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Sample records for laser-induced dynamic gratings

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

    SciTech Connect

    Rohlfing, E.A.

    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. Study of Mass Diffusion and Relaxation Processes in Polymer Systems by Laser Induced Holographic Grating Relaxation and Dynamic Light Scattering.

    NASA Astrophysics Data System (ADS)

    Xia, Jiulin

    The diffusion of dye molecules in various polymer systems is studied using the Laser Induced Holographic Grating Relaxation technique. The diffusion coefficients of camphorquinone (CQ), thymoquinone (TQ), diacetyl (DA) and azo compounds in these polymers are studied as a function of temperature, properties of both the polymers and the dye molecules. The effects of additives are also investigated. Due to the chemical reversibility of the azo compounds, the kinetics of their chemical processes are also analyzed. The mutual diffusion coefficients in poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) compatible polymer blends are measured by dynamic light scattering as a function of the molecular weight of PEO while keeping the molecular weight of PMMA fixed. The polymer chain relaxation processes of poly(isobornyl methacrylate) (PIMA) are also studied by using dynamic light scattering.

  3. Laser-induced transient grating setup with continuously tunable period

    NASA Astrophysics Data System (ADS)

    Vega-Flick, A.; Eliason, J. K.; Maznev, A. A.; Khanolkar, A.; Abi Ghanem, M.; Boechler, N.; Alvarado-Gil, J. J.; Nelson, K. A.

    2015-12-01

    We present a modification of the laser-induced transient grating setup enabling continuous tuning of the transient grating period. The fine control of the period is accomplished by varying the angle of the diffraction grating used to split excitation and probe beams. The setup has been tested by measuring dispersion of bulk and surface acoustic waves in both transmission and reflection geometries. The presented modification is fully compatible with optical heterodyne detection and can be easily implemented in any transient grating setup.

  4. 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.

  5. Femtosecond laser induced damage characterization of transmission volume phase gratings

    NASA Astrophysics Data System (ADS)

    Martnez-Matos, .; Hernndez-Garay, M. P.; Izquierdo, J. G.; Vaveliuk, P.; Baares, L.; Calvo, M. L.

    2014-07-01

    A procedure to characterize the induced damage and the incubation effects in volume transmission gratings under femtosecond laser pulse train illumination is presented. It was also developed a formalism that explains the damage processes. Our proposal was employed on glass gratings to show the effectiveness of the method and its potential to design transmission gratings with enhanced laser induced damage threshold. This procedure is able to be extended to any transmission grating composed by chemically non-uniform material, opening up new perspectives to femtosecond laser pulse shaping.

  6. Measuring Temperature By Laser-Induced-Grating Spectroscopy

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.

    1995-01-01

    Temperature computed from speed of laser-induced counter-propagating acoustic waves. Interference between intersecting pumping laser beams gives rise to spatially periodic heating, which in turn, creates oscillating diffraction grating probed by another laser beam. Oscillations in diffracted probe-laser intensity correspond to oscillations of counter-propagating acoustic waves generated by spatially periodic heating.

  7. Single shot thermometry using laser induced thermal grating

    NASA Astrophysics Data System (ADS)

    Qu, Pubo; Guan, Xiaowei; Zhang, Zhenrong; Wang, Sheng; Li, Guohua; Ye, Jingfeng; Hu, Zhiyun

    2015-05-01

    With the concern of environmental protection and reducing the fossil fuel consumption, combustion processes need to be more efficient and less contaminable. Therefore, the ability to obtain important thermophysical parameters is crucial to combustion research and combustor design. Traditional surveying techniques were difficult to apply in a confined space, especially the physically intrusions of detectors can alter the combustion processes. Laser-based diagnostic techniques, like CARS, SVRS, PLIF and TDLAS, allow the in situ, non-intrusive, spatially and temporally resolved measurements of combustion parameters in hostile environments. We report here a new non-intrusive optical diagnostic technique, based on laser-induced thermal grating. Thermal gratings generated in NO2/N2 binary mixtures, arise from the nonlinear interaction between the medium and the light radiation from the interference of two pulsed, frequency-doubled Nd:YAG lasers (532 nm). This leads to the formation of a dynamic grating through the resonant absorption and the subsequent collisional relaxation. By the temporally resolved detection of a continuous wave, frequency-doubled Nd:YVO4 probe laser beam (671 nm) diffracted by LITG. The temporal behavior of the signal is a function of the local temperature and other properties of gas, various parameters of the target gas can be extracted by analyzing the signal. The accurate singleshot temperature measurements were carried out at different test conditions using a stainless steel pressurized cell, data averaged on 100 laser shots were compared with simultaneously recorded thermocouple data, and the results were consistent with each other. The LITG signal is shown to grow with increasing the gas pressure and is spatially coherent, which makes the LITG thermometry technique a promising candidate in high pressure environments.

  8. Properties and Applications of Laser-Induced Gratings in Rare Earth Doped Glasses.

    NASA Astrophysics Data System (ADS)

    Behrens, Edward Grady

    Scope and method of study. Four-wave-mixing techniques were used in an attempt to create permanent laser-induced grating in Pr^{3+}-, Nd ^{3+}-, Eu^ {3+}-, and Er^{3+ }-doped glasses. The permanent laser-induced grating signal intensity and build-up and erase times were investigated as function of the write beam crossing angle, write beam power, and temperature. Thermal lensing measurements were conducted on Eu^{3+} - and Nd^{3+}-doped glasses and room temperature Raman and resonant Raman spectra were obtained for Eu^{3+}-doped glasses. The permanent laser-induced grating signal intensity was studied in Eu^{3+} -doped alkali-metal glasses as a function of the alkali -metal network modifier ion and a model was developed by treating the sample as a two-level system. Optical device applications of the permanent laser-induced gratings were studied by creating some simple devices. Findings and conclusions. Permanent laser-induced gratings were created in the Pr^{3+ }- and Eu^{3+} -doped glasses. The permanent laser-induced grating is associated with a structural phase change of the glass host. The structural change is produced by high energy phonons which are emitted by radiationless relaxation processes of the rare earth ion. Nd^{3+} and Er^{3+} relax nonradiatively by the emission of phonons of much lower energy which are unable to produce the structural phase change needed to form a permanent laser-induced grating. The difference in energy of the emitted phonons is responsible for the differing characteristics of the thermal lensing experiments. The model does a good job of predicting the experimental results for the asymmetry and other parameters of the two-level system. The application of these laser -induced gratings for optical devices demonstrates their importance to optical technology.

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

    SciTech Connect

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

    1995-05-26

    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 range of design options for high efficiency gratings. Metal gratings owe their high efficiency to their high conductivity. To avoid the inevitable light absorption that accompanies conductivity, we have developed designs for high efficiency reflection gratings that use only transparent dielectric materials. These combine the reflectivity of a multilayer dielectric stack with a diffraction grating. We report here our present understanding of short-pulse laser induced damage, as it applies to dielectric gratings.

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

    SciTech Connect

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

    1995-07-11

    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 range of design options for high efficiency gratings. Metal gratings owe their high efficiency to their high conductivity. To avoid the inevitable light absorption that accompanies conductivity, we have developed designs for high efficiency rejection gratings that use only transparent dielectric materials. These combine the reflectivity of a multi-layer dielectric stack with a diffraction grating. We report here our present understanding of short-pulse laser induced damage, as it applies to dielectric gratings.

  11. 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.

  12. Pulsed laser induced spontaneous gratings on a surface of azobenzene polymer

    SciTech Connect

    Tsutsumi, Naoto; Fujihara, Arata

    2004-11-15

    Self-organized spontaneous gratings were induced on a surface of azobenzene polymer by an irradiation of frequency doubled neodymium doped yttrium-aluminum-garnet pulsed laser. Irradiation of uniform single laser beam at normal incidence induced periodic line shaped structures on a polymer surface. The structure is so-called laser induced periodic surface structure (LIPSS) which was formed along the direction parallel to the polarization direction of pulsed laser. The LIPSS was formed above the critical thickness around 60 nm. Irradiation of s-polarized holographic interference beams induced the distinguished holographic surface relief grating (SRG) structures. Irradiation of p-polarized holographic interference beams induced egg crate-like (ECL) structures. A combination of holographic SRG and sequential LIPSS is the likely cause of the ECL patterns observed in this work.

  13. Laser-induced damage of multilayer dielectric gratings with picosecond laser pulses under vacuum and air

    NASA Astrophysics Data System (ADS)

    Kong, Fanyu; Jin, Yunxia; Huang, Haopeng; Zhang, Hong; Liu, Shijie; He, Hongbo

    2015-10-01

    In this study, laser damage tests of multilayer dielectric gratings (MDGs) are performed in vacuum (5×10-4 Pa) and in air at a wavelength of 1053 nm with pulse widths of 0.56 ps ~9.7 ps. The laser-induced damage threshold (LIDT) of MDGs in vacuum/air ranges from 2.1/2.2 J/cm2 to 4.4/4.8 J/cm2 for laser beams of normal incidence. The LIDT of MDGs follows a τ0.26 scaling in the pulse width regime considered. The typical damage morphologies in the two environments caused by the near threshold pulse were observed using a scanning electron microscope (SEM); the results indicate that the damage features of MDGs in vacuum are the same as those in air. The testing results reveal that a clean vacuum environment neither changes the laser damage mechanism nor lowers the LIDT of MDGs.

  14. Dynamic holographic gratings

    NASA Astrophysics Data System (ADS)

    Birabassov, Rouslan

    2001-10-01

    The work presented in this thesis is divided into two related areas. The first area of research was a study of photoanisotropic materials to record dynamic gratings. The second area was a study of stimulated diffusion backscattering in photorefractive crystals. The two areas are related by the fact that in the two cases we studied dynamic gratings. We studied reversible photochemical mechanisms using dye molecules suspended in polymer hosts that could record dynamic holograms. The self-developing refractive index changes in dye-doped or dye-attached polymer materials, in particularly azo-dye-doped polymer systems make them promising candidates for many applications (because of the large photoinduced birefringence). The mechanism of photoanisotropic recording in azo-dye-doped polymer materials is based on orientationally dependent photoisomerization of dye molecules that may be macroscopically described in terms of photoinduced linear dichroism and linear birefringence. We proposed a technique for the fabrication of thick photosensitized polymer materials for real-time (self- developing) holographic applications. Cross modulation experiments to study the photoinduced dichroism are then described and the discussion of photophysical mechanisms involved is given. We used azo-dye doped polymer materials to record thin and thick holograms (scalar and vector). We theoretically and experimentally demonstrated that one could successfully store (using a linearly and an elliptically polarized beams) and reconstruct an elliptical polarization state of light using photoanisotropic materials, even if a plane polarized reference beam is used for the recording and readout. Using photoanisotropic materials, we demonstrated experimentally and theoretically that macroscopic optical chirality may be generated in such systems with a proper choice of excitation beam polarization state. Linear diffraction gratings, that provide strongly asymmetric diffraction without surface modulation were also created and studied. Asymmetric diffraction may be achieved using blazed gratings. But in our case the spatial phase shift of the refractive index grating relative to the absorption grating is the origin of asymmetric behaviour. Experimental results made with thin mixed phase and absorption gratings in azo-dye-doped polymer films are in agreement with our theoretical results. In the second part of the thesis we analysed the stimulated diffusion backscattering (SDS) in photorefractive crystals based on the advantages of the reflection photorefractive gratings. The material research, which is the most acute direction, was studied. We believe that optimal crystal (its processing procedure and doping density) is still unknown even for visible range. We discussed the general analysis of the stimulated diffusion backscattering. We studied the relevant parameters for the sample, which demonstrated the most interesting stimulated diffusion backscattering response: measurements of gain, reflectivity, response rate, dark conductivity and grating decay. We clarified the principal possibilities to obtain self-phase conjugation at backward SDS in steady-state conditions. We also made the comparison of sensitivities of different geometries with respect to pump energy. Finally, we experimentally studied double-phase-conjugation geometry at double-loop reflection gratings.

  15. 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.

  16. Generation of inhomogeneous bulk plane acoustic modes by laser-induced thermoelastic grating near mechanically free surface

    SciTech Connect

    Gusev, Vitalyi

    2010-06-15

    The detailed theoretical description of how picosecond plane shear acoustic transients can be excited by ultrafast lasers in isotropic media is presented. The processes leading to excitation of inhomogeneous plane bulk compression/dilatation (c/d) and shear acoustic modes by transient laser interference pattern at a mechanically free surface of an elastically isotropic medium are analyzed. Both pure modes are dispersive. The modes can be evanescent or propagating. The mechanical displacement vector in both propagating modes is oriented obliquely to the mode propagation direction. Consequently the c/d mode is not purely longitudinal and shear mode is not purely transversal. Each of the propagating modes has a plane wave front parallel to the surface and the amplitude harmonically modulated along the surface. Inhomogeneous shear acoustic mode cannot be generated in isotropic medium by thermal expansion and is excited by mode conversion of laser-generated inhomogeneous c/d acoustic mode incident on the surface. The spectral transformation function of the laser radiation conversion into shear modes has one of its maxima at a frequency corresponding to transmission from laser-induced generation of propagating to laser-induced generation of evanescent c/d modes. At this particular frequency the shear waves are due to their Cherenkov emission by bulk longitudinal acoustic waves skimming along the laser-irradiated surface, which are generated by laser-induced gratings synchronously. There exists an interval of frequencies where only shear acoustic modes are launched in the material by laser-induced grating, while c/d modes generated by thermoelastic optoacoustic conversion are evanescent. Propagating picosecond plane shear acoustic fronts excited by interference pattern of fs-ps laser pulses can be applied for the determination of the shear rigidity by optoacoustic echoes diagnostics of thin films and coatings. Theoretical predictions are correlated with available results of experiments and of numerical modeling.

  17. Fabrication of high-temperature-resistant laser-induced gratings with large refractive index modulation: space-selective precipitation of Ge nanoparticles in glasses

    NASA Astrophysics Data System (ADS)

    Nishiyama, Hiroaki; Miyamoto, Isamu; Kintaka, Kenji; Nishii, Junji

    2004-10-01

    High-temperature-resistant laser-induced Bragg gratings were formed in Ge-B-SiO2 thin glass films fabricated by the plasma enhanced chemical vapor deposition method. Such gratings were induced by exposure of an interference pattern with KrF excimer laser and subsequently annealing at 600C. The SEM observation of the grating after HF etching revealed that the origin of the grating was the periodic precipitation of crystalline 20 - 40 nm-diameter Ge nanoparticles. Nanoparticles precipitated predominantly in the unirradiated region after laser-induced refractive index change completely erased after annealing up to 500C. The maximum value of refractive index modulation ?n was 6.8 x 10-3 at 632.8 nm, which corresponds to the ?n nearly 10 times as large as that before annealing. A channel waveguide with high-temperature-resistant-grating exhibited high diffraction efficiency and excellent thermal stability.

  18. 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.

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

    SciTech Connect

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

    2015-02-16

    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.

  20. 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 m 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.

  1. Laser-induced refractive index gratings formed in Pr3+-doped sodium-magnesium-aluminosilicate glasses

    NASA Astrophysics Data System (ADS)

    Hamad, Abdulatif Y.; Wicksted, James P.

    2005-03-01

    We report a systematic study of grating formation in which the Pr2O3 concentration [Pr2O3] in sodium-magnesium-aluminosilicate glasses is varied from 0.5to5mol%. The grating kinetics is reported as functions of the [Pr2O3] and the write-beam irradiance. The maximum persistent change in the index of refraction was 1×10-5. The persistent change in the index of refraction initially decreased linearly as a function of the [Pr2O3] and showed a limiting behavior at the highest [Pr2O3]. No appreciable transient change in the index of refraction, Δntran, was measured. This was attributed to the low probability of the multiphonon relaxation of the P03 level of the Pr3+ ions as determined through fluorescence measurements. The results of this study are consistent with a recently developed small modifier diffusion model.

  2. Electron acceleration in moving laser-induced gratings produced by chirped femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Kozák, Martin

    2015-10-01

    We propose nonrelativistic electron acceleration in a vacuum using interaction with two crossed chirped femtosecond laser pulses at different frequencies. Electron energy gain is optimized by the phase-matching of accelerated electron velocity to a maximum of ponderomotive force in the moving intensity grating by linear chirping of both pulses. Particle tracking simulations show acceleration gradients as high as 40 GeV m-1 (energy gain of hundreds of keV) using 25 fs pulses with peak power ≤500 GW. The dependence of electron energy gain and the deflection angle on experimental parameters (the amplitude of the electric field of laser pulses, and the initial phase shift between the electron and intensity grating) was studied in detail.

  3. Measurement of thermal conductivity of polycrystalline CVD diamond by laser-induced transient grating technique

    SciTech Connect

    Ivakin, E V; Sukhodolov, A V; Ralchenko, V G; Vlasov, A V; Khomich, A V

    2002-04-30

    The tangential thermal diffusivity D{sub ||} and thermal conductivity k{sub ||} of diamond plates grown from the gaseous phase by chemical vapour deposition (CVD diamond) are determined by the transient grating technique in the temperature range 25 - 200 {sup 0}C. Samples of insulating and boron-doped polycrystalline diamond of thickness about 0.3 mm and diameter 63 mm were synthesised in a microwave discharge in mixtures of methane and hydrogen. In view of the intense light scattering by the samples, a photosensitive grating recording technique was developed and used for measurements. It was found that the value k{sub ||} amounts to 18 - 20 W cm{sup -1} K{sup -1} at room temperature, approaching the thermal conductivity of the highest purity single crystals of diamond. A comparison of the value of k{sub ||} with the normal thermal conductivity k{sub perpendicular} determined by the flash method reveals a thermal conductivity anisotropy of about 10% - 20% associated with the texture of the diamond film, the normal component of thermal conductivity being larger than the tangential component. Boron-doped diamond displays a dependence of the transient grating kinetics on the excitation wavelength. The obtained results indicate that CVD diamond is a promising material for preparing efficient heat sinks, especially of large size, used in microelectronic devices and laser engineering. (laser applications and other topics in quantum electronics)

  4. Laser-Induced Spatiotemporal Dynamics of Magnetic Films

    NASA Astrophysics Data System (ADS)

    Shen, Ka; Bauer, Gerrit E. W.

    2015-11-01

    We present a theory for the coherent magnetization dynamics induced by a focused ultrafast laser beam in magnetic films, taking into account nonthermal (inverse Faraday effect) and thermal (heating) actuation. The dynamic conversion between spin waves and phonons is induced by the magnetoelastic coupling that allows efficient propagation of angular momentum. The anisotropy of the magnetoelastic coupling renders characteristic angle dependences of the magnetization propagation that are strikingly different for thermal and nonthermal actuation.

  5. Laser-Induced Spatiotemporal Dynamics of Magnetic Films.

    PubMed

    Shen, Ka; Bauer, Gerrit E W

    2015-11-01

    We present a theory for the coherent magnetization dynamics induced by a focused ultrafast laser beam in magnetic films, taking into account nonthermal (inverse Faraday effect) and thermal (heating) actuation. The dynamic conversion between spin waves and phonons is induced by the magnetoelastic coupling that allows efficient propagation of angular momentum. The anisotropy of the magnetoelastic coupling renders characteristic angle dependences of the magnetization propagation that are strikingly different for thermal and nonthermal actuation. PMID:26588408

  6. 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

  7. Dynamics of femtosecond laser-induced melting of silver

    SciTech Connect

    Chan Wailun; Averback, Robert S.; Cahill, David G.; Lagoutchev, Alexei

    2008-12-01

    We use optical third-harmonic generation to measure the melting dynamics of silver following femtosecond laser excitation. The dynamics reveals an unusual two-step process that is associated with the extreme electronic temperatures and very short time and length scales. In the first, which lasts a few picoseconds, the electron and phonon systems begin to equilibrate, and a thin surface layer undergoes melting. Heat conduction during this period is strongly suppressed by electron scattering from d-band excitations. In the second stage, the surface region remains above the melting temperature for a surprisingly long time, 20-30 ps, with the melt front propagating into the bulk at a velocity of {approx_equal}350 m s{sup -1}. In this stage, the electron and phonon systems again fall out of equilibrium and conduction of heat away from the surface region is now limited by the weak electron-phonon (e-p) coupling. From our model calculation, we propose that the melt depths in noble metals irradiated by femtosecond lasers are limited to thicknesses on the order of two to three times of the optical-absorption depth of the light.

  8. Dynamics of laser induced metal nanoparticle and pattern formation

    SciTech Connect

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

    2015-02-09

    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 μs. 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.

  9. Dynamics of laser induced micro bubble clusters on tissue phantoms

    NASA Astrophysics Data System (ADS)

    Fritz, Andreas; Zegelin, Andrea; Ptaszynski, Lars; Birngruber, Reginald; Brinkmann, Ralf

    2011-03-01

    Selective retina treatment (SRT) is a laser based method to treat retinal diseases associated with disorders of the retinal pigment epithelium (RPE) while preserving photoreceptors and choroid. Applying microsecond laser pulses to the 100- 200 strongly absorbing melanin granules inside the RPE cells induces transient micro bubbles which disrupt the cells. Aim of this work is to understand bubble dynamics in clusters with respect to the influence of the adjacent retina. Bubble dynamics were investigated in vitro on porcine RPE. An about 200 ?m thick layer of agarose gel was applied to the RPE layer in order to simulate the mechanical properties of retina. Different laser pulse durations from 1 ns (532 nm, Nd:YAG) to 1.7 ?s (527 nm, Nd:YLF) were used. The bubbles were investigated interferometrically (fiber interferometer @ 830 nm) and with fast flash photography (25 ns flash duration). Bubble lifetimes were measured. The results show that with retina phantoms the bubble formation threshold was reached at 2.5 times higher irradiation than without retina phantom for 1.7 ?s laser pulses. The microbubbles generated with 1 ns laser pulses were almost not influenced by the agarose layer. Irradiation twofold over bubble formation threshold resulted in 3.5 times longer bubble lifetimes for ?s and 2 times longer for ns pulse durations, respectively.

  10. Laser-induced perturbation into molecular dynamics localized in neuronal cell

    NASA Astrophysics Data System (ADS)

    Hosokawa, Chie; Takeda, Naoko; Kudoh, Suguru N.; Taguchi, Takahisa

    2015-03-01

    Molecular dynamics at synaptic terminals in neuronal cells is essential for synaptic plasticity and subsequent modulation of cellular functions in a neuronal network. For realizing artificial control of living neuronal network, we demonstrate laser-induced perturbation into molecular dynamics in the neuronal cells. The optical trapping of cellular molecules such as synaptic vesicles or neural cell adhesion molecules labeled with quantum dots was evaluated by fluorescence imaging and fluorescence correlation spectroscopy. The trapping and assembling dynamics was revealed that the molecular motion was constrained at the focal spot of a focused laser beam due to optical trapping force. Our method has a potential to manipulate synaptic transmission at single synapse level.

  11. 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.

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

    SciTech Connect

    Teng, L.-W.; Tsai, C.-Y.; Tseng, Y.-P.; I Lin

    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.

  13. Laser-induced magnetization dynamics of lanthanide-doped permalloy thin films.

    PubMed

    Radu, I; Woltersdorf, G; Kiessling, M; Melnikov, A; Bovensiepen, U; Thiele, J-U; Back, C H

    2009-03-20

    We investigate the effect of Ho, Dy, Tb, and Gd impurities on the femtosecond laser-induced magnetization dynamics of thin Permalloy films using the time-resolved magneto-optical Kerr effect. Varying the amount of Ho, Dy, Tb content from 0% to 8%, we observe a gradual change of the characteristic demagnetization time constant from approximately 60 to approximately 150 fs. In contrast, Gd concentrations up to 15% do not influence the time scale of the initial photoinduced magnetization loss. We propose a demagnetization mechanism that relies on strong magnetic inertia of the rare-earth dopant which stabilizes the ferrimagnetic ordering and thereby delays the demagnetization. PMID:19392235

  14. Structural and magnetic dynamics of a laser induced phase transition in FeRh.

    PubMed

    Mariager, S O; Pressacco, F; Ingold, G; Caviezel, A; Mhr-Vorobeva, E; Beaud, P; Johnson, S L; Milne, C J; Mancini, E; Moyerman, S; Fullerton, E E; Feidenhans'l, R; Back, C H; Quitmann, C

    2012-02-24

    We use time-resolved x-ray diffraction and magneto-optical Kerr effect to study the laser-induced antiferromagnetic to ferromagnetic phase transition in FeRh. The structural response is given by the nucleation of independent ferromagnetic domains (?(1)~30 ps). This is significantly faster than the magnetic response (?(2)~60 ps) given by the subsequent domain realignment. X-ray diffraction shows that the two phases coexist on short time scales and that the phase transition is limited by the speed of sound. A nucleation model describing both the structural and magnetic dynamics is presented. PMID:22463562

  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. Dynamics of dud, dut in superstrong laser fields for laser induced nuclear fusion

    NASA Astrophysics Data System (ADS)

    Bandrauk, Andre D.; Paramonov, Guennaddi

    2012-03-01

    Nuclear fusion occurs during the collision of selected isotopes of hydrogen with relative energy in the MeV(10**6 eV) regime. Such high energy ions can be generated by high power lasers applied to clusters [1] via the accumulated ponderomotive energies. However in such schemes laser induced collisions are random whereas as shown previously ultrashort superintense laser pulses can be used to control collisions in muonic molecules [2]. We present full 3-D dynamics from accurate Time-dependent Schroedinger equations, TDSE, s, of the isotopomers, pud, dud, dut in super intense laser pulses with intensities I 10**23 W/cm**2 to illustrate the possibility of inducing always head-on(zero-impact) collisions leading in principle to laser induced nuclear fusion, LINF. Due to its heavy mass(mu/me=185.8) the muonic molecular ions are stable to ionization up to intensities I=10**23 W/cm**2 and recollision of the heavy particles (p,td,t) will be shown to be controllable by few cycle superintense laser pulses leading to LINF.The nonsymmetric isotopomers dut and put manifest enhanced fusion due to the presence of permanent dipole moments.[4pt] [1] KWD Ledingham et al, Science 300, 1107 (2003)[0pt] [2] S Chelkowski, PB Corkum, AD Bandrauk, Phys Rev Lett 93, 083602(2004)

  17. 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.

  18. Dynamic model of thermal reaction of biological tissues to laser-induced fluorescence and photodynamic therapy.

    PubMed

    Seteikin, Alexey Yu; Krasnikov, Ilya V; Drakaki, Eleni; Makropoulou, Mersini

    2013-07-01

    The aim of this work was to evaluate the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed ultraviolet (UV) laser (?=337??nm) and a continuous-wave (cw) visible laser beam (?=632.8??nm) using Monte Carlo modeling. Finite-element methodology was used for heat transfer simulation. The analysis of the results showed that heat is not localized on the surface, but is collected inside the tissue in lower skin layers. The simulation was made with the pulsed UV laser beam (used as excitation source in laser-induced fluorescence) and the cw visible laser (used in photodynamic therapy treatments), in order to study the possible thermal effects. PMID:23839531

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

    SciTech Connect

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

    2015-01-07

    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 μs and 22.5 μs after breakdown, the electron density decreases from 3.3 × 10{sup 17 }cm{sup −3} to 9 × 10{sup 13 }cm{sup −3}, while the temperature drops from 3.2 eV to 0.1 eV. Spatially resolved Thomson scattering data recorded up to 17.5 μs reveal that during this time the laser induced plasma expands at a rate given by R ∼ t{sup 0.4} 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 μs. 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 He{sub 2}{sup +} molecular ion play an important role.

  20. Imaging ultrafast dynamics of molecules with laser-induced electron diffraction.

    PubMed

    Lin, C D; Xu, Junliang

    2012-10-14

    We introduce a laser-induced electron diffraction method (LIED) for imaging ultrafast dynamics of small molecules with femtosecond mid-infrared lasers. When molecules are placed in an intense laser field, both low- and high-energy photoelectrons are generated. According to quantitative rescattering (QRS) theory, high-energy electrons are produced by a rescattering process where electrons born at the early phase of the laser pulse are driven back to rescatter with the parent ion. From the high-energy electron momentum spectra, field-free elastic electron-ion scattering differential cross sections (DCS), or diffraction images, can be extracted. With mid-infrared lasers as the driving pulses, it is further shown that the DCS can be used to extract atomic positions in a molecule with sub-angstrom spatial resolution, in close analogy to the standard electron diffraction method. Since infrared lasers with pulse duration of a few to several tens of femtoseconds are already available, LIED can be used for imaging dynamics of molecules with sub-angstrom spatial and a few-femtosecond temporal resolution. The first experiment with LIED has shown that the bond length of oxygen molecules shortens by 0.1 in five femtoseconds after single ionization. The principle behind LIED and its future outlook as a tool for dynamic imaging of molecules are presented. PMID:22914800

  1. Study of collisional deactivation of O2( b 1?{/g +}) molecules in a hydrogen-oxygen mixture at high temperatures using laser-induced gratings

    NASA Astrophysics Data System (ADS)

    Kozlov, D. N.; Kobtsev, V. D.; Stel'makh, O. M.; Smirnov, V. V.

    2013-07-01

    Collisional deactivation of O2( b 1?{/g +}) molecules resonantly excited by a 10 ns pulse of laser radiation with a wavelength of 762 nm in H2/O2 mixtures is experimentally studied. The radiation intensity and hence the molecule excitation efficiency have a spatially periodic modulation that leads to the formation of laser-induced gratings (LIGs) of the refractive index. The study of LIG temporal evolution allows collisional relaxation rates of molecular excited states and gas temperature to be determined. In this work, the b 1?{/g +} state of O2 molecules deactivation rates are measured in a 4.3 vol % H2 mixture at the number density of 2 amg in the temperature range 291-850 K. The physical deactivation is shown to dominate in the collisions of H2 with O2( b 1?{/g +}) and O2( a 1? g ) up to temperatures of 780-790 K at time delays up to 10 ?s after the excitation pulse. The parameters of the obtained temperature dependence of the ( b 1?{/g +} state deactivation rate agree well with the data of independent measurements performed earlier at lower temperatures (200-400 K). Tunable diode laser absorption spectroscopy is used to measure the temperature dependence of the number density of the H2O molecules which appear as the mixture, as the result of the dark gross reaction with O2 molecules in the ground state, O2 + 2H2 ? 2H2O. The measurements show that this reaction results in complete transformation of H2 into H2O at temperatures of 790-810 K.

  2. Simultaneous measurements of terahertz emission and magneto-optical Kerr effect for resolving ultrafast laser-induced demagnetization dynamics

    NASA Astrophysics Data System (ADS)

    Huisman, T. J.; Mikhaylovskiy, R. V.; Tsukamoto, A.; Rasing, Th.; Kimel, A. V.

    2015-09-01

    Simultaneous detection of terahertz (THz) emission and transient magneto-optical response is employed to study ultrafast laser-induced magnetization dynamics in three different types of amorphous metallic alloys: Co, GdFeCo, and NdFeCo. A satisfactory agreement between the dynamics revealed with the help of these two techniques is obtained for Co and GdFeCo. For NdFeCo the THz emission indicates faster dynamics than the magneto-optical response. This observation indicates that in addition to spin dynamics of Fe, ultrafast laser excitation of NdFeCo triggers faster magnetization dynamics of Nd originating from its orbital momentum.

  3. Density jumps in the plasma of a nanosecond laser-induced spark and their dynamics

    SciTech Connect

    Malyutin, A A; Podvyaznikov, V A; Chevokin, V K

    2011-01-31

    Experimental investigation of the structure of a laser-induced spark emerging in the focusing of 50-ns radiation pulses is described. Two density jumps were discovered in the plasma of the laser-induced spark. One of them is localised in the vicinity of the focal plane of the lens, the other propagates from this plane in the laser propagation direction at a constant velocity of {approx}7.5 km s{sup -1}. (laser plasma)

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

    SciTech Connect

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

    2010-10-08

    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.

  5. Speckle photography during dynamic impact of an energetic material using laser-induced fluorescence

    SciTech Connect

    Asay, B.W.; Laabs, G.W.; Henson, B.F.; Funk, D.J.

    1997-08-01

    Laser and white light speckle photography have been used to observe surface displacement in a number of materials and over a varied range of strain rates. However, each suffers from limitations. We have developed a novel application of speckle photography in very difficult environments by using laser-induced fluorescence to generate the speckle pattern. This permits confinement of the free surface without undue degradation of the correlation upon which speckle methods are based. We have applied this method to measure the surface displacement of a reactive material during dynamic deformation at moderate strain rates. Conventional methods were tried but were unsuccessful, necessitating a novel approach. To the best of our knowledge, neither high-speed laser nor white light speckle photography has been performed using energetic materials. These measurements are very difficult because of the low material strength (yield strength {approximately}8{endash}80 MPa), and because significant out-of-plane motion and surface disruption occur during fracture, and early during the deformation process. We report results from experiments in which these major problems have been overcome. {copyright} {ital 1997 American Institute of Physics.}

  6. Formation dynamics of femtosecond laser-induced phase objects in transparent materials

    NASA Astrophysics Data System (ADS)

    Mermillod-Blondin, A.; Rosenfeld, A.; Stoian, R.; Audouard, E.

    2012-01-01

    Ultrashort pulse lasers offer the possibility to structure the bulk of transparent materials on a microscale. As a result, the optical properties of the irradiated material are locally modified in a permanent fashion. Depending on the irradiation parameters, different types of laser-induced phase objects can be expected, from uniform voxels (that can exhibit higher or lower refractive index than the bulk) to self-organized nanoplanes. We study the physical mechanisms that lead to material restructuring, with a particular emphasis on events taking place on a sub picosecond to a microsecond timescale following laser excitation. Those timescales are particularly interesting as they correspond to the temporal distances between two consecutive laser pulses when performing multiple pulse irradiation: burst microprocessing usually involves picosecond separation times and high repetition rate systems operate in the MHz range. We employ a time-resolved microscopy technique based on a phase-contrast microscope setup extended into a pump-probe scheme. This methods enables a dynamic observation of the complex refractive index in the interaction region with a time resolution better than 300 fs. In optical transmission mode, the transient absorption coefficient can be measured for different illumination wavelengths (400 nm and 800 nm). The phase-contrast mode provides qualitative information about the real part of the transient refractive index. Based on the study of those transient optical properties, we observe the onset and relaxation of the laser-generated plasma into different channels such as defect creation, sample heating, and shockwave generation. The majority of our experiments were carried out with amorphous silica, but our method can be applied to the study of all transparent media.

  7. Laser-induced fluorescence measurement of the dynamics of a pulsed planar sheath

    SciTech Connect

    Goeckner, M.J.; Malik, S.M. ); Conrad, J.R. ); Breun, R.A. )

    1994-04-01

    Using laser-induced fluorescence (LIF) the ion density near the edge of an expanding plasma sheath has been measured. These measurements utilized a transition of N[sup +][sub 2] [the P12 component of the [ital X] [sup 2][Sigma][sup +][sub [ital g

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Eschlbck-Fuchs, S.; Haslinger, M. J.; Hinterreiter, A.; Kolmhofer, P.; Huber, N.; Rssler, 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.

  10. 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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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

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

    SciTech Connect

    Barash, Danny; Orel, Ann E.; Baer, Roi

    2000-01-01

    An adiabatic-Floquet formalism is used to study the suppression of ionization in short laser pulses. In the high-frequency limit the adiabatic equations involve only the pulse envelope where transitions are purely ramp effects. For a short-ranged potential having a single-bound state we show that ionization suppression is caused by the appearance of a laser-induced resonance state, which is coupled by the pulse ramp to the ground state and acts to trap ionizing flux. (c) 1999 The American Physical Society.

  14. Demodulation System for Fiber Optic Bragg Grating Dynamic Pressure Sensing

    NASA Technical Reports Server (NTRS)

    Lekki, John D.; Adamovsky, Grigory; Floyd, Bertram

    2001-01-01

    Fiber optic Bragg gratings have been used for years to measure quasi-static phenomena. In aircraft engine applications there is a need to measure dynamic signals such as variable pressures. In order to monitor these pressures a detection system with broad dynamic range is needed. This paper describes an interferometric demodulator that was developed and optimized for this particular application. The signal to noise ratio was maximized through temporal coherence analysis. The demodulator was incorporated in a laboratory system that simulates conditions to be measured. Several pressure sensor configurations incorporating a fiber optic Bragg grating were also explored. The results of the experiments are reported in this paper.

  15. 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.

  16. Ultrahigh resolution optical spectrometry based on Brillouin dynamic grating

    NASA Astrophysics Data System (ADS)

    Dong, Yongkang; Jiang, Taofei; Teng, Lei; Zhang, Hongying; Chen, Liang; Bao, Xiaoyi; Lu, Zhiwei

    2014-05-01

    We demonstrate an ultrahigh resolution optical spectrometry based on Brillouin dynamic grating (BDG). Taking advantage of creating a long grating in an optical fiber, an ultra-narrow bandwidth optical filter is realized by operating a BDG in a long single-mode fiber (SMF), and the optical spectrometry is performed by sweeping the center wavelength of the filter through swept-tuned laser. In experiment, a 4-fm (0.5 MHz) spectral resolution is achieved by operating a BDG in a 400-m SMF, and the wavelength coverage can be readily extended to C+L band with a commercial tunable laser.

  17. Dynamic fiber Bragg grating sensing method

    NASA Astrophysics Data System (ADS)

    Ho, Siu Chun Michael; Ren, Liang; Li, Hongnan; Song, Gangbing

    2016-02-01

    The measurement of high frequency vibrations is important in many scientific and engineering problems. This paper presents a novel, cost effective method using fiber optic fiber Bragg gratings (FBGs) for the measurement of high frequency vibrations. The method uses wavelength matched FBG sensors, with the first sensor acting as a transmission filter and the second sensor acting as the sensing portion. Energy fluctuations in the reflection spectrum of the second FBG due to wavelength mismatch between the sensors are captured by a photodiode. An in-depth analysis of the optical circuit is provided to predict the behavior of the method as well as identify ways to optimize the method. Simple demonstrations of the method were performed with the FBG sensing system installed on a piezoelectric transducer and on a wind turbine blade. Vibrations were measured with sampling frequencies up to 1 MHz for demonstrative purposes. The sensing method can be multiplexed for use with multiple sensors, and with care, can be retrofitted to work with FBG sensors already installed on a structure.

  18. 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 μm. 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.

  19. Laser-induced dissociation dynamics of triatomic molecule in electronic excited states: A full-dimensional quantum mechanics study.

    PubMed

    Sun, Zhaopeng; Yang, Chuanlu; Zheng, Yujun

    2015-12-14

    We present a detailed theoretical approach to investigate the laser-induced dissociation dynamics of a triatomic molecule on its electronic excited state in full dimensional case. In this method, the time evolution of the time-dependent system is propagated via combined the split operator method and the expansion of Chebyshev polynomials (or short-time Chebyshev propagation) and the system wave functions are expanded in terms of molecular rotational bases. As an example of the application of this formalism, the dissociation dynamics of H3 (+)→H2 (+)+H induced by ultrashort UV laser pulses are investigated on new Born-Oppenheimer potential energy surfaces. Our numerical results show that the signals of dissociation products will be easier to observe as the increasing of field strength. Driving by a 266 nm laser beam, the calculated central value of kinetic-energy-release is 2.04 eV which shows excellent agreement with the experimental estimation of 2.1 eV. When the H3 (+) ion is rotationally excited, the spatial distribution of product fragments will become well converged. PMID:26671377

  20. Energy absorption behavior of polyurea coatings under laser-induced dynamic tensile and mixed-mode loading

    NASA Astrophysics Data System (ADS)

    Jajam, Kailash; Lee, Jaejun; Sottos, Nancy

    2015-06-01

    Energy absorbing, lightweight, thin transparent layers/coatings are desirable in many civilian and military applications such as hurricane resistant windows, personnel face-shields, helmet liners, aircraft canopies, laser shields, blast-tolerant sandwich structures, sound and vibration damping materials to name a few. Polyurea, a class of segmented block copolymer, has attracted recent attention for its energy absorbing properties. However, most of the dynamic property characterization of polyurea is limited to tensile and split-Hopkinson-pressure-bar compression loading experiments with strain rates on the order of 102 and 104 s-1, respectively. In the present work, we report the energy absorption behavior of polyurea thin films (1 to 2 μm) subjected to laser-induced dynamic tensile and mixed-mode loading. The laser-generated high amplitude stress wave propagates through the film in short time frames (15 to 20 ns) leading to very high strain rates (107 to 108 s-1) . The substrate stress, surface velocity and fluence histories are inferred from the displacement fringe data. On comparing input and output fluences, test results indicate significant energy absorption by the polyurea films under both tensile and mixed-mode loading conditions. Microscopic examination reveals distinct changes in failure mechanisms under mixed-mode loading from that observed under pure tensile loading. Office of Naval Research MURI.

  1. Laser-induced dissociation dynamics of triatomic molecule in electronic excited states: A full-dimensional quantum mechanics study

    NASA Astrophysics Data System (ADS)

    Sun, Zhaopeng; Yang, Chuanlu; Zheng, Yujun

    2015-12-01

    We present a detailed theoretical approach to investigate the laser-induced dissociation dynamics of a triatomic molecule on its electronic excited state in full dimensional case. In this method, the time evolution of the time-dependent system is propagated via combined the split operator method and the expansion of Chebyshev polynomials (or short-time Chebyshev propagation) and the system wave functions are expanded in terms of molecular rotational bases. As an example of the application of this formalism, the dissociation dynamics of H3 + → H2 + + H induced by ultrashort UV laser pulses are investigated on new Born-Oppenheimer potential energy surfaces. Our numerical results show that the signals of dissociation products will be easier to observe as the increasing of field strength. Driving by a 266 nm laser beam, the calculated central value of kinetic-energy-release is 2.04 eV which shows excellent agreement with the experimental estimation of 2.1 eV. When the H 3+ ion is rotationally excited, the spatial distribution of product fragments will become well converged.

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

    DOE PAGESBeta

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

    2014-10-24

    We report the first 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 the 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 are escaping into the vacuum at a nearly isotropic and constant velocity with an unusually high kinetic energy of more than 300 eV. We alsomore » 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.« less

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

    SciTech Connect

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

    2014-10-24

    We report the first 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 the 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 are escaping 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.

  4. 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 μs 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.

  5. 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.

  6. NT-32TISSUE ABLATION DYNAMICS DURING MAGNETIC RESONANCE-GUIDED LASER INDUCED THERMAL THERAPY FOR INTRACRANIAL TUMORS

    PubMed Central

    Sun, Xiaonan; Patel, Nitesh; Danish, Shabbar

    2014-01-01

    BACKGROUND: Magnetic Resonance-guided Laser Induced Thermal Therapy (MRgLITT) is a minimally-invasive procedure used in the treatment of intracranial tumors, epilepsy and pain. Thermal damage is estimated using real-time MR thermometry but little is known about the dynamics of the process and how various intracranial tumors affect overall ablation. OBJECTIVES: Determine the relationship between thermal energy delivery and the time to maximal estimated thermal damage in the setting of previously untreated glioblastoma multiforme (GBM), recurrent GBM, and metastatic tumors or radiation necrosis. We aim to understand whether differences exist between these intracranial malignancies and how the ablation process is affected. METHODS: We used real-time ablation data from 24 patients across five unique intracranial pathologies. Ablations were performed using the Visualase Thermal Therapy System (Visulase Inc.) using a 980-nm diffusing tip diode laser. Thermal damage area was plotted against time for each ablation. Subsequently, the duration required to reach 50% (t50) and 97% (t97) of maximum damage was estimated. Comparisons were then made between different intracranial pathologies. RESULTS: The average (mean SEM) t97 for previously untreated GBM (n = 7) recurrent GBM (n = 6) and tumor metastasis/radiation necrosis (n = 7) are 167 18, 165 22, 97 22 seconds, respectively. The mean t97 is significantly shorter for tumor metastasis/radiation necrosis when compared with previously untreated GBM (p < 0.05). CONCLUSIONS: While optimal duration of thermal ablation varies between intracranial tumors, we found that metastatic tumor/radiation necrosis requires significantly shorter duration of ablation. In most cases, maximal ablation was reached long before the industry recommended ablation time. Understanding the duration required to reach maximal ablation may reduce thermal exposure times during the ablation process. Future studies are needed to examine the relationship between ablation power, irrigation speed, and the effect of prior therapies on the ablation dynamics.

  7. Transient Dynamics of Laser-Induced Bubbles in an Ultrasonic Field

    NASA Astrophysics Data System (ADS)

    Kurz, Thomas; Wilken, Tobias; Krninger, Dennis; Wimann, Laurens; Lauterborn, Werner

    2008-06-01

    By combining optical bubble generation with acoustic excitation in a standing ultrasonic field the dynamics and light emission of a single bubble are studied at different conditions with high-speed imaging, optical, and acoustical measurements. In particular, the maximum bubble size and luminescence intensity are recorded for as long as the bubble remains stable. At high driving, luminescence intensity at first collapse increases when raising the driving amplitude or decreasing the water temperature. At suitable gas content and driving pressure the bubble remains stable but changes size by diffusion in a characteristic way, until finally switching on sonoluminescence and remaining stably trapped.

  8. 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.

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

    SciTech Connect

    Lin, Hui-Chi Yang, Meng-Ru; Tsai, Sheng-Feng; Yan, Shih-Chiang

    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.

  10. A multi-electrode velocity-map imaging apparatus to study laser induced molecular dynamics

    NASA Astrophysics Data System (ADS)

    de, S.; Ray, D.; Johnson, N. G.; Bocharova, I.; Magrakvelidze, M.; Cocke, C. L.; Litvinyuk, I. V.; Znakovskaya, I.; Wirth, A.; Kling, M. F.

    2009-05-01

    We have designed and built a multi-electrode VMI spectrometer capable of detecting up to 300 eV electrons with good momentum resolution. The spectrometer is based on an original design which utilizes a multiple electrostatic lens system to contain the high energy electrons, while maintaining good volume focusing. The spectrometer is used together with super-sonic atomic and molecular jet gas targets in the J. R. Macdonald Laboratory. We measured 3D momentum distributions of ATI electrons produced by intense femtosecond laser pulses to determine the resolution of the spectrometer experimentally and compare the result to Simion calculations. We will present first results on using this device to record phase dependent control of electron localization in the dissociative ionization of simple molecules in two-color intense laser fields and the dynamic alignment and orientation of carbon monoxide after excitation by a two-color laser field.

  11. Dynamics Of A Laser-Induced Plume Self-Similar Expansion

    SciTech Connect

    Bennaceur-Doumaz, D.; Djebli, M.

    2008-09-23

    The dynamics of a laser ablation plume during the first stage of its expansion, just after the termination of the laser pulse is modeled. First, we suppose the laser fluence range low enough to consider a neutral vapor. The expansion of the evaporated material is described by one-component fluid and one-dimensional Euler equations. The vapor is assumed to follow an ideal gas flow. For high energetic ions, the charge separation can be neglected and the hydrodynamics equations can be solved using self-similar formulation. The obtained ordinary differential equations are solved numerically. Secondly, the effect of ionization is investigated when the evaporated gas temperature is sufficiently high. In this case, Saha equation is included in the formulation of the model. We find a self-similar solution for a finite value of the similarity variable which depends on the laser ablation parameters.

  12. 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.

  13. Rapid Laser Induced Crystallization of Amorphous NiTi Films Observed by Nanosecond Dynamic Transmission Electron Microscopy (DTEM)

    SciTech Connect

    LaGrange, T; Campbell, G H; Browning, N D; Reed, B W; Grummon, D S

    2010-03-01

    The crystallization processes of the as-deposited, amorphous NiTi thin films have been studied in detail using techniques such as differential scanning calorimetry and, in-situ TEM. The kinetic data have been analyzed in terms of Johnson-Mehl-Avrami-Kolomogrov (JMAK) semi-empirical formula. The kinetic parameters determined from this analysis have been useful in defining process control parameters for tailoring microstructural features and shape memory properties. Due to the commercial push to shrink thin film-based devices, unique processing techniques have been developed using laser-based annealing to spatially control the microstructure evolution down to sub-micron levels. Nanosecond, pulse laser annealing is particularly attractive since it limits the amount of peripheral heating and unwanted microstructural changes to underlying or surrounding material. However, crystallization under pulsed laser irradiation can differ significantly from conventional thermal annealing, e.g., slow heating in a furnace. This is especially true for amorphous NiTi materials and relevant for shape memory thin film based microelectromechanical systems (MEMS) applications. There is little to no data on the crystallization kinetics of NiTi under pulsed laser irradiation, primarily due to the high crystallization rates intrinsic to high temperature annealing and the spatial and temporal resolution limits of standard techniques. However, with the high time and spatial resolution capabilities of the dynamic transmission electron microscope (DTEM) constructed at Lawrence Livermore National Laboratory, the rapid nucleation events occurring from pulsed laser irradiation can be directly observed and nucleation rates can be quantified. This paper briefly explains the DTEM approach and how it used to investigate the pulsed laser induced crystallization processes in NiTi and to determine kinetic parameters.

  14. Dynamic and interaction of fs-laser induced cavitation bubbles for analyzing the cutting effect

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Schumacher, S.; Nuzzo, V.; Ripken, T.; Lubatschowski, H.

    2009-07-01

    A prominent laser based treatment in ophthalmology is the LASIK procedure which nowadays includes a cutting of the corneal tissue based on ultra short pulses. Focusing an ultra short laser pulse below the surface of biological tissue an optical breakdown is caused and hence a dissection is obtained. The laser energy of the laser pulses is absorbed by nonlinear 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 duration of the treatment the current development of ultra short laser systems points to higher repetition rates in the range of hundreds of KHz or even MHz instead of tens of kHz. This in turn results in 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. 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 (> 1 MHz) repetition rates.

  15. Fiber Bragg grating sensors for dynamic machining applications

    NASA Astrophysics Data System (ADS)

    Bartow, Matthew J.; Calvert, Sean G.; Bayly, Philip V.

    2003-11-01

    Fiber Bragg grating sensors have attracted considerable attention for measurement applications due to their greatly reduced size, low weight, and immunity to electromagnetic interference in comparison with traditional sensing methods. Dynamic measurement of industrial machine tools is useful for gauging surface accuracy, monitoring tool condition, and predicting process stability, but requires a robust sensing scheme. The small size and high natural frequencies of micro machining tools coupled with a harsh manufacturing environment can render traditional sensors ineffective. This work presents a new method for measuring tool motion with fiber Bragg grating strain sensors. The feasibility of the sensing scheme is first demonstrated with a simple bench-top cantilever beam experiment. Then, a method for potting the sensors in the through coolant holes of a 1/8" carbide end mill with a high-viscosity gap-filling cyanoacrylate is demonstrated. Comparative structural analysis tests demonstrate the effectiveness of the sensors. Measurements of tool motion during cutting are presented. Finally, methods of noise reduction and improving signal accuracy are discussed.

  16. Supercooled water relaxation dynamics probed with heterodyne transient grating experiments.

    PubMed

    Taschin, Andrea; Bartolini, Paolo; Eramo, Roberto; Torre, Renato

    2006-09-01

    We report results from a heterodyne-detected transient grating experiment on liquid and supercooled water in a wide temperature range, from -17.5 to 90 degrees C. The measured signal covers an extremely large time window with an excellent signal-to-noise ratio that enables the investigation in a single experiment of the sound speed and attenuation, thermal diffusivity, and temperature dependence of the dielectric constant. The experimental data clearly show the effect of the density and the temperature fluctuations on the water dielectric function. In order to describe the experimental results, we introduce a comprehensive hydrodynamic model taking into account the coupled density and temperature variables and their relevance in the definition of the spontaneous and forced dielectric variations. We use this model to describe the measured signal in transient grating experiments, including the heating and the electrostrictive sources produced by the laser excitation. The fitting procedure enables the safe extraction of several dynamic properties of liquid and supercooled water: the sound velocity and its damping, the thermal diffusivity, and the ratio between the dielectric thermodynamic derivatives. The measured parameters are compared to the literature data and discussed in the complex scenario of water physics. PMID:17025635

  17. Dynamics of a femtosecond/picosecond laser-induced aluminum plasma out of thermodynamic equilibrium in a nitrogen background gas

    NASA Astrophysics Data System (ADS)

    Morel, Vincent; Bultel, Arnaud; Annaloro, Julien; Chambrelan, Cédric; Edouard, Guillaume; Grisolia, Christian

    2015-01-01

    Beyond the experimental studies, the assessment of the ability of ultra-short (femto or picosecond) laser pulses to provide correct estimates of the elemental composition of unknown samples using laser-induced breakdown spectroscopy requires the modeling of a typical situation. The present article deals with this modeling for aluminum in nitrogen. A spherical layer model is developed. The central aluminum plasma is produced by the ultra-short pulse. This plasma is described using our collisional-radiative model CoRaM-Al in an upgraded version involving 250 levels. Its expansion and relaxation take place in nitrogen, where the formation and the propagation of a shock wave are taken into account. In this shocked nitrogen layer, the equilibrium conditions are assumed. Mass, momentum and energy conservation equations written under an Eulerian form are used to correctly model the global dynamics. Energy losses are due to radiative recombination, thermal Bremsstrahlung and spontaneous emission. These elementary processes are implemented. The only input parameters are the pulse energy E0, the ablated mass M of the sample and the pressure p0 of the surrounding gas. The equilibrium composition involving N2, N, N2+, N+ and free electrons of the shocked nitrogen layer is calculated from the thermodynamic database of our collisional-radiative model CoRaM-N2. The conditions E0 = 10 mJ and M ≃ 10- 10 kg corresponding to a 532 nm laser pulse are chosen. The model assumes the initial equilibrium of the aluminum plasma produced by the laser pulse absorbed by the sample. Then, owing to the significant overpressure with respect to the background gas (p0 is assumed atmospheric), the surrounding gas starts to be compressed while the propagation of a shock wave takes place. The shock layer maximum pressure is obtained at approximately 20 ns. At this characteristic time, the nitrogen pressure is around 400 times the atmospheric pressure. A shock velocity of 7 km s- 1 is predicted. The central plasma is characterized by a rapidly decreasing pressure, which leads for a while to a very low temperature (3500 K) with respect to the initial one (65,000 K). Then, the aluminum plasma is in a moderate nonequilibrium situation for Al. For Al+, the nonequilibrium degree is higher and the excited states are very weakly populated. Then, the aluminum plasma temperature increases due to the compression by the shock layer. Later, the pressure converges to p0 owing to the momentum transfer with the shock layer, and the shock velocity decreases. The central plasma progressively tends to equilibrium. A maximum expansion of approximately 1 mm in radius and a lifetime of 40 μs are predicted for the aluminum plasma.

  18. Time-resolved laser-induced fluorescence measurement of ion and neutral dynamics in a Hall thruster during ionization oscillations

    NASA Astrophysics Data System (ADS)

    Lucca Fabris, Andrea; Young, Christopher V.; Cappelli, Mark A.

    2015-12-01

    The paper presents spatially and temporally resolved laser-induced fluorescence (LIF) measurements of the xenon ion and neutral velocity distribution functions in a 400 W Hall thruster during natural ionization oscillations at 23 kHz, the so-called "breathing mode." Strong fluctuations in measured axial ion velocity throughout the discharge current cycle are observed at five spatial locations and the velocity maxima appear in the low current interval. The spatio-temporal evolution of the ion velocity distribution function suggests a propagating acceleration front undergoing periodic motion between the thruster exit plane and 1 cm downstream into the plume. The ion LIF signal intensity oscillates almost in phase with the discharge current, while the neutral fluorescence signal appears out of phase, indicating alternating intervals of strong and weak ionization.

  19. 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.

  20. Dynamic Optical Gratings Accessed by Reversible Shape Memory.

    PubMed

    Tippets, Cary A; Li, Qiaoxi; Fu, Yulan; Donev, Eugenii U; Zhou, Jing; Turner, Sara A; Jackson, Anne-Martine S; Ashby, Valerie Sheares; Sheiko, Sergei S; Lopez, Rene

    2015-07-01

    Shape memory polymers (SMPs) have been shown to accurately replicate photonic structures that produce tunable optical responses, but in practice, these responses are limited by the irreversibility of conventional shape memory processes. Here, we report the intensity modulation of a diffraction grating utilizing two-way reversible shape changes. Reversible shifting of the grating height was accomplished through partial melting and recrystallization of semicrystalline poly(octylene adipate). The concurrent variations of the grating shape and diffraction intensity were monitored via atomic force microscopy and first order diffraction measurements, respectively. A maximum reversibility of the diffraction intensity of 36% was repeatable over multiple cycles. To that end, the reversible shape memory process is shown to broaden the functionality of SMP-based optical devices. PMID:26081101

  1. Dynamics of ps-pulse induced gratings in LC panels

    NASA Astrophysics Data System (ADS)

    Bartkiewicz, Stanislaw; Miniewicz, Andrzej; Sahraoui, Bouchta; Kajzar, Francois

    2002-06-01

    In the present work we focused our attention on studies of PVK:TNF hybrid polymer liquid crystal panels under short pulse laser illumination conditions. The diffraction gratings in a LC panel were induced by crossed beams generated by doubled in frequency Nd:YAG laser ((lambda) equals 532 nm) delivering pulses of 20 ps duration. So induced gratings were read by a cw laser radiation coming from a weak power He-Ne laser working at (lambda) equals 632.8 nm. The temporal evolution of intensity of first order diffraction measured in PVK:TNF hybrid liquid crystal panels shows many interesting features and complexity dependent on various experimental conditions. The substantial diffraction is observed already in time less than 1 ms after the pulse and the grating decay is completed within hundreds of milliseconds. At least three different steps of grating build-up can be distinguished which depend in various ways on the experimental conditions. A tentative mechanism of the observed responses is discussed in connection with the photoconductive properties of polymeric layers and the optical and electrical properties of the used liquid crystal E-7 (Merck).

  2. Wide dynamic range wavefront sensor using sub-wavelength grating array

    NASA Astrophysics Data System (ADS)

    Liang, Xiaobin; Li, Yanqiu; Liu, Ke

    2015-07-01

    We propose a new zonal wavefront sensor with a very wide dynamic range. The proposed sensor uses a sub-wavelength grating array to subdivide the input wavefront and produce transmitted light spots on CCD. The wavefront tilts are calculated from the transmissions of a sub-wavelength grating array. The dynamic range and resolution of the proposed sensor are respectively decided by the grating parameters and the sub-unit size of the array. So these two performances of the sensor are independent of one another, which enables the realization of wide dynamic range and high resolution simultaneously. We introduce the principle of the sensor by both Rigorous Coupled Wave Analysis and Finite-Difference Time-Domain methods. A simulation is designed to validate our proposed method, and the measurement errors are analyzed. The sensor performs good sensitivity for wide incident angles, which is particularly suitable for spherical input wavefront.

  3. Laser-induced electron localization in H2(+): mixed quantum-classical dynamics based on the exact time-dependent potential energy surface.

    PubMed

    Suzuki, Yasumitsu; Abedi, Ali; Maitra, Neepa T; Gross, E K U

    2015-10-28

    We study the exact nuclear time-dependent potential energy surface (TDPES) for laser-induced electron localization with a view to eventually developing a mixed quantum-classical dynamics method for strong-field processes. The TDPES is defined within the framework of the exact factorization [A. Abedi, N. T. Maitra, and E. K. U. Gross, Phys. Rev. Lett., 2010, 105, 123002] and contains the exact effect of the couplings to the electronic subsystem and to any external fields within a scalar potential. We compare its features with those of the quasistatic potential energy surfaces (QSPES) often used to analyse strong-field processes. We show that the gauge-independent component of the TDPES has a mean-field-like character very close to the density-weighted average of the QSPESs. Oscillations in this component are smoothened out by the gauge-dependent component, and both components are needed to yield the correct force on the nuclei. Once the localization begins to set in, the gradient of the exact TDPES tracks one QSPES and then switches to the other, similar to the description provided by surface-hopping between QSPESs. We show that evolving an ensemble of classical nuclear trajectories on the exact TDPES accurately reproduces the exact dynamics. This study suggests that the mixed quantum-classical dynamics scheme based on evolving multiple classical nuclear trajectories on the exact TDPES will be a novel and useful method to simulate strong field processes. PMID:26467353

  4. On-chip optical mode conversion based on dynamic grating in photonic-phononic hybrid waveguide

    PubMed Central

    Chen, Guodong; Zhang, Ruiwen; Sun, Junqiang

    2015-01-01

    We present a scheme for reversible and tunable on-chip optical mode conversion based on dynamic grating in a hybrid photonic-phononic waveguide. The dynamic grating is built up through the acousto-optic effect and the theoretical model of the optical mode conversion is developed by considering the geometrical deformation and refractive index change. Three kinds of mode conversions are able to be realized using the same hybrid waveguide structure in a large bandwidth by only changing the launched acoustic frequency. The complete mode conversion can be achieved by choosing a proper acoustic power under a given waveguide length. PMID:25996236

  5. On-chip optical mode conversion based on dynamic grating in photonic-phononic hybrid waveguide.

    PubMed

    Chen, Guodong; Zhang, Ruiwen; Sun, Junqiang

    2015-01-01

    We present a scheme for reversible and tunable on-chip optical mode conversion based on dynamic grating in a hybrid photonic-phononic waveguide. The dynamic grating is built up through the acousto-optic effect and the theoretical model of the optical mode conversion is developed by considering the geometrical deformation and refractive index change. Three kinds of mode conversions are able to be realized using the same hybrid waveguide structure in a large bandwidth by only changing the launched acoustic frequency. The complete mode conversion can be achieved by choosing a proper acoustic power under a given waveguide length. PMID:25996236

  6. Recent Results on the Study of Transverse Beam Dynamics Using the Laser-Induced-Fluorescence Diagnostic on the Paul Trap Simulator Experiment (PTSX)

    NASA Astrophysics Data System (ADS)

    Wang, Hua; Gilson, Erik; Davidson, Ronald; Efthimion, Philip; Majeski, Richard

    2014-10-01

    The Paul Trap Simulator Experiment (PTSX) is a compact Paul trap that simulates the nonlinear transverse dynamics of an intense charged particle beam propagating through an equivalent kilometers-long magnetic alternating-gradient (AG) focusing system. The recently developed laser- induced-fluorescence (LIF) diagnostic allowed us to measure the time dependent, transverse phase space profiles of the charge bunch and better understand critical issues in charged particle beam dynamics including emittance growth, and halo particle formation. The LIF diagnostic system includes an excimer laser, a dye laser, a CCD camera system and a stable high-density barium ion source. The measurements of the radial density profiles of the barium ion source using the LIF diagnostic are calibrated and compared to measurements using a charge collector. The design of the new barium ion source and the LIF diagnostic system will be discussed. The initial results of the radial density profiles measured by the LIF diagnostic will be presented. This research is supported by the U.S. Department of Energy.

  7. 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 10 kHz to several 100 kHz 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

  8. Nanometer resolution self-powered static and dynamic motion sensor based on micro-grated triboelectrification.

    PubMed

    Zhou, Yu Sheng; Zhu, Guang; Niu, Simiao; Liu, Ying; Bai, Peng; Jing, Qingsheng; Wang, Zhong Lin

    2014-03-19

    A one-dimensional displacement and speed sensing technology that consists of a pair of micro-grating structures and utilizes the coupling between the triboelectric effect and electrostatic induction is demonstrated. Its distinct advantages, including being self-powered, high resolution, large dynamic range, and long detecting distance, show extensive potential applications in automation, manufacturing, process control, and portable devices. PMID:24375783

  9. Dynamic characterizations of high diffraction efficiency in volume Bragg grating formed by holographic photopolymerization

    NASA Astrophysics Data System (ADS)

    Pu, Haihui; Yin, Dejin; Gao, Bin; Gao, Hongyue; Dai, Haitao; Liu, Jianhua

    2009-10-01

    Volume Bragg grating with 96% diffraction efficiency (DE) was efficiently formed by holographic photopolymerization in blend syrup of photocurable trimethylolpropane triacrylate monomer and nematic liquid crystal. The formation dynamics of the composite gratings was quantitatively characterized under the frame of one-dimensional reaction-diffusion model with a revision of individual decay constants for monomer diffusion and reaction. Initial parameters of diffusion and reaction were analytically determined from the measured first order DE at the beginning stage. Evolutions of the DE, both in curing and postcuring periods, were excellently simulated, especially with postcuring reaction been taken into account.

  10. Reaction dynamics of V(a 4FJ)+NO-->VO(X 4?-)+N studied by a crossed-beam laser-induced fluorescence technique

    NASA Astrophysics Data System (ADS)

    Ishida, M.; Yamashiro, R.; Matsumoto, Y.; Honma, Kenji

    2006-05-01

    The dynamics of the reaction, V(aFJ4)+NO ?VO(X?-4)+N was studied by using a crossed-beam technique at 16.4kJ/mol of collision energy. The V atomic beam was generated by laser vaporization and crossed with the O2 beam at a right angle. The laser-induced fluorescence (LIF) for the transition of VO(B?4-X?4) was used to determine the rotational state distribution of the reaction product in the vibrational ground state. Almost pure V(aFJ4) beam was obtained by using the mixture of NH3 with N2 as a carrier gas. Comparing the LIF spectra of VO measured for two carrier gases, i.e., NH3/N2 and pure N2, it was concluded that the vibrational ground state of VO(X?-4) is formed almost entirely from the reaction of V(aFJ4) and the contribution of the metastable V(aDJ6) is negligible. The observed rotational distribution was similar to a statistical prior prediction, and suggested that the title reaction proceeds via a long-lived intermediate, which is consistent with an electron transfer mechanism.

  11. Periodic Evolution of a Xe I Population in an Oscillatory Discharge: Comparison between Time-Synchronized Laser-Induced-Fluorescence Measurements and A Dynamic Collisional-Radiative Model

    NASA Astrophysics Data System (ADS)

    Lucca Fabris, Andrea; Young, Chris V.; Cappelli, Mark A.; Plasma Physics Laboratory Team

    2014-10-01

    We study the evolution of the Xe I 6 s '[ 1 / 2 ] 1 - 6 p '[ 3 / 2 ] 2 (834.68 nm air) transition lineshape in a plasma discharge oscillating at 60 Hz using time-synchronized laser induced fluorescence (LIF) measurements and a collisional-radiative model. Two different time-synchronized LIF techniques based on phase sensitive detection of the fluorescence signal are applied, yielding consistent results. The maximum observed peak fluorescence intensity occurs at low values of the discharge current, although the peak intensity drops to zero at zero discharge current. The peak intensity also decreases at the discharge current maximum. A dynamic collisional-radiative model of the weakly ionized xenon discharge is also implemented, based on a set of rate equations. The proper electron impact cross-sections and radiative decay rates are identified from the literature and used to compute accurate rate coefficients with the Boltzmann solver Bolsig+, including the time-varying electric field. The time evolution of the probed excited state density predicted by the model shows good agreement with the experimental measurements. This work is sponsored by the U.S. Air Force Office of Scientific Research with Dr. Mitat Birkan as program manager. CVY acknowledges support from the DOE NNSA Stewardship Science Graduate Fellowship under Contract DE-FC52-08NA28752.

  12. Experimental study on pressure, stress state, and temperature-dependent dynamic behavior of shear thickening fluid subjected to laser induced shock

    NASA Astrophysics Data System (ADS)

    Wu, Xianqian; Yin, Qiuyun; Huang, Chenguang

    2015-11-01

    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 by measuring the back free surface velocities of aluminum-shear thickening fluid (STF)-aluminum assembled targets. The results showed that the attenuation behavior of shock wave in the STF was dependent on shock pressure, stress state, and test temperature. The measured back free particle velocities of the targets and shock wave velocities in the STF decreased with the decrease in shock pressure while shocked at the same stress state and the same test temperature. In addition, two types of dragging mechanisms in the STF were observed while shocked at different stress states. For a uniaxial strain state, the impact induced jamming behavior in the STF is the dragging mechanism for the attenuation of shock wave, and a critical shock pressure was required for the impact induced thickening behavior. However, while the shock wave transformed from a uniaxial strain state to a dilatation state after transmitted to a certain distance, beside the dragging effect of impact induced jamming behavior, a strong dragging effect, induced by shear induced thickening behavior, was also observed.

  13. Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

    NASA Astrophysics Data System (ADS)

    Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

    1994-12-01

    The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 S. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 s leads to a decrease in the crater depth from 1600 to 300 m. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

  14. 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.

  15. 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.

  16. Laser-induced electron dynamics including photoionization: A heuristic model within time-dependent configuration interaction theory

    NASA Astrophysics Data System (ADS)

    Klinkusch, Stefan; Saalfrank, Peter; Klamroth, Tillmann

    2009-09-01

    We report simulations of laser-pulse driven many-electron dynamics by means of a simple, heuristic extension of the time-dependent configuration interaction singles (TD-CIS) approach. The extension allows for the treatment of ionizing states as nonstationary states with a finite, energy-dependent lifetime to account for above-threshold ionization losses in laser-driven many-electron dynamics. The extended TD-CIS method is applied to the following specific examples: (i) state-to-state transitions in the LiCN molecule which correspond to intramolecular charge transfer, (ii) creation of electronic wave packets in LiCN including wave packet analysis by pump-probe spectroscopy, and, finally, (iii) the effect of ionization on the dynamic polarizability of H2 when calculated nonperturbatively by TD-CIS.

  17. Hybrid Raman/fiber Bragg grating sensor for distributed temperature and discrete dynamic strain measurements.

    PubMed

    Toccafondo, Iacopo; Taki, Mohammad; Signorini, Alessandro; Zaidi, Farhan; Nannipieri, Tiziano; Faralli, Stefano; Di Pasquale, Fabrizio

    2012-11-01

    We propose and experimentally demonstrate a hybrid fiber optic sensing technique that effectively combines Raman optical time domain reflectometry and in-line time-division-multiplexing for fiber Bragg grating (FBG) dynamic interrogation. The highly integrated proposed scheme employs broadband apodized low reflectivity FBGs with a single narrowband optical source and a shared receiver block, allowing for simultaneous measurements of distributed static temperature and discrete dynamic strain, over the same sensing fiber. PMID:23114320

  18. LASERS: Theory of operation of a distributed-feedback laser with a dynamic grating of inverted-population burning

    NASA Astrophysics Data System (ADS)

    Afanas'ev, L. A.; Drits, V. V.; Samson, B. A.

    1995-04-01

    A theory is proposed for a distributed-feedback (DFB) dye laser with a dynamic grating of inverted-population burning. This grating is created by spatially modulated radiation, which is in resonance with the active transition in the laser. A system of equations describing the DFB laser kinetics is derived for arbitrary powers of the pump radiation and of the radiation which creates the grating. The conditions for the self-excitation of this DFB laser are found. The temporal and energy characteristics of the output radiation are investigated for a DFB laser with a second-order grating.

  19. Asymmetrisation of the profile of a thin dynamic holographic grating in a TV-locked optical feedback loop

    SciTech Connect

    Venediktov, Vladimir Yu; Ivanova, Natalya L; Freigang, N N; Laskin, V A

    2009-10-31

    A system for recording a dynamic holographic grating in an optically addressed liquid-crystal spatial light modulator is studied. The system provides the asymmetrisation of the grating profile by using a TV-locked optical feedback loop (nonlinear or adaptive interferometer). (laser applications and other topics in quantum electronics)

  20. Comparison of growth dynamics and temporal stability of Bragg gratings written in polymer fibers of different types

    NASA Astrophysics Data System (ADS)

    Statkiewicz-Barabach, G.; Kowal, D.; Mergo, P.; Urbanczyk, W.

    2015-08-01

    We compare the dynamics of the Bragg gratings formation in a microstructured polymer fiber made of pure PMMA and step-index PMMA fiber with a core made of PMMA/PS copolymer. The gratings were fabricated using a standard phase mask method. In the fiber with a PMMA/PS core, based on the rate of the Bragg peaks height and bandwidth rise versus the irradiation time, we identified three phases of the grating growth, named respectively type I, mixed and type II gratings. In the pure PMMA microstructured fiber we did not observe a significant increase in the Bragg peaks width during the inscription. We have monitored the behavior of the gratings for 8 months since the fabrication and demonstrated significant differences in the long-term stability depending on the grating type.

  1. 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.

  2. The Effect of an External Magnetic Field on the Plume Expansion Dynamics of Laser-Induced Aluminum Plasma

    NASA Astrophysics Data System (ADS)

    Atif, Hussain; Li, Qi; Hao, Zuoqiang; Gao, Xun; Lin, Jingquan

    2015-08-01

    In this work, we investigated the plasma morphology induced by a Nd:YAG laser with the aim of improving the understanding of the formation and dynamics of the plasma in two cases, with and without a magnetic field. Single laser pulse production of a plasma in the absence and presence of a magnetic field was performed with an aluminum target in air. A fast photography technique was employed to obtain information about the expansion dynamics and confinement of the aluminum plasma in each case. The generation of the laser plasma was allowed to expand at two locations with different magnetic field strengths, which correspond to the strength 0.58 T in the center of two magnetic poles and 0.83 T at a distance of 4 mm from the upper pole (N). The plume showed lateral confinement at longer delays when the target was placed at the center of the two poles. When the target was placed at a distance of 4 mm from the upper pole it was observed that the plume was divided into two lobes at the initial stage and traveled towards the center of the magnetic field with further elapse of time. supported by National Natural Science Foundation of China (No. 61178022), the Research Foundation for Doctoral Program of Higher Education of China (Nos. 20112216120006, 20122216120009 and 20122216110007) and also the Project of 14KP007

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

    SciTech Connect

    Jia, X.; Jia, T. Q. Peng, N. N.; Feng, D. H.; Zhang, S. A.; Sun, Z. R.

    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.

  4. Thermophysical and gas-dynamic characteristics of laser-induced gasplasma flows under femtosecond laser ablation of titanium in vacuum

    SciTech Connect

    Loktionov, E Yu; Protasov, Yu S; Protasov, Yu Yu

    2014-03-28

    We report the results of experimental investigation of thermophysical and gas-dynamic characteristics of the gas-plasma flows induced by ultrashort (45 – 60 fs) laser pulse irradiation (the radiation wavelength λ = 400, 800 nm) of a titanium target in vacuum (∼5 × 10{sup -4} mbar). The use of combined interferometric technique and complex experimental data processing allowed us to estimate the momentum coupling coefficient (C{sub m} ∼ 10{sup -4} N W{sup -1}), the efficiency of laser energy conversion to the kinetic energy of the gas-plasma flow (65% – 85%), the spatiotemporal distributions of the particle density (n{sub e} = 10{sup 18} – 10{sup 20} cm{sup -3}) and velocity ((v)=4 – 9 km s{sup -1}), the static (10{sup 6} – 10{sup 8} Pa) and total (10{sup 7} – 10{sup 11} Pa) pressure and temperature (T=7 – 50 kK) in the flow. Our data are compared with published data obtained by other methods. (interaction of laser radiation with matter. laser plasma)

  5. Influence of surrounding gas, composition and pressure on plasma plume dynamics of nanosecond pulsed laser-induced aluminum plasmas

    NASA Astrophysics Data System (ADS)

    Dawood, Mahmoud S.; Hamdan, Ahmad; Margot, Jolle

    2015-10-01

    In this article, we present a comprehensive study of the plume dynamics of plasmas generated by laser ablation of an aluminum target. The effect of both ambient gas composition (helium, nitrogen or argon) and pressure (from 5 10-7 Torr up to atmosphere) is studied. The time- and space- resolved observation of the plasma plume are performed from spectrally integrated images using an intensified Charge Coupled Device (iCCD) camera. The iCCD images show that the ambient gas does not significantly influence the plume as long as the gas pressure is lower than 20 Torr and the time delay below 300 ns. However, for pressures higher than 20 Torr, the effect of the ambient gas becomes important, the shortest plasma plume length being observed when the gas mass species is highest. On the other hand, space- and time- resolved emission spectroscopy of aluminum ions at ? = 281.6 nm are used to determine the Time-Of-Flight (TOF) profiles. The effect of the ambient gas on the TOF profiles and therefore on the propagation velocity of Al ions is discussed. A correlation between the plasma plume expansion velocity deduced from the iCCD images and that estimated from the TOF profiles is presented. The observed differences are attributed mainly to the different physical mechanisms governing the two diagnostic techniques.

  6. Two-channel IR vibration sensor based on dynamic gratings in semiconductors and pyro-electrics

    NASA Astrophysics Data System (ADS)

    Kukhtarev, N.; Kukhtareva, T.; Caulfield, J. H.; Wang, J. C.; Murray, T.; Gnatenko, Yu. P.; Faryna, I. O.; Bukivskij, P. M.; Gamernyk, R.; Grabar, A.

    2008-04-01

    Double-functional (optical and electrical) interferometer was realized using holographic recording of dynamic gratings in the semiconductor crystals of CdTe: V, CdTe:Ti and ferroelectric-pyroelectric crystal Sn2P2S6 (SPS). Also we introduce novel holographic single-beam wave-front division interferometer that is compact, do not need stabilization and are well suited for real-world applications.

  7. Colorizing pure copper surface by ultrafast laser-induced near-subwavelength ripples.

    PubMed

    Ou, Zhigui; Huang, Min; Zhao, Fuli

    2014-07-14

    We demonstrate that the colorizing effect of angle dependence can be efficiently and conveniently achieved on the rippled surface of pure copper processed by the femtosecond laser with an out-of-focus method, which greatly improves the machining speed. Such a laser-induced colorization can occur in a wide range of laser fluence, which determines the coverage and morphological characteristics of laser-induced ripples and thus can finely tune the colorizing effect. By inspecting the colors and corresponding spectra of treated areas at different angles, the relationship between the diffracted light central wavelength and the laser-induced near-subwavelength grating is analyzed quantitatively based on the fundamental grating equation with the experimental grating parameters. The spectrum analysis indicates that for the laser fluence increasing in a suitable range, the more clarity and regularity of formed ripples should bring out a more prominent grating effect, which becomes further matching of the grating equation in a larger inspecting angle for the elimination of the influence of the diffused reflection light. In short, the study confirms that the colorizing phenomenon mainly ascribes to the grating diffraction effect of the laser-induced periodic surface ripples, which would help to enable the flexible control of the colorizing effect induced by laser processing on pure copper. PMID:25090539

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

    SciTech Connect

    Alatas, Husin

    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.

  10. Control of the parameters of solid-state lasers by dynamic gratings in a DKDP crystal

    SciTech Connect

    Anikeev, B V; Kutsenko, S A; Sin'ko, D V; Sukhorukov, V S

    1999-04-30

    Pulsed and cw Nd{sup 3+}:YAG lasers were used in an experimental investigation of the influence of dynamic gratings in intracavity DKDP crystal elements on the main characteristics of the radiation emitted by solid-state lasers at room temperature. A hologram, formed in a DKDP crystal by a two-beam method, induced generation of pulsed laser radiation which had the spectral characteristics of a signal beam injected from outside in the form of radiation from a cw Nd{sup 3+}:YAG laser. In experiments on a cw Nd{sup 3+}:YAG laser the formation of a phase grating resulted in selection of transverse radiation modes. Such selection made the repetition period of the lasing spikes more regular and reduced their duration. A study was made of the dependence of the amplitude of a photoinduced electric field, inducing photorefraction, on the polarisation of the radiation of the 1.06 {mu}m wavelength. The formation of phase gratings in a DKDP crystal was the effect of excitation of impurity centres. The results obtained indicated feasibility of extending the range of control functions which can be performed by DKDP crystal elements. (control of laser radiation parameters)

  11. Photochromism of spirooxazine-doped polymers studied by monitoring dynamics of holographic gratings

    NASA Astrophysics Data System (ADS)

    Xie, Xin; Zheng, Meiling; Fu, Shencheng; Shi, Feng; Wang, Xiuli; Zhan, Naiyan

    2015-03-01

    As an organic photochromic material, spirooxazine attracted widespread attention because of its high fatigue resistance and thermal stability. In this paper, the photochromism of spirooxazine was studied by monitoring the dynamics of holographic gratings in spirooxazine-doped polymer films. A theoretical description for the transformation of spirooxazine and merocyanine molecules was carried out, which agrees well with the experimental results. The photochromism of spirooxazine-doped different matrixes were studied, the photochromic rate and fatigue resistance of spirooxazine-doped SiO2 films were found to be better than spirooxazine-doped PMMA films.

  12. Efficient distributed feedback solid state dye laser with a dynamic grating

    NASA Astrophysics Data System (ADS)

    Wadsworth, W. J.; McKinnie, I. T.; Woolhouse, A. D.; Haskell, T. G.

    We present the first operation of a distributed feedback solid state dye laser with a dynamic, pump-induced grating. Broadly tunable, narrow band operation in the region of 616 nm (604-649 nm) has been demonstrated with perylene red laser dye doped in poly(methyl methacrylate) (PMMA), when pumped with a frequency doubled Nd:YAG laser. Conversion efficiencies of 20%, corresponding to 35% optical-to-optical efficiency, have been measured. The laser bandwidth was between 0.01 and 0.04 nm, and smooth tuning over more than 200 GHz has been demonstrated.

  13. Laser-induced dispersion control.

    PubMed

    Rasskazov, Gennady; Ryabtsev, Anton; Lozovoy, Vadim V; Dantus, Marcos

    2014-06-01

    An intense laser pulse is used to control the spectral phase of a weak probe pulse as they overlap in fused silica. The laser-induced linear chirp is controlled by the delay time between pulses. Dependence from intensity and spectral phase of the pump pulse is also studied. Experimental data is validated by numerical simulation based on optical Kerr effect. Results show that laser-induced pulse shaping is possible and may be useful for intracavity pulse compression and shaping in enhancement cavities. PMID:24876014

  14. High dynamic range temperature-compensated fibre Bragg gratings sensor for structural monitoring of buildings

    NASA Astrophysics Data System (ADS)

    Smeu, E.; Gnewuch, H.; Jackson, D. A.; Podoleanu, A.

    2006-06-01

    The distance changes between structural elements inside a building (e.g. walls, pillars, stairs, etc.) ought to be monitored, especially in seismic-prone areas, in order to assess its stability. Fibre Bragg grating (FBG) sensors are now the most interesting choice for this purpose, since several gratings can be included in the fibre, resulting in a quasi-distributed sensor, which can be illuminated using a single light source and interrogated simply by a single optical spectrum analyzer (OSA), using wavelength multiplexing. The paper deals with such a sensor, which was installed for monitoring the distance changes in a construction joint between two building blocks inside the University "Politehnica" of Bucharest. Since this city is placed in a seismic-prone area, we use a fast scanning OSA, so that the dynamic behavior of the monitored construction joint is expected to be captured during future earthquakes. Slow drifts of the construction joint width will be also monitored. The paper describes the sensor structure and working principle, the experimental tests and main parameters evaluation. The reported sensor is temperature compensated. It has an estimated distance resolution better or equal to 10 ?m, and a linearity of +0.2%...-0.35% for displacements up to 0.55 mm. Simulated dynamic tests are also reported.

  15. Kinetic Approach for Laser-Induced Plasmas

    SciTech Connect

    Omar, Banaz; Rethfeld, Baerbel

    2008-10-22

    Non-equilibrium distribution functions of electron gas and phonon gas excited with ultrashort intense laser pulses are calculated for laser-induced plasmas occurring in solids. The excitation during femtosecond irradiation and the subsequent thermalization of the free electrons, as well as the dynamics of phonons are described by kinetic equations. The microscopic collision processes, such as absorption by inverse bremsstrahlung, electron-electron collisions, and electron-phonon interactions are considered by complete Boltzmann collision integrals. We apply our kinetic approach for gold by taking s-band electron into account and compare it with the case of excitation of d-band electrons.

  16. Laser induced forward transfer of soft materials

    NASA Astrophysics Data System (ADS)

    Palla-Papavlu, A.; Dinca, V.; Luculescu, C.; Shaw-Stewart, J.; Nagel, M.; Lippert, T.; Dinescu, M.

    2010-12-01

    A strong research effort is presently aimed at patterning methodologies for obtaining controlled defined micrometric polymeric structures for a wide range of applications, including electronics, optoelectronics, sensors, medicine etc. Lasers have been identified as appropriate tools for processing of different materials, such as ceramics and metals, but also for soft, easily damageable materials (biological compounds and polymers). In this work we study the dynamics of laser induced forward transfer (LIFT) with a gap between the donor and the receiver substrates, which is the basis for possible applications that require multilayer depositions with high spatial resolution.

  17. Investigation on the role of air in the dynamical evolution and thermodynamic state of a laser-induced aluminium plasma by spatial- and time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Cristoforetti, G.; Lorenzetti, G.; Legnaioli, S.; Palleschi, V.

    2010-09-01

    The amount and the spatial distribution of air atoms and ions in a laser-induced plasma in ambient air provide important information about the formation of the plasma and its successive evolution history. For this reason, in the present work, the air mixing in a laser-induced plasma in air at atmospheric pressure and its influence on its thermodynamic evolution were studied. Information about spatial distributions of atoms and ions from Al, N and O were achieved by Abel-inverted spectra in the plume. The occurrence of LTE in the plume was also assessed by the utilization of theoretical criteria, and by the analysis of experimental spectra. Aluminium atoms and ions were found to be in LTE, while nitrogen and oxygen were not because of their longer times of relaxation toward equilibrium. Nitrogen was found to be over-ionized with respect to Saha-Eggert equilibrium, indicating that the plasma is recombining. Experimental observations suggest that the concentration of air species in the plasma is larger than that of aluminium, even in the region closer to the target, where the aluminium lines are stronger. In the front part of the plume only emission lines from air species were observed. The results suggest that a Laser-Supported Detonation (LSD) regime occurs during the trailing part of the laser pulse, resulting in the strong inclusion into the plasma of air elements. In this scenario, also the thermodynamic history of the plume is affected by the predominance of air species.

  18. 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.

  19. Laser-induced thermal-acoustic velocimetry with heterodyne detection.

    PubMed

    Schlamp, S; Cummings, E B; Sobota, T H

    2000-02-15

    Laser-induced thermal acoustics (LITA) was used with heterodyne detection to measure simultaneously and in a single laser pulse the sound speed and flow velocity of NO>(2) -seeded air in a low-speed wind tunnel up to Mach number M =0.1 . The uncertainties of the velocity and the sound speed measurements were ~0.2 m/s and 0.5%, respectively. Measurements were obtained through a nonlinear least-squares fit to a general, analytic closed-form solution for heterodyne-detected LITA signals from thermal gratings. Agreement between theory and experiment is exceptionally good. PMID:18059836

  20. Characterization of temperature-dependent birefringence in polarization maintaining fibers based on Brillouin dynamic gratings

    NASA Astrophysics Data System (ADS)

    Kim, Yong Hyun; Song, Kwang Yong

    2015-07-01

    Temperature dependence of birefringence in various types of polarization-maintaining fibers (PMF's) is rigorously investigated by the spectral analysis of Brillouin dynamic grating (BDG). PANDA, Bowtie, and PM photonic crystal fibers are tested in the temperature range of -30 to 150 ºC, where nonlinear temperature dependence is quantified for each fiber to an accuracy of ±7.6 × 10-8. It is observed that the amount of deviation from the linearity varies according to the structural parameters of the PMF's and the existence of acrylate jacket. Experimental confirmation of the validity of the BDG-based birefringence measurement is also presented in comparison to the periodic lateral force method.

  1. Dynamic assessment of women pelvic floor function by using a fiber Bragg grating sensor system

    NASA Astrophysics Data System (ADS)

    Ferreira, Luis A.; Arajo, Francisco M.; Mascarenhas, Teresa; Natal Jorge, Renato M.; Fernandes, Antnio A.

    2006-02-01

    We present a novel sensing system consisting of an intravaginal probe and an optoelectronic measurement unit, which allows an easy, comfortable and quantitative dynamic evaluation of women pelvic floor muscle strength. The sensing probe is based on a silicone cylinder that transduces radial muscle pressure into axial load applied to a fiber Bragg grating strain sensor. The performance of a first sensor probe prototype with temperature referentiation and of the autonomous, portable optoelectronic measurement unit with data logging capabilities and graphical user interface is disclosed. The presented results refer to an ongoing collaboration work between researchers from the Medical, Optoelectronics and Mechanical areas, directed to the development of equipment that can assist in medical practice and help in the research of primary mechanisms responsible for several pelvic floor disorders, in particular urogenital prolapses.

  2. Coherent pulse compression Brillouin dynamic gratings reflectometry for slope-assisted, fast and distributed fiber strain sensing

    NASA Astrophysics Data System (ADS)

    Bergman, A.; Langer, T.; Tur, M.

    2015-09-01

    The performance of optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings in polarization-maintaining fibers, is significantly enhanced using coherent pulse compression techniques. The strain sensitivity of the reflectivity of a coded probe, orthogonally polarized to the pumps which generated the grating, depends on both pumps and probe detuning. Employing a 64 bit Golay code, the system sensitivity was enhanced eightfold, while retaining the high sampling rate of 1MHz. We report the measurement of 750Hz strain vibrations (limited by the bandwidth of the vibration source) with a spatial resolution of 20cm (limited by the bandwidth of the balanced photoreceivers).

  3. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Not Available

    1993-01-01

    We have used combined vibrational overtone excitation and laser induced fluorescence detection to study dissociation dynamics of hydroxylamine (NH[sub 2]OH), have performed our first laser induced grating experiments on water, and have begun assembling a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation. We study role of vibrational excitation in photodissociation dynamics by using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then to excite that molecule to a dissociative electronic state.

  4. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Crim, F.F.

    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.

  5. A fundamental understanding of the dependence of the laser-induced breakdown spectroscopy (LIBS) signal strength on the complex focusing dynamics of femtosecond laser pulses on either side of the focus.

    PubMed

    Zuhlke, Craig A; Bruce, John; Anderson, Troy P; Alexander, Dennis R; Parigger, Christian G

    2014-01-01

    We correlate the focusing dynamics of 50 femtosecond (fs) laser radiation as it interacts with a silicon sample to laser-induced breakdown spectroscopy (LIBS) signal strength. Presented are concentric ring-shaped variations in the electric field in the prefocus region due to lens aberrations and nonsymmetry between the prefocus and post-focus beam profile as a result of continuum generation, occurring around the focus. Experimental results show different signal trends for both atmospheric and vacuum conditions, attributed to the existence of a continuum for the former. Lens aberrations effects on the LIBS signal strength are investigated using a plano-convex spherical lens and an aspherized achromatic lens. High-resolution scanning electron micrographs of the silicon surface after ablation, along with theoretical simulations, reveal the electric field patterns near the focus. The research results contribute to fundamental understanding of the basic physics of ultrashort, femtosecond laser radiation interacting with materials. PMID:25226256

  6. Dynamic study of conduction carriers in YBa2Cu3O7-? thin films using a pulsed-laser-induced transient-thermoelectric-effect method

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Tai, G. X.; Tamura, S.; Inoue, M.

    1992-07-01

    The pulsed-laser-induced transient thermoelectric effect (TTE) has been measured for c-axis-oriented YBa2Cu3O7-? thin films over a wide time range (50 ns to 2 ms) and temperature range (10-300 K). The analysis of the decay curves of TTE voltages has revealed that the YBa2Cu3O7-? system has multiple conduction carriers, the semiconducting holes in the one-dimensional (1D) CuO chains and two types of holes (light-mass and heavy-mass holes) arising from the metallic 2D CuO2-derived band. From the observed relaxation times for thermal diffusions of light and heavy holes, we have estimated their mobilities, which show a ``critical slowing-down''-like anomaly near the superconducting transition temperature Tc. The temperature dependence of the hole mobilities can be reasonably explained by considering a critical divergent nature of the diffusion coefficients for conduction holes and a ``quasiparticle lifetime'' ?* in the superconducting state. In the superconducting state we have observed the stepwise-, shunt-, and plateau-type TTE signals above and/or below a characteristic temperature T*c (=35 K). The presence of T*c is indicative of an additional superconducting transition from phase I to II of the quasiparticle system.

  7. High pressure sensing and dynamics using high speed fiber Bragg grating interrogation systems

    NASA Astrophysics Data System (ADS)

    Rodriguez, G.; Sandberg, R. L.; Lalone, B. M.; Marshall, B. R.; Grover, M.; Stevens, G.; Udd, E.

    2014-06-01

    Fiber Bragg gratings (FBGs) are developing into useful sensing tools for measuring high pressure dynamics in extreme environments under shock loading conditions. Approaches using traditional diode array coupled FBG interrogation systems are often limited to readout speeds in the sub-MHz range. For shock wave physics, required detection speeds approaching 100 MHz are desired. We explore the use of two types of FBG sensing systems that are aimed at applying this technology as embedded high pressure probes for transient shock events. Both approaches measure time resolved spectral shifts in the return light from short (few mm long) uniform FBGs at 1550 nm. In the first approach, we use a fiber coupled spectrometer to demultiplex spectral channels into an array (up to 12) of single element InGaAs photoreceivers. By monitoring the detectors during a shock impact event with high speed recording, we are able to track the pressure induced spectral shifting in FBG down to a time resolution of 20 ns. In the second approach, developed at the Special Technologies Lab, a coherent mode-locked fiber laser is used to illuminate the FBG sensor. After the sensor, wavelength-to-time mapping is accomplished with a chromatic dispersive element, and entire spectra are sampled using a single detector at the modelocked laser repetition rate of 50 MHz. By sampling with a 12 GHz InGaAs detector, direct wavelength mapping in time is recorded, and the pressure induced FBG spectral shift is sampled at 50 MHz. Here, the sensing systems are used to monitor the spectral shifts of FBGs that are immersed into liquid water and shock compressed using explosives. In this configuration, the gratings survive to pressures approaching 50 kbar. We describe both approaches and present the measured spectral shifts from the shock experiments.

  8. High Pressure Sensing and Dynamics Using High Speed Fiber Bragg Grating Interrogation Systems

    SciTech Connect

    Rodriguez, G.; Sandberg, R. L.; Lalone, B. M.; Marshall, B. R.; Grover, M.; Stevens, G. D.; Udd, E.

    2014-06-01

    Fiber Bragg gratings (FBGs) are developing into useful sensing tools for measuring high pressure dynamics in extreme environments under shock loading conditions. Approaches using traditional diode array coupled FBG interrogation systems are often limited to readout speeds in the sub-MHz range. For shock wave physics, required detection speeds approaching 100 MHz are desired. We explore the use of two types of FBG sensing systems that are aimed at applying this technology as embedded high pressure probes for transient shock events. Both approaches measure time resolved spectral shifts in the return light from short (few mm long) uniform FBGs at 1550 nm. In the first approach, we use a fiber coupled spectrometer to demultiplex spectral channels into an array (up to 12) of single element InGaAs photoreceivers. By monitoring the detectors during a shock impact event with high speed recording, we are able to track the pressure induced spectral shifting in FBG down to a time resolution of 20 ns. In the second approach, developed at the Special Technologies Lab, a coherent mode-locked fiber laser is used to illuminate the FBG sensor. After the sensor, wavelength-to-time mapping is accomplished with a chromatic dispersive element, and entire spectra are sampled using a single detector at the modelocked laser repetition rate of 50 MHz. By sampling with a 12 GHz InGaAs detector, direct wavelength mapping in time is recorded, and the pressure induced FBG spectral shift is sampled at 50 MHz. Here, the sensing systems are used to monitor the spectral shifts of FBGs that are immersed into liquid water and shock compressed using explosives. In this configuration, the gratings survive to pressures approaching 50 kbar. We describe both approaches and present the measured spectral shifts from the shock experiments.

  9. 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.

  10. Laser-induced breakdown spectroscopy in China

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Yuan, Ting-Bi; Hou, Zong-Yu; Zhou, Wei-Dong; Lu, Ji-Dong; Ding, Hong-Bin; Zeng, Xiao-Yan

    2014-08-01

    Laser-induced breakdown spectroscopy (LIBS) has been regarded as a future superstar for chemical analysis for years due to its unique features such as little or no sample preparation, remote sensing, and fast and multi-element analysis. Chinese LIBS community is one of the most dynamically developing communities in the World. The aim of the work is to inspect what have been done in China for LIBS development and, based on the understanding of the overall status, to identify the challenges and opportunities for the future development. In this paper, the scientific contributions from Chinese LIBS community are reviewed for the following four aspects: fundamentals, instrumentation, data processing and modeling, and applications; and the driving force of LIBS development in China is analyzed, the critical issues for successful LIBS application are discussed, and in our opinion, the potential direction to improve the technology and to realize large scale commercialization in China is proposed.

  11. The photodissociation and reaction dynamics of vibrationally excited molecules. Technical progress report, 1992--1993

    SciTech Connect

    Not Available

    1993-04-01

    We have used combined vibrational overtone excitation and laser induced fluorescence detection to study dissociation dynamics of hydroxylamine (NH{sub 2}OH), have performed our first laser induced grating experiments on water, and have begun assembling a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation. We study role of vibrational excitation in photodissociation dynamics by using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then to excite that molecule to a dissociative electronic state.

  12. Experimental investigations on nonlinear dynamics of a semiconductor laser subject to optical injection and fiber Bragg grating feedback

    NASA Astrophysics Data System (ADS)

    Song, Jian; Zhong, Zhu-Qiang; Wei, Li-Xia; Wu, Zheng-Mao; Xia, Guang-Qiong

    2015-11-01

    Nonlinear dynamical characteristics of a slave semiconductor laser (S-SL) subject to optical injection from a master SL (M-SL) and optical feedback from a fiber Bragg grating (FBG) are investigated experimentally. First, we investigate the nonlinear dynamics of the S-SL subject to only optical injection. Through varying the injection coefficient and fixing the frequency detuning between the M-SL and S-SL, some dynamical states with typical characteristics are recorded and identified. Next, the variations of these dynamical states are further investigated with the introduction of a FBG feedback, and the according results show that these dynamical states may be changed after a FBG feedback is introduced into the S-SL. Finally, after collecting the mappings of the dynamical states of S-SL in the parameter space of injection coefficient and frequency detuning under different FBG feedback coefficients, the influences of FBG feedback on the nonlinear dynamics of the S-SL are analyzed.

  13. 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.

  14. Reaction dynamics of V(a {sup 4}F{sub J})+NO{yields}VO(X {sup 4}{sigma}{sup -})+N studied by a crossed-beam laser-induced fluorescence technique

    SciTech Connect

    Ishida, M.; Yamashiro, R.; Matsumoto, Y.; Honma, Kenji

    2006-05-28

    The dynamics of the reaction, V(a {sup 4}F{sub J})+NO{yields}VO(X {sup 4}{sigma}{sup -})+N was studied by using a crossed-beam technique at 16.4 kJ/mol of collision energy. The V atomic beam was generated by laser vaporization and crossed with the O{sub 2} beam at a right angle. The laser-induced fluorescence (LIF) for the transition of VO(B {sup 4}{pi}-X {sup 4}{sigma}) was used to determine the rotational state distribution of the reaction product in the vibrational ground state. Almost pure V(a {sup 4}F{sub J}) beam was obtained by using the mixture of NH{sub 3} with N{sub 2} as a carrier gas. Comparing the LIF spectra of VO measured for two carrier gases, i.e., NH{sub 3}/N{sub 2} and pure N{sub 2}, it was concluded that the vibrational ground state of VO(X {sup 4}{sigma}{sup -}) is formed almost entirely from the reaction of V(a {sup 4}F{sub J}) and the contribution of the metastable V(a {sup 6}D{sub J}) is negligible. The observed rotational distribution was similar to a statistical prior prediction, and suggested that the title reaction proceeds via a long-lived intermediate, which is consistent with an electron transfer mechanism.

  15. Fast dynamic interferometric lithography for large submicrometric period diffraction gratings production

    NASA Astrophysics Data System (ADS)

    Gt, Valentin; Bernaud, Gerard; Veillas, Colette; Cazier, Anthony; Vocanson, Francis; Jourlin, Yves; Langlet, Michel

    2013-09-01

    This paper describes a successful technological transfer, from a state laboratory to an industrial company, for writing long and large submicron period gratings (potentially square-meter sized), implemented in an industrial direct laser beam writing equipment at 355 nm wavelength (Dilase 750 from KLOE SA company). The writing head, which has been inserted in the machine, consists of a phase mask which enables it to project a set of fringes pattern of small area onto a photoresist-coated substrate. As the substrate is continuously moving, one-dimensional or two-dimensional gratings can be fabricated over large areas limited only by the machine's stage displacement range. The optical scheme is described from the beam shaping to the printing processes and the phase mask optimization. In order to demonstrate the technology, 600 nm period gratings of over 20 cm in length have been fabricated. Such submicron structures can be used in solar cell modules for photon trapping and as antireflection coatings.

  16. Dynamic index modulation mechanism in polarization-maintained fiber Bragg gratings induced by transverse acoustic waves.

    PubMed

    Miao, Ren; Zhang, Wei; Feng, Xue; Zhao, Jianhui; Liu, Xiaoming

    2009-08-20

    A novel index modulation mechanism of polarization-maintained fiber Bragg gratings based on the microbend of stress members induced by a transverse acoustic wave is proposed and investigated experimentally. The index modulation leads to a series of ghost gratings with specific polarization, whose wavelengths can be tuned by the acoustic wave frequency and whose intensities depend on the vibration direction of the transverse acoustic wave. Our method provides a novel way to achieve polarization-dependent narrowband acousto-optic tunable filters. PMID:19696859

  17. Interaction between jets during laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Hennig, G.; Delaporte, P.; Serra, P.

    2014-07-01

    Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.

  18. Interaction between jets during laser-induced forward transfer

    SciTech Connect

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P.; Hennig, G.; Delaporte, P.

    2014-07-07

    Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.

  19. Supersonic laser-induced jetting of aluminum micro-droplets

    SciTech Connect

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-04

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10–100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  20. Supersonic laser-induced jetting of aluminum micro-droplets

    NASA Astrophysics Data System (ADS)

    Zenou, M.; Sa'ar, A.; Kotler, Z.

    2015-05-01

    The droplet velocity and the incubation time of pure aluminum micro-droplets, printed using the method of sub-nanosecond laser induced forward transfer, have been measured indicating the formation of supersonic laser-induced jetting. The incubation time and the droplet velocity were extracted by measuring a transient electrical signal associated with droplet landing on the surface of the acceptor substrate. This technique has been exploited for studying small volume droplets, in the range of 10-100 femto-litters for which supersonic velocities were measured. The results suggest elastic propagation of the droplets across the donor-to-acceptor gap, a nonlinear deposition dynamics on the surface of the acceptor and overall efficient energy transfer from the laser beam to the droplets.

  1. High-sensitivity optical time-domain reflectometry based on Brillouin dynamic gratings in polarization maintaining fibers.

    PubMed

    Song, Kwang Yong

    2012-12-01

    A high-sensitivity optical time-domain reflectometry based on Brillouin dynamic grating (BDG) is proposed and experimentally demonstrated in polarization-maintaining fibers, where a single-end access to a fiber under test is applied with co-propagation of pump and probe pulses for the operation of BDG. Distributed measurements of the BDG spectra are presented with 80 cm spatial resolution in 935 m range, showing strain and temperature sensitivities of 1.37 MHz/με and -57.48 MHz/°C, respectively. PMID:23262688

  2. Attosecond pump-probe transition-state spectroscopy of laser-induced molecular dissociative ionization: Adiabatic versus nonadiabatic dressed-state dynamics

    NASA Astrophysics Data System (ADS)

    Lefebvre, C.; Nguyen-Dang, T. T.; Dion, F.; Vrakking, M. J. J.; Serov, V. N.; Atabek, O.

    2013-11-01

    We discuss how a recent pump-probe study [Kelkensberg , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.123005 103, 123005 (2009)] of the dissociative ionization of H2, under the combined effect of a single extreme ultraviolet attosecond pulse and an intense near-infrared pulse, actually represents a transition-state spectroscopy of the strong-field dissociation step, i.e., of the (probe-pulse-)dressed H2+ molecular ion. The way the dissociation dynamics is influenced by the duration of the near-infrared probe pulse, and by the time delay between the two pulses, is discussed in terms of adiabatic versus nonadiabatic preparation and transport of time-parametrized Floquet resonances associated with the dissociating molecular ion. Under a long probe pulse, the field-free vibrational states of the initial wave packet are transported, in a one-to-one manner, onto the Floquet resonances defined by the field intensity of the probe pulse and propagated adiabatically under the pulse. As the probe pulse duration shortens, nonadiabatic transitions between the Floquet resonances become important and manifest themselves in two respects: first, as a vibrational shake-up effect occurring near the peak of the short pulse, and second, through strong interference patterns in the fragment's kinetic energy spectrum, viewed as a function of the time delay between the pump and the probe pulses.

  3. 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.

  4. The influence of ion gratings on rotational wavepacket dynamics inH2

    SciTech Connect

    Stavros, Vasilios G.; Leone, Stephen R.

    2007-11-24

    We generalize earlier work [V.G. Stavros, E. Harel, S.R.Leone, J. Chem. Phys. 122 (2005) 064301]by illustrating the plausiblerole ofion gratings in time-dependent degenerate four-wave mixing(TD-DFWM) experiments in H2. We postulate that at high laserintensities(1014 1015 W/cm2), H2+/H+ ions generate a static ion grating,it s signature manifested in the transformation from homodyne- toheterodyne-detection of the TD-DFWM signal, depending on laser intensity.The change in signal detection agrees with the calculated intensity forbarrier suppression ionization (BSI) in H2 and the reported onset ofsaturation for H2+ and H+, pointing towards the likely role of iongratings in intense laser field, FWM experiments.

  5. Laser-induced formation of micro-pores in the tissues for cartilage repair and treatment of glaucoma

    NASA Astrophysics Data System (ADS)

    Sobol, Emil; Baum, Olga; Shnirelman, Alexander

    2015-03-01

    Laser-induced formation of pores in cartilage and sclera tissues is a basis of novel technologies for treatment of arthritis and glaucoma. The presented theoretical model describes dynamics of the pore formation and allows optimizing laser settings.

  6. 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.

  7. 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.

  8. Laser-induced caesium-137 decay

    SciTech Connect

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

    2014-08-31

    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 {sup 137m}Ba, and discuss potential applications of laser-induced caesium-137 decay in radioactive waste disposal. (letters)

  9. Fiber Bragg grating microphone system

    NASA Astrophysics Data System (ADS)

    Mohanty, Lipi; Koh, Liang Mong; Tjin, Swee Chuan

    2006-10-01

    A fiber Bragg grating microphone has been developed and tested in the audible frequency range. The fiber Bragg grating is longitudinally attached to a membrane that vibrates in response to acoustic vibrations and is prestrained. The frequency and amplitude of the sound are encoded in the wavelength shift. The microphone can also pick up voices dynamically from a distance of a few meters. The simplicity of principle and structure of this fiber grating sensor provides scope for commercialization as an optical microphone.

  10. Laser-Induced Underwater Plasma And Its Spectroscopic Applications

    SciTech Connect

    Lazic, Violeta

    2008-09-23

    Applications of Laser Induced Breakdown Spectroscopy (LIBS) for analysis of immersed solid and soft materials, and for liquid impurities are described. A method for improving the LIBS signal underwater and for obtaining quantitative analyses in presence of strong shot-to-shot variations of the plasma properties is proposed. Dynamic of the gas bubble formed by the laser pulse is also discussed, together with its importance in Double-Pulse (DP) laser excitation. Results of the studies relative to an application of multi-pulse sequence and its effects on the plasma and gas bubble formation are also presented.

  11. Laser-induced micro-jetting from armored droplets

    NASA Astrophysics Data System (ADS)

    Marston, J. O.; Thoroddsen, S. T.

    2015-07-01

    We present findings from an experimental study of laser-induced cavitation within a liquid drop coated with a granular material, commonly referred to as "armored droplets" or "liquid marbles." The cavitation event follows the formation of plasma after a nanosecond laser pulse. Using ultra-high-speed imaging up to 320,610 fps, we investigate the extremely rapid dynamics following the cavitation, which manifests itself in the form of a plethora of micro-jets emanating simultaneously from the spaces between particles on the surface of the drop. These fine jets break up into droplets with a relatively narrow diameter range, on the order of 10 ?m.

  12. Distributed measurement of intermodal beat length in an elliptic-core two-mode fiber by Brillouin dynamic grating

    NASA Astrophysics Data System (ADS)

    Kim, Yong Hyun; Song, Kwang Yong

    2014-05-01

    Optical time-domain measurement and characterization of intermodal beat length in an elliptic-core two-mode fiber (ecore TMF) is demonstrated using Brillouin dynamic grating. A mode-selective coupler is used for selective launch and retrieval of different modes, and the operations of BDG for four different pairs of pump-probe (LP01 x-LP11 x, LP01 x-LP11 y, LP01 y-LP11 x, LP01 y-LP11 y) are observed, representing a fine structure of modal birefringence in the e-core TMF. Distributed measurement of the BDG spectrum is performed for each pair of pump-probe with 1.5 m spatial resolution mapping the difference of the effective refractive indexes of spatial and polarization modes along a 75 m TMF.

  13. Structural health monitoring of composite-based UAVs using simultaneous fiber optic interrogation by static Rayleigh-based distributed sensing and dynamic fiber Bragg grating point sensors

    NASA Astrophysics Data System (ADS)

    Tur, Moshe; Sovran, Ido; Bergman, Arik; Motil, Avi; Shapira, Osher; Ben-Simon, Uri; Kressel, Iddo

    2015-09-01

    Embedded fiber-optic strain sensing networks for airworthy assessment of operational Unmanned Aerial Vehicles (UAVs) are presented. Sensing is based on in-flight fiber Bragg grating technology, as well as on on-ground Rayleigh backscattering distributed strain sensing. While the in-flight instrumentation monitors loads, looking for excessive values, the Rayleigh-based technique is used for high spatial resolution strain distribution along the UAV wings, under prescribed loading. Consistency of measurements over time indicates structural integrity. Simultaneous strain measurements using both distributed Rayleigh and fiber Bragg gratings, on the same fiber, promises to combine high spatial resolution, though practically static measurements with dynamic, though discrete ones.

  14. Study Of Laser-Induced Copolymerization

    NASA Technical Reports Server (NTRS)

    Miner, Gilda A.; Meador, Willard E.; Chang, C. Ken

    1993-01-01

    Report describes experiments on photopolymerization of styrene/maleic anhydride copolymer published as part of Laser Polymerization Program at NASA Langley Research Center. Presents basic study of copolymerization of styrene and maleic anhydride under laser-induced initiation and polymerization. Helps to clarify different theories on such initiation and represents significant advances in understanding of basic processes.

  15. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.

    1992-04-17

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  16. (Study of flow properties of wet solids using laser induced photo chemical anemometry)

    SciTech Connect

    Falco, B.

    1992-04-09

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  17. (Study of flow properties of wet solids using laser induced photo chemical anemometry)

    SciTech Connect

    Falco, B.

    1991-01-20

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  18. (Study of flow properties of wet solids using laser induced photochemical anemometry)

    SciTech Connect

    Falco, B.

    1990-12-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  19. Study of flow properties of wet solids using laser induced photochemical anemometry

    NASA Astrophysics Data System (ADS)

    Falco, B.

    1992-04-01

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  20. Study of flow properties of wet solids using laser induced photochemical anemometry

    NASA Astrophysics Data System (ADS)

    Falco, B.

    1992-04-01

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photoluminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  1. Temperature and Pressure Dependence of Signal Amplitudes for Electrostriction Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Herring, Gregory C.

    2015-01-01

    The relative signal strength of electrostriction-only (no thermal grating) laser-induced thermal acoustics (LITA) in gas-phase air is reported as a function of temperature T and pressure P. Measurements were made in the free stream of a variable Mach number supersonic wind tunnel, where T and P are varied simultaneously as Mach number is varied. Using optical heterodyning, the measured signal amplitude (related to the optical reflectivity of the acoustic grating) was averaged for each of 11 flow conditions and compared to the expected theoretical dependence of a pure-electrostriction LITA process, where the signal is proportional to the square root of [P*P /( T*T*T)].

  2. Laser-induced THz magnetization precession for a tetragonal Heusler-like nearly compensated ferrimagnet

    NASA Astrophysics Data System (ADS)

    Mizukami, S.; Sugihara, A.; Iihama, S.; Sasaki, Y.; Suzuki, K. Z.; Miyazaki, T.

    2016-01-01

    Laser-induced magnetization precessional dynamics was investigated in epitaxial films of Mn3Ge, which is a tetragonal Heusler-like nearly compensated ferrimagnet. The ferromagnetic resonance (FMR) mode was observed, the precession frequency for which exceeded 0.5 THz and originated from the large magnetic anisotropy field of approximately 200 kOe for this ferrimagnet. The effective damping constant was approximately 0.03. The corresponding effective Landau-Lifshitz constant is approximately 60 Mrad/s and is comparable with those of the similar Mn-Ga materials. The physical mechanisms for the Gilbert damping and for the laser-induced excitation of the FMR mode were also discussed in terms of the spin-orbit-induced damping and the laser-induced ultrafast modulation of the magnetic anisotropy, respectively.

  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. Post-treatment techniques for enhancing mode-coupling in long period fiber gratings induced by CO2 laser

    NASA Astrophysics Data System (ADS)

    Xu, Xizhen; Tang, Jian; Zhao, Jing; Yang, Kaiming; Fu, Cailing; Wang, Qiao; Liu, Shen; Liao, Changrui; Lian, Jiarong; Wang, Yiping

    2015-12-01

    Two promising post-treatment techniques, i.e. applying tensile strain and rising temperature, are demonstrated to enhance the mode-coupling efficiency of the CO2-laser-induced long period fiber gratings (LPFGs) with periodic grooves. Such two post-treatment techniques can be used to enhance the resonant attenuation of the grating to achieve a LPFG-based filter with an extremely large attenuation and to tailor the transmission spectrum of the CO2-laser-induced LPFG after grating fabrication.

  5. Laser-Induced Fluorescence of Estrogens

    NASA Astrophysics Data System (ADS)

    Meshalkin, Yu. P.; Cherkasova, O. P.; Fedorov, V. I.; Samo?lova, E. S.

    2002-01-01

    Spectra of the laser-induced fluorescence of estrogensestradiol, estriol, and estronewere measured under excitation by the fourth harmonic (?=266 nm) of a Nd:YAG laser. Quantum yields of the fluorescence were evaluated by the relative technique to be 0.107 for estradiol, 0.116 for estriol, and 0.0052 for estrone. The water solution of tryptophan is used as the standard.

  6. Interaction of Laser Induced Micro-shockwaves

    NASA Astrophysics Data System (ADS)

    Leela, Ch.; Bagchi, Suman; Tewari, Surya P.; Kiran, P. Prem

    Laser induced Shock Waves (LISWs) characterized by several optical methods provide Equation of State (EOS) for a variety of materials used in high-energy density physics experiments at Mbar pressures [1, 2]. Other applications include laser spark ignition for fuel-air mixtures, internal combustion engines, pulse detonation engines, laser shock peening [3], surface cleaning [4] and biological applications (SW lithotripsy) [5] to name a few.

  7. Laser Induced Breakdown Spectroscopy of Metals

    NASA Astrophysics Data System (ADS)

    Palmer, Andria; Lawhead, Carlos; Ujj, Laszlo

    2015-03-01

    Laser Induced Breakdown Spectroscopy (LIBS) is a very practical spectroscopy to determine the chemical composition of materials. Recent technical developments resulted in equipment used on the MARS Rover by NASA. It is capable of measuring the emission spectra of laser induced plasma created by energetic laser pulses focused on the sample (rocks, metals, etc.). We have develop a Laser Induced Breakdown Spectroscopy setup and investigated the necessary experimental and methodological challenges needed to make such material identification measurements. 355 and 532 nm laser pulses with 5 ns temporal duration was used to generate micro-plasma from which compositions can be determined based on known elemental and molecular emission intensities and wavelengths. The performance of LIBS depends on several parameters including laser wavelength, pulse energy, pulse duration, time interval of observation, geometrical configuration of collecting optics, and the properties of ambient medium. Spectra recorded from alloys (e.g. US penny coin) and pure metals will be presented. Special thanks for the financial support of the Office of Undergraduate Research of UWF.

  8. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization.

    PubMed

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M; Gordon, Reuven; Choi, Byoung C

    2015-01-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1?mJ/cm(2) due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording. PMID:26515296

  9. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization

    NASA Astrophysics Data System (ADS)

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M.; Gordon, Reuven; Choi, Byoung C.

    2015-10-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1?mJ/cm2 due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording.

  10. Nanorod Surface Plasmon Enhancement of Laser-Induced Ultrafast Demagnetization

    PubMed Central

    Xu, Haitian; Hajisalem, Ghazal; Steeves, Geoffrey M.; Gordon, Reuven; Choi, Byoung C.

    2015-01-01

    Ultrafast laser-induced magnetization dynamics in ferromagnetic thin films were measured using a femtosecond Ti:sapphire laser in a pump-probe magneto-optic Kerr effect setup. The effect of plasmon resonance on the transient magnetization was investigated by drop-coating the ferromagnetic films with dimensionally-tuned gold nanorods supporting longitudinal surface plasmon resonance near the central wavelength of the pump laser. With ~4% nanorod areal coverage, we observe a >50% increase in demagnetization signal in nanorod-coated samples at pump fluences on the order of 0.1?mJ/cm2 due to surface plasmon-mediated localized electric-field enhancement, an effect which becomes more significant at higher laser fluences. We were able to qualitatively reproduce the experimental observations using finite-difference time-domain simulations and mean-field theory. This dramatic enhancement of ultrafast laser-induced demagnetization points to possible applications of nanorod-coated thin films in heat-assisted magnetic recording. PMID:26515296

  11. Time-resolved digital holographic microscopy of laser-induced forward transfer process.

    PubMed

    Ma, H; Venugopalan, V

    2014-03-01

    We develop a method for time-resolved digital holographic microscopy to obtain time-resolved 3-D deformation measurements of laser induced forward transfer (LIFT) processes. We demonstrate nanometer axial resolution and nanosecond temporal resolution of our method which is suitable for measuring dynamic morphological changes in LIFT target materials. Such measurements provide insight into the early dynamics of the LIFT process and a means to examine the effect of laser and material parameters on LIFT process dynamics. PMID:24748724

  12. Slope-assisted complementary-correlation optical time-domain analysis of Brillouin dynamic gratings for high sensitivity, high spatial resolution, fast and distributed fiber strain sensing

    NASA Astrophysics Data System (ADS)

    Bergman, A.; Langer, T.; Tur, M.

    2015-07-01

    The performance of an optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings in polarization-maintaining fibers, can be significantly enhanced using Golay complementary sequences. The strain sensitivity of the reflectivity of a coded probe primarily depends on the detuning between the orthogonally polarized pumps, which generated the grating. The system broadband sensitivity for a 256 bit unipolar probe code was demonstrated to be 50nɛ/√Hz at a sampling rate of 2MHz, which to the best of our knowledge is a record sensitivity for Brillouin dynamic sensing. We report the measurement of 10kHz strain vibrations (which is the bandwidth limit of the vibration source) with a spatial resolution of 2cm. Owing to the system high sensitivity and spatial resolution, it has the potential to be used in distributed ultrasonic detection applications.

  13. Coherent pulse interrogation system for fiber Bragg grating sensing of strain and pressure in dynamic extremes of materials.

    PubMed

    Rodriguez, George; Jaime, Marcelo; Balakirev, Fedor; Mielke, Chuck H; Azad, Abul; Marshall, Bruce; La Lone, Brandon M; Henson, Bryan; Smilowitz, Laura

    2015-06-01

    A 100 MHz fiber Bragg grating (FBG) interrogation system is described and applied to strain and pressure sensing. The approach relies on coherent pulse illumination of the FBG sensor with a broadband short pulse from a femtosecond modelocked erbium fiber laser. After interrogation of the FBG sensor, a long multi-kilometer run of single mode fiber is used for chromatic dispersion to temporally stretch the spectral components of the reflected pulse from the FBG sensor. Dynamic strain or pressure induced spectral shifts in the FBG sensor are detected as a pulsed time domain waveform shift after encoding by the chromatic dispersive line. Signals are recorded using a single 35 GHz photodetector and a 50 G Samples per second, 25 GHz bandwidth, digitizing oscilloscope. Application of this approach to high-speed strain sensing in magnetic materials in pulsed magnetic fields to ~150 T is demonstrated. The FBG wavelength shifts are used to study magnetic field driven magnetostriction effects in LaCoO3. A sub-microsecond temporal shift in the FBG sensor wavelength attached to the sample under first order phase change appears as a fractional length change (strain: ΔL/L<10-4) in the material. A second application used FBG sensing of pressure dynamics to nearly 2 GPa in the thermal ignition of the high explosive PBX-9501 is also demonstrated. Both applications demonstrate the use of this FBG interrogation system in dynamical extreme conditions that would otherwise not be possible using traditional FBG interrogation approaches that are deemed too slow to resolve such events. PMID:26072789

  14. Medical applications of laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Schomacker, Kevin T.; Frisoli, Joan K.; Deutsch, Thomas F.

    1992-02-01

    Although lasers have traditionally been used in medicine as therapeutic devices, there has been considerable interest in using them as diagnostic tools. A number of groups have been studying the medical applications of laser-induced fluorescence (LIF). We describe three projects examining the potential use of LIF in medicine. They involve the classification of colonic polyps, the LIF-guided resection of brain tumor, and the advantages of LIF for studying photosensitizer pharmacokinetics. All three projects are only summarized; complete descriptions will appear elsewhere.

  15. 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.

  16. Laser induced surface stress on water droplets.

    PubMed

    Wang, Neng; Lin, Zhifang; Ng, Jack

    2014-10-01

    Laser induced stress on spherical water droplets is studied. At mechanical equilibrium, the body stress vanishes therefore we consider only the surface stress. The surface stress on sub-wavelength droplets is slightly weaker along the light propagation direction. For larger droplets, due to their light focusing effect, the forward stress is significantly enhanced. For a particle roughly 3 micron in radius, when it is excited at whispering gallery mode with Q ? 10? by a 1 Watt Gaussian beam, the stress can be enhanced by two orders of magnitude, and can be comparable with the Laplace pressure. PMID:25321955

  17. 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.

  18. 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.

  19. 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; Zagrebin, L V; Shestov, S S

    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)

  20. CW CO2 Laser Induced Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Pola, Joseph

    1989-05-01

    CW CO2 laser driven reactions between sulfur hexafluoride and carbon oxide, carbon suboxide, carbonyl sulfide and carbon disulfide proceed at subatmospheric pressures and yield fluorinated carbon compounds and sulfur tetrafluoride. CW CO2 laser driven reactions of organic compounds in the presence of energy-conveying sulfur hexafluoride show reaction course different from that normally observed due to elimination of reactor hot surface effects. The examples concern the decomposition of polychlorohydrocarbons, 2-nitropropane, tert.-butylamine, allyl chloride, spirohexane, isobornyl acetate and the oxidation of haloolefins. CW CO2 laser induced fragmentation of 1-methyl-l-silacyclobutanes and 4-silaspiro(3.4)octane in the presence of sulfur hexafluoride is an effective way for preparation and deposition of stable organosilicon polymers.

  1. Femtosecond laser induced breakdown for combustion diagnostics

    SciTech Connect

    Kotzagianni, M.; Couris, S.

    2012-06-25

    The focused beam of a 100 fs, 800 nm laser is used to induce a spark in some laminar premixed air-methane flames operating with variable fuel content (equivalence ratio). The analysis of the light escaping from the plasma revealed that the Balmer hydrogen lines, H{sub {alpha}} and H{sub {beta}}, and some molecular origin emissions were the most prominent spectral features, while the CN ({Beta}{sup 2}{Sigma}{sup +}-{Chi}{sup 2}{Sigma}{sup +}) band intensity was found to depend linearly with methane content, suggesting that femtosecond laser induced breakdown spectroscopy can be a useful tool for the in-situ determination and local mapping of fuel content in hydrocarbon-air combustible mixtures.

  2. Laser-induced autofluorescence of caries

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Hibst, Raimund; Flemming, Gabriela; Schneckenburger, Herbert

    1993-07-01

    The laser induced autofluorescence from carious regions of human teeth was studied using a krypton ion laser at 407 nm as an excitation source, a fiberoptical detection system combined with a polychromator and an optical multichannel analyzer. In addition, time-resolved and time-gated fluorescence measurements in the nanosecond range were carried out. It was found that carious regions contain different fluorophores which emit in the red spectral range. The emission spectra with maxima around 590 nm, 625 nm and 635 nm are typical for metalloporphyrins, copro- and protoporphyrin. During excitation the fluorescence was bleached. Non-carious regions showed a broad fluorescence band with a maximum in the short-wavelength spectral region with shorter fluorescence decay times than the carious regions. Therefore, caries can be detected by spectral analysis of the autofluorescence as well as by determination of the fluorescence decay times or by time-gated imaging.

  3. 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.

  4. Laser-induced fluorescence-cued, laser-induced breakdown spectroscopy biological-agent detection

    SciTech Connect

    Hybl, John D.; Tysk, Shane M.; Berry, Shaun R.; Jordan, Michael P

    2006-12-01

    Methods for accurately characterizing aerosols are required for detecting biological warfare agents. Currently, fluorescence-based biological agent sensors provide adequate detection sensitivity but suffer from high false-alarm rates. Combining single-particle fluorescence analysis with laser-induced breakdown spectroscopy (LIBS) provides additional discrimination and potentially reduces false-alarm rates. A transportable UV laser-induced fluorescence-cued LIBS test bed has been developed and used to evaluate the utility of LIBS for biological-agent detection. Analysis of these data indicates that LIBS adds discrimination capability to fluorescence-based biological-agent detectors.However, the data also show that LIBS signatures of biological agent simulants are affected by washing. This may limit the specificity of LIBS and narrow the scope of its applicability in biological-agent detection.

  5. Determination of Young’s modulus using optical fiber long-period gratings

    NASA Astrophysics Data System (ADS)

    Mosquera, L.; Osório, Jonas H.; Cordeiro, Cristiano M. B.

    2016-01-01

    Curvature sensitive CO2-laser induced long-period fiber gratings (LPGs) were employed to measure the Young’s moduli of materials. Two techniques, ‘bar resonance’ and ‘through transmission’, were used. In the first case, flexural vibrations of bars made of various industrial materials arranged in a cantilever configuration were probed by the LPG. The measured response allowed us to obtain the bar’s vertical movement as a function of time, its frequency components and the bar material’s Young’s modulus. In the second case, the optical response of LPGs was used to determine the propagation velocities of perturbations along a bar, which allowed the straightforward calculation of the Young’s modulus. The values obtained show good agreement with the ones reported in the literature. The results obtained in this paper demonstrate the feasibility of using LPGs to dynamically characterize a material’s elastic properties. To the best of our knowledge, this is the first demonstration of the use of long-period fiber gratings for dynamically determining Young’s modulus values.

  6. Laser pulse induced gold nanoparticle gratings

    SciTech Connect

    Hung, W.-C.; Cheng, W.-H.; Tsai, M.-S.; Chung, W.-C.; Jiang, I-M.; Yeh, Pochi

    2008-08-11

    We report the results of our experimental investigation of laser induced gold nanoparticle gratings and their optical diffraction properties. A single shot of a pair Nd-YAG laser pulses with the same polarization is directed toward a 6 nm thick gold film on a substrate of polymethyl methacrylate. As a result of the laser illumination, the thin gold film is fragmented into an array of nanoparticles. Through the observation of scanning electron and dark-field optical microscopes, we discovered that the morphology of the gold nanoparticle grating is dependent on the fluence of laser pulse. The spectrum of first order diffraction shows the dependence on the absorbance property due to the presence of the nanoparticles. The ablation of nanothickness thin films via the use of laser pulses may provide a simple and efficient method for the fabrication of nanoscale structures, including two dimensional arrays of nanoparticles.

  7. 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

  8. Shadowgraphic studies of triazene assisted laser-induced forward transfer of ceramic thin films

    SciTech Connect

    Kaur, K. S.; May-Smith, T. C.; Banks, D. P.; Grivas, C.; Eason, R. W.; Fardel, R.; Nagel, M.; Lippert, T.

    2009-06-01

    The laser-induced forward transfer process of solid ceramic donor materials (gadolinium gallium oxide and ytterbium doped yttrium aluminium oxide) was studied using triazene polymer as a sacrificial layer by means of a time-resolved nanosecond-shadowgraphy technique. The dependence of the ablation dynamics and quality of the ejected donor material on the laser fluence and thickness of the sacrificial and donor layers were investigated and discussed.

  9. Femtosecond laser-induced microstructures in glasses and applications in micro-optics.

    PubMed

    Qiu, Jianrong

    2004-01-01

    Femtosecond laser has been widely used in microscopic modifications to materials due to its ultra-short laser pulse and ultrahigh light intensity. When a transparent material e.g. glass is irradiated by a tightly focused femtosecond laser, the photo-induced reaction is expected to occur only near the focused part of the laser beam inside the glass due to the multiphoton processes. We observed various induced structures e.g. color center defects, refractive index change, micro-void and micro-crack, in glasses after the femtosecond laser irradiation. In this paper, we review the femtosecond laser induced phenomena and discuss the mechanisms of the observed phenomena. We also introduce the fabrication of various micro-optical components, e.g. optical waveguide, micro-grating, micro-lens, fiber attenuator, 3-dimensional optical memory by using the femtosecond laser-induced structures. The femtosecond laser will open new possibilities in the fabrication of micro-optical components with various optical functions. PMID:15057868

  10. Railgun system using a laser-induced plasma armature

    SciTech Connect

    Onozuka, M.; Oda, Y.; Azuma, K.

    1996-05-01

    Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun. {copyright} {ital 1996 American Institute of Physics.}

  11. Ultraviolet Laser-induced ignition of RDX single crystal

    PubMed Central

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-01-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

  12. Modeling chemical reactions in laser-induced plasmas

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Under the assumption of local thermal equilibrium, a numerical algorithm is proposed to find the equation of state for laser-induced plasmas (LIPs) in which chemical reactions are permitted in addition to ionization processes. The Coulomb interaction in plasma is accounted for by the Debye-Hckel method. The algorithm is used to calculate the equation of state for LIPs containing carbon, silicon, nitrogen, and argon. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules {N}_2, {C}_2, {Si}_2, {CN}, {SiN}, {SiC} and their ions. The algorithm is incorporated into a fluid dynamic numerical model based on the Navier-Stokes equations describing an expansion of LIP plumes into an ambient gas. The dynamics of LIP plumes obtained by the ablation of SiC, solid silicon, or solid carbon in an ambient gas containing {N}_2 and Ar is simulated to study formation of molecules and molecular ions.

  13. Ultraviolet Laser-induced ignition of RDX single crystal

    NASA Astrophysics Data System (ADS)

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-02-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique.

  14. Ultraviolet Laser-induced ignition of RDX single crystal.

    PubMed

    Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

    2016-01-01

    The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm(2). The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

  15. Hydraulic Capacity of an ADA Compliant Street Drain Grate

    SciTech Connect

    Lottes, Steven A.; Bojanowski, Cezary

    2015-09-01

    Resurfacing of urban roads with concurrent repairs and replacement of sections of curb and sidewalk may require pedestrian ramps that are compliant with the American Disabilities Act (ADA), and when street drains are in close proximity to the walkway, ADA compliant street grates may also be required. The Minnesota Department of Transportation ADA Operations Unit identified a foundry with an available grate that meets ADA requirements. Argonne National Laboratory’s Transportation Research and Analysis Computing Center used full scale three dimensional computational fluid dynamics to determine the performance of the ADA compliant grate and compared it to that of a standard vane grate. Analysis of a parametric set of cases was carried out, including variation in longitudinal, gutter, and cross street slopes and the water spread from the curb. The performance of the grates was characterized by the fraction of the total volume flow approaching the grate from the upstream that was captured by the grate and diverted into the catch basin. The fraction of the total flow entering over the grate from the side and the fraction of flow directly over a grate diverted into the catch basin were also quantities of interest that aid in understanding the differences in performance of the grates. The ADA compliant grate performance lagged that of the vane grate, increasingly so as upstream Reynolds number increased. The major factor leading to the performance difference between the two grates was the fraction of flow directly over the grates that is captured by the grates.

  16. 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; Huang Huan; Wang Yang; Wu Yiqun; Gan Fuxi; Zhu Weiling; Wang Wenfang; Chen Ke; Yao Daoxin; Lai Tianshu

    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.

  17. Reconstruction of two-dimensional molecular structure with laser-induced electron diffraction from laser-aligned polyatomic molecules

    DOE PAGESBeta

    Yu, Chao; Wei, Hui; Wang, Xu; Le, Anh -Thu; Lu, Ruifeng; Lin, C. D.

    2015-10-27

    Imaging the transient process of molecules has been a basic way to investigate photochemical reactions and dynamics. Based on laser-induced electron diffraction and partial one-dimensional molecular alignment, here we provide two effective methods for reconstructing two-dimensional structure of polyatomic molecules. We demonstrate that electron diffraction images in both scattering angles and broadband energy can be utilized to retrieve complementary structure information, including positions of light atoms. Lastly, with picometre spatial resolution and the inherent femtosecond temporal resolution of lasers, laser-induced electron diffraction method offers significant opportunities for probing atomic motion in a large molecule in a typical pump-probe measurement.

  18. [Study of flow properties of wet solids using laser induced photochemical anemometry]. Quarterly technical progress report, October--December 1991

    SciTech Connect

    Falco, B.

    1992-04-17

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  19. [Study of flow properties of wet solids using laser induced photochemical anemometry]. Quarterly technical progress report, July--September 1990

    SciTech Connect

    Falco, B.

    1990-12-23

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  20. Reconstruction of two-dimensional molecular structure with laser-induced electron diffraction from laser-aligned polyatomic molecules

    PubMed Central

    Yu, Chao; Wei, Hui; Wang, Xu; Le, Anh-Thu; Lu, Ruifeng; Lin, C. D.

    2015-01-01

    Imaging the transient process of molecules has been a basic way to investigate photochemical reactions and dynamics. Based on laser-induced electron diffraction and partial one-dimensional molecular alignment, here we provide two effective methods for reconstructing two-dimensional structure of polyatomic molecules. We demonstrate that electron diffraction images in both scattering angles and broadband energy can be utilized to retrieve complementary structure information, including positions of light atoms. With picometre spatial resolution and the inherent femtosecond temporal resolution of lasers, laser-induced electron diffraction method offers significant opportunities for probing atomic motion in a large molecule in a typical pump-probe measurement. PMID:26503116

  1. Reconstruction of two-dimensional molecular structure with laser-induced electron diffraction from laser-aligned polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Yu, Chao; Wei, Hui; Wang, Xu; Le, Anh-Thu; Lu, Ruifeng; Lin, C. D.

    2015-10-01

    Imaging the transient process of molecules has been a basic way to investigate photochemical reactions and dynamics. Based on laser-induced electron diffraction and partial one-dimensional molecular alignment, here we provide two effective methods for reconstructing two-dimensional structure of polyatomic molecules. We demonstrate that electron diffraction images in both scattering angles and broadband energy can be utilized to retrieve complementary structure information, including positions of light atoms. With picometre spatial resolution and the inherent femtosecond temporal resolution of lasers, laser-induced electron diffraction method offers significant opportunities for probing atomic motion in a large molecule in a typical pump-probe measurement.

  2. Laser-induced crystallization and crystal growth.

    PubMed

    Sugiyama, Teruki; Masuhara, Hiroshi

    2011-11-01

    Recent streams of laser studies on crystallization and crystal growth are summarized and reviewed. Femtosecond multiphoton excitation of solutions leads to their ablation at the focal point, inducing local bubble formation, shockwave propagation, and convection flow. This phenomenon, called "laser micro tsunami" makes it possible to trigger crystallization of molecules and proteins from their supersaturated solutions. Femtosecond laser ablation of a urea crystal in solution triggers the additional growth of a single daughter crystal. Intense continuous wave (CW) near infrared laser irradiation at the air/solution interface of heavy-water amino acid solutions results in trapping of the clusters and evolves to crystallization. A single crystal is always prepared in a spatially and temporally controlled manner, and the crystal polymorph of glycine depends on laser power, polarization, and solution concentration. Upon irradiation at the glass/solution interface, a millimeter-sized droplet is formed, and a single crystal is formed by shifting the irradiation position to the surface. Directional and selective crystal growth is also possible with laser trapping. Finally, characteristics of laser-induced crystallization and crystal growth are summarized. PMID:21721131

  3. 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.

  4. Laser-induced forward transfer of aluminium

    NASA Astrophysics Data System (ADS)

    Schultze, V.; Wagner, M.

    1991-12-01

    The laser-induced forward transfer (LIFT) of aluminium is experimentally investigated for aluminium target thickness up to some ?m. The aluminium is transferred to glazed ceramics and to silicon substrates with and without oxidized surface, respectively. Two types of laser beam sources are used: a Nd:YAG laser with a Gaussian beam profile and a Nd:glass laser system providing a homogenized flat top profile. The resulting deposition is determined by the removal mode of the Al from the target and by the interaction of the molten Al with the substrate. In a first removal mode (low laser intensities and/or thin targets) where melting through of the target precedes the onset of vaporization at the target front side the material can easily be transferred to the substrate. In a second mode (high laser intensities and/or thick targets) the blow-off process is characterized by higher vapor pressures which leads to disturbed deposits. The interaction of impacting material with the substrate causes the formation of droplets on oxidized surfaces due to the high surface tension of liquid metals.

  5. Laser Induced Fluorescence of the Iodine Ion

    NASA Astrophysics Data System (ADS)

    Hargus, William

    2014-10-01

    Iodine (I2) has been considered as a potential electrostatic spacecraft thruster propellant for approximately 2 decades, but has only recently been demonstrated. Energy conversion efficiency appears to be on par with xenon without thruster modification. Intriguingly, performance appears to exceed xenon at high acceleration potentials. As part of a continuing program for the development of non-intrusive plasma diagnostics for advanced plasma spacecraft propulsion, we have identified the I II 5d5D4 o state as metastable, and therefore containing a reservoir of excited state ions suitable for laser probing. The 5d5D4 o - 6p5P3 transition at 695.878 nm is convenient for diode laser excitation with the 5s5S2 o - 6p5P3 transition at 516.12 nm as an ideal candidate for non-resonant fluorescence collection. We have constructed a Penning type iodine microwave discharge lamp optimized for I II production for table-top measurements. This work demonstrates I II laser-induced fluorescence in a representative iodine discharge and will validate our previous theoretical work based on the limited available historical I II spectral data.

  6. Laser-induced fluorescence in medical diagnostics

    NASA Astrophysics Data System (ADS)

    Andersson-Engels, Stefan; Johansson, Jonas; Svanberg, Katarina; Svanberg, Sune

    1990-07-01

    We have performed extensive investigations using laser-induced fluorescence in animal as well as human tissue in order to localize diseased tissue and thus discriminate such tissue from normal surrounding areas. In characterizing different tissue types the endogenous fluorescence (autofluorescence) as well as specific fluorescence from different photosensitising substances was utilized. We have investigated different experimental and human malignant tumors in vivo and in vitro as well as atherosclerotic lesions in vitro. A fiber-optic fluorosensor was constructed and used in the experiments and in the clinical examination of patients. Dimensionless spectroscopic functions were formed to ensure that the signals were independent of clinically uncontrollable variables such as distance variations, tissue topography, light source fluctuations and variations in detection efficiency. A multi-color two-dimensional imaging system was constructed for real-time imaging. The system was tested peroperatively and during standard examination patient procedures. Besides utilizing the time-integrated fluorescence signal we have also investigated the possibility of incorporating time-resolved fluorescence characterization.

  7. Laser induced fluorescence of trapped molecular ions

    SciTech Connect

    Winn, J.S.

    1980-10-01

    Laser induced fluoresence (LIF) spectra (laser excitation spectra) are conceptually among the most simple spectra to obtain. One need only confine a gaseous sample in a suitable container, direct a laser along one axis of the container, and monitor the sample's fluorescence at a right angle to the laser beam. As the laser wavelength is changed, the changes in fluorescence intensity map the absorption spectrum of the sample. (More precisely, only absorption to states which have a significant radiative decay component are monitored.) For ion spectroscopy, one could benefit in many ways by such an experiment. Most optical ion spectra have been observed by emission techniques, and, aside from the problems of spectral analysis, discharge emission methods often produce the spectra of many species, some of which may be unknown or uncertain. Implicit in the description of LIF given above is certainty as to the chemical identity of the carrier of the spectrum. This article describes a method by which the simplifying aspects of LIF can be extended to molecular ions (albeit with a considerable increase in experimental complexity over that necessary for stable neutral molecules).

  8. Laser-induced lipolysis on adipose cells

    NASA Astrophysics Data System (ADS)

    Solarte, Efrain; Gutierrez, O.; Neira, Rodrigo; Arroyave, J.; Isaza, Carolina; Ramirez, Hugo; Rebolledo, Aldo F.; Criollo, Willian; Ortiz, C.

    2004-10-01

    Recently, a new liposuction technique, using a low-level laser (LLL) device and Ultrawet solution prior to the procedure, demonstrated the movement of fat from the inside to the outside of the adipocyte (Neira et al., 2002). To determine the mechanisms involved, we have performed Scanning and Transmission Electron Microscopy studies; Light transmittance measurements on adipocyte dilutions; and a study of laser light propagation in adipose tissue. This studies show: 1. Cellular membrane alterations. 2. LLL is capable to reach the deep adipose tissue layer, and 3. The tumescence solution enhances the light propagation by clearing the tissue. MRI studies demonstrated the appearance of fat on laser treated abdominal tissue. Besides, adipocytes were cultivated and irradiated to observe the effects on isolated cells. These last studies show: 1. 635 nm-laser alone is capable of mobilizing cholesterol from the cell membrane; this action is enhanced by the presence of adrenaline and lidocaine. 2. Intracellular fat is released from adipocytes by co joint action of adrenaline, aminophyline and 635 nm-laser. Results are consistent with a laser induced cellular process, which causes fat release from the adipocytes into the intercellular space, besides the modification of the cellular membranes.

  9. Molecular formation dynamics of 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one, 1,3,5-trinitroperhydro-1,3,5-triazine, and 2,4,6-trinitrotoluene in air, nitrogen, and argon atmospheres studied using femtosecond laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sreedhar, Sunku; Nageswara Rao, E.; Manoj Kumar, G.; Tewari, Surya P.; Venugopal Rao, S.

    2013-09-01

    Femtosecond laser induced breakdown spectroscopic (LIBS) studies were performed on three high energy materials namely 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and 2,4,6-trinitrotoluene (TNT). LIBS spectral features were obtained for these samples in three different atmospheres i.e. air, nitrogen, and argon. Different molecular to elemental ratios in these three atmospheres were investigated in detail. CN/C and CN/N ratios were observed to be prominent in nitrogen and air atmospheres. We attempt to elucidate the role of several reactions involving CN molecular formation in connection with discrepancies obtained in the measured ratios. The complete temporal dynamics of atomic C (247.82 nm) and CN (388.20 nm) molecular species in three different atmospheres are elaborated. The decay rates of C peak were found to be longest (96 ns-121 ns) in argon atmosphere for all the samples. The decay rates of CN peak (388.2 nm) were longer (161 ns-364 ns) in nitrogen compared to air and argon atmospheres. We also attempt to explicate the decay mechanisms with respect to the molecular species formation dynamics in different atmospheres.

  10. Classical cutoffs for laser-induced nonsequential double ionization

    SciTech Connect

    Milosevic, D.B.; Becker, W.

    2003-12-01

    Classical cutoffs for the momenta of electrons ejected in laser-induced nonsequential double ionization are derived for the recollision-impact-ionization scenario. Such simple cutoff laws can aid in the interpretation of the observed electron spectra.

  11. Acoustic transient generation by holmium-laser-induced cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Asshauer, T.; Rink, K.; Delacretaz, G.

    1994-11-01

    The acoustic effects of free-running 2.12 micron Cr:Tm:Ho:YAG laser pulses delivered in water are studied. Laser pulses of 10 to 1200 mJ energy and 230 microsecs duration (full width at half-maximum) are used. Delivery fiber diameters of 200 - 600 microns are investigated. Combined fast flash video imaging and needle probe hydrophone pressure sensing are used. The experimental results show that the laser-induced water vapor bubbles can generate strong acoustic transients at the bubble collapse several hundreds of microsecs after the start of the laser pulse. Pressures of up to 3600 bar are measured. Above a laser fluence threshold of 40 J/sq cm the pressure amplitude increases sharply, reaching a maximum value between 100 and 200 J/sq cm. At higher fluences up to more than 1000 J/sq cm, the pressure amplitude is found to decrease again. A two-phase mechanism is proposed to describe the complex bubble dynamics generated by the free-running pulses: The isotropic expansion of an initially superheated water volume is followed by a continuous ablation phase. The results suggest a mechanism of possible unwanted acoustic damage during Holmium laser medical applications in a liquid environment.

  12. 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

  13. Dynamic sensing performance of a point-wise fiber Bragg grating displacement measurement system integrated in an active structural control system.

    PubMed

    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

  14. 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.; Rodriguez, A.

    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.

  15. 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%.

  16. Calibration free laser-induced breakdown spectroscopy of oxide materials

    NASA Astrophysics Data System (ADS)

    Praher, B.; Palleschi, V.; Viskup, R.; Heitz, J.; Pedarnig, J. D.

    2010-08-01

    The quantitative determination of oxide concentration by laser-induced breakdown spectroscopy is relevant in various fields of applications (e.g.: analysis of ores, concrete, slag). Calibration free laser-induced breakdown spectroscopy and the multivariate calibration are among the methods employed for quantitative concentration analysis of complex materials. We measured the intensity of neutral and ionized atomic emission lines of oxide materials by laser-induced breakdown spectroscopy and we modified the calibration free laser-induced breakdown spectroscopy method to increase the accuracy. The concentration of oxides was obtained by using stoichiometric relations. Sample materials were prepared from oxide powder (Fe 2O 3, MgO, CaO) by mixing and pressing. The concentration was 9.8-33.3 wt.% Fe 2O 3, 7.6-33.3 wt.% MgO and 33.3-81.2 wt.% CaO for different samples. Nd:YAG laser (wavelength 1064 nm, pulse duration ? 6 ns) ablation was performed in air. The laser-induced plasma emission was measured by an Echelle spectrometer equipped with a sensitivity calibrated ICCD camera. The numerical calibration free laser-induced breakdown spectroscopy algorithm included the fast deconvolution of instrumental function, and the correction of self-absorption effects. The oxide concentration CCF calculated from calibration free laser-induced breakdown spectroscopy results and the nominal concentration CN were very close for all samples investigated. The relative error in concentration, | CCF- CN|/ CN, was < 10%, < 20%, and < 5% for Fe 2O 3, MgO, and CaO, respectively. The results indicate that this method can be employed for the analysis of major elements in multi-component technical materials.

  17. 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. Fleming, Graham R.; Monahan, Daniele; Dawlaty, Jahan M.

    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.”.

  18. 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

  19. 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.

  20. Laser-Induced-Fluorescence Photogrammetry and Videogrammetry

    NASA Technical Reports Server (NTRS)

    Danehy, Paul; Jones, Tom; Connell, John; Belvin, Keith; Watson, Kent

    2004-01-01

    An improved method of dot-projection photogrammetry and an extension of the method to encompass dot-projection videogrammetry overcome some deficiencies of dot-projection photogrammetry as previously practiced. The improved method makes it possible to perform dot-projection photogrammetry or videogrammetry on targets that have previously not been amenable to dot-projection photogrammetry because they do not scatter enough light. Such targets include ones that are transparent, specularly reflective, or dark. In standard dot-projection photogrammetry, multiple beams of white light are projected onto the surface of an object of interest (denoted the target) to form a known pattern of bright dots. The illuminated surface is imaged in one or more cameras oriented at a nonzero angle or angles with respect to a central axis of the illuminating beams. The locations of the dots in the image(s) contain stereoscopic information on the locations of the dots, and, hence, on the location, shape, and orientation of the illuminated surface of the target. The images are digitized and processed to extract this information. Hardware and software to implement standard dot-projection photogrammetry are commercially available. Success in dot-projection photogrammetry depends on achieving sufficient signal-to-noise ratios: that is, it depends on scattering of enough light by the target so that the dots as imaged in the camera(s) stand out clearly against the ambient-illumination component of the image of the target. In one technique used previously to increase the signal-to-noise ratio, the target is illuminated by intense, pulsed laser light and the light entering the camera(s) is band-pass filtered at the laser wavelength. Unfortunately, speckle caused by the coherence of the laser light engenders apparent movement in the projected dots, thereby giving rise to errors in the measurement of the centroids of the dots and corresponding errors in the computed shape and location of the surface of the target. The improved method is denoted laser-induced-fluorescence photogrammetry.

  1. 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.

  2. Modeling and prototyping of a fiber Bragg grating-based dynamic micro-coordinate measuring machine probe

    NASA Astrophysics Data System (ADS)

    Liu, Fangfang; Chen, Lijuan; Wang, Jingfan; Xia, Haojie; Li, Ruijun; Yu, Liandong; Fei, Yetai

    2016-02-01

    Higher-accuracy measurements of the 3D metrology of nano- and micro-structures are increasingly demanded. This paper details the prototyping of a novel 3D micro-scale coordinate measuring machine probe based on fiber Bragg grating sensors for true 3D measurements at micro- and nanometer scales. A new manufacturing technique for the high-precision cantilever used in the probe is also reported. Simulations are performed during the design and testing to help to test important aspects of the probe and to gain understanding about the influence of the probe geometrical parameters on the sensor sensitivity. The initial performance of the probe has been tested in both the vertical and horizontal directions, and the characterization results are promising. Further experimental results demonstrate that the probe is not affected by surface interaction forces.

  3. 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.

  4. Time-resolved aluminium laser-induced plasma temperature measurements

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2014-11-01

    We seek to characterize the temperature decay of laser-induced plasma near the surface of an aluminium target from laser-induced breakdown spectroscopy measurements of aluminium alloy sample. Laser-induced plasma are initiated by tightly focussing 1064 nm, nanosecond pulsed Nd:YAG laser radiation. Temperatures are inferred from aluminium monoxide spectra viewed at systematically varied time delays by comparing experimental spectra to theoretical calculations with a Nelder Mead algorithm. The temperatures are found to decay from 5173 270 to 3862 46 Kelvin from 10 to 100 ?s time delays following optical breakdown. The temperature profile along the plasma height is also inferred from spatially resolved spectral measurements and the electron number density is inferred from Stark broadened H? spectra.

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

    DOEpatents

    Vo-Dinh, Tuan; Panjehpour, Masoud; Overholt, Bergein F.

    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.

  6. 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.

  7. Laser-induced local transfer of glass-ceramic materials

    NASA Astrophysics Data System (ADS)

    Kasatkin, V. U.; Shakhno, E. A.

    2011-02-01

    Nowadays there is tendency to search new materials which have specific properties in various fields of practical applications including microelectronics and optoelectronics. These materials can be applied for fabrication of new type of devices. Fabrication of glass-ceramic films by method of laser-induced local transfer is interesting purpose. Glass-ceramic films can be applied for forming of micro-optic elements, elements of microelectronic and optoelectronic circuits. Process of laser-induced local transfer of sitall ST-50-1 by fiber laser (?=1,06 ?m) was investigated and its features were revealed. Film coverings having properties of polycrystalline glass-ceramic films were carried out by laser-induced local transfer of material from ST-50-1 sitall donor plate to K8 glass acceptor substrate. Estimation of deposited films quality and its thickness was carried out and optical properties were investigated.

  8. Laser-induced local transfer of glass-ceramic materials

    NASA Astrophysics Data System (ADS)

    Kasatkin, V. U.; Shakhno, E. A.

    2010-07-01

    Nowadays there is tendency to search new materials which have specific properties in various fields of practical applications including microelectronics and optoelectronics. These materials can be applied for fabrication of new type of devices. Fabrication of glass-ceramic films by method of laser-induced local transfer is interesting purpose. Glass-ceramic films can be applied for forming of micro-optic elements, elements of microelectronic and optoelectronic circuits. Process of laser-induced local transfer of sitall ST-50-1 by fiber laser (?=1,06 ?m) was investigated and its features were revealed. Film coverings having properties of polycrystalline glass-ceramic films were carried out by laser-induced local transfer of material from ST-50-1 sitall donor plate to K8 glass acceptor substrate. Estimation of deposited films quality and its thickness was carried out and optical properties were investigated.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    The airborne laser-induced spectral emission bands obtained simultaneously from water Raman backscatter and the fluorescence of chlorophyll and other naturally occurring 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.

  11. Laser Induced Material Modification in the Bulk KDP Crystals

    SciTech Connect

    Radousky, H.B.; Staggs, M.; Runkel, M.; Burnham, A.

    1999-12-16

    Laser induced material modifications in the bulk and on the surface of KDP (KH{sub 2}PO{sub 4}) and DKDP (70-80% deuterated KDP) are studied using fluorescence imaging and spectroscopy. Photoluminescence is observed at damaged regions following above threshold exposure with an emission peak centered at 550-nm. In addition, surfaces exposed to >100 high power, 355-nm laser pulses reveal a reduced surface finishing quality as evidenced by an associated emission under UV photoexcitation. The emission spectra from the laser-induced damage sites and the laser degraded surfaces are similar suggesting the generation of similar defect species.

  12. Laser induced breakdown spectroscopy stratigraphic characterization of multilayered painted surfaces

    NASA Astrophysics Data System (ADS)

    Staicu, A.; Apostol, I.; Pascu, A.; Iordache, I.; Damian, V.; Pascu, M. L.

    2012-08-01

    Laser spectroscopy techniques are modern and competitive methods for elemental analysis. Laser induced breakdown spectroscopy (LIBS), due to its advantages as minimally invasive method that provides real time monitoring and selectivity, is a suitable tool to analyze sample composition. Based on the known emission spectra of heavy metals such as Pb, Zn, Au, Ca, a stratigraphic study regarding the identification of the painting layers content of different mock-up samples was performed. LIBS was used to monitor the laser induced stepwise selective removal of the painting layers and to analyze their composition. The obtained LIBS spectra were correlated with profilometric measurements.

  13. Ultrafast molecular imaging by laser-induced electron diffraction

    NASA Astrophysics Data System (ADS)

    Peters, M.; Nguyen-Dang, T. T.; Cornaggia, C.; Saugout, S.; Charron, E.; Keller, A.; Atabek, O.

    2011-05-01

    We address the feasibility of imaging geometric and orbital structures 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.

  14. Ultrafast molecular imaging by laser-induced electron diffraction

    SciTech Connect

    Peters, M.; Nguyen-Dang, T. T.; Cornaggia, C.; Saugout, S.; Charron, E.; Keller, A.; Atabek, O.

    2011-05-15

    We address the feasibility of imaging geometric and orbital structures 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 CO{sub 2} 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.

  15. Mechanisms of laser induced reactions in opaque heterogeneous environments

    NASA Astrophysics Data System (ADS)

    Wilkinson, F.

    1993-11-01

    The technique of laser flash photolysis has been applied to both heterogeneous and homogeneous samples in order to increase understanding of the mechanisms of laser induced reactions at surfaces. Nanosecond diffuse reflectance laser flash photolysis has been used to study triplet state absorption and fluorescence emission of monomers and dimers of acridine orange and other dyes which are shown to aggregate when adsorbed on microcrystalline cellulose and on other surfaces. The properties of excited states within dyed fabrics have been evaluated in several cases. The mechanism of the yellowing of thermomechanical paper pulp has also been investigated and transients studied on nanosecond timescales for the first time. Triplet-triplet energy transfer from benzophenone to oxazine dyes, from eosin to anthracene, and from anthracene to azomethine dyes has been studied on both cellulose and silica surfaces. This work demonstrates the occurrence of energy transfer by static and dynamic mechanisms depending on both the nature of the surface and the adsorbed species. The first picosecond studies exciting directly into the charge transfer absorption bands of aromatic hydrocarbon/oxygen complexes formed in the presence of high pressures of oxygen have been carried out to demonstrate the role of charge-transfer interactions in determining the singlet oxygen formation efficiencies during quenching of electronically excited states by molecular oxygen. Nanosecond laser excitation of a series of naphthalene and anthracene derivatives in the presence and absence of oxygen has clearly demonstrated for the first time the importance of charge transfer interactions in determining oxygen quenching constants and singlet oxygen formation efficiencies.

  16. Lanthanide-based laser-induced phosphorescence for spray diagnostics

    NASA Astrophysics Data System (ADS)

    van der Voort, D. D.; Maes, N. C. J.; Lamberts, T.; Sweep, A. M.; van de Water, W.; Kunnen, R. P. J.; Clercx, H. J. H.; van Heijst, G. J. F.; Dam, N. J.

    2016-03-01

    Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (˜1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.

  17. Fiber-bragg grating-loop ringdown method and apparatus

    DOEpatents

    Wang, Chuji (Starkville, MS)

    2008-01-29

    A device comprising a fiber grating loop ringdown (FGLRD) system of analysis is disclosed. A fiber Bragg grating (FBG) or Long-Period grating (LPG) written in a section of single mode fused silica fiber is incorporated into a fiber loop. By utilizing the wing areas of the gratings' bandwidth as a wavelength dependent attenuator of the light transmission, a fiber grating loop ringdown concept is formed. One aspect of the present invention is temperature sensing, which has been demonstrated using the disclosed device. Temperature measurements in the areas of accuracy, stability, high temperature, and dynamic range are also described.

  18. Molecular-level mechanisms of nanoparticle detachment in laser-induced plasma shock waves

    SciTech Connect

    Zhou Dong; Cetinkaya, Cetin

    2006-04-24

    Detachment and detachment mechanisms of nanoparticles from flat surfaces subjected to shock waves are investigated by employing molecular gas dynamic simulations using the direct simulation Monte Carlo method and experimental transient pressure data. Two mechanisms for nanoparticle detachment based on rolling moment resistance of the adhesion bond and the elastic restitution effect are introduced. As a result of present simulations, it is computationally demonstrated that the pulsed laser-induced shock waves can generate sufficient rolling moments to detach sub-100-nm particles and initiate removal. The transient moment exerted on a 60 nm polystyrene latex particle on a silicon substrate is presented and discussed.

  19. 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.

  20. 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.

  1. Catwalk grate lifting tool

    SciTech Connect

    Gunter, Larry W.

    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.

  2. 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.

  3. Dynamic Strain Measurements on Automotive and Aeronautic Composite Components by Means of Embedded Fiber Bragg Grating Sensors

    PubMed Central

    Lamberti, Alfredo; Chiesura, Gabriele; Luyckx, Geert; Degrieck, Joris; Kaufmann, Markus; Vanlanduit, Steve

    2015-01-01

    The measurement of the internal deformations occurring in real-life composite components is a very challenging task, especially for those components that are rather difficult to access. Optical fiber sensors can overcome such a problem, since they can be embedded in the composite materials and serve as in situ sensors. In this article, embedded optical fiber Bragg grating (FBG) sensors are used to analyze the vibration characteristics of two real-life composite components. The first component is a carbon fiber-reinforced polymer automotive control arm; the second is a glass fiber-reinforced polymer aeronautic hinge arm. The modal parameters of both components were estimated by processing the FBG signals with two interrogation techniques: the maximum detection and fast phase correlation algorithms were employed for the demodulation of the FBG signals; the Peak-Picking and PolyMax techniques were instead used for the parameter estimation. To validate the FBG outcomes, reference measurements were performed by means of a laser Doppler vibrometer. The analysis of the results showed that the FBG sensing capabilities were enhanced when the recently-introduced fast phase correlation algorithm was combined with the state-of-the-art PolyMax estimator curve fitting method. In this case, the FBGs provided the most accurate results, i.e., it was possible to fully characterize the vibration behavior of both composite components. When using more traditional interrogation algorithms (maximum detection) and modal parameter estimation techniques (Peak-Picking), some of the modes were not successfully identified. PMID:26516854

  4. 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.

  5. 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.

  6. 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.

  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. Comprehensive optical diagnostics of laser-induced plasma objects

    NASA Astrophysics Data System (ADS)

    Goncharov, V. K.; Kozadaev, K. V.; Mikitchuk, H. P.; Novikau, A. G.

    2016-01-01

    A new research facility for comprehensive analysis of laser-induced plasma objects equipped with high resolution devices for space, time and spectral measurements was developed. The results of combined use of laser probing and spectral analysis of metal erosion laser jets (ELJ) allowed us to propose and justify models of laser erosion of metals for various modes of exposure.

  9. 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.

  10. Dynamic Strain Measurements on Automotive and Aeronautic Composite Components by Means of Embedded Fiber Bragg Grating Sensors.

    PubMed

    Lamberti, Alfredo; Chiesura, Gabriele; Luyckx, Geert; Degrieck, Joris; Kaufmann, Markus; Vanlanduit, Steve

    2015-01-01

    The measurement of the internal deformations occurring in real-life composite components is a very challenging task, especially for those components that are rather difficult to access. Optical fiber sensors can overcome such a problem, since they can be embedded in the composite materials and serve as in situ sensors. In this article, embedded optical fiber Bragg grating (FBG) sensors are used to analyze the vibration characteristics of two real-life composite components. The first component is a carbon fiber-reinforced polymer automotive control arm; the second is a glass fiber-reinforced polymer aeronautic hinge arm. The modal parameters of both components were estimated by processing the FBG signals with two interrogation techniques: the maximum detection and fast phase correlation algorithms were employed for the demodulation of the FBG signals; the Peak-Picking and PolyMax techniques were instead used for the parameter estimation. To validate the FBG outcomes, reference measurements were performed by means of a laser Doppler vibrometer. Sensors 2015, 15 27175 The analysis of the results showed that the FBG sensing capabilities were enhanced when the recently-introduced fast phase correlation algorithm was combined with the state-of-the-art PolyMax estimator curve fitting method. In this case, the FBGs provided the most accurate results, i.e. it was possible to fully characterize the vibration behavior of both composite components. When using more traditional interrogation algorithms (maximum detection) and modal parameter estimation techniques (Peak-Picking), some of the modes were not successfully identified. PMID:26516854

  11. Review of long period fiber gratings written by CO2 laser

    NASA Astrophysics Data System (ADS)

    Wang, Yiping

    2010-10-01

    This paper presents a systematic review of long period fiber gratings (LPFGs) written by the CO2 laser irradiation technique. First, various fabrication techniques based on CO2 laser irradiations are demonstrated to write LPFGs in different types of optical fibers such as conventional glass fibers, solid-core photonic crystal fibers, and air-core photonic bandgap fibers. Second, possible mechanisms, e.g., residual stress relaxation, glass structure changes, and physical deformation, of refractive index modulations in the CO2-laser-induced LPFGs are analyzed. Third, asymmetrical mode coupling, resulting from single-side laser irradiation, is discussed to understand unique optical properties of the CO2-laser-induced LPFGs. Fourthly, several pretreament and post-treatment techniques are proposed to enhance the efficiency of grating fabrications. Fifthly, sensing applications of the CO2-laser-induced LPFGs are investigated to develop various LPFG-based temperature, strain, bend, torsion, pressure, and biochemical sensors. Finally, communication applications of the CO2-laser-induced LPFGs are investigated to develop various LPFG-based band-rejection filters, gain equalizers, polarizers, and couplers.

  12. Ultrafast Excitation of an Inner-Shell Electron by Laser-Induced Electron Recollision

    NASA Astrophysics Data System (ADS)

    Deng, Yunpei; Zeng, Zhinan; Jia, Zhengmao; Komm, Pavel; Zheng, Yinhui; Ge, Xiaochun; Li, Ruxin; Marcus, Gilad

    2016-02-01

    Extreme ultraviolet attosecond pulses, generated by a process known as laser-induced electron recollision, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe subfemtosecond dynamics in atoms, molecules, and solids. However, extending attosecond metrology to scrutinize the dynamics of the inner-shell electrons is a challenge, that is because of the lower efficiency in generating the required soft x-ray (ℏω >300 eV ) attosecond bursts. A way around this problem is to use the recolliding electron to directly initiate the desired inner-shell process, instead of using the currently low flux x-ray attosecond sources. Such an excitation process occurs in a subfemtosecond time scale, and may provide the necessary "pump" step in a pump-probe experiment. Here we used a few cycle infrared (λ0≈1800 nm ) source and observed direct evidence for inner-shell excitations through the laser-induced electron recollision process. It is the first step toward time-resolved core-hole studies in the keV energy range with subfemtosecond time resolution.

  13. Ultrafast Excitation of an Inner-Shell Electron by Laser-Induced Electron Recollision.

    PubMed

    Deng, Yunpei; Zeng, Zhinan; Jia, Zhengmao; Komm, Pavel; Zheng, Yinhui; Ge, Xiaochun; Li, Ruxin; Marcus, Gilad

    2016-02-19

    Extreme ultraviolet attosecond pulses, generated by a process known as laser-induced electron recollision, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe subfemtosecond dynamics in atoms, molecules, and solids. However, extending attosecond metrology to scrutinize the dynamics of the inner-shell electrons is a challenge, that is because of the lower efficiency in generating the required soft x-ray (ℏω>300  eV) attosecond bursts. A way around this problem is to use the recolliding electron to directly initiate the desired inner-shell process, instead of using the currently low flux x-ray attosecond sources. Such an excitation process occurs in a subfemtosecond time scale, and may provide the necessary "pump" step in a pump-probe experiment. Here we used a few cycle infrared (λ_{0}≈1800  nm) source and observed direct evidence for inner-shell excitations through the laser-induced electron recollision process. It is the first step toward time-resolved core-hole studies in the keV energy range with subfemtosecond time resolution. PMID:26943536

  14. 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.; Lning, 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

  15. Influence of vacuum on nanosecond laser-induced surface damage morphology in fused silica at 1064 nm

    NASA Astrophysics Data System (ADS)

    Diaz, R.; Chambonneau, M.; Grua, P.; Rullier, J.-L.; Natoli, J.-Y.; Lamaignre, L.

    2016-01-01

    The influence of vacuum on nanosecond laser-induced damage at the exit surface of fused silica components is investigated at 1064 nm. In the present study, as previously observed in air, ring patterns surrounding laser-induced damage sites are systematically observed on a plane surface when initiated by multiple longitudinal modes laser pulses. Compared to air, the printed pattern is clearly more concentrated. The obtained correlation between the damage morphology and the temporal structure of the pulses suggests a laser-driven ablation mechanism resulting in a thorough imprint of energy deposit. The ablation process is assumed to be subsequent to an activation of the surface by hot electrons related to the diffusive expansion of a plasma formed from silica. This interpretation is strongly reinforced with additional experiments performed on an optical grating in vacuum on which damage sites do not show any ring pattern. Qualitatively, in vacuum, the intensity-dependent ring appearance speed V ? I1/2 is shown to be different than in air where V ? I1/3. This demonstrates that the mechanisms of formation of ring patterns are different in vacuum than in air. Moreover, the mechanism responsible of the propagation of the activation front in vacuum is shown to be outdone when experiments are performed in air.

  16. 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.

  17. 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.

  18. Laser formation of Bragg gratings in polymer nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Nazarov, M. M.; Khaydukov, K. V.; Sokolov, V. I.; Khaydukov, E. V.

    2016-01-01

    The method investigated in this work is based on the laser-induced, spatially inhomogeneous polymerisation of nanocomposite materials and allows control over the motion and structuring of nanoparticles. The mechanisms of nanoparticle concentration redistribution in the process of radical photopolymerisation are studied. It is shown that under the condition of spatially inhomogeneous illumination of a nanocomposite material, nanoparticles are diffused from the illuminated areas into the dark fields. Diffraction gratings with a thickness of 8 μm and a refractive index modulation of 1 × 10-2 are written in an OCM-2 monomer impregnated by silicon nanoparticles. The gratings may be used in the development of narrowband filters, in holographic information recording and as dispersion elements in integrated optical devices.

  19. Laser-induced multi-energy processing in diamond growth

    NASA Astrophysics Data System (ADS)

    Xie, Zhiqiang

    Laser-induced multi-energy processing (MEP) introduces resonant vibrational excitations of precursor molecules to conventional chemical vapor deposition methods for material synthesis. In this study, efforts were extended to explore the capability of resonant vibrational excitations for promotion of energy efficiency in chemical reactions, for enhancement of diamond deposition, and for control of chemical reactions. The research project mainly focused on resonant vibrational excitations of precursor molecules using lasers in combustion flame deposition of diamond, which led to: 1) promotion of chemical reactions; 2) enhancement of diamond growth with higher growth rate and better crystallizations; 3) steering of chemical reactions which lead to preferential growth of {100}-oriented diamond films and crystals; and 4) mode-selective excitations of precursor molecules toward bond-selective control of chemical reactions. Diamond films and crystals were deposited in open air by combustion flame deposition through resonant vibrational excitations of precursor molecules, including ethylene (C2H4) and propylene (C3H 6). A kilowatt wavelength-tunable CO2 laser with spectral range from 9.2 to 10.9 microm was tuned to match vibrational modes of the precursor molecules. Resonant vibrational excitations of these molecules were achieved with high energy efficiency as compared with excitations using a common CO2 laser (fixed wavelength at 10.591microm). With resonant vibrational excitations, the diamond growth rate was increased; diamond quality was promoted; diamond crystals with lengths up to 5 mm were deposited in open air; preferential growth of {100}-oriented diamond films and single crystals was achieved; mode-selective excitations of precursor molecules were investigated toward control of chemical reactions. Optical emission spectroscopy (OES), mass spectrometry (MS), and molecular dynamic simulations were conducted to obtain an in-depth understanding of the resonant vibrational excitations. Species concentrations in flames without and with laser excitations under different wavelengths were investigated both experimentally and theoretically. Detection of C2, CH, and OH radicals, as well as CxHy species and their oxides (CxH yO) (x=1, 2; y=05) using OES and MS, together with reaction pathway simulations, were used to explain the effect of vibrational excitations of precursor molecules on chemical reactions and on diamond depositions.

  20. Measurement of Fluorescence Spectra from Ambient Aerosol Particles Using Laser-induced Fluorescence Technique

    NASA Astrophysics Data System (ADS)

    Taketani, F.; Kanaya, Y.; Nakamura, T.; Moteki, N.; Takegawa, N.

    2011-12-01

    To obtain the information of composition of organic aerosol particles in atmosphere, we developed an instrument using laser-induced fluorescence (LIF) technique. To measure the fluorescence from a particle, we employed two lasers. Scattering light signal derived from a single particle upon crossing the 635nm-CW laser triggers the 266nm-pulsed laser to excite the particle. Fluorescence from the particle in the wavelength range 300-600nm is spectrally dispersed by a grating spectrometer and then detected by a 32-Ch photo-multiplier tube(PMT). The aerosol stream is surrounded by a coaxial sheath air flow and delivered to the optical chamber at atmospheric pressure. Using PSL particles with known sizes, we made a calibration curve to estimate particle size from scattering light intensity. With the current setup of the instrument we are able to detect both scattering and fluorescence from particles whose diameters are larger than 0.5um. Our system was able to differentiate particles composed of mono-aromatic species (e.g. Tryptophan) from those of Riboflavin, by their different fluorescence wavelengths. Also, measurements of fluorescence spectra of ambient particles were demonstrated in our campus in Yokosuka city, facing Tokyo bay in Japan. We obtained several types of florescence spectra in the 8 hours. Classification of the measured fluorescence spectra will be discussed in the presentation.

  1. Bioaerosol detection and classification using dual excitation wavelength laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Jonsson, Per; Wsterby, Pr.; Gradmark, Per-ke; Hedborg, Julia; Larsson, Anders; Landstrm, Lars

    2015-05-01

    We present results obtained by a detection system designed to measure laser-induced fluorescence from individual aerosol particles using dual excitation wavelengths. The aerosol is sampled from ambient air and via a 1 mm diameter nozzle, surrounded by a sheath air flow, confined into a particle beam. A continuous wave blue laser at 404 nm is focused on the aerosol beam and two photomultiplier tubes monitor the presence of individual particles by simultaneous measuring the scattered light and any induced fluorescence. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser at 263 nm and the corresponding fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channel photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 250 to 800 nm. In the present report, data were measured on different monodisperse reference aerosols, simulants of biological warfare agents, and different interference aerosol particles, e.g. pollen. In the analysis of the experimental data, i.e., the time-resolved scattered and fluorescence signals from 404 nm c.w. light excitation and the fluorescence spectra obtained by a pulsed 263 nm laser source, we use multivariate data analysis methods to classify each individual aerosol particle.

  2. 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.

  3. [Study of flow properties of wet solids using laser induced photo chemical anemometry]. Quarterly technical progress report, October--December 1990

    SciTech Connect

    Falco, B.

    1991-01-20

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  4. [Study of flow properties of wet solids using laser induced photo chemical anemometry]. Quarterly technical progress report, July--September 1991

    SciTech Connect

    Falco, B.

    1992-04-09

    A new diagnostic measurement technique is being developed that will enable the investigation of the dynamics of flowing wet solids. The technique involves the use of Laser Induced Photochemical Anemometry (LIPA), enhanced to enable two photochemical species to be excited. It uses laser induced photochromic and photo luminescent molecules to separately tag the two phases for times long enough for them to distort the tagging. Recording the distortions of the tagging caused by the movement of each phase enables us to obtain local characterization of flow properties of both phases of the wet solids at many positions simultaneously across a pipe.

  5. Biopolymer holographic diffraction gratings

    NASA Astrophysics Data System (ADS)

    Savi? evi?, Svetlana; Panteli?, Dejan

    2008-03-01

    Surface-relief diffraction gratings are holographically recorded in dextran sensitized with ammonium dichromate (DCD). DCD was exposed with single-frequency 200 mW diode pumped ND-YAG laser, at 532 nm. The diffraction grating profiles were analyzed by atomic force microscopy (AFM). It was found that different surface profiles could be obtained. Gratings with 330 lines/mm spatial frequencies were made. Existence of higher harmonics in Fourier Transform of non-sinusoidal profiles shows that DCD is capable of recording spatial frequencies up to 1320 lines/mm (four times fundamental frequency). The measured maximum relief depth of the DCD grating is 402 nm.

  6. 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.

  7. 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.

  8. Analysis of organic vapors with laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Nozari, Hadi; Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2015-09-01

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  9. Laser-induced fluorescence detection of dysplasia in Barrett's esophagus

    NASA Astrophysics Data System (ADS)

    Panjehpour, Masoud; Overholt, Bergein F.; Vo-Dinh, Tuan; Edwards, Donna H.; Buckley, Paul F., III; DeCosta, Joseph F.; Haggitt, Rodger C.

    1996-04-01

    A study was conducted to determine whether laser-induced fluorescence could detect high grade dysplasia in Barrett's esophagus. Four-hundred-ten nm laser light was used to induce autofluorescence of Barrett's mucosa in 36 patients during routine endoscopy. The spectra were analyzed using the Differential Normalized Fluorescence (DNF) Index technique to differentiate high grade dysplasia from either low grade or non-dysplastic mucosa. Each spectrum was classified as either premalignant or benign using two different DNF indices. Analyzing the fluorescence spectra from all patients using one DNF Index, 96% of non- dysplastic Barrett's samples classified as benign tissue. All low grade dysplasia samples classified as benign. Ninety percent of high grade dysplasia samples classified as premalignant. Twenty-eight percent of mixed low grade/focal high grade dysplasia samples classified as premalignant. In summary, high grade dysplasia in Barrett's esophagus patients can be detected by endoscopic laser-induced fluorescence spectroscopy using differential normalized fluorescence technique.

  10. Characterization of inorganic species in coal by laser-induced breakdown spectroscopy using UV and IR radiations

    NASA Astrophysics Data System (ADS)

    Mateo, M. P.; Nicolas, G.; Yaez, A.

    2007-12-01

    In this work, the capability of laser-induced breakdown spectroscopy for process control in a thermal power plant is presented through quantitative compositional characterization of the coal used for combustion. Laser-induced emission signal of seven samples with a range of concentrations was calibrated for quantification purposes. The eighth sample was subsequently analyzed five times as unknown in order to determine the precision and accuracy of the measurements. Two modes of operation, dynamic and static and two laser wavelengths, 1064 nm and 355 nm were employed in this study for comparison. The results revealed that UV wavelength provided better results than IR radiation in terms of accuracy for the quantification of inorganic species in coal after the comparison with conventional atomic absorption spectrometry characterization.

  11. Coherent microwave radiation from a laser induced plasma

    SciTech Connect

    Shneider, M. N.; Miles, R. B.

    2012-12-24

    We propose a method for generation of coherent monochromatic microwave/terahertz radiation from a laser-induced plasma. It is shown that small-scale plasma, located in the interaction region of two co-propagating plane-polarized laser beams, can be a source of the dipole radiation at a frequency equal to the difference between the frequencies of the lasers. This radiation is coherent and appears as a result of the so-called optical mixing in plasma.

  12. Laser-induced fluorescence of quinoline adsorbed on acidic zeolites

    NASA Astrophysics Data System (ADS)

    Lalo, C.; Deson, J.; Gédéon, A.; Fraissard, J.

    1997-11-01

    Laser-induced fluorescence spectra of quinoline adsorbed on different forms of acidic Y zeolite reveal interactions between the adsorbate and different polarizing sites in the supercages. Brønsted acid sites protonate quinoline whereas Lewis acid sites appear to give a charge-transfer complex whose fluorescence is strongly red-shifted compared to that of the quinolinium ion. An unstable hydrogen-bonded complex is formed with non-acidic silanol groups.

  13. Laser induced unzipping: A thermal route to polymer ablation

    NASA Astrophysics Data System (ADS)

    Blanchet, Graciela B.; Fincher, C. R., Jr.

    1994-09-01

    The data presented here show that polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) can be ablated by the evaporation of solid polymer targets with a pulsed ultraviolet laser. In situ measurements of the plume composition show that the products emitted under laser irradiation are primarily monomer and other species resulting from energetic collisions within the plasma. The similarities between the ablative and pyrolisis mass spectra suggest that ablation of PTFE and PMMA occur through a laser induced pyrolitic decomposition.

  14. High-Performance Pseudocapacitive Microsupercapacitors from Laser-Induced Graphene.

    PubMed

    Li, Lei; Zhang, Jibo; Peng, Zhiwei; Li, Yilun; Gao, Caitian; Ji, Yongsung; Ye, Ruquan; Kim, Nam Dong; Zhong, Qifeng; Yang, Yang; Fei, Huilong; Ruan, Gedeng; Tour, James M

    2016-02-01

    All-solid-state, flexible, symmetric, and asymmetric microsupercapacitors are fabricated by a simple method in a scalable fashion from laser-induced graphene on commercial polyimide films, followed by electrodeposition of pseudocapacitive materials on the interdigitated in-plane architectures. These microsupercapacitors demonstrate comparable energy density to commercial lithium thin-film batteries, yet exhibit more than two orders of magnitude higher power density with good mechanical flexibility. PMID:26632264

  15. Photodiagnostics of turbulent flows using laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

    Bershader, D.; Gross, K. P.

    1983-01-01

    An optical probe technique that will allow remote measurements of temperature (and density), along with their time dependent fluctuations, to be made in a supersonic turbulent wind tunnel flow was developed. Laser-induced fluorescence from nitric oxide which was seeded into the flowing gas medium (nitrogen) at low concentrations was used. The fluorescence emission intensity following laser excitation of the nitric oxide (NO) ground state rotational levels is then related to thermodynamic quantities of the bulk fluid.

  16. Lasing effects in a laser-induced plasma plume

    NASA Astrophysics Data System (ADS)

    Nagli, Lev; Gaft, Michael

    2015-11-01

    We have studied coherent emission from optically pumped preliminarily created laser induced plasma and demonstrate the possibility to create laser sources based on laser plasma as an active medium. The effect was studied in detail with Al plasma, and preliminary but promising results were also obtained with other atoms from the 13th and 14th groups of the periodic table. These lasers may be used as coherent light sources in a variety of optical applications.

  17. Excimer laser induced oxidation of ion-implanted silicon

    SciTech Connect

    Fogarassy, E.; White, C.W.; Slaoui, A.; Fuchs, C.; Siffert, P.; Pennycook, S.J.

    1988-10-31

    We have investigated laser-induced oxidation of ion-implanted Si using a repetitively pulsed ArF laser, working at low-energy density (100--500 mJ/cm/sup 2/). Oxidation is observed at energy densities between the melt threshold and that required for epitaxial recrystallization of the amorphous layer. At these energy densities, oxidation is not observed on virgin silicon. The factors that influence the oxidation process are discussed.

  18. 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.

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

    DOEpatents

    Miller, Steven M. (Chelmsford, MA)

    1988-01-01

    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.

  20. 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.

  1. 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.

  2. Femtosecond laser-induced optical anisotropy in a two-dimensional lattice of magnetic dots

    NASA Astrophysics Data System (ADS)

    Razdolski, I.; Krutyanskiy, V. L.; Murzina, T. V.; Rasing, Th.; Kimel, A. V.

    2014-02-01

    Using pump-probe optical polarimetry we demonstrate that femtosecond laser excitation of a 2D regular lattice of magnetic nanodots effectively changes the optical anisotropy of the array. Study of the dynamics of the femtosecond laser-induced anisotropy reveals four main mechanisms occurring in the electronic, spin, and lattice subsystems. Below 1 ps, a strong Kerr-like nonlinearity causes linear birefringence, with its axis directed along the electric field of the linearly polarized femtosecond laser pump pulse. In addition, a long-living linear birefringence is also induced due to slowly relaxing excitations. Also below 1 ps, ultrafast laser-induced demagnetization of Co leads to a partial breakdown of the circular birefringence of the magnetic nanodots. On the timescale up to 300 ps, optically triggered acoustic modes of the dots drive oscillations of the linear optical birefringence. During this process, the oscillations damp while transferring their energy into acoustic modes of the substrate. On the nanosecond timescale, the signal is dominated by acoustic oscillations at the surface of the substrate.

  3. Quantitative ultrasound method to detect and monitor laser-induced cavitation bubbles

    PubMed Central

    Karpiouk, Andrei B.; Aglyamov, Salavat R.; Bourgeois, Frederic; Ben-Yakar, Adela; Emelianov, Stanislav Y.

    2008-01-01

    An ultrasound technique to measure the spatial and temporal behavior of the laser-induced cavitation bubble is introduced. The cavitation bubbles were formed in water and in gels using a nanosecond pulsed Nd:YAG laser operating at 532 nm. A focused, single-element, 25-MHz ultrasound transducer was employed both to detect the acoustic emission generated by plasma expansion and to acoustically probe the bubble at different stages of its evolution. The arrival time of the passive acoustic emission was used to estimate the location of the cavitation bubbles origin and the time of flight of the ultrasound pulse-echo signal was used to define its spatial extent. The results of ultrasound estimations of the bubble size were compared and found to be in agreement with both the direct optical measurements of the stationary bubble and the theoretical estimates of bubble dynamics derived from the well-known Rayleigh model of a cavity collapse. The results of this study indicate that the proposed quantitative ultrasound technique, capable of detecting and accurately measuring laser-induced cavitation bubbles in water and in a tissue-like medium, could be used in various biomedical and clinical applications. PMID:18601556

  4. 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.

  5. Remote chlorophyll fluorescence measurements with the laser-induced fluorescence transient approach.

    PubMed

    Pieruschka, Roland; Klimov, Denis; Berry, Joseph A; Osmond, C Barry; Rascher, Uwe; Kolber, Zbigniew S

    2012-01-01

    The interaction of plants with their environment is very dynamic. Studying the underlying processes is important for understanding and modeling plant response to changing environmental conditions. Photosynthesis varies largely between different plants and at different locations within a canopy of a single plant. Thus, continuous and spatially distributed monitoring is necessary to assess the dynamic response of photosynthesis to the environment. Limited scale of observation with portable instrumentation makes it difficult to examine large numbers of plants under different environmental conditions. We report here on the application of a recently developed technique, laser-induced fluorescence transient (LIFT), for continuous remote measurement of photosynthetic efficiency of selected leaves at a distance of up to 50 m. The ability to make continuous, automatic, and remote measurements of photosynthetic efficiency of leaves with the LIFT provides a new approach for studying the interaction of plants with the environment and may become an important tool in phenotyping photosynthetic properties in field applications. PMID:22893285

  6. 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.

  7. Determination of cobalt in low-alloy steels using laser-induced breakdown spectroscopy combined with laser-induced fluorescence.

    PubMed

    Li, Jiaming; Guo, Lianbo; Zhao, Nan; Yang, Xinyan; Yi, Rongxing; Li, Kuohu; Zeng, Qingdong; Li, Xiangyou; Zeng, Xiaoyan; Lu, Yongfeng

    2016-05-01

    Cobalt element plays an important role for the properties of magnetism and thermology in steels. In this work, laser-induced breakdown spectroscopy combined with laser-induced fluorescence (LIBS-LIF) was studied to selectively enhance the intensities of Co lines. Two states of Co atoms were resonantly excited by a wavelength-tunable laser. LIBS-LIF with ground-state atom excitation (LIBS-LIFG) and LIBS-LIF with excited-state atom excitation (LIBS-LIFE) were compared. The results show that LIBS-LIFG has analytical performance with LoD of 0.82μg/g, R(2) of 0.982, RMSECV of 86μg/g, and RE of 9.27%, which are much better than conventional LIBS and LIBS-LIFE. This work provided LIBS-LIFG as a capable approach for determining trace Co element in the steel industry. PMID:26946032

  8. Warm Absorbers in X-rays (WAX), a comprehensive high resolution grating spectral study of a sample of Seyfert Galaxies: II. Warm Absorber dynamics and feedback to galaxies.

    NASA Astrophysics Data System (ADS)

    Laha, Sibasish; Guainazzi, Matteo; Chakravorty, Susmita; Dewangan, Gulab C.; Kembhavi, Ajit K.

    2016-02-01

    This paper is a sequel to the extensive study of warm absorber (WA) in X-rays carried out using high resolution grating spectral data from XMM-Newton satellite (WAX-I). Here we discuss the global dynamical properties as well as the energetics of the WA components detected in the WAX sample. The slope of WA density profile (n?r-?) estimated from the linear regression slope of ionization parameter ? and column density NH in the WAX sample is ? = 1.236 0.034. We find that the WA clouds possibly originate as a result of photo-ionised evaporation from the inner edge of the torus (torus wind). They can also originate in the cooling front of the shock generated by faster accretion disk outflows, the ultra-fast outflows (UFO), impinging onto the interstellar medium or the torus. The acceleration mechanism for the WA is complex and neither radiatively driven wind nor MHD driven wind scenario alone can describe the outflow acceleration. However, we find that radiative forces play a significant role in accelerating the WA through the soft X-ray absorption lines, and also with dust opacity. Given the large uncertainties in the distance and volume filling factor estimates of the WA, we conclude that the kinetic luminosity ?K of WA may sometimes be large enough to yield significant feedback to the host galaxy. We find that the lowest ionisation states carry the maximum mass outflow, and the sources with higher Fe M UTA absorption (15-17 ) have more mass outflow rates.

  9. DYNAMICS OF X-RAY-EMITTING EJECTA IN THE OXYGEN-RICH SUPERNOVA REMNANT PUPPIS A REVEALED BY THE XMM-NEWTON REFLECTION GRATING SPECTROMETER

    SciTech Connect

    Katsuda, Satoru; Tamagawa, Toru; Ohira, Yutaka; Mori, Koji; Tsunemi, Hiroshi; Koyama, Katsuji; Uchida, Hiroyuki

    2013-05-10

    Using the unprecedented spectral resolution of the reflection grating spectrometer (RGS) on board XMM-Newton, we reveal dynamics of X-ray-emitting ejecta in the oxygen-rich supernova remnant Puppis A. The RGS spectrum shows prominent K-shell lines, including O VII He{alpha} forbidden and resonance, O VIII Ly{alpha}, O VIII Ly{beta}, and Ne IX He{alpha} resonance, from an ejecta knot positionally coincident with an optical oxygen-rich filament (the so-called {Omega} filament) in the northeast of the remnant. We find that the line centroids are blueshifted by 1480 {+-} 140 {+-} 60 km s{sup -1} (the first and second term errors are measurement and calibration uncertainties, respectively), which is fully consistent with that of the optical {Omega} filament. Line broadening at 654 eV (corresponding to O VIII Ly{alpha}) is obtained to be {sigma} {approx}< 0.9 eV, indicating an oxygen temperature of {approx}< 30 keV. Analysis of XMM-Newton MOS spectra shows an electron temperature of {approx}0.8 keV and an ionization timescale of {approx}2 Multiplication-Sign 10{sup 10} cm{sup -3} s. We show that the oxygen and electron temperatures as well as the ionization timescale can be reconciled if the ejecta knot was heated by a collisionless shock whose velocity is {approx}600-1200 km s{sup -1} and was subsequently equilibrated due to Coulomb interactions. The RGS spectrum also shows relatively weak K-shell lines of another ejecta feature located near the northeastern edge of the remnant, from which we measure redward Doppler velocities of 650 {+-} 70 {+-} 60 km s{sup -1}.

  10. Dynamics of X-Ray-emitting Ejecta in the Oxygen-rich Supernova Remnant Puppis A Revealed by the XMM-Newton Reflection Grating Spectrometer

    NASA Astrophysics Data System (ADS)

    Katsuda, Satoru; Ohira, Yutaka; Mori, Koji; Tsunemi, Hiroshi; Uchida, Hiroyuki; Koyama, Katsuji; Tamagawa, Toru

    2013-05-01

    Using the unprecedented spectral resolution of the reflection grating spectrometer (RGS) on board XMM-Newton, we reveal dynamics of X-ray-emitting ejecta in the oxygen-rich supernova remnant Puppis A. The RGS spectrum shows prominent K-shell lines, including O VII He? forbidden and resonance, O VIII Ly?, O VIII Ly?, and Ne IX He? resonance, from an ejecta knot positionally coincident with an optical oxygen-rich filament (the so-called ? filament) in the northeast of the remnant. We find that the line centroids are blueshifted by 1480 140 60 km s-1 (the first and second term errors are measurement and calibration uncertainties, respectively), which is fully consistent with that of the optical ? filament. Line broadening at 654 eV (corresponding to O VIII Ly?) is obtained to be ? <~ 0.9 eV, indicating an oxygen temperature of <~ 30 keV. Analysis of XMM-Newton MOS spectra shows an electron temperature of ~0.8 keV and an ionization timescale of ~2 1010 cm-3 s. We show that the oxygen and electron temperatures as well as the ionization timescale can be reconciled if the ejecta knot was heated by a collisionless shock whose velocity is ~600-1200 km s-1 and was subsequently equilibrated due to Coulomb interactions. The RGS spectrum also shows relatively weak K-shell lines of another ejecta feature located near the northeastern edge of the remnant, from which we measure redward Doppler velocities of 650 70 60 km s-1.

  11. 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.

  12. Spectroscopy of ultracold neutrons diffracted by a moving grating

    NASA Astrophysics Data System (ADS)

    Kulin, G. V.; Frank, A. I.; Goryunov, S. V.; Geltenbort, P.; Jentschel, M.; Bushuev, V. A.; Lauss, B.; Schmidt-Wellenburg, P.; Panzarella, A.; Fuchs, Y.

    2016-03-01

    Spectra of ultracold neutrons that appeared in experiments on neutron diffraction by a moving grating were measured using the time-of-flight Fourier spectrometer. Diffraction lines of five orders were observed simultaneously. The obtained data are in good agreement with the theoretical predictions based on the multiwave dynamical theory of neutron diffraction by a moving grating.

  13. Enhancement of airborne shock wave by laser-induced breakdown of liquid column in laser shock cleaning

    SciTech Connect

    Jang, Deoksuk; Kim, Dongsik; Park, Jin-Goo

    2011-04-01

    In laser shock cleaning (LSC), the shock wave is generated by laser-induced breakdown of the ambient gas. The shock wave intensity has thus been a factor limiting the performance of the LSC process. In this work, a novel method of amplifying a laser-induced plasma-generated shock wave by the breakdown of a liquid column is proposed and analyzed. When the laser beam is focused on a microscale liquid column, a shock wave having a significantly amplified intensity compared to that generated by air breakdown alone can be generated in air. Therefore, substantially amplified cleaning force can be obtained. The dynamics of a shock wave induced by a Q-switched Nd:YAG laser was analyzed by laser flash shadowgraphy. The peak pressure of the laser-induced shock wave was approximately two times greater than that of air breakdown at the same laser fluence. The proposed method of shock wave generation is expected to be useful in various applications of laser shock processing, including surface cleaning.

  14. Response of fiber Bragg gratings to longitudinal ultrasonic waves.

    PubMed

    Minardo, Aldo; Cusano, Andrea; Bernini, Romeo; Zeni, Luigi; Giordano, Michele

    2005-02-01

    In the last years, fiber optic sensors have been widely exploited for several sensing applications, including static and dynamic strain measurements up to acoustic detection. Among these, fiber Bragg grating sensors have been indicated as the ideal candidate for practical structural health monitoring in light of their unique advantages over conventional sensing devices. Although this class of sensors has been successfully tested for static and low-frequency measurements, the identification of sensor performances for high-frequency detection, including acoustic emission and ultrasonic investigations, is required. To this aim, the analysis of feasibilty on the use of fiber Bragg grating sensors as ultrasonic detectors has been carried out. In particular, the response of fiber Bragg gratings subjected to the longitudinal ultrasonic (US) field has been theoretically and numerically investigated. Ultrasonic field interaction has been modeled, taking into account the direct deformation of the grating pitch combined with changes in local refractive index due to the elasto-optic effect. Numerical results, obtained for both uniform and Gaussian-apodized fiber Bragg gratings, show that the grating spectrum is strongly influenced by the US field in terms of shape and central wavelength. In particular, a key parameter affecting the grating response is the ratio between the US wavelength and the grating length. Normal operation characterized by changes in wavelength of undistorted Bragg peak is possible only for US wavelengths longer than the grating length. For US wavelengths approaching the grating length, the wavelength change is accompanied by subpeaks formation and main peak amplitude modulation. This effect can be attributed to the nonuniformity of the US perturbation along the grating length. At very high US frequencies, the grating is not sensitive any longer. The results of this analysis provide useful tools for the design of grating-based ultrasound sensors for meeting specific requirements in terms of field intensity and frequencies. PMID:15801318

  15. Q-Switched Alexandrite Laser-induced Chrysiasis

    PubMed Central

    Victor Ross, E.

    2015-01-01

    Background: Chyriasis is an uncommon side effect that occurs in patients who are receiving prolonged treatment with either intravenous or intramuscular gold as a distinctive blue-gray pigmentation of light-exposed skin. Laser-induced chrysiasis is a rarely described phenomenon in individuals who have received systemic gold and are subsequently treated with a Q-switched laser. Purpose: To describe the characteristics of patients with laser-induced chrysiasis. Methods: The authors describe a 60-year-old woman who developed chrysiasis at Q-switched alexandrite laser treatment sites. They also reviewed the medical literature using PubMed, searching the terms chrysiasis, gold, and laser-induced. Patient reports and previous reviews of these subjects were critically assessed and the salient features are presented. Results: Including the authors’ patient, laser-induced chrysiasis has been described in five Caucasian arthritis patients (4 women and 1 man); most of the patients had received more than 8g of systemic gold therapy during a period of 3 to 13 years. Gold therapy was still occurring or had been discontinued as long as 26 years prior to laser treatment. All of the patients immediately developed blue macules at the Q-switched laser treatment site. Resolution of the dyschromia occurred in a 70-year-old woman after two treatment sessions with a long-pulsed ruby laser and the authors’ patient after a sequential series of laser sessions using a long-pulsed alexandrite laser, followed by a nonablative fractional laser and an ablative carbon dioxide laser. Conclusion: Laser-induced chrysiasis has been observed following treatment with Q-switched lasers in patients who are receiving or have previously been treated with systemic gold. It can occur decades after treatment with gold has been discontinued. Therefore, inquiry regarding a prior history of treatment with gold—particularly in older patients with arthritis—should be considered prior to treatment with a Q-switched laser. Also, treatment with a long-pulsed laser should be entertained in patients with either idiopathic or laser-induced chrysiasis. (JClinAesthetDermatol. 2015;8(9):48-53.) Chrysiasis is a distinctive blue-gray pigmentation of light exposed skin occurring in individuals who are receiving parenteral gold therapy.1 The 755nm Q-switched alexandrite laser is effective for the treatment of facial lentigines since the melanin granules absorb a high proportion of the laser energy and other chromophores offer little competitive absorption.2 The authors describe a woman who developed chrysiasis at Q-switched alexandrite laser treatment sites and whose dyschromia was successfully treated with a sequential series of laser sessions using a long-pulsed alexandrite laser, followed by a nonablative fractional laser and an ablative carbon dioxide laser. PMID:26430491

  16. Spherical grating spectrometers

    NASA Astrophysics Data System (ADS)

    O'Donoghue, Darragh; Clemens, J. Christopher

    2014-07-01

    We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

  17. Laser induced short plane acoustic wave focusing in water

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

    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 flat acoustic wave with a cylindrical concave lens and the subsequent acoustic wave focusing. Numerical simulations showed the acoustic wave could be focused to several tens of microns in size and 7bars in pressure.

  18. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S.

    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.

  19. Trace metal mapping by laser-induced breakdown spectroscopy

    SciTech Connect

    Kaiser, Jozef; Novotny, Dr. Karel; Hrdlicka, A; Malina, R; Hartl, M; Kizek, R; Adam, V

    2012-01-01

    Abstract: Laser-Induced Breakdown Spectroscopy (LIBS) is a sensitive optical technique capable of fast multi-elemental analysis of solid, gaseous and liquid samples. The potential applications of lasers for spectrochemical analysis were developed shortly after its invention; however the massive development of LIBS is connected with the availability of powerful pulsed laser sources. Since the late 80s of 20th century LIBS dominated the analytical atomic spectroscopy scene and its application are developed continuously. Here we review the utilization of LIBS for trace elements mapping in different matrices. The main emphasis is on trace metal mapping in biological samples.

  20. Spatial confinement effects in laser-induced breakdown spectroscopy

    SciTech Connect

    Shen, X. K.; Sun, J.; Ling, H.; Lu, Y. F.

    2007-08-20

    The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. A KrF excimer laser was used to produce plasmas from Al targets in air. Al atomic emission lines show an obvious enhancement in the emission intensity when a pair of Al-plate walls were placed to spatially confine the plasma plumes. Images of the Al plasma plumes showed that the plasma plumes evolved into a torus shape and were compressed in the Al walls. The mechanism for the confinement effects was discussed using shock wave theory.

  1. Remote sensing of phytoplankton using laser-induced fluorescence

    SciTech Connect

    Babichenko, S.; Poryvkina, L.; Arikese, V. ); Kaitala, S. ); Kuosa, H. )

    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.

  2. 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

  3. 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.

  4. Laser-induced fluorescent spectroscopy of steroid hormones

    NASA Astrophysics Data System (ADS)

    Samoilova, Elena S.; Fedorov, Vyacheslav I.; Cherkasova, Olga P.; Meshalkin, Yuri P.

    2002-07-01

    The laser-induced fluorescence spectra of steroid hormones - estradiol, estriol, estrone, androstenedione - are obtained at excitation of the fourth harmonic of Nd:YAG laser radiation. The quantum yields of fluorescence of these substances were rated by means of the relative method. They are 1.11 X 10-1, 5.20 X 10-3, 8.47 X 10-5. The water solution of tryptophan was used as a standard. The set-up sensitivity for high and average quantum yields substances has been defined.

  5. H sup minus beam characterization using laser-induced neutralization

    SciTech Connect

    Yuan, V.W.; Garcia, R.; Johnson, K.F.; Saadatmand, K.; Sander, O.R.; Sandoval, D.; Shinas, M.

    1991-01-01

    The Laser-induced neutralization techniques, LINDA, is important as a noninterceptive diagnostic for quantitatively measuring beam emittance values. It is also valuable for its capability to characterize, both quantitatively and qualitatively, the performance and match of linac components. In this paper we present LINDA experimental results that show how the output beam of a radio-frequency quadrupole (RFQ) and drift-tube linac (DTL) combination changes with the variation of RFQ-DTL relative phase and of DTL cavity power. We also present results showing the effect of a longitudinal buncher on beam emissions. 2 refs., 4 figs.

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

    SciTech Connect

    Melikechi, N.; Ding, H.; Marcano, O. A.; Rock, S.

    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.

  7. Communication: Bubbles, crystals, and laser-induced nucleation

    NASA Astrophysics Data System (ADS)

    Knott, Brandon C.; LaRue, Jerry L.; Wodtke, Alec M.; Doherty, Michael F.; Peters, Baron

    2011-05-01

    Short intense laser pulses of visible and infrared light can dramatically accelerate crystal nucleation from transparent solutions; previous studies invoke mechanisms that are only applicable for nucleation of ordered phases or high dielectric phases. However, we show that similar laser pulses induce CO2 bubble nucleation in carbonated water. Additionally, in water that is cosupersaturated with argon and glycine, argon bubbles escaping from the water can induce crystal nucleation without a laser. Our findings suggest a possible link between laser-induced nucleation of bubbles and crystals.

  8. 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.

  9. Laser-Induced Nuclear Orientation of 1-?s 85Rbm

    NASA Astrophysics Data System (ADS)

    Shimkaveg, G.; Quivers, W. W., Jr.; Dasari, R. R.; Holbrow, C. H.; Pappas, P. G.; Attili, M. A.; Thomas, J. E.; Murnick, D. E.; Feld, M. S.

    1984-12-01

    Frequency-resolved laser-induced gamma-ray anisotropy has been achieved and used to measure the D1 hyperfine structure of the 1-?s isomer 85Rbm. The magnetic dipole moment obtained is (6.046+/-0.010)?N and the isomer shift relative to 85Rb is -52+/-9 MHz. The experiment was performed with a sealed cell containing radioactive 85Kr (3 mCi) and natural Rb(~ 10 mTorr). This method is simple and convenient and promises to be of wide usefulness.

  10. A phenomenological theory of nonphotochemical laser induced nucleation.

    PubMed

    Nardone, Marco; Karpov, Victor G

    2012-10-21

    We present a theory of electric field driven phase transitions that occur via nucleation of needle-shaped, metallic particles. The predictions of this theory have much in common with the observations related to nonphotochemical laser induced nucleation (NPLIN). That connection is rather paradoxical because the final NPLIN products are dielectric crystals. By elaborating on the unique features of field induced transitions and the complexities of liquid systems, we discuss how our theory may provide some insight into the open question of the NPLIN mechanism. A qualitative description of the post nucleation stage and conjectures about the microscopic nature of the metallic particles in liquids are also provided. PMID:22955565

  11. 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).

  12. Automatic separation system for marine meiobenthos based on laser-induced fluorescence technology.

    PubMed

    Ye, Shu-ming; Gao, Shao-jia; Pan, Yi; Yang, Jun-yi; Li, Shi-lun

    2005-06-01

    An automatic system for marine meiobenthos separation was developed by using laser-induced fluorescence technology. Rose Bengal was used as organism dye and the spectrums of Rose Bengal were measured. Laser-induced fluorescence system was established to detect marine meiobenthos in sediments. Data obtained from experiments were analyzed by using a mathematical model. The results showed that laser-induced fluorescence technology worked well in the system. The system could select the meiobenthos efficiently and precisely. PMID:15909339

  13. Trapping and manipulation of microparticles using laser-induced convection currents and photophoresis

    PubMed Central

    Flores-Flores, E.; Torres-Hurtado, S. A.; Páez, R.; Ruiz, U.; Beltrán-Pérez, G.; Neale, S. L.; Ramirez-San-Juan, J. C.; Ramos-García, R.

    2015-01-01

    In this work we demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents. Convection currents are generated due to laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film. The particles are dragged towards the beam's center by the convection currents (Stokes drag force) allowing trapping with powers as low as 0.8 mW. However, for powers >3 mW trapped particles form a ring around the beam due to two competing forces: Stokes drag and thermo-photophoretic forces. Additionally, we show that dynamic beam shaping can be used to trap and manipulate multiple particles by photophotophoresis without the need of lithographically created resistive heaters. PMID:26504655

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

    SciTech Connect

    Lim, Zhi Han; Sow, Chorng-Haur; Lee, Andrielle; Zhu, Yanwu; Lim, Kassandra Yu Yan

    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.

  15. 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.

  16. Measuring the dispersion of a surface layer by breaking waves using planar laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Marson, Alan E.; Schlicke, Ted; Greated, Clive A.

    2004-06-01

    Surface films can be found all over the world, from the algae blooms of the Mediterranean to oil or sewage pollution near harbours and cities. In this paper the experimental method of planar laser induced fluorescence is used to measure how breaking waves disperse these films. The method for preparing and extracting quantitative results from laboratory experiments is presented with sample results for depth, area and fractal dimension from mild spilling breakers. Two cases are examined, a single isolated breaker and an identical breaking wave occurring 32 s after an initial breaker has disturbed the film. Presented at the Rank Prize Fund Mini-Symposium on Optics in Fluid Dynamics, Meteorology and the Atmosphere, held at Grasmere, UK, on 12-15 August 2002.

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

    SciTech Connect

    Vinoth Kumar, L.; Manikanta, E.; Leela, Ch.; Prem Kiran, P.

    2014-08-11

    The radio frequency emissions scanned over broad spectral range (30?MHz1?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.

  18. Laser-Induced Kondo Effect in Ultracold Alkaline-Earth Fermions

    NASA Astrophysics Data System (ADS)

    Nakagawa, Masaya; Kawakami, Norio

    2015-10-01

    We demonstrate that laser excitations can coherently induce a novel Kondo effect in ultracold atoms in optical lattices. Using a model of alkaline-earth fermions with two orbitals, it is shown that the optically coupled two internal states are dynamically entangled to form the Kondo-singlet state, overcoming the heating effect due to the irradiation. Furthermore, a lack of SU (N ) symmetry in the optical coupling provides a peculiar feature in the Kondo effect, which results in spin-selective renormalization of effective masses. We also discuss the effects of interorbital exchange interactions, and reveal that they induce novel crossover or reentrant behavior of the Kondo effect owing to control of the coupling anisotropy. The laser-induced Kondo effect is highly controllable by tuning the laser strength and the frequency, and thus offers a versatile platform to study the Kondo physics using ultracold atoms.

  19. Laser-Induced Kondo Effect in Ultracold Alkaline-Earth Fermions.

    PubMed

    Nakagawa, Masaya; Kawakami, Norio

    2015-10-16

    We demonstrate that laser excitations can coherently induce a novel Kondo effect in ultracold atoms in optical lattices. Using a model of alkaline-earth fermions with two orbitals, it is shown that the optically coupled two internal states are dynamically entangled to form the Kondo-singlet state, overcoming the heating effect due to the irradiation. Furthermore, a lack of SU(N) symmetry in the optical coupling provides a peculiar feature in the Kondo effect, which results in spin-selective renormalization of effective masses. We also discuss the effects of interorbital exchange interactions, and reveal that they induce novel crossover or reentrant behavior of the Kondo effect owing to control of the coupling anisotropy. The laser-induced Kondo effect is highly controllable by tuning the laser strength and the frequency, and thus offers a versatile platform to study the Kondo physics using ultracold atoms. PMID:26550883

  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. On laser induced single bubble near a solid boundary: Contribution to the understanding of erosion phenomena

    NASA Astrophysics Data System (ADS)

    Isselin, Jean-Christophe; Alloncle, Anne-Patricia; Autric, Michel

    1998-11-01

    Cavitation erosion is an especially destructive and complex phenomenon. In order to understand its basic mechanism, the dynamics of laser-induced vapor bubbles have been investigated. Special experimental devices have been used to record ultrafast visualizations and pressure measurements. From these measurements, the different sources of stresses, induced on the solid wall by the presence of the bubble (shock wave, microjet), have been characterized. The "water hammer" pressure associated with the microjet velocity varies up to 210 MPa. When the bubble collapses near a solid wall, the pressure emitted is less than in an infinite medium. Pressure values up to 2.5 MPa have been found. These values have been associated with the duration of the pressure applied to the solid wall, which is about 30 ns for the microjet and more than 300 ns for the shock wave. These results have been correlated with the analysis of damage created on the surface sample.

  2. 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

    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.

  3. 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

  4. Thermal accommodation coefficients for laser-induced incandescence sizing of metal nanoparticles in monatomic gases

    NASA Astrophysics Data System (ADS)

    Daun, K. J.; Sipkens, T. A.; Titantah, J. T.; Karttunen, M.

    2013-09-01

    The capabilities of time-resolved laser-induced incandescence (TiRe-LII), a combustion diagnostic used almost exclusively to measure soot primary particles, could potentially be extended to size aerosolized metal nanoparticles. In order to do this, however, it is necessary to characterize the thermal accommodation coefficient, ?, which specifies the heat conduction rate between the laser-energized nanoparticles and the surrounding gas. This paper extends a molecular dynamics (MD) methodology to calculate ? for Fe/He, Fe/Ar, Mo/He, and Mo/Ar systems. A comparative analysis of the results shows that ? is most strongly influenced by the potential well between the gas molecule and nanoparticle surface. Finally, the MD-derived value for ? is used to recover the nanoparticle size distribution for TiRe-LII measurements made on molybdenum nanoparticles in argon.

  5. Trapping and manipulation of microparticles using laser-induced convection currents and photophoresis.

    PubMed

    Flores-Flores, E; Torres-Hurtado, S A; Páez, R; Ruiz, U; Beltrán-Pérez, G; Neale, S L; Ramirez-San-Juan, J C; Ramos-García, R

    2015-10-01

    In this work we demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents. Convection currents are generated due to laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film. The particles are dragged towards the beam's center by the convection currents (Stokes drag force) allowing trapping with powers as low as 0.8 mW. However, for powers >3 mW trapped particles form a ring around the beam due to two competing forces: Stokes drag and thermo-photophoretic forces. Additionally, we show that dynamic beam shaping can be used to trap and manipulate multiple particles by photophotophoresis without the need of lithographically created resistive heaters. PMID:26504655

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Lim, Zhi Han; Lee, Andrielle; Lim, Kassandra Yu Yan; Zhu, Yanwu; Sow, Chorng-Haur

    2010-03-01

    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 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.

  8. A comparative study of single and double pulse of laser induced breakdown spectroscopy of silver

    SciTech Connect

    Rashid, Babar; Ahmed, Rizwan; Ali, Raheel; Baig, M. A.

    2011-07-15

    We present a comparative study of the collinear and orthogonal pre-ablation dual pulse configurations of laser induced breakdown spectroscopy (LIBS) of silver using Nd:YAG lasers. The effect of the inter-pulse delay and the ratio of the laser pulse energies on the signal intensity enhancement for both the dual pulse configurations have been investigated. Using the first laser at 532 nm and second laser at 1064 nm delayed by 5 {mu}s, we achieved nearly 2 times signal enhancement in the collinear double-pulsed configuration and nearly 12 times in the pre-ablation orthogonal configuration as compared to SP LIBS. It is ascertained that at the optimized value of the inter-pulse delay between the two lasers, the intensity ratio of the neutral silver lines follows the local thermo dynamical equilibrium (LTE) condition and it is also in excellent agreement with that of the relative transitions probabilities ratio listed in the NIST data base.

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

    SciTech Connect

    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. 9 refs.

  10. Laser-induced agglomeration of gold nanoparticles dispersed in a liquid

    NASA Astrophysics Data System (ADS)

    Serkov, A. A.; Shcherbina, M. E.; Kuzmin, P. G.; Kirichenko, N. A.

    2015-05-01

    Dynamics of gold nanoparticles (NPs) ensemble in dense aqueous solution under exposure to picosecond laser radiation is studied both experimentally and theoretically. Properties of NPs are examined by means of transmission electron microscopy, optical spectroscopy, and size-measuring disk centrifuge. Theoretical investigation of NPs ensemble behavior is based on the analytical model taking into account collisions and agglomeration of particles. It is shown that in case of dense NPs colloidal solutions (above 1014 particles per milliliter) the process of laser fragmentation typical for nanosecond laser exposure turns into laser-induced agglomeration which leads to formation of the particles with larger sizes. It is shown that there is a critical concentration of NPs: at higher concentrations agglomeration rate increases tremendously. The results of mathematical simulation are in compliance with experimental data.

  11. 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.

  12. 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.

  13. Direct probing of chromatography columns by laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    McGuffin, V. L.

    1992-12-01

    This report summarizes the progress and accomplishments of this research project from 1 Sep. 1989 to 28 Feb. 1993. During this period, we have accomplished all of the primary scientific objectives of the research proposal: (1) constructed and evaluated a laser-induced fluorescence detection system that allows direct examination of the chromatographic column, (2) examined nonequilibrium processes that occur upon solute injection and elution, (3) examined solute retention in liquid chromatography as a function of temperature and pressure, (4) examined solute zone dispersion in liquid chromatography as a function of temperature and pressure, and (5) developed appropriate theoretical models to describe these phenomena. In each of these studies, substantial knowledge has been gained of the fundamental processes that are responsible for chromatographic separations. In addition to these primary research objectives, we have made significant progress in three related areas: (1) examined pyrene as a fluorescent polarity probe in supercritical fluids and liquids as a function of temperature and pressure, (2) developed methods for the class-selective identification of polynuclear aromatic hydrocarbons in coal-derived fluids by microcolumn liquid chromatography with fluorescence quenching detection, and (3) developed methods for the determination of saturated and unsaturated (including omega-3) fatty acids in fish oil extracts by microcolumn liquid chromatography with laser-induced fluorescence detection. In these studies, the advanced separation and detection techniques developed in our laboratory are applied to practical problems of environmental and biomedical significance.

  14. Laser-induced nucleation of carbon dioxide bubbles

    NASA Astrophysics Data System (ADS)

    Ward, Martin R.; Jamieson, William J.; Leckey, Claire A.; Alexander, Andrew J.

    2015-04-01

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm-2) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm-2) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm-2). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  15. Calibration analysis of zeolites by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Horňáčková, M.; Grolmusová, Z.; Horňáček, 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.

  16. Analytical application of femtosecond laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Melikechi, Noureddine; Markushin, Yuri

    2015-05-01

    We report on significant advantages provided by femtosecond laser-induced breakdown spectroscopy (LIBS) for analytical applications in fields as diverse as protein characterization and material science. We compare the results of a femto- and nanosecond-laser-induced breakdown spectroscopy analysis of dual-elemental pellets in terms of the shot-to-shot variations of the neutral/ionic emission line intensities. This study is complemented by a numerical model based on two-dimensional random close packing of disks in an enclosed geometry. In addition, we show that LIBS can be used to obtain quantitative identification of the hydrogen composition of bio-macromolecules in a heavy water solution. Finally, we show that simultaneous multi-elemental particle assay analysis combined with LIBS can significantly improve macromolecule detectability up to near single molecule per particle efficiency. Research was supported by grants from the National Science Foundation Centers of Research Excellence in Science and Technology (0630388), National Aeronautics and Space Administration (NX09AU90A). Our gratitude to Dr. D. Connolly, Fox Chase Cancer Center.

  17. Laser-induced breakdown spectroscopy of tantalum plasma

    SciTech Connect

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

    2013-07-15

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 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 (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, 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.

  18. A model for traumatic brain injury using laser induced shockwaves

    NASA Astrophysics Data System (ADS)

    Selfridge, A.; Preece, D.; Gomez, V.; Shi, L. Z.; Berns, M. W.

    2015-08-01

    Traumatic brain injury (TBI) represents a major treatment challenge in both civilian and military medicine; on the cellular level, its mechanisms are poorly understood. As a method to study the dysfunctional repair mechanisms following injury, laser induced shock waves (LIS) are a useful way to create highly precise, well characterized mechanical forces. We present a simple model for TBI using laser induced shock waves as a model for damage. Our objective is to develop an understanding of the processes responsible for neuronal death, the ways in which we can manipulate these processes to improve cell survival and repair, and the importance of these processes at different levels of biological organization. The physics of shock wave creation has been modeled and can be used to calculate forces acting on individual neurons. By ensuring that the impulse is in the same regime as that occurring in practical TBI, the LIS model can ensure that in vitro conditions and damage are similar to those experienced in TBI. This model will allow for the study of the biochemical response of neurons to mechanical stresses, and can be combined with microfluidic systems for cell growth in order to better isolate areas of damage.

  19. 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.

  20. Kr II laser-induced fluorescence for measuring plasma acceleration.

    PubMed

    Hargus, W A; Azarnia, G M; Nakles, M R

    2012-10-01

    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(4)D(7/2) to the 5p(4)P(5/2)(?) 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(4)D(7/2)-5p(4)P(5/2)(?) 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. PMID:23126755

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    Laser-induced breakdown spectroscopy (LIBS) in the vacuum ultraviolet range (VUV, ? < 200 nm) 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 F 2 laser (wavelength ? = 157 nm) with a laser pulse length of 20 ns, a pulse energy up to 50 mJ, and pulse repetition rate of 10 Hz. The optical radiation of the laser-induced plasma is measured by a VUV spectrometer with detection range down to ? = 115 nm. A gated photon-counting system is used to acquire time-resolved spectra. From LIBS measurements of certified polymer reference materials, we obtained a limit of detection (LOD) of 50 g/g for sulphur and 215 g/g for zinc, respectively. The VUV LIBS spectra of PE are dominated by strong emission lines of neutral and ionized carbon atoms. From time-resolved measurements of the carbon line intensities, we determine the temporal evolution of the electronic plasma temperature, Te. For this, we use Saha-Boltzmann plots with the electron density in the plasma, Ne, derived from the broadening of the hydrogen H-? line. With the parameters Te and Ne, we calculate the intensity ratio of the atomic sulphur and carbon lines at 180.7 nm and at 175.2 nm, respectively. The calculated intensity ratios are in good agreement with the experimentally measured results.

  2. Direct probing of chromatography columns by laser-induced fluorescence

    SciTech Connect

    McGuffin, V.L.

    1992-12-07

    This report summarizes the progress and accomplishments of this research project from September 1, 1989 to February 28, 1993. During this period, we have accomplished all of the primary scientific objectives of the research proposal: (1) constructed and evaluated a laser-induced fluorescence detection system that allows direct examination of the chromatographic column, (2) examined nonequilibrium processes that occur upon solute injection and elution, (3) examined solute retention in liquid chromatography as a function of temperature and pressure, (4) examined solute zone dispersion in liquid chromatography as a function of temperature and pressure, and (5) developed appropriate theoretical models to describe these phenomena. In each of these studies, substantial knowledge has been gained of the fundamental processes that are responsible for chromatographic separations. In addition to these primary research objectives, we have made significant progress in three related areas: (1) examined pyrene as a fluorescent polarity probe insupercritical fluids and liquids as a function of temperature and pressure, (2) developed methods for the class-selective identification of polynuclear aromatic hydrocarbons in coal-derived fluids by microcolumn liquid chromatography with fluorescence quenching detection, and (3) developed methods for the determination of saturated and unsaturated (including omega-3) fatty acids in fish oil extracts by microcolumn liquid chromatography with laser-induced fluorescence detection. In these studies, the advanced separation and detection techniques developed in our laboratory are applied to practical problems of environmental and biomedical significance.

  3. 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.

  4. 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

  5. Superfluid {sup 4}He Quantum Interference Grating

    SciTech Connect

    Sato, Yuki; Joshi, Aditya; Packard, Richard

    2008-08-22

    We report the first observation of quantum interference from a grating structure consisting of four weak link junctions in superfluid {sup 4}He. We find that an interference grating can be implemented successfully in a superfluid matter wave interferometer to enhance its sensitivity while trading away some of its dynamic range. We also show that this type of device can be used to measure absolute quantum mechanical phase differences. The results demonstrate the robust nature of superfluid phase coherence arising from quantum mechanics on a macroscopic scale.

  6. Evaluation of laser-induced thin-layer removal by using shadowgraphy and laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Rabasović, M. S.; Šević, D.; Lukač, N.; Jezeršek, M.; Možina, J.; Gregorčič, P.

    2016-03-01

    Shadow photography and laser-induced breakdown spectroscopy (LIBS) are studied as methods for monitoring the selective removal of thin (i.e., under 100 μm) layers by laser ablation. We used a laser pulse of 5 ns and 16 mJ at 1064 nm to ablate an 18-μm-thin copper layer from the fiberglass substrate. On the basis of shadowgraphs of the laser-induced shock waves, we measured the optodynamic energy-conversion efficiency, defined as the ratio between the mechanical energy of the shock wave and the excitation-pulse energy. Our results show that this efficiency is significantly higher for the laser pulse-copper interaction than for the interaction between the excitation pulse and the substrate. LIBS was simultaneously employed in our experimental setup. The optical emission from the plasma plume was collected by using a spectrograph and recorded with a streak camera. We show that advancing of laser ablation through the copper layer and reaching of the substrate can be estimated by tracking the spectral region between 370 and 500 nm. Therefore, the presented results confirm that LIBS method enables an on-line monitoring needed for selective removal of thin layers by laser.

  7. Nanosecond laser-induced ablation and laser-induced shockwave structuring of polymer foils down to sub-?m patterns

    NASA Astrophysics Data System (ADS)

    Lorenz, P.; Bayer, L.; Ehrhardt, M.; Zimmer, K.; Engisch, L.

    2015-03-01

    Micro- and nanostructures exhibit a growing commercial interest where a fast, cost-effective, and large-area production is attainable. Laser methods have a great potential for the easy fabrication of surface structures into flexible polymer foils like polyimide (PI). In this study two different concepts for the structuring of polymer foils using a KrF excimer laser were tested and compared: the laser-induced ablation and the laser-induced shock wave structuring. The direct front side laser irradiation of these polymers allows the fabrication of different surface structures. For example: The low laser fluence treatment of PI results in nano-sized cone structures where the cone density can be controlled by the laser parameters. This allows inter alia the laser fabrication of microscopic QR code and high-resolution grey-tone images. Furthermore, the laser treatment of the front side of the polymer foil allows the rear side structuring due to a laserinduced shock wave. The resultant surface structures were analysed by optical and scanning electron microscopy (SEM) as well as white light interferometry (WLI).

  8. Plume splitting and rebounding in a high-intensity CO{sub 2} laser induced air plasma

    SciTech Connect

    Chen Anmin; Jiang Yuanfei; Liu Hang; Jin Mingxing; Ding Dajun

    2012-07-15

    The dynamics of plasma plume formed by high-intensity CO{sub 2} laser induced breakdown of air at atmospheric pressure is investigated. The laser wavelength is 10.6 {mu}m. Measurements were made using 3 ns gated fast photography as well as space and time resolved optical emission spectroscopy. The behavior of the plasma plume was studied with a laser energy of 3 J and 10 J. The results show that the evolution of the plasma plume is very complicated. The splitting and rebounding of the plasma plume is observed to occur early in the plumes history.

  9. 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.

  10. Enthalpy Distributions of Arc Jet Flow Based on Measured Laser Induced Fluorescence, Heat Flux and Stagnation Pressure Distributions

    NASA Technical Reports Server (NTRS)

    Suess, Leonard E.; Milhoan, James D.; Oelke, Lance; Godfrey, Dennis; Larin, Maksim Y.; Scott, Carl D.; Grinstead, Jay H.; DelPapa, Steven

    2011-01-01

    The centerline total enthalpy of arc jet flow is determined using laser induced fluorescence of oxygen and nitrogen atoms. Each component of the energy, kinetic, thermal, and chemical can be determined from LIF measurements. Additionally, enthalpy distributions are inferred from heat flux and pressure probe distribution measurements using an engineering formula. Average enthalpies are determined by integration over the radius of the jet flow, assuming constant mass flux and a mass flux distribution estimated from computational fluid dynamics calculations at similar arc jet conditions. The trends show favorable agreement, but there is an uncertainty that relates to the multiple individual measurements and assumptions inherent in LIF measurements.

  11. 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.

  12. Wavelength dependence of femtosecond laser-induced damage threshold of optical materials

    SciTech Connect

    Gallais, L. Douti, D.-B.; Commandré, M.; Batavičiūtė, G.; Pupka, E.; Ščiuka, M.; Smalakys, L.; Sirutkaitis, V.; Melninkaitis, A.

    2015-06-14

    An experimental and numerical study of the laser-induced damage of the surface of optical material in the femtosecond regime is presented. The objective of this work is to investigate the different processes involved as a function of the ratio of photon to bandgap energies and compare the results to models based on nonlinear ionization processes. Experimentally, the laser-induced damage threshold of optical materials has been studied in a range of wavelengths from 1030 nm (1.2 eV) to 310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system. Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1 to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damage threshold with the bandgap and photon energy. A model based on the Keldysh photo-ionization theory and the description of impact ionization by a multiple-rate-equation system is used to explain the dependence of laser-breakdown with the photon energy. The calculated damage fluence threshold is found to be consistent with experimental results. From these results, the relative importance of the ionization processes can be derived depending on material properties and irradiation conditions. Moreover, the observed damage morphologies can be described within the framework of the model by taking into account the dynamics of energy deposition with one dimensional propagation simulations in the excited material and thermodynamical considerations.

  13. Erbium:YAG-laser induced vapor bubbles as a function of the quartz fiber tip geometry

    NASA Astrophysics Data System (ADS)

    Mrochen, Michael; Riedel, Peter; Donitzky, Christof; Seiler, Theo

    2001-07-01

    Background. The use of modern erbium: yttrium-aluminum- garnet (YAG) laser systems in ophthalmic microsurgery requires a precise knowledge of the size and dynamics of the laser induced vapor bubbles. The aim of this work was to clarify the possibilities of controlling the vapor bubble shape and size by using an optimized fiber tip geometry for various ophthalmic applications with the erbium:YAG laser. Methods. The mid-infrared radiation of free-running erbium:YAG laser was coupled optically into means of different low OH- quartz fiber tips to investigate the vapor bubble formation in water by high-speed photography. The core diameter of four fiber tips ranged from 200 up to 940 micrometers . Fourteen fiber tips were polished at an angle graduated from 10 degree(s) to 70 degree(s) over the full core diameter (seven fiber tips) and over the half core diameter (seven fiber tips). Three fiber tips were produced to have a curvature at the distal end with curvature radii of 160, 230, and 420 micrometers . Results. The shape as well as the size of erbium:YAG laser induced vapor bubbles can be controlled systematically by using adequate fiber tip geometries. In detail, the used different angles and curvatures demonstrate that the propagation direction of the vapor bubbles can be estimated by optical modeling considering Snell's law and the Fresnel laws at a quartz-air boundary. Beside this, the size of a vapor bubble can be predetermined by choosing ideal fiber tip geometries to reduce or increase the radiant exposure at the distal end of the quartz fiber tip. Conclusions. The good possibility of controlling the shape and size of vapor bubbles offers a wider range of new applications, especially in ophthalmic microsurgery such as erbium YAG laser vitrectomy.

  14. Neuroprotective therapy for argon-laser-induced retinal injury

    NASA Astrophysics Data System (ADS)

    Belkin, Michael; Rosner, Mordechai; Solberg, Yoram; Turetz, Yosef

    1999-06-01

    Laser photocoagulation treatment of the central retina is often complicated by an immediate side effect of visual impairment, caused by the unavoidable laser-induced destruction of the normal tissue lying adjacent to the lesion and not affected directly by the laser beam. Furthermore, accidental laser injuries are at present untreatable. A neuroprotective therapy for salvaging the normal tissue might enhance the benefit obtained from treatment and allow safe perifoveal photocoagulation. We have developed a rat model for studying the efficacy of putative neuroprotective compounds in ameliorating laser-induced retinal damage. Four compounds were evaluated: the corticosteroid methylprednisolone, the glutamate-receptor blocker MK-801, the anti-oxidant enzyme superoxide dismutase, and the calcim-overload antagonist flunarizine. The study was carried out in two steps: in the first, the histopathological development of retinal laser injuries was studied. Argon laser lesions were inflicted in the retinas of 18 pigmented rats. The animals were sacrificed after 3, 20 or 60 days and their retinal lesions were evaluated under the light microscope. The laser injury mainly involved the outer layers of the retina, where it destroyed significant numbers of photoreceptor cells. Over time, evidence of two major histopathological processes was observed: traction of adjacent nomral retinal cells into the central area of the lesion forming an internal retinal bulging, and a retinal pigmented epithelial proliferative reaction associated with subretinal neovascularization and invations of the retinal lesion site by phagocytes. The neuroprotective effects of each of the four compounds were verified in a second step of the study. For each drug tested, 12 rats were irradiated wtih argon laser inflictions: six of them received the tested agent while the other six were treated with the corresponding vehicle. Twenty days after laser expsoure, the rats were sacrificed and their lesions were subjected to image-analysis morphometry. The extent of retianl damage was assessed by measuring the lesion diameter and the amount of photoreceptor cell loss in the outer nuclear layer. Methylprednisolone and MI-801 were shown to ameliorate laser-induced retinal damage, whereas both superoxide dismutase and flunarizine were ineffective. Furthermore, MK-801 diminished the proliferative reaction of the retinal pigment epithelial cells. On the basis of our results we suggest that the pigmented rat model is suitable for studying and screening various compounds for their neuroprotective efficacy in treating retinal laser injury. We further suggest that glutamate might play a key role in mediating retinal injury induced by laser irradiation.

  15. 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

  16. 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…

  17. 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. PMID:25909007

  18. MoI density measurements by laser induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Orsitto, F.; Borra, M.; Coppotelli, F.; Gatti, G.; Neri, E.

    1999-01-01

    The density of molybdenum atoms produced by sputtering of a TZM (molybdenum) target by Ar+ ions is measured by laser induced fluorescence (LIF) using tunable dye laser. The excitation transition involved is a7S3-z5P30 at 345.64 nm, while the fluorescence signal is from the decay z5P30-a5S2 at 550.6 nm. The LIF measurements are carried out by varying the laser power incident on Mo atoms by means of neutral density filters. An absolute calibration of the detection system together with the realization of a well defined optical probe volume allows for the determination of the density of the emitting atoms. An evaluation of LIF diagnostic performance on Frascati Tokamak upgrade put a lower limit of 2.51014 atoms/m3 on the detectable local density of MoI close to the toroidal limiter.

  19. 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.

  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. Combined Endoscopic Optical Coherence Tomography and Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Barton, Jennifer K.; Tumlinson, Alexandre R.; Utzinger, Urs

    Optical coherence tomography (OCT) and laser-induced fluorescence (LIF) are promising modalities for tissue characterization in human patients and animal models. OCT detects coherently backscattered light, whereas LIF detects fluorescence emission of endogenous biochemicals, such as reduced nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD), collagen, and fluorescent proteins, or exogenous substances such as cyanine dyes. Given the complementary mechanisms of contrast for OCT and LIF, the combination of the two modalities could potentially provide more sensitive and specific detection of disease than either modality alone. Sample probes for both OCT and LIF can be implemented using small diameter optical fibers, suggesting a particular synergy for endoscopic applications. In this chapter, the mechanisms of contrast and diagnostic capability for both OCT and LIF are briefly examined. Evidence of complementary capability is described. Example published combined OCT-LIF systems are reviewed, one successful commercial instrument is discussed, and example applications are provided.

  2. Laser-induced modification of transparent crystals and glasses

    SciTech Connect

    Bulgakova, N M; Stoian, Razvan; Rosenfeld, A

    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)

  3. 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.

  4. 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.

  5. Laser-induced breakdown spectroscopy analysis of energetic materials

    NASA Astrophysics Data System (ADS)

    de Lucia, Frank C.; Harmon, Russell S.; McNesby, Kevin L.; Winkel, Raymond J.; Miziolek, Andrzej W.

    2003-10-01

    A number of energetic materials and explosives have been studied by laser-induced breakdown spectroscopy (LIBS). They include black powder, neat explosives such as TNT, PETN, HMX, and RDX (in various forms), propellants such as M43 and JA2, and military explosives such as C4 and LX-14. Each of these materials gives a unique spectrum, and generally the spectra are reproducible shot to shot. We observed that the laser-produced microplasma did not initiate any of the energetic materials studied. Extensive studies of black powder and its ingredients by use of a reference spectral library have demonstrated excellent accuracy for unknown identification. Finally, we observed that these nitrogen- and oxygen-rich materials yield LIBS spectra in air that have correspondingly different O:N peak ratios compared with air. This difference can help in the detection and identification of such energetic materials.

  6. Laser-induced acoustic desorption of natural and functionalized biochromophores.

    PubMed

    Sezer, Uğur; Wörner, Lisa; Horak, Johannes; Felix, Lukas; Tüxen, Jens; Götz, Christoph; Vaziri, Alipasha; Mayor, Marcel; Arndt, Markus

    2015-06-01

    Laser-induced acoustic desorption (LIAD) has recently been established as a tool for analytical chemistry. It is capable of launching intact, neutral, or low charged molecules into a high vacuum environment. This makes it ideally suited to mass spectrometry. LIAD can be used with fragile biomolecules and very massive compounds alike. Here, we apply LIAD time-of-flight mass spectrometry (TOF-MS) to the natural biochromophores chlorophyll, hemin, bilirubin, and biliverdin and to high mass fluoroalkyl-functionalized porphyrins. We characterize the variation in the molecular fragmentation patterns as a function of the desorption and the VUV postionization laser intensity. We find that LIAD can produce molecular beams an order of magnitude slower than matrix-assisted laser desorption (MALD), although this depends on the substrate material. Using titanium foils we observe a most probable velocity of 20 m/s for functionalized molecules with a mass m = 10,000 Da. PMID:25946522

  7. 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.

  8. Containerless study of metal evaporation by laser induced fluorescence

    NASA Technical Reports Server (NTRS)

    Schiffman, Robert A.; Nordine, Paul C.

    1987-01-01

    Laser induced fluorescence (LIF) detection of atomic vapors was used to study evaporation from electromagnetically levitated and CW CO2 laser-heated molybdenum spheres and resistively-heated tungsten filaments. Electromagnetic (EM) levitation in combination with laser heating of tungsten, zirconium, and aluminum specimens was also investigated. LIF intensity vs temperature data were obtained for molybdenum atoms and six electronic states of atomic tungsten, at temperatures up to the melting point of each metal. The detected fraction of the emitted radiation was reduced by self-absorption effects at the higher experimental temperatures. Vaporization enthalpies derived from data for which less than half the LIF intensity was self-absorbed were -636 + or - 24 kJ/g-mol for Mo and 831 + or - 32 kJ/g-mol for W. Space-based applications of EM levitation in combination with radiative heating are discussed.

  9. 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.; Mller, 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.

  10. 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.

  11. Laser-induced vibration of a thin soap film.

    PubMed

    Emile, Olivier; Emile, Janine

    2014-09-21

    We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems. PMID:25017934

  12. Femtosecond laser-induced microwelding of silver and copper.

    PubMed

    Huang, Hong; Hu, Anming; Peng, Peng; Duley, Walter Winston; Zhou, Yunhong

    2013-02-20

    Femtosecond (fs) laser irradiation has been shown to be effective for welding transparent materials and for transparent materials to metals. However, to date there is little work regarding similar applications in welding/bonding of metals. In this article, we for the first time to the best of our knowledge report on fs laser-induced microwelding of Ag microwires and Cu substrates. The influence of laser pulse number and fluence on fs laser microwelding is studied to explore an optimum welding window. Morphology analysis indicates that the primary weld of the Ag microwire and the Cu substrate was located at the edge of the Ag microwire and produced via the redeposition and local melting-induced welding of the ablated materials. PMID:23434991

  13. Laser-Induced Acoustic Desorption of Natural and Functionalized Biochromophores

    PubMed Central

    2015-01-01

    Laser-induced acoustic desorption (LIAD) has recently been established as a tool for analytical chemistry. It is capable of launching intact, neutral, or low charged molecules into a high vacuum environment. This makes it ideally suited to mass spectrometry. LIAD can be used with fragile biomolecules and very massive compounds alike. Here, we apply LIAD time-of-flight mass spectrometry (TOF-MS) to the natural biochromophores chlorophyll, hemin, bilirubin, and biliverdin and to high mass fluoroalkyl-functionalized porphyrins. We characterize the variation in the molecular fragmentation patterns as a function of the desorption and the VUV postionization laser intensity. We find that LIAD can produce molecular beams an order of magnitude slower than matrix-assisted laser desorption (MALD), although this depends on the substrate material. Using titanium foils we observe a most probable velocity of 20 m/s for functionalized molecules with a mass m = 10?000 Da. PMID:25946522

  14. Pulsed laser-induced formation of silica nanogrids

    NASA Astrophysics Data System (ADS)

    Ihlemann, Jrgen; Weichenhain-Schriever, Ruth

    2014-03-01

    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.

  15. 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.

  16. OH Planar Laser-Induced Fluorescence from Microgravity Droplet Combustion

    NASA Technical Reports Server (NTRS)

    Winter, Michael; Wegge, Jason; Kang, Kyung-Tae

    1997-01-01

    Droplet combustion under microgravity conditions has been extensively studied, but laser diagnostics have just begun to be employed in microgravity droplet experiments. This is due in part to the level of difficulty associated with laser system size, power and economic availability. Hydroxyl radical (OH) is an important product of combustion, and laser-induced fluorescence (LIF) has proved to be an adequate and sensitive tool to measure OH. In this study, a frequency doubled Nd:YAG laser and a doubled dye laser, compact and reliable enough to perform OH PLIF experiments aboard a parabolic flight-path aircraft, has been developed and successfully demonstrated in a methanol droplet flame experiment. Application to microgravity conditions is planned aboard parabolic flight-path aircraft.

  17. Optical properties of laser-induced heavily doped Si

    NASA Astrophysics Data System (ADS)

    Ravindra, N. M.; Mhoronge, J. F.; Jouanne, M.

    1985-09-01

    An analysis of experimental studies (Slaoui et al., 1983) of the optical properties of laser-induced heavily doped Si layers is presented. The analysis has been made on the basis of models like those of Penn (1962) and Breckenridge et al. (1974). The calculations show that, in general, the effective number of electrons contributing to optically induced electronic transitions, increases as does the imaginary part of the complex dielectric constant. This reflects an increased absorption coefficient for these As-doped samples. These studies have been carried out on samples of Si heavily doped by ion-implantation followed by a laser-annealing process. The conclusions based on these studies are seen to be in accord with those of Aspnes et al. (1984) and Vina and Cardona (1984).

  18. 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.

  19. Radioactive contamination screening with laser-induced fluorescence

    SciTech Connect

    Sheely, R.; Di Benedetto, J.

    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.

  20. Ultraviolet-laser-induced permanent electrical conductivity in polyimide

    NASA Astrophysics Data System (ADS)

    Feurer, T.; Sauerbrey, R.; Smayling, M. C.; Story, B. J.

    1993-03-01

    When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 ? cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The conduction mechanism is phonon-assisted variable range hopping, evident from the observed temperature and electric field dependence of the resistivity at low conductivities. The laser-induced conductivity depends on the ambient atmosphere during irradiation. Transmission spectroscopy in the visible region and infrared Fourier transform spectroscopy have been used to characterize the material. A thermal mechanism is proposed for the formation of conducting polyimide, by excimer-laser irradiation.

  1. 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 50nm 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

  2. The laser-induced fluorescence spectroscopy of yttrium monosulfide

    NASA Astrophysics Data System (ADS)

    Zang, Jianzheng; Zhang, Qun; Zhang, Deping; Qin, Chengbing; Zhang, Qiang; Chen, Yang

    2015-07-01

    We have investigated the laser-induced fluorescence (LIF) excitation spectra and dispersed fluorescence (DF) spectra of yttrium monosulfide (YS) in the energy range of 17 860-20 700 cm-1. Rotational analyses indicated that almost all of the intense vibronic bands can be attributed to the new [ 19.38 ]2?+ (??) - X2?+ (??) transition system. The missing (1, 2), (2, 1) and (3, 3) bands are caused by their very small Franck-Condon factors, as confirmed by our calculations. The new 2?+ state has been suggested to arise from the electronic configuration of (core)1?22?21?33?2?, featuring a charge-transfer nature. Moreover, the spin-rotation parameter ? for the newly observed 2?+ state has been determined to be 0.0206 cm-1, the magnitude of which is larger than the known ? (X2?+) (0.001427 cm-1) but smaller than ? (B2?+) (-0.1515 cm-1).

  3. Nanoparticle Generation During Laser Ablation and Laser-Induced Liquefaction

    NASA Astrophysics Data System (ADS)

    Haustrup, N.; O'Connor, G. M.

    Recently short-pulse laser sources have been investigated as a potential method for nanoparticle synthesis. Deposited aluminium, nickel and gold nanoparticles generated during nano- and femto-second laser ablation were analyzed using SEM and AFM. As the environment in which laser ablation takes place is known to influence the size of generated nanoparticles, a novel gas ambient that generates a transient liquid phase was investigated. This ambient offers favorable properties to overcome some issues typically encountered with ablation in gases or liquids alone. The Laser-Induced Liquefaction (LIL) process most notably lead to a reduced mean radius of aluminium nanoparticles from 36.8 nm in air to 12.7 nm.

  4. Laser induced spark ignition of methane-oxygen mixtures

    NASA Technical Reports Server (NTRS)

    Lee, T. W.; Santavicca, D. A.; Ho, C. M.; Reilly, B. J.

    1991-01-01

    The use of laser-induced spark ignition in liquid-propellant rocket engines is investigated by studying the ignition of mixtures of methane and oxygen. Specific attention is given to minimum ignition energy, spark efficiency, the effect of ignition energy on flame kernels, the effect of laser wavelength, and comparisons with electrode-spark ignition. A pulsed frequency-doubled Nd:YAG laser is tested at atmospheric pressure and 296 K under both laminar-premixed and turbulent-incompletely-mixed conditions. Laser sparks of 10 and 40 mJ and an electrode spark of 6 mJ are measured for flame-kernel radius as a function of time with pulsed laser shadowgraphy. Initially, the flame-kernel size is similar to those predicted by the Taylor spherical-blast-wave model, and subsequent growth is characterized by rapid acceleration. The growth rate is significantly affected by the effect of incomplete fuel-oxidizer mixing.

  5. Hydroxylapatite nanoparticles obtained by fiber laser-induced fracture

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

    This work presents the results of laser-induced fragmentation of hydroxylapatite microparticles in water dissolution. Calcined fish bones in form of powder, which were previously milled to achieve microsized particles, were used as precursor material. Two different laser sources were employed to reduce the size of the suspended particles: a pulsed Nd:YAG laser and a Ytterbium doped fiber laser working in continuous wave mode. The morphology as well as the composition of the obtained particles was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and conventional and high resolution transmission electron microscopy (TEM, HRTEM). The results show that nanometric particles of hydroxylapatite and β-tricalcium phosphate as small as 10 nm diameter can be obtained.

  6. 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.

  7. Laser-induced thermal bubbles for microfluidic applications.

    PubMed

    Zhang, Kai; Jian, Aoqun; Zhang, Xuming; Wang, Yu; Li, Zhaohui; Tam, Hwa-Yaw

    2011-04-01

    We present a unique bubble generation technique in microfluidic chips using continuous-wave laser-induced heat and demonstrate its application by creating micro-valves and micro-pumps. In this work, efficient generation of thermal bubbles of controllable sizes has been achieved using different geometries of chromium pads immersed in various types of fluid. Effective blocking of microfluidic channels (cross-section 500 40 ?m(2)) and direct pumping of fluid at a flow rate of 7.2-28.8 ?l h(-1) with selectable direction have also been demonstrated. A particular advantage of this technique is that it allows the generation of bubbles at almost any location in the microchannel and thus enables microfluidic control at any point of interest. It can be readily integrated into lab-on-a-chip systems to improve functionality. PMID:21331412

  8. Laser-induced microbubble poration of localized single cells.

    PubMed

    Fan, Qihui; Hu, Wenqi; Ohta, Aaron T

    2014-05-01

    Laser-induced microbubbles were used to porate the cell membranes of localized single NIH/3T3 fibroblasts. Microsecond laser pulses were focused on an optically absorbent substrate, creating a vapour microbubble that oscillated in size at the laser focal point in a fluidic chamber. The shear stress accompanying the bubble size oscillation was able to porate nearby cells. Cell poration was demonstrated with the delivery of FITC-dextran dye with various molecular weights. Under optimal poration conditions, the cell poration efficiency was up to 95.2 4.8%, while maintaining 97.6 2.4% cell viability. The poration system is able to target a single cell without disturbing surrounding cells. PMID:24632785

  9. 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.

  10. 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.

  11. Evaluating Photodynamic Therapy Efficacy Using Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fekry, O.; El-Batanouny, M. H.; El-Begawy, M. B.; Harith, M. A.

    2011-09-01

    Laser-induced breakdown spectroscopy (LIBS), is an excellent tool for trace elemental analysis, was exploited for a detecting concentrations of calcium and magnesium in malignant tissues before and after PDT. Calcium and magnesium concentrations are known tobe high in malignancy. Tissues were injected with methylene blue photosensitizer with concentrations 0.5%, 1% and 2%. Two different light sources were used with two different energy densities/each light sources. The results showed a decrease in tissue elements content after PDT application for both calcium and magnesium compared to before PDT application as shown in the tissue spectral lines' intensities which has been reflected in. Type of light source showed no effect on tissue elements content which showed slight differences among the different energy densities. It has been shown that LIBS technique can be adopted method to monitor tumor photodynamic therapy applications.

  12. Excimer-laser-induced absorption in fused silica

    NASA Astrophysics Data System (ADS)

    Moll, Johannes; Schermerhorn, Paul M.

    1999-07-01

    Excimer laser radiation changes the physical and optical properties of fused silica. These changes include compaction of the glass and induced absorption, both of which have an impact on the expected lifetime of silica lenses used in optical microlithography. We report on our ongoing study of excimer laser induced changes in fused silica. We use a fully automated experimental setup designed for marathon exposure of the sample at low fluence. In each setup, using either an ArF or a KrF laser, up to five samples are exposed simultaneously and their induced absorption is measured in situ. The spatial and temporal profiles of the laser beam can also be measured in the same setup. We present and discuss results from marathon test of fused silica at fluences close to the conditions expected in optical microlithography systems.

  13. Laser induced extraplanar propulsion for three-dimensional microfabrication

    SciTech Connect

    Birnbaum, A. J.; Pique, A.

    2011-03-28

    The laser induced extraplanar propulsion process is presented for the creation of controllable three-dimensional deformation of on-substrate components. It is demonstrated that the process is compatible with transparent substrates and ductile materials and is highly controllable in terms of the desired deformation via the adjustment of incident laser energy density. Copper films with thicknesses varying from 0.1-1 {mu}m are deformed over bending angles ranging from 0 deg. - 180 deg. A 355 nm laser at fluences ranging from 10-40 mJ/cm{sup 2} is used in conjunction with an indium-tin-oxide propulsion layer to demonstrate the process. Characterization is performed via electron and laser confocal microscopy.

  14. Analysis of fresco by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Caneve, L.; Diamanti, A.; Grimaldi, F.; Palleschi, G.; Spizzichino, V.; Valentini, F.

    2010-08-01

    The laser-based techniques have been shown to be a very powerful tool for artworks characterization and are used in the field of cultural heritage for the offered advantages of minimum invasiveness, in situ applicability and high sensitivity. Laser induced breakdown spectroscopy, in particular, has been applied in this field to many different kinds of ancient materials with successful results. In this work, a fragment of a Roman wall painting from the archaeological area of Pompeii has been investigated by LIBS. The sample elemental composition resulting from LIBS measurements suggested the presence of certain pigments. The ratio of the intensities of different lines related to some characteristic elements is proposed as an indicator for pigment recognition. The depth profiling permitted to put in evidence the presence of successive paint layers with different compositions. A comparison with the results obtained by the microscopy inspection of the sample has been done.

  15. Flexible Boron-Doped Laser-Induced Graphene Microsupercapacitors.

    PubMed

    Peng, Zhiwei; Ye, Ruquan; Mann, Jason A; Zakhidov, Dante; Li, Yilun; Smalley, Preston R; Lin, Jian; Tour, James M

    2015-06-23

    Heteroatom-doped graphene materials have been intensely studied as active electrodes in energy storage devices. Here, we demonstrate that boron-doped porous graphene can be prepared in ambient air using a facile laser induction process from boric acid containing polyimide sheets. At the same time, active electrodes can be patterned for flexible microsupercapacitors. As a result of boron doping, the highest areal capacitance of as-prepared devices reaches 16.5 mF/cm(2), 3 times higher than nondoped devices, with concomitant energy density increases of 5-10 times at various power densities. The superb cyclability and mechanical flexibility of the device are well-maintained, showing great potential for future microelectronics made from this boron-doped laser-induced graphene material. PMID:25978090

  16. Detection of early caries by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji

    2015-07-01

    To improve sensitivity of dental caries detection by laser-induced breakdown spectroscopy (LIBS) analysis, it is proposed to utilize emission peaks in the ultraviolet. We newly focused on zinc whose emission peaks exist in ultraviolet because zinc exists at high concentration in the outer layer of enamel. It was shown that by using ratios between heights of an emission peak of Zn and that of Ca, the detection sensitivity and stability are largely improved. It was also shown that early caries are differentiated from healthy part by properly setting a threshold in the detected ratios. The proposed caries detection system can be applied to dental laser systems such as ones based on Er:YAG-lasers. When ablating early caries part by laser light, the system notices the dentist that the ablation of caries part is finished. We also show the intensity of emission peaks of zinc decreased with ablation with Er:YAG laser light.

  17. Femtosecond laser-induced surface structures on carbon fibers.

    PubMed

    Sajzew, Roman; Schrder, Jan; Kunz, Clemens; Engel, Sebastian; Mller, Frank A; Grf, Stephan

    2015-12-15

    The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a femtosecond laser with a pulse duration ?=300??fs, a wavelength ?=1025??nm, and a peak fluence F=4??J/cm2. It was shown that linear polarization results in a well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform laser-induced periodic surface structures (LIPSS) patterns appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers. PMID:26670499

  18. Discriminating crude oil grades using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    El-Hussein, A.; Marzouk, A.; Harith, M. A.

    2015-11-01

    The analysis of crude oil using laser-based analytical techniques such as laser-induced breakdown spectroscopy (LIBS) has become of great interest to various specialists in different fields such as geology, petro-chemistry and environmental science. In this work, a detailed study is presented wherein the implementation of an efficient and simple LIBS technique to identify the elemental constituents of crude oil and to distinguish between different grades of petroleum crude oil is discussed. Laser-induced plasma (LIP) technique has been used in this work for direct measurements of atomic, ionic and molecular species in dry crude oil samples with API gravities ranging between 18 and 36. The technique was implemented using the first harmonic of a pulsed Nd-YAG laser source. Atomic and molecular emission bands were observed, consisting of characteristic spectral lines of atoms and diatomic molecular bands, namely from C, H, Si, Na, Ca, Mg, AL, Fe, Ti, Mo, C2 and CN. The intensities of high-resolution spectral lines for some atoms and molecules of elements such as Ca, Na, Fe, Mo, C2 and CN were evaluated at different wavelengths along the obtained spectra. The molecular bands and the elemental spectral lines were used to assess the possibility of adopting the LIBS technique in differentiating between crude oil samples with different American Petroleum Institute (API) gravity values. The results indicate the presence of a distinct correlation between the API gravity values of the various oil samples and the spectral line intensities of the elements and some molecular radical constituents. In addition, the possibility of identifying the API gravity values of unknown oil samples is also indicated.

  19. Kr II laser-induced fluorescence for measuring plasma acceleration

    SciTech Connect

    Hargus, W. A. Jr.

    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. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    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 most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  1. Experimental studies of laser-induced breakdown in transparent dielectrics

    NASA Astrophysics Data System (ADS)

    Carr, Christopher Wren

    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 KbT, are observed in the damage threshold at photon energies associated with the number of photons (3 → 2 or 4 → 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 florescence 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.

  2. Titanium monoxide spectroscopy following laser-induced optical breakdown

    SciTech Connect

    Parigger, Christian G.; Woods, Alexander C.; Keszler, Anna; Nemes, Laszlo; Hornkohl, James O.

    2012-07-30

    This work investigates Titanium Monoxide (TiO) in ablation-plasma by employing laser-induced breakdown spectroscopy (LIBS) with 1 to 10 TW/cm{sup 2} irradiance, pulsed, 13 nanosecond, Q-switched Nd:YAG laser radiation at the fundamental wavelength of 1064 nm. The analysis of TiO is based on our first accurate determination of transition line strengths for selected TiO A-X, B-X, and E-X transitions, particularly TiO A-X {gamma} and B-X {gamma} Prime bands. Electric dipole line strengths for the A{sup 3}{Phi}-X{sup 3}{delta} and B{sup 3}{Pi}-X{sup 3}{delta} bands of TiO are computed. The molecular TiO spectra are observed subsequent to laser-induced breakdown (LIB). We discuss analysis of diatomic molecular spectra that may occur simultaneously with spectra originating from atomic species. Gated detection is applied to investigate the development in time of the emission spectra following LIB. Collected emission spectra allow one to infer micro-plasma parameters such as temperature and electron density. Insight into the state of the micro-plasma is gained by comparing measurements with predictions of atomic and molecular spectra. Nonlinear fitting of recorded and computed diatomic spectra provides the basis for molecular diagnostics, while atomic species may overlap and are simultaneously identified. Molecular diagnostic approaches similar to TiO have been performed for diatomic molecules such as AlO, C{sub 2}, CN, CH, N{sub 2}, NH, NO and OH.

  3. 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.

  4. 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.

  5. Rat embryonic hippocampus and induced pluripotent stem cell derived cultured neurons recover from laser-induced subaxotomy

    PubMed Central

    Selfridge, Aaron; Chiang, Chai-Chun; Reyna, Sol M.; Weissmiller, April M.; Shi, Linda Z.; Preece, Daryl; Mobley, William C.; Berns, Michael W.

    2015-01-01

    Abstract. Axonal injury and stress have long been thought to play a pathogenic role in a variety of neurodegenerative diseases. However, a model for studying single-cell axonal injury in mammalian cells and the processes of repair has not been established. The purpose of this study was to examine the response of neuronal growth cones to laser-induced axonal damage in cultures of embryonic rat hippocampal neurons and induced pluripotent stem cell (iPSC) derived human neurons. A 532-nm pulsed Nd:YVO4 picosecond laser was focused to a diffraction limited spot at a precise location on an axon using a laser energy/power that did not rupture the cell membrane (subaxotomy). Subsequent time series images were taken to follow axonal recovery and growth cone dynamics. After laser subaxotomy, axons thinned at the damage site and initiated a dynamic cytoskeletal remodeling process to restore axonal thickness. The growth cone was observed to play a role in the repair process in both hippocampal and iPSC-derived neurons. Immunofluorescence staining confirmed structural tubulin damage and revealed initial phases of actin-based cytoskeletal remodeling at the damage site. The results of this study indicate that there is a repeatable and cross-species repair response of axons and growth cones after laser-induced damage. PMID:26157985

  6. 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.

  7. Gratings and waveguides

    NASA Technical Reports Server (NTRS)

    Bates, K. A.; Erwin, J. K.; Li, L.; Burke, J. J.; Ramanujam, N.

    1993-01-01

    Our immediate objective is to understand the limitations of guided-wave and grating coupler devices in their application to optical data storage. Our long-range goal is to develop and validate design codes for integrated optic devices. The principal research activity was in the development of numerical models for the design of a blue wavelength integrated optical source for data storage applications.

  8. Reaction Dynamics of Halorhodopsin Studied by Time-Resolved Diffusion

    PubMed Central

    Inoue, Keiichi; Kubo, Megumi; Demura, Makoto; Kamo, Naoki; Terazima, Masahide

    2009-01-01

    Reaction dynamics of a chloride ion pump protein, halorhodopsin (HR), from Natronomonas pharaonis (N. pharaonis) (NpHR) was studied by the pulsed-laser-induced transient grating (TG) method. A detailed investigation of the TG signal revealed that there is a spectrally silent diffusion process besides the absorption-observable reaction dynamics. We interpreted these dynamics in terms of release, diffusion, and uptake of the Cl? ion. From a quantitative global analysis of the signals at various grating wavenumbers, it was concluded that the release of the Cl? ion is associated with the L2 ? (L2 (or N) ? O) process, and uptake of Cl? occurs with the (L2 (or N) ? O) ? NpHR? process. The diffusion coefficient of NpHR solubilized in a detergent did not change during the cyclic reaction. This result contrasts the behavior of many photosensor proteins and implies that the change in the H-bond network from intra- to intermolecular is not significant for the activity of this protein pump. PMID:19413978

  9. Development of ultrasound technique to detect and characterize laser-induced microbubbles

    NASA Astrophysics Data System (ADS)

    Karpiouk, Andrei B.; Bourgeois, Frederic; Aglyamov, Salavat R.; Ben-Yakar, Adela; Emelianov, Stanislav Y.

    2007-02-01

    An ultrasound-based method to detect and characterize the laser-induced microbubbles was developed. This method is based on temporal measurement of passive acoustic emission from cavity during laser-tissue interaction and simultaneous active pulse-echo ultrasound probing of the cavitation bubble. These measurements were used to estimate the location of the nanosecond laser induced cavity and to monitor the spatial and temporal behavior of the microbubble. The measurements agreed with estimates derived from a well-known Rayleigh model of the cavity collapse. Overall, the studies indicate that the developed ultrasound technique can be used to detect and accurately measure laser-induced microbubbles in tissue.

  10. In Vitro Effect of Laser-Induced Hydrodynamics on Cancer Cells.

    PubMed

    Elagin, V V; Pavlikov, A I; Yusupov, V I; Shirmanova, M V; Zagaynova, E V; Bagratashvili, V N

    2015-11-01

    We studied the effect of laser-induced hydrodynamic on viability of Colo-26 murine colon carcinoma cells in vitro. Laser-induced hydrodynamics was generated by a laser (?=1.56 ?, power 3 W, 5 min exposure); to this end, the fiber end was submersed into a buffer above the cell monolayer. It was found that laser-induced hydrodynamics destructed the monolayer at standoff distances of between the working end of the laser fiber to cell monolayer of 1 and 5 mm and triggers apoptotic and necrotic death in remaining cells at a distance of 4 mm from the emitter. PMID:26597691

  11. Laser induced damage of fused silica polished optics due to a droplet forming organic contaminant.

    PubMed

    Bien-Aimé, Karell; Néauport, Jérome; Tovena-Pecault, Isabelle; Fargin, Evelyne; Labrugère, Christine; Belin, Colette; Couzi, Michel

    2009-04-20

    We report on the effect of organic molecular contamination on single shot laser induced damage density at the wavelength of 351 nm, with a 3 ns pulse length. Specific contamination experiments were made with dioctylphthalate (DOP) in liquid or gaseous phase, on the surface of fused silica polished samples, bare or solgel coated. Systematic laser induced damage was observed only in the case of liquid phase contamination. Different chemical and morphological characterization methods were used to identify and understand the damage process. We demonstrate that the contaminant morphology, rather than its physicochemical nature, can be responsible for the decrease of laser induced damage threshold of optics. PMID:19381171

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

    NASA Astrophysics Data System (ADS)

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

    2002-04-01

    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 conversion from conducting mode to keyhole mode (and vice versa) were investigated. A comparison of the characteristics of the spectrum emission, penetration characteristics and input welding parameters was also studied.

  13. Laser-induced configurational transitions in liquid crystals

    NASA Astrophysics Data System (ADS)

    Hu, Gongjian

    1997-11-01

    Nematic liquid crystal director reorientation in a spatially varying temperature field has been investigated experimentally and theoretically. Both planar and homeotropically aligned E7-D27 samples have been studied. The nonuniform temperature field is produced by focusing a He-Ne laser on the dye doped cell. A physical model is proposed, where reorientation results from the coupling between the flexo-electric polarization and the DC electric field induced by the order-electric effect. The predictions of the model are compared with the result of experiment. The calculation of the free energy shows that this configurational transition is second order. The effect of director reorientation on absorption and on the far field diffraction pattern are discussed. When a photon is absorbed by a molecule the angular momentum of the photon is transferred to that molecule, exerting a torque. The effect of such torques are observed in dye doped nematics when the incident laser beam is circularly polarized. A simple model is proposed to describe the resulting distortion. From the calculated director field the far field diffraction pattern is simulated. An experiment has been designed to observe this far field pattern. Due to the large birefringences of nematics, a small director reorientation can produce large effect on the propagating light. In a high intensity optical field, the transverse modulation of the liquid crystal director has been investigated. The far field pattern observed consists of diffraction spots and has a periodic structure. The linear stability of the system has been examined. The measured transverse modulation threshold intensity is in good agreement with the predicted value. Laser induced director reorientation is the source of the 'giant' optical nonlinearity which is important for optical power limiting and optical information recording. In this research we have explored the potential applications of laser induced director reorientation. We have found that laser writing is possible in polymer stabilized cholesteric texture (PSCT) materials, with line widths as small as 5/mu m. Laser writing was observed in both planar and focal conic states, with long term stability. These materials may therefore be useful for optical information storage applications.

  14. Experimental and numerical study of laser induced spallation into aluminum and copper targets

    SciTech Connect

    Boustie, M.; Cottet, F. )

    1991-06-01

    Laser driven shocks can lead to the dynamic failure, called spallation, of materials which undergo a dynamic tension at the crossing of two rarefaction waves. We present here a numerical and experimental study of ductile material scabbing with the particular laser shock conditions (very short durations and very high induced pressure levels). A cumulative damage criterion is implemented into both numerical codes SHYLAC and RADIOSS. Experiments have been carried out by laser irradiation of thin foils of pure aluminum, copper, and iron by laser pulses with the three durations at medium height 0.6, 2.5, and 27 ns, generating an incident flux ranging from 5{times}10{sup 11} to 5{times}10{sup 12} W/cm{sup 2}. The validity of the cumulative damage criterion is asserted by the consistency of numerical and experimental results for aluminum whose criterion parameters are known. The unknown constants for copper are determined by fitting the numerical simulations to the experimental data. The material influence on the scab thickness and on the spallation threshold is analyzed. Experimental laser induced spallation data given by irradiation of a rear stepped target have been validated experimentally and numerically.

  15. 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.

  16. Laser-induced-fluorescence studies of fragment ions: CH/sup +/ and CD/sup +/

    SciTech Connect

    O'Keefe, A.

    1981-08-01

    The dynamics of ion-molecule interactions within a mass selective rf quadrupole ion trap are studied for several ion-molecule systems. Laser induced fluorescence is used as a probe of the internal energy distributions of molecular ions under collision free conditions and under controlled collision conditions. The effects of collisions at near thermal energies (0.3 to 0.5 eV) are easily understood in terms of processes such as charge transfer and other energy transfer mechanisms. The A/sup 1/PI - X/sup 1/..sigma../sup +/ system of CH/sup +/ and CD/sup +/ has been examined under collision free conditions. The ions were produced from methane through electron impact ionization/dissociation. The observed energy distributions reflect the dynamical partitioning of dissociation exothermicity, excepting short lived electronic states. Many new transitions belonging to this electronic system have been observed and a reliable vibrational frequency for the X/sup 1/..sigma../sup +/ state has been obtained. The radiative lifetimes of CH/sup +/ and CD/sup +/ A/sup 1/PI(v = 0) states have been measured and a revised oscillator strength for the A-X transition has been derived from this data.

  17. 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.

  18. 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.

  19. Electro-optical tunable waveguide Bragg gratings in lithium niobate induced by femtosecond laser writing.

    PubMed

    Horn, W; Kroesen, S; Herrmann, J; Imbrock, J; Denz, C

    2012-11-19

    We report the fabrication of femtosecond laser-induced, first-order waveguide Bragg gratings in lithium niobate in the low repetition rate regime. Type-II waveguides are written into an x-cut lithium niobate wafer and structured periodically to achieve narrowband reflections at wavelengths around 1550 nm. Additionally, electrodes are employed to allow for electro-optic tuning of the spectral response. We demonstrate wavelength control of the central reflection peak by applying a static external electric field. A maximum shift of the reflection peak of ?? = 625 pm is observed. PMID:23187546

  20. Analysis of metallic multilayers using hypersonic surface waves induced by transient reflecting gratings

    NASA Astrophysics Data System (ADS)

    Shen, Qing; Harat, Akira; Sawada, Tsuguo

    1993-08-01

    Gigahertz surface accoustic waves (the Rayleigh-like modes) have been optically generated and detected on ultrathin (less than 1 micron) metallic single-layer and multilayered films attached to glass substrates using the laser-induced transient reflecting grating (TRG) technique. The dispersion relations of the excited Rayleigh-like modes could be constructed experimentally and theoretically. By finding the best fitting of the theoretical dispersion curves to the experimental data, this method can be used to deduce the elastic constants of ultrathin multilayered films.

  1. Characterization of nano-composite oxide ceramics and monitoring of oxide thin film growth by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Pedarnig, J. D.; Heitz, J.; Stehrer, T.; Praher, B.; Viskup, R.; Siraj, K.; Moser, A.; Vlad, A.; Bodea, M. A.; Buerle, D.; Babu, N. Hari; Cardwell, D. A.

    2008-10-01

    Multi-component oxide ceramics and epitaxial oxide thin films are analyzed by laser-induced breakdown spectroscopy (LIBS). Furthermore, pulsed-laser deposition (PLD) of thin films is investigated by long-term monitoring of the optical plasma emission. Both nano-composite high-temperature superconductors (HTS) consisting of YBa 2Cu 3O 7 - ? bulk and Y 2Ba 4MCuO x (M-2411, M = Ag, Nb) nano-particles, and semiconducting ZnO doped with Aluminum and Lithium are ablated by nano-second laser pulses. The plasma emission is recorded using grating spectrometers with intensified gated detectors. The LIBS signals of nano-particles correlate with the nominal content of the M-2411 phase (0-15 mol%) and reveal a strong signal of Ytterbium impurity (3-35 ppm). In situ monitoring of the PLD process shows element signals that are stable for more than 10,000 laser pulses for both HTS and ZnO ceramics. The relative concentration of elements in thin films and ceramics as determined by LIBS is almost the same.

  2. In-situ hydrocarbon delineation using laser-induced fluorescence

    SciTech Connect

    Taer, A.D.; Hastings, R.W.; Brown, A.Y.; Frend, R.

    1996-12-01

    An investigation of hydrocarbons in soils was conducted at an active Shell Oil Company petroleum products terminal, located in Carson, California. An investigation approach involving Laser-Induced Fluorescence (LIF) and Cone Penetrometer Testing (CPT) technologies was implemented to provide real-time, in-situ characterization of site stratigraphy, hydrocarbon distribution and importantly, hydrocarbon product differentiation. The area of investigation is located along a property boundary, where a plume of separate phase hydrocarbons has been actively recovered for several years. CPT/LIF technology was selected for the investigation since previous delineation efforts using hydrocarbon fingerprinting methods proved inconclusive. Additionally, the CPT/LIF technology had the potential to provide a cost effective solution to accomplish project objectives. Based on the information obtained during this investigation, it was determined that the plume of separate phase hydrocarbons along the northern property boundary is from a source distinctly different than any identified hydrocarbons known to be from on-site sources. In addition, the plume was determined to not be connected with any other known on-site hydrocarbon plumes. The results of this CPT/LIF investigation were consistent with the known hydrogeologic conditions. This evaluation determined that CPT/LIF technology was very effective in addressing project objectives and resulted in a significant cost savings.

  3. Sample treatment and preparation for laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Jantzi, Sarah C.; Motto-Ros, Vincent; Trichard, Florian; Markushin, Yuri; Melikechi, Noureddine; De Giacomo, Alessandro

    2016-01-01

    One of the most widely cited advantages of laser-induced breakdown spectroscopy (LIBS) is that it does not require sample preparation, but this may also be the biggest factor holding it back from becoming a mature analytical technique like LA-ICP-MS, ICP-OES, or XRF. While there are certain specimen types that have enjoyed excellent LIBS results without any sample treatment (mostly homogeneous solids such as metals, glass, and polymers), the possible applications of LIBS have been greatly expanded through the use of sample preparation techniques that have resulted in analytical performance (i.e., limits of detection, accuracy, and repeatability) on par with XRF, ICP-OES, and often ICP-MS. This review highlights the work of many LIBS researchers who have developed, adapted, and improved upon sample preparation techniques for various specimen types in order to improve the quality of the analytical data that LIBS can produce in a large number of research domains. Strategies, not only for solids, but also liquids, gases, and aerosols are discussed, including newly developed nanoparticle enhancement and biological imaging and tagging techniques.

  4. Laser-induced thermoelastic effects can evoke tactile sensations.

    PubMed

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-01-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5?C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli. PMID:26047142

  5. Hyperspectral laser-induced autofluorescence imaging of dental caries

    NASA Astrophysics Data System (ADS)

    Brmen, Miran; Fidler, Ale; Pernu, Franjo; Likar, Botjan

    2012-01-01

    Dental caries is a disease characterized by demineralization of enamel crystals leading to the penetration of bacteria into the dentine and pulp. Early detection of enamel demineralization resulting in increased enamel porosity, commonly known as white spots, is a difficult diagnostic task. Laser induced autofluorescence was shown to be a useful method for early detection of demineralization. The existing studies involved either a single point spectroscopic measurements or imaging at a single spectral band. In the case of spectroscopic measurements, very little or no spatial information is acquired and the measured autofluorescence signal strongly depends on the position and orientation of the probe. On the other hand, single-band spectral imaging can be substantially affected by local spectral artefacts. Such effects can significantly interfere with automated methods for detection of early caries lesions. In contrast, hyperspectral imaging effectively combines the spatial information of imaging methods with the spectral information of spectroscopic methods providing excellent basis for development of robust and reliable algorithms for automated classification and analysis of hard dental tissues. In this paper, we employ 405 nm laser excitation of natural caries lesions. The fluorescence signal is acquired by a state-of-the-art hyperspectral imaging system consisting of a high-resolution acousto-optic tunable filter (AOTF) and a highly sensitive Scientific CMOS camera in the spectral range from 550 nm to 800 nm. The results are compared to the contrast obtained by near-infrared hyperspectral imaging technique employed in the existing studies on early detection of dental caries.

  6. Optofluidic tunable lenses using laser-induced thermal gradient.

    PubMed

    Chen, Qingming; Jian, Aoqun; Li, Zhaohui; Zhang, Xuming

    2015-12-15

    This paper reports a new design of optofluidic tunable lens using a laser-induced thermal gradient. It makes use of two straight chromium strips at the bottom of the microfluidic chamber to absorb the continuous pump laser to heat up the moving benzyl alcohol solution, creating a 2D refractive index gradient in the entrance part between the two hot strips. This design can be regarded as a cascade of a series of refractive lenses, and is distinctively different from the reported liquid lenses that mimic the refractive lens design and the 1D gradient index lens design. CFD simulation shows that a stable thermal lens can be built up within 200 ms. Experiments were conducted to demonstrate the continuous tuning of focal length from initially infinite to the minimum 1.3 mm, as well as the off-axis focusing by offsetting the pump laser spot. Data analyses show the empirical dependences of the focal length on the pump laser intensity and the flow velocity. Compared with previous studies, this tunable lens design enjoys many merits, such as fast tuning speed, aberration-free focusing, remote control, and enabling the use of homogeneous fluids for easy integration with other optofluidic systems. PMID:26584422

  7. 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.

  8. 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.

  9. [The Progress in Remote Laser-Induced Breakdown Spectroscopy].

    PubMed

    Zhang, Ting-ting; Wan, Xiong; Shu, Rong; Liu, Peng-xi

    2015-07-01

    As a kind of spectroscopic technique, the remote laser-induced breakdown spectroscopy (Remote LIBS) can measure elemental compositions of remote targets by using high-power lasers and focusing approaches. In this paper, three remote detection approaches (open path LIBS, fiber optic LIBS and compact probe fiber optic LIBS) and their system architectures are summarized and analyzed. Conventional open path LIBS, with high requirement of specifications of lasers, optical systems, spectrographs and detectors, has always been a research focus in remote testing field. Fiber optic LIBS has the advantages of simplification of optical focusing system and high collection efficiency of the plasma light. This paper reviews the progress in new techniques of LIBS, for instance Filament-LIBS techniques and LIBS combines with other spectral detection techniques, and emphatically analyzes their characteristics and advantages. These new techniques have greatly broadened the detection range of LIBS, enhanced material recognition ability of LIBS, and made a great contribution to expanding applications of remote LIBS. Latest development of applications of remote LIBS in fields of deep space exploration, hazardous material detection, pollution testing, metallurgical industries and heritage restoration is introduced in detail. With the development of laser techniques, spectral detection and calibration techniques, the detection range of remote LIBS has been expended, their application fields has been extended, and the detection precision and accuracy have been improved. PMID:26717768

  10. 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.

  11. The stochastic nature of growth of laser-induced damage

    NASA Astrophysics Data System (ADS)

    Carr, C. W.; Cross, David A.; Liao, Zhi M.; Norton, Mary A.; Negres, Raluca A.

    2015-07-01

    Laser fluence and operational tempo of ICF systems operating in the UV are typically limited by the growth of laser- induced damage on their final optics (primarily silica optics). In the early 2000 time frame, studies of laser damage growth with relevant large area beams revealed that for some laser conditions damage sites located on the exit surface of a fused silica optic grew following an exponential growth rule: D(n) = D0 exp (n ?(?)), where D is final site diameter, D0 is the initial diameter of the site, ? is the laser fluence, ?(?) is the growth coefficient, and n is the number of exposures. In general ? is a linear function of ?, with a threshold of ?TH. In recent years, it has been found that that growth behavior is actually considerably more complex. For example, it was found that ? is not a constant for a given fluence but follows a probability distribution with a mean equal to ?(?). This is complicated by observations that these distributions are actually functions of the pulse shape, damage site size, and initial morphology of damage initiation. In addition, there is not a fixed fluence threshold for damage sites growth, which is better described by a probability of growth which depends on site size, morphology and laser fluence. Here will review these findings and discuss implications for the operation of large laser systems.

  12. Laser-induced fluorescence of collagen and cholestrol

    NASA Astrophysics Data System (ADS)

    Moise, N.; Carp, C.; Pascu, Mihail-Lucian

    1995-03-01

    In this paper, laser induced fluorescence (LIF) and fluorescence lifetime of collagen and cholesterol solutions when excited with 337.1 nm radiation emitted by subnanosecond (700 psec) nitrogen pulsed laser are reported: absorption and excitation spectra of these biomolecules were obtained, too. The fluorescence excitation of collagen and cholesterol solutions was performed focusing the laser radiation on a CeramOptec quartz optical fiber with a core of 1000 micrometers . The fluorescence emission was collected using quartz optical fiber with a core of 800 micrometers . The collagen fluorescence spectra, at concentrations between 0.1 mg/ml and 5.0 mg/ml in acetic acid of initial concentrations 0.01%, 0.1% and 1%, respectively, in distilled water, exhibit a peak at 415 nm with FWHM of about 100 nm; the cholesterol fluorescence spectra, at concentrations from 0.1 mg/ml to 5.0 mg/ml in isopropyl alcohol, have a peak at 395 nm and FWHM of 60 nm. The higher values of LIF signals for cholesterol are due to the higher quantum yield. The measurements of LIF lifetimes were performed using a fast PIN photodiode with a rise time of about 200 psec. For collagen solutions a fluorescence lifetime of 5 nsec was obtained; for cholesterol solutions the measured fluorescence lifetime was 6 nsec. The overall errors in fluorescence lifetime measurements was 6%.

  13. Future Development for Laser-Induced Thermal Acoustics

    NASA Astrophysics Data System (ADS)

    Schlamp, Stefan

    2002-07-01

    The development of novel flow diagnostic techniques typically proceeds in certain stages from a proof of principle in a laboratory to a commercial product either for use in industry or as turn-key research tool. While the first usable versions are brought to market, further progress is made in the laboratory by improvements, refinements, and extensions of the technique. Consider Particle Image Velocimetry (PIV), which started by double-exposing a photographic film with the image of an illuminated particle-laden flow and where today turn-key, off-the-shelf CCD systems are available for purchase, which include the necessary data analysis software. At the same time, 3d PIV, dual-plane PIV, Doppler Global Velocimetry (DGV), etc. are being used in laboratories and will doubtless be available as integrated systems in the near future. In this paper, the origin, an overview over the current status and an outlook on the future potential of Laser-Induced Thermal Acoustics (LITA) will be given, where the focus will be on the possible technique extensions to other than the current applications. As such, it represents a collection of ideas and avenues for future research, which have not been applied as of yet, but are conceptually feasible.

  14. Laser-induced breakdown spectroscopy for polymer identification.

    PubMed

    Grgoire, Sylvain; Boudinet, Marjorie; Pelascini, Frdric; 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

  15. 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.

  16. 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.

  17. 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.

  18. Laser-induced fluorescence for discrimination of crops and weeds

    NASA Astrophysics Data System (ADS)

    Hilton, Peter J.

    2000-11-01

    This paper reports the use of Laser Induced Fluorescence (LIF) of plants to discriminate between crops and weeds for potential use in an intelligent crop spraying system. Past and current work in intelligent crop spraying has concentrated on using multi-spectral reflectance data in particular using near infrared (NIR) and color. Texture and shape image processing has also been used with limited success and is usually computationally expensive. Also, most of these approaches are error prone since they rely on ambient solar illumination and so are susceptible to errors caused by cloud variations, shadows and other non-uniformities. There are several commercial spraying systems available that detect presence or absence of plants using the NIR 'red-edge' effect without discrimination between species. 'Weedseeker' and 'Detectspray' are two examples of such systems, the 'Weedseeker' system being one of the few active systems, incorporating its own light source. However, both systems suffer from poor spatial resolution. The use of plant or chlorophyll fluorescence for discrimination between species is a relatively under researched area. This paper shows that LIF of several crops and weeds can be used to discriminate between species. Spectra are presented for two crop and two weed species over a range of discrete laser excitation wavelengths. The technique can be directly implemented with a laser imaging system for real-time detection and discrimination of crops and weeds.

  19. Laser-induced acoustic emissions in experimental dental composites.

    PubMed

    Lee, S Y; Lin, C T; Keh, E S; Pan, L C; Huang, H M; Shih, Y H; Cheng, H C

    2000-07-01

    A laser thermoacoustic technique was innovated to evaluate laser-induced acoustic emissions (AEs) in experimental dental composites aged with 75% ethanol solution. Experimental composite systems of 75/25 BisGMA/TEGDMA resin filled with 0, 12.6, 30.0, and 56.5 vol% of 8-microm silanized and unsilanized BaSiO6 were analyzed. The sample size was 4.65 mm (diameter) x 0.5 mm (thick). Aging effects of immersing in 75% ethanol for up to 14 h on AEs were then evaluated. A continuous-wave CO2 laser was used to heat the samples. Acoustic emissions were collected as a function of filler fraction, laser power, silanization, and immersion time. Onset of burst-pattern acoustic signals characteristic of fracturing occurred at different laser powers for different tested groups. Acoustic emissions generally increased with laser power, in which lower laser powers produced low-amplitude (45-50 dB) signals; the amplitude distribution (50-85 dB) became more extensive as laser powers increased. After immersion, the lower laser powers could produce the same phenomenon. The higher the filler fraction, the fewer AEs generated. A large percentage AE reduction due to silanization was noted as a function of filler fraction. Unsilanized specimens showed more thermal damages than did silanized ones. PMID:10850935

  20. Laser induced focusing for over-dense plasma beams

    NASA Astrophysics Data System (ADS)

    Schmidt, Peter; Boine-Frankenheim, Oliver; Mulser, Peter

    2015-09-01

    The capability of ion acceleration with high power, pulsed lasers has become an active field of research in the past years. In this context, the radiation pressure acceleration (RPA) mechanism has been the topic of numerous theoretical and experimental publications. Within that mechanism, a high power, pulsed laser beam hits a thin film target. In contrast to the target normal sheath acceleration, the entire film target is accelerated as a bulk by the radiation pressure of the laser. Simulations predict heavy ion beams with kinetic energy up to GeV, as well as solid body densities. However, there are several effects which limit the efficiency of the RPA: On the one hand, the Rayleigh-Taylor-instability limits the predicted density. On the other hand, conventional accelerator elements, such as magnetic focusing devices are too bulky to be installed right after the target. Therefore, we present a new beam transport method, suitable for RPA-like/over-dense plasma beams: laser induced focusing.

  1. Laser-Induced Breakdown Spectroscopy of Cinematographic Film

    NASA Astrophysics Data System (ADS)

    Oujja, M.; Abrusci, C.; Gaspard, S.; Rebollar, E.; Amo, A. del; Catalina, F.; Castillejo, M.

    Laser-induced breakdown spectroscopy (LIBS) was used to characterize the composition of black-and-white, silver-gelatine photographic films. LIB spectra of samples and reference gelatine (of various gel strengths, Bloom values 225 and 75 and crosslinking degrees) were acquired in vacuum by excitation at 266 nm. The elemental composition of the gelatine used in the upper protective layer and in the underlying emulsion is revealed by the stratigraphic analysis carried out by delivering successive pulses on the same spot of the sample. Silver (Ag) lines from the light-sensitive silver halide salts are accompanied by iron, lead and chrome lines. Fe and Pb are constituents of film developers and Cr is included in the hardening agent. The results demonstrate the analytical capacity of LIBS for study and classification of different gelatine types and the sensitivity of the technique to minor changes in gelatine composition. In addition LIBS analysis allows extracting important information on the chemicals used as developers and hardeners of archival cinematographic films.

  2. Analysis of bakery products by laser-induced breakdown spectroscopy.

    PubMed

    Bilge, Gonca; Boyacı, İsmail Hakkı; Eseller, Kemal Efe; Tamer, Uğur; Çakır, 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 589 nm 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 69 ppm, 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

  3. 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, Agns; Clegg, Samuel M.; Sirven, Jean-Baptiste; Lasue, Jrmie

    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.

  4. 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.

  5. Laser-induced breakdown spectroscopy enhanced by a micro torch.

    PubMed

    Liu, L; Huang, X; Li, S; Lu, Yao; Chen, K; Jiang, L; Silvain, J F; Lu, Y F

    2015-06-01

    A commercial butane micron troch was used to enhance plasma optical emissions in laser-induced breakdown spectroscopy (LIBS). Fast imaging and spectroscopic analyses were used to observe plasma evolution in the atmospheric pressure for LIBS without and with using a micro torch. Optical emission intensities and signal-to-noise ratios (SNRs) as functions of delay time were studied. Enhanced optical emission and SNRs were obtained by using a micro torch. The effects of laser pulse energy on the emission intensities and SNRs were studied. The same spectral intensity could be obtained using micro torch with much lower laser pulse energy. The investigation of SNR evolution with delay time at different laser pulse energies showed that the SNR enhancement factor is higher for plasmas generated by lower laser pulse energies than those generated by higher laser energies. The calibration curves of emission line intensities with elemental concentrations showed that detection sensitivities of Mn I 404.136 nm and V I 437.923 nm were improved by around 3 times. The limits of detection for both Mn I 404.136 nm and V I 437.923 nm are reduced from 425 and 42 ppm to 139 and 20 ppm, respectively, after using the micro torch. The LIBS system with micro torch was demonstrated to be cost-effective, compact, and capable of sensitivity improvement, especially for LIBS system operating with low laser pulse energy. PMID:26072861

  6. Mechanism of laser-induced drug delivery in tumors

    NASA Astrophysics Data System (ADS)

    Esenaliev, Rinat O.; Larina, Irina V.; Larin, Kirill V.; Motamedi, Massoud; Evers, B. M.

    2000-06-01

    Penetration of anti-cancer drugs (especially macromolecular agents) from blood in tumor cells is limited due to the presence of physiological barriers: tumor capillary wall, slow diffusion in the interstitium, and cancer cell membrane. Interaction of exogenous nano- or microparticles with laser or ultrasonic radiation may enhance drug delivery in tumor cells due to laser- or ultrasound-induced cavitation. Our previous studies demonstrated enhanced delivery of model macromolecular anti-cancer drugs in tissues in vitro when laser or ultrasonic radiation is applied. In this paper, we studied laser-induced cavitation in suspension of strongly absorbing particles and laser-enhanced drug delivery in human colon tumors of nude mice in vivo. Cavitation kinetics and thresholds were measured for carbon and colored polystyrene particle suspensions. Histological examination of control and irradiated tumors with fluorescent microscopy demonstrated that Q-switched Nd:YAG laser irradiation enhances delivery of a model macromolecular drug (FITC-dextran) in tumor blood vessel and interstitium. Enhanced delivery of an anti-cancer drug (5-FU) that is currently used in clinics resulted in tumor necrosis and inhibited tumor growth. Results of our studies suggest that the drug delivery enhancement is due to cavitation produced by local heating of particles with pulsed laser radiation.

  7. Laser-induced breakdown spectroscopy analyses of tungsten surfaces

    NASA Astrophysics Data System (ADS)

    Nishijima, D.; Hollmann, E. M.; Doerner, R. P.; Rudakov, D. L.

    2016-02-01

    Tungsten (W) surfaces are analyzed with laser-induced breakdown spectroscopy (LIBS). Interactions of W with nanosecond (ns) and femtosecond (fs) laser pulses are found to be quite different in terms of the ambient Ar gas pressure dependence of the average ablation rate and W I line intensity. Collinear double-pulse LIBS (115 + 115 mJ) using two ns lasers (with interpulse separation ?t 12 = 5.32 ?s) improves the signal-to-noise ratio over the whole Ar pressure range P Ar = 6.7 10?1 ? 6.7 104 Pa in contrast with single-pulse LIBS (SP-LIBS) with 230 mJ, where a signal enhancement by a factor of ?23 is obtained only at P Ar > 103 Pa. SP-LIBS with a ns laser has succeeded in obtaining a sharp transition between thin W layer with a thickness of ?100 nm and the graphite substrate. A He I (587.5 nm) line has been successfully detected with SP-LIBS with a ns laser from W containing He bubbles (?2030 nm layers) in the near-surface region.

  8. 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.

  9. Enhancing the analytical performance of laser-induced breakdown spectroscopy

    SciTech Connect

    Cremers, D.A.; Chinni, R.C.; Pichahchy, A.E.; Thornquist, H.K.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this work is to enhance the analytical capabilities of laser-induced breakdown spectroscopy (LIBS). LIBS is a method of elemental analysis in which powerful laser pulses are focused on a sample to form a microplasma. LIBS is perhaps the most versatile elemental analysis method, applicable to a variety of different real-world analysis problems. Therefore, it is important to enhance the capabilities of the method as much as possible. Accomplishments include: (1) demonstration of signal enhancements of 5--30 times from soils and metals using a double pulse method; (2) development of a model of the observed enhancement obtained using double pulses; (3) demonstration that the analytical performance achievable using low laser-pulse energies (10 and 25 mJ) can match that achievable using an energy of 100 mJ; and (4) demonstration that time-gated detection is not necessary with LIBS.

  10. Laser-induced thermoelastic effects can evoke tactile sensations

    PubMed Central

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-01-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli. PMID:26047142

  11. Laser-induced differential fluorescence for cancer diagnosis without biopsy

    SciTech Connect

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

    1997-01-01

    An optical diagnostic procedure based on laser-induced fluorescence was developed for direct {ital in vivo} cancer diagnosis without requiring biopsy. The methodology was applied in a clinical study involving over 100 patients in order to differentiate normal tissue from malignant tumors of the esophagus. Endogenous fluorescence of normal and malignant tissues was measured directly with the use of a fiber-optic probe inserted through an endoscope. The measurements were performed {ital in vivo} during routine endoscopy. Detection of the fluorescence signal from the tissue was performed with the use of laser excitation. This report describes the differential normalized fluorescence (DNF) procedure using the amplified spectral differences between the normalized fluorescence of malignant tissue and normal mucosa. The results of this DNF approach were compared with histopathology results of the biopsy samples and indicated excellent agreement in the classification of normal tissue and malignant tumors for the samples investigated. Data related to various grades of Barrett{close_quote}s esophagus are discussed. The DNF procedure could lead to the development of a rapid and cost-effective technique for cancer diagnosis. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

  12. Laser-induced electron diffraction for probing rare gas atoms.

    PubMed

    Xu, Junliang; Blaga, Cosmin I; DiChiara, Anthony D; Sistrunk, Emily; Zhang, Kaikai; Chen, Zhangjin; Le, Anh-Thu; Morishita, Toru; Lin, C D; Agostini, Pierre; DiMauro, Louis F

    2012-12-01

    Recently, using midinfrared laser-induced electron diffraction (LIED), snapshots of a vibrating diatomic molecule on a femtosecond time scale have been captured [C.I. Blaga et al., Nature (London) 483, 194 (2012)]. In this Letter, a comprehensive treatment for the atomic LIED response is reported, a critical step in generalizing this imaging method. Electron-ion differential cross sections (DCSs) of rare gas atoms are extracted from measured angular-resolved, high-energy electron momentum distributions generated by intense midinfrared lasers. Following strong-field ionization, the high-energy electrons result from elastic rescattering of a field-driven wave packet with the parent ion. For recollision energies ?100 eV, the measured DCSs are indistinguishable for the neutral atoms and ions, illustrating the close collision nature of this interaction. The extracted DCSs are found to be independent of laser parameters, in agreement with theory. This study establishes the key ingredients for applying LIED to femtosecond molecular imaging. PMID:23368191

  13. 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.

  14. Oxide nanoparticles synthesis via laser-induced plasma in liquid

    NASA Astrophysics Data System (ADS)

    Goto, Taku; Weihs, Hansel; Honda, Mitsuhiro; Kulinich, Sergei; Shimizu, Yoshiki; Ito, Tsuyohito

    2014-10-01

    Laser ablation in fluids has recently attracted a lot of attention as one of synthetic techniques to prepare new attractive nanomaterials, with the ability to control both product chemistry and morphology in many systems. In this study, we generated laser-induced plasma in H2O - ethanol mixtures, while ablating metal targets to produce oxide nanoparticles and to study the effect of the medium on their properties. The ablated targets used in this study were Zn or Sn plates. A nanosecond Nd:YAG laser with the wavelength of 532 nm (10 Hz, 20--30 mJ/pulse) was applied to irradiate the targets. The liquid media were maintained at 0.1 to 30 MPa to study the effect of pressure. We found that the H2O/ethanol ratio (at atmospheric pressure) can control the properties of the produced ZnO nanoparticles, such as defects and oxidation degree. The properties were examined by photoluminescence (PL) spectroscopy, X-ray diffraction, electron microscopies, and so on. More details will be presented at the symposium.

  15. Thermal cleavage on glass by a laser-induced plume

    NASA Astrophysics Data System (ADS)

    Choi, Won Seok; Kim, Jong Hyeong; Kim, Joohan

    2014-02-01

    We developed a thermal cleaving process on glass using an infrared-laser-induced plume. A pulsed ytterbium fiber laser with a wavelength of 1070 nm and a laser pulse energy of 40 J was used to produce a plasma plume on a carbon-coated sacrificial glass substrate. The induced plasma plume affected the surface of the target glass substrate and changed its optical properties locally. The laser beam that was subsequently absorbed in the modified zone induced localized heating, which led to micro-crack initiation for the glass cleaving. Various processing parameters, such as the laser's power and pulse width, and the distance between the coating layer and the target glass substrate were investigated to optimize the quality of the glass cleave. The quality of the cutting edges and cross sections with respect to these parameters were examined. Numerical simulations of the micro-crack initiation due to heat accumulation were performed to investigate the fracture mechanism and to estimate the expected glass-cleaving line. The limits and applications of the process are also discussed.

  16. Intraoperative metastases detection by laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Vari, Sandor G.; Papazoglou, Theodore G.; van der Veen, Maurits J.; Fishbein, Michael C.; Young, J. D.; Chandra, Mudjianto; Papaioannou, Thanassis; Beeder, Clain; Shi, Wei-Qiang; Grundfest, Warren S.

    1991-06-01

    The authors studied the ability of Laser Induced Fluorescence Spectroscopy (LIFS) for the intraoperative identification of metastases using a photosensitizing agent Photofrin IIr to enhance spectroscopic detection. A He-Cd laser source (442 nm) was used to produce low-power illumination of tissue via a hand-held 400 micrometers fiberoptic probe. Through the same fiber, reflected and emitted light was returned to an optical multi-channel analyzer (OMA III) for analysis. Spectroscopic signals were displayed on a screen for immediate examination. Lobund Wistar rats, inoculated with Pollard rat adenocarcinoma cells, were used as an animal model. Photofrin IIr was administered intraperitoneal 24 or 48 hours prior to surgical exploration in doses varying from 0.75-7.5 mg/kg. Metastases detection was performed during abdominal exploration directed to ipsilateral and contralateral inguinal, iliac, para-aortic and renal lymph nodes. Nineteen tissue samples, identified as abnormal by LIFS, were removed for histologic analysis; 11 of these samples were larger than 5mm and histologic examination revealed malignancy in all cases. While LIFS signals showed malignancy in 8 tissue samples with dimensions less than 5mm, histology confirmed this in only 3. However, serial histologic sections were not performed. From the initial results, it was concluded that LIFS detection of malignant tissue is feasible and enhanced by the addition of Photofrin IIr. LIFS may be a promising technique for the intraoperative detection of primary malignant and metastatic tissue.

  17. Airborne laser induced fluorescence imaging. Innovative technology summary report

    SciTech Connect

    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.

  18. Laser-induced porous graphene films from commercial polymers

    PubMed Central

    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

    Synthesis and patterning of carbon nanomaterials cost effectively is a challenge in electronic and energy storage devices. Here report a one-step, scalable approach for producing and patterning porous graphene films with 3-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 mFcm?2 and power densities of ~9 mWcm?2. Theoretical calculations partially suggest that enhanced capacitance may result from LIGs 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

  19. Production of biomolecule microarrays through laser induced forward transfer

    NASA Astrophysics Data System (ADS)

    Fernandez-Pradas, Juan Marcos; Serra, Pere; Colina, Monica; Morenza, Jose-Luis

    2004-10-01

    Biomolecule microarrays are a kind of biosensors that consist in patterns of different biological molecules immobilized on a solid substrate and capable to bind specifically to their complementary targets. In particular, DNA and protein microarrays have been revealed to be very efficient devices for genen and protein identification, what has converted them in powerful tools for many applications, like clinical diagnose, drug discovery analysis, genomics and proteomics. The production of these devices requires the manipulation of tiny amounts of a liquid solution containing biomolecules without damaging them. In this work laser induced forward transfer (LIFT) has been used for spotting a biomolecule in order to check the viability of this technique for the production of microarrays. A pulsed Nd:YAG laser beam (355 nm wavelength) has been used to transfer droplets of a biomolecule containing solution onto a solid slide. Optical microscopy of the transferred material has been carried out to investigate the morphological characteristics of the droplets obtained under different irradiation conditions. Afterwards, a DNA microarray has been spotted. The viability of the transference has been tested by checking the biological activity of the biomolecule in front of its specific complementary target. This has revealed that, indeed, the LIFT technique is adequate for the production of DNA microarrays.

  20. Electron density determination of aluminium laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2015-06-01

    We present temporally and spatially resolved electron density results of laser-induced plasma initiated on the surface of an aluminium target. Aluminium 394.4 and 396.15 nm lines were fit to Lorentzian profiles to evaluate Stark widths and shifts. Experimentally determined electron density versus line width and shift relationships were applied. Fitting to the aluminium lines indicates an electron density of 1.9 0.2 and 3.2+/- 0.4 {{10}18} c{{m}-3} for Stark widths and 1.7 0.5 and 1.7+/- 0.5 {{10}18} c{{m}-3} for Stark shifts at a 0.3 ?s time delay following plasma initiation for the aluminium Al i 394.4 and 396.15 nm transitions, respectively. Simultaneous observations of the singly ionized nitrogen line, N ii, at 395.5 nm were also fit for a time delay of 0.2 ?s, indicating an electron density of 1.8+/- 1.0 {{10}18} c{{m}-3}. The differences between the nitrogen and aluminium electron densities show evidence of self absorption.

  1. Ophthalmic manifestations of laser-induced eye injuries

    NASA Astrophysics Data System (ADS)

    Belkin, Michael

    1996-04-01

    The basis for almost all laser-induced eye injuries is the concentration of the radiation in the visible and near infra red range on the retina. The effect of this concentration is that the energy required to produce a visible retinal lesion is minuscule, about 50 microjoule for a Q- switched 532 nm laser. Even at lower energies the radiation can cause dazzle and flash blindness. At higher energies it can produce lesions which are ophthalmoscopically invisible, and at even higher energies, lesions that are visible and permanent. Higher energies still produce vitreous hemorrhage. The functional results of visible lesions depend not only on the energy impinging on the retina but mostly on the location of the injury. Foveal lesions will cause permanent reduction in visual functions, extrafoveal injuries will cause temporary visual incapacitation, and lesions further away from the macula may cause unnoticeable damage. Temporary incapacitation by intraocular hemorrhage can be engendered by a lesion anywhere in the eye. The latter is usually absorbed spontaneously or can be surgically removed by vitrectomy. An over-threshold injury anywhere on the posterior pole of the eye will lead to severance of the retinal nerve fiber layer, and thus to blind spots in parts of the retina unaffected by the original lesion. A common late, visually devastating, effect of laser lesions is retinal scarring which may lead to retinal holes, retinal detachment and delayed blindness.

  2. Laser-induced thermoelastic effects can evoke tactile sensations

    NASA Astrophysics Data System (ADS)

    Jun, Jae-Hoon; Park, Jong-Rak; Kim, Sung-Phil; Min Bae, Young; Park, Jang-Yeon; Kim, Hyung-Sik; Choi, Seungmoon; Jung, Sung Jun; Hwa Park, Seung; Yeom, Dong-Il; Jung, Gu-In; Kim, Ji-Sun; Chung, Soon-Cheol

    2015-06-01

    Humans process a plethora of sensory information that is provided by various entities in the surrounding environment. Among the five major senses, technology for touch, haptics, is relatively young and has relatively limited applications largely due to its need for physical contact. In this article, we suggest a new way for non-contact haptic stimulation that uses laser, which has potential advantages such as mid-air stimulation, high spatial precision, and long working distance. We demonstrate such tactile stimulation can be enabled by laser-induced thermoelastic effects by means of physical and perceptual studies, as well as simulations. In the physical study, the mechanical effect of laser on a human skin sample is detected using low-power radiation in accordance with safety guidelines. Limited increases (< ~2.5 °C) in temperature at the surface of the skin, examined by both thermal camera and the Monte Carlo simulation, indicate that laser does not evoke heat-induced nociceptive sensation. In the human EEG study, brain responses to both mechanical and laser stimulation are consistent, along with subjective reports of the non-nociceptive sensation of laser stimuli.

  3. Laser-induced backside wet cleaning technique for glass substrates

    NASA Astrophysics Data System (ADS)

    Weng, Tsu-Shien; Tsai, Chwan-Huei

    2014-08-01

    The aim of this paper is to study the laser-induced backside wet cleaning techniques for glass substrates. Two kinds of laser cleaning techniques are proposed in this study. The first involves applying an Nd:YAG laser to the backside of the substrate which is submerged in water. A metal plate is placed below the glass substrate. Most of the laser energy will be absorbed by the metal plate. The metal then vaporizes the water and generates a turbulent bubble flow. The bubble flow removes the alumina particles from the surface of the glass substrate. The second involves using a CO2 laser to generate turbulent bubble flow to remove the particles. Both methods were successfully demonstrated for the removal of submicron particles of 0.5 ?m in size. The phenomena of bubble generation and diffusion are presented in the paper. Because the laser is applied to the backside of the substrate, the damage due to the laser heat can be significantly reduced. The quality and efficient of the backside processing is better than those of the front side processing. The proposed techniques have great potential to provide an improved solution for glass cleaning.

  4. 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.

  5. Drift mechanism of laser-induced electron acceleration in vacuum

    NASA Astrophysics Data System (ADS)

    Morgovsky, L.

    2015-12-01

    Laser-induced electron acceleration in vacuum is possible due to the ejection of electrons from the beam as a consequence of the transverse drift orthogonal to the propagation direction. The transverse drift is derived from the general solution of the equations of motion of the electrons in the field of a plane electromagnetic wave with arbitrary polarization. It is shown that the energy gain is proportional to the square of the field strength additionally modulated by the function of the injection and ejection phases. In particular, for a linearly polarized beam this function is reduced to the squared difference between the cosines of these phases. The finite laser pulse duration restricts the range of the field strength suitable for direct electron acceleration in vacuum within certain limits. It is demonstrated that the high efficiency of energy transfer from the laser wave into the kinetic energy of the accelerated electrons demands phase matching between the electron quiver phase at the exit point and the phase of the energy transfer.

  6. Analysis of human nails by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

  7. Pressure dependence of laser-induced fluorescence from acetone.

    PubMed

    Yuen, L S; Peters, J E; Lucht, R P

    1997-05-20

    The use of laser-induced fluorescence (LIF) from acetone is becoming increasingly widespread as a diagnostic of mixing processes in both reacting and nonreacting flows. One of the major reasons for its increasing use is that the acetone LIF signal is believed to be nearly independent of pressure because of fast intersystem crossing from the first excited singlet state, from which the fluorescence signal originates, to the first excited triplet state, which does not fluoresce. To evaluate the use of acetone LIF at pressures higher than atmospheric, we have performed a study of acetone LIF in a flowing gas cell at pressures up to 8 atm. We used four different buffer gases: air, nitrogen, methane, and helium. Surprisingly, we find that the acetone fluorescence quantum efficiency increases slightly (~30%-50%) as the buffer-gas pressure increases from 0.6 to 5 atm for all four buffer gases. When the buffer gas is air, we observe a decrease in the acetone fluorescence quantum efficiency as the buffer-gas pressure is increased from 5 to 8 atm; for the other three buffer gases the quantum efficiency is constant to within experimental error in this pressure regime. The observed pressure dependence of the acetone fluorescence signal is explained by use of a four-level model. The increase in the fluorescence quantum efficiency with pressure is probably the result of incomplete vibrational relaxation coupled with an increase in the intersystem crossing rate with increasing vibrational excitation in the first excited singlet manifold. PMID:18253335

  8. 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.

  9. 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.

  10. Dark current and light illumination effects on grating formation during periodic long-term operation in photorefractive polymers

    SciTech Connect

    Fujihara, T.; Mamiya, J.; Kawamoto, M.; Sassa, T.

    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.

  11. Laser-Induced Fluorescence Detection Using The Sheath-Flow Cuvette For Capillary Zone Electrophoresis

    NASA Astrophysics Data System (ADS)

    Cheng, Yung-Fong; Dovichi, Norman J.

    1988-04-01

    Laser induced fluorescence and the sheath flow cuvette are combined to quantitate fluorescein in flowing streams. When combined with capillary zone electrophoresis, detection limits (3σ) are 1.8 attomole or 1 million molecules injected.

  12. Penta(cyclopentadienyl)-[eta]5-cyclopentadienylmanganesetricarbonyl: Structure and laser-induced conversion to fullerenes

    SciTech Connect

    Barrow, Mark P.; Cammack, J. Kevin; Goebel, Matthias; Wasser, Ian M.; Vollhardt, K.Peter C.; Drewello, Thomas

    1998-08-28

    The title compound [Cp5CpMn(CO)3], 1, has been characterized by X-ray crystallography and shown by laser-induced desorption/ionization (LDI) to undergo coalescence to fullerene C60 and other carbon clusters.

  13. 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.

  14. 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...

  15. Investigation of laser-induced effects in molecular layers by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Grafstrm, S.; Schuller, P.; Kowalski, J.; Neumann, R.

    Aiming at the detection of laser-induced currents caused by resonant optical excitation of adsorbed molecules with a scanning tunneling microscope, we have developed a method that provides access to very small laser-induced effects normally hidden in the thermal background. An optical compensation setup based on two lasers with different wavelengths for controlling very precisely the thermal signal, together with a special scheme for signal averaging and interpolation, provides access to laser-induced signals down to <100 fA. We apply this method to molecular films consisting of islands of the dye perylene-tetracarboxylic-dianhydride (PTCDA) embedded in the liquid crystal octylcyanobiphenyl (8CB). Under complete compensation of the background, a statistically significant residual laser-induced current has been observed on the PTCDA islands with a magnitude of 125 fArms at a modulated laser intensity of 3.5 kWrms/cm2.

  16. Charged particle accelerator grating

    DOEpatents

    Palmer, R.B.

    1985-09-09

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. 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 onto 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.

  17. The Cryogenic Grating Spectrometer

    NASA Technical Reports Server (NTRS)

    Erickson, Edwin F.; Haas, Michael R.; Colgan, Sean W. J.; Simpson, Janet P.; Rubin, Robert H.

    1995-01-01

    The Cryogenic Grating Spectrometer (CGS) first flew on the KAO in 1982 December and has been open to guest investigators since 1984 October. In the past 12 years it has completed over 100 research flights supporting 13 different principal investigators studying a variety of objects. We briefly describe the instrument, its capabilities and accomplishments, and acknowledge the people who have contributed to its development and operation.

  18. Optical grating analyzer studies

    NASA Technical Reports Server (NTRS)

    Mcdonald, J. K.

    1974-01-01

    A spectrometer was specifically designed and developed to observe grating spectra over a range of incidence angles from normal to almost grazing incidence. A unique scanning and focusing mechanism is utilized to keep the exit slit on the Rowland circle. Polarization effects in the vacuum were investigated, and efficiency measurements and spectral scans were made simultaneously with the spectrometer. Results of measurements are given. Applications of the spectrometer to the space program and to the study of contamination on optical surfaces are indicated.

  19. 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.; Fernndez-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.

  20. Extended asymmetric-cut multilayer X-ray gratings.

    PubMed

    Prasciolu, Mauro; Haase, Anton; Scholze, Frank; Chapman, Henry N; Bajt, Saša

    2015-06-15

    The fabrication and characterization of a large-area high-dispersion blazed grating for soft X-rays based on an asymmetric-cut multilayer structure is reported. An asymmetric-cut multilayer structure acts as a perfect blazed grating of high efficiency that exhibits a single diffracted order, as described by dynamical diffraction throughout the depth of the layered structure. The maximum number of grating periods created by cutting a multilayer deposited on a flat substrate is equal to the number of layers deposited, which limits the size of the grating. The size limitation was overcome by depositing the multilayer onto a substrate which itself is a coarse blazed grating and then polish it flat to reveal the uniformly spaced layers of the multilayer. The number of deposited layers required is such that the multilayer thickness exceeds the step height of the substrate structure. The method is demonstrated by fabricating a 27,060 line pairs per mm blazed grating (36.95 nm period) that is repeated every 3,200 periods by the 120-μm period substrate structure. This preparation technique also relaxes the requirements on stress control and interface roughness of the multilayer film. The dispersion and efficiency of the grating is demonstrated for soft X-rays of 13.2 nm wavelength. PMID:26193502

  1. Laser-induced periodic annular surface structures on fused silica surface

    SciTech Connect

    Liu, Yi; Brelet, Yohann; Forestier, Benjamin; Houard, Aurelien; Yu, Linwei; Deng, Yongkai; Jiang, Hongbing

    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.

  2. Photoluminescence and terahertz emission from femtosecond laser-induced plasma channels.

    PubMed

    Hoyer, W; Knorr, A; Moloney, J V; Wright, E M; Kira, M; Koch, S W

    2005-03-25

    Luminescence as a mechanism for terahertz emission from femtosecond laser-induced plasmas is studied. By using a fully microscopic theory, Coulomb scattering between electrons and ions is shown to lead to luminescence even for a spatially homogeneous plasma. The spectral features introduced by the rod geometry of laser-induced plasma channels in air are discussed on the basis of a generalized mode-function analysis. PMID:15903868

  3. Excimer-laser-induced fluorescence of rabbit cornea: radiometric measurement through the cornea

    SciTech Connect

    Ediger, M.N. )

    1991-01-01

    The laser-induced fluorescence spectrum of rabbit cornea irradiated at ablative intensities was measured. This system directly measured the radiant exposure of fluorescence transmitted through the cornea when the anterior surface of the cornea was irradiated by an ArF excimer laser. Evidence of changing spectral characteristics as a function of total laser dose suggests photochemical changes in the cornea may be occurring. Results are compared with previous data of laser-induced fluorescence in other models and detection schemes.

  4. High Efficiency Binary Blazed Grating Waveguide Couplers

    NASA Technical Reports Server (NTRS)

    Watson, Michael D.; Abushagur, Mustafa A. G.; Ashley, Paul R.; Cole, Helen

    1998-01-01

    Binary blazed gratings are investigated as highly efficient waveguide couplers. Equations are derived for the design of efficient binary blazed grating waveguide couplers. The design approach relates waveguide blazed grating equations to Artificial Index Grating (AIG) equations to emulate a blazed grating. Using these relationships, binary blazed gratings can be accurately designed to output a single mode at a desired output angle. Binary blazed grating couplers can achieve single mode cladding output without substrate" radiation output modes. Much higher output angles can be achieved than with rectangular grating couplers. The use of the AIG grating structure simplifies fabrication approaches. Waveguide couplers were designed using these equations.

  5. On chemical reactions in the laser-induced breakdown of a liquid

    NASA Astrophysics Data System (ADS)

    Margulis, M. A.; Ovchinnikov, O. B.; Margulis, I. M.

    2006-06-01

    It is shown experimentally that a laser-induced breakdown of a liquid is accompanied by chemical reactions initiated by radicals and excited species formed in the spark. It is found that, in water, the laser-induced breakdown is accompanied by the dissociation of water and dissolved nitrogen molecules with the formation of HNO2 and HNO3, while, in a FeSO4 aqueous solution, by the Fe2+ ? Fe3+ oxidation reaction. It is assumed that the mechanism of the process is analogous to that of the action of ionizing radiations and the chemical action of ultrasonically induced cavitation (it is proposed that this mechanism of chemical action of a laser-induced spark proposed be termed indirect). Energy yields of these reactions are found to be of the same order of magnitude as for sonochemical redox reactions. It is shown that the laser-induced breakdown of an aqueous solution of maleic acid is accompanied by its stereoisomerization into fumaric acid, a process catalyzed by small amounts of an alkyl bromide. It is established that, for the formation of fumaric acid in a laser-induced spark, the energy yield is about five orders of magnitude higher than that typical of the above-mentioned redox reactions in the laser-induced spark.

  6. Subsurface defects of fused silica optics and laser induced damage at 351 nm.

    PubMed

    Hongjie, Liu; Jin, Huang; Fengrui, Wang; Xinda, Zhou; Xin, Ye; Xiaoyan, Zhou; Laixi, Sun; Xiaodong, Jiang; Zhan, Sui; Wanguo, Zheng

    2013-05-20

    Many kinds of subsurface defects are always present together in the subsurface of fused silica optics. It is imperfect that only one kind of defects is isolated to investigate its impact on laser damage. Therefore it is necessary to investigate the impact of subsurface defects on laser induced damage of fused silica optics with a comprehensive vision. In this work, we choose the fused silica samples manufactured by different vendors to characterize subsurface defects and measure laser induced damage. Contamination defects, subsurface damage (SSD), optical-thermal absorption and hardness of fused silica surface are characterized with time-of-flight secondary ion mass spectrometry (TOF-SIMS), fluorescence microscopy, photo-thermal common-path interferometer and fully automatic micro-hardness tester respectively. Laser induced damage threshold and damage density are measured by 351 nm nanosecond pulse laser. The correlations existing between defects and laser induced damage are analyzed. The results show that Cerium element and SSD both have a good correlation with laser-induced damage thresholds and damage density. Research results evaluate process technology of fused silica optics in China at present. Furthermore, the results can provide technique support for improving laser induced damage performance of fused silica. PMID:23736441

  7. 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.).

  8. Grating-structured metallic microsprings.

    PubMed

    Huang, Tao; Liu, Zhaoqian; Huang, Gaoshan; Liu, Ran; Mei, Yongfeng

    2014-08-21

    We fabricate grating-structured metallic microsprings with well-defined helical angles and diameters, which are self-rolled from strained nanomembranes patterned with gratings. The grating structures on the metal membrane, replicated from the imprinted polymer layer beneath, give rise to the controlled rolling direction after selective etching of the underlying sacrificial layer. The rolling direction of the grating-structured thin metal film is always perpendicular to the long side edge of gratings, offering a good way to roll up strained strips into well controlled three-dimensional (3D) microsprings simply by altering the dimension and orientation of the structured strips. The mechanical elasticity of these grating-structured metallic microsprings is verified for the potential application as a flow rate sensor. Our work may stimulate rigorous synthesis of highly functional and complex 3D helical micro and nanostructures, and hint a broad range of applications such as environmental sensors, micro-/nanoscale robots, metamaterials, etc. PMID:24728100

  9. Model-based planning and real-time predictive control for laser-induced thermal therapy

    PubMed Central

    Feng, Yusheng; Fuentes, David

    2014-01-01

    In this article, the major idea and mathematical aspects of model-based planning and real-time predictive control for laser-induced thermal therapy (LITT) are presented. In particular, a computational framework and its major components developed by authors in recent years are reviewed. The framework provides the backbone for not only treatment planning but also real-time surgical monitoring and control with a focus on MR thermometry enabled predictive control and applications to image-guided LITT, or MRgLITT. Although this computational framework is designed for LITT in treating prostate cancer, it is further applicable to other thermal therapies in focal lesions induced by radio-frequency (RF), microwave and high-intensity-focused ultrasound (HIFU). Moreover, the model-based dynamic closed-loop predictive control algorithms in the framework, facilitated by the coupling of mathematical modelling and computer simulation with real-time imaging feedback, has great potential to enable a novel methodology in thermal medicine. Such technology could dramatically increase treatment efficacy and reduce morbidity. PMID:22098360

  10. Thermal distribution in biological tissue at laser induced fluorescence and photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Krasnikov, I. V.; Seteikin, A. Yu.; Drakaki, E.; Makropoulou, M.

    2012-03-01

    Laser induced fluorescence spectroscopy and photodynamic therapy (PDT) are techniques currently introduced in clinical applications for visualization and local destruction of malignant tumours as well as premalignant lesions. During the laser irradiation of tissues for the diagnostic and therapeutic purposes, the absorbed optical energy generates heat, although the power density of the treatment light for surface illumination is normally low enough not to cause any significantly increased tissue temperature. In this work we tried to evaluate the utility of Monte Carlo modeling for simulating the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed UV laser and a continuous wave visible laser beam. The analysis of the results showed that heat is not localized on the surface, but it is collected inside the tissue. By varying the boundary conditions on the surface and the type of the laser radiation (continuous or pulsed) we can reach higher than normal temperature inside the tissue without simultaneous formation of thermally damaged tissue (e.g. coagulation or necrosis zone).

  11. Thermal distribution in biological tissue at laser induced fluorescence and photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Krasnikov, I. V.; Seteikin, A. Yu.; Drakaki, E.; Makropoulou, M.

    2011-10-01

    Laser induced fluorescence spectroscopy and photodynamic therapy (PDT) are techniques currently introduced in clinical applications for visualization and local destruction of malignant tumours as well as premalignant lesions. During the laser irradiation of tissues for the diagnostic and therapeutic purposes, the absorbed optical energy generates heat, although the power density of the treatment light for surface illumination is normally low enough not to cause any significantly increased tissue temperature. In this work we tried to evaluate the utility of Monte Carlo modeling for simulating the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed UV laser and a continuous wave visible laser beam. The analysis of the results showed that heat is not localized on the surface, but it is collected inside the tissue. By varying the boundary conditions on the surface and the type of the laser radiation (continuous or pulsed) we can reach higher than normal temperature inside the tissue without simultaneous formation of thermally damaged tissue (e.g. coagulation or necrosis zone).

  12. Laser-induced charge-disproportionated metallic state in LaCoO3

    NASA Astrophysics Data System (ADS)

    Izquierdo, M.; Karolak, M.; Trabant, C.; Holldack, K.; Fhlisch, 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. 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.; Fernndez-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%.

  14. 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.

  15. Study on the effects of ion motion on laser-induced plasma wakes

    SciTech Connect

    Zhou Suyun; Yu Wei; Yuan Xiao; Xu Han; Cao, L. H.; Cai, H. B.; Zhou, C. T.

    2012-09-15

    A 2D analytical model is presented for the generation of plasma wakes (or bubbles) with an ultra-intense laser pulse by taking into account the response of plasma ions. It is shown that the effect of ion motion becomes significant at the laser intensity exceeding 10{sup 21} W/cm{sup 2} and plasma background density below 10{sup 19} cm{sup -3}. In this regime, ion motion tends to suppress the electrostatic field induced by charge separation and makes the electron acceleration less effective. As a result, the assumption of immobile ions overestimates the efficiency of laser wake-field acceleration of electrons. Based on the analytical model, the dynamics of plasma ions in laser-induced wake field is investigated. It is found that only one bubble appears as the plasmas background density exceeds the resonant density and the deposited laser energy is concentrated into the bubble, resulting in the generation of an ion bunch with extremely high energy density.

  16. Chiral separation of benzoporphyrin derivative mono- and diacids by laser induced fluorescence-capillary electrophoresis.

    PubMed

    Peng, Xuejun; Sternberg, Ethan; Dolphin, David

    2002-01-01

    A method for the separation of benzoporphyrin derivative mono- and diacid (BPDMA, BPDDA) enantiomers by laser induced fluorescence-capillary electrophoresis (LIF-CE) has been developed. By using 300 mM borate buffer, pH 9.2, 25 mM sodium cholate and 10% acetronitrile as electrolyte, +10 kV electrokinetic sampling injection of 2 s and an applied +20 kV voltage across the ends of a 37 cm capillary (30 cm to the detector, 50 microm ID), all six BPD stereoisomers were baseline-separated within 20 min. Formation constants, free electrophoretic and complexation mobilities with borate and cholate were determined based on dynamic complexation capillary electrophoresis theory. The BPD enantiomers can be quantitatively determined in the range of 10(-2)-10(-5) mg mL(-1). The correlation coefficients (r2) of the least-squares linear regression analysis of the BPD enantiomers are in the range of 0.9914-0.9997. Their limits of detection are 2.18-3.5 x 10(-3) mg mL(-1). The relative standard deviations for the separation were 2.90-4.64% (n = 10). In comparison with high-performance liquid chromatography (HPLC), CE has better resolution and efficiency. This separation method was successfully applied to the BPD enantiomers obtained from a matrix of bovine serum and from liposomally formulated material as well as from studies with rat, dog and human microsomes. PMID:11824627

  17. Hydrogen Balmer Series Self-Absorption Measurement in Laser-Induced Air Plasma

    NASA Astrophysics Data System (ADS)

    Gautam, Ghaneshwar; Parigger, Christian

    2015-05-01

    In experimental studies of laser-induced plasma, we use focused Nd:YAG laser radiation to generate optical breakdown in laboratory air. A Czerny-Turner type spectrometer and an ICCD camera are utilized to record spatially and temporally resolved spectra. Time-resolved spectroscopy methods are employed to record plasma dynamics for various time delays in the range of 0.300 microsecond to typically 10 microsecond after plasma initiation. Early plasma emission spectra reveal hydrogen alpha and ionized nitrogen lines for time delays larger than 0.3 microsecond, the hydrogen beta line emerges from the free-electron background radiation later in the plasma decay for time delays in excess of 1 microsecond. The self-absorption analyses include comparisons of recorded data without and with the use of a doubling mirror. The extent of self-absorption of the hydrogen Balmer series is investigated for various time delays from plasma generation. There are indications of self-absorption of hydrogen alpha by comparison with ionized nitrogen lines at a time delay of 0.3 microsecond. For subsequent time delays, self-absorption effects on line-widths are hardly noticeable, despite the fact of the apparent line-shape distortions. Of interest are comparisons of inferred electron densities from hydrogen alpha and hydrogen beta lines as the plasma decays, including assessments of spatial variation of electron density.

  18. Cooling profiles of laser induced temperature fields for superconducting vanadium nitrate products

    NASA Astrophysics Data System (ADS)

    Emetere, Moses Eterigho

    2016-01-01

    The flexibility of vanadium nitrate makes it a good constituent for emerging superconductors. Its thermal instability engenders a disordered structure when doped by insulating constituents. The physics of the heat source i.e. the probe laser was theoretical derived to avoid deficiency of the superconducting material at low laser energy density. The mathematical experimentation was accomplished by queering the energy balance and heat conductivity of the individual constituents of the reagent. In-depth analysis of the layered distribution of laser induced temperature fields was carried out by cooling the compound via the forced convective cooling technique to about 150 C. The material was gradual heated via the laser probe to its superconducting state. The structural defect which explained different state of the thermal outcomes were explained and proven to correspond with experimental outcomes. The temperature distribution under the irradiating laser intensity (0.45 W) shows an effective decay rate probability density function which is peculiar to the concept of photoluminescence. The dynamics of the electronic structure of thermally-excited superconducting materials is hinged on the complementary stoichiometry signatures, thermal properties amongst others. The maximum possible critical temperatures of the inter-layer were calculated to be about 206 K.

  19. Laser-induced circular nanostructures in fused silica assisted by a self-assembling chromium layer

    NASA Astrophysics Data System (ADS)

    Lorenz, Pierre; Klppel, Michael; Frost, Frank; Ehrhardt, Martin; Zimmer, Klaus; Li, Pu

    2013-09-01

    Nanostructures have a widespread field of applications and are of growing industrial importance. However, the economic fabrication of nanostructures poses a critical challenge. In this work, a fundamental research of a laser-induced surface nanostructuring of fused silica using the dynamic self-assembling structure formation in metal layers is presented. This method may offer promising opportunities for nanostructuring of dielectrics. This new approach is demonstrated by the formation of randomly distributed concentric nanostructures into fused silica. The irradiation of chromium-covered fused silica samples with a KrF excimer laser results in melting, partial ablation, restructuring, and resolidification of both the metal layer and the dielectric surface. In this way, concentric circular structures into the dielectric were formed with dimensions that can be controlled by the laser fluence ? and by the pulse number N. The distance of the concentric rings increases with increasing laser fluence. The experimental results were compared with simulated structure dimensions taking into account the heat equation and the Navier-Stokes equation. Despite the currently applied decoupled approach for the simulations, i.e. separating the heat equation and the fluid flow, a good agreement of simulation results with experimental data was achieved.

  20. Assessment of femtosecond laser induced periodic surface structures on polymer films.

    PubMed

    Rebollar, Esther; Vzquez de Aldana, Javier R; Martn-Fabiani, Ignacio; Hernndez, Margarita; Rueda, Daniel R; Ezquerra, Tiberio A; Domingo, Concepcin; 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