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1

Particle analysis using laser ablation mass spectroscopy  

DOEpatents

The present invention provides a method of quickly identifying bioaerosols by class, even if the subject bioaerosol has not been previously encountered. The method begins by collecting laser ablation mass spectra from known particles. The spectra are correlated with the known particles, including the species of particle and the classification (e.g., bacteria). The spectra can then be used to train a neural network, for example using genetic algorithm-based training, to recognize each spectra and to recognize characteristics of the classifications. The spectra can also be used in a multivariate patch algorithm. Laser ablation mass specta from unknown particles can be presented as inputs to the trained neural net for identification as to classification. The description below first describes suitable intelligent algorithms and multivariate patch algorithms, then presents an example of the present invention including results.

Parker, Eric P.; Rosenthal, Stephen E.; Trahan, Michael W.; Wagner, John S.

2003-09-09

2

Femtosecond laser ablation of gallium arsenide investigated with time-of-flight mass spectroscopy  

E-print Network

Femtosecond laser ablation of gallium arsenide investigated with time- of-flight mass spectroscopy laser-induced ablation of gallium arsenide using time-of-flight mass spectroscopy. At the ablation solids laser ablation is not fully understood. In the case of metals and strongly absorbing

von der Linde, D.

3

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

E-print Network

Characterization of hydrocarbon and mixed layers in TEXTOR by laser induced ablation spectroscopy in TEXTOR by laser induced ablation spectroscopy N Gierse1,2 , S Brezinsek1 , T F Giesen2 , A Huber1 , M systematic laser-induced ablation spectroscopy (LIAS) measurements carried out on various surface layers

Giesen, Thomas

4

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation  

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

5

Time of Flight Mass Spectroscopy of Femtosecond Laser Ablation of Solid Surfaces  

E-print Network

1 Time of Flight Mass Spectroscopy of Femtosecond Laser Ablation of Solid Surfaces A. Cavalleri, K boiling causes material removal. After excitation with femtosecond laser pulses, ablation can be achieved with a 100 fs, 620 nm laser pulse. In order to provide information on single shot ablation, the sample

von der Linde, D.

6

Investigation Of Excimer Laser Ablated Y-Ba-Cu-O Superconductors Using Spectroscopy And Ion Probes  

NASA Astrophysics Data System (ADS)

KrF laser ablation of Y-Ba-Cu-O targets has been studied using time resolved visible-uv spectroscopy and ion collector probes. These techniques have allowed the principal luminous species, ablation velocity and extent of ionization in the plume to be deduced. Comparative work using the TEA CCD, laser shows that similar spectral signatures are generated by the plume but that higher electron temperatures may exist because of stronger plasma coupling effects with the long wavelength laser.

Dyer, Peter E.; Greenough, R. D.; Issa, Almoutaz; Key, Phillip H.

1989-04-01

7

Laser ablation absorption spectroscopy for remote analysis of uranium  

NASA Astrophysics Data System (ADS)

To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm2. The temporal evolution of the ablation plume was investigated in 800 Pa helium environment. It was found that the observation at 3-5 ?s after the ablation at the height of about 2.5 mm are most suited for obtaining higher sensitivity. Using the established conditions, we obtained the limit of detection of the isotope ratio (235U/238U) to be 0.01 %. In addition, the limit of detection of elemental abundance of uranium in uranium glass was also evaluated.

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

2013-04-01

8

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

E-print Network

1 Evolutions in time and space of laser ablated species by dual-laser photo-absorption spectroscopy 76801 Saint Etienne du Rouvray FRANCE ribiere@coria.fr, cheron@coria.fr An atmospheric aluminum laser range. The absorbed radiation is produced by a second aluminum laser induced plasma which is generated

Boyer, Edmond

9

Pulsed Nd:YAG laser selective ablation of surface enamel caries: I. Photoacoustic response and FTIR spectroscopy  

Microsoft Academic Search

Enamel caries lesions on extracted teeth were ablated with a pulsed Nd:YAG or Er:YAG laser. Tissue ablation was accompanied by a 'popping' sound (the photoacoustic response). Analysis of the photoacoustic response yields insights into the laser\\/tissue interactions. Fourier Transform Infrared (FTIR) Spectroscopy of lesions before ablation show a strong protein component associated with organic material (i.e., bacteria). Following ablation this

David M. Harris; Daniel Fried

2000-01-01

10

Quantitative analysis by resonant laser ablation with optical emission detection: Resonant laser-induced breakdown spectroscopy  

Microsoft Academic Search

Resonant laser ablation (RLA) is a solid sampling technique that makes use of radiation trapping, and desorption induced by electronic transitions (DIET), to produce enhanced numbers of analyte atoms in the laser-induced plasma (LIP). This is achieved by tuning the laser ablation wavelength to a gas-phase resonant transition of the analyte. In this paper, RLA was coupled with detection of

Danielle Cleveland; Robert G. Michel

2010-01-01

11

Laser-Induced Spectroscopy of Graphene Ablation in Air  

NASA Astrophysics Data System (ADS)

Carbon Swan spectra are observed following laser ablation of graphene in laboratory air. Previous experiments showed temperatures that ranged from 4500 to 7500 K for the ?v = 0 transition and 4200 to 4500 K for the ?v = ?1 transition for time delays on the order of 1.6 ?s to 70 ?s. This experiment explored in greater detail time delays > 10 ?s for both molecular bands. Temperatures were found to be similar, ranging from 4500 to 6700 K for the ?v = 1 transition and 3200 to 5500 K for the ?v = -1 transition. Investigation is also made into spatially resolving the plasma emissions along the slit height. In addition, efforts are made to investigate the applicability of the local thermodynamic equilibrium (LTE) assumption. Comparisons are discussed in view of previous work that utilized Stark broadening of the H? line, confirming LTE for delays < 10 ?s, yet further research needed for later delays.

Witte, M. J.; Parigger, C. G.

2014-11-01

12

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

13

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

E-print Network

Dynamics of femto- and nanosecond laser ablation plumes investigated using optical emission plasmas, brass targets were ablated in vacuum employing pulses either from a Ti:Sapphire ultrafast laser of Physics. [http://dx.doi.org/10.1063/1.4764060] I. INTRODUCTION Laser ablation (LA) and laser

Harilal, S. S.

14

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

15

Laser ablation of concrete.  

SciTech Connect

Laser ablation is effective both as an analytical tool and as a means of removing surface coatings. The elemental composition of surfaces can be determined by either mass spectrometry or atomic emission spectroscopy of the atomized effluent. Paint can be removed from aircraft without damage to the underlying aluminum substrate, and environmentally damaged buildings and sculptures can be restored by ablating away deposited grime. A recent application of laser ablation is the removal of radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on concrete samples using a high power pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied on various model systems consisting of Type I Portland cement with varying amounts of either fine silica or sand in an effort to understand the effect of substrate composition on ablation rates and mechanisms. A sample of non-contaminated concrete from a nuclear power plant was also studied. In addition, cement and concrete samples were doped with non-radioactive isotopes of elements representative of cooling waterspills, such as cesium and strontium, and analyzed by laser-resorption mass spectrometry to determine the contamination pathways. These samples were also ablated at high power to determine the efficiency with which surface contaminants are removed and captured. The results show that the neat cement matrix melts and vaporizes when little or no sand or aggregate is present. Surface flows of liquid material are readily apparent on the ablated surface and the captured aerosol takes the form of glassy beads up to a few tens of microns in diameter. The presence of sand and aggregate particles causes the material to disaggregate on ablation, with intact particles on the millimeter size scale leaving the surface. Laser resorption mass spectrometric analysis showed that cesium and potassium have similar chemical environments in the matrix, as do strontium and calcium.

Savina, M.

1998-10-05

16

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

Microsoft Academic Search

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

Masamitsu Haruna; Masato Ohmi; Mitsuo Nakamura; Shigeto Morimoto

2000-01-01

17

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

18

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

19

Time of flight mass spectroscopy of femtosecond laser ablation of solid Andrea Cavalleri(a,b), Klaus Sokolowski-Tinten(a), Jrg Bialkowski(a) and Dietrich von der Linde(a)  

E-print Network

Time of flight mass spectroscopy of femtosecond laser ablation of solid surfaces Andrea Cavalleri, two phase regime. 1. INTRODUCTION Femtosecond laser pulses offer some advantages in laser ablation are commonly used to induce ablation of absorbing solids. Femtosecond laser ablation of transparent materials

von der Linde, D.

20

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

21

Detection and Classification of Individual Airborne Microparticles using Laser Ablation Mass Spectroscopy and Multivariate Analysis  

SciTech Connect

We are developing a method for the real-time analysis of airborne microparticles based on laser ablation mass spectroscopy. Airborne particles enter an ion trap mass spectrometer through a differentially-pumped inlet, are detected by light scattered from two CW laser beams, and sampled by a 10 ns excimer laser pulse at 308 nm 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. In this work thousands of positive and negative ion spectra were collected for eighteen different species: six bacteria, six pollen, and six particulate samples. The data were then averaged and analyzed using the Multivariate Patch Algorithm (MPA), a variant of traditional multivariate anal ysis. The MPA correctly identified all of the positive ion spectra and 17 of the 18 negative ion spectra. In addition, when the average positive and negative spectra were combined the MPA correctly identified all 18 species. Finally, the MPA is also able to identify the components of computer synthesized mixtures of the samples studied

Gieray, R.A.; Lazar, A.; Parker, E.P.; Ramsey, J. M.; Reilly, P.T.A.; Rosenthal, S.E.; Trahan, M.W.; Wagner, J.S.; Whitten, W.B.

1999-04-27

22

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

23

Femtosecond laser ablation of copper  

NASA Astrophysics Data System (ADS)

In recent years, femtosecond (fs) laser ablation has attracted much interest in both basic and applied physics, mainly because of its potential application in micromachining and pulsed laser deposition. Ultrashort laser ablation have the capability to ablate materials precisely with little or no collateral damage, even with materials that are impervious to laser energy from conventional pulsed lasers. The extreme intensities and short timescale at which ultrashort pulsed lasers operate differentiate them from other lasers such as nanosecond laser. In this work, we investigate the expansion dynamics of Cu (copper) plasma generated by ultrashort laser ablation of pure copper targets by optically examining the plasma plume. Time-integrated optical emission spectroscopy measurements by using intensified charged couple detector array (ICCD) imaging were used to detect the species present in the plasma and to study the laser-generated plasma formation and evolution. Temporal emission profiles are measured. Our interest in the dynamics of laser-generated copper plasma arises from the fact that copper has been considered as a substitute for Aluminum (Al) interconnects/metallization in ULSI devices (for future technology). It is important to know the composition and behavior of copper plasma species for the understanding of the mechanisms involved and optimizing the micro-machining processes and deposition conditions.

Goh, Yeow-Whatt; Lu, Yong-Feng; Hong, Ming-Hui; Chong, Tow Chong

2003-02-01

24

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

25

Photoionization and Optical Spectroscopy of Atomic Clusters Generated via Laser Ablation.  

NASA Astrophysics Data System (ADS)

Laser ablation, combined with a pulsed-nozzle gas source, has been used to generate atomic clusters of three different classes: metal clusters, metal-doped rare gas clusters, and carbon molecules. Resonant and non-resonant photoionization spectroscopy, with mass spectrometric detection, has been used to characterize these species as described below. The ionization thresholds (IPs) for Al _{n} (n = 1 - 70) and In_{n} (n = 1 - 30) clusters have been measured, and fail to conform to the behavior predicted by the spherical jellium model. In the small-size regime, to n = 6, the initial increase in the observed IPs agrees with previous ab initio calculations and provides evidence for the hybridization of the s and p electronic bands. The size-evolution of IPs beyond n = 6 exhibits an electronic shell structure, although the apparent ordering of the shells does not follow the prediction of the spherical jellium model. The most plausible explanation which may account for the observed electronic level pattern is lowering of structural symmetry due to the ion core lattice. The synthesis and spectroscopy of metal containing rare-gas atomic clusters Al cdot Ar_{n} and Al cdot (N_2)_{n} for n = 1 - 200 has also been studied. The mass spectra of the neutral and ionized clusters are shown to be consistent with the icosahedral shell-structure sequence. The size-evolution of the photoionization and optical excitation properties of the core metal atom have been measured by photoionization spectroscopy and resonant two-photon ionization spectroscopy. The use of microscopic theory to calculate vertical and adiabatic ionization energies gives reasonable agreement with experiment. Dielectric continuum theory gives general agreement with the experiment if the strong short-range interactions in the neutral cluster is included. Finally, a new and unique application of laser desorption mass spectrometry has been demonstrated in which a simple carbon cluster, C_{18} , is generated in a molecular beam and detected using multiphoton ionization. The generation of a specific sized carbon cluster is accomplished by using a unique precursor molecule which is predisposed to fragment with the generation of C_{18}. The feasibility of using laser desorption on weakly bound molecules and for inducing chemical reactions in the desorption step has been demonstrated, providing the groundwork for generating cluster beams containing a single, well-characterized species.

Schriver, Kenneth Edward

1990-01-01

26

Representative sampling using single-pulse laser ablation withinductively coupled plasma mass spectroscopy  

SciTech Connect

Single pulse laser ablation sampling with inductively coupled plasma mass spectrometry (ICP-MS) was assessed for accurate chemical analysis. Elemental fractionation (e.g. Pb/U), the quantity of ablated mass (crater volume), ICP-MS intensity and the particle contribution (spike signal) during single pulse ablation of NIST 610 glass were investigated. Pb/U fractionation significantly changed between the first and second laser pulse and showed strong irradiance dependence. The Pb/U ratio obtained by the first pulse was usually higher than that of the second pulse, with the average value close to the representative level. Segregation during laser ablation is proposed to explain the composition change between the first and second pulse. Crater volume measurements showed that the second pulse produced significantly more ablated mass. A roll-off of the crater depth occurred at {approx}750 GW/cm{sup 2}. The absolute ICP-MS intensity from the second pulse showed no correlation with crater depth. Particle induced spikes on the transit signal showed irradiance and elemental species dependence.

Liu, Haichen; Mao, Xianglei; Russo, Richard E.

2001-04-02

27

Femtosecond laser ablation of copper  

Microsoft Academic Search

In recent years, femtosecond (fs) laser ablation has attracted much interest in both basic and applied physics, mainly because of its potential application in micromachining and pulsed laser deposition. Ultrashort laser ablation have the capability to ablate materials precisely with little or no collateral damage, even with materials that are impervious to laser energy from conventional pulsed lasers. The extreme

Yeow-Whatt Goh; Yong-Feng Lu; Ming-Hui Hong; Tow Chong Chong

2003-01-01

28

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

29

Characterization of automobile float glass with laser-induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry.  

PubMed

A comparative analysis of the discriminating power of laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), each coupled with refractive index (RI) measurements, is presented for a study of 23 samples of automobile float glass. Elemental emission intensity ratios (LIBS) and elemental concentration ratios (LA-ICP-MS) and their associated confidence intervals were calculated for each float glass sample. The ratios and confidence intervals were used to determine the discrimination power of each analytical method. It was possible to discriminate 83% of the glass samples with 99% confidence based on LIBS spectra alone, and 96-99% of the samples could be discriminated based on LIBS spectra taken in conjunction with RI data at the same confidence level. LA-ICP-MS data allowed for 100% discrimination of the samples without the need for RI data. The results provide evidence to support the use of LIBS combined with RI for forensic analysis of float glass in laboratories that do not have access to LA-ICP-MS. PMID:17059671

Bridge, Candice M; Powell, Joseph; Steele, Katie L; Williams, Mary; Macinnis, Jean M; Sigman, Michael E

2006-10-01

30

Microwave Frequency Transitions Requiring Laser Ablated Uranium Metal Discovered Using Chirp-Pulse Fourier Transform Spectroscopy  

NASA Astrophysics Data System (ADS)

A rod of depleted uranium metal (mp = 1,132° C) has been ablated with the fundamental operating frequency of a Nd:YAG laser. The resulting ablation plume of uranium was then mixed with argon gas and expanded between the transmit/receive horn antennae of a chirp-pulse Fourier transform microwave spectrometer. The recorded spectra show nine strong transitions which are not present when the laser is not used in the experimental procedure. A series of experiments in which the backing gas conditions were altered provides evidence that the nine observed transitions are carried by the same species. Should the transitions be from one species it is most likely an asymmetric top. The transitions persist even when ultra-pure argon is used as the sole backing gas. The oxide coating of the uranium metal likely provides a source of oxygen and, presently, the ``top" candidate for the unknown molecule is UO_3, which is known to have C_2v symmetry. Double resonance experiments are planned to aid transition assignments. A plausible explanation for an elusive assignment to date is the presence of pseudo-rotation.

Long, B. E.; Cooke, S. A.

2014-06-01

31

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

32

LASER ABLATION STUDIES OF CONCRETE  

EPA Science Inventory

Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. We 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-s...

33

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

34

Laser ablation studies of concrete  

Microsoft Academic Search

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

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

1999-01-01

35

Comparative investigation of laser ablation plumes in air and argon by analysis of spectral line shapes: Insights on calibration-free laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

We investigate the characteristic features of plume expansion in air and argon resulting from ultraviolet laser ablation of solid matter in conditions typically applied in material analysis via laser-induced breakdown spectroscopy (LIBS). Barite crown glass is chosen as a target material for the characteristic emission spectrum suitable for plasma diagnostics. The space-integrated plasma emission spectrum recorded with an echelle spectrometer coupled to a gated detector is compared to the computed spectral radiance of a nonuniform plasma in local thermodynamic equilibrium. In particular, resonance lines of neutral sodium atoms and barium ions are observed to probe gradients of temperature and density within the plume. It is shown that laser ablation in argon leads to an almost uniform plasma whereas gradients of temperature and density are evidenced in ambient air. The discrepancy is attributed to the different physical properties of both gases leading to a stronger vapor-gas energy exchange in the case of air. However, strong gradients occur only in a thin peripheral zone, close to the vapor-gas contact front. The larger plasma core appears almost uniform. The peripheral zone of low temperature mostly contributes to the plasma emission spectrum by absorption and material analysis via calibration-free LIBS in air may ignore the nonuniform character of the plasma if only transitions of small optical thickness are considered.

Hermann, Jörg; Gerhard, Christoph; Axente, Emanuel; Dutouquet, Christophe

2014-10-01

36

PROCEEDINGS288 ---c..*. LASER ABLATION: I:`.  

E-print Network

AIP I CONFERENCE PROCEEDINGS288 ---c..*. . LASER ABLATION: I:`. MECHANEMS ABSTRACT A one dimensional hydrodynamic' model of laser ablation and plume breakdown is presented. The en for KrF and XeCl excimer laser ablation of YBa,Cu30Y_xtargets in vacuum, XeF excimer laser ablation

Vertes, Akos

37

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

38

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

39

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

SciTech Connect

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; Ding, Hongbin, E-mail: hding@dlut.edu.cn [School of Physics and Optical Electronic Technology, Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Chinese Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Zhou, Yan; Yan, Longwen; Duan, Xuru [Southwestern Institute of Physics, P.O. Box 432, No. 3 South Section 3, Circle Road 2, Chengdu 610041, Sichuan (China)

2014-05-15

40

Magnesium distribution in paper subjected to deacidification investigated by means of Laser Ablation Inductively Coupled Plasma Mass Spectroscopy  

Microsoft Academic Search

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP MS) was used to investigate the distribution of magnesium in paper subjected to selected deacidification mass processes. Paper samples have been taken from the early XX century books, which had been previously deacidified with the use of either Book Saver or Bückeburg process. Both methods incorporate the use of magnesium compounds

Barbara Wagner; Ewa Bulska; W?adys?aw Sobucki

2008-01-01

41

Ablation characteristics of cubic-boron nitride ceramic with femtosecond and picosecond laser pulses  

NASA Astrophysics Data System (ADS)

Ablation of cubic-boron nitride (c-BN) ceramic irradiated by Ti:sapphire laser (110 fs, 790 nm) and Nd:YAG laser (100 ps, 1.064 ?m) pulses is comparatively studied. In the case of Ti:sapphire laser ablation, it is observed that the ablation depth per pulse has two different ablation regimes, being similar to the fs laser ablation of metals. The ablation threshold fluence for the 110 fs Ti:sapphire laser is estimated to be 15 mJ/cm2 for low fluence ablation, and 180 mJ/cm2 for high fluence ablation. With x-ray photoelectron spectroscopy signal and scanning electron microscope observation it is evident that the surface ablated with the 110 fs Ti:sapphire laser pulses remains as the BN layer itself and is not melted. With the 100 ps Nd:YAG laser ablation, the boron semiconductor layer is formed on the ablated surface.

Hirayama, Yoichi; Obara, Minoru

2001-12-01

42

Femtosecond Laser Ablation: Fundamentals and Applications  

E-print Network

Chapter 6 Femtosecond Laser Ablation: Fundamentals and Applications Sivanandan S. Harilal, Justin R of laser ablation process using ultrashort laser pulses are not still fully understood. Pulse duration in the sample lattice. This results in dif- ferent laser ablation and heat dissipation mechanisms as compared

Harilal, S. S.

43

Laser ablation based fuel ignition  

DOEpatents

There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition.

Early, James W. (Los Alamos, NM); Lester, Charles S. (San Juan Pueblo, NM)

1998-01-01

44

Laser ablation based fuel ignition  

DOEpatents

There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition. 3 figs.

Early, J.W.; Lester, C.S.

1998-06-23

45

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

46

Lee, C-T A Laser Ablation Data Reduction 2006 LASER ABLATION ICP-MS: DATA  

E-print Network

Lee, C-T A Laser Ablation Data Reduction 2006 1 LASER ABLATION ICP-MS: DATA REDUCTION Cin-Ty A. Lee 24 September 2006 Analysis and calculation of concentrations Laser ablation analyses are done in time by turning on the laser and ablating the sample, generating a time-dependent signal (Fig. 1). Measurements

Lee, Cin-Ty Aeolus

47

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

48

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

49

Analysis of aluminum alloys by resonance-enhanced laser-induced breakdown spectroscopy: How the beam profile of the ablation laser and the energy of the dye laser affect analytical performance  

NASA Astrophysics Data System (ADS)

In resonance-enhanced laser-induced breakdown spectroscopy, the sample was ablated by a laser pulse and the expanding plume was photoresonantly rekindled by a dye laser pulse. By sampling aluminum alloys for Mg, Pb, Si, and Cu, we showed that for the ablation step, Gaussian beams gave 2 to 3× better signal-to-noise ratio (SNR) than non-uniform beams. For the rekindling step, if no further sample destruction was allowed, dye laser pulses that intercepted the plume transversely gave 6 to 12× higher SNR than the longitudinal case. By combining Gaussian beams and transverse rekindling, the mass limit-of-detection for Mg was about 100 amol while non-resonant analysis was 10× more destructive. Sub-monolayer of oxides grown on laser-cleaned aluminum surfaces was detected by monitoring the AlO emissions of rekindled plumes; without resonant enhancements, they were not detectable no matter how destructive was the analysis. Time resolved studies showed that the Gaussian beam produced less dispersed plumes and that a stronger dye laser beam directed transversely heated up a bigger plume mass without over-heating the plume core. The analyte emissions were sustained while the continuum background remained low.

Yip, W. L.; Cheung, N. H.

2009-04-01

50

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

51

Subpicosecond UV laser ablation of metals  

Microsoft Academic Search

Laser ablation of Nickel, Copper, Molybdenum, Indium, Tungsten and Gold by short ultraviolet laser pulses (0.5 ps, 248 nm) in vacuum is reported for the first time. For Nickel and Indium, ablation is also studied in air to demonstrate the influence of the ambient atmosphere. Metal ablation in air is significantly less efficient than in vacuum due to redeposition of

S. Preuss; A. Demchuk; M. Stuke

1995-01-01

52

Laser ablation of silicone composites  

NASA Astrophysics Data System (ADS)

Silicone rubber based composites are widely used to produce outdoor insulators. In adverse weather conditions these can be damaged by surface discharge activity resulting in deterioration of their dielectric properties and an eventual need for replacement. Inclined plane tracking tests are frequently used to determine the relative performance of different material formulations used in their construction. An alternative approach to characterisation is to use an infra-red laser to deposit known amounts of energy at a known rate to the sample's surface allowing comparative ranking of different materials. In this paper several silicone based composites have been ranked using a laser ablation technique and the results were then compared to those obtained from tracking tests on the same materials. The comparison indicates that laser ablation ranks the materials in the same order as the tracking tests and may therefore constitute a quick and cost effective method for the routine characterisation of outdoor insulation components.

Hosier, I. L.; Abd Rahman, M. S.; Vaughan, A. S.; Krivda, A.; Kornmann, X.; Schmidt, L. E.

2011-08-01

53

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

54

Experimental investigation of the laser ablation process on wood surfaces  

NASA Astrophysics Data System (ADS)

Processing of wood by conventional mechanical tools like saws or planes leaves behind a layer of squeezed wood only slightly adhering to the solid wood surface. Laser ablation of this layer could improve the durability of coatings and glued joints. For technical applications, thorough knowledge about the laser ablation process is necessary. Results of ablation experiments by excimer lasers, Nd:YAG lasers, and TEA-CO 2 lasers on surfaces of different wood types and cut orientations are shown. The process of ablation was observed by a high-speed camera system and optical spectroscopy. The influence of the experimental parameters are demonstrated by SEM images and measurement of the ablation rate depending on energy density. Thermal effects like melting and also carbonizing of cellulose were found for IR- and also UV-laser wavelengths. Damage of the wood surface after laser ablation was weaker for excimer lasers and CO 2-TEA lasers. This can be explained by the high absorption of wood in the ultraviolet and middle infrared spectral range. As an additional result, this technique provides an easy way for preparing wood surfaces with excellently conserved cellular structure.

Panzner, M.; Wiedemann, G.; Henneberg, K.; Fischer, R.; Wittke, Th.; Dietsch, R.

1998-05-01

55

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

56

Laser Ablation Propulsion A Study  

NASA Astrophysics Data System (ADS)

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

Irfan, Sayed A.; Ugalatad, Akshata C.

57

Endometrial ablation  

MedlinePLUS

Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

58

RESEARCH Open Access Focal Laser Ablation of Prostate Cancer  

E-print Network

RESEARCH Open Access Focal Laser Ablation of Prostate Cancer: Numerical Simulation of Temperature between active surveillance and radical therapy. Focal laser ablation (FLA) could be one surgical method. Keywords: Prostate cancer focal laser ablation, thermal damage, bioheat transfer

Paris-Sud XI, Université de

59

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

60

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

61

Pulsed infrared laser ablation and clinical applications  

NASA Astrophysics Data System (ADS)

Sufficient light energy deposited in tissue can result in ablation and excessive thermal and mechanical damage to adjacent tissues. The goals of this research are to investigate the mechanisms of pulsed infrared laser ablation of tissue, to optimize laser parameters for minimizing unnecessary damage to healthy tissue, and to explore the potential of using pulsed infrared lasers for clinical applications, especially laser lithotripsy. A dual-channel optical low coherence reflectometer was implemented to measure the expansion and collapse velocities of a Q-switched Ho:YAG (? = 2.12 ?m) laser-induced cavitation in water. Cavitation wall velocities up to 11 m/s were measured with this technique, and the results were in fair agreement with those calculated from fast-flash photographic images. The dependence of ablation threshold fluence on calculus absorption was examined. Preliminary results indicated that the product of optical absorption and ablation threshold fluence, which is the heat of ablation, remained constant for a given urinary calculus type and laser pulse duration. An extended study examined the influence of optical absorption on pulsed infrared laser ablation. An analytical photothermal ablation model was applied and compared to experimental ablation results using an infrared free-electron laser at selected wavelengths between 2.12 ?m and 6.45 ?m Results were in good agreement with the model, and the ablation depths of urinary calculi were highly dependent upon the calculus optical absorption as well as light attenuation within the intrapulse ablation plume. An efficient wavelength for ablation corresponded to the wavelength of the Er:YAG laser (? = 2.94 ?m) suggested this laser should be examined for laser lithotripsy. Schlieren flash photography, acoustic transient measurements with a piezoelectric polyvinylidene-fluoride needle-hydrophone, mass loss measurements, and chemical analyses were employed to study the ablation mechanisms of the free-running pulsed Ho:YAG laser in lithotripsy. Results indicated that a photothermal ablative process with concomitant chemical decomposition of calculus components occurred. This discovery dispelled the hypothesis that laser lithotripsy fragments calculus by means of shockwaves. Finally, the Er:YAG laser was explored for use in laser lithotripsy. Preliminary mass loss measurements suggested that the Er:YAG laser was more efficient than the Ho:YAG laser for lithotripsy.

Chan, Kin Foong

62

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...

63

Numerical simulation of pulsed laser ablation in air  

Microsoft Academic Search

Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric

Bukuk Oh; Dongsik Kim; Wonseok Jang; Bosung Shin

2003-01-01

64

Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

Anderson localization of matter-waves in a controlled disorder: a quantum simulator? / A. Aspect ... [et al.] -- Squeezing and entanglement in a Bose-Einstein condensate / C. Gross ... [et al.] -- New physics in dipolar Bose-Einstein condensates / Y. Kawaguchi, H. Saito, and M. Ueda -- Observation of vacuum fluctuations in a spinor Bose-Einstein condensate / C. Klempt ... [et al.] -- Negative-index media for matter waves / F. Perales ... [et al.] -- Entanglement of two individual atoms using the Rydberg blockade / A. Browaeys ... [et al.] -- Array of mesoscopic ensembles on a magnetic atom chip / A. F. Tauschinsky ... [et al.] -- Stability of the proton-to-electron mass ratio tested with molecules using an optical link to primary clock / A. Amy-Klein ... [et al.] -- Metastable helium: lifetime measurements using cold atoms as a test of QED / K. G. H. Baldwin ... [et al.] -- Optical lattice clocks with single occupancy bosons and spin-polarized fermions toward 10[symbol] accuracy / M. Takamoto ... [et al.] -- Frequency measurements of Al[symbol] and Hg[symbol] optical standards / W. M. Itano ... [et al.] -- Switching of light with light using cold atoms inside a hollow optical fiber / M. Bajcsy ... [et al.] -- Room-temperature atomic ensembles for quantum memory and magnetometry / K. Jensen ... [et al.] -- Components for multi-photon non-classical state preparation and measurement / G. Puentes ... [et al.] -- Quantum field state measurement and reconstruction in a cavity by quantum nondemolition photon counting / M. Brune ... [et al.] -- XUV frequency comb spectroscopy / C. Gohle ... [et al.] -- Ultrahigh-repetition-rate pulse train with absolute-phase control produced by an adiabatic raman process / M. Katsuragawa ... [et al.] -- Strongly correlated bosons and fermions in optical lattices / S. Will ... [et al.] -- Bragg spectroscopy of ultracold bose gases in optical lattices / L. Fallani ... [et al.] -- Synthetic quantum many-body systems / C. Guerlin ... [et al.] -- Ultracold Ytterbium atoms in optical lattices / S. Sugawa ... [et al.] -- Ultracold polar molecules in the rovibrational ground state / J. Deiglmayr ... [et al.] -- Polar molecules near quantum degeneracy / J. Ye and D. S. Jin -- Production of a quantum gas of rovibronic ground-state molecules in an optical lattice / J. G. Danzl ... [et al.] -- Recent progress in x-ray nonlinear optics / K. Tamasaku, K. Sawada, and T. Ishikawa -- Gas in scattering media absorption spectroscopy - laser spectroscopy in unconventional environments / S. Svanberg -- Laser spectroscopy on relativistic ion beams / S. Reinhardt ... [et al.] -- Single frequency microcavity lasers and applications / L. Xu ... [et al.].

Katori, H.; Yoneda, H.; Nakagawa, K.; Shimizu, F.

2010-02-01

65

Laser ablation and micromachining with ultrashort laser pulses  

Microsoft Academic Search

The mechanisms of ultrashort-pulse laser ablation of materials are discussed, and the differences to that of long laser pulses are emphasized. Ultrashort laser pulses offer both high laser intensity and precise laser-induced breakdown threshold with reduced laser fluence. The ablation of materials with ultrashort pulses has a very limited heat-affected volume. The advantages of ultrashort laser pulses are applied in

X. Liu; D. Du; G. Mourou

1997-01-01

66

CuBr laser ablation of titanium surface  

NASA Astrophysics Data System (ADS)

Interaction of a CuBr laser, operating at 511 nm wavelength and pulse duration of 30 ns with titanium wafers was studied. It was investigated the efficiency of laser ablation, depending on the laser fluence, on the laser beam scanning speed, and laser pulse frequency. The titanium surface modification was studied by scanning electron microscopy (SEM) and XPS (X-ray Photoelectron Spectroscopy). Nanosecond laser irradiation of Ti led to the formation of high porous granular structures consisting of agglomerated small micro- and sub microparticles.

Balchev, Ivaylo; Minkovski, Nikolay; Dimitrov, Krasimir; Atanasov, Atanas; Stefanov, Plamen

2015-01-01

67

Excimer laser ablation of polymer-clay nanocomposites  

NASA Astrophysics Data System (ADS)

The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this work. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration. The excimer laser induced surface micro/nano structure formation and modification of PS-Clay Nanocomposites at various OMMT concentrations were also investigated. Scanning electron microscopy, atomic force microscopy and Fourier Transform Infrared (FTIR) spectroscopy with attenuated total reflectance accessory were utilized to analyze the ablated surface. Results show that, in general, better dispersion of OMMT leads to less continuous surface structures and more pronounced carbonyl regions on FTIR spectra. Clay nanoparticles are exposed on ablated surfaces and affect surface structure formation after irradiation by laser. A mechanism for the formation of excimer laser induced surface structures on injection molded parts is thus proposed.

Chang, I.-Ta

68

Resonant laser ablation: Applications and mechanistic aspects  

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. Since its original description, numerous research papers and review articles have appeared on various aspects of laser 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 low-power tunable lasers to ablate and resonantly ionize selected components in the ablation plume. This process has been termed resonant laser ablation (RLA). The authors report here on aspects of RLA behavior for a number of metals, alloys and thin films. 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 and multilayers is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation is discussed.

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

1995-12-31

69

Laser Ablation of Aluminium: Drops and Voids Johannes Roth1  

E-print Network

Laser Ablation of Aluminium: Drops and Voids Johannes Roth1 , Johannes Karlin1 , Christian Ulrich2 introduction to the process of laser ablation, its simulation by the molecular dynamics method, and results be simulated which form during laser ablation. Laser ablation is a process where material is removed from

Roth, Johannes

70

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

71

Selective ablation of Copper-Indium-Diselenide solar cells monitored by laser-induced breakdown spectroscopy and classification methods  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) and two classification methods, i.e. linear correlation and artificial neural networks (ANN), are used to monitor P1, P2 and P3 scribing steps of Copper-Indium-Diselenide (CIS) solar cells. Narrow channels featuring complete removal of desired layers with minimum damage on the underlying film are expected to enhance efficiency of solar cells. The monitoring technique is intended to determine that enough material has been removed to reach the desired layer based on the analysis of plasma emission acquired during multiple pass laser scribing. When successful selective scribing is achieved, a high degree of similarity between test and reference spectra has to be identified by classification methods in order to stop the scribing procedure and avoid damaging the bottom layer. Performance of linear correlation and artificial neural networks is compared and evaluated for two spectral bandwidths. By using experimentally determined combinations of classifier and analyzed spectral band for each step, classification performance achieves errors of 7, 1 and 4% for steps P1, P2 and P3, respectively. The feasibility of using plasma emission for the supervision of processing steps of solar cell manufacturing is demonstrated. This method has the potential to be implemented as an online monitoring procedure assisting the production of solar cells.

Diego-Vallejo, David; Ashkenasi, David; Lemke, Andreas; Eichler, Hans Joachim

2013-09-01

72

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

73

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

74

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

75

Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency  

NASA Astrophysics Data System (ADS)

The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3/J when the laser fluence was set at 6.51 J/cm2. For enamel, the maximum ablation efficiency was 0.009 mm3/J at a fluence of 7.59 J/cm2. Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value.

Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

2015-02-01

76

Femtosecond laser ablation of the stapes  

PubMed Central

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.

2014-01-01

77

PROCEEDINGS288 -;-m__c_ LASER ABLATION  

E-print Network

TAIP CONFERENCE PROCEEDINGS288 -;-m__c_ LASER ABLATION: MECHANISMSAND ..'m . . APPLICATIONS States of America. #12;Extending Laser Fusion Concepts Into the Lower Power ( 5 1 GW Heights, NY 10598 USA Claude PHIPPS Chemical and Laser Science Div., Los Alamos National Lab. Los Alamos

Vertes, Akos

78

Pulsed laser ablation of dental calculus in the near ultraviolet.  

PubMed

Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ?8??J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5??J/cm2 but has not been observed above this fluence. PMID:24549442

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

2014-02-01

79

Retained Foreign Body After Laser Ablation  

PubMed Central

Laser ablation for varicose veins is a common practice, and postoperative complications may happen. A retained foreign body could be left accidently in the treated leg. It is rarely reported in literature. We herein describe two cases of retained foreign body during the laser ablation for varicose veins. One patient with varicose veins received laser therapy 5 years earlier, and had experienced discomfort and pain. After investigation, an overlooked sheath fragment was removed surgically from the leg. Another patient with varicose veins had discomfort after laser ablation for 8 days, and has been asymptomatic after the removal of the retained foreign body in the leg. The essential preventive approach include to pinpoint the site of the tip of fiberoptic laser fiber and pull 1 to 2 cm of the sheath out of the patient, then withdrawal the fiberoptic fiber and sheath simultaneously. A white flash light in the trunk of the fiberoptic laser fiber is an important warning signal of an erroneous manipulation during the operation. The surgeon should routinely check the intact sheath and fiberoptic fiber after laser ablation. In conclusion, retained foreign body can be prevented by following some practical tips during laser ablation. PMID:23294067

Ren, Shiyan; Liu, Peng; Wang, Wei; Yang, Yuguan

2012-01-01

80

Dual beam optical system for pulsed laser ablation film deposition  

DOEpatents

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

Mashburn, D.N.

1996-09-24

81

Dual beam optical system for pulsed laser ablation film deposition  

DOEpatents

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target.

Mashburn, Douglas N. (Knoxville, TN)

1996-01-01

82

Effects of Laser Wavelength on Ablator Testing  

NASA Technical Reports Server (NTRS)

Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

White, Susan M.

2014-01-01

83

Analytical procedure for characterization of medieval wall-paintings by X-ray fluorescence spectrometry, laser ablation inductively coupled plasma mass spectrometry and Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Analytical procedure for the comprehensive chemical characterization of samples from medieval Nubian wall-paintings by means of portable X-ray fluorescence (pXRF), laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and Raman spectroscopy (RS) was proposed in this work. The procedure was used for elemental and molecular investigations of samples from archeological excavations in Nubia (modern southern Egypt and northern Sudan). Numerous remains of churches with painted decorations dated back to the 7th-14th century were excavated in the region of medieval kingdoms of Nubia but many aspects of this art and its technology are still unknown. Samples from the selected archeological sites (Faras, Old Dongola and Banganarti) were analyzed in the form of transfers (n = 26), small fragments collected during the excavations (n = 35) and cross sections (n = 15). XRF was used to collect data about elemental composition, LA-ICPMS allowed mapping of selected elements, while RS was used to get the molecular information about the samples. The preliminary results indicated the usefulness of the proposed analytical procedure for distinguishing the substances, from both the surface and sub-surface domains of the wall-paintings. The possibility to identify raw materials from the wall-paintings will be used in the further systematic, archeometric studies devoted to the detailed comparison of various historic Nubian centers.

Syta, Olga; Rozum, Karol; Choi?ska, Marta; Zieli?ska, Dobrochna; ?ukowska, Gra?yna Zofia; Kijowska, Agnieszka; Wagner, Barbara

2014-11-01

84

Basic ablation phenomena during laser thrombolysis  

NASA Astrophysics Data System (ADS)

This paper presents studies of microsecond ablation phenomena that take place during laser thrombolysis. The main goals were to optimize laser parameters for efficient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate for maximum material removal. The minimum radiant exposures to achieve ablation at any wavelength were measured. The results suggest that most visible wavelengths were equally efficient at removing material at radiant exposures above threshold. Ablation was initiated at surface temperatures just above 100 degrees Celsius. A vapor bubble was formed during ablation. Less than 5% of the total pulse energy is coupled into the bubble energy. A large part of the delivered energy is unaccounted for and is likely released partly as acoustic transients from the vapor expansion and partly wasted as heat. The current laser and delivery systems may not be able to completely remove large clot burden that is sometimes encountered in heart attacks. However, laser thrombolysis may emerge as a favored treatment for strokes where the occlusion is generally smaller and rapid recanalization is of paramount importance. A final hypothesis is that laser thrombolysis should be done at radiant exposures close to threshold to minimize any damaging effects of the bubble dynamics on the vessel wall.

Sathyam, Ujwal S.; Shearin, Alan; Prahl, Scott A.

1997-05-01

85

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

86

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

87

Improved laser ablation model for asteroid deflection  

NASA Astrophysics Data System (ADS)

This paper presents an improved laser ablation model and compares the performance - momentum coupling and deflection system mass - of laser ablation against contactless deflection methods based on ion-propulsion. The deflection of an asteroid through laser ablation is achieved by illuminating the surface of the asteroid with high intensity laser light. The absorbed energy induces the sublimation of the surface material and the generation of a plume of gas and ejecta. Similar to a rocket engine, the flow of expelled material produces a continuous and controllable thrust that could be used to modify the trajectory and tumbling motion of the asteroid. Recent results gained from a series of laser ablation experiments were used to improve the sublimation and deflection models. In each experiment a terrestrial olivine sample was ablated, under vacuum, with a 90 W continuous wave laser. The paper presents a model that better fits the outcomes of the experimental campaign, in particular in terms of mass flow rate and spot temperature.

Vasile, Massimiliano; Gibbings, Alison; Watson, Ian; Hopkins, John-Mark

2014-10-01

88

Molecular dynamics simulation of ultrafast laser ablation of fused silica  

E-print Network

Molecular dynamics simulation of ultrafast laser ablation of fused silica C Cheng, A Q Wu and X Xu-mail: xxu@ecn.purdue.edu Abstract. Ultrafast laser ablation of fused silica is studied using molecular that ultrafast laser is capable of microscale fabrication of glass. The process of "laser ablation

Xu, Xianfan

89

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

90

Polymers designed for laser ablation-inuence of photochemical properties  

E-print Network

Polymers designed for laser ablation-in¯uence of photochemical properties T. Lipperta,* , J applications for lasers have been developed. Nowadays, laser ablation is used e.g. in medicine [2], art conservation [3], and thin ®lm deposition [4]. Laser ablation of polymers was ®rst reported in 1982 [5

Dickinson, J. Thomas

91

Diagnostics and applications of ultrashort pulsed laser ablation /  

E-print Network

Diagnostics and applications of ultrashort pulsed laser ablation / deposition 694220044 #12 by pulsed laser ablation focused on the quality of thin film by pulsed laser deposition. Direct measurements of plasma plume in pulsed laser ablation. In this work, we have designed and constructed Eizel lens and time

92

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

93

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

94

Langmuir probe study of laser ablation plume dynamics  

Microsoft Academic Search

For many applications of pulsed laser ablation it is necessary to have an understanding of the expansion dynamics of the ablation plume both in vacuum and in low pressure gases. Knowledge of the ablation plume hydrodynamics can also contribute to the understanding of the laser ablation process. In this paper we will consider some of the existing theoretical models of

James G. Lunney; Brendan Doggett

2006-01-01

95

Femtosecond laser ablation properties of borosilicate glass  

SciTech Connect

We study the femtosecond laser ablation properties of borosilicate glass using atomic force microscopy and laser pulses of 200 fs duration, centered at 780 nm wavelength. We show that both single-shot and multishot ablation threshold fluences can be determined by studying the diameter and the depth of single-shot ablated craters. The linear relationship between the square of the crater diameter and the logarithm of the laser fluence in the form of D{sup 2}=2w{sub 0}{sup 2}ln(F{sub 0}/F{sub th}{sup N=1}) provides the single-shot ablation threshold, F{sub th}{sup N=1}, whereas the linear relationship between the ablation depth and the logarithm of laser fluence in the form of h{sub a}={alpha}{sub eff}{sup -1}ln(F{sub 0}/F{sub th}{sup N>1}) provides the multishot ablation threshold, F{sub th}{sup N>1}. The results depict a multishot ablation threshold of {approx_equal}1.7 J/cm{sup 2} independent of the atmospheric conditions. The slopes of the linear fits also provide a precise estimate of the beam radius at the surface, w{sub 0}{approx_equal}5.9 {mu}m, and the ''effective optical penetration depth,'' {alpha}{sub eff}{sup -1}{approx_equal}238 nm in air. The method is systematic, provides results that are consistent with the literature, and eliminates uncertainties because of instrument sensitivities. We also show that threshold measurement based on the extrapolation of volume to zero, a method used often in previous studies, is somewhat questionable. Finally, the measured dimensions of ablated craters reveal that the ablation volume per unit input energy is about 1.3-1.5 {mu}m{sup 3}/{mu}J at an intermediate fluence regime of 10ablation efficiency when compared to the ablation of glass with nanosecond ultraviolet laser pulses.

Ben-Yakar, Adela; Byer, Robert L. [Mechanical Engineering Department, University of Texas at Austin, Austin, Texas 78712 (United States); Applied Physics Department, Ginzton Lab, Stanford University, Stanford, California 94305 (United States); Applied Physics Department, Ginzton Lab, Stanford University, Stanford, California 94305 (United States)

2004-11-01

96

Surface Decontamination Using Laser Ablation Process - 12032  

SciTech Connect

A new decontamination method has been investigated and used during two demonstration stages by the Clean-Up Business Unit of AREVA. This new method is based on the use of a Laser beam to remove the contaminants present on a base metal surface. In this paper will be presented the type of Laser used during those tests but also information regarding the efficiency obtained on non-contaminated (simulated contamination) and contaminated samples (from the CEA and La Hague facilities). Regarding the contaminated samples, in the first case, the contamination was a quite thick oxide layer. In the second case, most of the contamination was trapped in dust and thin grease layer. Some information such as scanning electron microscopy (SEM), X-Ray scattering spectroscopy and decontamination factors (DF) will be provided in this paper. Laser technology appears to be an interesting one for the future of the D and D applications. As shown in this paper, the results in terms of efficiency are really promising and in many cases, higher than those obtained with conventional techniques. One of the most important advantages is that all those results have been obtained with no generation of secondary wastes such as abrasives, chemicals, or disks... Moreover, as mentioned in introduction, the Laser ablation process can be defined as a 'dry' process. This technology does not produce any liquid waste (as it can be the case with chemical process or HP water process...). Finally, the addition of a vacuum system allows to trap the contamination onto filters and thus avoiding any dissemination in the room where the process takes place. The next step is going to be a commercial use in 2012 in one of the La Hague buildings. (authors)

Moggia, Fabrice; Lecardonnel, Xavier; Damerval, Frederique [AREVA, Back End Business Group, Clean Up Business Unit (France)

2012-07-01

97

Laser Ablation-ICP-MS Analysis of Dissected Tissue: A  

E-print Network

Laser Ablation-ICP-MS Analysis of Dissected Tissue: A Conservation-Minded Approach to Assessing the animal. In this paper, we report on the application of laser ablation-ICP-MS (LA- ICP-MS) for sampling

Hopkins, William A.

98

Infrared Laser Ablation Atmospheric Pressure Photoionization Mass Spectrometry  

E-print Network

Infrared Laser Ablation Atmospheric Pressure Photoionization Mass Spectrometry Anu Vaikkinen, Washington, DC 20052, United States *S Supporting Information ABSTRACT: In this paper we introduce laser ablation atmo- spheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass

Vertes, Akos

99

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

100

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

101

Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation  

SciTech Connect

Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

Kim, B.M.; Feit, M.D.; Rubenchick, A.M.; Gold, D.M.; Darrown, C.B.; Da Silva, L.B.

1998-01-01

102

Generation of Core/shell Nanoparticles with Laser Ablation  

E-print Network

Two types of core/shell nanoparticles (CS-NPs) generation based on laser ablation are developed in this study, namely, double pulse laser ablation and laser ablation in colloidal solutions. In addition to the study of the generation mechanism of CS...

Jo, Young Kyong

2012-10-19

103

Femtosecond laser ablation for controlling micro and nano structuration  

E-print Network

Femtosecond laser ablation for controlling micro and nano structuration Dissertation zur Erlangung and sub micrometer scales. Laser ablation, which has the great advantage of precise material removal micrométriques et sub micrométriques. L'ablation laser, qui a le grand avantage d'un enlèvement de matière très

Paris-Sud XI, Université de

104

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires  

E-print Network

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires Wensheng Shi Kong, SAR, China Silicon carbide (SiC) nanowires were synthesized at 900°C by the laser ablation. Introduction THE laser ablation technique has been widely used for nano- struc tural processing because of its

Zheng, Yufeng

105

FEATURE ARTICLE A Microscopic View of Laser Ablation  

E-print Network

FEATURE ARTICLE A Microscopic View of Laser Ablation Leonid V. Zhigilei, Prasad B. S. Kodali applications of the breathing sphere model for molecular dynamics simulations of laser ablation of organic for microscopic simulations of laser ablation. I. Introduction The use of microscopic computer simulations

Zhigilei, Leonid V.

106

Femtosecond Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics  

E-print Network

Femtosecond Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics A thesis presented Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics Eric Mazur Brian R. Tull Abstract, with intense femtosecond laser pulses at energy densities exceeding the threshold for ablation (the macroscopic

Mazur, Eric

107

ORIGINAL ARTICLE Ultrashort pulsed laser ablation and stripping  

E-print Network

ORIGINAL ARTICLE Ultrashort pulsed laser ablation and stripping of freeze-dried dermis Huan Huang # Springer-Verlag London Ltd 2009 Abstract Plasma-mediated laser ablation and dissection of freeze was generally within 10 µm with 100 continuously repeated line scans. Ultrashort pulsed laser ablation

Guo, Zhixiong "James"

108

Femtosecond laser near-field ablation from gold nanoparticles  

E-print Network

LETTERS Femtosecond laser near-field ablation from gold nanoparticles ANTON PLECH1 *, VASSILIOS.plech@uni-konstanz.de Published online: 18 December 2005; doi:10.1038/nphys191 S hort-pulse laser ablation is promising owing to the low threshold for material removal from surfaces. In the laser-ablation process, solid material

Loss, Daniel

109

Plume dynamics and shielding by the ablation plume during Er:YAG laser ablation  

Microsoft Academic Search

Free-running Er:YAG lasers are used for precise tissue abla- tion in various clinical applications. The ablated material is ejected into the direction perpendicular to the tissue surface. We investigated the influence of shielding by the ablation plume on the energy depo- sition into an irradiated sample because it influences the ablation dy- namics and the amount of material ablated. The

Kester Nahen; Alfred Vogel

2002-01-01

110

Multidiagnostic analysis of ultrafast laser ablation of metals with pulse pair irradiation  

SciTech Connect

Copper targets are irradiated in the ablation regime by pairs of equal, time-delayed collinear laser pulses separated on a timescale going from {approx_equal}2 ps to {approx_equal}2 ns. The ablation plume is characterized by ion probe diagnostic, fast imaging, and temporally and spatially resolved optical emission spectroscopy. The variation in the ablation efficiency with the delay between the pulses is analyzed by measuring the ablation crater profile with a contact profilometer. The second laser pulse modifies the characteristics of the plasma plume produced by the first pulse and the ablation efficiency. The different mechanisms involved in double pulse ultrafast laser ablation are identified and discussed. The experimental findings are interpreted in the frame of a simple model of the interaction of the second pulse with the nascent ablation plume produced by the first pulse. This model yields consistent and quantitative agreement with the experimental findings predicting the observed experimental trends of the ablation depth reduction and ion yield increase with the delay between the pulses, as well as the characteristic timescale of the observed changes. The possibility of controlling the characteristics of the plumes produced during ultrafast laser ablation via an efficient coupling of the energy of the second pulse to the various ablation components produced by the first pulse is of particular interest in ultrafast pulsed laser deposition and microprobe analyses of materials.

Amoruso, S.; Bruzzese, R. [Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Wang, X. [CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); O'Connell, G.; Lunney, J. G. [School of Physics, Trinity College-Dublin, Dublin 2 (Ireland)

2010-12-01

111

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. PMID:22191028

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

2011-01-01

112

Short-pulse laser ablation of solid targets  

Microsoft Academic Search

Laser ablation of solid targets by Ti:sapphire laser radiation is studied. The solid targets are irradiated by 0.2–5000 ps laser pulses in the intensity range of 109 ? 5 × 1016Wcm2. Dependences of the ablation depth on the laser pulse energy and pulse duration are discussed. Advantages of sub-picosecond laser radiation for precise material processing are demonstrated.

Carsten Momma; Boris N Chichkov; Stefan Nolte; Ferdinand von Alvensleben; Andreas Tünnermann; Herbert Welling; Bernd Wellegehausen

1996-01-01

113

Zirconium carbide thin films deposited by pulsed laser ablation  

NASA Astrophysics Data System (ADS)

A study of the laser ablation and deposition of zirconium carbide has been carried out in our laboratory. The target has been vaporised by a doubled Nd:YAG laser and the ablation plume has been characterised by time-of-flight mass spectrometry, emission spectroscopy and ultrafast imaging performed by an Intensified Coupled Charge Device (ICCD). The results show a single ablation mechanism in the whole range of laser fluence used in the experiments (0.5-15 J/cm2) and this is quite different from the case of TiC. The gas phase data are confirmed by the analysis of the films deposited on oriented silicon. In fact, by X-ray diffraction and subsequent XPS analysis, their composition is fluence independent leading to films with constant characteristics on a large range of experimental conditions. The difference between ZrC and TiC ablation mechanisms may be explained in terms of chemical-physical properties and thermodynamic considerations which can also clarify the gas phase composition.

D'Alessio, L.; Santagata, A.; Teghil, R.; Zaccagnino, M.; Zaccardo, I.; Marotta, V.; Ferro, D.; De Maria, G.

2000-12-01

114

Modeling topology formation during laser ablation  

NASA Astrophysics Data System (ADS)

Micromachining high aspect-ratio structures can be accomplished through ablation of surfaces with high-powered lasers. Industrial manufacturers now use these methods to form complex and regular surfaces at the 10-1000 ?m feature size range. Despite its increasingly wide acceptance on the manufacturing floor, the underlying photochemistry of the ablation mechanism, and hence the dynamics of the machining process, is still a question of considerable debate. We have constructed a computer model to investigate and predict the topological formation of ablated structures. Qualitative as well as quantitative agreement with excimer-laser machined polyimide substrates has been demonstrated. This model provides insights into the drilling process for high-aspect-ratio holes.

Hodapp, T. W.; Fleming, P. R.

1998-07-01

115

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

116

Numerical simulation of laser ablation with cavity reflections  

Microsoft Academic Search

A self-consistent ablation, heat-conduction, and radiation-transport model is required to model laser ablation of reflective targets properly. In laser-ablation experiments on metal-loaded carbon targets, the shiny metallic crater formed by the beam can act as a focusing cavity. This phenomenon results in highly augmented ablation rates in small-spot laser tests in which the aspect ratio of the cavity (depth\\/spot diameter)

A. W. Bailey; A. Modak

1989-01-01

117

Pulsed holmium laser ablation of cardiac valves  

Microsoft Academic Search

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

Lothar Lilge; Wolfgang Radtke; Norman S. Nishioka

1989-01-01

118

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...

119

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

120

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

121

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

122

Laser-ablation processes (Invited Paper)  

NASA Astrophysics Data System (ADS)

The physical mechanisms associated with ablation of matter by laser irradiation are quite different in different regions of parameter space. The important parameters are the laser wavelength; the laser flux versus time, position, and angle of incidence at the target; and the target properties as well as the properties of the laser-transport medium adjacent to the irradiated target surface. Important target properties include surface contour, laser reflectivity and absorption depth, thermal diffusively, vaporization energy, Gruneisen coefficient, spall strength, ionization energies and plasma opacity versus temperature and density. As the flux increases, the process becomes less dependent on most of these target properties. Depending on the values of these various parameters, at relatively low fluxes targets can be vaporized and these vapors can be transparent to the laser beam. If a transparent liquid or solid transport medium exists in front of the vaporized target material, then a complicated contained- vaporization process takes place and the work done on the target by the vapors can be several orders of magnitude larger than with a gas or vacuum transport medium; the degree of work enhancement can depend strongly on the vapor condensability and condensed matter thermal conductivity. For short-pulselength irradiations of semi-transparent targets with a low- acoustic-impedance-laser-transport medium adjacent to the target, ablation needs to be a vacuum in order for the beam to be able to propagate to the target. For targets in a vacuum exposed to fluxes of this order (and considerably higher) and for long pulselengths, most of the laser energy will be absorbed (before reaching the critical surface) by inverse bremsstrahlung in material blown off from the target; at higher fluxes, the beam will be stopped at the critical surface producing localized absorption along with much higher energy densities and non-thermal equilibrium behavior. When the combination of pulselength, beam diameter, flux and target material are such that the blowoff becomes opaque to the laser and also the blowoff can traverse many beam diameters during the pulselength, then a complicated radiation-hydrodynamic process is involved with strong feedback between blowoff hydrodynamic expansion, laser absorption, radiation transport, and target ablation by plasma reradiation. In this paper the various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 1013 W/cm2, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, Ronald S.

1992-06-01

123

Investigations of Basic Ablation Phenomena During Laser Thrombolysis  

Microsoft Academic Search

This paper presents studies of microsecond ablation phenomena that take place during during laser thrombolysis. The main goals were to optimize laser parameters for e-cient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate

Ujwal S. Sathyam; Alan Shearin; Scott A. Prahl

124

Novel method for measuring excimer laser ablation thresholds of polymers  

NASA Astrophysics Data System (ADS)

Conical features produced on excimer laser ablated polymers are shown to provide a sensitive technique for determining ablation thresholds. This has been applied to polyimide, polyethylene terephthalate, polyethylene, and nylon 66 ablated using the 157 nm vacuum ultraviolet F2 laser.

Dyer, P. E.; Jenkins, S. D.; Sidhu, J.

1988-05-01

125

Ripple formation at laser ablation of chromium thin film  

Microsoft Academic Search

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

Kestutis Regelskis; Gediminas Raciukaitis; Paulius Gecys

2007-01-01

126

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

127

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

128

Nanosecond Infrared Laser for Tissue Ablation  

NASA Astrophysics Data System (ADS)

The Mark-III Free-Electron Laser (FEL), operating at the 6.45?m wavelength, has been used successfully in human surgery. Due to the FEL's size and cost, there has been interest in the development of a compact, inexpensive infrared laser for human surgical applications. We have investigated the role of the FEL superpulse, leading to the prediction that nanosecond pulses can satisfy the dynamic criteria for tissue ablation. We have developed a laser based on difference frequency mixing and stimulated Raman scattering with four stages of frequency conversion, emitting at a wavelength of 6.45?m with 3-5ns pulse duration, pulse energies of up to 2mJ, and a pulse repetition rate of 3MHz. The laser system successfully ablated tissue, where collateral thermal damage was limited to several microns. In the future, it will be necessary to increase the pulse repetition rate to achieve an ablation rate acceptable for human surgery. We acknowledge the grant support: R43 RR018435, N00014-99-1-0891, and F49620-00-1-0370.

Edwards, G. S.; Pearlstein, R. D.; Copeland, M. L.; Hutson, M. S.; Latone, K.; Spiro, A.; Pasmanik, G.

2007-03-01

129

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

130

Subcellular analysis by laser ablation electrospray ionization mass spectrometry  

DOEpatents

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

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

2014-12-02

131

Z .Applied Surface Science 127129 1998 111116 Explosive phase transformation in excimer laser ablation  

E-print Network

, IN 47907, USA Abstract This work investigated phase change mechanisms during excimer laser ablation and the velocity of the laser-ablated plume, the ablation rate per pulse, light scattering from the laser-ablated particles and the size of the laser-ablated particles, in the laser fluence range y2 y2 Z y2 y2 .between 2

Xu, Xianfan

132

Nanochemical effects in femtosecond laser ablation of metals  

SciTech Connect

We study chemical energy released from the oxidation of aluminum in multipulse femtosecond laser ablation in air and oxygen. Our study shows that the released chemical energy amounts to about 13% of the incident laser energy, and about 50% of the ablated material is oxidized. The ablated material mass per laser pulse is measured to be on the nanogram scale. Our study indicates that femtosecond laser ablation is capable of inducing nanochemical reactions since the femtosecond laser pulse can controllably produce nanoparticles, clusters, and atoms from a solid target.

Vorobyev, A. Y.; Guo, Chunlei [The Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)] [The Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2013-02-18

133

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

134

Ultraviolet-laser ablation of skin  

SciTech Connect

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 began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.

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

1985-05-01

135

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

136

Barium ferrite films grown by laser ablation  

Microsoft Academic Search

Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al2O3 single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe12O19 phase, very well oriented with (001) texture, and exhibit a large perpendicular magnetic anisotropy. In this case, the microstructure and the anisotropy orientation are not influenced by variation

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

1998-01-01

137

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 R.

1991-07-01

138

Solar cell contact formation using laser ablation  

DOEpatents

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

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

2014-07-22

139

Solar cell contact formation using laser ablation  

DOEpatents

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

140

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

141

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

142

Growth modes of ZnO nanostructures from laser ablation  

SciTech Connect

ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

Amarilio-Burshtein, I. [Faculty of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Tamir, S. [Institute of Metals, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Lifshitz, Y. [Faculty of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

2010-03-08

143

Atomistic Modeling of Short Pulse Laser Ablation of Metals: Connections between Melting, Spallation, and Phase Explosion  

E-print Network

Atomistic Modeling of Short Pulse Laser Ablation of Metals: Connections between Melting, Spallation. Introduction Short pulse laser ablation is the phenomenon that is actively usedinabroadrangeofapplications for small satellites.4 The mechanisms responsible for the material removal in laser ablation include

Zhigilei, Leonid V.

144

Computational model for multiscale simulation of laser ablation Leonid V. Zhigilei  

E-print Network

Computational model for multiscale simulation of laser ablation Leonid V. Zhigilei Department computational approach that combines different methods to study laser ablation phenomenon is presented of laser ablation, a combined MD - finite element method (FEM) approach for simulation of propagation

Zhigilei, Leonid V.

145

Laser-Induced Breakdown Spectroscopy---Capabilities and Limitations  

Microsoft Academic Search

During the past decade there has been intense activity in the field of laser-induced breakdown spectroscopy (LIBS). This activity includes studies of laser ablation and properties of the laser spark, the development of methods to enhance LIBS detection capabilities, and the application of LIBS to specific analysis needs. The unique capabilities of LIBS make it particularly suited for applications that

David A. Cremers; Rosemarie C. Chinni

2009-01-01

146

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

147

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

148

Ultrashort-pulse laser ablation of indium phosphide in air  

Microsoft Academic Search

.   Ablation of indium phosphide wafers in air was performed with low repetition rate ultrashort laser pulses (130 fs, 10 Hz)\\u000a of 800 nm wavelength. The relationships between the dimensions of the craters and the ablation parameters were analyzed. The\\u000a ablation threshold fluence depends on the number of pulses applied to the same spot. The single-pulse ablation threshold value\\u000a was estimated to be

J. Bonse; J. M. Wrobel; J. Krüger; W. Kautek

2001-01-01

149

Effect of ambient air on femtosecond laser ablation of highly oriented pyrolytic graphite.  

PubMed

Highly oriented pyrolytic graphite is ablated by femtosecond laser in air and vacuum, respectively. The morphologies and material components of the ablated target surface are examined by scanning electron microscopy and micro-Raman spectroscopy. For laser fluence no less than 0.5??J/cm(2), the laser-induced periodic surface grooves formed in air are found to be much less clearer than those formed in vacuum; beneath the amorphous carbon debris, the surface ablated in air is composed of nanocrystalline graphite, but in vacuum it retains the ordered graphite structure. The thermal relaxation of the ablated target induced by air-assisted heat transfer is considered to be the main reason for the differences. The transportation of air molecules along the surface, the classical size effect of heat conduction and high solid-air heat transfer coefficient in nanoscale enhance the air-assisted heat transfer. PMID:25531597

Feng, Peipei; Zhang, Nan; Wu, Han; Zhu, Xiaonong

2015-01-01

150

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

151

Endovenous laser ablation for the treatment of varicose veins.  

PubMed

Lower extremity venous insufficiency secondary to saphenous vein insufficiency is a common medical condition that decreases a patient's quality of life. Traditionally treated with high ligation and stripping, minimally invasive procedures using endovenous thermal ablation techniques, such as endovenous laser ablation, have evolved. The use of detailed imaging and advances in the understanding of the anatomy of truncal vein insufficiency are important for performing the endovenous laser ablation procedure successfully. Endovenous laser ablation eliminates reflux with less morbidity, faster recovery, and improved cosmetic results with high patient satisfaction. As such, it has become the preferred treatment method for varicose veins since it was first introduced a decade ago. PMID:22205579

O?uzkurt, Levent

2012-01-01

152

Arterial false aneurysm in the groin following endovenous laser ablation.  

PubMed

Endovenous laser ablation is a minimally invasive catheter-based procedure for the treatment of varicose veins. The procedure involves injecting tumescent anaesthesia around the catheterised truncal vein, before thermal ablation by the laser. We report a case of a false aneurysm arising from a branch of the inferior epigastric artery, following endovenous laser ablation. The false aneurysm was thought to be caused by injury to the artery by the needle used to inject the tumescent anaesthesia. Although a rare complication, newer tumescentless techniques such as mechanicochemical ablation and cyanoacrylate glue would prevent such a complication. PMID:24255091

Ostler, Alexandra E; Holdstock, Judy M; Harrison, Charmaine C; Whiteley, Mark S

2015-04-01

153

Ripple formation in the chromium thin film during laser ablation  

Microsoft Academic Search

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

Kestutis Regelskis; Gediminas Raciukaitis; Mindaugas Gedvilas

2007-01-01

154

Metal Ablation with Short and Ultrashort Laser Pulses  

Microsoft Academic Search

In laser microstructuring there is a general conflict between precision and efficiency. Short pulsed micro- and nanosecond systems generally allow high ablation rates. Yet, thermal damage of the workpiece cannot be avoided completely. Ultrafast picoand femtosecond systems allow a higher precision, yet at lower ablation efficiency. This on the one hand can be attributed to the generally lower medium laser

Karl-Heinz Leitz; Benjamin Redlingshöfer; Yvonne Reg; Andreas Otto; Michael Schmidt

2011-01-01

155

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

156

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

157

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

158

Laser ablation loading of a surface-electrode ion trap  

E-print Network

We demonstrate loading by laser ablation of $^{88}$Sr$^+$ ions into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful ($\\gtrsim$ 500 meV).

David R. Leibrandt; Robert J. Clark; Jaroslaw Labaziewicz; Paul Antohi; Waseem Bakr; Kenneth R. Brown; Isaac L. Chuang

2007-06-22

159

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

160

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

161

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

162

Deposition of polyimide precursor by resonant infrared laser ablation  

NASA Astrophysics Data System (ADS)

We report the successful deposition of a polyimide precursor using resonant infrared laser ablation (RIR-LA). A solution of poly(amic acid) (PAA) dissolved in N-methyl-2-pyrrolidinone (NMP), the melt processable precursor to polyimide, was frozen in liquid nitrogen for use as an ablation target in a high-vacuum chamber. Fourier transform infrared spectroscopy was used to determine that the local chemical structure remained unaltered. Gel permeation chromatography demonstrated that the transferred PAA retained its molecular weight, showing that RIR-LA is able to transfer the polymer intact, with no detectable chain fragmentation. These results are in stark contrast to UV-processing which degrades the polymer. After deposition the PAA may be removed with a suitable solvent; however, once the material has undergone cyclodehydration it forms an impenetrable three-dimensional network associated with thermosetting polymers. The transfer of uncured PAA precursor supports the hypothesis that RIR-LA is intrinsically a low temperature process, because the PAA is transferred without reaching the curing temperature. The RIR-LA also effectively removes the solvent NMP from the PAA, during both the ablation and deposition phases; this is a necessary step in generating PI films.

Dygert, N. L.; Gies, A. P.; Schriver, K. E.; Haglund, R. F., Jr.

2007-11-01

163

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

164

Band-pass filters for THz spectral range fabricated by laser ablation  

NASA Astrophysics Data System (ADS)

The terahertz resonant metal-mesh filters were fabricated using the laser direct writing technique. UV picosecond laser was employed to cut matrixes of cross-shaped holes in stainless steel foil and molybdenum layer deposited on polyimide substrate. Different laser processing strategies were developed: holes were cut through in the metal foil and the molybdenum film was removed from the polyimide by laser ablation. Band-pass filters with a different center frequency were designed and fabricated. The regular shape, smoothness of edges and sharpness of corners of the cross-shaped holes in the metal were the main attributes for quality assessment for the laser ablation process. Spectral characteristics of the filters, determined by the mesh period, cross-arm length, and its width, were investigated by terahertz time-domain spectroscopy and conventional space-domain Fourier transform spectroscopy. Experimental data were supported by three-dimensional finite-difference time-domain simulations.

Voisiat, B.; Bi?i?nas, A.; Kašalynas, I.; Ra?iukaitis, G.

2011-09-01

165

Plume collimation for laser ablation electrospray ionization mass spectrometry  

DOEpatents

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

Vertes, Akos; Stolee, Jessica A.

2014-09-09

166

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

167

Medieval glass from the Cathedral in Paderborn: a comparative study using X-ray absorption spectroscopy, X-ray fluorescence, and inductively coupled laser ablation mass spectrometry  

NASA Astrophysics Data System (ADS)

We have investigated four stained glass samples recovered from an archaeological excavation at the Cathedral in Paderborn (Germany) between 1978 and 1980. On two of the samples there are parts of paintings. Concentrations of major elements were determined using two independent techniques: LA-ICP-MS (a UV laser ablation microsampler combined with an inductively coupled plasma mass spectrometer) and synchrotron radiation X-ray excited X-ray fluorescence (SR-XRF). The SR-XRF data were quantified by using the program package PyMCA developed by the software group of the ESRF in Grenoble. Significant differences were found between the concentrations determined by the two techniques that can be explained by concentration gradients near the surface of the glasses caused, for example, by corrosion/leaching processes and the different surface sensitivities of the applied techniques. For several of the elements that were detected in the glass and in the colour pigments used for the paintings X-ray absorption near edge structure (XANES) spectra were recorded in order to determine the chemical speciation of the elements of interest. As was expected, most elements in the glass were found as oxides in their most stable form. Two notable exceptions were observed: titanium was not found as rutile—the most stable form of TiO2—but in the form of anatase, and lead was not found in one defined chemical state but as a complex mixture of oxide, sulphate, and other compounds.

Hormes, J.; Roy, A.; Bovenkamp, G.-L.; Simon, K.; Kim, C.-Y.; Börste, N.; Gai, S.

2013-04-01

168

Optimization of laser ablation and signal enhancement for nuclear material detection  

NASA Astrophysics Data System (ADS)

The purpose of the study was to investigate the role of different laser parameters on laser ablation properties, specifically in terms of performance in laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Many laser parameters affect laser ablation performance, including laser wavelength and pulse duration, as presented here. It was previously thought that wavelength plays no role in ultrafast laser ablation; however, it was found that shorter wavelength yields lower detection limits and ablation threshold. Our results also demonstrate that in the laser pulse duration range of 40 fs to 1 ps, negligible differences occur in signal intensity, elemental ratios, and detection limits. U/Pb and U/Th ratios, which were examined to ensure limited fractionation, give comparable results at all pulse widths investigated. A parametric study of plasma hydrodynamics will also be presented. An elemental detection method combining laser induced breakdown spectroscopy (LIBS) and LA-ICP-MS is developed, with plasma density and temperature actively monitored to investigate how plasma conditions affect ICP-MS results. The combination of these two methods will help to mitigate the disadvantages of using each technique individually. Depth and spatial analysis of thin films was performed using femtosecond LA-ICP-MS to study the stoichiometric distribution of the films. The thin film-substrate interface was probed, revealing intermixing between the two layers. Lastly, the persistence of uranium emission in laser-produced plasmas (LPP) was investigated under various Ar ambient environments. Plasma collisional effects and confinement play a very important role in emission intensity and persistence, yielding important results for future LIBS and laser absorption spectroscopy (LAS) research. Lastly, suggestions for future work are made, which include extension of the LIBS and LA-ICP-MS systems to other samples like oxide thin films and spatial and depth profiling of known heterogeneous materials.

LaHaye, Nicole L.

169

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

170

Nanosecond Pulsed Laser Ablation of Copper in Supercritical Carbon Dioxide  

NASA Astrophysics Data System (ADS)

A copper target in supercritical CO2 was ablated using nanosecond Nd:YAG laser pulses for a variety of different laser irradiation times, temperatures and pressures. The irradiated copper surface was evaluated by scanning electron microscopy and laser microscopy. Experiments were also conducted in atmospheric conditions with air and liquid hexane to evaluate the environmental dependence of ablation. The results demonstrated that laser ablation of a metal target in high pressure was affected by the pressure and the surrounding environment. An ablation crater with a depth of 6.9 µm was produced by ablating at a temperature of 40 °C, a pressure of 25 MPa, and an irradiation time of 500 s.

Kuwahara, Yutaka; Saito, Takashi; Haba, Minori; Iwanaga, Tomoki; Sasaki, Mitsuru; Goto, Motonobu

2009-04-01

171

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

NASA Astrophysics Data System (ADS)

The variation in surface morphology and plasma parameters of laser irradiated tungsten has been investigated as a function of irradiance. For this purpose, Nd:YAG laser (1064 nm, 10 ns, 10 Hz) is employed. Tungsten targets were exposed to various laser irradiances ranging from 6 to 50 GW/cm2 under ambient environment of argon at a pressure of 20 Torr. Scanning electron microscope analysis has been performed to analyze the surface modification of irradiated tungsten. It revealed the formation of micro- and nanoscale surface structures. In central ablated area, distinct grains and crack formation are observed, whereas peripheral ablated areas are dominated by cones and pinhole formation. It was observed that at irradiances exceeding a value of 13 GW/cm2, the morphological trend of the observed structures has been changed from erosion to melting and re-deposition dominant phase. Ablation efficiency as a function of laser irradiance has also been investigated by measuring the crater depth using surface profilometry analysis. It is found to be maximum at an irradiance of 13 GW/cm2 and decreases at high laser irradiances. In order to correlate the accumulated effects of plasma parameters with the surface modification, laser-induced breakdown spectroscopy analysis has been performed. The electron temperature and number density of tungsten plasma have been evaluated at various laser irradiances. Initially with the increase of the laser irradiance up to 13 GW/cm2, an increasing trend is observed for both plasma parameters due to enhanced energy deposition. Afterward, a decreasing trend is achieved which is attributed to the shielding effect. With further increase in irradiance, a saturation stage comes and insignificant changes are observed in plasma parameters. This saturation is explainable on the basis of the formation of a self-regulating regime near the target surface. Surface modifications of laser irradiated tungsten have been correlated with plasma parameters.

Akram, Mahreen; Bashir, Shazia; Rafique, Muhammad Shahid; Hayat, Asma; Mahmood, Khaliq; Dawood, Asadullah; Bashir, M. F.

2015-03-01

172

Investigation of nanoparticle formation in a plasma produced by femtosecond laser ablation of gold  

Microsoft Academic Search

The formation of nanoparticles in a plasma produced by the interaction of ultrashort laser pulses with gold has been investigated. Three different experimental techniques were employed. (i) The plume expansion was characterized using fast imaging with the aid of an intensified charge-coupled device. (ii) The plasma composition was analyzed using time- and space-resolved optical emission spectroscopy. (iii) The ablated material

P. Spiga; J. Hermann; T. Itina; D. Grojo; D. Neamtu; D. Pailharey; W. Marine

2005-01-01

173

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

174

Renaissance of laser interstitial thermal ablation.  

PubMed

Laser interstitial thermal therapy (LITT) is a minimally invasive technique for treating intracranial tumors, originally introduced in 1983. Its use in neurosurgical procedures was historically limited by early technical difficulties related to the monitoring and control of the extent of thermal damage. The development of magnetic resonance thermography and its application to LITT have allowed for real-time thermal imaging and feedback control during laser energy delivery, allowing for precise and accurate provision of tissue hyperthermia. Improvements in laser probe design, surgical stereotactic targeting hardware, and computer monitoring software have accelerated acceptance and clinical utilization of LITT as a neurosurgical treatment alternative. Current commercially available LITT systems have been used for the treatment of neurosurgical soft-tissue lesions, including difficult to access brain tumors, malignant gliomas, and radiosurgery-resistant metastases, as well as for the ablation of such lesions as epileptogenic foci and radiation necrosis. In this review, the authors aim to critically analyze the literature to describe the advent of LITT as a neurosurgical, laser excision tool, including its development, use, indications, and efficacy as it relates to neurosurgical applications. PMID:25727222

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

2015-03-01

175

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

176

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

177

Amalgam ablation with the Er:YAG laser  

Microsoft Academic Search

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

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

1995-01-01

178

Quantitative Measurements Of Pulsed Infrared Laser Tissue Ablation  

NASA Astrophysics Data System (ADS)

Several new lasers that emit infrared laser radiation are being considered for surgical applications. In order to understand the irradiation and tissue parameters that control the infrared laser ablation process, three different, yet related, experiments were conducted. Ablation of guinea pig skin and bovine aorta, myocardium and liver using a TEA CO2 laser with a pulse duration of 2 ?s was quantified by measuring the mass of tissue removed as a function of incident fluence per pulse. For per pulse fluences greater than 5 J/cm2 the ablation rate data are strongly dependent upon the mechanical strength of the tissue thus indicating a potential inadequacy of ablation models that do not consider tissue strength. The ablation of both soft and hard tissues using the normal-spiking-mode Er:YAG laser was quantified by measuring the number of pulses needed to perforate a measured thickness of tissue. The ablation of aorta and skin was more efficient than bone ablation. The ablation craters formed in skin and bone were the same shape as the incident laser beam, i.e. circular. In aorta, elliptical craters were formed at high fluence pulses; the long axis of the ellipse was always oriented perpendicular to the longitudinal axis of the aorta. Again, tissue mechanical properties were shown to be important. Er:YAG laser ablation dynamics were studied using flash photography and optical pump-probe techniques. The velocity of the plume front was found to be approximately Mach 4. It was also shown that each spike in the normal-spiking-mode pulse train was capable of ablating and rapidly ejecting tissue. The combined results of the three experiments indicate that removal of tissue by infrared laser radiation is an explosive process, the speed of which is determined in part by the mechanical strength of the tissue.

Walsh, Joseph T.

1989-08-01

179

The impact of laser ablation on optical soft tissue differentiation for tissue specific laser surgery-an experimental ex vivo study  

PubMed Central

Background Optical diffuse reflectance can remotely differentiate various bio tissues. To implement this technique in an optical feedback system to guide laser surgery in a tissue-specific way, the alteration of optical tissue properties by laser ablation has to be taken into account. It was the aim of this study to evaluate the general feasibility of optical soft tissue differentiation by diffuse reflectance spectroscopy under the influence of laser ablation, comparing the tissue differentiation results before and after laser intervention. Methods A total of 70 ex vivo tissue samples (5 tissue types) were taken from 14 bisected pig heads. Diffuse reflectance spectra were recorded before and after Er:YAG-laser ablation. The spectra were analyzed and differentiated using principal component analysis (PCA), followed by linear discriminant analysis (LDA). To assess the potential of tissue differentiation, area under the curve (AUC), sensitivity and specificity was computed for each pair of tissue types before and after laser ablation, and compared to each other. Results Optical tissue differentiation showed good results before laser exposure (total classification error 13.51%). However, the tissue pair nerve and fat yielded lower AUC results of only 0.75. After laser ablation slightly reduced differentiation results were found with a total classification error of 16.83%. The tissue pair nerve and fat showed enhanced differentiation (AUC: 0.85). Laser ablation reduced the sensitivity in 50% and specificity in 80% of the cases of tissue pair comparison. The sensitivity of nerve–fat differentiation was enhanced by 35%. Conclusions The observed results show the general feasibility of tissue differentiation by diffuse reflectance spectroscopy even under conditions of tissue alteration by laser ablation. The contrast enhancement for the differentiation between nerve and fat tissue after ablation is assumed to be due to laser removal of the surrounding lipid-rich nerve sheath. The results create the basis for a guidance system to control laser ablation in a tissue-specific way. PMID:22704127

2012-01-01

180

Laser ablation methods for analysis of urinary calculi: Comparison study based on calibration pellets  

NASA Astrophysics Data System (ADS)

Methods based on laser ablation, such as Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass/Optical Emission Spectrometry (LA-ICP-MS/OES) are particularly suitable for urinary calculi bulk and micro analysis. Investigation of spatial distribution of matrix and trace elements can help to explain their emergence and growth. However, quantification is still very problematic and these methods are often used only for qualitative elemental mapping. There are no commercially available standards, which would correspond to the urinary calculi matrix. Internal standardization is also difficult, mainly due to different crystalline phases in one kidney stone. The aim of this study is to demonstrate the calibration capabilities and examine the limitations of laser ablation based techniques. Calibration pellets were prepared from powdered human urinary calculi with phosphate, oxalate and urate matrix. For this comparative study, the most frequently used laser-ablation based analytical techniques were chosen, such as LIBS and LA-ICP-MS. Moreover, some alternative techniques such as simultaneous LIBS-LA-ICP-OES and laser ablation LA-LIBS were also utilized.

Št?pánková, K.; Novotný, K.; Vašinová Galiová, M.; Kanický, V.; Kaiser, J.; Hahn, D. W.

2013-03-01

181

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

182

Laser ablation system, and method of decontaminating surfaces  

DOEpatents

A laser ablation system comprising a laser head providing a laser output; a flexible fiber optic cable optically coupled to the laser output and transmitting laser light; an output optics assembly including a nozzle through which laser light passes; an exhaust tube in communication with the nozzle; and a blower generating a vacuum on the exhaust tube. A method of decontaminating a surface comprising the following steps: providing an acousto-optic, Q-switched Nd:YAG laser light ablation system having a fiber optically coupled output optics assembly; and operating the laser light ablation system to produce an irradiance greater than 1.times.10.sup.7 W/cm.sup.2, and a pulse width between 80 and 170 ns.

Ferguson, Russell L. (Idaho Falls, ID); Edelson, Martin C. (Ames, IA); Pang, Ho-ming (Ames, IA)

1998-07-14

183

Vacuum ultraviolet laser-induced breakdown spectroscopy analysis of polymers  

Microsoft Academic Search

Laser-induced breakdown spectroscopy (LIBS) in the vacuum ultraviolet range (VUV, ?<200nm) is employed for the detection of trace elements in polyethylene (PE) that are difficult to detect in the UV\\/VIS range. For effective laser ablation of PE, we use a F2 laser (wavelength ?=157nm) with a laser pulse length of 20ns, a pulse energy up to 50mJ, and pulse repetition

Juraj Jasik; Johannes Heitz; Johannes D. Pedarnig; Pavel Veis

2009-01-01

184

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. PMID:16714345

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

2006-01-01

185

Erbium oxide thin films on Si(100) obtained by laser ablation and electron beam evaporation  

NASA Astrophysics Data System (ADS)

Erbium oxide thin films have been obtained by laser ablation and electron beam evaporation techniques on Si(100) substrates. The samples were grown under different conditions of oxygen atmosphere and substrate temperature without any oxidation process after deposition. The crystal structure has been studied by X-ray diffraction. Films obtained by laser ablation are highly textured in the [ hhh] direction, although this depends on the conditions of oxygen pressure and substrate temperature. In order to study the depth composition profile of the thin films and the interdiffusion of erbium metal and oxygen towards the silicon substrates, X-ray photoelectron spectroscopy analyses have been carried out.

Queralt, X.; Ferrater, C.; Sánchez, F.; Aguiar, R.; Palau, J.; Varela, M.

1995-02-01

186

Physical mechanisms of short pulse laser ablation D. von der Linde and K. Sokolowski-Tinten  

E-print Network

Physical mechanisms of short pulse laser ablation D. von der Linde and K. Sokolowski and optical properties. Keywords: Laser ablation, femtosecond pulses 1. INTRODUCTION Laser processing removal of material from the surface following laser exposure, commonly called laser ablation or laser

von der Linde, D.

187

Wetting and other physical characteristics of polycarbonate surface textured using laser ablation  

NASA Astrophysics Data System (ADS)

Surface texturing of polycarbonate glass is carried out for improved hydrophobicity via controlled laser ablation at the surface. Optical and physical characteristics of the laser treated layer are examined using analytical tools including optical, atomic force, and scanning electron microscopes, Fourier transform infrared spectroscopy, and X-ray diffraction. Contact angle measurements are carried out to assess the hydrophobicity of the laser treated surface. Residual stress in the laser ablated layer is determined using the curvature method, and microhardnes and scratch resistance are analyzed using a micro-tribometer. Findings reveal that textured surfaces compose of micro/nano pores with fine cavities and increase the contact angle to hydrophobicity such a way that contact angles in the range of 120° are resulted. Crystallization of the laser treated surface reduces the optical transmittance by 15%, contributes to residual stress formation, and enhances the microhardness by twice the value of untreated polycarbonate surface. In addition, laser treatment improves surface scratch resistance by 40%.

Yilbas, B. S.; Khaled, M.; Abu-Dheir, N.; Al-Aqeeli, N.; Said, S. A. M.; Ahmed, A. O. M.; Varanasi, K. K.; Toumi, Y. K.

2014-11-01

188

Silica nano-ablation using laser plasma soft x-rays  

NASA Astrophysics Data System (ADS)

We have investigated nano-ablation of silica glass and ablation process using focused laser plasma soft Xrays. Laser plasma soft X-rays were generated by irradiation of a Ta target with Nd:YAG laser light. The soft X-rays were focused on silica glass plates using an ellipsoidal mirror at fluences up to 1 J/cm2. In order to fabricate nano-trenches, a silica glass plate was irradiated with laser plasma soft X-rays through the windows of a line and space mask. We demonstrated fabrication of nano-trenches with a width of 50 nm. It should be noted that the feature size is more precise than that estimated from the thermal diffusion length for the 10-ns X-rays (i.e. 80 nm). Furthermore, the ablated area has a depth of 470 nm and a roughness of 1 nm after ten shots of irradiation. Thus, the X-ray irradiation technique have a significant feature of direct nanomachining. The ablation occurs at fluences F beyond a ablation threshould Fth and ablation depth per pulse D obeys the law D = 1/? ln(F/Fth), where ? is an effective absorption coefficient. These results suggest that absorbed energy is accumulated in the absorbed region without energy diffusion until ablation occurs. In addition, time-resolved mass spectroscopy revealed that silica glass is broken into atomic ions and atomic neutrals during ablation. Because Si+ and O+ ions have kinetic energies of 10-30 eV, non-thermal process such as Coulomb explosion may be driving force behind the ablation. Such non-thermal process enables us to fabricate nano-structures on silica glass.

Makimura, Tetsuya; Torii, Shuichi; Niino, Hiroyuki; Murakami, Kouichi

2009-05-01

189

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., Jr.

1995-04-01

190

Corneal ablation using the pulse stretched free electron laser  

Microsoft Academic Search

The Mark-III Free Electron Laser (FEL), tuned to lambda=6.45 mum has been demonstrated to provide for efficient ablation in ocular and neural tissues with minimal collateral damage. To date, the role of the FEL pulse structure on the mechanism of ablation has not been determined. In an effort to study the role of the FEL micropulse on the ablation of

Mark A. Mackanos; Karen M. Joos; John A. Kozub; E. D. Jansen

2005-01-01

191

Influence of laser-induced air breakdown on femtosecond laser ablation of aluminum.  

PubMed

We investigated the influence of laser-induced air breakdown on the femtosecond laser ablation of aluminum target using time-resolved pump-probe shadowgraphic imaging method. The early-stage plasma expanding dynamics and subsequent expanding behaviors of shockwaves and material ejection plume were analyzed through shadowgraphs recorded at different time delays. The dominated mechanisms were clarified at different stages during femtosecond laser pulses ablating aluminum, which provide very valuable information for ultrashort laser ablation of metals. PMID:25835895

Zhang, Hang; Zhang, Fangteng; Du, Xi; Dong, Guoping; Qiu, Jianrong

2015-01-26

192

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

193

Epitaxial growth of RbTiOPO4 films on KTiOPO4 substrates by excimer laser ablation technique  

Microsoft Academic Search

Transparent single-phase rubidium titanyl phosphate (RTP) films having excellent crystalline properties have been deposited by excimer laser ablation method on (001)- and (010)-oriented potassium titanyl phosphate (KTP) substrates, respectively. X-ray theta-2 theta scans and pole figures showed that the laser-ablated RTP films grew epitaxially on, and had exactly the same orientations of, the underlying KTP substrates. X-ray photoelectron spectroscopy analysis

Z. G. Liu; J. M. Liu; N. B. Ming; J. Y. Wang; Y. G. Liu; M. H. Jiang

1994-01-01

194

Epitaxial growth of RbTiOPO4 films on KTiOPO4 substrates by excimer laser ablation technique  

Microsoft Academic Search

Transparent single-phase rubidium titanyl phosphate (RTP) films having excellent crystalline properties have been deposited by excimer laser ablation method on (001)- and (010)-oriented potassium titanyl phosphate (KTP) substrates, respectively. X-ray ?-2? scans and pole figures showed that the laser-ablated RTP films grew epitaxially on, and had exactly the same orientations of, the underlying KTP substrates. X-ray photoelectron spectroscopy analysis revealed

Z. G. Liu; J. M. Liu; N. B. Ming; J. Y. Wang; Y. G. Liu; M. H. Jiang

1994-01-01

195

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

196

A rotational study of laser ablated thiourea.  

PubMed

A laser ablation device in combination with a molecular beam Fourier-transform microwave spectrometer has allowed the observation of the rotational spectrum of solid thiourea for the first time. The sensitivity reached in the experiment allowed the observation of the isotopomers (34)S, (13)C, and (15)N in their natural abundance. The spectrum of D(4)-thiourea was also analyzed from an enriched sample. The complicated hyperfine structure arising from the presence of two (14)N quadrupolar nuclei has been fully resolved and analyzed. The substitution r(s) structure has been derived from the experimental moments of inertia. Thiourea in gas phase presents a planar heavy atom skeleton. Experimental inertial defect values and high-level ab initio calculations reveal that the amino groups hydrogen atoms lie out-of-plane with a C(2) symmetry configuration and are involved in large amplitude inversion motions. PMID:15267505

Lesarri, Alberto; Mata, Santiago; Blanco, Susana; Lopez, Juan C; Alonso, Jose L

2004-04-01

197

Formation of tribological structures by laser ablation  

NASA Astrophysics Data System (ADS)

Many technical applications can benefit from the use of tribological structures in minimizing abrasive material wear and energy consumption without the integration of additional materials in a working assembly. Especially in lubricated friction systems, the tribological character can be significantly improved through the addition of oriented and repetitive microstructure. In this study, experimental tests are discussed for a small range of structure dimensions to verify the effect of optimizing the tribological contact performance. A nanosecond pulsed fiber laser is used to create various test structures with different sizes and form. The quality of the fabricated surface pattern, particularly form correctness, feathering and material modification effects of the ablated area is characterized and optimized. The influence of pulse duration, pulse energy and pulse delay using normal pulsing is presented and compared to various burst modes.

Schilling, Niels; Paschke, Mike; Hendow, Sami T.; Klotzbach, Udo

2012-03-01

198

Outcomes of ablative fractional laser scar treatment.  

PubMed

Ablative fractional laser (AFL) systems are commonly used to treat various scars, and recent reports have indicated that early scar treatment with fractional lasers has good aesthetic results. Some scars respond dramatically to AFL treatment, incurring high levels of patient satisfaction; however, other scars respond poorly or became worse after treatment. This study was designed to clarify prognostic factors that predict AFL scar treatment outcomes. A total of 108 patients were included in this study. The fractional laser treatments were repeated every 4 weeks until the scar site was acceptable and no additional improvement was expected or the patient discontinued the treatment. The scar improvements were defined as changes in the Manchester scar scale (MSS) from before to after laser treatment. A digital camera was used to acquire digital photographs of the scars under the same light source, the same background, exposure, and white balance. This study developed a modification of the MSS for image analysis in which colour assessment was based on L*a*b* colour co-ordinates of the digital images. The mean MSS values prior to and after laser treatments were 11.6 ± 3.6 and 9.5 ± 2.9, respectively (p < 0.01). AFL treatment improved the qualities of each scar, and the improvements were evident in colour and contour. Scar elevation, pigmentation, high vascularity, early onset of treatment, and the number of treatment sessions were directly related to scar improvement after AFL therapy (p < 0.05). AFL treatments were effective methods for scar treatment. Clinicians can use these prognostic factors to determine treatment plans and to estimate scar improvement after AFL treatment. PMID:24845386

Kim, Deok-Woo; Hwang, Na-Hyun; Yoon, Eul-Sik; Dhong, Eun-Sang; Park, Seung-Ha

2015-04-01

199

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

200

Laser ablation of paper: Raman identification of products  

NASA Astrophysics Data System (ADS)

Old paper samples are bleached using pulsed laser radiation with a wavelength of 532 nm. The ablation products of five paper samples that differ by composition and production dates are studied using Raman microspectroscopy. Cellulose, protein, calcite, titanium dioxide (anatase, rutile, and brookite), quartz, lazurite, bonattite, and dolomite are identified as ablation products.

Balakhnina, Irina; Brandt, Nikolay; Chikishev, Andrey; Rebrikova, Natalia; Yurchuk, Yuliya

2014-12-01

201

Short pulse laser ablation is photomechanical, not thermal or chemical  

Microsoft Academic Search

Proposed mechanisms for pulsed laser ablation of biological tissue include photochemical, photothermal and photomechanical models. The principal observed effects which the correct model must explain include the high efficiency of the process, typically an order of magnitude less energy is required than for long pulse or cw ablation, and the minimal thermal damage to surrounding tissue. The photomechanical model postulates

I. Itzkan; D. Albagli; M. Dark; L. T. Perelman; C. von Rosenberg; M. S. Feld

1994-01-01

202

Transient States of Matter during Short Pulse Laser Ablation  

Microsoft Academic Search

Short pulse laser ablation of semiconductors and metals is studied by means of ultrafast time-resolved microscopy. The characteristic stages of the conversion of solid material into hot fluid matter undergoing ablation are identified. Initially metallic material transforms during the expansion into a transparent state with a high index of refraction.

K. Sokolowski-Tinten; J. Bialkowski; A. Cavalleri; D. von der Linde; A. Oparin; J. Meyer-Ter-Vehn; S. I. Anisimov

1998-01-01

203

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

204

Hydrocarbon level detection with nanosecond laser ablation  

NASA Astrophysics Data System (ADS)

Nanosecond laser induced breakdown in liquid is used as a technique to detect hydrocarbon levels in water. A Q-switched Nd:YAG laser was focused to generate optical breakdown associated with shock wave generation. The shock wave was propagated at the speed of sound in the medium after travelling 1 ?s outward from the center of optical breakdown. Different amplitudes of sound were traced with the aid of an ultrasonic probe. The optical properties of the hydrocarbon solution were quantified via fundamental refractive index measurement (the Snell law). A continuous mode diode pumped solid state laser with second harmonic generation was used as the illumination light source. A CCD video camera with Matrox version 4.2 software was utilized to analyze the recording image. Option line analysis was performed to analyze the intensity of optical breakdown at different input energies. Gray level analysis was also conducted on the scattering light after passing through the hydrocarbon solution at different concentrations. The hydrocarbon solution comprised impurities or particles that varied according to the concentration. The average of the gray level is assumed to present the size of the particle. Inherently, as the acoustic wave propagates outward, it transports the mass (particles or impurities) and impacts on the ultrasonic probe. As a result a higher concentration of hydrocarbons reveals a larger amplitude of sound waves. This phenomenon is identified as a finger print for hydrocarbon levels between 100 and 1000 ppm. The transient detection, without complicated sampling preparation and no hazardous chemical involvement, makes laser ablation a promising technique to detect in situ hydrocarbon levels in water.

Bidin, Noriah; Hosseinian S, Raheleh; Nugroho, Waskito; Mohd Marsin, Faridah; Zainal, Jasman

2013-12-01

205

Kinoform optics: direct fabrication by F2 laser ablation  

Microsoft Academic Search

A 64×64 element kinoform was microfabricated in fused silica by direct ablation with a pulsed 157-nm laser source that circumvents multistep lithographic patterning and etching routines. A 4-level design of ?300-nm etch layers is described.

Amir H. Nejadmalayeri; Andrew Yick; Jianzhao Li; Peter R. Herman

2003-01-01

206

Dental material ablation with the Er:YAG laser  

Microsoft Academic Search

It is essential for any laser which will be used in the clinic by dentists to remove existing dental materials for this laser to be a viable replacement of the dental drill. There is however a concern about the thermal damage which a laser can cause due to the heat that is generated by the ablation of these materials. The

H. Wigdor; S. R. Visuri

1994-01-01

207

Formation of ZnO nanoparticles by laser ablation in neat water Kuk Ki Kim a  

E-print Network

Formation of ZnO nanoparticles by laser ablation in neat water Kuk Ki Kim a , Daehyun Kim b , Sang by laser ablation with various ablation times (10­40 min), fluences (50­130 mJ/pulse), and wavelengths using physical and chemical methods [1­3]. Recently, laser ablation of a zinc metal target in liquid

Kim, Sang Kyu

208

Nanometer-scale ablation with a table-top soft x-ray laser  

E-print Network

Nanometer-scale ablation with a table-top soft x-ray laser G. Vaschenko, A. Garcia Etxarri, C. S Optical Society of America OCIS codes: 140.3390, 140.7240, 310.3840. Laser ablation of nanoscale features- rectly ablating sub-100 nm nanoscale holes using a focused soft x-ray laser beam. Very clean ablation

Rocca, Jorge J.

209

Nanoscale patterning of graphene through femtosecond laser ablation R. Sahin, E. Simsek, and S. Akturk  

E-print Network

Nanoscale patterning of graphene through femtosecond laser ablation R. Sahin, E. Simsek, and S.164.158.129 On: Mon, 10 Feb 2014 15:01:27 #12;Nanoscale patterning of graphene through femtosecond laser ablation femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold

Simsek, Ergun

210

Ciliary white-light: optical aspect of ultrashort laser ablation on transparent dielectrics  

E-print Network

1 Ciliary white-light: optical aspect of ultrashort laser ablation on transparent dielectrics Yi on a novel nonlinear optical phenomenon, coined as ciliary white-light, during laser ablation of transparent dynamics of the ablated surface, providing a real time in-situ observation of the laser ablation process

Paris-Sud XI, Université de

211

LASER ABLATION SYNTHESIS OF ZINC OXIDE CLUSTERS: A NEW FAMILY OF FULLERENES?  

E-print Network

1 LASER ABLATION SYNTHESIS OF ZINC OXIDE CLUSTERS: A NEW FAMILY OF FULLERENES? Alexander V stoichiometry were synthesized in the gas phase by excimer ArF laser ablation of a ZnO target and investigatedOm clusters of different stoichiometry in a laser-ablation plasma plume. The effect of ablation conditions

Paris-Sud XI, Université de

212

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

SciTech Connect

Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

Liedahl, Duane A.; Libby, Stephen B.; Rubenchik, Alexander [Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550 (United States)

2010-10-08

213

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris  

SciTech Connect

Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

Liedahl, D A; Libby, S B; Rubenchik, A

2010-02-04

214

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

215

Laser ablation for the synthesis of carbon nanotubes  

DOEpatents

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

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

2012-11-27

216

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 and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

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

2012-01-01

217

Laser ablation for the synthesis of carbon nanotubes  

DOEpatents

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/cm2 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.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

2010-04-06

218

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

219

Femtosecond laser ablation of indium tin-oxide narrow grooves for thin film solar cells  

E-print Network

Femtosecond laser ablation of indium tin-oxide narrow grooves for thin film solar cells Qiumei Bian in revised form 15 June 2012 Accepted 18 June 2012 Keywords: Ablation Femtosecond laser Indium tin oxide a b of laser pulse duration, laser fluence and laser scanning speed on the ablation of ITO. The single pulse

Van Stryland, Eric

220

Background gas collisional effects on expanding fs and ns laser ablation plumes  

E-print Network

Background gas collisional effects on expanding fs and ns laser ablation plumes S. S. Harilal · N of a background gas on expanding ultrafast and short pulse laser ablation plumes were investigated by varying are observed *20­50 Torr for both ns and fs laser ablation plumes. The differences in laser­target and laser

Harilal, S. S.

221

Transient Newton rings in dielectrics upon fs laser ablation  

E-print Network

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

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

2014-01-01

222

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

223

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

224

Improved picosecond laser ablation with second harmonic seeding  

NASA Astrophysics Data System (ADS)

We report on recent results of laser ablation in semiconductors obtained by simultaneous irradiation of the sample with a superposition of the fundamental beam of a picosecond-Neodymium-Vanadate (Nd:VAN) laser (1064 nm, 10 ps pulse duration) and a small fraction of its second harmonic (SH) produced in a thin nonlinear crystal. In this fashion, the ablation yield could be increased by 70%. In addition, the ablation quality was improved in terms of surface smoothness. The underlying mechanism can be attributed to a 'seeding' of the target area with free carriers by the 532 nm radiation.

Zoppel, S.; Zehetner, J.; Reider, G. A.

2006-03-01

225

Reflection of femtosecond laser light in multipulse ablation of metals  

SciTech Connect

The shot-to-shot reflectance of high-intensity laser light is studied as a function of both the number of laser shots and laser fluence in multipulse ablation of a metal when the irradiated surface undergoes structural changes from an initially smooth surface to a deep crater. Our study shows that the reflectance of the irradiated surface significantly decreases due to the high intensity of laser pulses and the laser-induced surface structures in ablation regimes typically used for femtosecond laser processing of materials. The high-intensity effect dominates in the reflection reduction at low numbers of laser shots when laser-induced surface structures do not cause the reflectance to decrease noticeably. With increasing the number of laser shots, the structural effect comes into play, and both high-intensity and structural effects quickly reduce the reflectance of the sample to a low value.

Vorobyev, A. Y.; Guo Chunlei [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2011-08-15

226

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

227

Ablation enhancement of silicon by ultrashort double-pulse laser ablation  

SciTech Connect

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

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

2014-09-15

228

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

229

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. PMID:24778794

Perälä, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriälä, Ilkka; Salmela, Pasi I; Tervonen, Osmo

2014-01-01

230

Ultraviolet versus infrared: Effects of ablation laser wavelength on the expansion of laser-induced plasma into one-atmosphere argon gas  

SciTech Connect

Laser-induced plasma from an aluminum target in one-atmosphere argon background has been investigated with ablation using nanosecond ultraviolet (UV: 355 nm) or infrared (IR: 1064 nm) laser pulses. Time- and space-resolved emission spectroscopy was used as a diagnostics tool to have access to the plasma parameters during its propagation into the background, such as optical emission intensity, electron density, and temperature. The specific feature of nanosecond laser ablation is that the pulse duration is significantly longer than the initiation time of the plasma. Laser-supported absorption wave due to post-ablation absorption of the laser radiation by the vapor plume and the shocked background gas plays a dominant role in the propagation and subsequently the behavior of the plasma. We demonstrate that the difference in absorption rate between UV and IR radiations leads to different propagation behaviors of the plasma produced with these radiations. The consequence is that higher electron density and temperature are observed for UV ablation. While for IR ablation, the plasma is found with lower electron density and temperature in a larger and more homogenous axial profile. The difference is also that for UV ablation, the background gas is principally evacuated by the expansion of the vapor plume as predicted by the standard piston model. While for IR ablation, the background gas is effectively mixed to the ejected vapor at least hundreds of nanoseconds after the initiation of the plasma. Our observations suggest a description by laser-supported combustion wave for the propagation of the plasma produced by UV laser, while that by laser-supported detonation wave for the propagation of the plasma produced by IR laser. Finally, practical consequences of specific expansion behavior for UV or IR ablation are discussed in terms of analytical performance promised by corresponding plasmas for application with laser-induced breakdown spectroscopy.

Ma Qianli; Motto-Ros, Vincent; Laye, Fabrice; Yu Jin [Universite de Lyon, F-69622, Lyon, France, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Lei Wenqi; Bai Xueshi; Zheng Lijuan; Zeng Heping [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai (China)

2012-03-01

231

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

232

Efficient space propulsion engines based on laser ablation  

SciTech Connect

Recent results have shown laser momentum transfer coefficients C{sub m} as large as 700 dynes/J from visible and near-infrared laser pulses with heterogeneous targets. Using inexpensive target materials, it is now possible to deliver a 1-tonne satellite from LEO to GEO in 21 days using a 10-kW onboard laser ablation engine, or to maintain several 1-tonne GEO satellites on station from Earth indefinitely using a laser with 100-W average power.

Phipps, C.R.

1993-08-01

233

Absorption-Ablation-Excitation Mechanism of Laser-Cluster Interactions in a Nanoaerosol System  

NASA Astrophysics Data System (ADS)

The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy. For 532 nm excitation, as the laser intensity increases beyond 0.16 GW /cm2 , the scattering cross section of TiO2 clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. With 1064 nm laser excitation, the atomic emissions are more than one order of magnitude weaker than that at 532 nm, indicating that the thermal effect is not the main mechanism. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensity, the cross section of clusters decreases during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by nondimensionalizing the Fokker-Planck equation, with analogous Strouhal SlE , Peclet PeE , and Damköhler DaE numbers defined to characterize the laser-induced aerothermochemical environment. For conditions where SlE?1 , PeE?1 , and DaE?1 , the electrons are excited to the conduction band by two-photon absorption, then relax to the bottom of the conduction band by electron energy loss to the lattice, and finally serve as the energy transfer media between laser field and lattice. The relationship between delay time and excitation intensity is well correlated by this simplified model with quasisteady assumption.

Ren, Yihua; Li, Shuiqing; Zhang, Yiyang; Tse, Stephen D.; Long, Marshall B.

2015-03-01

234

Absorption-ablation-excitation mechanism of laser-cluster interactions in a nanoaerosol system.  

PubMed

The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy. For 532 nm excitation, as the laser intensity increases beyond 0.16??GW/cm^{2}, the scattering cross section of TiO_{2} clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. With 1064 nm laser excitation, the atomic emissions are more than one order of magnitude weaker than that at 532 nm, indicating that the thermal effect is not the main mechanism. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensity, the cross section of clusters decreases during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by nondimensionalizing the Fokker-Planck equation, with analogous Strouhal Sl_{E}, Peclet Pe_{E}, and Damköhler Da_{E} numbers defined to characterize the laser-induced aerothermochemical environment. For conditions where Sl_{E}?1, Pe_{E}?1, and Da_{E}?1, the electrons are excited to the conduction band by two-photon absorption, then relax to the bottom of the conduction band by electron energy loss to the lattice, and finally serve as the energy transfer media between laser field and lattice. The relationship between delay time and excitation intensity is well correlated by this simplified model with quasisteady assumption. PMID:25793812

Ren, Yihua; Li, Shuiqing; Zhang, Yiyang; Tse, Stephen D; Long, Marshall B

2015-03-01

235

Separate Effects of the Microkeratome Incision and Laser Ablation on the Eye's  

E-print Network

Separate Effects of the Microkeratome Incision and Laser Ablation on the Eye's Wave Aberration, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ to the laser ablation and not the microkeratome cut. In addi- tion, the total and higher order root mean square

Williams, David

236

Velocity distributions of molecules ejected in laser ablation Leonid V. Zhigilei and Barbara J. Garrisona)  

E-print Network

Velocity distributions of molecules ejected in laser ablation Leonid V. Zhigilei and Barbara J applications of laser ablation are in mass spectrometry and thin film deposition. In mass spectrometry laser in laser ablation experiments for a variety of systems, such as mo- lecular solids,3,5 polymers,6,10 frozen

Zhigilei, Leonid V.

237

Emission features and expansion dynamics of nanosecond laser ablation plumes at different ambient pressures  

E-print Network

Emission features and expansion dynamics of nanosecond laser ablation plumes at different ambient deposition (PLD),1 laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS),2 laser.12 The interaction of a nanosecond laser ablation plume with an ambient gas has been studied

Harilal, S. S.

238

A Hybrid MD-DSMC Model of Picosecond Laser Ablation and Desorption  

E-print Network

A Hybrid MD-DSMC Model of Picosecond Laser Ablation and Desorption Michael I. Zeifman* , Barbara J model of the evolution of a plume generated by laser ablation of an organic solid is presented and discussed. The first stage of the laser ablation involves laser coupling to the target and ejection

Zhigilei, Leonid V.

239

Morphology of Femtosecond Laser Ablated Borosilicate Glass Surfaces Adela Ben-Yakar and Robert L. Byer  

E-print Network

Morphology of Femtosecond Laser Ablated Borosilicate Glass Surfaces Adela Ben-Yakar and Robert L that a thin rim is formed around ablated craters after a single laser pulse. When multiple laser pulses. The substrates were cleaned ultrasonically with alcohol before the experiments. After laser ablation, the debris

Harkin, Anthony

240

Toward Single-Cell Analysis by Plume Collimation in Laser Ablation Electrospray Ionization Mass Spectrometry  

E-print Network

Toward Single-Cell Analysis by Plume Collimation in Laser Ablation Electrospray Ionization Mass is used to deliver laser energy to a sample in laser ablation electrospray ionization (LAESI) mass.g., laser ablation electrospray ionization (LAESI),12 among a host of others.13 Some ambient methods, e

Vertes, Akos

241

Combined molecular dynamicsdirect simulation Monte Carlo computational study of laser ablation plume evolution  

E-print Network

Combined molecular dynamics­direct simulation Monte Carlo computational study of laser ablation of evolution of a plume generated by laser ablation of an organic solid is proposed and developed. The first stage of the laser ablation, which involves laser coupling to the target and ejection of molecules

Zhigilei, Leonid V.

242

Page 2 of 55 Low-cost photomask fabrication using laser ablation  

E-print Network

Page 2 of 55 Accepted M anuscript 2 Low-cost photomask fabrication using laser ablation G. Legeaya-coated on titanium. It is ablated with partially-overlapping laser impacts and undergoes self-combustion under laser beam. Proper heat treatments are applied before and after laser ablation to circumvent smearing

243

MICROANALYSIS OF SIDEROPHILE ELEMENTS IN FREMDLINGE USING LASER ABLATION ICP-MS. A. J. Campbell  

E-print Network

MICROANALYSIS OF SIDEROPHILE ELEMENTS IN FREMDLINGE USING LASER ABLATION ICP-MS. A. J. Campbell 1@midway.uchicago.edu). Introduction: Laser ablation ICP mass spectrome- try has been used to measure distributions of the highly vein in Allende (CV3-oxidized). Experimental: The laser ablation system utilized a CETAC LSX-200 laser

Grossman, Lawrence

244

Laser Ablation of Metals Johannes Roth, Carolina Trichet, Hans-Rainer-Trebin, and Steffen Sonntag  

E-print Network

Laser Ablation of Metals Johannes Roth, Carolina Trichet, Hans-Rainer-Trebin, and Steffen Sonntag@itap.physik.uni-stuttgart.de 1 Introduction Laser ablation is the process of removing material with very intensive, pulsed laser process itself still lacks behind. The time scales of the processes involved in laser ablation

Roth, Johannes

245

Solid sampling with 193-nm excimer laser ablation  

NASA Astrophysics Data System (ADS)

Reproducible and sensitive elemental analysis of solid samples is a crucial task in areas of geology (e.g. microanalysis of fluid inclusions), material sciences, industrial quality control as well as in environmental, forensic and biological studies. To date the most versatile detection method is mass-spectroscopic multi-element analysis. In order to obtain reproducible results, this requires transferring the solid sample into the gas-phase while preserving the sample's stoichiometric composition. Laser ablation in combination with Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a proven powerful technique to meet the requirements for reliable solid sample analysis. The sample is laser ablated in an air-tight cell and the aerosol is carried by an inert gas to a micro-wave induced plasma where its constituents are atomized and ionized prior to mass analysis. The 193 nm excimer laser ablation, in particular, provides athermal sample ablation with very precise lateral ablation and controlled depth profiling. The high photon energy and beam homogeneity of the 193 nm excimer laser system avoids elemental fractionation and permits clean ablation of even transmissive solid materials such as carbonates, fluorites and pure quartz.

Delmdahl, Ralph

2007-02-01

246

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

247

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

248

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

249

Ultrafast laser ablation ICP-MS: role of spot size, laser fluence, and repetition rate in signal intensity  

E-print Network

Ultrafast laser ablation ICP-MS: role of spot size, laser fluence, and repetition rate in signal,a Richard E. Russob and Ahmed Hassaneina Ultrafast laser ablation inductively coupled plasma mass system. Though ultrafast laser ablation sample introduction provides better accuracy and precision

Harilal, S. S.

250

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

251

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

252

Ultrafast photographic investigation on laser ablation of liquid metals  

NASA Astrophysics Data System (ADS)

The application of laser pulses as `photographic flash' gives the possibility to record ultrafast phenomena. Since the duration of the laser pulses may be tuned from fs to cw, it is easy to choose a right laser source to resolve the time domain to be investigated. In this study excimer laser ablation of molten metal targets was followed by ultrafast photography based on delayed dye laser pulses. Molten tin and bismuth were ablated in vacuum by an ArF excimer laser. Pictures of the surface and the ablated material were taken at different moments after the start of the excimer laser pulse with temporal resolution of 1 ns. The series of snapshots contain information on the initial phase of plume formation in the ns time regime, and on liquid motion (surface waves, protuberances, liquid jet formations, splashing) in microsecond time scale. The important result of this study is the registration of the processes leading to droplet emission from the ablated target surface, because the elimination of droplets is a crucial requirement in depositing thin films by the pulsed laser deposition technique.

Toth, Zsolt; Smausz, Tomi; Hopp, Bela; Ignacz, Ferenc; Kantor, Zoltan; Szoerenyi, Tamas; Bor, Zsolt

1998-08-01

253

Theory of shock wave propagation during laser ablation  

Microsoft Academic Search

Laser ablation consists of three coupled processes: (i) heat conduction within the solid, (ii) flow through a discontinuity layer (evaporation wave) attached to the solid surface, and (iii) shock wave expansion of the laser induced plume. In this paper, a one-dimensional solution for all three coupled processes is presented. The heat conduction and the evaporation wave are solved numerically. The

Zhaoyan Zhang; George Gogos

2004-01-01

254

Thermal oxidative degradation of molybdenum films under laser ablation  

NASA Astrophysics Data System (ADS)

The problems of laser ablation of molybdenum films that are related to the formation of topological patterns of contact masks are discussed. The thermal oxidative degradation of thin molybdenum films under high-intensity laser irradiation is analyzed. The results of theoretical estimations are compared with the Raman data on the chemical composition of molybdenum oxide.

Volkov, A. V.; Kazanskiy, N. L.; Moiseev, O. Yu.; Poletayev, S. D.

2015-02-01

255

The physical mechanisms of short-pulse laser ablation  

Microsoft Academic Search

Time-resolved experiments demonstrate that the removal of material from the surface of metals and semiconductors following irradiation with pico- or femtosecond laser pulses occurs on a nanosecond time scale. It is shown that short-pulse laser ablation can be interpreted in terms of transient thermal processes involving states of matter with unusual thermodynamic, hydrodynamic and optical properties.

D. von der Linde; K. Sokolowski-Tinten

2000-01-01

256

Stereotactic laser ablation of high-grade gliomas.  

PubMed

Evolving research has demonstrated that surgical cytoreduction of a high-grade glial neoplasm is an important factor in improving the prognosis of these difficult tumors. Recent advances in intraoperative imaging have spurred the use of stereotactic laser ablation (laser interstitial thermal therapy [LITT]) for intracranial lesions. Among other targets, laser ablation has been used in the focal treatment of high-grade gliomas (HGGs). The revived application of laser ablation for gliomas parallels major advancements in intraoperative adjuvants and groundbreaking molecular advances in neuro-oncology. The authors review the research on stereotactic LITT for the treatment of HGGs and provide a potential management algorithm for HGGs that incorporates LITT in clinical practice. PMID:25434378

Hawasli, Ammar H; Kim, Albert H; Dunn, Gavin P; Tran, David D; Leuthardt, Eric C

2014-12-01

257

UV solid state laser ablation of intraocular lenses  

NASA Astrophysics Data System (ADS)

Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (?=355 nm and ?=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at ?=213 nm reveal a smooth optical surface on the intraocular lens with no irregularities, observed with other wavelengths.

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

2013-06-01

258

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

259

Ultrashort pulse laser ablation of polycarbonate and polymethylmethacrylate  

Microsoft Academic Search

Ablation experiments with ultrashort laser pulses (pulse duration 150 fs, wavelength 800 nm) on polymers (PC, PMMA) relevant for biomedical technology have been performed in air. The lateral and vertical machining precision was evaluated by optical, atomic force and scanning electron microscopy. The ablation threshold reaches values in the range of 0.5–2.5 J\\/cm2 and depends significantly on the number of

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

2000-01-01

260

Enhancement of laser ablation yield by two color excitation  

NASA Astrophysics Data System (ADS)

We present ablation results of silicon obtained by simultaneous irradiation of the sample with the fundamental beam of a picosecond-neodymium-vanadate (Nd:VAN) laser (1064 nm, 10 ps pulse duration) and a small amount of second harmonic (SH) produced in a thin nonlinear crystal. In this fashion, the ablation yield could be increased by 70%. In addition, the ablation quality was improved in terms of surface smoothness. The underlying mechanism can be attributed to a ‘seeding’ of the target area with free carriers by the 532 nm radiation.

Zoppel, S.; Merz, R.; Zehetner, J.; Reider, G. A.

2005-09-01

261

Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water  

PubMed Central

Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence. PMID:20672115

2010-01-01

262

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

263

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

264

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

265

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

266

Optical, structural and morphological properties of zirconia nanoparticles prepared by laser ablation in liquids  

NASA Astrophysics Data System (ADS)

Absorption, fluorescence and Raman spectra, the structural composition and morphology of zirconia nanoparticles synthesised via the laser ablation of a metal in water and aqueous solutions of the sodium dodecyl sulphate (SDS) surfactant have been studied using absorption spectroscopy, Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The results demonstrate that, exposing zirconium to intense nanosecond laser pulses at a high repetition rate in these liquids, one can obtain stable cubic, tetragonal and monoclinic crystalline phases of nanozirconia with a particle size in the range 40 – 100 nm and a Zr – SDS organic – inorganic composite. The absorption and fluorescence of the synthesised zirconia strongly depend on the SDS concentration in the starting solution. The gas – vapour bubbles forming during ablation are shown to serve as templates for the formation of hollow nanoand microstructures.

Borodina, T. I.; Val'yano, G. E.; Gololobova, O. A.; Karpukhin, V. T.; Malikov, M. M.; Strikanov, D. A.

2014-09-01

267

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

268

Improved time control on Cretaceous coastal deposits: new results from Sr isotope measurements using laser ablation  

E-print Network

using laser ablation Stefan Burla,1 Felix Oberli,2 Ulrich Heimhofer,3 Uwe Wiechert4 and Helmut Weissert5 that laser ablation (LA) combined with multi-collector inductively cou- pled plasma mass spectrometry (MC

Gilli, Adrian

269

CO2 laser ablative etching of polyethylene terephthalate  

NASA Astrophysics Data System (ADS)

Films of polyethylene terephthalate (PET) can be successfully etched with 9 ?m radiation from a pulsed TEA CO2 laser. The relationship between etch depth and fluence is broadly similar to that observed for excimer laser etching but with a less well-defined threshold. Time-resolved photoacoustic measurements of stress waves generated in the interaction show that at a fluence of 1.8 J cm-2 ablation occurs 100 200 ns after the start of the laser pulse, a time which is consistent with the rate of thermal decomposition of PET. The volatile products of ablation are carbon monoxide, carbon dioxide, methane, ethyne, ethene, benzene, ethanal, and small quantities of other products. For fluences close to and appreciably above the threshold the ablated material consists predominantly of involatile species of relatively high molecular weight, whereas at higher fluences substantial fragmentation of the polymer to small molecules occurs.

Dyer, P. E.; Oldershaw, G. A.; Sidhu, J.

1989-06-01

270

Ablative fractional laser resurfacing helps treat restrictive pediatric scar contractures.  

PubMed

Conventional management of debilitating pediatric scar contractures, including hand therapy and surgery, may often be beset by delayed treatment, suboptimal results, and additional surgical morbidity. Ablative fractional laser resurfacing is an emerging adjunctive procedural option for scar contractures because of its promising efficacy and safety profile. However, its use to improve function has not been studied in the pediatric population. Herein we report 2 pediatric patients with recalcitrant scar contractures, causing persistent functional deficits, treated with an ablative fractional laser protocol. Both patients experienced rapid and cumulative subjective and objective improvements in range of motion and function as measured by an independent occupational therapist without reported complications. We highlight ablative fractional laser resurfacing as a novel and promising tool in the management of function-limiting scar contractures in children and propose that the technique be incorporated into existing scar treatment paradigms, guided by future research. PMID:25367535

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

2014-12-01

271

Pulsed laser ablation of Al Cu Fe quasicrystals  

NASA Astrophysics Data System (ADS)

Quasicrystalline Al65-Cu23-Fe12 targets have been ablated by a doubled Nd:YAG laser and deposited on silicon substrates. The results show evidence of distinct ablation mechanisms, which lead to different gas phase composition, as a function of the laser fluence. Films containing the quasicrystalline phase can be deposited only at fluences higher than about 6.5 J/cm2 while at lower fluences the aluminium content exceeds the stoichiometric value. The films obtained by laser ablation of quasicrystalline Al65-Cu23-Fe12 were compared with those obtained from the metallic alloy Al70-Cu20-Fe10. The differences between the two systems could be explained on the basis of the low thermal conductivity of the quasicrystalline phase.

Teghil, R.; D'Alessio, L.; Simone, M. A.; Zaccagnino, M.; Ferro, D.; Sordelet, D. J.

2000-12-01

272

Ultrafast laser ablation of gold thin film targets  

SciTech Connect

Ultrafast laser ablation of a gold thin film is studied and compared with that of a bulk target, with particular emphasis given to the process of nanoparticles generation. The process is carried out in a condition where a single laser shot removes all the irradiated film spot. The experimental results evidence interesting differences and, in particular, a reduction of the nanoparticles size, and a narrowing of a factor two of their size distribution in the case of ablation of a thin film target, a feature which we relate to a more uniform heating of the target material. We thus show that ultrashort laser ablation of thin films provides a promising way of controlling plume features and nanoparticles size.

Amoruso, S.; Ausanio, G.; Bruzzese, R. [Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Nedyalkov, N. N.; Atanasov, P. A. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsaridradsko shose Boulevard, Sofia 1784 (Bulgaria); Wang, X. [CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy)

2011-12-15

273

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

274

Nanoscale patterning of graphene through femtosecond laser ablation  

SciTech Connect

We report on nanometer-scale patterning of single layer graphene on SiO{sub 2}/Si substrate through femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold of graphene. It is shown that, even though both SiO{sub 2} and Si have more absorption in the linear regime compared to graphene, the substrate can be kept intact during the process. This is achieved by scanning the sample under laser illumination at speeds yielding a few numbers of overlapping pulses at a certain point, thereby effectively shielding the substrate. By adjusting laser fluence and translation speed, 400?nm wide ablation channels could be achieved over 100??m length. Raster scanning of the sample yields well-ordered periodic structures, provided that sufficient gap is left between channels. Nanoscale patterning of graphene without substrate damage is verified with Scanning Electron Microscope and Raman studies.

Sahin, R.; Akturk, S., E-mail: selcuk.akturk@itu.edu.tr [Department of Physics, Istanbul Technical University, Maslak 34469, Istanbul (Turkey); Simsek, E. [Electrical and Computer Engineering, The George Washington University, Washington, DC 20052 (United States)

2014-02-03

275

Direct coupling of a laser ablation cell to an AMS  

NASA Astrophysics Data System (ADS)

In rare cases, cleaned samples can be directly inserted into a negative ion source of an AMS and still meet the requirements for long-term and stable measurements. We present the coupling of a laser ablation system to the gas ion source of an AMS system (MICADAS, ETH Zurich) for direct and continuous CO2 introduction. Solid carbonate samples like stalagmites or corals are suitable sample materials, which can be ablated and decomposed continuously using a pulsed laser focused onto the surface of a solid sample, which is placed in an airtight ablation cell. CO2 formed during the ablation of a CaCO3 sample is continually flushed with He into the gas ion source. The production rate of CO2 can be adjusted via the laser pulse repetition rate (1-20 Hz), the crater diameter (1-150 ?m) and the energy density applied (0.2-3 mJ/pulse) of the laser (frequency quintupled Nd:YAG at 213 nm with 5 ns pulse duration). In our first test, measurements of one sample with known age were replicated within one sigma. Blanks showed 5% contamination of modern carbon of yet unknown origin. In order to develop LA-AMS into a routine sampling tool the ablation cell geometry and settings of the gas ion source have to be further optimized.

Wacker, L.; Münsterer, C.; Hattendorf, B.; Christl, M.; Günther, D.; Synal, H.-A.

2013-01-01

276

Laser ablation and influence of Debye temperature and laser parameters on size and number of nanoparticles  

NASA Astrophysics Data System (ADS)

Dependence of size and number of nanoparticles on kind of material, power of laser and pulse duration of laser in laser ablation is investigated by presenting a model based on Debye model for specific heat capacity. Simulations from the theory demonstrate that there is a critical power of laser which is very important for controlling size of nanoparticles in laser ablation method. The critical power of laser depends on material Debye temperature and pulse duration of laser. Finally difference between experimental diagrams of zinc and carbon is explained by using results of the theory.

Vaezzadeh, Majid; Saeidi, Mohammadreza; Zarei, Mohsen

2010-03-01

277

Optical time of flight studies of lithium plasma in double pulse laser ablation: Evidence of inverse Bremsstrahlung absorption  

SciTech Connect

The early stage of formation of lithium plasma in a collinear—double pulse laser ablation mode has been studied using optical time of flight (OTOF) spectroscopy as a function of inter-pulse delay time, the distance from the target surface and the fluence of the ablation lasers. The experimental TOF measurements were carried out for lithium neutral (670.8?nm and 610.3?nm), and ionic (548.4?nm and 478.8?nm) lines. These experimental observations have been compared with that for single pulse laser ablation mode. It is found that depending on the fluence and laser pulse shape of the first pre-ablation laser and the second main ablation laser, the plasma plume formation and its characteristic features can be described in terms of plume-plume or laser-plume interaction processes. Moreover, the enhancement in the intensity of Li neutral and ionic lines is observed when the laser-plume interaction is the dominant process. Here, we see the evidence of the role of inverse Bremsstrahlung absorption process in the initial stage of formation of lithium plasma in this case.

Sivakumaran, V.; Joshi, H. C.; Singh, R. K.; Kumar, Ajai, E-mail: ajai@ipr.res.in [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)

2014-06-15

278

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

279

Visual servoing of a laser ablation based cochleostomy  

NASA Astrophysics Data System (ADS)

The aim of this study is a defined, visually based and camera controlled bone removal by a navigated CO II laser on the promontory of the inner ear. A precise and minimally traumatic opening procedure of the cochlea for the implantation of a cochlear implant electrode (so-called cochleostomy) is intended. Harming the membrane linings of the inner ear can result in damage of remaining organ functions (e.g. complete deafness or vertigo). A precise tissue removal by a laser-based bone ablation system is investigated. Inside the borehole the pulsed laser beam is guided automatically over the bone by using a two mirror galvanometric scanner. The ablation process is controlled by visual servoing. For the detection of the boundary layers of the inner ear the ablation area is monitored by a color camera. The acquired pictures are analyzed by image processing. The results of this analysis are used to control the process of laser ablation. This publication describes the complete system including image processing algorithms and the concept for the resulting distribution of single laser pulses. The system has been tested on human cochleae in ex-vivo studies. Further developments could lead to safe intraoperative openings of the cochlea by a robot based surgical laser instrument.

Kahrs, Lüder A.; Raczkowsky, Jörg; Werner, Martin; Knapp, Felix B.; Mehrwald, Markus; Hering, Peter; Schipper, Jörg; Klenzner, Thomas; Wörn, Heinz

2008-03-01

280

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

281

The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled  

E-print Network

The effect of ultrafast laser wavelength on ablation properties and implications on sample wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate

Harilal, S. S.

282

Laser Ablative Structural Modification of Poly(ethylene-alt-maleic anhydride)  

E-print Network

Laser Ablative Structural Modification of Poly(ethylene-alt-maleic anhydride) Josef Pola Manuscript Received July 30, 2003 Pulsed IR laser ablation of poly(ethylene-alt-maleic anhydride) results rare example of laser ablative deposition of polymeric films that are structurally identical

Masoudi, Husain M.

283

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

E-print Network

The role of laser wavelength on plasma generation and expansion of ablation plumes in air A. E to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser

Harilal, S. S.

284

Major element analysis of natural silicates by laser ablation ICP-MS Munir Humayun,*a  

E-print Network

Major element analysis of natural silicates by laser ablation ICP-MS Munir Humayun,*a Fred A silicates has previously been accomplished only by combining laser ablation ICP-MS with electron microprobe a method for laser ablation ICP-MS analysis of major elements in silicate glasses and minerals that, when

Weston, Ken

285

High-Resolution Optical Coherence Tomography-Guided Laser Ablation of Surgical Tissue1  

E-print Network

High-Resolution Optical Coherence Tomography-Guided Laser Ablation of Surgical Tissue1 Stephen A backscattering properties of tissue, changes in tissue optical properties due to sur- gical laser ablation should to guide the placement and observe the dynamics of surgical laser ablation in a variety of tissue types

Boppart, Stephen

286

Phase explosion and its time lag in nanosecond laser ablation Xianfan Xu*  

E-print Network

Phase explosion and its time lag in nanosecond laser ablation Xianfan Xu* School of Mechanical kinetics during nanosecond pulsed excimer ablation of a metal. During laser heating, the surface can reach in ablation induced by nanosecond or shorter pulsed lasers. This paper discusses experiments for investigating

Xu, Xianfan

287

Analyses of femtosecond laser ablation of Ti, Zr and Hf. D. Grojo, J. Hermann*  

E-print Network

Analyses of femtosecond laser ablation of Ti, Zr and Hf. D. Grojo, J. Hermann* , S. Bruneau and T ABSTRACT Femtosecond laser ablation of Ti, Zr and Hf has been investigated by means of in-situ plasma ablation process. The expansion behaviour of these two components has been analysed as a function of laser

Paris-Sud XI, Université de

288

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement irradiation regimes  

E-print Network

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement material ejection at laser fluences above the ablation threshold. This phase explosion leads and photomechanical processes in laser ablation. In the present study we apply a molecular-level simulation technique

Zhigilei, Leonid V.

289

Femtosecond laser-induced ablation of graphite K. Sokolowski-Tinten1  

E-print Network

Femtosecond laser-induced ablation of graphite K. Sokolowski-Tinten1 , S. Kudryashov1 , V. Temnov1 the changes of the interatomic potentials due to electronic excitation. Femtosecond laser ablation of solids experimental and theoretical study of ultrashort laser pulse ablation of graphite, emphasizing how the specific

von der Linde, D.

290

Phase explosion in atmospheric pressure infrared laser ablation from water-rich targets  

E-print Network

Phase explosion in atmospheric pressure infrared laser ablation from water-rich targets Zhaoyang dynamics model was developed for the ablation of water-rich targets by infrared laser pulses at atmospheric explosion on laser ablation dynamics, and it is relevant for the preparative, analytical, and medical

Vertes, Akos

291

Metal ablation by picosecond laser pulses: A hybrid simulation Carsten Schafer and Herbert M. Urbassek*  

E-print Network

Metal ablation by picosecond laser pulses: A hybrid simulation Carsten Scha¨fer and Herbert M 2002; published 5 September 2002 We investigate picosecond laser ablation of metals using a hybrid UV laser irradiation of copper, we investigate the fluence dependence of the ablation yield

Zhigilei, Leonid V.

292

High-throughput metal nanoparticle catalysis by pulsed laser ablation Selim Senkan a,*, Michael Kahn a  

E-print Network

High-throughput metal nanoparticle catalysis by pulsed laser ablation Selim Senkan a,*, Michael online 18 July 2006 Abstract A high-throughput pulsed laser ablation (HT-PLA) system was developed for the preparation of multi-metallic nanoparticles that are anchored to the support materials. Pulsed laser ablation

Senkan, Selim M.

293

Femtosecond laser ablation properties of borosilicate glass Adela Ben-Yakara)  

E-print Network

Femtosecond laser ablation properties of borosilicate glass Adela Ben-Yakara) Mechanical) We study the femtosecond laser ablation properties of borosilicate glass using atomic force of the laser fluence in the form of D2 =2w0 2 ln F0/Fth N=1 provides the single-shot ablation threshold, Fth N

Byer, Robert L.

294

A Low Diffraction Laser Beam as Applied to Polymer Ablation Xuanhui Lu*  

E-print Network

A Low Diffraction Laser Beam as Applied to Polymer Ablation Xuanhui Lu* , Y. Lawrence Yao , and Kai that of a Gaussian beam. The effects of the improved beam quality on laser ablation process are investigated on polymeric material. A theoretical model is provided to predict laser ablated hole profile

Yao, Y. Lawrence

295

Summer 2010 Pulsed Laser Ablation of solid targets in a liquid  

E-print Network

Summer 2010 #12; Pulsed Laser Ablation of solid targets in a liquid environment has proved will be presented. #12;A high power laser is used to vaporize the target in an ablation plume. The particles (CVD)- APPROX. 100% FORMS NANOTUBES. Simply because Laser Ablation offers a very versatile means

Baltisberger, Jay H.

296

Catalytic nanoparticles for carbon nanotube growth synthesized by through thin film femtosecond laser ablation  

E-print Network

laser ablation C. M. Rouleau,1* M. Tian,2 A. A. Puretzky,1 M. Mahjouri-Samani,1 G. Duscher,2 and D. B of femtosecond-based through thin film laser ablation (TTFA) to that of ns TTFA, and testing the feasibility-described through thin film ablation (TTFA) and laser-induced jets of nanoparticle arrays, respectively, to create

Geohegan, David B.

297

Photoluminescence from gas-suspended SiOx nanoparticles synthesized by laser ablation  

E-print Network

Photoluminescence from gas-suspended SiOx nanoparticles synthesized by laser ablation David BOx particles formed by laser ablation of Si into 1­10 Torr He and Ar. Three spectral bands 1.8, 2.5 and 3.2 e clusters of 30 atoms .2 Laser ablation is a versatile vaporization tool, and has recently been used to form

Geohegan, David B.

298

Combining cell microdissection ... ... with laser ablation electrospray ionization (LAESI) mass spectrometry enables the  

E-print Network

. Combining cell microdissection ... ... with laser ablation electrospray ionization (LAESI) mass Gradients in Single Cells by Laser Ablation Electrospray Ionization Mass Spectrometry** Jessica A. Stolee are not available for analysis.[29­31] In laser ablation electrospray ionization (LAESI) of biological samples

Vertes, Akos

299

Morphology of femtosecond-laser-ablated borosilicate glass surfaces Adela Ben-Yakara)  

E-print Network

Morphology of femtosecond-laser-ablated borosilicate glass surfaces Adela Ben-Yakara) and Robert L. Our observations show that a thin rim is formed around ablated craters after a single laser pulse writing of microchannels in glass.3­6 Using this laser ablation technique, it is possible to fabricate

Byer, Robert L.

300

Dynamics of laser ablation plume penetration through low pressure background gases  

E-print Network

Dynamics of laser ablation plume penetration through low pressure background gases David B; accepted for publication 2 May 1995 The dynamics of laser-ablated yttrium plume propagation through . During expansion into low-pressure background gases, the ion flux in the laser ablation plasma plume

Geohegan, David B.

301

EFFECT OF PULSING PARAMETERS ON LASER ABLATIVE CLEANING OF COPPER Paper # M602  

E-print Network

EFFECT OF PULSING PARAMETERS ON LASER ABLATIVE CLEANING OF COPPER OXIDES Paper # M602 Jie Zhang the laser ablative cleaning process. In the model, property discontinuity and Stephan and kinetic boundary based on the working mechanism of laser ablation. Copper is the most widely utilized metal

Yao, Y. Lawrence

302

Laser Ablation Electrospray Ionization for Atmospheric Pressure Molecular Imaging Mass Spectrometry  

E-print Network

Chapter 9 Laser Ablation Electrospray Ionization for Atmospheric Pressure Molecular Imaging Mass Spectrometry Peter Nemes and Akos Vertes Abstract Laser ablation electrospray ionization (LAESI) is a novel-IR) MALDI (3), laser ablation S.S. Rubakhin, J.V. Sweedler (eds.), Mass Spectrometry Imaging, Methods

Vertes, Akos

303

A low diffraction laser beam as applied to polymer ablation Xuanhui Lu,a)  

E-print Network

A low diffraction laser beam as applied to polymer ablation Xuanhui Lu,a) Y. Lawrence Yao beam. The effects of the improved beam quality on a laser ablation process are investigated using a polymeric material. A theoretical model is provided to predict the laser ablated hole profile

Yao, Y. Lawrence

304

Photochemical fragmentation processes in laser ablation of organic Yaroslava G. Yingling a,*, Leonid V. Zhigilei b  

E-print Network

Photochemical fragmentation processes in laser ablation of organic solids Yaroslava G. Yingling a) laser ablation of molecular solids have received considerable attention due to its proven and potential applications. Despite its active practical use the mechanisms of laser ablation are still being studied

Zhigilei, Leonid V.

305

Sediment profiles of less commonly determined elements measured by Laser Ablation ICP-MS  

E-print Network

Sediment profiles of less commonly determined elements measured by Laser Ablation ICP on a short list of high-abundance trace elements. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry of this investigation is to harness the analytical power of Laser Ablation ICP-MS to explore the behavior of a large

Mcdonough, William F.

306

RAPID COMMUNICATION Quantifying the quality of femtosecond laser ablation of graphene  

E-print Network

RAPID COMMUNICATION Quantifying the quality of femtosecond laser ablation of graphene Ramazan Sahin laser ablation [9­19] might be a simple yet efficient alternative technique compared to standard litho, femtosecond (fs) laser ablation provides high quality and repeatable struc- tures due to its non

Simsek, Ergun

307

Laser ablation atmospheric pressure photoionization mass spectrometry imaging of phytochemicals from sage leaves  

E-print Network

Laser ablation atmospheric pressure photoionization mass spectrometry imaging of phytochemicals. In this contribution, we explore the feasibility of laser ablation atmospheric pressure photoionization (LAAPPI-time-of-flight (TOF)-MSI without any sample preparation. Leaf mass spectra were also recorded with laser ablation

Vertes, Akos

308

Mechanisms of small clusters production by short and ultra-short laser ablation  

E-print Network

Mechanisms of small clusters production by short and ultra-short laser ablation Tatiana E. Itina a The mechanisms involved into the formation of clusters by pulsed laser ablation are studied both numerically ablation: (i) direct cluster ejection upon the laser-material interaction, and (ii) collisional sticking

Zhigilei, Leonid V.

309

Multiscale simulation of laser ablation of organic solids: evolution of the plume  

E-print Network

Multiscale simulation of laser ablation of organic solids: evolution of the plume Michael I. The combined multiscale model addresses different processes involved in the laser ablation phenomenon distribution 1. Introduction The need to understand the mechanisms of plume expansion in laser ablation

Zhigilei, Leonid V.

310

In situ photography of picosecond laser ablation of nickel D.A. Willis1  

E-print Network

In situ photography of picosecond laser ablation of nickel D.A. Willis1 , X. Xu* School investigated the time evolution of nickel ablation induced by high-energy picosecond laser pulses. A Nd.V. All rights reserved. Keywords: Picosecond laser; Ablation; Heat transfer; Homogeneous nucleation

Xu, Xianfan

311

Limit of overheating and the threshold behavior in laser ablation Barbara J. Garrison  

E-print Network

Limit of overheating and the threshold behavior in laser ablation Barbara J. Garrison Department, designed to examine the threshold behavior in laser ablation, demonstrate that the rate of homogeneous demonstrated and ana- lytic theories 3 have predicted that there is a threshold for pulsed laser ablation

Zhigilei, Leonid V.

312

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

Microsoft Academic Search

Laser ablation milling with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials like metals, ceramics and polymers. A precise machining result with high surface quality requires a defined ablation process. Problems arise through the scatter in the resulting ablation depth of the laser beam machining process where material is removed in layers. Since

Volker Schulze; Patricia Weber

2010-01-01

313

Fundamental Mechanisms of Pulsed Laser Ablation of Biological Tissue  

NASA Astrophysics Data System (ADS)

The ability to cut and remove biological tissue with short pulsed laser light, a process called laser ablation, has the potential to revolutionize many surgical procedures. Ablation procedures using short pulsed lasers are currently being developed or used in many fields of medicine, including cardiology, ophthalmology, dermatology, dentistry, orthopedics, and urology. Despite this, the underlying physics of the ablation process is not well understood. In fact, there is wide disagreement over whether the fundamental mechanism is primarily photothermal, photomechanical, or photochemical. In this thesis, both experimental and theoretical techniques are developed to explore this issue. The photothermal model postulates that ablation proceeds through vaporization of the target material. The photomechanical model asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. I have developed a three dimensional 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. A complimentary experimental technique has been developed to verify this model, measure the needed physical properties of the tissue, and record the thermoelastic response of the tissue at the onset of ablation. The results of this work have been widely disseminated to the international research community and have led to significant findings which support the photomechanical model of ablation of tissue. First, the energy deposited in tissue is an order of magnitude less than that required for vaporization. Second, unlike the one-dimensional thermoelastic model of laser-induced stress generation that has appeared in the literature, the full three-dimensional model predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to occur. Third, although the laser-induced temperature rise is modest, the magnitude of the stresses is sufficient to initiate mechanically destructive phenomenon. In hard materials, including bone, a gradual weakening of material with each successive laser pulse is observed and correlated with the formation of permanent microcracks within the material. In meniscus, a representative soft tissue, the growth and collapse of mechanically destructive cavitation bubbles is observed. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Albagli, Douglas

314

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

315

Lasers in Surgery and Medicine 40:483493 (2008) Effects of Laser Repetition Rate on Corneal Tissue Ablation  

E-print Network

Ablation for 193-nm Excimer Laser Light Leia M. Shanyfelt, MS,1 Pamela L. Dickrell, PhD,1 Henry F generated at laser repetition rates of up to 400 Hz are comparable to ablations performed at rates effects of excimer laser repetition rate on the overall corneal ablation metrics revealed no measurable

Hahn, David W.

2008-01-01

316

Forensic comparative glass analysis by laser-induced breakdown spectroscopy  

Microsoft Academic Search

Glass samples of four types commonly encountered in forensic examinations have been analyzed by laser-induced breakdown spectroscopy (LIBS) for the purpose of discriminating between samples originating from different sources. Some of the glass sets were also examined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Refractive index (RI) measurements were also made on all glass samples and the refractive index data

Candice M. Bridge; Joseph Powell; Katie L. Steele; Michael E. Sigman

2007-01-01

317

KrF pulsed laser ablation of thin films made from fluorinated heterocyclic poly(naphthyl-imide)s.  

PubMed

Among the many aspects of laser ablation, development of conical structures induced by excimer laser radiation on polyimide surfaces has been thoroughly investigated. Because the mechanisms that produce these surface textures are not fully understood, two theories, photochemical bond breaking and thermal reaction, have been introduced. Here we present the first study of ultraviolet laser ablation behavior of thin films made from fluorinated poly(naphthyl-imide)s containing oxadiazole rings and the investigation of the mechanism of cone-like structure formation at two laser fluences, 57 and 240 mJ/cm(2). The morphology of thin films before and after laser ablation was studied by using various spectroscopy techniques such as Fourier transform infrared spectroscopy, time-resolved emission and X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurements. All of the data suggest impurities shielded at low fluence radiation (57 mJ/cm(2)) and a radiation hardening process at high value fluence (240 mJ/cm(2)), which are proposed as the main mechanisms for laser ablation of our polyimide films, and we bring evidence to support them. PMID:22640965

Damaceanu, Mariana-Dana; Rusu, Radu-Dan; Olaru, Mihaela Adriana; Timpu, Daniel; Bruma, Maria

2012-06-01

318

Vibration testing based on impulse response excited by laser ablation  

NASA Astrophysics Data System (ADS)

This paper proposes an innovative vibration testing method based on impulse response excited by laser ablation. In conventional vibration testing using an impulse hammer, high-frequency elements of over tens of kilohertz are barely present in the excitation force. A pulsed high-power YAG laser is used in this study for producing an ideal impulse force on a structural surface. Illuminating a point on a metal with the well-focused YAG laser, laser ablation is caused by generation of plasma on the metal. As a result, an ideal impulse excitation force generated by laser ablation is applied to the point on the structure. Therefore, it is possible to measure high-frequency FRFs due to the laser excitation. A water droplet overlay on the metal is used to adjust the force magnitude of laser excitation. An aluminum block that has nine natural frequencies below 40 kHz is employed as a test piece. The validity of the proposed method is verified by comparing the FRFs of the block obtained by the laser excitation, impulse hammer, and finite element analysis. Furthermore, the relationship between accuracy of FRF measurements and sensitivity of sensors is investigated.

Kajiwara, Itsuro; Hosoya, Naoki

2011-10-01

319

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

320

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

321

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

322

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. PMID:17933877

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

2008-01-01

323

CO{sub 2} Laser Ablation Propulsion Tractor Beams  

SciTech Connect

Manipulation of objects at a distance has already been achieved with no small measure of success in the realm of microscopic objects on the scale size of nanometers to micrometers in applications including laser trapping and laser tweezers. However, there has been relatively little effort to apply such remote control to macroscopic systems. A space tractor beam could be applied to a wide range of applications, including removal of orbital debris, facilitation of spacecraft docking, adjustment of satellite attitude or orbital position, etc. In this paper, an ablative laser propulsion tractor beam is demonstrated based on radiation from a CO{sub 2} laser. Cooperative, layered polymer targets were used for remote impulse generation using a CO{sub 2} laser. The use of a structured ablatant enabling switching between thrust directional parity (i.e., forward or reverse) and imparting torque to a remote target. Fluence-dependent results are presented in the context of polymer ablation modeling work and with consideration of confined ablation effects.

Sinko, John E. [Micro-Nano Global Center of Excellence, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan); Schlecht, Clifford A. [Institute for Materials and Complexity, Saint Louis, MO 63112 (United States)

2010-05-06

324

Effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion  

Microsoft Academic Search

Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion. A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 mum, 30 J pulse energy was used to ablate water contained in a quadrate quartz

C. Y. Cui; Y. J. Hong; J. F. Ye; M. Wen; N. L. Li

2011-01-01

325

Endometrial laser ablation in rabbits: A comparative study of three laser types  

SciTech Connect

Endometrial laser ablation is one of the alternatives to hysterectomy in cases of intractable uterine bleeding. It is currently performed using the Nd:YAG laser at 1.06 microns. The aim of this study was to compare the tissue effect of three types of laser irradiation (Nd:YAG laser at 1.06 and 1.32 microns and holmium laser at 2.12 microns) on the rabbit endometrium. Crater formation, coagulation necrosis, and muscle necrosis were evaluated at the time of ablation, as well as at 1 week and 4 weeks postablation. The results were assessed by determining the depth and width of the affected portion in the uterine wall (lumen to serosa). It was shown that Nd:YAG laser at 1.32 microns caused more generalized and extended effects as compared with the other laser types examined. Endometrial regeneration was faster after ablation by the Nd:YAG laser at 1.06 microns and the holmium laser than by the Nd:YAG laser at 1.32 microns. The widest range of ablation energy (defined as that causing ablation without muscle damage) was achieved by applying the holmium laser. Further evaluation of the holmium laser for this indication is recommended.

Rosenberg, C.; Tadir, Y.; Braslavsky, D.; Fisch, B.; Karni, Z.; Ovadia, J. (Beilinson Medical Center, Tel Aviv (Israel))

1990-01-01

326

Dynamics of Laser-Driven Ablatively Accelerated Targets.  

NASA Astrophysics Data System (ADS)

The characteristics of ablation plasma from planar targets, driven by long Nd: glass laser pulses (4 nsec, < 10('14) W/cm('2)), and the velocity of the ablatively accelerated targets are experimentally studied. Ablation plasma diagnostics include arrays of time-of-flight ion collectors, plasma calorimeters, and ballistic pendula which directly measure the plasma velocity, energy, and momentum. The ballistic pendula have been tested and calibrated in the experimental environment. A novel double-foil technique has been developed and used to study the velocity of the accelerated target. Using measurements of plasma energy, velocity, and momentum, we determine the scaling with irradiance and the absolute magnitudes of the ablation pressure, velocity and ablation depth (or mass ablation rate). These results are insensitive to laser spot-size effects that may introduce error under some experimental conditions. They imply that the hydrodynamic efficiency and initial thickness of targets acclerated to fusion velocities are weak and strong functions of absorbed irradiance respectively. Thus, target thickness and irradiance may be varied as necessary to alter the pellet-aspect-ratio or to increase laser nonuniformity smoothing with only small changes in hydrodynamic efficiency. We have determined that the accelerated target is composed of a high pressure, high density region preceeded by a low pressure, low desnity plasma. We have measured the velocity of the high density region and found that it agrees with target velocities predicted from the ablation parameters using a simple rocket model. We accelerated targets over a distances many times their own thickness to velocities of 100 km/sec with no apparent breakup. These dense target velocities are close to the implosion velocities required of hollow fusion-pellet shells.

Grun, Jacob

327

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

328

Laser Ablative Shaping of Plastic Optical Components for Phase Control  

NASA Astrophysics Data System (ADS)

A new scheme for phase control of optical components with laser ablation has been developed. One can ablate the surface shape of optical plastic material coated on a glass plate by using 193-nm laser light to control the transmission wave front. The surface shape is monitored in situ and corrected to attain the desired aberration level. The irradiation fluence is approximately 40 mJ cm 2 , and the ablation depth pulse is approximately 0.01 m pulse for UV-cured resin. A wave-front aberration of 3.0 is reduced to 0.17 for flat surface shaping. For spherical surface generation, an aberration of 2.5 is reduced to 0.2 . The increase in surface roughness is kept within acceptable levels.

Jitsuno, Takahisa; Tokumura, Keiu; Nakashima, Nobuaki; Nakatsuka, Masahiro

1999-05-01

329

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

330

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

331

Excimer laser ablation of thick SiOx-films: Etch rate measurements and simulation of the ablation threshold  

NASA Astrophysics Data System (ADS)

Excimer laser ablation of 4.5 ?m thick SiOx-films with x ? 1 is investigated at 193 nm, 248 nm, and 308 nm. Strong absorption enables precisely tunable removal depths. The ablation rates correlate with laser penetration depths calculated from low level absorption coefficients. The experimental ablation thresholds are in agreement with numerical simulations on the basis of linear absorption and one-dimensional heat flow. This behaviour is similar to that of strongly UV-absorbing polymers, leading to well controllable micro machining prospects. After laser processing, SiOx can be converted to SiO2, opening a route to laser based fabrication of micro optical components.

Ihlemann, J.; Meinertz, J.; Danev, G.

2012-08-01

332

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

333

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

334

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

335

Synthesis of cubic ruthenium nitride by reactive pulsed laser ablation  

Microsoft Academic Search

The recent synthesis of platinum nitride opens the possibility of novel platinum-group metal nitrides to exist. In this work we report the synthesis of ruthenium nitride by reactive pulsed laser ablation. Several plausible structures have been evaluated by ab initio calculations using the full potential linearized augmented plane wave method, in order to investigate the ruthenium nitride structural and electronic

M. G. Moreno-Armenta; J. Diaz; A. Martinez-Ruiz; G. Soto

2007-01-01

336

Direct writing of microlenses in polycarbonate with excimer laser ablation  

Microsoft Academic Search

A method for fabricating microlenses in polycarbonate material is reported. Using a direct-write technique based on scanning excimer laser ablation with a circular beam, we can etch an arbitrary shape in the polymer material. The beam is obtained by imaging a circular aperture onto the polymer surface, and scanning is realized by the translation stage carrying the sample, which makes

Kris Naessens; Heidi Ottevaere; Roel Baets; Peter van Daele; Hugo Thienpont

2003-01-01

337

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

338

Ablation by short optical and x-ray laser pulses  

Microsoft Academic Search

The paper is devoted to experimental and theoretical studies of ablation of condensed matter by optical (OL), extreme ultraviolet (EUV) and X-ray lasers (XRL). Results obtained at two different XRL are compared. The first XRL is collision Ag-plasma laser with pulse duration tauL = 7 ps and energy of quanta hv=89.3 eV, while the second one is EUV free electron

N. A. Inogamov; S. I. Anisimov; V. V. Zhakhovsky; A. Ya. Faenov; Yu. V. Petrov; V. A. Khokhlov; V. E. Fortov; M. B. Agranat; S. I. Ashitkov; P. S. Komarov; I. Yu. Skobelev; Y. Kato; T. A. Pikuz; V. V. Shepelev; Y. Fukuda; M. Tanaka; M. Kishimoto; M. Ishino; M. Nishikino; M. Kando; T. Kawachi; M. Nagasono; H. Ohashi; M. Yabashi; K. Tono; Y. Senba; T. Togashi; T. Ishikawa

2010-01-01

339

Laser ablation\\/ionization mass spectrometry on tokamak deposition probes  

Microsoft Academic Search

Laser ablation-ionization mass spectrometric surface analysis was applied in plasma diagnostic experiments on the MT-1M tokamak. Non-intrinsic impurities were injected into the discharges using laser blow-off in order to study the impurity transport processes. High purity silicon samples were used as deposition probes in the edge plasma of the tokamak. The distributions of the impurities deposited on the probe surfaces

M. Á. Kedves; J. S. Bakos; P. N. Ignácz; B. Kardon; J. Szigeti

1996-01-01

340

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

2008-02-01

341

Laser ablation in a model two-phase system Gareth J. Williams a,*, Leonid V. Zhigilei a,b  

E-print Network

Laser ablation in a model two-phase system Gareth J. Williams a,*, Leonid V. Zhigilei a,b , Barbara, University of Virginia, Charlottesville, VA 22903, USA Abstract Short pulse laser ablation of a model two methods; Laser ablation of hard tissue 1. Introduction Laser ablation is an increasingly important

Zhigilei, Leonid V.

342

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

343

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

Microsoft Academic Search

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

Seung H. Ko; Heng Pan; David J. Hwang; Jaewon Chung; Sangil Ryu; Costas P. Grigoropoulos; Dimos Poulikakos

2007-01-01

344

Recent advances in laser ablation modelling for asteroid deflection methods  

NASA Astrophysics Data System (ADS)

Over the past few years, a series of studies have demonstrated the theoretical benefits of using laser ablation in order to mitigate the threat of a potential asteroid on a collision course with earth. Compared to other slow-push mitigation strategies, laser ablation allows for a significant reduction in fuel consumption since the ablated material is used as propellant. A precise modelling of the ablation process is however difficult due to the high variability in the physical parameters encountered among the different asteroids as well as the scarcity of experimental studies available in the literature. In this paper, we derive a new thermal model to simulate the efficiency of a laser-based detector. The useful material properties are first derived from thermochemical tables and equilibrium thermodynamic considerations. These properties are then injected in a 3D axisymetrical thermal model developed in Matlab. A temperature-dependent conduction flux is imposed on the exterior boundary condition that takes into account the balance between the incident power and the power losses due to the vaporization process across the Knudsen layer and the radiations respectively. A non-linear solver is finally used and the solution integrated over the ablation front to reconstruct the net thrust and the global mass flow. Compared to an initial 1D model, this new approach shows the importance of the parietal radiation losses in the case of a CW laser. Despite the low energy conversion efficiency, this new model still demonstrates the theoretical benefit of using lasers over more conventional low-thrust strategies.

Thiry, Nicolas; Vasile, Massimiliano

2014-09-01

345

Preparation and characterization of bismuth nanostructures deposited by pulsed laser ablation  

NASA Astrophysics Data System (ADS)

Bismuth nanostructures, from nanoparticles to quasi-percolated films, were deposited by pulsed laser ablation (PLA) on different substrates using the 355 nm line of a Nd:YAG laser. The morphology and size distribution of the obtained nanostructures were investigated, as a function of the number of ablation pulses, by high resolution electron microscopy (HRTEM) and atomic force microscopy (AFM). Deposits with a small number of pulses, 50, are formed of separated isolated particles with diameters in the range from 5 to 20 nm. Further increase in the number of pulses (>100) results in coalescence of individual particles with the formation of dendritic structures and finally, for 500 pulses, quasi-percolated Bi films are obtained. Additionally, the nanostructures formed were characterized by XPS, and Raman spectroscopy in order to determine the physical and chemical properties of the deposited material.

Escobar-Alarcón, L.; Morales-Mendez, J. G.; Solís-Casados, D. A.; Romero, S.; Fernández, M.; Haro-Poniatowski, E.

2015-01-01

346

A review of Thulium fiber laser ablation of kidney stones  

NASA Astrophysics Data System (ADS)

The clinical solid-state Holmium:YAG laser lithotripter (?=2120 nm) is capable of operating at high pulse energies, but its efficient operation is limited to low pulse rates during lithotripsy. The diode-pumped experimental Thulium Fiber Laser (?=1908 nm) is limited to low pulse energies, but can operate at high pulse rates. This review compares stone ablation threshold, ablation rate, and retropulsion effects for Ho:YAG and TFL. Laser lithotripsy complications also include optical fiber bending failure resulting in endoscope damage and low irrigation rates leading to poor visibility. Both problems are related to fiber diameter and limited by Ho:YAG laser multimode spatial beam profile. This study exploits TFL spatial beam profile for higher power transmission through smaller fibers. A short taper is also studied for expanding TFL beam at the distal tip of a small-core fiber. Stone mass loss, stone crater depths, fiber transmission losses, fiber burn-back, irrigation rates, and deflection through a flexible ureteroscope were measured for tapered fiber and compared with conventional fibers. The stone ablation threshold for TFL was four times lower than for Ho:YAG. Stone retropulsion with Ho:YAG increased linearly with pulse energy. Retropulsion with TFL was minimal at pulse rates < 150 Hz, then rapidly increased at higher pulse rates. TFL beam profile provides higher laser power through smaller fibers than Ho:YAG laser, potentially reducing fiber failure and endoscope damage and allowing greater irrigation rates for improved visibility and safety. Use of a short tapered distal fiber tip also allows expansion of the laser beam, resulting in decreased fiber tip damage compared to conventional fibers, without compromising fiber bending, stone ablation efficiency, or irrigation rates.

Fried, Nathaniel M.; Blackmon, Richard L.; Irby, Pierce B.

2011-02-01

347

Epitaxial growth of RbTiOPO4 films on KTiOPO4 substrates by excimer laser ablation technique  

NASA Astrophysics Data System (ADS)

Transparent single-phase rubidium titanyl phosphate (RTP) films having excellent crystalline properties have been deposited by excimer laser ablation method on (001)- and (010)-oriented potassium titanyl phosphate (KTP) substrates, respectively. X-ray theta-2 theta scans and pole figures showed that the laser-ablated RTP films grew epitaxially on, and had exactly the same orientations of, the underlying KTP substrates. X-ray photoelectron spectroscopy analysis revealed that the RTP films prepared with this method are nearly stoichiometric. It appears to be possible to use these films as waveguides having sharp waveguide/substrate interfaces.

Liu, Z. G.; Liu, J. M.; Ming, N. B.; Wang, J. Y.; Liu, Y. G.; Jiang, M. H.

1994-12-01

348

Pulsed laser ablation plasmas generated in CO{sub 2} under high-pressure conditions up to supercritical fluid  

SciTech Connect

Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO{sub 2} at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Terashima, Kazuo [Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Baba, Motoyoshi; Suemoto, Tohru [Division of Advanced Spectroscopy, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

2012-11-26

349

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

350

Correlation of laser ablation plasma emission with ICP-AES signal intensity  

SciTech Connect

Laser ablation offers many favorable characteristics for direct solid sample chemical analysis. However, the technique usually provides poor precision in comparison to solution nebulization. The primary contributor to this imprecision is the irreproducibility of the laser material interaction. This paper describes a technique for monitoring changes in the laser material interaction directly, and using these data to improve inductively coupled atomic emission spectroscopy (ICP-AES). Simultaneous measurements of the spectral emission intensity in the laser-induced plasma (LIP) and the ICP-AES were made under different power density conditions. The LIP spatial profile and excitation temperature was measured. The data from the LIP show a strong correlation with ICP-AES signal intensity. Both emission signals increase linearly with the laser power density (log-log) and show a change in the slope for different spot sizes and laser powers. These results support the occurrence of two different ablation mechanisms, a less efficient interaction dominating at the higher power densities (> 1 GW/cm2) and a more efficient interaction in the lower power density regimes. The benefits of using simultaneous monitoring of the laser induced plasma for chemical analysis by ICP-AES will be discussed.

Fernandez, A.J.; Mao, X.L.; Shannon, M.A. [Lawrence Berkeley Lab., CA (United States)] [and others

1994-12-31

351

Pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser ablation of fibrocartilage and articular cartilage  

Microsoft Academic Search

A new, near-infrared, pulsed holmium laser (wave length, 2.1 ?m; pulse duration, 400 ?s) was used to ablate bovine articular cartilage and meniscal fibrocar tilage. Microscopic examination revealed zones of ther mal damage extending 550 ?m from ablation sites. Ablation rates were measured with a mass loss tech nique. Above threshold, mass removal rates were pro portional to laser radiant

Kenneth Trauner; Norman Nishioka; Dinesh Patel

1990-01-01

352

Vitreoretinal Ablation With the 193-nm Excimer Laser in Fluid Media  

E-print Network

Vitreoretinal Ablation With the 193-nm Excimer Laser in Fluid Media Daniel Palanker,* Itzhak Hemo of the laser. Ablation occurred only when the tip was held in contact with the tissue. Conclusions,-\\ Igor Turovets* Hanan Zauberman,\\ Galina Fish,* and Aaron Lewis* Purpose. To ablate retina and vitreous

Palanker, Daniel

353

Single laser based dual-wavelength ablation technique for emission enhancement during LIBS  

NASA Astrophysics Data System (ADS)

In this paper, a novel method of the dual-wavelength (laser-induced breakdown spectroscopy LIBS) technique using a single laser system is proposed and demonstrated. Experiments are performed using a pulsed Nd3+?:?YAG laser with a pair of 355-1064 nm and also with 532-1064 nm. The shorter wavelength laser is used for ablation and plasma formation, and the fundamental wavelength (1064 nm) is used for plasma re-excitation. The proposed dual-wavelength LIBS technique is used for lunar simulant samples under different ambient pressure conditions. Various characteristic parameters, such as the emission line-intensity enhancement, plasma temperature, lifetime and plasma area, are studied. Experimental studies clearly showed the emission line-intensity enhancement up to a factor of 3. Emission lifetime showed a longer sustained emission with an increase of up to 33% for the dual-wavelength approach. A theoretical simulation based on the hydrodynamic equations is also performed for dual-wavelength ablation and re-excitation. The estimated plasma temperature and ablation plume-front velocity clearly showed an increase in dual wavelength, which is in agreement with the experimental results.

Antony, Jobin K.; Vasa, Nilesh J.; Sreedhar Raja, V. L. N.; Laxmiprasad, A. S.

2012-09-01

354

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

355

Generic incubation law for laser damage and ablation thresholds  

NASA Astrophysics Data System (ADS)

In multi-pulse laser damage and ablation experiments, the laser-induced damage threshold (LIDT) usually changes with the number of pulses in the train, a phenomenon known as incubation. We introduce a general incubation model based on two physical mechanisms—pulse induced change of (i) absorption and (ii) critical energy that must be deposited to cause ablation. The model is applicable to a broad class of materials and we apply it to fit data for dielectrics and metals. It also explains observed changes of the LIDT as a function of the laser repetition rate. We discuss under which conditions the crater-size method to determine LIDTs can be applied in multi-pulse experiments.

Sun, Zhanliang; Lenzner, Matthias; Rudolph, Wolfgang

2015-02-01

356

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

357

Heat diffusion and ablation front dynamics in Er:YAG laser skin resurfacing  

NASA Astrophysics Data System (ADS)

Influence of pulse energy, duration and beam cross-section on the outcome of Er:YAG laser ablation of skin is interpreted on the basis of an analytical model of heat diffusion and ablation front dynamics. Derived expressions enable us to identify different ablation regimes in terms of ablation efficiency and depth of thermally affected tissue layer for any thermally driven laser ablation process. Influence of laser wavelength is also discussed, focusing on a comparison between Er:YAG and carbon-dioxide laser skin resurfacing. Preliminary experimental and clinical evidence in agreement with the model is also presented.

Majaron, Boris; Lukac, Matjaz; Drnovsek-Olup, Brigita; Vedlin, Boris; Rotter, Aleksander

1997-05-01

358

Saturation effects in femtosecond laser ablation of silicon-on-insulator  

SciTech Connect

We report a surface morphology study on single-shot submicron features fabricated on silicon on insulator by tightly focused femtosecond laser pulses. In the regime just below single-shot ablation threshold nano-tips are formed, whereas in the regime just above single-shot ablation threshold, a saturation in the ablation depth is found. We attribute this saturation by secondary laser absorption in the laser-induced plasma. In this regime, we find excellent agreement between the measured depths and a simple numerical model. When the laser fluence is further increased, a sharp increase in ablation depth is observed accompanied by a roughening of the ablated hole.

Zhang Hao; Oosten, D. van; Krol, D. M.; Dijkhuis, J. I. [Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80000, 3508 TA Utrecht (Netherlands)

2011-12-05

359

A rare complication of endovenous laser ablation: intravascular laser catheter breakage  

PubMed Central

During endovenous laser ablation, which is performed as an alternative to surgery for the treatment of superficial venous insufficiency of lower extremity and associated varicose veins, it was realised that the distal end of the catheter protecting the fibre sheared off; the retained catheter fragment in the saphenous vein was removed by a mini incision. Herein, we aim to present a rare complication of endovenous laser ablation. PMID:23513025

Bozoglan, Orhan; Mese, Bulent; Inci, Mehmet Fatih; Eroglu, Erdinc

2013-01-01

360

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

361

Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold  

Microsoft Academic Search

Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials---e.g., for aluminum versus LJ the ratio Tc\\/Ttr of critical to triple-point temperature

Arun K. Upadhyay; Nail A. Inogamov; Bärbel Rethfeld; Herbert M. Urbassek

2008-01-01

362

Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold  

Microsoft Academic Search

Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}\\/T{sub tr} of critical to

Arun K. Upadhyay; Nail A. Inogamov; Baerbel Rethfeld; Herbert M. Urbassek

2008-01-01

363

Planar laser-driven ablation model for nonlocalized absorption  

SciTech Connect

A model for planar laser-driven ablation is presented. Nonlocalized inverse bremsstrahlung absorption of laser energy at a density {ital n}{sub 1}{lt}{ital n}{sub {ital c}} is assumed. A steady-state solution in the conduction zone is joined to a rarefaction wave in the underdense plasma. The calculations relate all steady-state fluid quantities to only the material, absorbed intensity, and laser wavelength. The theory agrees well with results from a computer hydrodynamics code MEDUSA (Comput. Phys. Commun. {bold 7}, 271 (1974)) and experiments.

Dahmani, F.; Kerdja, T. (Haut Commissariat a la Recherche/CDTA, Laboratorire de Fusion Thermonucleaire, 2, Bd Frantz Fanon, BP 1017 Alger-Gare, Algiers, Algeria (DZ))

1991-05-01

364

PREFACE AND CONFERENCE INFORMATION: Eighth International Conference on Laser Ablation  

NASA Astrophysics Data System (ADS)

Laser ablation encompasses a wide range of delicate to extreme light interactions with matter that present considerably challenging problems for scientists to study and understand. At the same time, laser ablation also represents a basic process of significant commercial importance in laser material processing—defining a multi-billion dollar industry today. These topics were widely addressed at the 8th International Conference on Laser Ablation (COLA), held in Banff, Canada on 11-16 September 2005. The meeting took place amongst the majestic and natural beauty of the Canadian Rocky Mountains at The Banff Centre, where delegates enjoyed many inspiring presentations and discussions in a unique campus learning environment. The conference brought together world leading scientists, students and industry representatives to examine the basic science of laser ablation and improve our understanding of the many physical, chemical and/or biological processes driven by the laser. The multi-disciplinary research presented at the meeting underlies some of our most important trends at the forefront of science and technology today that are represented in the papers collected in this volume. Here you will find new processes that are producing novel types of nanostructures and nano-materials with unusual and promising properties. Laser processes are described for delicately manipulating living cells or modifying their internal structure with unprecedented degrees of control and precision. Learn about short-pulse lasers that are driving extreme physical processes on record-fast time scales and opening new directions from material processing applications. The conference papers further highlight forefront application areas in pulsed laser deposition, nanoscience, analytical methods, materials, and microprocessing applications. Laser ablation continues to grow and evolve, touching forefront areas in science and driving new technological trends in laser processing applications. Please enjoy the collection of papers in this proceeding. Also, please join us for COLA 2007, to be held in the Canary Islands, Spain (http://www.io.csic.es/cola07/index.php). Conference on Laser Ablation (COLA'05) September 11-16, 2005 Banff, Canada Supported by University of Toronto, Canada (UT) Pacific Northwest National Laboratory (PNNL) Sponsors Sponsorship from the following companies is gratefully acknowledged and appreciated AMBP Tech Corporation GSI Lumonics Amplitude Systèmes IMRA America, Inc. Andor Technologies Journal of Physics D: Applied Physics North Canadian Institute for Photonic Innovations LUMERA LASER GmbH Clark-MXR, Inc. Pascal Coherent, Lamdbda Physik, TuiLaser PVD Products, Inc. Continuum Staib Instruments, Inc. Cyber Laser Inc. Surface GAM LASER, Inc. International Steering Committee C. Afonso (Spain)W. Husinsky (Austria) D. Bäuerle (Austria)W. Kautek (Germany) I.W. Boyd (UK) H. Koinuma (Japan) E.B. Campbell (Sweden) H.U. Krebs (Germany) J.T. Dickinson (USA) D.H. Lowndes (USA) M. Dinescu (Romania) J.G. Lunney (Ireland) J.J. Dubowski (Canada) W. Marine (France) E. Fogarassy (France) K. Murakami (Japan) C. Fotakis (Greece) T. Okada (Japan) D. Geohegan (USA) R.E. Russo (USA) M. Gower (UK) J. Schou (Denmark) R.H. Haglund Jr. (USA) M. Stuke (Germany) R.R. Herman (Canada) K. Sugioka (Japan) W.P. Hess (USA) F. Traeger (Germany) J.S Horwitz (USA) A. Yabe (Japan) Local Organizing Committee Nikki Avery Pacific Northwest National Laboratory Ken Beck Pacific Northwest National Laboratory Jan J. Dubowski University of Alberta Robert Fedosejevs Université de Sherbrooke Alan Joly Pacific Northwest National Laboratory Michel Meunier École Polytechnique de Montréal Suwas Nikumb National Research Council Canada Ying Tsui University of Alberta Conference photograph.

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

2007-04-01

365

Ultrafast laser ablation of metals with a pair of collinear laser pulses  

SciTech Connect

We investigated the process of ultrafast laser ablation of metallic targets induced by a pair of identical laser pulses, with either p or s polarizations, temporally delayed from {approx_equal}1 ps to a few nanoseconds. We used fast ion probe diagnostics to characterize the ion plume at the moderate laser intensity ({approx_equal}10{sup 12} W/cm{sup 2}) typically employed in ultrafast laser deposition and material processing. We observed a consistent time-correlated enhancement of the ion yield and velocity, which lends itself to an interesting and useful method for manipulating ablation plasma characteristics. The mechanisms producing this feature are also discussed.

Amoruso, S.; Bruzzese, R.; Wang, X.; Xia, J. [Coherentia CNR-INFM and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy)

2008-11-10

366

Diatomic Molecular Emission Spectroscopy of Laser-induced Titanium Plasma  

NASA Astrophysics Data System (ADS)

Previous research regarding laser-induced breakdown spectroscopy (LIBS) of titanium normally focuses on the atomic and ionic Ti spectral transition lines. However, after a characteristic time subsequent to laser ablation, these lines are no longer discernable. During this temporal regime, the diatomic molecular transition lines of titanium monoxide (TiO) are prominent in the laser-induced plasma (LIP) emissions. TiO has long been studied in the contexts of stellar emissions, allowing for some of the molecular transition bands to be accurately computed from theory. In this research, optical emission spectroscopy (OES) of laser-induced plasma (LIP) generated by laser ablation of titanium is performed in order to infer temperature as a function of time subsequent to plasma formation. The emission spectra of the resulting ablation plume is imaged as a function of height above the sample surface. Temperatures are inferred over time delays following plasma formation ranging from 20 ?s-200 ?s. Computed TiO A3? – X3?, ?v = 0 transition lines are fit to spectral measurements in order to infer temperature. At tdelay = 20 ?s-80 ?s, the observed plume contains two luminescent regions each with a distinctly different temperature. As the plume evolves in time, the two regions combine and an overall temperature increase is observed.

Woods, A. C.; Parigger, C. G.

2014-11-01

367

Ablation depth in planar Sn targets during the interaction with a Nd:YAG laser for extreme ultraviolet lithography  

E-print Network

Ablation depth in planar Sn targets during the interaction with a Nd:YAG laser for extreme-0417-9642 ABSTRACT The depth of mass ablation in planar Sn targets during the interaction with a pulsed Nd:YAG laser of steady-state laser ablation developed for the laser fusion application, at which laser intensity

Najmabadi, Farrokh

368

Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO{sub 2}  

SciTech Connect

Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm{sup 2}; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO{sub 2} with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp{sup 3}-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 CO{sub 2} 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 CO{sub 2} is proposed as a practical method for synthesizing diamondoids.

Nakahara, Sho; Stauss, Sven; Kato, Toru; Terashima, Kazuo [Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8561 Chiba (Japan); Sasaki, Takehiko [Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8561 Chiba (Japan)

2011-06-15

369

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

370

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

371

Ablation and nanostructuring of metals by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ~109 s-1.

Ashitkov, S. I.; Komarov, P. S.; Ovchinnikov, A. V.; Struleva, E. V.; Zhakhovskii, V. V.; Inogamov, N. A.; Agranat, M. B.

2014-06-01

372

Hydrodynamic simulation of ultrashort pulse laser ablation of gold film  

NASA Astrophysics Data System (ADS)

The electron collision frequency in a hydrodynamic model was improved to match the laser energy absorbed with experimental data. The model calculation was used to investigate the ablation depth and the dependence of the threshold fluence of gold film on pulse width and wavelength. Two methods for estimating the ablation depth are introduced here with their respective scope of application. The dependence of the threshold fluence of gold film on the pulse width of the laser with a 1053 nm center wavelength agreed well with the experimental data. It was also observed that for pulses shorter than ~200 ps, the threshold fluence showed linear dependence on the logarithm of pulse width and increased with the wavelength, which was different from previous results.

Yu, Dong; Jiang, Lan; Wang, Feng; Shi, Xuesong; Qu, Liangti; Lu, Yongfeng

2015-03-01

373

Pico- and nanosecond laser ablation of mixed tungsten / aluminium films  

E-print Network

In order to extend the investigation of laser-assisted cleaning of ITER-relevant first mirror materials to the picosecond regime, a commercial laser system delivering 10 picosecond pulses at 355 nm at a frequency of up to 1 MHz has been used to investigate the ablation of mixed aluminium (oxide) / tungsten (oxide) layers deposited on poly- and nanocrystalline molybdenum as well as nanocrystalline rhodium mirrors. Characterization before and after cleaning using scanning electron microscopy (SEM) and spectrophotometry shows heavy dust formation, resulting in a degradation of the reflectivity. Cleaning using a 5 nanosecond pulses at 350 and 532 nm, on the other hand, proved very promising. The structure of the film remnants suggests that in this case buckling was the underlying removal mechanism rather than ablation. Repeated coating and cleaning using nanosecond pulses is demonstrated.

Wisse, M; Steiner, R; Mathys, D; Stumpp, A; Joanny, M; Travere, J M; Meyer, E

2014-01-01

374

Pre-ignition laser ablation of nanocomposite energetic materials  

SciTech Connect

Laser ignition of energetic material composites was studied for initiation with heating rates from 9.5 Multiplication-Sign 10{sup 4} to 1.7 Multiplication-Sign 10{sup 7} K/s. This is a unique heating rate regime for laser ignition studies because most studies employ either continuous wave CO{sub 2} lasers to provide thermal ignition or pulsed Nd:YAG lasers to provide shock ignition. In this study, aluminum (Al) and molybdenum trioxide (MoO{sub 3}) nanoparticle powders were pressed into consolidated pellets and ignited using a Nd:YAG laser (1064 nm wavelength) with varied pulse energy. Results show reduced ignition delay times corresponding to laser powers at the ablation threshold for the sample. Heating rate and absorption coefficient were determined from an axisymmetric heat transfer model. The model estimates absorption coefficients from 0.1 to 0.15 for consolidated pellets of Al + MoO{sub 3} at 1064 nm wavelength. Ablation resulted from fracturing caused by a rapid increase in thermal stress and slowed ignition of the pellet.

Stacy, S. C.; Massad, R. A.; Pantoya, M. L. [Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)] [Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

2013-06-07

375

FINAL REPORT. PARTICLE GENERATION BY LASER ABLATION IN SUPPORT OF CHEMICAL ANALYSIS OF HIGH LEVEL MIXED WASTE FROM PLUTONIUM PRODUCTION OPERATIONS  

EPA Science Inventory

We investigate particles produced by laser irradiation and their analysis by Laser Ablation Inductively Coupled Plasma Mass Spectroscopy (LA/ICP-MS), with a view towards optimizing particle production for analysis of high level waste materials and waste glass. LA/ICP-MS has consi...

376

Nanosecond Infrared Laser for Tissue Ablation  

Microsoft Academic Search

The Mark-III Free-Electron Laser (FEL), operating at the 6.45mum wavelength, has been used successfully in human surgery. Due to the FEL's size and cost, there has been interest in the development of a compact, inexpensive infrared laser for human surgical applications. We have investigated the role of the FEL superpulse, leading to the prediction that nanosecond pulses can satisfy the

G. S. Edwards; R. D. Pearlstein; M. L. Copeland; M. S. Hutson; K. Latone; A. Spiro; G. Pasmanik

2007-01-01

377

Morphology and oxidation of Zr-based amorphous alloy ablated by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Femtosecond laser ablation of an amorphous alloy in air, including single-pulse ablation, multi-pulse drilling and trenching has been investigated. Laser-induced ablation and related effects were examined by means of scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy and electron diffraction. Oxidation was observed in the multi-pulse ablation region surface. With selected parameters, molten trace, spatter and crystallization can be avoided in the vicinity of the machining area. The results show that femtosecond laser ablation with selected parameters is a promising method for micromachining amorphous alloys.

Wang, Xinlin; Lu, Peixiang; Dai, Nengli; Li, Yuhua; Liao, Changrui; Chang, Yanxiao; Yang, Guang; Zheng, Qiguang

2007-11-01

378

Reassembling Solid Materials by Femtosecond Laser Ablation: Case of Aluminum Nitride  

NASA Astrophysics Data System (ADS)

Through atomization and ionization, we could completely alter the composition of a nonconductive material, aluminum nitride, by femtosecond laser ablation. Preferential production of pure aluminum cluster cations Aln+ (n?32) reflects not only their higher energetic stability compared with mixed clusters AlnNm+ but also completion of thermal relaxation in ablation plasma. Observation of metastable dissociation of Aln+ indicates that cluster cations have still enough internal energy for dissociation to occur, although the process is much slower than the cluster formation. Almost no cluster formation has been observed after nanosecond laser ablation of aluminum nitride, which highlights the distinct nature of ablation plasma produced by femtosecond laser ablation.

Kobayashi, Tohru; Matsuo, Yukari

2013-06-01

379

The mesoscopic modeling of laser ablation  

NASA Astrophysics Data System (ADS)

It is common to look at the atomic processes of removal of atoms or ions from surfaces. At this microscopic scale, one has to understand which surface ions are involved, which excited states are created, how electrons are transferred and scattered, and how the excitation leads to ion removal. It is even more common to look at continuum models of energy deposition in solids, and at the subsequent heat transfer. In these macroscopic analyses, thermal conduction is combined with empirical assumptions about surface binding. Both these pictures are useful, and both pictures have weaknesses. The atomistic pictures concentrate on relatively few atoms, and do not recognize structural features or the energy and carrier fluxes on larger scales. The continuum macroscopic models leave out crystallographic information and the interplay of the processes with high nonequilibrium at smaller scales. Fortunately, there is a middle way: mesoscopic modeling, which both models the key microstructural features and provides a link between microscopic and macroscopic. In a mesoscopic model, the length scale is determined by the system; often this scale is similar to the grain size. Microstructural features like grain boundaries or dislocations are considered explicitly. The time scale in a mesoscopic model is determined by the ablation process (such as the pulse length) rather than the short time limitations of molecular dynamics, yet the highly nonequilibrium behavior is adequately represented. Mesoscopic models are especially important when key process rates vary on a short length scale. Some microstructural feature (like those in dentine or dental enamel) may absorb light much more than others; other features (like grain boundaries) may capture carriers readily, or allow easier evaporation, or capture and retain charge (like grain boundaries); it is these processes which need a mesoscopic analysis. The results described will be taken largely from the work on MgO of Ribeiro, Ramos, and Stoneham for ablation by sub-band gap light.

Stoneham, A. M.; Ramos, M. M. D.; Ribeiro, R. M.

380

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

381

Plasma ablation characterization by a laser beam deflection technique  

NASA Astrophysics Data System (ADS)

Laser probe beam and multiple-pass deflection techniques were used for real time monitoring of plumes of ablation materials in the mTorr pressure regime by chock wave characterization. Intensity and transit time of shock fronts were studied as functions of focal lens position, energy and pressure. The velocity of the shock wave was determined to be up to 30 km s-1 for a pressure of 40 mTorr.

Villagran-Muniz, Mayo; Sobral, H.; Sanchez Ake, C.; Escobar, L.; Camps, E.

2001-08-01

382

Ultrashort laser ablation of PMMA and intraocular lenses  

Microsoft Academic Search

The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials,\\u000a techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive\\u000a aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular

A. A. Serafetinides; M. Makropoulou; E. Fabrikesi; E. Spyratou; C. Bacharis; R. R. Thomson; A. K. Kar

2008-01-01

383

Optical feedback signal for ultrashort laser pulse ablation of tissue  

SciTech Connect

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

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

1997-07-01

384

Cavitation dynamics of laser ablation of bulk and wire-shaped metals in water during nanoparticles production.  

PubMed

Although the first nanoseconds to microseconds rule the resulting process yield of laser ablation in liquid, a comprehensive view involving combination of time-resolved measurement techniques is still lacking. In this paper, fundamental aspects of laser ablation of metals in water during the production of nanoparticles are discussed. Three fast diagnostic methods have been applied simultaneously. These are Optical Emission Spectroscopy for the plasma characterization, fast shadowgraph for plasma and cavitation bubble dynamics and laser scattering for the mechanisms of delivery of the produced materials in the liquid. Moreover, in order to validate the discussion, the effect on cavitation dynamics of the ablation of bulk and wire-shaped targets has been investigated together with the relative nanoparticles production yield. Unusual arrow-bow ejection phenomena between the cavitation bubble and the wire result in suppressed material back-deposition, causing efficient ejection of ablated matter into the liquid. The presented nanosecond and microsecond-resolved analysis allows estimating the timescale and role of the basic mechanisms involved in laser ablation in liquids as well as the thermodynamic characteristics of the processes. PMID:23198287

De Giacomo, A; Dell'Aglio, M; Santagata, A; Gaudiuso, R; De Pascale, O; Wagener, P; Messina, G C; Compagnini, G; Barcikowski, S

2013-03-01

385

Effect of ablation photon energy on the distribution of molecular species in laser-induced plasma from polymer in air  

NASA Astrophysics Data System (ADS)

Distribution of molecular species, C2 and CN, in laser-induced plasma from a polymer target (polyvinyl chloride: PVC) was observed for ablation with 266 nm and 355 nm pulses. The influence of ablation photon energy on the distribution of molecular species in the plasma has been thus studied. Time- and space-resolved emission spectroscopy was used for the observation which led to the determination of emission intensity profiles of C2 molecule and CN radical for different delays after the impact of the laser pulse on the target. The profiles of related elements, C, N, and excitation temperature in the plasma were further determined to correlate with those of molecular emission intensity. Different behaviors were clearly observed between plasmas induced by pulses with the two different wavelengths chosen to be close each other in the near ultraviolet (UV). A closer analysis shows the photon energy corresponding to 266 nm pulse of 4.66 eV is larger than bond energies of all the chemical bonds in the studied polymer, while that of 355 nm radiation of 3.49 eV is smaller than or in the same range of the involved bond energies. Observed different behaviors suggest therefore different ablation mechanisms of polymer by laser radiation, and consequently different channels of molecule formation in the plasma. Observation of the morphology of the craters on the target surface left by laser ablation confirmed further different ablation mechanisms with the two used wavelengths.

Lei, W. Q.; Ma, Q. L.; Motto-Ros, V.; Bai, X. S.; Zheng, L. J.; Zeng, H. P.; Yu, J.

2012-07-01

386

Interferometric diagnostic suite for ultrafast laser ablation of metals  

NASA Astrophysics Data System (ADS)

We report on the development of a suite of novel techniques to measure important characteristics in intense ultrashort laser solid target experiments such as critical surface displacement, ablation depth, and plasma characteristics. Measurement of these important characteristics on an ultrafast (~50 fs) time scale is important in understanding the primary event mechanisms in laser ablation of metal targets. Unlike traditional methods that infer these characteristics from spectral power shifts, phase shifts in frequency domain interferometry (FDI) or laser breakthrough studies of multiple shots on bulk materials, these techniques directly measure these characteristics from a single ultrafast heating pulse. These techniques are based on absolute displacement interferometry and nanotopographic applications of wavefront sensors. By applying all these femtosecond time-resolved techniques to a range of materials (Al, Au, and Au on plastic) over a range of pulse energies (1011 to 1016 W/cm2) and pulse durations (50 to 700 fs), greater insight into the ablation mechanism and its pulse parameter dependencies can be determined. Comparison of these results with hydrocode software programs also reveals the applicability of hydrocode models.

Clarke, Steven A.; Rodriguez, George; Taylor, Antoinette J.; Forsman, Andrew

2004-09-01

387

Laser ablation loading of a radiofrequency ion trap  

E-print Network

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

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

2012-01-01

388

Update On CO{sub 2} Laser Ablation Of Polyoxymethylene At 101 kPa  

SciTech Connect

Recent work has brought about a renewed interest in CO{sub 2} laser ablation studies of polyoxymethylene, due to its potential as a test target for enhancing modern understanding of the laser ablation process. In this paper, new results taken in air at atmosphere pressure are reported, including data measured at institutions in Germany and Japan, which increase the body of literature data on CO{sub 2} laser ablation of polyoxymethylene. The results are discussed in terms of aerospace parameters such as the momentum coupling coefficient and specific impulse, and are compared to a previous literature study. The threshold fluence is specified for ablation of polyoxymethylene by CO{sub 2} laser radiation. Fluences higher (and lower) than previously tested for CO{sub 2} laser ablation were studied herein, and record specific impulse values for CO{sub 2} laser ablation of flat polyoxymethylene are also reported here.

Sinko, John E. [Micro-Nano Global Center of Excellence, Nagoya University, Nagoya, 464-8603 (Japan); Scharring, Stefan; Eckel, Hans-Albert [Studies and Concepts Group, German Aerospace Center (DLR), D-70569 Stuttgart, Pfaffenwaldring 38-40 (Germany); Ogita, Naoya; Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Nagoya, 464-8603 (Japan); Roeser, Hans-Peter [Institute of Space Systems, University of Stuttgart, D-70569 Stuttgart, Pfaffenwaldring 31 (Germany)

2010-10-08

389

Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere  

SciTech Connect

We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near the laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times {<=}400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.

Harilal, S. S.; Miloshevsky, G. V.; Diwakar, P. K.; LaHaye, N. L.; Hassanein, A. [Center for Materials under Extreme Environment, and School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2012-08-15

390

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

391

ENERGY DEPOSITION AND NON-THERMAL ABLATION IN FEMTOSECOND LASER GROOVING OF SILICON  

Microsoft Academic Search

Ultra-short pulsed laser ablation of crystalline silicon is characterized by a complicated heat diffusion and material removal process. In this research, a computational investigation is undertaken to understand the temperature distribution and heat effect in femtosecond laser grooving of silicon. Energy accumulation and threshold fluence of silicon ablation by femtosecond lasers are estimated through solving coupled energy balance equations. Thermal

D. P. Wan; Jun Wang; Philip Mathew

2011-01-01

392

Microstructural evolution in laser-ablation-deposited Fe25 at.% Ge thin film  

E-print Network

Microstructural evolution in laser-ablation-deposited Fe­25 at.% Ge thin film Krishanu Biswasa in the solidifying droplets. I. INTRODUCTION The formation of coatings and thin films using pulsed laser ablation; accepted 3 October 2005) Films with Fe­25 at.% Ge composition are deposited by the process of laser

Srivastava, Kumar Vaibhav

393

Characteristics of focused soft X-ray free-electron laser beam determined by ablation  

E-print Network

Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic. Dyer, "Excimer laser polymer ablation: twenty years on," Appl. Phys. A77, 167-173 (2003) and references of coherent radiation, FLASH (Free-electron LASer in Hamburg) provides ultra-intense femtosecond radiation

von der Linde, D.

394

Generation of nanoparticles by laser ablation: Combined MD-DSMC computational study  

E-print Network

Generation of nanoparticles by laser ablation: Combined MD- DSMC computational study Tatiana E.1088/1742-6596/59/1/010 Eighth International Conference on Laser Ablation 44© 2007 IOP Publishing Ltd #12;condensation models. Itina1 and Leonid V. Zhigilei2 1 Laboratory of Lasers, Plasmas and Photonic Processing (LP3, UMR 6182

Zhigilei, Leonid V.

395

Laser ablation for analytical sampling: what can we learn from modeling?  

Microsoft Academic Search

The paper is built up in two parts. First, a rather comprehensive introduction is given, with a brief overview of the different application fields of laser ablation, focusing mainly on the analytical applications, and an overview of the different modeling approaches available for laser ablation. Further, a discussion is presented here about the laser evaporated plume expansion in vacuum or

Annemie Bogaerts; Zhaoyang Chen; Renaat Gijbels; Akos Vertes

2003-01-01

396

Invited Paper 505 In High-Power Laser Ablation V, Claude R. Phipps, Editor  

E-print Network

Invited Paper 505 In High-Power Laser Ablation V, Claude R. Phipps, Editor Proceedings of SPIE, Vol and disintegration of material in laser ablation. Recent progress in the development of new optical and x. 5448 (2004) Computer modeling of laser melting and spallation of metal targets Leonid V. Zhigilei

Zhigilei, Leonid V.

397

From polymer films to organic nanoparticles suspensions by means of excimer laser ablation in water  

NASA Astrophysics Data System (ADS)

This study highlights the preparation of organic nanoparticles (NP) by laser ablation (LA) of polymeric materials in water. Experiments focused on poly(ethylene terephtalate) (PET) were carried out with the KrF laser pulse (248 nm). Size distribution and concentration of nanoparticles were deduced from suspensions turbidity measurements with the aid of Mie model, by Atomic Force Microscopy (AFM) on the basis of a statistical study and Scanning Electron Microscopy (SEM). The obtained results show that assemblies of spherical NP with a mean diameter 50 nm were synthesised. Composition and surface chemistry of NP were investigated using the Confocal Micro-Raman Spectroscopy (CMRS) and X-ray Photoelectron Spectroscopy (XPS). It indicates that NP are graphitic carbon rich and have a polymeric structure like polyacetylene. The possible mechanisms responsible of NP synthesis by under water LA of polymers was briefly discussed by investigating other polymers targets.

Elaboudi, I.; Lazare, S.; Belin, C.; Talaga, D.; Labrugère, C.

2008-12-01

398

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

SciTech Connect

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 sensitively on the physical state of the sample (e.g., particle morphology, defect concentration, impurities, and presence of liquids). In this work, the authors examine how solid and condensed state properties of the sample affect the laser-substrate interaction, and the dynamic electronic, physical, and chemical processes which ultimately generate the signals that are detected for analytic purposes.

Langford, S.C.; Dickinson, J.T. [Washington State Univ., Pullman, WA (United States)

1996-12-31

399

1714 OPTICS LETTERS / Vol. 24, No. 23 / December 1, 1999 Focusing of a tabletop soft-x-ray laser beam and laser ablation  

E-print Network

beam and laser ablation B. R. Benware, A. Ozols,* and J. J. Rocca Department of Electrical and Computer the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray distribution near the exit of the amplifier was verified to also be annular; the unfocused laser beam ablated

Rocca, Jorge J.

400

Characteristics of Droplets Ejected from Liquid Propellants Ablated by Laser Pulses in Laser Plasma Propulsion  

NASA Astrophysics Data System (ADS)

The angular distribution and pressure force of droplets ejected from liquid water and glycerol ablated by nanosecond laser pulses are investigated under different viscosities in laser plasma propulsion. It is shown that with increasing viscosity, the distribution angles present a decrease tendency for two liquids, and the angular distribution of glycerol is smaller than that of water. A smaller distribution leads to a higher pressure force generation. The results indicate that ablation can be controlled by varying the viscosity of liquid propellant in laser plasma propulsion.

Zheng, Zhiyuan; Gao, Hua; Fan, Zhenjun; Xing, Jie

2014-03-01

401

Feasibility of characterizing laser-ablated carbon plasmas via planar laser induced fluorescence  

SciTech Connect

Planar laser induced fluorescence (PLIF) imaging can potentially assess ion distributions and coupling in the context of super-Alfvenic ablation plasma expansions into magnetized background plasmas. In this feasibility study, we consider the application of PLIF to rapidly expanding carbon plasmas generated via energetic laser ablation of graphite. By utilizing hydrodynamic and collisional-radiative simulations, we identify schemes accessible to commercially available tunable lasers for the C I atom, the C II ion, and the C V ion. We then estimate the signal-to-noise ratios yielded by the schemes under reasonable experimental configurations.

Bondarenko, A. S.; Schaeffer, D. B.; Everson, E. T.; Constantin, C. G.; Clark, S. E.; Niemann, C. [Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, California 90095 (United States)

2012-10-15

402

Dynamics of laser ablation for thin film growth by pulsed laser deposition  

SciTech Connect

Fundamental gas dynamic and laser-material interactions during pulsed laser deposition are explored through sensitive imaging and plasma spectroscopic diagnostics. Two recent phenomena, plume-splitting in background gases and the unusual dynamics of graphite ablation for amorphous diamond film growth, are presented.

Geohegan, D.B.; Puretzky, A.A.

1996-02-01

403

Optical probe investigation of laser ablated carbon plasma plume in nitrogen ambient  

SciTech Connect

We report the study of carbon plasma produced using 1064 nm laser in nitrogen ambient at atmospheric pressure using 2-dimensional fast imaging of ablated plume, optical emission spectroscopy, and optical probe at 532 nm for interferometry and shadowgraphy. The dominance of C{sub 2} and CN molecules over ionic species at later stages of expanding carbon plasma plume is reported. The observed ring structure in shadowgrams and change in the direction of fringe shift from positive to negative in recorded interferograms are correlated with the relative abundance of different species in the plasma plume as function of time delay with respect to ablating pulse. An agreement in observed onset time of formation of clusters/atomic species or low ionic species using different diagnostic techniques has been reported.

Singh, Ravi Pratap; Gupta, Shyam L.; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016 Uttar Pradesh (India)] [Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016 Uttar Pradesh (India)

2013-12-15

404

Plume dynamics and cluster formation in laser-ablated copper plasma in a magnetic field  

SciTech Connect

Laser-ablated copper plasma plume expanding in a nonuniform magnetic field and ambient gas is investigated to understand plume dynamics using optical emission spectroscopy and fast imaging of the plume. A peculiar oscillatory behavior of the plume observed in magnetic field is discussed. The appearance and enhancement of Cu{sub 2} (A-X) band in ambient gas and in the presence of magnetic field is reported. The presence of magnetic field favors the formation of copper clusters in the expanding plumes.

Pandey, Pramod K.; Thareja, R. K. [Department of Physics, Indian Institute of Technology, Kanpur, Kanpur 208016 (U.P.) (India)

2011-04-01

405

Laser microprobe and resonant laser ablation for depth profile measurements of hydrogen isotope atoms contained in graphite  

Microsoft Academic Search

We measured the depth profile of hydrogen atoms in graphite by laser microprobing combined with resonant laser ablation. Deuterium-implanted graphite was employed for the measurements. The sample was ablated by a tunable laser with a wavelength corresponding to the resonant wavelength of1S-2S of deuterium with two-photon excitation. The ablated deuterium was ionized by a 2 + 1 resonant ionization process.

Masafumi Yorozu; Tatsuya Yanagida; Terunobu Nakajyo; Yasuhiro Okada; Akira Endo

2001-01-01

406

Laser induced breakdown spectroscopy analysis of lunar simulants under high vacuum conditions  

Microsoft Academic Search

Application of laser induced breakdown spectroscopy (LIBS) is considered for compositional analysis of materials on planetary surfaces. In many such applications, LIBS measurements are conducted in high vacuum and the propagation of the plume produced during laser ablation plays a significant role. Therefore a proper understanding of the plasma parameters under high vacuum is significant for any improvement in the

Jobin K. Antony; Nilesh J. Vasa; V. L. N. Sridhar Raja; A. S. Laxmiprasad

2010-01-01

407

Stoichiometric analysis of compositionally graded combinatorial amorphous thin film oxides using laser-induced breakdown spectroscopy  

Microsoft Academic Search

Laser-induced breakdown spectroscopy (LIBS) is a recently developed locally destructive elemental analysis technique that can be used to analyze solid, liquid, and gaseous samples. In the system explored here, a neodymium-doped yttrium aluminum garnet laser ablates a small amount of the sample and spectral emission from the plume is analyzed using a set of synchronized spectrometers. We explore the use

N. Edwin Widjonarko; John D. Perkins; Jennifer E. Leisch; Philip A. Parilla; Calvin J. Curtis; David S. Ginley; Joseph J. Berry

2010-01-01

408

Laser ablation characteristics of yttria-doped zirconia in the nanosecond and femtosecond regimes  

NASA Astrophysics Data System (ADS)

The laser ablation characteristics of yttria-stabilized zirconia (YSZ) have been investigated as a function of the target microstructure and dopant level for different nanosecond- [ArF, KrF, and XeCl excimers; Nd:YAG (yttrium aluminum garnet) (fourth harmonic)] and femtosecond-laser sources [Ti:sapphire (fundamental and third harmonic)]. Particle ejection, which compromises the quality of coatings prepared by pulsed laser deposition (PLD), was analyzed in detail. Nanosecond-laser pulses cause a severe thermomechanical surface cracking and exfoliation of micron-sized fragments on a microsecond to millisecond time scale in the case of 8-9.5 mol % Y2O3-doped, fully stabilized zirconia (8YSZ and 9.5YSZ) targets. As a consequence of the intrinsic material brittleness, fully stabilized YSZ coatings deposited by PLD contained particles for all tested conditions. Lower doped partially stabilized zirconia (3YSZ) exhibits a superior fracture toughness attributed to a laser-induced partial transition to the monoclinic phase, detected by Raman spectroscopy, which enables the deposition of particle-free dense thin films by conventional PLD using nanosecond-UV laser radiation at moderate fluences of 1.2-1.5 J/cm2. The ablation dynamics of ultrashort laser pulses differ fundamentally from the nanosecond regime as evidenced, e.g., by time-resolved shadowgraphy and light scattering experiments. Femtosecond pulses prevent the exfoliation of micron-sized fragments but result invariably in a pronounced ejection of submicron particles. The resulting PLD coatings are porous and reveal a large surface roughness as they consist of an agglomeration of nanoparticles. Femtosecond-NIR pulses provide a factor of 2.5-10 higher material removal rates compared to nanosecond- and femtosecond-UV pulses. The ablation metrics, i.e., threshold fluence and effective absorptivity, mainly depend on the laser wavelength while the pulse duration, target microstructure, and dopant level are of minor importance. Evidence is presented that incubation effects play a significant role in nanosecond- and femtosecond-laser ablations of YSZ enabling material removal at comparatively low fluences for sub-bandgap photon energies.

Heiroth, S.; Koch, J.; Lippert, T.; Wokaun, A.; Günther, D.; Garrelie, F.; Guillermin, M.

2010-01-01

409

Properties of zirconia thin films deposited by laser ablation  

SciTech Connect

Zirconia thin films have been deposited by laser ablation of a ceramic ZrO{sub 2} target in vacuum or in oxygen background at 0.01 mbar. The laser beam generated by an ArF laser (?=193 nm, ?=40 Hz) has been focalized on the target through a spherical lens at an incident angle of 45°. The laser fluence has been established to a value from 2.0 to 3.4 Jcm{sup ?2}. A silicon (100) substrate has been placed parallel to the target, at a distance of 4 cm, and subsequently has been heated to temperatures ranging between 300 °C and 600 °C. Thin films morphology has been characterized by atomic force microscopy and secondary ion mass spectrometry. Biocompatibility of these thin films has been assessed by studying the cell attachment of L929 mouse fibroblasts.

Cancea, V. N. [Department of Physics, University of Craiova, Craiova 200585 (Romania); Filipescu, M.; Colceag, D.; Dinescu, M. [Department of Lasers, National Institute for Laser, Plasma and Radiation Physics, Magurele 077125 (Romania); Mustaciosu, C. [Horia Hulubei National Institute of Physics and Nuclear Engineering, Magurele, Bucharest (Romania)

2013-11-13

410

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

PubMed

Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process. PMID:25657872

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

2015-01-01

411

Corneal ablation using the pulse stretched free electron laser  

NASA Astrophysics Data System (ADS)

The Mark-III Free Electron Laser (FEL), tuned to ?=6.45 ?m has been demonstrated to provide for efficient ablation in ocular and neural tissues with minimal collateral damage. To date, the role of the FEL pulse structure on the mechanism of ablation has not been determined. In an effort to study the role of the FEL micropulse on the ablation of corneal tissue, the native pulse structure of the FEL, a 2.85 gigahertz repetition of picosecond pulses within a five microsecond macropulse envelope, was changed using a a pulse stretcher. This device changes the duration of the micropulse from 1 picosecond to 30-200 picoseconds in length, thus reducing the peak intensity of the micropulse by as much as 200x the original intensity, while the macropulse energy remains unchanged. Two basic metrics were studied: the ablation threshold on water and the ablation crater depth on gelatin. These metrics were employed at ?=6.45 and 6.1 ?m for 1, 100, and 200 picoseconds in micropulse duration. The results showed a very slight difference between the 1, 100, and 200 picosecond micropulse duration, given a 200 fold decrease in peak energy for both the threshold and crater depth measurements. Brightfield imaging was also performed to probe the ablation dynamics and showed no difference between the 1 and 200 ps micropulses. The effect of changing the micropulse duration was studied on the ablation of canine cornea. Craters (500 micron diameter) were created with 25 pulses at three times the ablation threshold as determined for water on freshly enucleated corneas within 12 hours of removal. Three rows of seven craters were created on the center of each cornea. The native one picosecond micropulse and 200 picosecond stretched micropulse were compared at ?=6.1 and 6.45 ?m. Histological data shows that less thermal damage is present at 6.1 ?m compared with 6.45 ?m however, there is no significant difference between the native and stretched pulses with respect to thermal damage.

Mackanos, Mark A.; Joos, Karen M.; Kozub, John A.; Jansen, E. D.

2005-04-01

412

Thermal nonlinear optical properties of TiO2 nanocrystals prepared through pulsed laser ablation  

NASA Astrophysics Data System (ADS)

Titanium dioxide (TiO2) nanoparticles (NPs) were synthesized using the pulsed laser ablation method by irradiating a titanium target immersed in distilled water with 1064 nm, Nd:YAG (yttrium aluminum garnet) laser pulses. The indirect band gap of the NPs was estimated with the aid of ultraviolet/visible spectroscopy. Transmission electron microscopy showed the NPs to be spherical in shape and to vary from 5 to 50 nm. The average size of the NPs and their crystalline phases were determined by means of x-ray diffraction analysis. The thermal conductivity of the nano-TiO2 colloids was measured at a temperature of 25?°C. The single-beam z-scan technique was employed to obtain the nonlinear index of refraction (n2) and the nonlinear absorption coefficient (?) under continuous wave He–Ne laser excitation at different input powers. Thermo-optical coefficients of the NPs were calculated using the z-scan results.

Moslehirad, F.; Majles Ara, M. H.; Torkamany, M. J.; Afsary, M.; Ghorannevis, M.; Sabbaghzadeh, J.

2013-05-01

413

Split-ring resonators manufactured on conductive layer by selective laser ablation  

NASA Astrophysics Data System (ADS)

In this paper an alternative method of manufacturing SRR structures through the selective removal of a thin layer of silver-palladium deposited on the surface of the Al2O3 ceramic by laser ablation process using nanosecond Nd:YAG laser (1064 nm) was presented. The SRR structures array were subject to transmittance measurements using the TDS (Time Domain Spectroscopy). Both electric and magnetic resonances were observed at frequencies determined by the structural parameters of the SRR. In case of the E field perpendicular to an SRR structure and one resonance area for 0.56 THz with the E field parallel to the structure, two characteristic resonant dips for 0.31 THz and 0.62 THz were obtained. Studies have confirmed that using selective laser removal process enables the preparation of the resonant structure in the range of THz.

Koziol, Pawe?; Anto?czak, Arkadiusz J.; Szymczyk, Patrycja E.; Stepak, Bogusz; ?azarek, ?ukasz; Wójcik, Micha? R.; Walczakowski, Micha?; Abramski, Krzysztof M.

2014-08-01

414

Nanoparticle generation and transport resulting from femtosecond laser ablation of ultrathin metal films: Time-resolved measurements and molecular dynamics  

E-print Network

Nanoparticle generation and transport resulting from femtosecond laser ablation of ultrathin metal thermo-elastic laser ablation mechanism on the generation of nanoparticles from thin gold films Appl.1063/1.3223331 Nanoparticles as potential risk during femtosecond laser ablation J. Laser Appl. 19, 65 (2007); 10

Geohegan, David B.

415

Direct femtosecond laser ablation of copper with an optical vortex beam K. K. Anoop,1,2  

E-print Network

Direct femtosecond laser ablation of copper with an optical vortex beam K. K. Anoop,1,2 R September 2014) Laser surface structuring of copper is induced by laser ablation with a femtosecond optical by nanoparticles produced during laser ablation. At large number of pulses (200

Marrucci, Lorenzo

416

Femtosecond laser plasma plume characteristics in the nanojoule ablation regime  

SciTech Connect

Laser ablation of chromium with nanojoule energy UV femtosecond pulses under background pressure conditions between 0.3 Torr and 700 Torr is studied and the corresponding plasma plume images at different times after irradiation are measured. The ablation focal spot is less than or the order of a micron when 170 nJ of laser pulse energy is used. This low pulse energy leads to short lifetimes of the plasma of the order of tens of nanoseconds. The plume shape changes with ambient pressure due to the collision with background gas. An axially stretched plume changes to a more circular plume as the pressure increases. In addition, a separation of the ionic and atomic components is observed at lower pressure. These two components move at significantly different velocities as well. The plasma plume expands at almost constant velocity at very low pressure but exhibits significant deceleration at higher pressure reaching an asymptotic stopping distance. Plume images are also obtained near the ablation threshold pulse energy. The plume characteristics are compared to different models of plume expansion.

Banerjee, S. P.; Chen, Zhijiang; Fedosejevs, R. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G2V4 (Canada)] [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G2V4 (Canada)

2013-05-14

417

A study of particle generation during laser ablation withapplications  

SciTech Connect

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

Liu, Chunyi

2005-08-12

418

On the efficiency of laser ablation of photopolymerizing compositions in liquid and solidified states  

NASA Astrophysics Data System (ADS)

The efficiency of laser ablation of photocuring compositions that are working substances of various laser-plasma facilities is investigated for the first time. A substantial difference in spectral-energetic laser ablation thresholds, specific mass consumption, momentum coupling coefficient, and conversion efficiency of the laser energy to the kinetic energy of gas-plasma flow for liquid and solidified phases is demonstrated. Application of this class of working media allows not only solving problems related to laser ablation of a target, transport, fine dosing, and obtaining long lifetime and reliability of laser-plasma-based technological setups, but also considerably broadens the range of their operational characteristics.

Loktionov, E. Yu.; Protasov, Yu. S.; Protasov, Yu. Yu.; Telekh, V. D.

2015-02-01

419

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

NASA Astrophysics Data System (ADS)

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

Tong, Huifeng; Yuan, Hong; Tang, Zhiping

2013-01-01

420

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

SciTech Connect

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

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

2013-01-28

421

IR laser ablation of doped poly(methyl methacrylate)  

NASA Astrophysics Data System (ADS)

We investigate the TEA CO 2 laser ablation of films of poly(methyl methacrylate), PMMA, with average MW 2.5, 120 and 996 kDa doped with photosensitive compounds iodo-naphthalene (NapI) and iodo-phenanthrene (PhenI) by examining the induced morphological and physicochemical modifications. The films casted on CaF 2 substrates were irradiated with a pulsed CO 2 laser (10P(20) line at 10.59 ?m) in resonance with vibrational modes of PMMA and of the dopants at fluences up to 6 J/cm 2. Laser induced fluorescence probing of photoproducts in a pump and probe configuration is carried out at 266 nm. Formation of naphthalene (NapH) and phenanthrene (PhenH) is observed in NapI and PhenI doped PMMA, respectively, with relatively higher yields in high MW polymer, in similarity with results obtained previously upon irradiation in the UV at 248 nm. Above threshold, formation of photoproducts is nearly complete after 200 ms. As established via optical microscopy, bubbles are formed in the irradiated areas with sizes that depend on polymer MW and filaments are observed to be ejected out of the irradiated volume in the samples made with high MW polymer. The implications of these results for the mechanisms of polymer IR laser ablation are discussed and compared with UV range studies.

Gaspard, S.; Oujja, M.; Rebollar, E.; Walczak, M.; Díaz, L.; Santos, M.; Castillejo, M.

2007-05-01

422

The influence of laser wavelength and fluence on palladium nanoparticles produced by pulsed laser ablation in deionized water  

NASA Astrophysics Data System (ADS)

Homogeneous spherical palladium (Pd) nanoparticles were synthesized by pulsed laser ablation of a solid Pd foil target submerged in deionized water, without the addition of any external chemical surfactant. The influence of laser wavelength (355, 532, and 1064 nm) and fluence (8.92, 12.74, and 19.90 J/cm2) on nucleation, growth, and aggregation of Pd nanoparticles were systematically studied. Microstructural and optical properties of the obtained nanoparticles were studied by field emission transmission electron microscopy (FETEM), energy dispersive X-ray spectroscopy, and UV-vis spectroscopy. FETEM micrographs indicate that the average nanocrystallite sizes are relatively low (3-6 nm) and homogeneous for the particles synthesized at the laser wavelengths of 355 and 532 nm. However, at a laser wavelength of 1064 nm, the average nanocrystallite size is relatively large and inhomogeneous in nature. Moreover, we observe that the mean diameter and production rate of particles increases with an increase in laser fluence. The selected area electron diffraction patterns obtained from isolated Pd nanoparticles show the characteristic diffused electron diffraction rings of polycrystalline materials with a face-centered cubic structure. Absorbance spectrum of the synthesized nanoparticle solution shows a broad absorption band, which corresponds to a typical inter-band transition of a metallic system, indicating the production of pure palladium nanoparticles. The present work provides new insights into the effect of laser wavelength and fluence on the control of size and aggregation of palladium nanoparticles in the liquid medium.

Kim, Jinil; Amaranatha Reddy, D.; Ma, Rory; Kim, Tae Kyu

2014-11-01

423

Ultrasensitive Laser Spectroscopy.  

ERIC Educational Resources Information Center

Examines techniques used to make ultrasensitive spectroscopic measurements. They include excitation, thermal lens, photo acoustic, and ionization spectroscopies. Guidelines and methods are provided for each technique; common uses and applications are explained. (DH)

Kliger, David S.

1985-01-01

424

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

SciTech Connect

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

Fiutowski, J.; Maibohm, C.; Kjelstrup-Hansen, J.; Rubahn, H.-G. [Mads Clausen Institute, NanoSYD, University of Southern Denmark, Alsion 2, DK-6400, Soenderborg (Denmark)

2011-05-09

425

Laser ablative synthesis of carbon nanotubes  

DOEpatents

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

Smith, Michael W. (Newport News, VA); Jordan, Kevin (Newport News, VA); Park, Cheol (Yorktown, VA)

2010-03-02

426

Testing of concrete by laser ablation  

SciTech Connect

A method of testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed.

Flesher, Dann J. (Benton City, WA); Becker, David L. (Kennewick, WA); Beem, William L. (Kennewick, WA); Berry, Tommy C. (Kennewick, WA); Cannon, N. Scott (Kennewick, WA)

1997-01-01

427

Testing of concrete by laser ablation  

DOEpatents

A method is disclosed for testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed. 1 fig.

Flesher, D.J.; Becker, D.L.; Beem, W.L.; Berry, T.C.; Cannon, N.S.

1997-01-07

428

Customized ablation using an all-solid-state deep-UV laser  

NASA Astrophysics Data System (ADS)

We show first deep UV ablation results achieved with our new all solid state laser system. The system parameters allow high repetition rate ablation with a small spot diameter of about 0.250mm and a fluence of 350 mJ/cm2 at a wavelength of 210 nm using sequential frequency conversion of a diode pumped laser source. The single shot and multishot ablation rates as well as the ablation profiles have been defined using MicroProf (Fries Research and Technology GmbH, Germany). By means of computer controlled scanning we produce smooth ablation profiles corresponding to a correction of myopia, hyperopia or astigmatism. Due to the small spot size and high repetition rate of the laser we are able to generate in short time intervals complicated ablation profiles described by higher order polynomial functions which are required for the needs of customized corneal ablation.

Korn, G.; Lenzner, M.; Kittelmann, O.; Zatonski, R.; Kirsch, M.; Kuklin, Y.

2003-07-01

429

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

SciTech Connect

Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom density (n{sub n} of order 10{sup 18} cm{sup -3}) and weakly ionized (n{sub e}/n{sub n}, < 0.001) at long time delays of order 200 ns. Recollections of Al plumes confirm the low plume divergence and demonstrate high material adhesion to the receiving substrate, as well as a higher Al material yield than that of conventional pulsed laser deposition. Al redepositions are also highly conductive at the deposit/substrate interface, suggesting possible applications in selective laser-assisted bonding.

BULLOCK, A B

1999-05-26

430

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry  

SciTech Connect

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime of Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.

Wicklein, S.; Koehl, A.; Dittmann, R. [Peter Gruenberg Institut and JARA-FIT, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Sambri, A.; Amoruso, S.; Wang, X.; Bruzzese, R. [CNR-SPIN and Dipartimento di Scienze Fisiche, Complesso Universitario di Monte Sant'Angelo, Via Cintia, I-80125 Napoli (Italy)

2012-09-24

431

Laser spectroscopy and quantum optics  

Microsoft Academic Search

In this paper the authors discuss recent advances and trends in laser spectroscopy and quantum optics. It is obvious that both are fields that experienced a tremendous development in the last twenty years. Therefore the survey must be incomplete, and only a few highlights are touched on.

T. W. Hänsch; H. Walther

1999-01-01

432

Characterization of the ablation of TeO2 crystals in air with femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Femtosecond (fs) laser pulse ablation (pulse duration of 150 fs, wavelength of 775 nm, repetition rate of 1 kHz) of single-crystalline TeO2 surfaces was performed in air using the direct focusing technique. The lateral and vertical dimensions of laser ablated craters as well as the laser damage thresholds were evaluated for different pulse numbers applied to the same spot. The joint observation using optical microscopy, atomic force microscopy and scanning electron microscopy revealed the surface morphology of the ablated craters and also showed that the ablation threshold depends significantly on the number of laser pulses applied to the same spot due to incubation effects. The incubation effects change the absorption processes involved in fs-laser ablation of the transparent material from multiphoton absorption to a single-photon absorption. These results are discussed on the basis of recent models of the interaction of fs-laser pulses with dielectrics.

Beke, S.; Sugioka, K.; Midorikawa, K.; Péter, Á.; Nánai, L.; Bonse, J.

2010-01-01

433

Simulation of nanosecond pulsed laser ablation of copper samples: A focus on laser induced plasma radiation  

SciTech Connect

A thermal model for nanosecond pulsed laser ablation of Cu in one dimension and in ambient gas, He at 1 atm, is proposed in which equations concerning heat conduction in the target and gas dynamics in the plume are solved. These equations are coupled to each other through the energy and mass balances at interface between the target and the vapor and also Knudsen layer conditions. By assumption of local thermal equilibrium, Saha-Eggert equations are used to investigate plasma formation. The shielding effect of the plasma, due to photoionization and inverse bremsstrahlung processes, is considered. Bremsstrahlung and blackbody radiation and spectral emissions of the plasma are also investigated. Spatial and temporal distribution of the target temperature, number densities of Cu and He, pressure and temperature of the plume, bremsstrahlung and blackbody radiation, and also spectral emissions of Cu at three wavelengths (510, 516, and 521 nm) are obtained. Results show that the spectral power of Cu lines has the same pattern as CuI relative intensities from National Institute of Standard and Technology. Investigation of spatially integrated bremsstrahlung and blackbody radiation, and also Cu spectral emissions indicates that although in early times the bremsstrahlung radiation dominates the two other radiations, the Copper spectral emission is the dominant radiation in later times. It should be mentioned that the blackbody radiation has the least values in both time intervals. The results can be used for prediction of the optimum time and position of the spectral line emission, which is applicable in some time resolved spectroscopic techniques such as laser induced breakdown spectroscopy. Furthermore, the results suggest that for distinguishing between the spectral emission and the bremsstrahlung radiation, a spatially resolved spectroscopy can be used instead of the time resolved one.

Aghaei, M.; Mehrabian, S.; Tavassoli, S. H. [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran, 1983963113 (Iran, Islamic Republic of)

2008-09-01

434

Laser ablation of CFRP using picosecond laser pulses at different wavelengths from UV to IR  

NASA Astrophysics Data System (ADS)

Laser processing of carbon fibre reinforced plastics (CFRP) has a great industrial relevance for high performance structural parts in airplanes, machine tools and cars. Through-holes drilled by nanosecond laser pulses show thermal induced molten layers and voids. Recently, picosecond lasers have demonstrated the ability to drill high-efficient and high-quality rivet through-holes. In this paper a high-power picosecond laser system operating at different wavelengths (355 nm, 532 nm and 1064 nm) has been used for CFRP ablation experiments to study the influence of different laser parameters in terms of machining quality and processing time.

Wolynski, Alexander; Herrmann, Thomas; Mucha, Patrick; Haloui, Hatim; L'huillier, Johannes

435

Laser-induced breakdown spectroscopy (LIBS) analysis of laser processing in active crystal with nanosecond laser pulses.  

PubMed

Laser-induced breakdown spectroscopy (LIBS) analysis is applied to study the ablation threshold and the main plasma features of active crystals used for laser processing with Nd(3+) ions. The experiments were conducted by using nanosecond laser pulses from a neodymium-doped yttrium aluminum garnet (Nd?:?YAG) laser and its harmonics. In particular, we have studied the ablation process in SBN, strontium barium niobate (SrxBa1-xNb2O6, x = 0.6), and SBN, sodium barium niobate (Ba2NaNb5O15), nonlinear and ferroelectric crystals. Two different ablation regimes have been identified by LIBS analysis with high sensitivity compared with the standard method of hole-diameter measurement. Analyzing spectroscopically the plasma emission, we have found a particular behavior with the excitation wavelength. For example, the electronic density and temperature in SBN-generated plasmas present an abnormal behavior with the excitation wavelength. We therefore conclude that the energy gap corresponding to these crystals plays an important role in describing this fact. Hence, the resonant ablation in doped crystals can be a suitable point for exploration in further works in order to use the plasma performances to optimize the laser processing by nanosecond pulses for technological applications. PMID:24694704

Alvira, F C; Ródenas, A; Torchia, G A

2014-01-01

436

Endovenous Laser Ablation of Incompetent Perforator Veins: A New Technique in Treatment of Chronic Venous Disease  

SciTech Connect

The aim of this study was to assess the feasibility of endovenous laser ablation of incompetent perforator veins in a patient with incompetency of the small saphenous vein and multiple perforator veins. Two different methods were used to ablate seven perforator veins with a laser giving 50-60 J/cm energy. Total occlusion was observed in six perforators, and partial ablation in one perforator, at 1-month follow-up. To our knowledge, endovenous laser ablation of incompetent perforator veins is easy and a good therapeutic method.

Ozkan, Ugur, E-mail: radugur@yahoo.co [Baskent University, Faculty of Medicine, Department of Radiology (Turkey)

2009-09-15

437

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration  

Microsoft Academic Search

PurposeTo study the optical changes induced by the microkeratome cut, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ keratomileusis (LASIK) eyes.

Jason Porter; Scott MacRae; Geunyoung Yoon; Cynthia Roberts; Ian G Cox; David R Williams

2003-01-01

438

The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: ablation metrics  

Microsoft Academic Search

Pulsed mid-infrared (6.45 µm) radiation has been shown to cut soft tissue with minimal collateral damage (<40 µm) however, the mechanism of ablation has not been elucidated to date. The goal of this research was to examine the role of the unique pulse structure of the Vanderbilt Mark-III free-electron laser (FEL) and its role in the efficient ablation of soft

Mark A. Mackanos; John A. Kozub; E. Duco Jansen

2005-01-01

439

The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: ablation metrics  

Microsoft Academic Search

Pulsed mid-infrared (6.45 m) radiation has been shown to cut soft tissue with minimal collateral damage (<40 m); however, the mechanism of ablation has not been elucidated to date. The goal of this research was to examine the role of the unique pulse structure of the Vanderbilt Mark-III free-electron laser (FEL) and its role in the efficient ablation of soft

Mark A Mackanos; John A Kozub; E Duco Jansen

2005-01-01

440

Efficiency and Plume Dynamics for Mid-IR Laser Ablation of Cornea  

Microsoft Academic Search

This paper reports ablation experiments on porcine corneal tissue using the Vanderbilt Mark III Free Electron Laser (FEL) and a tabletop Raman-shifted Alexandrite laser. These experiments were designed to test previous models that suggested wavelength and intensity dependent ablation mechanisms. In one test, we compare ablation efficiency and plume dynamics for two FEL wavelengths (lambda=2.77, 6.45 mum) chosen such that

Aroshan Jayasinghe; Borislav Ivanov; M. Shane Hutson

2009-01-01

441

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

Microsoft Academic Search

For conventional wavelength (UV–vis–IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, etch (ablation) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various very short-wavelength (?<100nm) lasers, emitting pulses with durations ranging from ?10fs to ?1ns, have recently been placed into routine operation. This has facilitated

L. Juha; M. Bittner; D. Chvostova; V. Letal; J. Krasa; Z. Otcenasek; M. Kozlova; J. Polan; A. R. Präg; B. Rus; M. Stupka; J. Krzywinski; A. Andrejczuk; J. B. Pelka; R. Sobierajski; L. Ryc; J. Feldhaus; F. P. Boody; M. E. Grisham; G. O. Vaschenko; C. S. Menoni; J. J. Rocca

2005-01-01

442

Production of warm aluminum cluster anions by femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We report on the production of warm aluminum cluster anions, Al{/n -} (1 ? n ? 26), after femtosecond laser ablation of an aluminum nitride substrate. Large cluster anions of n ? 8 suffer metastable dissociation after their production, which indicates the internal energy of the cluster anions is high enough for the dissociation of an Al atom. We find that the efficiency of metastable dissociation is dependent on the size of cluster anions and the dependence can be rationalized by the dissociation energy of an Al atom from the cluster anions calculated with thermochemical data of the clusters.

Kobayashi, T.; Matsuo, Y.

2015-02-01

443

Towards redistribution laser cooling of molecular gases: Production of candidate molecules SrH by laser ablation  

E-print Network

Laser cooling by collisional redistribution of radiation has been successfully applied in the past for cooling dense atomic gases. Here we report on progress of work aiming at the demonstration of redistribution laser cooling in a molecular gas. The candidate molecule strontium monohydride is produced by laser ablation of strontium dihydride in a pressurized noble gas atmosphere. The composition of the ablation plasma plume is analyzed by measuring its emission spectrum. The dynamics of SrH molecular density following the ablation laser pulse is studied as a function of the buffer gas pressure and the laser intensity.

Simon, Philipp; Weller, Lars; Sass, Anne; Weitz, Martin; 10.1117/12.2002379

2013-01-01

444

Laser Ablation (LA-ICPMS) at the Institute of Mineralogy, University of WÃrzburg  

NSDL National Science Digital Library

This website from the University of Wuerzburg briefly describes laser ablation, the most versatile in-situ solid sampling technique for ICP mass spectrometry. The website also features a section detailing applications for laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), including trace element concentration and chemical zoning, and others.

University of W& uuml Institute of Mineralogy

445

Measurement of depth profile of hydrogen isotope atom contained in solid material using resonant laser ablation  

Microsoft Academic Search

The depth profile of hydrogen isotope atoms was measured by using mass spectrometry combined with resonant laser ablation. A graphite sample was implanted with deuterium by a cyclotron and was employed for the measurements. The graphite sample was ablated by a tunable laser which wavelength was corresponding to the resonant wavelength of 1S - 2S for deuterium with two- photon

Masafumi Yorozu; Yasuhiro Okada; Terunobu Nakajyo; Akira Endo

1999-01-01

446

Modeling of nanosecond-laser ablation: calculations based on a nonstationary averaging technique (spatial moments)  

Microsoft Academic Search

Semi-analytical approach to a quantitative analysis of thermal ns laser ablation is presented. It permits one to take into account: (1) Arbitrary temperature dependences of material parameters, such as the specific heat, thermal conductivity, absorptivity, absorption coefficient, etc. (2) Arbitrary temporal profiles of the laser pulse. (3) Strong (Arrhenius- type) dependence of the ablation velocity on the temperature of the

N. D. Arnold; Boris S. Luk'yanchuk; Nikita M. Bityurin; D. Baeuerle

1998-01-01

447

Microfluidic cell counter with embedded optical fibers fabricated by femtosecond laser ablation  

E-print Network

Microfluidic cell counter with embedded optical fibers fabricated by femtosecond laser ablation using femtosecond laser ablation and anodic bonding. In a first application, we constructed a cell counting device based on small angle light scattering. The counter featured embedded optical fibers

448

Treatment of Vaginal Intraepithelial Neoplasia with Laser Ablation and Upper Vaginectomy  

Microsoft Academic Search

To assess the effectiveness of laser ablation and upper vaginectomy in the treatment of vaginal intraepithelial neoplasia (VAIN), we have reviewed the charts of 52 patients managed with laser ablation (28 patients) and upper colpectomy (24 patients). On the basis of our results, patient selection and operator skill have a significant influence on the outcome. In posthysterectomy patients with VAIN3

Emmanuel Diakomanolis; Alexandros Rodolakis; Zanis Boulgaris; Georgios Blachos; Stylianos Michalas

2002-01-01