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1

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

Microsoft Academic Search

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

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

2006-01-01

2

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

E-print Network

semiconductors, laser ablation near threshold can be described in terms of thermal processes even when fem is relatively high also in the range below the ablation threshold. Our results show that the non- thermallyFemtosecond laser ablation of gallium arsenide investigated with time- of-flight mass spectroscopy

von der Linde, D.

3

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

4

High resolution pulsed infrared cavity ringdown spectroscopy: Application to laser ablated carbon clusters  

E-print Network

light, followed by some method of blocking the laser so that the decay of radiation trappedHigh resolution pulsed infrared cavity ringdown spectroscopy: Application to laser ablated carbon ringdown spectrometer. Stimulated Raman scattering in H2 /D2 is used to downconvert the output of a SLM

Cohen, Ronald C.

5

Infrared femtosecond laser ablation of graphite in high vacuum probed by optical emission spectroscopy  

Microsoft Academic Search

We report infrared, ultra-short (780 nm, 120 fs) laser ablation of graphite in high vacuum. The plume characteristics are analyzed by wavelength-, time-, and spatially resolved optical emission spectroscopy. A multi-component structure of the plume is observed as a function of time, space, and laser fluence: (i) line emission from electronically excited carbon neutrals and ions; (ii) luminescence from excited C3 radicals;

S. Amoruso; G. Ausanio; M. Vitiello; X. Wang

2005-01-01

6

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Emission spectroscopy of a carbon plasma formed by laser ablation of graphite. II. Ablation by a CO2 laser and also simultaneously by XeCl and CO2 lasers  

NASA Astrophysics Data System (ADS)

The method of time-resolved emission spectroscopy was used to investigate the radiation emitted by a carbon plasma plume formed as a result of vacuum ablation of graphite by pulsed CO2 laser radiation. The spectrum of the radiation changed drastically in the course of emission from the plasma. The spectrum revealed successive appearance of various luminescence components contributed by C+ ions, C2 radicals, and microparticles. This spectrum differed considerably from that observed for a plasma formed by ablation with an XeCl laser, mainly because of the difference between the laser radiation wavelengths. Under certain conditions it was found that additional heating with CO2 laser radiation of a plasma formed by ablation of graphite with XeCl laser radiation altered greatly the emission spectrum. The changes indicated a higher degree of particle atomisation and a higher proportion of ions in such a plasma, compared with the plasma produced by one laser.

Dem'yanenko, A. V.; Letokhov, V. S.; Puretskii, A. A.; Ryabov, Evgenii A.

1998-01-01

7

Ablative and fractional ablative lasers.  

PubMed

The field of nonsurgical laser resurfacing for aesthetic enhancement continues to improve with new research and technological advances. Since its beginnings in the 1980s, the laser-resurfacing industry has produced a multitude of devices employing ablative, nonablative, and fractional ablative technologies. The three approaches largely differ in their method of thermal damage, weighing degrees of efficacy, downtime, and side effect profiles against each other. Nonablative technologies generate some interest, although only for those patient populations seeking mild improvements. Fractional technologies, however, have gained dramatic ground on fully ablative resurfacing. Fractional laser resurfacing, while exhibiting results that fall just short of the ideal outcomes of fully ablative treatments, is an increasingly attractive alternative because of its far more favorable side effect profile, reduced recovery time, and significant clinical outcome. PMID:19850197

Brightman, Lori A; Brauer, Jeremy A; Anolik, Robert; Weiss, Elliot; Karen, Julie; Chapas, Anne; Hale, Elizabeth; Bernstein, Leonard; Geronemus, Roy G

2009-10-01

8

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

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

9

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

PubMed

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

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

2014-02-01

10

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

SciTech Connect

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

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

2010-11-15

11

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

SciTech Connect

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

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

1993-11-01

12

Laser ablation of blepharopigmentation  

SciTech Connect

This article discusses laser ablation of blepharopigmentation in four stages: first, experimentally, where pigment vaporization is readily achieved with the argon blue-green laser; second, in the rabbit animal model, where eyelid blepharopigmentation markings are ablated with the laser; third, in human subjects, where the argon blue-green laser is effective in the ablation of implanted eyelid pigment; and fourth, in a case report, where, in a patient with improper pigment placement in the eyelid, the laser is used to safely and effectively ablate the undesired pigment markings. This article describes in detail the new technique of laser ablation of blepharopigmentation. Potential complications associated with the technique are discussed.

Tanenbaum, M.; Karas, S.; McCord, C.D. Jr. (Univ. of Miami School of Medicine, FL (USA))

1988-01-01

13

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

NASA Astrophysics Data System (ADS)

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

Verhoff, B.; Harilal, S. S.; Freeman, J. R.; Diwakar, P. K.; Hassanein, A.

2012-11-01

14

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

15

Laser-ablation processes  

SciTech Connect

The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10{sup 13} W/cm{sup 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, R.S.

1992-01-01

16

Laser-ablation processes  

SciTech Connect

The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10{sup 13} W/cm{sup 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

Dingus, R.S.

1992-05-01

17

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

18

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

19

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

20

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

21

Time-of-flight spectroscopy of the energy distribution of laser-ablated atoms and ions.  

PubMed

The growth of ultrathin films, deposited by laser ablation, crucially depends on the energy of the ablated species. Therefore, a time-of-flight (TOF) spectrometer has been constructed and measurements have been carried out in order to determine the energy distribution of laser-ablated Fe and Pt atoms and ions in the plasma created by nanosecond pulses of a frequency-doubled neodymium doped yttrium aluminum garnet laser. The experiments have been performed in ultrahigh vacuum at relatively low laser power. For measuring the spectra of the neutrals, a cross-beam electron source for postionization and electric as well as magnetic fields for repelling the ions are employed. Nevertheless, measurements of neutral particles are restricted to low plasma densities due to electrostatic shielding within the plasma, leading to an inefficient deflection of charged particles by electrostatic and magnetic fields. Test measurements have been performed by utilizing the TOF spectrometer as a pressure gauge and also by chopping the electron beam, running the TOF spectrometer as a residual gas mass spectrometer. The spectra of the laser-ablated plasmas have shown plasma conditions with a Debye length of approximately 10(-4) m, densities of 10(15)-10(16) m(-3) and ion energies up to 150 eV. Neutral spectra have shown an unexpectedly low fraction of neutrals (10(-3)-10(-4)) and hyperthermal energies up to several 10 eV, possibly contributed by recombination of ions and electrons in the plasma. Even though gas spectra had demonstrated the expected sensitivity of the TOF spectrometer for low-energy neutrals, no thermally evaporated neutral atoms could be found. PMID:18447522

Buchsbaum, A; Rauchbauer, G; Varga, P; Schmid, M

2008-04-01

22

Time-of-flight spectroscopy of the energy distribution of laser-ablated atoms and ions  

NASA Astrophysics Data System (ADS)

The growth of ultrathin films, deposited by laser ablation, crucially depends on the energy of the ablated species. Therefore, a time-of-flight (TOF) spectrometer has been constructed and measurements have been carried out in order to determine the energy distribution of laser-ablated Fe and Pt atoms and ions in the plasma created by nanosecond pulses of a frequency-doubled neodymium doped yttrium aluminum garnet laser. The experiments have been performed in ultrahigh vacuum at relatively low laser power. For measuring the spectra of the neutrals, a cross-beam electron source for postionization and electric as well as magnetic fields for repelling the ions are employed. Nevertheless, measurements of neutral particles are restricted to low plasma densities due to electrostatic shielding within the plasma, leading to an inefficient deflection of charged particles by electrostatic and magnetic fields. Test measurements have been performed by utilizing the TOF spectrometer as a pressure gauge and also by chopping the electron beam, running the TOF spectrometer as a residual gas mass spectrometer. The spectra of the laser-ablated plasmas have shown plasma conditions with a Debye length of approximately 10-4m, densities of 1015-1016m-3 and ion energies up to 150eV. Neutral spectra have shown an unexpectedly low fraction of neutrals (10-3-10-4) and hyperthermal energies up to several 10eV, possibly contributed by recombination of ions and electrons in the plasma. Even though gas spectra had demonstrated the expected sensitivity of the TOF spectrometer for low-energy neutrals, no thermally evaporated neutral atoms could be found.

Buchsbaum, A.; Rauchbauer, G.; Varga, P.; Schmid, M.

2008-04-01

23

Double-pulse and calibration-free laser-induced breakdown spectroscopy at low-ablative energies.  

PubMed

The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis generally depends on standards and calibration curves. To our knowledge, in this Letter, we report the first quantitative analysis based on DP-LIBS at low ablative energies with a self-calibrated method. We compare the effects of plasmas on the calibration-free LIBS technique, generated by DP-LIBS, and the traditional single-pulse (SP) LIBS on a steel sample. Our analyses reveal that when SP-LIBS and DP-LIBS reach comparable emission line intensities, plasma parameters and quantitative analysis are practically the same for both experiments. Additionally, we report the behavior of the emission enhancement of some elements (Fe and Cr) at low ablative pulse energies (0.2-8 mJ) using the orthogonal reheating DP-LIBS configuration. PMID:23164848

Contreras, V; Meneses-Nava, M A; Barbosa-García, O; Maldonado, J L; Ramos-Ortiz, G

2012-11-15

24

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...

25

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

26

Fundamental Characteristics of a Laser Ablation Microthruster  

NASA Astrophysics Data System (ADS)

The fundamental characteristics of a laser ablation microthruster were investigated for a 10 kg-class microspacecraft. A single-shot impulse measurement was performed using a thrust stand on which a prototype thruster was installed and the associate ablated mass was estimated from the pressure increase in the space chamber. The best performance of several polymer materials was obtained using polyvinylchloride as the propellant. More heavily carbon doped polyvinylchloride showed higher performance, which means absorption length has a large effect on performance. The intensity of the laser beam on the ablation material was changed using constant laser power, and it was shown that intensity had little effect on the performance. This qualitative behavior agreed with the results of a simple thermal analysis. Mass spectroscopy of the ablation plume showed that the dominant reaction was dehydrochlorination in the range of 470 to 640 K, and the low-temperature reaction resulted in the best performance for polyvinylchloride.

Koizumi, Hiroyuki; Inoue, Takayoshi; Komurasaki, Kimiya; Arakawa, Yoshihiro

27

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

28

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

29

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

E-print Network

. Plasma formation occurs when a high powered pulsed laser is focused onto a target such that the energy to the duration of the laser pulse (tp) being shorter than the electron to ion energy transfer time (sei) and heat, the laser beam does not interact with the laser- induced plasma causing the laser energy to be fully

Harilal, S. S.

30

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

PubMed

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

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

2014-05-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

32

Laser Ablation for Medical Applications  

NASA Astrophysics Data System (ADS)

Medical applications of laser are measurement, laser surgery, in-situ monitoring, and processing of medical devices. In this paper, author briefly reviews the trends of medical applications, describes some new applications, and then discuss about the future trends and problems of medical applications. At present, the domestic market of laser equipment for medical applications is nearly 1/10 of that for industrial applications, which has registered significant growth continuously. Laser surgery as a minimum invasive surgery under arthroscope is expected to decrease the pain of patients. Precise processing such as cutting and welding is suitable for manufacturing medical devices. Pulsed laser deposition has been successfully applied to the thin film coating. The corneal refractive surgery by ArF excimer laser has been widely accepted for its highly safe operation. Laser ablation for retinal implant in the visual prosthesis is one of the promising applications of laser ablation in medicine. New applications with femtosecond laser are expected in the near future.

Hayashi, Ken-Ichi

33

Ultrasonic characterization of laser ablation  

SciTech Connect

When a pulsed laser beam strikes the surface of an absorbing material, ultrasonic waves are generated due to thermoelectric expansion and, at higher laser power densities, ablation of the material. These sound generation mechanisms have been the subject of numerous theoretical and experimental studies and are now fairly well understood. In particular, it has been established that at low power densities the thermoelastic mechanism is well described by a surface center of expansion. This mechanism produces a characteristic waveform whose amplitude is proportional to the energy absorbed from the laser pulse and also dependent on the thermal and elastic properties of the material. The ablation ultrasonic source can be described by a point normal force acting on the material surface. For laser power densities near the ablation onset, the time dependence of the source is that of the laser pulse. The resultant waveform recorded on epicenter (source and detector collinear) has a sharp peak determined by the momentum impulse delivered to the material by the ablation process. Particularly in the near ablation onset region, this ultrasonic displacement peak can be used to characterize the ablation process occurring at the material surface. The onset power density for ablation and subsequent ablation dependence on power density are material dependent and thought to be a function of the heat capacity and thermal conductivity of the material. With this in mind, it is possible that these ablation signals could be used to characterize material microstructures, and perhaps material mechanical properties such as hardness, through microstructural changes of the material thermal parameters. This paper explores this question for samples of Type 304 stainless steel with microstructures controlled through work hardening and annealing.

Smith, J.A.; Telschow, K.L.

1991-01-01

34

Laser ablation of human tooth  

NASA Astrophysics Data System (ADS)

We report the measurements of ablation threshold of human tooth in air using photo-thermal deflection technique. A third harmonic (355nm) of Nd:YAG (yttrium aluminum garnet) laser was used for irradiation and a low power helium neon laser as a probe beam. The experimental observations of ablation threshold in conjunction with theoretical model based on heat conduction equations for simulating the interaction of a laser radiation with a calcified tissue are used to estimate the absorption coefficient of human tooth.

Franklin, Sushmita R.; Chauhan, P.; Mitra, A.; Thareja, R. K.

2005-05-01

35

Wrinkles and Acne Scars: Fractional Ablative Lasers  

Microsoft Academic Search

\\u000a Fractional ablative lasers create columns of ablated tissue separated by zones of intact tissue, resulting in rapid re-epithelialization\\u000a and induction of new collagen production. Fractional ablation provides a greater margin of safety compared to conventional\\u000a laser ablation by avoiding the production of open wounds. Fractional ablative lasers improve photodamage and scars in one\\u000a to two treatment sessions.

Arielle N. B. Kauvar; Melanie A. Warycha

36

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

37

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

38

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

39

Temporal pulse shaping effects on aluminium and boron ablation plumes generated by ultrashort pulsed laser ablation and analyzed by time- and space-resolved optical spectroscopy  

NASA Astrophysics Data System (ADS)

This paper focuses on the effect of temporal shaping of femtosecond laser pulses on laser ablation of aluminium and boron. The influence on plasma composition is deduced from optical emission investigations. Irradiation generated by the temporal tailoring of an incident laser pulse into double pulses or longer pulses is examined and compared to results deduced from hydrodynamic simulations of plasma temperature profiles. Above the ion formation threshold, increasing the delay in the double pulses sequence or increasing the pulse duration leads to an increase of the ion emission of the plasma plume of aluminium or boron. The observed increase with a saturation of ion emission at long delays or long pulse durations result from an interaction between the shaped laser pulse and the expanding matter after the onset of the plasma. Irradiation of boron with long pulses or double pulses reduces the production of nanoparticles, compared to the case of short pulses. Temporal shaping does not significantly affect the nanoparticle temperature, in spite of significant variations in the quantity of the ejected nanoparticles.

Bourquard, F.; Colombier, J.-P.; Guillermin, M.; Loir, A.-S.; Donnet, C.; Stoian, R.; Garrelie, F.

2012-09-01

40

Excimer laser ablation of ferrites  

NASA Astrophysics Data System (ADS)

Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20-50 ?m wide, with depths achieved as deep as 70 ?m . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a ``glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.

Tam, A. C.; Leung, W. P.; Krajnovich, D.

1991-02-01

41

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

42

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

PubMed

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

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

2000-01-01

43

Characterization of products of excimer laser ablation of collagen  

NASA Astrophysics Data System (ADS)

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

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

1995-05-01

44

Laser Navigation for Radiofrequency Ablation  

SciTech Connect

A 45-year-old male with renal cell carcinoma secondary to von-Hippel Lindau (VHL) disease presented for radiofrequency ablation (RFA) of kidney tumors. Due to his prior history of several partial nephrectomies and limited renal reserve, RFA was chosen because of its relatively nephron-sparing nature. A laser guidance device was used to help guide probe placement in an attempt to reduce procedure time and improve targeting accuracy. The device was successful at guiding needle placement, as both tumors were located with a single pass. Follow-up CT scan confirmed accurate needle placement, showing an area of coagulation necrosis covering the previously seen tumor.

Varro, Zoltan; Locklin, Julia K., E-mail: bwood@nih.gov; Wood, Bradford J. [National Institutes of Health, Warren G. Magnuson Clinical Center, Diagnostic Radiology Department (United States)

2004-09-15

45

Heterodyne laser spectroscopy system  

DOEpatents

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

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

1989-01-01

46

Heterodyne laser spectroscopy system  

DOEpatents

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

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

1990-01-01

47

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...

48

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_eergycoupling mechanisms include linear light_I__ absorption in solid, liquid and vapor phase, thermal and optical runaway

Vertes, Akos

49

Laser concrete ablation scaling effects.  

SciTech Connect

Surface scabbling of concrete by laser processing has been demonstrated in the literature for large-area problems ({approx}50 mm wide x 10 deep) using physically large, high-power consumption, multi-kW CW laser systems. With large spot diameters ({approx}50 mm) and low power densities ({approx} 300 W/cm{sup 2}), large volume thermal stresses are induced which promote concrete cracking. This process is highly power-density and heat-input (J/m) dependent. Too high power densities cause melting and generate potentially toxic fumes by vaporizing the cement matrix material. New applications require concrete removal with more portable, lower power equipment, and low particulate and fume generation. Recent results investigating the process for small-area ({approx} 2 x 2 mm) removal are examined and discussed. Tests performed were limited to < 700W output power. Ablation via thermal cracking was observed at larger spot sizes but as the spot size approached 10 mm (with constant power density) ablation ceased and melting predominated. Scaling effects involving temperature gradients through the ITZ (Interfacial Transition Zone), the probability of including an ITZ in the beam path at decreasing spot sizes, and the gradient effects on bulk properties between rock and sand zones will be presented and discussed.

MacCallum, Danny O'Neill; Norris, Jerome T.

2008-08-01

50

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

51

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

52

Characterization of an excimer laser-ablated plasma and applications  

NASA Astrophysics Data System (ADS)

Laser ablation and the subsequent development of a high energy dense plasma are receiving increased attention for spectrochemical analysis of solid materials. Observation of the plasma using atomic emission spectroscopy is the most direct method for analysis and offers the possibility of simultaneous multielement analysis. The use of a powerful UV excimer laser for ablation is of growing interest because of the low reflectivity for most solid materials. The excimer laser improves energy coupling efficiency by offering the relatively short wavelength. The details for construction and operation of an excimer laser-ablated plasma with a wavelength of 193 nm are described. The characterization and evaluation of a new kind of excimer laser-ablated plasma and applications for direct spectrochemical analysis were investigated through time- and space-resolved spectroscopy. The characteristics of the plasma that were studied included the appearance, excitation temperature, emission spectra, ambient gas breakdown, ionization efficiency, and analytical performances. The shape, size, emission spectra, and excitation temperatures of the laser-ablated plasma are largely dependent on the atmospheric surroundings, the ambient gas composition, the pressure, and laser energy. Spatial discrimination may be desirable to increase the line-to-background (L/B) ratio in atomic emission spectroscopy. A reduced pressure (optimum pressure; 10 Torr) in argon atmosphere may be useful for laser-ablated atomic emission spectroscopy (LAAES) applications which give a high intensity and large L/B ratio for the analytical signal. Metal ion formation in the plasma varies with time as well as location in the plasma. Ion lines were emitted close to the target, while the atomic lines appeared in the further regions of the plasma. The ion concentration was dependent on the position in the plasma and reflected the local temperature in the plasma. Gas breakdown in the plasma influenced the plasma formation and the analytical emission intensity. Argon gas breakdown was observed in the plasma. The relationship between gas breakdown and the physical properties of different metal species was deduced and provided a confirmation of theoretical modeling of the laser-ablated plasma interactions. A direct spectrochemical analytical method for solid samples with good linearity was developed using the excimer laser-AES. The sensitivity of the analytical signal varied depending on the chemical matrix of the solid samples. laser-AES for direct spectrochemical analysis.

Lee, Yong-Ill

53

Characterization of AN Excimer Laser-Ablated Plasma and Applications  

NASA Astrophysics Data System (ADS)

Laser ablation and the subsequent development of a high energy dense plasma are receiving increased attention for spectrochemical analysis of solid materials. Observation of the plasma using atomic emission spectroscopy is the most direct method for analysis and offers the possibility of simultaneous multielement analysis. The use of a powerful UV excimer laser for ablation is of growing interest because of the low reflectivity for most solid materials. The excimer laser improves energy coupling efficiency by offering the relatively short wavelength. The details for construction and operation of an excimer laser-ablated plasma with a wavelength of 193 nm are described. The characterization and evaluation of a new kind of excimer laser-ablated plasma and applications for direct spectrochemical analysis were investigated through time- and space-resolved spectroscopy. The characteristics of the plasma that were studied, included the appearance, excitation temperature, emission spectra, ambient gas breakdown, ionization efficiency, and analytical performances. The shape, size, emission spectra, and excitation temperatures of the laser-ablated plasma are largely dependent on the atmospheric surroundings, the ambient gas composition, the pressure, and laser energy. Spatial discrimination may be desirable to increase the line-to-background (L/B) ratio in atomic emission spectroscopy. A reduced pressure (optimum pressure; 10 Torr) in argon atmosphere may be useful for laser-ablated atomic emission spectroscopy (LAAES) applications which give a high intensity and large L/B ratio for the analytical signal. Metal ion formation in the plasma varies with time as well as location in the plasma. Ion lines were emitted close to the target, while the atomic lines appeared in the further regions of the plasma. The ion concentration was dependent on the position in the plasma and reflected the local temperature in the plasma. Gas breakdown in the plasma influenced the plasma formation and the analytical emission intensity. Argon gas breakdown was observed in the plasma. The relationship between gas breakdown and the physical properties of different metal species was deduced and provided a confirmation of theoretical modelling of the laser-ablated plasma interactions. A direct spectrochemical analytical method for solid samples with good linearity was developed using the excimer laser-AES. The sensitivity of the analytical signal varied depending on the chemical matrix of the solid samples. A typical detection limit for potassium in a glass matrix was 0.13 mug/g and for chromium in a steel-alloy matrix was 18.7 mug/g. These applications demonstrate the potential of excimer laser -AES for direct spectrochemical analysis.

Lee, Yong-Ill

54

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

55

Optical Properties of HfO2 Nanoparticles Produced by Laser Ablation  

NASA Astrophysics Data System (ADS)

The absorption and photoluminescence spectra of laser-ablated hafnium dioxide nanoparticles are studied by optical spectroscopy. The band gap of the nanoparticles is determined from the intrinsic absorption edge. The influence of the parameters of the laser ablation and the subsequent thermal annealing on the optical properties of the nanoparticles is studied.

Pugachevskii, M. A.; Panfilov, V. I.

2014-09-01

56

Fundamental Characteristics of a Laser Ablation Microthruster  

Microsoft Academic Search

The fundamental characteristics of a laser ablation microthruster were investigated for a 10 kg-class microspacecraft. A single-shot impulse measurement was performed using a thrust stand on which a prototype thruster was installed and the associate ablated mass was estimated from the pressure increase in the space chamber. The best performance of several polymer materials was obtained using polyvinylchloride as the

Hiroyuki Koizumi; Takayoshi Inoue; Kimiya Komurasaki; Yoshihiro Arakawa

2007-01-01

57

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

58

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

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

Hirata, Takafumi

2003-01-15

59

Nanosecond laser ablation of gold nanoparticle films  

SciTech Connect

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

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

2006-10-02

60

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

61

Highspeed laser ablation cutting of metal  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

62

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

SciTech Connect

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

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

2007-12-17

63

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

64

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

SciTech Connect

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

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

2008-07-01

65

Nanosecond laser ablation of silver nanoparticle film  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

66

Laser ablation of a polysilane material  

NASA Astrophysics Data System (ADS)

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

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

1987-08-01

67

UV laser ablation patterns in intraocular lenses  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

68

Interaction of flows of laser ablation plasmas  

SciTech Connect

Our studies of laser pulsed deposition of thin films, using 20-ns second-harmonic Nd:YAG laser operated at a few GW/cm{sup 2}, show that introduction of an obstacle like a grid screen into ablation plume with typical density 10{sup 18}cm{sup {minus}3} and temperature 3 eV substantially affects dynamics of plasma expansion and results in dramatic changes of plasma parameters. In this work, we report the effects typical for the later stage of plasma-grid interaction{emdash}effects related to the interaction of multiple plasma flows. Model experiments, performed employing method of emission spectroscopy, time-of-flight technique, and plasma imaging with CCD camera, show significant variation of plasma composition and transformation of velocity distribution due to plasmas interaction. Two modes of such transformation have been observed: linear growth of density in the resulting flow, and formation of the additional slow peak in the velocity distribution. The effect is shown to be velocity-resonant. {copyright} {ital 1997 American Institute of Physics.}

Derkach, Ogel M.; Sebrant, Andrey Y. [Institute for Laser Physics, Sadovaya-Spasskaya 21-151, Moscow, 107078 (Russia); Grishina, Valeria G. [TRINITI, Troitsk, Moscow Reg., 142092 (Russia)] Baranov, Vladimir Y. [National Research Center---Kurchatov Institute, Kurchatov Square, Moscow, 123098 (Russia)] Stepanova, Maria A. [Resonetics, Inc., 4 Bud Way No. 21, Nashua, New Hampshire 03063 (United States)

1997-04-01

69

Interaction of flows of laser ablation plasmas  

SciTech Connect

Our studies of laser pulsed deposition of thin films, using 20-ns second-harmonic Nd:YAG laser operated at a few GW/cm{sup 2}, show that introduction of an obstacle like a grid screen into ablation plume with typical density 10{sup 18} cm{sup -3} and temperature 3 eV substantially affects dynamics of plasma expansion and results in dramatic changes of plasma parameters. In this work, we report the effects typical for the later stage of plasma-grid interaction--effects related to the interaction of multiple plasma flows. Model experiments, performed employing method of emission spectroscopy, time-of-flight technique, and plasma imaging with CCD camera, show significant variation of plasma composition and transformation of velocity distribution due to plasmas interaction. Two modes of such transformation have been observed: linear growth of density in the resulting flow, and formation of the additional slow peak in the velocity distribution. The effect is shown to be velocity-resonant.

Derkach, Oleg N.; Sebrant, Andrey Y. [Institute for Laser Physics, Sadovaya-Spasskaya 21-151, Moscow, 107078 (Russian Federation); Anisimov, Vladimir N.; Grishina, Valeria G. [TRINITI, Troitsk, Moscow Reg., 142092 (Russian Federation); Baranov, Vladimir Y. [National Research Center--Kurchatov Institute, Kurchatov Square, Moscow, 123098 (Russian Federation); Stepanova, Maria A. [Resonetics, Inc., 4 Bud Way 21, Nashua, New Hampshire 03063 (United States)

1997-04-15

70

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

71

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

PubMed

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

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

2013-02-01

72

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

73

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

74

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

75

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

76

Ultrashort Pulse Laser Ablation for Depth Profiling of Bacterial Biofilms  

PubMed Central

Sample ablation by pulsed lasers is one option for removing material from a sample surface for in situ depth profiling during imaging mass spectrometry, but ablation is often limited by laser-induced damage of the remaining material. A preliminary evaluation was performed of sub-100 fs, 800 nm pulsed laser ablation for depth profiling of bacterial biofilms grown on glass by the drip flow method. Electron and optical microscopy were combined with laser desorption vacuum ultraviolet postionization mass spectrometry to analyze biofilms before and after ablation. Ultrashort laser pulses can ablate 10 – 100 µm thick sections of bacterial biofilms, leaving behind a layer of lysed cells. However, mass spectra from intact and ablated biofilms doped with antibiotic are almost identical, indicating little chemical degradation by ablation. These results are consistent with prior observations from laser surgery and support the use of ultrashort pulse laser ablation for minimally disruptive depth profiling of bacterial biofilms and intact biological samples. PMID:21031139

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

2010-01-01

77

The rotational spectrum of CuCCH(X~ 1Sigma+): A Fourier transform microwave discharge assisted laser ablation spectroscopy and millimeter\\/submillimeter study  

Microsoft Academic Search

The pure rotational spectrum of CuCCH in its ground electronic state (X~ 1Sigma+) has been measured in the frequency range of 7-305 GHz using Fourier transform microwave (FTMW) and direct absorption millimeter\\/submillimeter methods. This work is the first spectroscopic study of CuCCH, a model system for copper acetylides. The molecule was synthesized using a new technique, discharge assisted laser ablation

M. Sun; D. T. Halfen; J. Min; B. Harris; D. J. Clouthier; L. M. Ziurys

2010-01-01

78

Laser ablated copper plasmas in liquid and gas ambient  

NASA Astrophysics Data System (ADS)

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 (ne) determined using Stark broadening of the Cu I (3d104d1 2D3/2-3d104p1 2P3/2 at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (Te) 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.

2013-05-01

79

Excimer laser ablation of ferrite ceramics  

NASA Astrophysics Data System (ADS)

We study the ablation of Ni-Zn or Mn-7n ferrites by 248-nm KrF excimer laser irradiation for high-resolution patterning. A transfer lens system is used to project the image of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluente for ablation of the ferrite surface is about 0.3 J/cm2. A typical fluente of 1 J/cm2 is used to produce good-quality patterning. Scanning electron microscopy of the ablated area shows a "glassy" skin with extensive microcracks and solidified droplets being ejected that is frozen in action. This skin can be removed by ultrasonic cleaning.

Tam, A. C.; Leung, W. P.; Krajnovich, D.

80

Laser ablation and cryotherapy of melanoma metastases.  

PubMed

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

John, Hannah E; Mahaffey, Peter J

2014-03-01

81

Molecular dynamics simulation of ultrafast laser ablation of fused silica  

E-print Network

is considered as "thermal" ablation because it is caused by the high temperature in the material. On the other" ablation. Both thermal and non-thermal (Coulomb explosion) ablation processes have been discussedMolecular dynamics simulation of ultrafast laser ablation of fused silica C Cheng, A Q Wu and X Xu

Xu, Xianfan

82

Laser ablation mechanism of transparent dielectrics with picosecond laser pulses  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

83

Picosecond laser ablation of porcine sclera  

NASA Astrophysics Data System (ADS)

Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer's solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30?m. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.

Góra, Wojciech S.; Harvey, Eleanor M.; Dhillon, Baljean; Parson, Simon H.; Maier, Robert R. J.; Hand, Duncan P.; Shephard, Jonathan D.

2013-03-01

84

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

85

Ablation laser femtoseconde pour le dépôt de DLC  

NASA Astrophysics Data System (ADS)

Des films de Diamond-Like Carbon (DLC) ont été déposés, sous vide poussé, par ablation d'une cible de graphite avec un laser Ti : saphir (durée d'impulsion 150 fs, fréquence de répétition 1 kHz, énergie par impulsion 1,5 mJ, longueur d'onde 800 nm) sur substrat standard. Les propriétés de ces couches (structure, adhérence, propriétés nanomécaniques) ont été caractérisées, en fonction des conditions d'élaboration. La caractérisation par spectroscopie Raman de la structure des dépôts obtenus a révélé la présence de diamant nanocristallin au sein d'une matrice amorphe. Le taux d'hybridation sp^3 des couches, déterminé à partir des spectres obtenus par XANES (X-ray Absorption Near Edge Speciroscopy), est voisin de 70 %. Ces différents résultats sont corrélés avec la caractérisation par imagerie résolue en temps du panache plasma créé par ablation laser femtoseconde.

Loir, A.-S.; Garrelie, F.; Donnet, C.; Goutaland, F.; Belin, M.; Subtil, J.-L.; Le Harzic, R.; Rogemond, F.; Ouerdane, Y.; Laporte, P.

2003-06-01

86

Photochemical induced effects in material ejection in laser ablation  

E-print Network

in the ablation regime [8]. The dif- ferences between thermal and stress confinement regimes for pure photothermalPhotochemical induced effects in material ejection in laser ablation Yaroslava G. Yingling, Barbara ejection mechanisms in laser ablation of organic solids. The presence of photochemical decomposition

87

FEATURE ARTICLE A Microscopic View of Laser Ablation  

E-print Network

as a unit9-11 was used to explain the differences between ablative photodecomposition and thermal processesFEATURE 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

Zhigilei, Leonid V.

88

Femtosecond Laser Ablation of Silicon: Nanoparticles, Doping and Photovoltaics  

E-print Network

: thermal regime . . . . . . . . . . . . . . . . . 6 1.1.3 Melting and ablation: non-thermal regimeFemtosecond 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

Mazur, Eric

89

Near threshold femtosecond laser interactions with materials: Ablation thresholds, morphologies, and dynamics  

NASA Astrophysics Data System (ADS)

This dissertation reports the results of femtosecond (fs, 10-15 seconds) laser ablation studies performed on single crystal silicon with oxide thin films and the single crystal Ni-based superalloy, CMSX-4. Emphasis is placed on near threshold ablation (or material removal) phenomena where fs pulsed lasers show significant promise for industrial machining, characterization, materials processing, fabrication of structures, and other applications. Three specific topics are addressed: fs laser ablation thresholds, ablation morphologies, and ablation dynamics. These investigations demonstrate both fundamental aspects of the interaction of fs laser pulses with materials while also introducing novel, previously unobserved phenomena. The fs laser ablation threshold of single crystal silicon was observed to depend on its naturally occurring oxide, the presence of which increased the ablation threshold of silicon by ˜39% at grazing laser incidence relative to atomically clean silicon. Extension of these studies to ablation threshold measurements on silicon with thermally grown oxide films of varying thickness revealed that despite the high intensities and short timescales of such interactions, the linear optical properties of a surface significantly influence near threshold fs laser ablation. Femtosecond laser induced blistering or buckling of thin oxide films (20--1200 nm) from silicon substrates was observed. Thin film buckling mechanics were used to study the blister features, revealing that the fs laser induced ablation at the oxide film interface participated in the buckling by adding energy to the delaminated oxide film. Furthermore, isolated blisters could be connected together to create linear fluidic channels. A simple device for performing electrophoresis was fabricated with these channels, the characteristic of this device were studied. The dynamics of the ablation event were studied in-situ using the technique of pump-probe microscopy with sub-picosecond resolution. Previously developed models of near threshold fs laser ablation were verified and extended by comparing the dynamics captured from two different viewing angles. Furthermore, the dynamics within the first 10 ns of ablation were found to correlate with the final ablation morphology. Finally, an orthogonal, dual-pulse laser induced breakdown spectroscopy method was used to reduce the surface damage associated with this versatile spectroscopy technique.

McDonald, Joel P.

90

Spectral and Dynamic Characteristics of Helium Plasma Emission and its Effect on a Laser-Ablated Target Emission in a Double-Pulse Laser-Induced Breakdown Spectroscopy (LIBS) Experiment.  

PubMed

A systematic study has been performed on the spectral characteristics of the full spectrum of He emission lines and their time-dependent behaviors measured from the He gas plasmas generated by a nanosecond neodymium-doped yttrium aluminum garnet laser. It is shown that among the major emission lines observed, the triplet He(I) 587.6 nm emission line stands out as the most prominent and long-lasting line, associated with de-excitation of the metastable triplet (S = 1) excited state (1s(1) 3d(1)). The role of this metastable excited state is manifested in the intensity enhancement and prolonged life time of the Cu emission with narrow full width half-maximum, as demonstrated in an orthogonal double-pulse experiment using a picosecond laser for the target ablation and a nanosecond laser for the prior generation of the ambient He gas plasma. These desirable emission features are in dire contrast to the characteristics of emission spectra observed with N2 ambient gas having no metastable excited state, which exhibit an initial Stark broadening effect and rapid intensity diminution typical to thermal shock wave-induced emission. The aforementioned He metastable excited state is therefore responsible for the demonstrated favorable features. The advantage of using He ambient gas in the double-pulse setup is further confirmed by the emission spectra measured from a variety of samples. The results of this study have thus shown the potential of extending the existing laser-induced breakdown spectroscopy application to high-sensitivity and high-resolution spectrochemical analysis of wide-ranging samples with minimal destructive effect on the sample surface. PMID:25506688

Jobiliong, Eric; Suyanto, Hery; Marpaung, Alion Mangasi; Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Hedwig, Rinda; Ramli, Muliadi; Pardede, Marincan; Suliyanti, Maria Margaretha; Kagawa, Kiichiro; Fukumoto, Ken-Ichi; Tjia, May On; Lie, Tjung Jie; Lie, Zener Sukra; Kurniawan, Koo Hendrik

2015-01-01

91

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

92

Ultraviolet laser ablation of polyimide films  

NASA Astrophysics Data System (ADS)

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

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

1987-01-01

93

Experimental research of two-wavelength laser ablation biological tissue  

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

94

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

95

Modeling CO{sub 2} Laser Ablative Impulse with Polymers  

SciTech Connect

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

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

2010-10-08

96

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

97

Formation, structure and nonlinear optical properties of carbon nanoparticles synthesized by pulsed laser ablation  

Microsoft Academic Search

Carbon nanoparticles were prepared by pulsed laser ablation in argon gas for studying their formation, properties and applications. The nanoparticles were produced at different background pressures and different substrate temperatures, respectively. Micro-Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the samples. Nonlinear optical limiting properties of the carbon nanoparticles were characterized using nanosecond laser

G. X. Chen; M. H. Hong; Q. He; W. Z. Chen; H. I. Elim; W. Ji; T. C. Chong

2004-01-01

98

Femtosecond laser ablation of single-wall carbon nanotube-based material  

NASA Astrophysics Data System (ADS)

Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotube-based substrate at 515- and 1030?nm wavelengths was studied by scanning electron microscopy and micro-Raman spectroscopy. The laser ablation proceeds in two ways: as the low-fluence mesoscopic shallow disintegration of the surface nanotube packing, preserving the individual integrity and the semiconducting character of the nanotubes or as the high-fluence deep material removal apparently triggered by the strong intrinsic or impurity-mediated ablation of the individual carbon nanotubes on the substrate surface.

Danilov, Pavel A.; Ionin, Andrey A.; Kudryashov, Sergey I.; Makarov, Sergey V.; Mel’nik, Nikolay N.; Rudenko, Andrey A.; Yurovskikh, Vladislav I.; Zayarny, Dmitry V.; Lednev, Vasily N.; Obraztsova, Elena D.; Pershin, Sergey M.; Bunkin, Alexey F.

2014-10-01

99

Inertial effects in laser-driven ablation  

SciTech Connect

The gasdynamic partial differential equations (PDE's) governing the motion of an ablatively accelerated target (rocket) contain an inertial force term that arises from acceleration of the reference frame in which the PDE's are written. We give a simple, intuitive description of this effect, and estimate its magnitude and parametric dependences by means of approximate analytical formulas inferred from our computer hydrocode calculations. Often this inertial term is negligible, but for problems in the areas of laser fusion and laser equation of state studies we find that it can substantially reduce the attainable hydrodynamic efficiency of acceleration and implosion.

Harrach, R.J.; Szeoke, A.; Howard, W.M.

1983-07-15

100

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

101

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

102

Heat-affected zone and ablation rate of copper ablated with femtosecond laser  

SciTech Connect

We describe the experimental and molecular dynamics simulation study of crystalline copper (Cu) ablation using femtosecond lasers. This study is focused on the heat-affected zone after femtosecond laser ablation and the laser ablation rate. As a result of the x-ray diffraction measurement on the ablated surface, the crystallinity of the surface is partially changed from a crystal structure into an amorphous one. At the laser fluences below the ablation threshold, the entire laser energy coupled to the Cu target is absorbed, while during the fluence regime over the threshold fluence, the ablation rate depends on the absorption coefficient, and the residual energy which is not used for the ablation, is left in the Cu substrate. The heat-affected zone at the fluences below the threshold is estimated to be greater than that over the threshold fluence. In addition, the laser ablation of Cu is theoretically investigated by a two-temperature model and molecular dynamics (MD) simulation to explain the heat-affected zone and ablation rate. The MD simulation takes into account the electron temperature and thermal diffusion length calculated by the two-temperature model. Variation in the lattice temperature with time and depth is calculated by the MD simulation coupled with the two-temperature model. The experimental ablation rate and the heat-affected zone are theoretically well explained.

Hirayama, Yoichi; Obara, Minoru [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

2005-03-15

103

Masks for laser ablation technology: New requirements and challenges  

Microsoft Academic Search

Laser ablation is used as a dry patterning process in which an intense beam of light from an excimer laser is used to pattern a material directly. This process has found extensive application in the microelectronics industry for patterning of polymer materials. A typical laser ablation tool is very similar to a conventional optical lithography projection tool; the primary difference

James L. Speidell; Doris P. Pulaski; Rajesh S. Patel

1997-01-01

104

Precise laser ablation processing of black widow spider silk  

Microsoft Academic Search

Contact-free precise laser processing of black widow spider ( Latrodectus hesperus) dragline silk by laser ablation at ?=157 nm is achieved. At this wavelength, the small optical penetration depth, below 100 nm, allows efficient and gentle material removal above the ablation threshold of F th=29 mJ\\/cm 2. The ablation rate in nm\\/pulse is measured against laser fluence F and simultaneously calibrated with ultrapure

A. Moore; M. Koch; K. Mueller; M. Stuke

2003-01-01

105

Ablation dynamics in laser sclerotomy ab externo  

NASA Astrophysics Data System (ADS)

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

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

1996-01-01

106

Sensitization of PMMA to laser ablation at 308 nm  

Microsoft Academic Search

Pure polymethylmethacrylate (PMMA) is highly resistant to ablation at 308 nm. The value of PMMA in lithography and semiconductor packaging and the availability of reliable 308 nm optics has motivated the development of dopants to facilitate PMMA ablation at 308 nm. We investigate the laser ablation of solvent cast PMMA films with and without pyrene, a typical dopant. The presence

R. L. Webb; S. C. Langford; J. T. Dickinson; T. K. Lippert

1998-01-01

107

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

108

Dynamics of laser ablation of biological tissues  

NASA Astrophysics Data System (ADS)

We have developed a subnanosecond time resolution ultrafast photographic setup that can be used both as shadowgraph and Schlieren apparatus. With this setup a detailed study of the time history of the plume ejection and shock wave propagation have been preformed. We have shown that the shock wave fronts follow the behaviour predicted by shock wave theories, and that the planar shock wave fronts travel always perpendicular to the ablated surface. In addition to the earlier known hemispherical shock wave a new, head-wave type wave front was found that is presumably caused by a bunch of very fast particles preceding the formation of the main ablation plume. We have shown that the dynamics of short pulse Nd laser induced cavitation bubbles is considerably different in water and bovine cornea.

Bor, Z.; Szabó, G.; Hopp, B.; Márton, Zs.; Juhász, T.

1993-10-01

109

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/cm2, 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

110

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

111

Erbium: Yag Laser Trabecular Ablation with a Sapphire Optical Fiber  

Microsoft Academic Search

The purpose of the study was to evaluate the effect of erbium (Er): yttrium aluminum garnet (YAG) laser trabecular ablation with a sapphire optical fiber on outflow facility.After obtaining baseline outflow facility using a computerized differential pressure perfusion system, human cadaver eyes were subjected to Er: YAG laser trabecular ablation using a sapphire optical fiber. Single pulses at varying energy

M. LISA McHAM; DAN L. EISENBERG; JOEL S. SCHUMAN; NAN WANG

1997-01-01

112

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 and composite nanostructures,4 have been fabricated by this technique. Silicon carbide (SiC) is a wide

Zheng, Yufeng

113

Laser ablation of aluminum from normal evaporation to phase explosion  

SciTech Connect

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

Gragossian, A.; Tavassoli, S. H.; Shokri, B. [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 1983963113 (Iran, Islamic Republic of)

2009-05-15

114

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

115

Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles  

NASA Astrophysics Data System (ADS)

Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

Baladi, Arash; Sarraf Mamoory, Rasoul

2010-10-01

116

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

117

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

118

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

119

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

120

Elemental bioimaging of nanosilver-coated prostheses using X-ray fluorescence spectroscopy and laser ablation-inductively coupled plasma-mass spectrometry.  

PubMed

The distribution of different chemical elements from a nanosilver-coated bone implant was visualized, combining the benefits of two complementary methods for elemental bioimaging, the nondestructive micro X-ray fluorescence (?-XRF), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Challenges caused by the physically inhomogeneous materials including bone and soft tissues were addressed by polymer embedding. With the use of ?-XRF, fast sample mapping was achieved obtaining titanium and vanadium signals from the metal implant as well as phosphorus and calcium signals representing hard bone tissue and sulfur distribution representing soft tissues. Only by the use of LA-ICP-MS, the required high sensitivity and low detection limits for the determination of silver were obtained. Metal distribution within the part of cancellous bone was revealed for silver as well as for the implant constituents titanium, vanadium, and aluminum. Furthermore, the detection of coinciding high local zirconium and aluminum signals at the implant surface indicates remaining blasting abrasive from preoperative surface treatment of the nanosilver-coated device. PMID:24320121

Blaske, Franziska; Reifschneider, Olga; Gosheger, Georg; Wehe, Christoph A; Sperling, Michael; Karst, Uwe; Hauschild, Gregor; Höll, Steffen

2014-01-01

121

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

122

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

E-print Network

lag; Laser ablation 1. Introduction Laser ablation of a metal involves complex thermal phenomena liquid. The thermal mechanisms of pulsed laser ablation include surface normal evaporationPhase explosion and its time lag in nanosecond laser ablation Xianfan Xu* School of Mechanical

Xu, Xianfan

123

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

PubMed

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

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

2006-08-15

124

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

125

A new laser micromachining technique using a mixed-mode ablation approach  

Microsoft Academic Search

This paper presents a novel laser micromachining technique using a mixed-mode ablation approach. Some important techniques, which include laser drilling, laser ablation, and laser cutting, have been developed to overcome common problems in laser micromachining, such as material recast, big heat affected zone (HAZ) problem, and laser polarization effect. Ablation parameters for various microstructures on single crystalline silicon have been

Xiaoshan Zhu; Jin-Woo Choi; Robert Cole; Chong H. Ahn

2002-01-01

126

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

127

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

128

Dynamics of laser ablated colliding plumes  

SciTech Connect

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

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

2013-01-15

129

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

130

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

131

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

SciTech Connect

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

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

2007-12-24

132

Infrared Laser Ablation Atmospheric Pressure Photoionization Mass Spectrometry  

E-print Network

Infrared Laser Ablation Atmospheric Pressure Photoionization Mass Spectrometry Anu Vaikkinen ablation atmo- spheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass analytes are desolvated and ionized in the gas-phase by atmospheric pressure photoionization using a 10 e

Vertes, Akos

133

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

134

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

135

Enhancement of pulsed laser ablation in environmentally friendly liquid.  

PubMed

Enhancement of pulsed laser ablation can be achieved in acetic acid as an environmentally friendly liquid. This paper evaluates microholes and textured features induced by a nanosecond pulsed laser under different processing circumstances. The microholes are fabricated by laser drilling in acetic acid and found to be 100% deeper than in air. The textured features achieved in the liquid demonstrate a higher content of Copper and a lower content of Oxygen. The improvement of laser ablation efficiency in the liquid is attributed to the strong confinement of plasma plume accompanying with shockwave and cavitation bubbles. Meanwhile, the laser enhanced chemical etching by the weak acid plays a critical role. PMID:25321965

Luo, Fangfang; Guan, Yingchun; Ong, Weili; Du, Zheren; Ho, Ghimwei; Li, Fengping; Sun, Shufeng; Lim, Gniancher; Hong, Minghui

2014-10-01

136

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

137

Numerical simulation of pulsed laser ablation in air  

NASA Astrophysics Data System (ADS)

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 pressure is studied with emphasis on the vaporization model, especially recondensation ratio over the Knudsen layer. Furthermore, parametric studies are carried out to analyze the effect of laser fluence and background pressure on surface ablation and the dynamics of ablation plume. In the numerical calculation, the temperature, pressure, density, and vaporization flux on a solid substrate are obtained by a heat-transfer computation code based on the enthalpy method. The plume dynamics is calculated considering the effect of mass diffusion into the ambient air and plasma shielding. To verify the computation results, experiments for measuring the propagation of a laser induced shock wave are conducted as well.

Oh, Bukuk; Kim, Dongsik; Jang, Wonseok; Shin, Bosung

2003-11-01

138

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

PubMed

A novel high-energy explosive material, FOX-7 (1,1-diamino-2,2-dinitroethylene), was studied using a combination of laser-induced breakdown spectroscopy (LIBS) and selected ion flow tube mass spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (an ArF excimer laser) as the energy source to convert small quantities of a sample into plasma and to induce the emission of its molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three reagent ions, with the ability to determine concentrations of trace gases and vapors of volatile organic compounds in real time. SIFT-MS was used to study the release of NO, NO(2), HCN, HONO, HCHO, CH(3)CH(2)OH, and C(2)H(2) after laser ablation of the explosive compound FOX-7 in solid crystalline form. The radiation emitted after excitation was analyzed using a time-resolved UV-vis spectrometer with an ICCD detector. The electronic bands of CN (388 nm), OH (308.4 nm), and NO (237.1 nm) radicals and the atomic lines of C, N, and H were identified. PMID:21226460

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

2011-02-01

139

Formation of Nano Wires by Laser Ablation of Graphite  

Microsoft Academic Search

We report on preparation of carbon Nano wires by laser ablation of graphite targets using confined geometry in air. Nitrogen laser has been used to provide UV laser beam of wavelength 337 ± 2nm, pulses of duration 15± 1ns and power 1 MW per pulse. Using scanning electron microscopy, reveled that nano dots and nano wires were formed on stainless

Lotfia El Nadi; Magdy M. Omar; Hussein A. Moniem

2007-01-01

140

Formation of Nano Wires by Laser Ablation of Graphite  

Microsoft Academic Search

We report on preparation of carbon Nano wires by laser ablation of graphite targets using confined geometry in air. Nitrogen laser has been used to provide UV laser beam of wavelength 337 +\\/- 2nm, pulses of duration 15+\\/- 1ns and power 1 MW per pulse. Using scanning electron microscopy, reveled that nano dots and nano wires were formed on stainless

Lotfia El Nadi; Magdy M. Omar; Hussein A. Moniem

2007-01-01

141

Morphology of femtosecond-laser-ablated borosilicate glass surfaces  

Microsoft Academic Search

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

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

2003-01-01

142

A study of particle generation during laser ablation withapplications  

Microsoft Academic Search

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,

Chunyi

2005-01-01

143

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

144

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

E-print Network

, the laser ablation process is often described by a thermal desorption model, which considers the ablationMechanisms 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

Zhigilei, Leonid V.

145

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

E-print Network

reduces thermal damage to the surrounding area. In order to optimize a laser ablation process, and short pulse laser ablation is not well understood. Most ablation processes involve thermal transportIn situ photography of picosecond laser ablation of nickel D.A. Willis1 , X. Xu* School

Xu, Xianfan

146

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

147

High Current Cathodes Fabricated by KrF Laser Ablation  

SciTech Connect

In this paper we review several high power laser ablation techniques that have been utilized to fabricate high current (1-80 kA) electron beam cathodes for accelerators and microwave sources: 1) Projection Ablation Lithography (PAL) cathodes, 2) Ablation Line Focus (ALF) cathodes, and 3) Metal-Oxide-Junction (MOJ) cathodes. Laser-ablative micromachining techniques (PAL and ALF) have been utilized to generate micron-scale features on metal substrates that provide electric field (beta) enhancement for Fowler-Nordheim emission and plasma cathodes. Since these laser-ablated patterns are directly, laser-written on the substrate metal they exhibit much higher thermal conductivity for higher current capability and increased damage thresholds. Metal-Oxide-Junction (MOJ) cathodes exploit the triple-point electron emission that occurs at the interface between metal, insulator and vacuum.The ablation laser is a KrF excimer laser with a pulse energy of 600 mJ and pulselength of 20 ns. Cathode experiments were performed on the MELBA-C accelerator: V = -300 kV, pulselength = 0.5 microsecond. Data will be presented for PAL, ALF and MOJ cathodes.

Gilgenbach, Ronald M.; Lau, Y. Y. [Plasma, Pulsed-Power and Microwave Laboratory Nuclear Engineering and Radiological Sciences Department University of Michigan, Ann Arbor, MI 48109 (United States); Jones, M. C.; Johnston, M. D. [Sandia National Labs, Albuquerque, NM (United States); Jordan, N. M. [Cybernet Systems, Ann Arbor, MI (United States); Hoff, B. W. [Air Force Research Labs, Kirtland AFB, NM (United States)

2010-10-08

148

Laser ablation with applied magnetic field for electric propulsion  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

149

Porcine cortical bone ablation by ultrashort pulsed laser irradiation.  

PubMed

Ultrashort pulsed lasers in bone ablation show promise for many orthopedic applications. To minimize collateral tissue damage and control the ablation process, the ablation threshold fluence must be well characterized. Using an amplified femtosecond laser (170 fs, 800 nm, 1 kHz), the ablation threshold on unaltered porcine cortical bone was measured using the D(2) method at multiple incident pulse numbers ranging from 25 to 1000 pulses per spot. The lowered threshold at greater pulse numbers indicated an incubation effect. Using a power law model, the incubation coefficient of unaltered porcine cortical bone was found to be 0.89 ± 0.03. Through extrapolation, the single-pulse ablation threshold was found to be 3.29 ± 0.14 J/cm(2). PMID:22463049

Emigh, Brent; An, Ran; Hsu, Eugene M; Crawford, Travis H R; Haugen, Harold K; Wohl, Gregory R; Hayward, Joseph E; Fang, Qiyin

2012-02-01

150

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

151

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

152

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

153

Combination of erbium and holmium laser radiation for tissue ablation  

NASA Astrophysics Data System (ADS)

Erbium lasers emitting at 2.94 micrometers and holmium lasers emitting at 2.1 micrometers are interesting tools for cutting, drilling, smoothing and welding of water containing tissues. The high absorption coefficient of water at these wavelengths leads to their good ablation efficiency with controlled thermally altered zones around the ablation sites. Combination of pulses with both wavelengths transmitted through one fiber were used to perform incisions in soft tissue and impacts in bone disks. Histological results and scanning electron microscope evaluations reveal the strong influence of the absorption coefficient on tissue effects, especially on the ablation efficiency and the zone of thermally damaged tissue. It is demonstrated that the combination of high ablation rates and deep coagulation zones can be achieved. The results indicate that this laser system can be considered as a first step towards a multi-functional medical instrument.

Pratisto, Hans S.; Frenz, Martin; Koenz, Flurin; Altermatt, Hans J.; Weber, Heinz P.

1996-05-01

154

Laser Ablation in the Management of Obstructive Uropathy in Neonates.  

PubMed

Abstract Introduction: Endoscopic management of posterior urethral valves and congenital ureteroceles is the current standard to relieve the obstruction. While the most commonly used techniques involve cystoscopic incision with cold knife or electrosurgery, an alternative is to ablate the obstructive tissue with laser energy. With increasing prenatal diagnoses, there has been an increasing shift in the timing of intervention toward earlier periods. The literature contains only two reports of laser ablation in neonates for these disease entities. Materials and Methods: A case series was conducted by retrospectively reviewing our surgical database for all consecutive infants <28 days old (i.e., neonates) diagnosed in utero with obstructive uropathy and with postnatal imaging consistent with either urethral valves (anterior or posterior) or ureterocele. Holmium: yttrium aluminum-garnet (Ho:YAG) laser ablation was used as the exclusive modality of endoscopic management during the study period. All patients were followed with voiding cystourethrogram and renal/bladder ultrasounds postoperatively. Results: Seventeen neonates underwent retrograde transurethral laser ablation procedures at a median age of 7 days (range 3-27). There were nine cases of urethral valve ablation (seven posterior, two anterior) and eight ureterocele ablations. Median operative time was 23 minutes (range 18-33). There were no intraoperative complications or reoperative procedures required for any case. All patients voided after postoperative catheter removal, and no patient had evidence of residual valve tissue or urethral stricture at mean follow-up of 10.1 months. All patients with ureterocele demonstrated partial or complete decompression of the ureterocele and improvement in hydroureteronephrosis at 3 months. Conclusions: Ho:YAG laser ablation appears safe, effective, and efficient for the management of urethral valves and ureteroceles in the neonatal period. With a continuing trend toward early definitive intervention for these conditions, laser ablation remains an important alternative to electrosurgery in this population. PMID:25046584

Pagano, Matthew J; van Batavia, Jason P; Casale, Pasquale

2014-09-01

155

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

SciTech Connect

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

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

2006-12-04

156

Plasma mediated ablation of biological tissues with ultrashort laser pulses  

SciTech Connect

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

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

1995-03-08

157

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

158

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

159

Green synthesis of selenium nanoparticles by excimer pulsed laser ablation in water  

NASA Astrophysics Data System (ADS)

Pure selenium nanoparticles were successfully synthesized by Liquid Phase - Pulsed Laser Ablation (LP-PLA) in de-ionized water. Excimer laser (248 nm) operating at low fluence (F ˜ 1 J/cm2) was used to generate colloidal solutions of selenium nanoparticles. The obtained selenium nanoparticles were characterized by UV-visible spectroscopy, Raman spectroscopy, Dynamic Light Scattering, and Transmission Electron Microscopy. We describe the multi-modal size distributions generated and use the centrifugation method to isolate the smallest nanoparticles (˜60 nm in diameter).

Van Overschelde, O.; Guisbiers, G.; Snyders, R.

2013-10-01

160

EXCIMER LASER ABLATION OF GLASS FIBER IN REINFORCED POLYMER  

Microsoft Academic Search

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

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

2002-01-01

161

Femtosecond laser near-field ablation from gold nanoparticles  

NASA Astrophysics Data System (ADS)

Short-pulse laser ablation is promising owing to the low threshold for material removal from surfaces. In the laser-ablation process, solid material transforms into a volatile phase initiated by a rapid deposition of energy. Explosive boiling can be one of the mechanisms in which matter is heated close to the critical point. Other pathways of non-thermal excitation will be present for very short laser pulses. Here we observe a different channel of ablation from gold nanoparticles, which takes place below the particle melting point. This process is induced by the optical near-field, a subwavelength field enhancement close to curved surfaces, in particular. Using picosecond X-ray scattering, we can track the temporal and energetic structural dynamics during material ejection from the nanoparticles. This effect will limit any high-power laser manipulation of nanostructured surfaces, such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses.

Plech, Anton; Kotaidis, Vassilios; Lorenc, Maciej; Boneberg, Johannes

2006-01-01

162

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

163

Endovenous laser ablation with TM-fiber laser  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

164

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

165

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

E-print Network

like thermal ablation [2], electrostatic ablation [3], Coulomb explosion [4], phase explosion [5], etcAnalyses 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

Paris-Sud XI, Université de

166

Laser fiber migration into the pelvic cavity: A rare complication of endovenous laser ablation.  

PubMed

Endovenous laser ablation is an established alternative to surgery with stripping for the treatment of varicose veins. Ecchymoses and pain are frequently reported side effects of endovenous laser ablation. Device-related complications are rare but serious. We describe here an exceptional complication, necessitating an additional surgical procedure to remove a segment of laser fiber that had migrated into the pelvic cavity. Fortunately, severe damage had not occurred. This case highlights the importance of checking the completeness of the guidewire, catheter, and laser fiber after endovenous laser ablation. PMID:24965101

Lun, Yu; Shen, Shikai; Wu, Xiaoyu; Jiang, Han; Xin, Shijie; Zhang, Jian

2014-06-25

167

Erbium: YAG laser trabecular ablation with a sapphire optical fiber.  

PubMed

The purpose of the study was to evaluate the effect of erbium (Er): yttrium aluminum garnet (YAG) laser trabecular ablation with a sapphire optical fiber on outflow facility. After obtaining baseline outflow facility using a computerized differential pressure perfusion system, human cadaver eyes were subjected to Er: YAG laser trabecular ablation using a sapphire optical fiber. Single pulses at varying energy levels (10 to 20 mJ pulse-1) were applied in a nearly contiguous fashion over four clock hours of meshwork. Post-laser outflow facility was then determined utilizing the same perfusion system and histopathologic analysis performed. Of the ten eyes, nine were perfused to steady baseline facility. One eye was excluded from the study because of a leak in our system during the initial perfusion. The mean baseline facility was 0.283+/-0.08 microl min-1 mmHg-1. There was a significant increase in outflow facility after trabecular ablation, with a mean post-laser facility of 0.62+/-0.15 microl min-1 mmHg-1 (P=0.01). Eyes which received a sham treatment showed no increase or a minimal increase in facility. Histopathologic analysis revealed ablation into Schlemm's canal with some thermal damage to the outer wall at all energy levels. Er: YAG laser trabecular ablation with a sapphire fiber is capable of increasing outflow facility in human cadaver eyes. PMID:9268583

McHam, M L; Eisenberg, D L; Schuman, J S; Wang, N

1997-08-01

168

Lasers in Surgery and Medicine 44:805814 (2012) Femtosecond Plasma Mediated Laser Ablation Has  

E-print Network

-mediated ablation; thermal osteonecrosis INTRODUCTION Craniofacial defects due to congenital anomalies, trau- maLasers in Surgery and Medicine 44:805­814 (2012) Femtosecond Plasma Mediated Laser Ablation Has, collateral thermal, and mechanical trauma to adjacent bone tissue causes cell death and may delay healing

Palanker, Daniel

169

Ni nanoparticles fabricated by laser ablation in water  

NASA Astrophysics Data System (ADS)

Nickel nanoparticles were fabricated by ablating a bulk Ni target with pulsed 337-nm laser radiation in distilled water. Transmission electron microscope images of the removed material show spherical particles with two size scales: tens of nm and hundreds of nm. Phase explosion and Rayleigh-Plateau hydrodynamic instability are suggested as being responsible for this distribution. An X-ray diffraction pattern of the ablated material demonstrates the presence of both nickel and nickel oxide.

Musaev, O. R.; Yan, J.; Dusevich, V.; Wrobel, J. M.; Kruger, M. B.

2014-08-01

170

Tracer spectroscopy diagnostics of doped ablators in inertial confinement fusion experiments on OMEGA  

NASA Astrophysics Data System (ADS)

A technique has been developed for studying the time-dependent, local physical conditions in ablator samples in an inertial confinement fusion (ICF) hohlraum environment. This technique involves backlit point-projection absorption spectroscopy of thin tracer layers buried in the interior of solid samples mounted on laser-driven hohlraums. It is shown how detailed view-factor, atomic, hydrodynamics, and radiation-transport modeling can be used to infer time-dependent physical conditions in the interiors of these samples from the observed absorption spectra. This modeling is applied to the results of an experimental campaign on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] designed to compare radiation-wave velocities in doped and undoped ICF ablator materials.

Cohen, David H.; MacFarlane, Joseph J.; Jaanimagi, Paul; Landen, Otto L.; Haynes, Donald A.; Conners, David S.; Penrose, Katherine L.; Shupe, Nathan C.

2004-05-01

171

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

172

Nanometer thickness laser ablation for spatial control of cell attachment  

NASA Astrophysics Data System (ADS)

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

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

2002-10-01

173

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

174

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

175

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

176

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

177

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

178

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

179

Sensitization of PMMA to laser ablation at 308 nm  

NASA Astrophysics Data System (ADS)

Pure polymethylmethacrylate (PMMA) is highly resistant to ablation at 308 nm. The value of PMMA in lithography and semiconductor packaging and the availability of reliable 308 nm optics has motivated the development of dopants to facilitate PMMA ablation at 308 nm. We investigate the laser ablation of solvent cast PMMA films with and without pyrene, a typical dopant. The presence of residual solvent is shown to strongly promote laser ablation at low fluences in the case of chlorobenzene (CB), but not in the case of N-methyl 2-pyrrolidinone (NMP). At low laser fluences, many laser pulses may be required before significant neutral particle emissions are observed - an incubation effect. Scanning electron microscope observations indicate that the onset of emission coincides with the rupture of a thin surface layer, presumably depleted of solvent during film manufacture. The depleted layer would be relatively impervious to volatile fragments produced in the bulk. When this layer ruptures, volatile fragments escape and can be detected. Thus, the ablation behavior depends not only on the choice of dopant, but on the choice of solvent and the details of film manufacture.

Webb, R. L.; Langford, S. C.; Dickinson, J. T.; Lippert, T. K.

1998-05-01

180

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

181

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

182

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

183

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

SciTech Connect

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 was deposited on mica substrates and analyzed by means of atomic force microscopy. As a result, the size-distribution and the overall number of nanoparticles were determined as a function of the laser energy density incident on the target surface. The detection of particles with sizes in the nanometer range supports theoretical modeling according to which phase explosion is the dominant mechanism of metal ablation by ultrashort laser pulses.

Spiga, P.; Hermann, J.; Itina, T.; Grojo, D. [LP3, UMR 6182 CNRS-Faculte des Sciences de Luminy, Case 917, F-13288 Marseille (France); Neamtu, D. [NILPRP- Laser Department, P.O. Box MG-36, R-76900 Bucharest (Romania); Pailharey, D.; Marine, W. [CRMCN, UPR CNRS 7251-Faculte des Sciences de Luminy, Case 901, F-13288 Marseille (France)

2005-10-31

184

Laser Ablation With High Resolution Inductively Coupled Plasma Mass Spectrometry  

NASA Astrophysics Data System (ADS)

The advent of UV wavelength solid-state lasers and high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) has made possible significant advances in geochemical microanalysis. UV Solid- state lasers (266 nm, 213 nm, and 193 nm) create significantly smaller elemental fractionation than IR lasers. Magnetic sector ICP-MS instruments combine higher sensitivity and lower backgrounds at high mass elements than quadrupole ICP-MS instruments, and exhibit more uniform ionization of solid elements than possible by Secondary Ion Mass Spectrometry (SIMS). Further, high mass resolution enables the more sensitive analysis of elements that have significant isobaric interferences, e.g. Cr, Fe, etc. Calibration of LA-ICP-MS requires knowledge of the instrumental response using relative sensitivity factors (RSFs). New research shows that RSFs are not matrix-sensitive for a large range of elements with First Ionization Potential (FIP) less than 8 ev, provided an internal standard is used. Calibration of laser ablation for such elements is then possible using RSFs obtained from solution nebulization. A matrix-dependent ionization occurs for elements with high FIP that depends on the sample loading of the plasma. In comparison with SIMS, laser ablation provides better analysis of elements with high FIP, more rapid analysis, rapid sample change (no vacuum system), easier sample preparation, and a laser ablation system is at least three times cheaper than a comparable SIMS system. The coupling of laser ablation and multi-collector ICP-MS allows isotopic analysis of a wide range of elements, but the ICP source does not permit the analysis of stable isotopes of H, C, N, and O. A few applications of laser ablation microanalysis will be described, including the analysis of siderophile elements and analysis of major and trace elements in tiny particles.

Humayun, M.

2008-05-01

185

An effective focusing setting in femtosecond laser multiple pulse ablation  

NASA Astrophysics Data System (ADS)

Most of reported works on laser micro-machining have been carried out under ‘tight-focusing’ arrangement. However, defocusing has to be considered when dealing with depth evolution in multiple pulse ablation. In this paper, we show that laser intensity distribution is very sensitive to defocusing and, in multiple pulse ablation, defocusing is unavoidable even under the ‘tight focusing’. Both theoretic analysis and experimental result indicate that convergent defocusing is a better option for some micro-machining purposes. The optimal defocusing arrangement not only results in a maximum material removal rate (MRR) and maximum depth evolution, but also prevents harmful heat damage caused by extreme high intensity at the focal center.

Chang, Gang; Tu, Yiliu

2013-12-01

186

Accumulated IR-laser ablation of endothel at the inner wall of Schlemm's canal  

NASA Astrophysics Data System (ADS)

The typical approach for tissue ablation in laser microsurgery is to use a fiber tip in the contact-mode. An example is the laser trabecular ablation ab interno. The purpose of this paper is to describe the trabecular meshwork ablation with an Er:YAG laser in the none contact mode from inside Schlemm's canal using cavitations bubbles.

Specht, Holger; Voelcker, Hans E.; Burk, Reinhard O. W.

2001-06-01

187

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 to the ablation of glass with nanosecond ultraviolet laser pulses. © 2004 American Institute of Physics. [DOI: 10

Byer, Robert L.

188

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

E-print Network

) laser ablation provides high quality and repeatable structures due to its non-thermal nature; henceNanoscale 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

Simsek, Ergun

189

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

E-print Network

corresponded to thermal tissue damage during laser ablation. Conclusions. The ability of high-resolution highHigh-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

Boppart, Stephen

190

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

191

Thermal melting and ablation of silicon by femtosecond laser radiation  

NASA Astrophysics Data System (ADS)

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.; Seleznev, L. V.; Sinitsyn, D. V.; Bunkin, A. F.; Lednev, V. N.; Pershin, S. M.

2013-03-01

192

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

193

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

194

RESONANCE LASER ABLATION WITH AN OPTICAL PARAMETRIC OSCILLATOR LASER AND DETECTION BY A  

E-print Network

of solid samples was used for the determination of trace metals by use of either a pulsed excimer laser (20 ns, 308 nm) or a pulsed (6 ns) tunable optical parametric oscillator laser. The ablated trace metals Parametric Oscillator Laser Optical Parametric Oscillator-based laser systems1 have a tunable range

Michel, Robert G.

195

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

196

Laser trabecular ablation of human eyes with the erbium:YAG laser: a histopathologic study  

NASA Astrophysics Data System (ADS)

We postulated that ablation of trabecular meshwork can be accomplished without damage to Schlemm's canal and adjacent tissue. We performed Erbium:YAG laser trabecular ablation on human autopsy eyes and confirmed the results by histopathologic examination. We used an Erbium:YAG laser (2.94 micrometers ) equipped with a sapphire probe and a quartz tip (350 micrometers diameter). Energy levels of 5, 10, 15, 20, and 40 mJ per pulse were used. The probe was placed directly onto the trabecular meshwork viewed through an operating microscope and focal ablation was performed with single pulses. The tissue was then processed and examined under light and scanning microscopy. The histopathologic study of the trabecular meshwork revealed that a single pulse at an energy level of 15 mJ was optimal for ablating through the trabecular meshwork to Schlemm's canal with a minimal amount of coagulative damage to the surrounding tissue. The mean width of ablated tissue was 150 micrometers +/- 29 micrometers (n equals 18) and the mean depth of ablation was 133 +/- 48 micrometers (n equals 18) at this energy level. The mean width of coagulative damage to adjacent tissue was 16 +/- 8 micrometers (n equals 18). The ablation and coagulative damage increased with increasing energy levels. The Erbium:YAG laser equipped with a contact probe effectively ablates trabecular meshwork with little surrounding coagulative damage. This feature may minimize scarring and result in a high long-term patency rate of outflow channels created by laser trabecular ablation.

Kramer, Theresa R.; Noecker, Robert J.; Snyder, Robert W.; Ellsworth, Lansing G.; Yarborough, J. Michael

1994-06-01

197

Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors  

SciTech Connect

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

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

2010-10-08

198

Optical properties of Germanium nanoparticles synthesized by pulsed laser ablation in acetone  

NASA Astrophysics Data System (ADS)

Germanium (Ge) nanoparticles (NPs) are synthesized by means of pulsed laser ablation of bulk germanium target immersed in acetone with ns laser pulses at different pulse energies. The fabricated NPs are characterized by employing different techniques such as UV-visible absorption spectroscopy, photoluminescence, micro-Raman spectroscopy, transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The mean size of the Ge NPs is found to vary from few nm to 40 nm with the increase in laser pulse energy. Shift in the position of the absorption spectra is observed and also the photoluminescence peak shift is observed due to quantum confinement effects. High resolution TEM combined with micro-Raman spectroscopy confirms the crystalline nature of the generated germanium nanoparticles. The formation of various sizes of germanium NPs at different laser pulse energies is evident from the asymmetry in the Raman spectra and the shift in its peak position towards the lower wavenumber side. The FESEM micrographs confirm the formation of germanium micro/nanostructures at the laser ablated position of the bulk germanium. In particular, the measured NP sizes from the micro-Raman phonon quantum confinement model are found in good agreement with TEM measurements of Ge NPs.

Vadavalli, Saikiran; Valligatla, Sreeramulu; Neelamraju, Bharati; Dar, Mudasir; Chiasera, Alessandro; Ferrari, Maurizio; Desai, Narayana

2014-10-01

199

Temperature dependent ablation threshold in silicon using ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

We have experimentally investigated the ablation threshold in silicon as a function of temperature when applying ultrashort laser pulses at three wavelengths. By varying the temperature of a silicon substrate from room temperature to 320 °C, we observe that the ablation threshold for a 3 ps pulse using a wavelength of 1030 nm drops from 0.43 J/cm2 to 0.24 J/cm2, a reduction of 43%. For a wavelength of 515 nm, the ablation threshold drops from 0.22 J/cm2 to 0.15 J/cm2, a reduction of 35%. The observed ablation threshold for pulses at 343 nm remains constant with temperature, at 0.10 J/cm2. These results indicate that substrate heating is a useful technique for lowering the ablation threshold in industrial silicon processing using ultrashort laser pulses in the IR or visible wavelength range. In order to investigate and explain the observed trends, we apply the two-temperature model, a thermodynamic model for investigation of the interaction between silicon and ultrashort laser pulses. Applying the two-temperature model implies thermal equilibrium between optical and acoustic phonons. On the time scales encountered herein, this need not be the case. However, as discussed in the article, the two-temperature model provides valuable insight into the physical processes governing the interaction between the laser light and the silicon. The simulations indicate that ablation occurs when the number density of excited electrons reaches the critical electron density, while the lattice remains well below vaporization temperature. The simulated laser fluence required to reach critical electron density is also found to be temperature dependent. The dominant contributor to increased electron density is, in the majority of the investigated cases, the linear absorption coefficient. Two-photon absorption and impact ionization also generate carriers, but to a lesser extent. As the linear absorption coefficient is temperature dependent, we find that the simulated reduction in ablation threshold with increased substrate temperature is linked to the temperature dependence of the linear absorption coefficient. Another factor influencing the ablation threshold is the wavelength dependence of the interaction with the excited electron plasma. This wavelength dependence can explain that we observe experimentally similar ablation thresholds for a wavelength of 1030 nm at 320 °C and for 515 nm at room temperature, even though the linear absorption coefficient in the latter case is much higher.

Thorstensen, Jostein; Erik Foss, Sean

2012-11-01

200

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

201

Stable kilohertz rate molecular beam laser ablation sources  

NASA Astrophysics Data System (ADS)

We describe a stable kHz rate laser ablation/desorption supersonic molecular beam source for use in kHz rate laser experiments. With the development of modern lasers that typically operate at kHz rates, a need has arisen for stable molecular beam laser ablation/desorption sources for the study of involatile species. Many biomolecules of interest cannot be brought into the gas phase without thermal decomposition by simply heating the substrate and most (especially refractory) metals have melting and boiling points that are impossible to reach with conventional ovens. The source is based upon strong nonresonant interaction of a dithering laser focus with a rotating and translating solid rod, hydrodynamic transport of the ablated/desorbed material in helium or argon, and subsequent supersonic expansion. Further design details include flexible and easy adjustment of the source for rapid prototyping and optimization for kHz rate performance. Due to the high rate of sample removal, a major concern is clogging of the nozzle and laser input channel due to both material condensation and debris formation. In order to illustrate the range of applications, we demonstrate (1) the kHz laser ablation of a high temperature refractory metal (niobium) for use in studies of metal clusters; and (2) the kHz laser desorption and jet cooling of an involatile biomolecule (the DNA base guanine) for use in spectroscopic and dynamical studies. This kHz source design has been shown to be stable for over 12 continuous hours of operation (>4×107 laser shots) and can be readily scaled to even higher repetition rates (>10 kHz).

Smits, Marc; de Lange, C. A.; Ullrich, Susanne; Schultz, T.; Schmitt, M.; Underwood, Jonathan G.; Shaffer, James P.; Rayner, D. M.; Stolow, Albert

2003-11-01

202

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

Microsoft Academic Search

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation

Roci´o Ortiz; Iban Quintana; Jon Etxarri; Ainhoa Lejardi; Jose-Ramon Sarasua

2011-01-01

203

Effect of geometry measurements on characteristics of femtosecond laser ablation of HR4 nickel alloy  

NASA Astrophysics Data System (ADS)

This paper presents an investigation on ablation characteristics of HR4 nickel cast alloy with a Ti:Sapphire femtosecond laser (100 fs pulse width, 800 nm wavelength and 1 kHz repetition rate). The ablation characteristics including laser material interaction parameters, i.e. ablation threshold, optical penetration depth and incubation factor are estimated based on ablated geometries from two ablation methods, i.e. spot ablation and line ablation. The work shows that the single pulse ablation threshold is dependent on the laser fluence and the number of pulses (NOP). The ablation threshold decreases with the NOP, where it reaches an asymptotical value due to incubation effect. By varying the laser fluence, two ablation regimes are identified which are the low fluence ablation regime and the high fluence ablation regime. The former is governed by optical penetration depth; and the latter is governed by the energy penetration depth. It is also observed that the laser material interaction parameters obtained based on ablation diameters through the line ablation agree with the values obtained through the spot ablation but not with those obtained based on ablated depth through the line ablation. It is found that the evaluation of the laser material interaction parameters based on ablated diameters is more reliable compared to those based on ablated depth. The ablation threshold (low fluence ablation region) for the HR4 nickel alloy is estimated to be Fth1=0.39 J/cm with the incubation factor, ?=0.8 and optical penetration depth of 47.3 nm.

See, T. L.; Liu, Z.; Liu, H.; Li, L.; Chippendale, J.; Cheetham, S.; Dilworth, S.

2015-01-01

204

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

205

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

PubMed

Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable adhesive bonds. Surface preparation by laser ablation provides an alternative to the expensive, hazardous, polluting, and less precise practices used currently such as chemical-dip, manual abrasion and grit blast. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Surface roughness and surface chemical composition were characterized using interference microscopy and X-ray photoelectron spectroscopy, respectively. A technique for fluorescence visualization was developed which allowed for quantitative failure mode analysis. Wedge crack extension testing in a hot, humid environment indicated the relative effectiveness of various surface treatments. Increasing ablation duty cycle reduced crack propagation and adhesive failure. Single lap shear testing showed an increase in strength and durability as laser ablation duty cycle and power were increased. Chemical analyses showed trends for surface chemical species, which correlated with improved bond strength and durability. PMID:23317556

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

2013-02-01

206

Production of nanoparticles from natural hydroxylapatite by laser ablation.  

PubMed

Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism. PMID:21711800

Boutinguiza, Mohamed; Comesaña, Rafael; Lusquiños, Fernando; Riveiro, Antonio; Pou, Juan

2011-01-01

207

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

208

Mechanisms of decomposition of metal during femtosecond laser ablation  

SciTech Connect

The mechanisms of decomposition of a metal (nickel) during femtosecond laser ablation are studied using molecular dynamics simulations. It is found that phase explosion is responsible for gas bubble generation and the subsequent material removal at lower laser fluences. The phase explosion process occurs as combined results of heating, thermal expansion, and the propagation of tensile stress wave induced by the laser pulse. When the laser fluence is higher, it is revealed that critical point phase separation plays an important role in material removal.

Cheng Changrui; Xu Xianfan [School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2005-10-15

209

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

210

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

211

Laser ablation assisted adhesive bonding of automotive structural composites  

SciTech Connect

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

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

1999-07-03

212

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 for aluminium and a complex metallic alloy. Here we will concentrate on how drops or clusters and voids can part includes the formation of voids in the irradiated region and its temporal evolution. 2 Method

Roth, Johannes

213

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 in the management of patients with low grade and localized prostate tumours could represent a treatment option). Light was transmitted using a cylindrical diffusing fiber inserted inside a preclinical animal prostate

Paris-Sud XI, Université de

214

Optical limiting properties of silver nanoparticles fabricated by laser ablation  

NASA Astrophysics Data System (ADS)

Silver nanoparticles have been fabricated by laser ablation of a silver metal foil in solution. The presence of sodium bis(2-ethylhexyl) sulfosuccinate increases the yield of the nanoparticles and enhances their stability. The optical limiting performance of the silver nanoparticles embedded in a PMMA film is compared to that in an aqueous solution.

Ong, T. S.; Lee, S. S.; Van, L. H.; Hong, Ming Hui; Chong, Tow Chong

2004-10-01

215

Laser Ablation ICPMS Laboratory Department of Geosciences Virginia Tech  

E-print Network

Laser Ablation ICPMS Laboratory Department of Geosciences ­ Virginia Tech Facility Rates (Approved for Virginia Tech Faculty, Staff and Students properly trained. We are not allowed to offer those rates to people not affiliated with Virginia Tech; 2) Internal rates are available only for Virginia Tech users; 3

Bodnar, Robert J.

216

Phase explosion and its time lag in nanosecond laser ablation  

NASA Astrophysics Data System (ADS)

This work investigates interface kinetics during nanosecond pulsed excimer ablation of a metal. During laser heating, the surface can reach a temperature higher than the normal boiling point, resulting in a superheated,metastable state. Phase explosion occurs as the temperature approaches the thermodynamic critical point, which turns the melt into a mixture of liquid and vapor. However, for phase explosion, there is a certain time needed for a vapor embryo to grow to a critical nucleus, called the time lag of nucleation. This time lag becomes important in ablation induced by nanosecond or shorter pulsed lasers. This paper discusses experiments for investigating non-equilibrium phase change phenomena during nanosecond excimer laser ablation of a metal. Evidences of the metastable state in liquid and phase explosion are presented. The surface temperature-pressure relation is found to deviate from the commonly used equilibrium Clausius-Clapeyron equation. Also, for the first time, the time lag of nucleation during nanosecond laser ablation is found to be around 5 ns.

Xu, Xianfan

2002-09-01

217

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

NASA Astrophysics Data System (ADS)

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

Loktionov, E. Yu.

2014-05-01

218

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

219

Selective material ablation by the TEA CO2 laser  

Microsoft Academic Search

This paper reports two topics in the material processing using TEA CO2 lasers. We demonstrated selective ablation of hydrogenated amorphous silicon (a-Si:H) thin layer on a quartz substrate by the second harmonic (SH) radiation of TEA CO2 laser generated by AgGaSe2 nonlinear crystal. Si-H bonds contained in a-Si:H strongly absorb the 5 micrometers SH radiation and resulted in the selective

Tetsumi Sumiyoshi; Akira Shiratori; Yutaka Ninomiya; Minoru Obara

1995-01-01

220

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

Microsoft Academic Search

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

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

1997-01-01

221

Femtosecond pulsed laser ablation of thin gold film  

NASA Astrophysics Data System (ADS)

Laser micromachining on 1000 nm-thick gold film using femtosecond laser has been studied. The laser pulses that are used for this study are 400 nm in central wavelength, 150 fs in pulse duration, and the repetition rate is 1 kHz. Plano-concave lens with a focal length of 19 mm focuses the laser beam into a spot of 3 ?m (1/ e2 diameter). The sample was translated at a linear speed of 400 ?m/ s during machining. Grooves were cut on gold thin film with laser pulses of various energies. The ablation depths were measured and plotted. There are two ablation regimes. In the first regime, the cutting is very shallow and the edges are free of molten material. While in the second regime, molten material appears and the cutting edges are contaminated. The results suggest that clean and precise microstructuring can be achieved with femtosecond pulsed laser by controlling the pulse energy in the first ablation regime.

Venkatakrishnan, K.; Tan, B.; Ngoi, B. K. A.

2002-04-01

222

Laser spectroscopy of desorbing molecules  

Microsoft Academic Search

In this article the application of tunable dye lasers to desorption phenomena is illuminated. These lasers provide radiation continuously tunable from 105 nm in the vacuum ultraviolet to about 10 µm in the mid-IR. By employing either laser induced fluorescence (LIF) or resonance enhanced multiphoton ionization (REMPI) spectroscopy almost all diatomic and many polyatomic molecules can be probed with the

H. Zacharias

1988-01-01

223

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

SciTech Connect

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

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

2004-08-30

224

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

225

Measuring by laser Doppler vibrometry the recoil momentum of biological tissue under infrared laser ablation  

NASA Astrophysics Data System (ADS)

The recoil momentum of hard tissue induced by pulsed IR laser exposure was measured in a pendulum experiment using laser Doppler vibrometry. For the experiments bone was irradiated by holmium:YAG laser radiation and dentin by a superpulsed CO2 laser. Since the initial masses of the samples were known and the ablated masses were measured, this method allowed also an indirect determination of the velocity of the ablated particles. In a second experiment performed with the CO2 laser the velocities of the ablated particles were measured directly by the time of flight detected by the laser beam of the vibrometer. The technical realization as well as the limitations of the method is discussed; furthermore laser parameters are pointed out which induce critical acceleration risking serious damage to sensitive organs.

Barton, Thomas G.; Foth, Hans-Jochen; Meyer, Dirk H.; Postel, Adriaen

1998-06-01

226

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

227

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

228

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

229

Discharge-aided reactive laser ablation for ultrafine powder production  

NASA Astrophysics Data System (ADS)

Ultrafine alumina powder was produced by aluminum target ablation with a Nd:YAG laser beam (1064 nm wavelength; 340 mJ/pulse energy; 7 ns pulse duration; 10 pps repetition rate), in a 120 Torr O2 atmosphere. A theoretical approach for the ablation process, based on laser energy absorption and energy balance in the target, is used for comparison with the experimental production rate. Three experimental irradiation conditions were chosen: (1) energy density of 5 J/cm2, considered reference (RDE), (2) lower energy density of 2.5 J/cm2 (LDE) and (3) RDE with auxiliary discharge between an auxiliary electrode and target, triggered by the ablation plume (RDA). Calculated and experimental data of target weight loss show good agreement (135 ng/pulse, calculated, and 100, 110, 120 ng/pulse, experimentally, for RDE, LDE, RDA conditions, respectively). The X-Ray Diffraction spectra of alumina show formation of (gamma) -alumina particles only, especially in LDE and RDA conditions. From Scanning Electron Microscopy size analysis, a decrease of particle size, in LDE and RDA irradiating conditions, is observed. The decrease of laser beam fluence or aiding of ablation using an auxiliary discharge is both favorable for the production of high quality powder, without diminishing the production rate. This can be a good basis for future improvement of the ultrafine powder production process.

Chis, Ioan; Marcu, Aurelian; Yukawa, T.; Dragulinescu, Dumitru; Grigoriu, Constantin; Miu, Dana; Jiang, Weihua; Yatsui, Kiyoshi

1998-07-01

230

Laser Spectroscopy and Frequency Combs  

NASA Astrophysics Data System (ADS)

The spectrum of a frequency comb, commonly generated by a mode-locked femtosecond laser consists of several hundred thousand precisely evenly spaced spectral lines. Such laser frequency combs have revolutionized the art measuring the frequency of light, and they provide the long-missing clockwork for optical atomic clocks. The invention of the frequency comb technique has been motivated by precision laser spectroscopy of the simple hydrogen atom. The availability of commercial instruments is facilitating the evolution of new applications far beyond the original purpose. Laser combs are becoming powerful instruments for broadband molecular spectroscopy by dramatically improving the resolution and recording speed of Fourier spectrometers and by creating new opportunities for highly multiplexed nonlinear spectroscopy, such as two-photon spectroscopy or coherent Raman spectroscopy. Other emerging applications of frequency combs range from fundamental research in astronomy, chemistry, or attosecond science to telecommunications and satellite navigation.

Hänsch, Theodor W.; Picqué, Nathalie

2013-12-01

231

Signal enhancement of lead and arsenic in soil using laser ablation combined with fast electric discharge  

NASA Astrophysics Data System (ADS)

In comparison to the traditional single pulse laser induced breakdown spectroscopy (SP-LIBS), a significant enhancement of atomic emission of lead and arsenic from laser plasma of soil has been demonstrated by the use of a laser ablation and fast pulse discharge plasma spectroscopy technique (LA-FPDPS). In this technique, a specifically designed high voltage and rapid discharge circuit was used to reheat the laser plasma and to enhance the plasma emission. A rapid and time damped alternating discharge current was observed with a short oscillating period ˜ 0.6 ?s and sustained for about 6 ?s. The peak intensities of Pb (283.31 nm) and As (286.04 nm) lines from soil plasma emission were greatly enhanced when compare to the traditional single pulse (SP) LIBS system. In addition, the precision of measurements in terms of the relative standard deviation (RSD) and the signal to noise ( S/ N) ratios were also improved. Scanning electron microscopy (SEM) images of the laser ablation regions indicated that the plasma reheating by the discharge spark was presumably the main mechanism for observed signal enhancement in the LA-FPDPS technique.

Kexue, L. I.; Zhou, Weidong; Shen, Qinmei; Shao, Jie; Qian, Huiguo

2010-05-01

232

Effects of rf magnetron plasma on the particle size distribution in laser ablation deposition  

Microsoft Academic Search

The effect of the externally introduced rf magnetron plasma on the particle size distribution on films deposited by pulsed laser ablation is investigated. A cw low energy magnetron rf plasma is sustained between the target and the substrate during the laser ablation deposition process. The ablated droplets can be negatively charged and filtered by the plasma. For Si and Al

Tien-I. Bao; S. H. Tsai; I. Lin

1995-01-01

233

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

E-print Network

be explained by a thermal ablation model, which describes material removal as hydrodynamic expansionFemtosecond laser-induced ablation of graphite K. Sokolowski-Tinten1 , S. Kudryashov1 , V. Temnov1-laser ablation of graphite has been investigated experimentally and theoretically. The experimental observation

von der Linde, D.

234

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

E-print Network

and advocated by Miotello and Kelly 8 as being the prime phase transition in laser ablation in the thermal would expect that, in the thermal ablation regime, the essence of the phenomenon is similarLimit of overheating and the threshold behavior in laser ablation Barbara J. Garrison Department

Zhigilei, Leonid V.

235

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

236

Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments  

SciTech Connect

This paper describes a setup for thrust measurement in ablative laser propulsion experiments, based on a simple ballistic pendulum associated to an imaging system, which is being assembled at IEAv. A light aluminium pendulum holding samples is placed inside a 100 liters vacuum chamber with two optical windows: the first (in ZnSe) for the laser beam and the second (in fused quartz) for the pendulum visualization. A TEA-CO{sub 2} laser beam is focused to the samples providing ablation and transferring linear moment to the pendulum as a whole. A CCD video camera captures the oscillatory movement of the pendulum and the its trajectory is obtained by image processing. By fitting the trajectory of the pendulum to a dumped sinusoidal curve is possible to obtain the amplitude of the movement which is directly related to the momentum transfered to the sample.

Brazolin, H. [Instituto Tecnologico de Aeronautica 12.228-900-Sao Jose dos Campos (Brazil); Rodrigues, N. A. S.; Minucci, M. A. S. [Instituto de Estudos Avancados 12.228-001-Sao Jose dos Campos (Brazil)

2008-04-28

237

A Proton Source via Laser Ablation of Hydrogenated Targets  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

238

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

239

Direct laser/materials interaction: Laser ablation of superconductor materials and laser welding  

SciTech Connect

This paper considers two applications of direct laser/materials interaction, laser ablation of superconductor materials and Nd-YAG laser welding. The laser ablation experiments with 355 nm, 10 ns pulses have demonstrated uniform, thin superconductor films. The film uniformity was improved significantly be rotating both the laser target and the film support, and by vertically dithering the laser focus. The film stoichiometry does vary with laser fluence, but it is within 10% of the target material at high fluence. Annealing of the thallium-containing films restores lost oxygen. For the welding application we have investigated the conditions that influence the melt depth. High speed photography has shown the plume to consist of a series of regenerated pulses that move in a direction normal to the surface. The time for plume initiation and the laser power threshold for plume formation are dependent on the substrate material. The plume temperatures depended on the welding atmosphere. Temperatures and melt depths are higher for the reactive gases, air, O/sub 2/, and Sf/sub 6/, than for the nonreactive gases, He, Ar, and N/sub 2/. 18 refs., 13 figs.

Cremers, D.A.; Dixon, R.D.; Estler, R.C.; Lewis, G.K.; Lyman, J.L.; Muenchausen, R.E.; Nogar, N.S.; Pitch, M.

1989-01-01

240

Next generation Er:YAG fractional ablative laser  

NASA Astrophysics Data System (ADS)

Pantec Biosolutions AG presents a portable fractional ablative laser system based on a miniaturized diode pumped Er:YAG laser. The system can operate at repetition rates up to 500 Hz and has an incorporated beam deflection unit. It is smaller, lighter and cost efficient compared to systems based on lamp pumped Er:YAG lasers and incorporates a skin layer detection to guarantee precise control of the microporation process. The pulse parameters enable a variety of applications in dermatology and in general medicine, as demonstrated by first results on transdermal drug delivery of FSH (follicle stimulating hormone).

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

2011-03-01

241

Protein structural failure in mid-IR laser ablation of cornea  

NASA Astrophysics Data System (ADS)

Researchers have previously observed that tissue ablation with a free electron laser tuned to wavelengths between 6-7 ?m is accompanied by remarkably little collateral damage. Attempts to explain these observations have invoked a wavelength-dependent loss of protein structural integrity; however, the molecular nature of this structural failure has been heretofore ill-defined. In this report, we evaluate several candidates for the relevant transition by analyzing the non-volatile debris ejected during ablation. Porcine corneas were ablated with a free electron laser tuned to either 2.77 or 6.45 ?m - wavelengths that are equally well absorbed by hydrated corneas, but that respectively target water or protein as the primary chromophore. The ejected debris was characterized via gel electrophoresis, as well as FTIR, micro-Raman and 13C-NMR spectroscopy. We find that high-fluence (240 J/cm2) ablation at 6.45 ?m, but not at 2.77 ?m, leads to protein fragmentation. This fragmentation is accompanied by the accumulation of nitrile and alkyne species. Although these initial experiments did not detect significant protein unfolding, the loss of collagen triple-helix structure was evident using UV and vibrational circular dichroism. The candidate transition most consistent with all these observations is scission of the collagen protein backbone at N-alkylamide bonds. Identifying this transition is a key step towards understanding the observed wavelength-dependence of collateral damage.

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

2006-05-01

242

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

243

Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation.  

PubMed

Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures. PMID:24292197

Malskat, W S J; Stokbroekx, M A L; van der Geld, C W M; Nijsten, T E C; van den Bos, R R

2014-03-01

244

Modeling of nanosecond laser ablation with vapor plasma formation  

SciTech Connect

A thermal model for nanosecond pulsed laser ablation is developed, where the heat conduction equation in the target and the gas dynamic equations in the vapor and ambient gas phase are coupled through the Knudsen layer (KL) relations for evaporation/recondensation at the target-vapor interface. The plasma formation and laser-plasma interactions are simulated in the model, which are found to have a significant effect on the laser-induced evaporation process. The shielding effect of the plasma reduces the laser energy reaching the target surface and therefore decreases the surface temperature, and the laser energy deposition in the plasma contributes to the increase of the vapor pressure above the KL. All of these will make the transition earlier from sonic evaporation stage to the subsonic evaporation and then to the recondensation stage, and therefore decrease the laser-induced evaporation depth. The simulation results are compared with experimental data for the plasma transmissivity, plasma front locations and velocities, laser ablation depth, and average plasma temperatures, and reasonably good agreements are obtained. This model is valid when the phase explosion does not occur, that is, when the target surface temperature does not reach or exceed the target material critical temperature.

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

2006-04-15

245

Laser backwriting process on glass via ablation of metal targets  

NASA Astrophysics Data System (ADS)

Ablation of metal targets onto pyrex glass substrates, using a Q-switched Nd:YAG laser working at 355 nm, was used to study the potential of a laser backwriting process for the fabrication of optical waveguides via an index of refraction change. Metal foils of stainless steel, aluminum, copper, brass and gold have been used as blanks and irradiated by focusing the laser beam through a cylindrical lens under continuous movement in a direction perpendicular to the irradiation. An horizontal setup was found suitable to improve the effect of the plume in the sample. Results were obtained for two different configurations. Transversal profiles were analysed using a contact profilometer, comparing results obtained for the different configurations, traverse speeds and metal targets used. Two ablation regimes were identified, which are related to a critical laser fluence value of 2.7 J/cm 2. Surface micrographs obtained by scanning electron microscopy are discussed, together with the characteristics of the structures attained, taking into account the optical and thermal properties of the ablated metal blanks.

Castelo, A.; Nieto, D.; Bao, C.; Flores-Arias, M. T.; Pérez, M. V.; Gómez-Reino, C.; López-Gascón, C.; de la Fuente, G. F.

2007-05-01

246

Fiber Laser Based Nonlinear Spectroscopy  

E-print Network

practical. A nonlinear spectroscopy tool based on a single fiber laser, with electrically controlled wavelength-tuning and spectral resolution enhanced by a pulse shaping technique, will efficiently produce optical excitation that allows quantitative...

Adany, Peter

2012-08-31

247

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

248

Silver Nanoparticle Fabrication by Laser Ablation in Polyvinyl Alcohol Solutions  

NASA Astrophysics Data System (ADS)

A laser ablation technique is applied for synthesis of silver nanoparticles in different concentrations of polyvinyl alcohol (PVA) aqueous solution. The ablation of high pure silver plate in the solution is carried out by a nanosecond Q-switched Nd:YAG pulsed laser. X-ray diffraction and transmission electron microscopy are implemented to explore the particles sizes. The effects of PVA concentrations on the absorbance of the silver nanoparticles are studied as well, by using a UV-vis spectrophotometer. The preparation process is carried out for deionized water as a reference sample. The comparison of the obtained results with the reference sample shows that the formation efficiency of nanoparticles in PVA is much higher and the sizes of particles are also smaller.

Halimah Mohamed., K.; Mahmoud Goodarz, Naseri; Amir, Reza Sadrolhosseini; Arash, Dehzangi; Ahmad, Kamalianfar; Elias, B. Saion; Reza, Zamiri; Hossein Abastabar, Ahangar; Burhanuddin, Y. Majlis

2014-07-01

249

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

250

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

251

Excimer laser ablation of plasma polymers for cell and tissue culture applications  

NASA Astrophysics Data System (ADS)

The two-dimensional control of cell adhesion is desired for a number of cell- and tissue culture applications. Thus, a suitable method for the two-dimensional control over surface chemistry, which leads to the display of cell-adhesive and non-adhesive signals is required. In our study, allylamine plasma polymer (ALAPP) deposition has been used to provide a cell-adhesive substrate, while additional grafting of poly(ethylene oxide) (PEO) on ALAPP surfaces has been used to prevent cell adhesion. Two-dimensional control over the surface chemistry was achieved using excimer laser ablation. Ablation experiments were carried out using a 248 nm excimer laser with energy densities of 17 - 1181 mJ/cm2 and 1 - 16 pulses per area. Results obtained by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) show controlled thickness ablation of the plasma polymer and the additional PEO graft polymer. Cell culture experiments using bovine corneal epithelial cells show that two-dimensional control of cell adhesion can be achieved by using appropriate masks in the laser beam.

Thissen, Helmut; Hayes, Jason P.; Hartley, Patrick G.; Johnson, Graham; Harvey, Erol C.; Griesser, Hans J.

2001-04-01

252

Laser ablation of a silicon target in chloroform: formation of multilayer graphite nanostructures  

NASA Astrophysics Data System (ADS)

With the use of high-resolution transmission electron microscopy, selected area electron diffraction and x-ray photoelectron spectroscopy methods of analysis we show that the laser ablation of a Si target in chloroform (CHCl3) by nanosecond UV pulses (40 ns, 355 nm) results in the formation of about 50-80 nm core-shell nanoparticles with a polycrystalline core composed of small (5-10 nm) Si and SiC mono-crystallites, the core being coated by several layers of carbon with the structure of graphite (the shell). In addition, free carbon multilayer nanostructures (carbon nano-onions) are also found in the suspension. On the basis of a comparison with similar laser ablation experiments implemented in carbon tetrachloride (CCl4), where only bare (uncoated) Si nanoparticles are produced, we suggest that a chemical (solvent decomposition giving rise to highly reactive CH-containing radicals) rather than a physical (solvent atomization followed by carbon nanostructure formation) mechanism is responsible for the formation of graphitic shells. The silicon carbonization process found for the case of laser ablation in chloroform may be promising for silicon surface protection and functionalization.

Abderrafi, Kamal; García-Calzada, Raúl; Sanchez-Royo, Juan F.; Chirvony, Vladimir S.; Agouram, Saïd; Abargues, Rafael; Ibáñez, Rafael; Martínez-Pastor, Juan P.

2013-04-01

253

Experimental and theoretical investigations of femtosecond laser ablation of aluminum in vacuum  

SciTech Connect

We used time-gated optical emission spectroscopy to investigate the characteristics of aluminum plumes and their vacuum expansion after femtosecond laser ablation at different fluences. The prominent feature is the presence of two main classes of species in the plume: very fast Al atoms and ions preceding the plume bulk essentially constituted of much slower Al nanoparticles expanding with a ten times smaller average velocity. Atomic force microscopy of deposited Al nanoparticles evidenced an average size of about 10 nm with a pretty narrow size distribution. These results and the peculiar feature of nanoparticle formation during femtosecond laser irradiation of matter were very satisfactorily interpreted and reproduced by molecular-dynamics simulation of the process. Finally, the analysis of the dependence on laser fluence of the ablation process showed an initial logarithmic increase of ablation yield, up to about 500 mJ/cm{sup 2}, followed by a sudden and very steep increase at higher fluences. According to our numerical calculations, this latter feature can be ascribed to the increase of the overheated material volume due to electron heat diffusion.

Amoruso, S.; Bruzzese, R.; Vitiello, M.; Nedialkov, N.N.; Atanasov, P.A. [Coherentia-Istituto Nazionale per la Fisica della Materia (INFM) and Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, I-80126 Naples (Italy); Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsaridradsko shose Boulevard, Sofia 1784 (Bulgaria)

2005-08-15

254

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

255

Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers  

SciTech Connect

Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.

Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J.; Herman, S.; Lane, S.M.; London, R.A.; Matthews, D.L.; Perry, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Chang, T.D. [Veterans Administration Hospital, Martinez, CA (United States); Neev, J. [Beckman Laser Inst. and Medical Clinic, Irvine, CA (United States)

1996-05-01

256

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

257

Modeling of laser ablation and fragmentation of human calculi  

SciTech Connect

The large-scale radiation-hydrodynamics computer code LASNEX, has been used to model experimental results in the laser ablation and fragmentation of renal and biliary calculi. Recent experiments have demonstrated laser ablation and fragmentation of human calculi in vitro and in vivo. In the interaction, laser light incident upon the calculus is of sufficient intensity to produce a plasma (a hot ionized gas). The physical picture which emerges is as follows. The plasma couples to acoustic and shear waves which then propagate through the dense stone material, causing spall and fracture by reflection from material discontinuities or boundaries. Experiments have thus far yielded data on the interaction against which models can be tested. Data on the following have been published: (1) light emission, (2) absorption and emission spectra, (3) fragmentation efficiency, (4) cavitation bubble dynamics and (5) mass removal. We have performed one dimensional simulations of the laser-matter interaction to elucidate the important physical mechanisms. We find that good quantitative fits between simulation and experiment are obtained for visible light emission, electron temperature, electron density, plasma pressure and cavitation bubble growth. With regard to mass removal, experiment and simulation are consistent with each other and give an excellent estimate of the ablation threshold. The modeling indicates that a very small ablation layer at the surface of the calculus is responsible for significant mass loss by fragmentation within the bulk of the calculus. With such quantitative fits in hand, we believe this type of modeling can now be applied to the study of other procedures involving plasma formation of interest to the medical community. 25 refs., 7 figs.

Gitomer, S.; Jones, R.D.; Howsare, C.

1989-01-01

258

Beam Delivery System For UV Laser Ablation Of The Cornea  

NASA Astrophysics Data System (ADS)

We describe an electro-optical apparatus capable of delivering a homogenized, intensity-contoured 193 nm wavelength laser beam to the anterior surface of the cornea. Beam fluence is adequate to produce controlled ablation over areas as large as 7 mm diameter. Preliminary experimental results demonstrating recontouring of the corneal surface as a means of correcting myopia are presented. Means to be used for reducing hyperopia and astigmatism also are described.

Yoder, P. R.; Telfair, W. B.; Warner, J. W.; Martin, C. A.; Bennett, P. S.

1988-06-01

259

Comparison of kinetic theory models of laser ablation of carbon  

SciTech Connect

The paper compares the predictions of three-dimensional kinetic theory models of laser ablation of carbon. All the models are based on the moment solution of the Boltzmann equation for arbitrary strong evaporation but use different approximations. Comparison of the model predictions demonstrated that the choice of the particular model has very little influence on the results. The influence of the heat conduction from the gas to the solid phase was also found to be negligible in this problem.

Shusser, Michael [Faculty of Mechanical Engineering, Technion, Haifa 32000 (Israel)

2010-05-15

260

High-throughput metal nanoparticle catalysis by pulsed laser ablation  

Microsoft Academic Search

A high-throughput pulsed laser ablation (HT-PLA) system was developed to rapidly prepare uniformly sized single- and multi-metallic nanoparticles with different diameters for catalytic applications. Catalytic materials containing Rh, bimetallic Rh\\/Pt and trimetallic Rh\\/Pt\\/Au nanoparticles were synthesized from targets prepared by blending, tableting and sintering powders of pure metals, and by directly collecting the nanoparticles created on support materials. Nanoparticles exhibited

Selim Senkan; Michael Kahn; Shici Duan; Anna Ly; Craig Leidholm

2006-01-01

261

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

262

Holmium laser ablation of cartilage: effects of cavitation bubbles  

NASA Astrophysics Data System (ADS)

The ablation of fresh harvested porcine femur patellar groove cartilage by a 2.12 micrometers Cr:Tm:Ho:YAG laser in clinically used irradiation conditions was studied. Laser pulses were delivered via a 600 micrometers diameter fiber in isotonic saline. Ablation was investigated as a function of the angle of incidence of the delivery fiber with respect to the cartilage surface (0-90 degrees) and of radiant exposure. Laser pulses with energies of 0.5, 1.0 and 1.5 J and a duration of 250 microseconds were used. A constant fiber tip-tissue distance of 1 mm was maintained for all experiments. The dynamics of the induced vapor bubble and of the ablation process was monitored by time resolved flash videography with a 1 microseconds illumination. Acoustic transients were measured with a piezoelectric PVDF needle probe hydrophone. Bubble attachment to the cartilage surface during the collapse phase, leading to the direct exposition of the cartilage surface to the maximal pressure generated, was observed in all investigated irradiation conditions. Maximal pressure transients of up to 200 bars (at 1 mm distance from the collapse center) were measured at the bubble collapse at irradiation angles >= 60 degrees. No significant pressure variation was observed in perpendicular irradiation conditions as a function of radiant exposure. A significant reduction of the induced pressure for irradiation angles

Asshauer, Thomas; Jansen, Thomas; Oberthur, Thorsten; Delacretaz, Guy P.; Gerber, Bruno E.

1995-05-01

263

Characteristics of optical emission intensities and bubblelike phenomena induced by laser ablation in supercritical fluids  

NASA Astrophysics Data System (ADS)

We investigated the characteristics of laser ablation phenomena in supercritical fluids by optical emission and shadowgraph imaging. In comparison with laser ablation in liquid H2O, the optical emission of a laser ablation plasma produced in supercritical H2O had a longer lifetime and a larger transport length. It was found in supercritical CO2 that laser ablation plasmas with bright optical emissions were produced at a mass density of approximately 300 kg/m3. A clear correlation between the optical emission intensity and the density fluctuation was not observed in our experimental results, which were obtained in a regime deviated from the critical point. Bubblelike hollows were observed by shadowgraph imaging in both supercritical H2O and CO2. The dynamics of the bubblelike hollows were different from the dynamics of a cavitation bubble induced by laser ablation in a liquid medium but relatively similar to the dynamics of ambient gas in gas-phase laser ablation.

Takada, Noriharu; Machmudah, Siti; Goto, Hiroshi; Wahyudiono; Goto, Motonobu; Sasaki, Koichi

2014-01-01

264

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

265

Ablation plume movement in a pulsed laser deposition system  

NASA Astrophysics Data System (ADS)

A novel three-dimensional model has been proposed for simulating pulsed laser ablation plume behvior and 'micron-sized particles' movement. It describes the plume expansion in vacuum or into an environmental gas. The model combined the advantages of Monte-Carlo and Finite Element methods, being able to give a detailed image of particles behavior, both from microscopic and macroscopic points of view. The particle interaction with obstacles is aimed to provide us a more comprehensive understanding of Pulsed Laser Deposition (PLD) techniques, with the final objective of obtaining droplets-free surfaces.

Marcu, Aurelian; Grigoriu, Constantin; Cristea, V.; Yatsui, Kiyoshi

2004-10-01

266

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 for preparative, medical,13 and analytical applications11 e.g., atmospheric pressure matrix-assisted laser at atmospheric pressure in the presence of phase ex- plosion. Compared to laser ablation in vacuum, in a back

Vertes, Akos

267

Furnace geometry effects on plume dynamics in laser ablation for nanotube synthesis  

Microsoft Academic Search

Laser ablation (LA) has become a popular method for production of carbon nanotubes where formation of gaseous carbon plume and liberation of catalyst particles are caused by the laser pulse. The plume dynamics in laser ablation is somewhat similar to point explosion where a large amount of energy is liberated in a small volume. The aim of this study is

Diomar Cesar Lobão; Alex Povitsky

2004-01-01

268

Inter-element fractionation and correction in laser ablation inductively coupled plasma mass spectrometry  

E-print Network

Inter-element fractionation and correction in laser ablation inductively coupled plasma mass-element fractionation in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis is one-2 and SY-4) using a UV 266 nm laser. The study showed that the inter-element fractionation depends

Chen, Zhongxing

269

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 August 2003 We study the morphology of borosilicate glass surface machined by femtosecond laser pulses writing of microchannels in glass.3­6 Using this laser ablation technique, it is possible to fabricate

Byer, Robert L.

270

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

271

Modeling of Plume Dynamics in Laser Ablation  

Microsoft Academic Search

The aim of this study is to find thermal conditions for the formation of carbon annotates in a laser furnace. The proposed model includes a multi-species formulation for concentration of chemical components combined with the compressible Euler equations. An axisymmetric unsteady computational gas dynamic model of plume expansion into ambiance has been developed. In the present work, the system of

Diomar Lobao; Alex Povitsky

2003-01-01

272

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

273

Spectroscopic evidence of positive clusters in Ag colloids obtained by laser ablation in aqueous solutions  

NASA Astrophysics Data System (ADS)

We have found evidence of positive cluster formation during the laser ablation process of a silver target in aqueous solutions. In particular, by employing in situ shot-by-shot UV-vis spectroscopy in the early stages of the ablation, we observed a weak and unstable absorption band around 266 nm and a more stable one around 290 nm, which could be assigned to charged clusters like Ag{3/2+} and Ag{4/2+}, respectively. Surface-enhanced Raman scattering experiments performed with a test molecule adsorbed on a silver colloid obtained in pure water were compatible with the presence of Ag{4/2+} active sites on the surface of the Ag nanoparticles.

Giorgetti, E.; Marsili, P.; Muniz-Miranda, M.; Gellini, C.; Giammanco, F.

2014-10-01

274

Ammonia-sensitive photonic structures fabricated in Nafion membranes by laser ablation.  

PubMed

Here we report the fabrication and characterization of photonic structures in Nafion membranes sensitive to ammonia in the 0.19%-12.5% concentration range. The photonic structures were recorded by laser ablation of silver nanoparticles synthesized in situ by diffusion. The particles showed an average diameter of 17 nm with a narrow size distribution. After ablation, the nanoparticles generated a diffracting structure giving colorful reflections at defined peak wavelengths. The reflectivity at these wavelengths was directly proportional to concentration after ammonia exposure. The concentration range that can be measured with these membranes encompasses the fatal limit of exposure and the lower flammable limit of gaseous ammonia. Interrogation by reflection spectroscopy makes them suitable for remote sensing and real-time monitoring of gases. PMID:24803236

Hurtado, J L Martinez; Lowe, C R

2014-06-11

275

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

276

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

277

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

PubMed Central

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.

2014-01-01

278

On the Feasibility of Depth Profiling of Animal Tissue by Ultrashort Pulse Laser Ablation  

PubMed Central

Experiments were performed to examine the feasibility of MS depth profiling of animal tissue by ~75 fs, 800 nm laser pulses to expose underlying layers of tissue for subsequent MS analysis. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) was used to analyze phospholipids and proteins from both intact bovine eye lens tissue and tissue ablated by ultrashort laser pulses. Laser desorption postionization (LDPI-MS) with 10.5 eV single photon ionization was also used to analyze cholesterol and other small molecules in the tissue before and after laser ablation. Scanning electron microscopy was applied to examine the ablation patterns in the tissue and estimate the depth of the ablation craters. Ultrashort pulse laser ablation was found able to remove a layer of several tens of micrometers from the surface of eye lens tissue while leaving the underlying tissue relatively undamaged for subsequent MS analysis. MS analysis of cholesterol, phospholipids, peptides, and various unidentified species did not reveal any chemical damage caused by ultrashort pulse laser ablation for analytes smaller than ~6 kDa. However, a drop in intensity of larger protein ions was detected by MALDI-MS following laser ablation. An additional advantage was that ablated tissue displayed up to an order of magnitude higher signal intensities than intact tissue when subsequently analyzed by MS. These results support the use of ultrashort pulse laser ablation in combination with MS analysis to permit depth profiling of animal tissue. PMID:22482364

Milasinovic, Slobodan; Liu, Yaoming; Bhardwaj, Chhavi; Melvin, Blaze M.T.; Gordon, Robert J.; Hanley, Luke

2012-01-01

279

Self-Organized Micro-Columns and Nano-Spheres Generated by Pulsed Laser Ablation of Ti/Al Alloy in Water  

NASA Astrophysics Data System (ADS)

Dense arrays of micro-columns are formed on the surface of Ti-Al alloy by cumulative nanosecond pulsed laser ablation in water. The fabric-like structure characterized by Ti-Al nano-spheres absorbed on micro-cluster in liquid is most likely responsible for the occurrence of laser micro-etching and localized melting, resulting in continuous deepening of micro-holes and the formation of micro-columns. Laser induced plasma spectroscopy is carried out to reveal the effect of micro-columns on subsequent pulse laser ablation. The intensity of spectral lines from Ti ions by additional laser ablation of the modified spot is higher than that created over a smooth surface. These results suggest that the micro-columns lead to an enhanced absorption of the following laser energy. The proposed results and relevant discussions are of importance for the development of light-trapping coatings on a metal surface.

Cui, Qing-Qiang; Liu, Xiang-Dong; Chen, Ming; Zhao, Ming-Wen; Wang, Chun-Sheng; Li, Shuang

2014-01-01

280

Ablation and plasma emission produced by dual femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Pairs of 80fs, 800nm laser pulses were used to ablate Si, Cu, and CaF2 in air. The spectrally resolved plasma emission was measured as a function of laser fluence and pulse delay. After an initial dip, the fluorescence was found to increase monotonically with pulse delay, reaching a plateau after some tens of picoseconds, depending on the material and fluence. The enhancement ratio (defined as the ratio of the fluorescence produced by the pulse pair to that produced by a single pulse of the same total fluence) reaches a maximum value of 6 and 11 at a fluence of ˜6J /cm2 for Si and Cu, respectively, and declines to a value below 2 at higher fluences. In contrast, the enhancement for CaF2 increases slowly from zero near threshold to a broad maximum value of 2 near 50J /cm2. Using reflectivity and atomic force microscopy measurements as diagnostics, we interpret the Si and Cu behavior in terms of a two phase mechanism, in which the first pulse melts the surface of the crystal and the second pulse ablates the resulting liquid film. A qualitatively different mechanism initiated by multiphoton absorption is involved in CaF2 ablation.

Singha, Sima; Hu, Zhan; Gordon, Robert J.

2008-12-01

281

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

282

Growth rate and the cutoff wavelength of the Darrieus-Landau instability in laser ablation  

E-print Network

The main characteristics of the linear Darrieus-Landau instability in the laser ablation flow are investigated. The dispersion relation of the instability is found numerically as a solution to an eigenvalue stability problem, taking into account the continuous structure of the flow. The results are compared to the classical Darrieus-Landau instability of a usual slow flame. The difference between the two cases is due to the specific features of laser ablation: high plasma compression and strong temperature dependence of electron thermal conduction. It is demonstrated that the Darrieus-Landau instability in laser ablation is much stronger than in the classical case. In particular, the maximum growth rate in the case of laser ablation is about three times larger than that for slow flames. The characteristic length scale of the Darrieus-Landau instability in the ablation flow is comparable to the total distance from the ablation zone to the critical zone of laser light absorption. The possibility of experimental...

Modestov, Mikhail; Valiev, Damir; Marklund, Mattias

2009-01-01

283

hal-00121833,version1-22Dec2006 Hydrodynamic simulations of metal ablation by femtosecond laser irradiation  

E-print Network

to the laser-dielectric interaction where thermal and athermal ablation regimes probably takes place5,6,7 , the laser-metal interaction is mainly gov- erned by the thermal ablation one6,8 . The laser energyhal-00121833,version1-22Dec2006 Hydrodynamic simulations of metal ablation by femtosecond laser

Paris-Sud XI, Université de

284

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

SciTech Connect

This is the third paper in our series studying the laser-target-liquid interactions occurring in laser ablation in liquids (LAL). Here, laser ablation of a platinum target in pure water at 355 nm wavelength is studied as a function of laser energy. We describe three distinct reaction regimes between the ablated target species and water at different laser focusing conditions. At low laser fluence (<10 J/cm{sup 2}), material removal is caused by laser heating of the platinum surface and the primary products are small clusters with a large percentage of platinum atoms in a nonzero oxidation state. At intermediate fluences (10-70 J/cm{sup 2}), platinum nanoparticles are the primary products. Our previous studies demonstrated that in this fluence regime ablation occurs through both thermal vaporization and explosive ejection of molten droplets. In both cases reactivity is small due to the low reactivity of platinum with water. At high fluences (>70 J/cm{sup 2}), we find large, faceted particles that are attributed to the drying of PtO{sub x} gels formed by reactive plasma etching of the target. Taken together these results demonstrate that significant tunability in the target-liquid interaction is possible during nanomaterial synthesis by LAL.

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

285

Production of nanoparticles by laser-induced ablation of metals in liquids  

SciTech Connect

The production of noble metal (Ag and Au) nanoparticles upon the ablation of metal targets in liquids (H{sub 2}O, C{sub 2}H{sub 5}OH, etc.) caused by irradiation by a copper vapour laser is studied. The nanoparticles emerging in a liquid are investigated using X-ray diffractometry, optical absorption spectroscopy, and high-resolution transmission electron microscopy. The colloidal nanoparticle solutions exhibits a distinct plasmon resonance at 520 and 400 nm for Au and Ag, respectively. It is shown that the proximity of laser wavelength to the resonance makes it possible to decrease the dimension of nanoparticles by irradiating the colloidal solution. The size distribution function of nanoparticles is simulated taking into account the production, coagulation, and splitting of nanopartiles in the laser beam. (special issue devoted to the memory of academician a m prokhorov)

Bozon-Verduraz, F; Brayner, R [ITODYS, Universite Paris (France); Voronov, Valerii V [Laser Materials and Technology Research Center, A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Kirichenko, N A; Simakin, Aleksandr V; Shafeev, Georgii A [Wave Research Centre, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2003-08-31

286

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

287

Laser ablation in a running hall effect thruster for space propulsion  

NASA Astrophysics Data System (ADS)

Hall Effect Thrusters (HETs) are promising electric propulsion devices for the station-keeping of geostationary satellites (more than 120 in orbit to date). Moreover, they can offer a cost-effective solution for interplanetary journey, as proved by the recent ESA SMART-1 mission to the Moon. The main limiting factor of the HETs lifetime is the erosion of the annular channel ceramics walls. In order to provide a better understanding of the energy deposition on the insulated walls, a laser irradiation study has been carried out on a PPS100-ML thruster during its run in the PIVOINE-2G ground test facility (CNRS Orléans, France). Two distinct approaches have been followed: continuous wave fiber laser irradiation (generation of thermal defects) and nanosecond pulsed laser ablation (generation of topological defects). The irradiated zones have been monitored in situ by IR thermography and optical emission spectroscopy and further investigated ex situ by scanning electron microscopy and profilometry.

Balika, L.; Focsa, C.; Gurlui, S.; Pellerin, S.; Pellerin, N.; Pagnon, D.; Dudeck, M.

2013-07-01

288

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

289

Ablation of selected conducting layers by fiber laser  

NASA Astrophysics Data System (ADS)

Laser Direct Writing (LDW) are used in the manufacture of electronic circuits, pads, and paths in sub millimeter scale. They can also be used in the sensors systems. Ablative laser writing in a thin functional layer of material deposited on the dielectric substrate is one of the LDW methods. Nowadays functional conductive layers are composed from graphene paint or nanosilver paint, indium tin oxide (ITO), AgHTTM and layers containing carbon nanotubes. Creating conducting structures in transparent layers (ITO, AgHT and carbon nanotubes layers) may have special importance e.g. for flexi electronics. The paper presents research on the fabrication of systems of paths and appropriate pattern systems of paths and selected electronic circuits in AgHTTM and ITO layers deposited on glass and polymer substrates. An influence of parameters of ablative fiber laser treatment in nanosecond regime as well as an influence of scanning mode of laser beam on the pattern fidelity and on electrical parameters of a generated circuit was investigated.

Pawlak, Ryszard; Tomczyk, Mariusz; Walczak, Maria

2014-08-01

290

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

291

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

292

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

293

Enhanced ablation of human atheroma using a copper vapor laser  

NASA Astrophysics Data System (ADS)

The most suitable type of laser and delivery system for arterial recanalisation remains a matter of controversy. Atheroma demonstrates preferential absorption of laser light relative to normal vessel wall at wavelengths in the region of SOOnm. This phenomenon may be useful in laser angioplasty. A low power commercial quasi-continuous-wave copper vapour laser (CVL) licensed for photodynamic therapy (Oxford Lasers model CUb-A, Oxford, U.K.), emits light at 2 wavelengths - 51mm (green) and 578nm (yellow) [green/yellow ratio 2:1]. This laser may also be used to pump a dye laser producing a tunable output from 530-900nm. The output was coupled to a 1 mm diameter bare quartz optical fiber, and the effects of these wavelengths on atheroma were studied. Perforation thresholds in normal vessel were determined initially. Subsequently, tissue craters were created in sections of normal human femoral artery and in white fibrous atheromatous artery, using a total of 8 J of laser energy delivered with the fiber in contact and perpendicular to the tissue. Crater dimensions were determined histologically in 10 sections from each group, using an optical graticule. Results:- The dye laser pumping produced insufficient power output to achieve tissue ablation. The crater depth, width, and volume, in normal (N) and atheromatous (A) arterial wall achieved with the CVL were statistically compared using a Paired Student's t-test. Crater depth (mm) [mean (s.e.)]: N 0.91 (0.06), A 0.69 (0.05), pablation of atheroma using low power copper vapour laser light is possible. The CVL is an attractive alternative to argon ion laser and its potential application to laser angioplasty merits further study, preferably using a modified optical fibertip delivery system.

Ashley, Simon; Brooks, Stephen G.; Wright, Helena; Gehani, Abdurrazak A.; Rees, Michael R.

1990-07-01

294

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

295

Laser ablated particles behaviour in PLD systems  

NASA Astrophysics Data System (ADS)

A novel three-dimensional model has been proposed for simulating plume behavior and 'micron-sized particles' movement and interaction. It describes particles expansion in vacuum or into an environmental gas and particles interaction with various obstacles. The model simulates 'standard' Pulsed Laser Deposition (PLD) system behavior, but also some droplet reduction techniques used in PLD (e.g. shadow mask technique) having good results in plasma expansion for the first several centimeters from target. The carried out simulations have shown that in the PLD with plasma reflection (PLDPR) the influence of mass and particle's surface area on the droplets trajectory is significant. By increasing of the particle mass or by decreasing particle's surface, the probability of the particle to be driven into the deposition area by plume fine particles is considerably decreasing.

Marcu, A.; Grigoriu, C.; Yatsui, K.

2005-08-01

296

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

PubMed

A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of (57)Fe, obtained from iron sulfide (FeS(2)), demonstrated that the resulting signal intensity of (57)Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm(2)). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the (206)Pb/(238)U (f(Pb/U)) and (238)U/(232)Th (f(U/Th)) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of (56)Fe and the isotopic ratios ((57)Fe/(54)Fe and (56)Fe/(54)Fe) have been measured on a natural pyrite (FeS(2)) sample. Repeatability in signal intensity of (56)Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in (57)Fe/(54)Fe and (56)Fe/(54)Fe ratio measurements could be improved by the fs-laser ablation system. The data obtained here clearly demonstrate that, even with the fundamental wavelength (NIR operating at 780 nm), the fs-laser ablation system has the potential to become a significant tool for in-situ elemental and isotopic analysis of geochemical samples including heavy minerals and metallic materials. PMID:18332541

Hirata, Takafumi; Kon, Yoshiaki

2008-03-01

297

Synchronized videography of plasma plume expansion during femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

Femtosecond lasers are gaining industrial interest for surface patterning and structuring because of the reduced heat effects to the surrounding material, resulting in a good quality product with a high aspect ratio. Analysis of the plasma plume generated during ablation can provide useful information about the laser-material interactions and thereby the quality of the resulting surface patterns. As a low-cost alternative to rather complicated ICCD camera setups, presented here is an approach based on filming the laser machining process with a high speed camera and tuning the frame rate of the camera to slightly lower than the laser pulse frequency. The delay in frequency between the laser and camera results in frames taken from sequential pulses. Each frame represents a later phase of plume expansion although taken from different pulses. Assuming equal plume evolution processes from pulse to pulse, the sequence of images obtained completes a plume expansion video. To test the assumption of homogeneity between sequential plumes, the camera can be tuned to the frequency of the laser, as to capture consecutive plumes at the same phase in their evolution. This approach enables a relatively low-cost, high resolution visualization of plasma plume evolution suitable for industrial micromachining applications with femtosecond lasers. Using this approach we illustrate differences in plume expansion at the example of machining homogeneous surface patterns in different liquid and gaseous processing environments.

Paolasini, Steven; Kietzig, Anne

2014-03-01

298

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

299

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

300

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

301

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

302

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

303

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

304

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

E-print Network

behavior under extreme conditions that can hardly be achieved by any other means. Analysis of the laser and disintegration of material in laser ablation. Recent progress in the development of new optical and x

Zhigilei, Leonid V.

305

Laser Ablation Plume Expansion In The Presence Of Charged Impurities  

SciTech Connect

The expansion of plasma created by laser ablation is investigated using the fluid model. At the first stage of the expansion, electrons are considered in thermal equilibrium. The presence of highly charged impurities is considered through Poisson's equation. The set of nonlinear differential equations is solved using a moving boundary and taken into account the charge separation effect. The uniformly distributed impurities can accelerate or decelerate the ion motion depending on their charge and concentration. It is also found that the separation of the charge is valid for a specific time which depends on the impurities parameters.

Djebli, M. [Centre de Developpement des Technologies Avancees. Baba Hassen 16303 Algiers (Algeria); Theoretical Physics Laboratory, Faculty of Physics-USTHB-, B. P. 32 Bab Ezzouar 16079, Algiers (Algeria)

2008-09-23

306

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

307

Effects of pulsed CO2 laser in caries selective ablation  

NASA Astrophysics Data System (ADS)

We have evaluated the effect of pulsed carbon dioxide laser in the treatment for deep carious decay. The so called `caries profonda' is still a problem for conservative dentistry. A `Valvfivre' Master 20S carbon dioxide laser was pulsed to determine the effects on dentine and for testing the properties of softened dentine in selective ablation. Laser treatment parameters were from 1 to 2 W, 50 to 150 ms, 200 to 320 Hz. Fifteen human teeth samples were exposed to irradiation: extracted third molar were exposed to CO2 pulsed laser to determine in vitro the effects on pulp morphology. The tissue samples were analyzed histologically and by means of scanning electron microscopy for evidence of thermal damage. Next, we have evaluated the morphologic changes in vivo on 10 cases in patients with deep carious decay. Pulsed infrared lasers are capable of inducing physical and chemical changes in dentine structure. The results showed an artificially sclerosing and micro-hardness on the remaining dentine. CO2 laser can vaporized carious dentine.

Colojoara, Carmen; David, Ion; Marinovici, Mariana

1995-03-01

308

Approximate theory of highly absorbing polymer ablation by nanosecond laser pulses  

NASA Astrophysics Data System (ADS)

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

Furzikov, N. P.

1990-04-01

309

Real-time measurement of ArF excimer laser corneal tissue ablation rates using cross-  

E-print Network

Real-time measurement of ArF excimer laser corneal tissue ablation rates using cross- correlation of bovine cornea over a range of clinically relevant laser fluences. A linear relationship was observed between several cross-correlation metrics and the directly measured corneal ablation rate, yielding

Hahn, David W.

310

Improved Analytical Characterization of Solid Waste-Forms by Fundamental Development of Laser Ablation Technology  

Microsoft Academic Search

Laser ablation (LA) with inductively coupled plasma mass spectrometry (ICP-MS) has been demonstrated as a viable technology for sample characterization within the EM complex. Laser ablation systems have been set up at the Hanford Site, Savannah River Plant, the Pu immobilization program (MD), Los Alamos, and at numerous other DOE facilities. Characterization of elemental and isotopic chemical constituents is an

Richard E

2000-01-01

311

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 (EMP) analysis to provide complementary information on major element constituents. Here, we present a method for laser ablation ICP-MS analysis of major elements in silicate glasses and minerals that, when

Weston, Ken

312

FINAL REPORT. WASTE VOLUME REDUCTION USING SURFACE CHARACTERIZATION AND DECONTAMINATION BY LASER ABLATION  

EPA Science Inventory

Laser ablation was studied as a method for removing contaminated surface layers from concrete. The objectives of this research were to determine the mechanism and efficacy of laser ablation, to understand the chemistry of contaminated concrete surfaces, and to chemically and phys...

313

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

314

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

E-print Network

sputtering, plays an important role. The ablation process depends on thermal and optical propertiesPhysical mechanisms of short pulse laser ablation D. von der Linde and K. Sokolowski laser pulses is a thermal process involving states of matter having unusual thermodynamic, hydrodynamic

von der Linde, D.

315

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 of thermal confinement, a phase explosion of the overheated material is responsible for the collective material ejection at laser fluences above the ablation threshold. This phase explosion leads

Zhigilei, Leonid V.

316

Ultra-fast movies of thin-film laser ablation  

NASA Astrophysics Data System (ADS)

Ultra-short-pulse laser irradiation of thin molybdenum films from the glass substrate side initiates an intact Mo disk lift off free from thermal effects. For the investigation of the underlying physical effects, ultra-fast pump-probe microscopy is used to produce stop-motion movies of the single-pulse ablation process, initiated by a 660-fs laser pulse. The ultra-fast dynamics in the femtosecond and picosecond ranges are captured by stroboscopic illumination of the sample with an optically delayed probe pulse of 510-fs duration. The nanosecond and microsecond delay ranges of the probe pulse are covered by an electronically triggered 600-ps laser. Thus, the setup enables an observation of general laser ablation processes from the femtosecond delay range up to the final state. A comparison of time- and space-resolved observations of film and glass substrate side irradiation of a 470-nm molybdenum layer reveals the driving mechanisms of the Mo disk lift off initiated by glass-side irradiation. Observations suggest that a phase explosion generates a liquid-gas mixture in the molybdenum/glass interface about 10 ps after the impact of the pump laser pulse. Then, a shock wave and gas expansion cause the molybdenum layer to bulge, while the enclosed liquid-gas mixture cools and condenses at delay times in the 100-ps range. The bulging continues for approximately 20 ns, when an intact Mo disk shears and lifts off at a velocity of above 70 m/s. As a result, the remaining hole is free from thermal effects.

Domke, Matthias; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2012-11-01

317

Ins and outs of endovenous laser ablation: afterthoughts.  

PubMed

Physicists and medical doctors "speak" different languages. Endovenous laser ablation (EVLA) is a good example in which technology is essential to guide the doctor to the final result: optimal treatment. However, for the doctor, it is by far insufficient just to turn on the knobs of the laser. He should understand what is going on in the varicose vein. On the other hand, the physicist is usually not aware what problems the doctor finds on his road towards improving a new technique. We have tried to bring both languages together in the special on Ins and outs of endovenous laser ablation published in this issue of Lasers in Medical Science. The 13 articles include endovenous related clinical (de Roos 2014; Kockaert and Nijsten 2014; van den Bos and Proebstle 2014) and socioeconomical articles (Kelleher et al 2014), the first paper on the molecular pathophysiologic mechanisms (Heger et al 2014), fiber tips (Stokbroekx et al 2014), the future of EVLA (Rabe 2014), a review of EVLA with some important issues for debate (Malskat et al 2014), an excellent paper on transcutaneous laser therapies of spider and small varicose veins (Meesters et al 2014), as well as several scientific modeling articles, varying from a mathematical model of EVLA that includes the carbonized blood layer on the fiber tip (van Ruijven et al 2014) and its application to the simulation of clinical conditions (Poluektova et al 2014) via experimental measurements of temperature profiles in response to EVLA, radiofrequency waves, and steam injections (Malskat et al 2014) to a literature review and novel physics approach of the absorption and particularly scattering properties of whole blood also including the infrared wavelengths used by EVLA (Bosschaart et al 2014). The aim of our afterthoughts, the 14th article in this special, is to try to amalgamate the clinical and physical contents of these contributions, providing the reader with the bridge that overlaps these different backgrounds. PMID:24399461

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

2014-03-01

318

Comparison of holmium:YAG and thulium fiber laser lithotripsy: ablation thresholds, ablation rates, and retropulsion effects  

NASA Astrophysics Data System (ADS)

The holmium:YAG (Ho:YAG) laser lithotriptor is capable of operating at high pulse energies, but efficient operation is limited to low pulse rates (~10 Hz) during lithotripsy. On the contrary, the thulium fiber laser (TFL) is limited to low pulse energies, but can operate efficiently at high pulse rates (up to 1000 Hz). This study compares stone ablation threshold, ablation rate, and retropulsion for the two different Ho:YAG and TFL operation modes. The TFL (? = 1908 nm) was operated with pulse energies of 5 to 35 mJ, 500-?s pulse duration, and pulse rates of 10 to 400 Hz. The Ho:YAG laser (? = 2120 nm) was operated with pulse energies of 30 to 550 mJ, 350-?s pulse duration, and a pulse rate of 10 Hz. Laser energy was delivered through 200- and 270-?m-core optical fibers in contact mode with human calcium oxalate monohydrate (COM) stones for ablation studies and plaster-of-Paris stone phantoms for retropulsion studies. The COM stone ablation threshold for Ho:YAG and TFL measured 82.6 and 20.8 J/cm2, respectively. Stone retropulsion with the Ho:YAG laser linearly increased with pulse energy. Retropulsion with TFL was minimal at pulse rates less than 150 Hz, then rapidly increased at higher pulse rates. For minimal stone retropulsion, Ho:YAG operation at pulse energies less than 175 mJ at 10 Hz and TFL operation at 35 mJ at 100 Hz is recommended, with both lasers producing comparable ablation rates. Further development of a TFL operating with both high pulse energies of 100 to 200 mJ and high pulse rates of 100 to 150 Hz may also provide an alternative to the Ho:YAG laser for higher ablation rates, when retropulsion is not a primary concern.

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

2011-07-01

319

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

DOEpatents

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

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

2013-11-19

320

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

SciTech Connect

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

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

2011-11-01

321

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

NASA Astrophysics Data System (ADS)

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

Kang, H. W.; Rizoiu, I.; Welch, A. J.

2007-12-01

322

An observation of ablation effect of soft biotissue by pulsed Er:YAG laser  

NASA Astrophysics Data System (ADS)

Because of the unique properties with regard to the absorption in organic tissue, pulsed Er:YAG laser has found most interest for various application in medicine, such as dermatology, dentistry, and cosmetic surgery. However, consensus regarding the optimal parameters for clinical use of this tool has not been reached. In this paper, the laser ablation characteristics of soft tissue by Er:YAG laser irradiation was studied. Porcine skin tissue in vitro was used in the experiment. Laser fluences ranged from 25mJ/mm2 to 200mJ/mm2, repetition rates was 5Hz, spot sizes on the tissue surface was 2mm. The ablation effects were assessed by the means of optical microscope, ablation diameters and depths were measured with reading microscope. It was shown that the ablation of soft biotissue by pulsed Er:YAG laser was a threshold process. With appropriate choice of irradiation parameters, high quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam can be achieved. The curves of ablation crater diameter and depth versus laser fluence were obtained, then the ablation threshold and ablation yield were calculated subsequently, and the influence of the number of pulses fired into a crater on ablation crater depth was also discussed.

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

2007-02-01

323

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

SciTech Connect

The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm{sup 2}.

Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun, E-mail: wenjunwang@mail.xjtu.edu.cn; Wang, Kedian; Mei, Xuesong [School of Mechanical Engineering, Xi'an Jiaotong University, No. 28, Xianning Westroad, Xi'an 710049 (China) [School of Mechanical Engineering, Xi'an Jiaotong University, No. 28, Xianning Westroad, Xi'an 710049 (China); State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054 (China)

2014-03-15

324

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

E-print Network

Background and Objective: The goal of the present work is to assess whether bovine corneal ablationsLasers in Surgery and Medicine 40:483­493 (2008) Effects of Laser Repetition Rate on Corneal Tissue via imaging and transmission, corneal ablation profiles via scanning interferometry, and high

Hahn, David W.

325

Free-running and Q:Switched LIBS measurements during the laser ablation of Prickle Pears spines  

NASA Astrophysics Data System (ADS)

The pulse laser ablation (PLA) as a new method for spines elimination of Prickle Pear fruit is presented. The new technique works thanks to the use of the pulsed light that is absorbed in a selective way, specifically in the spines. An optical characterization of both spine and cactus cortex allows to find the most convenient pulse energy for selective absorption. By using laser-induced breakdown spectroscopy (LIBS) in Q:Switch and free-running regimes, it is possible to control the process in real time and to check the cleaning results online. The feasibility of performing the laser ablation of spines without visible damages to the substrate was proved by the optical microscopy observation.

Flores, T.; Ponce, L.; Arronte, M.; de Posada, E.

2009-05-01

326

Investigation of the particle size distribution of the ejected material generated during the single femtosecond laser pulse ablation of aluminium  

NASA Astrophysics Data System (ADS)

Single femtosecond laser pulses are employed to ablate an aluminium target in vacuum, and the particle size distribution of the ablated material deposited on a mica substrate is examined with atomic force microscopy (AFM). The recorded AFM images show that these particles have a mean radius of several tens of nanometres. It is also determined that the mean radius of these deposited nanoparticles increases when the laser fluence at the aluminium target increases from 0.44 J/cm2 to 0.63 J/cm2. The mechanism of the laser-induced nanoparticle generation is thought to be photomechanical tensile stress relaxation. Raman spectroscopy measurements confirm that the nanoparticles thus produced have the same structure as the bulk aluminium.

Wu, Han; Zhang, Nan; Zhu, Xiaonong

2014-10-01

327

Characterization of binary silver based alloys by nanosecond-infrared-laser-ablation-inductively coupled plasma-optical emission spectrometer  

NASA Astrophysics Data System (ADS)

A nanosecond infrared laser ablation (LA) system was examined to determine the composition of several silver-copper alloys through an inductively coupled plasma-optical emission spectrometer (ICP-OES). Samples with different concentrations were prepared and analyzed by atomic absorption, and ICP-OES after sample digestion, and compared with an energy-dispersive x-ray spectrometer-scanning electron microscopy (EDX-SEM). Elemental fractionation during the ablation process and within the ICP was investigated for different laser frequencies and fluences. Samples were used for optimizing and calibrating the coupling between LA to the ICP-OES system. Results obtained from the samples analysis were in agreement with those obtained by atomic absorption spectroscopy, ICP-OES and EDX-SEM, showing that fractionation was not significant for laser fluences higher than 55 J cm-2.

Márquez, Ciro; Sobral, Hugo

2013-11-01

328

Journal of Photochemistry and Photobiology A: Chemistry 145 (2001) 173181 The role of the photochemical fragmentation in laser ablation  

E-print Network

processes and their coupling with the thermal processes in UV laser ablation is still far from being of the photochemical fragmentation in laser ablation: a molecular dynamics study Yaroslava G. Yinglinga, Leonid V complete. In this work, the effects of the photochemical reactions on the laser ablation mechanism

Zhigilei, Leonid V.

329

Micropillar fabrication on bovine cortical bone by direct-write femtosecond laser ablation.  

PubMed

We investigated fabrication of cylindrical micropillars on bovine cortical bone using direct-write femtosecond laser ablation. The ablation threshold of the material was measured by single-pulse ablation tests, and the incubation coefficient was measured from linear scanned ablation tests. A motion system was programmed to apply multiple layers of concentric rings of pulses to machine pillars of various diameters and heights. The diameter of the top surface of the pillar was found to steadily decrease due to incubation of damage from successive layers of pulses during the machining process. Pillar top diameter was predicted based on a paraxial beam fluence approximation and single-pulse ablation threshold and incubation coefficient measurements. Pillar diameters predicted as successive layers of pulses were applied were well-matched to experiments, confirming that femtosecond laser ablation of the cortical bone was well-modeled by single-pulse ablation threshold measurements and an incubation coefficient. PMID:20059259

Lim, Yong C; Altman, Katrina J; Farson, Dave F; Flores, Katharine M

2009-01-01

330

Photoluminescence from gas-suspended nanoparticles synthesized by laser ablation: A pathway to optimized nanomaterials  

SciTech Connect

Laser ablation of solids into background gases is a proven cluster-assembly method. It was used to synthesize the first carbon fullerenes in 1985.(1) In this technique, a solid material is vaporized by a high-powered laser pulse to form a partially-ionized plasma containing atoms and small molecules. The hot plasma plume quickly expands to collisionless conditions unless confined by a background gas. In this case, the plume atoms become trapped together and can form clusters as small as a few atoms, or larger clusters of 1--10 nm diameter (25--26,000 atoms for silicon). However, until now very little was known of the temporal and spatial scales for nanoparticle formation in background gases, or how the nanoparticles are transported and deposited after their formation. It is often unclear whether nanoparticles found on substrates were grown in the gas phase or from nuclei formed on the substrate surface. Here, the formation and transport of silicon nanoparticles in laser ablation plumes is revealed by a comparison of Rayleigh-scattering and the first photoluminescence measurements of nanoparticles suspended in background gases. Combined with Z-contrast transmission electron microscopy (TEM) and high resolution electron energy loss spectroscopy (HREELS) analysis of individual nanoparticles, the authors investigate their fundamental light absorption and emission properties without the influence of neighboring nanoparticles or surrounding solid or liquid hosts. Such understanding is critical for the deposition of optimized films.

Geohegan, D.B.; Puretzky, A.A.; Duscher, G.; Pennycook, S.J.

1998-02-01

331

Polarimetric characterization of bismuth thin films deposited by laser ablation.  

PubMed

A Mueller-Stokes analysis is applied to pure bismuth thin film samples prepared by the laser ablation technique by using a polarimeter with a 632.8 nm continuum wavelength laser. The complex refractive index is determined in the range of 250-1100 nm. Results from the Mueller matrix show the high sensitivity of diattenuation and polarizance parameters as a function of the sample thickness and the incidence angle, except at the pseudo-Brewster angle, where they exhibit the same value. Results show that the knowledge of the polarimetric response, with appropriate incident polarization states, could be used to design photonic Bi-based devices for several applications. Polarization dependence is the result of changes on the surface morphology as a result of the small value of the skin depth. PMID:23262593

Espinosa-Luna, Rafael; Camps, Enrique; Cardona, Dagoberto; De la Rosa, Elder

2012-12-20

332

Adaptive Kinetic Simulation of Plasma Propulsion by Laser Ablation  

NASA Astrophysics Data System (ADS)

CPA Ti:Sa lasers can generate 10-30fs, ˜1-10mJ pulses at a ˜10KHz repetition rate, opening a wide range of average exerted forces against solid density targets. Estimates show that at 1KW mean power the reactive force of about 1mN is achievable. We are trying to assess via numerical simulation the prospects of thrust production using ultrafast target ablation. An adaptive kinetic method is being presently developed. It simulates self-consistent electromagnetic wave propagation, solid target ionization, laser light absorption by plasma, and plume formation and expansion. High accuracy, careful resolution of sharp fronts and shocks, and large simulation domain capability are achieved by combining adaptive grid RRC method with PIC-Vlasov hybrid approach. Possible thrust generation under various conditions and configurations is studied numerically. Results of our kinetic modeling will be presented and discussed. *This work is supported by US AFRL

Batishcheva, Alla; Batishchev, Oleg

2004-11-01

333

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Doppler diagnostics of nonstationary mass removal upon laser ablation of biotissues  

NASA Astrophysics Data System (ADS)

The possibilities of the use of autodyne detection of backscattered radiation for studies of nonstationary mass transfer upon ablation of biotissues by pulses from a CO2 laser are demonstrated. It is shown that the differences in the character of the laser-induced mass removal are caused by structural features of biotissues.

Dmitriev, A. K.; Kortunov, V. N.; Ul'yanov, V. A.

2001-04-01

334

[Progress in the application of laser ablation ICP-MS to surface microanalysis in material science].  

PubMed

In the present paper, apparatus and theory of surface analysis is introduced, and the progress in the application of laser ablation ICP-MS to microanalysis in ferrous, nonferrous and semiconductor field is reviewed in detail. Compared with traditional surface analytical tools, such as SEM/EDS (scanning electron microscopy/energy dispersive spectrum), EPMA (electron probe microanalysis analysis), AES (auger energy spectrum), etc. the advantage is little or no sample preparation, adjustable spatial resolution according to analytical demand, multi-element analysis and high sensitivity. It is now a powerful complementary method to traditional surface analytical tool. With the development of LA-ICP-MS technology maturing, more and more analytical workers will use this powerful tool in the future, and LA-ICP-MS will be a super star in elemental analysis field just like LIBS (Laser-induced breakdown spectroscopy). PMID:25508748

Zhang, Yong; Jia, Yun-hai; Chen, Ji-wen; Shen, Xue-jing; Liu, Ying; Zhao, Leiz; Li, Dong-ling; Hang, Peng-cheng; Zhao, Zhen; Fan, Wan-lun; Wang, Hai-zhou

2014-08-01

335

[Progress in the application of laser ablation ICP-MS to surface microanalysis in material science].  

PubMed

In the present paper, apparatus and theory of surface analysis is introduced, and the progress in the application of laser ablation ICP-MS to microanalysis in ferrous, nonferrous and semiconductor field is reviewed in detail. Compared with traditional surface analytical tools, such as SEM/EDS (scanning electron microscopy/energy dispersive spectrum), EPMA (electron probe microanalysis analysis), AES (auger energy spectrum), etc. the advantage is little or no sample preparation, adjustable spatial resolution according to analytical demand, multi-element analysis and high sensitivity. It is now a powerful complementary method to traditional surface analytical tool. With the development of LA-ICP-MS technology maturing, more and more analytical workers will use this powerful tool in the future, and LA-ICP-MS will be a super star in elemental analysis field just like LIBS (Laser-induced breakdown spectroscopy). PMID:25474969

Zhang, Yong; Jia, Yun-hai; Chen, Ji-wen; Shen, Xue-jing; Liu, Ying; Zhao, Leiz; Li, Dong-ling; Hang, Peng-cheng; Zhao, Zhen; Fan, Wan-lun; Wang, Hai-zhou

2014-08-01

336

Laser ablation and high precision patterning of biomaterials and intraocular lenses  

NASA Astrophysics Data System (ADS)

The use of intraocular lenses (IOL) is the most promising method for restoring excellent vision in cataract surgery. In addition, multifocal intraocular lenses for good distant and near vision are investigated. Several new materials, techniques and patterns are studied for the formation and etching of intraocular lenses in order to improve their optical properties and reduce the diffractive aberrations. As pulsed laser ablation is well established as a universal tool for surface processing of organic polymer materials, this study was focused in using laser ablation with short and ultra short laser pulses for surface modification of PMMA and intraocular lenses, instead of using other conventional techniques. The main advantage of using very short laser pulses, e.g. of ns, ps or fs duration, is that heat diffusion into the polymer material is negligible. As a result high precision patterning of the sample, without thermal damage of the surroundings, becomes possible. In this study, laser ablation was performed using commercially available hydrophobic acrylic IOLs, hydrophilic acrylic IOLs, and PMMA IOLs, with various diopters. We investigated the ablation efficiency and the phenomenology of the etched patterns by testing the ablation rate, versus laser energy fluence, at several wavelengths and the surface modification with atomic force microscopy (AFM), or scanning electron microscopy (SEM). The irradiated polymers have different optical properties, at the applied wavelengths, and therefore, present different ablation behaviour and morphology of the laser ablated crater walls and surrounding surfaces. The experimental results, some theoretical assumptions for mathematical modeling of the relevant ablation mechanisms are discussed.

Serafetinides, A. A.; Spyratou, E.; Makropoulou, M.

2010-10-01

337

Synthesis and optimization of tungsten and tungsten oxide films produced by laser ablation  

NASA Astrophysics Data System (ADS)

This work was aimed at achieving an optimal deposition process by pulsed laser ablation (PLA) on large area substrates, using pure tungsten as target. The films were deposited at different: wavelengths (355/532/1064 nm), fluences (1.5, 5 and 10 J/cm2), oxygen pressures (100 and 200 mTorr), substrate temperatures (room temperature, 200, 300, and 400°C). The morpho-structural and compositional investigations have been carried out by profilometer, scanning electron microscopy, X-ray diffraction, Rutherford backscattering spectroscopy and Fourier transform infrared spectroscopy. The study has shown that optimal conditions for tungsten deposition on large area surfaces are at 355 nm/ 5 J/cm2. Amorphous, orthorhombic and triclinic phases WO3 films were obtained.

Shuntaro, S.; Suzuki, T.; Hirai, M.; Suematsu, H.; Grigoriu, C.; Sima, C.; Nicolae, I.; Waldhauser, W.; Lackner, J. M.

2007-04-01

338

Endometrial ablation using SideFire laser fiber  

NASA Astrophysics Data System (ADS)

The first successful report using the neodymium:yttrium-aluminum-garnet (Nd:YAG) Laser to control hypermenorrhea was reported in 1981. Variations on the treatment technique have been attempted to improve the amenorrhea rate. Reports using the Nd:YAG laser with the blanching or non-touch technique seem to result in a better outcome and higher rate of total amenorrhea than using the dragging technique. Due to the report of improved rates of amenorrhea when using the blanching technique and the Nd:YAG laser, a fiber was developed to direct the laser energy at right angles to the axis of the fiber, therefore allowing a total treatment of the entire uterus in a perpendicular fashion. The theoretic benefit of this would be a more complete and predictable destruction of the endometrial lining, avoiding fluid overload by coagulating and sealing of the vessels and lymphatic. After a follow-up of 12 to 36 months, 56 of the 60 patients (93%) who underwent complete endometrial ablation with the SideFireTM technique had excellent results. Total absolute amenorrhea resulted in 50 patients (83%). Contrary to earlier reports, using the rollerball electrode, this procedure technique resulted in no decrease in results in younger patients. In conclusion, this seems to be a reasonable alternative which offers improved results when compared to previously available methods using electrosurgery or the Nd:YAG laser without the use of the SideFireTM device.

Everett, Royice B.

1996-05-01

339

Ultrashort pulsed laser ablation and stripping of freeze-dried dermis.  

PubMed

Plasma-mediated laser ablation and dissection of freeze-dried human dermis using an ultrashort pulsed laser of pulse width 900 fs and wavelength 1,552 nm were investigated. The surface ablation line width and depth in relation to irradiation fluence and pulse overlap rate were characterized and measured by scanning electron microscopy. The ablation threshold fluence for freeze-dried dermis was determined as 8.32 J/cm(2) and the incubation factor subject to pulse train irradiation was found to be 0.54. Histological examination showed no thermal damage with single line ablation. Even with multiline ablation, thermal damage was insignificant and the lateral damage zone was generally within 10 microm with 100 continuously repeated line scans. Ultrashort pulsed laser ablation of the interior of dry dermal tissue was shown to strip thin dermal slices with different thicknesses ranging from 20 to 40 microm. PMID:19997767

Huang, Huan; Guo, Zhixiong

2010-07-01

340

Morphological features of silicon substrate by using different frequency laser ablation in air and water  

NASA Astrophysics Data System (ADS)

The interaction of the nanosecond laser (FWHM = 30 ns, ? = 355 nm) and monocrystalline silicon is investigated in air and water. Conventional optical and scanning electron microscopes are used to characterize surface ablation of the monocrystalline silicon. A numerical model is used to ascertain the time of the bubble motion in water. Morphological features of the laser-induced crater are different under various environments and frequencies. More debris is found when using high frequency ablation, and a larger zone is affected by heat when using low frequency ablation in air. There is no debris found in water, and the morphology of craters is better in low frequency ablation than that in high frequency ablation because bubbles generated by high frequency ablation affect laser transmission.

Xu, J. Y.; Hu, H.; Lei, Y. L.

2014-10-01

341

Skin-tightening effect of fractional lasers: comparison of non-ablative and ablative fractional lasers in animal models.  

PubMed

This experimental study was performed to demonstrate the effects of non-ablative fractional laser (NAFL) and ablative fractional laser (AFL). Twenty male Sprague-Dawley rats were used for the study. Three 2×2-cm-sized squares were tattooed on the abdomen of the animals. Each tattooed square was used for NAFL, AFL and control experiments. The NAFL and AFL treatment were performed with the same total energy of 12,000 mJ cm(-2). The laser treatments consisted of four sessions, with an interval of 3 weeks between sessions. The areas of tattooed skin were serially measured, and skin samples were obtained for histologic examination after 4 months of treatment. NAFL did not cause immediate skin shrinkage, but the size of the NAFL-treated skin was reduced by 4.3% after 4 months. In contrast, AFL caused immediate skin shrinkage (11.5% reduction), and the size was maintained at 9% reduction after 4 months. In histologic examination, the dermal collagen was arranged flat and parallel to the skin surface in the upper dermis, and regenerated collagen fibres were clearly noticed in both NAFL-and AFL-treated skin samples. Immunohistochemical stains showed well-regenerated type I and III collagen fibres. Western blot analysis of skin samples showed that type I/III collagen ratio was not significantly changed after fractional laser treatment. Electron microscopic studies aimed to evaluate the long-term micro-architecture of the collagen fibrils. AFL treatment reduced D-band periodicity by 5.2% and fibril diameter by 14.8%, although there was no statistically significant difference (p>0.05). Fractional laser treatment shrinks the skin surface area and regenerates collagen. The AFL treatment showed more profound skin changes than NAFL. PMID:22633871

Park, Seung-Ha; Kim, Deok-Woo; Jeong, Taewon

2012-10-01

342

Single molecule laser spectroscopy.  

PubMed

In this article, we discussed some single molecule spectroscopy techniques and methods. We have chosen the simplicity in this survey based on our laboratory experience in this field. We concentrated on the imaging by both techniques the wide field and the scanning microscopes. Other imaging enhancements on the technique like extended resolution wide field, the total internal reflection imaging, and its derivatives are also reviewed. In addition to the imaging techniques, some diffusion techniques also are discussed like fluorescence correlation spectroscopy. The related methods like Forester resonance transfer, photo-induced electron transfer and anisotropy (steady state and time decay) are also discussed. In addition, we elucidated some simple details about the theory behind the FCS and its resulting curve fitting. This review is preceded by general introduction and ended with the conclusion. PMID:25156641

Atta, Diaa; Okasha, Ali

2015-01-25

343

Single molecule laser spectroscopy  

NASA Astrophysics Data System (ADS)

In this article, we discussed some single molecule spectroscopy techniques and methods. We have chosen the simplicity in this survey based on our laboratory experience in this field. We concentrated on the imaging by both techniques the wide field and the scanning microscopes. Other imaging enhancements on the technique like extended resolution wide field, the total internal reflection imaging, and its derivatives are also reviewed. In addition to the imaging techniques, some diffusion techniques also are discussed like fluorescence correlation spectroscopy. The related methods like Forester resonance transfer, photo-induced electron transfer and anisotropy (steady state and time decay) are also discussed. In addition, we elucidated some simple details about the theory behind the FCS and its resulting curve fitting. This review is preceded by general introduction and ended with the conclusion.

Atta, Diaa; Okasha, Ali

2015-01-01

344

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

NASA Astrophysics Data System (ADS)

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

Yan, Zijie

2011-12-01

345

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

PubMed

Currently, ablative laser therapy (with CO2/Er:YAG lasers) and deep chemical peeling are effective and promising methods of skin rejuvenation. The induction of collagen synthesis was observed after peelings with trichloroacetic acid or phenol as well as after treatments with the CO2 laser. In past years, the undesirable side effects and risks of these methods have led to intensified research in the fields of non-ablative facial rejuvenation and subsurfacing by means of ablative laser systems and intense pulsed light systems. The objective is to achieve selective, heat-induced denaturalisation of dermal collagen that leads to subsequent reactive synthesis but does not damage the epidermis. Recently, the results of numerous clinical and histological studies have indicated that these new technologies are successful. After critical review and assessment of current literature, we can say that in terms of their efficacy, non-ablative methods are not a comparable alternative to ablative skin resurfacing. PMID:12132294

Grema, H; Raulin, C; Greve, B

2002-06-01

346

Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes  

SciTech Connect

Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

Lopez-Arias, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Unidad Asociada Departamento de Quimica Fisica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid, and Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain); Oujja, M.; Sanz, M.; Castillejo, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T. [Institute of Electronics, Uzbekistan Academy of Sciences, Akademgorodok, 33, Dormon Yoli Street, Tashkent 100125 (Uzbekistan)

2012-02-15

347

In situ analysis of steel under reduced ambient pressure by laser-induced breakdown spectroscopy  

Microsoft Academic Search

We report on rapid in-situ analysis of liquid and solid steel samples under reduced ambient pressure by laser-induced breakdown spectroscopy (LIBS) using a transportable system. LIBS denotes a technique where a pulsed laser beam is used to ablate small amounts of the target material. The characteristic optical emission line intensities of the excited species in the laser-generated plasma plume allow

Johannes Heitz; Johann Gruber; Nikita Arnold; Dieter Bäuerle; Norbert Ramaseder; Wilfried Meyer; Johann Hochörtler

2003-01-01

348

Shock pressures induced in condensed matter by laser ablation.  

PubMed

The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m(2). States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the velocity history of the opposite surface. By varying the energy in the laser pulse, relations were inferred between the irradiance and the induced pressure. For samples in vacuo, an irradiance constant in time does not produce a constant pressure. Radiation hydrodynamics simulations were used to investigate the relationship between the precise pulse shape and the pressure history. In this regime of time and irradiance, it was possible to reproduce the experimental data to within their uncertainty by including conductivity-dependent deposition of laser energy, heat conduction, gray radiation diffusion, and three temperature hydrodynamics in the treatment of the plasma, with ionizations calculated using the Thomas-Fermi equation. States induced in the solid sample were fairly insensitive to the details of modeling in the plasma, so Hugoniot points may be estimated from experiments of this type given a reasonable model of the plasma. More useful applications include the generation of dynamic loading to investigate compressive strength and phase transitions, and for sample recovery. PMID:15089414

Swift, Damian C; Tierney, Thomas E; Kopp, Roger A; Gammel, J Tinka

2004-03-01

349

Proton extraction by laser ablation of transition metals  

NASA Astrophysics Data System (ADS)

A study on the proton beams extraction from a plasma generated by pulsed laser ablation by targets containing transition metals is presented. The targets used were pure disks of titanium and tantalum and disks of TiH2, obtained by compression of TiH2 powder. The plasma was produced by means of a nanosecond excimer KrF laser operating at low irradiance (109-1010 W/cm2). The proton and ions emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. Studies on the produced protons and ions at different laser irradiances from 2 to 15 GW/cm2 were performed. The characterization showed that it is possible to obtain good proton fluxes from these targets, up to 1011 proton/pulse. The results obtained are very interesting if compared with those available in literature where proton fluxes per pulse ranging from 108 to 109 by hydride targets were obtained, at the same laser irradiances.

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

2014-07-01

350

Fabrication of Fresnel microlens with excimer laser contour ablation  

NASA Astrophysics Data System (ADS)

Laser micromachining systems based on excimer lasers are usually oriented to work with mask projection regime because of the low pulse repetition rate as well as large beam aperture of the laser source. In case of fabricating of the complex 3D structures, this approach introduces a number of limitations. Alternative solution might be usage of direct writing laser mode. Some examples of the so called contour ablation approach for fabricating microlenses with an absolutely monotonically changing cross-sectional profile are presented in the literature. Based on this idea and introducing new variables like automatic mask selection as well as optimizing process algorithms led us to obtain more versatile method for shape approximation. Hence, there were fabricated structures with cross-sectional profiles described as functions that are monotonic on specified intervals such as Fresnel microlenses. In this paper we describe approximation of process parameters for obtaining desired cross-sectional profiles and finally fabrication of few exemplary microlenses. All structures were characterized by a digital optical microscopy and compared to the given profiles. The accuracy of reproduction of the desired structures at the level of single microns was achieved.

Wójcik, Micha? R.; Anto?czak, Arkadiusz J.; Kozio?, Pawe? E.; ?azarek, ?ukasz K.; Stepak, Bogusz D.; Abramski, Krzysztof M.

2014-08-01

351

Laser ablation of graphite in different buffer gases  

SciTech Connect

The KrF-laser ablation of graphite into 300 Torr of He, Ne, Ar, and Xe has been studied by fast imaging of the plasma emission and post-deposition analyses of collected film deposits. In each case, the soot which was redeposited on the irradiated rod following ablation was highly fullerene-deficient compared to the material collected on the sample disk 1.5 cm from the rod, as determined by laser desorption Fourier Transform Mass Spectrometry (FTMS) Investigation of the plasma plume propagation using fast ICCD photography reveals three main phases to the expansion: (1) forward motion, deceleration and stopping of the leading edge of the plume, (2) an apparent reflected shock within the plume which propagates backward and reflects from the rod surface, (3) coalescence of these two components, resulting in continued expansion and dissipation of the plasma and the appearance of glowing ultrafine particles. For the laser plume propagating in 300 Torr of Xe the characteristic time intervals for these three phases are 0-300 ns, 300-1000 ns, and 1-1000 {mu}s for phases (1), (2), and (3) respectively. The possible explanation of the observed difference in fullerene content is discussed on the basis of different plasma phases resulting in soot deposition on the rod and sample disk. The measurement of ro-vibrational spectra of electronically excited C{sub 2} has been performed. Rotational and vibrational temperatures, T{sub R} = 3000 {+-} 300K and T{sub V} = 6000 {+-} 500K have been obtained from the comparison of measured and calculated C{sub 2} -Swan band emission.

Puretzky, A.A. [Institute of Spectroscopy, Moscow (Russian Federation); Geohegan, D.B.; Haufler, R.E. [Oak Ridge National Lab., TN (United States)] [and others

1996-04-01

352

Silica nano-ablation using laser plasma soft x-rays  

Microsoft Academic Search

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

Tetsuya Makimura; Shuichi Torii; Hiroyuki Niino; Kouichi Murakami

2009-01-01

353

An advanced optical system for laser ablation propulsion in space  

NASA Astrophysics Data System (ADS)

We propose a novel space-based ablation driven propulsion engine concept utilizing transmitted energy in the form of a series of ultra-short optical pulses. Key differences are generating the pulses at the transmitting spacecraft and the safe delivery of that energy to the receiving spacecraft for propulsion. By expanding the beam diameter during transmission in space, the energy can propagate at relatively low intensity and then be refocused and redistributed to create an array of ablation sites at the receiver. The ablation array strategy allows greater control over flight dynamics and eases thermal management. Research efforts for this transmission and reception of ultra-short optical pulses include: (1) optical system design; (2) electrical system requirements; (3) thermal management; (4) structured energy transmission safety. Research has also been focused on developing an optical switch concept for the multiplexing of the ultra-short pulses. This optical switch strategy implements multiple reflectors polished into a rotating momentum wheel device to combine the pulses from different laser sources. The optical system design must minimize the thermal load on any one optical element. Initial specifications and modeling for the optical system are being produced using geometrical ray-tracing software to give a better understanding of the optical requirements. In regards to safety, we have advanced the retro-reflective beam locking strategy to include look-ahead capabilities for long propagation distances. Additional applications and missions utilizing multiplexed pulse transmission are also presented. Because the research is in early development, it provides an opportunity for new and valuable advances in the area of transmitted energy for propulsion as well as encourages joint international efforts. Researchers from different countries can cooperate in order to find constructive and safe uses of ordered pulse transmission for propulsion in future space-based missions.

Bergstue, Grant; Fork, Richard; Reardon, Patrick

2014-03-01

354

Outcome of Endovenous Laser Ablation of Varicose Veins  

PubMed Central

ABSTRACT Introduction: In Bosnia and Herzegovina according to available data, treatment of incompetent superficial lower extremity varicose veins by endovenous laser ablation (EVLA) has been introduced two years ago and so far no paper has been published regarding results of EVLA treatment of patients from our country. We wanted to present our results with EVLA treatment. Aim of study: to evaluate and compare primary posttreatment outcomes of endovenous laser ablation (EVLA) with classical surgical method of varicose vein treatment. Patients and methods: The study was clinical and prospective. It was carried out at Clinic for vascular surgery in Sarajevo where fifty-eight (58) patients received surgical treatment for varicose veins and in Aesthetic Surgery Center “Nasa mala klinika” in Sarajevo were sixty-one (61) patients with varicose veins were treated by endovenous laser ablation. Total 119 patients (limbs) with pathologic reflux only in great saphenous vein were evaluated between 1st of January 2013 and 31st of April 2014. Following primary outcome endpoints were evaluated smean day of return to normal everyday activities, patient subjective quantification of pain during first seven days after intervention, incidence of deep venous thrombosis (DVT), incidence of wound bleeding requiring surgical intervention, incidence of peri-saphenous vein hematoma and infection rate. Results: Mean of return to normal activities (expressed in days after intervention); EVLA vs. stripping (surgery) =1.21vs12.24, T test 13,619; p=0, 000, p<0,05. T test was used for comparing Mean value of visual pain analog scale for the first 7 days between groups, for all seven days pain was significantly higher in surgical group of patients as compared to EVLA group; p<0,05. Incidence of hematoma greater than 1% of total body surface area was significantly higher in patients receiving surgical treatment; Pearson Chi Square=23,830, p<0,05; odds ratio:10,453. Incidences of infection, deep venous thrombosis and posttreatment bleeding were not statistically different between analyzed groups; EVLA vs Surgery (Pearson Chi Square =3,237; p>0,05; Pearson Chi Square=2,139, p>0,05, Pearson Chi Square=2,139, p>0,05, respectively.) Conclusion: EVLA offers better patient recovery in terms of significantly lower post treatment pain, faster return to everyday activities and lower incidence of bruising (hematomas). PMID:25568583

Rustempasic, Nedzad; Cvorak, Alemko; Agincic, Alija

2014-01-01

355

Laser-dye ablation technique for removal of carious dentin and enamel  

NASA Astrophysics Data System (ADS)

A GaAlAs semiconductor diode laser operating at a wavelength of 796 nm has been sued in conjunction with Indocyanine Green (ICG) dye to ablate carious dentin and enamel from extracted human teeth. The laser-dye ablation technique offers selective ablation as it is controlled by the placement of the ICG dye. In contrast with other laser techniques, the risk of collateral thermal damage is substantially reduced. The diode laser is suitable for ordinary fiber delivery and is cheaper and more compact than the higher power CO2; Er:YAG, Nd:YAG and Argon lasers currently being used by researchers. This paper reports the ablation of dental caries in fifty extracted teeth with various laser diode powers and dye concentrations. The mass of material ablated, temperature rise in the pulp and surface temperature were measured. The ablation was found to be efficient with negligible thermal damage to surrounding tissue. At the same time average surface temperatures reached during ablation may be sufficient to sterilize the treated surface. Hardness measurements and scanning electron microscopy of the laser treated cavity surfaces show the new surfaces to be suitable for placement of a dental filling.

McNally-Heintzelman, Karen M.; Gillings, Barrie R.; Dawes, Judith M.

1997-05-01

356

Evaluation of ablation efficiency and surface morphology of human teeth upon irradiation with femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

This study investigates changes in ablation efficiency and surface morphology induced in human dental enamel and dentin upon interaction with femtosecond laser pulses at variable energies and number of laser pulses. Craters were created using a Ti:sapphire femtosecond laser ablation system operating at a wavelength of 785?nm, pulse width of 130?fs, and repetition rate of 20?Hz. Various techniques, such as optical and scanning electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS), were used to evaluate ablation depth, amount of material ablated, and surface morphology of the craters. Ablation rate (ablation depth per pulse) was found to be lower in enamel than dentin with the maximum rate occurring at fluence of 12.4?J?cm?2 in both materials. A drop in ablation rate was observed for fluence greater than 12.4?J?cm?2 and was attributed to attenuation of laser energy due to interaction with the laser-generated particles. Above this fluence, signs of thermal effects, such as melting and formation of droplets of molten material at the sample surface, were observed. The response of the ICP-MS indicated that the amount of ablated material removed from dentin is greater than that removed from enamel by a factor of 1.5 or more at all investigated fluence.

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

2014-11-01

357

Preparation of platinum modified titanium dioxide nanoparticles with the use of laser ablation in water.  

PubMed

We report on the preparation method of nanocrystalline titanium dioxide modified with platinum by using nanosecond laser ablation in liquid (LAL). Titania in the form of anatase crystals has been prepared in a two-stage process. Initially, irradiation by laser beam of a titanium metal plate fixed in a glass container filled with deionized water was conducted. After that, the ablation process was continued, with the use of a platinum target placed in a freshly obtained titania colloid. In this work, characterization of the obtained nanoparticles, based on spectroscopic techniques--Raman, X-ray photoelectron and UV-vis reflectance spectroscopy--is given. High resolution transmission electron microscopy was used to describe particle morphology. On the basis of photocatalytic studies we observed the rate of degradation process of methylene blue (MB) (a model organic pollution) in the presence of Pt modified titania in comparison to pure TiO2--as a reference case. Physical and chemical mechanisms of the formation of platinum modified titania are also discussed here. Stable colloidal suspensions containing Pt modified titanium dioxide crystalline anatase particles show an almost perfect spherical shape with diameters ranging from 5 to 30 nm. The TiO2 nanoparticles decorated with platinum exhibit much higher (up to 30%) photocatalytic activity towards the degradation of MB under UV illumination than pure titania. PMID:24937772

Siuzdak, K; Sawczak, M; Klein, M; Nowaczyk, G; Jurga, S; Cenian, A

2014-08-01

358

Numerical study of the thermal ablation of wet solids by ultrashort laser pulses  

SciTech Connect

The ablation by ultrashort laser pulses at relatively low fluences (i.e., in the thermal regime) of solids wetted by a thin liquid film is studied using a generic numerical model. In comparison with dry targets, the liquid is found to significantly affect ablation by confining the solid and slowing down the expansion of the laser-heated material. These factors affect the relative efficiency of the various ablation mechanisms, leading, in particular, to the complete inhibition of phase explosion at lower fluences, a reduced ablation yield, and significant changes in the composition of the plume. As a consequence, at fluences above the ablation threshold, the size of the ejected nanoclusters is lower in presence of the liquid. Our results provide a qualitative understanding of the effect of wetting layers on the ablation process.

Perez, Danny; Beland, Laurent Karim; Deryng, Delphine; Lewis, Laurent J. [Departement de Physique et Regroupement Quebecois sur les Materiaux de Pointe (RQMP), Universite de Montreal, Case Postal 6128, Succursale Centre-Ville, Montreal, Quebec, H3C 3J7 (Canada); Meunier, Michel [Laboratoire de Procedes par Laser, Departement de Genie Physique et Regroupement Quebecois sur les Materiaux de Pointe (RQMP), Ecole Polytechnique de Montreal, Case Postal 6079, Succursale Centre-Ville, Montreal, Quebec, H3C 3A7 (Canada)

2008-01-01

359

Comparison of silver nanoparticles confined in nanoporous silica prepared by chemical synthesis and by ultra-short pulsed laser ablation in liquid  

NASA Astrophysics Data System (ADS)

Hexagonally ordered mesoporous silica materials, MCM-41 and SBA-15, have been synthesized and loaded with Ag nanoparticles, utilizing both chemical synthesis and ultra-short pulsed laser ablation in liquid. In laser ablation, a silver target, immersed in aqueous suspension of ordered mesoporous silica SBA-15, was irradiated by ultra-short laser pulses to generate silver nanoparticles. For comparison, samples of similar silver contents were prepared either by incorporating silver into the SBA-15 during a hydrothermal synthesis or by introducing silver in MCM-41 by template ion-exchange. Samples were characterized by XRD, N2 physisorption, TEM and UV-vis spectroscopy. All preparations contained significant amount of 5-50 nm size silver agglomerates on the outer surface of the silica particles. The laser ablation process did not cause significant destruction of the SBA-15 structure and metallic silver (Ag0) nanoparticles were mainly generated. It is demonstrated that by laser ablation in aqueous silica suspension smaller and more uniform metallic silver particles can be produced and loaded on the surface of the silica support than by synthesis procedures. Catalytic properties of the samples have been tested in the total oxidation of toluene. Because of its favorable Ag dispersity, the Ag/SBA-15 catalyst, generated by the laser ablation method, had better catalytic stability and, relative to its Ag load, higher activity than the conventional Ag/SBA-15 preparations.

Szegedi, Á.; Popova, M.; Valyon, J.; Guarnaccio, A.; De Stefanis, A.; De Bonis, A.; Orlando, S.; Sansone, M.; Teghil, R.; Santagata, A.

2014-10-01

360

Simulation of Laser Interaction with Ablative Plasma and ydrodynamic of Laser Supported Plasma(LSP)  

NASA Astrophysics Data System (ADS)

A general Godunov finite difference schemes-WENO(Weighted Essentially Non-Oscillatory) Schemes which have fifth-order accuracy was used to make a numerical calculation for 2-dimensional axis symmetrical laser-supported plasma flow field under laser ablated solid target. The models of the calculation of ionization degree of plasma and the interaction between laser beam and plasma and the simplified eos(equation of state) of plasma were considered in the simulation. The plasma field parameters during and after laser duration variation with time are also obtained. The simulation results show that the laser beam power was strong absorbed by plasma of target surface, and the velocity of LSD(Laser Supported Detonation) wave is half of ideal LSD value which derived from C-J detonation theory.

Huifeng, Tong; Zhiping, Tang

2011-06-01

361

Ablation driven by hot electrons generated during the ignitor laser pulse in shock ignition  

SciTech Connect

An analytical model for the ablation driven by hot electrons is presented. The hot electrons are assumed to be generated during the high intensity laser spike used to produce the ignitor shock wave in the shock ignition driven inertial fusion concept, and to carry on the absorbed laser energy in its totality. Efficient energy coupling requires to keep the critical surface sufficiently close to the ablation front and this goal can be achieved for high laser intensities provided that the laser wavelength is short enough. Scaling laws for the ablation pressure and the other relevant magnitudes of the ablation cloud are found in terms of the laser and target parameters. The effect of the preformed plasma assembled by the compression pulse, previous to the ignitor, is also discussed. It is found that a minimum ratio between the compression and the ignitor pulses would be necessary for the adequate matching of the corresponding scale lengths.

Piriz, A. R.; Rodriguez Prieto, G. [E.T.S.I. Industriales, Universidad de Castilla-La Mancha and Instituto de Investigaciones Energeticas, 13071 Ciudad Real (Spain); Tahir, N. A. [GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstrasse 1, 64291 Darmstadt (Germany); Zhang, Y. [School of Physics and Optoelectronic Technology, Dalian University of Technology, 116024 Dalian (China); Liu, S. D.; Zhao, Y. T. [Institute of Modern Physics, Chinese Academy of Science, 730000 Lanzhou (China)

2012-12-15

362

The effect of polarization on ultrashort pulsed laser ablation of thin metal films  

NASA Astrophysics Data System (ADS)

Ultrashort pulse lasers have proven to have superior advantages over conventional continuous wave and long pulse lasers for ablation of thin metal films. Though several investigations have been carried out to understand the phenomena of ultrashort pulse laser machining, the effect of the beam polarization on ablation of thin metal films has been seldom investigated. In this article, we report our recent observations on how the shape of the machined feature and also the damage threshold of the material varies according to the polarization of the ultrashort pulse laser beam. Based on this we have explained how the polarization of the beam controls the laser cutting rate, kerf width, edge quality, and ablation depth of the ablated feature.

Venkatakrishnan, K.; Tan, B.; Stanley, P.; Sivakumar, N. R.

2002-08-01

363

Survey Of CO{sub 2} Laser Ablation Propulsion With Polyoxymethylene Propellant  

SciTech Connect

Polyoxymethylene (POM) has been widely studied as a laser propulsion propellant paired to CO{sub 2} laser radiation. POM is a good test case for studying ablation properties of polymer materials, and within limits, for study of general trends in laser ablation-induced impulse. Despite many studies, there is no general understanding of POM ablation that takes into account the ambient pressure, spot area, fluence, and effects from confinement and combustion. This paper reviews and synthesizes CO{sub 2} laser ablation propulsion research using POM targets. Necessary directions for future study are indicated to address incomplete regions of the various parameter spaces. Literature data is compared in terms of propulsion parameters such as momentum coupling coefficient and specific impulse, within a range of fluences from about 1-500 J/cm{sup 2}, ambient pressures from about 10{sup -2}-10{sup 5} Pa, and laser spot areas from about 0.01-10 cm{sup 2}.

Sinko, John E. [Micro-Nano Global Center of Excellence, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603 (Japan); Sasoh, Akihiro [Department of Aerospace Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603 (Japan)

2010-05-06

364

Fabrication of pillared PLGA microvessel scaffold using femtosecond laser ablation  

PubMed Central

One of the persistent challenges confronting tissue engineering is the lack of intrinsic microvessels for the transportation of nutrients and metabolites. An artificial microvascular system could be a feasible solution to this problem. In this study, the femtosecond laser ablation technique was implemented for the fabrication of pillared microvessel scaffolds of polylactic-co-glycolic acid (PLGA). This novel scaffold facilitates implementation of the conventional cell seeding process. The progress of cell growth can be observed in vitro by optical microscopy. The problems of becoming milky or completely opaque with the conventional PLGA scaffold after cell seeding can be resolved. In this study, PLGA microvessel scaffolds consisting of 47 ?m × 80 ?m pillared branches were produced. Results of cell culturing of bovine endothelial cells demonstrate that the cells adhere well and grow to surround each branch of the proposed pillared microvessel networks. PMID:22605935

Wang, Hsiao-Wei; Cheng, Chung-Wei; Li, Ching-Wen; Chang, Han-Wei; Wu, Ping-Han; Wang, Gou-Jen

2012-01-01

365

Spindle Assembly and Architecture: From Laser Ablation to Microtubule Nucleation  

NASA Astrophysics Data System (ADS)

Spindles are arrays of microtubules that segregate chromosomes during cell division. It has been difficult to validate models of spindle assembly due to a lack of information on the organization of microtubules in these structures. Here we present a novel method, based on femtosecond laser ablation, capable of measuring the detailed architecture of spindles. We used this method to study the metaphase spindle and find that microtubules are shortest near poles and become progressively longer towards the center of the spindle. These data, in combination with mathematical modeling, high resolution imaging, and biochemical perturbations, are sufficient to reject previously proposed mechanisms of spindle assembly. Our results support a new model of spindle assembly in which microtubule polymerization dynamics are not spatially regulated, microtubule transport locally sorts microtubules -- determining their proper organization in the spindle without moving them appreciable distances --, and the profile of microtubule nucleation controls the length of the spindle.

Needleman, Daniel; Brugues, Jan; Nuzzo, Valeria; Mazur, Eric

2012-02-01

366

Thermodynamic modeling of pulsed-laser-induced ablation  

NASA Astrophysics Data System (ADS)

The concept of equilibrium has a fundamental importance in thermodynamics and is related to the reversibility of any chemical and physical process involving a temperature cycle or a phase change. It is of major interest also for the models of high energy beam processing; a recent ablation model has shown that the non-equilibrium character of laser irradiation with pulse lengths ? of the order of some ns is essential to understand the mechanisms of thermal sputtering, in particular when overheating of a molten layer of metal surface is allowed to occur. It is known in fact that if the heating or surface recession rates overcome the nucleation rate of vapor bubbles, then the surface temperature Ts of the molten layer can increase above the thermodynamic boiling point Tb. This situation entails by consequence the rising of a temperature gradient within the boiling layer, whose thickness ? is controlled by the condition T >= Tb.

Tosto, Sebastiano

2003-04-01

367

Synthesis of stable silver colloids by laser ablation in water  

NASA Astrophysics Data System (ADS)

The stable colloid with silver nanoparticles has been produced by irradiation of metal target in deionized water by pulse 1064 nm laser. The dependences of the nanoparticle size and colloid stability on fluence, ablation time, surface conditions of the target, and thickness of the water layer have been studied. The sizes and shape of nanoparticles have been measured by dynamic light scattering and by scanning electron microscopy. It has been shown that decrease of the water layer thickness above the target surface leads to increase of the colloid stability. The proper number of treatment cycles allowed to prepare the target surface for production of the nanoparticles with average size about 34 nm obtained by statistical analysis of the scanning electron microscope images. Several methods have been used to increase the colloid stability: (1) increase of the laser fluence, (2) decrease of the water layer thickness above the target surface, (3) the treatment of the target surface by laser beam scanning. The subsequent increase of the colloid concentration by partial drying slightly enhanced the nanoparticle size. The optimized synthesis conditions and drying parameters allowed to produce the pure colloid with concentration about 0.5 g/l and stability over a month of almost spherical silver nanoparticles with typical size 45±5 nm.

Tyurnina, Anastasiya E.; Shur, Vladimir Y.; Kozin, Roman V.; Kuznetsov, Dmitry K.; Mingaliev, Evgeny A.

2013-11-01

368

Monitoring of tumor radio frequency ablation using derivative spectroscopy  

NASA Astrophysics Data System (ADS)

Despite the widespread use of radio frequency (RF) ablation, an effective way to assess thermal tissue damage during and after the procedure is still lacking. We present a method for monitoring RF ablation efficacy based on thermally induced methemoglobin as a marker for full tissue ablation. Diffuse reflectance (DR) spectra were measured from human blood samples during gradual heating of the samples from 37 to 60, 70, and 85°C. Additionally, reflectance spectra were recorded real-time during RF ablation of human liver tissue ex vivo and in vivo. Specific spectral characteristics of methemoglobin were extracted from the spectral slopes using a custom optical ablation ratio. Thermal coagulation of blood caused significant changes in the spectral slopes, which is thought to be caused by the formation of methemoglobin. The time course of these changes was clearly dependent on the heating temperature. RF ablation of liver tissue essentially led to similar spectral alterations. In vivo DR measurements confirmed that the method could be used to assess the degree of thermal damage during RF ablation and long after the tissue cooled.

Spliethoff, Jarich W.; Tanis, Erik; Evers, Daniel J.; Hendriks, Benno H. W.; Prevoo, Warner; Ruers, Theo J. M.

2014-09-01

369

Growth rate and the cutoff wavelength of the Darrieus-Landau instability in laser ablation  

SciTech Connect

The main characteristics of the linear Darrieus-Landau instability in the laser ablation flow are investigated. The dispersion relation of the instability is found numerically as a solution to an eigenvalue stability problem, taking into account the continuous structure of the flow. The results are compared to the classical Darrieus-Landau instability of a usual slow flame. The difference between the two cases is due to the specific features of laser ablation: sonic velocities of hot plasma and strong temperature dependence of thermal conduction. It is demonstrated that the Darrieus-Landau instability in laser ablation is much stronger than in the classical case. In particular, the maximum growth rate in the case of laser ablation is about three times larger than that for slow flames. The characteristic length scale of the Darrieus-Landau instability in the ablation flow is comparable to the total distance from the ablation zone to the critical zone of laser light absorption. The possibility of experimental observations of the Darrieus-Landau instability in laser ablation is discussed.

Modestov, Mikhail; Bychkov, Vitaly; Valiev, Damir; Marklund, Mattias [Department of Physics, Umeaa University, 901 87 Umeaa (Sweden)

2009-10-15

370

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Laser ablation plume dynamics in nanoparticle synthesis  

NASA Astrophysics Data System (ADS)

The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO2 laser pulse with a duration of ~500 ?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 ?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 (~10 ?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.

Osipov, V. V.; Platonov, V. V.; Lisenkov, V. V.

2009-06-01

371

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

PubMed

Pulsed mid-infrared (6.45 microm) radiation has been shown to cut soft tissue with minimal collateral damage (<40 microm); 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 tissue with minimal collateral damage. The effect of the picosecond micropulse was examined by running the native FEL pulse structure through a pulse stretcher in order to increase the micropulse length from 1 ps up to approximately 200 ps. This allowed us to determine whether or not the picosecond train of micropulses played any role in the ablation process. The ablation threshold was determined for water and mouse dermis for each micropulse length. While the results of the analysis showed a statistically significant difference between 1 and 200 ps, the average per cent difference amounts to only 28% and is not proportional to the 200-fold drop in peak irradiance. The ablation efficiency was also measured on gelatin and mouse dermis for the different micropulse lengths. A small but statistically significant difference was observed between 1 and 200 ps, with the 200 ps pulse being more efficient on gelatin, and with the opposite trend for mouse dermis. We have shown that there is a small effect of micropulse duration of the FEL on the ablation process; however, this effect is negligible between 1 and 200 ps given that there is a 200-fold decrease in peak intensity. These results suggest that as we move forward in developing alternative laser sources for tissue ablation to replace the FEL, the picosecond micropulse structure is not a critical parameter that needs to be duplicated. PMID:15815101

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

2005-04-21

372

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

NASA Astrophysics Data System (ADS)

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 tissue with minimal collateral damage. The effect of the picosecond micropulse was examined by running the native FEL pulse structure through a pulse stretcher in order to increase the micropulse length from 1 ps up to ~200 ps. This allowed us to determine whether or not the picosecond train of micropulses played any role in the ablation process. The ablation threshold was determined for water and mouse dermis for each micropulse length. While the results of the analysis showed a statistically significant difference between 1 and 200 ps, the average per cent difference amounts to only 28% and is not proportional to the 200-fold drop in peak irradiance. The ablation efficiency was also measured on gelatin and mouse dermis for the different micropulse lengths. A small but statistically significant difference was observed between 1 and 200 ps, with the 200 ps pulse being more efficient on gelatin, and with the opposite trend for mouse dermis. We have shown that there is a small effect of micropulse duration of the FEL on the ablation process; however, this effect is negligible between 1 and 200 ps given that there is a 200-fold decrease in peak intensity. These results suggest that as we move forward in developing alternative laser sources for tissue ablation to replace the FEL, the picosecond micropulse structure is not a critical parameter that needs to be duplicated.

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

2005-04-01

373

Laser-solid interaction and dynamics of the laser-ablated materials  

SciTech Connect

Rapid transformations through the liquid and vapor phases induced by laser-solid interactions are described by the authors` thermal model with the Clausius-Clapeyron equation to determine the vaporization temperature under different surface pressure condition. Hydrodynamic behavior of the vapor during and after ablation is described by gas dynamic equations. These two models are coupled. Modeling results show that lower background pressure results lower laser energy density threshold for vaporization. The ablation rate and the amount of materials removed are proportional to the laser energy density above its threshold. The authors also demonstrate a dynamic source effect that accelerates the unsteady expansion of laser-ablated material in the direction perpendicular to the solid. A dynamic partial ionization effect is studied as well. A self-similar theory shows that the maximum expansion velocity is proportional to c{sub s}{alpha}, where 1 {minus} {alpha} is the slope of the velocity profile. Numerical hydrodynamic modeling is in good agreement with the theory. With these effects, {alpha} is reduced. Therefore, the expansion front velocity is significantly higher than that from conventional models. The results are consistent with experiments. They further study how the plume propagates in high background gas condition. Under appropriate conditions, the plume is slowed down, separates with the background, is backward moving, and hits the solid surface. Then, it splits into two parts when it rebounds from the surface. The results from the modeling will be compared with experimental observations where possible.

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

1995-07-01

374

Laser hydrothermal reductive ablation of titanium monoxide: Hydrated TiO particles with modified Ti/O surface  

SciTech Connect

IR laser- and UV laser-induced ablation of titanium monoxide (TM) in hydrogen (50 Torr) is compared to the same process induced in vacuum and shown to result in deposition of hydrated surface modified nanostructured titanium suboxide films. Complementary analyses of the films deposited in vacuum and in hydrogen by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, X-ray diffraction and electron microscopy allowed to determine different features of both films and propose a mechanism of surface modification of ejected particles, which involves hydrothermal reduction of TM and subsequent reactions of evolved water. The films exert good adhesion to metal and quartz surfaces and are hydrophobic in spite of having their surface coated with adsorbed water. - Graphical abstract: Laser ablation of titanium monoxide (TiO) in hydrogen involves a sequence of H{sub 2} and H{sub 2}O eliminations and additions and yields hydrated amorphous nanostructured titanium suboxide which is richer in oxygen than TiO. Highlights: Black-Right-Pointing-Pointer IR and UV laser ablated particles of titanium monoxide (TiO) undergo amorphization. Black-Right-Pointing-Pointer Films deposited in vacuum have TiO stoichiometry and are oxidized in atmosphere. Black-Right-Pointing-Pointer Films deposited in hydrogen are hydrated and have more O in topmost layers. Black-Right-Pointing-Pointer Films modification in hydrogen is explained by reactions in hydrogen plasma.

Blazevska-Gilev, Jadranka [Laboratory of Laser Chemistry, Institute of Chemical Process Fundamentals, ASCR, Prague 16502 (Czech Republic); University St.Cyril and Methodious, Skopje 1000, Former Yugoslav Republic of Macedonia (Macedonia, The Former Yugoslav Republic of); Jandova, Vera [Laboratory of Laser Chemistry, Institute of Chemical Process Fundamentals, ASCR, Prague 16502 (Czech Republic); Kupcik, Jaroslav [Laboratory of Laser Chemistry, Institute of Chemical Process Fundamentals, ASCR, Prague 16502 (Czech Republic); Institute of Inorganic Chemistry, ASCR, Rez 25068 (Czech Republic); Bastl, Zdenek [J. Heyrovsky Institute of Physical Chemistry, ASCR, Prague 18223 (Czech Republic); Subrt, Jan; Bezdicka, Petr [Institute of Inorganic Chemistry, ASCR, Rez 25068 (Czech Republic); Pola, Josef, E-mail: pola@icpf.cas.cz [Laboratory of Laser Chemistry, Institute of Chemical Process Fundamentals, ASCR, Prague 16502 (Czech Republic)

2013-01-15

375

Femtosecond Laser Ablation Enhances Cell Infiltration into Three-Dimensional Electrospun Scaffolds  

PubMed Central

Electrospun scaffolds are used extensively in tissue engineering applications since they offer a cell-friendly microenvironment. However, one major limitation is the dense fibers, small pore size and consequently poor cell infiltration. Here, we employ a femtosecond (FS) laser system to ablate and create microscale features on electrospun poly(L-lactide) (PLLA) nanofibrous scaffolds. Upon determining the ablation parameters, we pattern structured holes of varying diameters of 50, 100, and 200 ?m and spacing of 50 and 200 ?m between adjacent holes on the scaffolds. The elastic moduli of ablated scaffolds decrease with the decrease of spacing and the increase of hole size. Cells seeded on the laser-ablated scaffolds exhibit different morphology but similar proliferation rate when compared with control (non-ablated) scaffold. Furthermore, animal studies indicate that ablated scaffolds facilitate endothelial cell ingrowth as well as drastically increase M2 macrophage and overall cell infiltration. These findings demonstrate that FS laser ablation can be used to increase cell infiltration into nanofibrous scaffolds. Laser ablation not only can create desired features in micrometer length scale but also presents a new approach in the fabrication of three-dimensional porous constructs for tissue engineering. PMID:22522128

Lee, Benjamin Li-Ping; Jeon, Hojeong; Wang, Aijun; Yan, Zhiqiang; Yu, Jian; Grigoropoulos, Costas; Li, Song

2012-01-01

376

Analysis of soft tissue ablation using the pulse stretched free electron laser  

Microsoft Academic Search

The Mark-III Free Electron Laser (FEL), tuned to 6.45 microns in wavelength has been demonstrated to provide for efficient ablation in ocular, neural, and dermal tissues with minimal collateral damage. To date, the role of the unique pulse structure of the FEL on the ablation mechanism has not been determined. In this study, the native pulse structure of the FEL,

Mark A. Mackanos; John A. Kozub; Darrel L. Ellis; E. Duco Jansen

2005-01-01

377

Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion  

SciTech Connect

We have investigated the dynamics of the nanosecond laser ablated plasma within and after the laser pulse irradiation using fast photography. A 1064 nm, 15 ns laser beam was focused onto a target made from various materials with an energy density in the order of J/mm{sup 2} in atmosphere. The plasma dynamics during the nanosecond laser pulse were observed, which could be divided into three stages: fast expansion, division into the primary plasma and the front plasma, and stagnation. After the laser terminated, a critical moment when the primary plasma expansion transited from the shock model to the drag model was resolved, and this phenomenon could be understood in terms of interactions between the primary and the front plasmas.

Wu, Jian; Wei, Wenfu; Li, Xingwen; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Shaanxi 710049 (China)] [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Shaanxi 710049 (China)

2013-04-22

378

NANOSTRUCTURES: Formation of nanostructures upon laser ablation of silver in liquids  

NASA Astrophysics Data System (ADS)

The formation of a dense array of nanospikes is studied upon ablation of a silver target immersed into water or ethanol by 350-ps pulses from a neodymium laser. The average height of nanospikes is 50 nm and their density amounts to 1010cm-2. The irradiated surface is studied by using reflection spectroscopy in the 200-600-nm range and an atomic force microscope. Small lateral dimensions of nanospikes confine plasmon oscillations of electrons, which is manifested in the colouring of the irradiated surface. The plasmon resonance of nanospikes is observed at 380 nm and shifts to the visible region upon oxidation in air. The initial spectrum of nanospikes is recovered after processing of their oxidised surface in an aqueous solution of ammonium. The use of nanospikes for observing surface enhanced Raman scattering is discussed.

Zavedeev, E. V.; Petrovskaya, A. V.; Simakin, Aleksandr V.; Shafeev, Georgii A.

2006-10-01

379

Spectroscopic study of emission coal mineral plasma produced by laser ablation  

NASA Astrophysics Data System (ADS)

Spectroscopic analysis of plasma produced by laser ablation of coal samples using 1064 nm radiation pulses from a Q-switched Nd:YAG on different target under air ambient, was performed. The emission of molecular band systems such as C2 Swan System (d3?g?a3?u), the First Negative System N2 (Band head at 501,53 nm) and emission lines of the C I, C II, were investigated using the optical emission spectroscopy technique. The C2 molecular spectra (Swan band) were analyzed to determine vibrational temperature (0,62 eV); the density and electron temperature of the plasma have been evaluated using Stark broadening and the intensity of the nitrogen emission lines N II, the found values of 1,2 eV and 2,2 x1018 cm-3 respectively.

Vera, L. P.; Pérez, J. A.; Riascos, H.

2014-05-01

380

Effect of ablation parameters on infrared pulsed laser deposition of poly(ethylene glycol) films  

NASA Astrophysics Data System (ADS)

Polymer thin films were deposited by laser ablation using infrared radiation both resonant (2.90, 3.40, 3.45, and 8.96 mum) and nonresonant (3.30, 3.92, and 4.17 mum) with vibrational modes in the starting material, polyethylene glycol. The chemical structure of the films was characterized by Fourier transform infrared spectroscopy, while the molecular weight distribution was investigated using gel permeation chromatography. The films deposited by resonant irradiation are superior to those deposited with nonresonant radiation with respect to both the chemical structure and the molecular weight distribution of the films. However, the molecular-weight distributions of films deposited at nonresonant infrared wavelengths show marked polymer fragmentation. Fluence and wavelength dependence studies show that the effects may be related to the degree of thermal confinement, and hence to the relative absorption strengths of the targeted vibrational modes.

Bubb, Daniel M.; Papantonakis, M. R.; Toftmann, B.; Horwitz, J. S.; McGill, R. A.; Chrisey, D. B.; Haglund, R. F., Jr.

2002-06-01

381

Ablation of metal thin films using femtosecond laser Bessel vortex beams  

NASA Astrophysics Data System (ADS)

Femtosecond lasers can provide submicron ablation resolution, making them suitable and attractive for various micro/nanofabrication applications. Laser beam shaping lends further advantages and increases the versatility of these sources. In this work, we report on the use of femtosecond laser pulses with first-order Bessel function (Bessel vortex) beam profiles in ablation of metal thin films. The diffraction-free nature of Bessel beams provides significant convenience regarding alignment and repeatability. Ablation profiles with Bessel vortex beams generally consist of single or multiple concentric rings, determined by pulse fluence on target. We investigate single-pulse ablation behavior with two laser wavelengths (1,030 and 515 nm) and three different Bessel beam cone angles. For each case, we measure inner and outer ring diameters and compare our results with theoretical calculations.

Sahin, Ramazan; Ersoy, Tansu; Akturk, Selcuk

2015-01-01

382

Bioavailable nanoparticles obtained in laser ablation of a selenium target in water  

NASA Astrophysics Data System (ADS)

The process of producing colloidal solutions of selenium nanoparticles in water using the laser ablation method is described. The prospects of using nanoparticles of elementary selenium as a nutrition source of this microelement are discussed.

Kuzmin, P. G.; Shafeev, Georgii A.; Voronov, Valerii V.; Raspopov, R. V.; Arianova, E. A.; Trushina, E. N.; Gmoshinskii, I. V.; Khotimchenko, S. A.

2012-11-01

383

Resonant effects in nonlinear photon absorption during femtosecond laser ablation of Nd-doped silicate glass.  

PubMed

This study investigates the resonant effects in nonlinear photon absorption in femtosecond laser ablation of Nd-doped silicate glass (Nd:glass). During the femtosecond laser ablation process, the resonant ablation threshold fluence is decreased by up to 40% compared with that of ordinary ablation. However, it is found that the resonant effect is closely related with laser intensity, and lower laser intensities are required to achieve a significant enhancement. When the intensity is lower than 2.28×10(14) W/cm(2) at which multiphoton ionization dominates, resonant effect is enhanced by a factor of 1.4 to 4.4. When the intensity is higher than 2.28×10(14) W/cm(2), at which intensity tunnel ionization dominates, the resonant effect becomes weak and gradually fades away. It is shown that the resonant effect is still important for multiphoton ionization yet insignificant for tunnel ionization. PMID:23052083

Zhao, Yadong; Jiang, Lan; Fang, Juqiang; Chen, Qianghua; Li, Xiaowei; Lu, Yongfeng

2012-10-10

384

Bioavailable nanoparticles obtained in laser ablation of a selenium target in water  

SciTech Connect

The process of producing colloidal solutions of selenium nanoparticles in water using the laser ablation method is described. The prospects of using nanoparticles of elementary selenium as a nutrition source of this microelement are discussed. (nanoparticles)

Kuzmin, P G; Shafeev, Georgii A; Voronov, Valerii V; Raspopov, R V; Arianova, E A; Trushina, E N; Gmoshinskii, I V; Khotimchenko, S A

2012-11-30

385

ORIGINAL ARTICLE Ultrashort pulsed laser ablation and stripping  

E-print Network

irradiation was found to be 0.54. Histological examination showed no thermal damage with single line ablation. Even with multiline ablation, thermal damage was insignificant and the lateral damage zone correction, microsurgery, and biomedical imaging [1]. Compared to thermal ablation and thermal therapies [2

Guo, Zhixiong "James"

386

A theoretical study of the effect of optical properties in laser ablation of tissue  

SciTech Connect

The role of optical properties in the distribution of laser light and the resulting thermodynamic processes in biological tissue is studied from a theoretical perspective. Light distribution is modeled by a discrete ordinate method and heat transfer and ablation is modeled by an immobilized finite element method. The effect of parametric variation of absorption, scattering anisotropicity on the dynamics of the ablation process is examined. The manifestation of higher than the ablation threshold temperature in the subsurface tissue is observed and discussed. Results indicate significant differences in the ablation behavior which may have important clinical implications.

Rastegar, S.; Motamedi, M.; Welch, A.J.; Hayes, L.J.

1989-12-01

387

A theoretical study of the effect of optical properties in laser ablation of tissue.  

PubMed

The role of optical properties in the distribution of laser light and the resulting thermodynamic processes in biological tissue is studied from a theoretical perspective. Light distribution is modeled by a discrete ordinate method and heat transfer and ablation is modeled by an immobilized finite element method. The effect of parametric variation of absorption, scattering anisotropicity on the dynamics of the ablation process is examined. The manifestation of higher than the ablation threshold temperature in the subsurface tissue is observed and discussed. Results indicate significant differences in the ablation behavior which may have important clinical implications. PMID:2606493

Rastegar, S; Motamedi, M; Welch, A J; Hayes, L J

1989-12-01

388

Preclinical Assessment of a 980-nm Diode Laser Ablation System in a Large Animal Tumor Model  

PubMed Central

Purpose To characterize the performance of a 980-nm diode laser ablation system in an in vivo tumor model. Materials and Methods This study was approved by the Institutional Animal Care and Use Committee. The ablation system consisted of a 15-W, 980-nm diode laser, flexible diffusing tipped fiber optic, and 17-gauge internally cooled catheter. Ten immunosuppressed dogs were inoculated subcutaneously with canine transmissible venereal tumor fragments in eight dorsal locations. Laser ablations were performed at 79 sites where inoculations were successful (99%) using powers of 10 W, 12.5 W, and 15 W, with exposure times between 60 and 180 seconds. In 20 cases, multiple overlapping ablations were performed. After the dogs were euthanized, the tumors were harvested, sectioned along the applicator track, measured and photographed. Measurements of ablation zone were performed on gross specimen. Histopathology and viability staining was performed using hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide hydrogen (NADH) staining. Results Gross pathology confirmed well-circumscribed ablation zone with sharp boundaries between thermally ablated tumor in the center surrounded by viable tumor tissue. When a single applicator was used, the greatest ablation diameters ranged from 12 mm at the lowest dose (10 W, 60 sec) to 26 mm at the highest dose (15 W, 180 sec). Multiple applicators created ablation zones of up to 42 mm in greatest diameter (with the lasers operating at 15 W for 120 sec). Conclusions The new 980-nm diode laser and internally cooled applicator effectively creates large ellipsoid thermal ablations in less than 3 minutes. PMID:20346883

Ahrar, Kamran; Gowda, Ashok; Javadi, Sanaz; Borne, Agatha; Fox, Matthew; McNichols, Roger; Ahrar, Judy U.; Stephens, Clifton; Stafford, R. Jason

2010-01-01

389

KrF laser-induced ablation and patterning of Y--Ba--Cu--O films  

SciTech Connect

The ablation and patterning of Y--Ba--Cu--O films on (100) SrTiO{sub 3} and (100) MgO substrates by KrF excimer-laser light projection was investigated. Three different regimes of laser-material interactions were observed. Transition temperatures and critical current densities in laser-fabricated strip lines were investigated.

Heitz, J.; Wang, X.Z.; Schwab, P.; Baeuerle, D. (Angewandte Physik, Johannes-Kepler-Universitaet Linz, A-4040 Linz (Austria)); Schultz, L. (Siemens AG, Research Laboratories, D-8520 Erlangen (Germany))

1990-09-01

390

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 the morphology of borosilicate glass surface machined by femtosecond laser pulses. Our observations show- fers a single-step method for direct writing of microchan- nels in glass [3­6]. Using this laser

Harkin, Anthony

391

Excimer laser ablation for spatially controlled protein patterns  

NASA Astrophysics Data System (ADS)

Two-dimensional control over the location of proteins on surfaces is desired for a number of applications including diagnostic tests and tissue engineered medical devices. Many of these applications require patterns of specific proteins that allow subsequent two-dimensionally controlled cell attachment. The ideal technique would allow the deposition of specific protein patterns in areas where cell attachment is required, with complete prevention of unspecific protein adsorption in areas where cells are not supposed to attach. In our study, collagen I was used as an example for an extracellular matrix protein known to support the attachment of bovine corneal epithelial cells. An allylamine plasma polymer was deposited on a silicon wafer substrate, followed by grafting of poly(ethylene oxide). Two-dimensional control over the surface chemistry was achieved using a 248 nm excimer laser. Results obtained by XPS and AFM show that the combination of extremely low-fouling surfaces with excimer laser ablation can be used effectively for the production of spatially controlled protein patterns with a resolution of less than 1 micrometers . Furthermore, it was shown that bovine corneal epithelial cell attachment followed exactly the created protein patterns. The presented method is an effective tool for a number of in vitro and in vivo applications.

Thissen, Helmut; Hayes, Jason P.; Kingshott, Peter; Johnson, Graham; Harvey, Erol C.; Griesser, Hans J.

2001-11-01

392

Particle formation by infrared laser ablation of MALDI matrix compounds.  

PubMed

The concentration and size distribution of particles ablated from the infrared matrix-assisted laser desorption/ionization matrix compounds succinic acid (butanedioic acid), ?-cyano-4-hydroxycinnamic acid, and glycerol were measured using an aerodynamic particle sizer combined with a scanning mobility particle sizer. The two sizing instruments together had a sizing range to from 10?nm to 20?µm. Thin layers of the matrix compounds were irradiated with fluences between 6.0 and 9.5?kJ/m(2) and wavelengths between 2.8 and 3.0?µm. The distribution of particles was characterized by a large concentration of clusters in the 20-nm-diameter range and large component of mass in the range of coarse particle with diameters greater than 1?µm. The wavelength dependence revealed a blue shift for the maximum particle production that is attributed to heating and disruption of the hydrogen bonds in the matrix that shifts the absorption to shorter wavelengths. This blue shift has been observed previously in infrared matrix-assisted laser desorption/ionization. PMID:25044838

Musapelo, Thabiso; Murray, Kermit K

2014-07-01

393

Fundamentals of femtosecond laser ablation of dielectric materials  

SciTech Connect

The modeling of laser-excited dielectric materials requires a detailed description of the electronic excitation. Dielectric materials do not absorb visible light by traditional linear absorption, so the dynamical generation of conduction-band electrons strongly couples to the absorption. The generation of free electrons is initiated by strong-field excitation and followed by multiplication through impact ionization by energetic electrons heated by the laser. The present paper describes an approach to solving the coupled problem of electron excitation and one-dimensional light propagation. The electronic excitation is described in the so-called multiple-rate-equation model, and the light is absorbed by a combination of strong-field excitation and linear absorption by the excited electrons, which are assumed to behave as a free-electron gas described by a Drude model. The model is generic and based on a few key parameters: the wavelength and the pulse duration of the light, and the band gap of the dielectric medium. This allows parametric investigations of ablation phenomena.

Byskov-Nielsen, J.; Le, D. Q. S.; Christensen, M. N.; Balling, P. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Christensen, B. H. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus C (Denmark)

2010-10-08

394

A Laser Ablation Method for the Synthesis of Crystalline Semiconductor Nanowires  

Microsoft Academic Search

A method combining laser ablation cluster formation and vapor-liquid-solid ( VLS) growth was developed for the synthesis of semiconductor nanowires. In this process, laser ablation was used to prepare nanometer-diameter catalyst clusters that define the size of wires produced by VLS growth. This approach was used to prepare bulk quantities of uniform single-crystal silicon and germanium nanowires with diameters of

Alfredo M. Morales; Charles M. Lieber

1998-01-01

395

Near threshold femtosecond laser interactions with materials: Ablation thresholds, morphologies, and dynamics  

Microsoft Academic Search

This dissertation reports the results of femtosecond (fs, 10-15 seconds) laser ablation studies performed on single crystal silicon with oxide thin films and the single crystal Ni-based superalloy, CMSX-4. Emphasis is placed on near threshold ablation (or material removal) phenomena where fs pulsed lasers show significant promise for industrial machining, characterization, materials processing, fabrication of structures, and other applications. Three

Joel P. McDonald

2007-01-01

396

Dentin bond strength after ablation using a CO2 laser operating at high pulse repetition rates  

Microsoft Academic Search

Pulsed CO2 lasers show great promise for the rapid and efficient ablation of dental hard tissues. Our objective was to demonstrate that CO2 lasers operated at high repetition rates can be used for the rapid removal of dentin without excessive thermal damage and without compromising adhesion to restorative materials. Human dentin samples (3x3mm2) were rapidly ablated with a pulsed CO2

Saba Hedayatollahnajafi; Michal Staninec; Larry Watanabe; Chulsung Lee; Daniel Fried

2009-01-01

397

Measurement of ablative laser propulsion parameters for aluminum, Co-Ni ferrite and polyurethane polymer  

NASA Astrophysics Data System (ADS)

Laser ablation propulsion is a form of beam-powered propulsion in which a pulsed laser ablates a target material thus producing thrust. We report in this work the measurements of various parameters related to laser-induced micropropulsion in toluene diisocyanate-based polyurethane polymer, aluminum and Co-Ni ferrite. The targets were irradiated by a Q-switched pulsed Nd-YAG laser at 1064 nm (pulse duration 5 ns) under atmospheric conditions. A contact-free optical triangulation method was used to measure the laser ablation induced thrust in the samples. The measurements and calculations depict that Co-Ni ferrite is better in terms of critical propulsion parameters C m and I sp. It has been observed that the propulsion parameters depend on the energy per pulse of the incident laser beam.

Jamil, Yasir; Saeed, Humaima; Raza Ahmad, M.; Ahmad Khan, Shakeel; Farooq, Hashim; Shahid, Muhammad; Zia, K. M.; Amin, Nasir

2013-01-01

398

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

399

Local wettability tuning with laser ablation redeposits on PDMS  

NASA Astrophysics Data System (ADS)

In this paper, we present a method to locally control the wettability behavior of PDMS surfaces by excimer laser ablation. In the ablation process, a micrometer scale roughness is formed in the irradiated regions while a nanometer scale roughness is formed by the redeposits surrounding the irradiated regions. The increase in surface roughness results in a change of the wettability behavior of the PDMS surface. By using a hexagonal pattern and tuning the patterning pitch, two different wetting behaviors were realized. A pitch smaller than 300 ?m resulted in a superhydrophobic surface with an advancing contact angle of ?adv = 165° and a receding contact angle of ?rec = 160°. A pitch between 300 and 500 ?m resulted in a sticky superhydrophobic surface with ?adv = 120-150° and ?rec = 80°. The contact angle hysteresis for the latter was larger than for untreated PDMS resulting in very sticky surfaces with high sliding angles. This gives the method great versatility since the two wetting behaviors are very different. By combining both behaviors, local surface features like pinning sites, non-wetting sites, barriers and guides can all be fabricated by a single method. As an application demonstrator of the method, we show that drops can be caught and released depending on size and tilting angle by creating slippery surfaces with sticky barriers. Additionally, the method is ideal for rapid prototyping as it consist of only a single step. It is a direct write method requiring no lithographic mask. Also the process works in ambient atmosphere, so it can be used for temperature or pressure sensitive applications.

van Pelt, Stijn; Frijns, Arjan; Mandamparambil, Rajesh; den Toonder, Jaap

2014-06-01

400

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

NASA Astrophysics Data System (ADS)

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

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

1998-06-01

401

Dynamics of ultrashort pulsed laser radiation induced non-thermal ablation of graphite  

NASA Astrophysics Data System (ADS)

We report on the dependence of a laser radiation induced ablation process of graphite on the applied pulse duration of ultrashort pulsed laser radiation smaller than 4 ps. The emerging so-called non-thermal ablation process of graphite has been confirmed to be capable to physically separate ultrathin graphitic layers from the surface of pristine graphite bulk crystal. This allows the deposition of ablated graphitic flakes on a substrate in the vicinity of the target. The observed ablation threshold determined at different pulse durations shows a modulation, which we ascribe to lattice motions along the c axis that are theoretically predicted to induce the non-thermal ablation process. In a simple approach, the ablation threshold can be described as a function of the energy penetration depth and the absorption of the applied ultrashort pulsed laser radiation. Based on the analysis of the pulse duration dependence of those two determining factors and the assumption of an invariant ablation process, we are able to reproduce the pulse duration dependence of the ablation threshold. Furthermore, the observed pulse duration dependences confirm the assumption of a fast material specific response of graphite target subsequent to optical excitation within the first 2 ps.

Reininghaus, M.; Kalupka, C.; Faley, O.; Holtum, T.; Finger, J.; Stampfer, C.

2014-12-01

402

Comparison of High Rate Laser Ablation and Resulting Structures Using Continuous and Pulsed Single Mode Fiber Lasers  

NASA Astrophysics Data System (ADS)

This paper compares high rate laser ablation and resulting structures of aluminum by using both a continuous wave and a ns-pulsed single mode fiber laser of high average laser power. Two different scan technologies were applied for fast deflection of the laser beams. In this work, 2.5D laser processing was studied by using a high aperture galvanometer scanner with a maximum scan speed of 18 m/s. By contrast, considerably higher scan speeds up to 1,000 m/s were achieved by using the in-house developed polygon scanner system. The ablation rates and the processing rates per unit area were analyzed by means of the depths of line-scan ablation tracks and laser processed cavities. In addition, SEM photograph of the machining samples will be presented in order to evaluate the machining quality. Finally the feasibility of this high rate technology for industrial application is demonstrated by machining examples.

Knebel, T.; Streek, A.; Exner, H.

403

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

PubMed Central

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

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

2014-01-01

404

Bubble formation induced by nanosecond laser ablation in water and its diagnosis by optical transmission technique  

NASA Astrophysics Data System (ADS)

In this paper, bubble formation and ablation rate in laser ablation of a thin-film aluminum target are studied. The target was an aluminum thin-film coated on a quartz substrate and interacted by a nanosecond Nd:YAG laser beam in ambient air and distilled water. Measuring optical transmission of a He-Ne beam through the ablation region shows that the ablation rate in water is higher than that in ambient air. The results also show that an initial peak appears in the transmission signal which is an evidence for bubble formation in water. Analyzing the data is useful for monitoring the bubble formation in water and relatively estimating the ablation rate.

Mahdieh, M. H.; Akbari Jafarabadi, M.

2014-09-01

405

Ablation dynamics and shock wave expansion during laser processing of CFRP with ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

Carbon fibre reinforced plastics (CFRP) have a large potential in the automotive lightweight construction due to their low density and high mechanical stability. Compared with today's laser processing methods of metals the main issues in laser processing of CFRP are the very differing thermal, optical and mechanical properties of the components. To understand the process in detail, the ablation process of CFRP with ultrashort laser pulses was investigated. The shock wave and the vapor resulting from processing with single laser pulses were recorded. Shadow photography and luminescence photography with an ultra-high-speed camera was used to show the ablation process with a temporary resolution of up to 3 ns. The field of view was 250 ?m × 250 ?m. An ultrashort laser pulse with pulse duration of 4 ps and a wavelength of 800 nm was focused onto the workpiece. The energy content of the shock wave was calculated from the resulting images. The energy content of the shock wave was about 20 % of the incident energy and the speed of propagation of the shock wave was more than 2000 m/s. The high intensities in the range of 1013 W/cm2 lead to formation of a plasma plume which was clearly seen in the shadow photography images.

Wiedenmann, Margit; Haist, Christoph; Freitag, Christian; Onuseit, Volkher; Weber, Rudolf; Graf, Thomas

2014-03-01

406

Laser-launched flyer plate and confined laser ablation for shock wave loading: Validation and applications  

NASA Astrophysics Data System (ADS)

We present validation and some applications of two laser-driven shock wave loading techniques: laser-launched flyer plate and confined laser ablation. We characterize the flyer plate during flight and the dynamically loaded target with temporally and spatially resolved diagnostics. With transient imaging displacement interferometry, we demonstrate that the planarity (bow and tilt) of the loading induced by a spatially shaped laser pulse is within 2-7mrad (with an average of 4±1mrad), similar to that in conventional techniques including gas gun loading. Plasma heating of target is negligible, in particular, when a plasma shield is adopted. For flyer plate loading, supported shock waves can be achieved. Temporal shaping of the drive pulse in confined laser ablation allows for flexible loading, e.g., quasi-isentropic, Taylor-wave, and off-Hugoniot loading. These techniques can be utilized to investigate such dynamic responses of materials as Hugoniot elastic limit, plasticity, spall, shock roughness, equation of state, phase transition, and metallurgical characteristics of shock-recovered samples.

Paisley, Dennis L.; Luo, Sheng-Nian; Greenfield, Scott R.; Koskelo, Aaron C.

2008-02-01

407

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

PubMed

The effect of asymmetry caused by oblique line-shaped laser ablation on the generation of ultrasonic waves in metal, especially the effect of transverse component of the ablation force source on the ultrasonic waves is analyzed. Due to the oblique force source, the displacements of shear wave increase obviously by the enhanced shear force, the energy concentration area of longitudinal wave deflects to the small range centered on the incident direction while that of shear wave is approximately perpendicular to incident direction. In addition, surface wave enhances in the direction of transverse power flow. Furthermore, some ultrasonic characteristics under vortex laser ablation condition are inferred. PMID:24514978

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

2014-01-13

408

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

PubMed

When using ultrafast laser ablation in some orthopedic applications where precise cutting/drilling is required with minimal damage to collateral tissue, it is challenging to produce large-sized and deep holes using a tightly focused laser beam. The feasibility of producing deep, millimeter-size structures under different ablation strategies is investigated. X-ray computed microtomography was employed to analyze the morphology of these structures. Our results demonstrated the feasibility of producing holes with sizes required in clinical applications using concentric and helical ablation protocols. PMID:23884158

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

2013-07-01

409

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

SciTech Connect

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

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

2014-01-15

410

Synthesis of Bimetallic Nanoalloy Layer using Simultaneous Laser Ablation of Monometallic Targets  

NASA Astrophysics Data System (ADS)

It is proposed to synthesize silver-gold alloy nanoparticles by direct pulsed laser ablation of joined Ag and Au monometallic targets. To avoid utilizing a high-vacuum chamber, this pulsed laser-assisted technique is performed in an isolated beaker containing pure helium gas at atmospheric pressure. The structure and formation mechanism of the homogeneous Ag-Au nanoalloy particles on the Si substrate surface are discussed. Here, as in other works, the formation of the Ag-Au alloy nanoparticles was verified by the appearance of a surface plasmon absorption maximum at 442 nm between the surface plasmon resonance peaks of the corresponding monometallic particles, and by results of X-ray photoelectron spectroscopy. Based on data of UV-visible spectroscopy and energy dispersive X-ray analysis, the atomic contents of Ag and Au are determined in the nanoalloy particles. Transmission electron microscopy (TEM) showed the synthesized semispherical nanoalloy particles, 5-35 nm in diameter, with a narrow particle size distribution. The related morphology, structure, and chemical composition are also investigated using atomic force microscopy, lateral force microscopy, and X-ray diffraction. The suggested approach is affordable, fast, and inexpensive.

Ganjali, Mansoureh; Ganjali, Monireh; Sangpour, Parvaneh

2014-01-01

411

Laser pulse guiding and electron acceleration in the ablative capillary discharge plasma  

SciTech Connect

The results of experiments are presented for the laser electron acceleration in the ablative capillary discharge plasma. The plasma channel is formed by the discharge inside the ablative capillary. The intense short laser pulse is guided over a 4 cm length. The generated relativistic electrons show both the quasimonoenergetic and quasi-Maxwellian energy spectra, depending on laser and plasma parameters. The analysis of the inner walls of the capillaries that underwent several tens of shots shows that the wall deformation and blistering resulted from the discharge and laser pulse effects.

Kameshima, T. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai, Kizugawa, Kyoto 619-0215 (Japan); Department of Accelerator Science, The Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan and XFEL Project Head Office, RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kotaki, H.; Kando, M.; Daito, I.; Kawase, K.; Fukuda, Y.; Homma, T.; Esirkepov, T. Zh. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai, Kizugawa, Kyoto 619-0215 (Japan); Chen, L. M. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Kondo, S. [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo, Hyogo 679-5198 (Japan); Bobrova, N. A.; Sasorov, P. V. [Institute for Theoretical and Experimental Physics, Bolshaya Cheremushkinskaya Street 25, Moscow 117259 (Russian Federation); Bulanov, S. V. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai, Kizugawa, Kyoto 619-0215 (Japan); A. M. Prokhorov Institute of General Physics, Russian Academy of Sciences, Vavilov Street 38, Moscow 199911 (Russian Federation)

2009-09-15

412

Non-contact acoustic tests based on nanosecond laser ablation: Generation of a pulse sound source with a small amplitude  

NASA Astrophysics Data System (ADS)

A method to generate a pulse sound source for acoustic tests based on nanosecond laser ablation with a plasma plume is discussed. Irradiating a solid surface with a laser beam expands a high-temperature plasma plume composed of free electrons, ionized atoms, etc. at a high velocity throughout ambient air. The shockwave generated by the plasma plume becomes the pulse sound source. A laser ablation sound source has two features. Because laser ablation is induced when the laser fluence reaches 1012-1014 W/m2, which is less than that for laser-induced breakdown (1015 W/m2), laser ablation can generate a lower sound pressure, and the sound source has a hemispherical radiation pattern on the surface where laser ablation is generated. Additionally, another feature is that laser-induced breakdown sound sources can fluctuate, whereas laser ablation sound sources do not because laser ablation is produced at a laser beam-irradiation point. We validate this laser ablation method for acoustic tests by comparing the measured and theoretical resonant frequencies of an impedance tube.

Hosoya, Naoki; Kajiwara, Itsuro; Inoue, Tatsuo; Umenai, Koh

2014-09-01

413

Ablation of ionic crystals induced by capillary-discharge XUV laser  

NASA Astrophysics Data System (ADS)

Single crystals of two fluorides (LiF and CaF2) and a tungstate (PbWO4) were irradiated by nanosecond pulses of 46.9- nm radiation provided by 10-Hz capillary-discharge Ne-like Ar laser (CDL). The damage threshold was determined in LiF using the CDL beam focused by a Sc/Si multilayer-coated spherical mirror. Irradiated samples have been investigated by Nomarski (DIC - Differential Interference Contrast) microscopy and optical (WLI - white light intereferometry) profiler. After an exposure by a certain number of CDL pulses, an ablation rate can be calculated from WLI measured depth of the crater created by the XUV ablation. Potential use of XUV ablation of ionic crystals in pulsed laser deposition (PLD) of thin layers of such a particular material, which is difficult to ablate by conventional UV-Vis- NIR lasers, is discussed in this contribution.

Pira, Peter; Burian, Tomáš; Vyšín, Ludék; Chalupský, Jaromír; Lan?ok, Ján; Wild, Jan; St?ižík, Michal; Zelinger, Zden?k; Rocca, Jorge J.; Juha, Libor

2011-06-01

414

Review on Japanese-German-U.S. Cooperation on Laser-Ablation Propulsion  

NASA Astrophysics Data System (ADS)

We report on an international cooperation between Nagoya University (NU), Japan and DLR Stuttgart, Germany on scaling issues in laser ablative propulsion. Lessons learned from collaborative work in the laboratory will be summarized with respect to the comparability of experimental methods and corresponding standardization issues. With the background of previous experimental research at the University of Alabama in Huntsville (UAH), experimental work with CO2 lasers in a moderate (NU) and high (DLR) pulse energy range on laser ablation of POM is presented. Profilometry results of target surfaces are compared with fluence distributions from beam propagation modeling. Ablation from flat targets is reported with respect to energy and area scaling and compared with results from ablative propulsion employing parabolic nozzles.

Scharring, Stefan; Sinko, John E.; Karg, Stephanie; Eckel, Hans-Albert; Röser, Hans-Peter; Sasoh, Akihiro; Ogita, Naoya; Umehara, Noritsugu; Tsukiyama, Yosuke

2011-11-01

415

Laser ablation characteristics of metallic materials: Role of Debye-Waller thermal parameter  

NASA Astrophysics Data System (ADS)

The interaction of a high intensity laser pulse with a solid target results in the formation of a crater and a plasma plume. The characteristics of both depend on physical properties of target material, environmental conditions, and laser parameters (e.g. wavelength, pulse duration, energy, beam diameter) etc. It has been shown for numerous metals and their alloys that plasma threshold fluence, plasma threshold energy, ablation efficiency, ablation yield, angular distribution of laser produced plasma (LPP) ions, etc. are a unique function of the Debye-Waller thermal parameter B or the mean-square amplitude of atomic vibration of the target material for given experimental conditions. The FWHM of the angular distribution of LPP ions, ablation yield, and ablation efficiency increase whereas plasma threshold fluence and plasma threshold energy decrease as B-factor of the target material increases.

Butt, M. Z.

2014-06-01

416

Transmission of 1064 nm laser radiation during ablation with an ultra-short pulse laser (USPL) system  

NASA Astrophysics Data System (ADS)

During ablation of oral hard tissue with an USPL system a small amount of the incident laser power does not contribute to the ablation process and is being transmitted. Partial transmission of ultra-short laser pulses could potentially affect the dental pulp. The aim of this study was to assess the transmission during ablation and to deduce possible risks for the patient. The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz and an average power of 9 W were chosen to achieve high ablation efficiency. A scanner system created square cavities with an edge length of 1 mm. Transmission during ablation of mammoth ivory and dentin slices with a thickness of 2 mm and 5 mm was measured with a power meter, placed directly beyond the samples. Effects on subjacent blood were observed by ablating specimens placed in contact to pork blood. In a separate measurement the temperature increase during ablation was monitored using an infrared camera. The influence of transmission was assessed by tuning down the laser to the corresponding power and then directly irradiating the blood. Transmission during ablation of 2 mm specimens was about 7.7% (ivory) and 9.6% (dentin) of the incident laser power. Ablation of specimens directly in contact to blood caused coagulation at longer irradiation times (t~18s). Direct irradiation of blood with the transmitted power provoked bubbling and smoke formation. Temperature measurements identified heat generation as the main reason for