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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

    SciTech Connect

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

    2015-12-15

    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. 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.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  11. Comparison of a transmission grating spectrometer to a reflective grating spectrometer for standoff laser-induced breakdown spectroscopy measurements

    SciTech Connect

    Weisberg, Arel; Craparo, Joseph; De Saro, Robert; Pawluczyk, Romuald

    2010-05-01

    We evaluate a new transmission grating spectrometer for standoff laser-induced breakdown spectroscopy (LIBS) measurements. LIBS spectra collected from standoff distances are often weak, with smaller peaks blending into the background and noise. Scattered light inside the spectrometer can also contribute to poor signal-to-background and signal-to-noise ratios for smaller emission peaks. Further, collecting standoff spectra can be difficult because most spectrometers are designed for laboratory environments and not for measurements in the field. To address these issues, a custom-designed small, lightweight transmission grating spectrometer with no moving parts was built that is well suited for standoff LIBS field measurements. The performance of the spectrometer was quantified through 10 m standoff LIBS measurements collected from aluminum alloy samples and measurements from spectra of a Hg-Ar lamp. The measurements were compared to those collected using a Czerny-Turner reflective grating spectrometer that covered a similar spectral range and used the same ICCD camera. Measurements using the transmission grating spectrometer had a 363% improved signal-to-noise ratio when measured using the 669 nm aluminum emission peak.

  12. Femtosecond laser-induced subwavelength ripples formed by asymmetrical grating splitting

    NASA Astrophysics Data System (ADS)

    Feng, Pin; Jiang, Lan; Li, Xin; Zhang, Kaihu; Shi, Xuesong; Li, Bo; Lu, Yongfeng

    2016-05-01

    The formation process and mechanism of subwavelength ripples were studied upon irradiation of ZnO by a femtosecond laser (800 nm, 50 fs, 1 kHz). An abnormally asymmetrical grating-splitting phenomenon was discovered. At relatively high laser fluences (F = 0.51-0.63 J/cm2), near-wavelength ripples were split asymmetrically to create subwavelength laser-induced periodic surface structures (LIPSS) with dual gaps (∼230 nm and ∼430 nm) on the primary grooves. At relatively low laser fluences (F = 0.4-0.45 J/cm2), near-wavelength ripples were split symmetrically, leading to the formation of uniform subwavelength structures with a period of ∼340 nm. The splitting phenomena are related to the varying laser beam dose induced by the overlapping during line scanning. The two grating-splitting types further imply that the dominated mechanism for LIPSS formation may be changed under different processing conditions.

  13. 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.

  14. 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.

  15. 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.

  16. 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 μm, 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  19. 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.

  20. 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.

  1. Reconstruction of laser-induced cavitation bubble dynamics based on a Fresnel propagation approach.

    PubMed

    Devia-Cruz, Luis Felipe; Camacho-López, Santiago; Cortés, Víctor Ruiz; Ramos-Muñiz, Victoria; Pérez-Gutiérrez, Francisco G; Aguilar, Guillermo

    2015-12-10

    A single laser-induced cavitation bubble in transparent liquids has been studied through a variety of experimental techniques. High-speed video with varying frame rate up to 20×107  fps is the most suitable to study nonsymmetric bubbles. However, it is still expensive for most researchers and more affordable (lower) frame rates are not enough to completely reproduce bubble dynamics. This paper focuses on combining the spatial transmittance modulation (STM) technique, a single shot cavitation bubble and a very simple and inexpensive experimental technique, based on Fresnel approximation propagation theory, to reproduce a laser-induced cavitation spatial dynamics. Our results show that the proposed methodology reproduces a laser-induced cavitation event much more accurately than 75,000 fps video recording. In conclusion, we propose a novel methodology to reproduce laser-induced cavitation events that combine the STM technique with Fresnel propagation approximation theory that properly reproduces a laser-induced cavitation event including a very precise identification of the first, second, and third collapses of the cavitation bubble. PMID:26836867

  2. Laser-induced vibrational dynamics of ozone in solid argon

    NASA Astrophysics Data System (ADS)

    Hansen, Flemming Y.; Amstrup, Bjarne; Henriksen, Niels E.

    1997-10-01

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, 16O 16O 18O and compare the dynamics in the gas phase and in solid argon. The vibrational dynamics is not perturbed by argon on a time-scale of a few picoseconds and selective bond-breaking in the molecule should be possible following the same laser control scheme as suggested in the gas phase.

  3. Experimental investigation on dynamic characteristics and strengthening mechanism of laser-induced cavitation bubbles.

    PubMed

    Ren, X D; He, H; Tong, Y Q; Ren, Y P; Yuan, S Q; Liu, R; Zuo, C Y; Wu, K; Sui, S; Wang, D S

    2016-09-01

    The dynamic features of nanosecond laser-induced cavitation bubbles near the light alloy boundary were investigated with the high-speed photography. The shock-waves and the dynamic characteristics of the cavitation bubbles generated by the laser were detected using the hydrophone. The dynamic features and strengthening mechanism of cavitation bubbles were studied. The strengthening mechanisms of cavitation bubble were discussed when the relative distance parameter γ was within the range of 0.5-2.5. It showed that the strengthening mechanisms caused by liquid jet or shock-waves depended on γ much. The research results provided a new strengthening method based on laser-induced cavitation shotless peening (CSP). PMID:27150764

  4. Probing Molecular Dynamics by Laser-Induced Backscattering Holography

    NASA Astrophysics Data System (ADS)

    Haertelt, Marko; Bian, Xue-Bin; Spanner, Michael; Staudte, André; Corkum, Paul B.

    2016-04-01

    We use differential holography to overcome the forward scattering problem in strong-field photoelectron holography. Our differential holograms of H2 and D2 molecules exhibit a fishbonelike structure, which arises from the backscattered part of the recolliding photoelectron wave packet. We demonstrate that the backscattering hologram can resolve the different nuclear dynamics between H2 and D2 with subangstrom spatial and subcycle temporal resolution. In addition, we show that attosecond electron dynamics can be resolved. These results open a new avenue for ultrafast studies of molecular dynamics in small molecules.

  5. Probing Molecular Dynamics by Laser-Induced Backscattering Holography.

    PubMed

    Haertelt, Marko; Bian, Xue-Bin; Spanner, Michael; Staudte, André; Corkum, Paul B

    2016-04-01

    We use differential holography to overcome the forward scattering problem in strong-field photoelectron holography. Our differential holograms of H_{2} and D_{2} molecules exhibit a fishbonelike structure, which arises from the backscattered part of the recolliding photoelectron wave packet. We demonstrate that the backscattering hologram can resolve the different nuclear dynamics between H_{2} and D_{2} with subangstrom spatial and subcycle temporal resolution. In addition, we show that attosecond electron dynamics can be resolved. These results open a new avenue for ultrafast studies of molecular dynamics in small molecules. PMID:27081975

  6. 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

  7. 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.

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

    PubMed

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

    2014-12-11

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

  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 μm 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 μs (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 μs 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 μs and 2 times longer for ns pulse durations, respectively.

  10. 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.

  11. Dynamics of laser induced metal nanoparticle and pattern formation

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    Discontinuous metal films are converted into either almost round, isolated, and randomly distributed nanoparticles (NPs) or fringed patterns of alternate non transformed film and NPs by exposure to single pulses (20 ns pulse duration and 193 nm wavelength) of homogeneous or modulated laser beam intensity. The dynamics of NPs and pattern formation is studied by measuring in real time the transmission and reflectivity of the sample upon homogeneous beam exposure and the intensity of the diffraction orders 0 and 1 in transmission configuration upon modulated beam exposure. The results show that laser irradiation induces melting of the metal either completely or at regions around intensity maxima sites for homogeneous and modulated beam exposure, respectively, within ≤10 ns. The aggregation and/or coalescence of the initially irregular metal nanostructures is triggered upon melting and continues after solidification (estimated to occur at ≤80 ns) for more than 1 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.

  12. 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.

  13. 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.

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

    PubMed Central

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

    2009-01-01

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

  15. A comparative study of laser-induced demagnetization dynamics in Fe, Co, and Ni

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, Maithreyi; Gentry, Christian; Zusin, Dmitriy; Grychtol, Patrik; Knut, Ronny; Shaw, Justin; Nembach, Hans; Mathias, Stefan; Aeschlimann, Martin; Oppeneer, Peter; Schneider, Claus; Kapteyn, Henry; Murnane, Margaret

    Even twenty years after the discovery of ultrafast demagnetization of ferromagnetic materials induced by a femtosecond laser pulse there is still an ongoing debate about the mechanisms that drive the process. Surprisingly, a comprehensive study that compares demagnetization dynamics in different materials on equal footing is lacking. Yet, the scientific community would greatly benefit from such study. We fill this gap by performing a systematic comparison of ultrafast demagnetization behavior in Iron, Cobalt and Nickel, the simplest itinerant ferromagnets, under a wide range of pump fluences. In this experiment, we utilize a tabletop broadband extreme ultraviolet source to probe magnetization dynamics at the M2,3 absorption edges of these three elements using the transverse magneto-optical Kerr effect. The obtained data can be used to inform theory and, thereby, assist in resolving the remaining questions about the micro- and macroscopic mechanisms behind ultrafast laser-induced magnetization dynamics in materials.

  16. Probing laser induced metal vaporization by gas dynamics and liquid pool transport phenomena

    SciTech Connect

    DebRoy, T.; Basu, S.; Mundra, K. )

    1991-08-01

    During laser beam welding of many important engineering alloys, an appreciable amount of alloying element vaporization takes place from the weld pool surface. As a consequence, the composition of the solidified weld pool is often significantly different from that of the alloy being welded. Currently there is no comprehensive theoretical model to predict, from first principles, laser induced metal vaporization rates and the resulting weld pool composition changes. The weld pool heat transfer and fluid flow phenomena have been coupled with the velocity distribution functions of the gas molecules at various locations above the weld pool to determine the rates of the laser induced element vaporization for pure metals. The procedure allows for calculations of the condensation flux based on the equations of conservation of mass, momentum and energy in both the vapor and the liquid phases. Computed values of the rates of vaporization of pure metals were found to be in good agreement with the corresponding experimentally determined values. The synthesis of the principles of gas dynamics and weld pool transport phenomena can serve as a basis for weld metal composition control.

  17. 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)

  18. 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.

  19. 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.

  20. Mathematical modeling of dynamic laser coagulation during laser-induced interstitial thermotherapy

    NASA Astrophysics Data System (ADS)

    Jiang, S. C.; Zhang, X. X.

    2006-09-01

    To describe the complex nonlinear process of laser tissue interactions during laser-induced interstitial thermotherapy (LITT), a two-dimensional mathematical model considering the dynamic changes in the physical tissue properties was developed. A modified Monte Carlo method was developed to simulate photon transport in tissue with a non-uniform optical property field, the finite volume method was used to numerically solve the Pennes bioheat equation to calculate the temperature distribution and the Arrhenius equation was used to predict the thennal damage extent. A temperature control heating method was also incorporated into present model to simulate the LITT clinical treatment to increase thermal damage volume and avoid evaporation and carbonization. The numerical results showed that the dynamic changes in the optical properties, the thermal properties and the blood perfusion rate significanfly affected the damage volume accumulation in tissue and should be included in munerical simulations of the LITT treatment.

  1. Ultrafast optical switching by instantaneous laser-induced grating formation and self-diffraction in barium fluoride

    NASA Astrophysics Data System (ADS)

    Schneider, T.; Wolfframm, D.; Mitzner, R.; Reif, J.

    A transient refractive index grating is formed in barium fluoride crystals under irradiation with femtosecond laser pulses from two non-collinear beams, at an intensity below the threshold for white light continuum generation. At low intensities, energy is coupled from one beam to the other, at high intensities a typical self-diffraction pattern is observed with an diffraction efficiency better than 10%. The response time for all effects is limited only by the temporal pulse shape, opening the way to an application in ultrafast optical switching.

  2. 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

  3. Formation Dynamics of Ultra-Short Laser Induced Micro-Dots in the Bulk of Transparent Materials

    NASA Astrophysics Data System (ADS)

    Mermillod-Blondin, A.; Ashkenasi, D.; Lemke, A.; Schwagmeier, M.; Rosenfeld, A.

    In this paper, we study the formation dynamics of ultra-short laser-induced micro dots under the surface of transparent materials. Laser-induced micro dots find their application in direct part marking, to address full life cycle traceability. We first demonstrate the possibility of direct laser part marking into the cladding of an optical fiber. Then, we monitor the laser affected zone with the help of a time-resolved phase contrast microscopy setup in a fused silica substrate. We show that the transient energy relaxation processes affect the host material over a region that exceeds the micro dot size by several micrometers.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  5. 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.

  6. Dynamic temperature monitoring and control with fully distributed fiber Bragg grating sensor

    NASA Astrophysics Data System (ADS)

    Ding, Yuetong; Chen, Na; Chen, Zhenyi; Pang, Fufei; Zeng, Xianglong; Wang, Tingyun

    2010-11-01

    In this paper, fiber Bragg grating (FBG) is used as a fully distributed sensor to monitor tissue dynamic temperature changes during laser-induced interstitial thermotherapy (LITT). This work is mainly realized by the correlative single particle (CSP) algorithm, which is a rapid algorithm for spectrum reconstruction. Experimental LITT treatment was set up by using 532nm laser applicator on a piece of fresh liver tissue. In the experiments, the dynamic temperature profile was successfully demodulated with a refreshing speed of 11 seconds. With the aid of dynamic feedback, the thermotherapy boundary temperature was well controlled around 35°C during the treatment by adjusting the laser output power in real-time. Therefore, with this method, it is promising to precisely control the tissue temperature in vivo and improve the safety of the LITT remarkably.

  7. 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)

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  9. 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.

  10. Ion dynamics in a DC magnetron microdischarge measured with laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Young, Christopher; Gascon, Nicolas; Lucca Fabris, Andrea; Ito, Tsuyohito; Cappelli, Mark

    2015-11-01

    We present evidence of coherent rotating azimuthal wave structures in a planar DC magnetron microdischarge operated with argon and xenon. The dominant stable mode structure varies with discharge voltage, and high frame rate camera imaging of plasma emission reveals propagating azimuthal waves in the negative E-> × B-> direction. This negative drift direction is attributed to a local field reversal arising from strong density gradients that drive excess ions towards the anode. Observed mode transitions are shown to be consistent with models of gradient drift-wave dispersion in such a field reversal when the fluid representation includes ambipolar diffusion parallel to the magnetic field direction. Time-averaged and time-resolved laser-induced fluorescence measurements interrogate xenon ion dynamics under the action of the field reversal. Time resolution is obtained by synchronizing with the coherent azimuthal wave frequency at fixed mode number. This work is sponsored by the U.S. Air Force Office of Scientific Research with Dr. Mitat Birkan as program manager. C.Y. acknowledges support from the DOE NNSA Stewardship Science Graduate Fellowship under Contract DE-FC52-08NA28752.

  11. Degenerate four-wave mixing and two-color laser induced grating spectra of S 1S 0 electronic transitions of benzene and monosubstituted benzenes in the gas phase

    NASA Astrophysics Data System (ADS)

    Ebata, Takayuki; Okazaki, Akihiro; Inokuchi, Yoshiya; Mikami, Naohiko

    1995-06-01

    S 1S 0 electronic spectra of gaseous benzene and monosubstituted benzenes have been measured by degenerate four-wave mixing (DFWM) spectroscopy and two-color laser induced grating (TC-LIG) spectroscopy. Dependence of the DFWM intensity on laser power ( I), molecular density ( M) and the absorption cross section (σ) was examined. The intensity was expressed by a formula I3M2σn( n = 3). For benzene, the DFWM spectrum in the channel three region was observed and the relative band intensity was compared with those of the absorption spectrum and laser induced fluorescence (LIF) spectrum. TC-LIG spectra were observed for benzene, toluene and chlorobenzenes. Drastic simplification was obtained for the TC-LIG spectra even at room temperature, demonstrating a remarkable reduction of spectral congestion of large polyatomic molecules.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Ultrafast laser-induced dynamics of noncollinear spin structures in amorphous NdFeCo and PrFeCo

    NASA Astrophysics Data System (ADS)

    Becker, J.; Tsukamoto, A.; Kirilyuk, A.; Maan, J. C.; Rasing, Th.; Christianen, P. C. M.; Kimel, A. V.

    2015-11-01

    The fanned out, noncollinear spin structure of the Fe(Co) sublattice in amorphous NdFeCo and PrFeCo alloys is shown to strongly affect its ultrafast laser-induced magnetization dynamics. An overshooting effect is discovered at low applied magnetic fields, where the magnetization temporarily increases above its equilibrium value. We explain this phenomenon by considering the dynamics of the noncollinear spin structure. After femtosecond laser excitation the system first reconstructs magnetic order on a time scale of 50-150 ps arriving at a state with a smaller opening angle of the fan. Subsequently, the original opening angle is restored on a time scale of nanoseconds. Increasing the field up to 0.6 T we can fully close the fan and therewith suppress the overshooting behavior.

  19. 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.

  20. 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.

  1. All-optical signal processing using dynamic Brillouin gratings

    PubMed Central

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

    2013-01-01

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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Doppler Spectrometry for Ultrafast Temporal Mapping of Density Dynamics in Laser-Induced Plasmas

    SciTech Connect

    Mondal, S.; Lad, Amit D.; Ahmed, Saima; Narayanan, V.; Pasley, J.; Rajeev, P. P.; Robinson, A. P. L.; Kumar, G. Ravindra

    2010-09-03

    We present high resolution measurements of the ultrafast temporal dynamics of the critical surface in moderately overdense, hot plasma by using two-color, pump-probe Doppler spectrometry. Our measurements clearly capture the initial inward motion of the plasma inside the critical surface of the pump laser which is followed by outward expansion. The measured instantaneous velocity and acceleration profiles are very well reproduced by a hybrid simulation that uses a 1D electromagnetic particle-in-cell simulation for the initial evolution and a hydrodynamics simulation for the later times. The combination of high temporal resolution and dynamic range in our measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations.

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

    PubMed

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

    2014-10-01

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

  8. 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

  9. Doppler spectrometry for ultrafast temporal mapping of density dynamics in laser-induced plasmas.

    PubMed

    Mondal, S; Lad, Amit D; Ahmed, Saima; Narayanan, V; Pasley, J; Rajeev, P P; Robinson, A P L; Kumar, G Ravindra

    2010-09-01

    We present high resolution measurements of the ultrafast temporal dynamics of the critical surface in moderately overdense, hot plasma by using two-color, pump-probe Doppler spectrometry. Our measurements clearly capture the initial inward motion of the plasma inside the critical surface of the pump laser which is followed by outward expansion. The measured instantaneous velocity and acceleration profiles are very well reproduced by a hybrid simulation that uses a 1D electromagnetic particle-in-cell simulation for the initial evolution and a hydrodynamics simulation for the later times. The combination of high temporal resolution and dynamic range in our measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations. PMID:20867525

  10. Spectrally resolved optical probing of laser induced magnetization dynamics in bismuth iron garnet.

    PubMed

    Koene, Benny; Deb, Marwan; Popova, Elena; Keller, Niels; Rasing, Theo; Kirilyuk, Andrei

    2016-07-13

    The spectrally resolved magnetization dynamics in bismuth iron garnet shows a fluence dependent light induced modification of the magneto-optical Faraday spectrum. It is demonstrated that the relative contributions from the tetrahedral and octahedral iron sites to the Faraday spectrum change due to the impact of the pump pulse. This change explains the observed deviation from a linear dependence of the amplitude of the oscillations on the fluence, as expected for the inverse Faraday effect. PMID:27213266

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Molecular dynamics simulations of laser-induced incandescence of soot using an extended ReaxFF reactive force field.

    PubMed

    Kamat, Amar M; van Duin, Adri C T; Yakovlev, Alexei

    2010-12-01

    Laser-induced incandescence (LII) of soot has developed into a popular method for making in situ measurements of soot volume fraction and primary particle sizes. However, there is still a lack of understanding regarding the generation and interpretation of the cooling signals. To model heat transfer from the heated soot particles to the surrounding gas, knowledge of the collision-based cooling as well as reactive events, including oxidation (exothermic) and evaporation (endothermic) is essential. We have simulated LII of soot using the ReaxFF reactive force field for hydrocarbon combustion. Soot was modeled as a stack of four graphene sheets linked together using sp(3) hybridized carbon atoms. To calculate the thermal accommodation coefficient of various gases with soot, graphene sheets of diameter 40 Å were used to create a soot particle containing 2691 atoms, and these simulations were carried out using the ReaxFF version incorporated into the Amsterdam Density Functional program. The reactive force field enables us to simulate the effects of conduction, evaporation, and oxidation of the soot particle on the cooling signal. Simulations were carried out for both reactive and nonreactive gas species at various pressures, and the subsequent cooling signals of soot were compared and analyzed. To correctly model N(2)-soot interactions, optimization of N-N and N-C-H force field parameters against DFT and experimental values was performed and is described in this paper. Subsequently, simulations were performed in order to find the thermal accommodation coefficients of soot with various monatomic and polyatomic gas molecules like He, Ne, Ar, N(2), CO(2), and CH(4). For all these species we find good agreement between our ReaxFF results and previously published accommodation coefficients. We thus believe that Molecular Dynamics using the ReaxFF reactive force field is a promising approach to simulate the physical and chemical aspects of soot LII. PMID:21067165

  16. 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.

  17. 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.

  18. Microchip laser-induced fluorescence detection of proteins at submicrogram per milliliter levels mediated by dynamic labeling under pseudonative conditions.

    PubMed

    Giordano, Braden C; Jin, Lianji; Couch, Abigail J; Ferrance, Jerome P; Landers, James P

    2004-08-15

    We have previously demonstrated on-column dynamic labeling of protein-SDS complexes on capillaries and microchips for laser-induced fluorescence (LIF) detection using both a commercially available fluor and a protein separation buffer. Upon binding to hydrophobic moieties (of the analyte or separation buffer), the fluor undergoes a conformational change allowing fluorescence detection at 590 nm following excitation with 488-nm light. Our original work showed on-chip limits of detection (LOD) comparable with those using UV detection (1 x 10(-5) M) on capillaries-falling significantly short of the detection limits expected for LIF. This was largely a function of the physicochemical characteristics of the separation buffer components, which provided significant background fluorescence. Having defined the contributing factors involved, a new separation buffer was produced which reduced the background fluorescence and, consequently, increased the available dye for binding to protein-SDS complexes, improving the sensitivity in both capillaries and microchips by at least 2 orders of magnitude. The outcome is a rapid, sensitive method for protein sizing and quantitation applicable to both capillary and microchip separations with a LOD of 500 ng/mL for bovine serum albumin. Interestingly, sensitivity on microdevices was improved by inclusion of the dye in the sample matrix, while addition of dye to samples in conventional CE resulted in a drastic reduction in sensitivity and resolution. This can be explained by the differences in the injection schemes used in the two systems. The linear range for protein quantitation covered at least 2 orders of magnitude in microchip applications. On-chip analysis of human sera allowed abnormalities, specifically the presence of elevated levels of gamma-globulins, to be determined. PMID:15307780

  19. Dynamics of laser-induced radial birefringence in silver-doped glasses.

    PubMed

    Ahangary, Ali Akbar; Bouchard, Frédéric; Santamato, Enrico; Karimi, Ebrahim; Khalesifard, Hamid Reza

    2015-09-01

    Silver ion-exchanged glass exhibits nonlinear optical properties upon interacting with intense light beams. The thermal effect due to the nanoparticles' light-absorption induces radial stress, and consequently, a radial birefringence on the glass surface. The induced birefringence possesses a topological charge of 1 in the transverse plane of the glass, i.e., cylindrical symmetry. Therefore, when the glass is illuminated with a circularly polarized light beam, a portion of the incoming beam flips its polarization handedness, since the plate is birefringent, and gains an orbital angular momentum of ±2 in units of the Planck constant. This is referred to as optical spin-to-orbital angular momentum conversion, and can be understood by means of the Pancharatnam-Berry phase. Here, we design a pump-probe setup to study and observe the dynamics of optical angular momentum coupling in real time. We show that this effect can be permanent or reversible, depending on the power and interaction time of the pump beam. In particular, an intrinsic power-dependent birefringence hysteresis is observed on the sample after interaction with and the relaxation of the irradiated point. PMID:26368712

  20. 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.

  1. Picosecond infrared laser-induced all-atom nonequilibrium molecular dynamics simulation of dissociation of viruses.

    PubMed

    Hoang Man, Viet; Van-Oanh, Nguyen-Thi; Derreumaux, Philippe; Li, Mai Suan; Roland, Christopher; Sagui, Celeste; Nguyen, Phuong H

    2016-04-28

    Since the discovery of the plant pathogen tobacco mosaic virus as the first viral entity in the late 1800s, viruses traditionally have been mainly thought of as pathogens for disease-resistances. However, viruses have recently been exploited as nanoplatforms with applications in biomedicine and materials science. To this aim, a large majority of current methods and tools have been developed to improve the physical stability of viral particles, which may be critical to the extreme physical or chemical conditions that viruses may encounter during purification, fabrication processes, storage and use. However, considerably fewer studies are devoted to developing efficient methods to degrade or recycle such enhanced stability biomaterials. With this in mind, we carry out all-atom nonequilibrium molecular dynamics simulation, inspired by the recently developed mid-infrared free-electron laser pulse technology, to dissociate viruses. Adopting the poliovirus as a representative example, we find that the primary step in the dissociation process is due to the strong resonance between the amide I vibrational modes of the virus and the tuned laser frequencies. This process is determined by a balance between the formation and dissociation of the protein shell, reflecting the highly plasticity of the virus. Furthermore, our method should provide a feasible approach to simulate viruses, which is otherwise too expensive for conventional equilibrium all-atom simulations of such very large systems. Our work shows a proof of concept which may open a new, efficient way to cleave or to recycle virus-based materials, provide an extremely valuable tool for elucidating mechanical aspects of viruses, and may well play an important role in future fighting against virus-related diseases. PMID:27071540

  2. Tunable and reconfigurable multi-tap microwave photonic filter based on dynamic Brillouin gratings in fibers.

    PubMed

    Sancho, J; Primerov, N; Chin, S; Antman, Y; Zadok, A; Sales, S; Thévenaz, L

    2012-03-12

    We propose and experimentally demonstrate new architectures to realize multi-tap microwave photonic filters, based on the generation of a single or multiple dynamic Brillouin gratings in polarization maintaining fibers. The spectral range and selectivity of the proposed periodic filters is extensively tunable, simply by reconfiguring the positions and the number of dynamic gratings along the fiber respectively. In this paper, we present a complete analysis of three different configurations comprising a microwave photonic filter implementation: a simple notch-type Mach-Zehnder approach with a single movable dynamic grating, a multi-tap performance based on multiple dynamic gratings and finally a stationary grating configuration based on the phase modulation of two counter-propagating optical waves by a common pseudo-random bit sequence (PRBS). PMID:22418495

  3. 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.

  4. Dynamic Landslide Deformation Monitoring with Fiber Bragg Grating Sensors

    NASA Astrophysics Data System (ADS)

    Moore, J. R.; Gischig, V.; Button, E.; Loew, S.

    2009-12-01

    Fiber optic (FO) strain sensors are a promising new technology for in-situ landslide monitoring. General performance advantages include high resolution, fast sampling rate, and insensitivity to electrical disturbances. Here we describe a new FO monitoring system based on long-gage fiber Bragg grating sensors installed at the Randa Rockslide Laboratory in southern Switzerland. We highlight the advantages and disadvantages of the system, describe relevant first results, and compare FO data to that from traditional instruments already installed on site. The Randa rock slope has been the subject of intensive research since its failure in 1991. Around 5 million cubic meters of rock remains unstable today, moving at rates up to 20 mm / year. Traditional in-situ monitoring techniques have been employed to understand the mechanics and driving forces of the currently unstable rock mass, however these investigations are limited by the resolution and low sampling rate of the sensors. The new FO monitoring system has micro-strain resolution and offers the capability to detect sub-micrometer scale deformations in both triggered-dynamic and continuous measurements. Two types of sensors have been installed: fully-embedded borehole sensors encased in grout at depths of 38, 40, and 68 m, and surface extensometers spanning active tension cracks. Dynamic measurements are triggered by sensor deformation and recorded at 100 Hz, while continuous measurements are logged every 5 minutes. Since installation in August 2008, the FO monitoring system has been operational 90% of the time. Time series deformation data show movement rates consistent with previous borehole extensometer surveys. Accelerated displacements following installation are likely related to long-term curing and dewatering of the grout. A number of interesting transients have been recorded, which in some cases were large enough to trigger rapid sampling. The combination of short- and long-term observation offers new insights into the deformation process. Controlled-source shotgun tests were performed to investigate the sensor response to dynamic inputs. These tests compared an independent measure of ground motion with the dynamic strain measured across a tension crack by the FO sensor. Low frequency signals are comparable but the fiber optic record suffers from aliasing, where undersampling of higher frequency signals generates false peaks in the spectrum. In the event of an earthquake, however, such high frequency energy will not be present and the FO sensors are expected to provide an accurate measure of dynamic strain.

  5. 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.

  6. 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.

  7. 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

  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. 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 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. 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.

  10. 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.

  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. 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.

  13. Time dynamics of self-pumped reflection gratings in a photorefractive polymer

    NASA Astrophysics Data System (ADS)

    Banerjee, P. P.; Buller, S. H.; Liebig, C. M.; Basun, S. A.; Cook, G.; Evans, D. R.; Blanche, P.-A.; Thomas, J.; Christenson, C. W.; Peyghambarian, N.

    2012-01-01

    The time dynamics of self-pumped reflection gratings in a commonly used photorefractive polymer PDCST:PVK:ECZ-BBP:C60 with no additional electron sources or traps is investigated. While holes are normally the mobile charges and responsible for grating formation, our experimental observations, analyzed using multi-exponential fitting curves, show evidence of electrons in addition to holes as charge carriers, particularly above an applied field of 40 V/μm. The dependence of effective carrier mobilities on the applied electric field, deduced from experimental results, show stronger field dependence of electron mobility at high electric fields. At an applied field of 70 V/μm, electron and hole mobilities become approximately equal, and the contribution of electrons on grating formation becomes significant.

  14. 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.

  15. 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 μm to 31.3 μm 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.

  16. 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

  17. Laser-Induced Thermal Acoustics

    NASA Astrophysics Data System (ADS)

    Cummings, Eric Bryant

    1995-01-01

    Laser-induced thermal acoustics (LITA) is a new technique for remote nonintrusive measurement of thermophysical gas properties. LITA involves forming, via opto-acoustic effects, grating-shaped perturbations of gas properties by the use of intersecting beams from a short-pulse laser. A third beam scatters coherently into a signal beam off the perturbation grating via acousto-optical effects. The evolution of the gas perturbations modulates the scattered signal beam. Accurate values of the sound speed, transport properties, and composition of the gas can be extracted by analyzing the signal beam. An analytical expression for the spectrum, absolute magnitude, and time history of the LITA signal is derived. The optoacoustic effects of thermalization and electrostriction are treated. Finite beam-diameter, beam-duration, and thermalization-rate effects are included in the analysis. The expression accurately models experimental signals over a wide range of gas conditions. Experimental tests using LITA have been conducted on pure and NO_2-seeded air and helium at pressures ranging from {~ }0.1 kPa-14 MPa. Carbon dioxide has been explored near its liquid-vapor critical point. Accuracies of 0.1% in sound speed measurements have been achieved in these tests. Accuracies of {~}1% have been achieved in measurements of thermal diffusivity, although beam misalignment effects have typically degraded this accuracy by a factor of {~} 10-20. Using LITA, susceptibility spectra have been taken of approximately a femtogram of NO_2 . The effects of fluid motion and turbulence have been explored. LITA velocimetry has been demonstrated, in which the Doppler shift of light scattered from a flowing fluid is measured. LITA velocimetry requires no particle seeding, has a coherent signal beam, and can be applied to pulsed flows. LITA has also been applied to measure single-shot |chi^{(1) }|^2 or "Rayleigh scattering" spectra of a gas by the use of a technique of wavelength -division multiplexing, called multiplex LITA. The LITA apparatus used in these tests costs about one-tenth that of many conventional laser diagnostics. Narrowband LITA measurements of the sound speed and transport properties and multiplex LITA measurements of the spectral properties of gases may be taken in a single laser shot.

  18. Laser-induced thermal acoustics

    NASA Astrophysics Data System (ADS)

    Cummings, Eric B.

    Laser-induced thermal acoustics (LITA) is a new technique for remote nonintrusive measurement of thermophysical gas properties. LITA involves forming, via opto-acoustic effects, grating-shaped perturbations of gas properties using intersecting beams from a short-pulse laser. A third beam scatters coherently into a signal beam off the perturbation grating via acousto-optical effects. The evolution of the gas perturbations modulates the scattered signal beam. Accurate values of the sound speed, transport properties, and composition of the gas can be extracted by analyzing the signal beam.An analytical expression for the spectrum, absolute magnitude, and time history of the LITA signal is derived. The optoacoustic effects of thermalization and electrostriction are treated. Finite beam-diameter, beam-duration, and thermalization-rate effects are included in the analysis. The expression accurately models experimental signals over a wide range of gas conditions.Experimental tests using LITA have been conducted on pure and [...]-seeded air and helium at pressures ranging from ~0.1 kPa-14 MPa. Carbon dioxide has been explored near its liquid-vapor critical point. Accuracies of 0.1% in sound speed measurements have been achieved in these tests. Accuracies of ~1% have been achieved in measurements of thermal diffusivity, although beam misalignment effects have typically degraded this accuracy by a factor of ~10-20. Using LITA, susceptibility spectra have been taken of approximately a femtogram of [...]. The effects of fluid motion and turbulence have been explored. LITA velocimetry has been demonstrated, in which the Doppler shift of light scattered from a flowing fluid is measured. LITA velocimetry requires no particle seeding, has a coherent signal beam, and can be applied to pulsed flows. LITA has also been applied to measure single-shot [...] or "Rayleigh scattering" spectra of a gas using a technique of wavelength-division multiplexing, called multiplex LITA. The LITA apparatus used in these tests costs about one-tenth that of many conventional laser diagnostics. Narrowband LITA measurements of the sound speed and transport properties and multiplex LITA measurements of the spectral properties of gases may be taken in a single laser shot.

  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. Predissociative linewidths of (4pσ) M 2Sigma + (v=1) and (3dσ,π) H 2Sigma + , Hscript 2Π (v=2) Rydberg states of NO studied by the two-color laser-induced grating technique

    NASA Astrophysics Data System (ADS)

    Ishii, Juntarou; Uehara, Kiyoji; Tsukiyama, Koichi

    1995-06-01

    The two-color laser-induced grating (TC-LIG) technique has been employed to probe the predissociative Rydberg states (4pσ) M 2Σ+ (v=1) and (3dσ,π) H 2Σ+, H' 2Π± (v=2) and the non-Rydberg B 2Π (v=26) state of nitric oxide. The ultraviolet pump laser frequency is fixed to a specific rotational line of the A 2Σ+ (v'=1 and 2)←X 2Π3/2 (v`=0) transition of NO. Interference of two pump laser beams crossing at a small angle in the gas sample forms a population grating. Then, the visible probe laser beam is diffracted off the grating as the signal beam when the probe laser frequency is resonant to a transition from the rotational level excited by the pump laser. Term values and rotational assignments of the H 2Σ+, H' 2Π± (v=2)-B 2Π3/2 (v=26) states have been established for the first time, resulting in the value of ˜1.77 cm-1 for the l-uncoupling constant. Line broadenings due to predissociation are observed in the TC-LIG spectra for the M 2Σ+ (v=1) and H 2Σ+, H' 2Π+ (v=2) states. The linewidths of the M 2Σ+ (v=1) state show no marked rotational dependence except for the N=4 level which is locally perturbed. On the other hand, the predissociative lifetimes of the H 2Σ+ and H' 2Π+ (v=2) states exhibit a significant rotational dependence: The linewidth of the former state decreases with N, while the reverse tendency is seen for the latter. The mixing between the H 2Σ+ and H' 2Π+ states caused by l-uncoupling explains the observed rotational dependence successfully.

  1. 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

  2. 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.

  3. 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)

  4. 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, Joëlle

    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 λ = 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.

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

    PubMed

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

    2012-03-26

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

  6. 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

  7. 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.

  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. Fully distributed chirped FBG sensor and application in laser-induced interstitial thermotherapy

    NASA Astrophysics Data System (ADS)

    Li, Chenglin; Chen, Na; Chen, Zhenyi; Wang, Tingyun

    2009-11-01

    In the laser induced interstitial thermotherapy (LITT), real-timely detecting the temperature distribution of the cured tissue is a bottleneck. In this paper, a fully distributed chirped Fiber Bragg grating (FBG) sensor, which is of small size, immune from electromagnetic interference (EMI) and high sensitivity, is proposed to solve this problem. An experiment simulation of LITT is set up, and only one chirped FBG is used to detect the dynamic spectral variation with different laser power. Meanwhile, a high-efficiency spectra inversion algorithm named MSAE of FBG is utilized to demodulate the system and obtain the temperature distribution. The spatial resolution is 0.25mm and the running time of demodulation is tens of seconds, which can help doctors control the laser parameters such as the laser power and the treatment time to guarantee the security of the therapy.

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

    NASA Astrophysics Data System (ADS)

    Sreekumar, K.; Asokan, S.

    2010-01-01

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

  11. 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)

  12. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    PubMed

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed. PMID:27139682

  13. 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.

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

    PubMed

    Antman, Yair; Levanon, Nadav; Zadok, Avi

    2012-12-15

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

  15. Highly effective dynamic holographic gratings in doped bismuth titanate crystals and applications to metrology

    NASA Astrophysics Data System (ADS)

    Dovgalenko, George E.; Wu, Ying

    2009-05-01

    Highly efficient volume reflective, dynamical holographic gratings in doped Ti12TiO20 crystals have been observed. We demonstrated doped Ti12TiO20 single, electro-optical crystal and experimental set up, which combines high reversibility, small response time, high diffraction efficiency and practically unlimited number of cycles hologram recording, readout and erasing. It allows using doped Ti12TiO20 crystal as an attractive diffractive optical element in Dynamical Holographic Sensor -DHS for metrology applications. The high image contrast of the real time dynamical holographic interferograms without application of external electric field has been obtained for non transparent diffuse reflective objects using commercial available CW He-Ne laser. DHS applications for nondestructive test of the most vital parts engineering constructions to prevent premature failure have has been demonstrated. DHS application for visualization of cryogenic fields in the near zone of cryoultrasonic cancer tissue destructor has been presented.

  16. 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.

  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. 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 μm, and a linearity of +0.2%...-0.35% for displacements up to 0.55 mm. Simulated dynamic tests are also reported.

  19. Adaptive demodulation of dynamic signals from fiber Bragg gratings using two-wave mixing technology

    NASA Astrophysics Data System (ADS)

    Qiao, Yi; Zhou, Yi; Krishnaswamy, Sridhar

    2006-07-01

    A two-wave mixing (TWM) interferometer using photorefractive (PRC) InP:Fe crystal is configured to demodulate the spectral shift of a fiber Bragg grating (FBG) sensor. The FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The wavelength shift is converted into phase shift by means of an unbalanced TWM interferometer. TWM wavelength demodulation is attractive for monitoring dynamic strains because it is adaptive and multiplexable. Adaptivity implies that it can selectively monitor dynamic strains without active compensation of large quasi-static strains and large temperature drifts that otherwise would cause system to drift. Multiplexability implies that several FBG sensors can be simultaneously demodulated using a single demodulator. TWM wavelength demodulation is therefore a cost-effective method of demodulating several spectrally encoded FBG sensors.

  20. Experimental investigation of a fiber Bragg grating integrated optical limiting amplifier with high dynamic range

    NASA Astrophysics Data System (ADS)

    Liaw, Shien Kuei; Chi, Sien

    1998-07-01

    By inserting a bidirectional erbium-doped fiber amplifier (EDFA) in between an optical circulator and a fiber Bragg grating (FBG), we realize an FBG-integrated optical limiting amplifier (OLA) with high dynamic range. The dual-pass OLA has a wide dynamic range of over 40 dB and a saturation signal output power of about 13.0 dBm. The performance of dual-pass OLA has no obvious degradation due to back reflection of the amplified signal. A negligible power penalty of about 0.3 dB is observed when compared with other conventional configurations. The FBG-integrated OLA configuration has potential application in wavelength division multiplexing systems where high saturated power is needed for multichannel transmission.

  1. 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

  2. Beam dynamics and wakefield simulations of the double grating accelerating structure

    SciTech Connect

    Najafabadi, B. Montazeri; Byer, R. L.; Ng, C. K.; England, R. J.; Peralta, E. A.; Soong, K.; Noble, R.; Wu, Z.

    2012-12-21

    Laser-driven acceleration in dielectric structures can provide gradients on the order of GeV/m. The small transverse dimension and tiny feature sizes introduce challenges in design, fabrication, and simulation studies of these structures. In this paper we present the results of beam dynamic simulation and short range longitudinal wakefield simulation of the double grating structure. We show the linear trend of acceleration in a dielectric accelerator design and calculate the maximum achievable gradient equal to 0.47E{sub 0} where E0 is maximum electric field of the laser excitation. On the other hand, using wakefield simulations, we show that the loss factor of the structure with 400nm gap size will be 0.12GV/m for a 10fC, 100as electron bunch which is an order of magnitude less than expected gradient near damage threshold of the device.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  4. 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.

  5. 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.

  6. 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).

  7. 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.

  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. 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.

  10. 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.

  11. Fiber Bragg Grating Based System for Temperature Measurements

    NASA Astrophysics Data System (ADS)

    Tahir, Bashir Ahmed; Ali, Jalil; Abdul Rahman, Rosly

    In this study, a fiber Bragg grating sensor for temperature measurement is proposed and experimentally demonstrated. In particular, we point out that the method is well-suited for monitoring temperature because they are able to withstand a high temperature environment, where standard thermocouple methods fail. The interrogation technologies of the sensor systems are all simple, low cost and effective as well. In the sensor system, fiber grating was dipped into a water beaker that was placed on a hotplate to control the temperature of water. The temperature was raised in equal increments. The sensing principle is based on tracking of Bragg wavelength shifts caused by the temperature change. So the temperature is measured based on the wavelength-shifts of the FBG induced by the heating water. The fiber grating is high temperature stable excimer-laser-induced grating and has a linear function of wavelength-temperature in the range of 0-285°C. A dynamic range of 0-285°C and a sensitivity of 0.0131 nm/°C almost equal to that of general FBG have been obtained by this sensor system. Furthermore, the correlation of theoretical analysis and experimental results show the capability and feasibility of the purposed technique.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  13. Effects of laser-induced plasma in machining of transparent materials

    NASA Astrophysics Data System (ADS)

    Kadan, Viktor M.; Blonsky, Ivan V.; Salnikov, Vadim O.; Orieshko, Evgen V.

    2005-01-01

    In this paper we report a new practical method of micromachining of transparent materials involving laser-induced plasma, using a conventional Q-switched Nd:KGW laser (1,06 μm). Micromarks and relieve grating with 3 μm pitch have been fabricated in sapphire, silica and glass, including the use of a LC numerical indicator as a mask. Influence of the cross-section size of a shined area on machining results was studied. It was found, that the density and temperature of laser-induced plasma at constant energy density of laser radiation rise with the increase of the cross-section size. Laser-induced plasma influences the ablation rate of transparent materials and metals in the opposite way.

  14. Super-resolution in digital holography by a two-dimensional dynamic phase grating.

    PubMed

    Paturzo, M; Merola, F; Grilli, S; De Nicola, S; Finizio, A; Ferraro, P

    2008-10-13

    An approach that uses an electro-optically tunable two dimensional phase grating to enhance the resolution in digital holographic microscopy is proposed. We show that, by means of a flexible hexagonal phase grating, it is possible to increase the numerical aperture of the imaging system, thus improving the spatial resolution of the images in two dimensions. The augment of the numerical aperture of the optical system is obtained by recording spatially multiplexed digital holograms. The grating tuneability allows one to adjust the intensity among the spatially multiplexed holograms maximizing the grating diffraction efficiency. Furthermore we demonstrate that the flexibility of the numerical reconstruction allows one to use selectively the diffraction orders carrying useful information for increasing the spatial resolution. The proposed approach can improve the capabilities of digital holography in three-dimensional imaging and microscopy. PMID:18852822

  15. Laser-induced tether & spouts

    NASA Astrophysics Data System (ADS)

    Delville, Jean-Pierre

    2004-03-01

    Since the seminal work of Ashkin and Dziedzic on the deformation of transparent free-surfaces induced by laser waves, the optical radiation pressure has been recognized as very appealing to locally manipulate liquid interfaces. While the first developments essentially exploited the interface bending for optical applications in adaptive lensing, radiation pressure effects have recently received renewed interest in connection with nano/bio-technologies, as a non-intrusive tool to probe microscopic surface properties of soft materials including cell stretching, or membrane and interface visco-elasticity. However, as the optical bending of a fluid interface is generally weak, these experiments were essentially limited to the linear regime in deformation. Non-linear behaviors can nevertheless be investigated using very soft transparent liquid interfaces to enhance light effects. At large optical excitation, either a large stable tether is formed, or else a break-up of the interface occurs, depending on the direction of the beam propagation. Physically, the reason for this asymmetry can be traced to whether total reflection of light at deformed interface occurs or not. Laser-induced interface instability leads to the formation of a stationary beam-centered liquid micro-jet emitting droplets, which anticipates the bases for new applications in micro-fluidics and liquid micro-spraying. On the other hand, the method can be extended to form microscopic liquid bridges of very large aspect ratio, because optical forces are able to overcome the fundamental Rayleigh-Plateau limitation. As laser-induced micro-jets, laser-sustained liquid columns are tunable in aspect ratio and adjustable in direction. Consequently, the applications range of "opto-hydrodynamic" interface instability is wide, going from micro-optics (i.e. liquid columns also behave as soft optical fibers) to micro-fluidics, as fluid transfer can be optically monitored and directed in three dimensions.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Gâté, 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

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

    SciTech Connect

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

    2010-08-15

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

  3. 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

  4. New MLD gratings adapted for tiling in petawatt-class lasers

    NASA Astrophysics Data System (ADS)

    Flamand, J.; de Villèle, G.; Cotel, A.; Touzet, B.; Kane, S.

    2006-06-01

    Laser-induced damage threshold of gratings remains the main limiting factor towards generating higher-energy compressed pulses (terawatt and petawatt). HORIBA Jobin Yvon has first developed the manufacturing of large gold coated gratings, dimensions up to half a meter. Then we have developed large multilayer dielectric (MLD) gratings for working at 1.053 microns with 2 to 3 times higher damage threshold than gold coated gratings for ps pulses, and higher efficiency (up to 96% averaged over the full aperture). In addition these large MLD gratings are optimised for mosaic (tiling) configurations, in which the total useful grating length may reach 1 meter or more.

  5. 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.

  6. [Research on the reflection spectrum of linear chirped fiber bragg grating under the impact of dynamic stress].

    PubMed

    Wang, Jing; Jiang, Shan-chao; Shi, Bin; Sui, Qing-mei; Wang, Zheng-fang; Li, Xiao-fei; Wang, Ning; Yang, Shuai

    2014-08-01

    Dynastic stress field detection based on the linear chirped fiber Bragg grating (LCFBG) was proposed. Firstly, the reflectance spectra strain sensing model of LCFBG adopting the transfer matrix method was constructed, and attenuation sine function was used to simulate the dynamic stress field along LCFBG. In the simulation experiment, the responding character of LCFBG reflection spectrum to different amplitude, different attenuation coefficient and different propagation speed of dynamic stress was studied in detail. The simulation results show that the reflectivity, wavelength and spectral shape of LCFBG reflection spec- trum are related to the dynamic stress. However, the LCFBG reflection spectrum has different response to different parameters of dynamic stress. In a range, maximum reflectivity of LCFBG reflectance spectra increases when the amplitude and propagation speed of dynastic stress field becomes larger, but it decreases when the attenuation coefficient increases. Eventually, vibration sensor using LCFBG as the sensing element was designed, and then LCFBG dynamic stress fluctuations experiment platform was build. The data obtained from experiment agrees with the simulation results. Therefore, a novel detection method of dynamic stress field through real-time acquisition of LCFBG full spectral information is proposed in this article. PMID:25474927

  7. [Research on the reflection spectrum of linear chirped fiber bragg grating under the impact of dynamic stress].

    PubMed

    Wang, Jing; Jiang, Shan-chao; Shi, Bin; Sui, Qing-mei; Wang, Zheng-fang; Li, Xiao-fei; Wang, Ning; Yang, Shuai

    2014-08-01

    Dynastic stress field detection based on the linear chirped fiber Bragg grating (LCFBG) was proposed. Firstly, the reflectance spectra strain sensing model of LCFBG adopting the transfer matrix method was constructed, and attenuation sine function was used to simulate the dynamic stress field along LCFBG. In the simulation experiment, the responding character of LCFBG reflection spectrum to different amplitude, different attenuation coefficient and different propagation speed of dynamic stress was studied in detail. The simulation results show that the reflectivity, wavelength and spectral shape of LCFBG reflection spec- trum are related to the dynamic stress. However, the LCFBG reflection spectrum has different response to different parameters of dynamic stress. In a range, maximum reflectivity of LCFBG reflectance spectra increases when the amplitude and propagation speed of dynastic stress field becomes larger, but it decreases when the attenuation coefficient increases. Eventually, vibration sensor using LCFBG as the sensing element was designed, and then LCFBG dynamic stress fluctuations experiment platform was build. The data obtained from experiment agrees with the simulation results. Therefore, a novel detection method of dynamic stress field through real-time acquisition of LCFBG full spectral information is proposed in this article. PMID:25508706

  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. 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.

  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 μm.

  12. 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.

  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. Quantum optics and laser induced breakdown spectroscopy: A dissertation in two parts

    NASA Astrophysics Data System (ADS)

    Perkins, Jeffrey J.

    In this dissertation, we solve for the form of the multiple pump mode spontaneous downconversion spectrum, by expanding the pump field in a superposition of Seigman's Complex Gauss-Hermite modes. We also examine the use of Diffraction Gratings as quantum state "cleaners," in that they may be used to distill a specific quantum state from a corresponding superposition of undesirable states. Work was also done in Laser Induced Breakdown Spectroscopy; we use the technique to determine the hydration state of hydrated sulfates in a Martian environment, and examine the effect of the bremmstrahlung background on the predictive ability of the technique.

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

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Zhou, Zhi; Ou, Jinping

    2012-06-01

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

  16. Diffraction by dual-period gratings.

    PubMed

    Skigin, Diana C; Depine, Ricardo A

    2007-03-20

    The dynamical characteristics of dual-period perfectly conducting gratings are explored. Gratings with several grooves (reflection) or slits (transmission) within each period are considered. A scalar approach is proposed to derive the general characteristics of the diffracted response. It was found that compound gratings can be designed to cancel as well as to intensify a given diffraction order. These preliminary estimations for finite gratings are validated by numerical examples for infinitely periodic reflection and transmission gratings with finite thickness, performed using an extension of the rigorous modal method to compound gratings, for both polarization cases. PMID:17334426

  17. (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.

  18. (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.

  19. (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.

  20. (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.

  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 regeneration of cartilage

    NASA Astrophysics Data System (ADS)

    Sobol, Emil; Shekhter, Anatoly; Guller, Anna; Baum, Olga; Baskov, Andrey

    2011-08-01

    Laser radiation provides a means to control the fields of temperature and thermo mechanical stress, mass transfer, and modification of fine structure of the cartilage matrix. The aim of this outlook paper is to review physical and biological aspects of laser-induced regeneration of cartilage and to discuss the possibilities and prospects of its clinical applications. The problems and the pathways of tissue regeneration, the types and features of cartilage will be introduced first. Then we will review various actual and prospective approaches for cartilage repair; consider possible mechanisms of laser-induced regeneration. Finally, we present the results in laser regeneration of joints and spine disks cartilages and discuss some future applications of lasers in regenerative medicine.

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

    SciTech Connect

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

    1982-01-01

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

  4. 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.

  5. Laser-Induced Fluorescence of Estrogens

    NASA Astrophysics Data System (ADS)

    Meshalkin, Yu. P.; Cherkasova, O. P.; Fedorov, V. I.; Samoĭlova, E. S.

    2002-01-01

    Spectra of the laser-induced fluorescence of estrogens—estradiol, estriol, and estrone—were measured under excitation by the fourth harmonic (λ=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. Carrier dynamics in quantum-dot sensitized solar cells measured by transient grating and transient absorption methods.

    PubMed

    Maeda, Naotaka; Hata, Hiroaki; Osada, Naoya; Shen, Qing; Toyoda, Taro; Kuwahara, Shota; Katayama, Kenji

    2013-07-14

    Carrier dynamics in quantum-dot sensitized solar cells (QDSSCs) was clarified by combining the information obtained by the heterodyne transient grating (HD-TG), transient absorption (TA) and transient photocurrent (TP) measurements under the short circuit conditions in the time range from microseconds to seconds. The HD-TG signal is sensitive to the ionic species at the electrode/electrolyte interface, and the electrons in the titanium oxide layer injected from quantum dots (QDs) were monitored by the TA signal, and the photocurrent as a final output was monitored by the TP signal. By using the compensating information, the whole picture of the charge dynamics was obtained in the time region after the initial electron injection from QDs into the titanium oxide layer. In the former part of this paper, the assignment of the responses for each measurement was clarified based on the previous paper on dye sensitized solar cells (S. Kuwahara, et al. Phys. Chem. Chem. Phys., 2013, 15(16), 5975-5981). In the latter part, the effect of the device parameters for actual QDSSCs, such as electrolyte concentrations, and coating times of surface passivation of QDs were investigated. PMID:23712641

  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. 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.

  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. Adsorption and laser-induced desorption of dimethylcadmium from silicon

    NASA Astrophysics Data System (ADS)

    Simonov, Alexander P.; Varakin, Vladimir N.

    1990-10-01

    The dynamics of Cd (cH ) 2 chemisorption and spontaneous decomposit ion on n-type 51(100) with native surface oxide the pathwa and efficiencies of the adsorbate desorption due to the absorption of the XeC1 laser radiation by silicon have been examined using laser-induced desorption miss spectrorrtry (LIDMS ) . The k inetics of these sur face processes has been found to depend on the preceding laser irradiation of the surface. The extremely fast chemisorption and efficient decomposition of the parent rrlecules have been observed on the irradiated silicon surface. The competition between intact dissociative and recombination desorption pathways was responsible for the observed laser fluence dependences of the desorption of Cd(CI-6) and i ts fragments. 1 . INTROOIJCTIct4 1 . 1 . Laser chemical vapour depos ition (LCVD). Laser-induced deposition of thin filme on solid surfaces by using volatile organometallic precursors has been the subject of numerous investigations in the 8Os2. Due to the spatial/temporal localization of laser radiation and the resonant nature of laser-rr1ecule interaction this deposition technique has such attractive features as submicrometer resolution of deposits high film growth rate and high quality lowtemperature processing. The deposition process can be controlled by varying the laser parameters (wavelength fluence beam spot on the substrate surface scanning speed ). A var iety of mater ials can be depos I ted using LCVD. Of special interest for microelectronics is the deposition of

  11. 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

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

    PubMed Central

    Ma, H.; Venugopalan, V.

    2014-01-01

    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

  13. 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.

  14. 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

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  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 ∼ 10⁴ 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. 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.

  19. 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.

  20. Laser-induced desorption from sapphire surfaces

    SciTech Connect

    Hamza, A.V.; Schildbach, M.A.

    1992-03-01

    Laser-induced desorption of energetic ({approximately}7eV) aluminum ions was observed from clean and water-covered sapphire (1102) surfaces using time-of-flight mass spectrometry with laser wavelengths of 1064, 355, and 266 nm. In sharp contrast, O{sup +} (H{sup +} and OH{sup +}) ions were observed in electron-induced desorption measurements with 300 eV electrons from the bare (water- covered) (1102) surface. Sapphire surfaces were characterized with low energy electron diffraction, reflection electron energy loss spectroscopy, and Auger electron spectroscopy. 8 refs.

  1. Application of the method of laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Fateeva, Natalia L.; Matvienko, Gennadii G.

    2004-02-01

    Great attention is now paid to ecology of the environment, in whic plants are of great importance. However the present methods of biophysical analysis of plant states are very labor-intensive and require a lot of time. The structure of protein-pigment complexes is known to break in different dissolvents that results in the shift of maxima of chlorophyll absorption and fluorescence bands. That is why development of methods for remote diagnostics of plants is of great scientific and practical interest. They would make it possible to determine species and state of plants rather quickly and accurately. We have developed a setup and methods for optical diagnostics of the physiological state of plants to investigate the dynamics of the fastest part of fluorescence of plants in vivo. The method of laser-induced fluorescence makes it possible to observe the level of vegetative development of living plants, as well as their state under the impact of some stress factors.

  2. Laser-induced desorption of dimethylcadmium from silicon

    NASA Astrophysics Data System (ADS)

    Varakin, Vladimir N.; Panesh, Anatoly M.; Simonov, Alexander P.

    1990-07-01

    A method of laser-induced desorption mass spectrometry (LIDMS) has been used to examine the dynamics of Cd(CH3)2 chemisorption and spontaneous decomposition on n type Si(100) with native surface oxide, the pathways and efficiencies of the adsorbate desorption due to the absorption of the XeCl. laser radiation by silicon. The extremely fast processes in the adlayer re caused by the preceding irradiation of the surface of the sample by intensive (with fluences up to 0.4 J/cm2 ) laser pulses . The conet It ion between intact, dissociative, and recombination desorption pathways s responsible for the observed laser fluence dependences of the desorption of Cd(CH3)2 and its fragments.

  3. Methodology for analyzing laser induced structural damage

    SciTech Connect

    Bryan, S.K.; Torvik, P.J.; Venkayya, V.B.

    1984-01-01

    The analysis of laser-induced structural damage requires the merging of a thermal analysis which includes the characterization of the laser damage with a structural analysis which enables the determination of the deformation and the residual load carrying ability. Three types of laser-induced damage are considered: loss of structure due to melting, change of material properties due to temperature changes, and addition of load due to thermal stress. The thermal solution is calculated from a set of finite difference equations obtained from heat balances performed at successive finite time increments on an array of finite cells. The structural analysis is performed by a re-analysis technique, applicable when changes in structural stiffness are small compared to the initial value. The combined procedure for evaluating laser damage is applied to two structures, representing two levels of complexity. The first was a simple two-dimensional plate and the second a three-dimensional wing structure. The displacement solutions were compared to results obtained from NASTRAN to determine the accuracy of the iterative solution technique. The procedure was found to be efficient, and permits the parametric studies needed for a-priori estimates of the effectiveness of potential laser weapons systems. 10 references.

  4. Laser induced breakdown spectroscopy of geological materials

    SciTech Connect

    Gamble, T.; Lippert, T.

    1996-09-01

    The authors have developed laser-induced breakdown spectroscopy (LIBS) as a tool for rapid field analysis of soils and mine tailings for heavy metals, including RCRA regulated metals. The goal of the work is production of a cost-effective, field-portable instrument that meets the needs for field screening of hazardous waste sites. Laser-induced breakdown spectroscopy is primarily an atomic emission technique. In the method, a short pulse of laser light is focused onto the surface of a material. Absorption of the light initially heats the material to 10,000K or greater. The high temperature vaporizes, atomizes and electronically excites some of the material in a single laser pulse. The authors have measured the figures of merit of LIBS instrumentation using parameters appropriate for fieldable equipment. Materials examined include NIST standard soil samples, local Los Alamos soil, and samples from mine tailing waste sites in Butte, Montana. Detection limits range from about 10 ppm for lead to 400 ppm for arsenic in the Los Alamos soil. Detection and slopes of curves using standard addition. These results were obtained in thirty second measurements using samples that had been dried and pressed. The dominate source of noise which limits the detection limit is typically sample inhomogeneity.

  5. The photodissociation and reaction dynamics of vibrationally excited molecules. Technical progress report, 1993--1994

    SciTech Connect

    Not Available

    1994-04-01

    Combined vibrational overtone excitation and laser induced fluorescence detection was used to study dissociation dynamics of hydroxylamine (NH{sub 2}OH), laser induced grating experiments on water were analyzed, discovering the important role that electrostriction and thermal relaxation play, and a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation was completed and the first measurements made. Role of vibrational excitation in photodissociation dynamics was studied using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then excite that molecule to a dissociative electronic state. Because the vibrational excitation alters the dissociation dynamics in the excited state, both by providing access to different portions of the excited state surface and by altering the motion of the system on the surface, it is usually refered to as vibrationally mediated photodissociation.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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)

  11. 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.

  12. 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.

  13. 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.

  14. Spectral and dynamic characteristics of helium plasma emission and its effect on a laser-ablated target emission in a double-pulse laser-induced breakdown spectroscopy (LIBS) experiment.

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. 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.

  17. 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

  18. 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

  19. The fluence threshold of femtosecond laser blackening of metals: The effect of laser-induced ripples

    NASA Astrophysics Data System (ADS)

    Ou, Zhigui; Huang, Min; Zhao, Fuli

    2016-05-01

    With the primary controlling factor of the laser fluence, we have investigated femtosecond laser blackening of stainless steel, brass, and aluminum in visible light range. In general, low reflectance about 5% can be achieved in appropriate ranges of laser fluences for all the treated metal surfaces. Significantly, towards stainless steel and brass a fluence threshold of blackening emerges unusually: a dramatic reflectance decline occurs in a specific, narrow fluence range. In contrast, towards aluminum the reflectance declines steadily over a wide fluence range instead of the threshold-like behavior from steel and brass. The morphological characteristics and corresponding reflectance spectra of the treated surfaces indicates that the blackening threshold of stainless steel and brass corresponds to the fluence threshold of laser-induced subwavelength ripples. Such periodic ripples growing rapidly near ablation threshold absorb visible light efficiently through grating coupling and cavity trapping promoted by surface plasmon polaritons. Whereas, for aluminum, with fluence increasing the looming ripples are greatly suppressed by re-deposited nanoparticle aggregates that present intrinsic colors other than black, and until the formation of large scale "ravines" provided with strong light-trapping, sufficient blackening is achieved. In short, there are different fluence dependencies for femtosecond laser blackening of metals, and the specific blackening fluence threshold for certain metals in the visible range originates in the definite fluence threshold of femtosecond laser-induced ripples.

  20. 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.}

  1. 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.

  2. 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

  3. 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

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

    SciTech Connect

    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.

  5. [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.

  6. [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.

  7. 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

  8. 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.

  9. Volume of a laser-induced microjet

    NASA Astrophysics Data System (ADS)

    Kawamoto, Sennosuke; Hayasaka, Keisuke; Noguchi, Yuto; Tagawa, Yoshiyuki

    2015-11-01

    Needle-free injection systems are of great importance for medical treatments. In spite of their great potential, these systems are not commonly used. One of the common problems is strong pain caused by diffusion shape of the jet. To solve this problem, the usage of a high-speed highly-focused microjet as needle-free injection system is expected. It is thus crucial to control important indicators such as ejected volume of the jet for its safe application. We conduct experiments to reveal which parameter influences mostly the ejected volume. In the experiments, we use a glass tube of an inner diameter of 500 micro-meter, which is filled with the liquid. One end is connected to a syringe and the other end is opened. Radiating the pulse laser instantaneously vapors the liquid, followed by the generation of a shockwave. We find that the maximum volume of a laser-induced bubble is approximately proportional to the ejected volume. It is also found that the occurrence of cavitation does not affect the ejected volume while it changes the jet velocity.

  10. 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.

  11. 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.

  12. 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

  13. Laser Induced Birefringence in Pure Liquids

    NASA Astrophysics Data System (ADS)

    Harrison, Neil J.

    1991-01-01

    Available from UMI in association with The British Library. Laser induced birefringence or the Optical Kerr effect is a subject that has undergone much research over previous years and is an established technique for the study of many classes of materials. To date the measurements on various media have been characterized by the substantial time required to obtain results and the generally poor sensitivity of the apparatus used. This work describes the development of a new apparatus which is the first in the field to automate the signal capture and analysis utilizing a 1 Gigasample/second digitizing oscilloscope connected to a microcomputer to provide fast, accurate transient analysis. Careful design of the apparatus enabled operation at two inducing wavelengths of 532nm and 1064nm. The sensitivity and accuracy of the apparatus coupled with the rapid transient evaluation was tested on a number of well characterized samples including benzene, nitrobenzene, toluene and benzoyl chloride and was found to give excellent agreement with other workers. The apparatus was used to investigate the properties of the organic pure liquid series the n-alkanes before making the first measurements on the 1-alkenes, 1-alkynes, alcohols, carboxylic acids and three alkdienes. Results from these experiments were used to evaluate the contributions of sigma and pi bonds to the Optical Kerr effect in simple organic molecules. A review of all previously published Optical Kerr effect results for pure liquids was also carried out and the first comprehensive table of results complied.

  14. Laser induced fluorescence in atmospheric pressure discharges

    NASA Astrophysics Data System (ADS)

    Dilecce, G.; Martini, L. M.; Tosi, P.; Scotoni, M.; De Benedictis, S.

    2015-06-01

    This paper offers an outline of laser induced fluorescence (LIF) diagnostics and practical recommendations for its use in atmospheric pressure discharges. LIF principles, technical requirements and rationalization of experimental outcomes by modelling are addressed. Important issues that are particularly relevant to small scale, spatially inhomogeneous discharges, like plasma-jets, are emphasized. For the first time, all collision processes and the spatial non-homogeneity of the laser beam are together accounted for in the LIF model. Saturation characteristics are discussed and used for the assessment of model parameters. A calibration procedure is discussed and implemented. Gas temperature measurements by LIF are also addressed. The whole description of the technique is given, without loss of generality, through the example of its application to the OH radical. Notes on other diatomic radicals, CH, NO and CN, are given along the paper. Some results in a RF plasma-jet are presented as an example of application in a discharge system where all the concepts developed in the paper are applied.

  15. 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).

  16. 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.

  17. PIC-DSMC analysis on interaction of a laser induced discharge and shock wave

    NASA Astrophysics Data System (ADS)

    Shimamura, Kohei

    2015-09-01

    Laser induced discharge and the shock wave have attracted great interest for use in the electrical engineering. When the high intensity laser (10 GW >) is focused in the atmosphere, the breakdown occurs and the discharge wave propagates toward to the laser irradiation. The shock wave is generated around the discharge wave, which is called as the laser supported detonation wave. After breakdown occurred, the initial electron of the avalanche ionization is produced by the photoionization due to the plasma radiation. It is well recognized that the radiation of the laser plasma affects the propagation mechanism of the laser induced discharge wave after the initiation of the breakdown. However, it is difficult to observe the interaction between the plasma radiation and the electron avalanche in the ionization-wave front in experimentally except in the high intensity laser. In the numerical calculation of the laser-induced discharge, the fluid dynamics based on the Navier-Stokes equation have been widely used. However, it is difficult to investigate the avalanche ionization at the wave front using the fluid dynamics simulation. To investigate the interaction of the ionization-wave front and the shock wave, it is appropriate to utilize the PIC-DSMC method. The present study showed the propagation of the ionization front of the discharge wave and the shock wave using the particle simulation. This work was supported by Kato Foundation for Promotion of Science and Japan Power Academy.

  18. 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.

  19. Holographic Gratings for Optical Processing

    NASA Technical Reports Server (NTRS)

    Kukhtarev, Nickolai

    2002-01-01

    Investigation of astronomical objects and tracking of man-made space objects lead to generation of huge amount of information for optical processing. Traditional big-size optical elements (such as optical telescopes) have a tendency for increasing aperture size in order to improve sensitivity. This tendency leads to increasing of weight and costs of optical systems and stimulate search for the new, more adequate technologies. One approach to meet these demands is based on developing of holographic optical elements using new polymeric materials. We have investigated possibility to use new material PQ-PMMA (phenantrenequinone-doped PMMA (Polymethyl Methacrylate)) for fabrication of highly selective optical filters and fast spatial-temporal light modulators. This material was originally developed in Russia and later was tested in CalTech as a candidate material for optical storage. Our theoretical investigation predicts the possibility of realization of fast spatial and temporal light modulation, using volume reflection-type spectral filter. We have developed also model of holographic-grating recording in PQ-PMMA material, based on diffusional amplification. This mechanism of recording allow to receive high diffraction efficiency during recording of reflection-type volume holographic grating (holographic mirror). We also investigated recording of dynamic gratings in the photorefractive crystals LiNbO3 (LN) for space-based spectroscopy and for adaptive correction of aberrations in the telescope's mirrors. We have shown, that specific 'photogalvanic' mechanism of holographic grating recording in LN allow to realize recording of blazed gratings for volume and surface gratings. Possible applications of dynamic gratings in LN for amplification of images, transmitted through an imaging fiber guide was also demonstrated.

  20. 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.

  1. Addressing the Numerical Challenges Associated With Laser-Induced Melt Convection

    NASA Astrophysics Data System (ADS)

    Weston, Brian; Nourgaliev, Robert; Delplanque, Jean Pierre; Anderson, Andy

    2015-11-01

    We present a new robust and efficient numerical framework for simulating multi-material flows with phase change. The work is motivated by laser-induced phase change applications, particularly the selective laser melting (SLM) process in additive manufacturing. Physics-based simulations of the laser melt dynamics requires a fully compressible framework, since incompressible flow solvers are inefficient for stiff systems, arising from laser-induced rapid phase change. In this study, the liquid and solid phases are both modeled with the compressible Navier-Stokes equations. The solid phase has an additional combined variable viscosity and drag force model to suppress the velocity in the solid. Our all-speed Navier-Stokes solver is based on a fully-implicit, high-order reconstructed Discontinuous Galerkin method. A Newton-Krylov based framework is used to solve the resulting set of non-linear equations, enabling robust simulations of the highly stiff compressible Navier-Stokes equations. We demonstrate the method's capabilities for phase change on several different melting and freezing configurations, including a three-dimensional laser-induced melt convection problem. Future model enhancements will incorporate material evaporation and rapid solidification.

  2. 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

  3. Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors: 1. Experiments

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    In this study we measure the in situ response of a fiber Bragg grating (FBG) sensor embedded in the adhesive layer of a single composite lap joint, subjected to harmonic excitation after fatigue loading. After a fully reversed cyclic fatigue loading is applied to the composite lap joint, the full-spectral response of the sensor is interrogated at 100 kHz during two loading conditions: with and without an added harmonic excitation. The full-spectral information avoided dynamic measurement errors often experienced using conventional peak wavelength and edge filtering techniques. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. The dynamic response of the FBG sensor indicated a transition to strong nonlinear dynamic behavior as fatigue-induced damage progressed. The ability to measure the dynamic response of the lap joint through sensors embedded in the adhesive layer can provide in situ monitoring of the lap joint condition.

  4. 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

  5. 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%.

  6. 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.

  7. 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.

  8. 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.

  9. 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 με and a low crosstalk of 950:1. PMID:22778619

  10. 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.”.

  11. Multilayer diffraction grating

    DOEpatents

    Barbee, Jr., Troy W.

    1990-01-01

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

  12. Multilayer diffraction grating

    DOEpatents

    Barbee, T.W. Jr.

    1990-04-10

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

  13. 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.

  14. Tracking the photodissociation dynamics of liquid nitromethane at 266 nm by femtosecond time-resolved broadband transient grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Honglin; Song, Yunfei; Yu, Guoyang; Wang, Yang; Wang, Chang; Yang, Yanqiang

    2016-05-01

    Femtosecond time-resolved transient grating (TG) technique was employed to get insight into the photodissociation mechanism of liquid nitromethane (NM). Broadband white-light continuum was introduced as the probe to observe the evolution of electronic excited states of NM molecules and the formation of photodissociation products simultaneously. The reaction channel of liquid NM under 266 nm excitation was obtained that NM molecules in excited state S2 relax through two channels: about 73% relax to low lying S1 state through S2/S1 internal conversion with a time constant of 0.24 ps and then go back to the ground state through S1/S0 internal conversion; the other 27% will dissociate with a time constant of 2.56 ps. NO2 was found to be one of the products from the experimental TG spectra, which confirmed that C-N bond rupture was the primary dissociation channel of liquid NM.

  15. 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.

  16. 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 μs 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 Hβ spectra.

  17. 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.

  18. 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.

  19. Advanced experimental applications for x-ray transmission gratings spectroscopy using a novel grating fabrication method

    SciTech Connect

    Hurvitz, G.; Ehrlich, Y.; Shpilman, Z.; Levy, I.; Fraenkel, M.; Strum, G.

    2012-08-15

    A novel fabrication method for soft x-ray transmission grating and other optical elements is presented. The method uses focused-ion-beam technology to fabricate high-quality free standing grating bars on transmission electron microscopy grids. High quality transmission gratings are obtained with superb accuracy and versatility. Using these gratings and back-illuminated CCD camera, absolutely calibrated x-ray spectra can be acquired for soft x-ray source diagnostics in the 100-3000 eV spectral range. Double grating combinations of identical or different parameters are easily fabricated, allowing advanced one-shot application of transmission grating spectroscopy. These applications include spectroscopy with different spectral resolutions, bandwidths, dynamic ranges, and may serve for identification of high-order contribution, and spectral calibrations of various x-ray optical elements.

  20. 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.

  1. Femtosecond laser induced surface melting and nanojoining for plasmonic circuits

    NASA Astrophysics Data System (ADS)

    Hu, A.; Deng, G. L.; Courvoisier, S.; Reshef, O.; Evans, C. C.; Mazur, E.; Zhou, Y.

    2013-09-01

    Femtosecond laser induced nonthermal processing is an emerging nanofabrication technique for delicate plasmonic devices. In this work we present a detailed investigation on the interaction between ultra-short pulses and silver nanomaterials, both experimentally and theoretically. We systematically study the laser-silver interaction at a laser fluent from 1 J/m2 to 1 MJ/m2. The optimal processing window for welding of silver nanowires occurs at fluences of 200-450 J/m2. The femtosecond laser-induced surface melting allows precise welding of silver nanowires for "T" and "X" shape circuits. These welded plasmonic circuits are successfully applied for routining light propagation.

  2. 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.

  3. 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.

  4. 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.

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

    PubMed

    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. PMID:27036779

  6. Laser-induced breakdown spectroscopy for remote elemental analysis of planetary surfaces

    NASA Astrophysics Data System (ADS)

    Blacic, J. D.; Pettit, D. R.; Cremers, D. A.; Roessler, N.

    One of the most fundamental pieces of information about any planetary body is the elemental and mineralogical composition of its surface materials. We are developing an instrument to obtain such data at ranges of up to several hundreds of meters using the technique of Laser-Induced Breakdown Spectroscopy, or LIBS. The elemental analysis is based on atomic emission spectroscopy of a laser-induced plasma or spark. A pulsed, diode-pumped ND:YAG laser of several hundred mJ optical energy is used to vaporize and electronically excite the constituent elements of a rock surface remotely located from the laser. Light emitted from the excited plasma is collected and introduced to the entrance slit of a small grating spectrometer. The spectrally dispersed spark light is detected with either a linear photodiode array or area CCD array. When the latter detector is used, the optical and spectrometer components of the LIBS instrument can also be used in a passive imaging mode to collect and integrate reflected sunlight from the same rock surface. Absorption spectral analysis of this reflected light gives mineralogical information that, when combined with the elemental analysis from the LIBS mode, provides a complete remote geochemical characterization of the rock surface. We have performed laboratory calibrations in air and in vacuum on standard rock powders to quantify the LIBS analysis. We have performed a preliminary field test using commonly available laboratory components to demonstrate remote LIBS analysis of terrestrial rock surfaces at ranges of over 25 meters. Based on these results, we believe that all major and most minor elements expected on planetary surfaces can be measured with absolute accuracy of 10-15 percent and much higher relative accuracy.

  7. 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.

  8. 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.

  9. Analysis of Laser-Induced Plume During Disk Laser Welding at Different Speeds

    NASA Astrophysics Data System (ADS)

    Wang, Teng; Gao, Xiangdong; Katayama, Seiji

    2013-08-01

    During high power disk laser welding, the high-speed photography was used to measure the dynamic images of the laser-induced plume at different laser welding speeds. Various plume features (area, height and brightness) were extracted from the images by the color space clustering algorithm. Combined with observation on the surface and the cross sections of welding samples, the effect of welding speed on welding stability was analyzed. From the experimental results, it was found that these features of plume could reflect the welding state. Thus changes of the plume features corresponded to different welding speeds, which was helpful for monitoring the laser welding stability.

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

    DOEpatents

    Wang, Chuji

    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.

  11. Coaxial cable Bragg grating

    NASA Astrophysics Data System (ADS)

    Wei, Tao; Wu, Songping; Huang, Jie; Xiao, Hai; Fan, Jun

    2011-09-01

    This paper reports a coaxial cable Bragg grating (CCBG) fabricated by drilling holes into the cable at periodic distances along the axial direction. Resonances were observed at discrete frequencies in both transmission and reflection spectra. The analogy of the CCBG with a fiber Bragg grating is shown. The grating was tested for the potential application as a strain-sensing device.

  12. 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.

  13. 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.

  14. Catwalk grate lifting tool

    DOEpatents

    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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  20. Dynamical studies of the mechanisms for optical nonlinearities of methyl-red dye doped blue phase liquid crystals.

    PubMed

    Chen, Chun-Wei; Lin, Tsung-Hsien; Khoo, Iam Choon

    2015-08-24

    Dynamical grating diffraction experiments and reflection/transmission polarization spectroscopy have been conducted on azo-dye doped Blue-Phase Liquid Crystal (BPLC) to investigate the mechanisms responsible for laser induced refractive index changes. The underlying mechanisms for the transient grating diffraction components are attributed to thermal indexing and lattice distortion, whereas the persistent component is due to lattice distortion/expansion caused by laser excited dye molecule isomerization. These mechanisms were distinguishable by their response dynamics and gave rise to the observed reflection spectra and photonic bandgap shift, polarization dependency and optical activity. Some preliminary studies have demonstrated the feasibility of using these mechanisms for coherent holographic and direct image writing operations. PMID:26368144

  1. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    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.

  2. 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.

  3. IKK2 Inhibition Attenuates Laser-Induced Choroidal Neovascularization

    PubMed Central

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

    2014-01-01

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

  4. IKK2 inhibition attenuates laser-induced choroidal neovascularization.

    PubMed

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

    2014-01-01

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

  5. Adaptable Diffraction Gratings With Wavefront Transformation

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  6. 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

  7. Time-dependent Liouville density functional theory for laser-induced ultrafast demagnetization in ferromagnets

    NASA Astrophysics Data System (ADS)

    Zhang, Guoping; Bai, Yihua; George, Thomas F.

    Abstract: The traditional time-dependent density functional theory is very powerful to simulate the dynamic process, but is very time consuming. When it was first used to understand laser-induced ultrafast demagnetization in ferromagnets, the results were disappointing, with the laser amplitude at least three orders of magnitude larger than the experimental one to achieve the similar spin reduction. We develop a new theory within the density functional theory (DFT) for laser-induced ultrafast demagnetization in ferromagnets. We first solve the Liouville equation in the time domain and then feed the excited state density into the DFT code, so the dynamics proceeds on the excited and constraint potential surface. We test this for several magnetic systems and find a significantly larger demagnetization than the static approach, but is still smaller than the experimental finding. Both the local density approximation and the generalized gradient approximation fail. Our finding strongly suggests that a new functional must be developed. As a first test, we introduce a spin power scaling method. Some primitive results will be presented. This work was solely supported by the U.S. Department of Energy under Contract No. DE-FG02-06ER46304. The research used resources of the National Energy Research Scientific Computing Center.

  8. 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

  9. 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.

  10. 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.; Lamaignère, 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.

  11. 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.

  12. 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.

  13. 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=0˜5) 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.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Jonsson, Per; Wästerby, Pär.; Gradmark, Per-Åke; Hedborg, Julia; Larsson, Anders; Landström, 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.

  18. [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.

  19. [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.

  20. 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.

  1. Laser-induced transformations of zero-valent iron particles

    NASA Astrophysics Data System (ADS)

    Petr, M.; Šišková, K.; Machala, L.; Kašlík, J.; Šafářová, K.; Zbořil, R.

    2012-10-01

    This paper deals with laser-induced transformations of zero-valent iron particles performed under ambient conditions. The excitation wavelength of 633 nm and several values of laser power, from 0.1 to 4.0 mW, have been used for the samples irradiation. Changes in phase composition and particle morphology, occurring during the transformations have been monitored by in-situ Raman spectroscopy, ex-situ Mössbauer spectroscopy, X-ray diffraction, and scanning electron microscopy. The results revealed that laser-induced oxidation is more pronounced in the sample with smaller particles. Furthermore, by this work, we also wanted to stress the fact that Raman spectroscopic technique has to be performed with caution when investigating zero-valent metal samples.

  2. Measurement of radiative properties of pulsed laser induced plasma

    SciTech Connect

    Xu, X.; Song, K.H.

    1996-12-31

    When high power, pulsed lasers are utilized in materials processing applications such as machining and pulsed laser deposition, plasma is generated by laser irradiation. Analysis of the energy transport process between the laser and the target is complicated by laser-induced plasma layer which mediates between the laser and the target. This work investigated the transient radiative properties of the laser-induced plasma. Novel diagnostic technique was developed to measure the transient transmission of the plasma layer, whole thickness varies between a few micrometers and a few hundred micrometers within the pulse duration. The transmissivity of plasma obtained from this study helps to understand the energy transport mechanism during high power, pulsed laser interaction with materials and quantifies the energy coupling efficiency between the laser and the target.

  3. 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.

  4. Microchip laser-induced breakdown spectroscopy: a preliminary feasibility investigation.

    PubMed

    Gornushkin, I B; Amponsah-Manager, K; Smith, B W; Omenetto, N; Winefordner, J D

    2004-07-01

    A commercial, 7 microJ/pulse, 550 ps microchip laser is used to induce plasma on Pb, Si, Cu, Fe, Ni, Ti, Zn, Ta, and Mo foils and a Si wafer. The measured plasma lifetime is comparable with the duration of the laser pulse (a few ns). The plasma continuum radiation is low, while some of the strong resonance lines (e.g., Zn 213.86 nm) show self-reversal. Quantitative analysis is possible using non-gated detectors but analytical lines should be chosen with care to avoid reduction in the linear dynamic range. The mass removed (0.5-20 ng/pulse) is sufficient to yield spectra that are detectable with portable grating spectrometers equipped with non-gated, non-intensified detector arrays. The spectrum of Cd is detected with a broadband portable spectrometer (200-950 nm). The combination of the broadband spectrometer and the microchip laser is very promising for material identification, especially in field applications. PMID:15282039

  5. Reflective diffraction grating

    DOEpatents

    Lamartine, Bruce C.

    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.

  6. 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.; Yañez, 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.

  7. Assessment of the upper particle size limit for quantitative analysis of aerosols using laser-induced breakdown spectroscopy.

    PubMed

    Carranza, Jorge E; Hahn, David W

    2002-11-01

    The laser-induced plasma vaporization of individual silica microspheres in an aerosolized air stream was investigated. The upper size limit for complete particle vaporization corresponds to a silica particle diameter of 2.1 microm for a laser pulse energy of 320 mJ, as determined by the deviation from a linear mass response of the silicon atomic emission signal. Comparison of the measured silica particle sampling rates and those predicted based on Poisson sampling statistics and the overall laser-induced plasma volume suggests that the primary mechanism of particle vaporization is related to direct plasma-particle interactions as opposed to a laser beam-particle interaction. Finally, temporal and spatial plasma evolution is discussed in concert with factors that may influence the vaporization dynamics of individual aerosol particles, such as thermophoretic forces and vapor expulsion. PMID:12433072

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

    DOEpatents

    Miller, Steven M.

    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.

  9. 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.

  10. 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

  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 spectroscopy for combustion diagnostics

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  13. 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.

  14. 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.

  15. Laser-Induced Fluorescence Helps Diagnose Plasma Processes

    NASA Technical Reports Server (NTRS)

    Beattie, J. R.; Mattosian, J. N.; Gaeta, C. J.; Turley, R. S.; Williams, J. D.; Williamson, W. S.

    1994-01-01

    Technique developed to provide in situ monitoring of rates of ion sputter erosion of accelerator electrodes in ion thrusters also used for ground-based applications to monitor, calibrate, and otherwise diagnose plasma processes in fabrication of electronic and optical devices. Involves use of laser-induced-fluorescence measurements, which provide information on rates of ion etching, inferred rates of sputter deposition, and concentrations of contaminants.

  16. Laser-induced gas breakdown - Spectroscopic and chemical studies.

    NASA Technical Reports Server (NTRS)

    De Montgolfier, PH.; Dumont, P.; Mille, Y.; Villermaux, J.

    1972-01-01

    Discussion of the results of several experimental investigations on laser-induced gas breakdown. The experiments included time-resolved spectroscopy, direct detection of H atoms with a TiO2 probe, and chemical reactions; each of them provided insight into the behavior of the medium at different times. Chemical reactions and explosions have been initiated by the laser beam when a plasma was created. No primary multiphotonic absorption and no macroscopic chemical reactions were observed below the breakdown threshold.

  17. Laser-induced breakdown spectroscopy for specimen analysis

    SciTech Connect

    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.

  18. 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.

  19. Biopolymer holographic diffraction gratings

    NASA Astrophysics Data System (ADS)

    Savić Šević, Svetlana; Pantelić, 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.

  20. 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 μs. 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.

  1. 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.

  2. 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 bubble’s 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

  3. Finite element simulation of cell-substrate decohesion by laser-induced stress waves.

    PubMed

    Miller, Phillip; Hu, Lili; Wang, Junlan

    2010-04-01

    Fundamental to the development and application of biomedical devices is an understanding of the adhesion of cells to substrates. There are many experimental techniques and papers dedicated to the study of cell adhesion. This work aims to elucidate on the cell detachment mechanism in a recently reported cell adhesion measurement experiment by laser-induced stress wave technique. In the experiment the absorption of an Nd:YAG laser pulse generates a stress wave of nanoseconds duration that interacts with and detaches the cell adhered to a Si substrate. Due to the ultra-short timescale involved in the experiment, details of the detachment process were not readily observable. In this work, dynamic finite element method is used to simulate the cell-substrate decohesion process under the laser-induced stress wave loading. The results show that the combined effect of nanosecond stress wave pulse and the specific cell geometry results in a complex stress-strain state along the cell-substrate interface. The principal failure mechanism is large interfacial strains realized from the cell's tendency to spread and elongate on the substrate as a result of substrate acceleration. The cells behave like a soft elastic solid during the detachment process due to the large difference between their characteristic response time and the ultra-short duration of the applied stress wave. Evolution of the cell geometry from hydrophobic to hydrophilic contact results in the same detachment process. PMID:20142111

  4. 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.

  5. Laser-induced fluorescence of isobutoxy in competition with ground state decomposition.

    PubMed

    Liang, Gaiting; Liu, Chengxuan; Hao, Haiyan; Zu, Lily; Fang, Weihai

    2013-12-19

    Spectroscopic detection is an important method to monitor alkoxy radicals in atmospheric photochemistry studies. In this work, we report the first observation of the laser-induced fluorescence (LIF) spectra of isobutoxy, 2-methyl-1-butoxy, and 3-methyl-1-butoxy in supersonic jet-cooled condition. Ground state unimolecular decomposition and isomerization as well as excited state relaxation dynamics of isobutoxy were discussed in combination with the theoretical calculations. Analysis of the experimental and theoretical results showed that methyl substitution on the β carbon of the alkoxy radicals changed the LIF spectra of alkoxy radicals significantly. The competition between the ground state reactions and the photoexcitation process depended strongly on the radical structure and hence affected the involvement of alkoxy radicals in the photochemical reactions in the upper troposphere. This study will help to understand the dynamic role of alkoxy radicals in the atmosphere. PMID:23617708

  6. 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

  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. Determinations of trace boron in superalloys and steels using laser-induced breakdown spectroscopy assisted with laser-induced fluorescence.

    PubMed

    Li, Changmao; Hao, Zhongqi; Zou, Zhimin; Zhou, Ran; Li, Jiaming; Guo, Lianbo; Li, Xiangyou; Lu, Yongfeng; Zeng, Xiaoyan

    2016-04-18

    Boron (B) is widely applied in microalloying of metals. As a typical light element, however, determination of boron in alloys with complex matrix spectra is still a challenge for laser-induced breakdown spectroscopy (LIBS) due to its weak line intensities in the UV-visible-NIR range and strong spectral interference from the matrix spectra. In this study, a wavelength-tunable laser was used to enhance the intensities of boron lines selectively. The intensities of B I 208.96 nm from boron plasmas were enhanced approximately 3 and 5.8 times while the wavelength-tunable laser was tuned to 249.68 and 249.77 nm, respectively. Utilizing the selective enhancement effect, accurate determinations of trace boron in nickel-based superalloys and steels were achieved by laser-induced breakdown spectroscopy assisted by laser-induced fluorescence (LIBS-LIF), with limits of detection (LoDs) of 0.9 and 0.5 ppm, respectively. The results demonstrated that LIBS-LIF can hopefully be used in boron determinations and has great potential for improving the ability of LIBS to determine light elements in alloys with a complex matrix. PMID:27137227

  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. 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.

  12. 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.

  13. 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.

  14. 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

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

    PubMed

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

    2006-11-24

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

  16. Laser-induced fluorescence measurement of combustion chemistry intermediates

    NASA Technical Reports Server (NTRS)

    Crosley, David R.

    1986-01-01

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

  17. 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.

  18. 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.

  19. Laser-induced breakdown in large transparent water droplets.

    PubMed

    Chang, R K; Eickmans, J H; Hsieh, W F; Wood, C F; Zhang, J Z; Zheng, J B

    1988-06-15

    Recent experiments on the laser-induced breakdown (LIB) of large transparent liquid droplets are reviewed. A physical model of LIB processes is presented with the aim of integrating the following recent results: (1) the internal and near-field distributions for large transparent spheres; (2) the location of LIB initiation based on spatially resolved plasma emission spectroscopic techniques; (3) spatially resolved but time-averaged density of the plasma plumes and temperature of the atomic species within the plasma; (4) the plasma front propagation velocities inside and outside the droplet; and (5) the fate of the remaining superheated droplet and the expelled material. PMID:20531767

  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. 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.

  3. Colloid formation and laser-induced bleaching in fluorite

    SciTech Connect

    LeBret, Joel B.; Cramer, Loren P.; Norton, M. Grant; Dickinson, J. T.

    2004-11-08

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

  4. 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.

  5. 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.

  6. Laser induced fluorescence of barium evaporating from a dispenser cathode

    NASA Astrophysics Data System (ADS)

    Zemyan, S. M.

    1982-03-01

    A continuous wave dye laser is used to induce resonance fluorescence in Ba atoms evaporating from a thermionic dispenser cathode. The laser is tuned to the 553.5 microns Ba I line by making use of the optogalvanic effect in a hollow cathode discharge tube. Photon counting equipment is used to measure the Ba fluorescent intensity as a function of cathode temperature and laser power. Ba concentrations and evaporation rates as functions of temperature are derived from the fluorescent intensity. Laser induced fluorescence is established as a technique for examining various species evaporating from cathodes. The technique can be used in attempts to determine cathode failure mechanisms.

  7. Laser-induced backward transfer of nanoimprinted polymer elements

    NASA Astrophysics Data System (ADS)

    Feinaeugle, Matthias; Heath, Daniel J.; Mills, Benjamin; Grant-Jacob, James A.; Mashanovich, Goran Z.; Eason, Robert W.

    2016-04-01

    Femtosecond laser-induced backward transfer of transparent photopolymers is demonstrated in the solid state, assisted by a digital micromirror spatial light modulator for producing shaped deposits. Through use of an absorbing silicon carrier substrate, we have been able to successfully transfer solid-phase material, with lateral dimensions as small as ~6 µm. In addition, a carrier of silicon incorporating a photonic waveguide relief structure enables the transfer of imprinted deposits that have been accomplished with surface features exactly complementing those present on the substrate, with an observed minimum feature size of 140 nm.

  8. Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain.

    PubMed

    Wang, Xueding; Pang, Yongjiang; Ku, Geng; Xie, Xueyi; Stoica, George; Wang, Lihong V

    2003-07-01

    Imaging techniques based on optical contrast analysis can be used to visualize dynamic and functional properties of the nervous system via optical signals resulting from changes in blood volume, oxygen consumption and cellular swelling associated with brain physiology and pathology. Here we report in vivo noninvasive transdermal and transcranial imaging of the structure and function of rat brains by means of laser-induced photoacoustic tomography (PAT). The advantage of PAT over pure optical imaging is that it retains intrinsic optical contrast characteristics while taking advantage of the diffraction-limited high spatial resolution of ultrasound. We accurately mapped rat brain structures, with and without lesions, and functional cerebral hemodynamic changes in cortical blood vessels around the whisker-barrel cortex in response to whisker stimulation. We also imaged hyperoxia- and hypoxia-induced cerebral hemodynamic changes. This neuroimaging modality holds promise for applications in neurophysiology, neuropathology and neurotherapy. PMID:12808463

  9. 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.

  10. 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.

  11. 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.

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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. Frequency domain and wavelet analysis of the laser-induced plasma shock waves

    NASA Astrophysics Data System (ADS)

    Burger, Miloš; Nikolić, Zoran

    2015-08-01

    In addition to optical emission, another trace of interest that laser-induced plasma provides is a form of acoustic feedback. The acoustic emission (AE) signals were obtained using both microphone and piezo transducers. This kind of optoacoustic signals have some distinct features resembling the short, burst-like sounds, that may differ significantly depending mainly on the sample exposed and irradiance applied. Experiments were performed on atmospheric pressure by irradiating various metallic samples. The recorded waveforms were examined and numerically processed. Single-shot acoustical spectra have shown significant potential of providing valuable supplementary information regarding plasma propagation dynamics. Moreover, the general approach suggests the possibility of making the whole measurement system cost-effective and portable.

  20. 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.

  1. 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.

  2. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, Antonio J.; Butler, Michael A.; Sinclair, Michael B.; Senturia, Stephen D.

    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).

  3. 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

  4. 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 (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 (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.

  5. 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.

  6. [Identification of invoice based on laser-induced photoluminescence spectrum].

    PubMed

    Yang, Qin; Yang, Yong; Tian, Yong-hong

    2011-12-01

    The rapid identification of invoice authenticity was studied based on laser-induced photoluminescence spectrum. First, the spectral curves of eighty invoice samples were obtained by laser-induced photoluminescence detection system, and genetic algorithm (GA) was applied to fit and separate overlapped spectral region between 566 and 669 nm by three Gaussian peaks. Spectral feature parameters extracted by GA were employed as the inputs of BP neural networks, and then an identification model was built. One hundred and four data were converted to 13 Gaussian parameters, and for authentic and false invoices the coefficients of determination (R2) were 0.99789 and 0.99683 and the relative standard deviations (RSD) were 0.017052 and 0.022362, respectively. It was showed that Gaussian fitting algorithm could not only simplify the parameters of models, but also improve the explanation of analysis models. Through comparison analysis of the results, it was found that the model, whose thirteen feature parameters and two evaluated parameters were all applied as BP inputs, was the best, and the corrected identification rates of sixty calibration samples and twenty validation samples were both 100%. So the identification method studied in the present research played a good role in the classification and identification, and offered a new approach to the rapid identification of invoice authenticity. PMID:22295788

  7. 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.

  8. 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.

  9. Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

    NASA Astrophysics Data System (ADS)

    Viljanen, Jan; Sun, Zhiwei; Alwahabi, Zeyad T.

    2016-04-01

    Signal enhancements in laser-induced breakdown spectroscopy (LIBS) using external microwave power are demonstrated in ambient air. Pulsed microwave at 2.45 GHz and of 1 millisecond duration was delivered via a simple near field applicator (NFA), with which an external electric field is generated and coupled into laser induced plasma. The external microwave power can significantly increase the signal lifetime from a few microseconds to hundreds of microseconds, resulting in a great enhancement on LIBS signals with the use of a long integration time. The dependence of signal enhancement on laser energy and microwave power is experimentally assessed. With the assistance of microwave source, a significant enhancement of ~ 100 was achieved at relatively low laser energy that is only slightly above the ablation threshold. A limit of detection (LOD) of 8.1 ppm was estimated for copper detection in Cu/Al2O3 solid samples. This LOD corresponds to a 93-fold improvement compared with conventional single-pulse LIBS. Additionally, in the microwave assisted LIBS, the self-reversal effect was greatly reduced, which is beneficial in measuring elements of high concentration. Temporal measurements have been performed and the results revealed the evolution of the emission process in microwave-enhanced LIBS. The optimal position of the NFA related to the ablation point has also been investigated.

  10. 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.

  11. 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.

  12. Detection of explosives with laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  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 thermal desorption of aniline from silica surfaces

    NASA Astrophysics Data System (ADS)

    Voumard, Pierre; Zenobi, Renato

    1995-10-01

    A complete study on the energy partitioning upon laser-induced thermal desorption of aniline from silica surfaces was undertaken. The measurements include characterization of the aniline-quartz adsorption system using temperature-programmed desorption, the extrapolation of quasiequilibrium desorption temperatures to the regime of laser heating rates on the order of 109-1010 K/s by computational means, measurement of the kinetic energy distributions of desorbing aniline using a pump-probe method, and the determination of internal energies with resonance-enhanced multiphoton ionization spectroscopy. The measurements are compared to calculations of the surface temperature rise and the resulting desorption rates, based on a finite-difference mathematical description of pulsed laser heating. While the surface temperature of laser-heated silica reaches about 600-700 K at the time of desorption, the translational temperature of laser-desorbed aniline was measured to be Tkin=420±60 K, Tvib was 360±60 K, and Trot was 350±100 K. These results are discussed using different models for laser-induced thermal desorption from surfaces.

  15. 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

  16. 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.

  17. Laser-induced nucleation of carbon dioxide bubbles.

    PubMed

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

    2015-04-14

    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. PMID:25877584

  18. Compact and High Performance Spectrometers based on Novel Transmission Gratings with High Dispersion.

    PubMed

    Rasmussen, Thomas Peter

    2016-05-01

    In this article we outline how ultra-compact, yet high performance spectrometers can be designed and built with highly dispersive transmission gratings. By using fused silica as the grating material, and by careful design of the detailed grating structure, we demonstrate an ultraviolet spectrometer with a high and nearly flat efficiency from 178 to 409 nm, a resolution of 0.2 nm, and dimensions of only 61 mm × 64 mm × 19 mm. We tested this spectrometer in a laser-induced breakdown spectroscopy experiment and showed that the spectral information gathered with the spectrometer can be used to obtain quantitative results for sulfur. PMID:27002126

  19. Subwavelength gratings and applications

    NASA Astrophysics Data System (ADS)

    Yu, Zhaoning

    This Ph. D thesis investigates the fabrication and applications of subwavelength gratings. The first objective of this study is aimed at finding low-cost, high throughput fabrication techniques that are capable of producing high-quality nano-scale gratings over a relatively large scale. The second objective is to explore the applications of nano-scale gratings in subwavelength optical elements (SOE), a new type of compact, highly efficient optical devices that are compatible with semiconductor device fabrication technologies and have the potential to be suitable for integration. This thesis is divided into 5 chapters. Chapter 1 is an introduction to the subject of gratings. A brief review of the evolution of different grating fabrication methods and applications is included in this chapter. Chapters 2, 3, and Chapter 4 of the thesis are devoted to the question of nano-scale grating fabrication. Technologies concerning the generation of high spatial-frequency periodic patterns over a large scale using interference lithography (IL) are covered in Chapter 2. The role of nanoimprint lithography (NIL) as a low-cost replication tool for the production of nano-gratings is discussed in detail in Chapters 3 and 4. More specifically: Chapter 3 presents several NIL-based technologies that are used to overcome some of the limitations inherent with the interference lithography fabrication process; Chapter 4 presents a novel mask technology promising for the large-scale production of gratings by NIL. Finally, several applications of nano-scale gratings in subwavelength optical elements (SOE) are discussed in Chapter 5. Most of the SOE devices investigated in this study are based on the birefringence and the index-averaging effects of nano-gratings in the long-wavelength domain. A brief summary of the general theory 103--104 proposed by P.Yeh et al. concerning the optical properties of subwavelength gratings can be found in Appendix A. Since the orientation-dependent wet chemical etching of silicon was used extensively in this research, a relatively detailed discussion of this technique is also included in Appendix B of this dissertation.

  20. 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.

  1. Blazed phononic crystal grating

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Liu, Jingfei; Declercq, Nico F.; Laude, Vincent

    2013-01-01

    It is well known that blazed optical diffraction gratings can significantly increase the diffraction efficiency of plane waves for a selected angle of incidence. We show that by combining blazing with a phononic band gap, diffraction efficiency approaching 100% can be achieved for acoustic waves. We obtain experimentally 98% diffraction efficiency with a two-dimensional phononic crystal of rotated steel rods of square cross-section immersed in water. This result opens the way toward the design of efficient phononic crystal gratings.

  2. 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.

  3. 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.

  4. On the long time holographic grating recording process in azo-polymer

    NASA Astrophysics Data System (ADS)

    Sobolewska, Anna; Bartkiewicz, Stanislaw

    2009-09-01

    The authors report on a complex diffraction efficiency dynamics of the holographic grating recording process in azobenzene-functionalized polymer for a long recording time. The nonexponential dynamics was explain by the mechanism which assumes (i) simultaneous formation of three coupling phase gratings with constant, equal 0 or π, phase shifts between them and (ii) occurrence of gratings erasure processes when the recording time is long. Based on these assumptions and applying the Bessel function, the diffraction efficiency dynamics was calculated.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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…

  12. 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

  13. 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.

  14. 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

  15. Laser-induced jet formation in liquid films

    NASA Astrophysics Data System (ADS)

    Brasz, Frederik; Arnold, Craig

    2014-11-01

    The absorption of a focused laser pulse in a liquid film generates a cavitation bubble on which a narrow jet can form. This is the basis of laser-induced forward transfer (LIFT), a versatile printing technique that offers an alternative to inkjet printing. We study the influence of the fluid properties and laser pulse energy on jet formation using numerical simulations and time-resolved imaging. At low energies, surface tension causes the jet to retract without transferring a drop, and at high energies, the bubble breaks up into a splashing spray. We explore the parameter space of Weber number, Ohnesorge number, and ratio of film thickness to maximum bubble radius, revealing regions where uniform drops are transferred.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Laser induced bunch lengthening on the ACO storage ring FEL

    NASA Astrophysics Data System (ADS)

    Robinson, K. E.; Madey, J. M. J.; Deacon, D. A. G.; Velghe, M. F.

    1983-03-01

    The experimental procedures and data obtained during a study of the laser-induced change in the electron bunch length are reported for trials with a free-electron laser (FEL). Bunch lengthening is thought to play a critical role in the efficiency and power output of an FEL. The experimental apparatus consisted of an external laser, an undulator ring, and a nonisochronous storage ring. Synchrotron light in the storage ring was measured by a photodiode, and bunch length changes were monitored by tuning the receiver mode to a harmonic of the orbit frequency. A Gaussian electron pulse shape was assumed, together with a Gaussian envelope for the Fourier transform, which was proven in a previous experiment. The power spectra of the photodiode were modeled analytically. It was found that high current conditions alter the electron excitation and require further theoretical modeling.

  2. Total angular momentum conservation in laser-induced femtosecond magnetism

    NASA Astrophysics Data System (ADS)

    Zhang, Guoping; Bai, Yihua; George, Thomas F.

    2009-03-01

    Spin momentum is not a classical quantity [1,2]. It is unclear how the conservation law affects spin momentum change in laser-induced femtosecond magnetization [3]. In solids, the rotational symmetry is lifted by the translational symmetry, and the spin and orbital momenta components of different total angular momenta mix to some extent. This mixing is the origin of the time-dependent total angular momentum in experiments. The remaining unmixed portion accounts for an extra spin change in three independent circularly-polarized laser experiments [4]. [0pt] [1] G. P. Zhang, Y. Bai, W. H"ubner, G. Lefkidis, and T. F. George, J. Appl. Phys. 103, 07B113 (2008). [2] G. P. Zhang and W. H"ubner, Phys. Rev. Lett. 85, 3025 (2000). [3] G. P. Zhang, Phys. Rev. Lett. 101, 187203 (2008). [4] G. P. Zhang and T. F. George, Phys. Rev. B 78, 052407 (2008).

  3. 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.

  4. 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.

  5. 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.

  6. Diagnostics of laser-induced plasma by optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Cvejić, M.

    2014-12-01

    The procedure for diagnostics of laser induced plasma (LIP) by optical emission spectroscopy technique is described. LIP was generated by focusing Nd:YAG laser radiation (1.064 nm, 50 mJ, 15 ns pulse duration) on the surface of pellet containing among other elements lithium. Details of the experimental setup and experimental data processing are presented. High speed plasma photography was used to study plasma evolution and decay. From those images optimum time for plasma diagnostics is located. The electron number density, Ne, is determined by fitting profiles of Li I lines while electron temperature, Te, was determined from relative intensities of Li I lines using Boltzmann plot (BP) technique. All spectral line recordings were tested for the presence of self-absorption and then if optically thin, Abel inverted and used for plasma diagnostic purposes.

  7. Radioactive contamination screening with laser-induced fluorescence

    SciTech Connect

    Sheely, R.; 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.

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

    PubMed

    Sajzew, Roman; Schröder, Jan; Kunz, Clemens; Engel, Sebastian; Müller, Frank A; Gräf, 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 τ=300  fs, a wavelength λ=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

  9. Laser-induced single point nanowelding of silver nanowires

    NASA Astrophysics Data System (ADS)

    Dai, Shuowei; Li, Qiang; Liu, Guoping; Yang, Hangbo; Yang, Yuanqing; Zhao, Ding; Wang, Wei; Qiu, Min

    2016-03-01

    Nanowelding of nanomaterials opens up an emerging set of applications in transparent conductors, thin-film solar cells, nanocatalysis, cancer therapy, and nanoscale patterning. Single point nanowelding (SPNW) is highly demanded for building complex nanostructures. In this letter, the precise control of SPNW of silver nanowires is explored in depth, where the nanowelding is laser-induced through the plasmonic resonance enhanced photothermal effect. It is shown that the illumination position is a critical factor for the nanowelding process. As an example of performance enhancement, output at wire end can be increased by 65% after welding for a plasmonic nanocoupler. Thus, single point nanowelding technique shows great potentials for high-performance electronic and photonic devices based on nanowires, such as nanoelectronic circuits and plasmonic nanodevices.

  10. 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

  11. Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements

    NASA Astrophysics Data System (ADS)

    Priya, Mallika; Satish Rao, B. S.; Ray, Satadru; Mahato, K. K.

    2014-06-01

    In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281 nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035 mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281 nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.

  12. 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.

  13. 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

  14. 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.

  15. Particulate measurement issues in diesel exhausts using laser induced incandescence

    SciTech Connect

    Gupta, S. B.; Poola, R. B.; Sekar, R.

    2000-07-03

    A number of studies in the recent past have identified Laser Induced Incandescence (LII) as a versatile technique for in-flame measurement of soot concentrations. Recently, a number of researchers have focused their attention in adapting this technique to measure particulate in diesel exhausts. However the agreement with established physical sampling techniques, such as the EPA recommended filter paper collection method, was found to be less than ideal. This paper reports the efforts to adapt this technique for diesel exhaust characterization. Many of the factors affecting LII signal were identified through computer modeling. Parameters that could not be determined through such a model were determined experimentally following a parametric study. Subsequently, LII measurements were performed in the exhaust of a modified lab burner, with conditions close to that of diesel engine exhausts. Such measurements show excellent agreement with those performed using the standard filter paper collection technique.

  16. Synthesis of diamond by laser-induced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kitahama, Katsuki; Hirata, Kazuhiko; Nakamatsu, Hirohide; Kawai, Shichio; Fujimori, Naoji; Imai, Takahiro; Yoshino, Hiroshi; Doi, Akira

    1986-09-01

    Diamond has been obtained by ArF excimer laser-induced chemical vapor deposition. The reaction was carried out by use of C2H2 diluted with H2 as a source gas and at the pressure range of 8-75 Torr. The products were characterized by scanning electron microscopy and reflection electron diffraction. Deposits prepared in the temperature range of 40-800 °C, which were measured by the thermocouple attached to the substrate, show several lines of diamond in the reflection electron diffraction photographs. The fact that the laser beam must be concentrated for the diamond formation to occur strongly suggests that the reaction proceeds through a multiple photon process.

  17. Quantitative investigation of soot distribution by laser-induced incandescence.

    PubMed

    Bryce, D J; Ladommatos, N; Zhao, H

    2000-09-20

    Strategies employed for quantitative measurement by laser-induced incandescence are detailed. Data are obtained for several laminar diffusion flames formed from blended Diesel fuels of known composition. A tomographic procedure is developed to scale the two-dimensional data to soot volume fraction and to correct for the trapping of signal by the soot field. Scaling is achieved by use of laser extinction along the measurement plane. The findings are used in discussions of measurement issues within turbulent environments. Data are augmented with elastic scattering measurements, allowing particle-size and number-density distributions to be inferred. A degree of axial and radial similarity among various flames suggests that the processes of soot formation and oxidation occur over similar time scales for each fuel. PMID:18350100

  18. 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.

  19. Laser induced sonofusion: A new road toward thermonuclear reactions

    NASA Astrophysics Data System (ADS)

    Sadighi-Bonabi, Rasoul; Gheshlaghi, Maryam

    2016-03-01

    The Possibility of the laser assisted sonofusion is studied via single bubble sonoluminescence (SBSL) in Deuterated acetone (C3D6O) using quasi-adiabatic and hydro-chemical simulations at the ambient temperatures of 0 and -28.5 °C. The interior temperature of the produced bubbles in Deuterated acetone is 1.6 × 106 K in hydro-chemical model and it is reached up to 1.9 × 106 K in the laser induced SBSL bubbles. Under these circumstances, temperature up to 107 K can be produced in the center of the bubble in which the thermonuclear D-D fusion reactions are promising under the controlled conditions.

  20. 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.

  1. 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.

  2. 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.

  3. Uncertainty analysis of planar laser-induced fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Tavoularis, Stavros; Vanderwel, Christina

    2014-11-01

    We present a thorough analysis of the uncertainty of the planar laser-induced fluorescence (PLIF) method. We consider the measurement of concentration maps in cross-sections parallel to and normal to the axis of a slender plume containing Rhodamine 6G as a passive scalar tracer and transported by a turbulent shear flow. In particular, we identify two previously unexplored sources of error contributed by non-uniformity of the concentration across the laser sheet and by secondary fluorescence. We propose new methods to evaluate and correct for these sources of error and demonstrate that the corrected concentration measurements accurately determined the injected dye mass flow rate of the plume in the far field. Supported by NSERC.

  4. Laser-induced chemical vapor deposition of titanium diboride

    NASA Astrophysics Data System (ADS)

    Elders, J.; v. Voorst, J. D. W.

    1994-01-01

    This paper investigates the CO(sub 2) laser induced chemical vapor deposition of titanium diboride by the H(sub 2) reduction of TiCl(sub 4) and BCl(sub 3), wherein the limitation on heat diffusion induces dendritic growth on alumina, while at higher temperatures the deposition becomes mass diffusion limited in addition to being heat diffusion limited. Variations in the hydrogen concentration has a big impact on the apparent activation energy, the growth rate, and the morphology - resulting in retarded growth, and smooth, dense morphology at high H(sub 2) concentrations. The 193 nm wavelength of the ArF excimer laser responsible for dissociating titanium tetrachloride, can increase the growth rate by a factor of two. High deposition temperatures probably enhance the growth rate is enhanced due to increased crystal growth, presumably due to the partly dissociated titanium tetrachloride.

  5. Laser induced fluorescence applied to turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Daily, J. W.

    1976-01-01

    The saturated fluorescence method makes use of the great simplifications which occur when under conditions of intense radiation the excitation process becomes saturated. A description is presented of the saturated fluorescence method, taking into account rate equations and saturation, radiative transfer, the two-level system, a multilevel system, and measurements under saturation conditions. The detectability limits of the method are investigated. Fluorescence trapping is found to place an upper limit on the number density of the fluorescing species that can be measured without signal loss. Turbulence places time and spatial constraints on the measurements, but otherwise poses no difficulties. Saturated laser induced fluorescence spectroscopy appears to be a most promising method for measuring species concentrations in flames.

  6. 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.

  7. 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.

  8. Laser induced breakdown spectroscopy for the discrimination of Candida strains.

    PubMed

    Manzoor, S; Ugena, L; Tornero-Lopéz, J; Martín, H; Molina, M; Camacho, J J; Cáceres, J O

    2016-08-01

    The present study reports the evaluation of Laser Induced Breakdown Spectroscopy (LIBS) and Neural Networks (NN) for the discrimination of different strains of various species of Candida. This genus of yeast was selected due to its medical relevance as it is commonly found in cases of fungal infection in humans. Twenty one strains belonging to seven species of Candida were included in the study. Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) was employed as a complementary technique to provide information about elemental composition of Candida cells. The use of LIBS spectra in combination with optimized NN models provided reliable discrimination among the distinct Candida strains with a high spectral correlation index for the samples analyzed, without any false positive or false negative. Therefore, this study indicates that LIBS-NN based methodology has the potential to be used as fast fungal identification or even diagnostic method. PMID:27216662

  9. Aluminum monoxide emission measurements in a laser-induced plasma.

    PubMed

    Surmick, David M; Parigger, Christian G

    2014-01-01

    We report temperature inferences from time-resolved emission spectra of a micro-sized plasma following laser ablation of an aluminum sample. The laser-induced breakdown event is created with the use of nanosecond pulsed laser radiation. Plasma temperatures are inferred from the aluminum monoxide spectroscopic emissions of the aluminum sample by fitting experimental to theoretically calculated spectra with a nonlinear fitting algorithm. The synthetic spectra used as a comparison for the experimental spectra are generated from accurate line strengths of aluminum monoxide bands. The inferred plasma temperatures are found to be 5315 ± 100 K at 20 μs following breakdown. At later time delays of 45 and 70 μs following breakdown, the plasma temperatures are found to be 4875 ± 95 and 4390 ± 80 K, respectively. Error analysis of the inferred temperatures is performed with the fitting algorithm. PMID:25226252

  10. 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.

  11. Noninvasive thermography of laser-induced hyperthermia using magnetic resonance

    NASA Astrophysics Data System (ADS)

    Maswadi, Saher M.; Glickman, Randolph D.; Dodd, Stephen J.; Gao, Jia Hong

    2004-07-01

    The possibility to induce selective hyperthermia in a target tissue or organ is of great interest for the treatment of cancer and other diseases. An emerging application of thermotherapy is for choroidal neovascularization, a complication of age-related macular degeneration. The therapy is currently limited because the temperature required for optimal tissue response is unknown. We report here an investigation of near infrared laser-induced heating in an ocular phantom. Magnetic resonance thermography (MRT) was used as a non-invasive method to determine the temperature distribution inside the phantom during exposure to a continuous wave diode laser at 806 nm wavelength with 1 watt maximum output. The laser beam had a quasi-gaussian profile, with a radius of 0.8-2.4 mm at target. High quality temperature images were obtained from temperature-dependent phase shifts in the proton resonance frequency with a resolution of 1deg C or better, using a 2T magnet. A phantom with a layer of bovine RPE melanin of 1.5 mm thickness was used to determine the spatial resolution of the MRT measurements. Three dimensional temperature maps were also constructed showing a spatial resolution of 0.25 mm in all direction. The heat distribution depended on the laser parameters, as well as the orientation of the melanin layer with respect to the incident laser beam. The temperature profiles determined by MRT closely followed predictions of a heat diffusion model, based on the optical properties of infrared light in melanin. These results support the use of MRT to optimize laser-induced hyperthermia in a small organ such as the eye.

  12. 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.

  13. 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.

  14. 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.

  15. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B.

    1986-01-01

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  16. 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.

  17. Time-resolved laser-induced plasma spectrometry for determination of minor elements in steelmaking process samples.

    PubMed

    Cabalín, L M; Romero, D; García, C C; Baena, J M; Laserna, J J

    2002-01-01

    A pulsed Nd:YAG laser operating on the fourth (266 nm) and second (532 nm) harmonics has been used to generate plasmas on the target surface in air at atmospheric pressure. The influence of wavelength on quantitative analysis of 4 minor elements in stainless steel samples (Si, Ti, Nb and Mo) was investigated. Stainless steel samples with different elemental concentrations were prepared and analyzed by laser-induced plasma spectrometry (LIPS). The effect of laser wavelength on analytical figures of merit (calibration curves, correlation coefficients, linear dynamic ranges, analytical precision, and accuracy values) was found to be negligible when internal standardization (an Fe line) and time-resolved laser-induced plasma are employed. For both wavelengths, the calibration curves presented a good linearity and an acceptable linear dynamic range in the concentration interval investigated. For the four elements studied, limits of detection lower than 150 microg g(-1) were achieved. To evaluate the influence of wavelength on precision and accuracy, a set of fifteen high-alloyed steel samples from different stages of steelmaking process have been analyzed. Finally, the long-term stability of the analytical measurements for Mo with 532 nm wavelength has been discussed. RSD values were lower than 5.3% for the elements studied. PMID:11936111

  18. 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.

  19. Development of laser induced breakdown spectroscopy instrumentatin for safeguards applications

    SciTech Connect

    Barefield Il, James E; Clegg, Samuel M; Le, Loan A; Lopez, Leon N

    2010-01-01

    In September 2006, a Technical Meeting on Application of Laser Spectrometry Techniques in IAEA Safeguards was held at IAEA headquarters (HQ). One of the principal recommendations from this meeting was the need to 'pursue the development of novel complementary access instrumentation based on laser induced breakdown spectroscopy (LIBS) for the detection of gaseous and solid signatures and indicators of nuclear fuel cycle processes and associated materials.' Pursuant to this recommendation the Department of Safeguards (SG) under the Division of Technical Support (SGTS) convened the Experts and Users Advisory Meeting on Laser Induced Breakdown Spectroscopy (LIBS) for Safeguards Applications. This meeting was held at IAEA HQ from July 7-11,2008 and hosted by the Novel Technologies Unit (NTU). The meeting was attended by 12 LIBS experts from the Czech Republic, the European Commission, France, the Republic of Korea, the United States of America, Germany, the United Kingdom of Great Britain, Canada, and Northern Ireland. After a presentation of the needs of the IAEA inspectors, the LIBS experts were in agreement that needs as presented could be partially or fully fulfilled using LIBS instrumentation. The needs of the IAEA inspectors were grouped in the following broad categories: (1) Improvements to in-field measurements/environmental sampling; (2) Monitoring status of activity in a Hot Cell; (3) Verifying status of activity at a declared facility via process monitoring; and (4) Need for pre-screening of environmental samples before analysis. Under the Department of Energy/National Nuclear Security Administration (DOE/NNSA) Next Generation Safeguards Initiative (NGSI) Los Alamos National Laboratory is exploring three potential applications of LIBS for international safeguards. As part of this work, we are developing: (1) a user-friendly man-portable LIBS system to characterize samples across a wide range of elements in the periodic table from hydrogen up to heavy elements like plutonium and uranium; (2) a LIBS system that can be deployed in harsh environments such as gloveboxes and hot cells providing relative compositional analysis of process streams for example ratios like Cm/Pu and Cm/U; and (3) an inspector field deployable system that can be used to analyze the elemental composition of microscopic quantities of samples containing plutonium and uranium. In this paper we will describe our current development and performance testing results both in a fixed lab and measurements in field deployable configurations using LIBS instrumentation developed for applications to international safeguards.

  20. 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.

  1. Theoretical analysis for temperature dependence of laser- induced damage threshold of optical thin films

    NASA Astrophysics Data System (ADS)

    Mikami, K.; Motokoshi, S.; Somekawa, T.; Jitsuno, T.; Fujita, M.; Tanaka, KA; Azechi, H.

    2016-03-01

    The temperature dependence of the laser-induced damage threshold on optical coatings was studied in detail for laser pulses from 123 K to 473 K at different temperatures. The laser-induced damage threshold increased with decreasing temperatures when we tested long pulses (200 ps and 4 ns). The temperature dependence, however, was reversed for pulses shorter than a few picoseconds (100 fs testing). We propose a scaling model with a flowchart that includes three separate processes: free-electron generation, electron multiplication, and electron heating. Furthermore, we calculated the temperature dependence of laser-induced damage thresholds at different temperatures. Our calculation results agreed well with the experimental results.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Line selection and parameter optimization for trace analysis of uranium in glass matrices by laser-induced breakdown spectroscopy (LIBS).

    PubMed

    Choi, Inhee; Chan, George C-Y; Mao, Xianglei; Perry, Dale L; Russo, Richard E

    2013-11-01

    Laser-induced breakdown spectroscopy (LIBS) has been evaluated for the determination of uranium in real-world samples such as uraninite. NIST Standard Reference Materials were used to evaluate the spectral interferences on detection of uranium. The study addresses the detection limit of LIBS for several uranium lines and their relationship to non-uranium lines, with emphasis on spectral interferences. The data are discussed in the context of optimizing the choice of emission lines for both qualitative and quantitative analyses from a complex spectrum of uranium in the presence of other elements. Temporally resolved spectral emission intensities, line width, and line shifts were characterized to demonstrate the parameter influence on these measurements. The measured uranium line width demonstrates that LIBS acquired with moderately high spectral resolution (e.g., by a 1.25 m spectrometer with a 2400 grooves/mm grating) can be utilized for isotope shift measurements in air at atmospheric pressure with single to tens of parts per million (ppm) level detection limits, as long as an appropriate transition is chosen for analysis. PMID:24160879

  8. Simultaneous Raman spectroscopy-laser-induced breakdown spectroscopy for instant standoff analysis of explosives using a mobile integrated sensor platform.

    PubMed

    Moros, Javier; Lorenzo, Juan Antonio; Lucena, Patricia; Tobaria, Luciano Miguel; Laserna, José Javier

    2010-02-15

    A novel experimental design combining Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) in a unique integrated sensor is described. The sensor presented herein aims to demonstrate the applicability of a hybrid dual Raman-LIBS system as an analytical tool for the standoff analysis of energetic materials. Frequency-doubled 532 nm Nd:YAG nanosecond laser pulses, first expanded and then focused using a 10x beam expander on targets located at 20 m, allowed simultaneous acquisition of Raman-LIBS spectra for 4-mononitrotoluene (MNT), 2,6-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), C4 and H15 (plastic explosives containing 90% and 75% of RDX by weight, respectively), and Goma2-ECO (Spanish denominated dynamite class high explosive mainly composed of ammonium nitrate, nitroglycol, and dinitrotoluene among other compounds), sodium chlorate, and ammonium nitrate. With the use of a Cassegrain telescope, both Raman and LIBS signals from the same laser pulses were collected and conducted through a bifurcated optical fiber into two identical grating spectrographs coupled to intensified charge-coupled device (iCCD) detectors. With the use of the appropriate timing for each detection mode, adjustment of the laser power on the beam focal conditions is not required. The ability of the present single hybrid sensor to simultaneously acquire, in real time, both molecular and multielemental information from the same laser pulses on the same cross section of the sample at standoff distances greatly enhances the information power of this approach. PMID:20085236

  9. High-speed machining of glass materials by laser-induced plasma-assisted ablation using a 532-nm laser

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Sugioka, K.; Midorikawa, K.

    In this communication, we report a high-speed machining of glass materials by a novel laser ablation technique using a conventional visible laser for the first time. A high-quality micrograting structure is fabricated in fused quartz by laser-induced plasma-assisted ablation (LIPAA) using a second harmonic of Q-switched Nd+:YAG laser (532 nm). The plasma generated from a silver (Ag) target by the laser irradiation effectively assists in ablation of the fused quartz substrate by the same laser beam, although the laser beam is transparent to the substrate. A grating with a cross-sectional shape like a square-wave (period 20 μm) is achieved using the mask projection technique. The ablation rate reaches several tens nm/pulse. In addition, LIPAA is applied to high-speed hole drilling (700 μm in diameter) of fused-quartz (0.5 mm thick) and Pyrex glass (0.5 mm thick).

  10. 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.

  11. Binary gratings with random heights

    SciTech Connect

    Rico-Garcia, Jose Maria; Sanchez-Brea, Luis Miguel

    2009-06-01

    We analyze the far-field intensity distribution of binary phase gratings whose strips present certain randomness in their height. A statistical analysis based on the mutual coherence function is done in the plane just after the grating. Then, the mutual coherence function is propagated to the far field and the intensity distribution is obtained. Generally, the intensity of the diffraction orders decreases in comparison to that of the ideal perfect grating. Several important limit cases, such as low- and high-randomness perturbed gratings, are analyzed. In the high-randomness limit, the phase grating is equivalent to an amplitude grating plus a ''halo.'' Although these structures are not purely periodic, they behave approximately as a diffraction grating.

  12. 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.

  13. 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

  14. 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.

  15. Laser-induced Forward Transfer of Ag Nanopaste

    PubMed Central

    Breckenfeld, Eric; Kim, Heungsoo; Auyeung, Raymond C. Y.; Piqué, Alberto

    2016-01-01

    Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip. PMID:27077645

  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. 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.

  18. 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

  19. Hyperspectral laser-induced autofluorescence imaging of dental caries

    NASA Astrophysics Data System (ADS)

    Bürmen, Miran; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan

    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.

  20. Slag analysis with laser-induced breakdown spectrometry.

    PubMed

    Kraushaar, M; Noll, R; Schmitz, H U

    2003-10-01

    Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis. PMID:14639759

  1. Multiphoton laser-induced-fluorescence studies of simple species

    SciTech Connect

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

    1983-01-01

    Recent studies have demonstrated multiple-photon excitation of atomic species. Bischel and coworkers have provided a detailed description of two-photon excitation fluorescence in the detection of atoms generated in a low pressure discharge and its possible application as a diagnostic tool in flame and plasmas. It is also believed that such techniques can be useful in detecting molecular transients which are difficult to detect otherwise as demonstrated in two-photon laser-induced fluorescence (LIF) detection of NO. In this paper, we discuss our recent two-photon LIF studies on I and Br atoms, which are produced via laser photolysis of molecular precursors. The two-photon LIF study of HS and DS radicals is presented as a test case for the detection of other important radical species such as C/sub 2/H and CH/sub 3/, which are currently being investigated in our laboratory. In addition, excitation of three-photon resonances of I/sub 2/, N/sub 2/, and H/sub 2/ is discussed.

  2. Multiphoton laser-induced fluorescence studies of simple species

    SciTech Connect

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

    1983-01-01

    Recent studies have demonstrated multiple-photon excitation of atomic species. Bischel and coworkers have provided a detailed description of two-photon excitation fluorescence in the detection of atoms generated in a low pressure discharge and its possible application as a diagnostic tool in flame and plasmas. It is also believed that such techniques can be useful in detecting molecular transients which are difficult to detect otherwise as demonstrated in two-photon laser-induced fluorescence (LIF) detection of NO. In this paper, recent two-photon LIF studies on I and Br atoms are discussed, which are produced via laser photolysis of molecular precursors. The two-photon LIF study of HS and DS radicals is presented as a test case for the detection of other important radical species such as C/sub 2/H and CH/sub 3/, which are currently being investigated in the laboratory. In addition, excitation of three-photon resonances of I/sub 2/, N/sub 2/, and H/sub 2/ is discussed.

  3. 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.

  4. 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.

  5. Kalman filtered MR temperature imaging for laser induced thermal therapies.

    PubMed

    Fuentes, D; Yung, J; Hazle, J D; Weinberg, J S; Stafford, R J

    2012-04-01

    The feasibility of using a stochastic form of Pennes bioheat model within a 3-D finite element based Kalman filter (KF) algorithm is critically evaluated for the ability to provide temperature field estimates in the event of magnetic resonance temperature imaging (MRTI) data loss during laser induced thermal therapy (LITT). The ability to recover missing MRTI data was analyzed by systematically removing spatiotemporal information from a clinical MR-guided LITT procedure in human brain and comparing predictions in these regions to the original measurements. Performance was quantitatively evaluated in terms of a dimensionless L(2) (RMS) norm of the temperature error weighted by acquisition uncertainty. During periods of no data corruption, observed error histories demonstrate that the Kalman algorithm does not alter the high quality temperature measurement provided by MR thermal imaging. The KF-MRTI implementation considered is seen to predict the bioheat transfer with RMS error < 4 for a short period of time, ∆t < 10 s, until the data corruption subsides. In its present form, the KF-MRTI method currently fails to compensate for consecutive for consecutive time periods of data loss ∆t > 10 sec. PMID:22203706

  6. 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 α(φ)), where D is final site diameter, D0 is the initial diameter of the site, φ is the laser fluence, α(φ) is the growth coefficient, and n is the number of exposures. In general α is a linear function of φ, with a threshold of φTH. In recent years, it has been found that that growth behavior is actually considerably more complex. For example, it was found that α is not a constant for a given fluence but follows a probability distribution with a mean equal to α(φ). 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.

  7. 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.

  8. Lead determination in glasses by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Carmona, N.; Oujja, M.; Gaspard, S.; García-Heras, M.; Villegas, M. A.; Castillejo, M.

    2007-02-01

    Laser-induced breakdown spectroscopy (LIBS) has been used to determine the lead content of different types of lead silicate glasses commercially designed as sonorous glass (which contain ˜ 10 wt.% PbO); crystal glass (with at least 24 wt.% PbO) and superior crystal glass (with at least 30 wt.% PbO). Seven different types of glass samples were selected, including historic-original, model and commercially available. The selected samples were artificially weathered under neutral, acid and alkaline attack. Analysis by LIBS was carried out in vacuum under excitation at 266 nm and results were compared with those obtained by conventional techniques used for glass characterization. Composition of the bulk glasses was analyzed by XRF (X-ray fluorescence) and the corroded surfaces were characterized by SEM/EDX (scanning electron microscopy/energy dispersive X-ray microanalysis). A linear correlation was obtained between the intensity of selected Pb lines in the LIB spectra and the PbO content. The effect of corrosion could be characterized by comparing successive LIB spectra recorded on the same area; acid attack resulted in a decrease of PbO, CaO and Na 2O content in the surface with respect to the bulk of the sample, while minor changes in the composition were noticed under alkaline attack. These results show LIBS as a useful technique to classify the different types of lead glasses by their lead content and to determine and asses the degree and type of corrosion.

  9. The motional stark effect with laser-induced fluorescence diagnostic

    NASA Astrophysics Data System (ADS)

    Foley, E. L.; Levinton, F. M.

    2010-05-01

    The motional Stark effect (MSE) diagnostic is the worldwide standard technique for internal magnetic field pitch angle measurements in magnetized plasmas. Traditionally, it is based on using polarimetry to measure the polarization direction of light emitted from a hydrogenic species in a neutral beam. As the beam passes through the magnetized plasma at a high velocity, in its rest frame it perceives a Lorentz electric field. This field causes the H-alpha emission to be split and polarized. A new technique under development adds laser-induced fluorescence (LIF) to a diagnostic neutral beam (DNB) for an MSE measurement that will enable radially resolved magnetic field magnitude as well as pitch angle measurements in even low-field (<1 T) experiments. An MSE-LIF system will be installed on the National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory. It will enable reconstructions of the plasma pressure, q-profile and current as well as, in conjunction with the existing MSE system, measurements of radial electric fields.

  10. 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.

  11. Applications of laser-induced breakdown spectroscopy to environmental monitoring

    SciTech Connect

    Cremers, D.A.; Ferris, M.J.; Foster, L.E.

    1994-12-31

    Focusing powerful laser pulses in a gas or liquid or on a solid produces a microplasma that vaporizes and excites a small amount of the material. By spectrally resolving the plasma emission, the elemental composition of the material can be determined. This method, termed laser-induced breakdown spectroscopy (LIBS), has many potential applications to environmental monitoring. These include the detection of toxic particles in air, the detection of contaminants on surfaces including lead in paint, and the analysis of soil for metals. Advantages of LIBS that make it particularly suited for field-based monitoring include: simplicity, multielement detection capability, minimal sample preparation, and remote analysis capability. In addition, the method can provide useful monitoring capabilities and possible with many other analysis techniques. For example, beryllium particles can be detected directly in air at levels of 1 microgram/cubic meter which is sufficient to provide warning of concentrations approaching harmful levels and lead in paint can be detected at concentrations down to 0.05 milligrams/sq. cm, significantly below required levels. Remote LIBS analysis is provided by focusing the laser pulses at a distance directly on a surface or by fiber optic delivery of the laser energy. Examples of the use of LIBS for these and other environmental monitoring situations will be discussed, some analytical results presented, and examples of prototype instrumentation described.

  12. Applications of laser-induced breakdown spectroscopy to environmental monitoring

    SciTech Connect

    Cremers, D.A.; Ferris, M.J.; Foster, L.E.

    1994-12-31

    Focusing powerful laser pulses in a gas or liquid or on a solid produces a microplasma that vaporizes and excited a small amount of the material. By spectrally resolving the plasma emission, the elemental composition of the material can be determined. This method, termed laser-induced breakdown spectroscopy (LIBS), has many potential applications to environmental monitoring. These include the detection of toxic particles in air, the detection of contaminants on surfaces including lead in paint, and the analysis of soil for metals. Advantages of LIBS that make it particularly suited for field-based monitoring include: simplicity, multielement detection capability, minimal sample preparation, and remote analysis capability. In addition, the method can provide useful monitoring capabilities not possible with many other analysis techniques. For example, beryllium particles can be detected directly in air at levels of 1 microgram/cubic meter which is sufficient to provide warning of concentrations approaching harmful levels and lead in paint can be detected at concentrations down to 0.05 milligrams/sq. cm, significantly below required levels. Remote LIBS analysis is provided by focusing the laser pulses at a distance directly on a surface or by fiber optic delivery of the laser energy. Examples of the use of LIBS for these and other environmental monitoring situations will be discussed, some analytical results presented, and examples of prototype instrumentation described.

  13. 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

  14. 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

  15. 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.

  16. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    NASA Astrophysics Data System (ADS)

    Forni, Olivier; Maurice, Sylvestre; Gasnault, Olivier; Wiens, Roger C.; Cousin, Agnès; Clegg, Samuel M.; Sirven, Jean-Baptiste; Lasue, Jérémie

    2013-08-01

    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Cavity ringdown and laser-induced incandescence measurements of soot.

    PubMed

    Vander Wal, R L; Ticich, T M

    1999-03-20

    Currently laser-induced incandescence (LII) is widely used for the measurement of soot volume fraction. A particularly important aspect of the technique that has received less attention, however, is calibration. The applicability of cavity ringdown (CRD) for measurement of soot volume fraction f(v) is assessed, and the calibration of LII by means of CRD is demonstrated. The accuracy of CRD for f(v) determination is validated by comparison with traditional light extinction and path-integrated LII. By use of CRD, the quantification of LII for parts in 10(9) (ppb) f(v) levels is demonstrated. Results are presented that demonstrate the accuracy of CRD for a single laser pulse to be better than ?5% for measurement of ppb soot volume-fraction levels over a 1-cm path length. By use of CRD, spatially resolved LII signals from soot within methane-air diffusion flames are calibrated for ppb f(v) levels, thereby avoiding the extrapolation required of less sensitive methods in current use. PMID:18305765

  2. Measuring turbulent fluid dispersion using laser induced phosphorescence

    NASA Astrophysics Data System (ADS)

    van der Voort, Dennis; Dam, Nico; van de Water, Willem; Kunnen, Rudie; Clercx, Herman; van Heijst, Gertjan

    2015-11-01

    Fluid dispersion due to turbulence is an important subject in both natural and engineering processes, from cloud formation to turbulent mixing and liquid spray combustion. The combination of small scales and often high velocities results in few experimental techniques that can follow the course of events. We introduce a novel technique, which measures the dispersion of ``tagged'' fluid particles by means of laser-induced phosphorescence, using a solution containing a europium-based molecular complex with a relatively long phosphorescence half-life. This technique is used to measure transport processes in both the dispersion of droplets in homogeneous isotropic turbulence and the dispersion of fluid of near-nozzle spray breakup processes. By tagging a small amount of droplets/fluid via laser excitation, the tagged droplets can be tracked in a Lagrangian way. The absolute dispersion of the droplets can be measured in a variety of turbulent flows. Using this technique it is shows that droplets around St =τp /τη ~ 1 (Stokes number) disperse faster than true fluid tracers in homogeneous isotropic turbulence, as well as differences between longitudinal and radial dispersion in turbulent sprays. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Dutch Organisation for Scientific Research (NWO).

  3. 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.

  4. 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 Δt 12 = 5.32 μs) 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 ˜2-3 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 (˜20-30 nm layers) in the near-surface region.

  5. 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.

  6. [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

  7. 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.

  8. 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.

  9. Kalman Filtered MR Temperature Imaging for Laser Induced Thermal Therapies

    PubMed Central

    Fuentes, D.; Yung, J.; Hazle, J. D.; Weinberg, J. S.; Stafford, R. J.

    2013-01-01

    The feasibility of using a stochastic form of Pennes bioheat model within a 3D finite element based Kalman filter (KF) algorithm is critically evaluated for the ability to provide temperature field estimates in the event of magnetic resonance temperature imaging (MRTI) data loss during laser induced thermal therapy (LITT). The ability to recover missing MRTI data was analyzed by systematically removing spatiotemporal information from a clinical MR-guided LITT procedure in human brain and comparing predictions in these regions to the original measurements. Performance was quantitatively evaluated in terms of a dimensionless L2 (RMS) norm of the temperature error weighted by acquisition uncertainty. During periods of no data corruption, observed error histories demonstrate that the Kalman algorithm does not alter the high quality temperature measurement provided by MR thermal imaging. The KF-MRTI implementation considered is seen to predict the bioheat transfer with RMS error < 4 for a short period of time, Δt < 10sec, until the data corruption subsides. In its present form, the KF-MRTI method currently fails to compensate for consecutive for consecutive time periods of data loss Δt > 10sec. PMID:22203706

  10. Fast analysis of wood preservers using laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Uhl, A.; Loebe, K.; Kreuchwig, L.

    2001-06-01

    Laser-induced breakdown spectroscopy (LIBS) is used for the investigation of wood preservers in timber and in furniture. Both experiments in laboratory and practical applications in recycling facilities and on a building site prove the new possibilities for the fast detection of harmful agents in wood. A commercial system was developed for mobile laser-plasma-analysis as well as for industrial use in sorting plants. The universal measuring principle in combination with an Echelle optics permits real simultaneous multi-element-analysis in the range of 200-780 nm with a resolution of a few picometers. It enables the user to detect main and trace elements in wood within a few seconds, nearly independent of the matrix, knowing that different kinds of wood show an equal elemental composition. Sample preparation is not required. The quantitative analysis of inorganic wood preservers (containing, e.g. Cu, Cr, B, As, Pb, Hg) has been performed exactly using carbon as reference element. It can be shown that the detection limits for heavy metals in wood are in the ppm-range. Additional information is given concerning the quantitative analysis. Statistical data, e.g. the standard deviation (S.D.), were determined and calibration curves were used for each particular element. A comparison between ICP-AES and LIBS is given using depth profile correction factors regarding the different penetration depths with respect to the different volumes in wood analyzed by both analytical methods.

  11. Laser-induced porous graphene films from commercial polymers.

    PubMed

    Lin, Jian; Peng, Zhiwei; Liu, Yuanyue; Ruiz-Zepeda, Francisco; Ye, Ruquan; Samuel, Errol L G; Yacaman, Miguel Jose; Yakobson, Boris I; Tour, James M

    2014-01-01

    The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp(3)-carbon atoms are photothermally converted to sp(2)-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4 mF cm(-2) and power densities of ~9 mW cm(-2). Theoretical calculations partially suggest that enhanced capacitance may result from LIG's unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices. PMID:25493446

  12. Laser-induced porous graphene films from commercial polymers

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Peng, Zhiwei; Liu, Yuanyue; Ruiz-Zepeda, Francisco; Ye, Ruquan; Samuel, Errol L. G.; Yacaman, Miguel Jose; Yakobson, Boris I.; Tour, James M.

    2014-12-01

    The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO2 infrared laser. The sp3-carbon atoms are photothermally converted to sp2-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4 mF cm-2 and power densities of ~9 mW cm-2. Theoretical calculations partially suggest that enhanced capacitance may result from LIG’s unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices.

  13. Laser Induced Breakdown Spectroscopy of Glass and Crystal Samples

    NASA Astrophysics Data System (ADS)

    Sharma, Prakash; Sandoval, Alejandra; Carter, Michael; Kumar, Akshaya

    2015-03-01

    Different types of quartz crystals and rare earth ions doped glasses have been identified using the laser induced breakdown spectroscopy (LIBS) technique. LIBS is a real time technique, can be used to identify samples in solid, liquid and gas phases. The advantage of LIBS technique is that no sample preparation is required and laser causes extremely minimal damage to the sample surface. The LIBS spectrum of silicate glasses, prepared by sol-gel method and doped with different concentration of rare earth ions, has been recorded. The limit of detection of rare earth ions in glass samples has been calculated. Total 10 spectrums of each sample were recorded and then averaged to get a final spectrum. The ocean optics LIBS2500 plus spectrometer along with a Q- switched Nd: YAG laser (Quantel, Big Sky) were used to record the LIBS spectrum. This spectrometer can analyze the sample in the spectral range of 200 nm to 980 nm. The spectrum was processed by OOILIBS-plus (v1.0) software. This study has application in the industry where different crystals can be easily identified before they go for shaping and polishing. Also, concentration of rare earth ions in glass can be monitored in real time for quality control.

  14. 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

  15. Construction of a Laser Induced Breakdown Spectroscopy Setup

    NASA Astrophysics Data System (ADS)

    Mays, Joseph; Palmer, Andria; Amos, James; Dynka, Tom; Ujj, Lazlo

    Laser Induced Breakdown Spectroscopy (LIBS) is a practical spectroscopy to determine the chemical and atomic composition of materials. The third harmonic output of a Nd:YAG Q-switched laser generating 5ns pulses with 10Hz repetition rate was used to ablate the sample and create a micro-plasma. The emission of the radiating plasma was focused into an optical fiber with 0.22 numerical aperture. The spectra was measured with an Ocean Optics micro spectrometer. A synchronized shutter was used to select single laser pulses. In order to reach the breakdown threshold of the sample using the available energy of the laser pulses (<5 mJ) a beam expander and a parabolic mirror was used for tight focusing. The optical and technical details including the characterization of the system will be presented. LIBS spectra taken from a variety of metal and organic samples show appropriate selectivity for quantitative and qualitative analysis for materials. UWF NIH MARC U-STAR 1T34GM110517-01, UWF Office of Undergraduate Research.

  16. 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

  17. Laser-induced plasma-assisted ablation and its applications

    NASA Astrophysics Data System (ADS)

    Hong, Ming Hui; Sugioka, Koji; Wu, Dong Jiang; Chew, K. J.; Lu, Y. F.; Midorikawa, Katsumi; Chong, Tow Chong

    2003-02-01

    It is a high challenge to fabricate glass microstructures in Photonics and LCD industries. Different from direct ablation with ultrafast or short wavelength lasers, laser-induced-plasma-assisted ablation (LIPAA) is one of the potential candidates for transparent substrate microfabrication with conventional visible laser sources. In the processing, laser beam goes through glass substrate first and then irradiates on a solid target behind. For laser fluence above target ablation threshold, plasma generated from target ablation flies forward at a high speed. At a small target-to-substrate distance, there are strong interactions among laser light, target plasma and glass substrate at its rear side surface. With target materials deposition on glass surface or even doping into the substrate, light absorption characteristic at the interaction zone is modified, which causes the glass ablation. LIPAA is used to get color printing of characters, structures and even images on the glass substrate. It is also used to obtain the glass surface metallization for electrodes and circuits fabrication. Potential application of this technique to fabricate functional microstructures, such as micro-Total-Analysis-System (TAS) for DNA analysis and holographic diffuser for IR wireless home networking, is also discussed.

  18. Laser-induced Forward Transfer of Ag Nanopaste.

    PubMed

    Breckenfeld, Eric; Kim, Heungsoo; Auyeung, Raymond C Y; Piqué, Alberto

    2016-01-01

    Over the past decade, there has been much development of non-lithographic methods(1-3) for printing metallic inks or other functional materials. Many of these processes such as inkjet(3) and laser-induced forward transfer (LIFT)(4) have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)(5-9), has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip. PMID:27077645

  19. 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 mF·cm−2 and power densities of ~9 mW·cm−2. Theoretical calculations partially suggest that enhanced capacitance may result from LIG’s unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices. PMID:25493446

  20. Laser-induced fluorescence temperature measurements in natural convection flowfields

    SciTech Connect

    Donohue, J.M.

    1997-07-01

    Planar laser-induced iodine fluorescence temperature measurements are presented in natural convection flowfields. The technique can be used to make spatially-resolved measurements in complex three-dimensional flowfields. The flowfield measured consists of a cubic enclosure, 8 inches on a side, with a one inch heated cube sitting on the bottom surface of the enclosure. An additional measurement is made where a glass plate is placed above the heated cube to divert the plume and makes the flowfield considerably more complex. The side and bottom walls of the enclosure are made of glass and the top wall is made of aluminum and is held at a constant temperature close to room temperature. A laser sheet is passed through a plane at the center of the flowfield. A fluorescence image, from trace amounts of iodine vapor introduced into the test cell, is collected with a cooled CCD camera. For the uniform seeding fraction, uniform absolute pressure conditions present in the test cell, the fluorescence intensities are functions only of the local temperature of the flow. The image intensities are scaled using a theoretical model of the fluorescence. For the tests presented here temperatures ranged from 20 to 150 C although the technique could be applied to significantly higher temperature conditions. The accuracy is estimated to be 4 C.

  1. 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.

  2. 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

  3. Imaging of the expansion of femtosecond-laser-produced silicon plasma atoms by off-resonant planar laser-induced fluorescence.

    PubMed

    Samek, Ota; Leis, Franz; Margetic, Vanja; Malina, Radomir; Niemax, Kay; Hergenröder, Roland

    2003-10-20

    Planar laser-induced fluorescence measurements were used to investigate the expansion dynamics of a femtosecond laser-induced plasma. Temporally and spatially resolved measurements were performed to monitor the atoms that were ablated from a silicon target. A dye laser (lambda = 288.16 nm) was used to excite fluorescence signals. The radiation of an off-resonant transition (Si 390.55 nm) was observed at different distances from the target surface. This allowed easy detection of the ablated Si atoms without problems caused by scattered laser light. Abel inversion was applied to obtain the radial distribution of the Si atoms. The atom distribution in the plasma shows some peculiarities, depending on the crater depth. PMID:14594057

  4. 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.

  5. Detection of chemically-induced dysplasia in rat urinary bladder with laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Schomacker, Kevin T.; Flotte, Thomas J.; Deutsch, Thomas F.

    1994-05-01

    The ability of laser-induced fluorescence (LIF) to detect flat dysplasia has not been carefully studied. A multiexcitation wavelength LIF system was used to develop an algorithm to detect chemically-induced dysplasia in the rat urinary bladder.

  6. Analysis of lead and sulfur in environmental samples by double pulse laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Burakov, V. S.; Tarasenko, N. V.; Nedelko, M. I.; Kononov, V. A.; Vasilev, N. N.; Isakov, S. N.

    2009-02-01

    In the present work, a model of double pulse laser-induced breakdown spectroscopy (LIBS) spectrometer has been developed and results from two different applications of double pulse LIBS for solving the problems of environmental interest are presented. In one case, laser induced breakdown spectroscopy has been applied to the determination of heavy and toxic metals (lead) in soil samples. In the second case, laser induced breakdown spectroscopy was used in preliminary experiments for the detection of sulfur content in coal, and on the basis of spectral features, ways to improve the sensitivity of laser induced breakdown spectroscopy detection of sulfur are proposed. The detection limit for lead in soil was estimated to be approximately 20 ppm that is lower than the regulatory standards for the presence of lead in soil.

  7. 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.

  8. 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.

  9. 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...

  10. Investigation on the laser-induced shock pressure with condensed matter model

    NASA Astrophysics Data System (ADS)

    Zhai, Pengcheng; Dong, Zhewei; Miao, Rui; Deng, Xiaoxu; Chen, Lei

    2015-05-01

    In this paper, based on the basic shock wave relations and the stiffened gas equation of state, the laser-induced shock pressures, which are generated with homogenous rectangular laser pulse at power density of several GW/cm2, are proposed theoretically and experimentally. The laser-induced shock pressures are affected by the laser power density as well as the shock velocities, initial densities and adiabatic exponents of the target material and confined water which are considered to be condensed matter other than “solid” or “perfect gas” in the previous work. Performed on Al-2024 alloys, the laser-induced shock wave was measured with the poly(vinylidene fluoride) transducer and recorded by the oscilloscope. The laser-induced shock pressure derived from the proposed method agrees much better with the experimental results than that using the “solid” or “perfect gas” theory.

  11. Effects of laser-induced quenching and restoration of photoluminescence in hybrid Si/SiOx nanoparticles

    NASA Astrophysics Data System (ADS)

    Bagratashvili, V. N.; Dorofeev, S. G.; Ischenko, A. A.; Kononov, N. N.; Panchenko, V. Ya; Rybaltovskii, A. O.; Sviridov, A. P.; Senkov, S. N.; Tsypina, S. I.; Yusupov, V. I.; Yuvchenko, S. A.; Zimnyakov, D. A.

    2013-09-01

    We studied the processes of pulsed and continuous-wave (CW) laser excitation of photoluminescence (PL) in nc-Si/SiOx nanoparticles. CW laser irradiation of the nc-Si/SiOx sol in dimethylsulfoxide (DMSO) and in a thin film was found to quench PL with an essentially nonexponential dynamics. The laser-induced variation of the Rayleigh scattering signal from the nc-Si/SiOx sol in DMSO was found to replicate that of the PL quenching. The IR and Raman spectra of the laser-exposed nc-Si/SiOx exhibited no new bands that could be evidence of their chemical transformations. There were also no perceptible effects pointing to laser-induced aggregation of the nc-Si/SiOx particles in the sol. 355 nm pulse-periodic laser irradiation of the nc-Si/SiOx particles preliminarily exposed to a 405 nm CW laser (which causes a strong PL quenching effect) was found to result in a rapid restoration of the original PL signal, which means that the effect of laser quenching of PL can be entirely reversible. We considered a mechanism of the reversible photosensitivity of nc-Si/SiOx, based on the processes of ionization of the photoluminescent oxygen-deficient centers in their suboxide shell and electron capture by traps, followed by their laser-assisted photorecombination.

  12. 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

  13. Spectroscopic analysis of fire suppressants and refrigerants by laser-induced breakdown spectroscopy.

    PubMed

    Lancaster, E D; McNesby, K L; Daniel, R G; Miziolek, A W

    1999-03-20

    Laser-induced breakdown spectroscopy is evaluated as a means of detecting the fire suppressants CF(3)Br, C(3)F(7)H, and CF(4) and the refrigerant C(2)F(4)H(2). The feasibility of employing laser-induced breakdown spectroscopy for time- and space-resolved measurement of these agents during use, storage, and recharge is discussed. Data are presented that demonstrate the conditions necessary for optimal detection of these chemicals. PMID:18305769

  14. Simultaneous measurement of Raman scattering and laser-induced OH fluorescence in nonpremixed turbulent jet flames.

    PubMed

    Barlow, R S; Dibble, R W; Lucht, R P

    1989-03-01

    Spontaneous Raman scattering and laser-induced fluorescence are combined to perform simultaneous point measurements of major species concentrations, temperature, and hydroxyl radical concentration in turbulent nonpremixed flames. The Raman-scattering data for major species concentrations and temperature characterize the instantaneous, local, collisional quenching environment of the OH molecule. Collisional quenching corrections are applied for each laser shot so that absolute hydroxyl concentrations are obtained in turbulent flames using linear laser-induced fluorescence. PMID:19749889

  15. 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.

  16. 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

  17. Aspheric concave grating spectrographs

    NASA Technical Reports Server (NTRS)

    Cash, W. C., Jr.

    1984-01-01

    The design of aspheric concave gratings for high-resolution spectroscopes is examined theoretically, using the requirements of the proposed Far-UV Spectroscopic Explorer (effective area 100 sq cm and lambda/delta lambda = 30,000 in the 90-120-nm range) as a concrete example and taking the limitations of current fabrication technology (straight grooves only and maximum density 6000 lines/mm) into account. The total-path function derived by Namioka (1961) for an ellipsoidal grating is subjected to aberration analysis to obtain the optical surface best suited to the design requirements; expressions for corrections to the conventional stigmatic Rowland-circle mount are obtained and shown to produce significant performance improvements; and the design advantages of coma-corrected non-Rowland geometries are explored. Ray tracings and deviation contours are provided.

  18. Partially athermalized waveguide gratings

    NASA Astrophysics Data System (ADS)

    Saleem, Muhammad Rizwan; Honkanen, Seppo; Turunen, Jari

    2012-06-01

    We investigated high efficiency organic-inorganic hybrid sub-wavelength binary diffraction gratings as partially athermalized waveguides. The performance of the grating is evaluated in terms of low spectral shifts in heating environment. The efficiency was determined to be least effective in temperature environment around room temperature. The spectral characteristics of waveguide remain thermally stable by selecting optical grade polymer materials with high thermal expansion coefficients, subsequently deposited by high index, amorphous TiO2 thin films by atomic layer deposition (ALD) process. The spectral shifts towards longer and shorter wavelengths were investigated in terms of two main parameters, thermal expansion coefficient (TEC) and thermo-optic coefficient (TOC) respectively. Realization of partially athermalized waveguides are described by complete agreement in theoretically calculated and experimentally measured results in the temperature range of 100 °C.

  19. 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.

  20. 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.