laser systems in dermatology and plastic surgery are discussed.

Fang, Qiyin

197

Laser ablation of aluminum from normal evaporation to phase explosion  

NASA Astrophysics Data System (ADS)

A study of laser ablation of Aluminum sample by nanosecond laser pulses considering two simultaneous mechanisms of normal evaporation and phase explosion is theoretically carried out. The temperature distribution in the sample is calculated by a one dimensional heat conduction equation. Ablation depth due to the evaporation and explosion is calculated as a function of laser pulse energies. Variation in some effective sample parameters during the laser ablation and their effects on laser ablation mechanisms are taken into account. At low irradiance, ablation is mainly due to the evaporation, while after a threshold intensity, the phase explosion becomes the dominant mechanism. Theoretical results of transition from the normal evaporation to the phase explosion are in good agreement with the experimental results.

Gragossian, A.; Tavassoli, S. H.; Shokri, B.

2009-05-01

198

Femtosecond laser ablation of brass in air and liquid media  

NASA Astrophysics Data System (ADS)

Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

2013-06-01

199

Femtosecond laser ablation of brass in air and liquid media  

SciTech Connect

Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

Shaheen, M. E. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada) [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); 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) [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)

2013-06-07

200

Laser ablation plume dynamics in nanoparticle synthesis  

SciTech Connect

The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO{sub 2} laser pulse with a duration of {approx}500 {mu}s (at the 0.03 level), energy of 1.0-1.3 J and peak power of 6-7 kW have been studied using high-speed photography of the plume luminescence and shadow. The targets were used to produce nanopowders by laser evaporation. About 200 {mu}s after termination of the pulse, shadowgraph images of the plumes above the YSZ and Nd:YAG targets showed dark straight tracks produced by large particles. The formation of large ({approx}10 {mu}m) particles is tentatively attributed to cracking of the solidified melt at the bottom of the ablation crater. This is supported by the fact that no large particles are ejected from graphite, which sublimes without melting. Further support to this hypothesis is provided by numerical 3D modelling of melt cooling in craters produced by laser pulses of different shapes. (interaction of laser radiation with matter. laser plasma)

Osipov, V V; Platonov, V V; Lisenkov, V V [Institute of Electrophysics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

2009-06-30

201

Picosecond laser ablation for silicon micro fuel cell fabrication  

NASA Astrophysics Data System (ADS)

We have investigated laser ablation as a microfabrication approach to produce micro fuel cells (MFCs) in silicon. Picosecond pulses (15 ps) at a wavelength of 355 nm are used to make all of the MFC structures. To assess the benefits and drawbacks of laser ablation, reference cells have been produced by deep reactive ion etching (DRIE) using matching geometries. Ablated and etched cells have been evaluated and compared side by side. Our conclusion is that picosecond laser ablation is very well suited for MFC fabrication. The ablated cells match or excel DRIE-microfabricated cells in terms of current and power densities. Ablated MFCs achieved 47.6 mW cm-2 of power density and 121 mA cm-2 current density.

Scotti, Gianmario; Trusheim, Daniel; Kanninen, Petri; Naumenko, Denys; Shulz-Ruhtenberg, Malte; Snitka, Valentinas; Kallio, Tanja; Franssila, Sami

2013-05-01

202

Laser ablation and plasma interferometry with a tabletop soft x-ray laser  

Microsoft Academic Search

We report the first study of laser ablation and the demonstration of plasma interferometry with a tabletop soft x-ray laser. A capillary discharge pumped Ne-like Ar laser (46.9 nm) was focused using multilayer optics to significantly exceed the energy density necessary for the ablation of metals. Ablation in brass, stainless steel and aluminum samples is reported. The ablation patterns on

Jorge J. Rocca; Jorge Filevich; Mario C. Marconi; A. Ozols; Kelly Kanizay; Brady R. Benware; Juan L. Chilla; Igor A. Artioukov; Yuriy S. Kasjanov; V. V. Kondratenko; Alexander V. Vinogradov

2000-01-01

203

Laser ablated copper plasmas in liquid and gas ambient  

SciTech Connect

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (n{sub e}) determined using Stark broadening of the Cu I (3d{sup 10}4d{sup 1} {sup 2}D{sub 3/2}-3d{sup 10}4p{sup 1} {sup 2}P{sub 3/2} at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (T{sub e}) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ?590 nm.

Kumar, Bhupesh; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)] [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)

2013-05-15

204

Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation  

SciTech Connect

A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm{sup 2}. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown.

Autrique, D. [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany) [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany); Department of Chemistry, University of Antwerp, 2610 Wilrijk (Belgium); Gornushkin, I. [Federal Institute for Materials Research and Testing - BAM, 12489 Berlin (Germany)] [Federal Institute for Materials Research and Testing - BAM, 12489 Berlin (Germany); Alexiades, V. [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1320 (United States)] [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1320 (United States); Chen, Z.; Bogaerts, A. [Department of Chemistry, University of Antwerp, 2610 Wilrijk (Belgium)] [Department of Chemistry, University of Antwerp, 2610 Wilrijk (Belgium); Rethfeld, B. [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany)] [Department of Physics and OPTIMAS Research Center, TU Kaiserslautern, 67653 Kaiserslautern (Germany)

2013-10-21

205

Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation  

NASA Astrophysics Data System (ADS)

A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm2. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown.

Autrique, D.; Gornushkin, I.; Alexiades, V.; Chen, Z.; Bogaerts, A.; Rethfeld, B.

2013-10-01

206

Oxidation and carbidation of laser-ablated amorphized Ti particles in carbon monoxide  

NASA Astrophysics Data System (ADS)

IR laser ablation of hexagonal titanium in vacuum leads to amorphization of ablated Ti particles and when carried out in gaseous carbon monoxide it proceeds as reactive ablation involving particles amorphization, oxidation and carbidation. The films deposited in vacuum and in the presence of CO were examined by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, X-ray and electron diffraction and electron microscopy. The Ti films become oxidized upon contact with air and the Ti/C/O films are composed of Ti-O, Ti-C and C-O bonds-containing structures with Ti in Ti2+-Ti4+ state and incorporating crystalline rutile and elemental carbon. The ablation in vacuum represents a new approach to amorphous titanium and it is judged that hot ablated Ti particles are modified by reactions with CO decomposition products into amorphous Ti oxycarbides which undergo rapid post-pulse amorphization.

Jandová, V?ra; Kup?ík, Jaroslav; Bastl, Zden?k; Šubrt, Jan; Pola, Josef

2013-05-01

207

Metal particles produced by laser ablation for ICP-MSmeasurements  

SciTech Connect

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.

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

2007-06-01

208

Imaging and blackbody emission spectra of hot particulates generated during laser ablation.  

National Technical Information Service (NTIS)

Blackbody emission from particulates generated during KrF-laser ablation of Y(sub 1)Ba(sub 2)Cu(sub 3)O(sub 7-x) (YBCO) and BN has been recorded for the first time by sensitive photography and emission spectroscopy in order to study the velocity, temperat...

D. B. Geohegan

1993-01-01

209

HFCVD diamond nucleation and growth on DLC carbon films obtained by laser ablation  

Microsoft Academic Search

Diamond deposition by hot filament chemical vapour deposition (HFCVD) on DLC films prepared by laser ablation (5 nm < thickness < 20 nm) was studied by electron spectroscopics, including X-ray photoemission, Auger electron and electron loss spectroscopy directly connected to the HFCVD growth chamber. It is shown that, whatever the thickness and the annealing procedure, this carbon layer is removed

J. Muller; F. Antoni; E. Fogarassy; F. Le Normand

1998-01-01

210

Plume dynamics in femtosecond laser ablation of metals  

SciTech Connect

In femtosecond laser ablation the plume has two components: a faster-moving plasma part and a slower nanoparticle plume which contains most of the ablated material. This paper describes the results of experiments to comprehensively characterize the plume in laser ablation of Ni with {approx_equal}300 fs pulses at 527 nm. Both single-pulse and double-pulse irradiation was used. The laser ablation depth was measured using white light interferometry. The dynamics of the plasma part of the ablation plume was measured using Langmuir ion probes. The shape of the overall ablation plume was recorded by depositing a thin film on a transparent substrate and measuring the thickness distribution. The expansion of the plasma plume is well described by the Anismov isentropic model of plume expansion. Just above the ablation threshold, the nanoparticle plume is also well described by the Anisimov expansion model. However, at higher fluence a wider plume is formed, perhaps due to the pressure exerted by plasma. For double-pulse ablation it is observed that as the second pulse is delayed beyond {approx_equal}20 ps the ablation depth is reduced and the ion yield is increased. This behaviour is due to reheating of the nascent plasma plume produced by the first pulse. This generates a pressure pulse that acts as a tamper which impedes the fragmentation and ablation of deeper layers of material.

Donnelly, T.; Lunney, J. G. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Amoruso, S.; Bruzzese, R.; Wang, X. [Coherentia CNR-INFM and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Fedrico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126, Napoli (Italy)

2010-10-08

211

The role of laser wavelength on plasma generation and expansion of ablation plumes in air  

NASA Astrophysics Data System (ADS)

We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

2013-04-01

212

The role of laser wavelength on plasma generation and expansion of ablation plumes in air  

SciTech Connect

We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

Hussein, A. E. [Center for Materials under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, McGill University, Montreal, Quebec H3A 0G4 (Canada); Diwakar, P. K.; Harilal, S. S.; Hassanein, A. [Center for Materials under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2013-04-14

213

Ablation of polymers by picosecond vibrational laser excitation  

Microsoft Academic Search

Polymers are attractive model materials for mechanistic studies of laser ablation because their vibrational, optical and thermo-mechanical properties are often very well known. We have studied the mechanism of infrared laser ablation in model polymers such as poly(ethylene glycol) (PEG) and poly(styrene) (PS) by resonant and non-resonant vibrational excitation, using a free-electron laser delivering tunable picosecond radiation in a microsecond-long

Michael Papantonakis; J. R. Haglund; Daniel Bubb; James Horwitz

2002-01-01

214

Application of Laser Ablation Processing in Electric Power System Industries  

NASA Astrophysics Data System (ADS)

The present status of laser ablation processing applied in electric power system industries is reviewed. High average power LD-pumped Nd:YAG lasers with Q-switch have been developed and currently introduced into various applications. Optical fiber based laser beam delivery systems for Q-switched pulse laser are also being developed these years. Based on such laser and beam delivery technology, laser ablation processes are gradually introduced in maintenance of nuclear power plant, thermal power plant and electrical power distribution system. Cost effectiveness, robustness and reliability of the process is highly required for wide utilization in these fields.

Konagai, Chikara; Sano, Yuji; Nittoh, Koichi; Kuwako, Akira

215

Ablation of crystalline oxides by infrared femtosecond laser pulses  

SciTech Connect

We use focused laser pulses with duration of 180 fs and wavelength of 800 nm to study the interactions of high power near-infrared light with the surfaces of single-crystal transparent oxides (sapphire, LaAlO{sub 3}, SrTiO{sub 3}, yttria-stabilized ZrO{sub 2}, and MgO); the morphologies of the ablation craters are studied by atomic force microscopy and scanning electron microscopy. With the exception of LaAlO{sub 3}, the high temperature annealing of these oxide crystals produces atomically flat starting surfaces that enable studies of the morphology of ablation craters with subnanometer precision. The threshold fluence for ablation is determined directly from atomic-force microscopy images and increases approximately linearly with the band gap of the oxide. For all oxides except sapphire, the depth of the ablation crater increases approximately as the square root of the difference between the peak laser fluence and the threshold fluence for ablation. Sapphire shows unique behavior: (i) at laser fluences within 1 J/cm{sup 2} of the threshold for ablation, the depth of the ablation crater increases gradually instead of abruptly with laser fluence, and (ii) the rms roughness of the ablation crater shows a pronounced minimum of <0.2 nm at a laser fluence of 1 J/cm{sup 2} above the threshold.

Watanabe, Fumiya; Cahill, David G.; Gundrum, Bryan; Averback, R. S. [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2006-10-15

216

Investigations on laser hard tissue ablation under various environments  

NASA Astrophysics Data System (ADS)

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 µm 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.

Kang, H. W.; Oh, J.; Welch, A. J.

2008-06-01

217

Wavelength-Dependent Collagen Fragmentation during Mid-IR Laser Ablation  

PubMed Central

Mid-infrared free-electron lasers have proven adept in surgical applications. When tuned to wavelengths between 6 and 7 ?m, such lasers remove defined volumes of soft tissue with very little collateral damage. Previous attempts to explain the wavelength-dependence of collateral damage have invoked a wavelength-dependent loss of protein structural integrity. However, the molecular nature of this structural failure has been heretofore ill-defined. In this report, we evaluate several candidates for the relevant transition by analyzing the nonvolatile debris ejected during ablation. Porcine corneas were ablated with a free-electron laser tuned to 2.77 or 6.45 ?m—wavelengths with matched absorption coefficients for hydrated corneas that respectively target either tissue water or protein. The debris ejected during these ablations was characterized via gel electrophoresis, as well as Fourier transform infrared spectroscopy, micro-Raman and 13C-NMR spectroscopy. We find that high-fluence (240 J/cm2) ablation at 6.45 ?m, but not at 2.77 ?m, leads to protein fragmentation accompanied by the accumulation of nitrile and alkyne species. The candidate transition most consistent with these observations is scission of the collagen protein backbone at N-alkylamide bonds. Identifying this transition is a key step toward understanding the observed wavelength-dependence of collateral damage in mid-infrared laser ablation.

Xiao, Yaowu; Guo, Mingsheng; Parker, Kevin; Hutson, M. Shane

2006-01-01

218

Wavelength-dependent collagen fragmentation during mid-IR laser ablation.  

PubMed

Mid-infrared free-electron lasers have proven adept in surgical applications. When tuned to wavelengths between 6 and 7 microm, such lasers remove defined volumes of soft tissue with very little collateral damage. Previous attempts to explain the wavelength-dependence of collateral damage have invoked a wavelength-dependent loss of protein structural integrity. However, the molecular nature of this structural failure has been heretofore ill-defined. In this report, we evaluate several candidates for the relevant transition by analyzing the nonvolatile debris ejected during ablation. Porcine corneas were ablated with a free-electron laser tuned to 2.77 or 6.45 microm-wavelengths with matched absorption coefficients for hydrated corneas that respectively target either tissue water or protein. The debris ejected during these ablations was characterized via gel electrophoresis, as well as Fourier transform infrared spectroscopy, micro-Raman and 13C-NMR spectroscopy. We find that high-fluence (240 J/cm2) ablation at 6.45 microm, but not at 2.77 microm, leads to protein fragmentation accompanied by the accumulation of nitrile and alkyne species. The candidate transition most consistent with these observations is scission of the collagen protein backbone at N-alkylamide bonds. Identifying this transition is a key step toward understanding the observed wavelength-dependence of collateral damage in mid-infrared laser ablation. PMID:16714345

Xiao, Yaowu; Guo, Mingsheng; Parker, Kevin; Hutson, M Shane

2006-08-15

219

Femtosecond pulsed laser ablation of molybdenum carbide: Nanoparticles and thin film characteristics  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

220

Amalgam ablation with the Er:YAG laser  

NASA Astrophysics Data System (ADS)

Any laser that will be used by dentist to replace the dental drill (handpiece) must remove dental hard tissues safely. These lasers must also have the ability to ablate the restorative dental materials which are present in the teeth being treated. Prior to any laser being used to treat humans a thorough knowledge of the effects of the laser treatment on dental materials must be understood. Cores of dental amalgam were created and sliced into thin wafers for this experiment. Ablation efficiency and thermal changes were evaluated with and without water. It appears as if the Er:YAG laser can effectively ablate amalgam dental material with and without water. The water prevents the temperature from increasing much above baseline and does not reduce efficiency of ablation.

Wigdor, Harvey A.; Visuri, Steven R.; Walsh, Joseph T.

1995-04-01

221

Excimer laser ablation of polycarbonate-based plastic substrates  

Microsoft Academic Search

Ablation of polycarbonate-based plastics under excimer laser irradiation has been studied, with emphasis on the influence of specific inorganic additives in the polymer to the ablation process. Such additives consisted of 0.2 ?m sized, (spherical) TiO2 grains, in either 5% or 10% mass concentration. Irradiation products are analyzed, with respect to roughness and ablation, by scanning electron microscopy, energy dispersive

M. Devalckenaere; A. Jadin; K. Kolev; L. D. Laude

1999-01-01

222

Modeling of stress generation induced by laser ablation  

NASA Astrophysics Data System (ADS)

In the present work we discuss in some details the development of the stress induced into the target by laser ablation in air. The analytical treatment based on the variable energy blast theory allowed to provide the scaling law of the peak and the temporal profile of the generated pressure wave. Measurements of the acoustic transient associated with excimer laser ablation of polyimide, obtained by means of polyvinyldenefloride (PVDF) sensors were successfully compared with the behaviors provided by the analysis. The description here proposed can be extended to pulsed laser ablation of soft tissues where the target material is removed in vapor or gaseous phases.

Siano, Salvatore; Pini, Roberto; Salimbeni, Renzo

1999-06-01

223

Laser ablation dynamics in metals: The thermal regime  

SciTech Connect

We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

Mezzapesa, F. P.; Brambilla, M.; Dabbicco, M.; Scamarcio, G. [CNR-IFN UOS Bari, via Amendola 173, I-70126 Bari (Italy); Dipartimento Interateneo di Fisica, Universita degli Studi e Politecnico di Bari, via Amendola 173, I-70126 Bari (Italy); Columbo, L. L. [CNR-IFN UOS Bari, via Amendola 173, I-70126 Bari (Italy); Dipartimento di Scienza ed Alta tecnologia, Universita dell'Insubria, via Valleggio 11, 22100 Como (Italy); Ancona, A.; Sibillano, T. [CNR-IFN UOS Bari, via Amendola 173, I-70126 Bari (Italy)

2012-07-02

224

Laser-Ablation Rates Measured Using X-Ray Laser Transmission  

SciTech Connect

The rate of laser ablation at irradiances of {approx}2x10{sup 14} W cm{sup -2} of solid iron has been measured using the transmission of a neonlike zinc x-ray laser at 21.2 nm through thin iron targets. Ablated iron becomes transparent to the x-ray laser flux, enabling the thickness of unablated material and hence the rate of ablation to be measured from time resolved x-ray laser transmission.

Edwards, M. H.; Whittaker, D. S.; Tallents, G. J.; Mistry, P.; Pert, G. J.; Rus, B.; Mocek, T.; Kozlova, M.; Polan, J.; Praeg, A.; Stupka, M.; Homer, P. [Department of Physics, University of York, York, YO10 5DD (United Kingdom); Department of X-ray Lasers, PALS Research Centre, Institute of Physics, Academy of Sciences of the Czech Republic, 182 21 Prague 8 (Czech Republic)

2007-11-09

225

Dynamics of laser ablated colliding plumes  

SciTech Connect

We report the dynamics of single and two collinearly colliding laser ablated plumes of ZnO studied using fast imaging and the spectroscopic measurements. Two dimensional imaging of expanding plume and temporal evolution of various species in interacting zones of plumes are used to calculate plume front velocity, electron temperature, and density of plasma. The two expanding plumes interact with each other at early stage of expansion ({approx}20 ns) resulting in an interaction zone that propagates further leading to the formation of stagnation layer at later times (>150 ns) at the lateral collision front of two plumes. Colliding plumes have larger concentration of higher ionic species, higher temperature, and increased electron density in the stagnation region. A one-to-one correlation between the imaging and optical emission spectroscopic observations in interaction zone of the colliding plumes is reported.

Gupta, Shyam L.; Pandey, Pramod K.; Thareja, Raj K. [Department of Physics, Indian Institute of Technology, Kanpur-208016 (India)

2013-01-15

226

Carbon nanofoam formed by laser ablation.  

PubMed

Foam-like carbon (carbon nanofoam, CNF) which belongs to the porous carbon family is formed by pulsed laser ablation of graphite in liquid nitrogen. Each bubble is about 3-10 nm in size and has a layered structure with typically one to four graphene layers. The CNF forms nanoparticles of about 100 nm in size. CNF encapsulating platinum nanoparticles (Pt@CNF) is formed when a mixture of graphite, platinum, and hexadecanoic acid is used as a target. Each bubble encapsulating a platinum nanoparticle is approximately 15 +/- 4 nm in diameter and contains typically 6 +/- 3 graphene walls. The platinum nanoparticles in the CNF are 9 +/- 4 nm in diameter. The annealing of the Pt@CNF at 300 degrees C for a week in vacuum reveals that the CNF effectively prevents the platinum nanoparticles from aggregating. PMID:22755133

Kohno, Hideo; Tatsutani, Kentaro; Ichikawa, Satoshi

2012-03-01

227

A prototype transition-metal olefin complex C2H4...AgCl synthesised by laser ablation and characterised by rotational spectroscopy and ab initio methods  

NASA Astrophysics Data System (ADS)

C2H4...Ag-Cl has been synthesised in the gas phase in a pulsed-jet, Fourier-transform microwave spectrometer by the reaction of laser-ablated metallic silver with carbon tetrachloride to give AgCl, which subsequently reacts with ethene to give the complex. The ground-state rotational spectra of six isotopologues (C2H4...107Ag35Cl, C2H4...109Ag35Cl, C2H4...107Ag37Cl, C2H4...109Ag37Cl, 13C2H4...107Ag35Cl, and 13C2H4...109Ag35Cl) were recorded and analysed to give rotational constants A0, B0, and C0, centrifugal distortion constants ?J and ?JK, and Cl nuclear quadrupole coupling constants ?aa(Cl) and ?bb(Cl) - ?cc(Cl). These spectroscopic constants were interpreted in terms of a geometry for C2H4...Ag-Cl of C2V symmetry in which the AgCl molecule lies along the C2 axis of ethene that is perpendicular to the C2H4 plane. The Ag atom forms a bond to the midpoint (*) of the ethene ? bond. A partial rs-geometry and a r0-geometry were determined, with the values r(*...Ag) = 2.1719(9) A?, r(C-C) = 1.3518(4) A?, and r(Ag-Cl) = 2.2724(8) A? obtained in the latter case. The C-C bond lengthens on formation of the complex. Detailed ab initio calculations carried out at the CCSD(T)/cc-pVQZ level of theory give results in good agreement with experiment and also reveal that the ethene molecule undergoes a small angular distortion. The distortion is such that the four H atoms move in a direction away from Ag but remain coplanar. The two C atoms are no longer contained in this plane, however. The electric charge redistribution when C2H4...Ag-Cl is formed and the strength of the ?...Ag bond are discussed.

Stephens, Susanna L.; Tew, David P.; Mikhailov, Victor A.; Walker, Nicholas R.; Legon, Anthony C.

2011-07-01

228

Plasma-assisted laser ablation of tungsten: Reduction in ablation power threshold due to bursting of holes/bubbles  

SciTech Connect

Nanosecond laser ablation of tungsten (W) exposed to helium plasma is investigated using optical emission spectroscopy. Submicrometer-sized holes/bubbles are formed on the surface of W when it was exposed to the helium plasma at a sufficiently high temperature (> or approx. 1500-1600 K). The emissions from a virgin W (before the helium plasma irradiation) cannot be detected when the fluence is <1 J/cm{sup 2}; however, the threshold fluence for the detection of neutral W emission after it was exposed to the helium plasma is {approx}0.2 J/cm{sup 2}. The physical mechanism of laser-induced bursting of holes/bubbles is proposed for achieving a significant reduction in ablation power threshold.

Kajita, Shin; Ohno, Noriyasu; Takamura, Shuichi; Sakaguchi, Wataru; Nishijima, Dai [Japan Atomic Energy Agency, Mukoyama 801-1, Naka, Ibaraki 311-0193 (Japan); EcoTopia Science Institute, Nagoya University, Nagoya 464-8603 (Japan); Aichi Institute of Technology, Yakusa-cho, Toyota 470-0392 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); National Institute of Advanced Industrial Science and Technology, Saga 841-0052 (Japan)

2007-12-24

229

Laser mass spectrometric studies of high temperature superconductor ablation  

SciTech Connect

Laser ablation of bulk High Temperature Superconductor (HTS) material promises to provide a useful means of producing high quality HTS thin films. Mass spectrometric probes of the ablation plume provide a microscopic understanding of the ablation event and plume development as well as providing a process monitor for the thin film production. Detection of the nascent ions in the plume provides real time analytical information, e.g., identification of impurities, major and minor ablation species, etc. The common contaminants sodium and strontium have been easily detected by this technique in a variety of different HTS bulk materials. In contrast, detection of the ablated neutral species by Resonance Ionization Mass Spectrometry (RIMS) provides physical information about the ablation process. Time-of-flight/RIMS detection of Cu, Y, and BaO ablated from YBa{sub 2}Cu{sub 3}O{sub x} indicates the ablation involves post-desorption gas phase collisions, thereby influencing the ablation chemistry and dynamics (e.g., angular and velocity distributions). Approximately equal velocities are observed for all neutral species at constant ablation laser fluence. 17 refs., 4 figs.

Estler, R.C.; Nogar, N.S.

1990-01-01

230

Precision ablation of dental enamel using a subpicosecond pulsed laser.  

PubMed

In this study we report the use of ultra-short-pulsed near-infrared lasers for precision laser ablation of freshly extracted human teeth. The laser wavelength was approximately 800nm, with pulsewidths of 95 and 150fs, and pulse repetition rates of 1kHz. The laser beam was focused to an approximate diameter of 50microm and was scanned over the tooth surface. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain below 5 degrees C when the tooth was air-cooled during laser treatment. The surface preparation of the ablated teeth, observed by optical and electron microscopy, showed no apparent cracking or heat effects, and the hardness and Raman spectra of the laser-treated enamel were not distinguishable from those of native enamel. This study indicates the potential for ultra-short-pulsed lasers to effect precision ablation of dental enamel. PMID:14738125

Rode, A V; Gamaly, E G; Luther-Davies, B; Taylor, B T; Graessel, M; Dawes, J M; Chan, A; Lowe, R M; Hannaford, P

2003-12-01

231

Solid state laser ablation effect on laser-proof composite coating applied in aerospace material  

NASA Astrophysics Data System (ADS)

This paper concentrates on the measurement and analysis of laser ablation effect of particularly prepared aerospace material, polycarbosilane (PCS). Laser ablation experiment setup is designed and built, based on a continuous-wave high-power solid-state laser (CWHPSSL). Steel samples with composite PCS coating are prepared. After that, a group of laser ablation experiment is performed. The samples are shot by laser beam with thousands W/cm2 fluence. The results, including the ablation morphology and temperature data, is shown and discussed. Temperature data gives a good demonstration of thermal protection effect of composite coating, and in the meanwhile the morphological features in the ablated region reveal the principle of PCS laser-proof effect. Theoretical investigation has also been carried out. The temperature field is simulated based on Fourier equation of heat conduction, and the simulation result provides a good demonstration on thermal-proof effect of PCS coating layer during laser ablation process.

Li, Jing; Zheng, Yi; Luo, Jing; Liu, Zhichao; Chen, Songlin; Zhang, Yuzhong; Wang, Zhiyong

2014-02-01

232

Generation of nanostructures on metals by laser ablation in liquids: new results  

SciTech Connect

Surface nanostructuring of titanium, nickel, molybdenum, and tungsten by ablation with pico- and femtosecond laser pulses in liquids is studied experimentally for the first time. The morphology and properties of obtained nanostructures are investigated using a field emission scanning electron microscope and Raman spectroscopy. The size of nanostructures depends on the laser pulse duration and energy density and on the target material. As a rule, the size distribution of structures is bimodal. Potential applications of such nanostructured substrates are discussed. (photonics and nanotechnology)

Barmina, E V; Shafeev, Georgii A [Wave Research Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Stratakis, E; Fotakis, K [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, (IESL-FORTH), P.O. Box 1527, Heraklion 711 10 (Greece)

2010-12-29

233

Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO2  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm2; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO2 with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3-hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography-mass spectrometry. Furthermore, gas chromatography-mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO2 during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO2 is proposed as a practical method for synthesizing diamondoids.

Nakahara, Sho; Stauss, Sven; Kato, Toru; Sasaki, Takehiko; Terashima, Kazuo

2011-06-01

234

In situ Diagnostics During Carbon Nanotube Production by Laser Ablation  

NASA Technical Reports Server (NTRS)

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.

Arepalli, Sivaram

1999-01-01

235

Deposition of functional nanoparticle thin films by resonant infrared laser ablation.  

NASA Astrophysics Data System (ADS)

We have deposited thin films containing functional nanoparticles, using tunable infrared light from a picosecond free-electron laser (FEL). Thin films of the green light-emitting molecule Alq3 were first deposited by resonant infrared laser ablation at 6.68 ?m, targeting the C=C ring mode of the Alq3. TiO2 nanoparticles 50-100 nm diameter were then suspended in a water matrix, frozen, and transferred by resonant infrared laser ablation at 2.94 ?m through a shadow mask onto the Alq3 film. Photoluminescence was substantially enhanced in the regions of the film covered by the TiO2 nanoparticles. In a second experiment, gold nanoparticles with diameters in the range of 50-100 nm were suspended in the conducting polymer and anti-static coating material PEDOT:PSS, which was diluted by mixing with N-methyl pyrrolidinone (NMP). The gold nanoparticle concentration was 8-10% by weight. The mixture was frozen and then ablated by tuning the FEL to 3.47 ?m, the C-H stretch mode of NMP. Optical spectroscopy of the thin film deposited by resonant infrared laser ablation exhibited the surface-plasmon resonance characteristic of the Au nanoparticles. These experiments illustrate the versatility of matrix-assisted resonant infrared laser ablation as a technique for depositing thin films containing functionalized nanoparticles.

Haglund, Richard; Johnson, Stephen; Park, Hee K.; Appavoo, Kannatessen

2008-03-01

236

Two-phase zirconium boride thin film obtained by ultra-short pulsed laser ablation of a ZrB12 target  

NASA Astrophysics Data System (ADS)

Two-phase zirconium boride thin films have been obtained by ultra-short pulsed laser ablation (PLA) of a zirconium dodecaboride (ZrB12) target performed in vacuum. The ablation source was a frequency doubled (? = 527 nm) Nd:glass laser with a pulse duration of 250 fs. Laser induced plasma has been studied by ICCD imaging and time and space resolved optical emission spectroscopy (OES), whereas the deposited films have been characterized by atomic force microscopy, scanning electron microscopy, X-Ray diffraction and micro-Raman spectroscopy. The film morphology and composition have been interpreted on the basis of the laser ablation mechanism.

De Bonis, A.; Santagata, A.; Rau, J. V.; Latini, A.; Mori, T.; Medici, L.; Teghil, R.

2013-10-01

237

Selective material ablation by the TEA CO2 laser  

NASA Astrophysics Data System (ADS)

This paper reports two topics in the material processing using TEA CO2 lasers. We demonstrated selective ablation of hydrogenated amorphous silicon (a-Si:H) thin layer on a quartz substrate by the second harmonic (SH) radiation of TEA CO2 laser generated by AgGaSe2 nonlinear crystal. Si-H bonds contained in a-Si:H strongly absorb the 5 micrometers SH radiation and resulted in the selective ablation of the a-Si:H layer. The successful ablation processing of ethylenetetrafluoroethylene (ETFE) copolymer by the 9.6 micrometers fundamental wavelength TEA CO2 laser is also reported. Only ETFE thin film adhered to an aluminum substrate can be ablated by the TEA CO2 laser.

Sumiyoshi, Tetsumi; Shiratori, Akira; Ninomiya, Yutaka; Obara, Minoru

1995-03-01

238

Imaging of excimer laser vascular tissue ablation by ultrafast photography  

NASA Astrophysics Data System (ADS)

Ablation and tissue removal of normal and atherosclerotic arterial tissue by UV excimer-laser radiation were probed by taking photographs with a dye laser as a flash light-source. The ablating pulses were transmitted through a fused silica fiber into a cuvette with the samples exposed to saline solution. The delay time of the probing dye-laser pulse with respect to the ablating excimer-laser pulse was varied in the nanosecond range up to several hundred microseconds. The ablation process and the resulting plume above the tissue surface were recorded with a CCD camera attached to a PC-based image processing system. All samples under investigation were fresh human cadaver aortic and femoral artery specimens which had been shock-frozen for less than 48 hours. The arterial segments showed different types of lipid-rich and calcified plaques. Big cavitation bubbles and small tissue particles emerging from the irradiated area have been recorded.

Nyga, Ralf; Neu, Walter; Preisack, M.; Haase, Karl K.; Karsch, Karl R.

1991-11-01

239

Peak polarity overturn for charged particles in laser ablation process  

Microsoft Academic Search

The charged particles emitted during laser ablation off a brass target are detected using a metal probe in air. A special phenomenon is found in the recorded signals: following a giant electromagnetic peak observed immediately after the emission of the pulsed laser, a minor peak occurs whose polarity merely depends on the distance between the probe and the laser focal

P. Zhang; Y. J. Ji; X. M. Lai; B. M. Bian; Z. H. Li

2006-01-01

240

Laser tattoo removal with preceding ablative fractional treatment  

NASA Astrophysics Data System (ADS)

A combined laser tattoo removal treatment, first the ablative fractional resurfacing (AFR) with an Er:YAG laser and then the q-switched (QSW) Nd:YAG laser treatment, was studied. Experiments show that significantly higher fluences can be used for the same tissue damage levels.

Cenci?, Boris; Možina, Janez; Jezeršek, Matija

2013-06-01

241

Morphology of femtosecond-laser-ablated borosilicate glass surfaces  

Microsoft Academic Search

We study the morphology of borosilicate glass surface machined by femtosecond laser pulses. Our observations show that a thin rim is formed around ablated craters after a single laser pulse. When multiple laser pulses are overlapped, the crater rims also overlap and produce a surface roughness. The rim appears to be a resolidified splash from a molten layer generated during

Adela Ben-Yakar; Robert L. Byer; Anthony Harkin; Jacqueline Ashmore; Howard A. Stone; Mengyan Shen; Eric Mazur

2003-01-01

242

Cleaning of large area by excimer laser ablation  

Microsoft Academic Search

Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser,

Marc L. Sentis; Philippe C. Delaporte; Vladimir I. Marine; Olivier Uteza

2000-01-01

243

Vapor breakdown during ablation by nanosecond laser pulses  

Microsoft Academic Search

Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. Although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no attempts made on vapor breakdown by nanosecond laser pulses. This work intends to fill the gap. A kinetic model is developed

C. L. Liu; J. N. Leboeuf; R. F. Wood; D. B. Geohegan; J. M. Donato; K. R. Chen; A. A. Puretzky

1995-01-01

244

Analysis of Atomic Beams Produced by Laser-Induced Ablation  

Microsoft Academic Search

Pulsed atomic beams with flux densities above 1016 cm-2 s-1 have been produced in vacuum with high reproducibility by laser induced ablation from titanium and iron targets. The power of the TEA CO2 laser was kept at a level where plasma production at the target surface was avoided: no ions were detectable. The beams were analysed by laser fluorescence. The

K P Selter; H-J Kunze

1982-01-01

245

Next generation Er:YAG fractional ablative laser  

Microsoft Academic Search

Pantec Biosolutions AG presents a portable fractional ablative laser system based on a miniaturized diode pumped Er:YAG laser. The system can operate at repetition rates up to 500 Hz and has an incorporated beam deflection unit. It is smaller, lighter and cost efficient compared to systems based on lamp pumped Er:YAG lasers and incorporates a skin layer detection to guarantee

A. Heinrich; A. Vizhanyo; P. Krammer; S. Summer; S. Gross; T. Bragagna; C. Böhler

2011-01-01

246

Experimental evaluation of optimized ablation patterns for laser refractive surgery.  

PubMed

A new experimental model based on plastic (Filofocon A) artificial eyes was used to study the ablation profiles and the outcomes of three state-of-the-art refractive surgery excimer lasers provided with narrow-beam flying spot and optimized algorithms (Ladarvision 4000, Alcon; Technolas 217 Z100, Bausch and Lomb; Allegretto wave Eye-Q, Wavelight). The 3-D ablation patterns produced by myopic laser corrections (-9, -6 and -3 D) on flat and spherical surfaces of Filofocon A were measured using high resolution optical profilometry. We found significant differences across lasers in the shape and depth of the ablation patterns. A comparison of the ablation patterns on flat and on spherical surfaces provided a measurement of the laser efficiency losses from the center to the periphery at each point of the spherical plastic corneas. This effect also varied across lasers, depending on their fluence (120-400 mJ/cm(2)). Estimates of the post-operative corneal shapes were obtained from the measurement on Filofocon A and plastic-corneal tissue correction factors. The predicted post-operative corneal ablation shape, ablated volume, asphericity and spherical aberration varied across lasers, as well as the relative contribution of ablation pattern designs and efficiency losses to the increased asphericity. Although the results show that the algorithms have been optimized to reduce the induction of spherical aberration, they would still benefit from the application of correction factors for efficiency effects derived from a systematic approach using experimental plastic models. These models have proved useful (1) to assess the outcomes of different lasers or ablation algorithms, (2) for precise calibration and testing of the lasers, and (3) to calculate experimental correction factors for efficiency effects. PMID:19688008

Dorronsoro, Carlos; Remon, Laura; Merayo-Lloves, Jesús; Marcos, Susana

2009-08-17

247

Femtosecond laser ablation of silicon–modification thresholds and morphology  

Microsoft Academic Search

.   We investigated the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses\\u000a of 5 to 400 fs duration. In accordance with earlier established models, we found the phenomena amorphization, melting, re-crystallization,\\u000a nucleated vaporization, and ablation to occur with increasing laser fluence down to the shortest pulse durations. We noticed\\u000a new morphological features (bubbles) as well

J. Bonse; S. Baudach; J. Krüger; W. Kautek; M. Lenzner

2002-01-01

248

Laser ablation for the synthesis of carbon nanotubes  

NASA Technical Reports Server (NTRS)

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 an 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.

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

2010-01-01

249

Optodynamic aspect of a pulsed laser ablation process  

NASA Astrophysics Data System (ADS)

A study of a pulsed laser ablation process is presented from a novel, optodynamic aspect. By quantitative analysis of laser-induced bulk ultrasonic and blast waves in the air the ablation dynamics is characterized. In this way the influence of the laser pulse parameters and of the interacting material on the ablation process was assessed. By the analysis of the laser drilling process of thin layered samples the material influence was demonstrated. Besides the ultrasonic evaluation of the laser pulse power density the plasma shielding for 10 ns laser pulses was analyzed by the same method. All measurements were noncontact. Bulk waves in the solid and blast waves in the air were measured simultaneously, an interferometric and a probe beam deflection method were used, respectively.

Hrovatin, Rok; Možina, Janez

1995-02-01

250

Laser ablation of iron: A comparison between femtosecond and picosecond laser pulses  

NASA Astrophysics Data System (ADS)

In this study, a comparison between femtosecond (fs) and picosecond (ps) laser ablation of electrolytic iron was carried out in ambient air. Experiments were conducted using a Ti:sapphire laser that emits radiation at 785 nm and at pulse widths of 110 ps and 130 fs, before and after pulse compression, respectively. Ablation rates were calculated from the depth of craters produced by multiple laser pulses incident normally to the target surface. Optical and scanning electron microscopy showed that picosecond laser pulses create craters that are deeper than those created by the same number of femtosecond laser pulses at the same fluence. Most of the ablated material was ejected from the ablation site in the form of large particles (few microns in size) in the case of picosecond laser ablation, while small particles (few hundred nanometers) were produced in femtosecond laser ablation. Thermal effects were apparent at high fluence in both femtosecond and picosecond laser ablation, but were less prevalent at low fluence, closer to the ablation threshold of the material. The quality of craters produced by femtosecond laser ablation at low fluence is better than those created at high fluence or using picosecond laser pulses.

Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

2013-08-01

251

Laser ablation of iron: A comparison between femtosecond and picosecond laser pulses  

SciTech Connect

In this study, a comparison between femtosecond (fs) and picosecond (ps) laser ablation of electrolytic iron was carried out in ambient air. Experiments were conducted using a Ti:sapphire laser that emits radiation at 785 nm and at pulse widths of 110 ps and 130 fs, before and after pulse compression, respectively. Ablation rates were calculated from the depth of craters produced by multiple laser pulses incident normally to the target surface. Optical and scanning electron microscopy showed that picosecond laser pulses create craters that are deeper than those created by the same number of femtosecond laser pulses at the same fluence. Most of the ablated material was ejected from the ablation site in the form of large particles (few microns in size) in the case of picosecond laser ablation, while small particles (few hundred nanometers) were produced in femtosecond laser ablation. Thermal effects were apparent at high fluence in both femtosecond and picosecond laser ablation, but were less prevalent at low fluence, closer to the ablation threshold of the material. The quality of craters produced by femtosecond laser ablation at low fluence is better than those created at high fluence or using picosecond laser pulses.

Shaheen, M. E. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada) [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); 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) [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)

2013-08-28

252

Laser ablation of a turbid medium: Modeling and experimental results  

SciTech Connect

Q-switched Nd:YAG laser ablation of a turbid medium (paint) is studied. The optical properties (absorption coefficient, scattering coefficient, and its anisotropy) of a paint are determined with a multiple scattering model (three-flux model), and from measurements of reflection-transmission of light through thin layers. The energy deposition profiles are calculated at wavelengths of 532 nm and 1.064 {mu}m. They are different from those described by a Lambert-Beer law. In particular, the energy deposition of the laser beam is not maximum on the surface but at some depth inside the medium. The ablated rate was measured for the two wavelengths and compared with the energy deposition profile predicted by the model. This allows us to understand the evolution of the ablated depth with the wavelength: the more the scattering coefficient is higher, the more the ablated depth and the threshold fluence of ablation decrease.

Brygo, F.; Semerok, A.; Weulersse, J.-M.; Thro, P.-Y.; Oltra, R. [Commissariat a l'Energie Atomique, DEN/DANS/DPC/SCP/LILM, Batiment 467, 91191 Gifs/Yvette (France); LRRS-UMR 5613 CNRS, Universite de Bourgogne 21078 Dijon (France)

2006-08-01

253

Collinear double pulse laser ablation in water for the production of silver nanoparticles.  

PubMed

Experiments of collinear Double Pulse Laser Ablation in Liquid (DP-LAL) were carried out for studying the production mechanisms of nanoparticles (NPs) in water, which revealed the fundamental role of the cavitation bubble dynamics in the formation of aqueous colloidal dispersions. In this work, DP-LAL was used to generate silver nanoparticles (AgNPs) from a silver target submerged in water at atmospheric pressure and room temperature, by using the second harmonic (532 nm) of two Nd:YAG lasers. The second laser pulse was shot at different delay times (i.e. interpulse delay) during the bubble temporal evolution of the first laser induced bubble. Optical Emission Spectroscopy, Shadowgraph Images, Surface Plasmon Resonance absorption spectroscopy and Dynamic Light Scattering were carried out to study the behaviour of laser-induced plasma and cavitation bubbles during the laser ablation in liquid, to monitor the generation of AgNPs under different conditions, and for characterization of NPs. The results of DP-LAL were always compared with the corresponding ones obtained with Single Pulse Laser Ablation in Liquid (SP-LAL), so as to highlight the peculiarities of the two different techniques. PMID:24196485

Dell'Aglio, Marcella; Gaudiuso, Rosalba; ElRashedy, Remah; De Pascale, Olga; Palazzo, Gerardo; De Giacomo, Alessandro

2013-12-28

254

Laser Ablation Increases PEM/Catalyst Interfacial Area  

NASA Technical Reports Server (NTRS)

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 as indications that laser-roughened PEMs should function well in fuel cells and, in particular, should exhibit current and power densities greater than those attainable by use of smooth membranes.

Whitacre, Jay; Yalisove, Steve

2009-01-01

255

Laser ablation of a platinum target in water. I. Ablation mechanisms  

SciTech Connect

This is the first in a series of three papers aimed at better understanding the processes that lead to nanomaterial formation during laser ablation of solid targets in liquids. Here we study the variation of the target surface morphology versus laser fluence and wavelength in order to suggest an ablation mechanism. A key finding is that an explosive ablation mechanism is prominent for a wide range of laser fluences for all wavelengths tested. Interestingly, however, ultraviolet (355 nm) and infrared (1064 nm) wavelengths show characteristically different explosive behaviors. In the infrared case, numerous large craters with diameters around 20 {mu}m form at localized points within the laser irradiated area. In contrast, ultraviolet ablation results in a striking transition to nanoscale surface roughness across the entire irradiated area. This texture is attributed to spinodal decomposition at the molten target surface. We propose that the wavelength and fluence dependence of the ablation craters can be explained by the amount of energy absorbed in the target. The consequences of the ablation mechanism for nanomaterial synthesis are discussed.

Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto [Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

2006-12-01

256

Synthesis of ultraviolet luminescent silicon nanocrystals by nanosecond pulsed laser ablation in water  

NASA Astrophysics Data System (ADS)

We report the preparation of silicon nanocrystals with efficient ultraviolet luminescence by nanosecond pulsed laser ablation in de-ionized water at a high laser fluence condition. Atomic force microscopy results show that nano-grains form in the process of laser ablation. Fourier transform infrared spectroscopy analyses indicate that silicon nanocrystals are formed and partially oxidized during synthesis. The photoluminescence measurement and the ultraviolet-visible transmittance spectroscopy of the samples prepared at various fluences reveal that all the prepared samples present an efficient ultraviolet emission at room temperature and it can be attributed to the quantum confinement effect and surface defect states. The emission wavelength of silicon nanocrystals is far shorter than visible light, which means potential applications in optoelectronic devices.

Yu, Wei; Li, Ligong; Gao, Huixia; Wu, Shujie; Fu, Guangsheng

2008-11-01

257

Femtosecond laser ablation of Au film around single pulse threshold  

NASA Astrophysics Data System (ADS)

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 'phi'0. From the plot of the accumulated laser fluence N'phi'_(th)(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.

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

2006-04-01

258

Cluster emission under femtosecond laser ablation of silicon  

NASA Astrophysics Data System (ADS)

Rich populations of clusters have been observed after femtosecond laser ablation of bulk silicon in vacuum. Size and velocity distributions of the clusters as well as their charge states have been analyzed by reflectron time-of-flight mass spectrometry. An efficient emission of both neutral silicon clusters Sin (up to n = 6) and their cations Sin+ (up to n = 10) has been observed. The clusters are formed even at very low laser fluences, below ablation threshold, and their relative yield increases with fluence. We show the dependencies of the cluster yield as well as the expansion dynamics on both laser wavelength and laser fluence. The mechanisms of the cluster formation are discussed.

Bulgakov, A.

2004-04-01

259

Mechanisms of Carbon Nanotube Production by Laser Ablation Process  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

260

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

NASA Astrophysics Data System (ADS)

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.

Canteli, D.; Fernandez, S.; Molpeceres, C.; Torres, I.; Gandía, J. J.

2012-09-01

261

Modification of polyimide wetting properties by laser ablated conical microstructures  

NASA Astrophysics Data System (ADS)

Laser texturing of Kapton® HN polyimide was performed by low-fluence ablation using a pulsed, frequency tripled (349 nm) Nd:YLF laser. The laser was scanned in two dimensions in order to generate texture over a large area. The laser overlap percentage and fluence were varied and the resulting texture was studied. The texture features were inspected by electron microscopy and energy dispersive X-Ray spectroscopy (EDS), while the static contact angle of de-ionized water was measured by a contact angle goniometer. Rounded bump features were formed at all fluences, which decreased in areal density with fluence and number of laser pulses. Conical microstructures or "cones" were also formed at most fluences. Cones were larger than the bumps and thus had lower areal density, which increased as a function of the number of laser pulses. The polyimide was hydrophilic before texturing, with a contact angle of approximately 76°. For most of the experimental conditions the contact angle increased as a result of texturing, with the contact angle exceeding 90° for some textured surfaces, and reaching values as high as 118°. In general, the surfaces with significant increases in contact angle had high density of texture features, either bumps or cones. The surfaces that experienced a decrease in contact angle generally had low density of texture features. The increase in contact angle from a wetting (? < 90°) to a nonwetting surface (? > 90°) cannot be explained by texturing alone. EDS measurements indicate that textured regions had higher carbon content than the untextured regions due to depletion of oxygen species. The increase in carbon content relative to the oxygen content increased the native contact angle of the surface, causing the transition from hydrophilic to hydrophobic behavior. The contact angle of a textured surface increased as the relative spacing of features (diameter to spacing) decreased.

Least, Brandon T.; Willis, David A.

2013-05-01

262

Ripple formation at laser ablation of chromium thin film  

NASA Astrophysics Data System (ADS)

Ablation characteristics of chromium thin film on a glass substrate by nanosecond laser pulses were investigated. The laser beam was tightly focused through the glass substrate to a stripe-like spot using the acylindrical lens. The metal was removed only by the central part of the laser beam, where local laser fluence exceeded the well-defined ablation threshold. Formation of a wide area cleaned by the series of laser pulses caused some side effects. The stripe ablated by a single laser pulse had sharp edges on both sides, while the partially overlapping pulses formed a wide stripe with a complicated structure made of the remaining metal. Regular structures, ripples, were developed when laser fluence was slightly above the threshold and the shift between pulses was less than a half width of the line ablated by a single laser pulse. The ripples were located periodically (~4 ?) and were orientated perpendicularly to the long axis of the beam spot (in parallel to the laser pulse shift direction). Their direction did not depend on the laser beam polarization. Different models of the ripple formation in the thin metal film were considered, and instability of the moving vapor-liquid- solid contact line during evaporation of thin liquid films appear to be the most appropriate process responsible for the observed phenomena. Regular gratings with the unlimited line length can be produced by using the technique.

Regelskis, Kestutis; Raciukaitis, Gediminas; Gecys, Paulius

2007-02-01

263

MRI-guided laser ablation of neuroendocrine tumor hepatic metastases  

PubMed Central

Background Neuroendocrine tumors (NET) represent a therapeutically challenging and heterogeneous group of malignancies occurring throughout the body, but mainly in the gastrointestinal system. Purpose To describe magnetic resonance imaging (MRI)-guided laser ablation of NET liver metastases and assess its role within the current treatment options and methods. Material and Methods Two patients with NET tumor hepatic metastases were treated with MRI-guided interstitial laser ablation (LITT). Three tumors were treated. Clinical follow-up time was 10 years. Results Both patients were successfully treated. There were no local recurrences at the ablation site during the follow-up. Both patients had survived at 10-year follow-up. One patient is disease-free. Conclusion MRI-guided laser ablation can be used to treat NET tumor liver metastases but combination therapy and a rigorous follow-up schedule are recommended.

Perala, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriala, Ilkka; Salmela, Pasi I; Tervonen, Osmo

2014-01-01

264

Moessbauer Study of Iron Films Produced by Laser Ablation  

SciTech Connect

Iron atoms evaporated by laser ablation were deposited on Al substrates and Si substrates. The iron and alloy (Fe-Al and Fe-Si) films thus formed were evaluated using Moessbauer spectroscopy in order to study their magnetic and chemical properties. Neat iron films (thicker than 50 nm) deposited on Al substrates at 10 K were found to have spin orientations parallel to the surface plane. Formation of Fe-Al alloy was observed at the boundary between the Fe-films and the Al substrate, and the composition of the Fe-Al alloy was a function of the Al substrate temperature during the deposition. Doublet absorption of FeAl was observed for the sample formed at 10 K, and distributed magnetic splitting with disordered compositions of Fe-Al alloy was observed for the samples formed at 293 K. When the sample was formed at 573 K, two sets of sextets with sharp absorptions were observed indicating the formation of Fe3Al. The films were also examined using scanning electron microscopy (SEM). Similarly, samples of laser-evaporated iron on Si substrates were studied, and alloys of Fe-Si were found. Fe3Si and FeSi were produced when the laser-deposition was performed on Si substrates at 573 K.

Namiki, Kentarou; Yokoyama, Daisuke; Yamada, Yasuhiro [Department of Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)

2005-04-26

265

Comparison of tissue ablation with pulsed holmium and thulium lasers  

SciTech Connect

The ablation rates and tissue effects produced by a pulsed holmium laser (wavelength 2.12 {mu}m, pulse duration 250 {mu}s) and a pulsed thulium laser (wavelength 2.01 {mu}m, pulse duration 250 {mu}s) are compared. Because the absorption coefficient of water is almost three times greater at the shorter wavelength (65 versus 24 cm{sup {minus}1}), the thulium laser should have a significantly lower threshold of ablation and produce significantly less residual thermal injury. These hypotheses were tested in vitro. Ablation rates were measured using fresh liver and a mass loss technique and found to increase linearly with delivered radiant exposure. The threshold radiant exposure for ablation was derived from the mass loss measurements and found to be 36 J/cm{sup 2} for the holmium laser and 29 J/cm{sup 2} for the thulium laser. The corresponding heats of ablation were 10 kJ/cm{sup 3} for the holmium laser and 9.7 kJ/cm{sup 3} for the thulium laser. These values were not statistically different.

Nishioka, N.S.; Domankevitz, Y. (Massachusetts General Hospital, Boston, MA (US))

1990-12-01

266

Laser cutting of carbon fiber reinforced plastics (CFRP) by UV pulsed laser ablation  

NASA Astrophysics Data System (ADS)

In this paper, we report on a micro-cutting of carbon fiber reinforced plastics (CFRP) by nanosecond-pulsed laser ablation with a diode-pumped solid state UV laser (DPSS UV laser, ?= 355nm). A well-defined cutting of CFRP which were free of debris and thermal-damages around the grooves, were performed by the laser ablation with a multiple-scanpass irradiation method. CFRP is a high strength composite material with a lightweight, and is increasingly being used various applications. UV pulsed laser ablation is suitable for laser cutting process of CFRP materials, which drastically reduces a thermal damage at cut regions.

Niino, Hiroyuki; Kurosaki, Ryozo

2011-02-01

267

Production of microscale particles from fish bone by gas flow assisted laser ablation  

NASA Astrophysics Data System (ADS)

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.

Boutinguiza, M.; Lusquiños, F.; Comesaña, R.; Riveiro, A.; Quintero, F.; Pou, J.

2007-12-01

268

Time Resolved Diagnostic of Dual-Pulsed Laser Ablation on Graphite Targets  

SciTech Connect

Plasma emission produced by Dual Pulsed Laser Ablation (DPLA) on two perpendicular graphite targets, separated 3 mm, was analyzed. Ablation was carried out in vacuum (10-6 Torr) by an excimer (248 nm) and a Nd: YAG (1064 nm) lasers, delayed up to 20 {mu}s. Spatial and temporal measurements were performed by time resolved optical emission spectroscopy, fast photography and two color interferometry. Time of flight was studied in order to determine the kinetic energies from the carbon species (C I, C II and C III). Comparison between dual-laser and single excimer laser ablation reveals that, ion energy distribution can be controlled by changing pulse delay between lasers. Results show that the highest reduction in the second pulse species velocities occurs at temporal delay between lasers from 1 to 5 {mu}s. Under these experimental conditions, the temporal evolution of temperature, electron and neutral densities was determined. Two colors interferometry allows study the plasma only up to 1.5 mm from the surface target. Thus no changes on the density values in single and dual pulse experiments were observed. On the other hand, time resolved optical emission spectroscopy shows an increase in temperature and electron density in dual pulse configuration at a distance of 10 mm from the target.

Sangines de Castro, R.; Sanchez Ake, C.; Sobral, H.; Villagran-Muniz, M. [Laboratorio de Fotofisica. Centro de Ciencias Aplicadas y Desarrollo Tecnologico. Universidad Nacional Autonoma de Mexico. Apartado Postal 70-186, Mexico D.F. 04510 (Mexico)

2006-12-04

269

Cleaning of large area by excimer laser ablation  

NASA Astrophysics Data System (ADS)

Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser, beam deliver, particle collection cell, real time control of cleaning processes. Results concerning surface laser interaction and substrate modifications are presented.

Sentis, Marc L.; Delaporte, Philippe C.; Marine, Vladimir I.; Uteza, Olivier

2000-01-01

270

Acoustic wave monitoring during laser ablation of tissue  

Microsoft Academic Search

The homogeneous and inhomogeneous model media, human aorta tissue were investigated under irradiation of Q-switched Nd-YAG laser and XeCl excimer laser. Temporal course of acoustic pressure with resolution of 3 - 5 ns, the efficiency of ablation, the distribution of ejected droplets over sizes were studied for laser fluencies 0.1 - 15 J\\/cm2. Pressure course depends on laser fluence and

Alexander A. Karabutov; Natalia B. Podymova; Vladilen S. Letokhov

1996-01-01

271

Time progression of ultrashort laser ablation in a transparent material  

NASA Astrophysics Data System (ADS)

Laser ablation on the ultra-short-pulses regime (femtosecond), has an impact on materials processing and micromachining in a quite profound ways. The investigation of the time progression of the laser ablation process within the material can produce much information and it is not conventionally used. The implementation of such study is the main aim of this paper. The temporal dependence of the diameter and depth of micro-drilling in the sample was verified, beyond the simple understanding of the mechanism for plasma generated during the ablation. From the monitoring of the time progression of the ablation, the time dependence for the velocity of ablation had been determined. In most cases, fume attenuation of the incoming laser beam and fume escape paths, produce dominant influence the characteristics of the region ablated. The method here employed is simple and can be carried out in real time without interruption of the process. In the implemented method light scattered from an auxiliary source allow visualization and record of the ablated geometry as it progress.

Nicolodelli, G.; Lizarelli, R. F. Z.; Costa, M. M.; Bagnato, V. S.

2011-08-01

272

Utilization of selected laser-ablation-based diagnostic methods for study of elemental distribution in various solid samples  

NASA Astrophysics Data System (ADS)

Here we report on the recent developments and upgrades of our Laser-Induced Breakdown Spectroscopy setups and their different modification for high-resolution mapping. Mapping capabilities of Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry are compared. The applied improvements as an autofocus algorithm, together with the realization of double-pulse LIBS or combination of LIBS by Laser-Induced Fluorescence Spectroscopy (LIFS) with technique are detailed. The signal enhancement obtained by double-pulse approach is demonstrated. The state of the art on development of portable remote LIBS apparatus is also presented.

Kaiser, J.; Novotný, K.; Hrdli?ka, A.; Malina, R.; Novotný, J.; Prochazka, D.; Petrilak, M.; Krajcarová, L.; Vítková, G.; Ku?erová, P.

2010-09-01

273

Femtosecond laser ablation of CaF2: Plasma characterization and thin films deposition  

NASA Astrophysics Data System (ADS)

Nanostructured thin films of CaF2 have been deposited in vacuum by ultra-short pulse laser ablation. The laser-induced plasma, characterized by optical emission spectroscopy and ICCD fast imaging, shows the presence of Ca and F atomic species, neutral and ionized, together with the CaF molecular species. Although continuous blackbody-like emission has not been detected from the plasma, the deposited films, characterized by Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy, are apparently formed by the coalescence of a large number of nanoparticles composed by stoichiometric CaF2.

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

2014-05-01

274

Wavelength scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency in laser fusion  

SciTech Connect

We examine the scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency with the wavelength of the laser, using a recent theoretical analysis of ablative laser driven implosions as a tool. Symmetrization by a hot atmosphere is most effective for long wavelength lasers, whereas ablation pressure and hydrodynamic efficiency are best for shorter laser wavelengths.

Max, C.E.; Lindl, J.D.; Mead, W.C.

1981-07-31

275

Plasma mediated ablation of biological tissues with ultrashort laser pulses  

SciTech Connect

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.

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

276

Gel-modulated photo ablation using noncontact photoacoustic spectroscopy control: a new concept  

NASA Astrophysics Data System (ADS)

Refractive gels, applied on the corneal surface in situ act as laser beam modulators. Depending upon their surface shape and absorbency, they can be used to reshape irregular surfaces or induce refractive effects. Three gels (Palm I Pallikaris, Greece; Refrax 33, Imperial, USA; Biomask, Maverick USA) have been investigated using Non Contact Photoacoustic Spectroscopy (NCPAS). Their use requires on line detection and monitoring of the ablation process, indicating when the gel is ablated and the corneal tissue is exposed to the incident laser pulse. NCPAS enables this on line control. With the gels in their present form, stable ablation rates where achieved only after 200 - 400 pulses, depending upon the gel. The typical frequency shift of the Fourier -- transformed time signal of NCPAS, observed for different target materials (gels, human, and porcine cornea) allowed the discrimination of the different gels as well as from human and porcine corneal tissue (epithelium and stroma). NCPAS discriminates and identifies even those gels with similar ablation rates, using the typical frequency shift (difference >= 1 kHz). Refractive gels in combination with a powerful on-line control such as NCPAS has a potential to be used as a low cost approach for reducing or minimizing the amount of surface bound corneal optical aberrations; it could thus bypass the complexity and costs of corneal reshaping systems, using topography or wavefront based customized treatment algorithms.

Jean, Benedikt J.; Bende, Thomas

2000-06-01

277

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

PubMed

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. PMID:24894923

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

2014-07-01

278

Preparation of GaN Nanostructures by Laser Ablation of ga Metal  

NASA Astrophysics Data System (ADS)

In the present study, GaN nanodots (0D) and nanowires (1D) nanostructures were prepared on stainless steal substrates applying laser ablation technique. The target of Ga metal mixed with NaNO2 was introduced in a central bore of a graphite rod of a confined geometry set up. The laser beam was normally focused onto the central bore and the ablated plume of Ga metal was deposited on stainless steal substrate lying below the graphite rod in an atmosphere of slow flow of nitrogen gas with or without ammonia vapor. The pulsed N2 laser beam having a wavelength of 337± 2 nm, pulse duration 15±1 ns and energy per pulse of 15±1 m J, could be focused on the central bore by a cylindrical quartz lens to a spot of dimensions 500 × 700 ?m2 t providing target irradiance of 0.2-0.3 GW/cm2 per pulse. The ablated plum was collected after several thousand laser shots. The morphology and structure of the formed nanostructures were investigated by Scanning electron microscope and Energy Dispersive X-Ray Spectroscopy. The growth mechanism is most likely by Solid-Liquid-Vapor phase during the laser ablation processes. The role of the carbon, the NaNO2 and the flowing gas on the growth of Nanostructures of GaN are discussed.

El Nadi, Lotfia; Omar, Magdy M.; Mehena, Galila A.; Moniem, Hussien M. A.

2011-06-01

279

Laser Ablation Surface Preparation of Ti-6A1-4V for Adhesive Bonding  

NASA Technical Reports Server (NTRS)

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.

Palmieri, Frank L.; Watson, Kent A.; Morales, Guillermo; Williams, Thomas; Hicks, Robert; Wohl, Christopher J.; Hopkins, John W.; Connell, John W.

2012-01-01

280

Optical properties of petal-like aggregated nanocrystalline zinc oxide synthesized by laser ablation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Petal like ZnO nanocrystals are synthesized by high frequency laser ablation in water. Black-Right-Pointing-Pointer Optical band gap of ZnO nanocrystals was tunable by changing the laser pulse energy. Black-Right-Pointing-Pointer Nonlinear optical properties and limiting threshold were obtained by Z-scan technique. -- Abstract: The results of the investigations carried out on the third-order nonlinearity in zinc oxide (ZnO) nanocrystals (NCs) by Z-scan technique are included in this paper. ZnO NCs show negative nonlinearity and good nonlinear absorption behavior at 532 nm. The third-order optical susceptibility {chi}(3) increases with enlargement of NCs due to the size dependent enhancement of exciton oscillator strength. The synthesis of ZnO NCs was performed by laser ablation from a high-purity metallic target of Zn in distilled water medium. For the ablation process, a high frequency pulsed Nd:YAG laser was employed operating at 532 nm with 100 ns pulse duration. UV-vis absorption spectroscopy illustrated the enhancement of the size of ZnO NCs upon increasing the laser pulse energy applied in ablation process. Accordingly the corresponding optical band gap (E{sub g}) decrease by increasing the size of NCs. X-ray diffraction (XRD) associated with transmission electron microscopy (TEM) was utilized to characterize the crystalline phase and also for determining the ZnO NCs morphology.

Jafarkhani, P.; Chehrghani, A. [Iranian National Centre for Laser Science and Technology (INLC), PO Box: 14665-576, Tehran (Iran, Islamic Republic of)] [Iranian National Centre for Laser Science and Technology (INLC), PO Box: 14665-576, Tehran (Iran, Islamic Republic of); Torkamany, M.J., E-mail: mjtorkamany@inlc.ir [Iranian National Centre for Laser Science and Technology (INLC), PO Box: 14665-576, Tehran (Iran, Islamic Republic of)

2012-03-15

281

Parallel femtosecond laser ablation with individually controlled intensity.  

PubMed

The use of computer generated holograms together with spatial light modulator (SLM) enable highly parallel laser micromachining. Usually SLM is used for splitting the original laser beam to desired number of beams with equal intensity. However, this technique also enables that the intensity of every beam can be controlled individually. Example of the hologram designing procedure for separation of the original beam to 400 beams with individually controlled intensity is presented. The proposed technique is demonstrated by femtosecond laser ablation of grayscale pictures so that grey scale of the pixel is addressed with corresponding beam intensity in the ablated picture. PMID:24663553

Silvennoinen, Martti; Kaakkunen, Jarno; Paivasaari, Kimmo; Vahimaa, Pasi

2014-02-10

282

EXCIMER LASER ABLATION OF GLASS FIBER IN REINFORCED POLYMER  

Microsoft Academic Search

In excimer laser ablation of glass fiber reinforced polymer, the fibers were found to be acting as refocusing lenses and caused partial fiber removal within the fiber. An analytical analysis based on Snell's law of refraction was used to calculate the laser intensity within the fiber, and the results of which were able to explain the partial removal phenomenon.

T. M. Yue; S. M. Mei; K. C. Chan

2002-01-01

283

Vapor breakdown during ablation by nanosecond laser pulses.  

National Technical Information Service (NTIS)

Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. Although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no ...

C. L. Liu D. B. Geohegan J. M. Donato J. N. Leboeuf R. F. Wood

1995-01-01

284

Metal ablation by picosecond laser pulses: A hybrid simulation  

Microsoft Academic Search

We investigate picosecond laser ablation of metals using a hybrid simulation scheme. Laser energy input into the electron system and heat conduction within it are modeled using a finite-difference scheme for solving the heat conduction equation. Atom motion in the near-surface part (72 nm) of the sample is modeled using molecular dynamics. Energy transfer between the electronic and atomic subsystems

Carsten Schäfer; Herbert M. Urbassek; Leonid V. Zhigilei

2002-01-01

285

Endovenous laser ablation with TM-fiber laser  

NASA Astrophysics Data System (ADS)

Endovenous Laser Ablation (EVLA) has become a popular minimally invasive alternative to stripping in the treatment of saphenous vein reflux. Several wavelengths have been proposed; of which 810, 940 and 980- nm are the most commonly used. However, the most appropriate wavelength is still the subject of debate. Thermal shrinkage of collagenous tissue during EVLA plays a significant role in the early and late results of the treatment. The aim of this study is to compare the efficacy of 980 and 1940-nm laser wavelengths in the treatment of varicose veins. In this study, 980 and 1940-nm lasers at different power settings (8/10W for 980-nm, 2/3W for 1940-nm) were used to irradiate stripped human veins. The most prominent contraction and narrowing in outer and inner diameter were observed with the 1940-nm at 2W, following 980-nm at 8W, 1940-nm at 3W and finally 980-nm at 10W. The minimum carbonization was observed with the 1940-nm at 2W. As a conclusion, 1940-nm Tm-fiber laser which has a significant effect in the management of varicose veins due to more selective energy absorption in water and consequently in the vein is a promising method in the management of varicose veins.

Somunyudan, Meral Filiz; Topaloglu, Nermin; Ergenoglu, Mehmet Umit; Gulsoy, Murat

2011-02-01

286

Laser ablation and arc\\/spark solid sample introduction into inductively coupled plasma mass spectrometers  

Microsoft Academic Search

Sample introduction using laser ablation and arc and spark ablation is reviewed. Few references were found in the literature on the use of spark or arc ablation as a sample introduction technique into the ICP-MS and emphasis is therefore placed on the use of laser ablation sampling, particularly for Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection; however, many of the

Detlef Günther; Simon E. Jackson; Henry P. Longerich

1999-01-01

287

Pulsed infrared laser ablation rates and characteristics in otic capsule  

NASA Astrophysics Data System (ADS)

Holmium:YAG (2.1 micrometers ) and Erbium:YAG (2.9 micrometers ) lasers have been suggested for use in neurotologic operations. The relatively high absorption in biologic tissues and minimal thermal diffusion associated with pulsed lasers make them attractive alternatives to CO2 and visible wavelength lasers, which currently enjoy widespread clinical use. There has been no systematic investigation of the properties of these lasers in a tissue model relevant to temporal bone operations, though there are numerous clinically oriented studies using these wavelengths. The microarchitecture of otic capsule (bone tissue of the inner ear) differs dramatically from bone found elsewhere in the body. Porcine otic capsule was machined into 0.8 mm thick specimens. The ablation rates of Ho:YAG and Erbium:YAG lasers were determined with incident flux varying from 6 - 20 J/cm2/pulse at 4 Hz PPR. Otic capsule specimens were ablated under both wet (physiologic) and dry (chemical dehydration) conditions. With Ho:YAG irradiation, dry otic capsule ablated with multiple episodes of stalling out. The relative number of specimens where stalling out occurred decreased with increasing laser flux. Wet tissue demonstrated similar characteristics, but with a lower ablation rate for a given fluence. In Erbium:YAG treated tissue, similar observations were noted, but the dependence on fluence is less clear in both wet and dry tissues. Water is shown to play a key role in the ablation process. The threshold of ablation is lower in wet tissue than in dehydrated tissue. The homogeneous microarchitecture of otic tissue also strongly influences the ablation process. Possible mechanisms are discussed.

Wong, Brian J.; Neev, Joseph; Sung, Vivian; Simonian, Belinda; Cheung, Eric M.; Berns, Michael W.

1995-05-01

288

Ablation studies of erbium:YAG laser radiation with ?  

NASA Astrophysics Data System (ADS)

The ablative mechanisms associated with 0022-3727/29/11/001/img2 radiation produced by a free-running Er:YAG laser have been studied using pellethane as a target medium. Probe beam techniques have been used and provide evidence that each individual relaxation oscillation within the free-running pulse can lead to ablation. A simple model, which takes into account the presence of the ablation plume, has been applied to the data and fits well. A threshold fluence for ablation of 0022-3727/29/11/001/img3 was obtained with an absorption coefficient of 0022-3727/29/11/001/img4. The studies may have relevance to medical applications of the laser.

Wannop, N. M.; Dickinson, M. R.; Farrar, S. R.; King, T. A.

1996-11-01

289

Optical properties measurement of the laser-ablated tissues for the combined laser ablation with photodynamic therapy  

NASA Astrophysics Data System (ADS)

Laser ablation therapy combined with photodynamic therapy (PDT) is studied for treatment of advanced cancers. The clinical outcome of PDT may be improved by the accurate knowledge about the light distribution within tissue. Optical properties [absorption coefficient (?a), scattering coefficient (?s), anisotropy factor (g), refractive index, etc.] of tissues help us realizing a light propagation through the tissue. It is important to understand of the effect of laser coagulation formed by laser ablation to PDT. The aim of this study is to estimate of influence of coagulated region to PDT for effective PDT combined laser ablation therapy. We evaluated the optical property of mouse tumor tissue in native and coagulated state using a double integrating sphere system and an inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. After laser ablation, the ?a and reduced scattering coefficient spectra of coagulated tissues were increased in the wavelength range from 350 to 1000 nm. The optical penetration depth of coagulated tissues is 1.2-2.9 times lower than the native state in the wavelength range from 350 to 1000 nm. The intensity of the light energy inside the coagulated tissue falls to about 60% of its original value at the end of coagulated layer. The evaluation of light energy distribution by the determination of the tissues optical properties could be useful for optimization of the treatment procedure in combined laser ablation with PDT.

Honda, Norihiro; Ishii, Katsunori; Awazu, Kunio

2012-02-01

290

Mechanism of laser ablation in an absorbing fluid field  

SciTech Connect

Selection of a laser source for intravascular applications has frequently been predicated upon assumptions involving transmissibility in blood of the wavelength of light emitted by a given laser. Standard absorption curves for ultraviolet radiation in blood and infrared radiation in water would suggest that transmission of ultraviolet radiation through a blood field and infrared radiation through any aqueous fluid field would be insufficient for tissue ablation. The present series of experiments was undertaken to determine whether these theoretical predictions would in fact obviate the use of these wavelengths in a blood field. Specimens of normal human myocardium and/or polyvinylchloride were submerged under blood and water and irradiated with ultraviolet radiation (351 nm) delivered as a focused beam and via an optical fiber and infrared radiation (10,600 nm) delivered as a focused beam. Ablation of myocardium was successfully accomplished with a focused beam of both ultraviolet and infrared radiation under as much as 5 mm of blood and with ultraviolet radiation via an optical fiber with the fiber tip up to 3 mm distant from the tissue specimen. High-speed cine recordings of ablation carried out using a focused beam of laser radiation demonstrated that formation of a dynamic optical cavity is the basis for successful pulsed ultraviolet and infrared laser transanguineous tissue ablation. These results thus demonstrate that prediction of wavelength transmission through fluid media based on optical properties of a static fluid does not predict ability to accomplish ablation under dynamic circumstances of laser irradiation.

Isner, J.M.; DeJesus, S.R.; Clarke, R.H.; Gal, D.; Rongione, A.J.; Donaldson, R.F.

1988-01-01

291

Corneal sensitivity and nerve regeneration after excimer laser ablation.  

PubMed

We studied the recovery of corneal sensitivity and corneal regeneration after excimer laser and manual epithelial debridement. The corneal epithelia of right eyes of New Zealand white rabbits (n = 21) were manually debrided and the corneal epithelia of the left eyes were ablated with the excimer laser (47 mm depth, 5 Hz, and 160 mJ/cm2). The relative density of innervation on the intraepithelial layer was measured using gold chloride staining and light microscopy. Wound healing and corneal sensitivity also were observed. Laser-ablated corneal sensitivity increased rapidly to a normal level by day 5, then increased gradually and reached a maximum at day 42. It remained elevated until 126 days, then returned to normal at 210 days. There were significant differences in the recovery of sensitivity after excimer ablation and manual epithelial removal. At day 35, relative density of innervation in the intraepithelial layer treated with excimer laser ablation was significantly higher than that treated with manual debridement. We observed a correlation between increased sensitivity and increased nerve density after excimer ablation. Compared with manual debridement, laser treatment resulted in an increase in networks of axons with terminal endings. This may not be the only factor correlating directly with hypersensitivity after corneal debridement, but it may indicate a quicker recovery route by using a presurgical manual debridement technique. PMID:8033572

Ishikawa, T; del Cerro, M; Liang, F Q; Loya, N; Aquavella, J V

1994-05-01

292

Molecular dynamics simulations studies of laser ablation in metals  

SciTech Connect

An overview of several aspects of our recent molecular dynamics simulations of femtosecond laser ablation is presented. This includes the study of phase diagrams for suitable interactions, analysis of ablated material and bubble formation below threshold, study of two-pulse ablation and the classification of materials with respect to electron properties and electron-phonon coupling in the two-temperature model. A treatment of boundary conditions and of an extended twotemperature model is also included. Most of the results apply to aluminum, others also to copper and iron, and to metals in general.

Roth, Johannes; Sonntag, Steffen; Karlin, Johannes; Paredes, Carolina Trichet; Sartison, Marc; Krauss, Armin; Trebin, Hans-Rainer [Institute for Theoretical and Applied Physics, University Stuttgart, Pfaffenwaldring 57/IV, 70550 Stuttgart (Germany)

2012-07-30

293

Tridimensional ablation region in femtosecond laser micromachining with diffractive lenses  

NASA Astrophysics Data System (ADS)

Increment of the axial region of ablation in a micromachining process is demonstrated when a refractive lens (RL) is replaced by a diffractive lens (DL). The depth of focus of a DL and a RL with the same numerical aperture are compared. For ultrashort pulses, the broadband spectrum of the laser together with the chromatic aberrations associated to the DL made its ablation region greater than the one corresponding to a RL. We measure experimentally the tridimensional ablation region for both types of lenses with 100 fs and 30 fs pulses. This study is expected to be promising to alleviate the mechanical tolerances in femtosecond micromachining with diffractive optical elements (DOEs).

Torres-Peiró, S.; González Ausejo, J.; Mendoza-Yero, O.; Mínguez-Vega, G.; Lancis, J.

2013-11-01

294

A spectroscopic study of laser ablation plasma from Mo target  

NASA Astrophysics Data System (ADS)

The goal of this contribution is to present time-resolved optical spectroscopy studies of laser ablation of the Mo target with ? 3.5 ns, 0.4 J pulses delivered by the Nd-YAG laser system at 1.06 ?m. The sample was placed in a vacuum chamber under 5 × 10?5 mbar pressure and irradiated, with power densities varied up to 22.7 GW cm?2. The ion emission from the plasma plume was measured using an electrostatic ion energy analyzer (IEA) and ion collector, which allowed us to estimate the ion kinetic energy and charge independent of the applied power densities. The signal collected by the IEA indicated the presence of molybdenum ions up to eight-ion charge. Simultaneously after the ion emission, the optical spectra acquired within 2 ?s of exposure time were observed in the wavelength range from 200 to 1000 nm with a Mechelle 5000 spectrometer equipped with an iCCD (iStar) detector. The plasma electron temperature was estimated from a Boltzmann plot based on the registered spectra as well as from the ion measurements.

Jakubowska, Katarzyna; Kubkowska, Monika; Blagoev, Alexander; Rosi?ski, Marcin; Parys, Piotr; G?sior, Pawe?

2014-05-01

295

Raman mapping of laser-induced changes and ablation of InAs nanowires  

NASA Astrophysics Data System (ADS)

Indium arsenic (InAs) nanowires were irradiated with a focused laser beam, followed by in situ Raman spectroscopy mapping and scanning electron microscopy imaging to investigate the changes of the nanowires due to laser irradiation. It was found that laser irradiation with the power intensity above a certain threshold causes arsenic (As) atoms to disintegrate from InAs and accumulate on the surface of the nanowire; the accumulated As atoms evaporate under the continued laser irradiation. This process reduces the As content in the nanowire. The reduction of As content, in turn, lowers the melting temperature of the nanowire locally and facilitates laser ablation, which eventually fractures the nanowire. The laser irradiation induced changes of the InAs nanowires are attributed to the local temperature rises due to the irradiation, as confirmed by the Raman peak shifts. The results from this work show that in situ Raman spectroscopy mapping can provide detailed information about the entire process of laser-induced change and ablation of InAs nanowires and has the potential to become a powerful tool for the characterization of laser modification of nanowires and other nanometer-sized objects.

He, Jiayu; Chen, Pingping; Lu, Wei; Dai, Ning; Zhu, Da-Ming

2013-08-01

296

Raman mapping of laser-induced changes and ablation of InAs nanowires  

NASA Astrophysics Data System (ADS)

Indium arsenic (InAs) nanowires were irradiated with a focused laser beam, followed by in situ Raman spectroscopy mapping and scanning electron microscopy imaging to investigate the changes of the nanowires due to laser irradiation. It was found that laser irradiation with the power intensity above a certain threshold causes arsenic (As) atoms to disintegrate from InAs and accumulate on the surface of the nanowire; the accumulated As atoms evaporate under the continued laser irradiation. This process reduces the As content in the nanowire. The reduction of As content, in turn, lowers the melting temperature of the nanowire locally and facilitates laser ablation, which eventually fractures the nanowire. The laser irradiation induced changes of the InAs nanowires are attributed to the local temperature rises due to the irradiation, as confirmed by the Raman peak shifts. The results from this work show that in situ Raman spectroscopy mapping can provide detailed information about the entire process of laser-induced change and ablation of InAs nanowires and has the potential to become a powerful tool for the characterization of laser modification of nanowires and other nanometer-sized objects.

He, Jiayu; Chen, Pingping; Lu, Wei; Dai, Ning; Zhu, Da-Ming

2014-06-01

297

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

SciTech Connect

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.

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

1993-10-01

298

Generation of low work function, stable compound thin films by laser ablation  

DOEpatents

Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

Dinh, Long N. (Concord, CA); McLean, II, William (Oakland, CA); Balooch, Mehdi (Berkeley, CA); Fehring, Jr., Edward J. (Dublin, CA); Schildbach, Marcus A. (Livermore, CA)

2001-01-01

299

Optical emission and mass spectrometric characterization of laser ablation process of Ca, Mg, and Ba at 1064 nm  

SciTech Connect

A systematic experimental study of the laser ablation of three alkaline-earth metals (Ca, Mg, and Ba) was carried out to understand the ablation processes of the metals. In this work the infrared laser ablation of alkaline-earth metals was studied by mass spectrometry together with the optical emission spectroscopy of the species generated in the ablation process. The analysis and modeling of the results were done using a heuristic equation that includes the Arrhenius, the screening, and the lineal regions that describe the three different regimes usually observed as a function of the laser fluence. We intend to prove that this equation depends on a fit surface parameter that includes the roughness surface, and it allows us to determine a critical fluence that can be related to the physical properties of the metal target.

Cabanillas-Vidosa, Ivan; Rinaldi, Carlos A.; Ferrero, Juan C. [Centro Laser de Ciencias Moleculares, INFIQC, Departamento de Fisicoquimica Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, 5000 Cordoba (Argentina)

2007-07-01

300

Laser Ablation of Biological Tissue Using Pulsed CO{sub 2} Laser  

SciTech Connect

Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO{sub 2} laser (wavelength: 10.6 {mu}m; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi [School of Science and Engineering, Electric and Electronics Engineering, Kinki University, 3-4-1 Kowakae, Higashi-Osaka City, Osaka, 577-8502 (Japan)

2010-10-13

301

Laser ablation in liquids: an efficient sample preparation technique in ICP elemental analysis of art materials  

NASA Astrophysics Data System (ADS)

Laser ablation in liquid media is proposed as a new sample preparation technique in elemental composition analysis of art pigments using inductively coupled plasma optical emission spectroscopy (ICP-OES). Solid samples are transformed to colloidal solutions of nanosized analyte particles. This makes the technique compatible with convevtional solutionbased standardization. The dissociation of particles in solution is improved, which increases the accuracy of quantitative ICP measurements.

Klyachkovskaya, E. V.; Kozhukh, N. M.; Muravitskaya, E. V.; Rosantsev, V. A.; Belkov, M. V.; Ershov-Pavlov, E. A.

2007-08-01

302

Ablative Laser Propulsion Using Multi-Layered Material Systems  

NASA Technical Reports Server (NTRS)

Experimental investigations are ongoing to study the force imparted to materials when subjected to laser ablation. When a laser pulse of sufficient energy density impacts a material, a small amount of the material is ablated. A torsion balance is used to measure the momentum produced by the ablation process. The balance consists of a thin metal wire with a rotating pendulum suspended in the middle. The wire is fixed at both ends. Recently, multi-layered material systems were investigated. These multi-layered materials were composed of a transparent front surface and opaque sub surface. The laser pulse penetrates the transparent outer surface with minimum photon loss and vaporizes the underlying opaque layer.

Nehls, Mary; Edwards, David; Gray, Perry; Schneider, T.

2002-01-01

303

Fabrication of iron oxide nanoparticles using laser ablation in liquids  

NASA Astrophysics Data System (ADS)

Nanoparticles of iron oxides were synthesized through the ablation of the bulk-targets of Fe, Fe3O4, and Fe2O3 in water by the irradiation of a Nd:YAG laser. Our samples prepared via the laser ablation method displayed small (ca. 1 nm in diameter) and large (over 5 nm in diameter) particles. The small particles were well-dispersed, whereas large particles were agglomerated. The FeO and Fe3O4 phases were formed in the synthesized powders irrespective of the kind of targets. The formation of the other phases, Fe and Fe2O3, changed depending on the the kind of targets used in the laser ablation. Poly(N-vinyl-2-pyrrolidone) (PVP) as a protective reagent was employed to disperse large particles in our samples, and accordingly, their dispersibility was improved as mole concentration of PVP increased.

Iwamoto, T.; Ishigaki, T.

2013-06-01

304

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy : ablation properties and analytical behaviour.  

SciTech Connect

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1-15 GW cm{sup 2} Zr deficient, 40-250 GW cm{sup 2} Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP. Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.

Goodall, P. S.; Wood, E. L.; Johnson, S. G.; Fuels and Engineering (Argonne-West)

1995-12-01

305

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy: ablation properties and analytical behavior  

NASA Astrophysics Data System (ADS)

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1-15 GW cm -2 Zr deficient, 40-250 GW cm -2 Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP. Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.

Goodall, Phillip; Johnson, Stephen G.; Wood, Elon

1995-12-01

306

RODEO MRI guided laser ablation of breast cancer  

NASA Astrophysics Data System (ADS)

This study explores the feasibility of image directed laser ablation of breast tumors as an alternative to traditional surgery. A series of 22 treatments were performed in 12 patients. The cancers were targeted with pre- and post- gadolinium enhanced RODEO breast MRI. 18 g MRI compatible needles were stereotaxically placed with RODEO breast MRI guidance. Laser ablation was implemented with a diode laser at 3 watts of power for about 500 seconds. The treatment was performed interactively with dynamic RODEO MRI control. The treatment zone was manifested as a hypointense zone on the dynamic images. The needle or treatment duration can be adjusted during the course of the ablation depending upon the location of the tumor and hypointense zone. In all cases correlation with conventional surgical excision with serial sectioning of the specimen was performed. PCNA stains of the treatment zone was used to confirm effective ablation and correlate the treatment zone size with the hypointense zone demonstrated on MRI. This study demonstrates the potential for RODEO breast MRI as an effective method for coordinating the interactive deliver of laser ablation in the treatment of breast cancer.

Harms, Steven E.; Mumtaz, Hamid; Hyslop, Brian; Klimberg, Suzanne; Westbrook, Kent; Kourourian, Sohelia

1999-06-01

307

Laser ablation of a platinum target in water. II. Ablation rate and nanoparticle size distributions  

SciTech Connect

This is the second in a series of three papers examining nanomaterial formation in laser ablation in liquids (LAL). Here we study the effect of the laser wavelength and fluence on the mass yield and size distribution of nanoparticles prepared by laser ablation of a platinum target immersed in water. For all wavelengths tested, laser fluences in the range of 10-70 J/cm{sup 2} resulted in spheroidal, nonagglomerated platinum nanoparticles with sizes ranging from 1 to 30 nm. Nanoparticle size distributions are found to be composed of two modes that are attributed to thermal vaporization and explosive boiling mechanisms. The peak of the smaller size mode remains nearly constant at 3 nm for all laser conditions, which is suggested to be due to the strong confinement of the vapor plume by the liquid. The larger size mode peaks in the range of 5-15 nm with a population that is strongly dependent on the laser parameters. It is concluded that changes in the mean size reported in many earlier studies on LAL of metal targets are a result of the relative quantity of nanoparticles from each mechanism rather than direct control over the ablation process. Additionally, it was observed that the yield of platinum nanoparticles was significantly larger for 1064 nm wavelength at fluences greater than 10 J/cm{sup 2}. The maximum ablation rate was approximately 4.4 mg/h, with an estimated ablation and collection efficiency of 0.9 {mu}g/J. Dependence of the mass yield on wavelength and fluence is seen to be dependent primarily on the extent of the explosive mechanism.

Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto [Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

2006-12-01

308

Glass particles produced by laser ablation for ICP-MSmeasurements  

SciTech Connect

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.

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

2007-06-01

309

Photomechanical basis of laser ablation of biological tissue  

NASA Astrophysics Data System (ADS)

The photomechanical picture of laser ablation of biological tissue asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. We have developed a three-dimensional theoretical model of the thermoelastic response of tissue to short-pulsed laser irradiation which allows the time-dependent stress distribution to be calculated given the optical, thermal and mechanical properties of the target. In addition, we have developed a complimentary interferometric technique which can measure the laser- induced thermoelastic expansion of a material with nanometer spatial resolution on a nanosecond time scale. The complex features of this expansion allow the needed optical, thermal, and mechanical properties of the target to be determined, which then allows the stress distribution to be calculated. This work has led to several significant results which support the photomechanical model of ablation of biological tissue. First, unlike the one-dimensional model predicts the development of significant tensile stressed on the surface of the target, precisely where ablation is observed to occur. Experimental results from bone are consistent with mechanical fracture caused by laser-induced stresses. Experimental results from human meniscus, a representative soft tissue, show additional behavior consistent with the growth and collapse of cavitation bubbles within the tissue caused by laser-induced stresses.

Perelman, Lev T.; Albagli, Douglas; Dark, Marta; von Rosenberg, Charles; Itzkan, Irving; Feld, Michael S.; Schaffer, Jonathan

1995-05-01

310

Evolution and imaging of nanoparticles observed in laser ablated carbon plume  

SciTech Connect

We report evidence of nanoparticles formation in laser ablated carbon plasma created by irradiating a graphite target with nanosecond neodymium doped yttrium aluminum garnet laser. The temporal evolution and spatial distribution of C{sub 2} molecules in the plasma is studied using optical emission spectroscopy, dynamic imaging and laser induced fluorescence techniques. The laser induced fluorescence spectrum and imaging of C{sub 2} fluorescence corresponding to transition d {sup 3}PI{sub g}-a {sup 3}PI{sub u} (0, 1) (lambda=563.5 nm) is investigated by probing the expanding plume using a dye laser. The temporal evolution of ground state number density of C{sub 2} shows density varying from 2.6x10{sup 20}/m{sup 3} to 1.2x10{sup 22}/m{sup 3} on varying delay between the ablating and probe pulse from 200 to 600 ns. A peculiar bifurcation of carbon plume into two parts at approx270 ns after the formation of plasma is attributed to recombination of carbon species and formation of nanoparticles. This study may help in quantitatively understanding of formation of carbon molecular species and the nanoparticles produced in laser ablated carbon plume.

Yadav, Dheerendra; Gupta, Varun; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (UP) (India)

2009-09-15

311

Laser ablated zirconium plasma: A source of neutral zirconium  

NASA Astrophysics Data System (ADS)

The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped using planner laser induced fluorescence imaging and total ablated mass of neutral zirconium atoms is estimated. Temporal and spatial evolutions of electron density and temperature are discussed by measuring Stark broadened profile and ratio of intensity of emission lines, respectively.

Yadav, Dheerendra; Thareja, Raj K.

2010-10-01

312

Effect of dry and wet ambient environment on the pulsed laser ablation of titanium  

NASA Astrophysics Data System (ADS)

Surface and structural properties of the laser irradiated titanium targets have been investigated under dry and wet ambient environments. For this purpose KrF Excimer laser of wavelength 248 nm, pulse duration of 20 ns and repetition rate of 20 Hz has been employed. The targets were exposed for various number of laser pulses ranging from 500 to 2000 in the ambient environment of air, de-ionized water and propanol at a fluence of 3.6 J/cm2. The surface morphology, chemical composition and crystallographical analysis were performed by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD), respectively. For both central and peripheral ablated areas, significant difference in surface morphology has been observed in case of dry and wet ambient conditions. Large sized and diffused grains are observed in case of dry ablation. Whereas, in case of wet ablation, small sized, and well defined grains with distinct grain boundaries and significantly enhanced density are revealed. This difference is ascribed to the confinement effects of the liquid. The peripheral ablated area shows redeposition in case of dry ablation whereas small sized grain like structures are formed in case of wet ablation. EDS analysis exhibits variation in chemical composition under both ambient conditions. When the targets are treated in air environment, enhancement of the oxygen as well as nitrogen content is observed while in case of de-ionized water and propanol only increase in content of oxygen is observed. X-ray diffraction analysis exhibits formation of oxides and nitrides in case of air, whereas, in case of de-ionized water and propanol only oxides along with hydrides are formed. For various number of laser pulses the variation in the peak intensity, crystallinity and d-spacing is observed under both ambient conditions.

Ali, Nisar; Bashir, Shazia; Umm-i-Kalsoom; Akram, Mahreen; Mahmood, Khaliq

2013-04-01

313

Ablation characteristics of Au, Ag, and Cu metals using a femtosecond Ti:sapphire laser  

Microsoft Academic Search

Femtosecond laser ablation of metallic bulk crystals of Au, Ag and Cu was experimentally studied with laser pulse widths ranging from 120 fs through 800 fs at a center wavelength of 780 nm for micro-machining applications. Two different ablation regimes were found in terms of the laser fluence. The characteristic length of different ablation regimes was explained in terms of

K. Furusawa; K. Takahashi; H. Kumagai; K. Midorikawa; M. Obara

1999-01-01

314

Ionization in vacuum ultraviolet F2 laser ablated polymer plumes  

NASA Astrophysics Data System (ADS)

An experimental investigation of ion generation in the 157-nm vacuum ultraviolet (VUV) F2 laser ablation of three selected polymers glycidyl azide polymer (GAP), a triazene polymer (TP6) and polyimide is described. An ion collector probe is used to determine the relative ion yield and white-light interferometry of ablated surfaces to ascertain mass-removal levels. The findings indicate that ions are generated under the action of the VUV laser pulse at fluences down to at least as low as the threshold for material removal. A two-photon photoionization model is proposed that provides a good description of the results.

Dyer, P. E.; Pervolaraki, M.; Walton, C. D.; Lippert, T.; Kuhnke, M.; Wokaun, A.

2008-03-01

315

Below-Band-Gap Laser Ablation Of Diamond For TEM  

NASA Technical Reports Server (NTRS)

Thin, electron-transparent layers of diamond for examination in transmission electron microscope (TEM) fabricated from thicker diamond substrates by using laser beam to ablate surface of substrate. Involves use of photon energy below band gap. Growing interest in use of diamond as bulk substrate and as coating material in variety of applications has given rise to increasing need for TEM for characterization of diamond-based materials. Below-band-gap laser ablation method helps to satisfy this need. Also applied in general to cutting and etching of diamonds.

George, Thomas; Foote, Marc C.; Vasquez, Richard P.; Fortier, Edward P.; Posthill, John B.

1995-01-01

316

Ablation-initiated Isotope-selective Atomic Absorption Spectroscopy of Lanthanide Elements  

NASA Astrophysics Data System (ADS)

For remote isotope analysis of low-decontaminated trans-uranium (TRU) fuel, absorption spectroscopy has been applied to a laser-ablated plume of lanthanide elements. To improve isotopic selectivity and detection sensitivity of the ablated species, various experimental conditions were optimized. Isotope-selective absorption spectra were measured by observing the slow component of the plume produced under low-pressure rare-gas ambient. The measured minimum line width of about 0.9 GHz was close to the Doppler width of the Gd atomic transition at room temperature. The relaxation rate of high-lying metastable state was found to be higher than that of the ground state, which suggests that higher analytical sensitivity can be obtained using low-lying state transition. Under helium gas environment, Doppler splitting was caused from particle motion. This effect was considered for optimization for isotope selection and analysis. Some analytical performances of this method were determined under optimum conditions and were discussed.

Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Maruyama, Y.; Wakaida, I.; Watanabe, K.

2009-03-01

317

Ultrashort-pulse laser ablation of nanocrystalline aluminum  

SciTech Connect

Molecular-dynamics simulations of the ablation of nanocrystalline Al films by ultrashort laser pulses in the low-fluence (no-ionization) regime (0-2.5 times the ablation threshold, F{sub th}) are reported. The simulations employ an embedded-atom method potential for the dynamics of the ions and a realistic two-temperature model for the electron gas (and its interactions with the ion gas), which confers different electronic properties to the monocrystalline solid, nanocrystalline solid, and liquid regions of the targets. The ablation dynamics in three nanocrystalline structures is studied: two dense targets with different crystallite sizes (d=3.1 and 6.2 nm on average) and a d=6.2 nm porous sample. The results are compared to the ablation of monocrystalline Al. Significant differences are observed, the nanocrystalline targets showing, in particular, a lower ablation threshold and a larger melting depth, and yielding pressure waves of higher amplitude than the monocrystalline targets. Furthermore, it is shown that nanocrystalline targets experience no residual stress associated with thermal expansion and lateral constraints, and that little crystal growth occurs in the solid during and after ablation. Laser-induced spallation of the back surface of the films is also investigated; we find, in particular, that the high-strain fracture resistance of nanocrystalline samples is significantly reduced in comparison to the crystalline material.

Gill-Comeau, Maxime; Lewis, Laurent J. [Departement de Physique et Regroupement Quebecois sur les Materiaux de Pointe (RQMP), Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, Quebec, H3C 3J7 (Canada)

2011-12-01

318

Thermal melting and ablation of silicon by femtosecond laser radiation  

SciTech Connect

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.

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)] [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)] [Russian Academy of Sciences, General Physics Institute (Russian Federation)

2013-03-15

319

Generation of nanoparticles of bronze and brass by laser ablation in liquid  

NASA Astrophysics Data System (ADS)

Nanoparticles of brass and bronze are generated by ablation of corresponding bulk targets in liquid ethanol. The experiments were performed using three pulsed lasers with different pulse duration: ytterbium fiber laser (80 ns), a Neodymium:YAG laser (10 ps), and femtosecond Ti:sapphire laser (200 fs). The generated nanoparticles (NPs) are characterized by UV-vis absorption spectroscopy, X-ray diffractometry, Raman scattering, and Transmission Electron Microscopy. The size of generated NPs lies in the range 10-25 nm depending on the laser source. The X-ray diffractometry reveals the change of phase composition of brass NPs compared to the initial target in case of ablation with 80 ns laser source, while with 10 ps laser pulses this effect is less pronounced. Brass NPs generated with pico- and femtosecond laser radiation show the plasmon resonance in the vicinity of 560 nm and no plasmon peak for NPs generated with longer laser pulses. Raman analysis shows the presence of Cu2O in generated NPs. The stability of generated NPs of both brass and bronze to oxidation is compared to that of Cu NPs generated in similar experimental conditions.

Sukhov, I. A.; Shafeev, G. A.; Voronov, V. V.; Sygletou, M.; Stratakis, E.; Fotakis, C.

2014-05-01

320

Plume dynamics of cross-beam pulsed-laser ablation of graphite  

SciTech Connect

The dynamics of the interaction between two plasmas induced by cross-beam pulsed-laser ablation was analyzed by time resolved optical emission spectroscopy and fast photography. The plasmas were created in vacuum by irradiating two perpendicular graphite targets with an excimer (248 nm) and a Nd:yttrium-aluminum-garnet (1064 nm) laser. In this configuration, a laser is focused onto a target generating a highly directed plume; subsequently, an additional laser produces a second plasma from the perpendicular target which expands through the first plume. Collisional processes cause a reduction of the kinetic energy of the second plume species as compared to the single pulse experiment. For a fixed delay between lasers of 2 {mu}s, the second plume was divided in two perpendicular directions. The dynamics of this plasma has been compared with laser-induced plume propagation through a background gas in terms of the drag model.

Sanchez Ake, C.; Sangines de Castro, R.; Sobral, H.; Villagran-Muniz, M. [Laboratorio de Fotofisica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-186, Mexico Distrito Federal, 04510 (Mexico)

2006-09-01

321

Formation and characterization of nanoparticles via laser ablation in solution  

NASA Astrophysics Data System (ADS)

The work presented in this thesis encompassed laser ablation of various transition metals within a liquid environment. Through an improved understanding of the ablation process, control over the properties of the resultant nanoparticles can be obtained, and thusly nanoparticles can be tailored with specific properties. Creation of nanoparticles via laser ablation in solution is a relatively youngtechnique for nanoparticle synthesis, and the work presented should prove useful in guiding further exploration in ablation processes in liquids for nanomaterial production. When a laser is focused onto a target under a liquid environment, the target material and its surrounding liquid are vaporized. The concoction of vapor is ejected normal to the surface as a bubble. The bubble has a temperature reaching the boiling point of the metal, and has a gradient to the boiling point of the solvent. The bubble expands until it reaches a critical volume, and then subsequently collapses. It is within this bubble that nanoparticle formation occurs. As the bubble expands, the vapor cools and nanoparticle growth transpires. During the bubble collapse, pressures reaching GigaPascals have been reported, and a secondary nanoparticle formation occurs as a result of these high pressures. Chapter 1 delves a little more into the nanoparticle formation mechanisms, as well as an introduction to the analytical techniques used for characterization. Ablation of titanium took place in isopropanol, ethanol, water, and n-hexane, under various fluences, with a 532 nm Nd:YAG operating at 10 Hz. It was found that a myriad of nanoparticles could be made with vastly different compositions that were both solvent and fluence dependent. Nanoparticles were made that incorporated carbon and oxygen from the solvent, showing how solvent choice is an important factor in nanoparticle creation. Chapter 3 discusses the results of the titanium work in great detail and demonstrates carbide production with ablation in isopropyl alcohol. Ablation in n-hexane also showed diffraction patterns correlating with carbides, and water showed oxygen incorporation. These results showed the ability to utilize the solvent in tailoring nanoparticles to achieve desired properties. Zirconium and nickel were ablated with the Nd:YAG at 532 nm. These studies utilized a stainless steel chamber designed and built to improve control over the experimental variables. The nickel study showcased the new chamber's ability for reproducibility in a size dependence study based upon laser fluence. The results of ablation with the Nd:YAG were compared to femtosecond ablation experiments performed with a titanium:sapphire femtosecond laser system. The Ti:sapphire femtosecond laser operated at 10 Hz, produced femtosecond pulses centered at ˜795 nm. The pulse duration was varied from 100 fs to 390 fs, the nanoparticles created from each condition were characterized, and the results are presented in chapters 5 and 6. Aluminum nanoparticles were made using both nanosecond and femtosecond laser ablation techniques. Aluminum nanoparticles have a great deal of potential for use as fuel additives as well as in paints and coatings. The nanosecond ablation process rendered large nanoparticles (over 200 nm) and the results are briefly shown in Appendix A. The femtosecond system produced a much smaller distribution of nanoparticles, with nanoparticles remaining in suspension for over a month's time, as evidenced by their unique UV-Vis absorbance. These nanoparticles were produced in isopropyl alcohol, and were stabilized by the solvent, as TEM analysis showed nanoparticles with very little oxygen incorporation. The solvent is bound to the nanoparticles as a result of the formation process and as a result forms a protective coating, which prevents further oxidation over time. The remarkable stability of these aluminum nanoparticles is a testament of employing the high energy scheme of the laser ablation process in a manner to tailor the production of novel nanomaterials. (Abstract shortened by UMI.)

Golightly, Justin Samuel

322

Combined optical tweezers and laser dissector for controlled ablation of functional connections in neural networks  

NASA Astrophysics Data System (ADS)

Regeneration of functional connectivity within a neural network after different degrees of lesion is of utmost clinical importance. To test pharmacological approaches aimed at recovering from a total or partial damage of neuronal connections within a circuit, it is necessary to develop a precise method for controlled ablation of neuronal processes. We combined a UV laser microdissector to ablate neural processes in vitro at single neuron and neural network level with infrared holographic optical tweezers to carry out force spectroscopy measurements. Simultaneous force spectroscopy, down to the sub-pico-Newton range, was performed during laser dissection to quantify the tension release in a partially ablated neurite. Therefore, we could control and measure the damage inflicted to an individual neuronal process. To characterize the effect of the inflicted injury on network level, changes in activity of neural subpopulations were monitored with subcellular resolution and overall network activity with high temporal resolution by concurrent calcium imaging and microelectrode array recording. Neuronal connections have been sequentially ablated and the correlated changes in network activity traced and mapped. With this unique combination of electrophysiological and optical tools, neural activity can be studied and quantified in response to controlled injury at the subcellular, cellular, and network level.

Difato, Francesco; Dal Maschio, Marco; Marconi, Emanuele; Ronzitti, Giuseppe; Maccione, Alessandro; Fellin, Tommasso; Berdondini, Luca; Chieregatti, Evelina; Benfenati, Fabio; Blau, Axel

2011-05-01

323

Infrared laser ablation of dental enamel: influence of an applied water layer on ablation rate and peripheral damage  

NASA Astrophysics Data System (ADS)

Studies have shown that a water spray may augment the laser ablation rate of dental hard tissues in addition to reducing heat accumulation. However, the mechanism of augmentation is controversial and poorly understood. The influence of an optically thick applied water layer on the ablation rate was investigated at wavelengths in which water is a primary absorber and the magnitude of absorption varies markedly. Water was manually applied with a pipette and troughs were cut in enamel blocks using a laser scanning system. Q- switched and free running Er:YSGG and Er:YAG, free running Ho:YAG and 9.6 micrometers TEA CO2 laser systems were investigated. The addition of water increased the rate of ablation and produced a more desirable surface morphology during enamel ablation with all the erbium systems. Ablation was markedly more efficient for the Q-switched erbium lasers than for the longer free-running laser systems when a water layer was added. Although, the addition of a thick water layer reduced the rate of ablation during CO2 laser ablation, the addition of the water removed undesirable deposits of non-apatite mineral phases from the crater surface. There was extensive peripheral damage after irradiation with the Ho:YAG laser with and without added water without effective ablation of enamel. The results of this study suggest that water augments the ablation of dental enamel by aiding in the removal of loosely attached deposits of non-apatite mineral phase from the crater surface, thus producing a more desirable crater surface morphology. The non-apatite mineral phase interfere with subsequent laser pulses during erbium laser irradiation reducing the rate of ablation and their removal aids in maintaining efficient ablation during multiple pulses irradiation.

Ashouri, Nahal; Shori, Ramesh K.; Cheung, Jason M.; Fried, Daniel

2001-04-01

324

Wavelength-Dependent Conformational Changes in Collagen after Mid-Infrared Laser Ablation of Cornea  

PubMed Central

We ablated porcine corneas with a free electron laser tuned to either 2.77 or 6.45 ?m, two matched wavelengths that predominantly target water and protein, respectively. The ejected nonvolatile debris and the crater left behind were examined by circular dichroism, Raman spectroscopy, and scanning electron microscopy to characterize the postablation conformation of collagen proteins. We found near-complete unfolding of collagen secondary and tertiary structure at either ablating wavelength. On the other hand, we found excess fibril swelling and evidence for excess cis-hydroxyproline in the 6.45-?m debris. These results support the hypothesis that the favorable ablative properties of protein-targeting wavelengths rest on selective heating of tissue proteins.

Xiao, Yaowu; Guo, Mingsheng; Zhang, Peng; Shanmugam, Ganesh; Polavarapu, Prasad L.; Hutson, M. Shane

2008-01-01

325

Surface ablation of transparent polymers with femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

In this work, a study of the laser ablation on the surface of poly methyl-methacrylate (PMMA) is presented. Experiments were performed with a femtosecond laser delivering 450 fs pulses at a wavelength of 1027 nm. The laser beam energy was controlled through a polarizer based attenuator and measured by a calibrated photodiode energy meter. A focusing method called z-scan is used to place the sample on the beam waist. This method uses a second energy meter placed behind the sample, which was used to monitor the energy transmitted across the sample in situ. Thus, the absorption was evaluated by comparing the measurements of both energy meters. The z-scan method is evaluated by studying the laser ablation in three different positions between the sample and the laser beam waist. It is found that above a threshold energy that depends on the focusing conditions, the absorbance of the samples increases with the pulse energy. After irradiation, dimensional analysis of the craters produced at different pulse energies is performed in order to determine the best focusing conditions and the ablation threshold for ablation of PMMA samples.

Florian, C.; Caballero-Lucas, F.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P.

2014-05-01

326

Small glass particle cloud generation induced by laser ablation  

NASA Astrophysics Data System (ADS)

Burst of small fragments of glass has been evidenced in the present study, when ground glass surface is laser ablated. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of metal or polymer ablation. In this case, no additional metal coating has been made to further enhance absorption of laser pulse. Pulse laser shadowgraph has been taken to study the details of the phenomena in air and in vacuum. At least in vacuum, particle burst is found almost normal to the surface. By using ns-duration Nd:YAG laser of 100 mJ/pulse, observed particle velocity ranges 0.5 km/s to 1.5 km/s in case of in air and the maximum velocity is extended up to 1.5-2 km/s in vacuum. SEM observation of the ground surface reveals that glass surface is covered with micro cracks with several microns deep, which might attribute to macro particle production. In this sense, not surface roughness but also surface structure will be important in the ablation phenomena of glass. It is plausible that absorption of laser beam at the glass surface causes spallation like phenomena as well as production of an amount of plasma, and the plasma production might be responsible for the acceleration of broken fragments of glass. We applied the phenomena to ignite PETN powder explosive, and succeeded in igniting PETN powder only by laser ablation of ground glass.

Nagayama, Kunihito; Kotsuka, Yuriko; Nakahara, Motonao; Kubota, Shiro

2005-03-01

327

Laser ablation of silicon in neon gas: Study of excitation mechanism of neon neutrals by ablated silicon ions  

SciTech Connect

The excitation mechanism of buffer gas in the laser-ablation process was investigated by time- and space-resolved emission spectroscopies. A silicon disk was ablated in neon gas at a pressure of 1 torr by the fundamental beam output of a Nd: yttrium aluminum garnet laser (1064 nm). The time-resolved emission spectra showed the generation of excited silicon ions Si{sup n+}*(n=1-3) and excited neon neutrals Ne* to the 2p{sub 1} level immediately after laser irradiation. Excitation of Ne to the 2p{sub n}(n=2-10) levels was delayed by 150 ns. The temporal evolutions of the space-resolved emission from Ne* indicated excitation by fast (<100 ns) and/or slow (<300 ns) processes. The slow process contributed to all 2p{sub n} levels, while the fast process was observed only in excitation to the 2p{sub 1} level. This means that the fast process involves level-selective excitation. Based on temporal evolutions, the energy levels, and the collision cross sections of Ne and Si{sup n+}, we assigned the fast and slow processes to excitations by electronic-to-electronic energy transfer from Si{sup 2+}* and translational-to-electronic energy transfer from Si{sup +}, respectively.

Saeki, Morihisa; Hirata, Kohichi; Sakka, Tetsuo; Ohba, Hironori; Yokoyama, Atsushi [Department of Materials Science, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Department of Materials Science, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

2005-08-15

328

Surface quality of excimer laser corneal ablation with different frequencies.  

PubMed

To test the effects of different frequencies of a 193-nm excimer laser on the surface smoothness of the ablated materials and the damage to the adjacent structure, four different frequencies (5, 10, 15, and 20 Hz) of a 193-nm excimer laser were used to perform ablations on 20 rabbit corneas and four polymethylmethacrylate blocks at a fluence of 160 mJ/cm2. Each frequency was tested five times on five corneas. The ablated materials were processed and examined with scanning electron microscopy (SEM) and light and transmission electron microscopy (TEM) and a Zygo interference microscope, which quantitatively evaluates the surface smoothness. The results from the Zygo microscope show that there is no statistically significant difference in surface smoothness between any two different frequencies. The SEM reveals similar regularity and uniformity on the ablated surfaces, with no relationship between the laser frequencies and the amount of surface deposits. The TEM demonstrates no correlation between the various frequencies and the thickness of the superficial pseudomembrane and the amount of collateral damage in the adjacent stroma. It appears that the higher frequencies are comparable to the lower one (5 Hz) as to ablation quality, with the benefit of curtailing surgical time and decreasing the chances of eye movement. PMID:8261781

Liang, F Q; Ishikawa, T; Kim, J; del Cerro, M; Park, S B; Aquavella, J V

1993-11-01

329

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors  

NASA Astrophysics Data System (ADS)

A comparative experimental study of pulsed laser ablation in vacuum of two binary semiconductors, zinc oxide and indium phosphide, has been performed using IR- and visible laser pulses with particular attention to cluster generation. Neutral and cationic ZnnOm and InnPm particles of various stoichiometry have been produced and investigated by time-of-flight mass spectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters are mainly stoichiometric in the ablation plume. In contrast, indium phosphide clusters are strongly indium-rich with In4P being a magic cluster. Analysis of the plume composition upon laser exposure has revealed congruent vaporization of ZnO and a disproportionate loss of phosphorus by the irradiated InP surface. Plume expansion conditions under ZnO ablation are shown to be favorable for stoichiometric cluster formation. A delayed vaporization of phosphorus under InP ablation has been observed that results in generation of off-stoichiometric clusters.

Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G.; Ozerov, Igor; Marine, Wladimir

2010-10-01

330

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors  

SciTech Connect

A comparative experimental study of pulsed laser ablation in vacuum of two binary semiconductors, zinc oxide and indium phosphide, has been performed using IR- and visible laser pulses with particular attention to cluster generation. Neutral and cationic Zn{sub n}O{sub m} and In{sub n}P{sub m} particles of various stoichiometry have been produced and investigated by time-of-flight mass spectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters are mainly stoichiometric in the ablation plume. In contrast, indium phosphide clusters are strongly indium-rich with In{sub 4}P being a magic cluster. Analysis of the plume composition upon laser exposure has revealed congruent vaporization of ZnO and a disproportionate loss of phosphorus by the irradiated InP surface. Plume expansion conditions under ZnO ablation are shown to be favorable for stoichiometric cluster formation. A delayed vaporization of phosphorus under InP ablation has been observed that results in generation of off-stoichiometric clusters.

Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G. [Institute of Thermophysics SB RAS, Lavrentyev Ave. 1, 630090 Novosibirsk (Russian Federation); Ozerov, Igor; Marine, Wladimir [Universite de la Mediterranee, CINaM, UPR CNRS 3118, 13288 Marseille (France)

2010-10-08

331

Laser ablative surface treatment for enhanced bonding of Ti-6Al-4V alloy.  

PubMed

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 adhesive bonds. Surface preparation by laser ablation provides an alternative to the expensive, hazardous, polluting, and less precise practices used currently such as chemical-dip, manual abrasion and grit blast. 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. Surface roughness and surface chemical composition were characterized using interference microscopy and X-ray photoelectron spectroscopy, respectively. A technique for fluorescence visualization was developed which allowed for quantitative failure mode analysis. Wedge crack extension testing in a hot, humid environment indicated the relative effectiveness of various surface treatments. Increasing ablation duty cycle reduced crack propagation and adhesive failure. Single lap shear testing showed an increase in strength and durability as laser ablation duty cycle and power were increased. Chemical analyses showed trends for surface chemical species, which correlated with improved bond strength and durability. PMID:23317556

Palmieri, Frank L; Watson, Kent A; Morales, Guillermo; Williams, Thomas; Hicks, Robert; Wohl, Christopher J; Hopkins, John W; Connell, John W

2013-02-01

332

Computational modeling of physical processes during laser ablation  

SciTech Connect

A combined theoretical and experimental effort to model various physical processes during laser ablation of solids (silicon) using a variety of computational techniques is described. Currently the focus of the modeling is on the following areas: (a) rapid transformations through the liquid and vapor phases under possibly nonequilibrium thermodynamic conditions induced by laser-solid interactions, (b) breakdown of the vapor into a plasma in the early stages of ablation through both electronic and photoionization processes, (c) hydrodynamic behavior of the vapor/plasma during and after ablation, and (d) effects of initial conditions in the vapor, in particular, the nature of the initial velocity distribution, on the characteristics of subsequent vapor expansion. Results from the modeling are compared with experimental observations where possible.

Liu, C.L.; Leboeuf, J.N.; Wood, R.F.; Geohegan, D.B.; Donato, J.M.; Chen, K.R.; Puretzky, A.A.

1994-09-01

333

High resolution selective multilayer laser processing by nanosecond laser ablation of metal nanoparticle films  

SciTech Connect

Ablation of gold nanoparticle films on polymer was explored using a nanosecond pulsed laser, with the goal to achieve feature size reduction and functionality not amenable with inkjet printing. The ablation threshold fluence for the unsintered nanoparticle deposit was at least ten times lower than the reported threshold for the bulk film. This could be explained by the combined effects of melting temperature depression, lower conductive heat transfer loss, strong absorption of the incident laser beam, and the relatively weak bonding between nanoparticles. The ablation physics were verified by the nanoparticle sintering characterization, ablation threshold measurement, time resolved ablation plume shadowgraphs, analysis of ablation ejecta, and the measurement and calculation of optical properties. High resolution and clean feature fabrication with small energy and selective multilayer processing are demonstrated.

Ko, Seung H.; Pan Heng; Hwang, David J.; Chung, Jaewon; Ryu, Sangil; Grigoropoulos, Costas P.; Poulikakos, Dimos [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich (Switzerland)

2007-11-01

334

Micro-ablation with high power pulsed copper vapor lasers  

NASA Astrophysics Data System (ADS)

Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser

Knowles, Martyn

2000-07-01

335

Effects of laser ablated silver nanoparticles on Lemna minor.  

PubMed

The present study investigates and models the effect of laser ablated silver nanoparticles (AgNPs) on the development of the aquatic macrophyte Lemna minor. Toxic effects of five different AgNP concentrations (8, 16, 32, 96 and 128 ?g L(-1)) on L. minor were recorded over seven days under simulated natural conditions. Biosorption of AgNPs by L. minor was modeled using four sorption isotherms, and the sorption behavior was found to agree most closely with the Langmuir-Freundlich model (R(2)=0.997). While toxic effects of AgNPs could be observed in all models and concentrations, the greatest increase in toxicity was in the 8-32 ?g L(-1) range. Dry weight- and frond number-based inhibition experiments suggest that growth inhibition does not necessarily scale with AgNP concentration, and that slight fluctuations in inhibition rates exist over certain concentration ranges. Very close fits (R(2)=0.999) were obtained for all removal models, suggesting that the fluctuations are not caused by experimental variation. In addition, L. minor was found to be a successful bioremediation agent for AgNPs, and displayed higher removal rates for increasing AgNP doses. FT-IR spectroscopy suggests that carbonyl groups are involved in AgNP remediation. PMID:24529395

Üçüncü, Esra; Özkan, Alper D; Kur?ungöz, Canan; Ülger, Zeynep E; Ölmez, Tolga T; Tekinay, Turgay; Ortaç, Bülend; Tunca, Evren

2014-08-01

336

Spin-offs from laser ablation in art conservation  

NASA Astrophysics Data System (ADS)

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 decontamination, dermatology, nuclear weapons effects simulation, and graffiti control. It was readily apparent that the customary diffusion of advanced technologies from science and industry into the art conservation field had been reversed. In this paper we trace the migration and adaptation of radiation divestment developments in art conservation to numerous applications in science, industry, and consumer products. Examples described include the robotized hybrid "Flashjet" aircraft paint stripping system, the "Novotronic" anthrax remediation installation in the Pentagon Building, the InTa automated graffiti removal system employing a carbon dioxide TEA laser, the Bellalite body hair removal product incorporating flashlamp technology, and the Foodco line of optical radiation products for the sterilization of food products. The Foodco products are also applied to the sterilization and/or pasteurization of beverages and beverage containers. A similar device has been adapted to seafood irradiation in order to increase shelf life, as well as for the ablative removal of skin and scales. The Goodyear Tire and Rubber Company, to etch logos and identification information into the sidewalls of pneumatic tires, also developed a flashlamp-based ablation technology. The founders of the CYMER Corporation applied UV irradiation technology to the manufacture of high-performance integrated circuits (viz., memory chips, etc.) In several instances former CASS students and Visiting Fellows consciously adapted the above-learned art conservation methodologies to still other purposes. Thus, these examples of technology transfer may be termed: "Art in the service of Science." Alternatively, it is evident that many associated innovations developed from independent activities, unconnected serendipity, or through the normal diffusion of information and knowledge across disciplines.

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

2013-05-01

337

Infrared Laser Ablation Sample Transfer for MALDI and Electrospray  

NASA Astrophysics Data System (ADS)

We have used an infrared laser to ablate materials under ambient conditions that were captured in solvent droplets. The droplets were either deposited on a MALDI target for off-line analysis by MALDI time-of-flight mass spectrometry or flow-injected into a nanoelectrospray source of an ion trap mass spectrometer. An infrared optical parametric oscillator (OPO) laser system at 2.94 ?m wavelength and approximately 1 mJ pulse energy was focused onto samples for ablation at atmospheric pressure. The ablated material was captured in a solvent droplet 1-2 mm in diameter that was suspended from a silica capillary a few millimeters above the sample target. Once the sample was transferred to the droplet by ablation, the droplet was deposited on a MALDI target. A saturated matrix solution was added to the deposited sample, or in some cases, the suspended capture droplet contained the matrix. Peptide and protein standards were used to assess the effects of the number of IR laser ablation shots, sample to droplet distance, capture droplet size, droplet solvent, and laser pulse energy. Droplet collected samples were also injected into a nanoelectrospray source of an ion trap mass spectrometer with a 500 nL injection loop. It is estimated that pmol quantities of material were transferred to the droplet with an efficiency of approximately 1%. The direct analysis of biological fluids for off-line MALDI and electrospray was demonstrated with blood, milk, and egg. The implications of this IR ablation sample transfer approach for ambient imaging are discussed.

Park, Sung-Gun; Murray, Kermit King

2011-08-01

338

Temperature monitoring by infrared radiation measurements during ArF excimer laser ablation with cornea  

NASA Astrophysics Data System (ADS)

We measured infrared thermal radiation from porcine cornea during various fluences ArF excimer laser ablations with 1 microsecond(s) rise time. To obtain absolute temperature by means of Stefan-Boltzman law of radiation, we carried out a collection efficiency and detective sensitivity by a pre-experiment using panel heater. We measured the time course of the thermal radiation intensity with various laser fluences. We studied the relation between the peak cornea temperature during the ablation and irradiation fluences. We found the ablation situations, i.e., sub-ablation threshold, normal thermal ablation, and over-heated ablation, may be judged by both of the measured temperature transient waveforms and peak temperature. The boundary fluences corresponding to normal thermal ablation were 90 and 160 mJ/cm2. Our fast remote temperature monitoring during cornea ablation might be useful to control ablation quality/quantity of the cornea ArF laser ablation, that is PRK.

Ishihara, Miya; Arai, Tsunenori; Sato, Shunichi; Nakano, Hironori; Obara, Minoru; Kikuchi, Makoto

1999-06-01

339

Laser induced modification and ablation of InAs nanowires  

SciTech Connect

InAs nanowires were irradiated locally under an ambient condition using a focused laser beam, which led to laser ablation and thinning of the nanowires. We show that the laser beam can induce a reduction of the local As concentration in an InAs nanowire; the change leads to a significant decrease of local melting temperature of InAs, which results in the thinning and eventually breaking of the nanowire. The results indicate that chemical and mechanical modifications of an InAs nanowire can be accomplished by using a confocal laser beam, which may prove to be a convenient approach in fabricating nanostructural materials and nanodevices.

He Jiayu; Chen Pingping; Lu Wei; Dai Ning [Shanghai Institute of Technical Physics, Academy Science of China, Shanghai (China); Zhu Daming [Department of Physics, University of Missouri - Kansas City, Kansas City, Missouri 64110 (United States)

2012-05-01

340

Diagnostics and Impulse Performance of Laser-Ablative Propulsion  

SciTech Connect

Pressure time variations and associated flows induced by pulsed laser ablation were experimentally studied using the Velocity Interferometer System for Any Reflector (VISAR) and framing Schlieren visualization. The combination of either aluminum or polyacetal target and TEA CO{sub 2} laser pulse were examined. The VISAR measurement resolved that the pressure modulated from the laser power variation in the impulse generation processes. Integrated impulse induced by repetative CO{sub 2} laser pulses was measured using a torsion-type impulse balance. The effect of the ambient pressure was significant. The measured impulse characteristics were closely associated with target surface morphology and fluid dynamics.

Sasoh, Akihiro; Mori, Koichi [Department of Aerospace Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Anju, Kohei; Suzuki, Koji; Shimono, Masaya; Sawada, Keisuke [Department of Aerospace Engineering, Tohoku University, 6-6-2 Aramaki-Aza-Aoba, Sendai 980-8579 (Japan)

2008-04-28

341

Production of nanoparticles from natural hydroxylapatite by laser ablation  

PubMed Central

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.

2011-01-01

342

The physics of UV laser cornea ablation  

Microsoft Academic Search

Experiments to determine the optimum parameters of an excimer irradiation of the cornea for clinical application are reported. The materials, procedures, and results are described. A theoretical model of cornea ablation that takes into consideration the thermal effects and mechanical stresses is suggested

Moishe S. Kitai; Valery L. Popkov; V. A. Semchischen; Alexei A. Kharizov

1991-01-01

343

Laser-ablation-assisted microparticle acceleration for drug delivery  

Microsoft Academic Search

Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected

V. Menezes; K. Takayama; T. Ohki; J. Gopalan

2005-01-01

344

Strongly Polarized Plasma Emission Produced by Laser Ablation of Aluminum  

Microsoft Academic Search

We have found that continuum emission produced in the laser ablation of a material may be strongly polarized, whereas as discrete atomic or ionic emission lines appear as minima in the plasma polarization spectrum [1]. This effect is indicative of strong directionality of electrons recombining in the plasma. By placing a polarizer before the detector, it is possible to suppress

Robert Gordon; Yaoming Liu; John Penczak; Youbo Zhao

2009-01-01

345

Cluster generation under pulsed laser ablation of zinc oxide  

NASA Astrophysics Data System (ADS)

Neutral and cationic Zn n O m clusters of various stoichiometry have been produced by nanosecond laser ablation of ZnO in vacuum and investigated by time-of-flight mass spectrometry. Particular attention was paid to the effect of laser wavelength (in the range from near-IR to UV) on cluster composition. Under 193-nm laser ablation, the charged clusters are essentially substoichiometric with ZnnO_{n-1}+ and ZnnO_{n-3}+ being the most abundant series. Both sub- and stoichiometric cationic clusters are generated in abundance at 532- and 1064-nm ablation whose composition depends on the cluster size. The reactivity of small stoichiometric ZnnOn+ clusters ( n<11) toward hydrogen is found to be high, while oxygen-deficient species are less reactive. The neutral plume particles are mainly stoichiometric with Zn4O4 tetramer being a magic cluster. It is suggested that the Zn4O4 loss is the dominant fragmentation channel of large zinc oxide clusters upon electron impact. Plume expansion conditions under ZnO ablation with visible and IR laser pulses are shown to be favorable for stoichiometric cluster formation.

Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G.; Ozerov, Igor; Marine, Wladimir

2010-12-01

346

Pulsed laser ablation of pepsin on an inorganic substrate  

NASA Astrophysics Data System (ADS)

Pressed pepsin pellets used as targets were ablated with the pulses of the Nd-YAG laser. The activity of the pepsin thin layer, deposited on a glass substrate, was successfully detected by analyzing the proteolytic degradation areas on the polyacrylamide gel (PA-gel) copolymerized with albumin from the hen egg white (ovalbumin), used as an enzymatic substrate.

Cicco, N.; Lopizzo, T.; Marotta, V.; Morone, A.; Verrastro, M.; Viggiano, V.

2009-03-01

347

Trace contaminant determination in fish scale by laser ablation technique.  

National Technical Information Service (NTIS)

Laser ablation on rings of fish scale has been used to analyze the historical accumulation of polychlorinated biphenyls (PCB) in striped bass in the Watts Bar Reservoir. Rings on a fish scale grow in a pattern that forms a record of the fish's chemical in...

I. Lee, C. C. Coutant, E. T. Arakawa

1993-01-01

348

Manipulation of Laser Ablation Plume by Magnetic Field Application  

Microsoft Academic Search

Time- and wavelength-resolved observation of a laser ablation plume from a strontium titanate target was performed under a dipole magnetic field applied from the substrate side. In contrast to the conventional method, the present method gave rise to increasing ionization of the growth species in the plume in the vicinity of the substrate. Using this method, NiO films could be

Minoru Tachiki; Takeshi Kobayashi

1999-01-01

349

Preheat Studies on Laser Ablatively-Accelerated Foils.  

National Technical Information Service (NTIS)

The achievement of laser fusion requires the inward acceleration of pellet shells to very high velocity without excessive preheat of the pellet fuel. In a study of ablatively accelerated thin planar Al foils, we have determined the complete time history o...

E. A. McLean S. H. Gold J. A. Stamper R. R. Whitlock H. R. Griem

1980-01-01

350

Perfluorocarbon compounds: transmitting liquids for infrared laser tissue ablation  

NASA Astrophysics Data System (ADS)

One concern during IR-laser ablation of tissue under water is the mechanical injury that may be induced in tissue due to rapid bubble expansion and collapse or due to strong laser-induced pressure waves. The objective of this study was to evaluate the feasibility of using a liquid which is transparent to the IR-region of the spectrum in order to minimize these undesired mechanical side-effects. As transmitting medium perfluorocarbon liquid was used. Free- running Er:YAG and Ho:YAG laser pulses were delivered into the liquid via a 400 micrometers fiber. Bubble formation during the ablation process was recorded with fast flash photography while pressure transients were measured with a needle hydrophone. The effect of the surrounding material (air, water, perfluorooctane) on the tissue response of chicken breast was evaluated in vitro using histology. It was observed that a large bubble (up to 6 mm in diameter) was formed under perfluorooctane driven by the ablation products. This bubble, however, does not generate a pressure wave when collapsing. Although perfluorooctane only shows a weak absorption for infrared radiation, laser-induced thermal lensing in the liquid strongly decreases the radiant exposure and therefore the ablation efficiency.

Frenz, Martin; Pratisto, Hans S.; Toth, Cindy A.; Jansen, E. Duco; Altermatt, Hans J.; Welch, Ashley J.; Weber, Heinz P.

1996-05-01

351

Elemental fractionation in laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

The major challenge to the use of laser ablation sample introduction, combined with inductively coupled plasma mass spectrometry, is the problem of calibration. In the geological analysis of minerals, calibration is complicated by the extraordinarily wide variety of sample matrices which may be encountered. While there is a lack of mineral standards with well characterized concentrations near 1 g\\/g, the NIST

H. P. Longerich; D. Günther; S. E. Jackson

1996-01-01

352

Study of Laser Ablation Efficiency for an Acrylic-Based Photopolymerizing Composition  

NASA Astrophysics Data System (ADS)

Results are presented from study of the effi ciency (ablated mass per unit energy, mechanical recoil momentum per unit energy) of laser ablation for a light-curable polymer. A substantial difference is seen between the thresholds and indicated criteria for laser ablation effi ciency in the liquid and cured phases. The highest energy effi ciency for laser ablation (~22.6 %) is achieved when the initially liquid polymer is exposed to radiation with the wavelength optimal for photopolymerization (365 ± 15 nm).

Loktionov, E. Yu.

2014-05-01

353

A novel approach to the synthesis of photoluminescent germanium nanoparticles by reactive laser ablation  

NASA Astrophysics Data System (ADS)

We propose a novel approach to the synthesis of photoluminescent Ge nanoparticles using reactive laser ablation. The deposition of germanium under low oxygen pressure (2-100 mTorr) yields Ge nanoparticles embedded in a Ge oxide matrix. Ge nanostructures were characterized by transmission electron microscopy, x-ray photoelectron spectroscopy and photoluminescence (PL) spectroscopy. The oxygen pressure determines the degree of oxidation of GeOx films (0<=x<=2). A strong PL signal depending on oxygen pressure was observed. The PL maximum is detected for 10 mTorr of oxygen corresponding to a nanoparticle size of 1.8 ± 0.5 nm.

Riabinina, Daria; Durand, Christophe; Chaker, Mohamed; Rowell, Nelson; Rosei, Federico

2006-05-01

354

Laser-plasma interactions in 532 nm ablation of Si  

Microsoft Academic Search

Single-crystal Si was ablated by pulsed 532 nm laser radiation, and the volume of removed material and the time-resolved current of ejected ions were measured. These data were used to determine the ion fraction of ejected material. The ion fractions provide direct evidence that the break point is due to the laser-plasma interaction. This is confirmed by the speed distributions

Gyoowan Han; P. Terrence Murray

2000-01-01

355

Infrared Laser Ablation Sample Transfer for MALDI and Electrospray  

Microsoft Academic Search

We have used an infrared laser to ablate materials under ambient conditions that were captured in solvent droplets. The droplets\\u000a were either deposited on a MALDI target for off-line analysis by MALDI time-of-flight mass spectrometry or flow-injected into\\u000a a nanoelectrospray source of an ion trap mass spectrometer. An infrared optical parametric oscillator (OPO) laser system at\\u000a 2.94 ?m wavelength and approximately

Sung-Gun Park; Kermit King Murray

2011-01-01

356

Laser ablation of organic coatings as a basis for micropropulsion  

Microsoft Academic Search

The micro laser plasma thruster (?LPT) is a new micropropulsion device which is competitive with the pulsed plasma thruster (?PPT) for steering or propelling 10–100 kg ‘microsatellites’. It is driven by a cluster of fiber-coupled infrared diode lasers, focused onto a two-layer ablating tape. Electrical to optical conversion efficiency is 50%. The tape consists of a transparent supporting layer through

C. Phipps; J. Luke; T. Lippert

2004-01-01

357

Plasma diagnostics during laser ablation in a cavity  

Microsoft Academic Search

The formation of a laser-induced plasma in a cavity and the effects of a cavity on the ablation process were investigated. Cavities were fabricated in fused silica with equal depths and variable diameters to provide aspect ratios (depth\\/diameter) of 1, 3 and 6. The temperature and electron number density of the pulsed laser-induced plasma in the cavities were determined from

Xianzhong Zeng; Samuel S. Mao; Chunyi Liu; Xianglei Mao; Ralph Greif; Richard E. Russo

2003-01-01

358

Acoustic transient generation in pulsed holmium laser ablation under water  

Microsoft Academic Search

In this study the role of acoustical transients during pulsed holmium laser ablation is addressed. For this the collapse of cavitation bubbles generated by 2.12 micrometers Cr:Tm:Ho:YAG laser pulses delivered via a fiber in water is investigated. Multiple consecutive collapses of a single bubble generating acoustic transients are documented. Pulse durations are varied from 130 - 230 microsecond(s) and pulse

Thomas Asshauer; Klaus Rink; Guy P. Delacretaz; Rene-Paul Salathe; Bruno E. Gerber; Martin Frenz; Hans Pratisto; Michael Ith; Valerio Romano; Heinz P. Weber

1994-01-01

359

Laser ablation in liquids as a new technique of sampling in elemental analysis of solid materials  

NASA Astrophysics Data System (ADS)

Laser ablation in liquid media is considered as a new sample preparation technique in the elemental composition analysis of materials using optical emission spectroscopy of inductively coupled plasma (ICP-OES). Solid samples are transformed into uniform colloidal solutions of nanosized analyte particles using laser radiation focused onto the sample surface. High homogeneity of the resulting solution allows performing the ICP-OES quantitative analysis especially for the samples, which are poorly soluble in acids. The technique is compatible with the conventional solution-based standards.

Muravitskaya, E. V.; Rosantsev, V. A.; Belkov, M. V.; Ershov-Pavlov, E. A.; Klyachkovskaya, E. V.

2009-02-01

360

Laser Spectroscopy of Transuranium Elements  

Microsoft Academic Search

The present paper aims to discuss the prospects for nuclear structure investigation of the transuranium elements by laser spectroscopy. The authors lay stress on two peculiarities of the nuclear structure in this region: the deformed shell closure at neutron number N = 152 and the appearance of superdeformed isomeric states. A laser spectroscopic experimental method is proposed for studying these

Yu. P. Gangrsky; D. V. Karaivanov; K. P. Marinova; B. N. Markov; Yu. E. Penionshkevich; S. G. Zemlyanoi

2005-01-01

361

Comparative study on laser tissue ablation between PV and HPS lasers  

NASA Astrophysics Data System (ADS)

Laser therapy for obstructive benign prostatic hyperplasia (BPH) has gained broad adoption due to effective tissue removal, immediate hemostasis, and minor complications. The aim of this study is to quantitatively compare ablation characteristics of PV (Photoselective Vaporization) and the newly introduced HPS (High Performance System) 532 nm lasers. Bovine prostatic tissues were ablated in vitro, using a custom-made scanning system. Laser-induced volume produced by two lasers was quantified as a function of applied power, fiber working distance (WD), and treatment speed. Given the same power of 80 W and speed of 4 mm/s, HPS created up to 50 % higher tissue ablation volume than PV did. PV induced a rapid decrease of ablation volume when WD increased from 0.5 mm to 3 mm while HPS yielded almost constant tissue removal up to 3 mm for both 80 W and 120 W. As the treatment speed increased, both lasers reached saturation in tissue ablation volume. Lastly, both PV and HPS lasers exhibited approximately 1 mm thick heat affected zone (HAZ) in this study although HPS created twice deeper ablation channels with a depth of up to 4 mm. Due to a smaller beam size and a higher output power, HPS maximized tissue ablation rate with minimal thermal effects to the adjacent tissue. Furthermore, more collimated beam characteristics provides more spatial flexibility and may even help to decrease the rate of fiber degradation associated with thermal damage from debris reattachment to the tip.

Kang, Hyun Wook; Jebens, David; Mitchell, Gerald; Koullick, Ed

2008-03-01

362

Femtosecond laser ablation of aluminum in vacuum and air at high laser intensity  

NASA Astrophysics Data System (ADS)

In this study, the ablation of aluminum by a near-infrared femtosecond laser pulse (800 nm, 100 fs) at different intensity is investigated by a two-dimensional hydrodynamic model. The ablation rates are compared between the cases in vacuum and in air over a wide range of laser power density. It has been reported before that at low (<1013 W/cm2) and moderate laser intensity (1013-1014 W/cm2), two different ablation regimes exist, and the ablation depth per pulse is dependent on the optical penetration depth and electron heat penetration depth, respectively. By considering both collisional and collisionless absorptions, the model in this study predicts the third ablation regime with a much higher ablation rate increase with respect to laser intensity in the high intensity range (>1014 W/cm2) in vacuum, which shows good agreement with the experimental data. This phenomenon is attributed to the change of dominant absorption mechanism from collisional to collisionless absorption. For the case in air, the ablation depth increases slowly with the laser intensity in the high intensity regime, and is much smaller than that in vacuum. It is revealed that this is due to the strong early plasma-laser interaction in air.

Zhao, Xin; Shin, Yung C.

2013-10-01

363

Investigation of mechanisms of ultrashort laser pulse ablation through experiments and simulations  

Microsoft Academic Search

Ultrashort laser pulse (USLP) ablation has been investigated over a decade long. The machining quality, however, as well as ablation efficiency and understanding of the ablation mechanism, still need improvement. ^ First, a combined molecular dynamics (MD) and Monte Carlo (MC) method is used to investigate the particle transport and energy transport phenomena in USLP ablation. It is found that

Wenqian Hu

2011-01-01

364

Ablative and transport fractionation of trace elements during laser sampling of glass and copper  

Microsoft Academic Search

The fractionation of trace elements due to ablation and transport processes was quantified during Q-switched infrared laser sampling of glass and copper reference materials. Filter-trapping of the ablated product at different points in the sample introduction system showed ablation and transport sometimes caused opposing fractionation effects, leading to a confounded measure of overall (ablative + transport) fractionation. An unexpected result

P. M. Outridge; W. Doherty; D. C. Gregoire

1997-01-01

365

Analysis of the influence of substrate temperature on hydroxyapatite deposited by laser ablation method using ArF laser  

NASA Astrophysics Data System (ADS)

Hydroxyapatite layers (Ca 10(PO 4)6(OH) II) were deposited by means of laser ablation method using an ArF excimer laser (193 nm). The influence of substrate temperature on the structure of deposited layers was studied. The layers were deposited on Ti6Al4V titanium alloy which temperature varied from 250 °C to 700 °C. The characteristics of the hydroxyapatite coatings were determined by means of Fourier Transform Infrared spectroscopy (FTIR). The obtained spectra reveal that the presence and abundance of the PO 4 absorption bands depend on the substrate temperature. The topography of the deposited layers were analyzed with the use of an Atomic Force Microscope.

Mróz, Waldemar; Jedy?ski, Marcin; Szyma?ski, Zygmunt; Prokopiuk, Artur; Burdy?ska, Sylwia

2007-02-01

366

Near-infrared laser ablation of poly tetrafluoroethylene (Teflon) sensitized by nanoenergetic materials  

SciTech Connect

Laser ablation of Teflon doped with size-selected (30-250 nm) Al nanoparticles is studied. Unlike pure Teflon, which requires a vacuum-ultraviolet or femtosecond excimer laser for ablation, this sensitized Teflon can be ablated with a near-infrared laser. Using 100 ps duration pulses, near-infrared ablation thresholds are lower by about a factor of 10 from excimer ablation of pure Teflon. A mechanism is discussed that involves Teflon decomposition by spherical shock fronts originating at each irradiated nanoparticle. Studies of the distance dependence of this process as a function of particle diameter and oxide layer thickness suggest ways of optimizing the ablation process.

Yang Yanqiang; Wang Shufeng; Sun Zhaoyong; Dlott, Dana D. [School of Chemical Sciences, Box 01-6 CLSL, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States)

2004-08-30

367

Stereotactic laser ablation of epileptogenic periventricular nodular heterotopia.  

PubMed

Periventricular nodular heterotopia (PVNH) is a neuronal migrational disorder often associated with pharmacoresistant epilepsy (PRE). Resective surgery for PVNH is limited by its deep location, and the overlying eloquent cortex or white matter. Stereotactic MR guided laser interstitial thermal therapy (MRgLITT) has recently become available for controlled focal ablation, enabling us to target these lesions. We here demonstrate the novel application and techniques for the use of MRgLITT in the management of PVNH epilepsy. Comprehensive presurgical evaluation, including intracranial EEG monitoring in two patients revealed the PVNH to be crucially involved in their PRE. We used MRgLITT to maximally ablate the PVNH in both cases. In the first case, seizure medication adjustment coupled with PVNH ablation, and in the second, PVNH ablation in addition to temporal lobectomy rendered the patient seizure free. A transient visual deficit occurred following ablation in the second patient. MRgLITT is a promising minimally invasive technique for ablation of epileptogenic PVNH, a disease not generally viewed as surgically treatable epilepsy. We also show here the feasibility of applying this technique through multiple trajectories and to create lesions of complex shapes. The broad applicability and long term efficacy of MRgLITT need to be elaborated further. PMID:24518890

Esquenazi, Yoshua; Kalamangalam, Giridhar P; Slater, Jeremy D; Knowlton, Robert C; Friedman, Elliott; Morris, Saint-Aaron; Shetty, Anil; Gowda, Ashok; Tandon, Nitin

2014-03-01

368

Picosecond laser ablation of nickel-based superalloy C263  

NASA Astrophysics Data System (ADS)

Picosecond laser (10.4 ps, 1064 nm) ablation of the nickel-based superalloy C263 is investigated at different pulse repetition rates (5, 10, 20, and 50 kHz). The two ablation regimes corresponding to ablation dominated by the optical penetration depth at low fluences and of the electron thermal diffusion length at high fluences are clearly identified from the change of the surface morphology of single pulse ablated craters (dimples) with fluence. The two corresponding thresholds were measured as F {th(D1)/1}=0.68±0.02 J/cm2 and F {th(D2)/1}=2.64±0.27 J/cm2 from data of the crater diameters D 1,2 versus peak fluence. The surface morphology of macroscopic areas processed with a scanning laser beam at different fluences is characterised by ripples at low fluences. As the fluence increases, randomly distributed areas among the ripples are formed which appear featureless due to melting and joining of the ripples while at high fluences the whole irradiated surface becomes grainy due to melting, splashing of the melt and subsequent resolidification. The throughput of ablation becomes maximal when machining at high pulse repetition rates and with a relatively low fluence, while at the same time the surface roughness is kept low.

Semaltianos, N. G.; Perrie, W.; Cheng, J.; French, P.; Sharp, M.; Dearden, G.; Watkins, K. G.

2010-02-01

369

Porous nanoparticles of Al and Ti generated by laser ablation in liquids  

NASA Astrophysics Data System (ADS)

Experimental results are presented on the generation of porous nanoparticles of either Al or Ti by laser ablation of solid targets in ethanol, water, and n-propanol saturated with hydrogen. The nanoparticles are characterized by high resolution transmission electron microscopy (HR TEM) and optical absorption spectroscopy. Saturation of the liquid with gaseous hydrogen leads to the formation of internal cavities in nanoparticles. In the case of short laser pulses (180 fs, Ti:sapphire laser at 800 nm wavelength), the nanoparticles are mostly spherical with the size of 30-50 nm at concentration about 1015 cm-3. The cavity occupies from 20 to 50% of the particle volume. Longer laser pulses (70 ns, Nd:YAG laser at 1064 nm wavelength) generate facetted nanoparticles with facetted cavities inside. The mechanism of formation of cavities is discussed on the basis of temperature-dependent solubility of hydrogen in metals.

Kuzmin, P. G.; Shafeev, G. A.; Viau, G.; Warot-Fonrose, B.; Barberoglou, M.; Stratakis, E.; Fotakis, C.

2012-09-01

370

Comparison of ablation stake measurements and Airborne Laser Scanning results  

NASA Astrophysics Data System (ADS)

Ablation measurements using ablation stakes are a well-established method in glaciology, which sees a lot of use. However, ablation stakes cannot always be installed and read at a sufficient number of points on a glacier or on multiple glaciers, due to limited personnel and financial capacities or because of inaccessible areas due to dangerous zones (crevasses, rock falls, avalanches) or remote terrain. Furthermore, ablation stakes only enable measurements of surface melt, whereas basal or internal melt processes as well as surface change related to glacier dynamics cannot be measured. Multi temporal Airborne laser scanning (ALS) can provide high resolution and very accurate topographic information for the whole glacier area, which allows the calculation of the difference in surface height and therefore - if the density profile is known or can be estimated - the determination of the local mass balance, including processes like basal melt at least to a certain degree. To gain a better understanding of the differences between ablation stake readings and differential ALS data at the stake locations, the results of both methods have been compared in detail. At Langenferner, a glacier in the Italian Eastern Alps, where mass balance measurements have been carried out since 2004, three ALS campaigns have been conducted at the end of the hydrological year in 2005, 2010 and 2013. There are about 30 ablation stakes installed at the glacier, which have been read during or very close to the time of the flight campaigns. The ablation measurements are then compared to the surface differences calculated from ALS data at the locations of the ablation stakes. To take the movement of the stakes due to glacier dyanmics into account, the position of the stakes has been measured with a differential GPS.

Rieg, Lorenzo; Galos, Stephan; Klug, Christoph; Sailer, Rudolf

2014-05-01

371

INTERACTION OF LASER RADIATION WITH MATTER: Production of copper and brass nanoparticles upon laser ablation in liquids  

NASA Astrophysics Data System (ADS)

The production of nanoparticles upon ablation of copper and brass by pulsed radiation from Nd:YAG and copper lasers in water, ethanol, and acetone is studied. The nanoparticles were investigated by the methods of X-ray diffractometry, optical spectroscopy, and transmission electron microscopy. The produced copper and brass nanoparticles were shown to exhibit a plasmon resonance lying in the visible spectral range near 580 and 510 nm. The brass nanoparticles produced by ablation in ethanol have a shell approximately 10-nm thick for an average dimension of 20-30 nm. A chemical modification of ethanol was observed, which manifested itself in the appearance of intense UV absorption bands. Upon laser irradiation of brass nanoparticles in a liquid their absorption spectrum gradually transformed into the spectrum of copper nanoparticles.

Kazakevich, Pavel V.; Voronov, Valerii V.; Simakin, Aleksandr V.; Shafeev, Georgii A.

2004-10-01

372

Characterization of Ag and Au nanoparticles created by nanosecond pulsed laser ablation in double distilled water  

NASA Astrophysics Data System (ADS)

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) ( ? = 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 2 to tens of J/cm 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.

Nikolov, A. S.; Nedyalkov, N. N.; Nikov, R. G.; Atanasov, P. A.; Alexandrov, M. T.

2011-04-01

373

Nanosecond polarization-resolved laser-induced breakdown spectroscopy.  

PubMed

It is shown that the continuum emission produced in the ablation of an Al target with nanosecond laser pulses is much more strongly polarized than the discrete line emission. This effect may be utilized to improve the resolution of the laser-induced breakdown spectroscopy spectrum by using a polarizer to filter out the continuum background. The effects of laser fluence and focal position are also reported. It is further shown that the lifetime of the emission closely tracks the intensity spectrum. PMID:20081938

Liu, Yaoming; Penczak, John S; Gordon, Robert J

2010-01-15

374

Ultraviolet laser ablation of polycarbonate and glass in air  

SciTech Connect

The fundamental physical processes that follow ultraviolet laser ablation of polycarbonate and borosilicate glass in air have been investigated using photodeflection as a function of the distance from the surface to probe laser. Four features were observed in the data sets for each material. Two of these features correlate well with gas dynamical predictions for the expansion of the shock wave and gas plume. The third feature is consistent with the propagation of the popping sound of the laser ablation event. The final feature, which occurs at very early times and does not shift significantly in time as the surface to probe distance is increased from 0 to greater than 6 mm, has been tentatively ascribed to the ejection of fast electrons. The final significant observation is complete blocking of the probe laser, only observed during borosilicate ablation, which is attributed to scattering of the probe laser light by macroscopic SiO{sub x} particles that grow in the final stages of plume expansion and cooling.

Bormotova, T. A.; Blumenthal, R. [Auburn University, Alabama 36849 (United States)

2009-02-01

375

Ripple formation in the chromium thin film during laser ablation  

NASA Astrophysics Data System (ADS)

The beam of a nanosecond pulse laser tightly focused to a line was applied for the back-side ablation of the chromium thin film on a glass substrate. The stripe ablated with a single laser pulse had sharp edges on both sides and ridges of the melted metal around it. The partially overlapping pulses formed a wide cleaned area with a complicated structure made of the metal remaining from the ridges. Regular structures, ripples, were developed when laser fluence was slightly above the single-pulse removal threshold and the shift between pulses was less than half width of the line ablated with a single laser pulse. The ripples were located periodically (˜4 ?m) and were orientated perpendicularly to the long axis of the beam spot. Their orientation did not depend on the laser beam polarization. Different models of the ripple formation in the thin metal film were considered, and instability of the moving vapor-liquid-solid contact line during evaporation of thin liquid films appears to be the most probable process responsible for the observed phenomena. Formation of regular gratings with the unlimited line length was experimentally implemented by using the above-mentioned technique.

Regelskis, K?stutis; Ra?iukaitis, Gediminas; Gedvilas, Mindaugas

2007-05-01

376

A Proton Source via Laser Ablation of Hydrogenated Targets  

NASA Astrophysics Data System (ADS)

In this work we present results on the extraction of proton beams from a plasma generated by pulsed laser ablation of solid hydrogenated targets. The laser used was an excimer KrF operating at low irradiances (108–109 W/cm2) and nanosecond pulse duration. The ablated targets were disks obtained by compression of TiH2 powder. The ion emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. In order to improve the ion yield, an electrostatic extraction system was applied. Studies on the produced plasma for different laser irradiances and accelerating voltages have been performed. The results obtained show that this setup is suitable for a high yield proton source.

Delle Side, D.; Nassisi, V.; Velardi, L.

2014-04-01

377

Ultrafast laser ablation of metal films on flexible substrates  

NASA Astrophysics Data System (ADS)

For the development of organic electronics on flexible substrates, we study the potentialities of direct laser patterning of conductive films deposited on plastic foils. The materials under study are silver and platinum films (100-nm thick) deposited on Kapton® substrates. The experiments are done using a laser source operating at 1030 nm, 500 fs, under different irradiation conditions: single and multiple pulses at various frequencies. The laser ablation thresholds are measured and the ablation morphologies are analyzed with scanning electron microscopy. The results of these investigations show that photomechanical effects lead to delamination of the film and that depending of the irradiation conditions, incubation or heat accumulation effects can occur. The experimental results are compared to simulations based on the two-temperature model. Particularly we study the heat accumulation effects that can occur in the case of multiple pulses and that are detrimental for plastic substrates.

Gallais, L.; Bergeret, E.; Wang, B.; Guerin, M.; Bènevent, E.

2014-04-01

378

A unified model in the pulsed laser ablation process  

NASA Astrophysics Data System (ADS)

In this unified model, we introduce the electron-phonon coupling time ( t ie ) and laser pulse width ( t p ). 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.

Hu, De-Zhi

2008-07-01

379

Dual-beam ablation of fused silica by multiwavelength excitation process using KrF excimer and F 2 lasers  

Microsoft Academic Search

A new technique of dual-beam laser ablation of fused silica by multiwavelength excitation process using a 248-nm KrF excimer laser (ablation beam) coupled with a 157-nm F2 laser (excitation beam) in dry nitrogen atmosphere is reported. The dual-beam laser ablation greatly reduced debris deposition and, thus, significantly improved the ablation quality compared with single-beam ablation of the KrF laser. High-quality

J. Zhang; K. Sugioka; T. Takahashi; K. Toyoda; K. Midorikawa

2000-01-01

380

Femtosecond laser ablation on dental hard tissues—Analysis of ablated profile near an interface using local effective intensity  

NASA Astrophysics Data System (ADS)

This study evaluated the process of ablation produced by a Ti:Sapphire femtosecond laser under different average powers taking place at the enamel/dentin interface. Based on the geometry of ablated microcavities the effective intensity for ablation was obtained. This study shows the validity for the local effective intensity analysis and allows a quantification of the variation in the ablation geometry taking place at the interface of two naturally different materials. It shows that the variation of the diameter of the ablated region as a function of the cavity depth comes essentially from a mechanism of effective intensity attenuation, as a result of a series of complex effects. Additionally, our data are sufficient to predict that a discontinuity on the ablation profile will occur on the interface between two biological media: enamel-dentin, showing a suddenly jump on the ablated cavity dimensions.

Dutra-Correa, M.; Nicolodelli, G.; Rodrigues, J. R.; Kurachi, C.; Bagnato, V. S.

2011-05-01

381

Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes  

NASA Technical Reports Server (NTRS)

Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT.

Greendyke, R. B.; Creel, J. R.; Payne, B. T.; Scott, C. D.

2005-01-01

382

Elemental fractionation of glass using laser ablation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Three laser wavelengths (1064, 532, and 266 nm) were employed for laser ablation at varied laser pulse energies to study the effect of irradiance and wavelength upon analytical results for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Two important results were observed and are reported here: (1) the intensity of the MS signal came to a local minimum when

Deborah Figg; Michael S. Kahr

1997-01-01

383

Microsecond laser ablation of thrombus and gelatin under clear liquids: Contact versus noncontact  

Microsoft Academic Search

Laser thrombolysis is a procedure for removing blood clots in occluded arteries using pulsed laser energy. The laser light is delivered through an optical fiber to the thrombus. The ablation process is profoundly affected by whether the optical fiber tip is inside a catheter or is in contact with the thrombus. This study measured ablation efficiency of 1-?s laser pulses

HanQun Shangguan; Lee W. Casperson; Scott A. Prahl

1996-01-01

384

Focusing of a tabletopsoft-x-ray laser beam and laser ablation  

Microsoft Academic Search

We focused the beam of a high-repetition-rate capillary-discharge tabletop laser operating at a wavelength of 46.9 nm, using a spherical SiSc multilayer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray-tracing computations to characterize the focused beam. The radiation intensity within the 2-mm-diameter central region of

B. R. Benware; A. Ozols; J. J. Rocca; I. A. Artioukov; V. V. Kondratenko; A. V. Vinogradov

1999-01-01

385

Laser trabecular ablation of human eyes with the erbium:YAG laser: a histopathologic study  

Microsoft Academic Search

We postulated that ablation of trabecular meshwork can be accomplished without damage to Schlemm's canal and adjacent tissue. We performed Erbium:YAG laser trabecular ablation on human autopsy eyes and confirmed the results by histopathologic examination. We used an Erbium:YAG laser (2.94 micrometers ) equipped with a sapphire probe and a quartz tip (350 micrometers diameter). Energy levels of 5, 10,

Theresa R. Kramer; Robert J. Noecker; Robert W. Snyder; Lansing G. Ellsworth; J. Michael Yarborough

1994-01-01

386

Focusing of a tabletop soft-x-ray laser beam and laser ablation  

Microsoft Academic Search

We focused the beam of a high-repetition-rate capillary-discharge tabletop laser operating at a wavelength of 46.9 nm, using a spherical Si\\/Sc multilayer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray-tracing computations to characterize the focused beam. The radiation intensity within the 2-μm -diameter central region

B. R. Benware; A. Ozols; J. J. Rocca; I. A. Artioukov; V. V. Kondratenko; A. V. Vinogradov

1999-01-01

387

Synthesis efficiency of heavy carbon clusters from ETFE ablated by different numbers of laser pulse in vacuum  

Microsoft Academic Search

We have carried out mass spectral analysis of positive ions produced by laser ablation of a copolymer of ethylene and tetrafluoroethylene (ETFE: [?CH2?CH2?CF2?CF2?]n) in vacuum using time-of-flight mass spectrometry (TOF-MS). The surfaces of the ETFE targets irradiated by different numbers of laser pulse were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Heavy carbon cluster ions Cn+

K. Shibagaki; N. Takada; K. Sasaki; K. Kadota

2002-01-01

388

Influence of the plasma parameters on the properties of aluminum oxide thin films deposited by laser ablation  

Microsoft Academic Search

The plasma produced by the ablation of a high purity Al2O3 target, using the fundamental line (1064 nm) of a Nd:YAG laser, was characterized. The laser fluence was varied in order\\u000a to study its effect on the characteristics of the produced plasma as well as on the properties of the material deposited.\\u000a Optical emission spectroscopy (OES) was used to determine

L. Escobar-Alarcón; A. Arrieta; E. Camps; S. Romero; M. Fernandez; E. Haro-Poniatowski

2008-01-01

389

Protein structural failure in mid-IR laser ablation of cornea  

NASA Astrophysics Data System (ADS)

Researchers have previously observed that tissue ablation with a free electron laser tuned to wavelengths between 6-7 ?m is accompanied by remarkably little collateral damage. Attempts to explain these observations have invoked a wavelength-dependent loss of protein structural integrity; however, the molecular nature of this structural failure has been heretofore ill-defined. In this report, we evaluate several candidates for the relevant transition by analyzing the non-volatile debris ejected during ablation. Porcine corneas were ablated with a free electron laser tuned to either 2.77 or 6.45 ?m - wavelengths that are equally well absorbed by hydrated corneas, but that respectively target water or protein as the primary chromophore. The ejected debris was characterized via gel electrophoresis, as well as FTIR, micro-Raman and 13C-NMR spectroscopy. We find that high-fluence (240 J/cm2) ablation at 6.45 ?m, but not at 2.77 ?m, leads to protein fragmentation. This fragmentation is accompanied by the accumulation of nitrile and alkyne species. Although these initial experiments did not detect significant protein unfolding, the loss of collagen triple-helix structure was evident using UV and vibrational circular dichroism. The candidate transition most consistent with all these observations is scission of the collagen protein backbone at N-alkylamide bonds. Identifying this transition is a key step towards understanding the observed wavelength-dependence of collateral damage.

Hutson, M. Shane; Xiao, Yaowu; Guo, Mingsheng

2006-05-01

390

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

PubMed

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. PMID:23571876

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

2013-04-01

391

Modeling of dynamical processes in laser ablation  

SciTech Connect

Various physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed-laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume, plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms, hydrodynamic and collisional descriptions of plume transport, and molecular dynamics models of the interaction of plume particles with the deposition substrate.

Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

1995-12-31

392

Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation.  

PubMed

Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures. PMID:24292197

Malskat, W S J; Stokbroekx, M A L; van der Geld, C W M; Nijsten, T E C; van den Bos, R R

2014-03-01

393

Damage mechanism and morphology characteristics of chromium film in femtosecond laser rear-side ablation  

Microsoft Academic Search

In this paper, damage mechanism and morphology characteristics of chromium film in femtosecond laser rear-side ablation are investigated. The film removing process includes two key sub-processes: the laser ablation dynamic process and subsequent breaking and ejecting dynamic process. Film morphology in rear-side ablation is determined by the interrelation between the laser energy and the film strength. When lower laser energy

Wenjun Wang; Gedong Jiang; Xuesong Mei; Kedian Wang; Jinyou Shao; Chengjuan Yang

2010-01-01

394

Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers.  

National Technical Information Service (NTIS)

Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ...

L. B. Da Silva B. C. Stuart P. M. Celliers M. D. Feit M. E. Glinsky

1996-01-01

395

Excimer laser surface ablation: a review of recent literature.  

PubMed

The aim was to review the recently published literature on excimer laser surface ablation procedures, including photorefractive keratectomy (PRK), laser sub-epithelial keratomileusis (LASEK), microkeratome-assisted PRK (epi-LASIK) and trans-epithelial (laser-assisted) PRK, to help elucidate where and how surface ablation may best fit into current refractive surgical practice. The emphasis was on publications within the last three years and included systemic reviews, meta-analyses and randomised controlled trials. Where such evidence did not exist, selective large series cohort studies, case-controlled studies and case series with follow-up preferably greater than six months were examined and included. Refractive and visual outcomes are excellent and comparable to those after LASIK even in complex cases after previous corneal surgery. Indeed, surface ablation combined with corneal collagen cross-linking may be used in selected eyes with biomechanical instability, where LASIK is contraindicated. In addition, there is evidence to suggest that there may be less induction of higher order aberrations with surface techniques. Long-term stability and safety appear to be extremely satisfactory. The literature supports the use of modern excimer laser surface treatments, with outcomes comparable to those after LASIK and evidence of less induction of higher-order aberrations. Follow-up studies at 10 to 20 years indicate excellent stability and safety. PMID:23656608

O'Brart, David P S

2014-01-01

396

Role of Optical Coherence Tomography on Corneal Surface Laser Ablation  

PubMed Central

This paper focuses on reviewing the roles of optical coherence tomography (OCT) on corneal surface laser ablation procedures. OCT is an optical imaging modality that uses low-coherence interferometry to provide noninvasive cross-sectional imaging of tissue microstructure in vivo. There are two types of OCTs, each with transverse and axial spatial resolutions of a few micrometers: the time-domain and the fourier-domain OCTs. Both have been increasingly used by refractive surgeons and have specific advantages. Which of the current imaging instruments is a better choice depends on the specific application. In laser in situ keratomileusis (LASIK) and in excimer laser phototherapeutic keratectomy (PTK), OCT can be used to assess corneal characteristics and guide treatment decisions. OCT accurately measures central corneal thickness, evaluates the regularity of LASIK flaps, and quantifies flap and residual stromal bed thickness. When evaluating the ablation depth accuracy by subtracting preoperative from postoperative measurements, OCT pachymetry correlates well with laser ablation settings. In addition, OCT can be used to provide precise information on the morphology and depth of corneal pathologic abnormalities, such as corneal degenerations, dystrophies, and opacities, correlating with histopathologic findings.

Ventura, Bruna V.; Moraes, Haroldo V.; Kara-Junior, Newton; Santhiago, Marcony R.

2012-01-01

397

Real time assessment of RF cardiac tissue ablation with optical spectroscopy  

SciTech Connect

An optical spectroscopy approach is demonstrated allowing for critical parameters during RF ablation of cardiac tissue to be evaluated in real time. The method is based on incorporating in a typical ablation catheter transmitting and receiving fibers that terminate at the tip of the catheter. By analyzing the spectral characteristics of the NIR diffusely reflected light, information is obtained on such parameters as, catheter-tissue proximity, lesion formation, depth of penetration of the lesion, formation of char during the ablation, formation of coagulum around the ablation site, differentiation of ablated from healthy tissue, and recognition of micro-bubble formation in the tissue.

Demos, S G; Sharareh, S

2008-03-20

398

In-situ and ex-situ investigations of pulsed laser ablation of Y target  

Microsoft Academic Search

High purity yttrium was ablated by using frequency quadrupled ultra-violet pulses of a Nd:YAG laser (?=266nm, ?FWHM=7ns) with power density of about 1GW\\/cm2. Laser ablation process was studied using in-situ mass spectrometry of the ablated species in combination with ex-situ analyses of both target surface and deposited films. An increase on the Y ablation rate was found at the beginning,

A. Lorusso; F. Gontad; A. Perrone

2011-01-01

399

KrF laser ablation of a polyethersulfone film: Effect of pulse duration on structure formation  

NASA Astrophysics Data System (ADS)

Polyethersulfone (PES) films were processed with KrF laser irradiation of different pulse durations ( ?). Scanning electron microscopy (SEM) and Raman spectroscopy were employed for the examination of the morphology and chemical composition of the irradiated surfaces, respectively. During ablation with 500 fs and 5 ps pulses, localized deformations (beads), micro-ripple and conical structures were observed on the surface depending on the irradiation fluence ( F) and the number of pulses ( N). In addition, the number density of the structures is affected by the irradiation parameters ( ?, F, N). Furthermore, at longer pulse durations ( ? = 30 ns), conical structures appear at lower laser fluence values, which are converted into columnar structures upon irradiation at higher fluences. The Raman spectra collected from the top of the structures following irradiation at different pulse durations revealed graphitization of the ns laser treated areas, in contrast to those processed with ultra-short laser pulses.

Pazokian, Hedieh; Selimis, Alexandros; Stratakis, Emmanuel; Mollabashi, Mahmoud; Barzin, Jalal; Jelvani, Saeid

2011-10-01

400

Study of polymer ablation products obtained by ultraviolet laser ablation — inductively coupled plasma atomic emission spectrometry  

NASA Astrophysics Data System (ADS)

A study of the nature of aerosols following polymer laser ablation was performed. A glass sample was used for comparison. Aerosol fractions were analyzed by using simple methods based on transport efficiency and filters. Three different tube lengths, i.e. 4, 29 and 54 m, were inserted between the ablation cell and the inductively coupled plasma atomic emission spectrometry (ICP-AES) injector. For the glass sample, 10 elements were studied. Only Na and K exhibited different results as the particle size, i.e. tube length, was varied. The polymers used were poly(vinyl chloride), PVC, and poly(ethylene), PE. Three elements (Ca, Ti and Sn) under different chemical forms were measured. Unlike Ti and Sn the ablated aerosol particle size (mass) seemed to depend on the Ca chemical form. Another PVC sample containing 11 elements was also studied. Na, Al and C exhibited a different behavior with particle size with respect to the remaining elements. Then, the carbon signal was studied after a 0.3 ?m pore size filter had been placed between the ablation cell and the ICP torch. The results indicated that carbon was mainly present under gaseous form and particles smaller than 0.3 ?m size. The analysis of the aerosol gaseous phase by thermal desorption GC-MS confirmed the presence of polymer volatile thermal degradation products. These results explained why carbon could not be applied as an efficient internal standard.

Todolí, J.-L.; Mermet, J.-M.

1998-10-01

401

Complete prostatic ablation using a two-stage laser  

NASA Astrophysics Data System (ADS)

Laser photoirradiation has been delivered endoscopically for the treatment of both benign prostatic hyperplasia and early localized prostatic carcinoma. In treating carcinoma, aggressive transurethral resection of the prostate has been followed with laser irradiation to the remnants of malignant capsular disease. No attempt has been made heretofore to completely destroy the glandular prostate using laser irradiation alone. We performed a two-stage endoscopic laser prostatectomy in 6 adult mongrel dogs in an attempt to completely destroy the glandular prostate. Although no complications developed, histologic evaluation of the prostate revealed viable glandular elements in the midst of necrosis and atrophy. We conclude that in order to accomplish total ablation of the glandular prostate using laser photoirradiation, more precise thermal telemetry is needed.

Sayer, Jeanie; Cromeens, Douglas M.; Price, Roger E.; Johnson, Douglas E.

1993-05-01

402

Experimental and theoretical investigations of femtosecond laser ablation of aluminum in vacuum  

SciTech Connect

We used time-gated optical emission spectroscopy to investigate the characteristics of aluminum plumes and their vacuum expansion after femtosecond laser ablation at different fluences. The prominent feature is the presence of two main classes of species in the plume: very fast Al atoms and ions preceding the plume bulk essentially constituted of much slower Al nanoparticles expanding with a ten times smaller average velocity. Atomic force microscopy of deposited Al nanoparticles evidenced an average size of about 10 nm with a pretty narrow size distribution. These results and the peculiar feature of nanoparticle formation during femtosecond laser irradiation of matter were very satisfactorily interpreted and reproduced by molecular-dynamics simulation of the process. Finally, the analysis of the dependence on laser fluence of the ablation process showed an initial logarithmic increase of ablation yield, up to about 500 mJ/cm{sup 2}, followed by a sudden and very steep increase at higher fluences. According to our numerical calculations, this latter feature can be ascribed to the increase of the overheated material volume due to electron heat diffusion.

Amoruso, S.; Bruzzese, R.; Vitiello, M.; Nedialkov, N.N.; Atanasov, P.A. [Coherentia-Istituto Nazionale per la Fisica della Materia (INFM) and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, I-80126 Naples (Italy); Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsaridradsko shose Boulevard, Sofia 1784 (Bulgaria)

2005-08-15

403

Laser-ablation-assisted microparticle acceleration for drug delivery  

NASA Astrophysics Data System (ADS)

Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected to laser ablation on its backface such that a shock wave propagates through the foil. Due to shock wave loading, the surface of the foil containing microparticles is accelerated to very high speeds, ejecting the deposited particles at hypersonic speeds. The ejected particles have sufficient momentum to penetrate soft body tissues, and the penetration depth observed is sufficient for most of the pharmacological treatments. We have tried delivering 1 ?m tungsten particles into gelatin models that represent soft tissues, and liver tissues of an experimental rat. Sufficient penetration depths have been observed in these experiments with minimum target damage.

Menezes, V.; Takayama, K.; Ohki, T.; Gopalan, J.

2005-10-01

404

Targets on superhydrophobic surfaces for laser ablation ion sources  

NASA Astrophysics Data System (ADS)

Target preparation techniques for a laser ablation ion source at the Penning-trap mass spectrometer TRIGA-TRAP have been investigated with regard to future experiments with actinides. To be able to perform mass measurements on these nuclides considering their limited availability, an efficient target preparation technique is mandatory. Here, we report on a new approach for target production using backings, which are pretreated in a way that a superhydrophobic surface is formed. This resulted in improved targets with a more homogeneous distribution of the target material compared to standard techniques with unmodified backings. It was demonstrated that the use of these new targets in a laser ablation ion source improved the ion production significantly.

Renisch, D.; Beyer, T.; Blaum, K.; Block, M.; Düllmann, Ch. E.; Eberhardt, K.; Eibach, M.; Nagy, Sz.; Neidherr, D.; Nörtershäuser, W.; Smorra, C.

2012-06-01

405

Laser ablated carbon plume flow dynamics under magnetic field  

NASA Astrophysics Data System (ADS)

The dynamics of a conducting laser ablated carbon plume flow in the ablation furnace typical for nanoparticle synthesis is investigated by numerical modeling. The effect of magnetic field on the flow is accounted through the Lorentz body force. The study begins with benchmark calculations of two simple test cases, the Kelvin-Helmholtz instability and Hartmann layer. The evolution of plume is then studied for longitudinal and transverse magnetic fields. It is observed that the transverse magnetic fields have more impact than longitudinal fields on plume evolution for this application. Ionization and heat capacity variation in the plume are accounted through the Saha equation and the Shomate equation, respectively. Multiple plume ejections typical for pulsed laser deposition of thin films are also discussed.

Pathak, Kedar A.; Chandy, Abhilash J.

2009-04-01

406

CdTe nanoparticles synthesized by laser ablation  

SciTech Connect

Nanoparticle generation by laser ablation of a solid target in a liquid environment is an easy, fast, and 'green' method for a large scale production of nanomaterials with tailored properties. In this letter we report the synthesis of CdTe nanoparticles by femtosecond laser [387 nm, 180 fs, 1 kHz, pulse energy=6 {mu}J (fluence=1.7 J/cm{sup 2})] ablation of the target material. Nanoparticles with diameters from {approx}2 up to {approx}25 nm were observed to be formed in the colloidal solution. Their size distribution follows the log-normal function with a statistical median diameter of {approx_equal}7.1 nm. Their crystal structure is the same as that of the bulk material (cubic zincblende) and they are slightly Cd-rich (Cd:Te percentage ratio {approx}1:0.9). Photoluminescence emission from the produced nanoparticles was detected in the deep red ({approx}652 nm)

Semaltianos, N. G.; Logothetidis, S. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki GR-54124 (Greece); Perrie, W.; Romani, S.; Potter, R. J.; Dearden, G.; Watkins, K. G. [Department of Engineering, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom); Sharp, M. [General Engineering Research Institute, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF (United Kingdom)

2009-07-20

407

Optoacoustic monitoring of cutting and heating processes during laser ablation  

NASA Astrophysics Data System (ADS)

Laser-tissue interaction during laser surgery can be classified into two biophysical processes: tissue removal in the focal zone of the laser beam and heating in the surrounding tissue. In order to ensure a precise cut and minimal collateral thermal damage, the surgeon has to control several parameters, such as power, repetition rate and fiber movement velocity. In this study we propose utilizing optoacoustics for providing the necessary real-time feedback of cutting and heating processes. A single Q-switched Nd-YAG laser (532nm, 4 KHz, 18 W, pulse duration 7.6ns) was used for ablation and generation of optoacoustic signals in fresh bovine tissue samples. Both shockwaves, generated due to tissue removal, as well as normal optoacoustic responses from the surrounding tissue were detected using a single 10MHz piezoelectric transducer. It has been observed that rapid reduction in the shockwave amplitude occurs as more material is being removed from the focal zone, indicating decrease in cutting efficiency of the laser beam, whereas gradual decrease in the optoacoustic signal likely corresponds to coagulation around the ablation crater. Further heating of surrounding tissue leads to carbonization accompanied by a significant shift of spectral components of the optoacoustic signal. Our results hold promise for real-time monitoring of cutting efficiency and collateral thermal damage during laser surgery.

Bay, Erwin; Douplik, Alexandre; Razansky, Daniel

2013-03-01

408

Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers  

SciTech Connect

Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.

Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J.; Herman, S.; Lane, S.M.; London, R.A.; Matthews, D.L.; Perry, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Chang, T.D. [Veterans Administration Hospital, Martinez, CA (United States); Neev, J. [Beckman Laser Inst. and Medical Clinic, Irvine, CA (United States)

1996-05-01

409

Excimer laser ablation based microlens fabrication in polymer materials  

Microsoft Academic Search

We demonstrate that excimer laser ablation can be applied successfully to fabricate microlenses and arrays of microlenses in an easy set-up allowing great flexibility in terms of size, shape and focal length of the lenses. Due to the non-contact and direct-write nature of the process, the technique allows easy insertion of micro-optics in a late phase of a heterogeneous optoelectronic

K. Naessens; P. Van Daele; R. Baets

2002-01-01

410

Selective non-ablative wrinkle reduction by laser  

Microsoft Academic Search

BACKGROUNDANDOBJECTIVES: Skin resurfacing and wrinkle removal is a large medical laser market. However, the rate of undesirable side effects is high andsometimes is not warrantedby the aesthetic improvement observed. The authors have evaluated the poten- tial bene®ts of an approach to selective non-ablative wrinkle reduction. MATERIALSANDMETHODS:Thistech- nique selectively targets the micro- vasculature which plays a key role in the stimulation

Peter Bjerring; Marc Clement; Lene Heickendorff; Henrik Egevist; Mike Kiernan

2000-01-01

411

Nanofibre fabrication by femtosecond laser ablation of silica glass  

NASA Astrophysics Data System (ADS)

: This article presents a fabrication technique for generating densely populated and randomly oriented silica nanofibres by direct ablation of silica glass using a femtosecond laser with 12.4 MHz repetition rate and a pulse width of 214 fs, under ambient conditions. Four types of nanofibres with diameters ranging from a few tens of nanometers to a few hundreds of nanometers were formed. Some fibers reach lengths of 10 mm. The possible mechanisms for fibre formation have been explored.

Venkatakrishnan, Krishnan; Vipparty, Dheeraj; Tan, Bo

2011-08-01

412

Nanofibre fabrication by femtosecond laser ablation of silica glass.  

PubMed

This article presents a fabrication technique for generating densely populated and randomly oriented silica nanofibres by direct ablation of silica glass using a femtosecond laser with 12.4 MHz repetition rate and a pulse width of 214 fs, under ambient conditions. Four types of nanofibres with diameters ranging from a few tens of nanometers to a few hundreds of nanometers were formed. Some fibers reach lengths of 10 mm. The possible mechanisms for fibre formation have been explored. PMID:21934939

Venkatakrishnan, Krishnan; Vipparty, Dheeraj; Tan, Bo

2011-08-15

413

Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Principles and Applications  

Microsoft Academic Search

The application of laser ablation inductively plasma mass spectrometry (LA?ICP?MS) to the determination of major, minor, and trace elements as well as isotope?ratio measurements offers superior technology for direct solid sampling in analytical chemistry. The advantages of LA?ICP?MS include direct analysis of solids; no chemical dissolution is necessary, reduced risk of contamination, analysis of small sample mass, and determination of

N. S. Mokgalaka; J. Gardea-Torresdey

2006-01-01

414

Modeling of laser ablation and fragmentation of human calculi  

SciTech Connect

The large-scale radiation-hydrodynamics computer code LASNEX, has been used to model experimental results in the laser ablation and fragmentation of renal and biliary calculi. Recent experiments have demonstrated laser ablation and fragmentation of human calculi in vitro and in vivo. In the interaction, laser light incident upon the calculus is of sufficient intensity to produce a plasma (a hot ionized gas). The physical picture which emerges is as follows. The plasma couples to acoustic and shear waves which then propagate through the dense stone material, causing spall and fracture by reflection from material discontinuities or boundaries. Experiments have thus far yielded data on the interaction against which models can be tested. Data on the following have been published: (1) light emission, (2) absorption and emission spectra, (3) fragmentation efficiency, (4) cavitation bubble dynamics and (5) mass removal. We have performed one dimensional simulations of the laser-matter interaction to elucidate the important physical mechanisms. We find that good quantitative fits between simulation and experiment are obtained for visible light emission, electron temperature, electron density, plasma pressure and cavitation bubble growth. With regard to mass removal, experiment and simulation are consistent with each other and give an excellent estimate of the ablation threshold. The modeling indicates that a very small ablation layer at the surface of the calculus is responsible for significant mass loss by fragmentation within the bulk of the calculus. With such quantitative fits in hand, we believe this type of modeling can now be applied to the study of other procedures involving plasma formation of interest to the medical community. 25 refs., 7 figs.

Gitomer, S.; Jones, R.D.; Howsare, C.

1989-01-01

415

High-throughput metal nanoparticle catalysis by pulsed laser ablation  

Microsoft Academic Search

A high-throughput pulsed laser ablation (HT-PLA) system was developed to rapidly prepare uniformly sized single- and multi-metallic nanoparticles with different diameters for catalytic applications. Catalytic materials containing Rh, bimetallic Rh\\/Pt and trimetallic Rh\\/Pt\\/Au nanoparticles were synthesized from targets prepared by blending, tableting and sintering powders of pure metals, and by directly collecting the nanoparticles created on support materials. Nanoparticles exhibited

Selim Senkan; Michael Kahn; Shici Duan; Anna Ly; Craig Leidholm

2006-01-01

416

Control over a phase state of the laser plume ablated by femtosecond laser: Spatial pulse shaping  

Microsoft Academic Search

The conditions for the formation of a fully atomized laser-ablated plume using subpicosecond laser pulses have been studied theoretically and implemented experimentally. It is shown that the low-intensity wings, which generally exist in the spatial distribution of laser intensity in the focal plane and can contain a substantial part of the incident laser energy, are responsible for low-threshold phase transformations

E. G. Gamaly; Australia A. V. Rode; O. Uteza; V. Kolev; B. Luther-Davies; T. Bauer; J. Koch; F. Korte; B. N. Chichkov

2004-01-01

417

Optogalvanic laser spectroscopy of flames  

SciTech Connect

The authors describe a technique for the laser spectroscopy of metal vapors which involves the evaporation, combustion, and ionization of a metal salt in a flame placed within the resonator of a dye laser spectrometer. The technique is based on the premise that at the moment that a laser pulse passes through the flame, the concentration of ions and electrons between the two electrodes placed in the flame changes, resulting in a current pulse in the measuring circuit. The technique is both mathematically and experimentally verified by testing for the detection limits of lithium, europium, and samarium.

Udartsev, A.M.; Kim, V.G.; Iordanidi, G.K.; Mashakova, S.M.; Ksandopulo, G.I.

1987-07-01

418

Fourier-transform laser spectroscopy.  

PubMed

The development of microphotonic sensors based on Fourier-transform laser spectroscopy (FT-LS) is discussed. The application demonstrated is for measurement of vapors from the hydrocarbon fuels JP-8, diesel fuel, and gasoline. The two-laser prototype FT-LS sensor used for our research employs distributed-feedback lasers in the near-infrared spectral region (1.3- and 1.7-microm wavelength). An extension of this research to multilaser arrays is discussed. We believe that this is the first measurement of middle-distillate fuel-vapor concentrations using this optical mixing technique. PMID:12716154

McNesby, Kevin L; Miziolek, Andrzej W

2003-04-20