Sample records for laser-induced dynamic gratings

  1. Applications of laser-induced gratings to spectroscopy and dynamics

    SciTech Connect

    Rohlfing, E.A. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    This program has traditionally emphasized two principal areas of research. The first is the spectroscopic characterization of large-amplitude motion on the ground-state potential surface of small, transient molecules. The second is the reactivity of carbonaceous clusters and its relevance to soot and fullerene formation in combustion. Motivated initially by the desire to find improved methods of obtaining stimulated emission pumping (SEP) spectra of transients, most of our recent work has centered on the use of laser-induced gratings or resonant four-wave mixing in free-jet expansions. These techniques show great promise for several chemical applications, including molecular spectroscopy and photodissociation dynamics. The author describes recent applications of two-color laser-induced grating spectroscopy (LIGS) to obtain background-free SEP spectra of transients and double resonance spectra of nonfluorescing species, and the use of photofragment transient gratings to probe photodissociation dynamics.

  2. Laser-induced thermal grating effects in flames

    Microsoft Academic Search

    Skip Williams; Larry A. Rahn; Phillip H. Paul; Jon W. Forsman; Richard N. Zare

    1994-01-01

    Light scattering from a laser-induced thermal grating produced in an atmospheric-pressure H[sub 2]\\/O[sub 2] flame is observed with a phase-matching geometry commonly used in resonant four-wave mixing and laser-induced grating spectroscopy. The presence of thermal gratings is confirmed in both the time and the frequency domains in two distinct experiments. Diluting the flame with helium decreases the thermal grating signal

  3. Investigation of ultrafast photothermal surface expansion and diffusivity in GaAs via laser-induced dynamic gratings

    SciTech Connect

    Pennington, D.M.

    1992-04-01

    This thesis details the first direct ultrafast measurements of the dynamic thermal expansion of a surface and the temperature dependent surface thermal diffusivity using a two-color reflection transient grating technique. Studies were performed on p-type, n-type, and undoped GaAs(100) samples over a wide range of temperatures. By utilizing a 90 fs ultraviolet probe with visible excitation beams, the effects of interband saturation and carrier dynamics become negligible; thus lattice expansion due to heating and subsequent contraction caused by cooling provided the dominant influence on the probe. At room temperature a rise due to thermal expansion was observed, corresponding to a maximum net displacement of {approximately} 1 {Angstrom} at 32 ps. The diffracted signal was composed of two components, thermal expansion of the surface and heat flow away from the surface, thus allowing a determination of the rate of expansion as well as the surface thermal diffusivity, D{sub S}. By varying the fringe spacing of the grating, this technique has the potential to separate the signal contributions to the expansion of the lattice in the perpendicular and parallel directions. In the data presented here a large fringe spacing was used, thus the dominant contribution to the rising edge of the signal was expansion perpendicular to the surface. Comparison of he results with a straightforward thermal model yields good agreement over a range of temperatures (20--300{degrees}K). Values for D{sub S} in GaAs were measured and found to be in reasonable agreement with bulk values above 50{degrees}K. Below 50{degrees}K, D{sub S} were determined to be up to an order of magnitude slower than the bulk diffusivity due to increased phonon boundary scattering. The applicability and advantages of the TG technique for studying photothermal and photoacoustic phenomena are discussed.

  4. Laser induced damage in multilayer dielectric gratings due to ultrashort laser pulses

    Microsoft Academic Search

    B. W. Shore; B. C. Stuart; M. D. Feit; A. M. Rubenchik; M. D. Perry

    1995-01-01

    Chirped pulse amplification is increasingly used to produce intense ultrashort laser pulses. When high-efficiency gratings are the dispersive element, as in the LLNL Petawatt laser, their susceptibility to laser induced damage constitutes a limitation on the peak intensities that can be reached. To obtain robust gratings, it is necessary to understand the causes of short-pulse damage, and to recognize the

  5. Laser induced damage in multilayer dielectric gratings due to ultrashort laser pulses. Revision 1

    Microsoft Academic Search

    B. W. Shore; B. C. Stuart; M. D. Feit; A. M. Rubenchik; M. D. Perry

    1995-01-01

    Chirped pulse amplification is increasingly used to produce intense ultrashort laser pulses. When high-efficiency gratings are the dispersive element, as in the LLNL Petawatt laser, their susceptibility to laser induced damage constitutes a limitation on the peak intensities that can be reached. To obtain robust gratings, it is necessary to understand the causes of short-pulse damage, and to recognize the

  6. Laser-induced damage in multilayer dielectric gratings due to ultrashort laser pulses

    Microsoft Academic Search

    Bruce W. Shore; Brent C. Stuart; Michael D. Feit; Alexander M. Rubenchik; Michael D. Perry

    1995-01-01

    Chirped pulse amplification is increasingly used to produce intense ultrashort laser pulses. When high efficiency gratings are the dispersive element, as in the LLNL Petawatt laser, their susceptibility to laser induced damage constitutes a limitation on the peak intensities that can be reached. To obtain robust gratings, it is necessary to understand the causes of short-pulse damage, and to recognize

  7. Development of Laser-induced Grating Spectroscopy for Underwater Temperature Measurement in Shock Wave Focusing Regions

    NASA Technical Reports Server (NTRS)

    Gojani, Ardian B.; Danehy, Paul M.; Alderfer, David W.; Saito, Tsutomu; Takayama, Kazuyoshi

    2003-01-01

    In Extracorporeal Shock Wave Lithotripsy (ESWL) underwater shock wave focusing generates high pressures at very short duration of time inside human body. However, it is not yet clear how high temperatures are enhanced at the spot where a shock wave is focused. The estimation of such dynamic temperature enhancements is critical for the evaluation of tissue damages upon shock loading. For this purpose in the Interdisciplinary Shock Wave Research Center a technique is developed which employs laser induced thermal acoustics or Laser Induced Grating Spectroscopy. Unlike most of gasdynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm3 and 400 ns, respectively. Preliminary experiments in still water demonstrated that this method detected sound speed and hence temperature in water ranging 283 K to 333 K with errors of 0.5%. These results may be used to empirically establish the equation of states of water, gelatin or agar cells which will work as alternatives of human tissues.

  8. Observation of ? in a flame by two-colour laser-induced-grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, G. C.

    1997-08-01

    By using two-colour laser-induced-grating spectroscopy (TC-LIGS), we observed the third-overtone spectrum of the O - H stretch of water vapour at a point in a stoichiometric 0957-0233/8/8/013/img2 - air flame. We also demonstrated the extension of these point measurements to a line image in a flame. Only thermal gratings could be observed. The reasons for this and the difficulties in making a practical combustion diagnostic are discussed.

  9. Study on the test of laser-induced damage threshold of multilayer dielectric gratings

    NASA Astrophysics Data System (ADS)

    Kong, Weijin; Wang, Tao; Shao, Jianda; Fan, Zhengxiu

    2004-12-01

    Multi-layer dielectric gratings (MDG) have been more and more used in the chirped-pulse amplification (CPA) system because of its higher diffraction efficiencies and higher damage threshold, which is compared with metallic gratings. Design parameter of multi-layer dielectric and gratings are both given. Laser-induced damage threshold (LIDT) of MDG has been test by employing 1-on-1 methods. The result is 3.24J/cm2 at 1064nm and 12ns pulselength (51.2° incidence). The mechanics of damage is also discussed in several ways.

  10. Investigation of Laser-Induced Damage on Multi-Layer Dielectric Gratings

    NASA Astrophysics Data System (ADS)

    Kong, Wei-Jin; Shen, Zi-Cai; Shen, Jian; Shao, Jian-Da; Fan, Zheng-Xiu

    2005-07-01

    We investigate mechanisms of laser induced damage thresholds (LIDTs) of multi-layer dielectric gratings (MDGs). It is found that the laser damage thresholds of MDGs and unstructured dielectric multi-layer coatings (the substrate of MDG) are 3.15 J/cm2 and 9.32 J/cm2, respectively, at 1064 nm (12 ns) with the Littrow angle 51.2 degrees and the TEM00 mode. The laser-induced damage mechanism of multi-layer dielectric is presented with the analysis of the following factors: The dominant factor is the pollution on the corrugated surface, which is induced by the complex manufacture process of multi-layer dielectric gratings; another is the electric field distribution along the corrugated surface. The third reason is due to the reduction in stoichiometry of oxide films, resulting from the manufacture process of etching.

  11. Femtosecond laser induced fiber Bragg gratings for harsh environment sensing applications

    NASA Astrophysics Data System (ADS)

    Mihailov, S. J.; Grobnic, D.; Walker, R. B.; Lu, P.; Ding, H.

    2014-09-01

    Fiber Bragg grating sensors have been developed beyond a laboratory curiosity to become a mainstream sensing technology because of their small size, passive nature, immunity to electromagnetic interference, and capability to simultaneously measure multiple physical parameters such as temperature, strain and pressure. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This presentation will give a review of some of the more recent developments of femtosecond laser induced fiber Bragg gratings.

  12. Dynamical behavior of laser-induced nanoparticles during remote processing

    NASA Astrophysics Data System (ADS)

    Scholz, Tobias; Dickmann, Klaus; Ostendorf, Andreas

    2014-02-01

    Laser remote processing is used in a wide field of industrial applications. Among other things, it is characterized by flexible beam guidance in combination with high processing velocities. But in most cases process gas support in the interaction zone is omitted. Consequently, interaction mechanism between the vapor plume and the incident laser radiation can dynamically affect the process stability. Referring to remote welding with high brilliant laser sources having a wavelength around 1 ?m, the interaction between the incident laser radiation and formed particles plays an important role. The presented work shows results of the investigation of the laser-induced particle formation during the laser welding of stainless steel with a 2 kW fiber laser under remote conditions. It is therefore concentrated on the dynamical behavior of the laser-induced particle formation and the dependence of the particle formation on the laser beam power. TEM images of formed particles were analyzed. In addition, the radiation of a LED was directed through the vapor plume. On the one hand, the dynamic of the attenuation was considered. On the other hand, the Rayleigh approximation was used in order to evaluate the detected signals.

  13. Ultrafast dynamics of the laser-induced solid-to-liquid phase transition in aluminum

    E-print Network

    Mazur, Eric

    Ultrafast dynamics of the laser-induced solid-to-liquid phase transition in aluminum A thesis dynamics of the laser-induced solid-to-liquid phase transition in aluminum Eric Mazur Maria Kandyla Abstract This dissertation reports the ultrafast dynamics of aluminum during the solid-to- liquid phase

  14. Dynamic response of shear thickening fluid under laser induced shock

    NASA Astrophysics Data System (ADS)

    Wu, Xianqian; Zhong, Fachun; Yin, Qiuyun; Huang, Chenguang

    2015-02-01

    The dynamic response of the 57 vol./vol. % dense spherical silica particle-polyethylene glycol suspension at high pressure was investigated through short pulsed laser induced shock experiments. The measured back free surface velocities by a photonic Doppler velocimetry showed that the shock and the particle velocities decreased while the shock wave transmitted in the shear thickening fluid (STF), from which an equation of state for the STF was obtained. In addition, the peak stress decreased and the absorbed energy increased rapidly with increasing the thickness for a thin layer of the STF, which should be attributed to the impact-jammed behavior through compression of particle matrix, the deformation or crack of the hard-sphere particles, and the volume compression of the particles and the polyethylene glycol.

  15. Time-resolved measurement of the local equivalence ratio in a gaseous propane injection process using laser-induced gratings

    NASA Astrophysics Data System (ADS)

    Seeger, Thomas; Kiefer, Johannes; Weikl, Markus C.; Leipertz, Alfred; Kozlov, Dimitrii N.

    2006-12-01

    For the first time laser-induced gratings (LIGs) have been used for the investigation of a non-stationary pulse-repetitive injection process of gaseous propane, C3H8, into air. By recording and evaluating single-shot LIG signals it was possible to determine, on a cycle-averaged basis, the temporal evolution of the local (within a probe volume 300 µm in diameter and 10 mm in length) equivalence ratio and by this the fuel-air ratio. Two different data treatment strategies, subject to C3H8 concentration range, were first tested at stationary conditions and then used to evaluate the LIG signals obtained during the injection process. The relative standard deviation of single-shot measurements were estimated to be 0.14 and 0.32 at 0.8 % and 10 % of propane concentration, respectively.

  16. Surface plasmon resonance in eccentric femtosecond-laser-induced fiber Bragg gratings.

    PubMed

    Chah, Karima; Voisin, Valérie; Kinet, Damien; Caucheteur, Christophe

    2014-12-15

    Highly localized refractive index modulations are photo-written in the core of pure silica fiber using point-by-point focused UV femtosecond pulses. These specific gratings exhibit a comb-like transmitted amplitude spectrum, with polarization-dependent narrowband cladding mode resonances. In this work, eccentric gratings are surrounded by a gold sheath, allowing the excitation of surface plasmon polaritons (SPP) for radially-polarized light modes. The spectral response is studied as a function of the surrounding refractive index and a maximum sensitivity of 50??nm/RIU (refractive index unit) is reported for a well-defined cladding-mode resonance among the spectral comb. This novel kind of plasmonic fiber grating sensor offers rapidity of production, design flexibility, and high temperature stability. PMID:25503022

  17. Laser induced temperature jump investigations of fast protein folding dynamics

    NASA Astrophysics Data System (ADS)

    Qiu, Linlin

    Protein folding has a large parameter space, diverse mechanism, and multipath kinetics. However, there are some common features many proteins share in their folding processes: all seem to fold at the rates much faster than the random conformation search, and all fold into the structures which have the highly regular motifs like alpha-helices, beta-sheets and turns. Understanding how fast proteins can fold is one of the central issues in solving the protein folding problem. Ultrafast folding kinetics had not been accessible until a few sub-millisecond probes were invented and applied lately. We constructed a laser induced temperature jump spectrometer which is a great utility in identifying the local structure and tertiary contact formation of proteins on the time scale from 10 -8 to 10-3 s with time resolution of 10 -9 s. With this spectrometer we studied the fast folding mini-protein, TrpCage and a few short stable beta-hairpins, the TrpZip series. Studying TrpCage was a major breakthrough it was a pioneer protein model which brought experiment and simulation very close: its structures measured by NMR and predicted by the molecular dynamics were amazingly alike. Our kinetic results showed that it folds in 4 mus at room temperature which turned out to be the fastest ever known for protein-like molecules. Also this folding time constant is consistent with what was later on simulated by distributed computation. TrpZips are among the smallest and stablest polypeptide chains which form secondary structures. They are slightly different from each other based on structural stability and by forming various types of beta-hairpins which are the minimum units of beta tertiary structure. The beta-hairpins form in the time range of 1--10 mus that confirms the theory that loop formation is controlled by the diffusion process (˜mus). We also investigated the kinetics of the protein chain collapse, a very controversial problem. By comparing the collapse of the foldable 104-residue protein cytochrome c and its unfoldable fragments F1-65 and F1-80, we concluded that the collapse of the protein molecule is not significantly different from those of unfoldable peptide chains. Burial of hydrophobic core and the presence of the interactions among chain residues and the interactions between amino acids and solvent molecules limit the collapse rate of a polypeptide chain on the time scale of the order of ten microseconds.

  18. Effect of pulse duration on laser induced damage threshold of multilayer dielectric gratings

    NASA Astrophysics Data System (ADS)

    Kong, Fanyu; Jin, Yunxia; Li, Dawei; Chen, Weixiao; Zhu, Meiping; Wang, Tao; Li, Chaoyang; He, Hongbo; Xu, Guang; Shao, Jianda

    2012-11-01

    Multilayer dielectric gratings (MDGs) are more and more used to compress pulse in the next generation of chirped-pulse amplification (CPA) system for high-energy petawatt (HEPW)-class lasers due to their high efficiency and high damage threshold for picosecond pulses. The damage tests for MDGs were carried out with long pulse (12ns) in air and short pulse (0.66~9.7ps) in vacuum at 1053nm, respectively. The experiment methodologies and results were discussed. For both long and short pulse, the initial damage locates at the grating ridges opposite to the incoming wave, which is consistent with the maximum normalized electric field intensity (NEFI). For long pulse, the damage is characterized by melting and boiling. And for short pulse, the damage is ascribed to multiphoton-induced avalanche ionization because of the electric field enhancement in the grating groove structure. And Measurement results of the dependence of damage threshold on the pulse width are presented. And the damage threshold of MDG in beam normal is 4.4J/cm2 at 70° incidence angle for 9.7ps pulse.

  19. In situ detection and analysis of laser-induced damage on a 1.5-m multilayer-dielectric grating compressor for high-energy, petawatt-class laser systems.

    PubMed

    Qiao, J; Schmid, A W; Waxer, L J; Nguyen, T; Bunkenburg, J; Kingsley, C; Kozlov, A; Weiner, D

    2010-05-10

    A grating-inspection system and a damage-analysis method have been developed to measure in situ laser-induced damage on a 1.5-m tiled-grating assembly of the OMEGA EP pulse compressor during a 15-ps, 2.2-kJ energy ramp. The beam fluence at which significant damage growth occurred was determined. This is the first report on beam fluence versus laser-induced-damage growth of meter-sized multilayer-dielectric-diffraction gratings. This result was correlated to the damage-probability measurement conducted on a small grating sample and is consistent with the fluence, corresponding to 100% damage probability. PMID:20588897

  20. Dynamic behaviour of KDP for laser-induced damage applications

    NASA Astrophysics Data System (ADS)

    Hebert, David; Hallo, Ludovic; Voisin, Luc; Desanlis, Thierry; Galtie, Alain; Bicrel, Beatrice; Maunier, Cedric; Mercier, Patrick; Duchateau, Guillaume

    2011-06-01

    High power lasers as NIF in the USA or LMJ in France are being developed in order to produce inertial fusion confinement. However, the efficiency of these apertures is limited by laser-induced damage which occurs in the potassium dihydrogen phosphate (KDP) crystals allowing the frequency conversion. We present here hydrodynamic simulations that investigate the major processes following absorption of the laser energy on precursor defects, leading to the creation of a shock wave whose pressure lies in the GPa range. An associated rarefaction wave forms a cavity at the place of the precursor defect. In order to perform quantitative predictions, a reliable equation of state is required, along with strength properties. A review of available experimental data is presented and used to discuss the validity of different models for KDP.

  1. Simultaneous measurement of speed of sound, thermal diffusivity, and bulk viscosity of 1-ethyl-3-methylimidazolium-based ionic liquids using laser-induced gratings.

    PubMed

    Kozlov, Dimitrii N; Kiefer, Johannes; Seeger, Thomas; Fröba, Andreas P; Leipertz, Alfred

    2014-12-11

    The technique of laser-induced gratings (LIGs) has been applied to the simultaneous determination of speed of sound and thermal diffusivity of four 1-ethyl-3-methylimidazolium ([EMIm])-based room temperature ionic liquids (RTILs)-[EMIm][N(CN)2], [EMIm][MeSO3], [EMIm][C(CN)3], and [EMIm][NTf2]-at ambient pressure (1 bar (0.1 MPa)) and temperature (28 °C (301 K)). Transient laser-induced gratings were created as a result of thermalization of a quasi-resonant excitation of highly lying combinational vibrational states of the RTIL molecules and electrostrictive compression of the liquid by radiation of a pulse-repetitive Q-switched Nd:YAG pump laser (1064 nm). The LIGs temporal evolution was recorded using Bragg diffraction of the radiation from a continuous-wave probe laser (532 nm). By fitting the temporal profiles of the LIG signals, the speed of sound and thermal diffusivity were determined, and the isentropic compressibility and thermal conductivity were calculated. Independently, the special experimental arrangement allowed the measurement of the damping of the laser-excited acoustic waves and the derivation of the RTIL bulk viscosity for the first time. PMID:25415848

  2. Dynamical theory of diffraction on moving grating

    E-print Network

    Bushuev, V A; Kulin, G V

    2015-01-01

    In the framework of the approximation of slowly varying amplitudes a multiwave dynamical theory of neutron diffraction on a moving phase grating was developed. The influence of the velocity of the grating, its period and height of the slits on the discrete energy spectrum and intensity of various diffraction orders was analyzed.

  3. Dynamical theory of diffraction on moving grating

    E-print Network

    V. A. Bushuev; A. I. Frank; G. V. Kulin

    2015-02-16

    In the framework of the approximation of slowly varying amplitudes a multiwave dynamical theory of neutron diffraction on a moving phase grating was developed. The influence of the velocity of the grating, its period and height of the slits on the discrete energy spectrum and intensity of various diffraction orders was analyzed.

  4. Laser-induced magnetization dynamics and reversal in ferrimagnetic alloys

    NASA Astrophysics Data System (ADS)

    Kirilyuk, Andrei; Kimel, Alexey V.; Rasing, Theo

    2013-02-01

    This review discusses the recent studies of magnetization dynamics and the role of angular momentum in thin films of ferrimagnetic rare-earth-transition metal (RE-TM) alloys, e.g. GdFeCo, where both magnetization and angular momenta are temperature dependent. It has been experimentally demonstrated that the magnetization can be manipulated and even reversed by a single 40 fs laser pulse, without any applied magnetic field. This switching is found to follow a novel reversal pathway, that is shown however to depend crucially on the net angular momentum, reflecting the balance of the two opposite sublattices. In particular, optical excitation of ferrimagnetic GdFeCo on a time scale pertinent to the characteristic time of the exchange interaction between the RE and TM spins, i.e. on the time scale of tens of femtoseconds, pushes the spin dynamics into a yet unexplored regime, where the two exchange-coupled magnetic sublattices demonstrate substantially different dynamics. As a result, the reversal of spins appears to proceed via a novel transient state characterized by a ferromagnetic alignment of the Gd and Fe magnetic moments, despite their ground-state antiferromagnetic coupling. Thus, optical manipulation of magnetic order by femtosecond laser pulses has developed into an exciting and still expanding research field that keeps being fueled by a continuous stream of new and sometimes counterintuitive results. Considering the progress in the development of plasmonic antennas and compact ultrafast lasers, optical control of magnetic order may also potentially revolutionize data storage and information processing technologies.

  5. Laser-induced magnetization dynamics and reversal in ferrimagnetic alloys.

    PubMed

    Kirilyuk, Andrei; Kimel, Alexey V; Rasing, Theo

    2013-02-01

    This review discusses the recent studies of magnetization dynamics and the role of angular momentum in thin films of ferrimagnetic rare-earth-transition metal (RE-TM) alloys, e.g. GdFeCo, where both magnetization and angular momenta are temperature dependent. It has been experimentally demonstrated that the magnetization can be manipulated and even reversed by a single 40 fs laser pulse, without any applied magnetic field. This switching is found to follow a novel reversal pathway, that is shown however to depend crucially on the net angular momentum, reflecting the balance of the two opposite sublattices. In particular, optical excitation of ferrimagnetic GdFeCo on a time scale pertinent to the characteristic time of the exchange interaction between the RE and TM spins, i.e. on the time scale of tens of femtoseconds, pushes the spin dynamics into a yet unexplored regime, where the two exchange-coupled magnetic sublattices demonstrate substantially different dynamics. As a result, the reversal of spins appears to proceed via a novel transient state characterized by a ferromagnetic alignment of the Gd and Fe magnetic moments, despite their ground-state antiferromagnetic coupling.Thus, optical manipulation of magnetic order by femtosecond laser pulses has developed into an exciting and still expanding research field that keeps being fueled by a continuous stream of new and sometimes counterintuitive results. Considering the progress in the development of plasmonic antennas and compact ultrafast lasers, optical control of magnetic order may also potentially revolutionize data storage and information processing technologies. PMID:23377279

  6. Time-resolved diffraction profiles and atomic dynamics in short-pulse laser-induced structural transformations: Molecular dynamics study

    E-print Network

    Zhigilei, Leonid V.

    Time-resolved diffraction profiles and atomic dynamics in short-pulse laser-induced structural on the atomic-level structural rearrangements available from the simulations to the diffraction spectra measured of the irradiated surface and provides limited direct information on atomic structural rearrangements. Recent

  7. Dynamics of laser induced metal nanoparticle and pattern formation

    NASA Astrophysics Data System (ADS)

    Peláez, R. J.; Kuhn, T.; Rodríguez, C. E.; Afonso, C. N.

    2015-02-01

    Discontinuous metal films are converted into either almost round, isolated, and randomly distributed nanoparticles (NPs) or fringed patterns of alternate non transformed film and NPs by exposure to single pulses (20 ns pulse duration and 193 nm wavelength) of homogeneous or modulated laser beam intensity. The dynamics of NPs and pattern formation is studied by measuring in real time the transmission and reflectivity of the sample upon homogeneous beam exposure and the intensity of the diffraction orders 0 and 1 in transmission configuration upon modulated beam exposure. The results show that laser irradiation induces melting of the metal either completely or at regions around intensity maxima sites for homogeneous and modulated beam exposure, respectively, within ?10 ns. The aggregation and/or coalescence of the initially irregular metal nanostructures is triggered upon melting and continues after solidification (estimated to occur at ?80 ns) for more than 1 ?s. The present results demonstrate that real time transmission rather than reflectivity measurements is a valuable and easy-to-use tool for following the dynamics of NPs and pattern formation. They provide insights on the heat-driven processes occurring both in liquid and solid phases and allow controlling in-situ the process through the fluence. They also evidence that there is negligible lateral heat release in discontinuous films upon laser irradiation.

  8. Dynamics of Laser-Induced Phase Transitions in Cadmium Telluride

    SciTech Connect

    Kovalev, A.A.; Zhvavyi, S.P.; Zykov, G.L. [Institute of Electronics, Belarussian Academy of Sciences, Minsk, 220090 (Belarus)

    2005-11-15

    A numerical simulation of the dynamics of phase transitions induced by nanosecond pulsed radiation from a ruby laser in CdTe has been carried out. It is shown that evaporation of Cd atoms results in cooling of the surface; consequently, a nonmonotonic profile of the temperature field is formed, with the maximum temperature being attained in the bulk of the semiconductor at a distance of about 10-30 nm from the surface. At radiation energy densities above the threshold, the molten state formed under the surface extends both to the surface and into the depth of the semiconductor. Crystallization also proceeds in two directions, namely, from the surface into the depth of the samples due to the growth of nucleation centers in the melt, which is highly depleted in Cd atoms under the conditions of intense heat removal, and from the substrate to the surface due to epitaxial growth.

  9. Micro Dynamics of Pulsed Laser Induced Bubbles in Dusty Plasma Liquids

    SciTech Connect

    Teng, L.-W.; Tsai, C.-Y.; Tseng, Y.-P.; I Lin [Department of Physics, National Central University, Jhungli, Taiwan 32001 (China)

    2008-09-07

    We experimentally study the micro dynamics of the laser induced plasma bubble in a dusty plasma liquid formed by negatively charged dust particles suspended in a low pressure rf Ar glow discharge. The plume from the ablation of the suspended dust particles pushes away dust particle and generates a dust-free plasma bubble. It then travels downward. The spatio-temporal evolution of the dust density fluctuation surrounding the bubble is monitored by directly tracking dust motion through optical video microscopy. The micro dynamics of the bubble associated dust acoustic type solitary oscillation in the wake field is investigated and discussed.

  10. Laser-induced magnetization dynamics in a cobalt/garnet heterostructure

    NASA Astrophysics Data System (ADS)

    Pashkevich, M.; Stupakiewicz, A.; Kimel, A.; Kirilyuk, A.; Stognij, A.; Novitskii, N.; Maziewski, A.; Rasing, Th.

    2014-01-01

    We report on magnetization dynamics triggered in a Co/garnet heterostructure by femtosecond laser pulses. Although laser excitation of a bare Co-doped yttrium iron garnet leads to magnetization precession, the phase of which strongly depends on the linear polarization of the light pulses, the deposition of an ultrathin Co layer on a top of a garnet film results in substantial changes of the laser-induced dynamics. The precession in the garnet is shown to lose its sensitivity to the polarization. Instead, light triggers polarization insensitive precession in both the magnetostatically coupled Co layer and the garnet film at two distinct frequencies typical for Co and garnet layers.

  11. Simultaneous single-shot measurement of temperature and pressure along a one-dimensional line by use of laser-induced thermal grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Stevens, Robert; Ewart, Paul

    2006-04-01

    We report a new technique, based on laser-induced thermal grating spectroscopy (LITGS), for time- and space-resolved simultaneous measurement of temperature and pressure along a one-dimensional line. LITGS signals generated in NO2/N2 mixtures along a 5mm line produce a time-varying image that is recorded on a streak camera. The temperature is derived with a precision of 0.3% from the streak images using a rapid Fourier method with a spatial resolution of 150 ?m along the line. The principle of pressure measurement is demonstrated using a sequence of images, and a simple extension of the method to single-shot pressure measurement is discussed.

  12. Six orders of magnitude dynamic range in capillary electrophoresis with ultrasensitive laser-induced fluorescence detection

    PubMed Central

    Whitmore, Colin D.; Essaka, David; Dovichi, Norman J.

    2009-01-01

    An ultrasensitive laser-induced fluorescence detector was used with capillary electrophoresis for the study of 5-carboxy-tetramethylrhodamine. The raw signal from the detector provided roughly three orders of magnitude dynamic range. The signal saturated at high analyte concentrations due to the dead time associated with the single-photon counting avalanche photodiode employed in the detector. The signal can be corrected for the detector dead time, providing an additional order of magnitude dynamic range. To further increase dynamic range, two fiber-optic beam-splitters were cascaded to generate a primary signal and two attenuated signals, each monitored by a single-photon counting avalanche photodiode. The combined signals from the three photodiodes are reasonably linear from the concentration detection limit of 3 pM to 10 ?M, the maximum concentration investigated, a range of 3,000,000. Mass detection limits were 150 yoctomoles injected onto the capillary. PMID:19836546

  13. Laser-induced breathing modes in metallic nanoparticles: a symmetric molecular dynamics study.

    PubMed

    Ng, Ming-Yaw; Chang, Yia-Chung

    2011-03-01

    A highly efficient simulation method based on molecular dynamics and group theory is adopted to investigate the laser-induced breathing oscillation of gold and silver nanospheres. Nanoparticles with size ranging from 5.8 to 46.2 nm are discussed. The effect due to laser-induced heating is modeled by a symmetric sudden expansion of the nanospheres by increasing the interatomic distances. A long-range empirical potential model which is capable of describing the phonon dispersion curves of noble metals in the full frequency range is established. Group theory is fully exploited to increase the computation efficiency, and the oscillation behavior of nanospheres of over 3 × 10(6) atoms can be simulated efficiently. Oscillation frequencies of nanospheres are obtained by calculating the Fourier transform of the velocity autocorrelation function. The breathing modes of nanospheres are identified as the excitation of A(1g) modes with in-phase radial displacement of atoms in the nanospheres. The resulting oscillation spectra are in very good agreement with experimental data. PMID:21384959

  14. Laser-induced breathing modes in metallic nanoparticles: A symmetric molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Ng, Ming-Yaw; Chang, Yia-Chung

    2011-03-01

    A highly efficient simulation method based on molecular dynamics and group theory is adopted to investigate the laser-induced breathing oscillation of gold and silver nanospheres. Nanoparticles with size ranging from 5.8 to 46.2 nm are discussed. The effect due to laser-induced heating is modeled by a symmetric sudden expansion of the nanospheres by increasing the interatomic distances. A long-range empirical potential model which is capable of describing the phonon dispersion curves of noble metals in the full frequency range is established. Group theory is fully exploited to increase the computation efficiency, and the oscillation behavior of nanospheres of over 3 × 106 atoms can be simulated efficiently. Oscillation frequencies of nanospheres are obtained by calculating the Fourier transform of the velocity autocorrelation function. The breathing modes of nanospheres are identified as the excitation of A1g modes with in-phase radial displacement of atoms in the nanospheres. The resulting oscillation spectra are in very good agreement with experimental data.

  15. Effects of an absorptive coating on the dynamics of underwater laser-induced shock process

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao Thi Phuong; Tanabe, Rie; Ito, Yoshiro

    2014-09-01

    The effects of an absorptive coating on the dynamics of underwater laser-induced shock process have been observed from the end of laser pulse to hundreds of microseconds after irradiation by time-resolved imaging techniques. A laser pulse of 13 ns at 1,064 nm was focused by a 40-mm focal length lens onto the surface of epoxy-resin blocks immersed in water to induce the shock process in the confining regime. A custom-designed time-resolved photoelasticity imaging technique and a high-speed laser stroboscopic videography technique in photoelasticity mode were used to analyze the evolution of shock waves in the water phase, the strength of stress waves in the solid phase, the oscillation of cavitation bubbles, and the generation of bubble-collapse-induced shock waves. We showed that black paint coating enhances the strength of laser-induced stress wave inside the solid, drives faster shock waves traveling in the water phase, and produces higher-energy cavitation bubbles. We propose that even at power densities of 1 GW/cm2 and above, an absorptive coating can intensify the shock process by enhancing the absorption of laser energy by plasma.

  16. Investigating the dynamics of laser induced sparks in atmospheric helium using Rayleigh and Thomson scattering

    NASA Astrophysics Data System (ADS)

    Nedanovska, E.; Nersisyan, G.; Morgan, T. J.; Hüwel, L.; Murakami, T.; Lewis, C. L. S.; Riley, D.; Graham, W. G.

    2015-01-01

    We have used optical Rayleigh and Thomson scattering to investigate the expansion dynamics of laser induced plasma in atmospheric helium and to map its electron parameters both in time and space. The plasma is created using 9 ns duration, 140 mJ pulses from a Nd:YAG laser operating at 1064 nm, focused with a 10 cm focal length lens, and probed with 7 ns, 80 mJ, and 532 nm Nd:YAG laser pulses. Between 0.4 ?s and 22.5 ?s after breakdown, the electron density decreases from 3.3 × 1017 cm-3 to 9 × 1013 cm-3, while the temperature drops from 3.2 eV to 0.1 eV. Spatially resolved Thomson scattering data recorded up to 17.5 ?s reveal that during this time the laser induced plasma expands at a rate given by R ˜ t0.4 consistent with a non-radiative spherical blast wave. This data also indicate the development of a toroidal structure in the lateral profile of both electron temperature and density. Rayleigh scattering data show that the gas density decreases in the center of the expanding plasma with a central scattering peak reemerging after about 12 ?s. We have utilized a zero dimensional kinetic global model to identify the dominant particle species versus delay time and this indicates that metastable helium and the He2+ molecular ion play an important role.

  17. Laser-induced breathing modes in metallic nanoparticles: A symmetric molecular dynamics study

    SciTech Connect

    Ng, Ming-Yaw; Chang, Yia-Chung [Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 115-29, Taiwan (China)

    2011-03-07

    A highly efficient simulation method based on molecular dynamics and group theory is adopted to investigate the laser-induced breathing oscillation of gold and silver nanospheres. Nanoparticles with size ranging from 5.8 to 46.2 nm are discussed. The effect due to laser-induced heating is modeled by a symmetric sudden expansion of the nanospheres by increasing the interatomic distances. A long-range empirical potential model which is capable of describing the phonon dispersion curves of noble metals in the full frequency range is established. Group theory is fully exploited to increase the computation efficiency, and the oscillation behavior of nanospheres of over 3 x 10{sup 6} atoms can be simulated efficiently. Oscillation frequencies of nanospheres are obtained by calculating the Fourier transform of the velocity autocorrelation function. The breathing modes of nanospheres are identified as the excitation of A{sub 1g} modes with in-phase radial displacement of atoms in the nanospheres. The resulting oscillation spectra are in very good agreement with experimental data.

  18. Laser-Induced Fluorescence Photogrammetry for Dynamic Characterization of Transparent and Aluminized Membrane Structures

    NASA Technical Reports Server (NTRS)

    Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.; Pappa, Richard S.

    2003-01-01

    Photogrammetry has proven to be a valuable tool for static and dynamic profiling of membrane based inflatable and ultra-lightweight space structures. However, the traditional photogrammetric targeting techniques used for solid structures, such as attached retro-reflective targets and white-light dot projection, have some disadvantages and are not ideally suited for measuring highly transparent or reflective membrane structures. In this paper, we describe a new laser-induced fluorescence based target generation technique that is more suitable for these types of structures. We also present several examples of non-contact non-invasive photogrammetric measurements of laser-dye doped polymers, including the dynamic measurement and modal analysis of a 1m-by-1m aluminized solar sail style membrane.

  19. Dynamics of the laser-induced nanostructuring of thin metal layers: experiment and theory

    NASA Astrophysics Data System (ADS)

    Lorenz, P.; Klöppel, M.; Smausz, T.; Csizmadia, T.; Ehrhardt, M.; Zimmer, K.; Hopp, B.

    2015-02-01

    Nanostructures are of increasing importance in manifold application fields such as electronics, optics and beyond. However, the fast and cost-effective production of nanostructures is a big technological challenge for laser machining. One promising approach is laser irradiation of thin metal layers, which allows the fabrication of metal nanostructures induced by a melting and transformation process. The influence of laser parameters (laser fluence, laser pulse number) on the morphology of the nanopatterned film and the dynamics of the nanostructure formation during excimer laser irradiation of a 20 nm chromium film on fused silica were studied. The dynamics of nanopatterning, comprising hole and droplet formation, were investigated by time-dependent reflection and transmission measurements as well as time-dependent optical microscopy. The resulting patterns were investigated by optical and scanning electron microscopy (SEM). However, for an optimization of this process a better understanding of the underlying physical phenomena is necessary. Therefore, experimental data of laser-induced nanopatterning were compared with results of physical simulations that consider the heat equation (laser–solid interaction including melting and evaporation) and the Navier–Stokes equation (transformation processes of the molten phase). The simulations, making use of laser fluence-dependent effective material parameters (surface tension and viscosity), are in good agreement with the experimental results.

  20. Laser-Induced Forward Transfer Using Triazene Polymer Dynamic Releaser Layer

    NASA Astrophysics Data System (ADS)

    Stewart, James Shaw; Lippert, Thomas; Nagel, Matthias; Nüesch, Frank; Wokaun, Alexander

    2010-10-01

    This article presents a short review of the use of triazene polymer as a dynamic release layer (DRL) for laser-induced forward transfer (LIFT), before looking at the latest research in more detail. The field of triazene polymer ablation only started around 20 years ago and has grown rapidly into a number of different application areas. Most promisingly, triazene ablation has been refined as a method for propulsion, bringing the benefits of LIFT to the deposition of sensitive transfer materials. The key to understanding LIFT with a triazene DRL is to understand the more fundamental nature of triazene polymer ablation in both frontside and backside orientations. This article focuses on the most recent experimental results on LIFT with a triazene DRL: the effect of picosecond pulse lengths compared with nanosecond pulse lengths; the effect of reduced air pressure; and the improvements in transfer in terms of range of transfer materials, and transfer across a gap. The results all help improve fundamental understanding of triazene-based LIFT, and the transfer of functioning OLEDs demonstrates the capability of the technique.

  1. OH formation dynamics in 193 nm photolysis of 2-methoxyethanol: A laser induced fluorescence study

    NASA Astrophysics Data System (ADS)

    SenGupta, Sumana; Upadhyaya, Hari P.; Kumar, Awadhesh; Naik, Prakash D.

    2014-10-01

    Dynamics of OH radical formation in the 193 nm photolysis of 2-methoxyethanol is studied using Laser Photolysis-Laser Induced Fluorescence technique. The nascent state distribution of the OH radical is measured. The OH fragments are formed vibrationally cold, characterized by a Boltzmann-like single rotational temperature of 450 ± 100 K. The spin-orbit and ? -doublet ratios of OH fragments are measured. The relative average translational energy of the OH channel is determined to be 17.0 ± 3.0 kcal/mol. The experimental studies along with theoretical calculations suggest a complex mechanism for OH formation consisting of at least three pathways. The prominent pathway at shorter timescale (<50 ns) involves crossing over to the nearby repulsive state, whereas, at longer timescale (>1 ms) involves a series of reaction with initial H3C-OCH2CH2OH bond cleavage, followed by rearrangement of OCH2CH2OH to CH2OCH2OH, and a final concerted step to generate OH and ethylene epoxide.

  2. Numerical Simulations of femtosecond-laser-induced dynamic alignment of molecules in the high-frequency off-resonance regime

    Microsoft Academic Search

    J. Chen; X. Cui; S. Zhuo; B. Huang; X. Jiang

    2006-01-01

    The motion equation for ? between the molecular axis and laser polarization direction in a high-frequency off-resonance femtosecond\\u000a laser field is deduced while simultaneously examining the effects of a permanent dipole moment and field-induced polarizability\\u000a and hyperpolarizability to molecular rotation. Femtosecond-laser-induced dynamic alignment of CO, N2, and Br2 molecules are investigated by numerically solving the obtained rotation equation for the

  3. Observation of Laser Induced Magnetization Dynamics in Co/Pd Multilayers with Coherent X-ray Scattering

    SciTech Connect

    Wu, Benny

    2012-04-05

    We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.

  4. Ultrafast dynamics of femtosecond laser-induced nanostructure formation on metals

    NASA Astrophysics Data System (ADS)

    Hwang, Taek Yong; Vorobyev, A. Y.; Guo, Chunlei

    2009-09-01

    We perform a comparison study on femtosecond laser-induced nanostructures on three noble metals, Cu, Ag, and Au. Under identical experimental conditions, the three metals each gain a different amount of surface area increase resulting from nanostructuring. We show that the different surface area increase from nanostructuring directly relates to the competition of two ultrafast processes, electron-phonon coupling and hot electron diffusion, following femtosecond laser heating of metals.

  5. Dynamics of Spatially and Temporally Resolved Laser Induced Al-plasma

    Microsoft Academic Search

    H. Imam; G. Abdellatif; V. Palleschi; M. A. Harith; Yosr E-El. Gamal

    2007-01-01

    In the present study the temporal and spatial evolution of the plasma produced by interaction of Q-switched Nd:YAG laser pulses at 532 nm with pure aluminum target are investigated via optical emission spectroscopy (OES) in vacuum (10-5 torr). Comparison of the spectra taken at different distances from the target surface facilitates discussing fundamental concepts of the Laser Induced Plasma (LIP).

  6. Influence of sample temperature on the expansion dynamics and the optical emission of laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Eschlböck-Fuchs, S.; Haslinger, M. J.; Hinterreiter, A.; Kolmhofer, P.; Huber, N.; Rössler, R.; Heitz, J.; Pedarnig, J. D.

    2013-09-01

    We investigate the influence of sample temperature on the dynamics and optical emission of laser induced plasma for various solid materials. Bulk aluminum alloy, silicon wafer, and metallurgical slag samples are heated to temperature TS ? 500 °C and ablated in air by Nd:YAG laser pulses (wavelength 1064 nm, pulse duration approx. 7 ns). The plasma dynamics is investigated by fast time-resolved photography. For laser-induced breakdown spectroscopy (LIBS) the optical emission of plasma is measured by Echelle spectrometers in combination with intensified CCD cameras. For all sample materials the temporal evolution of plume size and broadband plasma emission vary systematically with TS. The size and brightness of expanding plumes increase at higher TS while the mean intensity remains independent of temperature. The intensity of emission lines increases with temperature for all samples. Plasma temperature and electron number density do not vary with TS. We apply the calibration-free LIBS method to determine the concentration of major oxides in slag and find good agreement to reference data up to TS = 450 °C. The LIBS analysis of multi-component materials at high temperature is of interest for technical applications, e.g. in industrial production processes.

  7. Dynamics of primary and secondary microbubbles created by laser-induced breakdown of an optically trapped nanoparticle

    PubMed Central

    Arita, Y.; Antkowiak, M.; Venugopalan, V.; Gunn-Moore, F. J.; Dholakia, K.

    2012-01-01

    Laser-induced breakdown of an optically trapped nanoparticle is a unique system for studying cavitation dynamics. It offers additional degrees of freedom, namely the nanoparticle material, its size, and the relative position between the laser focus and the center of the optically trapped nanoparticle. We quantify the spatial and temporal dynamics of the cavitation and secondary bubbles created in this system and use hydrodynamic modeling to quantify the observed dynamic shear stress of the expanding bubble. In the final stage of bubble collapse, we visualize the formation of multiple submicrometer secondary bubbles around the toroidal bubble on the substrate. We show that the pattern of the secondary bubbles typically has its circular symmetry broken along an axis whose unique angle rotates over time. This is a result of vorticity along the jet towards the boundary upon bubble collapse near solid boundaries. PMID:22400669

  8. Dynamics of Spatially and Temporally Resolved Laser Induced Al-plasma

    NASA Astrophysics Data System (ADS)

    Imam, H.; Abdellatif, G.; Palleschi, V.; Harith, M. A.; E-El. Gamal, Yosr

    2007-02-01

    In the present study the temporal and spatial evolution of the plasma produced by interaction of Q-switched Nd:YAG laser pulses at 532 nm with pure aluminum target are investigated via optical emission spectroscopy (OES) in vacuum (10-5 torr). Comparison of the spectra taken at different distances from the target surface facilitates discussing fundamental concepts of the Laser Induced Plasma (LIP). Such measurements have been exploited to understand the main processes involved and must be taken into account for the analysis of this kind of plasma. The LIP mean expansion velocity has been determined by measuring the ionic emission temporal profiles usually referred to as the Time of Flight (TOF) profiles. The temporal behavior of the spectral emission has been explained and interpreted in view of the three body recombination processes. Problems concerning the existence of and departure from the local thermodynamic equilibrium (LTE) in the LIP are studied carefully as observed in the performed experiment.

  9. High-resolution imaging of ejection dynamics in laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Pohl, R.; Visser, C. W.; Römer, G. R. B. E.; Sun, C.; Huis in't Veld, A. J.; Lohse, D.

    2014-03-01

    Laser-induced Forward Transfer (LIFT) is a 3D direct-write method suitable for precision printing of various materials. As the ejection mechanism of picosecond LIFT has not been visualized in detail, the governing physics are not fully understood yet. Therefore, this article presents an experimental imaging study on the ejection process of gold-based LIFT. The LIFT experiments were performed using a 6.7 picosecond Yb:YAG laser source equipped with a SHG. The beam was focused onto a 200 nm thick gold donor layer. The high magnification images were obtained using bright field illumination by a 6 ns pulsed Nd:YAG laser source and a 50× long-distance microscope objective that was combined with a 200 mm tube lens. For laser fluence levels up to two times the donor-transfer-threshold, the ejection of a single droplet was observed. The typical droplet radius was estimated to be less than 3 ?m. A transition of ejection features towards higher fluence, indicates a second fluence-regime in the ejection process. For higher laser fluence, the formation of an elongated gold jet was observed. This jet fragments into multiple relatively small droplets, resulting in a spray of particles on the receiving substrate.

  10. Dynamic Optical Grating Device and Associated Method for Modulating Light

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Chu, Sang-Hyon (Inventor)

    2012-01-01

    A dynamic optical grating device and associated method for modulating light is provided that is capable of controlling the spectral properties and propagation of light without moving mechanical components by the use of a dynamic electric and/or magnetic field. By changing the electric field and/or magnetic field, the index of refraction, the extinction coefficient, the transmittivity, and the reflectivity fo the optical grating device may be controlled in order to control the spectral properties of the light reflected or transmitted by the device.

  11. A feasible method for measuring the blood flow velocity in superficial artery based on the laser induced dynamic thermography

    NASA Astrophysics Data System (ADS)

    Jin, Chao; He, Zhizhu; Zhang, Shanshan; Qi, Minchao; Sun, Ziqiao; Di, Derui; Liu, Jing

    2012-11-01

    Infrared thermography has been proved to be a useful tool to detect thermal physiologic changes associated with various diseases. However, static and single point temperature mapping on skin surface provided by the infrared thermography has not been able to meet the requirements for evaluating the complicated physiological status of human body. In order to explore more physiological variables for possible disease diagnostics, the present paper has developed a laser induced dynamic thermographic modality to estimate the average velocity of the superficial blood flow by means of tracking thermal transport along blood flow direction. A conceptual in vivo experiment is designed to record dynamic temperature response of rabbit auricle skin by thermograph, which is then used to estimate the blood flow velocity through a derived theoretical model. In addition, the lumped parameter model is developed to calibrate the estimated error by compensating the thermal response time induced by the tissue temperature change that the current infrared thermal imaging system with limited thermal sensitivity may fail to capture. The final calibrated results are fitting well with that from the Doppler ultrasound measurement, which indeed verified the practicality and feasibility of the method developed in this work.

  12. Dynamics of charge clouds ejected from laser-induced warm dense gold nanofilms.

    PubMed

    Zhou, Jun; Correa, Alfredo A; Li, Junjie; Tang, Shao; Ping, Yuan; Ogitsu, Tadashi; Li, Dong; Zhou, Qiong; Cao, Jianming

    2014-10-01

    We report a systematic study of the ejected charge dynamics surrounding laser-produced 30-nm warm dense gold films using single-shot femtosecond electron shadow imaging and deflectometry. The results reveal a two-step dynamical process of the ejected electrons under high pump fluence conditions: an initial emission and accumulation of a large amount of electrons near the pumped surface region, followed by the formation of hemispherical clouds of electrons on both sides of the film, which escape into the vacuum at a nearly isotropic and constant velocity with an unusually high kinetic energy of more than 300 eV. We also developed a model of the escaping charge distribution that not only reproduces the main features of the observed charge expansion dynamics but also allows us to extract the number of ejected electrons remaining in the cloud. PMID:25375431

  13. Influence of static pressure on dynamic characteristics of laser-induced cavitation and hard-tissue ablation under liquid environment

    NASA Astrophysics Data System (ADS)

    Chen, Chuanguo; Li, Xuwei; Zhang, Xianzeng; Zhan, Zhenlin; Xie, Shusen

    2014-11-01

    Several studies have demonstrated that laser-induced hard tissue ablation effects can be enhanced by applying an additional water-layer on tissue surface. However, the related mechanism has not yet been presented clearly. In this paper, the influence of static pressure on dynamic characteristics of cavitation induced by pulse laser in liquid and its effect on bovine shank bone ablation were investigated. The laser source is fiber-guided free-running Ho:YAG laser with wavelength of 2080 nm, pulse duration of 350 ?s and energy of 1600 mJ. The tissue samples were immerged in pure water at different depths of 11, 16, 21, 26 and 31 mm. The working distance between the fiber tip and tissue surface was fixed at 1 mm for all studies. The dynamic interaction between laser, water and tissue were recorded by high-speed camera, and the morphological changes of bone tissue were assessed by stereomicroscope and OCT. The results showed that many times expansion and collapse of bubble were observed, more than four pulsation periods were accurately achieved with the most energy deposited in the first period and the bubble became more and more irregular in shape. The longitudinal length (7.49--6.74 mm) and transverse width (6.69--6.08 mm) of bubble were slowly decreased while volume (0.0586--0.0124 mm3) of ablation craters were drastically reduced, with static pressure increasing. The results also presented that the water-layer on hard-tissue surface can not only reduce thermal injury but also improve lubricity of craters, although the water-layer reduced ablation efficiency.

  14. Trends in Ln(III) Sorption to Quartz Assessed by Molecular Dynamics Simulations and Laser Induced Flourescence Studies

    SciTech Connect

    Kuta, Jadwiga; Wander, Matthew C F.; Wang, Zheming; Jiang, Siduo; Wall, Nathalie; Clark, Aurora E.

    2011-11-08

    Molecular dynamics simulations were performed to examine trends in trivalent lanthanide [Ln(III)] sorption to quartz surface SiOH0 and SiO- sites across the 4f period. Complementary laser induced fluorescence studies examined Eu(III) sorption to quartz at varying ionic strength such that the surface sorbed species could be extrapolated at zero ionic strength, the conditions under which the simulations are performed. This allowed for direct comparison of the data, enabling a molecular understanding of the surface sorbed species and the role of the ion surface charge density upon the interfacial reactivity. Thus, this combined theoretical and experimental approach aids in the prediction of the fate of trivalent radioactive contaminants at temporary and permanent nuclear waste storage sites. Potential of mean force molecular dynamics, as well as simulations of pre-sorbed Ln(III) species agrees with the spectroscopic study of Eu(III) sorption, indicating that strongly bound inner-sphere complexes are formed upon sorption to an SiO- site. The coordination shell of the ion contains 6-7 waters of hydration and it is predicted that surface OH groups dissociate from the quartz and bind within the inner coordination shell of Eu(III). Molecular simulations predict less-strongly bound inner2 sphere species in early lanthanides and more strongly bound species in late lanthanides, following trends in the ionic radius of the 4f ions. The participation of surface dissociated OHgroups within the inner coordination shell of the Ln(III) ion is, however, consistent across the series studied. Sorption to a fully protonated quartz surface is not predicted to be favorable by any Ln(III), except perhaps Lu.

  15. Laser-induced resonance states as dynamic suppressors of ionization in high-frequency short pulses

    E-print Network

    Baer, Roi

    -dependent wave-packet computations 25 . The shape of the pulse envelope is known to have an effect on the dynamic the adiabatic equations involve only the pulse envelope where transitions are purely ramp effects. For a short electron with high-frequency continuous- wave CW laser fields. Gavrila and co-workers developed a high

  16. Behavior of materials at dynamic stress conditions using laser-induced shock waves

    NASA Astrophysics Data System (ADS)

    Gilath, Irith; Eliezer, S.; Bar-Noy, T.; Englman, R.; Jaeger, Z.

    1993-08-01

    A high irradiance short pulsed Nd:glass operated in TEM00 mode was used to generate shock waves in different materials to study their behavior at dynamic stress condition. Dynamic fracture at hypervelocity impact regime was observed as a result of reflected shock waves as tensile waves from the back surface of the samples. Damage development from incipient spallation to complete sample perforation were obtained for planar and hemispherical shock waves. Maximum elongation at fracture at ultra high strain rate was measured for several metals. Shock wave attenuation and dynamic strength were evaluated for metals and composites. A linear dependence was obtained for the pressure decay as a function of target thickness for planar shock wave. The experimental results of threshold for spall and spall width at this energy were compared with numerical simulations. The laser pulses were also used to generate hemispherical shock waves in targets (focal spot smaller than target thickness). A linear experimental relationship was obtained between laser energy for threshold spall conditions and the cubic target thickness. This relation is equivalent with the propagation of a strong point explosion where the internal energy per unit volume of the shocked materials is constant. The shock wave was modeled by an expanding pressure front, which creates micro-damage in the laser impacted layer and extrudes a bulge at the far surface. The calculated bulge size compares well with that observed by us for metal-adhesive-metal sandwiches. The micro-defects joining into macro-damage or fracture can be described by percolation theory.

  17. Laser-induced damage in biological tissue: Role of complex and dynamic optical properties of the medium

    NASA Astrophysics Data System (ADS)

    Ahmed, Elharith M.

    Since its invention in the early 1960's, the laser has been used as a tool for surgical, therapeutic, and diagnostic purposes. To achieve maximum effectiveness with the greatest margin of safety it is important to understand the mechanisms of light propagation through tissue and how that light affects living cells. Lasers with novel output characteristics for medical and military applications are too often implemented prior to proper evaluation with respect to tissue optical properties and human safety. Therefore, advances in computational models that describe light propagation and the cellular responses to laser exposure, without the use of animal models, are of considerable interest. Here, a physics-based laser-tissue interaction model was developed to predict the spatial and temporal temperature and pressure rise during laser exposure to biological tissues. Our new model also takes into account the dynamic nature of tissue optical properties and their impact on the induced temperature and pressure profiles. The laser-induced retinal damage is attributed to the formation of microbubbles formed around melanosomes in the retinal pigment epithelium (RPE) and the damage mechanism is assumed to be photo-thermal. Selective absorption by melanin creates these bubbles that expand and collapse around melanosomes, destroying cell membranes and killing cells. The Finite Element (FE) approach taken provides suitable ground for modeling localized pigment absorption which leads to a non-uniform temperature distribution within pigmented cells following laser pulse exposure. These hot-spots are sources for localized thermo-elastic stresses which lead to rapid localized expansions that manifest themselves as microbubbles and lead to microcavitations. Model predictions for the interaction of lasers at wavelengths of 193, 694, 532, 590, 1314, 1540, 2000, and 2940 nm with biological tissues were generated and comparisons were made with available experimental data for the retina, cornea or the skin. Good agreement between model and experimental results established the validity of the model.

  18. Dynamics of a laser-induced relativistic electron beam inside a solid dielectric

    NASA Astrophysics Data System (ADS)

    Sarkisov, G. S.; Ivanov, V. V.; Sentoku, Y.; Yates, K.; Leblanc, P.; Wiewior, P.; Kindel, J.; Bychenkov, V. Yu.; Jobe, D.; Spielman, R.

    2010-11-01

    Two-frame interferometry and shadowgraphy were used to investigate the dynamics of interaction of a powerful laser (UNR Leopard 2x10^18 W/cm^2, 0.5ps, 1057nm) with a glass target. The two-frame laser diagnostic reveals an ionization wave propagating inside the glass with half the speed of light. The interferometry delineates regions of ionization and excitation inside the glass target. A ``fountain effect'' of fast electrons inside the solid dielectric has been observed for the first time: a radially compact electron beam with sub-light speed fans out from the axis of the original beam, heading back to the target surface. Comparison with French (˜10^19W/cm^2) and UK (˜10^17W/cm^2) experiments implies a logarithmic dependence of the ionization depth with the laser intensity. Relativistic electron beam dynamics stemming from intense laser-glass interaction is a critical concern for the NIF ``fast ignition'' concept.

  19. All-optical signal processing using dynamic Brillouin gratings

    PubMed Central

    Santagiustina, Marco; Chin, Sanghoon; Primerov, Nicolay; Ursini, Leonora; Thévenaz, Luc

    2013-01-01

    The manipulation of dynamic Brillouin gratings in optical fibers is demonstrated to be an extremely flexible technique to achieve, with a single experimental setup, several all-optical signal processing functions. In particular, all-optical time differentiation, time integration and true time reversal are theoretically predicted, and then numerically and experimentally demonstrated. The technique can be exploited to process both photonic and ultra-wide band microwave signals, so enabling many applications in photonics and in radio science. PMID:23549159

  20. Gelator-doped liquid-crystal phase grating with multistable and dynamic modes

    SciTech Connect

    Lin, Hui-Chi, E-mail: huichilin@nfu.edu.tw; Yang, Meng-Ru; Tsai, Sheng-Feng; Yan, Shih-Chiang [Department of Electro-Optical Engineering, National Formosa University, Yunlin 632, Taiwan (China)] [Department of Electro-Optical Engineering, National Formosa University, Yunlin 632, Taiwan (China)

    2014-01-06

    We demonstrate a gelator-doped nematic liquid-crystal (LC) phase grating, which can be operated in both the multistable mode and the dynamic mode. Thermoreversible association and dissociation of the gelator molecules can vary and fix the multistable diffraction efficiencies of the gratings. A voltage (V) can also be applied to modulate dynamically the diffraction efficiencies of the grating, which behaves as a conventional LC grating. Experimental results show that the variations of the diffraction efficiencies in the multistable and dynamic modes are similar. The maximum diffraction efficiency is approximately 30% at V?=?2?V.

  1. Nanoparticle removal using laser induced plasma (LIP) technique and study of detachment modes based on molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Peri, M. D. Murthy

    Nanoparticle contamination is a major problem in many industries. In the semiconductor industry, as the device (integrated circuit) size shrinks with each technological node (DRAM half-pitch), the feature size that has to be fabricated shrinks. Consequently, the minimum tolerable particle defect size also reduces to sub-100 nm level. In order to attain the stringent small size features, Extreme Ultraviolet Lithography (EUVL) technique is being explored in the semiconductor industry. As the EUVL masks are reflective and pellicle free, the cleaning techniques employed to remove the native particle defects must be more effective for the removal of the sub-100 nm particles without any substrate damage. The effectiveness of Laser Induced Plasma (LIP) technique, considered as a next generation cleaning method, for removal of 30 nm PSL particles from silicon substrate was previously demonstrated by our group. In the current study, the removal of 100 nm PSL particles from photomask and 300 nm PSL particles from 500 nm patterns was investigated. It was observed that the patterns were damaged which could be attributed to the radiation heating of the plasma, and this necessitated pressure amplification techniques to amplify the transient pressure and minimize the risk of damage. As a potential solution, shocktubes were designed and transient pressure measurements were carried out in air medium. Also, plasma was generated in water, in order to take advantage of the density of the medium, to generate stronger shocks and consequently higher pressure. The performance of the shocktubes was characterized based on their pressure amplification factor. The shocktubes resulted in a pressure amplification factor of 11 in air. The particle removal experiments with shocktubes on 150 nm patterns were performed and no damage to the patterns was observed. However, there were particle adders due to the ablation of the shocktube material. Molecular Dynamics (MD) simulations were initiated and the objective was two fold, to understand (i) nanoparticle-shockwave and (ii) nanoparticle-substrate, interactions. To study the effect of nano-scale particle size on and their interaction with the LIP shockwaves, Direct Simulation Monte Carlo (DSMC) simulations were performed. Two potential nanoparticle removal mechanisms, namely rolling resistance moment and the rocking frequency criterion were identified. Large scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) simulations were initiated to understand the nanoparticle-substrate adhesion at atomic levels. The rolling resistance moment calculated from the slope of force-displacement curves obtained when the particle was pushed in the lateral direction was in good agreement with the rolling resistance moment calculated using the two-dimensional adhesion theory. In the case of an irregular particle, rolling is initiated and this resulted in the liftoff of the particle from the substrate, as most of the particle lost contact with the substrate during rolling. The experimental results demonstrating successful local area (spot) cleaning of the native particles from the EUVL mask, using the Laser Shock Cleaning tool were presented.

  2. Direct methods for dynamic monitoring of secretions from single cells by capillary electrophoresis and microscopy with laser-induced native fluorescence detection

    SciTech Connect

    Tong, W.

    1997-10-08

    Microscale separation and detection methods for real-time monitoring of dynamic cellular processes (e.g., secretion) by capillary electrophoresis (CE) and microscopic imaging were developed. Ultraviolet laser-induced native fluorescence (LINF) provides simple, sensitive and direct detection of neurotransmitters and proteins without any derivatization. An on-column CE-LINF protocol for quantification of the release from single cell was demonstrated. Quantitative measurements of both the amount of insulin released from and the amount remaining in the cell ({beta}TC3) were achieved simultaneously. Secretion of catecholamines (norepinephrine (NE) and epinephrine (E)) from individual bovine adrenal chromaffin cells was determined using the on-column CE-LINF. Direct visualization of the secretion process of individual bovine adrenal chromaffin cells was achieved by LINF imaging microscopy with high temporal and spatial resolution. The secretion of serotonin from individual leech Retzius neurons was directly characterized by LINF microscopy with high spatial resolution.

  3. Dynamic Encoder/Decoder Based on Fiber Bragg Gratings for Optical Security System

    NASA Astrophysics Data System (ADS)

    Peng, Peng-Chun; Peng, Wei-Ren; Lin, Wen-Piao; Chi, Sien

    2004-12-01

    A novel dynamic encoder/decoder based on fiber Bragg gratings for optical security systems is presented in this paper. The encoded and decoded optical communication signals can be realized by controlling the optical switches and fiber Bragg grating arrangement. We describe the system operation principle and set up an experimental encoder/decoder to demonstrate the feasibility of the proposed scheme.

  4. Laser-induced nanowelding of gold nanoparticles

    Microsoft Academic Search

    Seol Ji Kim; Du-Jeon Jang

    2005-01-01

    Picosecond laser pulses are employed to adjoin, to hold closely, and to weld gold nanoparticles on carbon-coated copper grids. Microscopic images and profiles indicate that gold particles are well connected showing single-phased nanocontact. Our results suggest that laser-induced nanowelding can be achieved in a programmed manner to produce ohmic contact by considering the size-dependent thermodynamic, dynamic, and kinetic properties of

  5. Laser-induced ultrafast spin dynamics in di-, tri- and tetranuclear nickel clusters, and the M process

    NASA Astrophysics Data System (ADS)

    Chaudhuri, D.; Xiang, H. P.; Lefkidis, G.; Hübner, W.

    2014-12-01

    In this manuscript we present an ab initio picture of ultrafast magneto-optical dynamics in clusters containing 2, 3, and 4 Ni atoms. The presence of the magnetic centers in the clusters renders our systems of choice highly interesting for studying ultrafast spin dynamics. Here we systematically study functional cooperativity by increasing both the number of active centers and the spin multiplicities included in our Hilbert space (singlets ? triplets ? quintets), and deriving several ultrafast, laser-driven, spin-manipulation scenarios. Our results indicate various cooperative effects like spin flip by the M process, and simultaneous spin flip and spin transfer, as well as reversible and irreversible demagnetization scenarios. As it turns out the functional cooperativity of the clusters strongly benefits from the delicate interplay of the spin multiplicity and the number of active centers.

  6. Quantum dynamical simulations of the femtosecond-laser-induced ultrafast desorption of H2 and D2 from Ru(0001).

    PubMed

    Füchsel, Gernot; Tremblay, Jean Christophe; Klamroth, Tillmann; Saalfrank, Peter

    2013-05-10

    We investigate the recombinative desorption of hydrogen and deuterium from a Ru(0001) surface initiated by femtosecond laser pulses. We adopt a quantum mechanical two-state model including three molecular degrees of freedom to describe the dynamics within the desorption induced by electronic transition (DIET) limit. The energy distributions as well as the state-resolved and ensemble properties of the desorbed molecules are analyzed in detail by using the time-energy method. Our results shed light on the experimentally observed 1) large isotopic effects regarding desorption yields and translational energies and 2) the nonequal energy partitioning into internal and translational modes. In particular, it is shown that a single temperature is sufficient to characterize the energy distributions for all degrees of freedom. Further, we confirm that quantization effects play an important role in the determination of the energy partitioning. PMID:23426934

  7. Dynamics of femtosecond laser-induced periodic surface structures on silicon by high spatial and temporal resolution imaging

    SciTech Connect

    Jia, X., E-mail: jiaxin@sdju.edu.cn [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Department of Mathematics and Physics, Shanghai Dianji University, Shanghai 201306 (China); Jia, T. Q., E-mail: tqjia@phy.ecnu.edu.cn; Peng, N. N.; Feng, D. H.; Zhang, S. A.; Sun, Z. R. [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China)

    2014-04-14

    The formation dynamics of periodic ripples induced by femtosecond laser pulses (pulse duration ??=?50 fs and central wavelength ??=?800?nm) are studied by a collinear pump-probe imaging technique with a temporal resolution of 1?ps and a spatial resolution of 440?nm. The ripples with periods close to the laser wavelength begin to appear upon irradiation of two pump pulses at surface defects produced by the prior one. The rudiments of periodic ripples emerge in the initial tens of picoseconds after fs laser irradiation, and the ripple positions keep unmoved until the formation processes complete mainly in a temporal span of 1500?ps. The results suggest that the periodic deposition of laser energy during the interaction between femtosecond laser pulses and sample surface plays a dominant role in the formation of periodic ripples.

  8. Laser-Induced Incandescence Calibration via Gravimetric Sampling

    NASA Technical Reports Server (NTRS)

    VanderWal, R. L.; Zhou, Z.; Choi, M. Y.

    1995-01-01

    Various beam imaging and/or sheet forming optics delivered light at 1064 nm from a pulsed Nd:YAG laser for use either as a beam of 3 mm radius or as a laser sheet. Imaging measurements were performed with a grated intensified array camera equipped with an ultraviolet f4.5 lens and a 40 mm extension tube. Point measurements were performed using an ultraviolet 250 mm focal length lens to collect and focus the laser induced incandescence (LII) signal into a 1 meter long quartz optical fiber which directed the LII signal to a 1/4 meter monochromator. An aperture preceding the lens restricted the signal collection region to 1 cm along the laser beam at the center of the gravimetric chimney. Signals from the PMT were processed by a boxcar integrator whereas the images were captured digitally using a frame-grabber with 16 MByte of on-board memory. Both 'point' and planar measurements were made with detector gates of 250 ns to minimize possible morphology bias in collection of the LII signal. Additionally, the imaging measurements were performed with broadband spectral collection of the LII signal to maximize the signal and again minimize any potential effects of morphology dependent heating and/or cooling rates. Digital delay generators controlled the firing of he laser, detector gates and data acquisition. Neutral density filters were used for both sets of measurements to maintain signal levels within linear dynamic ranges of the detectors, the range being determined prior to experiments.

  9. Dynamic interrogator for elastic wave sensing using Fabry Perot filters based on fiber Bragg gratings.

    PubMed

    Harish, Achar V; Varghese, Bibin; Rao, Babu; Balasubramaniam, Krishnan; Srinivasan, Balaji

    2015-07-01

    Use of in-fiber Fabry-Perot (FP) filters based on fiber Bragg gratings as both sensor as well as an interrogator for enhancing the detection limit of elastic wave sensing is investigated in this paper. The sensitivity of such a demodulation scheme depends on the spectral discrimination of the sensor and interrogator gratings. Simulations have shown that the use of in-fiber FP filters with high finesse provide better performance in terms of sensitivity compared to the demodulation using fiber Bragg gratings. Based on these results, a dynamic interrogator capable of sensing acoustic waves with amplitude of less than 1 micro-strain over frequencies of 10kHz to several 100kHz has been implemented. Frequency response of the fiber Bragg gratings in the given experimental setup has been compared to that of the conventional piezo sensors demonstrating that fiber Bragg gratings can be used over a relatively broad frequency range. Dynamic interrogator has been packaged in a compact box without any degradation in its performance. PMID:25783780

  10. Dynamic analysis and temperature measurements of concrete cantilever beam using fibre Bragg gratings

    Microsoft Academic Search

    Jean Carlos Cardozo da Silva; Cicero Martelli; Hypolito José Kalinowski; Elisabeth Penner; John Canning; Nathaniel Groothoff

    2007-01-01

    We analyzed the action of fire, causing degradation in a concrete cantilever beam using dynamic testing. The structure was fitted with two fibre Bragg gratings (FBG) sensors. One of them measured vibration and the other measured the temperature inside of the cantilever beam, while the beam was exposed to fire. A high-temperature probe based on a simple packaging system, which

  11. Quenched by ice: Transient grating measurements of vibronic dynamics in bromine-doped ice

    E-print Network

    Apkarian, V. Ara

    Quenched by ice: Transient grating measurements of vibronic dynamics in bromine-doped ice I. U April 2006; published online 25 May 2006 In both water and in ice, the absorption spectra of bromine of clathrate hydrates,1,2 bromine hydrate being one of the earliest discovered.3 The concept is to use

  12. Detection, Evaluation, and Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitations

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Lekki, John; Lock, James A.

    2002-01-01

    The dynamic response of a fiber optic Bragg grating to mechanical vibrations is examined both theoretically and experimentally. The theoretical expressions describing the consequences of changes in the grating's reflection spectrum are derived for partially coherent beams in an interferometer. The analysis is given in terms of the dominant wavelength, optical bandwidth, and optical path difference of the interfering signals. Changes in the reflection spectrum caused by a periodic stretching and compression of the grating were experimentally measured using an unbalanced Michelson interferometer, a Michelson interferometer with a non-zero optical path difference. The interferometer's sensitivity to changes in dominant wavelength of the interfering beams was measured as a function of interferometer unbalance and was compared to theoretical predictions. The theoretical analysis enables the user to determine the optimum performance for an unbalanced interferometer.

  13. Super-resolution imaging in digital holography by using dynamic grating with a spatial light modulator

    NASA Astrophysics Data System (ADS)

    Lin, Qiaowen; Wang, Dayong; Wang, Yunxin; Rong, Lu; Chang, Shifeng

    2015-03-01

    A super-resolution imaging method using dynamic grating based on liquid-crystal spatial light modulator (SLM) is developed to improve the resolution of a digital holographic system. The one-dimensional amplitude cosine grating is loaded on the SLM, which is placed between the object and hologram plane in order to collect more high-frequency components towards CCD plane. The point spread function of the system is given to confirm the separation condition of reconstructed images for multiple diffraction orders. The simulation and experiments are carried out for a standard resolution test target as a sample, which confirms that the imaging resolution is improved from 55.7 ?m to 31.3 ?m compared with traditional lensless Fourier transform digital holography. The unique advantage of the proposed method is that the period of the grating can be programmably adjusted according to the separation condition.

  14. Dynamically selective multiwavelength cross-connect based on fibre Bragg gratings and mechanical optical switches

    Microsoft Academic Search

    YUNG-KUANG CHEN; SHIEN-KUEI LIAW; CHIEN-CHUNG LEE

    1998-01-01

    A dynamically selective multiwavelength cross-connect for wavelength division multiplexed (WDM) networks based on fibre Bragg gratings (FBGs) and optical switches is reported. Dynamically single- or multi-channel cross-connect functionality can be realized according to control of the optical switches and the FBGs' arrangement. Bit-error-rate performance with negligible power penalty is achieved in a 2.5Gbs-1x3 WDM channels over 100km conventional single-mode fibre

  15. PLANAR LASER-INDUCED FLUORESCENCE (PLIF) H2 O2 COMBUSTION

    E-print Network

    Texas at Arlington, University of

    PLANAR LASER-INDUCED FLUORESCENCE (PLIF) OF H2 ­ O2 COMBUSTION The members of the Committee approve (PLIF) OF H2 ­ O2 COMBUSTION by TAKASHI YOKOMAE Presented to the Faculty of the Graduate School, Chris Roseberry and Philip Panicker, just to name a few. I am grateful to my mother, Tsugiko

  16. Laser-induced fluorescence imaging of subsurface tissue structures with a volume holographic

    E-print Network

    Barton, Jennifer K.

    Laser-induced fluorescence imaging of subsurface tissue structures with a volume holographic, 2008 A three-dimensional imaging system incorporating multiplexed holographic gratings to visualize such as a phenanthrenquinone poly(methyl methacrylate) photopolymer have narrowband angular and spectral transmittance

  17. Single grating x-ray imaging for dynamic biological systems

    NASA Astrophysics Data System (ADS)

    Morgan, Kaye S.; Paganin, David M.; Parsons, David W.; Donnelley, Martin; Yagi, Naoto; Uesugi, Kentaro; Suzuki, Yoshio; Takeuchi, Akihisa; Siu, Karen K. W.

    2012-07-01

    Biomedical studies are already benefiting from the excellent contrast offered by phase contrast x-ray imaging, but live imaging work presents several challenges. Living samples make it particularly difficult to achieve high resolution, sensitive phase contrast images, as exposures must be short and cannot be repeated. We therefore present a single-exposure, high-flux method of differential phase contrast imaging [1, 2, 3] in the context of imaging live airways for Cystic Fibrosis (CF) treatment assessment [4]. The CF study seeks to non-invasively observe the liquid lining the airways, which should increase in depth in response to effective treatments. Both high spatial resolution and sensitivity are required in order to track micron size changes in a liquid that is not easily differentiated from the tissue on which it lies. Our imaging method achieves these goals by using a single attenuation grating or grid as a reference pattern, and analyzing how the sample deforms the pattern to quantitatively retrieve the phase depth of the sample. The deformations are mapped at each pixel in the image using local cross-correlations comparing each 'sample and pattern' image with a reference 'pattern only' image taken before the sample is introduced. This produces a differential phase image, which may be integrated to give the sample phase depth.

  18. Laser-induced plasmas from the ablation of metallic targets: The problem of the onset temperature, and insights on the expansion dynamics

    SciTech Connect

    Bleiner, Davide; Bogaerts, Annemie; Belloni, Fabio; Nassisi, Vincenzo [Department of Chemistry, University of Antwerpen, Universiteitsplein 1, Antwerp, 2610 Flanders (Belgium); Department of Physics, University of Lecce, via Arnesano, CP 193, 73100 Lecce (Italy)

    2007-04-15

    Laser-induced plasmas are transient systems rapidly aging in few nanoseconds of evolution. Time-of-flight spectrometry allowed studying initial plasma characteristics based on frozen translational degrees of freedom, hence overcoming intrinsic limitations of optical spectroscopy. Experimental ion velocity distributions were reconstructed as developed during the longitudinal plasma expansion. The obtained onset plasma temperatures are in the range of {approx}18-45 eV depending on the ablated metals. Also the ion angular spreads were found to be a function of ablated metal, e.g., the narrowest for Fe, the broadest for Al, due to different collisional coupling in the plasma population.

  19. The pecularities of formation of dynamic gratings in metal vapors at the optical pumping of atomic hyperfine sublevels

    SciTech Connect

    Nazarov, V.N. [Vavilov State Optical Institute, St. Petersburg (Russian Federation)

    1994-07-01

    The properties of the resonant dynamic gratings produced in atomic cesium vapors by low-power beams of a semiconductor laser are studied. It is shown, both experimentally and theoretically, that the efficiency of laser-beam diffraction on dynamic gratings in a three-level atomic medium can be appreciably increased owing to the compensation of medium bleaching by the increase in initial atomic concentration. The spatial frequency response of an atomic medium during optical pumping is shown to be substantially non-uniform and to have a strong rise in the range of low spatial frequencies of the gratings. 22 refs., 4 figs.

  20. Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps.

    PubMed

    Antman, Y; Primerov, N; Sancho, J; Thevenaz, L; Zadok, A

    2012-03-26

    A novel technique for the localization of stimulated Brillouin scattering (SBS) interaction is proposed, analyzed and demonstrated experimentally. The method relies on the phase modulation of two counter-propagating optical waves by a common pseudo-random bit sequence (PRBS), these waves being spectrally detuned by the Brillouin frequency shift. The PRBS symbol duration is much shorter than the acoustic lifetime. The interference between the two modulated waves gives rise to an acoustic grating that is confined to narrow correlation peaks, as short as 1.7 cm. The separation between neighboring peaks, which is governed by the PRBS length, can be made arbitrarily long. The method is demonstrated in the generation and applications of dynamic gratings in polarization maintaining (PM) fibers. Localized and stationary acoustic gratings are induced by two phase modulated pumps that are polarized along one principal axis of the PM fiber, and interrogated by a third, readout wave which is polarized along the orthogonal axis. Using the proposed technique, we demonstrate the variable delay of 1 ns-long readout pulses by as much as 770 ns. Noise due to reflections from residual off-peak gratings and its implications on the potential variable delay of optical communication data are discussed. The method is equally applicable to the modulation of pump and probe waves in SBS over standard fibers. PMID:22453458

  1. Sensing of halocarbons using femtosecond laser-induced fluorescence.

    PubMed

    Gravel, J-F; Luo, Q; Boudreau, D; Tang, X P; Chin, S L

    2004-08-15

    A femtosecond laser-induced clean fluorescence technique was explored as a means to monitor halogenated alkanes in the atmosphere. Characteristic difluorocarbene radical (CF2) fluorescence in the UV-vis can be generated inside a femtosecond laser-induced filament for different halocarbons. We show that, due to different dissociation and excitation kinetics leading to fluorescence emission, it is possible to temporally resolve the characteristic fluorescence of CF2-containing halocarbons from that of background species, therefore enhancing the signal-to-noise ratio. Laboratory-scale experiments demonstrate the potential use of femtosecond laser-induced clean fluorescence for the remote sensing of halocarbons in the atmosphere. The combination of this detection strategy with LIDAR could allow the long-range monitoring of several atmospheric species with a single laser source, eventually leading to a better understanding of chemical and dynamic processes affecting global warming, ozone loss, tropospheric pollution, and weather prediction. PMID:15307791

  2. Dynamics of Jacobi's elliptic spatial waves in a nonlinear optical grating

    SciTech Connect

    Alatas, Husin [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jl. Meranti, Kampus IPB Darmaga, Bogor 16680 (Indonesia)

    2011-04-15

    This paper presents the results of our study on the dynamics of Jacobi's elliptic spatial waves in a nonlinear optical grating based on a generalized coupled-mode model. We discuss the characteristics of their amplitudes, widths, and spatial periods as well as their bifurcation in the associated phase plane. Our study on the dynamical propagation of perturbed profiles reveal that these waves can suffer breathing and broadening due to the diffraction effect. A remarkable split-off phenomenon of a spatial wave with wide stripes into several narrow and shallow oblique stripes is observed, as well as their passing and bouncing collisions.

  3. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Crim, F.F. [Univ. of Wisconsin, Madison (United States)

    1993-12-01

    This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.

  4. Compact fiber Bragg grating dynamic strain sensor cum broadband thermometer for thermally unstable ambience

    NASA Astrophysics Data System (ADS)

    Sreekumar, K.; Asokan, S.

    2010-01-01

    An instrument for simultaneous measurement of dynamic strain and temperature in a thermally unstable ambience has been proposed, based on fiber Bragg grating technology. The instrument can function as a compact and stand-alone broadband thermometer and a dynamic strain gauge. It employs a source wavelength tracking procedure for linear dependence of the output on the measurand, offering high dynamic range. Two schemes have been demonstrated with their relative merits. As a thermometer, the present instrumental configuration can offer a linear response in excess of 500 °C that can be easily extended by adding a suitable grating and source without any alteration in the procedure. Temperature sensitivity is about 0.06 °C for a bandwidth of 1 Hz. For the current grating, the upper limit of strain measurement is about 150 µ? with a sensitivity of about 80 n? Hz-1/2. The major source of uncertainty associated with dynamic strain measurement is the laser source intensity noise, which is of broad spectral band. A low noise source device or the use of optical power regulators can offer improved performance. The total harmonic distortion is less than 0.5% up to about 50 µ?,1.2% at 100 µ? and about 2.3% at 150 µ?. Calibrated results of temperature and strain measurement with the instrument have been presented. Traces of ultrasound signals recorded by the system at 200 kHz, in an ambience of 100-200 °C temperature fluctuation, have been included. Also, the vibration spectrum and engine temperature of a running internal combustion engine has been recorded as a realistic application of the system.

  5. Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves.

    PubMed

    Antman, Yair; Levanon, Nadav; Zadok, Avi

    2012-12-15

    A method for long variable all-optical delay is proposed and simulated, based on reflections from localized and stationary dynamic Brillouin gratings (DBGs). Inspired by radar methods, the DBGs are inscribed by two pumps that are comodulated by perfect Golomb codes, which reduce the off-peak reflectivity. Compared with random bit sequence coding, Golomb codes improve the optical signal-to-noise ratio (OSNR) of delayed waveforms by an order of magnitude. Simulations suggest a delay of 5??Gb/s data by 9 ns, or 45 bit durations, with an OSNR of 13 dB. PMID:23258071

  6. Characterization of distributed modal birefringence in a few-mode fiber based on Brillouin dynamic grating.

    PubMed

    Li, An; Hu, Qian; Chen, Xi; Kim, Byoung Yoon; Shieh, William

    2014-06-01

    We propose and demonstrate generation of Brillouin dynamic grating (BDG) in a few-mode fiber (FMF) with a Gaussian pulse pump and a counterpropagating continuous wave pump in LP01 mode. Brillouin optical time-domain analysis (BOTDA) is achieved by launching a third Gaussian pulse probe in LP11 mode. With coherent detection and time-domain analysis on the backreflected probe signal, the modal birefringence of the FMF is characterized via the distributed BDG with high spatial resolution and high accuracy. PMID:24876000

  7. Laser induced shock waves in deformation processing

    Microsoft Academic Search

    H. Schulze Niehoff; F. Vollertsen

    Processes based on laser induced shock waves in deformation processing are reviewed in this paper. One widely used process is laser shock processing (LSP) for mechanical surface hardening, which is presented on the basis of a literature inquiry. Two further processes are laser stretch forming and assistance of laser induced shock waves in bending of hybrid blanks. These two processes

  8. Impact of self-steepening on the dynamics of a passively modelocked fiber laser containing a long period fiber grating

    NASA Astrophysics Data System (ADS)

    Karar, Abdullah S.; Smy, Tom; Steele, Alan L.

    2008-06-01

    We report on a numerical investigation of the effect of self-steepening on the dynamics of a passively modelocked fiber laser containing a long period fiber grating. The numerical model is based on the normalized complex Ginzburg-Landau equation and the nonlinear coupled mode equations of the grating. The nonlinear dynamics of the laser are observed through plotting the pulse energy against the linearly increasing gain so obtaining bifurcation diagrams. The inclusion of self-steepening was found to result in a temporal walk-off with no significant pulse width or energy alternations, while exhibiting different regions of period doubling bifurcation.

  9. Laser induced melting and crystallization of boron doped amorphous silicon

    SciTech Connect

    Nebel, C.E.; Schoeniger, S.; Dahlheimer, B.; Stutzmann, M.

    1997-07-01

    Transient reflectivity experiments have been performed to measure the dynamics of laser-induced melting of amorphous silicon (a-Si) and the crystallization to {micro}c-Si of films with different thicknesses on Corning 7059 glass. The laser-induced melting takes place with a velocity of 13 to 24 m/s, while the solidification is about a factor 10 slower. The crystallization starts at the Si/glass interface and at the surface. In the center of the films Si remains liquid for an extended period of time. The crystallization dynamics point towards an heterogeneous morphology of laser-crystallized Si, where the surface and the interface layers are composed of small grains and the bulk of larger grains.

  10. Dynamic trapping of terahertz waves by silicon-filled metallic grating structure

    NASA Astrophysics Data System (ADS)

    Yuan, Yinghao; Liu, Jinsong; He, Jian; Yao, Jianquan

    2014-12-01

    We investigate the feasibility of dynamic trapping of terahertz waves using a silicon-filled metallic grating structure. Using the dispersion relation analysis and the two-dimensional finite element method simulations, we reveal that, if a graded refractive index distribution in the grooves is optical induced, the device has the ability to dynamic trap terahertz waves of different frequencies at different positions (so-called trapping rainbow). Moreover, we demonstrate that the trapped position of a certain frequency of the terahertz waves can be moved continuously along the grooves in subwavelength scale by ingenious control of the distributions of the refractive indices of silicon filled in the grooves. Our design has the potential for the construction of active plasmonic terahertz devices, such as optical controlled terahertz filter, router and demultiplexer in a broadband terahertz communication system.

  11. Ultrafast heterodyne-detected grating studies of heme protein dynamics using diffractive optics

    NASA Astrophysics Data System (ADS)

    Goodno, Gregory Douglas

    1999-10-01

    The initial structural evolution of carboxymyoglobin (MbCO) following photodissociation of CO is measured with a novel technique of optically heterodyne-detected transient grating spectroscopy that is based on the use of a diffractive optic phase mask to generate the appropriate spatial beam pattern. This method increases the sensitivity, generates tilted pulse fronts to greatly reduce temporal broadening in non-collinear beam geometries, and provides an inherent acoustic reference that enables unambiguous separation of the real and imaginary components to the nonlinear susceptibility. With the latter advance, both the absorption anisotropy and its real counterpart, the phase anisotropy, can be measured with this technique. Access to the real part of the material anisotropy provides new information that can be correlated to thermal relaxation and structural changes in the protein. The phase anisotropy of MbCO is found to develop on picosecond time scales and is much greater than can be attributed to the symmetry of the heme dipole transition. A geometric decomposition of the grating signals into contributions relative to the molecular axes provides evidence that the shape of the protein changes within 500 femtoseconds following photodissociation. The asymmetric nature of the protein structure presumably plays an integral role in the development of the nonuniform displacements. The anisotropic relaxation and observed dynamics provide strong evidence that the low-frequency collective modes of the protein are involved in transducing the reaction forces of the Fe ligation site into directed motions associated with the initial ligated to deligated tertiary structure change.

  12. Molecular dynamics in azobenzene liquid crystal polymer films studied by transient grating technique

    NASA Astrophysics Data System (ADS)

    Katayama, Kenji; Fujii, Tomomi; Kuwahara, Shota; Takado, Kiyohide; Ikeda, Tomiki

    2014-10-01

    We studied the effect of the ratio between the monomer and cross-linker molecules in the azobenene included liquid crystal polymer films by using the heterodyne transient grating (HD-TG) technique, which is one of the time-resolved measurement techniques. Depending on the ratio, the magnitude of the refractive index change, its anisotropy, and the lifetime of the cis isomer of azobenzene, generated by a UV pulse irradiation. By increasing the cross-linker ratio, the refractive index change and its anisotropy was reduced, indicating less ability for the motion, while slower lifetime was observed by increasing the monomer ratio, indicating that the film is difficult to return the original shape by a visiblelight irradiation. The obtained dynamics was consistent with the functionality of the films.

  13. Grating dynamics in a photorefractive polymer with Alq(3) electron traps.

    PubMed

    Christenson, C W; Thomas, J; Blanche, P-A; Voorakaranam, R; Norwood, R A; Yamamoto, M; Peyghambarian, N

    2010-04-26

    The electron transporting molecule tris(8-hydroxyquinoline) aluminum (Alq(3)) was added in low concentrations to a photorefractive polymer composite to provide trapping sites for electrons. This sample exhibited larger two-beam coupling gain, higher diffraction efficiency at lower voltages, and an increased dielectric breakdown strength compared to a control sample. The dynamics also revealed the presence of a competing grating, and a bipolar charge transport model is shown to fit the data. Overall, Alq(3) improves the response time, efficiency, and breakdown voltage without a significant increase in absorption or loss of phase stability. This has applications for reflection displays and pulsed writing, where charge trapping and generation are major factors limiting the usefulness of photorefractive polymers. PMID:20588782

  14. A laser-induced ultrasonic probe of the mechanical properties of aligned lipid multibilayers.

    PubMed Central

    Eyring, G; Fayer, M D

    1985-01-01

    The recently developed laser-induced phonon spectroscopy (LIPS) technique is applied to the determination of dynamic mechanical properties of aligned dilauroylphosphatidylcholine (DLPC) multibilayer arrays containing 2 and 20% water by weight. Sample excitation by two crossed 100-ps laser pulses generates a longitudinal ultrasonic wave whose wavelength depends on the crossing angle. In these experiments, the acoustic wave propagates parallel to the bilayer planes. The ultrasonic velocity and attenuation are monitored through the diffraction of a variably delayed probe pulse by the acoustic grating. The velocity measures the lateral area compressibility of the bilayers, while the attenuation is related to the viscosity. Velocities obtained in the gel and liquid crystal phases are compared with those found previously using Brillouin scattering. The acoustic attenuation is shown to be an order of magnitude more sensitive to the gel-liquid crystal phase transition than the velocity. The lipid area compressibility and viscosity of DLPC-20% water multilayers with and without 100 mM CaCl2 are found to be identical within our experimental error. PMID:3978188

  15. Dynamics of Ultrashort Pulse Interaction with Linear and Nonlinear Fibre Bragg Gratings

    Microsoft Academic Search

    Vijay Janyani; Ana Vukovic; Trevor Benson; John Paul; Phillip Sewell

    2006-01-01

    The paper investigates the reflection and transmission of ultra-short pulses propagating through linear and nonlinear narrowband fibre Bragg gratings, FBGs. The pulse-grating interaction is being exploited today in many applications requiring pulse shaping and pulse slicing including those in multi-wavelength communications. The time domain transmission line modelling, TLM, method is used to study the temporal pulse-grating interaction. This interaction is

  16. Dynamic Strain Sensing in a Long-Span Suspension Bridge Using Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Yinian; Zhu, Yan-Jin; Balogun, Oluwaseyi; Zhu, Songye; Xu, You-Lin; Krishnaswamy, Sridhar

    2011-06-01

    Optical fiber sensors are ideal for monitoring continuous deterioration conditions of civil infrastructure, especially of long-span bridges. Typically, a network of sensors is used to measure the strains or low frequency vibrational response of the structure. In this work, we demonstrate dynamic spectral demodulation of fiber Bragg grating (FBG) sensor responses with a stabilized Michelson interferometer for monitoring mechanical strains in a model of long-span bridge. A series of experiments has been performed, including the measurements of the natural resonant modes of the model bridge, impact response of a bridge member and acoustic emissions in a fractured aluminum bar. The experimental results not only reveal that dynamic spectral demodulation of FBG strain responses at frequencies extending up to about 3.5 MHz is possible, but also suggest that the method may be suitable for monitoring high frequency mechanical strains in civil structures that result from cracking or impact loading, thus providing a tool for local detection of structural damage.

  17. Long-lived laser-induced microwave plasma guides in the atmosphere: Self-consistent plasma-dynamic analysis and numerical simulations

    SciTech Connect

    Shneider, M. N.; Miles, R. B. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544-5263 (United States); Zheltikov, A. M. [Department of Physics, International Laser Center, M. V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation)

    2010-08-15

    A detailed model of plasma dynamics, which self-consistently integrates plasma-kinetic, Navier-Stokes, electron heat conduction, and electron-vibration energy transfer equations, is used to quantify the limitations on the lifetime of microwave plasma waveguides induced in the atmosphere through filamentation with high-intensity ultrashort laser pulses further sustained by long laser pulses. We demonstrate that a near-infrared or midinfrared laser pulse can tailor plasma decay in the wake of a filament, efficiently suppressing, through electron temperature increase, the attachment of electrons to neutral species and dissociative recombination, thus substantially increasing the plasma-guide lifetime and facilitating long-distance transmission of microwaves.

  18. Dynamic fiber Bragg gratings based health monitoring system of composite aerospace structures

    NASA Astrophysics Data System (ADS)

    Panopoulou, A.; Loutas, T.; Roulias, D.; Fransen, S.; Kostopoulos, V.

    2011-09-01

    The main purpose of the current work is to develop a new system for structural health monitoring of composite aerospace structures based on real-time dynamic measurements, in order to identify the structural state condition. Long-gauge Fibre Bragg Grating (FBG) optical sensors were used for monitoring the dynamic response of the composite structure. The algorithm that was developed for structural damage detection utilizes the collected dynamic response data, analyzes them in various ways and through an artificial neural network identifies the damage state and its location. Damage was simulated by slightly varying locally the mass of the structure (by adding a known mass) at different zones of the structure. Lumped masses in different locations upon the structure alter the eigen-frequencies in a way similar to actual damage. The structural dynamic behaviour has been numerically simulated and experimentally verified by means of modal testing on two different composite aerospace structures. Advanced digital signal processing techniques, e.g. the wavelet transform (WT), were used for the analysis of the dynamic response for feature extraction. WT's capability of separating the different frequency components in the time domain without loosing frequency information makes it a versatile tool for demanding signal processing applications. The use of WT is also suggested by the no-stationary nature of dynamic response signals and the opportunity of evaluating the temporal evolution of their frequency contents. Feature extraction is the first step of the procedure. The extracted features are effective indices of damage size and location. The classification step comprises of a feed-forward back propagation network, whose output determines the simulated damage location. Finally, dedicated training and validation activities were carried out by means of numerical simulations and experimental procedures. Experimental validation was performed initially on a flat stiffened panel, representing a section of a typical aeronautical structure, manufactured and tested in the lab and, as a second step, on a scaled up space oriented structure, which is a composite honeycomb plate, used as a deployment base for antenna arrays. An integrated FBG sensor network, based on the advantage of multiplexing, was mounted on both structures and different excitation positions and boundary conditions were used. The analysis of operational dynamic responses was employed to identify both the damage and its position. The system that was designed and tested initially on the thin composite panel, was successfully validated on the larger honeycomb structure. Numerical simulation of both structures was used as a support tool at all the steps of the work providing among others the location of the optical sensors used. The proposed work will be the base for the whole system qualification and validation on an antenna reflector in future work.

  19. Dynamic dispersion compensation in a 10Gb\\/s optical system using a novel voltage tuned nonlinearly chirped fiber Bragg grating

    Microsoft Academic Search

    K.-M. Feng; J.-X. Chai; V. Grubsky; D. S. Starodubov; M. I. Hayee; S. Lee; X. Jiang; A. E. Willner; J. Feinberg

    1999-01-01

    We experimentally demonstrate dynamic dispersion compensation using a novel nonlinearly chirped fiber Bragg grating in a 10-Gb\\/s system. A single piezoelectric transducer continuously tunes the induced dispersion from 300 to 1000 ps\\/nm. The system achieves a bit-error rate=10-9 after both 50 and 104 km of single-mode fiber by dynamically tuning the dispersion of the grating between 500 and 1000 ps\\/nm,

  20. Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method

    E-print Network

    Okamoto, Koichi

    inhomogeneity of In composition. Recently, InGaN/GaN-based light emitting diodes (LEDs) have been commercialized (3 nm) and a GaN cap (5 nm) layer. LED structure of GaN/InGaN SQW is composed of GaN (30 nm), nCarrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method

  1. Laser induced forward transfer of conducting polymers

    NASA Astrophysics Data System (ADS)

    Kandyla, M.; Chatzandroulis, S.; Zergioti, I.

    2010-12-01

    We report on laser printing of conducting polymers directly from the solid phase. Laser induced forward transfer is employed to deposit P3HT:PCBM films on glass/ITO/PEDOT:PSS substrates. P3HT:PCBM is widely used as the active material in organic solar cells. Polyaniline films, which are also printed by laser induced forward transfer, find many applications in the field of biotechnology. Laser printing parameters are optimized and results are presented. To apply solid-phase laser printing, P3HT:PCBM films are spun cast on quartz substrates, while aniline is in-situ polymerized on quartz substrates.

  2. Laser induced forward transfer of conducting polymers

    Microsoft Academic Search

    M. Kandyla; S. Chatzandroulis; I. Zergioti

    2010-01-01

    We report on laser printing of conducting polymers directly from the solid phase. Laser induced forward transfer is employed\\u000a to deposit P3HT:PCBM films on glass\\/ITO\\/PEDOT:PSS substrates. P3HT:PCBM is widely used as the active material in organic solar\\u000a cells. Polyaniline films, which are also printed by laser induced forward transfer, find many applications in the field of\\u000a biotechnology. Laser printing parameters

  3. Laser-induced caesium-137 decay

    NASA Astrophysics Data System (ADS)

    Barmina, E. V.; Simakin, A. V.; Shafeev, G. A.

    2014-08-01

    Experimental data are presented on the laser-induced beta decay of caesium-137. We demonstrate that the exposure of a gold target to a copper vapour laser beam (wavelengths of 510.6 and 578.2 nm, pulse duration of 15 ns) for 2 h in an aqueous solution of a caesium-137 salt reduces the caesium-137 activity by 70%, as assessed from the gamma activity of the daughter nucleus 137mBa, and discuss potential applications of laser-induced caesium-137 decay in radioactive waste disposal.

  4. Damage detection in FRP structures using fiber Bragg grating dynamic strain sensing systems

    NASA Astrophysics Data System (ADS)

    Zhu, Yan; Zhu, Yinian; Hui, Li; Krishnaswamy, Sridhar

    2011-04-01

    Fiber optic sensors have become widely used for structural health monitoring in recent decades. The aim of this research is to characterize the dynamic failure signals emitted in fiber reinforced polymer (FRP) stay cable and specimens using Fiber Bragg Gratings (FBGs) and two types of interferometric demodulation systems, namely Michelson interferometer (MI) and two-wave mixing interferometer (TWMI) for detection. Due to its one-dimensional form, only one FBG and the Michelson interferometer are used for damage monitoring in a carbon FRP stay cable under various types of loading. Michelson interferometer is capable of detecting frequency contents extending up to 500 kHz, where frequency contents below 250 kHz are categorized as matrix failure and those above 300 kHz corresponded to fiber failure. Two channels of FBGs are used with the TWM interferometer to track local damage in coupon-size FRP samples. Using TWM scheme, continuous and burst acoustic emission events are detected with frequency responses extending up to 125 kHz in coupon-size GFRP specimens, limited only by the sampling rate of the data acquisition system. The experimental results suggest that both types of FBG demodulation systems may be suitable for monitoring high frequency mechanical strains in civil structures, providing a tool for local structural damage detection.

  5. Interaction dynamics of fs-laser induced cavitation bubbles and their impact on the laser-tissue-interaction of modern ophthalmic laser systems

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Ripken, T.; Lubatschowski, H.; Heisterkamp, A.

    2011-07-01

    A today well-known laser based treatment in ophthalmology is the LASIK procedure which nowadays includes cutting of the corneal tissue with ultra-short laser pulses. Instead of disposing a microkeratome for cutting a corneal flap, a focused ultra-short laser pulse is scanned below the surface of biological tissue causing the effect of an optical breakdown and hence obtaining a dissection. Inside the tissue, the energy of the laser pulses is absorbed by non-linear processes; as a result a cavitation bubble expands and ruptures the tissue. Hence, positioning of several optical breakdowns side by side generates an incision. Due to a reduction of the amount of laser energy, with a moderate duration of treatment at the same time, the current development of ultra-short pulse laser systems points to higher repetition rates in the range of even Megahertz instead of tens or hundreds of Kilohertz. In turn, this results in a pulse overlap and therefor a probable occurrence of interaction between different optical breakdowns and respectively cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. Thus, the aim of this study is to analyse the dynamic and interaction of two cavitation bubbles by using high speed photography. The applied laser pulse energy, the energy ratio and the spot distance between different cavitation bubbles were varied. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape or jet formation are observed. The effects will be discussed regarding the medical ophthalmic application of fs-lasers. Based on these results a further research seems to be inevitable to comprehend and optimize the cutting effect of ultra-short pulse laser systems with high (> 500 kHz) repetition rates.

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

    SciTech Connect

    BULLOCK, A B

    1999-05-26

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

  7. Electro-optical properties and dynamic light scattering studies of polymer-stabilized cholesteric diffraction gratings

    Microsoft Academic Search

    Kyongok Kang

    2003-01-01

    Polymer-stabilized cholesteric liquid crystal diffraction gratings (PSCDGs) are electrically responsive, transmission diffraction gratings, which are formed when an electric field-induced light diffracting state of a cholesteric liquid crystal is stabilized by an internal polymer network. The planar diffracting state can then be stabilized by photopolymerization of a low concentration (˜3--5 wt%) of reactive diacrylate monomer and photoinitiator components, which are

  8. Removal of Nanoparticles With Laser Induced Plasma

    Microsoft Academic Search

    Ivin Varghese; M. D. Murthy Peri; Thomas Dunbar; Brian Maynard; Derek A. Thomas; Cetin Cetinkaya

    2008-01-01

    A review of the recent progress in the understanding of the laser induced plasma (LIP) technique utilized for nanoparticle removal is presented. LIP nanoparticle removal technique has been successfully demonstrated for removal of 10–60 nm polystyrene latex (PSL) particles from silicon substrates. The motivation for LIP technique stems from the requirement for defect-free cleaning of wafers and lithography photomasks in

  9. Microstructures fabricated by laser-induced polymerization

    Microsoft Academic Search

    Xinming Huang; Robert O. Warrington; Craig R. Friedrich

    1998-01-01

    The application of laser technology has shown great advantages in the fast growing area where electronic and mechanical components are combined to form miniature structures. Use of laser-induced polymerization (LIP) in making microstructures has drawn increasing attention. A focused laser beam can be guided directly to write three-dimensional patterns. The advantages are high cure speed, constant intensity along the curing

  10. A Laser Induced Breakdown Spectroscopy application based on Local Thermodynamic Equilibrium assumption for the elemental analysis of alexandrite gemstone and copper-based alloys

    Microsoft Academic Search

    A. De Giacomo; M. Dell’Aglio; R. Gaudiuso; A. Santagata; G. S. Senesi; M. Rossi; M. R. Ghiara; F. Capitelli; O. De Pascale

    Laser Induced Breakdown Spectroscopy (LIBS) is an appealing technique to study laser-induced plasmas (LIPs), both from the basic diagnostics point of view and for analytical applications. LIPs are complex dynamic systems, expanding at supersonic velocities and undergoing a transition between different plasma regimes. If the Local Thermodynamic Equilibrium (LTE) condition is valid for such plasmas, several analytical methods can be

  11. Experimental and theoretical comparison of single-pulse and double-pulse laser induced breakdown spectroscopy on metallic samples

    Microsoft Academic Search

    A. De Giacomo; M. Dell'Aglio; D. Bruno; R. Gaudiuso; O. De Pascale

    2008-01-01

    In this paper, single pulse (SP)- and double pulse (DP)- Laser Induced Breakdown Spectroscopy (LIBS) on metallic titanium, aluminum-based alloy and copper-based alloy have been studied by spectrally resolved imaging to find out the fundamental difference in terms of fluid-dynamic and chemical aspects. To better clarify the different nature of SP- and DP-Laser Induced Plasma (LIP) a qualitative theoretical model

  12. Two-dimensional axisymmetric models of laser induced plasmas relevant to laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Shabanov, S. V.; Gornushkin, I. B.

    2014-10-01

    A dynamical model of a laser induced plasma with axial symmetry is developed to systematically study the effects of the plasma equation of state, radiation transfer, various transport phenomena (viscosity, thermal conductivity, diffusion), and the ablation surface on the observable quantities such as spectra emitted by LIBS plasmas containing multiple species. Theoretical and numerical foundations of the model are described in detail. It is shown that the plasma spectra simulated with the equation of state based on the energy balance that includes the kinetic (thermal) energy, ionization energy, and energy of electronic excitations in atoms and ions differ significantly from the spectra obtained for plasmas modeled in the ideal gas approximation (where only the kinetic energy is included into the energy balance). Various transport phenomena, such as viscosity, diffusion, and thermal conductivity, are shown to have a little effect on the spectra. Radiation losses are proved to have noticeable effects. The effects of various interactions (adhesion, heat exchange, mass inflows) of the evolving plasma with the ablation surface are also illustrated by numerical simulations for typical LIBS plasmas. The model provides a numerical tool to assess various settings for LIBS plasma experiments as well as to interpret experimental data.

  13. Change in refractive index of muscle tissue during laser-induced interstitial thermotherapy.

    PubMed

    Chen, Na; Chen, Meimei; Liu, Shupeng; Guo, Qiang; Chen, Zhenyi; Wang, Tingyun

    2014-01-01

    This paper presents a long-period fiber-grating (LPG) based Michelson interferometric refractometry to monitor the change in refractive index of porcine muscle during laser-induced interstitial thermotherapy (LITT). As the wavelength of RI interferometer alters with the change in refractive index around the probe, the LPG based refractometry is combined with LITT system to measure the change in refractive index of porcine muscle when irradiated by laser. The experimental results show the denaturation of tissue alters the refractive index significantly and the LPG sensor can be applied to monitor the tissue state during the LITT. PMID:24211967

  14. Laser-induced gas vortices.

    PubMed

    Steinitz, Uri; Prior, Yehiam; Averbukh, Ilya Sh

    2012-07-20

    Recently, several femtosecond-laser techniques have demonstrated molecular excitation to high rotational states with a preferred sense of rotation. We consider collisional relaxation in a dense gas of such unidirectionally rotating molecules, and suggest that due to angular momentum conservation, collisions lead to the generation of macroscopic vortex gas flows. This argument is supported using the Direct Simulation Monte Carlo method, followed by a computational gas-dynamic analysis. PMID:22861845

  15. Recent Applications of Laser-Induced Breakdown Spectrometry: A Review of Material Approaches

    Microsoft Academic Search

    Jianyong Wu; Joseph Sneddon

    2004-01-01

    The use of laser?induced breakdown spectrometry (LIBS) has grown steadily, and it has proven to be a relatively dynamic research activity for performing direct spectrochemical elemental or metal analysis of a variety of materials, solids, liquids, and gases, with none or little sample pretreatment procedures. Significant progress has been made during the last several years on the diverse and versatile

  16. Hydrogen migration during laser -induced two-body Coulomb explosion in polyatomic hydrocarbon molecules

    Microsoft Academic Search

    S. Roither; M. Schoffler; D. Kartashov; X. Xie; J. Wild; B. Ulrich; M. Kuhnel; G. Reider; A. Scrinzi; M. Lezius; R. Dorner; A. Baltuska; M. Kitzler

    2009-01-01

    Laser-induced fragmentation of a highly polarisable polyatomic hydrocarbon molecule, 1,3-butadiene is investigated. Cold target recoil-ion momentum spectroscopy is used to record the three-dimensional momentum distributions of the fragments. Fragmentation is accompanied by fast hydrogen migration and chemical bonds are governed by intramolecular dynamics of electrons.

  17. Laser-Induced Fluorescence diagnostic of barium ion plasmas in the Paul Trap Simulator Experiment

    Microsoft Academic Search

    Moses Chung; Erik P. Gilson; Ronald C. Davidson; Philip C. Efthimion; Richard Majeski; Edward A. Startsev

    2005-01-01

    The Paul Trap Simulator Experiment (PTSX) is a cylindrical Paul trap whose purpose is to simulate the nonlinear dynamics of intense charged particle beam propagation in alternating-gradient magnetic transport systems. To investigate the ion plasma microstate in PTSX, including the ion density profile and the ion velocity distribution function, a laser-induced fluorescence diagnostic system is being developed as a nondestructive

  18. Pressure amplification of laser induced plasma shockwaves with shock tubes for nanoparticle removal

    Microsoft Academic Search

    Thomas Dunbar; Brian Maynard; Derek A. Thomas; M. D. Murthy Peri; Ivin Varghese; Cetin Cetinkaya

    2007-01-01

    A method using shock tubes for amplifying the dynamic pressure of Laser Induced Plasma (LIP) shockwaves for removing sub-100-nm nanoparticles is introduced and demonstrated. The higher the amplitude of the pressure generated, the smaller the particles that can be removed and, thus the more useful for a variety of applications. Constraining the expansion of the LIP core with a shock

  19. Kinetic model of titanium laser induced plasma expansion in nitrogen environment

    NASA Astrophysics Data System (ADS)

    Casavola, A. R.; Colonna, G.; Capitelli, M.

    2009-05-01

    A theoretical model to investigate the laser induced plasma (LIP) produced by a nanosecond laser pulse interacting with a metallic titanium target in a nitrogen environment is presented. In this work the influence of chemical processes on the plume expansion has been investigated, applying a 2D fluid dynamic code under local thermodynamic equilibrium or chemical non-equilibrium approximations.

  20. Kinetic model of titanium laser induced plasma expansion in nitrogen environment

    Microsoft Academic Search

    A. R. Casavola; G. Colonna; M. Capitelli

    2009-01-01

    A theoretical model to investigate the laser induced plasma (LIP) produced by a nanosecond laser pulse interacting with a metallic titanium target in a nitrogen environment is presented. In this work the influence of chemical processes on the plume expansion has been investigated, applying a 2D fluid dynamic code under local thermodynamic equilibrium or chemical non-equilibrium approximations.

  1. Submerged laser-induced plasma amplification of shockwaves using shock tubes for nanoparticle removal

    Microsoft Academic Search

    Thomas J. Dunbar; M. D. Murthy Peri; Ivin Varghese; Cetin Cetinkaya

    2007-01-01

    Amplifying the dynamic pressure of submerged laser-induced plasma (LIP) shockwaves using shock tubes is introduced and demonstrated. The higher the amplitude of the pressure generated, the smaller the particles that can be removed, thus proving more useful for a variety of nanoparticle removal applications. Limiting the expansion of the submerged LIP core with a shock tube is a non-contact approach

  2. Multiple-photon laser-induced fluorescence. [HS and DS radicals

    SciTech Connect

    Tiee, J.J.; Ferris, M.J.; Loge, G.W.; Wampler, F.B.; Hartford, A.

    1982-01-01

    The technique of multiple-photon laser-induced fluorescence has been used to study the spectroscopy and dynamics of atoms, molecules, and free radicals. Among the species investigated were iodine atoms (I), carbon monoxide (CO), molecular iodine (I/sub 2/), and HS and DS radicals. 7 figures.

  3. Synchronous detection of laser-induced fluorescence

    SciTech Connect

    Quigley, G.P.

    1982-01-01

    Many toxic or carcinogenic organic molecules have large absorption and fluorescence emission cross sections and can thus be detected by laser-induced fluorescence (LIF) in liquid samples at parts-per-billion levels or better. The technique of synchronous detection of laser-induced fluorescence (SDLIF) provides a way to distinguish between the fluorescence from a toxic molecule and the fluorescence from a background substance. This is done by synchronously scanning the laser excitation and fluorescence detection wavelengths at a fixed wavelength separation. What is measured in the overlap integral of the excitation and emission spectra that is considerably narrower than the entire fluorescence spectrum. The discussion of these techniques is centered on the point and remote detection of polynuclear aromatic hydrocarbons, aromatic amines, and organophosphates having applications in certain manufacturing processes as well as in coal liquefaction and gasification plants.

  4. Planar laser induced fluorescence in aqueous flows

    Microsoft Academic Search

    J. P. Crimaldi

    2008-01-01

    Planar laser-induced fluorescence (PLIF) is a non-intrusive technique for measuring scalar concentrations in fluid flows.\\u000a A fluorescent dye is used as a scalar proxy, and local fluorescence caused by excitation from a thin laser sheet can be related\\u000a to dye concentration. This review covers quantitative PLIF in aqueous flows, with discussions of fluorescence theory, experimental\\u000a methods and equipment, image processing

  5. Applications of Laser-Induced Breakdown Spectrometry

    Microsoft Academic Search

    Kyuseok Song; Yong-Ill Lee; Joseph Sneddon

    1997-01-01

    When a high-powered laser beam is focused onto a small area or spot of a solid surface, the temperature of the locally heated region rises rapidly to the vaporization temperature of the solid material and an optically induced plasma, frequently called a laser-induced plasma (LIP) or laser-ablated plasma (LAP) or laser spark is formed at the surface. The plasma will

  6. Nanoparticle removal from EUV photomasks using laser induced plasma shockwaves

    NASA Astrophysics Data System (ADS)

    Kadaksham, John; Zhou, Dong; Peri, M. D. Murthy; Varghese, Ivin; Eschbach, Florence; Cetinkaya, Cetin

    2006-05-01

    In recent years, it has been demonstrated that nanoparticles can be detached and removed from substrates using laser-induced plasma (LIP) shockwaves. While it was experimentally established the effectiveness of the LIP technique for removing nanoparticles in the sub-100nm range, the removal mechanisms were not well-understood. In this article, we introduce a set of particle removal mechanisms based on moment resistance of the particle-substrate bond and discuss their effectiveness and applicability in laser-induced plasma shock nanoparticle removal. The mechanical interactions between nanoparticles and shockwaves are studied by utilizing molecular dynamic simulation approach. The forces and moments acting on nanoparticles are calculated and are related to the detachment mechanisms. It is demonstrated that sub-100nm particles can be detached from various substrates. Experiments and simulations are performed to study the effect of LIP on optical and EUVL/LTEM substrates in terms of substrate damage. Initial experiments and simulations reveal the window of safe operation of LIP and the mechanisms responsible for material alterations if any at close distances of operation of LIP above the substrate.

  7. Dynamics of pulse propagation in phase-shifted fibre Bragg gratings: a numerical investigation

    Microsoft Academic Search

    Vijay Janyani; Ana Vukovic; Trevor Benson; John Paul; Phillip Sewell

    2007-01-01

    Fibre Bragg gratings (FBGs) are an integral component of optical fibre based communication systems for signal processing.\\u000a Uniform FBGs and phase-shifted FBGs find major applications as add-drop filters in dense wavelength division multiplexing\\u000a (DWDM) systems where these are used to filter out channels and to shape the signal spectrum. We investigate numerically the\\u000a spatiotemporal deformation of pulses as they propagate

  8. Laser-induced image technology (yesterday, today, and tomorrow)

    NASA Astrophysics Data System (ADS)

    Troitski, Igor

    2005-03-01

    Methods and systems of laser-induced image technology and ways of their development are discussed. These methods depend on kind of laser-induced etch points (marks), which are used for image creation. Today, the marks, which are usually used for this purpose, are laser-induced damages which are a result of breakdown phenomena. The ways for increasing quality of such images are discussed. However, there are also other marks appearing as a result of interaction of power laser radiation with transparent material. The use of these marks opens new opportunities for creation of laser-induced images with special characteristics. These opportunities are also subject of our discussion.

  9. Microfabrication of polystyrene microbead arrays by laser induced forward transfer

    NASA Astrophysics Data System (ADS)

    Palla-Papavlu, Alexandra; Dinca, Valentina; Paraico, Iurie; Moldovan, Antoniu; Shaw-Stewart, James; Schneider, Christof W.; Kovacs, Eugenia; Lippert, Thomas; Dinescu, Maria

    2010-08-01

    In this study we describe a simple method to fabricate microarrays of polystyrene microbeads (PS-?beads) on Thermanox coverslip surfaces using laser induced forward transfer (LIFT). A triazene polymer layer which acts as a dynamic release layer and propels the closely packed microspheres on the receiving substrate was used for this approach. The deposited features were characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. Ultrasonication was used to test the adherence of the transferred beads. In addition, the laser ejection of the PS-?bead pixels was investigated by time resolved shadowgraphy. It was found that stable PS-?beads micropatterns without any specific immobilization process could be realized by LIFT. These results highlight the increasing role of LIFT in the development of biomaterials, drug delivery, and tissue engineering.

  10. Ion kinetic energy distributions in laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohua; Zhang, Shudi; Cheng, Xiaoling; Zhu, Eryi; Hang, Wei; Huang, Benli

    2014-09-01

    Studies of ion emissions from laser-induced plasmas (LIPs) provide insights into the hydrodynamic expansion of the plume. Investigations of the kinetic energy distributions (KEDs) of ionized species for various experimental conditions are vital for a fundamental understanding of the formation and expansion dynamics of plasma. This knowledge, in turn, leads to promising improvements in LIP-based technological applications. This article aims to review some of the dominating mechanisms concerning ion emission kinetics during laser-surface interactions from a basic point of view. The diagnostic methods for ion KEDs are roughly classified. Interesting features of ion KEDs and their angular distributions, as well as the dependence on laser beam properties, ambient surroundings, and target properties, are summarized.

  11. Modeling of Laser-Induced Metal Combustion

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2008-02-20

    Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

  12. Laser induced fluorescence technique for environmental applications

    NASA Astrophysics Data System (ADS)

    Utkin, Andrei B.; Felizardo, Rui; Gameiro, Carla; Matos, Ana R.; Cartaxana, Paulo

    2014-08-01

    We discuss the development of laser induced fluorescence sensors and their application in the evaluation of water pollution and physiological status of higher plants and algae. The sensors were built on the basis of reliable and robust solid-state Nd:YAG lasers. They demonstrated good efficiency in: i) detecting and characterizing oil spills and dissolved organic matter; ii) evaluating the impact of stress on higher plants (cork oak, maritime pine, and genetically modified Arabidopsis); iii) tracking biomass changes in intertidal microphytobenthos; and iv) mapping macroalgal communities in the Tagus Estuary.

  13. Laser Induced Fluorescence Spectrum of Iridium Monophosphide

    NASA Astrophysics Data System (ADS)

    Pang, H. F.; Liu, Anwen; Cheung, A. S.-C.

    2009-06-01

    Laser induced fluorescence spectrum of IrP in the spectral region between 380-600 nm has been studied. Reacting laser ablated iridium atoms with 1% PH_3 seeded in argon produced the IrP molecule. A few vibronic transitions have been recorded. Preliminary analysis of the rotational structure indicated that these vibronic bands are with ?^' = 0 and ?^'' = 0 and is likely to be ^{1}? - X ^{1}? transition. Vibrational separation of the excited state is estimated to be about 442 cm^{-1}. The ground state bond length is determined to be 1.766 Å. This work represents the first experimental investigation of the spectra of IrP.

  14. Dynamic measurement of inside strain distributions in adhesively bonded joints by embedded fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Murayama, Hideaki; Ning, Xiaoguang; Kageyama, Kazuro; Wada, Daichi; Igawa, Hirotaka

    2014-05-01

    Long-length fiber Bragg grating (FBG) with the length of about 100 mm was embedded onto the surface of a carbon fiber reinforced plastics (CFRP) substrate and two CFRP adherends were joined by adhesive to form an adhesive bonded single-lap joint. The joint was subjected to 0.5 Hz cyclic tensile load and longitudinal strain distributions along FBG were measured at 5 Hz by the fiber-optic distributed sensing system based on optical frequency domain reflectometry (OFDR). We could successfully monitor the strain distributions accurately with high spatial resolution of around 1 mm.

  15. Flame front tracking by laser induced fluorescence spectroscopy and advanced

    E-print Network

    Hamarneh, Ghassan

    information from high speed Planar Laser Induced Fluores- cence (PLIF) data obtained from turbulent flamesFlame front tracking by laser induced fluorescence spectroscopy and advanced image analysis Rafeef. The application of non-linear anisotropic diffusion filtering and of Active Contour Mod- els (Snakes) is described

  16. Laser induced fluorescence measurements of the cylindrical Hall thruster plume

    E-print Network

    Laser induced fluorescence measurements of the cylindrical Hall thruster plume R. Spektor,1 K. D 2010 An investigation of a fully cylindrical Hall thruster was performed using laser induced Institute of Physics. doi:10.1063/1.3475433 I. INTRODUCTION Hall thrusters are not easily amendable

  17. Elemental chemical analysis of submerged targets by double-pulse laser-induced breakdown spectroscopy.

    PubMed

    De Giacomo, A; Dell'Aglio, M; Casavola, A; Colonna, G; De Pascale, O; Capitelli, M

    2006-05-01

    Double-pulse laser-induced plasma spectroscopy (DP-LIPS) is applied to submerged targets to investigate its feasibility for elemental analysis. The role of experimental parameters, such as inter-pulse delay and detection time, has been discussed in terms of the dynamics of the laser-induced bubble produced by the first pulse and its confinement effect on the plasma produced by the second laser pulse. The analytical performance of this technique applied to targets in a water environment are discussed. The elemental analysis of submerged copper alloys by DP-LIPS has been compared with conventional (single-pulse) LIBS in air. Theoretical investigation of the plasma dynamics in water bubbles and open air has been performed. PMID:16544131

  18. Laser-Induced Incandescence: Detection Issues

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.

    1996-01-01

    Experimental LII (laser-induced incandescence) measurements were performed in a laminar gasjet flame to test the sensitivity of different LII signal collection strategies to particle size. To prevent introducing a particle size dependent bias in the LII signal, signal integration beginning with the excitation laser pulse is necessary . Signal integration times extending to 25 or 100 nsec after the laser pulse do not produce significant differences in radial profiles of the LII signal due to particle size effects with longer signal integration times revealing a decreased sensitivity to smaller primary particles. Long wavelength detection reduces the sensitivity of the LII signal to primary particle size. Excitation of LII using 1064 nm light is recommended to avoid creating photochemical interferences thus allowing LII signal collection to occur during the excitation pulse without spectral interferences.

  19. Laser induced fluorescence of dental caries

    NASA Technical Reports Server (NTRS)

    Albin, S.; Byvik, C. E.; Buoncristiani, A. M.

    1988-01-01

    Significant differences between the optical spectra taken from sound regions of teeth and carious regions have been observed. These differences appear both in absorption and in laser induced fluorescence spectra. Excitation by the 488 nm line of an argon ion laser beam showed a peak in the emission intensity around 553 nm for the sound dental material while the emission peak from the carious region was red-shifted by approximately 40 nm. The relative absorption of carious region was significantly higher at 488 nm; however its fluorescence intensity peak was lower by an order of magnitude compared to the sound tooth. Implications of these results for a safe, reliable and early detection of dental caries are discussed.

  20. Dynamic behavior monitoring and damage evaluation for arch bridge suspender using GFRP optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Zhou, Zhi; Ou, Jinping

    2012-06-01

    Suspenders, as the main bearing components in an arch bridge, can only manage to serve for about tens of years, or even a few years due to the influences of corrosion and fatigue load. This paper proposes a method of testing the suspender dynamic behavior with optical fiber Bragg grating sensors embedded in the glass fiber reinforced polymer (GFRP-OFBGS). Firstly, layout method of FRP-OFBGS among the suspender and protection technology are studied, and the self-monitoring smart suspender is developed. Secondly, stretching experiments were carried out on the smart suspender. The test experimental results demonstrated that the whole procedure of the stretching test can be perfectly monitored. Finally, the self-monitoring smart suspender successfully was applied in Ebian Bridge to monitor the strain history of suspenders under traffic load, and traffic effect to suspenders with various lengths and to different steel strands of a single suspender. Based on the monitoring data, the arch bridge suspenders fatigue damage dynamic evaluation methods and calculation results were given. The field monitoring results demonstrated that, the self-monitoring smart suspender mentioned in this paper is capable of monitoring suspender dynamic response and possible fatigue damages.

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

    PubMed

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

    2015-01-26

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

  2. Increasing dynamic range of a fibre Bragg grating edge-filtering interrogator with a proportional control loop

    NASA Astrophysics Data System (ADS)

    Stan, Nikola; Bailey, D. C.; Chadderdon, S. L.; Webb, S.; Zikry, M.; Peters, K. J.; Selfridge, R. H.; Schultz, S. M.

    2014-06-01

    We present a fibre Bragg grating (FBG) interrogator that uses a microcontroller board and a tunable optical filter in a proportional control loop to increase dynamic range and achieve high strain sensitivity. It is an edge-filtering interrogator with added proportional control loop that locks the operating wavelength to the mid-reflection point on the FBG spectrum. The interrogator separates low-frequency (LF) components of strain and measures them with extended dynamic range, while at the same time measuring high-frequency (HF) strain without loss in strain sensitivity. In this paper, we describe the implementation of the interrogator and analyse the characteristics of individual components, such as the speed and voltage resolution of the microcontroller and the tunable optical filter. We measure the performance of the proportional control loop at frequencies up to 1 kHz and characterize the system using control theory. We illustrate the limitation of the conventional interrogator to measure strains greater than 40 ?? and demonstrate successful application of the proposed interrogator for simultaneous measurement of 450 ?? LF strain at 50 Hz superimposed with 32 kHz HF strain.

  3. Recording and self-enhancement of dynamic polarization gratings in degenerate four-wave-mixing geometry

    NASA Astrophysics Data System (ADS)

    Ozols, A.; Belyaev, A.; Kokars, V.; Augustovs, P.; Traskovskis, K.; Saharov, D.

    2014-10-01

    Scalar and vectorial degenerate four-wave-mixing (DFWM) in azobenzene molecular K-RJ-4-3 [N,N-bis(5,5,5- tryphenylpentyl)-4-((4-tritylphenyl)diazenyl)aniline] and in chalcogenide a-As2S3 glassy films is experimentally investigated. A coherent self-enhancement (CSE) of holographic gratings (HG) in this geometry was experimentally confirmed, for the first time to our knowledge, thus establishing a new method of HG recording, the DFWM CSE recording. Scalar linear s-s, p-p and circular R-R(right) polarizations and orthogonal linear s-p and circular L(left)-R polarizations were used for HG recording with 2 ?m period at 532 nm. In the case of K-RJ-4-3 film L-R polarizations were the most efficient enabling the maximum DFWM efficiency ?max=14.5% whereas in the case of a-As2S3 film s-s polarizations were the best with ?max=6.0%. DFWM CSE recording has exhibited a different polarization dependence compared to normal DWFM recording. CSE factor ?/?0 (?0 being the initial ?) was the highest for K-RJ-4-3 film (6.8) with s-s polarizations compared to 3 for a-As2S3 film with p-p polarizations. Two-wave HG recording was also studied for comparison.

  4. Non-steady-state photo-electromotive-force induced by dynamic gratings in partially compensated photoconductors

    NASA Astrophysics Data System (ADS)

    Petrov, M. P.; Sokolov, I. A.; Stepanov, S. I.; Trofimov, G. S.

    1990-09-01

    This paper gives a thorough treatment of a new effect of non-steady-state photo-electromotive-force (emf). The effect consists of an alternating electric current arising in a short-circuited bulk sample of a photoconductor illuminated by a vibrating sinusoidal pattern. As a detailed theoretical analysis shows, the frequency transfer function of the effect is identical with that of a differentiating RC circuit having a time constant equal to the characteristic time of a space-charge grating formation within the sample volume ?sc. For high excitation frequencies (???-1sc), the photo-emf signal peaks at spatial frequency K=L-1D (LD is the mean diffusion length of photoinduced carriers) and the photovoltage amplitude in an open-circuit sample can be as high as kBT/e times the number of fringes of the interference pattern in the interelectrode spacing. The basic conclusions of the theoretical analysis of the effect are supported by the experimental evidence obtained for cubic photoconducting Bi12SiO20 crystals.

  5. Superhydrophobic and colorful copper surfaces fabricated by picosecond laser induced periodic nanostructures

    NASA Astrophysics Data System (ADS)

    Long, Jiangyou; Fan, Peixun; Zhong, Minlin; Zhang, Hongjun; Xie, Yongde; Lin, Chen

    2014-08-01

    In this study, functional copper surfaces combined with vivid structural colors and superhydrophobicity were fabricated by picosecond laser. Laser-induced periodic surface structures (LIPSS), i.e. ripples, were fabricated by picosecond laser nanostructuring to induce rainbow-like structural colors which are uniquely caused by the grating - type structure. The effects of laser processing parameters on the formation of ripples were investigated. We also discussed the formation mechanism of ripples. With different combinations of the laser processing parameters, ripples with various morphologies were fabricated. After the modification with triethoxyoctylsilane, different types of ripples exhibited different levels of wettability. The fine ripples with minimal redeposited nanoparticles exhibited high adhesive force to water. The increased amount of nanoscale structures decreased the adhesive force to water and increased the contact angle simultaneously. In particular, a specific type of ripples exhibited superhydrophobicity with a large contact angle of 153.9 ± 3.2° and a low sliding angle of 11 ± 3°.

  6. Characteristics of laser-induced plasma as a spectroscopic light emission source

    NASA Astrophysics Data System (ADS)

    Ma, Q. L.; Motto-Ros, V.; Lei, W. Q.; Wang, X. C.; Boueri, M.; Laye, F.; Zeng, C. Q.; Sausy, M.; Wartelle, A.; Bai, X. S.; Zheng, L. J.; Zeng, H. P.; Baudelet, M.; Yu, J.

    2012-05-01

    Laser-induced plasma is today a widespread spectroscopic emission source. It can be easily generated using compact and reliable nanosecond pulsed lasers and finds applications in various domains with laser-induced breakdown spectroscopy (LIBS). It is however such a particular medium which is intrinsically a transient and non-point light emitting source. Its timeand space-resolved diagnostics is therefore crucial for its optimized use. In this paper, we review our work on the investigation of the morphology and the evolution of the plasma. Different time scales relevant for the description of the plasma's kinetics and dynamics are covered by suitable techniques. Our results show detailed evolution and transformation of the plasma with high temporal and spatial resolutions. The effects of the laser parameters as well as the background gas are particularly studied.

  7. Effects of the background environment on formation, evolution and emission spectra of laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    De Giacomo, A.; Dell'Aglio, M.; Gaudiuso, R.; Amoruso, S.; De Pascale, O.

    2012-12-01

    In this paper the most important features of Laser Induced Plasma (LIP) evolution were analyzed from the fundamental point of view, in order to point out the effects of background environment on the plasma emission spectra. In particular, the main differences between air and vacuum Laser-Induced Breakdown (LIBS) are discussed, as well as those arising in high-pressure gases and in liquid environment. As can be expected, the dynamics of the plasma is strongly dependent on the environment where the plasma itself expands, which can be exploited for several different applications, ranging from chemical analysis and process diagnostics to materials science. The effect of other experimental conditions, such as the state of aggregation of the irradiated target, and the effect of laser pulse duration are also briefly reviewed.

  8. Improved Imaging With Laser-Induced Eddy Currents

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    System tests specimen of material nondestructively by laser-induced eddy-current imaging improved by changing method of processing of eddy-current signal. Changes in impedance of eddy-current coil measured in absolute instead of relative units.

  9. Gene delivery to skin with laser-induced stress wave

    Microsoft Academic Search

    Makoto Ogura; Shunichi Sato; Mitsuhiro Terakawa; Hiroshi Ashida; Minoru Obara

    2005-01-01

    We investigated gene delivery by laser-induced stress waves (LISWs) generated by irradiating a solid target with nanosecond laser pulses. Highly efficient and site-specific gene transfer has been achieved by applying a few pulses of LISWs.

  10. Laser-induced plasma spectroscopy: principles, methods and applications

    SciTech Connect

    Lazic, Violeta; Colao, Francesco; Fantoni, Roberta; Spizzichino, Valeria [ENEA, FIS-LAS, V. E. Fermi 45, Frascati (RM) (Italy); Jovicevic, Sonja [Institute of Physics, 11080 Belgrade, Pregrevica 118 (Serbia and Montenegro)

    2006-12-01

    Principles of the Laser Induced Plasma Spectroscopy and its advances are reported. Methods for obtaining quantitative analyses are described, together with discussion of some applications and the specific problems.

  11. Ion soliton observation with laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Claire, N.; Bachet, G.; Skiff, F.

    2003-12-01

    Many theoretical and experimental studies of solitons in plasma have been performed [Phys. Fluids 16 (1973) 1668; Plasma Phys. 25 (1983) 943; IEEE Trans. Plasma Phys. PS 10 (1982) 180; Plasma Phys. 5 (1998) 4144] and most of the properties such as the relation between the amplitude, the velocity and the width, for soliton or soliton-dust interaction, have been obtained. The agreement between experiment and theoretical model is not always good [Phil. Mag. Ser. 39 (1895) 422; Phys. Rev. Lett. 17 (1966) 996; Phys. Rev. E 51 (1995) 4796]. The experimental observations typically involve Langmuir probes. However, the ion acoustic soliton propagation can be observed by laser induced fluorescence (LIF) in double plasma device. This direct observation of ion perturbation with LIF points out the importance of the optical pumping effect [Rev. Sci. Instrum. 72 (2001) 4372] in the measurement of fast velocity propagation of ion phenomena like solitons are. With the LIF we discovered that a train of soliton propagates easier in the device if a weak backward ion flux plasma, having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, as close to the grid the solitons separation occurs; the precursors ions is in fact a collective phenomenon.

  12. Medical Applications of Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pathak, A. K.; Rai, N. K.; Singh, Ankita; Rai, A. K.; Rai, Pradeep K.; Rai, Pramod K.

    2014-11-01

    Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail.

  13. Femtosecond laser-induced crystallization of amorphous Sb{sub 2}Te{sub 3} film and coherent phonon spectroscopy characterization and optical injection of electron spins

    SciTech Connect

    Li Simian [State Key Laboratory of Optoelectronic Materials and Technology, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Hebei Key Laboratory of Optoelectronic Information and Geo-detection Technology Shijiazhuang University of Economics, Shijiazhuang 050031 (China); Huang Huan; Wang Yang; Wu Yiqun; Gan Fuxi [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhu Weiling; Wang Wenfang; Chen Ke; Yao Daoxin; Lai Tianshu [State Key Laboratory of Optoelectronic Materials and Technology, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2011-09-01

    A femtosecond laser-irradiated crystallizing technique is tried to convert amorphous Sb{sub 2}Te{sub 3} film into crystalline film. Sensitive coherent phonon spectroscopy (CPS) is used to monitor the crystallization of amorphous Sb{sub 2}Te{sub 3} film at the original irradiation site. The CPS reveals that the vibration strength of two phonon modes that correspond to the characteristic phonon modes (A{sub 1g}{sup 1} and E{sub g}) of crystalline Sb{sub 2}Te{sub 3} enhances with increasing laser irradiation fluence (LIF), showing the rise of the degree of crystallization with LIF and that femtosecond laser irradiation is a good post-treatment technique. Time-resolved circularly polarized pump-probe spectroscopy is used to investigate electron spin relaxation dynamics of the laser-induced crystallized Sb{sub 2}Te{sub 3} film. Spin relaxation process indeed is observed, confirming the theoretical predictions on the validity of spin-dependent optical transition selection rule and the feasibility of transient spin-grating-based optical detection scheme of spin-plasmon collective modes in Sb{sub 2}Te{sub 3}-like topological insulators.

  14. Laser Induced Phonons (LIPs) in MBE grown ZnSe

    Microsoft Academic Search

    K. Welford

    1991-01-01

    Thin film ZnSe, grown by the MBE method, has been examined using the technique of degenerate four wave mixing, DFWM, using laser illumination at 532 nm. Laser induced phonons are observed in this thin film material but are not seen in a sample of bulk polycrystalline ZnSe. This observation of laser induced phonons is the first reported in ZnSe.

  15. Picosecond polarization-selective transient grating experiments in sodium-seeded flames

    E-print Network

    Fayer, Michael D.

    techniques such as coherent anti-Stokes Raman scattering (CARS) ,2V3laser induced fluorescence (LIF),4 the laser beams (CARS and FWM), of a different frequency than some or all of the laser beams (LIF, CARS) Electric field picture for one fringe of an intensity grating. The electric field amplitude varies

  16. Fiber grating sensors

    Microsoft Academic Search

    Alan D. Kersey; Michael A. Davis; Heather J. Patrick; Michel LeBlanc; K. P. Koo; C. G. Askins; M. A. Putnam; E. Joseph Friebele

    1997-01-01

    We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors

  17. Interfacial Effects in the Relaxation Dynamics of Silver Nanometal-Glass Composites Probed by Transient Grating Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiménez, J. A.; Lysenko, S.; Vikhnin, V. S.; Liu, H.

    2010-01-01

    Relaxation dynamics of silver nanoparticles (NPs) embedded in glass have been studied by picosecond time-resolved transient grating (TG) spectroscopy. Phosphate-based glasses were prepared by melting and heat-treatment processes by which two different nanometal-glass composites were produced. The first is a glass system containing silver and tin in which Ag NPs are embedded in the matrix upon heat treatment. The second is a heat-treated silver-doped glass with spectroscopic indications of Ag+-Ag0 pairs located at or near the surface of the NPs. The time evolution of the light-induced TG for the Ag/Sn-doped glass shows an uncommon relaxation on the nanosecond time scale. Such behavior is explained in terms of energy transfer processes between polaronic and/or excitonic states in the near-interface region of the glass matrix and the NPs. In contrast, a faster monotonic relaxation is observed for the Ag-doped nanocomposite. This result is attributed to Ag NP ? Ag+-Ag0 plasmon resonance energy transfer.

  18. Multiple fiber Bragg grating sensor network with a rapid response and wide spectral dynamic range using code division multiple access

    NASA Astrophysics Data System (ADS)

    Kim, Youngbok; Jeon, Sie-Wook; Park, Chang-Soo

    2011-05-01

    Fiber Bragg grating (FBG) sensor networks have been intensively researched in optical sensor area and it developed in wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies which was adopted for its interrogating many optical sensors. In particular, WDM technology can be easily employed to interrogate FBG sensor however, the number of FBG sensors is limited. On the other hand, the TDM technique can extremely expand the number of sensor because the FBG sensors have same center wavelength. However, it suffers from a reduced sensor output power due to low reflectivity of FBG sensor. In this paper, we proposed and demonstrated the FBG sensor network based on code division multiple access (CDMA) with a rapid response and wide spectral dynamic range. The reflected semiconductor optical amplifier (RSOA) as a light source was directly modulated by the generated pseudorandom binary sequence (PRBS) code and the modulated signal is amplified and goes through FBG sensors via circulator. When the modulated optical signal experienced FBG sensor array, the optical signal which was consistent with center wavelength of FBGs is reflected and added from each sensors. The added signal goes into dispersion compensating fiber (DCF) as a dispersion medium. After through the DCF, the optical signal is converted into electrical signal by using photodetector (PD). For separate individual reflected sensor signal, the sliding correlation method was used. The proposed method improves the code interference and it also has advantages such as a large number of sensors, continuously measuring individual sensors, and decreasing the complexity of the sensor network.

  19. Laser-induced fluorescence detection of lead atoms in a laser-induced plasma: An experimental analytical optimization study

    Microsoft Academic Search

    Stéphane Laville; Christian Goueguel; Hakim Loudyi; François Vidal; Mohamed Chaker; Mohamad Sabsabi

    2009-01-01

    The combination of the laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) techniques was investigated to improve the limit of detection (LoD) of trace elements in solid matrices. The influence of the main experimental parameters on the LIF signal, namely the ablation fluence, the excitation energy, and the inter-pulse delay, was studied experimentally and a discussion of the results was

  20. Liquids microprinting through laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Serra, P.; Duocastella, M.; Fernández-Pradas, J. M.; Morenza, J. L.

    2009-03-01

    Laser-induced forward transfer (LIFT) is a direct-writing technique which allows the deposition of tiny amounts of material from a donor thin film onto a receptor substrate. When LIFT is applied to liquid donor films, the laser radiation affects only a localized fraction of the liquid, thereby impelling the unaffected portion towards the receptor substrate. Thus, transfer takes place with no melting or vaporization of the deposited fraction and, in this way, LIFT can be used to successfully print complex materials like inorganic inks and pastes, biomolecules in solution, and even living cells and microorganisms. In addition, and for a wide range of liquid rheologies, the material can be deposited in the form of circular microdroplets; this provides LIFT with a high degree of spatial resolution leading to feature sizes below 10 ?m, and making it competitive in front of conventional printing techniques. In this work, a revision of the main achievements of the LIFT of liquids is carried out, correlating the morphological characteristics of the generated features with the results of the study of the transfer process. Special emphasis is put on the characterization of the dynamics of liquid ejection, which has provided valuable information for the understanding of microdroplets deposition. Thus, new time-resolved imaging analyses have shown a material release behavior which contrasts with most of the previously made assumptions, and that allows clarifying some of the questions open during the study of the LIFT technique.

  1. Femtosecond laser-induced periodic surface structures on silica

    SciTech Connect

    Hoehm, S.; Rosenfeld, A. [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Strasse 2A, D-12489 Berlin (Germany); Krueger, J.; Bonse, J. [BAM Bundesanstalt fuer Materialforschung und-pruefung, Unter den Eichen 87, D-12205 Berlin (Germany)

    2012-07-01

    The formation of laser-induced periodic surface structures (LIPSS) on two different silica polymorphs (single-crystalline synthetic quartz and commercial fused silica glass) upon irradiation in air with multiple linearly polarized single- and double-fs-laser pulse sequences ({tau} = 150 fs pulse duration, {lambda} = 800 nm center wavelength, temporal pulse separation {Delta}t < 40 ps) is studied experimentally and theoretically. Two distinct types of fs-LIPSS [so-called low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL)] with different spatial periods and orientations were identified. Their appearance was characterized with respect to the experimental parameters peak laser fluence and number of laser pulses per spot. Additionally, the 'dynamics' of the LIPSS formation was addressed in complementary double-fs-pulse experiments with varying delays, revealing a characteristic change of the LSFL periods. The experimental results are interpreted on the basis of a Sipe-Drude model considering the carrier dependence of the optical properties of fs-laser excited silica. This new approach provides an explanation of the LSFL orientation parallel to the laser beam polarisation in silica - as opposed to the behaviour of most other materials.

  2. Metal surface nitriding by laser induced plasma

    NASA Astrophysics Data System (ADS)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several ?m depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (?=10.6 ?m) and a XeCl excimer laser (?=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features as purity, thickness, and surface morphology.

  3. Single cell transfection by laser-induced breakdown of an optically trapped gold nanoparticle

    NASA Astrophysics Data System (ADS)

    Arita, Yoshihiko; Ploschner, Martin; Antkowiak, Maciej; Gunn-Moore, Frank; Dholakia, Kishan

    2014-03-01

    Cell selective introduction of therapeutic agents remains a challenging problem. Cavitation-based therapies including ultrasound-induced sonoporation and laser-induced optoporation have led the way for novel approaches to provide the potential of sterility and cell selectivity compared with viral or biochemical counterparts. Acoustic streaming, shockwaves and liquid microjets associated with the cavitation dynamics are implicated in gene and drug delivery. These approaches, however, often lead to non-uniform and sporadic molecular uptake that lacks refined spatial control and suffers from a significant loss of cell viability. Here we demonstrate spatially controlled cavitation instigated by laser-induced breakdown of an optically trapped single gold nanoparticle. Our unique approach employs optical tweezers to trap a single nanoparticle, which when irradiated by a nanosecond laser pulse is subject to laser-induced breakdown followed by cavitation. Using this method for laser-induced cavitation, we can gain additional degrees of freedom for the cavitation process - the particle material, its size, and its position relative to cells or tissues. We show the energy breakdown threshold of gold nanoparticles of l00nm with a single nanosecond laser pulse at 532 nm is three orders of magnitude lower than that for water, which leads to gentle nanocavitation enabling single cell transfection. We optimize the shear stress to the cells from the expanding bubble to be in the range of 1-10 kPa for transfection by precisely positioning a trapped gold nanoparticle, and thus nanobubble, relative to a cell of interest. The method shows transfection of plasmid-DNA into individual mammalian cells with an efficiency of 75%.

  4. Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

    SciTech Connect

    Pan, A.; Dias, A.; Gomez-Aranzadi, M.; Olaizola, S. M. [CIC microGUNE, Goiru Kalea 9 Polo Innovación Garaia, 20500 Arrasate-Mondragón (Spain); CEIT-IK4 and Tecnun, University of Navarra, Manuel Lardizábal 15, 20018 San Sebastián (Spain); Rodriguez, A. [CIC microGUNE, Goiru Kalea 9 Polo Innovación Garaia, 20500 Arrasate-Mondragón (Spain)

    2014-05-07

    The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800?nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600?nm) and High Spatial Frequency LIPSS, showing a periodicity around 300?nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100?nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.

  5. Laser-Induced Damage of Calcium Fluoride

    SciTech Connect

    Espana, A.; Joly, A.G.; Hess, W.P.; Dickinson, J.T.

    2004-01-01

    As advances continue to be made in laser technology there is an increasing demand for materials that have high thresholds for laser-induced damage. Laser damage occurs when light is absorbed, creating defects in the crystal lattice. These defects can lead to the emission of atoms, ions and molecules from the sample. One specific field where laser damage is of serious concern is semiconductor lithography, which is beginning to use light at a wavelength of 157 nm. CaF2 is a candidate material for use in this new generation of lithography. In order to prevent unnecessary damage of optical components, it is necessary to understand the mechanisms for laser damage and the factors that serve to enhance it. In this research, we study various aspects of laser interactions with CaF2, including impurity absorbance and various forms of damage caused by incident laser light. Ultraviolet (UV) laser light at 266 nm with both femtosecond (fs) and nanosecond (ns) pulse widths is used to induce ion and neutral particle emission from cleaved samples of CaF2. The resulting mass spectra show significant differences suggesting that different mechanisms for desorption occur following excitation using the different pulse durations. Following irradiation by ns pulses at 266 nm, multiple single-photon absorption from defect states is likely responsible for ion emission whereas the fs case is driven by a multi-photon absorption process. This idea is further supported by the measurements made of the transmission and reflection of fs laser pulses at 266 nm, the results of which reveal a non-linear absorption process in effect at high incident intensities. In addition, the kinetic energy profiles of desorbed Ca and K contaminant atoms are different indicating that a different mechanism is responsible for their emission as well. Overall, these results show that purity plays a key role in the desorption of atoms from CaF2 when using ns pulses. On the other hand, once the irradiance reaches high levels, like that of the fs case, significant desorption is possible due to multi-photon absorption by the intrinsic material.

  6. Laser induced incandescence and laser induced breakdown spectroscopy based sensor development

    NASA Astrophysics Data System (ADS)

    Eseller, Kemal Efe

    In this doctoral dissertation, two laser-based sensors were evaluated for different applications. Laser Induced Incandescence (LII) is a technique which can provide non-intrusive quantitative measurement of soot and it provides a unique diagnostic tool to characterize engine performance. Since LII is linearly proportional to the soot volume fraction, it can provide in situ, real time measurement of soot volume fraction with high temporal and spatial resolution. LII has the capability to characterize soot formation during combustion. The soot volume fraction from both flames and a soot generator was investigated with LII. The effects of experimental parameters, such as laser fluence, gate delay, gate width and various laser beam focusing, on LII signal was studied. Laser Induced Breakdown Spectroscopy (LIBS), a diagnostic tool for in situ elemental analysis, has been evaluated for on-line, simultaneous, multi-species impurity monitoring in hydrogen. LIBS spectra with different impurity levels of nitrogen, argon, and oxygen were recorded and the intensity of the spectral lines of Ar, O, N, and H observed were used to form calibration plots for impurities in hydrogen measurements. An ungated detection method for LIBS has been developed and applied to equivalence ratio measurements of CH4/air and biofuel/air. LIBS has also been used to quantitatively analyze the composition of a slurry sample. The quenching effect of water in slurry samples causes low LIBS signal quality with poor sensitivity. Univariate and multivariate calibration was performed on LIBS spectra of dried slurry samples for elemental analysis of Mg, Si and Fe. Calibration results show that the dried slurry samples give good correlation between spectral intensity and elemental concentration.

  7. Laser-induced differential normalized fluorescence method for cancer diagnosis

    DOEpatents

    Vo-Dinh, Tuan (Knoxville, TN); Panjehpour, Masoud (Knoxville, TN); Overholt, Bergein F. (Knoxville, TN)

    1996-01-01

    An apparatus and method for cancer diagnosis are disclosed. The diagnostic method includes the steps of irradiating a tissue sample with monochromatic excitation light, producing a laser-induced fluorescence spectrum from emission radiation generated by interaction of the excitation light with the tissue sample, and dividing the intensity at each wavelength of the laser-induced fluorescence spectrum by the integrated area under the laser-induced fluorescence spectrum to produce a normalized spectrum. A mathematical difference between the normalized spectrum and an average value of a reference set of normalized spectra which correspond to normal tissues is calculated, which provides for amplifying small changes in weak signals from malignant tissues for improved analysis. The calculated differential normalized spectrum is correlated to a specific condition of a tissue sample.

  8. Laser-induced differential normalized fluorescence method for cancer diagnosis

    DOEpatents

    Vo-Dinh, T.; Panjehpour, M.; Overholt, B.F.

    1996-12-03

    An apparatus and method for cancer diagnosis are disclosed. The diagnostic method includes the steps of irradiating a tissue sample with monochromatic excitation light, producing a laser-induced fluorescence spectrum from emission radiation generated by interaction of the excitation light with the tissue sample, and dividing the intensity at each wavelength of the laser-induced fluorescence spectrum by the integrated area under the laser-induced fluorescence spectrum to produce a normalized spectrum. A mathematical difference between the normalized spectrum and an average value of a reference set of normalized spectra which correspond to normal tissues is calculated, which provides for amplifying small changes in weak signals from malignant tissues for improved analysis. The calculated differential normalized spectrum is correlated to a specific condition of a tissue sample. 5 figs.

  9. Laser-induced fluorescence of space-exposed polyurethane

    NASA Technical Reports Server (NTRS)

    Hill, Ralph H., Jr.

    1993-01-01

    The object of this work was to utilize laser-induced fluorescence technique to characterize several samples of space-exposed polyurethane. These samples were flown on the Long Duration Exposure Facility (LDEF), which was in a shuttle-like orbit for nearly 6 years. Because of our present work to develop laser-induced-fluorescence inspection techniques for polymers, space-exposed samples and controls were lent to us for evaluation. These samples had been attached to the outer surface of LDEF; therefore, they were subjected to thermal cycling, solar ultraviolet radiation, vacuum, and atomic oxygen. It is well documented that atomic oxygen and ultraviolet exposure have detrimental effects on many polymers. This was a unique opportunity to make measurements on material that had been naturally degraded by an unusual environment. During our past work, data have come from artificially degraded samples and generally have demonstrated a correlation between laser-induced fluorescence and tensile strength or elasticity.

  10. Ion soliton observation with laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Claire, N.; Bachet, G.; Skiff, F.

    2002-12-01

    A laser-induced fluorescence observation of ion-acoustic waves in a collisionless unmagnetized double plasma multipolar device is presented. The optical pumping effect is found to be critical for the interpretation of fast changes of the ion velocity distribution functions induced by the propagation of a soliton. To take this effect into account, the continuity equation is used. The laser-induced fluorescence diagnostic shows that the separation of solitons requires a small plasma drift in the backward direction (reverse direction of the soliton propagation) and that the precursor ions are in fact a precursor wave.

  11. Ultrafast Molecular Imaging by Laser Induced Electron Diffraction

    E-print Network

    Michel Peters; Tung Nguyen-Dang; Christian Cornaggia; Sébastien Saugout; Eric Charron; Arne Keller; Osman Atabek

    2011-06-08

    We address the feasibility of imaging geometric and orbital structure of a polyatomic molecule on an attosecond time-scale using the laser induced electron diffraction (LIED) technique. We present numerical results for the highest molecular orbitals of the CO2 molecule excited by a near infrared few-cycle laser pulse. The molecular geometry (bond-lengths) is determined within 3% of accuracy from a diffraction pattern which also reflects the nodal properties of the initial molecular orbital. Robustness of the structure determination is discussed with respect to vibrational and rotational motions with a complete interpretation of the laser-induced mechanisms.

  12. In Search of Multi-Peaked Reflective Spectrum with Optic Fiber Bragg Grating Sensor for Dynamic Strain Measurement

    NASA Technical Reports Server (NTRS)

    Tai, Hsiang

    2006-01-01

    In a typical optic fiber Bragg grating (FBG) strain measurement, unless in an ideal static laboratory environment, the presence of vibration or often disturbance always exists, which often creates spurious multiple peaks in the reflected spectrum, resulting in a non-unique determination of strain value. In this report we attempt to investigate the origin of this phenomenon by physical arguments and simple numerical simulation. We postulate that the fiber gratings execute small amplitude transverse vibrations changing the optical path in which the reflected light traverses slightly and non-uniformly. Ultimately, this causes the multi-peak reflected spectrum.

  13. Degenerate two-wave mixing via a dynamic grating in Fe{sub 3}O{sub 4} nanoparticle suspensions

    SciTech Connect

    Ageev, E Yu; Litvinov, Rudol'f V; Khat'kov, N D [Tomsk State University of Control Systems and Radioelectronics, Tomsk (Russian Federation); Zagrebin, L V; Shestov, S S [Center for Information and Cell Medicine, Ltd, Moscow (Russian Federation)

    2009-05-31

    Optical-gradient-force-induced spatially inhomogeneous disturbances of the dielectric permittivity of a suspension of spherical nanoparticles are analysed in the Maxwell Garnett approximation. Degenerate two-wave mixing in such media is shown to cause the formation of a spatial nanoparticle grating and the associated permittivity grating in the colloid. Relations are derived for the complex coupling constant of the waves. Codirectional and contradirectional two-wave mixing in suspensions of light-absorbing nanoparticles is considered. The two-beam coupling gain at 640 nm in various suspensions of Fe{sub 3}O{sub 4} nanoparticles may reach {approx}10 cm{sup -1}. (nonlinear optical phenomena)

  14. Experimental and theoretical investigation of laser-induced plasma of a titanium target.

    PubMed

    Casavola, Anna Rita; Colonna, Gianpiero; De Giacomo, Alessandro; De Pascale, Olga; Capitelli, Mario

    2003-10-20

    We present a theoretical approach to interpreting optical emission spectroscopy measurements for nonequilibrium conditions. In this approach both the fluid dynamics and the kinetics of laser-induced plasma are taken into account, and the results obtained by the numerical model are applied to the spectroscopic observation of the plasma induced by the interaction between a KrF laser and a metallic Ti target. We have generalized the theoretical method to calculate the initial conditions for the plume expansion that show the best agreement with experimental results. PMID:14594052

  15. Quantitative characterization of a nonreacting, supersonic combustor flowfield using unified, laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Fletcher, D. G.; Mcdaniel, J. C.

    1989-01-01

    A calibrated, nonintrusive optical technique, laser-induced iodine fluorescence (LIIF) was used to quantify the steady, compressible flowfield of a nonreacting, supersonic combustor. The combustor was configured with single and staged, transverse-air injection into a supersonic-air freestream behind a rearward-facing step. Pressure, temperature, two-velocity components, and injectant mole fraction were measured with high spatial resolution in the three-dimensional flowfields. These experimental results provide a benchmark set of data for validation of computational fluid dynamic (CFD) codes being developed to model supersonic combustor flowfields.

  16. Quasi-distributed measurement on femtosecond laser-induced scattering voids using incoherent OFDR and OTDR

    NASA Astrophysics Data System (ADS)

    Liehr, Sascha; Burgmeier, Jörg

    2013-05-01

    We propose to use focused femtosecond laser pulses to create scattering damage in standard singlemode optical fibres as reference points for quasi-distributed sensing applications. Such sensor fibres are interrogated with incoherent optical frequency domain reflectometry (I-OFDR) technique and optical time domain reflectometry (OTDR). A performance comparison of both techniques with the clear advantage of the I-OFDR is presented as well as a quasi-distributed length change measurement application. Also dynamic measurement based on the I-OFDR technique is demonstrated on a femtosecond laser-induced sensor chain.

  17. Airborne simultaneous spectroscopic detection of laser-induced water Raman backscatter and fluorescence from chlorophyll a and other naturally occurring pigments

    SciTech Connect

    Hoge, F.E.; Swift, R.N.

    1981-09-15

    The airborne laser-induced spectral emission bands obtained simultaneously from water Raman backscatter and the fluorescence of chlorophyll and other naturally occuring waterborne pigments are reported here for the first time. The importance of this type data lies not only in its single-shot multispectral character but also in the application of the Raman line for correction or calibration of the spatial variation of the laser penetration depth without the need for in situ water attenuation measurements. The entire laser-induced fluorescence and Raman scatter emissions resulting from each separate 532-nm 10-nsec laser pulse are collected and spectrally dispersed in a diffraction grating spectrometer having forty photomultiplier tube detectors. Results from field experiments conducted in the North Sea and the Chesapeake Bay/Potomac River are presented. Difficulties involving the multispectral resolution of the induced emissions are addressed, and feasible solutions are suggested together with new instrument configurations and future research directions.

  18. Signal-to-noise ratio evaluation with draw tower fibre Bragg gratings (DTGs) for dynamic strain sensing at elevated temperatures and corrosive environment

    NASA Astrophysics Data System (ADS)

    De Pauw, B.; Lamberti, A.; Vanlanduit, S.; Van Tichelen, K.; Geernaert, T.; Berghmans, F.

    2014-05-01

    Measuring strain at the surface of a structure can help to estimate the dynamical properties of the structure under test. Such a structure can be a fuel assembly of a nuclear reactor consisting of fuel pins. In this paper we demonstrate a method to integrate draw tower gratings (DTGs) in a fuel pin and we subject this pin to conditions close to those encountered in a heavy liquid metal (HLM) reactor. More specifically, we report on the performance of DTGs used as a strain sensor when immersed in HLM during thermal cycles (up to 300_C) for up to 700 hours.

  19. Wet-cleaning of contaminants on the surface of multilayer dielectric pulse compressor gratings by the Piranha solution

    Microsoft Academic Search

    Shangbi Chen; Bin Sheng; Xiangdong Xu; Shaojun Fu

    2010-01-01

    Contaminants are deemed to be the initial source of optical-damage mechanisms as well as the main reason to decrease the Laser Induced Damage Threshold (LIDT) of multilayer dielectric pulse compressor gratings (PCG). In this paper, the Piranha solution was used effectively and nondestructively to remove the residual contaminants on the surface of PCG. The surface cleanliness was evaluated by Scanning

  20. Laser-Induced Breakdown Spectroscopy of Trace Metals

    NASA Technical Reports Server (NTRS)

    Simons, Stephen (Technical Monitor); VanderWal, Randall L.; Ticich, Thomas M.; West, Joseph R., Jr.

    2004-01-01

    An alternative approach for laser-induced breakdown spectroscopy (LIBS) determination of trace metal determination in liquids is demonstrated. The limits of detection (LOD) for the technique ranged from 10 ppb to 10 ppm for 15 metals metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb) tested.

  1. Laser-induced fluorescence used in localizing atherosclerotic lesions

    Microsoft Academic Search

    S. Andersson-Engels; A. Gustafson; J. Johansson; U. Stenram; K. Svanberg; S. Svanberg

    1989-01-01

    We have investigated laser-induced fluorescence frompost mortem human arteries in order to find spectroscopic properties allowing discrimination between normal and atherosclerotic vessel wall. A pulsed nitrogen laser emitting light at a wavelength of 337.1 nm was used as an excitation source. The fluorescence spectrum from 370 to 700 nm was captured and analysed by an optical multichannel analyser. Dimensionless contrast

  2. Numerical simulation of laser--induced breakdown of air

    Microsoft Academic Search

    Shankar Ghosh; Krishnan Mahesh

    2007-01-01

    The laser--induced breakdown of air is studied using numerical simulation. When focused onto a small volume of air, a laser beam heats and ionizes the air, causing a plasma to form. Three models of air with varing levels of physical complexity are considered. The simulations are challenging due to presence of very strong shock waves and very low densities in

  3. Using Laser-Induced Incandescence To Measure Soot in Exhaust

    NASA Technical Reports Server (NTRS)

    Bachalo, William D.; Sankar, Subramanian V.

    2005-01-01

    An instrumentation system exploits laser-induced incandescence (LII) to measure the concentration of soot particles in an exhaust stream from an engine, furnace, or industrial process that burns hydrocarbon fuel. In comparison with LII soot-concentration-measuring systems, this system is more complex and more capable.

  4. Laser induced short plane acoustic wave focusing in water

    Microsoft Academic Search

    Seung H. Ko; Sang G. Ryu; Nipun Misra; Heng Pan; Costas P. Grigoropoulos; Nick Kladias; Elias Panides; Gerald A. Domoto

    2007-01-01

    Laser induced high frequency acoustic wave generation, propagation, and focusing in water are studied. A large area, flat, and short duration acoustic wave was generated by the thermoelastic interaction of a homogenized short pulsed laser beam with the liquid-solid interface and propagated at the speed of sound. Laser flash Schlieren photography was used to visualize the transient interaction of the

  5. Laser-Induced Mouse Model of Chronic Ocular Hypertension

    E-print Network

    Sakaguchi, Donald S.

    Laser-Induced Mouse Model of Chronic Ocular Hypertension Sinisa D. Grozdanic,1,2 Daniel M. Betts,1) is considered a primary risk factor for the initiation and progression of glaucomatous neuropathy.2 However of a mouse model in glaucoma studies.16 A procedure for the reliable induction of chronic ocular hypertension

  6. Laser-Induced Breakdown Spectroscopy---Capabilities and Limitations

    Microsoft Academic Search

    David A. Cremers; Rosemarie C. Chinni

    2009-01-01

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

  7. Plasma erosion rate diagnostics using laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

    Gaeta, C. J.; Turley, R. S.; Matossian, J. N.; Beattie, J. R.; Williamson, W. S.

    1992-01-01

    An optical technique for measuring the sputtering rate of a molybdenum surface immersed in a xenon plasma has been developed and demonstrated. This approach, which may be useful in real-time wear diagnostics for ion thrusters, relies on laser-induced fluorescence to determine the density of sputtered molybdenum atoms.

  8. Non-equilibrium conditions during a laser induced plasma expansion

    Microsoft Academic Search

    A. Casavola; G. Colonna; M. Capitelli

    2003-01-01

    A theoretical model to simulate the laser induced plasma (LIP) expansion with chemical kinetics has been developed for a Ti target. Our attention has been also focused on the influence of initial conditions on the plume expansion. In particular, changing the initial speed, temperature, pressure and plume extension, the speed of expansion and the width of the time of flight

  9. The role of continuum radiation in laser induced plasma spectroscopy

    Microsoft Academic Search

    A. De Giacomo; R. Gaudiuso; M. Dell'Aglio; A. Santagata

    2010-01-01

    This paper focuses on the interpretation of the origin of the continuum radiation in Laser Induced Plasma (LIP) emission spectra, a subject that has received little consideration in the literature when compared to the analysis of the line emission spectrum. The understanding of the spectral peculiarities observed immediately after the laser pulse, when the continuum radiation prevails on discrete emission

  10. Laser induced electron acceleration in vacuum K. P. Singha)

    E-print Network

    Singh, Kunwar Pal

    Laser induced electron acceleration in vacuum K. P. Singha) Department of Physics, Indian Institute acceleration by a plane polarized laser wave has been studied in vacuum. Relativistic equations of motion have been solved exactly for electron trajectory and energy as a function of laser intensity, phase

  11. Overview of applications of Laser-Induced Breakdown Spectroscopy (LIBS)

    SciTech Connect

    Cremers, D.A.

    1987-01-01

    Laser-induced breakdown spectroscopy (LIBS) is a method of performing elemental analyses of solids, liquids, and gases using the microplasma produced by a focused laser pulse. Because the microplasma is formed by optical radiation, LIBS has some important advantages compared to conventional laboratory based analytical methods. Three applications are discussed which use the LIBS method. 6 refs., 8 figs., 2 tabs.

  12. Woodhead Publishing Limited, 2010 Advances in laser-induced plastic

    E-print Network

    Yao, Y. Lawrence

    © Woodhead Publishing Limited, 2010 535 18 Advances in laser-induced plastic deformation processes laser energy in order to induce plastic deformation resulting in either a desired final part geometrySP), thermal forming, plasticity. 18.1 Introduction laser forming (lF) is a process which utilizes transient

  13. Effect of sample temperature on laser-induced breakdown spectroscopy

    Microsoft Academic Search

    S. H. Tavassoli; A. Gragossian

    2009-01-01

    The effect of initial sample temperature on spectral emission of laser-induced plasma has been investigated. The plasma has been produced on aluminum alloy surface at ambient air pressure. The sample has been uniformly heated by a heating element up to 150°C. The spectral emission of aluminum at different initial sample temperature and gate delay times has been measured. A simple

  14. Laser-induced copper deposition with weak reducing agents

    NASA Astrophysics Data System (ADS)

    Kochemirovsky, V. A.; Fateev, S. A.; Logunov, L. S.; Tumkin, I. I.; Safonov, S. V.; Khairullina, E. M.

    2013-11-01

    The study showed that organic alcohols with 1,2,3,5,6 hydroxyl groups can be used as reducing agents for laser-induced copper deposition from solutions (LCLD).Multiatomic alcohols, sorbitol, xylitol, and glycerol, are shown to be effective reducing agents for performing LCLD at glass-ceramic surfaces. High-conductivity copper tracks with good topology were synthesized.

  15. Interlaced spin grating for optical wave filtering

    NASA Astrophysics Data System (ADS)

    Linget, H.; Chanelière, T.; Le Gouët, J.-L.; Berger, P.; Morvan, L.; Louchet-Chauvet, A.

    2015-02-01

    Interlaced spin grating is a scheme for the preparation of spectrospatial periodic absorption gratings in an inhomogeneously broadened absorption profile. It relies on the optical pumping of atoms in a nearby long-lived ground state sublevel. The scheme takes advantage of the sublevel proximity to build large contrast gratings with unlimited bandwidth and preserved average optical depth. It is particularly suited to Tm-doped crystals in the context of classical and quantum signal processing. In this paper, we study the optical pumping dynamics at play in an interlaced spin grating and describe the corresponding absorption profile shape in an optically thick atomic ensemble. We show that, in Tm:YAG, the diffraction efficiency of such a grating can reach 18.3 % in the small-angle and 11.6 % in the large-angle configuration when the excitation is made of simple pulse pairs, considerably outperforming conventional gratings.

  16. Investigations of laser-induced plasma in argon by Thomson scattering A. Mendys a,

    E-print Network

    as of the electron density (ne) and electron temperature (Te). For laser induced plasma (LIP), the electron densityInvestigations of laser-induced plasma in argon by Thomson scattering A. Mendys a, , K. Dzierega Accepted 8 August 2011 Available online 16 August 2011 Keywords: Laser-induced breakdown spectroscopy

  17. Investigation of the local thermodynamic equilibrium of laser-induced aluminum plasma by Thomson scattering technique

    E-print Network

    induced plasma (LIP) has many applications, including: laser plasma igniters, high intensity X-ray sourcesInvestigation of the local thermodynamic equilibrium of laser-induced aluminum plasma by Thomson 28 March 2014 Available online 8 April 2014 Keywords: Laser-induced plasma Laser-induced breakdown

  18. What can we learn about laser-induced plasmas from Thomson scattering experiments

    E-print Network

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 1. Introduction Laser-induced plasmas (LIPs) have found numerous applications in- cluding pulsedReview What can we learn about laser-induced plasmas from Thomson scattering experiments K. Dziere scattering Rayleigh scattering Laser-induced plasma Shock wave Thermodynamic equilibrium This article

  19. Elemental analysis by microwave-assisted laser-induced breakdown spectroscopy: Evaluation on ceramics

    E-print Network

    Richardson, Martin C.

    -frequency plasma, microwave plasma, glow discharges, laser-induced plasma.1,3 Laser-induced plasma emission spec the laser intensity onto the sample and create a plasma, collection optics (free space or fiberElemental analysis by microwave-assisted laser-induced breakdown spectroscopy: Evaluation

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

    E-print Network

    Giesen, Thomas

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

  1. Detection of nickel atom by laser induced fluorescence during carbon nanotube formation in a laser produced plume

    NASA Astrophysics Data System (ADS)

    De Boer, G.; Arepalli, S.; Holmes, W.; Nikolaev, P.; Range, C.; Scott, C.

    2001-05-01

    In situ monitoring of catalyst nickel atoms by laser induced fluorescence during carbon nanotube formation in a laser-produced plume was performed at the Johnson Space Center nanotube production laboratory. The results indicate that ablation of nickel and plume dynamics are strongly related to the oven temperature. Nickel atoms have a long lifetime of several milliseconds and have an electronic temperature of at least 1500 K during carbon nanotube formation.

  2. IKK2 Inhibition Attenuates Laser-Induced Choroidal Neovascularization

    PubMed Central

    Lu, Huayi; Lu, Qingxian; Gaddipati, Subhash; Kasetti, Ramesh Babu; Wang, Wei; Pasparakis, Manolis; Kaplan, Henry J.; Li, Qiutang

    2014-01-01

    Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-?B pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either Ikk2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding Ikk2?/flox mice with Nestin-Cre mice. Deletion of Ikk2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-?B signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD. PMID:24489934

  3. Investigation of the early stages in laser-induced ignition by Schlieren photography and laser-induced fluorescence spectroscopy

    Microsoft Academic Search

    Maximilian Lackner; S. Charareh; F. Winter; K. F. Iskra; D. Rüdisser; T. Neger; H. Kopecek; E. Wintner

    2004-01-01

    Laser ignition has been discussed widely as a potentially superior ignition source for technical appliances such as internal combustion engines. Ignition strongly affects overall combustion, and its early stages in particular have strong implications on subsequent pollutant formation, flame quenching, and extinction. Our research here is devoted to the experimental investigation of the early stages of laser-induced ignition of CH4\\/air

  4. Design of a novel laser-induced fluorescence spectrophotometer for water quality monitor based on virtual instrument and linear CCD

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Huang, Shuanggen; Liu, Guodong; Huang, Zhen; Zeng, Lvming

    2011-06-01

    Since the water resource is being seriously polluted with the development of the human society, the monitoring of the available water resource is an impending task. The concentration of the dissolved organic matter, oxygen and inorganic salt in water can be checked by means of some methods, e.g. electrolysis, electrochemical method, colorimetry. But because some drawbacks are existed in these methods, the laser-induced fluorescence (LIF) spectrophotometry method is adopted into this paper. And a novel LIF spectrophotometer for water quality monitor (WQM) is designed. In this WQM, the 3rd harmonic of the Q switched Nd:YAG laser is used as the induced fluorescence light-source. And for the splitting-light system of the spectrophotometer for WQM, in order to improve the resolution and light-passing efficiency, a novel volume holography transmissive(VHT) grating is used as the diffraction grating instead of the plane or holography grating. Meanwhile, the linear CCD with combined data acquisition (DAQ) card is used as the fluorescence spectral detection system and virtual instrument (VI) technology based on LabVIEW is used to control the spectral acquisition and analysis. Experimental results show that the spatial resolution of the novel spectrophotometer for WQM is improved, its resolution can reach 2nm. And the checking accuracy of this WQM is higher than others. Therefore, the novel LIF spectrophotometer for WQM has the potential value in the water quality monitoring and biochemical application.

  5. Assessment of damage in composite laminates through dynamic, full-spectral interrogation of fiber Bragg grating sensors

    Microsoft Academic Search

    A. Propst; K. Peters; M. A. Zikry; S. Schultz; W. Kunzler; Z. Zhu; M. Wirthlin; R. Selfridge

    2010-01-01

    In this study, we demonstrate the full-spectral interrogation of a fiber Bragg grating (FBG) sensor at 535 Hz. The sensor is embedded in a woven, graphite fiber-epoxy composite laminate subjected to multiple low-velocity impacts. The measurement of unique, time dependent spectral features from the FBG sensor permits classification of the laminate lifetime into five regimes. These damage regimes compare well

  6. Investigating the role of superdiffusive currents in laser induced demagnetization of ferromagnets with nanoscale magnetic domains

    PubMed Central

    Moisan, N.; Malinowski, G.; Mauchain, J.; Hehn, M.; Vodungbo, B.; Lüning, J.; Mangin, S.; Fullerton, E. E.; Thiaville, A.

    2014-01-01

    Understanding the loss of magnetic order and the microscopic mechanisms involved in laser induced magnetization dynamics is one of the most challenging topics in today's magnetism research. While scattering between spins, phonons, magnons and electrons have been proposed as sources for dissipation of spin angular momentum, ultrafast spin dependent transport of hot electrons has been pointed out as a potential candidate to explain ultrafast demagnetization without resorting to any spin dissipation channel. Here we use time resolved magneto-optical Kerr measurements to extract the influence of spin dependent transport on the demagnetization dynamics taking place in magnetic samples with alternating domains with opposite magnetization directions. We unambiguously show that whatever the sample magnetic configuration, the demagnetization takes place during the same time, demonstrating that hot electrons spin dependent transfer between neighboring domains does not alter the ultrafast magnetization dynamics in our systems with perpendicular anisotropy and 140?nm domain sizes. PMID:24722395

  7. Laser Induced Aluminum Surface Breakdown Model

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wnag, Ten-See (Technical Monitor)

    2001-01-01

    Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid., pressure-based computational aerothermodynamics, platform, several sub-nio"'dels describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (113) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

  8. Laser Induced Aluminum Surface Breakdown Model

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wang, Ten-See (Technical Monitor)

    2002-01-01

    Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid, pressure-based computational aerothermodynamics; platform, several sub-models describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (IB) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

  9. Laser-induced optical changes in amorphous multilayers

    NASA Astrophysics Data System (ADS)

    Malyovanik, M.; Ivan, S.; Csik, A.; Langer, G. A.; Beke, D. L.; Kökényesi, S.

    2003-01-01

    It is shown that the well-known blueshift of the fundamental absorption edge in as-deposited compositionally modulated amorphous Si/Ge and As6Se94/Se80Te20 multilayers (with periods of 4-8 nm) is further enhanced due to the thermal or laser-induced intermixing of adjacent layers. The laser-induced intermixing process, as supported by experiments and model calculations, can be attributed to both the local heating and photo-effects in As6Se94/Se80Te20 multilayers, while only the thermal effects were observed for Si/Ge multilayers. Structural transformations, based on this enhanced interdiffusion, provide good capability for spatially patterning optoelectronic devices and digital information recording.

  10. Laser-induced periodic surface structuring of biopolymers

    NASA Astrophysics Data System (ADS)

    Pérez, Susana; Rebollar, Esther; Oujja, Mohamed; Martín, Margarita; Castillejo, Marta

    2013-03-01

    We report here on a systematic study about the formation of laser-induced periodic surface structures (LIPSS) on biopolymers. Self-standing films of the biopolymers chitosan, starch and the blend of chitosan with the synthetic polymer poly (vinyl pyrrolidone), PVP, were irradiated in air with linearly polarized laser beams at 193, 213 and 266 nm, with pulse durations in the range of 6-17 ns. The laser-induced periodic surface structures were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via Raman spectroscopy. Formation of LIPSS parallel to the laser polarization direction, with periods similar to the laser wavelength, was observed at efficiently absorbed wavelengths in the case of the amorphous biopolymer chitosan and its blend with PVP, while formation of LIPSS is prevented in the crystalline starch biopolymer.

  11. Laser-induced incandescence calibration via gravimetric sampling

    NASA Technical Reports Server (NTRS)

    Choi, M. Y.; Vander Wal, R. L.; Zhou, Z.

    1996-01-01

    Absolute calibration of laser-induced incandescence (LII) is demonstrated via comparison of LII signal intensities with gravimetrically determined soot volume fractions. This calibration technique does not rely upon calculated or measured optical characteristics of soot. The variation of the LII signal with gravimetrically measured soot volume fractions ranging from 0.078 to 1.1 ppm established the linearly of the calibration. With the high spatial and temporal resolution capabilities of laser-induced incandescence (LII), the spatial and temporal fluctuations of the soot field within a gravimetric chimney were characterized. Radial uniformity of the soot volume fraction, f(sub v) was demonstrated with sufficient averaging of the single laser-shot LII images of the soot field thus confirming the validity of the calibration method for imaging applications. As illustration, instantaneous soot volume fractions within a Re = 5000 ethylene/air diffusion flame measured via planar LII were established quantitatively with this calibration.

  12. Femtosecond laser-induced nanostructure formation in Sb?Te?

    SciTech Connect

    Li, Yuwei [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States); Stoica, Vladimir A. [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States); Endicott, Lynn [Univ. of Michigan, Ann Arbor, MI (United States); Wang, Guoyu [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States); Sun, Huarui [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States); Pipe, Kevin P. [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States); Uher, Ctirad [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States); Clarke, Roy [Center for Solar and Thermal Energy Conversion, Univ. of Michigan, Ann Arbor, MI (United States)

    2011-01-01

    We report femtosecond laser-induced nanotracks in highly absorbing Sb?Te?. Groups of nanotracks are observed with widths ?50 nm and periodicity ?130 nm, their area of coverage extending with the increase of laser fluence. We demonstrate that under a narrow range of laser fluences and laser irradiation times, long highly aligned nanotracks can be formed in Sb?Te?. The results suggest a promising avenue for laser nanostructuring of chalcogenide thermoelectrics, with implications for high efficiency thermoelectric energy conversion.

  13. Laser-induced fluorescence spectroscopy for combustion diagnostics

    NASA Technical Reports Server (NTRS)

    Crosley, D. R.; Smith, G. P.

    1983-01-01

    The types of spectroscopic and collisional measurements that are needed to develop laser-induced fluorescence as a diagnostic technique are discussed, with emphasis placed on combustion measurements. The spectroscopic measurements under collision-free conditions include production of radicals, excitation scan studies, lifetime measurements, and fluorescence scans. The collisional studies discussed here are quenching, energy transfer, and polarization phenomena. The results of recent laboratory experiments are presented.

  14. Forensic comparative glass analysis by laser-induced breakdown spectroscopy

    Microsoft Academic Search

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

    2007-01-01

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

  15. Laser induced tuning of cholesteric liquid crystal without alignment layers

    NASA Astrophysics Data System (ADS)

    Cheng, M.-C.; Huang, T.-C.; Lee, C.-Y.; Hsiao, Vincent K. S.

    2014-12-01

    We demonstrate a laser induced tuning effect on non-chiral azobenzene-doped CLC (Azo-CLCs) without using orientated substrate. The reversible tuning range is 90 nm under alternative violet (405 nm) and green (532 nm) laser exposure corresponded to the response time of 3 and 15 s, respectively. The current demonstrations may find applications in photoactive micro- or nano-photonic devices where orientated substrate is difficult to be incorporated.

  16. Numerical simulation of laser-induced thin film delamination

    Microsoft Academic Search

    Yueming Liang; Xiaopeng Bi; Junlan Wang

    2008-01-01

    Laser-induced thin film spallation has been developed to be one of the most powerful tools for quantitative measurement of thin film interfacial adhesion. High-energy laser pulse absorption generates stress pulse that can be used to delaminate a thin film–substrate interface. Interfacial strength is obtained from the measured surface motion of the thin film using elastic wave mechanics. Due to the

  17. Numerical simulation of laser induced plasma during pulsed laser deposition

    Microsoft Academic Search

    Zhaoyan Zhang; Zhen-Xue Han; George S. Dulikravich

    2001-01-01

    A numerical study of the laser induced evaporation and ionization process during pulsed laser deposition is presented. The process is separated into three domains: (i) conduction inside the solid, (ii) a discontinuity layer between solid and vapor, and (iii) expansion of high temperature vapor\\/plasma. A quasi-one-dimensional model is solved to predict the temperature field inside the solid. Mass, momentum, and

  18. Ultratrace analysis of transuranic actinides by laser-induced fluorescence

    DOEpatents

    Miller, S.M.

    1983-10-31

    Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

  19. Laser-induced breakdown spectroscopy for specimen analysis

    DOEpatents

    Kumar, Akshaya; Yu-Yueh, Fang; Burgess, Shane C.; Singh, Jagdish P.

    2006-08-15

    The present invention is directed to an apparatus, a system and a method for detecting the presence or absence of trace elements in a biological sample using Laser-Induced Breakdown Spectroscopy. The trace elements are used to develop a signature profile which is analyzed directly or compared with the known profile of a standard. In one aspect of the invention, the apparatus, system and method are used to detect malignant cancer cells in vivo.

  20. Laser-induced spall in metals: Experiment and simulation

    Microsoft Academic Search

    Shalom Eliezer; Irith Gilath; Tuvia Bar-Noy

    1990-01-01

    Spall at ultra high strain rate (107 s?1) was investigated using short pulsed laser-induced shock waves in copper and aluminum foils. The intensities of the 3.9-ns Nd:Glass laser were in the range of 1010–1012 W\\/cm2, and the foil thickness was in the 100–600 ?m range. The laser-generated shock wave pressure was in the range of a few hundred kilobars (kb).

  1. Velocity measurements using the laser-induced phosphorescence of biacetyl

    Microsoft Academic Search

    H. S. Lowry III

    1987-01-01

    A method using the laser-induced phosphorescence (LIP) of biacetyl is used to obtain velocity measurements of flows created by a sonic orifice, and over surfaces of varying thickness and porosities, in a 4 x 10-ft cylindrical vacuum chamber. Measurements for a variety of flow rates and background pressures are in good agreement with flow-field velocity calculations. Measurements were made with

  2. Nanoparticle removal from EUV photomasks using laser induced plasma shockwaves

    Microsoft Academic Search

    John Kadaksham; Dong Zhou; M. D. Murthy Peri; Ivin Varghese; Florence Eschbach; Cetin Cetinkaya

    2006-01-01

    In recent years, it has been demonstrated that nanoparticles can be detached and removed from substrates using laser-induced plasma (LIP) shockwaves. While it was experimentally established the effectiveness of the LIP technique for removing nanoparticles in the sub-100nm range, the removal mechanisms were not well-understood. In this article, we introduce a set of particle removal mechanisms based on moment resistance

  3. Nanoparticle Removal Using Laser-Induced Plasma Shock Waves

    Microsoft Academic Search

    M. D. Murthy Peri; Ivin Varghese; Dong Zhou; Arun John; Chen Li; Cetin Cetinkaya

    2007-01-01

    Removal of sub-100 nm particles from substrates such as wafers and photo masks is an essential requirement in semiconductor, microelectronics, and nanotechnology applications. The proposed laser-induced plasma (LIP) based approach is an effective technique for removal of sub-100 nm particles, as the minimum tolerable particle on the substrates shrinks to sub-100 nm levels with each technological node. In the current study, our progress

  4. Laser-induced plasma spectroscopy (LIPS) for characterization of hydrocolloids

    Microsoft Academic Search

    Ulrich Panne; C. Haisch; Reinhard Niessner

    1997-01-01

    Laser-induced plasma spectroscopy (LIPS) was used to study the nature and abundance of heavy metal hydrocolloids with particle diameters between 0.1 micrometer and 1 micrometer in aquifer systems. A miniaturized ultrafiltration system with a 0.1 micrometer membrane filter was employed for on site analysis. For representative heavy metal colloids absolute limits of detection in the ng-range were achieved with good

  5. Laser-induced breakdown spectroscopy using ultrashort and dual pulses

    Microsoft Academic Search

    Kristine Lynn Eland

    2001-01-01

    Laser-induced breakdown spectroscopy (LIBS) is a very simple and rapid form of elemental analysis, in which emission from a laser generated plasma is used to identify the elemental constituents of virtually any type of sample without sample preparation. Because only optical access is required, LIBS can be coupled with fiber-optics and used for remote and on-line applications. However, the use

  6. Vacuum ultraviolet laser-induced breakdown spectroscopy analysis of polymers

    Microsoft Academic Search

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

    2009-01-01

    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

  7. Dynamics of perceptual bi-stability for stereoscopic slant rivalry and a comparison with grating, house-face, and Necker cube rivalry.

    PubMed

    van Ee, Raymond

    2005-01-01

    A way to study conscious perception is to expose the visual system to an ambiguous stimulus that instigates bi-stable perception. This provides the opportunity to study neural underpinnings related to the percepts rather than to the stimulus. We have recently developed a slant-rivalry paradigm that has beneficial metrical (quantitative) aspects and that exhibits temporal aspects of perceptual reversals that seemed to be under considerable voluntary control of the observer. Here we examined a range of different aspects of the temporal dynamics of the perceptual reversals of slant rivalry and we compared these with the dynamics of orthogonal grating rivalry, house-face rivalry, and Necker cube rivalry. We found that slant rivalry exhibits a qualitatively similar pattern of dynamics. The drift of the perceptual reversal rate, both across successive experimental repetitions, and across successive 35-s portions of data were similar. The sequential dependence of the durations of perceptual phases, too, revealed very similar patterns. The main quantitative difference, which could make slant rivalry a useful stimulus for future neurophysiological studies, is that the percept durations are relatively long compared to the other rivalry stimuli. In the paper that accompanies this paper [van Ee, R., van Dam, L. C. J., Brouwer, G. J. (2005). Voluntary control and the dynamics of perceptual bi-stability. Vision Research,] we focused on the role of voluntary control in the dynamics of perceptual reversals. PMID:15571736

  8. Dynamic Sensing Performance of a Point-Wise Fiber Bragg Grating Displacement Measurement System Integrated in an Active Structural Control System

    PubMed Central

    Chuang, Kuo-Chih; Liao, Heng-Tseng; Ma, Chien-Ching

    2011-01-01

    In this work, a fiber Bragg grating (FBG) sensing system which can measure the transient response of out-of-plane point-wise displacement responses is set up on a smart cantilever beam and the feasibility of its use as a feedback sensor in an active structural control system is studied experimentally. An FBG filter is employed in the proposed fiber sensing system to dynamically demodulate the responses obtained by the FBG displacement sensor with high sensitivity. For comparison, a laser Doppler vibrometer (LDV) is utilized simultaneously to verify displacement detection ability of the FBG sensing system. An optical full-field measurement technique called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) is used to provide full-field vibration mode shapes and resonant frequencies. To verify the dynamic demodulation performance of the FBG filter, a traditional FBG strain sensor calibrated with a strain gauge is first employed to measure the dynamic strain of impact-induced vibrations. Then, system identification of the smart cantilever beam is performed by FBG strain and displacement sensors. Finally, by employing a velocity feedback control algorithm, the feasibility of integrating the proposed FBG displacement sensing system in a collocated feedback system is investigated and excellent dynamic feedback performance is demonstrated. In conclusion, our experiments show that the FBG sensor is capable of performing dynamic displacement feedback and/or strain measurements with high sensitivity and resolution. PMID:22247683

  9. Multilayer diffraction grating

    DOEpatents

    Barbee, T.W. Jr.

    1990-04-10

    This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages. 2 figs.

  10. Water-cooled grate

    SciTech Connect

    Lis, P.; Olausson, K.

    1980-07-22

    A description is given of a furnace for the combustion of solid fuel comprising: a first, inclined grate portion having an upper end and a lower end, the upper end adjacent to a side wall defining the furnace, said first grate portion extending outwardly below a combustion space; means for supplying fuel to the upper end of said inclined, first grate portion; an angular, second grate portion spaced apart from the lower end of said first grate portion and comprising a first, mainly upwardly part facing said first grate portion, and a second, mainly horizontal part extending backwards, below said first grate portion to receive fuel residues therefrom; means for suppyling combustion air to said first and said second grate portions; and a passageway for conducting combustion gases from said second part of said second portion to the upper end of said first grate portion.

  11. Multilayer diffraction grating

    DOEpatents

    Barbee, Jr., Troy W. (Palo Alto, CA)

    1990-01-01

    This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages.

  12. Analysis of moving surface structures at a laser-induced boiling front

    NASA Astrophysics Data System (ADS)

    Matti, R. S.; Kaplan, A. F. H.

    2014-10-01

    Recently ultra-high speed imaging enabled to observe moving wave patterns on metal melts that experience laser-induced boiling. In laser materials processing a vertical laser-induced boiling front governs processes like keyhole laser welding, laser remote fusion cutting, laser drilling or laser ablation. The observed waves originate from temperature variations that are closely related to the melt topology. For improved understanding of the essential front mechanisms and of the front topology, for the first time a deeper systematic analysis of the wave patterns was carried out. Seven geometrical shapes of bright or dark domains were distinguished and categorized, in particular bright peaks of three kinds and dark valleys, often inclined. Two categories describe special flow patterns at the top and bottom of the front. Dynamic and statistical analysis has revealed that the shapes often combine or separate from one category to another when streaming down the front. The brightness of wave peaks typically fluctuates during 20-50 ?s. This variety of thermal wave observations is interpreted with respect to the accompanying surface topology of the melt and in turn for governing local mechanisms like absorption, shadowing, boiling, ablation pressure and melt acceleration. The findings can be of importance for understanding the key process mechanisms and for optimizing laser materials processing.

  13. Transient phonon vacuum squeezing due to femtosecond-laser-induced bond hardening

    NASA Astrophysics Data System (ADS)

    Cheenicode Kabeer, Fairoja; Grigoryan, Naira S.; Zijlstra, Eeuwe S.; Garcia, Martin E.

    2014-09-01

    Ultrashort optical pulses can be used both to create fundamental quasiparticles in crystals and to change their properties. In noble metals, femtosecond lasers induce bond hardening, but little is known about its origin and consequences. Here we simulate ultrafast laser excitation of silver at high fluences. We compute laser-excited potential-energy surfaces by all-electron ab initio theory and analyze the resulting quantum lattice dynamics. We also consider incoherent lattice heating due to electron-phonon interactions using the generalized two-temperature model. We find phonon hardening, which we attribute to the excitation of s electrons. We demonstrate that this may result in phonon vacuum squeezed states with an optimal squeezing factor of ˜0.001 at the L-point longitudinal mode. This finding implies that ultrafast laser-induced bond hardening may be used as a tool to manipulate the quantum state of opaque materials, where, so far, the squeezing of phonons below the zero-point motion has only been realized in transparent crystals by a different mechanism. On the basis of our finding, we further propose a method for directly measuring bond hardening.

  14. Modeling of dual emission laser induced fluorescence for slurry thickness measurements in chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Gray, Caprice; Rogers, Chris B.; Manno, Vincent P.; White, Robert D.

    2011-07-01

    Dual emission laser induced fluorescence (DELIF) is a technique for measuring the instantaneous thin fluid film thickness in dynamic systems. Two fluorophores within the system produce laser induced emissions that are filtered and captured by two cameras. The ratio of the images from these cameras is used to cancel the effect of the laser beam profile on the image intensity. The resultant intensity ratio can be calibrated to a fluid film thickness. The utilization of a 2-dye system when applied to Chemical Mechanical Polishing (CMP) is complicated by the fluorescence of the polymeric polishing pad and the light scattering particles in the polishing slurry. We have developed a model of DELIF for CMP with 1-dye employing the polishing pad as the second fluorophore. While scattering particles in the slurry decrease the overall intensity of the individual images, the contrast in the image ratio increases. Using the 1-dye DELIF system to measure thin slurry films, our model results indicate that a cubic calibration may be needed. However, experimental results suggest a linear calibration is achieved for slurry films between 0 and 133 ?m thick with scattering coefficients as high as 8.66 mm-1 at a wavelength equal to 410 nm.

  15. Study of fast laser induced cutting of silicon materials

    NASA Astrophysics Data System (ADS)

    Weinhold, S.; Gruner, A.; Ebert, R.; Schille, J.; Exner, H.

    2014-03-01

    We report on a fast machining process for cutting silicon wafers using laser radiation without melting or ablating and without additional pretreatment. For the laser induced cutting of silicon materials a defocused Gaussian laser beam has been guided over the wafer surface. In the course of this, the laser radiation caused a thermal induced area of tension without affecting the material in any other way. With the beginning of the tension cracking process in the laser induced area of tension emerged a crack, which could be guided by the laser radiation along any direction over the wafer surface. The achieved cutting speed was greater than 1 m/s. We present results for different material modifications and wafer thicknesses. The qualitative assessment is based on SEM images of the cutting edges. With this method it is possible to cut mono- and polycrystalline silicon wafers in a very fast and clean way, without having any waste products. Because the generated cracking edge is also very planar and has only a small roughness, with laser induced tension cracking high quality processing results are easily accessible.

  16. Diatomic Molecular Emission Spectroscopy of Laser-induced Titanium Plasma

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  17. Analysis on laser-induced thermoelastic deformation of DMs

    NASA Astrophysics Data System (ADS)

    Wei, Binbin; Liu, Wenguang; Xie, Kun; Jiang, Zongfu; Zhou, Qiong

    2014-11-01

    Laser-induced static surface shape changes of deformable mirrors will cause difficulties for beam control of the laser system. The overall peak and valley (PV) value of the deformable mirror (DM) will reach the scale of micrometer when irradiated by high power lasers. We have investigated changes in the static surface shape of a 37-element DM caused by laser-induced thermoelastic deformation. It is found that the laser-induced profile change of the mirror shows a high-order characteristic. In this paper the finite element method is used to analyze the surface shape of the DM when it is irradiated by high power lasers. The surface shape is fitted using the Zernike polynomials and the influence functions to see the characteristic of it and the DM's ability to compensate it. The fitting results show that the lower-order aberrations can be corrected by the DM itself with the cost of a reduced ability of aberration correction, as the available amount of stroke will decrease. In addition, changes of the influence functions are simulated and the modified influence functions are calculated. Furthermore, the performances of the DM in three different situations are simulated to reveal the impact of thermoelastic deformation on the DM's aberration correcting ability.

  18. Correlation between grade of pearlite spheroidization and laser induced spectra

    NASA Astrophysics Data System (ADS)

    Yao, Shunchun; Dong, Meirong; Lu, Jidong; Li, Jun; Dong, Xuan

    2013-12-01

    Laser induced breakdown spectroscopy (LIBS) which is used traditionally as a spectrochemical analytical technique was employed to analyze the grade of pearlite spheroidization. Three 12Cr1MoV steel specimens with different grades of pearlite spheroidization were ablated to produce plasma by pulse laser at 266 nm. In order to determine the optimal temporal condition and plasma parameters for correlating the grade of pearlite spheroidization and laser induced spectra, a set of spectra at different delays were analyzed by the principal component analysis method. Then, the relationship between plasma temperature, intensity ratios of ionic to atomic lines and grade of pearlite spheroidization was studied. The analysis results show that the laser induced spectra of different grades of pearlite spheroidization can be readily identifiable by principal component analysis in the range of 271.941–289.672 nm with 1000 ns delay time. It is also found that a good agreement exists between the Fe ionic to atomic line ratios and the tensile strength, whereas there is no obvious difference in the plasma temperature. Therefore, LIBS may be applied not only as a spectrochemical analytical technique but also as a new way to estimate the grade of pearlite spheroidization.

  19. Validation of Laser-Induced Fluorescent Photogrammetric Targets on Membrane Structures

    NASA Technical Reports Server (NTRS)

    Jones, Thomas W.; Dorrington, Adrian A.; Shortis, Mark R.; Hendricks, Aron R.

    2004-01-01

    The need for static and dynamic characterization of a new generation of inflatable space structures requires the advancement of classical metrology techniques. A new photogrammetric-based method for non-contact ranging and surface profiling has been developed at NASA Langley Research Center (LaRC) to support modal analyses and structural validation of this class of space structures. This full field measurement method, known as Laser-Induced Fluorescence (LIF) photogrammetry, has previously yielded promising experimental results. However, data indicating the achievable measurement precision had not been published. This paper provides experimental results that indicate the LIF-photogrammetry measurement precision for three different target types used on a reflective membrane structure. The target types were: (1) non-contact targets generated using LIF, (2) surface attached retro-reflective targets, and (3) surface attached diffuse targets. Results from both static and dynamic investigations are included.

  20. Simultaneous spatially and temporally resolved laser induced incandescence and laser induced fluorescence measurements in jet propulsion fuel 8 and heptane pool fires

    Microsoft Academic Search

    Tara Leigh Henriksen

    2008-01-01

    Medium scale pool fires can be used to validate models of large scale accidental fires. In order to provide a relevant data set for model validation, laser induced incandescence (LII) was used to quantify soot volume fraction levels in heavily sooting pool fires of JP-8 and heptane. Qualitative measurements of OH were simultaneously imaged by a laser induced fluorescence (LIF)

  1. Laser induced shock studies at RRCAT, Indore

    NASA Astrophysics Data System (ADS)

    Naik, P. A.; Arora, V.; Bagchi, S.; Prasad, Y. B. S. R.; Barnwal, S.; Gupta, P. D.

    2012-07-01

    The knowledge of material response under shock compression is important in terms of proper understanding of the process and in view of the wide range of technological applications associated with it. At the Laser Plasma Division, RRCAT, Indore, among other things, we are also involved in studying the material response from two different perspectives. On one front, we have developed capability for acquiring Equation of State (EOS) of materials using laser generated shock waves with long pulse lasers (>200 ps). On the other front, we have started shock experiments on single crystals using time resolved x-ray diffraction technique, using ultra-short pulse lasers (< 1 ps). In these initial experiments, characteristic sub-picosecond, high brightness K? x-ray pulses generated by Ti: sapphire femtosecond laser produced plasmas of different target materials (Ti, Fe, and Cu) were used to probe the effect of compression generated by moderately intense (GW/cm2) sub-nanosecond laser (200 ps) pulse irradiation on the crystal surface. The dynamics of the shock propagation is manifested in terms of the temporal evolution of the rocking curve of shocked sample. The shock velocity deduced from these measurements is 12 km/s, consistent with the predicted velocities and probe depth. The observed maximum compression is 0.4 % which corresponds to a pressure of 0.8 GPa.

  2. A wide dynamics and fast scan interrogating method for a fiber Bragg grating sensor network implemented using code division multiple access.

    PubMed

    Kim, Youngbok; Jeon, Sie-Wook; Kwon, Won-Bae; Park, Chang-Soo

    2012-01-01

    We propose and demonstrate a fiber Bragg grating (FBG) sensor network employing the code division multiple access (CDMA) technique to identify information from individual sensors. To detect information without considering time delays between sensors, a sliding correlation method is applied, in which two different signals with the same pseudo-random binary sequence (PRBS) pattern, but slightly different frequencies, are applied to the source and detector sides. Moreover, for time domain detection, a wavelength-to-time conversion technique using a wavelength dispersive medium is introduced. The experimental results show that the proposed sensor network has a wide strain dynamic range of 2,400 ?? and a low crosstalk of 950:1. PMID:22778619

  3. A Wide Dynamics and Fast Scan Interrogating Method for a Fiber Bragg Grating Sensor Network Implemented Using Code Division Multiple Access

    PubMed Central

    Kim, Youngbok; Jeon, Sie-Wook; Kwon, Won-Bae; Park, Chang-Soo

    2012-01-01

    We propose and demonstrate a fiber Bragg grating (FBG) sensor network employing the code division multiple access (CDMA) technique to identify information from individual sensors. To detect information without considering time delays between sensors, a sliding correlation method is applied, in which two different signals with the same pseudo-random binary sequence (PRBS) pattern, but slightly different frequencies, are applied to the source and detector sides. Moreover, for time domain detection, a wavelength-to-time conversion technique using a wavelength dispersive medium is introduced. The experimental results show that the proposed sensor network has a wide strain dynamic range of 2,400 ?? and a low crosstalk of 950:1. PMID:22778619

  4. Two-dimensional fluorescence-detected coherent spectroscopy with absolute phasing by confocal imaging of a dynamic grating and 27-step phase-cycling

    SciTech Connect

    De, Arijit K., E-mail: akde@lbl.gov; Fleming, Graham R., E-mail: grfleming@lbl.gov [Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94702 (United States); Department of Chemistry, University of California at Berkeley, Berkeley, California 94702 (United States); Monahan, Daniele; Dawlaty, Jahan M. [Department of Chemistry, University of California at Berkeley, Berkeley, California 94702 (United States)

    2014-05-21

    We present a novel experimental scheme for two-dimensional fluorescence-detected coherent spectroscopy (2D-FDCS) using a non-collinear beam geometry with the aid of “confocal imaging” of dynamic (population) grating and 27-step phase-cycling to extract the signal. This arrangement obviates the need for distinct experimental designs for previously developed transmission detected non-collinear two-dimensional coherent spectroscopy (2D-CS) and collinear 2D-FDCS. We also describe a novel method for absolute phasing of the 2D spectrum. We apply this method to record 2D spectra of a fluorescent dye in solution at room temperature and observe “spectral diffusion.”.

  5. Quantitative measurement of transverse injector and free stream interaction in a nonreacting SCRAMJET combustor using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Fletcher, D. G.; Mcdaniel, J. C.

    1987-01-01

    A preliminary quantitative study of the compressible flowfield in a steady, nonreacting model SCRAMJET combustor using laser-induced iodine fluorescence (LIIF) is reported. Measurements of density, temperature, and velocity were conducted with the calibrated, nonintrusive, optical technique for two different combustor operating conditions. First, measurements were made in the supersonic flow over a rearward-facing step without transverse injection for comparison with calculated pressure profiles. The second configuration was staged injection behind the rearward-facing step at an injection dynamic pressure ratio of 1.06. These experimental results will be used to validate computational fluid dynamic (CFD) codes being developed to model supersonic combustor flowfields.

  6. Simulation and characterization of laser induced deformation processes

    NASA Astrophysics Data System (ADS)

    Fan, Yajun

    2006-04-01

    Laser induced deformation processes include laser forming (LF) and laser shock processing. LF is a recently developed and highly flexible thermal forming technique, and laser shock processing is an innovative mechanical process in which shock waves up to 10GPa are generated by a confined laser ablation process. The generated high pressure imparts beneficial residual stress into the surface layer of metal parts as well as shapes thin metal parts. In laser forming, it has been known that microstructural evolution has an important effect on the deformation process, and that the typical thermal cycles in laser forming are much steeper than those in other thermal mechanical processes like welding and hot rolling. In this study, microstructural evolution in laser forming has been investigated, and a thermal-microstructural-mechanical model is developed to predict microstructural changes (phase transformations and recrystallization) and their effects on flow behavior and deformation. Grain structure and phase transformation in heat affected zone (HAZ) is experimentally characterized, and measurement of bending curvature also helps to validate the proposed model. Based on the similar methodology, two different materials have been studied: AISI 1010 low carbon steel and Ti-6Al-4V alloy. In the case of Ti-6A1-4V alloy, the initial phase ratio of Ti-alpha and Ti-beta need to be measured by X-ray diffraction. In laser shock processing, under shock loading solid material behavior is fluidlike and shock-solid interactions play a key role in determining the induced residual stress distributions and the final deformed shape. In this work shock-solid interactions under high pressure and thus high strain rate in laser shock processing are studied and simulated based on conservation's law, equation of state and elastoplasticity of material. A series of carefully controlled experiments, including spatially resolved residual stress measurement by synchrotron X-ray diffraction and measurement of local & global bending curvatures, is conducted to validate the model. Based on numerical results, the attenuation and shock velocity variation of shock wave in laser shock processing are further analyzed. In addition, based on the well validated shock wave propagation model, opposing dual sided laser shock peening has also been investigated. In opposing dual sided LSP, the workpiece can be simultaneously irradiated or irradiated with different time lags to create different surface residual stress patterns by virtue of the interaction between the opposing shock waves. In order to better understand the wave-wave interactions under different conditions, the residual stress profiles corresponding to various workpiece thicknesses and various irradiation times were evaluated. The dynamics and anisotropy in micro scale laser peen forming of single crystal Al has been also studied based on meso scale crystal plasticity integrated with consideration of dynamics and pressure dependent crystal elastic moduli.

  7. Assessment of damage in composite laminates through dynamic, full-spectral interrogation of fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Propst, A.; Peters, K.; Zikry, M. A.; Schultz, S.; Kunzler, W.; Zhu, Z.; Wirthlin, M.; Selfridge, R.

    2010-01-01

    In this study, we demonstrate the full-spectral interrogation of a fiber Bragg grating (FBG) sensor at 535 Hz. The sensor is embedded in a woven, graphite fiber-epoxy composite laminate subjected to multiple low-velocity impacts. The measurement of unique, time dependent spectral features from the FBG sensor permits classification of the laminate lifetime into five regimes. These damage regimes compare well with previous analysis of the same material system using combined global and local FBG sensor information. Observed transient spectral features include peak splitting, wide spectral broadening and a strong single peak at the end of the impact event. Such features could not be measured through peak wavelength interrogation of the FBG sensor. Cross-correlation of the measured spectra with the original embedded FBG spectrum permitted rapid visualization of average strains and the presence of transverse compressive strain on the optical fiber, but smeared out the details of the spectral profile.

  8. Renewable liquid reflection grating

    DOEpatents

    Ryutov, Dmitri D.; Toor, Arthur

    2003-10-07

    A renewable liquid reflection grating. Electrodes are operatively connected to a conducting liquid in an arrangement that produces a reflection grating and driven by a current with a resonance frequency. In another embodiment, the electrodes create the grating by a resonant electrostatic force acting on a dielectric liquid.

  9. Catwalk grate lifting tool

    DOEpatents

    Gunter, Larry W. (615 Sandpit Rd., Leesville, SC 29070)

    1992-01-01

    A device for lifting catwalk grates comprising an elongated bent member with a handle at one end and a pair of notched braces and a hook at the opposite end that act in conjunction with each other to lock onto the grate and give mechanical advantage in lifting the grate.

  10. Catwalk grate lifting tool

    DOEpatents

    Gunter, L.W.

    1992-08-11

    A device is described for lifting catwalk grates comprising an elongated bent member with a handle at one end and a pair of notched braces and a hook at the opposite end that act in conjunction with each other to lock onto the grate and give mechanical advantage in lifting the grate. 10 figs.

  11. Spectroscopic investigation of laser-induced plasma in laser beam welding

    Microsoft Academic Search

    J. Bruncko; Frantisek Uherek; Dusan Chorvat; Miroslav Michalka; P. Fodrek

    2002-01-01

    The contribution deals with the diagnostics of laser induced plasma (LIP) by optical emission spectroscopy. Laser induced plasma occurs during laser welding and reveals important information about technological process. The performed experiments were concerned with in-time spectral analysis (wavelength range: 200-800 nm) of laser induced plasma of austenitic steel (18% Cr, 9% Ni) during cw CO2 laser welding. Circumstances of

  12. Femtosecond-laser-induced destruction of boron-nitride nanotubes and boron-nitride doped graphene

    NASA Astrophysics Data System (ADS)

    Bauerhenne, Bernd; Eschstruth, Nils; Zijlstra, Eeuwe S.; Garcia, Martin E.

    2013-11-01

    By means of first principles calculations we studied the intense femtosecond-laser excitation of several boron­ nitride nanotubes and a boron-nitride doped graphene layer up to irradiation levels where these structures disintegrate. We performed molecular dynamics simulations using our in-house Code for Highly excited Valence Electron Systems (CHIVES). For different boron-nitride nanotubes we determined the damage threshold in terms of the electronic temperature and the absorbed energy per atom. We found that all nanotubes studied were destroyed in the first 200 fs after an ultrafast laser excitation heating the electrons to 108 mHa (34103 K). Some tubes also disintegrated at lower electronic temperatures. For the boron-nitride doped graphene we found that at a laser-induced electronic temperature of 100 mHa (31577 K) bonds break and the boron-nitride dimer leaves the structure.

  13. Investigation of laser-induced iodine fluorescence for the measurement of density in compressible flows

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C., Jr.

    1982-01-01

    Laser induced fluorescence is an attractive nonintrusive approach for measuring molecular number density in compressible flows although this technique does not produce a signal that is directly related to the number density. Saturation and frequency detuned excitation are explored as means for minimizing the quenching effect using iodine as the molecular system because of its convenient absorption spectrum. Saturation experiments indicate that with available continuous wave laser sources of Gaussian transverse intensity distribution only partial saturation could be achieved in iodine at the pressures of interest in gas dynamics. Using a fluorescence lineshape theory, it is shown that for sufficiently large detuning of a narrow bandwidth laser from a molecular transition, the quenching can be cancelled by collisional broadening over a large range of pressures and temperatures. Experimental data obtained in a Mach 4.3 underexpanded jet of nitrogen seeded with iodine for various single mode argon laser detunings from a strong iodine transition at 5145 A are discussed.

  14. Spectral selective radio frequency emissions from laser induced breakdown of target materials

    SciTech Connect

    Vinoth Kumar, L.; Manikanta, E.; Leela, Ch.; Prem Kiran, P., E-mail: premkiranuoh@gmail.com [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046 (India)

    2014-08-11

    The radio frequency emissions scanned over broad spectral range (30?MHz–1?GHz) from single shot nanosecond (7?ns) and picosecond (30 ps) laser induced breakdown (LIB) of different target materials (atmospheric air, aluminum, and copper) are presented. The dominant emissions from ns-LIB, compared to those from the ps-LIB, indicate the presence and importance of atomic and molecular clusters in the plasma. The dynamics of laser pulse-matter interaction and the properties of the target materials were found to play an important role in determining the plasma parameters which subsequently determine the emissions. Thus, with a particular laser and target material, the emissions were observed to be spectral selective. The radiation detection capability was observed to be relatively higher, when the polarization of the input laser and the antenna is same.

  15. Simulated characterization of soot in the flame based on laser induced incandescence

    NASA Astrophysics Data System (ADS)

    Hou, Yanping; Chen, Jun; Yang, Huinan; Cai, Xiaoshu

    2014-12-01

    The unburned carbon particle, formed due to incomplete combustion of fossil fuel, biofuel, and biomass, raises great environmental and health problems. During the measurement of flames, a non-intrusive and in situ optical method is preferred rather than probe sampling method. Also the method with high spatial resolution and high temporal resolution is required for fast dynamic reactions such as combustion research. The technique based on laser-induced incandescence (LII) has been developed to characterize the soot particles. In this work, the simulation of LII signals have been did. In the simulation, different parameters have been applied and acquired corresponding results. The method provides theoretical results to analyze LII signals, and will eventually use in experimentation

  16. NO2-based laser-induced fluorescence (LIF) technique to measure cold-flow mixing

    NASA Astrophysics Data System (ADS)

    Gulati, A.; Warren, R. E., Jr.

    1992-01-01

    The paper examines the sensitivity and resolution capabilities of NO2-based laser-induced fluorescence (LIF) for studying cold-flow mixing in high-pressure applications. Calibrated fuel-air mixtures with known NO2 concentrations are investigated with LIF in cases of high pressures of up to 200 psig. The redshifted fluorescence is monitored during excitation by a CW argon-ion laser, and attention is given to the effects of pressure and mixture composition on signal quenching. Calibration is used to account for the quenching effects, and a resolution of 0.2 percent of the fuel stream is demonstrated at atmospheric pressures. At very high pressures the dynamic range is reduced, and some practical considerations are discussed regarding the practical application of the technique. The technique is shown to resolve small fuel-air eddies with good spatial and temporal resolution when applied to the study of a turbulent jet in coflowing air.

  17. NO2-based laser-induced fluorescence (LIF) technique to measure cold-flow mixing

    SciTech Connect

    Gulati, A.; Warren, R.E., JR. (General Electric Co., Schenectady, NY (United States))

    1992-01-01

    The paper examines the sensitivity and resolution capabilities of NO2-based laser-induced fluorescence (LIF) for studying cold-flow mixing in high-pressure applications. Calibrated fuel-air mixtures with known NO2 concentrations are investigated with LIF in cases of high pressures of up to 200 psig. The redshifted fluorescence is monitored during excitation by a CW argon-ion laser, and attention is given to the effects of pressure and mixture composition on signal quenching. Calibration is used to account for the quenching effects, and a resolution of 0.2 percent of the fuel stream is demonstrated at atmospheric pressures. At very high pressures the dynamic range is reduced, and some practical considerations are discussed regarding the practical application of the technique. The technique is shown to resolve small fuel-air eddies with good spatial and temporal resolution when applied to the study of a turbulent jet in coflowing air. 9 refs.

  18. Systematic investigation of sustained laser-induced incandescence in carbon nanotubes

    SciTech Connect

    Lim, Zhi Han; Sow, Chorng-Haur [Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542 (Singapore); National University of Singapore Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117542 (Singapore); Lee, Andrielle; Zhu, Yanwu [Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542 (Singapore); Lim, Kassandra Yu Yan [Hwa Chong Institution, 661 Bukit Timah Rd., Singapore 269734 (Singapore)

    2010-03-15

    A focused laser beam irradiating on aligned carbon nanotubes (CNTs) in moderate vacuum results in bright and sustained laser-induced incandescence (LII) in CNTs. The incandescence corresponds to blackbody radiation from laser-heated CNTs at {approx}2400 K. Post-LII craters with well-defined ring boundaries in the CNT array were observed and examined with scanning electron microscopy and Raman spectroscopy. The enhanced purity of CNTs after LII as indicated by Raman spectroscopy studies was attributed to the removal of amorphous carbons on the as-grown CNTs during LII. A dynamic study of the crater formation further elucidates the nature of such craters. Through a systematic study of the effect of vacuum level and gaseous environment on LII, we discovered the process of thermal runaway during LII in CNTs. Thermal runaway is a threat to a sustained LII and can be prevented in nitrogen and argon environments. Oxygen was found to be responsible for thermal runaway reactions.

  19. Dipolar distribution generated by laser-induced plasma (LIP) in air in earliest instants

    NASA Astrophysics Data System (ADS)

    Paulin Fuentes, J. Mauricio; Sánchez-Aké, C.; Bredice, Fausto O.; Villagrán-Muniz, Mayo

    2013-12-01

    We present an experimental investigation of the electric field potential and magnetic field generated by a laser-induced plasma in air, for time delays 0 ? t ? 50 ns. The laser used is a Nd?:?YAG, ? = 1064 nm, 10 ns at FWHM, and the irradiance applied is I = (1011-1012) W cm-2. We find that the collective effect of the charges in the plasma form a dynamic dipole distribution aligned with the laser beam axis. This experimental result is explained based on the mobility of the electric charges detected by mapping near the plasma with a coaxial cable probe. Shadowgraphy and fast photography techniques show that the plasma ionization front advances asymmetrically and mostly toward the lens. The intrinsic dipole moment is estimated by applying an external electric field. The magnetic diagnostic shows the presence of a current aligned with the laser beam that gives rise to an azimuthal magnetic field, corroborating the observed dipolar configuration.

  20. Numerical study of ambient pressure for laser-induced bubble near a rigid boundary

    NASA Astrophysics Data System (ADS)

    Li, BeiBei; Zhang, HongChao; Han, Bing; Lu, Jian

    2012-07-01

    The dynamics of the laser-induced bubble at different ambient pressures was numerically studied by Finite Volume Method (FVM). The velocity of the bubble wall, the liquid jet velocity at collapse, and the pressure of the water hammer while the liquid jet impacting onto the boundary are found to increase nonlinearly with increasing ambient pressure. The collapse time and the formation time of the liquid jet are found to decrease nonlinearly with increasing ambient pressure. The ratios of the jet formation time to the collapse time, and the displacement of the bubble center to the maximal radius while the jet formation stay invariant when ambient pressure changes. These ratios are independent of ambient pressure.

  1. Laser-induced shock wave can spark triboluminescence of amorphous sugars.

    PubMed

    Tsuboi, Yasuyuki; Seto, Toshiaki; Kitamura, Noboru

    2008-07-24

    We investigated the triboluminescence (TL) of sugars using an innovative experimental approach: the laser-induced shock wave (LISW) technique. We found that the LISW could induce very bright TL in crystalline sugars, the intensity of which was shown to be 10(5) times higher than that obtained by conventional manual hand rubbing. We also applied the LISW technique to amorphous sugar samples. Although it was supposed that TL could not be excited in amorphous solids of sugars having isotropic structures, we revealed that LISW could induce bright TL in amorphous sugars similar to that induced in crystalline sugars. On the basis of the experimental results showing the dynamic behavior of the sample fracture combined with those of the TL, we discuss these novel TL mechanisms in sugars. We believe that the shock wave technique opens a new channel for investigating the nature of TL. PMID:18582023

  2. Experimental investigation of a supersonic swept ramp injector using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J.; Hollo, Steven D.; Mcdaniel, James C.

    1990-01-01

    Planar measurements of injectant mole fraction and temperature have been conducted in a nonreacting supersonic combustor configured with underexpanded injection in the base of a swept ramp. The temperature measurements were conducted with a Mach 2 test section inlet in streamwise planes perpendicular to the test section wall on which the ramp was mounted. Injection concentration measurements, conducted in cross flow planes with both Mach 2 and Mach 2.9 free stream conditions, dramatically illustrate the domination of the mixing process by streamwise vorticity generated by the ramp. These measurements, conducted using a nonintrusive optical technique (laser-induced iodine fluorescence), provide an accurate and extensive experimental data base for the validation of computation fluid dynamic codes for the calculation of highly three-dimensional supersonic combustor flow fields.

  3. Effect of damping on the laser induced ultrafast switching in rare earth-transition metal alloys

    SciTech Connect

    Oniciuc, Eugen; Stoleriu, Laurentiu; Cimpoesu, Dorin; Stancu, Alexandru, E-mail: alstancu@uaic.ro [Faculty of Physics and CARPATH Center, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania)

    2014-06-02

    In this paper, we present simulations of thermally induced magnetic switching in ferrimagnetic systems performed with a Landau-Lifshitz-Bloch (LLB) equation for damping constant in a wide range of values. We have systematically studied the GdFeCo ferrimagnet with various concentrations of Gd and compared for some values of parameters the LLB results with atomistic simulations. The agreement is remarkably good, which shows that the dynamics described by the ferrimagnetic LLB is a reasonable approximation of this complex physical phenomenon. As an important element, we show that the LLB is able to also describe the intermediate formation of a ferromagnetic state which seems to be essential to understand laser induced ultrafast switching. The study reveals the fundamental role of damping during the switching process.

  4. Diagnostics of stone samples by laser-induced flurorescence

    NASA Astrophysics Data System (ADS)

    Colao, Francesco; Fantoni, Roberta; Fiorani, L.; Palucci, Antonio; Striber, Joakim

    2004-10-01

    In this paper we present the first results obtained at the ENEA Research Center of Frascati in the diagnosis of stone samples by laser induced fluorescence. The characteristics of the fluorescence spectra (intensity, shape, bands) were both analyzed in coincidence with the laser excitation and up to the fluorescence decay. Two kinds of stones were examined: marble and tuff. In particular, we focused our interest in the different response to the light excitation of the clean and dirty parts of marble. Moreover, a first attempt to detect stone surfaces under water has been carried out. Complementary information has been obtained with measurements of spectral reflectance.

  5. Nonresonant Referenced Laser-Induced Thermal Acoustics Thermometry in Air

    NASA Astrophysics Data System (ADS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, Gregory C.

    1999-01-01

    We report a detailed investigation of nonresonant laser-induced thermal acoustics (LITA) for the single-shot measurement of the speed of sound ( v S ) in an oven containing room air. A model for the speed of sound that includes important acoustic relaxation effects is used to convert the speed of sound into temperature. A reference LITA channel is used to reduce uncertainties in v S . Comparing thermocouple temperatures with temperatures deduced from our v S measurements and model, we find the mean temperature difference from 300 to 650 K to be 1% ( 2 ). The advantages of using a reference LITA channel are discussed.

  6. Femtosecond Visualization of Laser-Induced Optical Relativistic Electron Microbunches

    NASA Astrophysics Data System (ADS)

    Xiang, Dao; Hemsing, Erik; Dunning, Michael; Hast, Carsten; Raubenheimer, Tor

    2014-10-01

    It has long been known that lasers can interact with relativistic electrons in magnetic undulators to imprint sinusoidal modulations that can be used to slice electrons into microbunches equally separated at the laser wavelength. Here we report on the first direct measurement of laser-induced microbunching of a relativistic electron beam with femtosecond resolution in the time domain. Using a modified zero-phasing technique to map the electron beam's temporal structures into the energy space, we show that this method can be used to directly quantify the time and spectral content of coherent current modulations imprinted on the beam for harmonic and multicolor lasing applications in accelerator-based light sources.

  7. Search for laser-induced formation of antihydrogen atoms.

    PubMed

    Amoretti, M; Amsler, C; Bonomi, G; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Charlton, M; Ejsing, A M; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Kellerbauer, A; Lagomarsino, V; Lodi Rizzini, E; Macrì, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Posada, L G C; Pruys, H; Regenfus, C; Rotondi, A; Telle, H H; Testera, G; Van der Werf, D P; Variola, A; Venturelli, L; Yamazaki, Y; Zurlo, N

    2006-11-24

    Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration. PMID:17155742

  8. Quasiadiabatic approach for laser-induced single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Sadighi-Bonabi, Rasoul; Razeghi, Fatemeh; Ebrahimi, Homa; Fallahi, Shadi; Lotfi, Erik

    2012-01-01

    The luminescence parameters of laser-induced bubble in the presence of an acoustic field in water are studied. A comparison is made between parameters such as bubble radius, interior temperature, and pressure of the bubble induced by laser and an acoustic field influenced by different driving pressure amplitudes. It is found that the bubble volume induced by laser at the collapse instant is more than 106 times larger than the one induced by an acoustic field. It is also noticed, by increasing the driving pressure amplitude, the bubble radius decreases in both cases, however, the bubble interior pressure and temperature increase.

  9. Quasiadiabatic approach for laser-induced single-bubble sonoluminescence.

    PubMed

    Sadighi-Bonabi, Rasoul; Razeghi, Fatemeh; Ebrahimi, Homa; Fallahi, Shadi; Lotfi, Erik

    2012-01-01

    The luminescence parameters of laser-induced bubble in the presence of an acoustic field in water are studied. A comparison is made between parameters such as bubble radius, interior temperature, and pressure of the bubble induced by laser and an acoustic field influenced by different driving pressure amplitudes. It is found that the bubble volume induced by laser at the collapse instant is more than 10(6) times larger than the one induced by an acoustic field. It is also noticed, by increasing the driving pressure amplitude, the bubble radius decreases in both cases, however, the bubble interior pressure and temperature increase. PMID:22400653

  10. Laser-induced breakdown spectroscopy of alcohols and protein solutions

    SciTech Connect

    Melikechi, N.; Ding, H.; Marcano, O. A.; Rock, S. [Center for Research and Education in Optical Science and Applications, Applied Optics Center, and Department of Physics and Pre-Engineering, Delaware State University, 1200 N DuPont Highway, Dover, Delaware 19901 (United States)

    2008-04-15

    We report on the use of laser-induced breakdown spectroscopy for the study of organic samples that exhibit similar elemental composition. We evaluate the method for its potential application for the measurement of small spectroscopic differences between samples such as alcohols and water solution of proteins. We measure differences in the relative amplitudes of the oxygen peaks for alcohols and find that these correlate with the relative amount of oxygen atoms within the molecule. We also show that the spectra of proteins reveal differences that can be used for their detection and identification.

  11. Laser-induced reaction alumina coating on ceramic composite

    NASA Astrophysics Data System (ADS)

    Xiao, Chenghe

    Silicon carbide ceramics are susceptible to corrosion by certain industrial furnace environments. It is also true for a new class of silicon carbide-particulate reinforced alumina-matrix composite (SiCsb(P)Alsb2Osb3) since it contains more than 55% of SiC particulate within the composite. This behavior would limit the use of SiCsb(P)Alsb2Osb3 composites in ceramic heat exchangers. Because oxide ceramics corrode substantially less in the same environments, a laser-induced reaction alumina coating technique has been developed for improving corrosion resistance of the SiCsb(P)Alsb2Osb3 composite. Specimens with and without the laser-induced reaction alumina coating were subjected to corrosion testing at 1200sp°C in an air atmosphere containing Nasb2COsb3 for 50 ˜ 200 hours. Corroded specimens were characterized via x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The uncoated SiCsbP/Alsb2Osb3 composite samples experienced an initial increase in weight during the exposure to Nasb2COsb3 at 1200sp°C due to the oxidation of residual aluminum metal in the composite. There was no significant weight change difference experienced during exposure times between 50 and 200 hours. The oxidation layer formed on the as-received composite surface consisted of Si and Alsb2Osb3 (after washing with a HF solution). The oxidation layer grew outward and inward from the original surface of the composite. The growth rate in the outward direction was faster than in the inward direction. The formation of the Si/Alsb2Osb3 oxidation layer on the as-received composite was nonuniform, and localized corrosion was observed. The coated samples experienced very little mass increase. The laser-induced reaction alumina coating effectively provided protection for the SiCsbP/Alsb2Osb3 composite by keeping the corrodents from contacting the composite and by the formation of some refractory compounds such as Nasb2OAlsb2Osb3SiOsb2 and Nasb2Alsb{22}Osb{34}. After exposure to 1200sp°C for 200 hours, the bonding between the laser-induced reaction alumina coating and the composite appeared to be unattacked. For both the coated and uncoated samples, porosity within the composite increased after exposure due to the reaction: 3SiOsb2(s) + 4Al(l) -> 2Alsb2Osb3(s) + Si(s).

  12. Remote sensing of phytoplankton using laser-induced fluorescence

    SciTech Connect

    Babichenko, S.; Poryvkina, L.; Arikese, V. (Inst. of Ecology and Marine Research, Tallinn (Estonia)); Kaitala, S. (Univ. of Helsinki (Finland)); Kuosa, H. (Tvaerminne Zoological Station, Hanko (Finland))

    1993-06-01

    The results of remote laser sensing of brackish-water phytoplankton on board a research vessel are presented. Field data of laser-induced fluorescence of phytoplankton obtained during the several cruises in the mouth of tile Gulf of Finland are compared with the results of standard chlorophyll a analysis of water samples and phytoplankton species determination by microscopy. The approach of fluorescence excitation by tunable laser radiation is applied to study the spatial distribution of a natural phytoplankton community. The remote analysis of the pigment composition of a phytoplankton community using the method of selective pigment excitation is described. The possibility of elaborating methods of quantitative laser remote biomonitoring is discussed.

  13. Colloid formation and laser-induced bleaching in fluorite

    SciTech Connect

    LeBret, Joel B.; Cramer, Loren P.; Norton, M. Grant; Dickinson, J. T. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164 (United States); Materials Science Program, Washington State University, Pullman, Washington 99164 (United States); School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164 (United States); Materials Science Program, Washington State University, Pullman, Washington 99164 (United States)

    2004-11-08

    Colloid formation and subsequent laser-induced bleaching in fluorite has been studied by transmission electron microscopy and electron diffraction. At high incident electron-beam (e-beam) energies, Ca colloids with diameter {approx}10 nm form a simple cubic superlattice with lattice parameter a{approx}18 nm. The colloids themselves are topotactic with the fluorite matrix forming low-energy interfaces close to a {sigma}=21 special grain boundary in cubic materials. Laser irradiation using {lambda}=532 nm has been shown to effectively bleach the e-beam-irradiated samples returning the fluorite to its monocrystalline state. The bleached samples appear more resistant to further colloid formation.

  14. Towards Friction Control using laser-induced periodic Surface Structures

    NASA Astrophysics Data System (ADS)

    Eichstädt, J.; Römer, G. R. B. E.; Veld, A. J. Huis in't.

    This paper aims at contributing to the study of laser-induced periodic surface structures (LIPSS) and the description of their tribological properties in order to facilitate the knowledge for contact mechanical applications. To obtain laser parameters for LIPSS formation, we propose to execute two D2-Experiments. For the transfer of results from static experiments to areas of LIPSS we propose the discrete accumulation of fluences. Areas covered by homogeneously distributed LIPSS were machined. Friction force of these areas was measured using a tribometer in a ball on flat configuration. The friction force was found to be higher on the structured area than on the initial surface.

  15. Optimization of confocal laser induced fluorescence in a plasma

    NASA Astrophysics Data System (ADS)

    VanDervort, R.; Elliott, D.; McCarren, D.; McKee, J.; Soderholm, M.; Sears, S.; Scime, E.

    2014-11-01

    Laser Induced Fluorescence (LIF) provides measurements of flow speed, temperature, and density of ions or neutrals in a plasma. Traditionally, a LIF measurement requires two ports on a plasma device; one for laser injection and one for emission collection. Proper alignment of LIF optics is time consuming and sensitive to mechanical vibration. We describe a confocal configuration for LIF that requires a single port and requires no alignment. The measurement location is scanned radially by physically moving the entire optical structure. Confocal LIF measurements are compared to traditional LIF measurements over the same radial range.

  16. Optimization of confocal laser induced fluorescence in a plasma.

    PubMed

    VanDervort, R; Elliott, D; McCarren, D; McKee, J; Soderholm, M; Sears, S; Scime, E

    2014-11-01

    Laser Induced Fluorescence (LIF) provides measurements of flow speed, temperature, and density of ions or neutrals in a plasma. Traditionally, a LIF measurement requires two ports on a plasma device; one for laser injection and one for emission collection. Proper alignment of LIF optics is time consuming and sensitive to mechanical vibration. We describe a confocal configuration for LIF that requires a single port and requires no alignment. The measurement location is scanned radially by physically moving the entire optical structure. Confocal LIF measurements are compared to traditional LIF measurements over the same radial range. PMID:25430315

  17. Evidence of laser induced degradation and graphitization of aromatic pollutants

    NASA Astrophysics Data System (ADS)

    Mele, A.; Letardi, T.; di Lazarro, P.

    The laser-induced photodecomposition and graphitization of polynuclear aromatic hydrocarbons is investigated by irradiating solid pollutant samples with an Nd-YAG laser, leaving a carbon-rich, black powder. The irradiation of anthracene and benzopyrene forms the ions Cn(+)-, CnH(+)-, and CnH2(+)- in a wide plume produced by a pulsed-CO2 laser. The tendency of aromatic compounds to fragment is noted, and the notion that ion formation is governed by the mechanism that produces ablation in the laser cloud is suggested. Optical multichannel analyzer emission spectra indicate the production of the Cn species, suggesting applications to the treatment of aromatic product wastes.

  18. Laser induced fluorescence of biochemical for UV LIDAR application.

    PubMed

    Gupta, L; Sharma, R C; Razdan, A K; Maini, A K

    2014-05-01

    Laser induced fluorescence spectroscopy in the ultraviolet regime has been used for the detection of biochemical through a fiber coupled CCD detector from a distance of 2 m. The effect of concentration and laser excitation energy on the fluorescence spectra of nicotinamide adenine dinucleotide (NADH) has been investigated. The signature fluorescence peak of NADH was centred about 460 nm. At lower concentration Raman peak centred at 405 nm was also observed. The origin of this peak has been discussed. Detection limit with the proposed set up is found to be 1 ppm. PMID:24337816

  19. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S. [Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720 (United States)

    2008-08-04

    We develop a theoretical analysis to model plasma initiation at the early stage of femtosecond laser irradiation of metal surfaces. The calculation reveals that there is a threshold intensity for the formation of a microscale electronic plasma at the laser-irradidated metal surface. As the full width at half maximum of a laser pulse increases from 15 to 200 fs, the plasma formation threshold decreases by merely about 20%. The dependence of the threshold intensity on laser pulse width can be attributed to laser-induced surface electron emission, in particular due to the effect of photoelectric effect.

  20. Laser-induced fluorescence measurement of combustion chemistry intermediates

    NASA Technical Reports Server (NTRS)

    Crosley, David R.

    1986-01-01

    Laser-induced fluorescence (LIF) can measure the trace (often free radical) species encountered as intermediates in combustion chemistry; OH, CS, NH, NS, and NCO are typical of the species detected in flames by LIF. Attention is given to illustrative experiments designed to accumulate a quantitative data base for LIF detection in low pressure flow systems and flames, as well as to flame measurements conducted with a view to the detection of new chemical intermediaries that may deepen insight into the chemistry of combustion.

  1. Laser induced breakdown spectroscopy in paintings and sculptures research

    NASA Astrophysics Data System (ADS)

    Sarzy?ski, A.; Skrzeczanowski, W.; Marczak, J.

    2007-07-01

    Application of Laser Induced Breakdown Spectroscopy (LIBS) for investigation of chemical constitution and stratigraphy of artworks, and metallic objects with multilayer structures is described in the paper. Physical phenomena accompanying LIBS investigations, especially temporal evolution and spectral lines broadening are described. Operational characteristics of experimental equipment are shown. Results obtained with use of two different echelle spectrometers are compared. Pigments used in oil paintings are analyzed and analysis results are presented. Experimental results of measurements of various objects like paintings, sculptures and artifacts are shown. Works on dating of investigated paintings are described.

  2. Applications of laser-induced filaments for optical communication links

    NASA Astrophysics Data System (ADS)

    Hening, Alexandru; Wayne, David; Lovern, Mike; Lasher, Mark

    2014-10-01

    Free-space laser communications are subjected to performance degradation when heavy fog or smoke obscures the line of sight (high-loss optical media). On the other hand, it has been demonstrated that laser-induced plasma filaments (LIPF) can propagate for long distances (up to a few kilometers) through clouds and/or turbulent (lossy) atmosphere. Here we propose to use LIPF to improve and/or restore laser communication in adverse, high-loss and/or denied conditions. This work is focused on demonstrating the proof of concept and is dedicated primarily to gaseous, optically transparent media.

  3. Laser-induced shock waves effects in materials

    SciTech Connect

    Dingus, R.S.; Shafer, B.P.

    1990-01-01

    A review of the effects of pressure pulses on materials is presented with an orientation toward laser-induced shock wave effects in biological tissue. The behavior is first discussed for small amplitudes, namely sound waves, since many important features in this region are also applicable at large amplitudes. The generation of pressure pulses by lasers is discussed along with amplitudes. The origin and characteristic properties of shock waves are discussed along with the different types of effects they can produce. The hydrodynamic code techniques required for shock wave calculations are discussed along with the necessary empirical data base and methods for generating that data base. 7 refs., 15 figs.

  4. Adaptable Diffraction Gratings With Wavefront Transformation

    NASA Technical Reports Server (NTRS)

    Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christoph M.

    2010-01-01

    Diffraction gratings are optical components with regular patterns of grooves, which angularly disperse incoming light by wavelength. Traditional diffraction gratings have static planar, concave, or convex surfaces. However, if they could be made so that they can change the surface curvature at will, then they would be able to focus on particular segments, self-calibrate, or perform fine adjustments. This innovation creates a diffraction grating on a deformable surface. This surface could be bent at will, resulting in a dynamic wavefront transformation. This allows for self-calibration, compensation for aberrations, enhancing image resolution in a particular area, or performing multiple scans using different wavelengths. A dynamic grating gives scientists a new ability to explore wavefronts from a variety of viewpoints.

  5. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, Michael D. (Livermore, CA); Britten, Jerald A. (Oakley, CA); Nguyen, Hoang T. (Livermore, CA); Boyd, Robert (Livermore, CA); Shore, Bruce W. (Livermore, CA)

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  6. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

    1999-05-25

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

  7. Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors: 2. Simulations

    NASA Astrophysics Data System (ADS)

    Webb, S.; Shin, P.; Peters, K.; Zikry, M. A.; Stan, N.; Chadderdon, S.; Selfridge, R.; Schultz, S.

    2014-02-01

    In this paper, we simulate the response of fiber Bragg grating (FBG) sensors embedded in the adhesive layer of a composite lap that is subjected to harmonic excitation. To simulate accumulated fatigue damage at the adhesive layer, two forms of numerical nonlinearities are introduced into the model: (1) progressive plastic deformation of the adhesive and (2) changing the boundary of an interfacial defect at the adhesive layer across the overlap shear area. The simulation results are compared with previous measurements of the dynamic, full-spectral response of such FBG sensors for condition monitoring of the lap joint. Short-time Fourier transforms (STFT) of the locally extracted axial strain time histories reveal a transition to nonlinear behavior of the composite lap joint by means of intermittent frequencies that were observed in the experimental measurements and are not associated with the external excitation. The simulation results verify that the nonlinear changes in measured dynamic FBG responses are due to the progression of damage in the lap joint.

  8. Laser-induced fluorescence detection of stomach cancer using hypericin

    NASA Astrophysics Data System (ADS)

    Dets, Sergiy M.; Buryi, Alexander N.; Melnik, Ivan S.; Joffe, Alexander Y.; Rusina, Tatyana V.

    1996-12-01

    Natural photodynamic pigment hypericin having intrinsic antitumor properties was applied for fluorescence detection of cancer. Clinical investigation of hypericin was performed to ensure high tumor/normal fluorescence contrast in digestion organs. Laser-induced autofluorescence and exogenous fluorescence analysis of normal tissue and stomach adenocarcinoma was performed using helium-cadmium laser (8 mW, 442 nm). Twenty-one patients have undergone procedure of fluorescence detection of tumors before and after photosensitization. For sensitization of patients we used five or seven capsules containing hypericin in amount of 1 mg which have been administered orally. Strong yellow-red fluorescence of hypericin in tissue with maximum at 603 nm and autofluorescence peak at 535 nm gives an intensity ratio I(603 nm)/I(535 nm) of 2 - 2.5 from cancerous tissue and provides 85% specificity. Preliminary in vivo results of auto- and fluorescence analysis using hypericin photosensitization from one patient with esophageal cancer and eleven patients with stomach cancer proven histologically are encouraging and indicate the high reliability of laser-induced fluorescence technique with hypericin in detection of early stage malignant lesions.

  9. Detection of hydrogen peroxide using photofragmentation laser-induced fluorescence.

    PubMed

    Johansson, O; Bood, J; Aldén, M; Lindblad, U

    2008-01-01

    Photofragmentation laser-induced fluorescence (PF-LIF) is for the first time demonstrated to be a practical diagnostic tool for detection of hydrogen peroxide. Point measurements as well as two-dimensional (2D) measurements in free-flows, with nitrogen as bath gas, are reported. The present application of the PF-LIF technique involves one laser, emitting radiation of 266 nm wavelength, to dissociate hydrogen peroxide molecules into OH radicals, and another laser, emitting at 282.25 nm, to electronically excite OH, whose laser-induced fluorescence is detected. The measurement procedure is explained in detail and a suitable time separation between photolysis and excitation pulse is proposed to be on the order of a few hundred nanoseconds. With a separation time in that regime, recorded OH excitation scans were found to be thermal and the signal was close to maximum. The PF-LIF signal strength was shown to follow the same trend as the vapor pressure corresponding to the hydrogen peroxide liquid concentration. Thus, the PF-LIF signal appeared to increase linearly with hydrogen peroxide vapor-phase concentration. For 2D single shot measurements, a conservatively estimated value of the detection limit is 30 ppm. Experiments verified that for averaged point measurements the detection limit was well below 30 ppm. PMID:18230210

  10. Probing Electron Correlation with Sequential Laser--Induced Tunnel ionization

    NASA Astrophysics Data System (ADS)

    Corkum, Paul

    2011-03-01

    Since 1964 we have known that multiphoton ionization could be approximated by tunnel ionization for long wavelength light. Aside from re-collision, since then multiple ionization has been treated as successive, independent single ionization events. Our results show that this long-held belief is false. Tunnelling is highly directional and highly sensitive to the ionization potential (Ip) of the accessible ionic states (which itself can depend on the direction of ionization). Using rare gas atoms as examples, we show that laser induced tunnelling is suppressed or enhanced depending on how the field is applied. We image the hole left by the first tunnelling electron by measuring in the spatial correlation of the second electron. Laser induced tunnelling gives us experimental access to one of the most difficult to measure properties of matter -- electron-electron correlations [1]. [4pt] [1] A. Fleischer, H.J. W"orner, L. Arissian, L.R. Liu, M. Meckel, A. Rippert, R. D"orner, D.M. Villeneuve, A. Staudte and P.B. Corkum, unpublished results.

  11. Laser-induced breakdown spectroscopy of tantalum plasma

    NASA Astrophysics Data System (ADS)

    Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan-ul-Haq

    2013-07-01

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (? ˜ 1064 nm, ? ˜ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO2: N2: He), O2, N2, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

  12. Calibration analysis of zeolites by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Hor?á?ková, M.; Grolmusová, Z.; Hor?á?ek, M.; Rakovský, J.; Hudec, P.; Veis, P.

    2012-08-01

    Laser induced breakdown spectroscopy was used for calibration analysis of different types of microporous crystalline aluminosilicates with exactly ordered structure — zeolites. The LIBS plasma was generated using a Q-switched Nd:YAG laser operating at the wavelength of 532 nm and providing laser pulses of 4 ns duration. Plasma emission was analysed by echelle type emission spectrometer, providing wide spectral range 200-950 nm. The spectrometer was equipped with intensified CCD camera providing rapid spectral acquisition (gating time from 5 ns). The optimum experimental conditions (time delay, gate width and laser pulse energy) have been determined for reliable use of LIBS for quantitative analysis. Samples of different molar ratios of Si/Al were used to create the calibration curves. Calibration curves for different types of zeolites (mordenite, type Y and ZSM-5) were constructed. Molar ratios of Si/Al for samples used for calibration were determined by classical wet chemical analysis and were in the range 5.3-51.8 for mordenite, 2.3-12.8 for type Y and 14-600 for ZSM-5. Zeolites with these molar ratios of Si/Al are usually used as catalysts in alkylation reactions. Laser induced breakdown spectroscopy is a suitable method for analysis of molar ratio Si/Al in zeolites, because it is simple, fast, and does not require sample preparation compared with classical wet chemical analysis which are time consuming, require difficult sample preparation and manipulation with strong acids and bases.

  13. Laser induced fluorescence imaging system for localization of nasopharyngeal carcinoma

    NASA Astrophysics Data System (ADS)

    Liu, Lina; Xie, Shusen

    2007-11-01

    A laser induced fluorescence imaging system for localization of Nasopharyngeal Carcinoma is developed. In this fluorescence imaging system, the fluorescence intensity with information of detected objection is gained by an image intensifier, which makes color information of the fluorescence image eliminated and the result is a monochrome image of the fluorescence with thermally induced noise. The monochrome fluorescence image is sent to a CCD and captured by an image board, which is controlled by a computer. Image processing is carried out to improve the image quality and therefore improve the system's ability to differentiate carcinomas from normal tissue. Gaussian smoothing is implemented in order to reduce the noise. Image binarizing process is realized to obtain an optimal threshold of the image. Image pixels with grey value below this threshold are assigned as diseased and those above are normal. A pseudo color processing is then accomplished to get better visual perception and understanding of the image, greatly increasing the detail resolution of the grey image. The processed image is then displayed on the screen of the computer in real time. The real time laser induced fluorescence imaging system with the image processing methods developed is efficient for localization of the nasopharyngeal carcinoma.

  14. Detection of explosives with laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Qian-Qian; Liu, Kai; Zhao, Hua; Ge, Cong-Hui; Huang, Zhi-Wen

    2012-12-01

    Our recent work on the detection of explosives by laser-induced breakdown spectroscopy (LIBS) is reviewed in this paper. We have studied the physical mechanism of laser-induced plasma of an organic explosive, TNT. The LIBS spectra of TNT under single-photon excitation are simulated using MATLAB. The variations of the atomic emission lines intensities of carbon, hydrogen, oxygen, and nitrogen versus the plasma temperature are simulated too. We also investigate the time-resolved LIBS spectra of a common inorganic explosive, black powder, in two kinds of surrounding atmospheres, air and argon, and find that the maximum value of the O atomic emission line SBR of black powder occurs at a gate delay of 596 ns. Another focus of our work is on using chemometic methods such as principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) to distinguish the organic explosives from organic materials such as plastics. A PLS-DA model for classification is built. TNT and seven types of plastics are chosen as samples to test the model. The experimental results demonstrate that LIBS coupled with the chemometric techniques has the capacity to discriminate organic explosive from plastics.

  15. TGCat, The Chandra Transmission Grating Catalog and Archive: Systems, Desgin and Accessibility

    E-print Network

    Mitschang, Arik W.

    The recently released Chandra Transmission Grating Catalog and Archive, TGCat, presents a fully dynamic on-line catalog allowing users to browse and categorize Chandra gratings observations quickly and easily, generate ...

  16. Planar measurement of flow field parameters in a nonreacting supersonic combustor using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1990-01-01

    A nonintrusive optical technique, laser-induced iodine fluorescence, has been used to obtain planar measurements of flow field parameters in the supersonic mixing flow field of a nonreacting supersonic combustor. The combustor design used in this work was configured with staged transverse sonic injection behind a rearward-facing step into a Mach 2.07 free stream. A set of spatially resolved measurements of temperature and injectant mole fraction has been generated. These measurements provide an extensive and accurate experimental data set required for the validation of computational fluid dynamic codes developed for the calculation of highly three-dimensional combustor flow fields.

  17. Detection of trace phosphorus in steel using laser-induced breakdown spectroscopy combined with laser-induced fluorescence.

    PubMed

    Shen, X K; Wang, H; Xie, Z Q; Gao, Y; Ling, H; Lu, Y F

    2009-05-01

    Monitoring of light-element concentration in steel is very important for quality assurance in the steel industry. In this work, detection in open air of trace phosphorus (P) in steel using laser-induced breakdown spectroscopy (LIBS) combined with laser-induced fluorescence (LIF) has been investigated. An optical parametric oscillator wavelength-tunable laser was used to resonantly excite the P atoms within plasma plumes generated by a Q-switched Nd:YAG laser. A set of steel samples with P concentrations from 3.9 to 720 parts in 10(6) (ppm) were analyzed using LIBS-LIF at wavelengths of 253.40 and 253.56 nm for resonant excitation of P atoms and fluorescence lines at wavelengths of 213.55 and 213.62 nm. The calibration curves were measured to determine the limit of detection for P in steel, which is estimated to be around 0.7 ppm. The results demonstrate the potential of LIBS-LIF to meet the requirements for on-line analyses in open air in the steel industry. PMID:19412215

  18. Detection of trace phosphorus in steel using laser-induced breakdown spectroscopy combined with laser-induced fluorescence

    SciTech Connect

    Shen, X. K.; Wang, H.; Xie, Z. Q.; Gao, Y.; Ling, H.; Lu, Y. F.

    2009-05-01

    Monitoring of light-element concentration in steel is very important for quality assurance in the steel industry. In this work, detection in open air of trace phosphorus (P) in steel using laser-induced breakdown spectroscopy (LIBS) combined with laser-induced fluorescence (LIF) has been investigated. An optical parametric oscillator wavelength-tunable laser was used to resonantly excite the P atoms within plasma plumes generated by a Q-switched Nd:YAG laser. A set of steel samples with P concentrations from 3.9 to 720 parts in 10{sup 6}(ppm) were analyzed using LIBS-LIF at wavelengths of 253.40 and 253.56 nm for resonant excitation of P atoms and fluorescence lines at wavelengths of 213.55 and 213.62 nm. The calibration curves were measured to determine the limit of detection for P in steel, which is estimated to be around 0.7 ppm. The results demonstrate the potential of LIBS-LIF to meet the requirements for on-line analyses in open air in the steel industry.

  19. Towards the clinical application of laser-induced breakdown spectroscopy for rapid pathogen diagnosis Qassem Mohaidat

    E-print Network

    Rehse, Steven J.

    Towards the clinical application of laser-induced breakdown spectroscopy for rapid pathogen Provost Enhancement Fund Our Group's Publications: ·"Towards the clinical application of laser identification and discrimination using laser-induced breakdown spectroscopy," S.J. Rehse, N. Jeyasingham, J

  20. Laser Induced Nuclear Physics and Applications K.W.D. Ledingham,

    E-print Network

    Strathclyde, University of

    because of the potential applications e.g. isotope production, transmutation studies, laser induced only deals with laser induced PET isotope production and laser transmutation studies. These two applications will be dealt with in separate sections. 1. PET isotope production Introduction Recent experiments

  1. Laser light scattering in a laser-induced argon plasma: Investigations of the B. Pokrzywka a

    E-print Network

    . Introduction Laser-induced plasma (LIP) is an object of great interest, as it gives insight and complimentary experimental approach in LIP studies is the application of active laser methods: Raman, RayleighLaser light scattering in a laser-induced argon plasma: Investigations of the shock wave B

  2. Feasibility of Laser Induced Plasma Micro-machining Kumar Pallav1

    E-print Network

    Boyer, Edmond

    Feasibility of Laser Induced Plasma Micro-machining (LIP-MM) Kumar Pallav1 , Kornel F. Ehmann1 removal. 1.1 The Laser-induced Plasma Micromachining (LIP-MM) Process The underlying principle of the proposed LIP-MM process rests on the fact that when an ultra-short pulsed laser beam is tightly focused

  3. A LASER-INDUCED ULTRASONIC PROBE OF THE MECHANICAL PROPERTIES OF ALIGNED LIPID

    E-print Network

    Fayer, Michael D.

    ABSTRACr The recently developed laser-induced phonon spectroscopy (LIPS) technique is appliedA LASER-INDUCED ULTRASONIC PROBE OF THE MECHANICAL PROPERTIES OF ALIGNED LIPID MULTIBILAYERS arrays containing 2 and 20% water by weight. Sample excitation by two crossed 100-ps laser pulses

  4. Laser-Induced Breakdown Spectroscopy for Ambient Air Particulate Monitoring: Correlation of Total and Speciated

    E-print Network

    Hahn, David W.

    spectroscopy (LIPS), is an atomic emission spectroscopy technique that uses a pulsed laser beam to produceLaser-Induced Breakdown Spectroscopy for Ambient Air Particulate Monitoring: Correlation of Total between laser-induced breakdown spectroscopy (LIBS)-based speciated aerosol monitoring and non-speci- ated

  5. Spectroscopic characterization of laser-induced tin plasma S. S. Harilal,a

    E-print Network

    Harilal, S. S.

    efficiency. Laser-induced plasma LIP tech- niques are also used in space applications such as in chemi- cal as in the detection of bio- logical molecules.3,4 Other important applications of LIP in- clude pulsed laserSpectroscopic characterization of laser-induced tin plasma S. S. Harilal,a Beau O'Shay, and Mark. S

  6. Carbon dioxide UV laser-induced fluorescence in high-pressure flames

    E-print Network

    Lee, Tonghun

    Carbon dioxide UV laser-induced fluorescence in high-pressure flames W.G. Bessler a , C. Schulz a; in final form 16 May 2003 Published online 10 June 2003 Abstract Laser-induced fluorescence (LIF) of carbon dioxide is investigated with excitation between 215 and 255 nm with spectrally resolved detection in 5

  7. Escherichia coli identification and strain discrimination using nanosecond laser-induced breakdown spectroscopy

    E-print Network

    Rehse, Steven J.

    Escherichia coli identification and strain discrimination using nanosecond laser-induced breakdown April 2007 Three strains of Escherichia coli, one strain of environmental mold, and one strain and E. coli strains. This analysis showed efficient discrimination between laser-induced breakdown

  8. Laser-Induced Fluorescence in Gaseous [I[subscript]2] Excited with a Green Laser Pointer

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2007-01-01

    A green laser pointer could be used in a flashy demonstration of laser-induced fluorescence in the gas phase by directing the beam of the laser through a cell containing [I[subscript]2] at its room temperature vapor pressure. The experiment could be used to provide valuable insight into the requirements for laser-induced fluorescence (LIF) and the…

  9. Laser induced damage thresholds and laser safety levels. Do the units of measurement matter?

    Microsoft Academic Search

    R. M. Wood

    1998-01-01

    The commonly used units of measurement for laser induced damage are those of peak energy or power density. However, the laser induced damage thresholds, LIDT, of all materials are well known to be absorption, wavelength, spot size and pulse length dependent. As workers using these values become divorced from the theory it becomes increasingly important to use the correct units

  10. Investigation of the local structure variance of water molecules in laser-induced thermal desorption process

    NASA Astrophysics Data System (ADS)

    Ju, Shin-Pon; Weng, Cheng-I.

    2004-05-01

    This paper presents the use of molecular dynamics simulation in the study of laser-induced thermal desorption (LITD) of water molecules adjacent to a laser-heated Au substrate. The local structure of the water molecules is investigated by considering the densities of the oxygen and hydrogen atoms, the average number of neighbors, nNN, and the average number of H-bonds, nHB. At an equilibrium temperature of 300 K, the simulation results show that three adsorption water layers are formed in the immediate vicinity of the Au surface, and that each four-fold hollow site on the uppermost Au(0 0 1) surface is occupied by a single water molecule. Following laser-induced heating of the Au substrate with a sub-picosecond laser pulse of 350 fs, the substrate temperature increases to 1000 K. This causes a gradual heating of the adjacent water film, which is accompanied by a decrease in the values of nNN and nHB. Hence, it can be concluded that an increase in the water film temperature destroys the hydrogen-bonding network throughout the water film. Although the maximum local temperature of the water film occurs in the region immediately adjacent to the Au substrate, it is determined that the attractive energy between the Au atoms and the water molecules in this region causes the water molecules to aggregate together to form three-dimensional water clusters. Furthermore, this energy prevents the hydrogen bonds in this region from breaking apart as violently as those within the phase explosion region. Finally, it is observed that the phase explosion phenomenon occurs in the region of the water film where the values of nNN and nHB are at a minimum.

  11. Influence of absorption induced thermal initiation pathway on irradiance threshold for laser induced breakdown

    PubMed Central

    Varghese, Babu; Bonito, Valentina; Jurna, Martin; Palero, Jonathan; Verhagen, Margaret Hortonand Rieko

    2015-01-01

    We investigated the influence of thermal initiation pathway on the irradiance threshold for laser induced breakdown in transparent, absorbing and scattering phantoms. We observed a transition from laser-induced optical breakdown to laser-induced thermal breakdown as the absorption coefficient of the medium is increased. We found that the irradiance threshold after correction for the path length dependent absorption and scattering losses in the medium is lower due to the thermal pathway for the generation of seed electrons compared to the laser-induced optical breakdown. Furthermore, irradiance threshold gradually decreases with the increase in the absorption properties of the medium. Creating breakdown with lower irradiance threshold that is specific at the target chromophore can provide intrinsic target selectivity and improve safety and efficacy of skin treatment methods that use laser induced breakdown.

  12. Procedure for calibration of a portable, real-time beryllium aerosol monitor based on laser-induced breakdown spectroscopy

    E-print Network

    Killough, David Thomas

    2000-01-01

    7300, "Elements by ICP." The most objectionable disadvantage to NIOSH Method 7300 is that a waiting period of approximately 8 hours is required to obtain results. Laser-induced Breakdown Spectroscopy (LIBS), sometimes called Laser-induced Plasma...

  13. Reflective diffraction grating

    DOEpatents

    Lamartine, Bruce C. (Los Alamos, NM)

    2003-06-24

    Reflective diffraction grating. A focused ion beam (FIB) micromilling apparatus is used to store color images in a durable medium by milling away portions of the surface of the medium to produce a reflective diffraction grating with blazed pits. The images are retrieved by exposing the surface of the grating to polychromatic light from a particular incident bearing and observing the light reflected by the surface from specified reception bearing.

  14. Femtosecond spectral pulse shaping with holographic gratings recorded in photopolymerizable glasses.

    PubMed

    Hernández-Garay, M P; Martínez-Matos, O; Izquierdo, J G; Calvo, M L; Vaveliuk, P; Cheben, P; Bañares, L

    2011-01-17

    The majority of the applications of ultrashort laser pulses require a control of its spectral bandwidth. In this paper we show the capability of volume phase holographic gratings recorded in photopolymerizable glasses for spectral pulse reshaping of ultrashort laser pulses originated in an Amplified Ti: Sapphire laser system and its second harmonic. Gratings with high laser induce damage threshold (LIDT) allowing wide spectral bandwidth operability satisfy these demands. We have performed LIDT testing in the photopolymerizable glass showing that the sample remains unaltered after more than 10 million pulses with 0,75 TW/cm2 at 1 KHz repetition rate. Furthermore, it has been developed a theoretical model, as an extension of the Kogelnik's theory, providing key gratings design for bandwidth operability. The main features of the diffracted beams are in agreement with the model, showing that non-linear effects are negligible in this material up to the fluence threshold for laser induced damage. The high versatility of the grating design along with the excellent LIDT indicates that this material is a promising candidate for ultrashort laser pulses manipulations. PMID:21263693

  15. Laser-induced breakdown spectroscopy (LIBS): applications in environmental issues

    NASA Astrophysics Data System (ADS)

    Couris, Stelios; Hatziapostolou, A.; Anglos, Dmitrios; Mavromanolakis, A.; Fotakis, Costas

    1996-11-01

    Results are presented from three different applications of laser induced breakdown spectroscopy (LIBS) in problems of environmental interest. In one case, LIBS is applied in the on-line control of the nickel recovery process, by monitoring the nickel content of molten ferronickel slabs, in a laboratory scale experiment. In a second case, LIBS is used in the identification of polymer materials, and on the basis of spectral features, criteria are proposed for the distinction among different types of plastic materials. Also, in preliminary experiments, the use of LIBS with respect to the detection of heavy and toxic metals in paints and the possibility of performing depth profile analysis of multiple paint layers is examined.

  16. Defect geometries and laser-induced damage in multilayer coatings

    SciTech Connect

    Tench, R.J.; Kozlowski, M.R.; Chow, R.

    1994-07-01

    A correlation between laser-induced damage and the height of a coating defect was found from an examination of HfO{sub 2}/SiO{sub 2} mirrors made by three different coating vendors. The nodular defects in these reactive e-beam deposited mirrors were studied using the combination of SEM, optical microscopy, FIB and AFM techniques. Each vendor had small defects in common, but characteristically different large defects. Also the majority of seeds that caused the defects were made of hafnia, not silica. The apparent mechanical stability of the defects within the coating plays a major role in the laser resistance (1064 nm and l0ns) of a high damage threshold coating.

  17. Elemental analysis of slurry samples with laser induced breakdown spectroscopy

    SciTech Connect

    Eseller, Kemal E.; Tripathi, Markandey M.; Yueh, Fang-Yu; Singh, Jagdish P.

    2010-05-01

    Direct analysis of wet slurry samples with laser induced breakdown spectroscopy (LIBS) is challenging due to problems of sedimentation, splashing, and surface turbulence. Also, water can quench the laser plasma and suppress the LIBS signal, resulting in poor sensitivity. The effect of water on LIBS spectra from slurries was investigated. As the water content decreased, the LIBS signal was enhanced and the standard deviation was reduced. To improve LIBS slurry analysis, dried slurry samples prepared by applying slurry on PVC coated slides were evaluated. Univariate and multivariate calibration was performed on the LIBS spectra of the dried slurry samples for elemental analysis of Mg, Si, and Fe. Calibration results show that the dried slurry samples give a good correlation between spectral intensity and elemental concentration.

  18. Laser-induced modification of transparent crystals and glasses

    SciTech Connect

    Bulgakova, N M [S S Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Stoian, Razvan [Laboratoire Hubert Curien, UMR 5516 CNRS, Universite Jean Monnet, 42000 Saint Etienne, Universite de Lyon, 42023 Saint Etienne (France); Rosenfeld, A [Max-Born-Institut fur Nichtlineare Optik und Kurzzeitspektroskopie, Berlin (Germany)

    2010-12-29

    We analyse the processes taking place in transparent crystals and glasses irradiated by ultrashort laser pulses in the regimes typical of various applications in optoelectronics and photonics. We consider some phenomena, which have been previously described by the authors within the different model representations: charging of the dielectric surface due to electron photoemission resulting in a Coulomb explosion; crater shaping by using an adaptive control of the laser pulse shape; optimisation of the waveguide writing in materials strongly resistant to laser-induced compaction under ordinary irradiation conditions. The developed models and analysis of the processes relying on these models include the elements of the solid-state physics, plasma physics, thermodynamics, theory of elasticity and plasticity. Some important experimental observations which require explanations and adequate description are summarised. (photonics and nanotechnology)

  19. Characterization of laser - induced plasmas by atomic emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Díaz Pace, Diego M.; Bertuccelli, Graciela; D'Angelo, Cristian A.

    2011-01-01

    In this work, Laser-induced breakdown spectroscopy (LIBS) has been applied to characterization of plasmas generated in air at atmospheric pressure from a calcium hydroxide sample with a known concentration of Mg by using an infrared Nd:YAG laser. The influence of laser irradiance on plasma morphology and emission intensity was studied. Spatially-integrated intensities of Mg I-II lines along the line-of-sight were measured for different laser energies and delay times. The plasma temperature and the electron density were determined in each case by using and algorithm that calculates the optical thickness of the spectral lines and reproduces their experimental profiles in a framework of an homogeneous plasma in LTE that takes into account the effects of self-absorption. The results obtained showed the usefulness of this approach to provide additional information retrieved from the optical thickness of spectral lines for plasma characterization in LIBS experiments.

  20. Femtosecond visualization of laser-induced optical relativistic electron microbunches.

    PubMed

    Xiang, Dao; Hemsing, Erik; Dunning, Michael; Hast, Carsten; Raubenheimer, Tor

    2014-10-31

    It has long been known that lasers can interact with relativistic electrons in magnetic undulators to imprint sinusoidal modulations that can be used to slice electrons into microbunches equally separated at the laser wavelength. Here we report on the first direct measurement of laser-induced microbunching of a relativistic electron beam with femtosecond resolution in the time domain. Using a modified zero-phasing technique to map the electron beam's temporal structures into the energy space, we show that this method can be used to directly quantify the time and spectral content of coherent current modulations imprinted on the beam for harmonic and multicolor lasing applications in accelerator-based light sources. PMID:25396374

  1. Hydrogen retention in tungsten materials studied by Laser Induced Desorption

    NASA Astrophysics Data System (ADS)

    Zlobinski, M.; Philipps, V.; Schweer, B.; Huber, A.; Reinhart, M.; Möller, S.; Sergienko, G.; Samm, U.; 't Hoen, M. H. J.; Manhard, A.; Schmid, K.; Textor Team

    2013-07-01

    Development of methods to characterise the first wall in ITER and future fusion devices without removal of wall tiles is important to support safety assessments for tritium retention and dust production and to understand plasma wall processes in general. Laser based techniques are presently under investigation to provide these requirements, among which Laser Induced Desorption Spectroscopy (LIDS) is proposed to measure the deuterium and tritium load of the plasma facing surfaces by thermal desorption and spectroscopic detection of the desorbed fuel in the edge of the fusion plasma. The method relies on its capability to desorb the hydrogen isotopes in a laser heated spot. The application of LID on bulk tungsten targets exposed to a wide range of deuterium fluxes, fluences and impact energies under different surface temperatures is investigated in this paper. The results are compared with Thermal Desorption Spectrometry (TDS), Nuclear Reaction Analysis (NRA) and a diffusion model.

  2. Two-Photon/Laser-Induced Fluorescence (TP/LIF) sensor

    NASA Technical Reports Server (NTRS)

    Bradshaw, John D.

    1994-01-01

    The Two-Photon/Laser-Induced Fluorescence (TP/LIF) technique is based on the stepwise excitation of the OH transitions, X(exp 2)II, v(exp '') = 0 yields X(exp 2)II, v(exp '') = 1 (lambda = 2.9 microns) and X(exp 2)II v(exp '') = 1 yields A(exp2)Sigma, v' = 0 (lambda = 345 nm) with background free fluorescence monitoring of the A(exp 2)Sigma, v' = 0 yields X(exp 2)II, v(exp '') = 0 transition near 309 nm. This technique has awaited the advent of a suitable mid-infrared (2.9 microns) laser source. Turnable mid-IR lasers now exist that are capable of meeting the specifications required of a high sensitivity TP/LIF OH sensor.

  3. Laser-induced photo-thermal magnetic imaging

    NASA Astrophysics Data System (ADS)

    Thayer, David A.; Lin, Yuting; Luk, Alex; Gulsen, Gultekin

    2012-08-01

    Due to the strong scattering nature of biological tissue, optical imaging beyond the diffusion limit suffers from low spatial resolution. In this letter, we present an imaging technique, laser-induced photo-thermal magnetic imaging (PMI), which uses laser illumination to induce temperature increase in a medium and magnetic resonance imaging to map the spatially varying temperature, which is proportional to absorbed energy. This technique can provide high-resolution images of optical absorption and can potentially be used for small animal as well as breast cancer and lymph node imaging. First, we describe the theory of PMI, including the modeling of light propagation and heat transfer in tissue. We also present experimental data with corresponding predictions from theoretical models, which show excellent agreement.

  4. Laser-induced silver nanojoining of gold nanoparticles.

    PubMed

    Son, Myounghee; Kim, Seol Ji; Kim, Jong-Yeob; Jang, Du-Jeon

    2013-08-01

    Gold nanoparticles have been silver-joined to fabricate nanowires by irradiating gold nanospheres of 25 nm in diameter and silver nanospheres of 8 nm in diameter held together on a carbon-coated copper grid with a 30 ps laser pulse of 532 nm for 20 min at a fluence of 3.0 mJ/cm2. Laser-induced nanojoining of silver nanoparticles as well as that of gold nanoparticles has also been carried out by varying the wavelength and fluence of irradiation laser pulses. Irradiation at an optimum condition of laser fluence is essential for the proper silver nanojoining of gold nanospheres to produce gold@silver core-shell composite nanowires. The excitation of the surface plasmon resonances of the base-metallic gold nanospheres rather than the filler-metallic silver nanospheres paves the way for the silver nanojoining of gold nanoparticles. PMID:23882834

  5. The role of continuum radiation in laser induced plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    De Giacomo, A.; Gaudiuso, R.; Dell'Aglio, M.; Santagata, A.

    2010-05-01

    This paper focuses on the interpretation of the origin of the continuum radiation in Laser Induced Plasma (LIP) emission spectra, a subject that has received little consideration in the literature when compared to the analysis of the line emission spectrum. The understanding of the spectral peculiarities observed immediately after the laser pulse, when the continuum radiation prevails on discrete emission lines, can be extremely important to retrieve the initial conditions of LIP and to correlate the produced plasma to the ablation mechanism. In this work, in addition to a qualitative interpretation of the LIP continuum in the initial stage of expansion, a methodology is proposed for a better measurement of the atomic temperature in the expansion stage of the LIP. Such methodology is based on the analysis of the combined Boltzmann and Planck plots. The results obtained stress once again the importance of considering non equilibrium effects in the initial stage of LIP expansion.

  6. Diagnostics of laser-induced plasma by optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Cveji?, M.

    2014-12-01

    The procedure for diagnostics of laser induced plasma (LIP) by optical emission spectroscopy technique is described. LIP was generated by focusing Nd:YAG laser radiation (1.064 nm, 50 mJ, 15 ns pulse duration) on the surface of pellet containing among other elements lithium. Details of the experimental setup and experimental data processing are presented. High speed plasma photography was used to study plasma evolution and decay. From those images optimum time for plasma diagnostics is located. The electron number density, Ne, is determined by fitting profiles of Li I lines while electron temperature, Te, was determined from relative intensities of Li I lines using Boltzmann plot (BP) technique. All spectral line recordings were tested for the presence of self-absorption and then if optically thin, Abel inverted and used for plasma diagnostic purposes.

  7. Radioactive contamination screening with laser-induced fluorescence

    SciTech Connect

    Sheely, R. [Oak Ridge K-25 Site, TN (United States); Di Benedetto, J. [EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations

    1994-06-01

    The ability to induce, detect and discriminate fluorescence of uranium oxides makes available new capabilities for screening the surface of large complex facilities for uranium. This paper will present the results of field tests evaluate laser-induced fluorescence (LIF) as a contamination screening tool and report on the progress to produce a field portable instrument for uranium surveys on exposed surfaces. The principal effect is to illuminate the surface of an object or an area with a remotely-located light source, and to evaluate the re-radiated emission energy. A gated intensified CCD camera was used with ultraviolet (UV) laser excitation to discriminate the phosphorescent (persistent) green uranium emission from the prompt background fluorescence which results from excitation of plants, concrete, soils, and other background materials.

  8. Alloying aluminum with Fe using laser induced plasma technique

    NASA Astrophysics Data System (ADS)

    Alwafi, Y. A.; Bidin, N.; Gustiono, D.; Harun, S. W.

    2012-08-01

    A new surface modification technique is demonstrated using laser induced plasma (LIP) to increase the hardness of the surface layer. This LIP treatment provides a very high heating and fast cooling mechanism that can be used to form alloyed layer on a material surface. The hardness of the alloyed material is measured and the results show that the alloyed surface is 3 times as hard as the un-treated surface and a single Fe alloyed aluminum surface is harder than the one formed by the mixture of Fe and Cu. The micro-hardness of the alloy increases with the number of pulses at a rate of around 4 HV/pulse. The maximum hardness of 93.0 HV is obtained with the use of single Fe after exposure to 7 pulses of the laser.

  9. Apparatus, system, and method for laser-induced breakdown spectroscopy

    DOEpatents

    Effenberger, Jr., Andrew J; Scott, Jill R; McJunkin, Timothy R

    2014-11-18

    In laser-induced breakdown spectroscopy (LIBS), an apparatus includes a pulsed laser configured to generate a pulsed laser signal toward a sample, a constructive interference object and an optical element, each located in a path of light from the sample. The constructive interference object is configured to generate constructive interference patterns of the light. The optical element is configured to disperse the light. A LIBS system includes a first and a second optical element, and a data acquisition module. The data acquisition module is configured to determine an isotope measurement based, at least in part, on light received by an image sensor from the first and second optical elements. A method for performing LIBS includes generating a pulsed laser on a sample to generate light from a plasma, generating constructive interference patterns of the light, and dispersing the light into a plurality of wavelengths.

  10. Elemental Analysis of Soils by Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gondal, Mohammed Ashraf; Dastageer, Mohamed A.

    The chemical and elemental composition of soil is very complex as it contains many constituents like minerals, organic matters, living organisms, fossils, air and water. Considering the diversity of soil contents, quality and usability, a systematic scientific study on the elemental and chemical composition of soil is very important. In order to study the chemical composition of soil, Laser induced breakdown spectroscopy (LIBS) has been applied recently. The important features of LIBS system and its applications for the measurement of nutrients in green house soil, on-line monitoring of remediation process of chromium polluted soil, determination of trace elements in volcanic erupted soil samples collected from ancient cenozoic lava eruption sites and detection of toxic metals in Gulf war oil spill contaminated soil using LIBS are described in this chapter.

  11. On the cutoff law of laser induced high harmonic spectra

    NASA Astrophysics Data System (ADS)

    Guo, Dong-Sheng; Yu, Chao; Zhang, Jingtao; Gao, Ju; Sun, Zhi-Wei; Sun, Zhenrong

    2015-04-01

    The currently well accepted cutoff law for laser induced high harmonic spectra predicts the cutoff energy as a linear combination of two interaction energies, the ponderomotive energy U p and the atomic biding energy I p , with coefficients 3.17 and 1.32, respectively. Even though, this law has been there for twenty years or so, the background information for these two constants, such as how they relate to fundamental physics and mathematics constants, is still unknown. This simple fact, keeps this cutoff law remaining as an empirical one. Based on the cutoff property of Bessel functions and the Einstein photoelectric law in the multiphoton case, we show these two coefficients are algebraic constants, and , respectively. A recent spectra calculation and an experimental measurement support the new cutoff law.

  12. Laser-induced atomic adsorption: A mechanism for nanofilm formation

    NASA Astrophysics Data System (ADS)

    Martins, Weliton S.; Passerat de Silans, Thierry; Oriá, Marcos; Chevrollier, Martine

    2013-11-01

    We demonstrate and interpret a technique of laser-induced formation of thin metallic films using alkali atoms on the window of a dense-vapour cell. We show that this intriguing photo-stimulated process originates from the adsorption of Cs atoms via the neutralization of Cs+ ions by substrate electrons. The Cs+ ions are produced via two-photon absorption by excited Cs atoms very close to the surface, which enables the transfer of the laser spatial intensity profile to the film thickness. An initial decrease of the surface work function is required to guarantee Cs+ neutralization and results in a threshold in the vapour density. This understanding of the film growth mechanism may facilitate the development of new techniques of laser-controlled lithography, starting from thermal vapours.

  13. Laser-induced fluorescence spectroscopy in tissue local necrosis detection

    NASA Astrophysics Data System (ADS)

    Cip, Ondrej; Buchta, Zdenek; Lesundak, Adam; Randula, Antonin; Mikel, Bretislav; Lazar, Josef; Veverkova, Lenka

    2014-03-01

    The recent effort leads to reliable imaging techniques which can help to a surgeon during operations. The fluorescence spectroscopy was selected as very useful online in vivo imaging method to organics and biological materials analysis. The presented work scopes to a laser induced fluorescence spectroscopy technique to detect tissue local necrosis in small intestine surgery. In first experiments, we tested tissue auto-fluorescence technique but a signal-to-noise ratio didn't express significant results. Then we applied a contrast dye - IndoCyanine Green (ICG) which absorbs and emits wavelengths in the near IR. We arranged the pilot experimental setup based on highly coherent extended cavity diode laser (ECDL) used for stimulating of some critical areas of the small intestine tissue with injected ICG dye. We demonstrated the distribution of the ICG exciter with the first file of shots of small intestine tissue of a rabbit that was captured by high sensitivity fluorescent cam.

  14. Ion Soliton Observation in Plasma with Laser Induced

    NASA Astrophysics Data System (ADS)

    Claire, Nicolas; Bachet, Gerard; Skiff, Fred

    2003-10-01

    The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device can be observed by laser induced fluorescence (LIF). Comparison between LIF and Langmuir probe measurements demonstrate that the pumping effect has to be taken into account by using a classical fluid model. One main contribution of the LIF has been to show that a train of soliton propagates easier in the device if a weak backward ion flux plasma having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, the closer to the grid the soliton separation occurs. The other contribution of the LIF concerns the bump observed in front of the first soliton edge which was generally identified as precursors ions : in fact this bump results from a collective motion of the argon ions.

  15. Adaptive femtosecond laser-induced breakdown spectroscopy of uranium

    NASA Astrophysics Data System (ADS)

    Ko, P.; Hartig, K. C.; McNutt, J. P.; Schur, R. B. D.; Jacomb-Hood, T. W.; Jovanovic, I.

    2013-01-01

    Laser-induced breakdown spectroscopy (LIBS) is an established technique for material characterization applicable to a variety of problems in research, industry, environmental studies, and security. LIBS conducted with femtosecond laser pulses exhibits unique properties, arising from the characteristics of laser-matter interactions in this pulse width regime. The time evolution of the electric field of the pulse determines its interaction with sample materials. We present the design and performance of a femtosecond LIBS system developed to systematically optimize the technique for detection of uranium. Sample analysis can be performed in vacuum environment, and the spectral and temporal diagnostics are coupled through an adaptive feedback loop, which facilitates optimization of the signal-to-noise ratio by pulse shaping. Initial experimental results of LIBS on natural uranium are presented.

  16. Laser-induced breakdown spectroscopy expands into industrial applications

    NASA Astrophysics Data System (ADS)

    Noll, Reinhard; Fricke-Begemann, Cord; Brunk, Markus; Connemann, Sven; Meinhardt, Christoph; Scharun, Michael; Sturm, Volker; Makowe, Joachim; Gehlen, Christoph

    This paper presents R&D activities in the field of laser-induced breakdown spectroscopy for industrial applications and shows novel LIBS systems running in routine operation for inline process control tasks. Starting with a comparison of the typical characteristics of LIBS with XRF and spark-discharge optical emission spectrometry, the principal structure of LIBS machines embedded for inline process monitoring will be presented. A systematic requirement analysis for LIBS systems following Ishikawa's scheme was worked out. Stability issues are studied for laser sources and Paschen-Runge spectrometers as key components for industrial LIBS systems. Examples of industrial applications range from handheld LIBS systems using a fiber laser source, via a set of LIBS machines for inline process control tasks, such as scrap analysis, coal analysis, liquid slag analysis and finally monitoring of drill dust.

  17. Laser-induced stress transients: applications for molecular delivery

    NASA Astrophysics Data System (ADS)

    Flotte, Thomas J.; Lee, Shun; Zhang, Hong; McAuliffe, Daniel J.; Douki, Tina; Doukas, Apostolos G.

    1995-05-01

    Lasers can be used to enhance the delivery of a number of molecules. Other investigators have demonstrated local release of molecules from liposomes following laser irradiation, microbeam disruption of the cell membrane to increase cell transport, microbeam ablation of the zona pellucida surrounding the ovum to increase the chances of fertilization, and increased transcutaneous transport following ablation of the stratum corneum. Our experiments have shown that laser-induced stress transients can be utilized as a vector for intracellular delivery of molecules that may or may not normally cross the cell membrane. These two conditions have been tested with Photofrin and DNA. This technology may have applications in cell and molecular biology, cancer therapy, gene therapy, and others.

  18. Pulsed laser-induced formation of silica nanogrids

    PubMed Central

    2014-01-01

    Silica grids with micron to sub-micron mesh sizes and wire diameters of 50 nm are fabricated on fused silica substrates. They are formed by single-pulse structured excimer laser irradiation of a UV-absorbing silicon suboxide (SiO x ) coating through the transparent substrate. A polydimethylsiloxane (PDMS) superstrate (cover layer) coated on top of the SiO x film prior to laser exposure serves as confinement for controlled laser-induced structure formation. At sufficiently high laser fluence, this process leads to grids consisting of a periodic loop network connected to the substrate at regular positions. By an additional high-temperature annealing, the residual SiO x is oxidized, and a pure SiO2 grid is obtained. PACS 81.07.-b; 81.07.Gf; 81.65.Cf PMID:24581305

  19. Kr II laser-induced fluorescence for measuring plasma acceleration

    SciTech Connect

    Hargus, W. A. Jr. [AFRL/RQRS, Edwards AFB, California 93524 (United States); Azarnia, G. M.; Nakles, M. R. [ERC, Inc., Edwards AFB, California 93524 (United States)

    2012-10-15

    We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d{sup 4}D{sub 7/2} to the 5p{sup 4}P{sub 5/2}{sup Ring-Operator} state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d{sup 4}D{sub 7/2}-5p{sup 4}P{sub 5/2}{sup Ring-Operator} transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume.

  20. Experimental Studies of Laser-Induced Breakdown in Transparent Dielectrics

    SciTech Connect

    Carr, C W

    2003-09-23

    The mechanisms by which transparent dielectrics damage when exposed to high power laser radiation has been of scientific and technological interest since the invention of the laser. In this work, a set of three experiments are presented which provide insight into the damage initiation mechanisms and the processes involved in laser-induced damage. Using an OPO (optical parametric oscillator) laser, we have measured the damage thresholds of deuterated potassium dihydrogen phosphate (DKDP) from the near ultraviolet into the visible. Distinct steps, whose width is of order K{sub b}T, are observed in the damage threshold at photon energies associated with the number of photons (3{yields}2 or 4{yields}3) needed to promote a ground state electron across the energy gap. The wavelength dependence of the damage threshold suggests that a primary mechanism for damage initiation in DKDP is a multi-photon process in which the order is reduced through excited defect state absorption. In-situ fluorescence microscopy, in conjunction with theoretical calculations by Liu et al., has been used to establish that hydrogen displacement defects are potentially responsible for the reduction in the multi-photon cross-section. During the damage process, the material absorbs energy from the laser pulse and produces an ionized region that gives rise to broadband emission. By performing a time-resolved investigation of this emission, we demonstrate both that it is blackbody in nature, and we provide the first direct measurement of the localized temperature during and following laser damage initiation for various optical materials. For excitation using nanosecond laser pulses, the plasma, when confined in the bulk, is in thermal equilibrium with the lattice. These results allow for a detailed characterization of temperature, pressure, and electron densities occurring during laser-induced damage.

  1. Simultaneous measurement of electron and heavy particle temperatures in He laser-induced plasma by Thomson and Rayleigh scattering

    E-print Network

    .1063/1.4801467] Laser-induced plasmas (LIP) have found numerous appli- cations, including laser ablation, shortSimultaneous measurement of electron and heavy particle temperatures in He laser-induced plasma particle temperatures in He laser-induced plasma by Thomson and Rayleigh scattering K. Dzier_zeRga,1 A

  2. Observation of Femtosecond, Sub-Angstrom Molecular Bond Relaxation Using Laser-Induced Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Blaga, Cosmin I.; Dichiara, Anthony D.; Zhang, Kaikai; Sistrunk, Emily; Agostini, Pierre; Dimauro, Louis F.; Xu, Junliang; Lin, Chii-Dong; Miller, Terry A.

    2011-06-01

    Imaging, or the determination of the atomic positions in molecules, has always occupied an essential role in physical, chemical and biological sciences. For structural determination, the well established methods of X-ray and electron diffraction easily achieve sub-Angstrom spatial resolution. However, these conventional approaches are not suitable for investigating structural transformations, such as the reaction of molecules or the function of biological systems that occur on the timescales faster than a picosecond. Over the past decade, major efforts directed at developing femtosecond pulsed sources, e.g. X-ray free-electron lasers and electron beams, have resulted in pioneering investigations on imaging large biological molecules and condensed phase dynamics. We report on a different approach, laser-induced electron diffraction (LIED), for achieving sub-femtosecond, sub-Angstrom spatio-temporal resolution for investigating gas-phase molecular dynamics. In contrast to the above mentioned techniques, the LIED method generates bursts of coherent electron wave packets directly from the molecule under interrogation. The study is performed by measuring the diffracted photoelectron momentum distribution produced by strong-field ionization of oxygen and nitrogen molecules at several mid-infrared wavelengths (1.7-2.3 ?m). The bond lengths retrieved from the LIED analysis show sensitivity to a change of 0.05 Å in 1 fs. This initial report provides the first direct evidence of bond relaxation following an electronic excitation and establishes the foundation of the LIED method as a general approach for ultrafast imaging of molecular dynamics.

  3. Water-cooled grate

    Microsoft Academic Search

    P. Lis; K. Olausson

    1980-01-01

    A description is given of a furnace for the combustion of solid fuel comprising: a first, inclined grate portion having an upper end and a lower end, the upper end adjacent to a side wall defining the furnace, said first grate portion extending outwardly below a combustion space; means for supplying fuel to the upper end of said inclined, first

  4. Formation of carbon nanotubes: In situ optical analysis using laser-induced incandescence and laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Cau, M.; Dorval, N.; Attal-Trétout, B.; Cochon, J.-L.; Foutel-Richard, A.; Loiseau, A.; Krüger, V.; Tsurikov, M.; Scott, C. D.

    2010-04-01

    Gas-phase production of carbon nanotubes in presence of a metal catalyst with a continuous wave CO2 laser is investigated by combining coherent anti-Stokes Raman scattering (CARS), laser-induced fluorescence (LIF), and laser-induced incandescence (LII). These in situ techniques provide a unique investigation of the different transformation processes of the primarily carbon and metal vapors issued from the vaporization of the target by the laser and the temperature at which these processes occur. Continuous-wave laser provides with stable continuous vaporization conditions very well suited for such in situ investigations. Temperature profiles inside the reactor are known from CARS measurements and flow calculations. Carbon soot, density, and size of carbon aggregates are determined by LII measurements. LIF measurements are used to study the gas phases, namely, C2 and C3 radicals which are the very first steps of carbon recombination, and metal catalysts gas phase. Spectral investigations allow us to discriminate the signal from each species by selecting the correct pair of excitation/detection wavelengths. Spatial distributions of the different species are measured as a function of target composition and temperature. The comparison of LIF and LII signals allow us to correlate the spatial evolution of gas and soot in the scope of the different steps of the nanotube growth already proposed in the literature and to identify the impact of the chemical nature of the catalyst on carbon condensation and nanotube nucleation. Our study presents the first direct evidence of the nanotube onset and that the nucleation proceeds from a dissolution-segregation process from metal particles as assumed in the well-known vapor-liquid-solid model. Comparison of different catalysts reveals that this process is strongly favored when Ni is present.

  5. Non-linear optical studies of adsorbates: Spectroscopy and dynamics

    SciTech Connect

    Zhu, Xiangdong.

    1989-08-01

    In the first part of this thesis, we have established a systematic procedure to apply the surface optical second-harmonic generation (SHG) technique to study surface dynamics of adsorbates. In particular, we have developed a novel technique for studies of molecular surface diffusions. In this technique, the laser-induced desorption with two interfering laser beams is used to produce a monolayer grating of adsorbates. The monolayer grating is detected with diffractions of optical SHG. By monitoring the first-order second-harmonic diffraction, we can follow the time evolution of the grating modulation from which we are able to deduce the diffusion constant of the adsorbates on the surface. We have successfully applied this technique to investigate the surface diffusion of CO on Ni(111). The unique advantages of this novel technique will enable us to readily study anisotropy of a surface diffusion with variable grating orientation, and to investigate diffusion processes of a large dynamic range with variable grating spacings. In the second part of this work, we demonstrate that optical infrared-visible sum-frequency generation (SFG) from surfaces can be used as a viable surface vibrational spectroscopic technique. We have successfully recorded the first vibrational spectrum of a monolayer of adsorbates using optical infrared-visible SFG. The qualitative and quantitative correlation of optical SFG with infrared absorption and Raman scattering spectroscopies are examined and experimentally demonstrated. We have further investigated the possibility to use transient infrared-visible SFG to probe vibrational transients and ultrafast relaxations on surfaces. 146 refs.

  6. Collective spin Hall effect for electron-hole gratings.

    PubMed

    Shen, Ka; Vignale, G

    2013-09-27

    We show that an electric field parallel to the wave fronts of an electron-hole grating in a GaAs quantum well generates, via the electronic spin Hall effect, a spin grating of the same wave vector and with an amplitude that can exceed 1% of the amplitude of the initial density grating. We refer to this phenomenon as the "collective spin Hall effect." A detailed study of the coupled spin-charge dynamics for quantum wells grown in different directions reveals rich features in the time evolution of the induced spin density, including the possibility of generating a helical spin grating. PMID:24116799

  7. Experimental and theoretical comparison of single-pulse and double-pulse laser induced breakdown spectroscopy on metallic samples

    NASA Astrophysics Data System (ADS)

    De Giacomo, A.; Dell'Aglio, M.; Bruno, D.; Gaudiuso, R.; De Pascale, O.

    2008-07-01

    In this paper, single pulse (SP)- and double pulse (DP)- Laser Induced Breakdown Spectroscopy (LIBS) on metallic titanium, aluminum-based alloy and copper-based alloy have been studied by spectrally resolved imaging to find out the fundamental difference in terms of fluid-dynamic and chemical aspects. To better clarify the different nature of SP- and DP-Laser Induced Plasma (LIP) a qualitative theoretical model including both fluid-dynamics and chemical processes has been applied for the interpretation of the experimental results. Moreover, an attempt to quantify the mechanisms inducing the DP-LIBS enhancement has been made. By the analysis of spectrally resolved imaging data, the temporal and spatial maps of the emission signal and of the corresponding DP-LIBS enhancement have been built in order to improve the analytical information conveyed. Finally, it has been pointed out the important effect of the different environment where SP- and DP-LIPs expand, as well as its relevance to the understanding of the basic questions underlying the comparison between SP- and DP-LIBS.

  8. Semiconductor laser asymmetry cutting glass with laser induced thermal-crack propagation

    NASA Astrophysics Data System (ADS)

    Zhao, Chunyang; Zhang, Hongzhi; Wang, Yang

    2014-12-01

    Laser induced thermal-crack propagation (LITP) makes the material to produce an uneven temperature field, maximum temperature can't soften or melt the material, induces the thermal stress, then the crack separates along the cutting path. One of the problems in laser asymmetry cutting glass with LITP is the cutting deviation along scanning trajectory. This study lays great emphasis on considering the dynamic extension of crack to explain the reason of the cutting deviation in laser asymmetry cutting glass, includes asymmetric linear cutting and a quarter of a circular curve cutting. This paper indicates the experiments of semiconductor laser asymmetry cutting glass with LITP. Optical microscope photographs of the glass sheet are obtained to examine the cutting deviation. The extended finite element method (XFEM) is used to simulate the dynamic propagation of crack; the crack path does not have to be specified a priori. The cutting deviation mechanism and the crack propagation process are studied by the stress fields using finite element software ABAQUS. This work provides a theoretical basis to investigate the cutting deviation in laser asymmetry cutting glass. In semiconductor laser asymmetry cutting glass, the tensile stress is the basis of crack propagation, then the compressive stress not only makes the crack to extend stably, but also controls the direction of crack propagation.

  9. Laser-induced incandescence measurements in a fired diesel engine at 3 kHz

    NASA Astrophysics Data System (ADS)

    Boxx, I. G.; Heinold, O.; Geigle, K. P.

    2015-01-01

    Laser-induced incandescence (LII) was performed at 3 kHz in an optically accessible cylinder of a fired diesel engine using a commercially available diode-pumped solid-state laser and an intensified CMOS camera. The resulting images, acquired every 3° of crank angle, enabled the spatiotemporal tracking of soot structures during the expansion/exhaust stroke of the engine cycle. The image sequences demonstrate that soot tends to form in thin sheets that propagate and interact with the in-cylinder flow. These sheets tend to align parallel to the central axis of the cylinder and are frequently wrapped into conical spirals by aerodynamic swirl. Most of the soot is observed well away from the cylinder walls. Quantitative soot measurements were beyond the scope of this study but the results demonstrate the practical utility of using kHz-rate LII to acquire ensemble-averaged statistical data with high crank angle resolution over a complete engine cycle. Based on semi-quantitative measures of soot distribution, it was possible to identify soot dynamics related to incomplete charge exchange. This study shows that long-duration, multi-kHz acquisition rate LII measurements are viable in a fired diesel engine with currently available laser and camera technology, albeit only in the expansion and exhaust phase of the cycle at present. Furthermore, such measurements yield useful insight into soot dynamics and therefore constitute an important new tool for the development and optimization of diesel engine technology.

  10. Development of laser induced breakdown spectroscopy instrumentatin for safeguards applications

    SciTech Connect

    Barefield Il, James E [Los Alamos National Laboratory; Clegg, Samuel M [Los Alamos National Laboratory; Le, Loan A [Los Alamos National Laboratory; Lopez, Leon N [Los Alamos National Laboratory

    2010-01-01

    In September 2006, a Technical Meeting on Application of Laser Spectrometry Techniques in IAEA Safeguards was held at IAEA headquarters (HQ). One of the principal recommendations from this meeting was the need to 'pursue the development of novel complementary access instrumentation based on laser induced breakdown spectroscopy (LIBS) for the detection of gaseous and solid signatures and indicators of nuclear fuel cycle processes and associated materials.' Pursuant to this recommendation the Department of Safeguards (SG) under the Division of Technical Support (SGTS) convened the Experts and Users Advisory Meeting on Laser Induced Breakdown Spectroscopy (LIBS) for Safeguards Applications. This meeting was held at IAEA HQ from July 7-11,2008 and hosted by the Novel Technologies Unit (NTU). The meeting was attended by 12 LIBS experts from the Czech Republic, the European Commission, France, the Republic of Korea, the United States of America, Germany, the United Kingdom of Great Britain, Canada, and Northern Ireland. After a presentation of the needs of the IAEA inspectors, the LIBS experts were in agreement that needs as presented could be partially or fully fulfilled using LIBS instrumentation. The needs of the IAEA inspectors were grouped in the following broad categories: (1) Improvements to in-field measurements/environmental sampling; (2) Monitoring status of activity in a Hot Cell; (3) Verifying status of activity at a declared facility via process monitoring; and (4) Need for pre-screening of environmental samples before analysis. Under the Department of Energy/National Nuclear Security Administration (DOE/NNSA) Next Generation Safeguards Initiative (NGSI) Los Alamos National Laboratory is exploring three potential applications of LIBS for international safeguards. As part of this work, we are developing: (1) a user-friendly man-portable LIBS system to characterize samples across a wide range of elements in the periodic table from hydrogen up to heavy elements like plutonium and uranium; (2) a LIBS system that can be deployed in harsh environments such as gloveboxes and hot cells providing relative compositional analysis of process streams for example ratios like Cm/Pu and Cm/U; and (3) an inspector field deployable system that can be used to analyze the elemental composition of microscopic quantities of samples containing plutonium and uranium. In this paper we will describe our current development and performance testing results both in a fixed lab and measurements in field deployable configurations using LIBS instrumentation developed for applications to international safeguards.

  11. A Laser Induced Breakdown Spectroscopy application based on Local Thermodynamic Equilibrium assumption for the elemental analysis of alexandrite gemstone and copper-based alloys

    NASA Astrophysics Data System (ADS)

    De Giacomo, A.; Dell'Aglio, M.; Gaudiuso, R.; Santagata, A.; Senesi, G. S.; Rossi, M.; Ghiara, M. R.; Capitelli, F.; De Pascale, O.

    2012-04-01

    Laser Induced Breakdown Spectroscopy (LIBS) is an appealing technique to study laser-induced plasmas (LIPs), both from the basic diagnostics point of view and for analytical applications. LIPs are complex dynamic systems, expanding at supersonic velocities and undergoing a transition between different plasma regimes. If the Local Thermodynamic Equilibrium (LTE) condition is valid for such plasmas, several analytical methods can be employed and fast quantitative analyses can be performed on a variety of samples. In the present paper, a discussion about LTE is carried out and an innovative application to the analysis of the alexandrite gemstone is presented. In addition, a study about the influence of plasma parameters on the performance of LTE-based methods is reported for bronze and brass targets.

  12. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, Antonio J. (Albuquerque, NM); Butler, Michael A. (Albuquerque, NM); Sinclair, Michael B. (Albuquerque, NM); Senturia, Stephen D. (Brookline, MA)

    1998-01-01

    An electrically-programmable diffraction grating. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers).

  13. Laser-induced decompression shock development in fused silica Junlan Wang,a)

    E-print Network

    Sottos, Nancy R.

    Laser-induced decompression shock development in fused silica Junlan Wang,a) Richard L. Weaver. A decompression shock forms and greatly enhances interfacial failure of a thin film deposited on the substrate

  14. Laser-induced particle generation in carbon disulfide and carbonyl sulfide

    NASA Astrophysics Data System (ADS)

    Vlahoyannis, Y. P.; Patsilinakou, E.; Fotakis, C.; Stockdale, J. A. D.

    Laser-induced clustering has been studied in carbon disulfide and carbonyl sulfide from 308 to 340 nm. The results support a single-photon excitation mechanism in carbon disulfide and two-photon dissociation in carbonyl sulfide.

  15. Laser-induced fluorescence detection strategies for sodium atoms and compounds in high-pressure combustors

    NASA Technical Reports Server (NTRS)

    Weiland, Karen J. R.; Wise, Michael L.; Smith, Gregory P.

    1993-01-01

    A variety of laser-induced fluorescence schemes were examined experimentally in atmospheric pressure flames to determine their use for sodium atom and salt detection in high-pressure, optically thick environments. Collisional energy transfer plays a large role in fluorescence detection. Optimum sensitivity, at the parts in 10 exp 9 level for a single laser pulse, was obtained with the excitation of the 4p-3s transition at 330 nm and the detection of the 3d-3p fluorescence at 818 nm. Fluorescence loss processes, such as ionization and amplified spontaneous emission, were examined. A new laser-induced atomization/laser-induced fluorescence detection technique was demonstrated for NaOH and NaCl. A 248-nm excimer laser photodissociates the salt molecules present in the seeded flames prior to atom detection by laser-induced fluorescence.

  16. Red-shift law of intense laser-induced electro-absorption in solids

    NASA Astrophysics Data System (ADS)

    Deng, Hong-Xiang; Zu, Hao-Yue; Wu, Shao-Yi; Sun, Kai; Zu, Xiao-Tao

    2014-02-01

    A theoretical study on the red-shift of laser-induced electro-absorption is presented. It is found that laser-induced red-shift scales with the cube root of the pump laser intensity in the optical tunneling regime and has an obvious deviation from this scale in the multi-photon regime. Our results show that in the optical tunneling regime, the laser-induced red shift has the same law as that in the direct current (DC) approximation. Though the scales are the same in the optical tunneling regime, the physical pictures in the two cases are quite different. The electro-absorption in the DC case is a tunneling-assisted transition process, while the laser-induced electro-absorption is a mixed multi-photon process.

  17. Laser-Induced Breakdown Spectroscopy as a Tool to Differentiate Compositions of Iron-Bearing Minerals

    NASA Astrophysics Data System (ADS)

    Rosen-Gooding, A. L.; Ollila, A. M.; Gordon, S. R.; Newsom, H. E.; Williams, A. J.; Martinez, R. K.; Wiens, R. C.; Clegg, S. M.

    2014-07-01

    This study demonstrates that laser-induced breakdown spectroscopy onboard the MSL Curiosity rover can be used to differentiate various classes of iron-rich minerals on Mars using principle component analysis of specific elemental peaks.

  18. APPLICATIONS OF CAPILLARY ELECTROPHORESIS/LASER-INDUCED FLUORESCENCE DETECTION TO GROUND WATER MIGRATION STUDIES

    EPA Science Inventory

    Capillary electrophoresis (CE) has been applied to the determination of groundwater migration based on laser-induced fluorescence (LIF) detection and traditional spectrofluorimetry. The detection limits of injected dye-fluorescent whitening agent (tinopal) in the low parts per tr...

  19. In-vivo targeted gene transfer to skin by nanosecond pulsed laser-induced stress waves

    Microsoft Academic Search

    M. Ogura; M. Obara

    2003-01-01

    We demonstrated that laser-induced stress waves enhanced transfection efficiency in rat's skin in vivo by a factor of 120 over the naked DNA injection. Site-and tissue specific gene expressions were observed.

  20. CAPILLARY ELECTROPHORESIS/LASER-INDUCED FLUORESCENCE DETECTION OF FLUORESCEIN AS A GROUNDWATER MIGRATION TRACER

    EPA Science Inventory

    Capillary electrophoresis (CE) has been applied to the determination of the groundwater migration tracer dye fluorescein based on laser-induced fluorescence (LIF) detection and compared to determinations obtained with traditional spectrofluorimetry. Detection limits of injected d...

  1. Laser-induced porous graphene films from commercial polymers.

    PubMed

    Lin, Jian; Peng, Zhiwei; Liu, Yuanyue; Ruiz-Zepeda, Francisco; Ye, Ruquan; Samuel, Errol L G; Yacaman, Miguel Jose; Yakobson, Boris I; Tour, James M

    2014-01-01

    The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp(3)-carbon atoms are photothermally converted to sp(2)-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4?mF?cm(-2) and power densities of ~9?mW?cm(-2). Theoretical calculations partially suggest that enhanced capacitance may result from LIG's unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices. PMID:25493446

  2. Seedless Laser Velocimetry Using Heterodyne Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Balla, R. Jeffrey; Herring, G. C.; Jenkins, Luther N.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    A need exists for a seedless equivalent of laser Doppler velocimetry (LDV) for use in low-turbulence or supersonic flows or elsewhere where seeding is undesirable or impractical. A compact laser velocimeter using heterodyne non-resonant laser-induced thermal acoustics (LITA) to measure a single component of velocity is described. Neither molecular (e.g. NO2) nor particulate seed is added to the flow. In non-resonant LITA two beams split from a short-pulse pump laser are crossed; interference produces two counterpropagating sound waves by electrostriction. A CW probe laser incident on the sound waves at the proper angle is directed towards a detector. Measurement of the beating between the Doppler-shifted light and a highly attenuated portion of the probe beam allows determination of one component of flow velocity, speed of sound, and temperature. The sound waves essentially take the place of the particulate seed used in LDV. The velocimeter was used to study the flow behind a rearward-facing step in NASA Langley Research Center's Basic Aerodynamics Research Tunnel. Comparison is made with pitot-static probe data in the freestream over the range 0 m/s - 55 m/s. Comparison with LDV is made in the recirculation region behind the step and in a well-developed boundary layer in front of the step. Good agreement is found in all cases.

  3. Laser-induced fluorescence instrument for measuring atmospheric SO 2

    NASA Astrophysics Data System (ADS)

    Matsumi, Yutaka; Shigemori, Hiroyuki; Takahashi, Kenshi

    We report on the development of a high-sensitive detection system for measuring atmospheric SO 2 using a laser-induced fluorescence (LIF) technique at around 220 nm. Second harmonics of a tunable broad-band optical parametric oscillator (OPO) pumped by the third harmonic of a Nd:YAG laser is used as a fluorescence excitation source. The laser wavelength is alternatively tuned to the peak and the bottom wavelengths in the photoabsorption spectrum of SO 2 at 220.6 and 220.2 nm, respectively, and the difference signal at the two wavelengths is used to extract the SO 2 concentration. This procedure can give a good selectivity for SO 2 and avoid interferences of fluorescent or particulate species other than SO 2 in the sample air. The SO 2 instrument developed has a sensitivity of 5 pptv in 60 s and S/N=2. The practical performance of the detection system is tested in the suburban area. The inter-comparisons between the LIF instrument and a commercial instrument using Xe flash lamp excitation for the fluorescence detection have been performed. The correlation between two instruments is measured up to 70 ppbv. A good linear relationship between the LIF measurements and commercial instrument measurements is obtained.

  4. Analysis of human nails by laser-induced breakdown spectroscopy.

    PubMed

    Hosseinimakarem, Zahra; Tavassoli, Seyed Hassan

    2011-05-01

    Laser-induced breakdown spectroscopy (LIBS) is applied to analyze human fingernails using nanosecond laser pulses. Measurements on 45 nail samples are carried out and 14 key species are identified. The elements detected with the present system are: Al, C, Ca, Fe, H, K, Mg, N, Na, O, Si, Sr, Ti as well as CN molecule. Sixty three emission lines have been identified in the spectrum that are dominated by calcium lines. A discriminant function analysis is used to discriminate among different genders and age groups. This analysis demonstrates efficient discrimination among these groups. The mean concentration of each element is compared between different groups. Correlation between concentrations of elements in fingernails is calculated. A strong correlation is found between sodium and potassium while calcium and magnesium levels are inversely correlated. A case report on high levels of sodium and potassium in patients with hyperthyroidism is presented. It is shown that LIBS could be a promising technique for the analysis of nails and therefore identification of health problems. PMID:21639580

  5. Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys

    NASA Astrophysics Data System (ADS)

    Summonte, C.; Rizzoli, R.; Servidori, M.; Milita, S.; Nicoletti, S.; Bianconi, M.; Desalvo, A.; Iencinella, D.

    2004-10-01

    Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si1-xCx:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si1-xCx:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250°C or 350°C and the stoichiometry was changed from x =0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248nm ) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x <0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted.

  6. Airborne laser induced fluorescence imaging. Innovative technology summary report

    SciTech Connect

    NONE

    1999-06-01

    Laser-Induced Fluorescence (LIF) was demonstration as part of the Fernald Environmental Management Project (FEMP) Plant 1 Large Scale Demonstration and Deployment Project (LSDDP) sponsored by the US Department of Energy (DOE) Office of Science and Technology, Deactivation and Decommissioning Focus Area located at the Federal Energy Technology Center (FETC) in Morgantown, West Virginia. The demonstration took place on November 19, 1996. In order to allow the contaminated buildings undergoing deactivation and decommissioning (D and D) to be opened to the atmosphere, radiological surveys of floors, walls and ceilings must take place. After successful completion of the radiological clearance survey, demolition of the building can continue. Currently, this process is performed by collecting and analyzing swipe samples for radiological analysis. Two methods are used to analyze the swipe samples: hand-held frisker and laboratory analysis. For the purpose of this demonstration, the least expensive method, swipe samples analyzed by hand-held frisker, is the baseline technology. The objective of the technology demonstration was to determine if the baseline technology could be replaced using LIF.

  7. Kalman Filtered MR Temperature Imaging for Laser Induced Thermal Therapies

    PubMed Central

    Fuentes, D.; Yung, J.; Hazle, J. D.; Weinberg, J. S.; Stafford, R. J.

    2013-01-01

    The feasibility of using a stochastic form of Pennes bioheat model within a 3D finite element based Kalman filter (KF) algorithm is critically evaluated for the ability to provide temperature field estimates in the event of magnetic resonance temperature imaging (MRTI) data loss during laser induced thermal therapy (LITT). The ability to recover missing MRTI data was analyzed by systematically removing spatiotemporal information from a clinical MR-guided LITT procedure in human brain and comparing predictions in these regions to the original measurements. Performance was quantitatively evaluated in terms of a dimensionless L2 (RMS) norm of the temperature error weighted by acquisition uncertainty. During periods of no data corruption, observed error histories demonstrate that the Kalman algorithm does not alter the high quality temperature measurement provided by MR thermal imaging. The KF-MRTI implementation considered is seen to predict the bioheat transfer with RMS error < 4 for a short period of time, ?t < 10sec, until the data corruption subsides. In its present form, the KF-MRTI method currently fails to compensate for consecutive for consecutive time periods of data loss ?t > 10sec. PMID:22203706

  8. Elemental analysis of cotton by laser-induced breakdown spectroscopy

    SciTech Connect

    Schenk, Emily R.; Almirall, Jose R.

    2010-05-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the elemental characterization of unprocessed cotton. This research is important in forensic and fraud detection applications to establish an elemental fingerprint of U.S. cotton by region, which can be used to determine the source of the cotton. To the best of our knowledge, this is the first report of a LIBS method for the elemental analysis of cotton. The experimental setup consists of a Nd:YAG laser that operates at the fundamental wavelength as the LIBS excitation source and an echelle spectrometer equipped with an intensified CCD camera. The relative concentrations of elements Al, Ba, Ca, Cr, Cu, Fe, Mg, and Sr from both nutrients and environmental contributions were determined by LIBS. Principal component analysis was used to visualize the differences between cotton samples based on the elemental composition by region in the U.S. Linear discriminant analysis of the LIBS data resulted in the correct classification of >97% of the cotton samples by U.S. region and >81% correct classification by state of origin.

  9. Update of laser-induced thermotherapy for liver tumors.

    PubMed

    Usatoff, V; Habib, N A

    2001-01-01

    Surgical resection generally offers the only chance of long-term survival for patients with primary or secondary liver tumors. Difficulties relating to the stage of the tumor, the extent of underlying liver cirrhosis and the general condition of the patient make this technique unsuitable for the majority of patients. Many nonresectional methods of in-situ tumor ablation have been recently described. These include alcohol injection, cryotherapy, radiofrequency and intraoperative radiotherapy. Recently more interest has been directed to the use of laser as a source of ablative energy. Laser-induced interstitial thermotherapy is an experimental technique used to destroy tumors within the liver. Initially this was in the form of bare-tipped photocoagulation but the development of a diffuser tip has enabled the formation of larger diameter lesions using heat to produce an area of coagulative necrosis. Less heat is lost if hepatic vascular inflow is occluded during the procedure and consequently a larger area of tumor necrosis is produced. The prospect of a simpler, more efficient system of tumor ablation is attractive so we undertook a review of the current issues surrounding this emerging treatment. PMID:11379302

  10. Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys

    SciTech Connect

    Summonte, C.; Rizzoli, R.; Servidori, M.; Milita, S.; Nicoletti, S.; Bianconi, M.; Desalvo, A.; Iencinella, D. [CNR-IMM Section of Bologna, Via Gobetti 101, I-40129 Bologna (Italy); DICASM, University of Bologna, Viale Risorgimento 2, I-40136 Bologna (Italy)

    2004-10-01

    Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si{sub 1-x}C{sub x}:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si{sub 1-x}C{sub x}:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100 MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250 deg. C or 350 deg. C and the stoichiometry was changed from x=0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248 nm) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x<0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted.

  11. Laser-induced focused ultrasound for nondestructive testing and evaluation

    NASA Astrophysics Data System (ADS)

    Kozhushko, Victor V.; Hess, Peter

    2008-06-01

    Focused ultrasound pulses generated by photoacoustic transformation at a metal surface immersed in water possess a pronounced compression phase on the nanosecond time scale. For 8 ns laser pump pulses, the spectrum of the initially generated ultrasonic pulse covered a frequency range between 0.1 and 150 MHz. A concave spherical geometry of the light-absorbing metal surface can be used to achieve focusing. In the present experiments a conical ultrasound beam was directed at a solid glass plate or silicon wafer, where the tilt of the normal of the metal mirror defined the efficiency of mode conversion at the water-solid interface. Depending on the configuration, focused bulk waves as well as Rayleigh and Lamb waves could be launched in the sample with this setup. The laser probe-beam-deflection method was employed for local detection of elastic disturbances at the sample surface. Due to the nonlinear elastic response of water and harmonics generation, frequencies >100 MHz were realized, despite a strong attenuation in this frequency range. Gradual increase of the laser power density from 5 to 14 MW/cm2 led to shock formation in the compressive pressure pulse in water and shortening of the Rayleigh pulse induced at the surface of the glass plate. The observed transient surface profiles were highly sensitive to nearby mechanical discontinuities such as a microcrack in glass or an edge discontinuity in silicon. Therefore, laser-induced focused ultrasound seems to be a very promising method of accomplishing diverse tasks of nondestructive evaluation.

  12. Infrared laser induced plasma diagnostics of silver target

    SciTech Connect

    Ahmat, L., E-mail: lubnaphysics@yahoo.com; Nadeem, Ali [Laser Spectroscopy Laboratory, National Institute of Lasers and Optronics (NILOP), P.O. Nilore, Islamabad 45650 (Pakistan); Ahmed, I. [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), P.O. Nilore, Islamabad 45650 (Pakistan)

    2014-09-15

    In the present work, the optical emission spectra of silver (Ag) plasma have been recorded and analyzed using the laser induced breakdown spectroscopy technique. The emission line intensities and plasma parameters were investigated as a function of lens to sample distance, laser irradiance, and distance from the target surface. The electron number density (n{sub e}) and electron temperature (T{sub e}) were determined using the Stark broadened line profile and Boltzmann plot method, respectively. A gradual increase in the spectral line intensities and the plasma parameters, n{sub e} from 2.89?×?10{sup 17} to 3.92?×?10{sup 17?}cm{sup ?3} and T{sub e} from 4662 to 8967?K, was observed as the laser irradiance was increased 2.29?×?10{sup 10}–1.06?×?10{sup 11} W cm{sup ?2}. The spatial variations in n{sub e} and T{sub e} were investigated from 0 to 5.25?mm from the target surface, yielding the electron number density from 4.78?×?10{sup 17} to 1.72?×?10{sup 17?}cm{sup ?3} and electron temperature as 9869–3789?K. In addition, the emission intensities and the plasma parameters of silver were investigated by varying the ambient pressure from 0.36 to 1000 mbars.

  13. Laser-induced breakdown spectroscopy in industrial and security applications

    SciTech Connect

    Bol'shakov, Alexander A.; Yoo, Jong H.; Liu Chunyi; Plumer, John R.; Russo, Richard E.

    2010-05-01

    Laser-induced breakdown spectroscopy (LIBS) offers rapid, localized chemical analysis of solid or liquid materials with high spatial resolution in lateral and depth profiling, without the need for sample preparation. Principal component analysis and partial least squares algorithms were applied to identify a variety of complex organic and inorganic samples. This work illustrates how LIBS analyzers can answer a multitude of real-world needs for rapid analysis, such as determination of lead in paint and children's toys, analysis of electronic and solder materials, quality control of fiberglass panels, discrimination of coffee beans from different vendors, and identification of generic versus brand-name drugs. Lateral and depth profiling was performed on children's toys and paint layers. Traditional one-element calibration or multivariate chemometric procedures were applied for elemental quantification, from single laser shot determination of metal traces at {approx}10 {mu}g/g to determination of halogens at 90 {mu}g/g using 50-shot spectral accumulation. The effectiveness of LIBS for security applications was demonstrated in the field by testing the 50-m standoff LIBS rasterizing detector.

  14. Wavelet-based laser-induced ultrasonic inspection in pipes

    NASA Astrophysics Data System (ADS)

    Baltazar-López, Martín E.; Suh, Steve; Chona, Ravinder; Burger, Christian P.

    2006-02-01

    The feasibility of detecting localized defects in tubing using Wavelet based laser-induced ultrasonic-guided waves as an inspection method is examined. Ultrasonic guided waves initiated and propagating in hollow cylinders (pipes and/or tubes) are studied as an alternative, robust nondestructive in situ inspection method. Contrary to other traditional methods for pipe inspection, in which contact transducers (electromagnetic, piezoelectric) and/or coupling media (submersion liquids) are used, this method is characterized by its non-contact nature. This characteristic is particularly important in applications involving Nondestructive Evaluation (NDE) of materials because the signal being detected corresponds only to the induced wave. Cylindrical guided waves are generated using a Q-switched Nd:YAG laser and a Fiber Tip Interferometry (FTI) system is used to acquire the waves. Guided wave experimental techniques are developed for the measurement of phase velocities to determine elastic properties of the material and the location and geometry of flaws including inclusions, voids, and cracks in hollow cylinders. As compared to the traditional bulk wave methods, the use of guided waves offers several important potential advantages. Some of which includes better inspection efficiency, the applicability to in-situ tube inspection, and fewer evaluation fluctuations with increased reliability.

  15. Laser-induced endothelial cell activation supports fibrin formation

    PubMed Central

    Atkinson, Ben T.; Jasuja, Reema; Chen, Vivien M.; Nandivada, Prathima; Furie, Bruce

    2010-01-01

    Laser-induced vessel wall injury leads to rapid thrombus formation in an animal thrombosis model. The target of laser injury is the endothelium. We monitored calcium mobilization to assess activation of the laser-targeted cells. Infusion of Fluo-4 AM, a calcium-sensitive fluorochrome, into the mouse circulation resulted in dye uptake in the endothelium and circulating hematopoietic cells. Laser injury in mice treated with eptifibatide to inhibit platelet accumulation resulted in rapid calcium mobilization within the endothelium. Calcium mobilization correlated with the secretion of lysosomal-associated membrane protein 1, a marker of endothelium activation. In the absence of eptifibatide, endothelium activation preceded platelet accumu-lation. Laser activation of human umbilical vein endothelial cells loaded with Fluo-4 resulted in a rapid increase in calcium mobilization associated cell fluorescence similar to that induced by adenosine diphosphate (10?M) or thrombin (1 U/mL). Laser activation of human umbilical vein endothelial cells in the presence of corn trypsin inhibitor treated human plasma devoid of platelets and cell microparticles led to fibrin for-mation that was inhibited by an inhibitory monoclonal anti–tissue factor antibody. Thus laser injury leads to rapid endothelial cell activation. The laser activated endothelial cells can support formation of tenase and prothrombinase and may be a source of activated tissue factor as well. PMID:20675401

  16. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    NASA Astrophysics Data System (ADS)

    Forni, Olivier; Maurice, Sylvestre; Gasnault, Olivier; Wiens, Roger C.; Cousin, Agnès; Clegg, Samuel M.; Sirven, Jean-Baptiste; Lasue, Jérémie

    2013-08-01

    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches.

  17. Laser induced fluorescence measurements of the cylindrical Hall thruster plume

    SciTech Connect

    Spektor, R.; Diamant, K. D.; Beiting, E. J. [Aerospace Corporation, P.O. Box 92957-M2-341, Los Angeles, California 90009-2957 (United States); Raitses, Y.; Fisch, N. J. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States)

    2010-09-15

    An investigation of a fully cylindrical Hall thruster was performed using laser induced fluorescence (LIF) to measure ion velocity profiles in the plume. The measurements confirm a previously reported 9% increase in the exhaust energy when the cathode keeper draws an excess current (overrun mode). Furthermore, the velocity directions in the plume remain relatively unchanged for the cusped and direct magnetic field configuration in both overrun and nonoverrun modes. Previously reported plume narrowing in the overrun mode was confirmed and found to be due to the shift of the acceleration and ionization regions toward the anode. The electric field inferred from the LIF measurements allowed calculation of the electron ExB drift. Close to the centerline of the thruster, electrons drift azimuthally with velocity decreasing away from the centerline, thus creating shear. This shear can be a source of plasma instabilities and influence electron transport. Further away from the centerline, electrons drift in the opposite direction with their velocity increasing with increasing radius. In that region, electrons rotate without shear.

  18. Evaluation of immunoglobulins in bovine colostrum using laser induced fluorescence.

    PubMed

    Abdel-Salam, Z; Abdel Ghany, Sh; Harith, M A

    2014-11-01

    The objective of the present study was to exploit laser induced fluorescence (LIF) as a spectrochemical analytical technique for evaluation of immunoglobulin (IgG) in bovine colostrum. Colostrum samples were collected from different American Holstein cows at different times after calving. Four samples were gathered from each cow; the first three samples were obtained from the first three milkings (colostrum) and the fourth sample (milk) was obtained a week after calving. It has been demonstrated that LIF can be used as a simple, fast, sensitive and less costly spectrochemical analytical technique for qualitative estimation of IgG in colostrum. LIF results have been confirmed via the quantitative evaluation of IgG in the same samples adopting the single radial immunodiffusion conventional technique and a very good agreement has been obtained. Through LIF it was possible to evaluate bovine colostrum after different milking times and to differentiate qualitatively between colostrum from different animals which may reflect their general health status. A fluorescence linear calibration curve for IgG concentrations from 0 up to 120 g L(-1) has been obtained. In addition, it is feasible to adopt this technique for in situ measurements, i.e. in dairy cattle farms as a simple and fast method for evaluation of IgG in bovine colostrum instead of using lengthy and complicated conventional techniques in laboratories. PMID:25127559

  19. Visualization of plasma turbulence with laser-induced fluorescence (invited)

    SciTech Connect

    Levinton, Fred M.; Trintchouk, Fedor

    2001-01-01

    Turbulence is a key factor limiting the performance of fusion devices. Plasma edge turbulence determines the boundary values of the plasma density and temperature, which in turn determine the internal gradients and controls global plasma transport. In recent years, significant progress has been made in modeling turbulence behavior in plasmas and its effect on transport. Progress has also been made in diagnostics for turbulence measurement; however, there is still a large gap in our understanding of it. An approach to improve this situation is to experimentally visualize the turbulence, that is, a high resolution 2-D image of the plasma density. Visualization of turbulence can improve the connection to theory and help validate theoretical models. One method that has been successfully developed to visualize turbulence in gases and fluids is planar laser-induced fluorescence. We have recently applied this technique to visualize turbulence and structures in a plasma. This was accomplished using an Alexandrite laser that is tunable between 700 and 800 nm, and from 350 to 400 nm with second harmonic generation. The fluorescence light from an argon ion transition has been imaged onto an intensified charged coupled device camera that is gated in synchronization with the laser. Images from the plasma show a rotating structure at 30 kHz in addition to small scale turbulence.

  20. Analysis of bakery products by laser-induced breakdown spectroscopy.

    PubMed

    Bilge, Gonca; Boyac?, ?smail Hakk?; Eseller, Kemal Efe; Tamer, U?ur; Çak?r, Serhat

    2015-08-15

    In this study, we focused on the detection of Na in bakery products by using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method. LIBS experiments were performed to examine the Na at 589nm to quantify NaCl. A series of standard bread sample pellets containing various concentrations of NaCl (0.025-3.5%) were used to construct the calibration curves and to determine the detection limits of the measurements. Calibration graphs were drawn to indicate functions of NaCl and Na concentrations, which showed good linearity in the range of 0.025-3.5% NaCl and 0.01-1.4% Na concentrations with correlation coefficients (R(2)) values greater than 0.98 and 0.96. The obtained detection limits for NaCl and Na were 175 and 69ppm, respectively. Performed experimental studies showed that LIBS is a convenient method for commercial bakery products to quantify NaCl concentrations as a rapid and in situ technique. PMID:25794738

  1. The LILIA (laser induced light ions acceleration) experiment at LNF

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Anania, M. P.; Caresana, M.; Cirrone, G. A. P.; De Martinis, C.; Delle Side, D.; Fazzi, A.; Gatti, G.; Giove, D.; Giulietti, D.; Gizzi, L. A.; Labate, L.; Londrillo, P.; Maggiore, M.; Nassisi, V.; Sinigardi, S.; Tramontana, A.; Schillaci, F.; Scuderi, V.; Turchetti, G.; Varoli, V.; Velardi, L.

    2014-07-01

    Laser-matter interaction at relativistic intensities opens up new research fields in the particle acceleration and related secondary sources, with immediate applications in medical diagnostics, biophysics, material science, inertial confinement fusion, up to laboratory astrophysics. In particular laser-driven ion acceleration is very promising for hadron therapy once the ion energy will attain a few hundred MeV. The limited value of the energy up to now obtained for the accelerated ions is the drawback of such innovative technique to the real applications. LILIA (laser induced light ions acceleration) is an experiment now running at LNF (Frascati) with the goal of producing a real proton beam able to be driven for significant distances (50-75 cm) away from the interaction point and which will act as a source for further accelerating structure. In this paper the description of the experimental setup, the preliminary results of solid target irradiation and start to end simulation for a post-accelerated beam up to 60 MeV are given.

  2. Laser-Induced Temperature Jump Infrared Measurements of RNA Folding

    PubMed Central

    Dyer, R. Brian; Brauns, Eric B.

    2011-01-01

    Probing a sample using infrared spectroscopy following a laser-induced temperature jump is a powerful method to monitor fast relaxation kinetics. Here, we describe how this approach is used to study the kinetics of RNA folding. We begin with a concise summary of the infrared spectral properties of RNA in the 1500–1800 cm?1 region. The infrared transitions in this region are directly related to the double bond stretching vibrations and ring modes of the nucleotide bases. When RNA undergoes a conformational change, the local environments of the nucleotides are altered. Consequently, the changes in the corresponding infrared spectrum are associated with the structural changes. Experimentally, temperature is used to systematically vary the RNA structure. When a short laser pulse is used to produce a rapid temperature increase in the sample, the structural changes that ensue can be followed in real time. In this contribution, we discuss experimental methods including sample preparation, instrumentation, and data analysis. We conclude with several experimental examples that highlight usefulness of the technique. PMID:20946798

  3. Femtosecond laser induced nanostructuring for surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Messaoudi, H.; Das, S. K.; Lange, J.; Heinrich, F.; Schrader, S.; Frohme, M.; Grunwald, R.

    2014-03-01

    The formation of periodical nanostructures with femtosecond laser pulses was used to create highly efficient substrates for surface-enhanced Raman spectroscopy (SERS). We report about the structuring of silver and copper substrates and their application to the SERS of DNA (herring sperm) and protein molecules (egg albumen). The maximum enhancement factors were found on Ag substrates processed with the second harmonic generation (SHG) of a 1-kHz Ti:sapphire laser and structure periods near the SHG wavelength. In the case of copper, however, the highest enhancement was obtained with long-period ripples induced with at fundamental wavelength. This is explained by an additional significant influence of nanoparticles on the surface. Nanostructured areas in the range of 1.25 mm2 were obtained in 10 s. The surfaces were characterized by scanning electron microscopy, Fast Fourier Transform and Raman spectroscopy. Moreover, the role of the chemical modification of the metal structures is addressed. Thin oxide layers resulting from working in atmosphere which improve the biocompatibility were indicated by vibration spectra. It is expected that the detailed study of the mechanisms of laser-induced nanostructure formation will stimulate further applications of functionalized surfaces like photocatalysis, selective chemistry and nano-biology.

  4. Infrared laser induced plasma diagnostics of silver target

    NASA Astrophysics Data System (ADS)

    Ahmat, L.; Ahmed, I.; Nadeem, Ali

    2014-09-01

    In the present work, the optical emission spectra of silver (Ag) plasma have been recorded and analyzed using the laser induced breakdown spectroscopy technique. The emission line intensities and plasma parameters were investigated as a function of lens to sample distance, laser irradiance, and distance from the target surface. The electron number density (ne) and electron temperature (Te) were determined using the Stark broadened line profile and Boltzmann plot method, respectively. A gradual increase in the spectral line intensities and the plasma parameters, ne from 2.89 × 1017 to 3.92 × 1017 cm-3 and Te from 4662 to 8967 K, was observed as the laser irradiance was increased 2.29 × 1010-1.06 × 1011 W cm-2. The spatial variations in ne and Te were investigated from 0 to 5.25 mm from the target surface, yielding the electron number density from 4.78 × 1017 to 1.72 × 1017 cm-3 and electron temperature as 9869-3789 K. In addition, the emission intensities and the plasma parameters of silver were investigated by varying the ambient pressure from 0.36 to 1000 mbars.

  5. Laser-Induced Incandescence Measurements in Low Gravity

    NASA Technical Reports Server (NTRS)

    VanderWal, R. L.

    1997-01-01

    A low-gravity environment offers advantages to investigations concerned with soot growth or flame radiation by eliminating of buoyancy-induced convection. Basic to each type of study is knowledge of spatially resolved soot volume fraction, (f(sub v). Laser-induced incandescence (LII) has emerged as a diagnostic for soot volume fraction determination because it possesses high temporal and spatial resolution, geometric versatility and high sensitivity. Implementation and system characterization of LII in a drop tower that provides 2.2 sec of low-gravity (micro)g) at the NASA Lewis Research Center are described here. Validation of LII for soot volume fraction determination in (micro)g is performed by comparison between soot volume fraction measurements obtained by light extinction [20] and LII in low-gravity for a 50/50 mixture (by volume) of 0 acetylene/nitrogen issuing into quiescent air. Quantitative soot volume fraction measurements within other laminar flames of ethane and propane and a turbulent diffusion flame in (micro)g via LII are also demonstrated. An analysis of LII images of a turbulent acetylene diffusion flame in 1-g and (micro)g is presented.

  6. Laser-induced breakdown spectroscopy for polymer identification.

    PubMed

    Grégoire, Sylvain; Boudinet, Marjorie; Pelascini, Frédéric; Surma, Fabrice; Detalle, Vincent; Holl, Yves

    2011-07-01

    This study aims at differentiating several organic materials, particularly polymers, by laser induced breakdown spectroscopy. The goal is to apply this technique to the fields of polymer recycling and cultural heritage conservation. We worked with some usual polymers families: polyethylene (PE), polypropylene (PP), polyoxymethylene, (POM), poly(vinyl chloride), polytetrafluoroethylene, polyoxyethylene (POE), and polyamide for the aliphatic ones, and poly(butylene terephthalate), acrylonitrile-butadiene-styrene, polystyrene, and polycarbonate for the aromatic ones. The fourth harmonic of a Nd:YAG laser (266 nm) in ambient air at atmospheric pressure was used. A careful analysis of the C(2) Swan system (0,0) band in polymers containing no C-C (POM), few C-C (POE), or aromatic C-C linkages led us to the conclusion that the C(2) signal might be native, i.e., the result of direct ablation from the sample. With use of these results, aliphatic and aromatic polymers could be differentiated. Further data treatments, such as properly chosen line ratios, principal component analysis, and partial least squares regression, were evaluated. It was shown that many polymers could be separated, including PE and PP, despite their similar chemical structures. PMID:21465098

  7. Electron impact ionization and dissociation probed by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Abramzon, Nina

    A combination of electron scattering and laser-induced fluorescence (LIF) techniques has been employed in the direct experimental determination of the absolute N2+(x2?g) ionization cross section as a function of electron energy from threshold to 200 eV. Electron impact on N2 produces N2+ ground-state ions which are detected by pumping the (X2? g+ --> B2?u +) (0,0) vibrational transition at 391 nm with a tunable dye laser and detecting the subsequent LIF of the (B2?u + --> X2?g+) (0,1) vibrational transition at 428 nm. LIF spectra, obtained at different electron energies yield the relative N2+ (X) cross section which is put on an absolute scale by independent calibration to the well-known ``benchmark'' cross section for the production of He atoms in the 2s 3S state by electron impact at 20.4 eV on He in the 1s 1S ground state. Our results are compared with the recent measurement by Doering and Yang (J. Geophysical Research, 102, 9683 (1997)) obtained from electron-electron coincidence (e,2e) experiments at 100 eV and with a recent estimate by Van Zyl and Pendelton (J. Geophysical Research, 100, 23755(1995)).

  8. Dust Removal on Mars Using Laser-Induced Breakdown Spectroscopy

    NASA Technical Reports Server (NTRS)

    Graff, T. G.; Morris, R. V.; Clegg, S. M.; Wiens, R. C.; Anderson, R. B.

    2011-01-01

    Dust coatings on the surface of Mars complicate and, if sufficiently thick, mask the spectral characteristics and compositional determination of underlying material from in situ and remote sensing instrumentation. The Laser-Induced Breakdown Spectroscopy (LIBS) portion of the Chemistry & Camera (ChemCam) instrument, aboard the Mars Science Laboratory (MSL) rover, will be the first active remote sensing technique deployed on Mars able to remove dust. ChemCam utilizes a 5 ns pulsed 1067 nm high-powered laser focused to less than 400 m diameter on targets at distances up to 7 m [1,2]. With multiple laser pulses, dust and weathering coatings can be remotely analyzed and potentially removed using this technique [2,3]. A typical LIBS measurement during MSL surface operations is planned to consist of 50 laser pulses at 14 mJ, with the first 5 to 10 pulses used to analyze as well as remove any surface coating. Additionally, ChemCam's Remote Micro-Imager (RMI) is capable of resolving 200 m details at a distance of 2 m, or 1 mm at 10 m [1,4]. In this study, we report on initial laboratory experiments conducted to characterize the removal of dust coatings using similar LIBS parameters as ChemCam under Mars-like conditions. These experiments serve to better understand the removal of surface dust using LIBS and to facilitate the analysis of ChemCam LIBS spectral data and RMI images.

  9. Time-resolved laser-induced fluorescence system

    NASA Astrophysics Data System (ADS)

    Bautista, F. J.; De la Rosa, J.; Gallegos, F. J.

    2006-02-01

    Fluorescence methods are being used increasingly in the measurement of species concentrations in gases, liquids and solids. Laser induced fluorescence is spontaneous emission from atoms or molecules that have been excited by laser radiation. Here we present a time resolved fluorescence instrument that consists of a 5 ?J Nitrogen laser (337.1 nm), a sample holder, a quartz optical fiber, a spectrometer, a PMT and a PC that allows the measurement of visible fluorescence spectra (350-750 nm). Time response of the system is approximately 5 ns. The instrument has been used in the measurement of colored bond paper, antifreeze, diesel, cochineal pigment and malignant tissues. The data acquisition was achieved through computer control of a digital oscilloscope (using General Purpose Interface Bus GPIB) and the spectrometer via serial (RS232). The instrument software provides a graphic interface that lets make some data acquisition tasks like finding fluorescence spectra, and fluorescence lifetimes. The software was developed using the Lab-View 6i graphic programming package and can be easily managed in order to add more functions to it.

  10. Laser-induced porous graphene films from commercial polymers

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Peng, Zhiwei; Liu, Yuanyue; Ruiz-Zepeda, Francisco; Ye, Ruquan; Samuel, Errol L. G.; Yacaman, Miguel Jose; Yakobson, Boris I.; Tour, James M.

    2014-12-01

    The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp3-carbon atoms are photothermally converted to sp2-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4?mF?cm?2 and power densities of ~9?mW?cm?2. Theoretical calculations partially suggest that enhanced capacitance may result from LIG’s unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices.

  11. Laser induced damage and fracture in fused silica vacuum windows

    SciTech Connect

    Campbell, J.H.; Hurst, P.A.; Heggins, D.D.; Steele, W.A.; Bumpas, S.E.

    1996-11-01

    Laser-induced damage, that initiates catastrophic fracture, has been observed in large ({le}61 cm dia) fused silica lenses that also serve as vacuum barriers in Nova and Beamlet lasers. If the elastic stored energy in the lens is high enough, the lens will fracture into many pieces (implosion). Three parameters control the degree of fracture in the vacuum barrier window: elastic stored energy (tensile stress), ratio of window thickness to flaw depth, and secondary crack propagation. Fracture experiments were conducted on 15-cm dia fused silica windows that contain surface flaws caused by laser damage. Results, combined with window failure data on Beamlet and Nova, were used to develop design criteria for a ``fail-safe`` lens (that may catastrophically fracture but not implode). Specifically, the window must be made thick enough so that the peak tensile stress is less than 500 psi (3.4 MPa) and the thickness/critical flaw size is less than 6. The air leak through the window fracture and into the vacuum must be rapid enough to reduce the load on the window before secondary crack growth occurs. Finite element stress calculations of a window before and immediately following fracture into two pieces show that the elastic stored energy is redistributed if the fragments ``lock`` in place and thereby bridge the opening. In such cases, the peak stresses at the flaw site can increase, leading to further (i.e. secondary) crack growth.

  12. Slag analysis with laser-induced breakdown spectrometry.

    PubMed

    Kraushaar, M; Noll, R; Schmitz, H U

    2003-10-01

    Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis. PMID:14639759

  13. Use of laser induced fluorescence method for phytoplankton communities describing

    NASA Astrophysics Data System (ADS)

    Salyuk, Pavel A.; Bukin, Oleg A.; Permyakov, Mikhail S.

    2005-06-01

    THe seawater flurescence spectra were measured by laser induced fluorescence (LIF) method. ND:YAG laser with frquency-doubled output at 532 nm was used to induce the fluorescence. The laser fluorometer measured the fluorescence spectral distribution in the band from 540 nm to 740 nm. Chlorophyll-a concentration and conventional concentration of dissolved organic matter fluorescence (FDOM) in wavelength range from 560nm to 740nm wer calulated from LIF spectra. The correlation coefficient between chlorophyll-a and FDOM concentrations was calculated in the floating window along ship track. High value coefficient means that FDOM produced by phhytoplankton living on the investigation sea area at the given time interval. Chlorophyll-a-FDOM relationships were described by linear regression. Intercept coefficient is a background FDOM (or FDOM do not produced by phytoplankton living on the investigation sea area in given time interval) and the slope coefficient is FDOM productivity by one ?g/l of chlorophyll-a of phytoplankton. The clusters were determined from calculated slope, intercept and correlation coefficients. The clusters correspond to phytoplankton communities and calculating coefficients characterize condition and the evloution stage of these phytoplakton communities.

  14. Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    W, A. Farooq; M, Atif; W, Tawfik; M, S. Alsalhi; Z, A. Alahmed; M, Sarfraz; J, P. Singh

    2014-12-01

    Laser-induced breakdown spectroscopy (LIBS) technique has been applied to investigate two different types of bacteria, Escherichia coli (B1) and Micrococcus luteus (B2) deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, Cl, Fe, Al, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

  15. Development and applications of laser-induced incandescence

    NASA Technical Reports Server (NTRS)

    Vanderwal, Randy L.; Dietrich, Daniel L.; Zhou, Zhiquang; Choi, Mun Y.

    1995-01-01

    Several NASA-funded investigations focus on soot processes and radiative influences of soot in diffusion flames given their simplicity, practical significance, and potential for theoretical modeling. Among the physical parameters characterizing soot, soot volume fraction, f(sub v), a function of particle size and number density, is often of chief practical interest in these investigations, as this is the geometrical property that directly impacts radiative characteristics and the temperature field of the flame and is basic to understanding soot growth and oxidation processes. Diffusion flames, however, present a number of challenges to the determination of f(sub v) via traditional extinction measurements. Laser-induced incandescence (LII) possesses several advantages compared to line-of-sight extinction techniques for determination of f(sub v). Since LII is not a line-of-sight technique, similar to fluorescence, it possesses geometric versatility allowing spatially resolved measurements of f(sub v) in real time in nonaxisymmetric systems without using deconvolution techniques. The spatial resolution of LII is determined by the detector and imaging magnification used. Neither absorption by polycyclic aromatic hydrocarbons (PAH's) nor scattering contributes to the signal. Temporal capabilities are limited only by the laser pulse and camera gate duration, with measurements having been demonstrated with 10 ns resolution. Because of these advantages, LII should be applicable to a variety of combustion processes involving both homogeneous and heterogeneous phases. Our work has focussed on characterization of the technique as well as exploration of its capabilities and is briefly described.

  16. Chemical characterization of single micro- and nano-particles by optical catapulting-optical trapping-laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Fortes, Francisco J.; Fernández-Bravo, Angel; Javier Laserna, J.

    2014-10-01

    Spectral identification of individual micro- and nano-sized particles by the sequential intervention of optical catapulting, optical trapping and laser-induced breakdown spectroscopy is presented. The three techniques are used for different purposes. Optical catapulting (OC) serves to put the particulate material under inspection in aerosol form. Optical trapping (OT) permits the isolation and manipulation of individual particles from the aerosol, which are subsequently analyzed by laser-induced breakdown spectroscopy (LIBS). Once catapulted, the dynamics of particle trapping depends both on the laser beam characteristics (power and intensity gradient) and on the particle properties (size, mass and shape). Particles are stably trapped in air at atmospheric pressure and can be conveniently manipulated for a precise positioning for LIBS analysis. The spectra acquired from the individually trapped particles permit a straightforward identification of the material inspected. Variability of LIBS signal for the inspection of Ni microspheres was 30% relative standard deviation. OC-OT-LIBS permits the separation of particles in a heterogeneous mixture and the subsequent analysis of the isolated particle of interest. In order to evaluate the sensitivity of the approach, the number of absolute photons emitted by a single trapped particle was calculated. The limit of detection (LOD) for Al2O3 particles was calculated to be 200 attograms aluminium.

  17. Influence of oscillating features of a laser-induced bubble on laser propulsion in water environment near different interfaces

    NASA Astrophysics Data System (ADS)

    Chen, J.; Han, B.; Dou, L.; Pan, Y.-X.; Shen, Z.-H.; Lu, J.; Ni, X.-W.

    2010-12-01

    Laser propulsion in a water environment is influenced by oscillating features of a laser-induced bubble. In our study an optical beam deflection method is used to investigate dynamics of laser-induced semispherical cavitation bubbles near three different interfaces: the rigid boundary (water-solid interface), the free surface (water-air interface) and the liquid-liquid interface (water-soybean oil interface), and in the bulk. The maximum radius of the first bubble oscillation Rmax1 was widened and the collapse time T1 is prolonged in the case of the rigid boundary. Rmax1 is diminished and T1 is shortened in the case of the free surface and the water-oil interface, among which the latter makes Rmax1 even smaller. In order to get the maximum propelling force in different distances near different medium interfaces, different pulse energy of the laser is used. The bubble moves toward the rigid boundary and moves away from the free surface during its oscillations. This will change the application point of the propelling force on the object, and cause a change in the propelling direction of the object.

  18. Laser-induced periodic annular surface structures on fused silica surface

    SciTech Connect

    Liu, Yi; Brelet, Yohann; Forestier, Benjamin; Houard, Aurelien [Laboratoire d'Optique Appliquee, ENSTA/CNRS/Ecole Polytechnique, 828, Boulevard des Marechaux, Palaiseau F-91762 (France)] [Laboratoire d'Optique Appliquee, ENSTA/CNRS/Ecole Polytechnique, 828, Boulevard des Marechaux, Palaiseau F-91762 (France); He, Zhanbing [Electron Microscopy for Materials Research (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp B-2020 (Belgium)] [Electron Microscopy for Materials Research (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp B-2020 (Belgium); Yu, Linwei [Laboratoire de Physique des Interfaces et des Couches Minces, Ecole Polytechnique, CNRS, Palaiseau F-91128 (France)] [Laboratoire de Physique des Interfaces et des Couches Minces, Ecole Polytechnique, CNRS, Palaiseau F-91128 (France); Deng, Yongkai; Jiang, Hongbing [Department of Physics and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871 (China)] [Department of Physics and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2013-06-24

    We report on the formation of laser-induced periodic annular surface structures on fused silica irradiated with multiple femtosecond laser pulses. This surface morphology emerges after the disappearance of the conventional laser induced periodic surface structures, under successive laser pulse irradiation. It is independent of the laser polarization and universally observed for different focusing geometries. We interpret its formation in terms of the interference between the reflected laser field on the surface of the damage crater and the incident laser pulse.

  19. Direct numerical simulation of the interaction of a laser-induced plasma with isotropic turbulence

    Microsoft Academic Search

    Shankar Ghosh

    2008-01-01

    Numerical simulations have been used to study laser-induced breakdown in air and interaction of a laser-induced plasma with isotropic turbulence. A parallel compressible Navier-Stokes solver has been developed for the purpose. A number of numerical issues have been addressed. Three different models for air with increasing levels of physical complexity are used in the simulations. Spherical energy deposition is studied

  20. Pulsed laser induced acoustic wave propagation and interaction in liquid: experiment and simulation

    Microsoft Academic Search

    Sang Gil Ryu; Seung Hwan Ko; Nipun Misra; Heng Pan; Costas P. Grigoropoulos; Nick Kladias; Elias Panides; Gerald A. Domoto

    2008-01-01

    In-situ experimental work on laser induced pressure waves in water is presented in this paper. A double frequency Nd:YAG laser(532 nm, 4 ns pulse width) was irradiated on a chromium thin film on quartz substrate in contact with water. A plane pressure wave with high temporal and spatial resolution was generated by the laser induced thermoelastic stress around 8~12 mJ\\/cm2

  1. A new model for laser-induced thermal damage in the retina

    Microsoft Academic Search

    S. J. Till; J. Till; P. K. Milsom; G. Rowlands

    2003-01-01

    We describe a new model for laser-induced retinal damage. Our treatment is prompted by the failure of the traditional approach\\u000a to accurately describe the image size dependence of laser-induced retinal injuries and by a recently reported study which\\u000a demonstrated that laser injuries to the retina might not appear for up to 48 h post exposure.\\u000a \\u000a We propose that at threshold

  2. Enhanced efficiency of laser shock cleaning process by geometrical confinement of laser-induced plasma

    Microsoft Academic Search

    Deoksuk Jang; Joon Ho Oh; Jong-Myoung Lee; Dongsik Kim

    2009-01-01

    Surface cleaning based on the laser-induced breakdown of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. Accordingly, several studies were performed to expand the cleaning capability of the process. In this work, the cleaning process using laser-induced plasma (LIP) under geometrical confinement is analyzed both theoretically and experimentally. Two-dimensional numerical analysis is conducted

  3. Enhanced Laser-Induced Breakdown Spectroscopy By Second-Pulse Selective Wavelength Excitation

    Microsoft Academic Search

    F. Vidal; M. Chaker; C. Goueguel; S. Laville; H. Loudyi; K. Rifai; M. Sabsabi

    2008-01-01

    We investigate the use of a second laser with a selected wavelength to improve the limit of detection (LoD) of trace elements in the Laser-Induced Breakdown Spectroscopy (LIBS) technique. We consider the combination of LIBS with Laser-Induced Fluorescence (LIF), in which the second laser is used to excite trace elements in the plasma. The influence of the main experimental parameters

  4. Femtosecond laser induced photoluminescence in poly(methyl methacrylate) and three-dimensional optical storage

    Microsoft Academic Search

    Zhaogang Nie; Ki-Soo Lim; Heungyeol Lee; Myeongkyu Lee; Takayoshi Kabayashi

    2011-01-01

    We report on a femtosecond-laser induced photoluminescence (PL) in poly(methyl methacrylate) and its potential application to three-dimensional optical storage. Irradiation with a focused 800nm, 1kHz, 100fs pulsed laser induced a strong PL change in UV–visible region. Absorption spectra and Fourier-transform infrared spectra before and after laser irradiation indicate the PL may result from the emissive oxidized products of photo-degradation reaction

  5. Laser Induced Phonon Spectroscopy of Dppc\\/cholesterol Multibilayers: a New Method of Acoustic Spectroscopy

    Microsoft Academic Search

    Todd Allen Guion

    1992-01-01

    Using Laser Induced Phonon Spectroscopy (LIPS), a novel laser-induced ultrasonic probe, the bulk viscoelastic properties of fully hydrated dipalmitoylphosphatidyl-choline (DPPC) aligned multibilayers and DPPC\\/cholesterol aligned multibilayers were examined. The viscoelastic properties of anisotropic materials are defined by the elastic coefficient (C_{ij}) and the viscosity coefficient (h_{ij}). The initial work on DPPC\\/cholesterol multibilayers, measured only the in-plane coefficient C_{11 } and

  6. Use of fiber optic guided, laser induced acoustic waves for nde

    E-print Network

    Duffer, Charles Edward

    1990-01-01

    USE OF FIBER OPTIC GUIDED, LASER INDUCED ACOUSTIC WAVES FOR NDE A Thesis by CHARLES EDWARD DUFFER Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE December 1990 Major Subject: Mechanical Engineering USE OF FIBER OPTIC GUIDED, LASER INDUCED ACOUSTIC WAVES FOR NDE A Thesis by CHARLES EDWARD DUFFER Approved as to style and content by: Christian P. Burger (Chair of Committee) Peter...

  7. Color separation gratings

    NASA Technical Reports Server (NTRS)

    Farn, Michael W.; Knowlden, Robert E.

    1993-01-01

    In this paper, we describe the theory, fabrication and test of a binary optics 'echelon'. The echelon is a grating structure which separates electromagnetic radiation of different wavelengths, but it does so according to diffraction order rather than by dispersion within one diffraction order, as is the case with conventional gratings. A prototype echelon, designed for the visible spectrum, is fabricated using the binary optics process. Tests of the prototype show good agreement with theoretical predictions.

  8. Wire Diffraction Gratings

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2004-02-01

    In the summer of 1972, I attended the workshop on recreating classic experiments in physics at Barnard College. This was developed by Samuel Devons, and it was a defining experience that set me toward a research career involving early physics teaching apparatus. During the course of the workshop, I became curious about the original diffraction gratings developed by Fraunhofer and built a wire diffraction. A short note about the gratings was published in the American Journal of Physics the next year.2

  9. Laser-induced synergistic effects around absorbing nanoclusters in live cells

    NASA Astrophysics Data System (ADS)

    Zharov, Vladimir P.; Letfullin, Renat R.; Galitovskay, Elena

    2005-04-01

    Background and Objective: The application of nanotechnology for laser thermal-based killing of abnormal cells (e.g. cancer cells) targeted with absorbing nanoparticles (e.g. gold solid nanospheres, nanoshells, or rod) is becoming an extensive area of research. We develop an approach to enhance the efficiency of selective nanophotothermolysis of cancer cells through laser-induced synergistic effects around gold nanoparticles aggregated in nanoclusters on cell membrane. Study Design/Materials and Methods: A concept of selective target damages by laser-induced synergistic interaction of optical, thermal, and acoustic fields around clustered nanoparticles is presented with focus on overlapping bubbles from nanoparticles aggregated on cell's membrane. The experimental verification of this concept in vitro was performed by the use a tunable laser pulses (420-570 nm, 8-12 ns, 0.1-300 ?J, laser flux of 0.1-10 J/cm2) for irradiation of MDA-MB-231 breast cancer cells targeted with primary antibodies to which selecttively 40-nm gold nanoparticles were attached by the means of secondary antibodies. The photothermal, electron and atomic force microscopes in combination with viability test (annexin -V-Propidium iodide) were employed to study the nanoparticle's spatial organization, the dynamics of microbubble formations around the particle's clusters, and cells damage. Results: An aggregation of nanoparticles on cell membrane was observed with simultaneous increase bubble formation phenomena, and red-shifted absorption due to plasmon-plasmon resonances into nanoclusters. It led to a significant enhancement, at least two orders of magnitude, of the efficiency of selectively killing cancer cells with nanosecond laser pulses. Conclusion: Described approach allows using relatively small nanoparticles which would be easier delivery to target site with further creation of nanoclusters with larger sizes which provide more profound thermal and related phenomena leading to more efficient laser killing of cancer cells. This nanocluster model might be promising also for treatment or modification different targets (e.g. bacteria, virus, vascular lesions, fat, etc.) as well as teh use different type energy deposition (focused ultrasound, microwave, magnetic field, etc.).

  10. Grate for coal stove

    SciTech Connect

    Harman, D.P.

    1989-02-14

    A stove grate for guiding fuel in two flows is described. The grate includes a stationary floor extending between opposed ends of the grate; spaced sidewalls extending along the sides of the floor between the ends of the grate. The floor includes an entrance section at one end of the gate, a fire support section at the other end of the grate above the entrance section and rise section means extending upwardly between the entrance section and the fire support section for guiding a lower fuel flow upwardly along the floor to the fire support section. It also guides an upper fuel flow located above the first flow up to fill a fuel reservoir located above the floor at the entrance section and at the lower part of the rise section means without overflowing the sidewalls. A plurality of combustion air openings in the floor of the grate extend along the upper part of the rise section means and along the fire support section, the entrance section and the lower part of the rise section being free of combustion air openings.

  11. Development of a New Time-Resolved Laser-Induced Fluorescence Technique

    NASA Astrophysics Data System (ADS)

    Durot, Christopher; Gallimore, Alec

    2012-10-01

    We are developing a time-resolved laser-induced fluorescence (LIF) technique to interrogate the ion velocity distribution function (VDF) of EP thruster plumes down to the microsecond time scale. Better measurements of dynamic plasma processes will lead to improvements in simulation and prediction of thruster operation and erosion. We present the development of the new technique and results of initial tests. Signal-to-noise ratio (SNR) is often a challenge for LIF studies, and it is only more challenging for time-resolved measurements since a lock-in amplifier cannot be used with a long time constant. The new system uses laser modulation on the order of MHz, which enables the use of electronic filtering and phase-sensitive detection to improve SNR while preserving time-resolved information. Statistical averaging over many cycles to further improve SNR is done in the frequency domain. This technique can have significant advantages, including (1) larger spatial maps enabled by shorter data acquisition time and (2) the ability to average data without creating a phase reference by modifying the thruster operating condition with a periodic cutoff in discharge current, which can modify the ion velocity distribution.

  12. Laser-induced charge-disproportionated metallic state in LaCoO3

    NASA Astrophysics Data System (ADS)

    Izquierdo, M.; Karolak, M.; Trabant, C.; Holldack, K.; Föhlisch, A.; Kummer, K.; Prabhakaran, D.; Boothroyd, A. T.; Spiwek, M.; Belozerov, A.; Poteryaev, A.; Lichtenstein, A.; Molodtsov, S. L.

    2014-12-01

    Understanding the origin of the spin transition in LaCoO3 is one of the long-standing aims in condensed matter physics. Aside from its fundamental interest, a detailed description of this crossover will have a direct impact on the interpretation of the semiconductor-to-metal transition (SMT) and the properties of the high-temperature metallic phase in this compound, which has shown to have important applications in environmentally friendly energy production. To date, the spin transition has been investigated mainly as a function of temperature in thermal equilibrium. These results have hinted at dynamical effects. In this paper, we have investigated the SMT by means of pump-probe soft x-ray reflectivity experiments at the O K , Co L , and La M edges and theoretical calculations within a DFT++ formalism. The results point towards a laser-induced metallization in which the optical transitions stabilize a metallic state with high-spin configuration and increased charge disproportionation.

  13. Assessment of femtosecond laser induced periodic surface structures on polymer films.

    PubMed

    Rebollar, Esther; Vázquez de Aldana, Javier R; Martín-Fabiani, Ignacio; Hernández, Margarita; Rueda, Daniel R; Ezquerra, Tiberio A; Domingo, Concepción; Moreno, Pablo; Castillejo, Marta

    2013-07-21

    In this work we present the formation of laser induced periodic surface structures (LIPSS) on spin-coated thin films of several model aromatic polymers including poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly carbonate bis-phenol A upon irradiation with femtosecond pulses of 795 and 265 nm at fluences well below the ablation threshold. LIPSS are formed with period lengths similar to the laser wavelength and parallel to the direction of the laser polarization vector. Formation of LIPSS upon IR irradiation at 795 nm, a wavelength at which the polymers absorb weakly, contrasts with the absence of LIPSS in this spectral range upon irradiation with nanosecond pulses. Real and reciprocal space characterization of LIPSS obtained by Atomic Force Microscopy (AFM) and Grazing Incidence Small Angle X-ray Scattering (GISAXS), respectively, yields well correlated morphological information. Comparison of experimental and simulated GISAXS patterns suggests that LIPSS can be suitably described considering a quasi-one-dimensional paracrystalline lattice and that irradiation parameters have an influence on the order of such a lattice. Fluorescence measurements, after laser irradiation, provide indirect information about dynamics and structure of the polymer at the molecular level. Our results indicate that the LIPSS are formed by interference of the incident and surface scattered waves. As a result of this process, heating of the polymer surface above its glass transition temperature takes place enabling LIPSS formation. PMID:23728307

  14. Production of aerosols by optical catapulting: Imaging, performance parameters and laser-induced plasma sampling rate

    NASA Astrophysics Data System (ADS)

    Abdelhamid, M.; Fortes, F. J.; Fernández-Bravo, A.; Harith, M. A.; Laserna, J. J.

    2013-11-01

    Optical catapulting (OC) is a sampling and manipulation method that has been extensively studied in applications ranging from single cells in heterogeneous tissue samples to analysis of explosive residues in human fingerprints. Specifically, analysis of the catapulted material by means of laser-induced breakdown spectroscopy (LIBS) offers a promising approach for the inspection of solid particulate matter. In this work, we focus our attention in the experimental parameters to be optimized for a proper aerosol generation while increasing the particle density in the focal region sampled by LIBS. For this purpose we use shadowgraphy visualization as a diagnostic tool. Shadowgraphic images were acquired for studying the evolution and dynamics of solid aerosols produced by OC. Aluminum silicate particles (0.2-8 ?m) were ejected from the substrate using a Q-switched Nd:YAG laser at 1064 nm, while time-resolved images recorded the propagation of the generated aerosol. For LIBS analysis and shadowgraphy visualization, a Q-switched Nd:YAG laser at 1064 nm and 532 nm was employed, respectively. Several parameters such as the time delay between pulses and the effect of laser fluence on the aerosol production have been also investigated. After optimization, the particle density in the sampling focal volume increases while improving the aerosol sampling rate till ca. 90%.

  15. Temperature effect on laser-induced breakdown spectroscopy spectra of molten and solid salts

    SciTech Connect

    Cynthia Hanson; Supathorn Phongikaroon; Jill R. Scott

    2014-07-01

    Laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential analytical tool to improve operations and safeguards for electrorefiners, such as those used in processing spent nuclear fuel. This study set out to better understand the effect of sample temperature and physical state on LIBS spectra of molten and solid salts by building calibration curves of cerium and assessing self-absorption, plasma temperature, electron density, and local thermal equilibrium (LTE). Samples were composed of a LiCl–KCl eutectic salt, an internal standard of MnCl2, and varying concentrations of CeCl3 (0.1, 0.3, 0.5, 0.8, and 1.0 wt.% Ce) under different temperatures (773, 723, 673, 623, and 573 K). Analysis of salts in their molten form is preferred as plasma plumes from molten samples experienced less self-absorption, less variability in plasma temperature, and higher clearance of the minimum electron density required for local thermal equilibrium. These differences are attributed to plasma dynamics as a result of phase changes. Spectral reproducibility was also better in the molten state due to sample homogeneity.

  16. Laser-induced fluorescence spectra of Ba{sup +}*-He exciplexes produced in cold He gas

    SciTech Connect

    Fukuyama, Yoshimitsu; Matsuo, Yukari [RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Moriwaki, Yoshiki [Department of Physics, Toyama University, 3190 Gofuku, Toyama 930-8555 (Japan)

    2004-04-01

    We report the observation of laser-induced fluorescence spectra of Ba{sup +*}-He exciplexes. The experiment is carried out in an environment of cold gaseous helium at a temperature range of 3-30 K. We have observed the emission spectra of exciplexes by means of excitation of the 6p {sup 2}P{sub 32}<-6s {sup 2}S{sub 12} transition of Ba{sup +} ions. It is found that these spectra are redshifted from the D2 emission line in the free space and are composed of several peaks. The experimental results are reproduced well by theoretical calculation of the emission spectra for vibrational levels of Ba{sup +*}-He. We also investigate the vibrational dynamics of the 6p {sup 2}{pi}{sub 32} state of Ba{sup +}*-He, and we have determined the collision-induced vibrational relaxation cross sections of the 6p {sup 2}{pi}{sub 32} state to be 9.7{+-}1.1 A{sup 2} at 15 K.

  17. Temperature effect on laser-induced breakdown spectroscopy spectra of molten and solid salts

    NASA Astrophysics Data System (ADS)

    Hanson, Cynthia; Phongikaroon, Supathorn; Scott, Jill R.

    2014-07-01

    Laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential analytical tool to improve operations and safeguards for electrorefiners, such as those used in processing spent nuclear fuel. This study set out to better understand the effect of sample temperature and physical state on LIBS spectra of molten and solid salts by building calibration curves of cerium and assessing self-absorption, plasma temperature, electron density, and local thermal equilibrium (LTE). Samples were composed of a LiCl-KCl eutectic salt, an internal standard of MnCl2, and varying concentrations of CeCl3 (0.1, 0.3, 0.5, 0.8, and 1.0 wt.% Ce) under different temperatures (773, 723, 673, 623, and 573 K). Analysis of salts in their molten form is preferred as plasma plumes from molten samples experienced less self-absorption, less variability in plasma temperature, and higher clearance of the minimum electron density required for local thermal equilibrium. These differences are attributed to plasma dynamics as a result of phase changes. Spectral reproducibility was also better in the molten state due to sample homogeneity.

  18. Laser-induced growth of nanocrystals embedded in porous materials

    PubMed Central

    2013-01-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows extracting the best experimental conditions to obtain an efficient particle production and to avoid stability or oxidation problems. PMID:23742134

  19. Laser-induced fluorescence in diagnosis of dental caries

    NASA Astrophysics Data System (ADS)

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

    2003-09-01

    The autofluorescence spectra of hard dental tissues, both in normal and pathological areas were investigated in this study. The measurements were performed both on the intact hard tissues of the examined teeth, such as enamel, dentine, cementum, and root canal, and on the tissues pathologically affected by caries (superficial, intermediate, and deep). Various laser wavelengths (337 nm, 488 nm, and 514 nm) were used to irradiate the dental surfaces and a computer-controlled spectrograph captured the fluorescent spectra. The emission signals were stored, measured, analyzed and quantified in terms of wavelength distribution and the relative photon intensity. Results indicated that the fluorescent spectra from healthy enamel, dentine, and cementum were almost identical in form, depending on the excitation wavelength. The intact and affected hard tissues were greatly different in the integral fluorescent intensity. Healthy areas were found to produce the most pronounced fluorescent intensity, whereas the carious regions produced the weaker fluorescent intensity. Independently of the laser excitation wavelength, dentin regions were found to produce the most pronounced fluorescent intensity than any other dental component. The fluorescence signal of carious affected dental structure revealed a reed shifted spectral curve, more pronounced after 488 nm excitation. There was a pronounced red shift for deep caries (crown -- root caries), after ultraviolet laser excitation. Excitation with visible wavelengths did not produce such differences between intact and cervical, deep carious affected tissue. Using a monochromatic light source without any light output at the wavelengths of fluorescence, e.g. a laser with the appropriate filters, the difference in fluorescence between intact and carious enamel was generally easy to observe. Finally, we found that the blue line of an argon ion laser is preferable for superficial caries detection, while the ultraviolet emitting nitrogen laser induces better discrimination in deep caries diagnosis.

  20. Infrared laser-induced decomposition of GAP. [Glycidyl Azido Polymer

    SciTech Connect

    Haas, Y.; Eliahu, Y.B. (Hebrew Univ. of Jerusalem (Israel). Dept. of Physical Chemistry and the Farkas Center for Light Induced Processes); Welner, S. (Armament Development Authority, Haifa (Israel))

    1994-02-01

    The laser-induced decomposition of a solid azido polymer (GAP) is reported. A TEA CO[sub 2] laser (tunable in the 920--1,080 cm[sup [minus]1] range) is used and the dissociation yield is shown to correlate with the one photon absorption spectrum, although about 15 photons per molecule are required to break the weakest bond. At high laser fluence, complete decomposition of the whole sample can be affected using a single laser pulse, leading mostly to gaseous products. When irradiated under vacuum using medium laser fluence (up to 5 J/cm[sup 2]), only a small fraction of the polymer dissociates and the main gaseous products are N[sub 2], Co, C[sub 2]H[sub 4], HCN, and probably H[sub 2]. Many other products are formed in much lesser yields, but two compounds-formaldehyde and ammonia--that have been reported as major products upon thermal decomposition, are absent. In addition a powdery polymeric material containing a [minus]CH=NH group is formed. The overall yield is roughly proportional to the laser pulse energy in the range 30--150 mJ (corresponding to about 1--5 J/cm[sup 2]). Addition of helium or oxygen leads to a dramatic reduction in the HCN relative yield and a smaller reduction of acetylene yield with little change in other major products yields and to the formation of a sticky amber colored polymer. The results are consistent with the initial rupture of a N-N[sub 2] bond of the azido group, followed by creation of reactive species that lead to the formation of the solid polymer and the final gaseous products. The effect of added gases is presumably cooling of these primary reactive species.

  1. Laser induced spark ignition of methane-oxygen mixtures

    NASA Technical Reports Server (NTRS)

    Santavicca, D. A.; Ho, C.; Reilly, B. J.; Lee, T.-W.

    1991-01-01

    Results from an experimental study of laser induced spark ignition of methane-oxygen mixtures are presented. The experiments were conducted at atmospheric pressure and 296 K under laminar pre-mixed and turbulent-incompletely mixed conditions. A pulsed, frequency doubled Nd:YAG laser was used as the ignition source. Laser sparks with energies of 10 mJ and 40 mJ were used, as well as a conventional electrode spark with an effective energy of 6 mJ. Measurements were made of the flame kernel radius as a function of time using pulsed laser shadowgraphy. The initial size of the spark ignited flame kernel was found to correlate reasonably well with breakdown energy as predicted by the Taylor spherical blast wave model. The subsequent growth rate of the flame kernel was found to increase with time from a value less than to a value greater than the adiabatic, unstretched laminar growth rate. This behavior was attributed to the combined effects of flame stretch and an apparent wrinkling of the flame surface due to the extremely rapid acceleration of the flame. The very large laminar flame speed of methane-oxygen mixtures appears to be the dominant factor affecting the growth rate of spark ignited flame kernels, with the mode of ignition having a small effect. The effect of incomplete fuel-oxidizer mixing was found to have a significant effect on the growth rate, one which was greater than could simply be accounted for by the effect of local variations in the equivalence ratio on the local flame speed.

  2. Characterisation of CFRP surface contamination by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawel H.; Sawczak, Miroslaw; Wandowski, Tomasz; Ostachowicz, Wieslaw M.; Cenian, Adam

    2014-03-01

    The application of Carbon Fibre Reinforced Polymers (CFRP) in aeronautics has been increasing. The CFRP elements are joint using rivets and adhesive bonding. The reliability of the bonding limits the use of adhesive bonding for primary aircraft structures, therefore it is important to assess the bond quality. The performance of adhesive bonds depends on the physico-chemical properties of the adhered surfaces. This research is focused on characterization of surfaces before bonding. In-situ examination of large surface materials, determine the group of methods that are preferred. The analytical methods should be non-destructive, enabling large surface analysis in relatively short time. In this work a spectroscopic method was tested that can be potentially applied for surface analysis. Four cases of surface condition were investigated that can be encountered either in the manufacturing process or during aircraft service. The first case is related to contamination of CFRP surface with hydraulic fluid. This fluid reacts with water forming a phosphoric acid that can etch the CFRP. Second considered case was related to silicone-based release agent contamination. These agents are used during the moulding process of composite panels. Third case involved moisture content in CFRP. Moisture content lowers the adhesion quality and leads to reduced performance of CFRP resulting in reduced performance of the adhesive bond. The last case concentrated on heat damage of CFRP. It was shown that laser induced fluorescence method can be useful for non-destructive evaluation of CFRP surface and some of the investigated contaminants can be easily detected.

  3. Detection of uranium using laser-induced breakdown spectroscopy.

    PubMed

    Chinni, Rosemarie C; Cremers, David A; Radziemski, Leon J; Bostian, Melissa; Navarro-Northrup, Claudia

    2009-11-01

    The goal of this work is a detailed study of uranium detection by laser-induced breakdown spectroscopy (LIBS) for application to activities associated with environmental surveillance and detecting weapons of mass destruction (WMD). The study was used to assist development of LIBS instruments for standoff detection of bulk radiological and nuclear materials and these materials distributed as contaminants on surfaces. Uranium spectra were analyzed under a variety of different conditions at room pressure, reduced pressures, and in an argon atmosphere. All spectra displayed a high apparent background due to the high density of uranium lines. Time decay curves of selected uranium lines were monitored and compared to other elements in an attempt to maximize detection capabilities for each species in the complicated uranium spectrum. A survey of the LIBS uranium spectra was conducted and relative emission line strengths were determined over the range of 260 to 800 nm. These spectra provide a guide for selection of the strongest LIBS analytical lines for uranium detection in different spectral regions. A detection limit for uranium in soil of 0.26% w/w was obtained at close range and 0.5% w/w was achieved at a distance of 30 m. Surface detection limits were substrate dependent and ranged from 13 to 150 microg/cm2. Double-pulse experiments (both collinear and orthogonal arrangements) were shown to enhance the uranium signal in some cases. Based on the results of this work, a short critique is given of the applicability of LIBS for the detection of uranium residues on surfaces for environmental monitoring and WMD surveillance. PMID:19891832

  4. Remote laser-induced breakdown spectroscopy (LIBS) for lunar exploration

    NASA Astrophysics Data System (ADS)

    Lasue, J.; Wiens, R. C.; Clegg, S. M.; Vaniman, D. T.; Joy, K. H.; Humphries, S.; Mezzacappa, A.; Melikechi, N.; McInroy, R. E.; Bender, S.

    2012-01-01

    Laser-induced breakdown spectroscopy (LIBS) is an active analytical technique that makes use of a laser pulse to analyze materials of interest at a distance by creating a plasma, which emits photons at characteristic emission line wavelengths. We validate the technique for planetary exploration under vacuum conditions. We review the capability and advantages of the LIBS technique for lunar regolith analysis at 1.5 m distance from a lunar rover, and we characterize its potential for the detection of resources for future exploration, such as the determination of regolith water content. The limits of detection determined for the major elements (typically <1 wt %) help to determine regolith parent material such as feldspathic highland rocks, rocks from the ancient magmatic high magnesian suite (Mg-suite), Fe-rich mare basalts or potassium, rare earth element, and phosphorus-rich (KREEP-rich) samples. Compositional parameters commonly used to classify lunar regoliths such as TiO2, Al2O3, and K2O abundances are readily determined by LIBS. Certain elements support regolith analysis: For example, Ba and Zr can be used to confirm KREEP-like composition, while quantifying the Ni and Co content can be used to infer the amount of meteoritic material. Finally, it is shown that the ice content of lunar soil produces strong H emissions with the LIBS techniques at the 25 wt % H2O level, while measurements on altered basalts give a limit of detection of about 1 wt % for H2O content. This demonstrates that the 5.6 wt % water content detected by the recent LCROSS experiment should be easily detectable and quantifiable by LIBS analysis.

  5. Gold coated nano gratings for atom optics

    NASA Astrophysics Data System (ADS)

    Lonij, Vincent; Perreault, John; Kornilov, Oleg; Cronin, Alex

    2007-06-01

    The Van der Waals (VdW) interaction between neutral atoms is important to the dynamics of mechanical systems on nanometer scales. We used diffraction of sodium atoms from nano gratings to measure the Van der Waals potentials for atoms and different surfaces with improved precision. Atoms passing through the grating acquire an additional phase shift due to the attractive potential between the atoms and the grating bars, causing the diffraction pattern to be modified [1]. Previous measurements reported the VdW coefficient for sodium atoms and a silicon-nitride(SiNx) surface [2]. In our experiment we used a SiNx grating coated with a 2 nm layer of gold and we were able to measure a 40% increase in the VdW coefficient due to the gold. We also improved precision by combing results from the sodium diffraction experiment with results from a diffraction experiment with helium atoms on the same gratings. [1] R. E. Grisenti, W. Schollkopf, J. P. Toennies, G. C. Hegerfeldt, and T. Kohler. Phys. Rev. Lett., 83(9):1755, 1999. [2] J. D. Perreault, A. D. Cronin, and T. A. Savas. Phys. Rev. A, 71(5):053612, 2005.

  6. Ultrafast dynamics of plasma microclouds induced by strong-field ionization in atomic and molecular gases

    Microsoft Academic Search

    Ryan Compton; Alex Filin; Dmitri Romanov; Robert Levis

    2009-01-01

    The model presented for the ultrafast dynamics of laser-induced plasma channels reveals the connections among the fundamental processes of laser-induced tunnel ionization, plasma cooling dynamics of the produced plasma channel, and the residual fluorescence of the channel. The results obtained link the dynamic behavior of the underdense plasma formation with the internal degrees of freedom of the constituent species suggesting

  7. Suppression of laser-induced choroidal neovascularization by intravitreal injection of tristetraprolin

    PubMed Central

    Cho, Yong Wun; Han, Yong Seop; Chung, In Young; Kim, Seong Jae; Seo, Seong Wook; Yoo, Ji Myong; Park, Jong Moon

    2014-01-01

    AIM To examine the effect of intravitreal adenoviral vector-mediated tristetraprolin (Ad-TTP) on VEGF mRNA expression in a rat model of laser-induced choroidal neovascularization. METHODS Ad-TTP was prepared using a commercial kit. Retinal laser-induced photocoagulation (10 spots per eye) was performed on rats in this experimental choroidal neovascularization (CNV) model. Rats were divided into four groups: control (single intravitreal injection of balanced salt solution, n=10), laser-induced CNV (photocoagulation only, n=20), laser-induced CNV plus Ad-TTP injection (photocoagulation plus a single intravitreal Ad-TTP injection, n=20) and Ad-TTP injection only (n=10). Changes in choroidal morphology were evaluated in ten rats in the laser only and the laser plus Ad-TTP groups. Two weeks after laser injury, the size of CNV was calculated by perfusion with high-molecular-weight fluorescein isothiocyanate (FITC)-dextran. VEGF mRNA expression in retina-choroid tissue from ten rats in each group was measured by reverse transcription polymerase chain reaction (RT-PCR). RESULTS Two weeks after treatment, the area of laser-induced CNV was reduced by approximately 60% in the rats given the Ad-TTP injection compared with that in the laser-only group. There was a tendency toward decreased VEGF mRNA expression in the Ad-TTP injection groups. CONCLUSION A single intravitreal injection of Ad-TTP significantly suppressed CNV size in this experimental laser-induced CNV model. Ad-TTP injection also decreased VEGF mRNA expression compared with that in the laser-induced CNV group. The present study is meaningful as the first study to investigate the effect of tristetraprolin delivered via intravitreal injection. PMID:25540745

  8. Experimental study of the spectral characteristics of laser-induced air plasma

    SciTech Connect

    Lin Zhaoxiang; Wu Jinquan; Sun Fenglou; Gong Shunsheng

    2010-05-01

    The characteristics of laser-induced air, N2, and O2 plasma spectra are investigated spectroscopically. The study concentrates mainly on the temporal behavior of laser-induced plasma after breakdown. We used delayed spectra and spectra evolution for this study. Except for the general one-beam laser-induced breakdown experiment, a second laser beam was added to further probe the behavior of plasma during its decay. We report the experimental results of spectra composition, spectra time evolution, and spectra affected by a second laser beam. We determined that all the laser-induced air plasma spectra are from a continuous spectrum and some line spectra superposed on the continuous spectrum. The stronger short wavelength continuous spectrum is caused by bremsstrahlung radiation of electrons in the plasma, and the weaker long wavelength continuous spectrum is caused by electron and ion recombination. Line spectra originate from excited molecules, atoms, and their first-order ions, but no line spectra form higher-order ions. The results show that the temporal behavior of some spectra is a decay-rise-redecay pattern. With the two laser beam experiment we found that all the spectra intensities are enhanced by the second laser beam, but the response of various spectra to the delay of the second laser beam is quite different, in particular, the intensity increments of some spectra increase with the delay of the second laser beam. Some microscopic processes of laser-induced plasma obtained from the experimental results are discussed. These results are useful for a better understanding of some laser-induced air plasma related applications, such as laser-guided lightning and laser-induced breakdown spectroscopy.

  9. Aerosol beam-focus laser-induced plasma spectrometer device

    DOEpatents

    Cheng, Meng-Dawn (Oak Ridge, TN)

    2002-01-01

    An apparatus for detecting elements in an aerosol includes an aerosol beam focuser for concentrating aerosol into an aerosol beam; a laser for directing a laser beam into the aerosol beam to form a plasma; a detection device that detects a wavelength of a light emission caused by the formation of the plasma. The detection device can be a spectrometer having at least one grating and a gated intensified charge-coupled device. The apparatus may also include a processor that correlates the wavelength of the light emission caused by the formation of the plasma with an identity of an element that corresponds to the wavelength. Furthermore, the apparatus can also include an aerosol generator for forming an aerosol beam from bulk materials. A method for detecting elements in an aerosol is also disclosed.

  10. Bioanalytical and photophysical applications of sensitive nonlinear wave-mixing spectroscopy based on laser-induced gratings

    Microsoft Academic Search

    James Eugene Knittle

    2004-01-01

    Nonlinear degenerate four-wave mixing is presented as a sensitive optical absorption-based detection and measurement technique for condensed-phase systems. By taking advantage of the inherent properties of this method, one can design a measurement system offering minimal optical path lengths (less than 100 mum) and miniscule probe volumes (often approaching just a few pico liters) using a single laser. This is

  11. Laser-Induced Thermal Acoustic Measurements in a Highly Back-Pressured Scramjet Isolator Model: A Research Plan

    NASA Technical Reports Server (NTRS)

    Middleton, Troy F.; Balla, Robert J.; Baurle, Robert A.; Wilson, Lloyd G.

    2008-01-01

    Under the Propulsion Discipline of NASA s Fundamental Aeronautics Program s Hypersonics Project, a test apparatus, for testing a scramjet isolator model, is being constructed at NASA's Langley Research Center. The test apparatus will incorporate a 1-inch by 2-inch by 15-inch-long scramjet isolator model supplied with 2.1 lbm/sec of unheated dry air through a Mach 2.5 converging-diverging nozzle. The planned research will incorporate progressively more challenging measurement techniques to characterize the flow field within the isolator, concluding with the application of the Laser-Induced Thermal Acoustic (LITA) measurement technique. The primary goal of this research is to use the data acquired to validate Computational Fluid Dynamics (CFD) models employed to characterize the complex flow field of a scramjet isolator. This paper describes the test apparatus being constructed, pre-test CFD simulations, and the LITA measurement technique.

  12. Application of underwater shock wave and laser-induced liquid jet to neurosurgery

    NASA Astrophysics Data System (ADS)

    Tominaga, T.; Nakagawa, A.; Hirano, T.; Sato, J.; Kato, K.; Hosseini, S. H. R.; Takayama, K.

    2006-03-01

    Paper deals with applications of underwater shock waves to medicine. A historical development of underwater shock wave generation by using pulsed Ho:YAG laser beam irradiation in water is briefly described and an overview is given regarding potential applications of shock waves to neuro-surgery. The laser beam irradiation in a liquid-filled catheter produces water vapor bubble and shock waves intermittently produces micro-liquid jets in a controlled fashion from the exit of the catheter. Correlations between shock dynamics and bubble dynamics are emphasized. To optimize the jet motion, results of basic parametric studies are briefly presented. The liquid jet discharged from the catheter exit has an impulse high enough to clearly exhibit effectiveness for various medical purposes. In liquid jets we observed reasonably strong shock waves and hence invented a compact shock generator aiming to apply to microsurgery. We applied it to a rat's bone window and developed an effective method of brain protection against shock loading. The insertion of Gore-Tex® sheet is found to attenuate shock waves drastically even for very short stand off distance and its physical mechanism is clarified. The laser-induced liquid jet (LILJ) is successfully applied to soft tissue dissection. Animal experiments were performed and results of histological observations are presented in details. Results of animal experiments revealed that LILJ can sharply dissect soft tissue with a minimum amount of liquid consumption, while blood vessels larger than 0.2 mm in diameter are preserved. Shock waves and LILJ have a potential to be indispensable tools in neuro-surgery.

  13. Application of femtosecond-laser induced nanostructures in optical memory.

    PubMed

    Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka; Qiu, Jiarong; Kazansky, Peter G; Fujita, Koji; Hirao, Kazuyuki

    2007-01-01

    The femtosecond laser induced micro- and nanostructures for the application to the three-dimensional optical data storage are investigated. We have observed the increase of refractive index due to local densification and atomic defect generation, and demonstrated the real time observation of photothermal effect after the femtosecond laser irradiation inside a glass by the transient lens (TrL) method. The TrL signal showed a damped oscillation with about an 800 ps period. The essential feature of the oscillation can be reproduced by the pressure wave creation and propagation to the outward direction from the irradiated region. The simulation based on elastodynamics has shown that a large thermoelastic stress is relaxed by the generation of the pressure wave. In the case of soda-lime glass, the velocity of the pressure wave is almost same as the longitudinal sound velocity at room temperature (5.8 microm/ns). We have also observed the localized photo-reduction of Sm3+ to Sm2+ inside a transparent and colorless Sm(3+)-doped borate glass. Photoluminescence spectra showed that some the Sm3+ ions in the focal spot within the glass sample were reduced to Sm2+ ions after femtosecond laser irradiation. A photo-reduction bit of 200 nm in three-dimensions can be recorded with a femtosecond laser and readout clearly by detecting the fluorescence excited by Ar+ laser (lambda = 488 nm). A photo-reduction bit can be also erased by photo-oxidation with a cw Ar+ laser (lambda = 514.5 nm). Since photo-reduction bits can be spaced 150 nm apart in a layer within glass, a memory capacity of as high as 1 Tbit can be achieved in a glass piece with dimensions of 10 mm x 10 mm x 1 mm. We have also demonstrated the first observation of the polarization-dependent periodic nanostructure formation by the interference between femtosecond laser light and electron acoustic waves. The observed nanostructures are the smallest embedded structures ever created by light. The period of self-organized nanostructures can be controlled from approximately 140 to 320 nm by the pulse energy and the number of irradiated pulses. Furthermore, we have also observed the self-assembled sub-wavelength periodic structures created in silica glass by femtosecond pulses on the plane of the propagation of light. PMID:17455477

  14. Birefringence Bragg Binary (3B) grating, quasi-Bragg grating and immersion gratings

    NASA Astrophysics Data System (ADS)

    Ebizuka, Noboru; Morita, Shin-ya; Yamagata, Yutaka; Sasaki, Minoru; Bianco, Andorea; Tanabe, Ayano; Hashimoto, Nobuyuki; Hirahara, Yasuhiro; Aoki, Wako

    2014-07-01

    A volume phase holographic (VPH) grating achieves high angular dispersion and very high diffraction efficiency for the first diffraction order and for S or P polarization. However the VPH grating could not achieve high diffraction efficiency for non-polarized light at a large diffraction angle because properties of diffraction efficiencies for S and P polarizations are different. Furthermore diffraction efficiency of the VPH grating extinguishes toward a higher diffraction order. A birefringence binary Bragg (3B) grating is a thick transmission grating with optically anisotropic material such as lithium niobate or liquid crystal. The 3B grating achieves diffraction efficiency up to 100% for non-polarized light by tuning of refractive indices for S and P polarizations, even in higher diffraction orders. We fabricated 3B grating with liquid crystal and evaluated the performance of the liquid crystal grating. A quasi-Bragg (QB) grating, which consists long rectangle mirrors aligned in parallel precisely such as a window shade, also achieves high diffraction efficiency toward higher orders. We fabricated QB grating by laminating of silica glass substrates and glued by pressure fusion of gold films. A quasi-Bragg immersion (QBI) grating has smooth mirror hypotenuse and reflector array inside the hypotenuse, instead of step-like grooves of a conventional immersion grating. An incident beam of the QBI grating reflects obliquely at a reflector, then reflects vertically at the mirror surface and reflects again at the same reflector. We are going to fabricate QBI gratings by laminating of mirror plates as similar to fabrication of the QB grating. We will also fabricate silicon and germanium immersion gratings with conventional step-like grooves by means of the latest diamond machining methods. We introduce characteristics and performance of these gratings.

  15. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B. (Shoreham, NY)

    1986-01-01

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  16. Analysis of plutonium oxide surrogate residue using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Hongbo; Yueh, Fang Yu; Miller, Tracy; Singh, Jagdish P.; Zeigler, Kristine E.; Marra, James C.

    2008-09-01

    Laser-induced breakdown spectroscopy was used to determine the elemental composition of a CeO 2 composite powder for process control verification during lanthanide borosilicate glass fabrication. Cerium oxide is used as a surrogate for plutonium oxide, which along with other canister contents will be combined with frit to make glass. Laser-induced breakdown spectroscopy data for the composition of the CeO 2 batch containing concentrations of Ce, Cr, Si, Fe, Ta, Ni, Zn, Al Mg, Gd, and W were quantitatively determined from laser-induced breakdown spectroscopy spectra of both pellet and powder samples. The results of both forms were compared and it was determined that the pellet data gave slightly better precision than the powder sample.

  17. Sensitive Measurement of Trace Mercury Using Low Pressure Laser-Induced Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Zhenzhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Zhang, Xiaobo; Yan, Junjie; Liu, Jiping

    2013-11-01

    The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results.

  18. Nanosecond laser induced damage in RbTiOPO4: the missing influence of crystal quality.

    PubMed

    Hildenbrand, Anne; Wagner, Frank R; Natoli, Jean-Yves; Commandré, Mireille

    2009-09-28

    Nanosecond laser induced damage in RbTiOPO(4) (RTP) an isomorphic material to the more widely known KTiOPO(4) (KTP) is studied in crystals with varying properties. The ionic conductivity along the z-axes of the tested crystals ranged from 1.5 10(-9) S/cm to 1.1 10(-12) S/cm. Further, different growth sectors with different absorption in the range of hundreds of ppm/cm and differing zones in inhomogeneous crystals have been investigated. Despite these important differences in crystal quality, no significant difference could be observed in the laser damage resistance at 1064 nm. Thus growth induced defects only play a minor role in nanosecond laser induced damage in RTP. Transient, laser induced defects are discussed in analogy with KTP as possible laser damage precursors. PMID:19907617

  19. Photophysics of Laser Dye-Doped Polymer Membranes for Laser-Induced Fluorescence Photogrammetry

    NASA Technical Reports Server (NTRS)

    Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.

    2004-01-01

    Laser-induced fluorescence target generation in dye-doped polymer films has recently been introduced as a promising alternative to more traditional photogrammetric targeting techniques for surface profiling of highly transparent or reflective membrane structures. We investigate the photophysics of these dye-doped polymers to help determine their long-term durability and suitability for laser-induced fluorescence photogrammetric targeting. These investigations included experimental analysis of the fluorescence emission pattern, spectral content, temporal lifetime, linearity, and half-life. Results are presented that reveal an emission pattern wider than normal Lambertian diffuse surface scatter, a fluorescence time constant of 6.6 ns, a pump saturation level of approximately 20 micro J/mm(exp 2), and a useful lifetime of more than 300,000 measurements. Furthermore, two demonstrations of photogrammetric measurements by laser-induced fluorescence targeting are presented, showing agreement between photogrammetric and physically measured dimensions within the measurement scatter of 100 micron.

  20. Laser-induced plasmas in ambient air for incoherent broadband cavity-enhanced absorption spectroscopy.

    PubMed

    Ruth, Albert A; Dixneuf, Sophie; Orphal, Johannes

    2015-03-01

    The emission from a laser-induced plasma in ambient air, generated by a high power femtosecond laser, was utilized as pulsed incoherent broadband light source in the center of a quasi-confocal high finesse cavity. The time dependent spectra of the light leaking from the cavity was compared with those of the laser-induced plasma emission without the cavity. It was found that the light emission was sustained by the cavity despite the initially large optical losses of the laser-induced plasma in the cavity. The light sustained by the cavity was used to measure part of the S1 ? S0 absorption spectrum of gaseous azulene at its vapour pressure at room temperature in ambient air as well as the strongly forbidden ?-band in molecular oxygen: b1?g+(?'=2)?X3?g-(?''=0). PMID:25836833

  1. Anti-SPARC oligopeptide inhibits laser-induced CNV in mice

    PubMed Central

    Uehara, Hironori; Luo, Ling; Simonis, Jacquelyn; Singh, Nirbhai; Taylor, Ethan Will; Ambati, Balamurali K.

    2010-01-01

    It is known that SPARC gates VEGF-A signal transduction towards KDR, the primary angiogenic VEGF receptor. We sought to determine whether inhibition of SPARC activity using anti-SPARC peptide could inhibit laser-induced CNV by promoting binding of VEGF-A to FLT-1. We created anti-SPARC L-peptide and retro-inverso anti-SPARC D-peptide. Anti-SPARC peptides or PBS were injected intravitreally one day before or after laser induction. Intravitreal injection of anti-SPARC L-peptide one day before laser induction promotes Flt-1 phosphorylation and inhibited laser-induced CNV and anti-SPARC D-peptide had no effect. Injection one day after laser injury did not affect size of laser-induced CNV. Inhibition of SPARC activity could be complementary to existing anti–CNV therapy. PMID:20005890

  2. Laser-induced breakdown spectroscopy detection of heavy metal in water based on graphite conch method

    NASA Astrophysics Data System (ADS)

    Wang, Chunlong; Liu, Jianguo; Zhao, Nanjing; Shi, Huan; Liu, Lituo; Ma, Mingjun; Zhang, Wei; Chen, Dong; Liu, Jing; Zhang, Yujun; Liu, Wenqing

    2012-10-01

    The laser-induced breakdown spectroscopy emission characteristics of trace heavy metal lead in water is studied based on graphite conch method, with a 1064nm wavelength Nd: YAG laser as excitation source, the echelle spectrometer and ICCD detector are used for spectral separation and high sensitive detection with high resolution and wide spectral range. The delay time 900ns and gate time 1600ns are determined in the experiment. The calibration curve of Pb is plotted based on the different concentration measurement results, and a limit of detection of 0.0138mg / L is obtained for Pb in water. Graphite conch method effectively overcomes the current problems on laser-induced breakdown spectroscopy detection of heavy metal in water. The detection limits and stability are improved. The reference data is provided for further study on the fast measurement of trace heavy metals in water by laser induced breakdown spectroscopy technique.

  3. [Study on physical deviation factors on laser induced breakdown spectroscopy measurement].

    PubMed

    Wan, Xiong; Wang, Peng; Wang, Qi; Zhang, Qing; Zhang, Zhi-Min; Zhang, Hua-Ming

    2013-10-01

    In order to eliminate the deviation between the measured LIBS spectral line and the standard LIBS spectral line, and improve the accuracy of elements measurement, a research of physical deviation factors in laser induced breakdown spectroscopy technology was proposed. Under the same experimental conditions, the relationship of ablated hole effect and spectral wavelength was tested, the Stark broadening data of Mg plasma laser induced breakdown spectroscopy with sampling time-delay from 1.00 to 3.00 micros was also studied, thus the physical deviation influences such as ablated hole effect and Stark broadening could be obtained while collecting the spectrum. The results and the method of the research and analysis can also be applied to other laser induced breakdown spectroscopy experiment system, which is of great significance to improve the accuracy of LIBS elements measuring and is also important to the research on the optimum sampling time-delay of LIBS. PMID:24409698

  4. Femtosecond laser induced associative desorption of H2 from Ru(0001): comparison of "first principles" theory with experiment.

    PubMed

    Luntz, A C; Persson, M; Wagner, S; Frischkorn, C; Wolf, M

    2006-06-28

    A three dimensional model based on molecular dynamics with electronic frictions is developed to describe the femtosecond laser induced associative desorption of H2 from Ru(0001)(1 x 1)H. Two molecular coordinates (internuclear separation d and center of mass distance to surface z) and a single phonon coordinate are included in the dynamics. Both the potential energy surface and the electronic friction tensor are calculated by density functional theory so that there are no adjustable parameters in the comparison of this model with the wide range of experiments available for this system. This "first principles" dynamic model gives results in semiquantitative agreement with all experimental results; nonlinear fluence dependence of the yield, isotope effect, two pulse correlation, and energy partitioning. The good agreement of theory with experiment supports a description of this surface femtochemistry in terms of thermalized hot electron induced chemistry with coupling to nuclear coordinates through electronic frictions. By comparing the dynamics with the analytical one dimensional frictional model used previously to fit the experiments for this system, we show that the success of the one dimensional model is based on the rapid intermixing of the z and d coordinates as the H-H climbs out of the adsorption well. However, projecting the three dimensional dynamics onto one dimension introduces a fluence (adsorbate temperature) dependent "entropic" barrier in addition to the potential barrier for the chemistry. This implies that some caution must be used in interpreting activation energies obtained in fitting experiments to the one dimensional model. PMID:16821991

  5. Tactile discrimination of gratings

    Microsoft Academic Search

    J. W. Morley; A. W. Goodwin; I. Darian-Smith

    1983-01-01

    Human subjects were required to differentiate grating surfaces of alternating grooves and ridges by moving a finger back and forth across the surface. Their discriminative capacities were measured, as well as the movement and force profiles that they selected. To measure discrimination, a forced choice paradigm was used in which three surfaces were presented on each trial. Two surfaces were

  6. Bragg grating rogue wave

    E-print Network

    Degasperis, Antonio; Aceves, Alejandro B

    2015-01-01

    We derive the rogue wave solution of the classical massive Thirring model, that describes nonlinear optical pulse propagation in Bragg gratings. Combining electromagnetically induced transparency with Bragg scattering four-wave mixing, may lead to extreme waves at extremely low powers.

  7. Simultaneous spatially and temporally resolved laser induced incandescence and laser induced fluorescence measurements in jet propulsion fuel 8 and heptane pool fires

    NASA Astrophysics Data System (ADS)

    Henriksen, Tara Leigh

    Medium scale pool fires can be used to validate models of large scale accidental fires. In order to provide a relevant data set for model validation, laser induced incandescence (LII) was used to quantify soot volume fraction levels in heavily sooting pool fires of JP-8 and heptane. Qualitative measurements of OH were simultaneously imaged by a laser induced fluorescence (LIF) light sheet spatially overlapping the LII sheet. Findings are presented and the challenges of simultaneous imaging in heavily sooting turbulent conditions are identified. Supplemental multichord light extinction measurements served to calibrate the LII system, qualify the degree of axisymmetry of the turbulent flames, determine a correlation between extinction frequency and puffing frequency, and provide an independent method of measuring average soot volume fraction. Soot refractive index variation with sampling height (residence time) was investigated, and a discussion about whether or not diagnostic measurements warrant correction for its variation are discussed.

  8. Multiscale analysis of the laser-induced damage threshold in optical coatings

    SciTech Connect

    Capoulade, Jeremie; Gallais, Laurent; Natoli, Jean-Yves; Commandre, Mireille

    2008-10-10

    We have investigated the influence of laser beam size on laser-induced damage threshold (LIDT) in the case of single- and multiple-shot irradiation. The study was performed on hafnia thin films deposited with various technologies (evaporation, sputtering, with or without ion assistance). LIDT measurements were carried out at 1064 nm and 12 ns with a spot size ranging from a few tens to a few hundreds of micrometers, in 1-on-1 and R-on-1 modes. These measurements were compared with simulations obtained with the statistical theory of laser-induced damage caused by initiating inclusions.

  9. Escherichia coli identification and strain discrimination using nanosecond laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Diedrich, Jonathan; Rehse, Steven J.; Palchaudhuri, Sunil

    2007-04-01

    Three strains of Escherichia coli, one strain of environmental mold, and one strain of Candida albicans yeast have been analyzed by laser-induced breakdown spectroscopy using nanosecond laser pulses. All microorganisms were analyzed while still alive and with no sample preparation. Nineteen atomic and ionic emission lines have been identified in the spectrum, which is dominated by calcium, magnesium, and sodium. A discriminant function analysis has been used to discriminate between the biotypes and E. coli strains. This analysis showed efficient discrimination between laser-induced breakdown spectroscopy spectra from different strains of a single bacteria species.

  10. Evaluation of a laser-induced fluorescence system for uranium analysis

    SciTech Connect

    White, L.E.

    1980-05-01

    A laser-induced fluorescence method for total uranium analysis of industrial process waters, waste waters, and leachates has been evaluated as a possible alternative for the normal, sodium fluoride and lithium fluoride, flame-fusion fluorescence method currently employed. Since the lower reporting limit of the laser fluorometer is on the order of 0.05 ..mu..g/L, samples for normal analysis can usually be diluted from 100 to 1000 fold which virtually eliminates interferences from quenching substances. Also, since the uranium determination is done in aqueous solution, laser-induced fluorescence entirely eliminates the need for organic extraction and the subsequent fusion process.

  11. Transition probabilities of Ni II spectral lines measured by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Manrique, J.; Aguilera, J. A.; Aragón, C.

    2013-05-01

    Experimental transition probabilities for 48 lines of the transition array 3d84s-3d84p of Ni II have been obtained by laser induced breakdown spectroscopy. A procedure based on the measurement and fitting of curves of growth that avoids the systematic error due to self-absorption has been used. The laser induced plasmas are generated using a Nd:YAG laser from a set of Ni-Cu alloys with different Ni concentrations. A comparison is made of our results with the available experimental and theoretical values.

  12. Single-Walled Carbon Nanotubes, Carbon Nanofibers and Laser-Induced Incandescence

    NASA Technical Reports Server (NTRS)

    Schubert, Kathy (Technical Monitor); VanderWal, Randy L.; Ticich, Thomas M.; Berger, Gordon M.; Patel, Premal D.

    2004-01-01

    Laser induced incandescence applied to a heterogeneous, multi-element reacting flows is characterized by a) temporally resolved emission spectra, time-resolved emission at selected detection wavelengths and fluence dependence. Laser fluences above 0.6 Joules per square centimeter at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence beyond this value lead to a super-heated plasma, well above the vaporization of temperature of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solid-like structures.

  13. Online compositional analysis in coal gasification environment using laser-induced plasma technology

    NASA Astrophysics Data System (ADS)

    Deng, Kung-Li; Wu, Juntao; Wang, Zhe; Lee, Boon; Guida, Renato

    2006-08-01

    Integrated Gasification Combined Cycle (IGCC) power plants have great potential for future clean-coal power generation. Today, the quality of coal is measured by sampling coal using various offline methods, and the syn-gas composition is determined by taking samples downstream of the gasifier and measured by gas chromatograph (GC). Laser induced plasma technology has demonstrated high sensitivity for elementary detection. The capability of free space transmission and focusing of laser beam makes laser induced plasma a unique technology for online compositional analysis in coal gasification environment and optimization control.

  14. Laser induced damage thresholds and laser safety levels. Do the units of measurement matter?

    NASA Astrophysics Data System (ADS)

    Wood, R. M.

    1998-04-01

    The commonly used units of measurement for laser induced damage are those of peak energy or power density. However, the laser induced damage thresholds, LIDT, of all materials are well known to be absorption, wavelength, spot size and pulse length dependent. As workers using these values become divorced from the theory it becomes increasingly important to use the correct units and to understand the correct scaling factors. This paper summarizes the theory and highlights the danger of using the wrong LIDT units in the context of potentially hazardous materials, laser safety eyewear and laser safety screens.

  15. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    SciTech Connect

    Chen, Anmin [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China) [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China); Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Ding, Dajun [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)] [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Shao, Junfeng; Wang, Tingfeng [State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)] [State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Huang, Xuri [Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China)] [Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China); Jin, Mingxing [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China) [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2013-10-15

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  16. Describing Autophagy via Analysis of Individual Organelles by Capillary Electrophoresis with Laser Induced Fluorescence Detection

    PubMed Central

    Satori, Chad P.

    2013-01-01

    Autophagy is a cellular process responsible for the degradation of intracellular cargo. Its dynamic nature and the multiple types of autophagy organelles present at a given time make current measurements, such as those done by Western blotting, insufficient to understand autophagy and its roles in aging and disease. Capillary electrophoresis coupled to laser induced fluorescence detection (CE-LIF) has been used previously to count and determine properties of individual organelles, but has never been used on autophagy organelles or for determination of changes of such properties. Here we used autophagy organelles isolated from L6 cells expressing GFP-LC3, which is an autophagy marker, to develop a CE-LIF method for the determination of the number of autophagy organelles, their individual GFP-LC3 fluorescence intensities, and their individual electrophoretic mobilities. These properties were compared under basal and rapamycin-driven autophagy, which showed differences in the number of detected organelles and electrophoretic mobility distributions of autophagy organelles. Vinblastine treatment was also used to halt autophagy and further characterize changes and provide additional insight on the nature of autophagy organelles. This approach revealed dramatic and opposite directions in changes of organelle numbers, GFP-LC3 contents, and electrophoretic mobilities during the duration of the vinblastine treatment. These trends suggested the identity of organelle types being detected. These observations demonstrate that individual organelle analysis by CE-LIF is a powerful technology to investigate the complexity and nature of autophagy, a process that plays critical roles in response to drug treatments, aging, and disease. PMID:24164243

  17. Visualization of two-phase fluid distributions using laser-induced exciplex fluorescence

    NASA Astrophysics Data System (ADS)

    Kim, Jonguk

    Experimental optical methods have been developed for the purpose of visualizing two-phase fluid distributions. Laser-induced exciplex (excited state complex) fluorescence has been used to generate two-dimensional images of dispersed liquid and vapor phases with spectrally well resolved two-color emissions. In this method, the vapor phase is tagged by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. For the purpose of observing the highly turbulent dynamic behavior of injected liquid through a small orifice, exciplex visualization provides a non-intrusive diagnostic with good spectral and spatial resolution. A new exciplex visualization system consisting of DMA (N,N-dimethylaniline) and 1,4,6-TMN (trimethylnaphthalene) in an isooctane (2,2,4- trimethylpentane) solvent was developed. Among the many formulations tested, a 5%DMA?5%1,4,6-TMN exciplex system, in 90% isooctane solvent, showed outstanding optical characteristics. The kinetics of exciplex formation and decay have been examined as a function of temperature and pressure in detail and related to the photophysics of the system. The direct calibration of the fluorescence intensity as a function of the fluorescing dopant concentrations then permitted the determination of quantitative concentration maps of liquid and vapor phases in the flow-field. The exciplex visualization methods developed have been applied to examine a liquid- vapor spray which evolves rapidly in time and space. The results have a direct bearing on the fuel injection process in the direct-injection spark-ignition engine and will lead to improved understanding of engine efficiency and the formation of pollutants.

  18. Thermal loading of laser induced plasma shockwaves on thin films in nanoparticle removal

    SciTech Connect

    Varghese, Ivin; Zhou Dong; Peri, M. D. Murthy; Cetinkaya, Cetin [Department of Mechanical and Aeronautical Engineering, Center for Advanced Materials Processing, Wallace H. Coulter School of Engineering, Clarkson University, Potsdam, New York 13699-5725 (United States)

    2007-06-01

    Damage concerns, such as substrate/film material alterations, damage, and delamination of thin films, have become a central problem in sub-100 nm particle removal applications. In the laser induced plasma (LIP) removal technique both LIP shockwave and radiation heating are potential sources of thermomechanical damage. The specific objective of current study is to conduct a computational investigation of the LIP shockwave effect on the thermoelastic response of a thin chromium (Cr) film deposited on a quartz substrate and to identify the conditions leading to the onset of plastic film deformations. The experimentally characterized shockwave pressure and temperature (approximated from gas dynamic relations) were prescribed as boundary conditions in the computational analysis. From the shockwave arrival times for different travel distances, the shockwave radius as well as the velocity were obtained as a function of the shockwave propagation time. Radial (and circumferential) stresses, caused by thermal expansion of the Cr film, were most dominant and, hence, of damage concern. It is determined that the resultant temperature rise utilizing a 1064 nm Nd:yttrium-aluminum-garnet (YAG) laser (450 mJ) due to the film-shockwave interactions was not sufficiently high to initiate film and/or substrate damage. No material alteration/damage of the Cr film is predicted due to the temperature and pressure of LIP shockwaves at the firing distance of 2 mm, with a high strain rate gain factor of two (minimum), though damage was observed experimentally for 1064 nm Nd:YAG laser at the pulse energy of 370 mJ. Reported results indicate that the leading cause of observed thin film damage during nanoparticle removal is almost certainly radiation heating from the LIP core.

  19. Laser-Induced Acoustic Desorption Coupled with a Linear Quadrupole Ion Trap Mass Spectrometer

    PubMed Central

    Habicht, Steven C.; Amundson, Lucas M.; Duan, Penggao; Vinueza, Nelson R.; Kenttämaa, Hilkka I.

    2009-01-01

    In recent years, laser-induced acoustic desorption (LIAD) coupled with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer has been demonstrated to provide a valuable technique for the analysis of a wide variety of nonvolatile, thermally labile compounds, including analytes that could not previously be analyzed by mass spectrometry. Although FT-ICR instruments are very powerful, they are also large and expensive, and hence mainly used as research instruments. In contrast, linear quadrupole ion trap (LQIT) mass spectrometers are common due to several qualities that make these instruments attractive for both academic and industrial settings, such as high sensitivity, large dynamic range, and experimental versatility. Further, the relatively small size of the instruments, comparatively low cost and the lack of a magnetic field provide some distinct advantages over FT-ICR instruments. Hence, we have coupled the LIAD technique with a commercial LQIT, the Finnigan LTQ mass spectrometer. The LQIT was modified for a LIAD probe by outfitting the removable back plate of the instrument with a 6” ConFlat flange (CFF) port, gate valve and sample lock. Reagent ions were created using the LQIT's atmospheric pressure ionization source and trapped in the mass analyzer for up to 10 s to allow chemical ionization reactions with the neutral molecules desorbed via LIAD. These initial experiments focused on demonstrating the feasibility of performing LIAD in the LQIT. Hence, the results are compared to those obtained using an FT-ICR mass spectrometer. Despite the lower efficiency in the transfer of desorbed neutral molecules into the ion trap, and the smaller maximum number of available laser pulses, the higher intrinsic sensitivity of the LQIT resulted in a net higher sensitivity relative to the FT-ICR. PMID:20000769

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

    SciTech Connect

    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

    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.

  1. Numerical modelling of a straw-fired grate boiler

    Microsoft Academic Search

    Søren K. Kær

    2004-01-01

    The paper presents a computational fluid dynamics (CFD) analysis of a 33MW straw-fired grate boiler. Combustion on the grate plays a key-role in the analysis of these boilers and in this work a stand-alone code was used to provide inlet conditions for the CFD analysis. Model predictions were compared with available gas temperature and species concentration measurements showing good agreement.

  2. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

    1998-05-26

    An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

  3. Numerical Simulation of Laser-Induced Rayleigh Wave and Its Interaction with SubSurface Void in Solid

    Microsoft Academic Search

    Zhao Yan; Shen Zhonghua; Lu Jian; Ni Xiaowu; Cui Yiping

    2010-01-01

    In this paper, the laser-induced Rayleigh wave and its interaction with sub-surface void in solid is numerically simulated by the finite element method. Typical calculation is executed for laser induced Rayleigh wave at the surface of solid without void and solid with circular void. The results provide necessary theoretical background for the nondestructive detection of laser ultrasonic.

  4. Imaging monitoring techniques applications in the transient gratings detection

    NASA Astrophysics Data System (ADS)

    Zhao, Qing-ming

    2009-07-01

    Experimental studies of Degenerate four-wave mixing (DFWM) in iodine vapor at atmospheric pressure and 0? and 25? are reported. The Laser-induced grating (LIG) studies are carried out by generating the thermal grating using a pulsed, narrow bandwidth, dye laser .A new image processing system for detecting forward DFWM spectroscopy on iodine vapor is reported. This system is composed of CCD camera, imaging processing card and the related software. With the help of the detecting system, phase matching can be easily achieved in the optical arrangement by crossing the two pumps and the probe as diagonals linking opposite corners of a rectangular box ,and providing a way to position the PhotoMultiplier Tube (PMT) . Also it is practical to know the effect of the pointing stability on the optical path by monitoring facula changing with the laser beam pointing and disturbs of the environment. Finally the effects of Photostability of dye laser on the ration of signal to noise in DFWM using forward geometries have been investigated in iodine vapor. This system makes it feasible that the potential application of FG-DFWM is used as a diagnostic tool in combustion research and environment monitoring.

  5. Dark current and light illumination effects on grating formation during periodic long-term operation in photorefractive polymers

    SciTech Connect

    Fujihara, T. [Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Mamiya, J. [Chemical Resources Laboratory, Tokyo Institute of Technology, R1-12, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Kawamoto, M. [Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Nano Medical Engineering Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Sassa, T., E-mail: tsassa@riken.jp [Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)

    2014-01-14

    Photorefractive grating formation dynamics in long-timescale writing and the effects of periodic writing through the control of writing beam irradiation or electric field application were investigated using typical photorefractive polymers. Both dark current and writing beam irradiation affected grating formation dynamics. Dark current in polymers changed the effective trap density over time through deep trap filling and/or detrapping and thus affected grating formation considerably. The writing beam irradiation also affected grating development in the presence of an electric field owing to the accumulation of filled deep traps. However, grating development recovered after the elimination of the electric field freed up the filled deep traps.

  6. Water cooled rolling grate incinerator

    SciTech Connect

    Ettehadieh, B.

    1991-08-27

    This patent describes a water cooled roller grate incinerator cooperatively associated with a boiler. It comprises cylindrical shaped roller grates, each having a plurality of circular arrays of spaced apart cooling tubes separated by perforated webs and connected at each end to a ring header; a rotary joint associated with each cylindrical roller grate for supplying cooling fluid to the circular array of tubes to keep them cool and returning heated fluid to the boiler; each roller grate being disposed to rotate about a centrally disposed axis; the axes of the roller grates being disposed in an inclined plane generally parallel to each other so as to form an undulating surface; a waster hopper with a waste feed ram disposed on the lower end of the hopper for feeding waste to the undulating surface; a combustion air system for supplying combustion air through the perforated webs to the waste pushed on the undulating surface by the waste feed ram to burn the waste; a separate drive system for each grate, the drive system regulating the rate at which the burning waste progresses across the undulating surface portion of each grate as the grates rotate transferring the waste from one roller grate to the next lower roller grate as the waste burns.

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

    Microsoft Academic Search

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

    2010-01-01

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

  8. Laser-Induced Damage Threshold and Certification Procedures for Optical Materials

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This document provides instructions for performing laser-induced-damage-threshold tests and pass-fail certification tests on optical materials used in pulsed-laser systems. The optical materials to which these procedures apply include coated and uncoated optical substrates, laser crystals, Q-switches, polarizers, and other optical components employed in pulsed-laser systems.

  9. Laser-induced fluorescence of metal-atom impurities in a neutral beam

    SciTech Connect

    Burrell, C.F.; Pyle, R.V.; Sabetimani, Z.; Schlachter, A.S.

    1984-10-01

    The need to limit impurities in fusion devices to low levels is well known. We have investigated, by the technique of laser-induced fluorescence, the concentration of heavy-metal atoms in a neutral beam caused by their evaporation from the hot filaments in a conventional high-current multifilament hydrogen-ion source.

  10. A combined OH\\/acetone planar laser-induced fluorescence imaging technique for visualizing combusting flows

    Microsoft Academic Search

    B. Yip; M. F. Miller; A. Lozano; R. K. Hanson

    1994-01-01

    A combined OH\\/acetone planar laser-induced fluorescence (PLIF) imaging technique that provides simultaneous visualizations of regions of unburned fuel and of combustion in a reacting flow is described. OH marks the location of chemical reaction and of combustion products, and acetone vapor, which is seeded into the fuel stream, marks unburned fuel. A single pulse from an ultraviolet laser is used

  11. Particle image velocimetry and planar laser-induced fluorescence measurements on lobed jet mixing flows

    E-print Network

    Hu, Hui

    Particle image velocimetry and planar laser-induced fluorescence measurements on lobed jet mixing have been used to reduce take-off jet noise and speci®c fuel consumption (SFC) (Tillman and Presz 1993 of the vortical and turbulent structures in lobed jet mixing ¯ows was con- ducted. The techniques of planar laser

  12. EFFECT OF LASER INDUCED CRYSTALLINITY MODIFICATION ON BIODEGRADATION PROFILE OF POLY(L-LACTIC ACID)

    E-print Network

    Yao, Y. Lawrence

    EFFECT OF LASER INDUCED CRYSTALLINITY MODIFICATION ON BIODEGRADATION PROFILE OF POLY(L-LACTIC ACID attention due to their biocompatibility and biodegradability. Being biodegradable, poly(L-lactic acid) (PLLA it favorable in drug delivery because it hydrolyzes in the human body into lactic acid, which is then excreted

  13. Laser induced fluorescence in a pulsed argon plasma Earl Scime,a)

    E-print Network

    Choueiri, Edgar

    Laser induced fluorescence in a pulsed argon plasma Earl Scime,a) Costel Biloiu, Christopher fluorescence (LIF) technique for pulsed argon plasmas is described. A low power, tunable diode laser pumps detection, i.e., using a lock-in amplifier. Pulsed plasmas present the additional challenge of requiring

  14. PAPER www.rsc.org/loc | Lab on a Chip Laser-induced cavitation based micropump

    E-print Network

    Ohl, Claus-Dieter

    of cavitation in microfluidics, for example in microfluidic phase- change heat-exchangers.6 Yet, in the authorsPAPER www.rsc.org/loc | Lab on a Chip Laser-induced cavitation based micropump Rory Dijkinka as versatile and robust pumping techniques. Here, we present a cavitation based technique, which is able

  15. Femtosecond laser-induced cavitations in the lens of the human eye

    Microsoft Academic Search

    Line Kessel; Jose Nymand; Michael Harbst; Mike van der Poel; Lars Eskildsen; Michael Larsen

    2007-01-01

    Ultrafast femtosecond lasers are used increasingly for a wide range of medical purposes. The immediate tissue response to pulses above a certain threshold is optically or laser induced breakdown, which is often visible as gas-filled cavities that persist for some time. In the present study, we attempted to define the cavitation threshold in the human lens in vitro using multiphoton

  16. Near-infrared, laser-induced fluorescence detection for DNA sequencing applications

    Microsoft Academic Search

    Steven A. Soper; D. C. Williams; R. P. Hammer

    1996-01-01

    Laser-induced fluorescence detection has become the detection strategy of choice in many large-scale DNA sequencing applications due to its ease of Implementation, sensitivity and the ability to identify the constituent bases of DNA in a single separation lane when the probes used have a distinct spectral characteristic. While the common strategy is to use fluorescent dyes which show absorption and

  17. Evidence of laser induced decomposition of triaminotrinitrobenzene from surface enhanced Raman spectroscopy

    Microsoft Academic Search

    F. J. Owens

    2011-01-01

    It is observed that the focused 632 nm laser of the confocal micro-Raman spectrometer decomposes triaminotrinitrobenzene (TATB). The temperature generated in the laser spot determined by measuring the ratio of the intensities of the anti-Stokes to Stokes spectra is too low to cause thermal decomposition. The observed decomposition is suggested to be a result of laser induced electronic excitation. The

  18. Laser-induced deflection (LID) technique for thermal lens evaluation and direct absorption measurements

    Microsoft Academic Search

    Ch. Mühlig; A. Bochmann; W. Triebel; S. Kufert

    2008-01-01

    Thermal lens effects are one of the major problems in using optics for high power laser applications such as optical lithography or material processing. The thermal lens results from the combination of the absorption in the bulk material or the optical coatings, the thermal conductivity and the temperature change of the refractive index (dn\\/dT). We present how the laser induced

  19. Laser induced deflection (LID) method for absolute absorption measurements of optical materials and thin films

    Microsoft Academic Search

    Christian Mühlig; Simon Bublitz; Wolfgang Paa

    2011-01-01

    We use optimized concepts to measure directly low absorption in optical materials and thin films at various laser wavelengths by the laser induced deflection (LID) technique. An independent absolute calibration, using electrical heaters, is applied to obtain absolute absorption data without the actual knowledge of the photo-thermal material properties. Verification of the absolute calibration is obtained by measuring different silicon

  20. Use of laser induced breakdown spectroscopy for the analysis of poultry products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Laser Induced Breakdown Spectroscopy is evaluated as a potential method to characterize a wide range of poultry product quality and safety characteristics. In one part of this study, breast meat quality indices, including pH and water holding capacity, were treated as dependent variables for correla...

  1. Laser induced plane acoustic wave generation, propagation, and interaction with rigid structures in water

    Microsoft Academic Search

    Seung H. Ko; Sang G. Ryu; Nipun Misra; Heng Pan; Costas P. Grigoropoulos; Nick Kladias; Elias Panides; Gerald A. Domoto

    2008-01-01

    Short pulsed laser induced single acoustic wave generation, propagation, interaction with rigid structures, and focusing in water are experimentally and numerically studied. A large area short duration single plane acoustic wave was generated by the thermoelastic interaction of a homogenized nanosecond pulsed laser beam with a liquid-solid interface and propagated at the speed of sound in water. Laser flash schlieren

  2. Physical characteristics and biological effects of laser-induced stress waves

    Microsoft Academic Search

    A. G. Doukas; T. J. Flotte

    1996-01-01

    Laser-induced stress waves can be generated by one of the following mechanisms: optical breakdown, ablation, or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The effects of stress waves on cells and tissues can be quite

  3. Laser-induced fluorescence images of NO distribution after needle-plane pulsed negative corona discharge

    Microsoft Academic Search

    Gregory J. Roth; Martin A. Gundersen

    1999-01-01

    Images showing the spatial distribution of nitric oxide (NO) following propagation of a 30 ns pulsed, negative streamer between needle-plane electrodes, in 25 parts per million (ppm) NO seeded air, are reported. The images were generated using laser-induced fluorescence, and show uniform destruction of 10 ppm NO between the cathode and anode. This evidence shows that processes associated with the

  4. Laser-induced breakdown spectrometry — applications for production control and quality assurance in the steel industry

    Microsoft Academic Search

    Reinhard Noll; Holger Bette; Adriane Brysch; Marc Kraushaar; Ingo Mönch; Laszlo Peter; Volker Sturm

    2001-01-01

    Recent progress in sensitivity and signal processing opened a broad field of application for laser-induced breakdown spectrometry (LIBS) in the steel making and processing industry. Analyzed substances range from top gas of the blast furnace, via liquid steel up to finished products. This paper gives an overview of R&D activities and first routine industrial applications of LIBS. The continuous knowledge

  5. Study of mid IR fiber transmission and mode patterns under laser induced stimulated Brillouin scattering

    NASA Technical Reports Server (NTRS)

    Yu, C.; Chong, Yat C.; Zhou, Hongyi

    1990-01-01

    Mid IR fiber transmission and exit radiation mode patterns at various incident CO2 laser power levels appear to be effective diagnostic tools for monitoring laser induced stimulated Brillouin scattering in various mid IR fibers. Such processes are deemed to be essential mechanisms for fiber-optic amplifiers and switches as potential replacements of current repeaters and bistable devices.

  6. Detection of fecal residue on poultry carcasses by laser induced fluorescence imaging techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential use of laser-induced fluorescence imaging techniques was investigated for the detection of diluted fecal matters from various parts of the digestive tract, including colon, ceca, small intestine, and duodenum, on poultry carcasses. One of the challenges for using fluorescence imaging f...

  7. Characterization of colloidal particles by laser-induced plasma spectroscopy (LIPS)

    Microsoft Academic Search

    C. Haisch; J. Liermann; U. Panne; R. Niessner

    1997-01-01

    To study the nature and abundance of colloids in aquifer systems Laser-Induced Plasma Spectroscopy (LIPS) was used for elemental analysis of heavy metal colloids with particle diameters between 0.1 and 1 ?m. Different experimental approaches to the qualitative and quantitative characterization of inorganic colloids are examined. Some of the inherent problems associated with a direct detection are discussed. A direct

  8. Thermal loading of laser induced plasma shockwaves on thin films in nanoparticle removal

    Microsoft Academic Search

    Ivin Varghese; Dong Zhou; M. D. Murthy Peri; Cetin Cetinkaya

    2007-01-01

    Damage concerns, such as substrate\\/film material alterations, damage, and delamination of thin films, have become a central problem in sub-100 nm particle removal applications. In the laser induced plasma (LIP) removal technique both LIP shockwave and radiation heating are potential sources of thermomechanical damage. The specific objective of current study is to conduct a computational investigation of the LIP shockwave

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

    Microsoft Academic Search

    Danielle Cleveland; Robert G. Michel

    2010-01-01

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

  10. Structures of soot generated by laser induced pyrolysis of metal-graphite composite targets

    Microsoft Academic Search

    E. Muñoz; A. M. Benito; L. C. Estepa; J. Fernández; Y. Maniette; M. T. Martínez; G. F. de la Fuente

    1998-01-01

    The first results of a novel laser induced pyrolysis (LIP) method for high yield production of fullerene and single walled nanotubes are reported. The pyrolysis process of graphite targets is carried out by means of a continuous CO2 laser under a flowing argon atmosphere. The vaporization of the targets and the deposition of the generated soot take place in a

  11. Tuning micropillar cavity birefringence by laser induced surface defects Cristian Bonato,1,a

    E-print Network

    Exter, Martin van

    Tuning micropillar cavity birefringence by laser induced surface defects Cristian Bonato,1,a Dapeng properties of micropillar cavities by creating small defects on the sample surface near the cavity region a controlled and permanent birefringence to the optical micropillar cavities. In this way the frequency shift

  12. Optimization of laser-induced fluorescence detection system for microfluidic chip

    Microsoft Academic Search

    Pan Shi; Xiaoming Hu; Qin Li

    2008-01-01

    Laser-induced fluorescence (LIF) detection is widely utilized in microfluidic chip due to its high sensitivity and selectivity. In this paper, a LIF detection system for the microscope chip based on a 473 nm laser diode is described. To improve the performance of the detection system, the confocal configuration is adopted in our experiment. Some factors that are important to the

  13. Line laser beam based laser-induced fluorescence detection system for microfluidic chip electrophoresis analysis

    Microsoft Academic Search

    Baojian Xu; Mo Yang; Hua Wang; Honglian Zhang; Qinghui Jin; Jianlong Zhao; Huimin Wang

    2009-01-01

    In this work, a new laser-induced fluorescence (LIF) detection system based on a line laser beam for microfluidic chip electrophoresis analysis was developed. This detection system had the advantages of simple optical structure, compactness, and ease in constructing. Highly sensitive detection was realized by detecting the fluorescence light emitted in the micro-channel through the vertical intersection between the line laser

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

    Microsoft Academic Search

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

    2010-01-01

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

  15. Feasibility of Detection and Identification of Individual Bioaerosols Using Laser-Induced

    E-print Network

    Hahn, David W.

    of Bacillus atrophaeous, Bacillus pumilus, and Bacil- lus stearothemophilus were introduced into an aerosol laser-induced breakdown spectroscopy (LIBS) is investigated using aerosolized Bacillus spores. Spores flow stream in a prescribed manner such that single-par- ticle LIBS detection was realized. Bacillus

  16. Luminescence from acoustic-driven laser-induced cavitation bubbles Claus-Dieter Ohl*

    E-print Network

    Ohl, Claus-Dieter

    Luminescence from acoustic-driven laser-induced cavitation bubbles Claus-Dieter Ohl* Drittes second harmonic driving. However, the need to levitate a bubble by the same sound field may limit at infinity is P P0 Pa(t), where Pa(t) is the imposed acoustic driving term. We assume a sinusoidal

  17. Monte Carlo simulation of laser induced chemical vapor deposition Yehuda Zeiri, Uzi Atzmony, and Joseph Bloch

    E-print Network

    Zeiri, Yehuda

    Monte Carlo simulation of laser induced chemical vapor deposition Yehuda Zeiri, Uzi Atzmony 21 September 1989; accepted for publication 30 November 1990) We have used a Monte Carlo method developed a Monte Carlo procedure which was used to simulate the LICVD process. The beam inten- sities used

  18. Prospects for single-molecule detection in liquids by laser-induced fluorescence

    SciTech Connect

    Trkula, M.; Keller, R.A.; Martin, J.C.; Jett, J.H.; Dovichi, N.J.

    1983-01-01

    A laser-induced fluoresence determination of aqueous solutions of rhodamine 6G resulted in a detection limit of 18 attograms, or 22,000 molecules, of rhodamine 6G. These results allow the projection to single-molecule detection with reasonable improvements in the experimental apparatus.

  19. Characterization of laser induced plasmas by optical emission spectroscopy: A review of experiments and methods

    Microsoft Academic Search

    C. Aragon; J. A. Aguilera

    2008-01-01

    Advances in characterization of laser induced plasmas by optical emission spectroscopy are reviewed in this article. The review is focused on the progress achieved in the determination of the physical parameters characteristic of the plasma, such as electron density, temperature and densities of atoms and ions. The experimental issues important for characterization by optical emission spectroscopy, as well as the

  20. MULTISPECTRAL LASER-INDUCED FLUORESCENCE IMAGING SYSTEM FOR LARGE BIOLOGICAL SAMPLES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Presented is a detailed description of a common aperture, multispectral laser-induced fluorescence imaging system developed to allow detection of fecal matter on agricultural products. With an expanded, 355 nm, Nd:YAG laser beam as the excitation source, fluorescence emission images in the blue, gr...