Sample records for laser-induced dynamic gratings

  1. 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.

  2. 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.

  3. Electrostrictive laser-induced gratings for time-resolved observation of translational-rotational energy transfer in H 2

    Microsoft Academic Search

    W. Hubschmid; R. Bombach

    2011-01-01

    Electrostrictive laser-induced gratings (LIG) have been formed in H2 of various pressures (0.5…5 bar) and with frequencies of the Brillouin modes (sound waves) of about 14 MHz. Under these conditions,\\u000a the rotational degrees of freedom can only partially follow the temperature variation from the acoustic oscillation. A model\\u000a is given, which completes the linearized fluid dynamical equations with equations for

  4. Laser-induced grating spectroscopy of alexandrite crystals

    NASA Astrophysics Data System (ADS)

    Gilliland, Guy D.; Suchocki, Andrzej; Ver Steeg, Keith W.; Powell, Richard C.; Heller, Donald F.

    1988-09-01

    Four-wave-mixing techniques were used to establish and probe population gratings of Cr3+ ions in alexandrite crystals at temperatures between 10 and 300 K. The results were interpreted in terms of the interaction of the laser radiation with a two-level atomic system. They provide information about the characteristics of four-wave-mixing signals for this physical situation as well as being useful in characterizing the properties of energy transfer and dephasing within the ensemble of Cr3+ ions. The patterns of the transient four-wave-mixing signals are consistent with a model based on the pumping dynamics of ions in the mirror and inversion crystal-field sites. The variation of the signal intensity with laser power is strongly affected by beam depletion. The characteristics of exciton migration among Cr3+ ions in mirror sites were determined from the results of measuring the variation of the signal decay rate with grating spacing. The temperature dependences of the ion-ion interaction rate, the exciton-phonon scattering rate, and the diffusion coefficient were determined. These are found to be essentially the same for pumping into the 4T2 and 2E levels, but the effects of scattering from a grating of ions in inversion sites is much stronger for 4T2 pumping. The dephasing times for the atomic system were found from analyzing the variation of the signal intensity with grating spacing. For pumping into the 4T2 level the dephasing is dominated by radiationless decay processes. A model is presented for the decay channel that provides a theoretical explanation for the decay process which is consistent with the measured temperature and frequency dependences of the results as well as their variation with crystal-field strength. For pumping into the 2E level the dephasing is dominated by dephasing processes associated with the inhomogeneous linewidth of the transition.

  5. Development of laser-induced grating spectroscopy for underwater temperature measurement in shock wave focusing regions

    NASA Astrophysics Data System (ADS)

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

    2004-02-01

    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 gas-dynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm 3 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 are used to empirically establish the equation of states of water, gelatin or agar cell which will work as alternatives of human tissues.

  6. Double-resonance laser-induced grating spectroscopy of nitric oxide

    NASA Astrophysics Data System (ADS)

    McCormack, E. F.; Pratt, S. T.; Dehmer, P. M.; Dehmer, J. L.

    1993-08-01

    Double-resonance laser-induced grating spectroscopy (LIGS), including two-color laser-induced grating spectroscopy (TC-LIGS) and degenerate four-wave mixing (DFWM) spectroscopy, has been used to probe the E 2?, ?=0?A 2?, ?'=0?X 2? 1/2, ??=0 double-resonance transitions in NO. Several different double-resonance schemes have been implemented and their relative merits are discussed. The results demonstrate that double-resonance LIGS shows considerable promise for obtaining state-selective absorption spectra of rovibronically excited states for a wide variety of molecules.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  8. Measurement of the thermal diffusivity and speed of sound of hydrothermal solutions via the laser-induced grating technique

    Microsoft Academic Search

    T. J. Butenhoff

    1995-01-01

    We use the laser-induced grating technique to measure the thermal difusivity and speed of sound of hydrothermal solutions. In this noninvasive optical technique, a transient grating is produced in the hydrothermal solution by optical absorption from two crossed, time-coincident nanosecond laser pulses. The grating is probed by measuring the diffraction efficiency of a third laser beam. The grating relaxes via

  9. Phase-controlled, heterodyne laser-induced transient grating measurements of thermal transport properties in opaque material

    E-print Network

    Johnson, Jeremy A.

    The methodology for a heterodyned laser-induced transient thermal grating technique for non-contact, non-destructive measurements of thermal transport in opaque material is presented. Phase-controlled heterodyne detection ...

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  11. CO2 laser induced long period gratings in optical microfibers.

    PubMed

    Xuan, Haifeng; Jin, Wei; Zhang, Min

    2009-11-23

    Long period gratings (LPGs) are fabricated by use of focused high frequency CO(2) laser pulses to periodically modify the transverse dimension of silica microfibers. A 20-period LPG with a 27 dB attenuation dip is realized in a microfiber with a diameter of approximately 6.3 microm. The resonant wavelength has a negative temperature coefficient and a high sensitivity to external refractive index. The microfiber LPGs may be useful in micron scale in-fiber devices and sensors. PMID:19997432

  12. Electrostrictive laser-induced gratings for time-resolved observation of translational-rotational energy transfer in H2

    NASA Astrophysics Data System (ADS)

    Hubschmid, W.; Bombach, R.

    2011-06-01

    Electrostrictive laser-induced gratings (LIG) have been formed in H2 of various pressures (0.5…5 bar) and with frequencies of the Brillouin modes (sound waves) of about 14 MHz. Under these conditions, the rotational degrees of freedom can only partially follow the temperature variation from the acoustic oscillation. A model is given, which completes the linearized fluid dynamical equations with equations for the rotational state relaxation, separately for the average relaxation of the states for Ortho-H2 and Para-H2. Using such a model, the dispersion of sound frequency is reproduced with an accuracy of a few percent. However, the total dissipation of sound and the observed strong alternation in peak heights in the temporal evolution of the LIG intensity is only approximately predicted by the model.

  13. November 1, 1994 / Vol. 19, No. 21 / OPTICS LETTERS 1681 Laser-induced thermal grating effects in flames

    E-print Network

    Zare, Richard N.

    and E2 are supplied from a cw ring-dye laser that was pulse amplified by a single-mode Nd:YAG- pumpedNovember 1, 1994 / Vol. 19, No. 21 / OPTICS LETTERS 1681 Laser-induced thermal grating effects, Stanford University, Stanford, California 94305 Received May 9, 1994 Light scattering from a laser

  14. Multistate interactions in nitric oxide probed by laser-induced grating spectroscopy

    NASA Astrophysics Data System (ADS)

    McCormack, E. F.; Dehmer, P. M.; Dehmer, J. L.; Pratt, S. T.

    1995-03-01

    Two-color laser-induced grating spectroscopy (TC-LIGS) via the A 2?+, v'=0 state has been used to study the B 2?, v=28 and L 2?, v=8 valence states and the Q 2?, v=0 5p? Rydberg state of NO. Energies for previously unobserved or unresolved transitions to the perturbed L 2?1/2,3/2, v=8 and Q 2?1/2,3/2, v=0 states are reported for the first time. The interaction between these states is reconsidered in light of the new assignments. A comparison of different detection methods made for the B 2?1/2,3/2, v=28?A 2?+, v'=0 transitions demonstrates the ability of TC-LIGS to detect states that are difficult to detect by ionization or fluorescence-dip detection.

  15. Observation of hyperfine quantum beats in two-color laser-induced grating spectroscopy of nitric oxide

    NASA Astrophysics Data System (ADS)

    McCormack, E. F.; Pratt, S. T.; Dehmer, P. M.; Dehmer, J. L.

    1994-09-01

    Two-color laser-induced grating spectroscopy of NO via the A 2? +, v'=0 state has been used to study the time evolution of population gratings produced in a supersonic molecular beam. For a specific polarization configuration of the input laser beams, quantum beats due to the hyperfine structure of the A 2? +, v'=0 state have been observed by varying the delay between the grating-forming laser pulses and the grating-probing laser pulse. This form of quantum beat spectroscopy has the advantages of background-free detection, two-color state selectivity, a quadratic dependence on the level population, and a beat signal independent of the decay mode.

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

    NASA Astrophysics Data System (ADS)

    Gusev, Vitalyi

    2010-06-01

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

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

    SciTech Connect

    Gusev, Vitalyi [LPEC, UMR-CNRS 6087, ENSIM, PRES UNAM, Universite du Maine, 72085 Le Mans (France)

    2010-06-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  19. Formation of gratings and two-dimensional photonic structures by laser-induced nanocrystallization

    NASA Astrophysics Data System (ADS)

    Fujiwara, Takumi; Ogawa, Ryoh; Benino, Yasuhiko; Komatsu, Takayuki; Nishii, Junji

    2003-07-01

    We propose and demonstrate gratings and two-dimensional (2D) photonic structure of nanometer-scale crystals/particles in glass surface created by one of the most simple way every reported. Grating structures consisting of nanocrystals have been fabricated on surface of tellurite-based glasses, with a composition of 15K2O-15Nb2O5-70TeO2 (mol%), using photoinduced nano-crystallization. A conventional phase mask technique was performed for the grating fabrication with a XeCl excimer laser operating at 308 nm. Periodic structure with 400 nm pitch constructed by lines of regularly ordered nanoparticles having a diameter up to about 100 nm was confirmed by atomic force microscopy and scanning electron microscopy. It is strongly suggest from measurement of X-ray diffraction that the photoinduced nanoparticles have a crystalline phase, and also suggested from measurement of optical frequency doubling that the periodic nanoparticle structure exhibits second harmonic generation (SHG) with an unique polarization dependence of SHG based on nano-structures of dielectric polarization. In addition, such a simple method of phase mask usage was applied to formation of 2D array, and the 2D structures of nano-particles/holes were successfully obtained by laser irradiations.

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

    PubMed

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

    2010-05-10

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

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

    PubMed

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

    2014-12-11

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

  2. 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.

  3. Dynamics of laser induced metal nanoparticle and pattern formation

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    SciTech Connect

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

    2008-09-07

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

  5. Characterisation Of Excited Atom Reaction Dynamics By Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Wissenfeld, John R.; Harmon, Troy M.; Jursich, Gregory M.; Kagan, Mark R.

    1986-06-01

    Recent advances in laser technology have made available to chemists reliable sources of tunable, narrow bandwidth radiation in the ultraviolet and vacuum ultraviolet regions. It has thus become possible to detect with unprecedented sensitivity the diatomic products of bimolecular chemical reactions with resolution of electronic, vibrational, rotational, and even fine structure states. In our laboratory, special attention has been given to studies of the reactivity of optically metastable, electronically excited carbon an0 oxygen atoms, C( D) and 0('D). Examined in detail has been the reaction of C('D) with H2 in which the population of the product CH(v"=O) A doublet states is found to Be inverted. The reaction was further shcown to proceed via a long-lived 'CH collision complex. Extensive studies of 0(±D) + H2 ? OH + H using hydrogen isotopes have demonstrated the importance of angular momentum constraints on the dynamics of HOH collision complex dissociation. Most recently, we have been successful in detecting the CN product of C('D) + NO ? CN + 0('D), evidence for excited oxygen formation having been inferred from the observed CN product energetics. Also to be discussed will be the detection of highly vibrationally excited OH radicals by off-diagonal LIF in the Av = -1i -2 progressions. These experiments provide the first direct evidence that 0('D) + H2 proceeds exclusively by insertion/dissociation with no significant contribution from direct hydrogen abstraction.

  6. Fabrication of Long-Period Gratings by Femtosecond Laser-Induced Filling of Air-Holes in Photonic Crystal Fibers

    Microsoft Academic Search

    Shujing Liu; Long Jin; Wei Jin; Yiping Wang; D. N. Wang

    2010-01-01

    A new method for fabricating long-period gratings (LPGs) in photonic crystal fibers (PCFs) is presented. A tightly focused femtosecond infrared laser beam scans across a PCF periodically, resulting in periodic filling of cladding air-holes through a micro-explosion and redeposition process and forming an LPG. Strong resonance of ~26 dB has been demonstrated with a grating length of <;5 mm. An

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

    SciTech Connect

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

    2011-03-07

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

  8. 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.

  9. Laser-induced ultrafast spin dynamics and ERASE functionality on quasilinear molecular ions

    NASA Astrophysics Data System (ADS)

    Lefkidis, Georgios; Li, Chun; Zhang, Shaobin; Hübner, Wolfgang

    2015-03-01

    We present an ab initio investigation of the ?-process-based ultrafast spin manipulation on positively charged two-magnetic-center molecular ions bridged by non-magnetic oxygen. Multiple derived spin-switching and spin-transfer scenarios on the quasilinear structure [Fe-O-Co]+ are used to build two closed, irreversible spin-dynamics cycles with respect to the spin localization and orientation. A mechanism addressing the ``ERASE'' functionality is proposed by properly exploiting the irreversibility of some laser-induced spin-manipulation scenarios, and the resulting Shannon entropy change is analyzed. We compare with a presiously suggested mechanism based on chirped laser pulses. Such controllable spin-dynamics cycles and logic functionality demonstrate promising applications in the design of spintronic devices on isolated magnetic molecules.

  10. 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.

  11. 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.

  12. Dynamics of 3-mercaptopropionic acid dissociation at 193 nm: OH detection by laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Pushpa, Kumbil K.; Upadhyaya, Hari P.; Kumar, Awadhesh; Naik, Prakash D.; Bajaj, Paramanand

    2007-09-01

    Photodissociation of 3-mercaptopropionic acid (MPA), in the gas phase, at 193 nm generates OH, as detected by laser-induced fluorescence. Measurements on the nascent OH( v? = 0, J?) reveal that it is produced mostly vibrationally cold, with a rotational population distribution characterized by a temperature of 925 ± 75 K. A major portion of the available energy (˜30%) is channeled into relative translation of the photofragments, implying the presence of an exit barrier and that dissociation occurs from an excited state of MPA. Both experimental and theoretical results on dissociation of MPA are compared with that of its isomer, thiolactic acid, and almost similar dynamics are observed from the ground electronic states, but different from the excited states.

  13. Predissociative linewidths of (4p?) M 2?+ (v=1) and (3d?,?) H 2?+, H’ 2&Pgr; (v=2) Rydberg states of NO studied by the two-color laser-induced grating technique

    Microsoft Academic Search

    Juntarou Ishii; Kiyoji Uehara; Koichi Tsukiyama

    1995-01-01

    The two-color laser-induced grating (TC-LIG) technique has been employed to probe the predissociative Rydberg states (4p?) M 2?+ (v=1) and (3d?,?) H 2?+, H’ 2&Pgr;± (v=2) and the non-Rydberg B 2&Pgr; (v=26) state of nitric oxide. The ultraviolet pump laser frequency is fixed to a specific rotational line of the A 2?+ (v’=1 and 2)?X 2&Pgr;3\\/2 (v‘=0) transition of NO.

  14. CO2-laser induced long-period fiber gratings in nano-engineered bend insensitive single-mode fiber

    NASA Astrophysics Data System (ADS)

    Rao, Yunjiang; Wang, Wenhua; Wang, Zinan; Chiang, Kin Seng; Gong, Yuan

    2012-02-01

    Long-period fiber gratings (LPFGs) written in nano-engineered bend insensitive single-mode fiber (NEBI-SMF) were reported. It is found that, only when the pitches of the gratings are in two wavelength ranges (270-305 ?m and 420-480 ?m), obvious resonance peaks can be obtained within the band of 1200-1650 nm, due to the cladding mode separation caused by the nano-engineered ring in the fiber cladding. The strain sensitivity of the LPFG with a pitch of 295 ?m in the range of 270-305 ?m is 2.8 pm/??, while the LPFG with a pitch of 470 ?m in the range of 420-480 ?m is insensitive to strain. The temperature sensitivities of the two LPFGs are 0.145 nm/oC and 0.098 nm/oC, respectively. Due to the special structure of the NEBI-SMF, more interesting phenomenon could be explored by carrying out further theoretical and experimental study of these novel LPFGs, such as the bending and twisting characteristics, etc.

  15. Reflection spectrum analysis of stimulated Brillouin scattering dynamic grating

    Microsoft Academic Search

    S Nouri Jouybari; H Latifi; F Farahi

    2012-01-01

    The reflection spectrum of Brillouin dynamic grating is calculated by a numerical method called piecewise approach. A sawtooth frequency modulation is proposed to be used in Brillouin dynamic grating localization along a fiber. It is shown that the reflection spectrum has a flat band where its linewidth depends on the amplitude of frequency modulation. The maximum reflection of dynamic grating

  16. Laser-Induced Thermal Acoustics

    Microsoft Academic Search

    Eric Bryant Cummings

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  18. Observation of a thermal phase-grating contribution to diffraction in erythrosin-doped gelatin films

    Microsoft Academic Search

    R. Y. Choie; T. H. Barnes; W. J. Sandle; A. D. Woolhouse; I. T. McKinnie

    2000-01-01

    Dynamic laser-induced gratings were written into gelatin films doped with the xanthene dye – erythrosin B. The diffraction signal relaxation time from the transient grating was analysed as a function of the pump beam fluence and grating period. Also, the relaxation time of the transient absorption signal was measured with a pump–probe technique to determine the triplet lifetime of the

  19. 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 [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    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)

  20. Reflection spectrum analysis of stimulated Brillouin scattering dynamic grating

    NASA Astrophysics Data System (ADS)

    Nouri Jouybari, S.; Latifi, H.; Farahi, F.

    2012-08-01

    The reflection spectrum of Brillouin dynamic grating is calculated by a numerical method called piecewise approach. A sawtooth frequency modulation is proposed to be used in Brillouin dynamic grating localization along a fiber. It is shown that the reflection spectrum has a flat band where its linewidth depends on the amplitude of frequency modulation. The maximum reflection of dynamic grating can be adjusted by the amplitude of modulation and the power of pump waves, which generates the grating. This grating can be useful as a fiber laser cavity mirror.

  1. Dynamic Brillouin gratings permanently sustained by chaotic lasers.

    PubMed

    Santagiustina, M; Ursini, L

    2012-03-01

    A method to induce only one permanent and localized dynamic Brillouin grating in polarization maintaining optical fibers is introduced. The generation of the grating exploits the thumbtack correlation of the chaotic laser signals. A numerical calculation, corroborated by a theoretical analysis, is performed and the grating properties, length, and reflectance determined. PMID:22378429

  2. Dynamic gratings in optical fibers: Synthesis and sensing applications

    NASA Astrophysics Data System (ADS)

    He, Zuyuan; Hotate, Kazuo

    2012-03-01

    We proposed two schemes of generating and localizing dynamic gratings in optical fibers: one is based on the gain saturation in erbium-doped fiber; the other is based on Brillouin scattering in the fiber. By using these dynamic gratings, fully distributed strain/temperature sensors have been demonstrated. In this presentation, we review the principles, basic schemes, and experimental demonstrations of the novel dynamic grating techniques.

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

    E-print Network

    Mazur, Eric

    for aluminum by optical exper- iments that demonstrated transition of the optical properties from solid properties during the solid-to-liquid phase transition in aluminum agree with the results obtained to the conclusion that the laser-induced, solid-to-liquid phase transition in aluminum is a thermal process. #12

  4. Observation of narrowband intrinsic spectra of Brillouin dynamic gratings.

    PubMed

    Song, Kwang Yong; Yoon, Hyuk Jin

    2010-09-01

    We experimentally demonstrate that the reflection spectrum of a Brillouin dynamic grating in a polarization-maintaining fiber can be much narrower than the intrinsic linewidth of the stimulated Brillouin scattering, matching well with the theory of a fiber Bragg grating in terms of the linewidth and the reflectivity. A 3 dB bandwidth as narrow as 10.5 MHz is observed with the Brillouin dynamic grating generated in a 9 m uniform fiber. PMID:20808382

  5. Brillouin dynamic grating in optical fibers and its applications

    Microsoft Academic Search

    Kwang Yong Song

    2009-01-01

    A novel kind of all-optical dynamic grating with the reflectance and the center wavelength controlled by another optical wave can be realized based on Brillouin scattering in polarization-maintaining optical fibers. This grating, called Brillouin dynamic grating (BDG), has proved to be useful based on its unique characteristics in several applications such as high performance distributed sensors and optically-tunable delay lines.

  6. Brillouin dynamic grating in optical fibers and its applications

    NASA Astrophysics Data System (ADS)

    Song, Kwang-Yong

    2009-11-01

    A novel kind of all-optical dynamic grating with the reflectance and the center wavelength controlled by another optical wave can be realized based on Brillouin scattering in polarization-maintaining optical fibers. This grating, called Brillouin dynamic grating (BDG), has proved to be useful based on its unique characteristics in several applications such as high performance distributed sensors and optically-tunable delay lines.

  7. Dissociation dynamics of CH3I in electric spark induced breakdown revealed by time-resolved laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Liu, Wei-long; Song, Yun-fei; Duo, Li-ping; Liu, Yu-qiang; Yang, Yan-qiang

    2015-02-01

    The electric discharge spark dissociation of gas CH3I is found to be similar to its femtosecond laser photodissociation. The almost identical spectra of the two processes show that their initial ionization conditions are very similar. The initial ionization followed by molecular fragmentation is proposed as the dissociation mechanism, in which the characteristic emissions of I+, CH3, CH2, CH, H, and I2 are identified as the dissociation products. The emission band of 505 nm I2 is clearly observed in the time-resolved laser induced breakdown spectroscopy (LIBS). The dynamic curve indicates that I2? molecules are formed after the delay time of ?4.7 ns. The formation of I2? molecule results from the bimolecular collision of the highly excited iodine atom I?(4P) and CH3I molecule. This dynamical information can help understand the process of electric discharge spark dissociation of CH3I.

  8. Chirped Brillouin dynamic gratings for storing and compressing light.

    PubMed

    Winful, Herbert G

    2013-04-22

    We demonstrate theoretically that chirped dynamic gratings can be created in optical fibers through stimulated Brillouin scattering with frequency-chirped "signal" and "write" pulses. When the grating is interrogated with a third pulse of the opposite chirp, a compressed signal pulse is retrieved. This provides a method to regenerate stored pulses and enhance signal levels for communications applications. PMID:23609709

  9. Dynamic gratings in optical fibers: Synthesis and sensing applications

    Microsoft Academic Search

    Zuyuan He; Kazuo Hotate

    2010-01-01

    We proposed two schemes of generating and localizing dynamic gratings in optical fibers: one is based on the gain saturation\\u000a in erbium-doped fiber; the other is based on Brillouin scattering in the fiber. By using these dynamic gratings, fully distributed\\u000a strain\\/temperature sensors have been demonstrated. In this presentation, we review the principles, basic schemes, and experimental\\u000a demonstrations of the novel

  10. Simulation of laser-induced coupled electron-nuclear dynamics and time-resolved harmonic spectra in complex systems

    SciTech Connect

    Lisinetskaya, Polina G.; Mitric, Roland [Fachbereich Physik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin (Germany)

    2011-03-15

    We present a theoretical approach for the simulation of time-resolved harmonic spectra, including the effect of nuclear dynamics, which is applicable to complex systems involving many nuclear degrees of freedom. The method is based on the combination of our semiclassical field-induced surface hopping approach for the treatment of laser-induced nuclear dynamics with the time-dependent density functional theory for electron dynamics. We apply our method to the simulation of ultrafast nonadiabatic dynamics and time-resolved harmonic spectra in small silver clusters (Ag{sub 2} and Ag{sub 8}), which exhibit discrete molecularlike electronic transitions. We demonstrate that the harmonic signal is highly sensitive to the nuclear dynamics and thus can be used as a probe of coupled electron-nuclear dynamics, which is complementary to common pump-probe methods such as time-resolved photoelectron spectroscopy. Our simulations allowed us also to determine the mechanism and the time scale of nonradiative relaxation in the 'magic' Ag{sub 8} cluster and have provided a fundamental insight into ultrafast dynamics of metal nanoclusters in the size regime where 'each atom counts'. The excited-state dynamics of Ag{sub 8} involves an isomerization process from the initial structure with T{sub d} symmetry to the quadratic antiprism structure with D{sub 4d} symmetry which takes place on a time scale of {approx}3600 fs and is clearly identified in a time-resolved harmonic signal. Our theoretical approach is generally applicable for the prediction of time-resolved harmonic spectra in complex systems with many nuclear degrees freedom and should serve to stimulate new ultrafast experiments utilizing harmonic signals as a probe for nonadiabatic processes in molecular systems.

  11. Demodulation system for fiber optic Bragg grating dynamic pressure sensing

    Microsoft Academic Search

    John D. Lekki; Grigory Adamovsky; Bertram Floyd

    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

  12. Variable delay using stationary and localized Brillouin dynamic gratings

    NASA Astrophysics Data System (ADS)

    Antman, Yair; Primerov, Nikolay; Sancho, Juan; Thévenaz, Luc; Zadok, Avi

    2012-03-01

    Reflections from movable, dynamic acoustic gratings in polarization maintaining (PM) fibers are employed in the long variable delay of periodic, isolated pulses. The gratings are introduced by stimulated Brillouin scattering (SBS) interaction between two counter-propagating pump waves, which are spectrally detuned by the Brillouin frequency shift of the PM fiber and are both polarized along one of its principal axes. The gratings are interrogated by the reflections of read-out signals that are polarized along the orthogonal principal axis. High-rate phase modulation of both pump waves by a pseudo-random binary sequence introduces dynamic gratings that are both localized and stationary, at specific locations in which the modulated pumps are correlated. The separation between adjacent correlation peaks can be made arbitrarily long. Long variable delays are readily obtained by scanning the grating along the fiber, via changing either the length or the rate of the modulation sequence. At the same time, the short length of the gratings, on the order of a cm, accommodates the delay of broadband pulses. The technique is therefore free of the delay-times-bandwidth product limitation that undermines the performance of SBS-based 'slow light' delay: we report the delay 1-ns long pulses by as much as 770 ns. In addition, the combined reflections from two dynamic gratings with a variable separation are used to implement radio-frequency photonic filters of tunable free spectral range. At the current stage, the technique is restricted by noise from residual scattering that takes place outside of the correlation peaks. Hence, it is thus far limited to the processing of repetitive signals, for which the noise may be effectively averaged out.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  15. 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.

  16. 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

    2014-10-01

    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. Wemore »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.« less

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

    NASA Astrophysics Data System (ADS)

    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.

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

    DOE PAGESBeta

    Zhou, Jun [Florida State Univ., Tallahassee, FL (United States); Li, Junjie [Brookhaven National Lab. (BNL), Upton, NY (United States); Correa, Alfredo A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tang, Shao [Florida State Univ., Tallahassee, FL (United States); Ping, Yuan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ogitsu, Tadashi [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Li, Dong [Florida State Univ., Tallahassee, FL (United States); Zhou, Qiong [Florida State Univ., Tallahassee, FL (United States); Cao, Jianming [Florida State Univ., Tallahassee, FL (United States)

    2014-10-01

    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.

  19. Generation of dynamic Brillouin grating in polarization maintaining fiber

    NASA Astrophysics Data System (ADS)

    Sengupta, Dipankar; Santagiustina, Marco; Chiarello, Fabrizio; Palmieri, Luca

    2014-09-01

    We report an experimental demonstration and characterization of dynamic Brillouin gratings (DBGs) in a 5m long polarization-maintaining fiber (PMF) using heterodyne detection. The dependence of DBG reflectivity on the Brillouin gain and on the pumps and the probe powers is studied and reported.

  20. Brillouin dynamic grating in optical fibers and its applications

    Microsoft Academic Search

    Kwang-Yong Song

    2009-01-01

    A novel kind of all-optical dynamic grating with the reflectance and the center wavelength controlled by other optical waves can be realized based on Brillouin scattering in optical fibers. The operation principle and the potential applications like an optically-tunable delay line and a high performance distributed sensor will be presented.

  1. Dynamic response of fiber Bragg gratings strain sensors

    NASA Astrophysics Data System (ADS)

    Silva, Gleison E.; Santos, J. C.

    2013-05-01

    This paper presents the results of strain tests performed with fiber Bragg gratings written by interferometric or phasemask methods. The results show a significant difference on dynamic response these sensors when subject same conditions of temperature and mechanical stress. This effect may suggest a limitation on use of sensors based on this technique in applications requiring precise and fast responses.

  2. Laser-Induced Thermotherapy

    Microsoft Academic Search

    Birger Mensel; Christiane Weigel; Norbert Hosten

    Laser-induced interstitial thermotherapy is a method for controlled tissue destruction. Cells compounds are destroyed in situ by hyperthermia. Laser-induced thermotherapy (LITT) is able to induce a circumscript necrosis in targeted tissue while maximally surrounding tissue. The first patients were treated 20 years ago and pos sible gains in therapy of oncologic patients were quickly recognized. LITT has gained broad clinical

  3. Under-the-barrier dynamics in laser-induced relativistic tunneling.

    PubMed

    Klaiber, Michael; Yakaboylu, Enderalp; Bauke, Heiko; Hatsagortsyan, Karen Z; Keitel, Christoph H

    2013-04-12

    The tunneling dynamics in relativistic strong-field ionization is investigated with the aim to develop an intuitive picture for the relativistic tunneling regime. We demonstrate that the tunneling picture applies also in the relativistic regime by introducing position dependent energy levels. The quantum dynamics in the classically forbidden region features two time scales, the typical time that characterizes the probability density's decay of the ionizing electron under the barrier (Keldysh time) and the time interval which the electron spends inside the barrier (Eisenbud-Wigner-Smith tunneling time). In the relativistic regime, an electron momentum shift as well as a spatial shift along the laser propagation direction arise during the under-the-barrier motion which are caused by the laser magnetic field induced Lorentz force. The momentum shift is proportional to the Keldysh time, while the wave-packet's spatial drift is proportional to the Eisenbud-Wigner-Smith time. The signature of the momentum shift is shown to be present in the ionization spectrum at the detector and, therefore, observable experimentally. In contrast, the signature of the Eisenbud-Wigner-Smith time delay disappears at far distances for pure quasistatic tunneling dynamics. PMID:25167261

  4. Ultrahigh resolution optical spectrometry based on Brillouin dynamic grating

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  5. 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.

  6. 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.

  7. Time-dependent dynamics of an intense laser-induced above-threshold Coulomb explosion

    SciTech Connect

    Esry, B. D.; Ben-Itzhak, I. [J.R. Macdonald Laboratory and Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

    2010-10-15

    We use our recently proposed model to extract information about the nuclear dynamics from the Coulomb explosion data of Staudte et al. [Phys. Rev. Lett. 98, 073003 (2007)]. Those data, taken at multiple intensities near the ionization appearance intensity for both H{sub 2} and D{sub 2} in linearly and circularly polarized light, show remarkable structure and regularity not easily explained by conventional models. Because our model does fit the spectra well, we can infer the qualitative time-dependent evolution of the system. In addition, it suggests a possible experimental signature of rescattering leading to above-threshold Coulomb explosion.

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  9. Time-resolved dynamics of nanosecond laser-induced phase explosion

    NASA Astrophysics Data System (ADS)

    Porneala, Cristian; Willis, David A.

    2009-08-01

    Visualization of Nd : YAG laser ablation of aluminium targets was performed by a shadowgraph apparatus capable of imaging the dynamics of ablation with nanosecond time resolution. Direct observations of vaporization, explosive phase change and shock waves were obtained. The influence of vaporization and phase explosion on shock wave velocity was directly measured. A significant increase in the shock wave velocity was observed at the onset of phase explosion. However, the shock wave behaviour followed the form of a Taylor-Sedov spherical shock below and above the explosive phase change threshold. The jump in the shock wave velocity above phase explosion threshold is attributed to the release of stored enthalpy in the superheated liquid surface. The energy released during phase explosion was estimated by fitting the transient shock wave position to the Taylor scaling rules. Results of temperature calculations indicate that the vapour temperature at the phase explosion threshold is slightly higher than the critical temperature at the early stages of the shock wave formation. The shock wave pressure nearly doubled when transitioning from normal vaporization to phase explosion.

  10. 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

  11. All-optical signal processing using dynamic Brillouin gratings

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  12. Observation of Brillouin dynamic grating in a photonic chip.

    PubMed

    Pant, Ravi; Li, Enbang; Poulton, Christopher G; Choi, Duk-Yong; Madden, Steve; Luther-Davies, Barry; Eggleton, Benjamin J

    2013-02-01

    We report demonstration of a Brillouin dynamic grating (BDG) in a photonic chip. A BDG was characterized in a 6.5 cm long chalcogenide (As(2)S(3)) rib waveguide using CW pumps in x polarization and read using a CW probe in y polarization. The measured reflectivity, on-off ratio, and 3 dB bandwidth (f(3 dB)) for the BDG were 0.4%, ~28 dB, and ~6 GHz, respectively. PMID:23381419

  13. Self-Mixing-Based Demodulation Technique for Dynamic Fiber Bragg Grating Strain Sensors

    Microsoft Academic Search

    H. C. Seat; Y. Wang; T. Bosch; W. Hu; X. Chen; L. Zhang

    2006-01-01

    We report a novel demodulation scheme for the detection of small Bragg wavelength shifts in a fiber Bragg grating strain sensor by exploiting the optical feedback reflected from the grating structure back into a 1310 nm laser diode integrating a photodiode. The dynamic strain generated by a mechanical vibrator is applied transversely to the fiber Bragg grating and the desired

  14. Diffraction of Gaussian and Finite Beams by Dynamical and Stationary Gratings Combinations

    Microsoft Academic Search

    Talatnaz Haghighatjou

    1987-01-01

    An analysis of the interaction of an infinite plane wave with mixed traveling gratings composed of both phase and amplitude components is developed. Dynamic intensities are calculated for the zero and +\\/-1 orders of diffraction using different types of stationary reference gratings (SRG). Analytical expressions are obtained that describe the diffraction characteristics of mixed gratings. The optimum efficiencies for detection

  15. Brillouin distributed sensing using localized and stationary dynamic gratings

    NASA Astrophysics Data System (ADS)

    Primerov, Nikolay; Antman, Yair; Sancho, Juan; Zadok, Avi; Thevenaz, Luc

    2012-04-01

    In this work, we apply a recent technique for the generation of stimulated Brillouin scattering (SBS) dynamic gratings that are both localized and stationary to realize high-resolution distributed temperature sensing. The gratings generation method relies on the phase modulation of two pump waves by a common pseudo-random bit sequence (PRBS), with a symbol duration that is much shorter than the acoustic lifetime. This way the acoustic wave can efficiently build up in the medium at discrete locations only, where the phase difference between the two waves does not temporarily vary. The separation between neighboring correlation peaks can be made arbitrarily long. Using the proposed method, we experimentally demonstrate distributed temperature sensing with 5 cm resolution, based on modifications to both the local birefringence and the local Brillouin frequency shift in polarization maintaining fibers. The localization method does not require wideband detection and can generate the grating at any random position along the fiber, with complete flexibility. The phase-coding method is equally applicable to high-resolution SBS distributed sensing over standard fibers.

  16. Nine Orders of Magnitude Dynamic Range: Picomolar to Millimolar Concentration Measurement in Capillary Electrophoresis with Laser Induced Fluorescence Detection Employing Cascaded Avalanche Photodiode Photon Counters

    PubMed Central

    Dada, Oluwatosin O.; Essaka, David C.; Hindsgaul, Ole; Palcic, Monica M.; Prendergast, Jillian; Schnaar, Ronald L.

    2011-01-01

    The dynamic range of capillary electrophoresis analysis is ultimately limited by molecular shot noise at low concentrations and by concentration-induced band broadening at high concentrations. We report a system that approaches these fundamental limits. A laser-induced fluorescence detector is reported that employs a cascade of four fiber-optic beam-splitters connected in series to generate a primary signal and four attenuated signals, each monitored by a single-photon counting avalanche photodiode. Appropriate scaling of the signals from the five photodiodes produces a linear optical calibration curve for 5-carboxyl-tetramethylrhodamine from the concentration detection limit of 1 pM to the upper limit of 1 mM. Mass detection limits are 120 yoctomoles (70 molecules) injected into the instrument. The very-wide dynamic range instrument was used to study the metabolic products of the fluorescently labeled glycosphingolipid GM1-TMR produced by single cells isolated from the rat cerebellum. PMID:21410138

  17. Laser induced copper plating

    Microsoft Academic Search

    A. K. Al-Sufi; H. J. Eichler; J. Salk; H. J. Riedel

    1983-01-01

    Argon laser induced plating of copper spots and lines from copper sulfate solutions on glass and phenolic resin paper has been investigated. The substrates had to be precoated with an evaporated copper film. The highest plating rates have been obtained with a small film thickness of 25 nm. Spots with a thickness up to 30 ?m were plated.

  18. Photodissociation dynamics of 2-chloro-6-nitrotoluene and nitrocyclopentane in gas phase: Laser-induced fluorescence detection of OH

    NASA Astrophysics Data System (ADS)

    Kawade, Monali N.; Saha, Ankur; Upadhyaya, Hari P.; Kumar, Awadhesh; Naik, Prakash D.

    2014-10-01

    Photodissociation of 2-chloro-6-nitrotoluene (ClNT) at 193, 248 and 266 nm and nitrocyclopentane (NCP) at 193 nm leads to the formation of OH, as detected by laser-induced fluorescence (LIF). The nascent OH produced from the photolysis of ClNT at all the wavelengths is vibrationally cold, with the Boltzmann type rotational state distributions. However, the nascent OH product from NCP is in the ground and vibrationally excited states with the measured average relative population in ?? = 1 to that in ?? = 0 of 0.12 ± 0.03, and these levels are characterized by rotational temperatures of 650 ± 180 K and 1570 ± 90 K, respectively. The translational energy partitioned in the OH fragment has been measured for photodissociation of both ClNT and NCP. On the basis of both the experimental results and the ground state molecular orbital (MO) calculations, a plausible mechanism for the OH formation has been proposed.

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

    SciTech Connect

    Tong, W.

    1997-10-08

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

  20. Tunable multiplication of the repetition rate of an optical pulse train using dynamic Brillouin gratings in optical fibers

    Microsoft Academic Search

    S. ChinI; N. Primerov; S. Sales; L. Thevenaz

    2011-01-01

    configuration, which renders the system very attractive for future applications in optical communications. This system makes use of dynamic Brillouin grating (OBG) reflectors implemented in highly birefringent fibers, and the repetition rate of a pulse train is readily reconfigurable by simply changing the number of dynamic grating reflectors positioned in the fiber. The generation of dynamic Brillouin gratings is based

  1. Formation mechanism and dynamics in polymer surface gratings

    Microsoft Academic Search

    T. M. Geue; M. G. Saphiannikova; O. Henneberg; U. Pietsch; P. L. Rochon; A. L. Natansohn

    2002-01-01

    We present the results of time-dependent x-ray and visible light (VIS) scattering measurements during formation of surface relief grating (SRG). These gratings are formed on polymer films containing azobenzene side groups during pulselike exposure with a holographic pattern of circularly polarized light at 488 nm. The SRG formation is accompanied by a density grating just below the film surface. Assuming

  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. Nonequilibrium protein folding dynamics: laser-induced pH-jump studies of the helix-coil transition

    NASA Astrophysics Data System (ADS)

    Causgrove, Timothy P.; Dyer, R. Brian

    2006-03-01

    The kinetics of the helix-coil transition of poly- L-glutamate were measured in the range of 40 ns to 10 s using a laser-induced pH-jump coupled with time-resolved infrared spectroscopy. Folding of the polypeptide in D 2O was initiated by photolyzing o-nitrobenzaldehyde, which releases a deuteron, creating a rapid decrease in pD. Side-chain deuteration and conformational changes were monitored independently by varying the IR probe wavelength. The kinetics of the peptide conformational changes observed in the amide I region depended on the initial fraction of helical residues. With essentially no initial helix, amide I absorption changes were indistinguishable from those of instrument response, leading to the conclusion that helix initiation occurs in less than 40 ns. When the initial helix fraction is 0.13, the folding lifetime is lengthened to 625 ns, as predicted by helix-coil theory. We also observe evidence for a kinetically-trapped, nonproductive intermediate formed as the result of rapid deuteration of the unfolded state.

  4. Spectral Analysis of Brillouin Dynamic Grating Based on Heterodyne Detection

    NASA Astrophysics Data System (ADS)

    Zou, Weiwen; Chen, Jianping

    2013-12-01

    Spectral analysis based on heterodyne detection is used to investigate Brillouin dynamic grating (BDG) in a small-core polarization-maintaining optical fiber. Thanks to direct heterodyning of the readout and diffraction waves, essential BDG properties can be fully investigated. It is experimentally characterized that the BDG diffraction wave has an identical frequency downshift from the readout wave as the pump-probe frequency offset in the BDG generation, which straightforwardly verifies the theoretical estimation of the BDG's phase-matching condition for the first time to our best knowledge. The spectral analysis also confirms that the maximum power of the main peak changes in the same way with the stimulated Brillouin gain and has an exponential (linear) dependence on the pump (probe) power.

  5. Detection Sensitivity Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitation

    Microsoft Academic Search

    John Lekki; James A. Lock

    2003-01-01

    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.

  6. Dynamics of long-period gratings tuned with internal fiber electrodes.

    PubMed

    Yu, Zhangwei; Malmström, M; Sterner, C; Tarasenko, O; Margulis, W; Fonjallaz, P-Y

    2011-03-01

    The physics of electrically switched long-period grating in a twin-hole fiber with internal electrodes is studied. Dynamic measurements for the two polarizations show how the grating spectra shift in time due to the mechanical stress and heat transfer in the core and the cladding. PMID:21368931

  7. Time-Domain Distributed Fiber Sensor With 1 cm Spatial Resolution Based on Brillouin Dynamic Grating

    Microsoft Academic Search

    Kwang Yong Song; Sanghoon Chin; Nikolay Primerov; Luc Thevenaz

    2010-01-01

    We demonstrate an optical time-domain distributed fiber sensor showing the highest spatial resolution ever reported based on Brillouin dynamic grating in a polarization-maintaining fiber. In our scheme, the acoustic gratings containing the information on the local Brillouin frequency are generated by a long pump pulse in one polarization, and read out by a short probe pulse in the orthogonal polarization

  8. All-optical dynamic grating generation based on Brillouin scattering in polarization maintaining fiber

    Microsoft Academic Search

    Kwang-Yong Song; Kazuo Hotate

    2008-01-01

    We report a novel kind of all-optical dynamic grating based on Brillouin scattering in polarization maintaining fiber (PMF). A moving acoustic grating is generated by stimulated Brillouin scattering between optical waves in one polarization, and used to reflect orthogonally polarized waves at different wavelength. A 3-dB bandwidth of ~ 100 MHz is observed with the tunable reflectivity of up to

  9. Tunable optical delays based on Brillouin dynamic grating in a polarization maintaining fiber

    Microsoft Academic Search

    Kwang-Yong Song; Kwanil Lee; Hyuk-Jin Yoon; Sang Bae Lee

    2009-01-01

    We demonstrate a novel kind of tunable optical delays based on dynamic grating generated by Brillouin scattering in an optical fiber. An axial strain gradient is applied to a 15 m section of a polarization-maintaining fiber, and the Brillouin reflection grating is generated positionselectively by controlling the optical frequencies of Brillouin pump waves. Tunable time delays of up to 132

  10. Design considerations for a fibre Bragg grating interrogation system utilizing an arrayed waveguide grating for dynamic strain measurement

    NASA Astrophysics Data System (ADS)

    John, R. N.; Read, I.; MacPherson, W. N.

    2013-07-01

    Dynamic strain signals are important for many structural monitoring applications, but the high-speed interrogation of strain sensors based on fibre Bragg gratings (FBGs) remains a challenge. Arrayed waveguide grating (AWG) interrogation schemes have been proposed, and by using modelling and validation experiments several design considerations are investigated and their relationship to system performance indicators determined. The Bragg grating length has an impact on the ability of the grating to ‘observe’ the transient strain field, while the spectral widths of both the FBG and AWG influence the recovered strain resolution. The system performance was examined for both high frequency noise as well as the long-term drifts over an hour, with a strain resolution of 1.4 µ? observed and drift of less than 3.1 µ? h-1. The noise dependence on the relative overlap of the AWG and FBG spectra was found to be significant and the inclusion of a semiconductor optical amplifier to boost light intensity at the detectors was found to significantly improve performance with an improvement in the signal-to-noise ratio up to 200%.

  11. Ultra wide range tunable delay line using dynamic grating reflectors in optical fibers

    Microsoft Academic Search

    Nikolay Primerov; Sanghoon Chin; Kwang Yong Song; Luc Thévenaz

    2010-01-01

    We experimentally demonstrate a novel technique to realize a tunable delay line based on dynamic Brillouin gratings in a high birefringence fiber. A 8 ns pulse signal is continuously delayed up to 184 ns with minor distortion.

  12. Dynamic Brillouin gratings: A new tool in fibers for all-optical signal processing

    Microsoft Academic Search

    Luc Thevenaz; Nikolay Primerov; Sanghoon Chin; Marco Santagiustina

    2011-01-01

    The recent possibility to generate dynamic Bragg gratings by the interaction of 2 optical waves through stimulated Brillouin scattering in highly birefringent fibers has opened a new field to realize all-optical fiber-based functions.

  13. Optical time-domain measurement of Brillouin dynamic grating spectrum in a polarization-maintaining fiber.

    PubMed

    Song, Kwang Yong; Zou, Weiwen; He, Zuyuan; Hotate, Kazuo

    2009-05-01

    We demonstrate the distributed measurement of Brillouin dynamic grating spectra in a polarization-maintaining fiber based on time-domain analysis. Local reflection spectra of the Brillouin dynamic grating are acquired by synchronized propagation of the pump and the probe pulses based on the map of the Brillouin frequency distribution. Large temperature sensitivity as high as -50.9 MHz/ degrees C is observed with 2 m spatial resolution in 100 m range. PMID:19412279

  14. Optical time-domain measurement of Brillouin dynamic grating spectrum in a polarization maintaining fiber

    Microsoft Academic Search

    Kwang Yong Song; Weiwen Zou; Zuyuan He; Kazuo Hotate

    2009-01-01

    We demonstrate the distributed measurement of Brillouin dynamic grating spectrum in a polarization maintaining fiber based on time-domain analysis. By synchronized propagation of the pump and the probe pulses, the local spectrum of Brillouin dynamic grating is acquired together with the local Brillouin gain spectrum in a single experimental setup. The temperature sensitivity as high as -370 MHz\\/degC is observed

  15. Laser-induced electron localization in H$_2^+$: Mixed quantum-classical dynamics based on the exact time-dependent potential energy surface

    E-print Network

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

    2015-01-01

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

  16. 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.

  17. 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.

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

    Microsoft Academic Search

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

    1997-01-01

    Transient reflectivity experiments have been performed to measure the dynamics of laser-induced melting of amorphous silicon (a-Si) and the crystallization to 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

  19. Formation and dynamics of polymer surface relief gratings

    Microsoft Academic Search

    O. Henneberg; Th. Geue; M. Saphiannikova; U. Pietsch; P. Rochon; A. Natansohn

    2001-01-01

    Time resolved VIS and X-ray scattering experiments have been performed during the formation of a surface relief grating on a polymer film containing an azobenzene side-chain homopolymer (poly{(4-nitrophenyl)[4-[[2-(methacryloyloxy)ethyl]ethylamino]phenyl]diazene} (pDR1M), TG=129°C) upon holographic exposure with circularly polarised laser light of 488nm. Using fixed geometric conditions for both experiments, the time evolution of the first order grating peak was observed. Short time

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

    PubMed

    Klinkusch, Stefan; Saalfrank, Peter; Klamroth, Tillmann

    2009-09-21

    We report simulations of laser-pulse driven many-electron dynamics by means of a simple, heuristic extension of the time-dependent configuration interaction singles (TD-CIS) approach. The extension allows for the treatment of ionizing states as nonstationary states with a finite, energy-dependent lifetime to account for above-threshold ionization losses in laser-driven many-electron dynamics. The extended TD-CIS method is applied to the following specific examples: (i) state-to-state transitions in the LiCN molecule which correspond to intramolecular charge transfer, (ii) creation of electronic wave packets in LiCN including wave packet analysis by pump-probe spectroscopy, and, finally, (iii) the effect of ionization on the dynamic polarizability of H(2) when calculated nonperturbatively by TD-CIS. PMID:19778110

  1. All-optical dynamic grating generation based on Brillouin scattering in polarization-maintaining fiber.

    PubMed

    Song, Kwang Yong; Zou, Weiwen; He, Zuyuan; Hotate, Kazuo

    2008-05-01

    We report a novel kind of all-optical dynamic grating based on Brillouin scattering in a polarization maintaining fiber (PMF). A moving acoustic grating is generated by stimulated Brillouin scattering between writing beams in one polarization and used to reflect an orthogonally polarized reading beam at different wavelengths. The center wavelength of the grating is controllable by detuning the writing beams, and the 3 dB bandwidth of approximately 80 MHz is observed with the tunable reflectance of up to 4% in a 30 m PMF. PMID:18451941

  2. Laser induced ignition

    NASA Astrophysics Data System (ADS)

    Liedl, G.; Schuöcker, D.; Geringer, B.; Graf, J.; Klawatsch, D.; Lenz, H. P.; Piock, W. F.; Jetzinger, M.; Kapus, P.

    2007-05-01

    Nowadays, combustion engines and other combustion processes play an overwhelming and important role in everyday life. As a result, ignition of combustion processes is of great importance, too. Usually, ignition of a combustible material is defined in such a way that an ignition initiates a self-sustained reaction which propagates through the inflammable material even in the case that the ignition source has been removed. In most cases, a well defined ignition location and ignition time is of crucial importance. Spark plugs are well suited for such tasks but suffer from some disadvantages, like erosion of electrodes or restricted positioning possibilities. In some cases, ignition of combustible materials by means of high power laser pulses could be beneficial. High power lasers offer several different possibilities to ignite combustible materials, like thermal ignition, resonant ignition or optical breakdown ignition. Since thermal and resonant ignitions are not well suited on the requirements mentioned previously, only optical breakdown ignition will be discussed further. Optical breakdown of a gas within the focal spot of a high power laser allows a very distinct localization of the ignition spot in a combustible material. Since pulse duration is usually in the range of several nanoseconds, requirements on the ignition time are fulfilled easily, too. Laser peak intensities required for such an optical breakdown are in the range of 10 11 W/cm2. The hot plasma which forms during this breakdown initiates the following self-propagating combustion process. It has been shown previously that laser ignition of direct injection engines improves the fuel consumption as well as the exhaust emissions of such engines significantly. The work presented here gives a brief overview on the basics of laser induced ignition. Flame propagation which follows a successful ignition event can be distinguished into two diffrent regimes. Combustion processes within an engine are usually quite slow - the reaction velocity is mainly determined by the heat conductivity of the combustible. Such deflagrations processes show propagation velocities well below the speed of sound. On the other hand, detonations show much higher propagation velocities. In contrast to deflagrations, detonations show propagation velocities higher than the speed of sound within the combustible. The shock front which propagates through a combustible in the case of a detonation is responsible for a considerable pressure gradient moving at supersonic velocity. Basics and possible examples of laser induced ignitions of deflagrations and detonations are given and pros and cons of laser ignition systems are discussed briefly.

  3. Tunable optical delays based on Brillouin dynamic grating in a polarization maintaining fiber

    NASA Astrophysics Data System (ADS)

    Song, Kwang-Yong; Lee, Kwanil; Yoon, Hyuk-Jin; Lee, Sang Bae

    2009-10-01

    We demonstrate a novel kind of tunable optical delays based on dynamic grating generated by Brillouin scattering in an optical fiber. An axial strain gradient is applied to a 15 m section of a polarization-maintaining fiber, and the Brillouin reflection grating is generated positionselectively by controlling the optical frequencies of Brillouin pump waves. Tunable time delays of up to 132 ns are achieved with an 82 ns Gaussian pulse.

  4. Fiber Ring Laser Operated by Dynamic Local Phase Shifting of a Chirped Grating

    Microsoft Academic Search

    Ana Gonzalez-Segura; Pere Perez-Millan; JosÉ Luis Cruz; Miguel V. Andres

    2009-01-01

    An ultranarrow linewidth erbium-doped fiber ring laser is presented. It is based on the filtering properties of a phase-shifted chirped fiber Bragg grating, which is inserted inside the cavity of the laser. A dynamic control of the phase shifting, which is induced by a magnetostrictive transducer, permits both tunable continuous-wave and actively Q-switched operation. The use of a chirped grating

  5. Tunable optical delays based on Brillouin dynamic grating in optical fibers.

    PubMed

    Song, Kwang Yong; Lee, Kwanil; Lee, Sang Bae

    2009-06-01

    We demonstrate a novel kind of tunable optical delays based on dynamic grating generated by Brillouin scattering in an optical fiber. An axial strain gradient is applied to a 15 m section of a polarizationmaintaining fiber, and the Brillouin reflection grating is generated position-selectively by controlling the optical frequencies of Brillouin pump waves. Tunable time delays of up to 132 ns are achieved with an 82 ns Gaussian pulse. PMID:19506688

  6. Operation of Brillouin dynamic grating in single-mode optical fibers.

    PubMed

    Song, Kwang Yong

    2011-12-01

    The first (to our knowledge) observation of Brillouin dynamic grating in conventional single-mode fibers is reported, and the characterization is demonstrated with respect to the external parameters for the grating generation. When a 100 m single-mode fiber is used, a reflectance of 8% with a spectral bandwidth as low as 2.4 MHz is achieved, which is less than 10% of ordinary Brillouin gain bandwidth. PMID:22139284

  7. All-optical dynamic grating generation based on Brillouin scattering in polarization maintaining fiber

    NASA Astrophysics Data System (ADS)

    Song, Kwang-Yong; Hotate, Kazuo

    2008-04-01

    We report a novel kind of all-optical dynamic grating based on Brillouin scattering in polarization maintaining fiber (PMF). A moving acoustic grating is generated by stimulated Brillouin scattering between optical waves in one polarization, and used to reflect orthogonally polarized waves at different wavelength. A 3-dB bandwidth of ~ 100 MHz is observed with the tunable reflectivity of up to 2% in a 30 m PMF.

  8. Dynamic guided-mode resonant grating filter with quadratic electro-optic effect

    Microsoft Academic Search

    Hiroyuki Ichikawa; Hisao Kikuta

    2005-01-01

    We propose a novel and simple concept of dynamic switching of guided-mode resonant grating filters with quadratic electro-optic effect within a waveguide layer modulated by external fields due to comb-shaped electrodes that also behave as a grating. As the device has subwavelength structure, the performance must be analyzed electromagnetically. We describe numerical simulation with the finite-difference time-domain method specially modified

  9. Observation of the laser-induced surface dynamics by the single-shot x-ray laser interferometer

    NASA Astrophysics Data System (ADS)

    Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Sasaki, Akira; Terakawa, Kota; Minami, Yasuo; Tomita, Takuro; Yamamoto, Minoru; Umeda, Yoshifumi; Yamagiwa, Mitsuru; Suemoto, Tohru

    2011-09-01

    We have developed a soft x-ray laser (SXRL) interferometer capable of the single-shot imaging of nano-scaled structure dynamics. The interferometer consisted of the reflection optics including double Lloyd's mirrors and focusing optics, and the interference fringes are produced on the detector surface. The depth and lateral resolutions of the interferometer were about 1 nm and 1.8 ?m, respectively. By using this interferometer, the initial stage (~50 ps) of the ablation process of the Pt surface pumped by a 70 fs Ti:Sapphire laser pulse was observed. The expansion speed of the surface estimated from the result (34 nm/50 ps) indicated that the nano-bubble structures were formed in the initial stage of the ablation. In order to observe the detailed dynamics, the temporal synchronization between the pump and probe pulses was improved to be 3 ps by adopting a portion of the SXRL and pump beams as the time fiducials, to which the pump and probe timing was adjusted by using the x-ray streak camera.

  10. Dynamic Optical Gratings Accessed by Reversible Shape Memory.

    PubMed

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

    2015-07-01

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

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

    SciTech Connect

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

    2014-04-14

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

  12. Four-wave mixing analysis of Brillouin dynamic grating in a polarization-maintaining fiber: theory and experiment.

    PubMed

    Zhou, Da-Peng; Dong, Yongkang; Chen, Liang; Bao, Xiaoyi

    2011-10-10

    We investigate the Brillouin dynamic grating generation and detection process in polarization-maintaining fibers for the case of continuous wave operation both theoretically and experimentally. The four interacting light waves couple together through the material density variation due to stimulated Brillouin scattering. The four coupled equations describing this process are derived and solved analytically for two cases: moving fiber Bragg grating approximation and undepleted pump and probe waves approximation. We show that the conventional grating model oversimplifies the Brillouin dynamic grating generation and detection process, since it neglects the coupling between all the four waves, while the four-wave mixing model clearly demonstrates this coupling process and it is verified experimentally by measuring the reflection of the Brillouin dynamic grating. The trends of the theoretical calculation and experimental results agree well with each other confirming that the Brillouin dynamic grating generation and detection process is indeed a four-wave mixing process. PMID:21997088

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

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Debapriya; Xiang, Hongping; Lefkidis, Georgios; Hübner, Wolfgang

    2015-03-01

    We present a theoretical investigation of the ultrafast magneto-optical dynamics in clusters with 2, 3 and 4 Ni atoms. We study cooperative effects by increasing both the number of active centers and the multiplicities (up to quintets) in our Hilbert space. In the dinuclear cluster Ni2 a novel spin-flip scenario based on the M process is established. This process is highly operative in case the standard ? process fails. In the trinuclear cluster Ni3Na2 simultaneous spin-flip and spin-transfer is observed. Local spin-switch is also achieved via a non-linear M process which involves two off-resonant transitions. Finally, in the tetranuclear cluster (Ni2)2 the use of quintets provides an insight into an irreversible demagnetization scenario. We believe that our systematic investigation allows us to establish a relation between the magnetic centers and the multiplicities. Our research represents an important step towards the miniaturization of spintronic devices and functionalization of various logic elements based on molecular structures.

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

    NASA Astrophysics Data System (ADS)

    Liang, Xiaobin; Li, Yanqiu; Liu, Ke

    2015-07-01

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

  15. 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

  16. Effects of induced birefringence on Brillouin dynamic gratings in single-mode optical fibers.

    PubMed

    Song, Kwang Yong

    2012-06-15

    The effects of linear or circular birefringence on the operation of Brillouin dynamic grating are experimentally investigated where the birefringence is induced by bending or twisting a single-mode optical fiber, respectively. Experimental results show that the reflection spectrum of the dynamic grating in a 5 m fiber is split by bend-induced linear birefringence with the separation frequency dependent on the bending diameter, matching well with the theoretical model. Meanwhile, the spectrum is almost immune to circular birefringence induced by twist with a rate of up to 24??turns/m. PMID:22739864

  17. Quantitative, dynamic fuel distribution measurements in combustion-related devices using laser-induced fluorescence imaging of biacetyl in iso-octane

    Microsoft Academic Search

    James D. Smith; Volker Sick

    2007-01-01

    Knowledge of in-situ fuel distributions in practical combustion devices, such as internal combustion engines, is crucial for research and devlopment purposes. Numerous imaging techniques, mostly based on laser-induced fluorescence (LIF), have been developed and yield high levels of 2-D spatial information, but generally lack the temporal resolution (frame rates) necessary to resolve important timescales at sub-millisecond levels for sustained times.

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

    PubMed

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

    2015-07-01

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

  19. Dynamic Temperature Compensating Interrogation Technique for Strain Sensors With Tilted Fiber Bragg Gratings

    Microsoft Academic Search

    Yinping Miao; Bo Liu; Weihua Zhang; Bo Dong; Haibin Zhou; Qida Zhao

    2008-01-01

    In this letter, we propose a novel method of edge filter linear demodulation using tilted fiber Bragg gratings (TFBGs) in a fiber sensor system. Based on the filter characteristics of TFBGs and the same temperature characteristics as the FBG, the strain sensor demodulation system with dynamic temperature compensation can be achieved. An experimental system is built up to achieve one

  20. Time-domain distributed sensor with 1 cm spatial resolution based on Brillouin dynamic gratings

    Microsoft Academic Search

    Kwang-Yong Song; Sanghoon Chin; Nikolay Primerov; Luc Thévenaz

    2009-01-01

    We propose and experimentally demonstrate the highest-resolution BOTDA system ever reported using Brillouin dynamic grating in a polarization-maintaining fiber (PMF). Acoustic waves containing the information of local Brillouin frequency are generated by a long pump pulse in one polarization, and read out by a short probe pulse in the orthogonal polarization at a clearly distinct optical frequency from the pump.

  1. All-optical Brillouin dynamic grating generation in few-mode optical fiber.

    PubMed

    Li, Shenping; Li, Ming-Jun; Vodhanel, Richard S

    2012-11-15

    We report, for the first time (to our knowledge), generation of Brillouin dynamic gratings (BDGs) in few-mode optical fibers. A moving acoustic grating is generated by stimulated Brillouin scattering using a writing beam in one fiber mode, which is used to reflect a reading beam at a different wavelength in another fiber mode. With single-end pumping, a BDG with a tunable reflectance of up to 0.1% is demonstrated in a 15 km specially designed two-mode optical fiber. PMID:23164871

  2. Impact-ionization cooling in laser-induced plasma filaments.

    PubMed

    Filin, A; Compton, R; Romanov, D A; Levis, R J

    2009-04-17

    The ionization rates and subsequent electron dynamics for laser-induced plasma channels are measured for the noble gas series He, Ne, Ar, Kr, and Xe at 1.0 atm. The cw fluorescence emission increases superlinearly in the series from He to Xe in agreement with Ammosov-Delone-Krainov tunnel ionization calculations. The electron temperature after laser-induced plasma formation, measured by four-wave mixing, evolves from >20 eV to <1 eV kinetic energies with time constants ranging from 1 ns for He to 100 ps for Xe in agreement with an impact-ionization cooling model. PMID:19518642

  3. Impact-Ionization Cooling in Laser-Induced Plasma Filaments

    SciTech Connect

    Filin, A.; Romanov, D. A. [Center for Advanced Photonics Research, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Compton, R.; Levis, R. J. [Center for Advanced Photonics Research, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)

    2009-04-17

    The ionization rates and subsequent electron dynamics for laser-induced plasma channels are measured for the noble gas series He, Ne, Ar, Kr, and Xe at 1.0 atm. The cw fluorescence emission increases superlinearly in the series from He to Xe in agreement with Ammosov-Delone-Krainov tunnel ionization calculations. The electron temperature after laser-induced plasma formation, measured by four-wave mixing, evolves from >20 eV to <1 eV kinetic energies with time constants ranging from 1 ns for He to 100 ps for Xe in agreement with an impact-ionization cooling model.

  4. 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.

  5. Correlation-based distributed measurement of SBS-generated dynamic grating spectrum in a polarization-maintaining fiber

    NASA Astrophysics Data System (ADS)

    Zou, Weiwen; He, Zuyuan; Song, Kwang-Yong; Hotate, Kazuo

    2008-04-01

    The distribution of temperature-induced changes in Brillouin frequency shift and that of birefringence-determined frequency deviation in the spectrum of SBS-generated dynamic grating in a PMF have been measured with 1.2-meter spatial resolution and 110-meter measurement range. Synchronously controlled sinusoidal frequency-modulations are applied into two laser sources that are used for pump (probe) light and readout light, respectively, enabling distributed generation and detection of the dynamic grating.

  6. 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

  7. Time-domain distributed sensor with 1 cm spatial resolution based on Brillouin dynamic gratings

    NASA Astrophysics Data System (ADS)

    Song, Kwang-Yong; Chin, Sanghoon; Primerov, Nikolay; Thevenaz, Luc

    2009-10-01

    We propose and experimentally demonstrate the highest-resolution BOTDA system ever reported using Brillouin dynamic grating in a polarization-maintaining fiber (PMF). Acoustic waves containing the information of local Brillouin frequency are generated by a long pump pulse in one polarization, and read out by a short probe pulse in the orthogonal polarization at a clearly distinct optical frequency from the pump. In the experiment, a distributed strain measurement with 1 cm spatial resolution is performed over a 20 m fiber.

  8. Effect of decorrelation on 3-D grating detection with static and dynamic random-dot stereograms

    Microsoft Academic Search

    Stephen Palmisano; Robert S. Allison; Ian P. Howard

    2006-01-01

    Three experiments examined the effects of image decorrelation on the stereoscopic detection of sinusoidal depth gratings in static and dynamic random-dot stereograms (RDS). Detection was found to tolerate greater levels of image decorrelation as: (i) density increased from 23 to 676dots\\/deg2; (ii) spatial frequency decreased from 0.88 to 0.22cpd; (iii) amplitude increased above 0.5arcmin; and (iv) dot lifetime decreased from

  9. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

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

    1993-12-01

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

  10. Laser Induced Blue Luminescence Phenomenon

    NASA Astrophysics Data System (ADS)

    Zhu, Haiyong; Duan, Yanmin; Zhang, Ge; Zhang, Yaoju; Yang, Fugui

    2011-09-01

    Laser induced strange blue luminescence in several Raman crystals has been investigated. The blue luminescence at about 473 nm has the characteristic of no orientation and only produced in the crystal where the fundament laser oscillated. The experimental results show that the blue luminescence must result from the fundamental laser around 1.0 µm rather than Stokes-shifting. The spectrum detected is similar for different crystals. This blue luminescence is obviously strange and inconsistent with traditional luminescence theories, which maybe a brand-new luminescence theory.

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

    SciTech Connect

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

    2011-04-15

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

  12. Photofragmentation dynamics of ketene at 308 nm: Initial vibrational and rotational state distributions of CO product by vacuum UV laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Nesbitt, David J.; Petek, Hrvoje; Foltz, M. Frances; Filseth, Stephen V.; Bamford, Douglas J.; Moore, C. Bradley

    1985-07-01

    The vibration-rotation state distribution of CO(v,J) from CH2CO flash photolysis at 308 nm has been determined by pulsed VUV laser-induced fluorescence. The excited ketene molecule appears to internally convert to vibrationally excited ground singlet state and to dissociate on that surface, CH2CO+308 nm?CH2(1A1)+CO+6.7 kcal/mol. There are no energetic CO molecules which would indicate formation of the lower energy CH2 triplet state. The observed rotational distributions of CO(v=0) and CO(v=1) are roughly matched by rotational temperatures of 1300 and 550 K, respectively; the data are accurately matched by phase space theory (PST). PST assumes that all energetically accessible product states have equal probability; it contains no adjustable parameters. PST predicts the ratio of v=1 to v=0 populations to be 0.013 compared to an observed value of 0.09±0.05. A Franck-Condon calculation gives too much vibrational excitation, 0.22±0.07. The separate statistical ensemble (SSE) model of Wittig which decouples overall ketene rotation from the other internal degrees of freedom gives 0.082 in agreement with experiment. This type of statistical distribution is likely to characterize bond fissions for which the barrier is just the dissociation limit itself.

  13. Dynamic response of QWS-DFB lasers with convex tapered grating structure and non-zero facet reflection

    Microsoft Academic Search

    N. Bazhdanzadeh; V. Ahmadi; H. Ghafoorifard; F. Shahshahani

    2008-01-01

    Using finite difference time domain (FDTD) method, we analyze static and dynamic response of non-uniform grating quarter-wavelength shift distributed feedback QWS-DFB laser with non-zero facet reflection coefficients, both for large signal transient and small signal modulation. By introducing a convex tapered grating structure for QWS-DFB laser (XTG-DFB), it is shown that single mode stability of laser enhances and laser is

  14. Study of the Dynamic Formation of Transmission Gratings Recorded in Photopolymers and Holographic Polymer-Dispersed Liquid Crystals

    Microsoft Academic Search

    Sébastien Massenot; Jean-Luc Kaiser; Raymond Chevallier; Yvon Renotte

    2004-01-01

    Local and nonlocal models for the diffusion of photopolymers are applied to the dynamic formation of transmission gratings recorded in photopolymers and holographic polymer-dispersed liquid crystals (H-PDLCs). We retrieve the main parameters of H-PDLCs (refractive-index modulation and diffusion coefficient) by combining a solution of the one-dimensional diffusion equation and the rigorous coupled-wave theory applied to transmission gratings. The rigorous coupled-wave

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

    NASA Astrophysics Data System (ADS)

    Sreekumar, K.; Asokan, S.

    2010-01-01

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

  16. Laser induced shock waves in deformation processing

    Microsoft Academic Search

    H. Schulze Niehoff; F. Vollertsen

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

  17. 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.

  18. Dynamics of N-OH bond dissociation in cyclopentanone and cyclohexanone oxime at 193 nm: laser-induced fluorescence detection of nascent OH (v'', J'').

    PubMed

    Kawade, Monali N; Saha, Ankur; Upadhyaya, Hari P; Kumar, Awadhesh; Naik, Prakash D

    2010-12-01

    Cyclohexanone oxime (CHO) and cyclopentanone oxime (CPO) in the vapor phase undergo N-OH bond scission upon excitation at 193 nm to produce OH, which was detected state selectively employing laser-induced fluorescence. The measured energy distribution between fragments for both oximes suggests that in CHO the OH produced is mostly vibrationally cold, with moderate rotational excitation, whereas in CPO the OH fragment is also formed in v'' = 1 (~2%). The rotational population of OH (v'' = 0, J'') from CHO is characterized by a rotational temperature of 1440 ± 80 K, whereas the rotational populations of OH (v'' = 0, J'') and OH (v'' = 1, J'') from CPO are characterized by temperatures of 1360 ± 90 K and 930 ± 170 K, respectively. A high fraction of the available energy is partitioned to the relative translation of the fragments with f(T) values of 0.25 and 0.22 for CHO and CPO, respectively. In the case of CHO, the ?-doublet states of the nascent OH radical are populated almost equally in lower rotational quantum levels N'', with a preference for ?(+) (A') states for higher N''. However, there is no preference for either of the two spin orbit states ?(3/2) and ?(1/2) of OH. The nascent OH product in CPO is equally distributed in both ?-doublet states of ?(+) (A') and ?(-) (A'') for all N'', but has a preference for the ?(3/2) spin orbit state. Experimental work in combination with theoretical calculations suggests that both CHO and CPO molecules at 193 nm are excited to the S(2) state, which undergoes nonradiative relaxation to the T(2) state. Subsequently, molecules undergo the N-OH bond dissociation from the T(2) state with an exit barrier to produce OH (v'', J''). PMID:21058634

  19. 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

  20. High-resolution Brillouin optical time domain analysis based on Brillouin dynamic grating.

    PubMed

    Song, Kwang Yong; Yoon, Hyuk Jin

    2010-01-01

    We propose and experimentally demonstrate a high-resolution distributed measurement of the Brillouin gain spectrum in a polarization-maintaining fiber (PMF) using Brillouin dynamic grating. In our approach, acoustic waves which contain the information of the local Brillouin frequency are generated by a long pump pulse in one polarization along the PMF and are read out by a short probe pulse with an orthogonal polarization at a different optical frequency from the pump. In experiments, a distributed strain measurement with a 10 cm spatial resolution is demonstrated in a 105 m PMF. PMID:20664670

  1. Brillouin dynamic grating time-domain slope-assisted fast and distributed strain sensing

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    A new fast and distributed optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings (BDG) in polarization-maintaining (PM) fibers, is proposed and demonstrated. The strain sensitivity of the reflectivity of a pulsed probe, orthogonally polarized to the pumps which generated the BDG, is shown to depend on both pump and probe detuning. An optimum detuning point is then found, which provides maximum strain sensitivity. We report the measurement of 400Hz strain vibrations with a spatial resolution of 4.2cm at a sampling rate of 16kHz.

  2. 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.

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

    Microsoft Academic Search

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

    2011-01-01

    Dual emission laser induced fluorescence (DELIF) is a technique for measuring the instantaneous thin fluid film thickness\\u000a in dynamic systems. Two fluorophores within the system produce laser induced emissions that are filtered and captured by two\\u000a cameras. The ratio of the images from these cameras is used to cancel the effect of the laser beam profile on the image intensity.

  4. 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.

  5. Interaction between jets during laser-induced forward transfer

    SciTech Connect

    Patrascioiu, A.; Florian, C.; Fernández-Pradas, J. M.; Morenza, J. L.; Serra, P., E-mail: pserra@ub.edu [Departament de Física Aplicada i Òptica, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona (Spain); Hennig, G. [DI Projekt AG, Flugplatz, CH-3368 Bleienbach (Switzerland); Delaporte, P. [Aix Marseille University, CNRS, LP3 UMR 7341, 163 Avenue de Luminy, 13288 Marseille (France)

    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.

  6. Static and dynamic property experiments of giant magnetostrictive material-fiber Bragg grating magnetic field sensors

    NASA Astrophysics Data System (ADS)

    Ding, Guoping; Liu, Jiayi; Gao, Bin; Zhang, Biyun

    2015-02-01

    Nowadays, there are many kinds of magnetic field sensors such as Hall sensor, Gauss meter and so on. But few of them can be used in the small air gaps which size is about millimeter. A thin-slice Giant Magnetostrictive Material-fiber Bragg grating (GMM-FBG) magnetic field sensor was proposed with the size of 14mm×7mm×1.5mm. The FBG was bonded along the GMM slice length orientation, perpendicular to the major magnetostriction orientation, to measure the GMM's strain caused by external magnetic field. Experiment systems were established to test the GMM-FBG sensor's static and dynamic properties. The results show that the sensor's static property is consistent with the theoretical prediction, and the dynamic response is feasible in low frequencies from 1Hz to 20Hz.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

    Ishida, M.; Yamashiro, R.; Matsumoto, Y.; Honma, Kenji [Department of Material Science, University of Hyogo, 3-2-1 Kohto, Kamigori, Hyogo 678-1297 (Japan)

    2006-05-28

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

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

    PubMed Central

    Eyring, G; Fayer, M D

    1985-01-01

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

  10. Dynamic fiber-optic add-drop multiplexer using Bragg gratings and acousto-optic-induced coupling

    Microsoft Academic Search

    A. Diez; M. Delgado-Pinar; J. Mora; J. L. Cruz; M. V. Andres

    2003-01-01

    We report a novel dynamic fiber-optic add-drop multiplexer that combines the properties of Bragg gratings and the acousto-optic effect in optical fibers. It is a noninterferometric, nonfrequency shifting device that allows adding\\/dropping a certain optical channel when it is required. The prototype presented here exhibits a time response of ?95?s.

  11. High-precision characterization of dynamic acoustic grating induced by stimulated Brillouin scattering in a high-birefringence optical fiber

    Microsoft Academic Search

    Weiwen Zou; Zuyuan He; Kazuo Hotate

    2008-01-01

    A novel experimental method is demonstrated to precisely characterize optical-frequency deviation within plusmn4 MHz between orthogonal axes in a high-birefringence fiber arising from the SBS-induced dynamic acoustic-grating. This precision means a birefringence accuracy of 3times10-8.

  12. Distributed discrimination of strain and temperature based on Brillouin dynamic grating in an optical fiber

    NASA Astrophysics Data System (ADS)

    Hotate, Kazuo; Zou, Weiwen; Yamashita, Rodrigo Kendy; He, Zuyuan

    2013-12-01

    This paper reviews distributed discrimination of strain and temperature by use of an optical fiber based on fiber optic nerve systems. The preliminary method based on multiple resonance peaks of the Brillouin gain spectrum in a specially-designed fiber is firstly introduced. The complete discrimination of strain and temperature based on the Brillouin dynamic grating in a polarization maintaining fiber is extensively presented. The basic principle and two experimental schemes of distributed discrimination based on fiber optic nerve systems are demonstrated. The performance of the high discriminative accuracy (0.1 °C-0.3°C and 5 ??-12??) and high spatial resolution (˜10 cm) with the effective measurement points of about 50 for a standard system configuration or about 1000 for a modified one will be highly expected in real industry applications.

  13. 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. [Stanford University, Stanford, CA (United States); SLAC National Accelerator Laboratory, Menlo Park, CA (United States)

    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.

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

    NASA Astrophysics Data System (ADS)

    Sobol, Emil; Baum, Olga; Shnirelman, Alexander

    2015-03-01

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

  15. Laser-induced breakdown spectroscopy combined with spatial heterodyne spectroscopy.

    PubMed

    Gornushkin, Igor B; Smith, Ben W; Panne, Ulrich; Omenetto, Nicoló

    2014-01-01

    A spatial heterodyne spectrometer (SHS) is tested for the first time in combination with laser-induced breakdown spectroscopy (LIBS). The spectrometer is a modified version of the Michelson interferometer in which mirrors are replaced by diffraction gratings. The SHS contains no moving parts and the gratings are fixed at equal distances from the beam splitter. The main advantage is high throughput, about 200 times higher than that of dispersive spectrometers used in LIBS. This makes LIBS-SHS a promising technique for low-light standoff applications. The output signal of the SHS is an interferogram that is Fourier-transformed to retrieve the original plasma spectrum. In this proof-of-principle study, we investigate the potential of LIBS-SHS for material classification and quantitative analysis. Brass standards with broadly varying concentrations of Cu and Zn were tested. Classification via principal component analysis (PCA) shows distinct groupings of materials according to their origin. The quantification via partial least squares regression (PLS) shows good precision (relative standard deviation < 10%) and accuracy (within ± 5% of nominal concentrations). It is possible that LIBS-SHS can be developed into a portable, inexpensive, rugged instrument for field applications. PMID:25226262

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

    SciTech Connect

    Rodriguez, G. [LANL; Sandberg, R. L. [LANL; Lalone, B. M. [NSTec; Marshall, B. R. [NSTec; Grover, M. [NSTec; Stevens, G. D. [NSTec; Udd, E. [Columbia Gorge Research

    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.

  17. Dynamics of surface thermal expansion and diffusivity using two-color reflection transient gratings

    SciTech Connect

    Pennington, D.M.; Harris, C.B. [California Univ., Berkeley, CA (United States). Dept. of Chemistry

    1993-02-01

    We report 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 at several temperatures. Using a 75 fs ultraviolet probe with visible excitation beams, the electronic effects that dominate single color experiments become negligible; thus surface expansion due to heating and the subsequent contraction caused by cooling provide the dominant influence on the diffracted probe. The diffracted signal was composed of two components, thermal expansion of the surface and heat flow away from the surface, allowing the determination of the rate of expansion as well as the surface thermal diffusivity. At room temperature a signal rise due to thermal expansion was observed, corresponding to a maximum average displacement of {approx} 1 {angstrom} at 32 ps. Large fringe spacings were used, thus the dominant contributions to the signal were expansion and diffusion perpendicular to the surface. Values for the surface thermal diffusivity of GaAs were measured and found to be in reasonable agreement with bulk values above 50{degrees}K. Below 50{degrees}K, the diffusivity at the surface was more than an order of magnitude slower than in the bulk due to increased phonon boundary scattering. Comparison of the results with a straightforward thermal model yields good agreement over a range of temperatures (12--300{degrees}K). The applicability and advantages of the transient grating technique for studying photothermal and photoacoustic phenomena are discussed.

  18. Finite Elements numerical analysis of the dynamic response of POLICRYPS gratings

    Microsoft Academic Search

    Ilias G. Manolis; Jeroen Beeckman; Chris Desimpel; Domenico Donisi; Rita Asquini; Romeo Beccherelli

    Recently an improved technique was introduced in order to realize permanent switchable liquid crystal (LC) volume gratings in polymer\\/LC composite mixtures. By ensuring that diffusion takes place faster than actual polymerization, researchers succeeded into fabricating grating structures in which well-defined polymer slices alternate with uniformly aligned slices of LC material. The new gratings, which are know as POLICRYPS (Polymer-Liquid-Crystal-Polymer-Slices) (1)

  19. Laser induced forward transfer of conducting polymers

    Microsoft Academic Search

    M. Kandyla; S. Chatzandroulis; I. Zergioti

    2010-01-01

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

  20. Laser-Induced Underwater Plasma And Its Spectroscopic Applications

    SciTech Connect

    Lazic, Violeta [ENEA, FIS-LAS, Via. E. Fermi 45, 00044 Frascati (Italy)

    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.

  1. On two optomechanical effects of laser-induced electrostriction in dielectric liquids

    NASA Astrophysics Data System (ADS)

    Gojani, Ardian B.; Bejtullahu, Rasim; Obayashi, Shigeru

    2014-09-01

    This paper presents electrostriction from the phenomenological perspective, and gives details on two mechanical effects arising from laser-matter interaction. Electrostriction is the tendency of materials to compress in the presence of a varying electric field. In this paper, the investigated materials are polar and nonpolar dielectric liquids. It is stressed that the dominant factor is the time evolution of the laser pulse, which causes tensile stresses and acoustic waves. The study is supported by experimental realization of electrostriction, which can be detected only at favorable conditions (observed in water, but not in castor oil). This study will shed light in developing measurement techniques (e.g., laser-induced grating spectroscopy) and in explaining the onset of cavities and laser-induced liquid breakdown.

  2. One-laser-based generation/detection of Brillouin dynamic grating and its application to distributed discrimination of strain and temperature.

    PubMed

    Zou, Weiwen; He, Zuyuan; Hotate, Kazuo

    2011-01-31

    This paper presents a novel scheme to generate and detect Brillouin dynamic grating in a polarization-maintaining optical fiber based on one laser source. Precise measurement of Brillouin dynamic grating spectrum is achieved benefiting from that the pump, probe and readout waves are coherently originated from the same laser source. Distributed discrimination of strain and temperature is also achieved with high accuracy. PMID:21369054

  3. Correlation-based distributed measurement of SBS-generated dynamic grating spectrum in a polarization-maintaining fiber

    Microsoft Academic Search

    Weiwen Zou; Zuyuan He; Kwang-Yong Song; Kazuo Hotate

    2008-01-01

    The distribution of temperature-induced changes in Brillouin frequency shift and that of birefringence-determined frequency deviation in the spectrum of SBS-generated dynamic grating in a PMF have been measured with 1.2-meter spatial resolution and 110-meter measurement range. Synchronously controlled sinusoidal frequency-modulations are applied into two laser sources that are used for pump (probe) light and readout light, respectively, enabling distributed generation

  4. Simultaneous measurement of temperature and strain distribution by optical time-domain analysis of Brillouin dynamic grating

    Microsoft Academic Search

    Kwang Yong Song; Jae Hak Kim; Hyuk Jin Yoon

    2010-01-01

    Discriminative measurements of strain and temperature distribution are demonstrated based on optical time-domain analysis of Brillouin dynamic grating (BDG) in a polarization-maintaining fiber. The local information of the Brillouin frequency and the BDG frequency are acquired with a 1.2 m spatial resolution, and analyzed together to provide the distribution map of temperature and strain variation with the accuracies of ±1

  5. Variable delay of Gbit/s data using coded Brillouin dynamic gratings

    NASA Astrophysics Data System (ADS)

    Antman, Yair; Yaron, Lior; Langer, Tomy; Tur, Moshe; Zadok, Avi

    2013-03-01

    Dynamic Brillouin gratings (DBGs), inscribed by co-modulating two writing pump waves with a bi-phase code, are analyzed theoretically, simulated numerically, demonstrated and characterized experimentally. A comparison is made between modulation by pseudo-random bit sequences (PRBS) and perfect Golomb codes. Numerical analysis shows that Golomb codes provide lower off-peak reflectivity, due to the unique properties of their cyclic auto-correlation function. Golomb coded DBGs can therefor allow for the long variable delay of one-time probe waveforms with higher signal-tonoise ratios, and without averaging. A figure of merit is proposed, in terms of the optical signal-to-noise ratio of reflected waveforms and the delay-bandwidth product of the setup. As an example, the variable delay of return-to-zero, on-off keyed data at 1 Gbit/s rate, by as much as 10 ns, is successfully demonstrated. The eye diagram of the reflected waveform remains open, whereas PRBS modulation of the pump waves results in a closed eye.

  6. All-fiber probe for laser-induced thermotherapy with integrated temperature measurement capabilities

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Chen, W.; Yu, H.; Gassino, R.; Braglia, A.; Olivero, M.; Perrone, Guido; Vallan, A.

    2015-03-01

    The paper presents our recent results towards the development of a miniaturized all-fiber probe for laser induced thermal ablation of tumor cells, which combines the optimal delivery of a near-infrared high power ablating beam, a low power visible aiming beam and fast Bragg grating (FBG) temperature sensors. Specific combiner and probe end-cap based on dual cladding fibers have been developed to allow the simultaneous handling of the laser beams and of the signal that feeds the temperature sensor. Moreover, a very fast FBG interrogation system has been implemented to track abrupt temperature variations during medical treatment.

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

    Microsoft Academic Search

    Jianyong Wu; Joseph Sneddon

    2004-01-01

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

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

    E-print Network

    for lithography, pulsed laser deposition or laser-induced breakdown spectroscopy (LIBS). In re- cent years LIBS the local thermo- dynamic equilibrium (LTE). The LSBE is the basis of the calibration-free LIBS (CF-LIBS) analytical method originally introduced by Ciucci and coworkers [3]. In the CF- LIBS procedure, the full

  9. Enhancement of Laser-Induced Fluorescence by Intense Terahertz Pulses in Gases

    Microsoft Academic Search

    Jingle Liu; Xi-Cheng Zhang

    2011-01-01

    The enhancement of laser-induced fluorescence by in- tense terahertz pulses was studied both theoretically and experi- mentally using selected gases. Semiclassical physical picture incor- porating photoionization, electron heating, impact excitation, and dissociative recombination was used to explain the plasma dynam- ics under terahertz radiation in picosecond scale. The dependences of enhanced fluorescence on the terahertz field, laser intensity, and atomic

  10. Slow light based on holographic gratings

    Microsoft Academic Search

    Guoquan Zhang

    2011-01-01

    We have reviewed recent progresses on slow light based on holographic gratings such as stationary gratings, nonlinearly induced dynamic gratings and atomic coherence gratings. Several applications such as addressable multi-channel all-optical buffer memory and stored phase conjugate light wave based on slow light and stopped light pulses will be addressed. I. INTRODUCTION Slow light has been studied intensively in the

  11. 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.

  12. Synchronous detection of laser-induced fluorescence

    SciTech Connect

    Quigley, G.P.

    1982-01-01

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

  13. Modeling of Laser Induced Periodic Surface Structures

    Microsoft Academic Search

    J. Z. P. Skolski; G. R. B. E. Römer; A. J. Huis in't Veld; V. S. Mitko; J. V. Obona; V. Ocelik; Hosson de J. Th. M

    2010-01-01

    In surfaces irradiated by short laser pulses, Laser Induced Periodic Surface Structures (LIPSS) have\\u000abeen observed on all kind of materials for over forty years. These LIPSS, also referred to as ripples,\\u000aconsist of wavy surfaces with periodicity equal or smaller than the wavelength of the laser radiation.\\u000aUnfortunately, the physical phenomena explaining ripple initiation, growth and transitions toward other

  14. Laser-Induced Fluorescence Plasma Ion Diagnostics

    Microsoft Academic Search

    Roger McWilliams

    1999-01-01

    In nearly 25 years plasma laser-induced fluorescence (LIF) has evolved from proof-of-principle experiments.(R. Stern and J. Johnson, Phys. Rev. Lett. 34, 1548 (1975).) to using the latest advances in diodes lasers.(G.D. Severn, D.A. Edrich, and R. McWilliams, Rev. Sci. Instrum. 69, 10 (1998).) LIF can provide time- and space-resolved plasma ion distribution, f_i(x,v,t), measurements (typically on musec and mm scales)

  15. 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.

  16. 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)].

  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. 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/?? and -57.48 MHz/°C, respectively. PMID:23262688

  19. Dynamics and performance of hybrid distributed Bragg reflector lasers including a chirped fiber grating

    NASA Astrophysics Data System (ADS)

    Duan, GuangHua; Helmers, H.; Leroy, A.; Brosson, Philippe; Jacquet, Joel

    2002-06-01

    In this work, we report the spectral and modulation characteristics, as well as bit-error-rate performances of stabilized hybrid distributed Bragg reflector lasers including a chirped fiber grating. An original analysis of such lasers based on a modified second order rate equation will also be presented to explain the observed stability behavior.

  20. Laser-induced electric breakdown in solids

    NASA Technical Reports Server (NTRS)

    Bloembergen, N.

    1974-01-01

    A review is given of recent experimental results on laser-induced electric breakdown in transparent optical solid materials. A fundamental breakdown threshold exists characteristic for each material. The threshold is determined by the same physical process as dc breakdown, namely, avalanche ionization. The dependence of the threshold on laser pulse duration and frequency is consistent with this process. The implication of this breakdown mechanism for laser bulk and surface damage to optical components is discussed. It also determines physical properties of self-focused filaments.

  1. Laser induced surface stress on water droplets.

    PubMed

    Wang, Neng; Lin, Zhifang; Ng, Jack

    2014-10-01

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

  2. Laser Induced Chemical Liquid Phase Deposition (LCLD)

    SciTech Connect

    Nanai, Laszlo; Balint, Agneta M. [University of Szeged, JGYPK, Department of General and Environmental Physics H-6725 Szeged, Boldogasszony sgt. 6 (Hungary); West University of Timisoara, Faculty of Physics, Department of Physics, Bulv. V. Parvan 4, Timisoara 300223 (Romania)

    2012-08-17

    Laser induced chemical deposition (LCLD) of metals onto different substrates attracts growing attention during the last decade. Deposition of metals onto the surface of dielectrics and semiconductors with help of laser beam allows the creation of conducting metal of very complex architecture even in 3D. In the processes examined the deposition occurs from solutions containing metal ions and reducing agents. The deposition happens in the region of surface irradiated by laser beam (micro reactors). Physics -chemical reactions driven by laser beam will be discussed for different metal-substrate systems. The electrical, optical, mechanical properties of created interfaces will be demonstrated also including some practical-industrial applications.

  3. 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.

  4. Pressure effects in laser-induced plasmas of trinitrotoluene and pyrene by laser-induced breakdown spectroscopy (LIBS).

    PubMed

    Delgado, Tomás; Vadillo, José M; Laserna, J Javier

    2014-01-01

    The influence of the ambient atmosphere on the dynamics of plasma expansion, besides the interaction between excited plasma and gas molecules, has been studied for specific organic aromatic compounds. To analyze the influence of air on the formation pathways of atomic and molecular species inside the plasma plume, the spectral emissions in laser-induced breakdown spectroscopy (LIBS) of 2,4,6-trinitrotoluene (TNT) and pyrene were compared at different pressure environments, from high vacuum to atmospheric pressure. Pelletized samples of the compounds were introduced in a vacuum chamber for excitation with the fourth harmonic output of an Nd : YAG laser (266 nm). The optical emission signal was collected with an optical fiber connected to a spectrograph fitted with a intensified charge-coupled device detector. Results from LIBS spectra indicate that changes in pressure level affect the kinetics of the characteristic excited species and their spatial distribution inside the plasma plume. PMID:24405951

  5. Correlation-based distributed measurement of a dynamic grating spectrum generated in stimulated Brillouin scattering in a polarization-maintaining optical fiber.

    PubMed

    Zou, Weiwen; He, Zuyuan; Song, Kwang-Yong; Hotate, Kazuo

    2009-04-01

    We study the principle of correlation-based distributed generation and readout of dynamic grating spectrum generated in stimulated Brillouin scattering in a polarization-maintaining optical fiber. The experimental validation is demonstrated by applying synchronous sinusoidal frequency modulations to two orthogonally polarized laser sources that serve as the Brillouin pump-probe light and readout light of the dynamic grating, respectively. Temperature-induced opposite changes in the Brillouin frequency shift and in the birefringence-determined optical frequency deviation are clearly observed with 1.2 m spatial resolution and a 110 m measurement range. PMID:19340241

  6. Laser-induced fluorescence spectroscopy at endoscopy

    NASA Astrophysics Data System (ADS)

    Qu, Jianan Y.; MacAulay, Calum E.; Lam, Stephen; Palcic, Branko

    1994-07-01

    A spectrofluorometry system has been developed for the collection of laser induced fluorescense spectra of tissue during endoscopy. In this system, a catheter with seven optical fibers was used to deliver the excitation light and collect the emitted fluorescence. The system enables one to switch from regular endoscopy into fluorescence measurement in 50 ms using a computerized shutter system. The fluorescence spectra can be recorded in 100 ms. This spectrofluorometry system has been used to obtain spectra from bronchial, larynx and nasopharyngeal tissues when employed with the appropriate endoscopes. The results demonstrate that laser induced fluorescence can be used to differentiate abnormal tissue from normal tissue. The illumination and fluorescence collection patterns of this system have been modeled using a Monte Carlo simulation. The Monte Carlo simulation data shows that the spectra recorded by our collection pattern is very close to the intrinsic spectra of tissue. The experimental results and the Monte Carlo simulation suggest that changes in fluorescence intensity are more robust for the detection of early cancers than the differences in spectral characteristics.

  7. Interrogation of Fiber Bragg Grating Dynamic Strain Sensors by Self-Mixing Interferometry

    Microsoft Academic Search

    Maha Suleiman; Han Cheng Seat; Thierry Bosch

    2008-01-01

    An innovative investigation of optical feedback or self-mixing interference within the cavity of a single-longitudinal-mode laser is described as an integral part of a novel interrogation scheme to be employed in a fiber Bragg grating-based sensor for strain measurement. The entire sensor device simply consists of a laser diode with an integrated photodiode which is coupled to a fiber Bragg

  8. Non-uniform Grating Effects On Dynamic Characteristics of Bistable DFB Semiconductor Laser Amplifiers

    Microsoft Academic Search

    M. Aleshams; M. K. Morawej-Farshi; M. H. Sheikhi

    2008-01-01

    In this paper, we have proposed a procedure to analyze transient response of bistable distributed feedback semiconductor laser amplifiers (DFB-SLAs). The results of the analysis show among bistable DFB-SLA's with different gratings including uniform, quarter wavelength phase-shifted (QWS), and tapered, a tapered DFB-SLA has the best switching behavior. This behavior includes relaxation oscillation, switching-on time and switching-off time of the

  9. The dynamics of the electromagnetic wave propagation in the nonlinear Bragg grating structure

    Microsoft Academic Search

    A. V. Sadovnikov; A. G. Rozhnev

    2010-01-01

    The process of the electromagnetic wave propagation in the nonlinear Bragg grating system has been numerically studied. The nonlinear Kerr materials were considered. The values of the cut-off frequencies were approximately estimated with the modification of the effective refractive index method. A Finite-Difference-Time-Domain method was used to analyze the periodic nonlinear structures and to investigate the multiple gap-soliton formation within

  10. Dynamic analysis of mode-locked sampled-grating distributed Bragg reflector laser diodes

    Microsoft Academic Search

    Byoung-Sung Kim; Younchul Chung; Sen-Ho Kim

    1999-01-01

    A mode-locked sampled-grating distributed-Bragg-reflector (SGDBR) laser diode for generating a train of light pulses at terahertz repetition rates is proposed with a numerical analysis based on a time-domain large-signal model. The device consists of three parts: the saturable absorber section which serves as a mode-locker, the gain section as an amplifier, and the SGDBR as a spectrum filter. It is

  11. Dynamic characterization of a 2DOF circular resonator-driven vibratory grating scanner with geometric nonlinearity

    Microsoft Academic Search

    Yu Du; Guangya Zhou; Fook Siong Chau; Koon Lin Cheo; Qingxin Zhang; Hanhua Feng

    2009-01-01

    A micro-sized 2-DOF grating laser scanner which is made to vibrate in-plane by an electrical comb-driven circular resonator drive is fabricated and tested. The frequency response of the prototype scanner in atmosphere to different driving voltages and the variations of its natural frequency with scanning amplitude are measured. The results are compared with those from finite element simulations using a

  12. Comparision of laser-induced and classical ultasound

    Microsoft Academic Search

    Joel J. Niederhauser; Michael Jaeger; Martin Frenz

    2003-01-01

    A classical medical ultrasound system was combined with a pulsed laser source to allow laser-induced ultrasound imaging (optoacoustics). Classical ultrasound is based on reflection and scattering of an incident acoustic pulse at internal tissue structures. Laser-induced ultrasound is generated in situ by heating optical absorbing structures, such as blood vessels, with a 5 ns laser pulse (few degrees or fraction

  13. MICROSTRUCTURATION OF PROTEIN MATRICES BY LASER-INDUCED PHOTOCHEMISTRY

    E-print Network

    Paris-Sud XI, Université de

    MICROSTRUCTURATION OF PROTEIN MATRICES BY LASER-INDUCED PHOTOCHEMISTRY M . Iosin1 ,2, O. Stephan1 BY LASER-INDUCED PHOTOCHEMISTRY M. Iosin1,2 , O. Stephan1 , S. Astilean2 , A. Dupperay3,4 , P.L. Baldeck1 1, cross-linking, protein, cells adhesion 1. Introduction Two-photon induced photochemistry is a promising

  14. [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

  15. [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

  16. 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.

  17. 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.

  18. Femtosecond laser induced breakdown for combustion diagnostics

    SciTech Connect

    Kotzagianni, M. [Department of Physics, University of Patras, 26504 Patras (Greece); Institute of Chemical Engineering and High Temperature Chemical Processes (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), 26504 Patras (Greece); Couris, S. [Department of Physics, University of Patras, 26504 Patras (Greece); Institute of Chemical Engineering and High Temperature Chemical Processes (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), 26504 Patras (Greece); Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), Universite de Bourgogne, 21078 Dijon Cedex (France)

    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.

  19. Laser-Induced Incandescence: Detection Issues

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.

    1996-01-01

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

  20. Laser induced fluorescence spectroscopy of ruthenium monoboride

    NASA Astrophysics Data System (ADS)

    Wang, Na; Ng, Y. W.; Cheung, A. S.-C.

    2012-09-01

    Laser induced fluorescence spectrum of ruthenium monoboride (RuB) in the visible region between 500 and 575 nm was studied. RuB molecule was produced by reacting laser ablated ruthenium atom with 0.5% diborane (B2H6) seeded in argon. Three transition bands of the [18.4]2.5-X2?5/2 transition were recorded and rotationally analyzed. The ground state symmetry and bond length, ro, were determined to be X2?5/2 state and 1.7099 Å, respectively, which is consistent with a 2?i state predicted from electronic configuration using a molecular orbital energy level diagram. This work represents the first experimental investigation of the spectrum of the RuB molecule.

  1. Surface Restricted Grating Studies of Interfacial Charge Transfer Dynamics at N-Gallium ARSENIDE(100) Liquid Junction.

    NASA Astrophysics Data System (ADS)

    Wang, Xiangdong

    1995-01-01

    Heterogeneous electron transfer involves the coupling of a dense manifold of highly delocalized electronic levels of the solid state to a discrete molecular state as well as an abrupt change in phase in the reaction coordinate. These features make this problem unique relative to homogeneous solution phase or gas phase reaction mechanisms which involve coupling between discrete states within a uniform medium. In this work, the advances in Surface Restricted Transient Grating Spectroscopy (Surface Restricted Transient Grating) are discussed in the context of studying interfacial charge transfer processes at single crystal semiconductor surfaces as a means to probe the primary processes governing heterogeneous electron transfer. In situ grating studies of n-GaAs/(Se ^{-2/-1}) aqueous liquid junction have observed 1 ~ 2 picosecond decay components in the presence of the selenium redox couple. Bias voltage and injection intensity dependencies have shown that field focusing of the hole carrier distribution to the surface reaction plane was achieved. Based on the bias voltage and injection intensity dependence, and known hole scavenging properties of Se^{ -2}, the fast initial decay is assigned to interfacial hole transfer. This time scale is coincident with the highly damped diffusive relaxation components of water under the high ionic concentrations present in the Helmholtz double layer of the GaAs electrode surface. The similarity in time scales between charge transfer and the rate limiting nuclear motion in the barrier crossing dynamics indicates that the electronic coupling at the interface is in the strong coupling regime. This study was the first direct time-resolved measurement of interfacial electron transfer from a single crystal surface. The observation that the dynamics are essentially in the strong coupling limit is contrary to conventional treatments of interfacial transfer processes, which assume weak coupling conditions. This result is important as it demonstrates that there is no intrinsic barrier to electron transfer processes at the electrode surface and the interfacial charge transfer can approach the theoretical upper limit to the charge transfer processes. This work should be important in fully optimizing charge transfer at surfaces. The observed dynamics also illustrates the feasibility of hot electron channels for solar energy conversion.

  2. 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. [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Fardel, R. [General Energy Research Department, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Laboratory for Functional Polymers, EMPA-Swiss Federal Laboratories for Materials Testing and Research, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Nagel, M. [Laboratory for Functional Polymers, EMPA-Swiss Federal Laboratories for Materials Testing and Research, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Lippert, T. [General Energy Research Department, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)

    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.

  3. 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.

  4. Full-spectrum interrogation of fiber Bragg grating sensors for dynamic measurements in composite laminates

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    This paper presents a new means for collecting fiber Bragg grating (FBG) data during drop-tower measurements used to assess damage to composite structures. The high repetition-rate collection process reveals transient features that cannot be resolved in quasi-static measurements. The experiments made at a repetition rate of about 500 Hz show that the detected FBG spectrum broadens for a short period of time and relaxes quickly to a narrower static state. Furthermore, this relaxation time increases dramatically as the strike count increases. The information gained by such measurements will enhance the ability to characterize and distinguish failure modes and predict the remaining lifetime in composite laminate structures.

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

    NASA Astrophysics Data System (ADS)

    Kim, Yong Hyun; Song, Kwang Yong

    2014-05-01

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

  6. Noble gas halogen laser induced fluorescence of benzene: Some of its derivatives, difluoromethyl radicals; and carbon monoxide

    Microsoft Academic Search

    W. Langel

    1980-01-01

    The dynamics of molecules excited by laser absorption into well defined vibrational states were investigated. An apparatus was built in order to study laser induced fluorescence. A noble gas halogen excimer laser (pulse energy 10 mJ for KrF) was also constructed. Fluorescence of gaseous or liquid substances was examined by a high resolution monochromator, a transient recorder and a computer.

  7. Laser-Induced Damage of Calcium Fluoride

    SciTech Connect

    Espana, Aubrey L.; Joly, Alan G.; Hess, Wayne P.; Dickinson, J T.

    2004-12-01

    Radiation damage of materials has long been of fundamental interest, especially since the growth of laser technology. One such source of damage comes from UV laser light. Laser systems continue to move into shorter wavelength ranges, but unfortunately are limited by the damage threshold of their optical components. For example, semiconductor lithography is making its way into the 157nm range and requires a material that can not only transmit this light (air cannot), but also withstand the highly energetic photons present at this shorter wavelength. CaF2, an alkaline earth halide, is the chosen material for vacuum UV 157 nm excimer radiation. It can transmit light down to 120 nm and is relatively inexpensive. Although it is readily available through natural and synthetic sources, it is often times difficult to find in high purity. Impurities in the crystal can result in occupied states in the band gap that induce photon absorption [2] and ultimately lead to the degradation of the material. In order to predict how well CaF2 will perform under irradiation of short wavelength laser light, one must understand the mechanisms for laser-induced damage. Laser damage is often a two-step process: initial photons create new defects in the lattice and subsequent photons excite these defects. When laser light is incident on a solid surface there is an initial production of electron-hole (e-h) pairs, a heating of free electrons and a generation of local heating around optically absorbing centers [3]. Once this initial excitation converts to the driving energy for nuclear motion, the result is an ejection of atoms, ions and molecules from the surface, known as desorption or ablation [3]. Secondary processes further driving desorption are photoabsorption, successive excitations of self-trapped excitons (STE's) and defects, and ionization of neutrals by incident laser light [3]. The combination of laser-induced desorption and the alterations to the electronic and geometrical structure of the lattice result in defect formation. In the material CaF2 some of these defects take the form of F-centers, an electron trapped at a halogen vacancy [4], and H-centers, a F2- molecular ion at a single lattice site [5]. While the F-centers are stable, the H-centers are transient but can form into aggregates that are stable. There are many different configurations the defects can take based on the relative position of F and H centers in the lattice and this is extensively discussed in literature [1,4,5]. Once these defects have formed they cause further absorption of light, which ultimately induces particle emission and the production of even more defects. Various forms of laser-induced damage of CaF2 have been studied. For example, the mechanism for photon-stimulated desorption (PSD) of F+ from CaF2 (111) is discussed in ref. 6 and the energy threshold, distribution and kinetics governing electron-stimulated desorption (ESD) is investigated in ref. 7. The desorption of neutral Ca and F atoms has also been explored [1]. In this paper I focus on the emission of ions and neutrals from CaF2 under the irradiation of pulsed laser light at 266 nm, in addition to a brief study of its purity and transmittance.

  8. 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°.

  9. 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.

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

    SciTech Connect

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

    2006-12-01

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

  11. 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 Fluorescence on Molecular Discharges

    NASA Astrophysics Data System (ADS)

    Mulders, Hjalmar; Rijke, Arij; Girault, Vincent; Stoffels, Winfred

    2008-10-01

    In the last half century, mercury has been used widely as the radiating species in many low pressure fluorescent lamps. Mercury primarily radiates at 254 nm and 185 nm. These photons excite a phosphor that fluoresces back to the ground state producing visible photons. This process reduces the efficiency because much of the energy of the UV photons has to be discarded. Using a species that emits light closer to or even in the visible range reduces these losses. Ideally the species (or a mixture of several species) should build up the whole visible spectrum, much like in HID lamps. InBr seems to be a good candidate for such a lamp, because it is an efficient radiator that emits most of its light around 370 nm; much closer to the visible part of the spectrum. In order to get insight in the energy transfer processes going on in these molecules we have conducted a laser induced fluorescence (LIF) experiment on InBr vapour and on a plasma. We have measured the decay times of different rovibrational levels of the InBr-molecule as well as the spectral distribution of the fluorescence from these levels. From the former we calculated the rotational temperature of the plasma and from the latter we calculated the Franck-Condon factors for the A-state as well as the vibrational temperature.

  13. 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.

  14. Laser-induced thermal acoustics: simple accurate gas measurements

    Microsoft Academic Search

    E. B. Cummings

    1994-01-01

    Received February 17, 1994 Laser-induced thermal acoustics (LITA), an optical four-wave mixing technique, has been used for sensitive measurement of the sound speed, thermal diffusivity, acoustic damping rate, and complex susceptibility of a gas. In LITA, laser-induced acoustic waves scatter laser light into a coherent, modulated signal beam. A simple expression accurately describes the signal. Atmospheric sound speeds accurate to

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

    SciTech Connect

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

    2011-09-01

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

  16. 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

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

    E-print Network

    Fayer, Michael D.

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

  18. Laser-induced-plasma-assisted ablation for glass microfabrication

    NASA Astrophysics Data System (ADS)

    Hong, Minghui; Sugioka, Koji; Wu, Ding J.; Wong, L. L.; Lu, Yongfeng; Midorikawa, Katsumi; Chong, Tow Chong

    2001-10-01

    Glass is a hard transparent material with many applications in Photonics and advanced display industries. It is a high challenge to achieve crack-free glass microfabrication due to its special material characteristics. Laser-induced-plasma- assisted ablation is applied in this study to get the high quality glass microfabrication. In this processing, the laser beam goes through the glass substrate first and then irradiates on a solid target behind. For laser fluence above ablation threshold for the target, the generated plasma flies forward at a high speed. At a small target-to-substrate distance, there are strong interactions among laser light, target plasma and glass materials at the rear side of the substrate. Light absorption characteristic at the glass substrate is modified since the plasma may soften and dope into the glass in the interaction area. To have a better understanding of this processing, signal diagnostics are carried out to study the dynamic interaction. It is found that glass microfabrication is closely related to laser fluence, target-to-substrate distance, laser spot size and laser beam scanning speed. With proper control of the processing parameters, glass surface marking patterning and cutting can be achieved. With different materials as the targets, color marking of glass substrate can be obtained.

  19. Metal surface nitriding by laser induced plasma

    NASA Astrophysics Data System (ADS)

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

    1996-10-01

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

  20. Laser-induced autofluorescence diagnosis of tumors

    NASA Astrophysics Data System (ADS)

    Avrillier, S.; Tinet, E.; Ettori, D.; Anidjar, M.

    1997-01-01

    The feasibility of routine real-time clinical detection of precancerous lesions such as severe dysplasia and carcinoma in situ (CIS) by laser induced autofluorescence (LIAF), that is without the use of exogenous fluorescent marker, has been recently demonstrated in several medical fields. We present here an in vivo autofluorescence study we have undergone on normal, suspicious and tumoral areas of human bladder. Three different pulsed laser wavelengths were alternately used for excitation: 488 nm (Dye laser), 337 nm (Nitrogen laser), and 308 nm (XeCl excimer laser). A clinical endoscopic study was performed on 25 patients. Spectroscopic results were compared with histological analysis. For 488 nm and 337 nm excitation a single fluorescence broad band was obtained in any case, but for tumors the overall intensity was significantly reduced compared to normal mucosa. For 308 nm excitation we observed two main broad bands, centered respectively at about 360 nm and 440 nm. In case of neoplastic lesions (including carcinoma in situ), the intensity ratio [I(360nm)/I(440nm)] was always greater than 2, for normal or inflammatory areas it was less than 2. A clear diagnosis could then be achieved for 308 nm excitation with no need of absolute intensity measurements. However, in turbid media, the optical properties of the medium are wavelength dependent. As a consequence the observed fluorescence signals are different from the isolated fluorophores spectra and their shape depends also on the illumination and detection geometry. We show how this phenomenon can be taken into account for useful comparison of results from different groups.

  1. Nonlinear laser-induced damage and absorptance effects in dielectric coatings by using ultra-short pulses

    NASA Astrophysics Data System (ADS)

    Starke, K.; Jupé, M.; Jensen, L.; Mädebach, H.; Lappschies, M.; Ristau, D.; Ostendorf, A.

    2006-09-01

    The power handling capability of optical components is still one of the most important limitations for the further improvement of ultra-short pulse lasers in respect of average power and pulse energy. Laser-induced damage of functional dielectric coatings on laser crystals, pockels cells, out-coupling polarizers and compressor gratings is severely inhibiting the wide dispersion of ultra-short pulse laser systems especially in industrial production environments. Since the underlying physical causes for laser-induced damage with ultra-short pulses are distinctly differing from those in the nanosecond time scale, novel approaches must be found for an unambiguous improvement in damage resistance of optical coatings. In previous investigations, the band-gap of the coating material and the maximum field strength in the layer stack were identified as most important influences on the laser-induced damage with ultra-short pulses. Furthermore, a significant nonlinear increase of absorptance in dielectric coatings was found to be strongly related to the band-gap of the material. These effects were traced back to the multi-photon and avalanche-ionization as driving mechanisms for producing a critical conduction band population. In the current investigations, numerous model layer systems were investigated concerning laser-induced damage and non-linear absorptance. Adapting the ion beam sputtering coating process for achieving co-deposition of high and low index materials, coatings with continuously tunable refractive indices were produced. The results of the experiments exhibit a strong correlation of the damage threshold to the controllable shifting band-gaps of the coating materials.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  3. 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.

  4. 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: ?L/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

  5. Grating shearography

    NASA Astrophysics Data System (ADS)

    Bulhak, Jacek; Surrel, Yves

    1999-08-01

    This paper describes grating shearography as a technique for direct measurement of in-plane strains and out-of-plane slopes. This technique has many interesting features for mechanical engineering: strains are measured without numerical differentiation, so a good spatial resolution can be obtained; it is also fairly insensitive to vibrations; full in-plane and out-of-plane information can be gathered simultaneously; finally, it is easy to switch from grating shearography to grating interferometry, in order to have also the displacement field. We present the theoretical basis of the method and the preliminary measurements on a graphite/epoxy composite sample under Iosipescu shear testing. Results are compared with FEM simulation.

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

    NASA Astrophysics Data System (ADS)

    Eseller, Kemal Efe

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

  7. Crystal structure of laser-induced subsurface modifications in Si

    NASA Astrophysics Data System (ADS)

    Verburg, P. C.; Smillie, L. A.; Römer, G. R. B. E.; Haberl, B.; Bradby, J. E.; Williams, J. S.; Huis in't Veld, A. J.

    2015-06-01

    Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this work, we investigate the geometry and crystal structure of laser-induced subsurface modifications in monocrystalline silicon wafers. In addition to the generation of lattice defects, we found that transformations to amorphous silicon and Siuc(-iii)/Siuc(-xii) occur as a result of the laser irradiation.

  8. Spectrum method for laser induced damage in dielectric thin films

    NASA Astrophysics Data System (ADS)

    Cai, Yue; Zhou, Meng-lian; Ma, Zhi-liang; Wang, Li-jun

    2015-05-01

    This paper shows some tentative results with which laser induced damage on dielectric thin films is analyzed by using the transmission spectrum. The damage characters were extracted in high-resolution images of damaged films, and transmission spectrum of damaged thin films was measured. The mathematical model of transmission was built based on the matrix optics theory with the optical properties, which include the effective refractive index, effective extinction coefficient, effective thickness and wavelength, and so on. Changes of optical properties in different damaged degree were analyzed by the transmittance spectrum. Through which laser-induced damage mechanisms had been analyzed with the micro-examinations of films.

  9. Measurement and simulation of laser-induced fluorescence from non-equilibrium ultracold neutral plasmas

    E-print Network

    Denning, A; Robicheaux, F

    2009-01-01

    We report new measurements and simulations of laser-induced fluorescence in ultracold neutral plasmas. We focus on the earliest times, when the plasma equilibrium is evolving and before the plasma expands. In the simulation, the ions interact via the Yukawa potential in a small cell with wrapped boundary conditions. We solve the optical Bloch equation for each ion in the simulation as a function of time. Both the simulation and experiment show the initial Bloch vector rotation, disorder-induced heating, and coherent oscillation of the rms ion velocity. Detailed modeling of the fluorescence signal makes it possible to use fluorescence spectroscopy to probe ion dynamics in ultracold and strongly coupled plasmas.

  10. 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.

  11. Investigation of laser-induced cell lysis using time-resolved imaging

    NASA Astrophysics Data System (ADS)

    Rau, Kaustubh R.; Guerra, Arnold; Vogel, Alfred; Venugopalan, Vasan

    2004-04-01

    Using time-resolved imaging, we investigated the lysis of confluent PtK2 cell cultures by pulsed laser microbeam irradiation. Images obtained at time delays of 0.5 ns to 50 ?s demonstrate lysis to be mediated by laser-induced plasma formation resulting in pressure wave propagation and cavitation bubble formation. Image analysis enabled quantitative characterization of the pressure wave and cavitation bubble dynamics. The zone of cell damage exceeded the plasma size and serves to implicate cavitation bubble expansion as the primary agent of cell injury.

  12. 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.

  13. Comparison and Validation of Compressible Flow Simulations of Laser-Induced Cavitation

    E-print Network

    Comparison and Validation of Compressible Flow Simulations of Laser-Induced Cavitation Bubbles)). The validation is performed for the case of laser-induced cavitation bubbles collapsing in an infinite medium

  14. Grating shearography

    Microsoft Academic Search

    Jacek Bulhak; Yves Surrel

    1999-01-01

    This paper describes grating shearography as a technique for direct measurement of in-plane strains and out-of-plane slopes. This technique has many interesting features for mechanical engineering: strains are measured without numerical differentiation, so a good spatial resolution can be obtained; it is also fairly insensitive to vibrations; full in-plane and out-of-plane information can be gathered simultaneously; finally, it is easy

  15. Laser-induced fluorescence of collagen and cholestrol

    Microsoft Academic Search

    N. Moise; C. Carp; Mihail L. Pascu

    1995-01-01

    In this paper, laser induced fluorescence (LIF) and fluorescence lifetime of collagen and cholesterol solutions when excited with 337.1 nm radiation emitted by subnanosecond (700 psec) nitrogen pulsed laser are reported: absorption and excitation spectra of these biomolecules were obtained, too. The fluorescence excitation of collagen and cholesterol solutions was performed focusing the laser radiation on a CeramOptec quartz optical

  16. Laser Induced Fluorescence Measurements of Ion Temperatures in Helium Plasmas

    Microsoft Academic Search

    Christopher Compton; Robert Boivin; Robert Hardin; Earl Scime; Xuan Sun

    2002-01-01

    The lack of a suitable Laser Induced Fluorescence (LIF) scheme for helium ions at visible wavelengths has prevented LIF from being employed in helium plasmas for measurements of ion temperature and bulk ion flow speeds. In this work, we will present LIF measurements of helium ions in a helicon source plasma using an infrared, tunable diode laser operating at 1012.36

  17. Laser Induced Fluorescence of Helium Ions in a Helicon Plasma

    Microsoft Academic Search

    C. S. Compton; C. Biloui; R. A. Hardin; A. M. Keesee; E. E. Scime; R. Boivin

    2003-01-01

    The lack of a suitable Laser Induced Fluorescence (LIF) scheme for helium ions at visible wavelengths has prevented LIF from being employed in helium plasmas for measurements of ion temperature and bulk ion flow speeds. In this work, we will discuss our attempts to perform LIF of helium ions in a helicon source plasma using an infrared, tunable diode laser

  18. Laser induced breakdown spectroscopy in paintings and sculptures research

    Microsoft Academic Search

    A. Sarzynski; W. Skrzeczanowski; J. Marczak

    2007-01-01

    Application of Laser Induced Breakdown Spectroscopy (LIBS) for investigation of chemical constitution and stratigraphy of artworks, and metallic objects with multilayer structures is described in the paper. Physical phenomena accompanying LIBS investigations, especially temporal evolution and spectral lines broadening are described. Operational characteristics of experimental equipment are shown. Results obtained with use of two different echelle spectrometers are compared. Pigments

  19. Quantification of Coating Adhesion Using Laser Induced Decohesion Spectroscopy

    Microsoft Academic Search

    J. S. Meth; D. Sanderson; C. Mutchler; S. J. Bennison

    1998-01-01

    We present a new technique, laser induced decohesion spectroscopy (LIDS), which is capable of measuring the practical work of adhesion G between a transparent polymer coating and an opaque coating or substrate. In LIDS, a laser pulse directed onto the sample creates a blister at the transparent\\/opaque interface. The blister's internal pressure depends on the laser pulse energy, and at

  20. Laser-Induced Iodine Fluorescence Applied to Confined Supersonic Mixing

    Microsoft Academic Search

    Marc Havermann

    A laser-induced fluorescence (LIF) measurement system is presented and applied to the study of supersonic gas flows at low density. The LIF technique uses atomic or molecular tracers instead of microscopic particles so that particle lag effects, which are remarkable in low density flows, are avoided. The fluorescence signal of laser- excited molecules provides information about the gas velocity, temperature

  1. 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.

  2. Plasma erosion rate diagnostics using laser-induced fluorescence

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  3. Quantitative analysis using remote laser-induced breakdown spectroscopy (LIBS)

    Microsoft Academic Search

    C. M. Davies; H. H. Telle; D. J. Montgomery; R. E. Corbett

    1995-01-01

    A measurement system for quantitative, remote materials analysis has been realised. It is based on the method of laser-induced breakdown spectroscopy (LIBS), utilising an optical fibre system, both to deliver the laser radiation to the sample specimen and to collect the light emission from the luminous plasma plume. Distances of up to 100 m between the remote location and the

  4. Femtosecond laser-induced crystallization of protein in gel medium

    Microsoft Academic Search

    Kazuhiko Nakamura; Yosuke Sora; Hiroshi Y. Yoshikawa; Yoichiroh Hosokawa; Ryota Murai; Hiroaki Adachi; Yusuke Mori; Takatomo Sasaki; Hiroshi Masuhara

    2007-01-01

    We succeeded in generating femtosecond laser-induced crystallization of hen egg-white lysozyme (HEWL) in the irradiated area by suppressing convection of the solution using a highly concentrated gel. When a laser pulse, whose energy was above the threshold energy for bubble formation, was focused along with a linear scanning of the stage, HEWL crystallization was enhanced at the surface of bubbles

  5. Fundamentals and Applications of Laser-Induced Breakdown Spectroscopy

    Microsoft Academic Search

    D. A. Rusak; B. C. Castle; B. W. Smith; J. D. Winefordner

    1997-01-01

    Laser-induced breakdown spectroscopy is reviewed by dividing the literature into three categories according to target phase: solid, liquid, or gas. Within each category, the literature is further divided into a fundamental studies section and an analytical results and applications section.

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

    Microsoft Academic Search

    David A. Cremers; Rosemarie C. Chinni

    2009-01-01

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

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

    E-print Network

    Singh, Kunwar Pal

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

  8. Strategies for laser-induced fluorescence detection of nitric oxide in high-pressure flames.

    E-print Network

    Lee, Tonghun

    Strategies for laser-induced fluorescence detection of nitric oxide in high-pressure flames. III, and Ronald K. Hanson Laser-induced fluorescence LIF has proven a reliable technique for nitric oxide. Introduction Laser-induced fluorescence LIF is an important tool1­3 to help understand nitric oxide

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

    Microsoft Academic Search

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

    2006-01-01

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

  10. Short-pulse Laser Induced Transient Structure Formation and Ablation Studied with Time-resolved Coherent XUV-scattering

    NASA Astrophysics Data System (ADS)

    Sokolowski-Tinten, Klaus; Barty, Anton; Boutet, Sebastien; Shymanovich, Uladzimir; Chapman, Henry; Bogan, Mike; Marchesini, Stefano; Hau-Riege, Stefan; Stojanovic, Nikola; Bonse, Jörn; Rosandi, Yudi; Urbassek, Herbert M.; Tobey, Ra'anan; Ehrke, Henri; Cavalleri, Andrea; Düsterer, Stefan; Redlin, Harald; Frank, Matthias; Bajt, Sasa; Schulz, Joachim; Seibert, Marvin; Hajdu, Janos; Treusch, Rolf; Bostedt, Christoph; Hoener, M.; Möller, T.

    2010-10-01

    The structural dynamics of short-pulse laser irradiated surfaces and nano-structures has been studied with nm spatial and ultrafast temporal resolution by means of single-shot coherent XUV-scattering techniques. The experiments allowed us to time-resolve the formation of laser-induced periodic surface structures, and to follow the expansion and disintegration of nano-objects during laser ablation.

  11. IKK2 Inhibition Attenuates Laser-Induced Choroidal Neovascularization

    PubMed Central

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

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Tai, Hsiang

    2006-01-01

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

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

    SciTech Connect

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

    2009-05-31

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

  14. 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.

  15. All-optical generation of Brillouin dynamic grating based on multiple acoustic modes in a single-mode dispersion-shifted fiber.

    PubMed

    Zou, Weiwen; Chen, Jianping

    2013-06-17

    We demonstrate an all-optical generation of Brillouin dynamic grating (BDG) in a single-mode dispersion-shifted fiber (DSF). The feature of multiple-peak Brillouin gain spectrum (BGS) owing to the existence of the multiple acoustic modes in the single-mode DSF is utilized. Two inharmonic lock-in detections are newly introduced to characterize the BGS and the frequency-maintained or frequency-shifted BDG reflection. The frequency-shifted property of the BDG in the DSF with hundreds of MHz can find great potential applications in optical fiber sensing or all-optical signal processing. PMID:23787664

  16. Effect of pump-read optical path difference on the measurement of Brillouin dynamic grating spectra localized by the correlation domain technique with a single laser setup

    NASA Astrophysics Data System (ADS)

    Yamashita, Rodrigo Kendy; Kishi, Masato; Hotate, Kazuo

    2014-05-01

    In correlation domain distributed measurement of Brillouin dynamic grating (BDG) in polarization maintaining fiber, adjustment of the frequency modulation (FM) phase between the pump and read lightwaves is essential. We experimentally evaluated the phase difference impact on the measurement. A single laser setup can acquire the BDG spectra with higher stability, but the FM phase relation is fixed. Therefore the FM synchronization is not guaranteed for all points of the fiber under test due to the birefringence of the fiber. In this report, we varied the optical path difference between the pump and the read lightwaves, showing the spectrum degradation.

  17. A single-longitudinal-mode Brillouin fiber laser passively stabilized at the pump resonance frequency with a dynamic population inversion grating

    NASA Astrophysics Data System (ADS)

    Spirin, V. V.; López-Mercado, C. A.; Kinet, D.; Mégret, P.; Zolotovskiy, I. O.; Fotiadi, A. A.

    2013-01-01

    We demonstrate a single-longitudinal-mode Brillouin ring fiber laser passively stabilized at the resonance frequency with a 1.7 m section that is an unpumped polarization-maintaining erbium-doped fiber. The two coupled all-fiber Fabry–Perot interferometers that comprise the cavity, in combination with the dynamical population inversion gratings self-induced in the active fiber, provide adaptive pump-mode selection and Stokes wave generation at the same time. The laser is shown to emit a single-frequency Stokes wave with a linewidth narrower than 100 Hz.

  18. Tunable stimulated-Brillouin-scattering resonator started by feedback provided by Bragg scattering from the dynamic grating within an active medium.

    PubMed

    Kim, H S; Ko, D K; Jung, E C; Lim, C; Lim, G; Cha, B H; Lee, J

    2000-03-15

    We report a tunable stimulated-Brillouin-scattering resonator that does not require a starting mirror or a wavelength selector. The resonator is based on the Bragg scattering from the dynamic grating within the active medium itself. The laser dye (Rhodamine 6G dissolved in ethanol) was utilized as the active medium and was pumped by a frequency-doubled Nd:YAG laser. The quality factor (M(2)) of the output beam was 2.2. A single short pulse (<1 ns) with a pumping efficiency of ~4% was observed. PMID:18059892

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

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

    PubMed Central

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

    2014-01-01

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

  1. Coupled wave theory for thick hologram gratings

    Microsoft Academic Search

    Herwig Kogelnik

    1969-01-01

    A coupled wave analysis is given of the Bragg diffraction of light by thick hologram gratings, which is analogous to Phariseau's treatment of acoustic gratings and to the dynamical theory of X-ray diffraction. The theory remains valid for large diffraction efficiencies where the incident wave is strongly depleted. It is applied to transmission holograms and to reflection holograms. Spatial modulations

  2. Temporal behavior of neutral and ionic lines emitted from a laser induced plasma on an aqueous surface

    NASA Astrophysics Data System (ADS)

    Ahmed, J. Ben; Jaïdane, N.

    2009-05-01

    The temporal behavior of spectral lines emitted from a laser induced plasma has been studied. The plasma was created by using a Nd:YAG pulsed laser in air at atmospheric pressure focused on the surface of an aqueous solution. This work is an extension of previous published work [J. Ben Ahmed, Z. Ben Lakhdar, G. Taieb, Kinetics of laser induced plasma on an aqueous surface, Laser chem. 20 (2002) 123-134.]. The time evolution of lines intensities emitted from Ca, Ca +, Mg and Mg + has been experimentally observed and simulated using a simple theoretical approach based on electron-ion recombination. It was shown that the plasma temperature and electron density are correlated to the dynamics of plasma emission. Finally, the time evolution of the optical depth of Ca + resonance line at 393.4 nm was also studied.

  3. 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.

  4. 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.

  5. 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.

  6. Laser-induced periodic surface structuring of biopolymers

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  7. Applications of planar laser induced fluorescence in turbulent reacting flows

    NASA Astrophysics Data System (ADS)

    Cessou, A.; Meier, U.; Stepowski, D.

    2000-07-01

    The basic principles of laser induced fluorescence are described with progressive presentation of simple and multi-level interaction schemas providing the relationship between the fluorescence signal and the local concentration of the investigated species in the laser field. Essential differences between laser induced fluorescence and flame chemiluminescence emissions are given. Techniques for imaging in the planar LIF configuration and procedures for calibration of the fluorescence intensity in absolute concentration values are described. Then, examples of imaging applications are given for instantaneous mapping of OH, CH, O2 and temperature fields in turbulent reacting flows. In spite of uncertainties mainly due to collisional quenching effects, these imaging experiments are useful to interpret the interaction processes involved in turbulent combustion especially when several quantities can be simultaneously or conditionally registered.

  8. 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.

  9. Diode laser-induced infrared fluorescence of water vapour

    Microsoft Academic Search

    Hejie Li; Ronald K. Hanson; Jay B. Jeffries

    2004-01-01

    Infrared laser-induced fluorescence (LIF) of water vapour was investigated for its potential as a spatially resolved gasdynamic diagnostic. A cw diode laser operating near 1392 nm was scanned across a single absorption transition in the ngr1 + ngr3 band of H2O in a static cell, and the resulting fluorescence signal was collected near 2.7 µm (both ngr1 and ngr3 bands).

  10. 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.

  11. Laser induced thermal imaging of vacuum-coated OLED materials

    Microsoft Academic Search

    Sergey Lamansky; Thomas R. Hoffend Jr.; Ha Le; Vivian Jones; Martin B. Wolk; William A. Tolbert

    2005-01-01

    Laser Induced Thermal Imaging (LITI) allows for high-resolution patterning of a variety of materials that often cannot be patterned efficiently by other conventional techniques such as photolithography. Application of LITI towards patterning vacuum-coated OLED materials is particularly attractive because of high LITI patterning resolution and accuracy and good compatibility of vacuum-coated OLED materials. However, LITI may induce thermal transfer defects

  12. Laser induced fluorescence in a pulsed argon plasma

    Microsoft Academic Search

    Earl Scime; Costel Biloiu; Christopher Compton; Forrest Doss; Daniel Venture; John Heard; Edgar Choueiri; Rostislav Spektor

    2005-01-01

    A time-resolved laser induced fluorescence (LIF) technique for pulsed argon plasmas is described. A low power, tunable diode laser pumps a three level Ar II transition sequence at a wavelength of 668.6138 nm. With a standard LIF system designed for steady-state plasmas (e.g., 4 kHz optical chopper, 20 kHz band-width detector, and a lock-in amplifier), we demonstrate that the evolution

  13. Laser induced damage in optical materials: 7th ASTM symposium

    Microsoft Academic Search

    A. J. Glass; A. H. Guenther

    1976-01-01

    The Seventh ERDA-ASTM-ONR-NBS Symposium on Laser Induced Damage in Optical Materials was held at the National Bureau of Standards in Boulder, Colorado, on 29--31 July 1975. These Symposia are held as part of the activities in ASTM Subcommittee II on Lasers and Laser Materials, which is charged with the responsibilities of formulating standards and test procedures for laser materials, components,

  14. Laser-induced fluorescence diagnostic for measuring magnetic fields (abstract)

    Microsoft Academic Search

    T. G. Jones; W. A. Noonan; J. M. Neri; P. F. Ottinger

    1999-01-01

    A novel, spatially resolved diagnostic is being developed to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as is envisioned for ion-driven inertial confinement fusion. The diagnostic technique uses laser-induced fluorescence spectroscopy, and can be varied to measure either small or large fields. Small fields, as expected in ballistic beam transport, produce Zeeman shifts, ??Z,

  15. Laser-induced fluorescence diagnostic for measuring magnetic fields (abstract)

    Microsoft Academic Search

    T. G. Jones; W. A. Noonan; J. M. Neri; P. F. Ottinger

    1999-01-01

    A novel, spatially resolved diagnostic is being developed to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as is envisioned for ion-driven inertial confinement fusion. The diagnostic technique uses laser-induced fluorescence spectroscopy, and can be varied to measure either small or large fields. Small fields, as expected in ballistic beam transport, produce Zeeman shifts, DeltalambdaZ,

  16. Laser-induced spark ignition of CH 4\\/air mixtures

    Microsoft Academic Search

    Tran X. Phuoc; Fredrick P. White

    1999-01-01

    Laser-induced spark ignition of CH4-air mixtures was experimentally investigated using a nanosecond pulse at 1064 nm from a Q-switched Nd-Yag laser. Laser irradiance in the order of 1012 to 1013 W\\/cm2 was found to be sufficient to ignite a mixture having from 6.5 to 17% methane by volume (equivalence ratio, ER, from 0.66 to 1.95). The dependence of the breakdown

  17. Pressure Dependence of Laser-Induced Dielectric Breakdown in Water

    Microsoft Academic Search

    Jonathan Robert Sukovich; Ashwinkumar Sampathkumar; R. Glynn Holt

    2011-01-01

    The effects of pressure on laser-induced breakdown events at superthreshold irradiances in water were investigated over a range of pressures from 0 to 1380 bar. Breakdown events were generated using 5-ns Nd:YAG laser pulses of wavelength 532-nm. Observations of breakdown events were made using imaging and single detector techniques. Applications for use as a static and\\/or acoustic pressure sensor were

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

    Microsoft Academic Search

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

    2009-01-01

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

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

    DOEpatents

    Miller, Steven M. (Chelmsford, MA)

    1988-01-01

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

  20. Laser Induced Breakdown Spectroscopy for Chemical Mapping of Materials

    Microsoft Academic Search

    V. Piñon; M. P. Mateo; G. Nicolas

    2012-01-01

    Analytical techniques able to perform spatially-resolved analysis are highly demanded in the surface analysis and material science fields. Comparing with other analytical techniques usually employed, Laser Induced Breakdown Spectroscopy (LIBS) offers several advantages such as simplicity and robustness of the instrumentation which permits on-line and in-situ measurements. None or minimal sample preparation is required and the analysis of any sample

  1. Femtosecond laser-induced crystallization of protein in gel medium

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazuhiko; Sora, Yosuke; Yoshikawa, Hiroshi Y.; Hosokawa, Yoichiroh; Murai, Ryota; Adachi, Hiroaki; Mori, Yusuke; Sasaki, Takatomo; Masuhara, Hiroshi

    2007-05-01

    We succeeded in generating femtosecond laser-induced crystallization of hen egg-white lysozyme (HEWL) in the irradiated area by suppressing convection of the solution using a highly concentrated gel. When a laser pulse, whose energy was above the threshold energy for bubble formation, was focused along with a linear scanning of the stage, HEWL crystallization was enhanced at the surface of bubbles on the irradiated line. The relation between the bubble formation process and the crystallization is discussed.

  2. Excimer laser induced etching of InP

    Microsoft Academic Search

    V. M. Donnelly; T. R. Hayes

    1990-01-01

    We report 193 nm ArF excimer laser induced etching of InP in Cl2. Etching occurs by desorption of an In-chloride layer, as evidenced by an etch rate which increases linearly with laser repetition rate and is nearly pressure independent between 2 and 50 mTorr Cl2. At substrate temperatures near 150 °C, the etch rate increases above a ‘‘threshold’’ fluence of

  3. Laser-Induced Current Transients in Strained-Si Diodes

    Microsoft Academic Search

    Hyunwoo Park; Daniel J. Cummings; Rajan Arora; Jonathan A. Pellish; Robert A. Reed; Ronald D. Schrimpf; Dale McMorrow; S. E. Armstrong; Ukjin Roh; Toshikazu Nishida; Mark E. Law; Scott E. Thompson

    2009-01-01

    Laser-induced current transients are measured on uniaxially stressed silicon (Si) N+\\/P diodes using a high speed measurement system. Controlled external mechanical stress along the (110) direction is applied via a four-point bending jig while the samples are irradiated using a cavity-dumped dye laser with a wavelength of 590 nm. A decrease in the peak current is observed for increasing tensile

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

    E-print Network

    Fayer, Michael D.

    to the determina- tion of dynamic mechanical properties ofaligned dilauroylphosphatidylcholine (DLPC) multibilayer and attenuation are monitored through the diffraction of a variably delayed probe pulse by the acoustic grating using Brillouin scattering. The acoustic attenuation is shown to be an order of magnitude more sensitive

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  6. Analysis on laser-induced thermoelastic deformation of DMs

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  7. Fiber grating spectra

    Microsoft Academic Search

    T. Erdogan

    1997-01-01

    In this paper, we describe the spectral characteristics that can be achieved in fiber reflection (Bragg) and transmission gratings. Both principles for understanding and tools for designing fiber gratings are emphasized. Examples are given to illustrate the wide variety of optical properties that are possible in fiber gratings. The types of gratings considered include uniform, apodized, chirped, discrete phase-shifted, and

  8. 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.

  9. Extended dynamic range detection system for in-fibre Bragg grating strain sensors based on two cascaded interferometric wavelength scanners

    Microsoft Academic Search

    Y. J. Rao; D. A. Jackson; L. Zhang; I. Bennion

    1997-01-01

    A novel interferometric wavelength-shift detection system based on the use of two cascaded two-beam interferometers with different optical path differences (OPDs) is developed for static and quasi-static strain measurement with in-fibre Bragg grating (FBG) sensors. These two interferometers are frequency-division-multiplexed and used to provide two sets of interferometric fringes induced by strain. The optical phase output from interferometer 1 with

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

    SciTech Connect

    Jang, Deoksuk; Kim, Dongsik [Department of Mechanical Engineering POSTECH, 790-784, Pohang (Korea, Republic of); Park, Jin-Goo [Department of Materials Engineering, Hanyang University, 426-791, Ansan (Korea, Republic of)

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  12. 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

  13. Multilayer diffraction grating

    DOEpatents

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

    1990-01-01

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

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  17. 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. [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan)

    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.

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

    SciTech Connect

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

    2014-06-02

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  20. 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

  1. Laser induced nanoparticles and crystals and their characterization

    NASA Astrophysics Data System (ADS)

    Rezaee, Mohammadreza; Compton, Robert

    2014-03-01

    Intense nanosecond lasers are used to fabricate nanoparticles by direct laser solid interactions as well as laser produced shock wave induced crystallization in saturated solutions. In particular, laser graphite interactions under liquid nitrogen results in variety of interesting new carbon nanoclusters. In particular, exfoliation of graphite to produce graphene is considered. Laser produced shock wave in unsaturated salt (e.g. NaCl, NaClO3) solution immediately produces thousands of tiny crystals. These nonmaterials are examined using Raman spectroscopy under liquid nitrogen, RUN), laser induced fluorescence, plasma spectroscopy, UV-Vis spectroscopy as well as conventional characterization methods such as SEM and HRTEM imaging.

  2. 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

  3. Laser induced breakdown spectroscopy in paintings and sculptures research

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

  4. Progress in fieldable laser-induced breakdown spectroscopy (LIBS)

    NASA Astrophysics Data System (ADS)

    Miziolek, Andrzej W.

    2012-06-01

    In recent years there has been great progress in the Laser Induced Breakdown Spectroscopy (LIBS) technology field. Significant advances have been made both in fundamental and applied research as well as in data processing/chemometrics. Improvements in components, most notably lasers/optics and spectrometers are enabling the development of new devices that are suitable for field use. These new commercial devices recently released to the marketplace, as well as ones currently under development, are bringing the potential of LIBS for CBRNE threat analysis into real-world applications.

  5. Multiple structure of a laser-induced underwater shock wave

    E-print Network

    Tagawa, Yoshiyuki; Hayasaka, Keisuke; Kameda, Masaharu

    2015-01-01

    The structure of a laser-induced underwater shock wave is examined. Plasma formation, shock-wave expansion, and temporal evolution of shock pressure are observed simultaneously using a combined measurement system that obtains high-resolution nanosecond-order image sequences. In contrast to a well-known spherical-shock model, these detailed measurements reveal a non-spherically-symmteric distribution of pressure peak for a wide range of experimental parameters. The structure is determined to be a collection of multiple spherical shocks originated from elongated plasmas.

  6. Interaction of laser-induced stress waves with metals

    NASA Technical Reports Server (NTRS)

    Clauer, A. H.; Fairand, B. P.

    1979-01-01

    An investigation of the effect of high intensity laser induced stress waves on the hardness and tensile strength of 2024 and 7075 aluminum and on the fatigue properties of 7075 aluminum were investigated. Laser shocking increases the hardness of the underaged 2024-T351 but has little or no effect on the peak aged 2024-T351 and 7075-T651 or the overaged 7075-T73. The fretting fatigue life of fastener joints of 7075-T6 was increased by orders of magnitude by laser shocking the region around the fastener hole; the fatigue crack propagation rates were decreased by laser shocking.

  7. Laser-Induced Nuclear Orientation of 1-mus 85Rbm

    Microsoft Academic Search

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

    1984-01-01

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

  8. Trace metal mapping by laser-induced breakdown spectroscopy

    SciTech Connect

    Kaiser, Jozef [ORNL; Novotny, Dr. Karel [Masaryk University; Hrdlicka, A [Brno University of Technology, Czech Republic; Malina, R [Brno University of Technology, Czech Republic; Hartl, M [Brno University of Technology, Czech Republic; Kizek, R [Mendel University of Brno; Adam, V [Mendel University of Brno

    2012-01-01

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

  9. Spatial confinement effects in laser-induced breakdown spectroscopy

    SciTech Connect

    Shen, X. K.; Sun, J.; Ling, H.; Lu, Y. F. [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0511 (United States)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  11. Laser-induced reaction alumina coating on ceramic composite

    NASA Astrophysics Data System (ADS)

    Xiao, Chenghe

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

  12. Intense UV excimer radiation from laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    Onkels, E. D.; Seelig, W.

    1997-08-01

    Investigations of laser-induced plasmas have been undertaken with the aim of generating intense excimer fluorescence radiation. Experiments carried out on a KrF* excimer plasma system had very promising results. Through an unconventional intra-cavity arrangement of the pump laser it is possible to obtain homogeneity and stability together with an induced plasma with an overall length of about 10 cm. The attained optical gain of the plasma on the KrF* band at 248 nm reaches 25 m-1, which amounts to approximately twice the gain of conventional gas discharges. This paper gives a brief description of the theoretical modeling and applied experimental techniques.

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

    SciTech Connect

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

    2014-05-21

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

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

    NASA Astrophysics Data System (ADS)

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

    1996-12-01

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

  15. Laser-induced breakdown spectroscopy of tantalum plasma

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  16. Ion mobility spectrometry coupled to laser-induced fluorescence.

    PubMed

    Frankevich, Vladimir; Martinez-Lozano Sinues, Pablo; Barylyuk, Konstantin; Zenobi, Renato

    2013-01-01

    We report on interfacing a differential mobility analyzer (DMA) with laser-induced fluorescence (LIF) to simultaneously retrieve two-dimensional information on the electrical mobility and fluorescence spectroscopy of gas-phase ions. The fact that the separation of ions within DMA takes place in space rather than in time allows for the continuous selection of ion beams within a narrow range of mobilities that are further analyzed by LIF. Combination of DMA with LIF is simple and robust. It allows one to detect fluorescence from specified ions, including clusters, which would not survive in a mass spectrometer. Complex mixtures of fluorescent compounds can be separated by the DMA and studied by LIF. LIF is a sensitive technique and useful in the study of molecular interactions. DMA with LIF detection can be used for studies of gas-phase fluorescence of small molecules such as different dyes and their conjugates. This unique instrument combination may also provide a powerful platform for probing fluorescent proteins in the gas phase, which is of great fundamental interest for better understanding of their physical and chemical properties. In the present work, we have studied the gas-phase laser-induced fluorescence of mobility-selected rhodamine 6G ions. PMID:23198857

  17. Calibration analysis of zeolites by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  18. Laser-induced nuclear magnetic resonance splitting in hydrocarbons.

    PubMed

    Ikäläinen, Suvi; Lantto, Perttu; Manninen, Pekka; Vaara, Juha

    2008-09-28

    Irradiation of matter with circularly polarized light (CPL) shifts all nuclear magnetic resonance (NMR) lines. The phenomenon arises from the second-order interaction of the electron cloud with the optical field, combined with the orbital hyperfine interaction. The shift occurs in opposite directions for right and left CPL, and rapid switching between them will split the resonance lines into two. We present ab initio and density functional theory predictions of laser-induced NMR splittings for hydrocarbon systems with different sizes: ethene, benzene, coronene, fullerene, and circumcoronene. Due to the computationally challenging nature of the effect, traditional basis sets could not be used for the larger systems. A novel method for generating basis sets, mathematical completeness optimization, was employed. As expected, the magnitude of the spectral splitting increases with the laser beam frequency and polarizability of the system. Massive amplification of the effect is also observed close to the optical excitation energies. A much larger laser-induced splitting is found for the largest of the present molecules than for the previously investigated noble gas atoms or small molecules. The laser intensity required for experimental detection of the effect is discussed. PMID:19045001

  19. Laser induced damage in optical materials: 7th ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1976-06-01

    The Seventh ERDA-ASTM-ONR-NBS Symposium on Laser Induced Damage in Optical Materials was held at the National Bureau of Standards in Boulder, Colorado, on 29-31 July 1975. These Symposia are held as part of the activities in ASTM Subcommittee II on Lasers and Laser Materials, which is charged with the responsibilities of formulating standards and test procedures for laser materials, components, and devices. The Chairman of Subcommittee II is Haynes Lee, of Owens-Illinois, Inc. Co-chairmen for the Damage Symposia are Arthur Guenther of the Air Force Weapons Laboratory and Alexander J. Glass of Law-rence Livermore Laboratory. Over 150 attendees at the Symposium heard forty-five papers on topics relating fabrication procedures to laser induced damage in optical materials; on metal mirrors; in ir window materials; the multipulse, wavelength, and pulse length dependence of damage thresholds; damage in dielectric films and at exposed surfaces; as well as theoretical discussions on avalanche ionization and multiphoton processes of importance at shorter wavelengths. Of particular importance were the scaling relations developed from several parametric studies relating fundamental properties (refractive index, surface roughness etc.) to the damage threshold. This year many of the extrinsic influences tending to reduce a materials damage resistance were isolated such that measures of their egregious nature could be quantified. Much still needs to be accomplished to improve processing and fabrication procedures to allow a measurable approach to a materials intrinsic strength to be demonstrated. PMID:20165214

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Liu, Lina; Xie, Shusen

    2007-11-01

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

  2. 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.

  3. 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.

  4. Fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Othonos, Andreas

    1997-12-01

    Since the discovery of photosensitivity in optical fibers there has been great interest in the fabrication of Bragg gratings within the core of a fiber. The ability to inscribe intracore Bragg gratings in these photosensitive fibers has revolutionized the field of telecommunications and optical fiber based sensor technology. Over the last few years, the number of researchers investigating fundamental, as well as application aspects of these gratings has increased dramatically. This article reviews the technology of Bragg gratings in optical fibers. It introduces the phenomenon of photosensitivity in optical fibers, examines the properties of Bragg gratings, and presents some of the important developments in devices and applications. The most common fabrication techniques (interferometric, phase mask, and point by point) are examined in detail with reference to the advantages and the disadvantages in utilizing them for inscribing Bragg gratings. Reflectivity, bandwidth, temperature, and strain sensitivity of the Bragg reflectors are examined and novel and special Bragg grating structures such as chirped gratings, blazed gratings, phase-shifted gratings, and superimposed multiple gratings are discussed. A formalism for calculating the spectral response of Bragg grating structures is described. Finally, devices and applications for telecommunication and fiber-optic sensors are described, and the impact of this technology on the future of the above areas is discussed.

  5. History of grating images

    Microsoft Academic Search

    Fujio Iwata

    2001-01-01

    Toppan Printing Co., Ltd. originated the name of 'grating image'. It means an image that consists of diffraction grating dots that look similar to the halftone dots of conventional printing. We proposed this new display method using simple gratings in order to enhance the visual effects when illumination is made by a fluorescent lamp. We considered the use of simple

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

  8. 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.

  9. 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 [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  11. PHYSICAL REVIEW LETTERS Evidence for the Thermal Nature of Laser-Induced Polymer Ablation

    Microsoft Academic Search

    D. Dijkkamp; A. S. Gozdz; T. Venkatesan; X. D. Wu

    We report the results of an experiment designed to study the role of thermal processes in pulsed- laser-induced ablation of polymers. Using nonabsorbing polymer films on absorbing substrates and time-resolved reflectivity measurements, we show that laser-induced nanosecond heat pulses can cause rapid decomposition of polymers. This process exhibits all properties of so-called \\

  12. Time-Resolved Studies of Laser-Induced Phase Transitions in GaAs

    E-print Network

    Mazur, Eric

    .2.1 Self-Phase Modulation and Self-Focusing . . . 40 2.2.2 Fiber Characteristics and Preparation . . . . 45­ i ­ Time-Resolved Studies of Laser-Induced Phase Transitions in GaAs A thesis presented by Yakir-resolved experiments of the linear and nonlinear optical properties of GaAs during laser-induced phase transitions

  13. Laser-induced breakdown spectroscopy of copper with a 2 m thulium fiber laser

    E-print Network

    Richardson, Martin C.

    Laser-induced breakdown spectroscopy of copper with a 2 µm thulium fiber laser Matthieu Baudelet@creol.ucf.edu Abstract: We report the first implementation of a 2 µm thulium fiber laser in a Laser-Induced Breakdown-IR Thulium-fiber-laer Nanosecond Pulse at 2µm" presented at the 2nd North America Symposium on Laser

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

    E-print Network

    Lee, Tonghun

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

  15. Radial Variation of Refractive Index, Plasma Frequency and Phase Velocity in Laser Induced Air Plasma

    Microsoft Academic Search

    Manny Mathuthu; Rita M. Raseleka; Andrew Forbes; Nicholas West

    2006-01-01

    Laser-induced breakdown spectroscopy (LIBS) is a nonintrusive technique that needs no sample preparation and even recently, quantitative measurements were done without the need for calibration standards. Much research has been done on the laser induced air plasma to study the spatial variation of plasma parameters in the axial direction of the laser beam. In this paper, we report investigation on

  16. Remote Femtosecond Laser Induced Breakdown Spectroscopy (LIBS) in a Standoff Detection Regime

    E-print Network

    Van Stryland, Eric

    Remote Femtosecond Laser Induced Breakdown Spectroscopy (LIBS) in a Standoff Detection Regime C in response to the increasing threat to homeland security. Laser Induced Breakdown Spectroscopy (LIBS) has that femtosecond lasers may have advantages over nanosecond lasers for LIBS analysis in terms of SNR. Furthermore

  17. Thermoelectric generator fabricated via laser-induced forward transfer M.Feinaeugle1

    E-print Network

    Thermoelectric generator fabricated via laser-induced forward transfer M.Feinaeugle1 , C.L. Sones1 of a thermoelectric generator with the rapid, lithography-less technique of laser-induced forward transfer (LIFT on one substrate. The design of the proposed thermoelectric generator was selected to demonstrate

  18. Analysis of laser-induced breakdown images measuring the sizes of mixed aquatic nanoparticles

    Microsoft Academic Search

    J. W. Kim; J. A. Son; J. I. Yun; E. C. Jung; S. H. Park; J. G. Choi

    2008-01-01

    Sizes of aquatic colloidal nanoparticles are determined by utilizing the laser-induced breakdown detection technique. Specifically, the number of breakdown events is measured as a function of area in laser-induced plasma images, generated from a mixture of two different size nanoparticles in aqueous solution, by minimizing the energy of the incident laser irradiation to generate the plasma. We find that the

  19. Application of laser-induced breakdown spectroscopy to the analysis of metals in soils

    Microsoft Academic Search

    R. Barbini; F. Colao; R. Fantoni; A. Palucci; F. Capitelli

    1999-01-01

    In this paper, the influence of plasma temperature on quantitative laser-induced breakdown spectroscopy (LIBS) measurements is discussed, and a simple theoretical approach is used to model the plasma generation. It is shown that an estimate of the temperature of the laser-induced plasma and its inclusion in a model for line emission allows for substantial reduction of the matrix effect. To

  20. Discrete particle detection and metal emissions monitoring using laser-induced breakdown spectroscopy

    Microsoft Academic Search

    D. W. Hahn; W. L. Flower; K. R. Hencken

    1997-01-01

    The unique conditions for the application of laser-induced breakdown spectroscopy (LIBS) as a metal emissions monitoring technology have been discussed. Because of the discrete, particulate nature of effluent metals, the utilization of LIBS is considered in part as a statistical sampling problem involving the finite laser-induced plasma volume, as well as the concentration and size distribution of the target metal

  1. Laser induced fluorescence in Nd3+ : LaCl3 Hyperfine structures

    E-print Network

    Boyer, Edmond

    855 Laser induced fluorescence in Nd3+ : LaCl3 I. 2014 Hyperfine structures N. Pelletier décembre 1979, accepté le 13 mars 1980) Résumé. 2014 La technique d'affinement des raies de fluorescence trois niveaux. Abstract. 2014 The laser induced fluorescence line-narrowing technique has been used

  2. Conformational change of electrosprayed cytochrome c studied by laser-induced uorescence

    E-print Network

    Clemmer, David E.

    Conformational change of electrosprayed cytochrome c studied by laser-induced ¯uorescence Shozo The laser-induced ¯uorescence technique is applied to electrosprayed cytochrome c (cyt-c). While is required to obtain conformational in- formation directly relevant to those in solution. Cytochrome c (cyt

  3. Measurement of neutral density profile in a tokamak plasma using the principle of laser induced ionization

    Microsoft Academic Search

    V. I. Gladushchak; V. K. Gusev; M. Yu. Kantor; Yu. V. Petrov; G. T. Razdobarin; V. V. Semenov; S. Yu. Tolstyakov

    1995-01-01

    An application is discussed of a new method based on laser induced ionization that is an alternative to the laser induced fluorescence diagnostics. Here ionization of the hydrogen upper atomic states gives the local hydrogen densities in a plasma. On the basis of a rate equation analysis for a diffusion dominated plasma a probe saturation flux density of a few

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

    SciTech Connect

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

    2009-05-01

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

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

    E-print Network

    Killough, David Thomas

    2000-01-01

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

  6. 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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Cveji?, M.

    2014-12-01

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

  9. Laser-induced photo-thermal magnetic imaging.

    PubMed

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

    2012-08-20

    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. PMID:22991481

  10. Laser-induced photo-thermal magnetic imaging

    PubMed Central

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

    2012-01-01

    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. PMID:22991481

  11. Laser-Induced Microbubble Poration of Localized Single Cells†

    PubMed Central

    Hu, Wenqi; Ohta, Aaron T.

    2014-01-01

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

  12. 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.

  13. Radioactive contamination screening with laser-induced fluorescence

    SciTech Connect

    Sheely, R. [Oak Ridge K-25 Site, TN (United States); Di Benedetto, J. [EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations

    1994-06-01

    The ability to induce, detect and discriminate fluorescence of uranium oxides makes available new capabilities for screening the surface of large complex facilities for uranium. This paper will present the results of field tests evaluate laser-induced fluorescence (LIF) as a contamination screening tool and report on the progress to produce a field portable instrument for uranium surveys on exposed surfaces. The principal effect is to illuminate the surface of an object or an area with a remotely-located light source, and to evaluate the re-radiated emission energy. A gated intensified CCD camera was used with ultraviolet (UV) laser excitation to discriminate the phosphorescent (persistent) green uranium emission from the prompt background fluorescence which results from excitation of plants, concrete, soils, and other background materials.

  14. 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.

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

    PubMed

    Sezer, U?ur; 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

  16. A Spectral Analysis of Laser Induced Fluorescence of Iodine

    E-print Network

    Bayram, S B

    2015-01-01

    When optically excited, iodine absorbs in the 490- to 650-nm visible region of the spectrum and, after radiative relaxation, it displays an emission spectrum of discrete vibrational bands at moderate resolution. This makes laser-induced fuorescence spectrum of molecular iodine especially suitable to study the energy structure of homonuclear diatomic molecules at room temperature. In this spirit, we present a rather straightforward and inexpensive experimental setup and the associated spectral analysis which provides an excellent exercise of applied quantum mechanics fit for advanced laboratory courses. The students would be required to assign spectral lines, fill a Deslandres table, process the data to estimate the harmonic and anharmonic characteristics of the ground vibronic state involved in the radiative transitions, and thenceforth calculate a set of molecular constants and discuss a model of molecular vibrator.

  17. Laser-induced stress transients: applications for molecular delivery

    NASA Astrophysics Data System (ADS)

    Flotte, Thomas J.; Lee, Shun; Zhang, Hong; McAuliffe, Daniel J.; Douki, Tina; Doukas, Apostolos G.

    1995-05-01

    Lasers can be used to enhance the delivery of a number of molecules. Other investigators have demonstrated local release of molecules from liposomes following laser irradiation, microbeam disruption of the cell membrane to increase cell transport, microbeam ablation of the zona pellucida surrounding the ovum to increase the chances of fertilization, and increased transcutaneous transport following ablation of the stratum corneum. Our experiments have shown that laser-induced stress transients can be utilized as a vector for intracellular delivery of molecules that may or may not normally cross the cell membrane. These two conditions have been tested with Photofrin and DNA. This technology may have applications in cell and molecular biology, cancer therapy, gene therapy, and others.

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

    NASA Technical Reports Server (NTRS)

    Bradshaw, John D.

    1994-01-01

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

  19. 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

  20. Laser induced extraplanar propulsion for three-dimensional microfabrication

    SciTech Connect

    Birnbaum, A. J.; Pique, A. [Materials Science and Technology Division, Code 6364, Naval Research Laboratory, Washington, DC 20375 (United States)

    2011-03-28

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

  1. Containerless study of metal evaporation by laser induced fluorescence

    NASA Technical Reports Server (NTRS)

    Schiffman, Robert A.; Nordine, Paul C.

    1987-01-01

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

  2. Evaluation of Laser-Induced Breakdown Spectroscopy as Technetium Monitor

    SciTech Connect

    Spencer, W.A.; Yueh, F.Y.; Sharma, R.C.; Singh, J.P.; Zhang, H.

    2000-11-14

    The analytical figure of merit of a laser-induced breakdown (LIBS) system was evaluated for technetium measurements in liquid. LIBS data of elements that have similar properties to Tc such as Cr, Mn, and Re were studied. Various optical geometries which produce the laser spark in and at the liquid sample were tested. The calibration curve for Mn, Cr, and Re were obtained at the optimized experimental conditions with bulk liquid and liquid jet. We found that measurements using a liquid jet provide better detection limits than the bulk liquid measurements. The detection limits of Mg, Cr, Mn, and Re in a liquid jet measurement are found to be 0.1, 0.4, 0.7, and 10 ppm, respectively.

  3. Quantitative analysis of gallstones using laser-induced breakdown spectroscopy

    SciTech Connect

    Singh, Vivek K.; Singh, Vinita; Rai, Awadhesh K.; Thakur, Surya N.; Rai, Pradeep K.; Singh, Jagdish P

    2008-11-01

    The utility of laser-induced breakdown spectroscopy (LIBS) for categorizing different types of gallbladder stone has been demonstrated by analyzing their major and minor constituents. LIBS spectra of three types of gallstone have been recorded in the 200-900 nm spectral region. Calcium is found to be the major element in all types of gallbladder stone. The spectrophotometric method has been used to classify the stones. A calibration-free LIBS method has been used for the quantitative analysis of metal elements, and the results have been compared with those obtained from inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements. The single-shot LIBS spectra from different points on the cross section (in steps of 0.5 mm from one end to the other) of gallstones have also been recorded to study the variation of constituents from the center to the surface. The presence of different metal elements and their possible role in gallstone formation is discussed.

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

    PubMed Central

    2015-01-01

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

  5. Development of Isotope Analysis Based on Laser Induced Fluorescence

    SciTech Connect

    Sakai, T.; Watanabe, K.; Uritani, A. [Department of Materials, Physics and Energy Engineering, Nagoya University (Japan); Tomita, H.; Iguchi, T. [Department of Quantum Engineering, Nagoya University (Japan)

    2009-03-17

    We have proposed Laser Induced Fluorescence analysis using Doppler Shift of laser ablated atoms for Isotope Analysis (LIF-DS-IA). This isotope analysis is expected to have a small mass discrimination effect because the detection target is fluorescence photons instead of ions, which distort the measured isotope ratio by the space charge effect. We demonstrate this technique to be feasible through the model calculations. We experimentally confirmed the fundamental behavior in LIF-DS-IA that the shift in the irradiating laser frequency corresponds to that of peak position in the time domain LIF spectra. The reason of poor mass resolution in the present system was considered to be inadequate definition in the field of view of the fluorescence detector.

  6. Optical properties of laser induced oxynitride films on titanium

    NASA Astrophysics Data System (ADS)

    Skowro?ski, ?.; Anto?czak, A. J.; Trzcinski, M.; ?azarek, ?.; Hiller, T.; Bukaluk, A.; Wronkowska, A. A.

    2014-06-01

    This paper presents a study of the optical properties and chemical composition of laser-induced color oxynitride films formed on titanium substrates in a normal-pressure atmospheric environment. The samples were investigated by spectroscopic ellipsometry and X-ray photoelectron spectroscopy. The influence of the laser fluence F on the optical properties of oxynitride films has been found. The thickness of the layers ranges from ?20 nm to ?40 nm and increases linearly with F. The determined complex dielectric functions demonstrate two absorption bands, one of them appears in the visible-light wavelength range. We show that the color created by oxynitride films formed on the titanium surface depends not only on the interference effect as commonly assumed, but is also a function of the changes of the optical properties of these coatings.

  7. Encoding terahertz signatures into laser-induced plasma acoustic waves

    NASA Astrophysics Data System (ADS)

    Clough, Benjamin; Liu, Jingle; Zhang, X.-C.

    2011-02-01

    The enhancement of acoustic waves from a laser-induced plasma, from audible into the ultrasonic range, is a linear function of the terahertz (THz) intensity incident on the plasma, making THz-enhanced acoustics (TEA) useful for THz detection at a standoff distance. When a femtosecond laser of sufficient peak energy is focused into air, the gas is ionized and acoustic waves are launched through the photoacoustic process. THz field-induced energy transfer through acceleration of free electrons, and the following electron-molecule collisions, results in an enhanced acoustic emission from the plasma. A physical understanding of free electron manipulation inside a dual-color laser filament is used to encode THz spectroscopic information into acoustic waves, making it possible to coherently detect the electric field profile of the THz pulse by simply "listening" to the plasma from a distance. Our most recent results utilizing TEA as method for remote THz detection will be presented.

  8. 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.

  9. Laser-Induced Breakdown Spectroscopy: A Novel Technology for the Rapid Detection, Identification, and Discrimination of Biological Agents

    E-print Network

    Rehse, Steven J.

    Laser-Induced Breakdown Spectroscopy: A Novel Technology for the Rapid Detection, Identification. Adam, and J. Amouroux, "Detection of bacteria by time-resolved laser-induced breakdown spectroscopy, "Laser-induced breakdown spectroscopy of bacterial spores, molds, pollens, and protein: initial studies

  10. Titanium monoxide spectroscopy following laser-induced optical breakdown

    SciTech Connect

    Parigger, Christian G.; Woods, Alexander C.; Keszler, Anna; Nemes, Laszlo; Hornkohl, James O. [The University of Tennessee/UT Space Institute, Center for Laser Applications, 411 B.H. Goethert Parkway, Tullahoma, TN 37388-9700 (United States); Chemical Research Center of the Hungarian Academy of Sciences, Institute of Materials and Environmental Chemistry, Pusztaszeri ut 59-67, H-1025 Budapest (Hungary); Chemical Research Center of the Hungarian Academy of Sciences, Laser Spectroscopy Laboratory, Pusztaszeri ut 59-67, H-1025 Budapest (Hungary); Hornkohl Consulting, Tullahoma, TN 37388 (United States)

    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. History of grating images

    NASA Astrophysics Data System (ADS)

    Iwata, Fujio

    2001-06-01

    Toppan Printing Co., Ltd. originated the name of 'grating image'. It means an image that consists of diffraction grating dots that look similar to the halftone dots of conventional printing. We proposed this new display method using simple gratings in order to enhance the visual effects when illumination is made by a fluorescent lamp. We considered the use of simple gratings as elemental dots, and used a number of elemental dots to display a 2D image. This method produces an effect something like the halftone dots of printing. The grating image technology grows from its starting to become able to produce 3D images and a 3D-video system using an electron beam grating-writing system.

  13. Biopolymer holographic diffraction gratings

    Microsoft Academic Search

    Svetlana Savi? Ševi?; Dejan Pantelic

    2008-01-01

    Surface-relief diffraction gratings are holographically recorded in dextran sensitized with ammonium dichromate (DCD). DCD was exposed with single-frequency 200mW diode pumped ND-YAG laser, at 532nm. The diffraction grating profiles were analyzed by atomic force microscopy (AFM). It was found that different surface profiles could be obtained. Gratings with 330lines\\/mm spatial frequencies were made. Existence of higher harmonics in Fourier Transform

  14. Grating image technology

    NASA Astrophysics Data System (ADS)

    Iwata, Fujio

    1995-07-01

    The word 'grating image' was first named by Toppan Printing Company, Ltd. It means that an image consists of grating dots. In 1988, we presented this new technology at the Optical Security Systems Symposium, in Switzerland. Then it was improved and applied in display application. Recently, it was further applied in 3D video systems. In this report, the development history and the recent situations of grating image technology are described.

  15. Multivariate Analysis of Laser-Induced Breakdown Spectroscopy for Discrimination between Explosives and Plastics

    NASA Astrophysics Data System (ADS)

    Wang, Qian-Qian; Liu, Kai; Zhao, Hua

    2012-04-01

    A method to distinguish explosives from plastics using laser-induced breakdown spectroscopy is discussed. A model for classification with cross-validation theory is built based on the partial least-square discriminant analysis method. Seven types of plastics and one explosive are used as samples to test the model. The experimental results demonstrate that laser-induced breakdown spectroscopy has the capacity to discriminate explosives from plastics combined with chemometrics methods. The results could be useful for prospective research of laser-induced breakdown spectroscopy on the differentiation of explosives and other materials.

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

    SciTech Connect

    Bien-Aime, Karell; Neauport, Jerome; Tovena-Pecault, Isabelle; Fargin, Evelyne; Labrugere, 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.

  17. Biopolymer holographic diffraction gratings

    NASA Astrophysics Data System (ADS)

    Savi? Ševi?, Svetlana; Panteli?, Dejan

    2008-03-01

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

  18. 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.

  19. 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.

  20. Laser-induced optogalvanic signal oscillations in miniature neon glow discharge plasma.

    PubMed

    Saini, V K

    2013-06-20

    Laser-induced optogalvanic (OG) signal oscillations detected in miniature neon glow discharge plasma are investigated using a discharge equivalent-circuit model. The damped oscillations in OG signal are generated when a pulsed dye laser is tuned to a specific neon transition (1s5?2p2) at 588.2 nm under the discharge conditions where dynamic resistance changes its sign. Penning ionization via quasi-resonant energy transfer collisions between neon gas atoms in metastable state and sputtered electrode atoms in ground state is discussed to explain the negative differential resistance properties of discharge plasma that are attributed to oscillations in the OG signal. The experimentally observed results are simulated by analyzing the behavior of an equivalent discharge-OG circuit. Good agreement between theoretically calculated and experimental results is observed. It is found that discharge plasma is more sensitive and less stable in close vicinity to dynamic resistance sign inversion, which can be useful for weak-optical-transition OG detection. PMID:23842186

  1. 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

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

    SciTech Connect

    Barefield Il, James E [Los Alamos National Laboratory; Clegg, Samuel M [Los Alamos National Laboratory; Le, Loan A [Los Alamos National Laboratory; Lopez, Leon N [Los Alamos National Laboratory

    2010-01-01

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

  3. Laser-induced fluorescence photobleaching anemometer for flow velocity measurement in sub-microscale fluidic channels

    Microsoft Academic Search

    G. R. Wang; J. Guo; Y. Lin; J. Feng; J. Wei; Y. Wang; S. Krishnamoorthy; S. Sundaram

    2006-01-01

    A non-particle tracing technique based on laser-induced fluorescence photobleaching is demonstrated for measuring the flow velocity in microfluidic channels. The technique can give high spatial and temporal resolution in the measurement of velocity in microfluidic channels

  4. CAPILLARY ELECTROPHORESIS/LASER-INDUCED FLUORESCENCE DETECTION OF FLUORESCEIN AS A GROUNDWATER MIGRATION TRACER

    EPA Science Inventory

    Capillary electrophoresis (CE) has been applied to the determination of the groundwater migration tracer dye fluorescein based on laser-induced fluorescence (LIF) detection and compared to determinations obtained with traditional spectrofluorimetry. Detection limits of injected d...

  5. 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.

  6. Enhanced and suppressed birefringence in fiber Bragg gratings

    Microsoft Academic Search

    Suresh Pereira; J. E. Sipe; R. E. Slusher; Stefan Spalter

    2002-01-01

    We demonstrate theoretically and experimentally that two orthogonal polarizations of light see an unequal index contrast in a UV-induced fiber Bragg grating. We have found that in a Bragg grating the phase-velocity mismatch is a function of detuning, and hence we can introduce an effective birefringence. The description of the polarization dynamics that we developed was confirmed by a set

  7. Micromachined Vibratory Diffraction Grating Scanner for Multiwavelength Collinear Laser Scanning

    Microsoft Academic Search

    Guangya Zhou; Fook Siong Chau

    2006-01-01

    This paper presents an effective method to achieve multiwavelength collinear laser scanning using micromachined vibratory grating scanners, which have the potential to scan at high frequencies without the optical performance degradation resulting from dynamic nonrigid-body deformation. An optical simulation model has been developed to predict the scanning patterns of the vibratory grating scanners. The proposed multiwavelength collinear scanning method was

  8. Grating image technology

    Microsoft Academic Search

    Fujio Iwata

    1995-01-01

    The word 'grating image' was first named by Toppan Printing Company, Ltd. It means that an image consists of grating dots. In 1988, we presented this new technology at the Optical Security Systems Symposium, in Switzerland. Then it was improved and applied in display application. Recently, it was further applied in 3D video systems. In this report, the development history

  9. Laser-induced fluorescence of collagen and cholestrol

    NASA Astrophysics Data System (ADS)

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

    1995-03-01

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

  10. Evaluation of immunoglobulins in bovine colostrum using laser induced fluorescence.

    PubMed

    Abdel-Salam, Z; Abdel Ghany, Sh; Harith, M A

    2014-11-01

    The objective of the present study was to exploit laser induced fluorescence (LIF) as a spectrochemical analytical technique for evaluation of immunoglobulin (IgG) in bovine colostrum. Colostrum samples were collected from different American Holstein cows at different times after calving. Four samples were gathered from each cow; the first three samples were obtained from the first three milkings (colostrum) and the fourth sample (milk) was obtained a week after calving. It has been demonstrated that LIF can be used as a simple, fast, sensitive and less costly spectrochemical analytical technique for qualitative estimation of IgG in colostrum. LIF results have been confirmed via the quantitative evaluation of IgG in the same samples adopting the single radial immunodiffusion conventional technique and a very good agreement has been obtained. Through LIF it was possible to evaluate bovine colostrum after different milking times and to differentiate qualitatively between colostrum from different animals which may reflect their general health status. A fluorescence linear calibration curve for IgG concentrations from 0 up to 120 g L(-1) has been obtained. In addition, it is feasible to adopt this technique for in situ measurements, i.e. in dairy cattle farms as a simple and fast method for evaluation of IgG in bovine colostrum instead of using lengthy and complicated conventional techniques in laboratories. PMID:25127559

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

    PubMed

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

    2012-12-01

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

  12. Diode laser-induced infrared fluorescence of water vapour

    NASA Astrophysics Data System (ADS)

    Li, Hejie; Hanson, Ronald K.; Jeffries, Jay B.

    2004-07-01

    Infrared laser-induced fluorescence (LIF) of water vapour was investigated for its potential as a spatially resolved gasdynamic diagnostic. A cw diode laser operating near 1392 nm was scanned across a single absorption transition in the ngr1 + ngr3 band of H2O in a static cell, and the resulting fluorescence signal was collected near 2.7 µm (both ngr1 and ngr3 bands). Experiments were conducted at low pressure in pure water vapour and mixtures of water vapour and N2 using a 20 mW laser in a double-pass arrangement. A simple analytical model was developed to relate LIF intensity to gas properties as a function of laser power. The spectrally resolved, single-line excitation spectrum was fitted with a Voigt profile, allowing inference of the water vapour temperature from the Doppler-broadened component of the measured fluorescence lineshape. A two-line excitation scheme was also investigated as a means of measuring temperature with reduced measurement time. From these initial measurements, we estimate that a practical sensor for atmospheric pressure applications would require a minimum of 1-2 W of laser power for two-line, fixed-wavelength temperature measurements and a minimum of about 70 W of power for scanned-wavelength measurements.

  13. Laser-Induced Temperature Jump Infrared Measurements of RNA Folding

    PubMed Central

    Dyer, R. Brian; Brauns, Eric B.

    2011-01-01

    Probing a sample using infrared spectroscopy following a laser-induced temperature jump is a powerful method to monitor fast relaxation kinetics. Here, we describe how this approach is used to study the kinetics of RNA folding. We begin with a concise summary of the infrared spectral properties of RNA in the 1500–1800 cm?1 region. The infrared transitions in this region are directly related to the double bond stretching vibrations and ring modes of the nucleotide bases. When RNA undergoes a conformational change, the local environments of the nucleotides are altered. Consequently, the changes in the corresponding infrared spectrum are associated with the structural changes. Experimentally, temperature is used to systematically vary the RNA structure. When a short laser pulse is used to produce a rapid temperature increase in the sample, the structural changes that ensue can be followed in real time. In this contribution, we discuss experimental methods including sample preparation, instrumentation, and data analysis. We conclude with several experimental examples that highlight usefulness of the technique. PMID:20946798

  14. 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

  15. 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.

  16. 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.

  17. Electron density determination of aluminium laser-induced plasma

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  18. 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

  19. Laser-induced autofluorescence study of caries model in vitro.

    PubMed

    Borisova, Ekaterina; Uzunov, Tzonko; Avramov, Latchezar

    2006-04-01

    Laser-induced autofluorescence spectra of teeth irradiated by a 337 nm nitrogen laser were measured during in vitro caries formation through initial enamel demineralization and introducing of carious bacterial flora in the lesions developed. Spectra obtained from sound teeth consist of an intensive maximum at 480-500 nm and secondary maximum at 430-450 nm. In the process of caries formation, we observed an increase in the intensity at 430-450 nm and the appearance of two maxima in the red spectral region-at 590-650 nm. The intensity increase at 430-450 nm was related to the tooth demineralization. Bacteria presence and their metabolism products induced an increase in the absorption in the UV-blue spectral region at 350-420 nm and the appearance of a fluorescence signal in the long-wave spectral region at 590-650 nm. From the point of view of tissue optics, these results allow caries to be considered as consisting of two different phenomena-tissue destruction and bacterial flora and its metabolism products increase. The results could be used to obtain a more complete picture of caries formation on the base of its fluorescent properties. PMID:16568211

  20. Laser-induced surface modification and metallization of polymers

    NASA Astrophysics Data System (ADS)

    Frerichs, Hartmut; Wesner, David A.; Kreutz, Ernst-Wolfgang

    1995-04-01

    Laser-induced surface modification of various polymers is presented as a suitable pretreatment of surfaces in a two-step metallization process. Materials such as polyamide (PA), polypropylene (PP), polystyrene (PS), polycarbonate (PC), acrylbutadienestyrene (ABS), styreneacrylnitril (SAN), polybutadieneterphtalate (PBT), and polyoxymethylen (POM) were treated by excimer laser radiation ((lambda) equals 248 nm) in air. The aim of this study is to investigate different processing regimes of surface modification. Therefore the laser processing variables fluence F, repetition rate v and pulse number N are varied and the absorption coefficient, optical penetration depth, ablation depth and ablation threshold are determined. The surface morphology and surface roughness are studied by optical surface profilometry and secondary electron microscopy (SEM). The influence of laser treatment on chemical composition of modified and ablated surfaces is analyzed by X-ray photoelectron spectroscopy (XPS). Depending on the processing parameters and materials properties different microstructures and values of surface roughness are generated on the micrometer length scale. Pretreatment for the subsequent metallization is performed with laser radiation, wet chemical and plasma etching. The metallization of polymers is investigated for different surface morphologies. The used metallization processes are electroplating and physical vapor deposition (PVD). Adhesion of the deposited films, measured with scratch and tape test methods, is used as a criterion for determining regimes of suitable surface modification for subsequent metallization.

  1. 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

  2. Laser-induced fluorescence diagnostic for measuring magnetic fields (abstract)

    NASA Astrophysics Data System (ADS)

    Jones, T. G.; Noonan, W. A.; Neri, J. M.; Ottinger, P. F.

    1999-01-01

    A novel, spatially resolved diagnostic is being developed to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as is envisioned for ion-driven inertial confinement fusion. The diagnostic technique uses laser-induced fluorescence spectroscopy, and can be varied to measure either small or large fields. Small fields, as expected in ballistic beam transport, produce Zeeman shifts, ??Z, much smaller than the transition linewidth ??. High sensitivity to measure these sub-Doppler shifts is achieved by a variation on the Babcock technique.Reference 1 Large fields, as expected in self-pinched beam transport, produce ??Z larger than ??. These ??Z will be resolved using a Fabry-Pérot interferometer, in a novel technique similar to that for small fields. Results from benchtop experiments using calibrated B fields for the small-field technique will be presented. Available results from a proof-of-principle experiment for the large-field technique will also be presented.

  3. Wavelet-based laser-induced ultrasonic inspection in pipes

    NASA Astrophysics Data System (ADS)

    Baltazar-López, Martín E.; Suh, Steve; Chona, Ravinder; Burger, Christian P.

    2006-02-01

    The feasibility of detecting localized defects in tubing using Wavelet based laser-induced ultrasonic-guided waves as an inspection method is examined. Ultrasonic guided waves initiated and propagating in hollow cylinders (pipes and/or tubes) are studied as an alternative, robust nondestructive in situ inspection method. Contrary to other traditional methods for pipe inspection, in which contact transducers (electromagnetic, piezoelectric) and/or coupling media (submersion liquids) are used, this method is characterized by its non-contact nature. This characteristic is particularly important in applications involving Nondestructive Evaluation (NDE) of materials because the signal being detected corresponds only to the induced wave. Cylindrical guided waves are generated using a Q-switched Nd:YAG laser and a Fiber Tip Interferometry (FTI) system is used to acquire the waves. Guided wave experimental techniques are developed for the measurement of phase velocities to determine elastic properties of the material and the location and geometry of flaws including inclusions, voids, and cracks in hollow cylinders. As compared to the traditional bulk wave methods, the use of guided waves offers several important potential advantages. Some of which includes better inspection efficiency, the applicability to in-situ tube inspection, and fewer evaluation fluctuations with increased reliability.

  4. Stimulated laser induced fluorescence holography for imaging fluorescent species

    NASA Astrophysics Data System (ADS)

    Amer, Eynas; Gren, Per; Sjödahl, Mikael

    2013-01-01

    In this paper pulsed digital holographic detection is coupled to the stimulated laser induced fluorescence (LIF) effect for imaging fluorescent species. A frequency tripled Q-switched Nd-YAG laser (wavelength 355 nm, pulse duration 12 ns) has been used to pump Coumarin 153 dye solved in ethanol. Simultaneously a frequency doubled pulse (532 nm) from the same laser is used to probe the solvent resulting in a gain through stimulated emission. The resulting gain of the probe beam is recorded using digital holography by blending it with a reference beam on the detector. Intensity maps were calculated from the recorded digital holograms and used to calculate the gain of the probe beam due to stimulated fluorescence emission which is coupled to the concentration of the dye. The results show that the amplification of the probe beam (532 nm) due to stimulated LIF emission is seen in the intensity maps. The gain is about 40% at a dye concentration of 0.32 g/L and decreases to be about 20% at a dye concentration of 0.04 g/L for a probe beam energy density of 0.1 mJ/cm2. Spectroscopic measurements have been carried out to confirm the holographic results. The results show that stimulated LIF holography is a promising technique for quantitative imaging of fluorescent species.

  5. Evidence of New Turbulence Physics in Laser Induced Plasma*

    NASA Astrophysics Data System (ADS)

    Mezonlin, E.-D.; Podder, N. K.; Johnson, J. A., III; Johnson, Lewis E.; Alexander, A. B.

    2002-11-01

    Distinct signatures have been found in a variety of turbulent plasmas showing both a sensitivity to molecular parameters and behaviors consistent with an approach to turbulence using nonequilibrium statistical mechanics. This includes glow discharge plasmas, plasmas produced by microwaves, and hypersonic and stationary plasmas produced with ionizing shock waves. In this work, we study the turbulent characterizing parameters in a plasma generated by our Nd:YAG lasers. The laser pulse duration is <10 ns and the pulse energy ranges from 10 to 300 mJ. A spectrometer combined with a CCD camera records the evolution of neutral emissions from ion collisions at 20 MHz sampling rate. Intensity fluctuation data of a spectral line are also collected at 500 MHz sampling rate. We determine three distinct turbulent regimes in the laser induced plasma turbulence. We find characterizing frequencies in the turbulent behaviors consistent with previous observations and thereby potentially predictive of turbulent transport coefficients. We will report on the dependence of these effects on changing plasma atomic constituents. *This work was supported in part by grants from NASA MURED, DOE Office of Fusion Energy Science and from Boeing.

  6. Laser Induced Fluorescence Diagnostic for the Plasma Couette Experiment

    NASA Astrophysics Data System (ADS)

    Katz, Noam; Skiff, Fred; Collins, Cami; Weisberg, Dave; Wallace, John; Clark, Mike; Garot, Kristine; Forest, Cary

    2010-11-01

    The Plasma Couette Experiment (PCX) at U. Wisconsin-Madison consists of a rotating high-beta plasma and is well-suited to the study of flow-driven, astrophysically-relevant plasma phenomena. PCX confinement relies on alternating rings of 1kG permanent magnets and the rotation is driven by electrode rings, interspersed between the magnets, which provide an azimuthal ExB. I will discuss the development of a laser-induced fluorescence diagnostic (LIF) to characterize the ion distribution function of argon plasmas in PCX. The LIF system--which will be scanned radially--will be used to calibrate internal Mach probes, as well as to measure the time-resolved velocity profile, ion temperature and density non-perturbatively. These diagnostics will be applied to study the magneto-rotational instability in a plasma, as well as the buoyancy instability thought to be involved in producing the solar magnetic field. This work is supported by NSF and DOE.

  7. Peak soot temperature in laser-induced incandescence measurements

    NASA Astrophysics Data System (ADS)

    de Iuliis, S.; Migliorini, F.; Cignoli, F.; Zizak, G.

    2006-06-01

    In order to understand the processes involved in the laser-induced incandescence (LII) technique, the value of soot temperature at the peak of the incandescence signal has been studied. To this purpose, an absolute two-color LII technique has been applied on ethylene and methane diffusion flames, based on the comparison with a calibrated tungsten ribbon lamp. The dependence of peak temperature on the fluence has been investigated by using a sharply edged probe beam. Above a certain fluence threshold a value close to 4000 K was obtained for both flames at all locations, that means in largely different soot conditions. At a suitably selected laser fluence, radial and axial profiles of peak soot temperature and volume fraction were performed. Soot volume fraction data have been validated with results from laser extinction technique measurements. The quite low values observed for methane prove the sensitivity of the LII technique. Moreover, a discussion about soot refractive index is presented. In the visible region a test of its influence on both soot volume fraction and soot peak temperature was carried out, while in the infrared the heating process was analyzed.

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

    PubMed Central

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

    2013-01-01

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

  9. Elemental analysis of fertilizer using laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Farooq, W. A.; Al-Mutairi, F. N.; Khater, A. E. M.; Al-Dwayyan, A. S.; AlSalhi, M. S.; Atif, M.

    2012-06-01

    In recent years, the use of fertilizers has increased to achieve high growth rate of agriculture products. With this increase the chemical impact of agricultural activities on the environment has also been enhanced. In order to keep the environment healthy, and clean, it is necessary to identify contaminants and characterize the sources of contamination. In this study, a comprehensive chemical characterization of a DAP fertilizer has been carried out using laser induced breakdown spectroscopy. Phosphorous, manganese, magnesium, iron, titanium, molybdenum, nickel, cobalt, aluminum, chromium, lead, and uranium traces are detected. Relative abundances of Phosphorous, manganese, magnesium, molybdenum, iron, titanium, nickel, vanadium, calcium, cobalt, cadmium, tin are 26.64, 17.75, 13 97, 8.25, 7.97, 7.11, 5.07, 3.15, 2.94, 1.94, 1,55, 1.73 percent, respectively, whereas relative abundances of sulfur, aluminum, chromium, lead, and uranium are less than 1% and their sum is 1.93% of the total sample.

  10. 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.

  11. 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.

  12. 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.

  13. The LILIA (laser induced light ions acceleration) experiment at LNF

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Anania, M. P.; Caresana, M.; Cirrone, G. A. P.; De Martinis, C.; Delle Side, D.; Fazzi, A.; Gatti, G.; Giove, D.; Giulietti, D.; Gizzi, L. A.; Labate, L.; Londrillo, P.; Maggiore, M.; Nassisi, V.; Sinigardi, S.; Tramontana, A.; Schillaci, F.; Scuderi, V.; Turchetti, G.; Varoli, V.; Velardi, L.

    2014-07-01

    Laser-matter interaction at relativistic intensities opens up new research fields in the particle acceleration and related secondary sources, with immediate applications in medical diagnostics, biophysics, material science, inertial confinement fusion, up to laboratory astrophysics. In particular laser-driven ion acceleration is very promising for hadron therapy once the ion energy will attain a few hundred MeV. The limited value of the energy up to now obtained for the accelerated ions is the drawback of such innovative technique to the real applications. LILIA (laser induced light ions acceleration) is an experiment now running at LNF (Frascati) with the goal of producing a real proton beam able to be driven for significant distances (50-75 cm) away from the interaction point and which will act as a source for further accelerating structure. In this paper the description of the experimental setup, the preliminary results of solid target irradiation and start to end simulation for a post-accelerated beam up to 60 MeV are given.

  14. 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.

  15. Measurement of Formaldehyde by Laser Induced Fluorescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cryer, D. R.; Ingham, T.; Whalley, L. K.; Heard, D. E.

    2014-12-01

    Gas phase formaldehyde (HCHO) is a key species in the troposphere. It is formed as an intermediate product during the removal of almost all volatile organic compounds (VOCs) by the hydroxyl radical (OH) and is a tracer of overall oxidising capacity. A new instrument has been developed for the measurement of [HCHO] by laser induced fluorescence (LIF) spectroscopy and deployed in the field. Ultra-violet (UV) radiation from a tuneable fibre laser was used to excite HCHO in a low pressure cell (~130 Torr) at ca. 353 nm with fluorescence collected between 390 - 550 nm. The resulting fluorescence was detected by a photomultiplier tube (PMT) and processed by photon counting techniques. The instrument performance will be described in detail in addition to a novel calibration method where a known quantity of HCHO was produced through photolysis of methanol (CH3OH) vapour in the presence of oxygen. The instrument was first deployed in June 2014 at a suburban site in York (UK). Data from this campaign and interpretation will be presented in addition to observations from more recent field measurements.

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

    SciTech Connect

    NONE

    1999-06-01

    Laser-Induced Fluorescence (LIF) was demonstration as part of the Fernald Environmental Management Project (FEMP) Plant 1 Large Scale Demonstration and Deployment Project (LSDDP) sponsored by the US Department of Energy (DOE) Office of Science and Technology, Deactivation and Decommissioning Focus Area located at the Federal Energy Technology Center (FETC) in Morgantown, West Virginia. The demonstration took place on November 19, 1996. In order to allow the contaminated buildings undergoing deactivation and decommissioning (D and D) to be opened to the atmosphere, radiological surveys of floors, walls and ceilings must take place. After successful completion of the radiological clearance survey, demolition of the building can continue. Currently, this process is performed by collecting and analyzing swipe samples for radiological analysis. Two methods are used to analyze the swipe samples: hand-held frisker and laboratory analysis. For the purpose of this demonstration, the least expensive method, swipe samples analyzed by hand-held frisker, is the baseline technology. The objective of the technology demonstration was to determine if the baseline technology could be replaced using LIF.

  17. 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.

  18. 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

  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. 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.

  1. Picosecond laser induced periodic surface structure on copper thin films

    NASA Astrophysics Data System (ADS)

    Huynh, Thi Trang Dai; Petit, Agnès; Semmar, Nadjib

    2014-05-01

    LIPSS (Laser Induced Periodic Surface Structure) formation on copper thin films induced by a picosecond laser beam (Nd:YAG laser at 266 nm, 42 ps and 10 Hz) was studied experimentally. Copper thin films were deposited on glass and silicon substrates by magnetron sputtering. The surface modifications of irradiated zones were analyzed by scanning electron microscopy. Two distinct types of LIPSS were identified with respect to the laser fluence (F), number of laser shots (N) and substrate material. Namely, with a number of laser shots (1000 < N < 10,000) and a fluence of (200 mJ/cm2 < F < 500 mJ/cm2), Low Spatial Frequency LIPSS (LSFL with a spatial period of ? ? 260 nm and an orientation perpendicular to polarization) and High Spatial Frequency LIPSS (HSFL with a spatial period of ? ? 130 nm and an orientation parallel to the polarization) were observed. The regime of regular spikes formation was determined for N ? 1000. Moreover, the 2D-map of the relationship among LIPSS formation, laser fluence and number of laser shots on copper thin film with two different substrates was established. A physics interpretation of regular spikes and LIPSS formation on copper thin film induced by ps laser with overlapping multi-shots is proposed based on experimental data and the theory of Plateau-Rayleigh instability.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  3. Laser-induced chemistry: an advanced tool for micro structuring, synthesis, and modification of materials

    Microsoft Academic Search

    Simeon Metev; Andreas Stephen; Joerg Schwarz; Carsten Wochnowski

    2004-01-01

    Laser-induced technological chemical processes can significantly contribute to the development of new methods for micro treatment of materials and hence to the broadening of the application spectrum of laser microtechnology. In this paper three typical laser-activated chemical technological methods in liquids, gases and solids and their possible applications are presented and discussed: (1) Laser-induced liquid-phase jet-chemical etching of metals. In

  4. Quantitative determination of element concentrations in industrial oxide materials by laser-induced breakdown spectroscopy

    Microsoft Academic Search

    B. Praher; R. Rössler; E. Arenholz; J. Heitz; J. D. Pedarnig

    Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) method is employed for quantitative determination of oxide\\u000a concentrations in multi-component materials. Industrial oxide materials from steel industry are laser ablated in air, and\\u000a the optical plasma emission is collected by spectrometers and gated detectors. The temperature and electron number density\\u000a of laser-induced plasma are determined from measured LIBS spectra. Emission lines of aluminium (Al),

  5. Laser-induced periodic annular surface structures on fused silica surface

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Brelet, Yohann; He, Zhanbing; Yu, Linwei; Forestier, Benjamin; Deng, Yongkai; Jiang, Hongbing; Houard, Aurélien

    2013-06-01

    We report on the formation of laser-induced periodic annular surface structures on fused silica irradiated with multiple femtosecond laser pulses. This surface morphology emerges after the disappearance of the conventional laser induced periodic surface structures, under successive laser pulse irradiation. It is independent of the laser polarization and universally observed for different focusing geometries. We interpret its formation in terms of the interference between the reflected laser field on the surface of the damage crater and the incident laser pulse.

  6. Experimental study of underwater rock drilling using a pulsed Ho:YAG laser-induced jets

    Microsoft Academic Search

    K. Ohtani; D. Numata; K. Takayama; T. Kobayashi; K. Okatsu

    2009-01-01

    This paper is primarily an assessment of laser-induced water jets for boring rock surfaces. It also reports the result of\\u000a preliminary experiments of pulsed Ho:YAG laser-induced jets applied to drill a submerged rock specimen. The irradiation of\\u000a pulsed Ho:YAG laser beams at 3 Hz inside a thin metal tube produces intermittent water vapor bubbles which result in liquid\\u000a jet discharge from

  7. Laser-induced damage and two-photon absorption measurements in CdTe

    Microsoft Academic Search

    M. J. Soileau; E. W. van Stryland; W. E. Williams; M. W. Woodall; S. F. Brown

    1982-01-01

    The results of laser-induced damage and nonlinear absorption measured for CdTe and other selected II-VI materials are reported. These studies were conducted using pulsed 1.06-micron radiation from a Nd:YAG laser. The laser pulsewidth was varied from approximately 40 psec to 9,000 psec (9 nsec). The laser-induced breakdown irradiance measured for CdTe over this pulsewidth range scaled as t sub p

  8. Trace pollutants analysis in soil by a time-resolved laser-induced breakdown spectroscopy technique

    Microsoft Academic Search

    A. Ciucci; V. Palleschi; S. Rastelli; R. Barbini; F. Colao; R. Fantoni; A. Palucci; S. Ribezzo; H. J. L. van der Steen

    1996-01-01

    The results of a joint experiment of IFAM-Pisa and ENEA-Frascati for the detection of traces of pollutants in soil by a time-resolved laser-induced spectroscopy technique are reported. Using samples of soil with known pollutants' concentration [Geochemical Exploration Reference (GXR) silicate from US Geological Survey], we were able to estimate the sensitivity of this Laser-Induced Breakdown Spectroscopy (LIBS) technique to be

  9. Detection of bacteria by time-resolved laser-induced breakdown spectroscopy

    Microsoft Academic Search

    Stéphane Morel; Nicolas Leone; Philippe Adam; Jacques Amouroux

    2003-01-01

    A laser-induced breakdown spectroscopy technique for analyzing biological matter for the detection of biological hazards is investigated. Eight species were considered in our experiment: six bacteria and two pollens in pellet form. The experimental setup is described, then a cumulative intensity ratio is proposed as a quantitative criterion because of its linearity and reproducibility. Time-resolved laser-induced breakdown spectroscopy (TRELIBS) exhibits

  10. A procedure for correcting self-absorption in calibration free-laser induced breakdown spectroscopy

    Microsoft Academic Search

    D. Bulajic; M Corsi; G Cristoforetti; S Legnaioli; V Palleschi; A Salvetti; E Tognoni

    2002-01-01

    A model of the self-absorption effect in laser-induced plasma has been developed, with the aim of providing a tool for its automatic correction in the Calibration-Free algorithm recently developed for standardless analysis of materials by LIBS (Laser Induced Breakdown Spectroscopy). As a test of the model, the algorithm for self-absorption correction is applied to three different certified steel NIST samples

  11. SOI-based micro scanning grating interferometers: device characterization, control and demonstration of parallel operation

    Microsoft Academic Search

    O G Karhade; F L Degertekin; T R Kurfess

    2008-01-01

    An array of micro scanning grating interferometers (?SGIs) with tunable gratings is designed, fabricated and successfully tested for simultaneous static and dynamic displacement measurements. Each ?SGI has capabilities of an optical scanning interferometer and in addition, miniaturization has made array operation feasible. All of the ?SGIs in an array can actively tune the distances between the gratings and the corresponding

  12. Femtosecond laser damage threshold of pulse compression gratings for petawatt scale laser systems.

    PubMed

    Poole, Patrick; Trendafilov, Simeon; Shvets, Gennady; Smith, Douglas; Chowdhury, Enam

    2013-11-01

    Laser-induced femtosecond damage thresholds of Au and Ag coated pulse compression gratings were measured using 800 nm laser pulses ranging in duration from 30 to 200 fs. These gratings differ from conventional metal-on-photoresist pulse compression gratings in that the gratings patterns are generated by etching the fused silica substrate directly. After etching, the metal overcoating was optimized based on diffraction efficiency and damage threshold considerations. The experiment on these gratings was performed under vacuum for single-shot damage. Single-shot damage threshold, where there is a 0% probability of damage, was determined to be within a 400-800 mJ/cm(2) range. The damage threshold exhibited no clear dependence on pulse width, but showed clear dependence on gold overcoat surface morphology. This was confirmed by electromagnetic field modeling using the finite element method, which showed that non-conformal coating morphology gives rise to significant local field enhancement near groove edges, lowering the diffraction efficiency and increasing Joule heating. Large-scale gratings with conformal coating have been installed successfully in the 500 TW Scarlet laser system. PMID:24216857

  13. Nanosecond laser-induced nanostructuring of thin metal layers and dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Lorenz, P.; Klöppel, M.; Ehrhardt, M.; Zimmer, K.; Schwaller, P.

    2015-03-01

    Nanostructuring of dielectric surfaces has a widespread field of applications. In this work the recently introduced laser method validates this novel concept for complex nanostructuring of dielectric surfaces. This concept combines the mechanism of self-assembly of metal films due to laser irradiation with the concept of laser-assisted transfer of these patterns into the underlying material. The present work focuses on pattern formation in fused silica near the border of the laser spot, where distorted nested ring-like patterns were found in contrast to concentric ring patterns at homogeneous laser irradiation. For the experiments a lateral homogeneous spot of a KrF excimer laser (? = 248 nm) and a Gaussian beam Yb fiber laser (? = 1064 nm) was used for irradiation of a thin chromium layer onto fused silica resulting in the formation of different ring structures into the fused silica surface. The obtained structures were analysed by AFM and SEM. It is found that the mechanism comprises laser-induced metal film melting, contraction of the molten metal, and successive transfer of the metal hole geometry to the fused silica. Simulations taking into account the heat and the Navier-Stokes equations were compared with the experimental results. A good agreement of simulation results with experimental data was found. These first results demonstrate that the variation of the laser beam profile allows the local control of the melt dynamics which causes changes of the shape and the size of the ring patterns. Hence, a light-controlled self-assembly is feasible.

  14. Study on the effects of ion motion on laser-induced plasma wakes

    SciTech Connect

    Zhou Suyun [Institute of Modern Optical Technologies, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); School of Materials Sciences and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Yu Wei [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); Yuan Xiao [Institute of Modern Optical Technologies, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Xu Han [National Laboratory for Parallel and Distributed Processing, School of Computer Science, National University of Defense Technology, Changsha 410073 (China); Cao, L. H.; Cai, H. B.; Zhou, C. T. [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

    2012-09-15

    A 2D analytical model is presented for the generation of plasma wakes (or bubbles) with an ultra-intense laser pulse by taking into account the response of plasma ions. It is shown that the effect of ion motion becomes significant at the laser intensity exceeding 10{sup 21} W/cm{sup 2} and plasma background density below 10{sup 19} cm{sup -3}. In this regime, ion motion tends to suppress the electrostatic field induced by charge separation and makes the electron acceleration less effective. As a result, the assumption of immobile ions overestimates the efficiency of laser wake-field acceleration of electrons. Based on the analytical model, the dynamics of plasma ions in laser-induced wake field is investigated. It is found that only one bubble appears as the plasmas background density exceeds the resonant density and the deposited laser energy is concentrated into the bubble, resulting in the generation of an ion bunch with extremely high energy density.

  15. Laser-induced charge-disproportionated metallic state in LaCoO3

    NASA Astrophysics Data System (ADS)

    Izquierdo, M.; Karolak, M.; Trabant, C.; Holldack, K.; Föhlisch, A.; Kummer, K.; Prabhakaran, D.; Boothroyd, A. T.; Spiwek, M.; Belozerov, A.; Poteryaev, A.; Lichtenstein, A.; Molodtsov, S. L.

    2014-12-01

    Understanding the origin of the spin transition in LaCoO3 is one of the long-standing aims in condensed matter physics. Aside from its fundamental interest, a detailed description of this crossover will have a direct impact on the interpretation of the semiconductor-to-metal transition (SMT) and the properties of the high-temperature metallic phase in this compound, which has shown to have important applications in environmentally friendly energy production. To date, the spin transition has been investigated mainly as a function of temperature in thermal equilibrium. These results have hinted at dynamical effects. In this paper, we have investigated the SMT by means of pump-probe soft x-ray reflectivity experiments at the O K , Co L , and La M edges and theoretical calculations within a DFT++ formalism. The results point towards a laser-induced metallization in which the optical transitions stabilize a metallic state with high-spin configuration and increased charge disproportionation.

  16. Examination of laser-induced cell lysis by time resolved imaging

    NASA Astrophysics Data System (ADS)

    Rau, Kaustubh R.; Guerra, Arnold, III; Vogel, Alfred; Venugopalan, Vasan

    2004-07-01

    Highly focused laser microbeams are being used with increasing regularity for targeted cell lysis, cellular microsurgery and molecular delivery via transient cell membrane permeabilization. To examine the mechanisms of laser induced cell lysis, we performed time-resolved imaging of confluent PtK2 cell cultures following the delivery of a single 6 ns, 532 nm Nd:YAG laser pulse. The laser pulse energies employed correspond to 1x and 3x threshold for plasma formation. The resulting plasma formation, pressure wave propagation and cavitation bubble dynamics were imaged over a temporal range spanning 5 orders of magnitude (0.5 ns - 50 microsec.). Time-resolved imaging enabled determination of process characteristics including pressure wave speed and amplitude and cavitation bubble energies. The time-resolved images also revealed the onset of cellular damage to occur on nano-second time scales and complete within 1 microsecond. Moreover, the size of the damage zone was larger than the plasma but smaller than the maximum cavitation bubble size. This indicated that mechanisms apart from plasma vaporization namely pressure wave propagation and cavitation bubble expansion are contributors to cellular damage. Dye exclusion assays showed that the majority of cells experiencing considerable deformation due to fluid flow generated by the cavitation bubble expansion remain viable over 24 hours.

  17. Assessment of femtosecond laser induced periodic surface structures on polymer films.

    PubMed

    Rebollar, Esther; Vázquez de Aldana, Javier R; Martín-Fabiani, Ignacio; Hernández, Margarita; Rueda, Daniel R; Ezquerra, Tiberio A; Domingo, Concepción; Moreno, Pablo; Castillejo, Marta

    2013-07-21

    In this work we present the formation of laser induced periodic surface structures (LIPSS) on spin-coated thin films of several model aromatic polymers including poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly carbonate bis-phenol A upon irradiation with femtosecond pulses of 795 and 265 nm at fluences well below the ablation threshold. LIPSS are formed with period lengths similar to the laser wavelength and parallel to the direction of the laser polarization vector. Formation of LIPSS upon IR irradiation at 795 nm, a wavelength at which the polymers absorb weakly, contrasts with the absence of LIPSS in this spectral range upon irradiation with nanosecond pulses. Real and reciprocal space characterization of LIPSS obtained by Atomic Force Microscopy (AFM) and Grazing Incidence Small Angle X-ray Scattering (GISAXS), respectively, yields well correlated morphological information. Comparison of experimental and simulated GISAXS patterns suggests that LIPSS can be suitably described considering a quasi-one-dimensional paracrystalline lattice and that irradiation parameters have an influence on the order of such a lattice. Fluorescence measurements, after laser irradiation, provide indirect information about dynamics and structure of the polymer at the molecular level. Our results indicate that the LIPSS are formed by interference of the incident and surface scattered waves. As a result of this process, heating of the polymer surface above its glass transition temperature takes place enabling LIPSS formation. PMID:23728307

  18. Sympathetic crystallization of CaH{sup +} produced by a laser-induced reaction

    SciTech Connect

    Kimura, Naoki; Okada, Kunihiro; Takayanagi, Toshinobu [Department of Physics, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554 (Japan); Wada, Michiharu [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Ohtani, Shunsuke [Institute for Laser Science (ILS), University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585 (Japan); Schuessler, Hans A. [Department of Physics, Texas A and M University, College Station, Texas 77843 (United States)

    2011-03-15

    We investigated sympathetic Coulomb crystallization of CaH{sup +} ions produced by a laser-induced reaction through an excited state according to {sup 40}Ca{sup +}(4p {sup 2}P{sub 1/2}) + H{sub 2} {yields} {sup 40}CaH{sup +} + H. {sup 40}CaH{sup +} ions stored in a linear Paul trap were characterized by their secular-motion excitation spectrum and by the modified fluorescence images of crystallized Ca{sup +} ions. The number of two-species crystallized ions, the secular motion temperature, and the structure were determined by molecular dynamics simulations. Both the observed two-species ion crystals and simulation images demonstrate that the CaH{sup +} ions were sympathetically crystallized with their secular-motion temperature being less than 10 mK. We determined reaction rates from fluorescence images of two-species Coulomb crystals by systematically changing the reaction time. In addition a lower limit for the reaction rate coefficient k=8x10{sup -10} cm{sup 3}/s was obtained.

  19. Laser induced forward transfer of metals by temporally shaped femtosecond laser pulses.

    PubMed

    Klini, A; Loukakos, P A; Gray, D; Manousaki, A; Fotakis, C

    2008-07-21

    Temporally shaped, femtosecond laser pulses have been used for controlling the size and the morphology of micron-sized metallic structures obtained by using the Laser Induced Forward Transfer (LIFT) technique. We report the effect of pulse shaping on the size and morphology of the deposited structures of Au, Zn, Cr on a function of the pulse separation time ??t (from 0 to 10 ps) of double pulses of variable intensities generated by using a liquid crystal spatial light modulator (SLM). The observed differences in size and morphology are correlated with the outcome of pump-probe experiments for the study of electron-phonon scattering dynamics and subsequent energy transfer processes to the bulk in the different metals employed. We propose that in metals with weak electron-lattice coupling, the electron ballistic motion and the resulting fast electron scattering at the film surface, as well as the internal electron thermalization process are crucial to the morphology and size of the transferred material. Therefore, temporal shaping within the corresponding time scales of these processes may be used for tailoring the features of the metallic structures obtained by LIFT. PMID:18648449

  20. 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 [RIKEN - Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Ohira, Yutaka [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe Sagamihara 252-5258 (Japan); Mori, Koji [Department of Applied Physics, Faculty of Engineering, University of Miyazaki, 1-1 Gakuen Kibana-dai Nishi, Miyazaki 889-2192 (Japan); Tsunemi, Hiroshi; Koyama, Katsuji [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 60-0043 (Japan); Uchida, Hiroyuki [Department of Physics, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo, Kyoto 606-8502 (Japan)

    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}.

  1. Laser-induced fluorescence in diagnosis of dental caries

    NASA Astrophysics Data System (ADS)

    Drakaki, Eleni A.; Makropoulou, Mersini I.; Khabbaz, Maruan; Serafetinides, Alexandros A.

    2003-09-01

    The autofluorescence spectra of hard dental tissues, both in normal and pathological areas were investigated in this study. The measurements were performed both on the intact hard tissues of the examined teeth, such as enamel, dentine, cementum, and root canal, and on the tissues pathologically affected by caries (superficial, intermediate, and deep). Various laser wavelengths (337 nm, 488 nm, and 514 nm) were used to irradiate the dental surfaces and a computer-controlled spectrograph captured the fluorescent spectra. The emission signals were stored, measured, analyzed and quantified in terms of wavelength distribution and the relative photon intensity. Results indicated that the fluorescent spectra from healthy enamel, dentine, and cementum were almost identical in form, depending on the excitation wavelength. The intact and affected hard tissues were greatly different in the integral fluorescent intensity. Healthy areas were found to produce the most pronounced fluorescent intensity, whereas the carious regions produced the weaker fluorescent intensity. Independently of the laser excitation wavelength, dentin regions were found to produce the most pronounced fluorescent intensity than any other dental component. The fluorescence signal of carious affected dental structure revealed a reed shifted spectral curve, more pronounced after 488 nm excitation. There was a pronounced red shift for deep caries (crown -- root caries), after ultraviolet laser excitation. Excitation with visible wavelengths did not produce such differences between intact and cervical, deep carious affected tissue. Using a monochromatic light source without any light output at the wavelengths of fluorescence, e.g. a laser with the appropriate filters, the difference in fluorescence between intact and carious enamel was generally easy to observe. Finally, we found that the blue line of an argon ion laser is preferable for superficial caries detection, while the ultraviolet emitting nitrogen laser induces better discrimination in deep caries diagnosis.

  2. Laser induced damage in optical materials: tenth ASTM symposium.

    PubMed

    Glass, A J; Guenther, A H

    1979-07-01

    The tenth annual Symposium on Optical Materials for High Power Lasers (Boulder Damage Symposium) was held at the National Bureau of Standards in Boulder, Colorado, 12-14 September 1978. The symposium was held under the auspices of ASTM Committee F-1, Subcommittee on Laser Standards, with the joint sponsorship of NBS, the Defense Advanced Research Project Agency, the Department of Energy, and the Office of Naval Research. About 175 scientists attended, including representatives of the United Kingdom, France, Canada, Japan, West Germany, and the Soviet Union. The symposium was divided into sessions concerning the measurement of absorption characteristics, bulk material properties, mirrors and surfaces, thin film damage, coating materials and design, and breakdown phenomena. As in previous years, the emphasis of the papers presented was directed toward new frontiers and new developments. Particular emphasis was given to materials for use from 10.6 microm to the UV region. Highlights included surface characterization, thin film-substrate boundaries, and advances in fundamental laser-matter threshold interactions and mechanisms. The scaling of damage thresholds with pulse duration, focal area, and wavelength was also discussed. In commemoration of the tenth symposium in this series, a number of comprehensive review papers were presented to assess the state of the art in various facets of laser induced damage in optical materials. Alexander J. Glass of Lawrence Livermore Laboratory and Arthur H. Guenther of the Air Force Weapons Laboratory were co-chairpersons. The eleventh annual symposium is scheduled for 30-31 October 1979 at the National Bureau of Standards, Boulder, Colorado. PMID:20212622

  3. Standoff laser-induced thermal emission of explosives

    NASA Astrophysics Data System (ADS)

    Galán-Freyle, Nataly Y.; Pacheco-Londoño, Leonardo C.; Figueroa-Navedo, Amanda; Hernandez-Rivera, Samuel P.

    2013-05-01

    A laser mediated methodology for remote thermal excitation of analytes followed by standoff IR detection is proposed. The goal of this study was to determine the feasibility of using laser induced thermal emission (LITE) from vibrationally excited explosives residues deposited on surfaces to detect explosives remotely. Telescope based FT-IR spectral measurements were carried out to examine substrates containing trace amounts of threat compounds used in explosive devices. The highly energetic materials (HEM) used were PETN, TATP, RDX, TNT, DNT and ammonium nitrate with concentrations from 5 to 200 ?g/cm2. Target substrates of various thicknesses were remotely heated using a high power CO2 laser, and their mid-infrared (MIR) thermally stimulated emission spectra were recorded. The telescope was configured from reflective optical elements in order to minimize emission losses in the MIR frequencies and to provide optimum overall performance. Spectral replicas were acquired at a distance of 4 m with an FT-IR interferometer at 4 cm- 1 resolution and 10 scans. Laser power was varied from 4-36 W at radiation exposure times of 10, 20, 30 and 60 s. CO2 laser powers were adjusted to improve the detection and identification of the HEM samples. The advantages of increasing the thermal emission were easily observed in the results. Signal intensities were proportional to the thickness of the coated surface (a function of the surface concentration), as well as the laser power and laser exposure time. For samples of RDX and PETN, varying the power and time of induction of the laser, the calculated low limit of detections were 2 and 1 ?g/cm2, respectively.

  4. Laser induced spark ignition of methane-oxygen mixtures

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Results from an experimental study of laser induced spark ignition of methane-oxygen mixtures are presented. The experiments were conducted at atmospheric pressure and 296 K under laminar pre-mixed and turbulent-incompletely mixed conditions. A pulsed, frequency doubled Nd:YAG laser was used as the ignition source. Laser sparks with energies of 10 mJ and 40 mJ were used, as well as a conventional electrode spark with an effective energy of 6 mJ. Measurements were made of the flame kernel radius as a function of time using pulsed laser shadowgraphy. The initial size of the spark ignited flame kernel was found to correlate reasonably well with breakdown energy as predicted by the Taylor spherical blast wave model. The subsequent growth rate of the flame kernel was found to increase with time from a value less than to a value greater than the adiabatic, unstretched laminar growth rate. This behavior was attributed to the combined effects of flame stretch and an apparent wrinkling of the flame surface due to the extremely rapid acceleration of the flame. The very large laminar flame speed of methane-oxygen mixtures appears to be the dominant factor affecting the growth rate of spark ignited flame kernels, with the mode of ignition having a small effect. The effect of incomplete fuel-oxidizer mixing was found to have a significant effect on the growth rate, one which was greater than could simply be accounted for by the effect of local variations in the equivalence ratio on the local flame speed.

  5. Characterisation of CFRP surface contamination by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawel H.; Sawczak, Miroslaw; Wandowski, Tomasz; Ostachowicz, Wieslaw M.; Cenian, Adam

    2014-03-01

    The application of Carbon Fibre Reinforced Polymers (CFRP) in aeronautics has been increasing. The CFRP elements are joint using rivets and adhesive bonding. The reliability of the bonding limits the use of adhesive bonding for primary aircraft structures, therefore it is important to assess the bond quality. The performance of adhesive bonds depends on the physico-chemical properties of the adhered surfaces. This research is focused on characterization of surfaces before bonding. In-situ examination of large surface materials, determine the group of methods that are preferred. The analytical methods should be non-destructive, enabling large surface analysis in relatively short time. In this work a spectroscopic method was tested that can be potentially applied for surface analysis. Four cases of surface condition were investigated that can be encountered either in the manufacturing process or during aircraft service. The first case is related to contamination of CFRP surface with hydraulic fluid. This fluid reacts with water forming a phosphoric acid that can etch the CFRP. Second considered case was related to silicone-based release agent contamination. These agents are used during the moulding process of composite panels. Third case involved moisture content in CFRP. Moisture content lowers the adhesion quality and leads to reduced performance of CFRP resulting in reduced performance of the adhesive bond. The last case concentrated on heat damage of CFRP. It was shown that laser induced fluorescence method can be useful for non-destructive evaluation of CFRP surface and some of the investigated contaminants can be easily detected.

  6. Experimental study of the spectral characteristics of laser-induced air plasma

    SciTech Connect

    Lin Zhaoxiang; Wu Jinquan; Sun Fenglou; Gong Shunsheng

    2010-05-01

    The characteristics of laser-induced air, N2, and O2 plasma spectra are investigated spectroscopically. The study concentrates mainly on the temporal behavior of laser-induced plasma after breakdown. We used delayed spectra and spectra evolution for this study. Except for the general one-beam laser-induced breakdown experiment, a second laser beam was added to further probe the behavior of plasma during its decay. We report the experimental results of spectra composition, spectra time evolution, and spectra affected by a second laser beam. We determined that all the laser-induced air plasma spectra are from a continuous spectrum and some line spectra superposed on the continuous spectrum. The stronger short wavelength continuous spectrum is caused by bremsstrahlung radiation of electrons in the plasma, and the weaker long wavelength continuous spectrum is caused by electron and ion recombination. Line spectra originate from excited molecules, atoms, and their first-order ions, but no line spectra form higher-order ions. The results show that the temporal behavior of some spectra is a decay-rise-redecay pattern. With the two laser beam experiment we found that all the spectra intensities are enhanced by the second laser beam, but the response of various spectra to the delay of the second laser beam is quite different, in particular, the intensity increments of some spectra increase with the delay of the second laser beam. Some microscopic processes of laser-induced plasma obtained from the experimental results are discussed. These results are useful for a better understanding of some laser-induced air plasma related applications, such as laser-guided lightning and laser-induced breakdown spectroscopy.

  7. Suppression of laser-induced choroidal neovascularization by intravitreal injection of tristetraprolin

    PubMed Central

    Cho, Yong Wun; Han, Yong Seop; Chung, In Young; Kim, Seong Jae; Seo, Seong Wook; Yoo, Ji Myong; Park, Jong Moon

    2014-01-01

    AIM To examine the effect of intravitreal adenoviral vector-mediated tristetraprolin (Ad-TTP) on VEGF mRNA expression in a rat model of laser-induced choroidal neovascularization. METHODS Ad-TTP was prepared using a commercial kit. Retinal laser-induced photocoagulation (10 spots per eye) was performed on rats in this experimental choroidal neovascularization (CNV) model. Rats were divided into four groups: control (single intravitreal injection of balanced salt solution, n=10), laser-induced CNV (photocoagulation only, n=20), laser-induced CNV plus Ad-TTP injection (photocoagulation plus a single intravitreal Ad-TTP injection, n=20) and Ad-TTP injection only (n=10). Changes in choroidal morphology were evaluated in ten rats in the laser only and the laser plus Ad-TTP groups. Two weeks after laser injury, the size of CNV was calculated by perfusion with high-molecular-weight fluorescein isothiocyanate (FITC)-dextran. VEGF mRNA expression in retina-choroid tissue from ten rats in each group was measured by reverse transcription polymerase chain reaction (RT-PCR). RESULTS Two weeks after treatment, the area of laser-induced CNV was reduced by approximately 60% in the rats given the Ad-TTP injection compared with that in the laser-only group. There was a tendency toward decreased VEGF mRNA expression in the Ad-TTP injection groups. CONCLUSION A single intravitreal injection of Ad-TTP significantly suppressed CNV size in this experimental laser-induced CNV model. Ad-TTP injection also decreased VEGF mRNA expression compared with that in the laser-induced CNV group. The present study is meaningful as the first study to investigate the effect of tristetraprolin delivered via intravitreal injection. PMID:25540745

  8. Optimization of an Image-Guided Laser-Induced Choroidal Neovascularization Model in Mice

    PubMed Central

    Sun, Ye; Fu, Zhongjie; Liu, Chi-Hsiu; Evans, Lucy; Tian, Katherine; Saba, Nicholas; Fredrick, Thomas; Morss, Peyton; Chen, Jing; Smith, Lois E. H.

    2015-01-01

    The mouse model of laser-induced choroidal neovascularization (CNV) has been used in studies of the exudative form of age-related macular degeneration using both the conventional slit lamp and a new image-guided laser system. A standardized protocol is needed for consistent results using this model, which has been lacking. We optimized details of laser-induced CNV using the image-guided laser photocoagulation system. Four lesions with similar size were consistently applied per eye at approximately double the disc diameter away from the optic nerve, using different laser power levels, and mice of various ages and genders. After 7 days, the mice were sacrificed and retinal pigment epithelium/choroid/sclera was flat-mounted, stained with Isolectin B4, and imaged. Quantification of the area of the laser-induced lesions was performed using an established and constant threshold. Exclusion criteria are described that were necessary for reliable data analysis of the laser-induced CNV lesions. The CNV lesion area was proportional to the laser power levels. Mice at 12-16 weeks of age developed more severe CNV than those at 6-8 weeks of age, and the gender difference was only significant in mice at 12-16 weeks of age, but not in those at 6-8 weeks of age. Dietary intake of omega-3 long-chain polyunsaturated fatty acid reduced laser-induced CNV in mice. Taken together, laser-induced CNV lesions can be easily and consistently applied using the image-guided laser platform. Mice at 6-8 weeks of age are ideal for the laser-induced CNV model. PMID:26161975

  9. Tunable fiber Bragg grating based on responsive photonic crystals

    NASA Astrophysics Data System (ADS)

    Ding, Haibo; Cheng, Yao; Gu, Hongcheng; Zhao, Yuanjin; Wang, Baoping; Gu, Zhongze

    2013-11-01

    A tunable fiber Bragg grating (FBG) was developed by using stress-responsive colloidal crystals. In addition, the FBGs with the function of dynamically filtering multiple wavelengths were also demonstrated by incorporating multiple colloidal crystal segments into the fibers.

  10. Superfluid {sup 4}He Quantum Interference Grating

    SciTech Connect

    Sato, Yuki; Joshi, Aditya; Packard, Richard [Physics Department, University of California, Berkeley, California 94720 (United States)

    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.

  11. Direct visualization of secretion from single bovine adrenal chromaffin cells by laser-induced native fluorescence imaging microscopy

    SciTech Connect

    Tong, W.; Yeung, E.S. [Ames Laboratory---USDOE and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory---USDOE and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)

    1998-03-01

    Direct visualization of the secretion process of individual bovine adrenal chromaffin cells was achieved with laser-induced native fluorescence imaging microscopy. By monitoring the native fluorescence of catecholamines excited by the 275 nm laser line with an intensified charge-coupled-device (CCD) camera, we obtained good temporal and spatial resolution simultaneously without using additional fluorescent probes. Large variations were found among individual cells in terms of the amounts of catecholamines secreted and the rates of secretion. Different regions of a cell also behave differently during the secretion process. However, the degree of this local heterogeneity is smaller than in neurons and neuralgia. The influence of deep-ultraviolet (UV) laser excitation on cells is also discussed. This quantitative imaging technique provides a useful noninvasive approach for the study of dynamic cellular changes and the understanding of the molecular mechanisms of secretory processes. {copyright} {ital 1998} {ital Society for Applied Spectroscopy}

  12. Laser-Induced Thermal Acoustic Measurements in a Highly Back-Pressured Scramjet Isolator Model: A Research Plan

    NASA Technical Reports Server (NTRS)

    Middleton, Troy F.; Balla, Robert J.; Baurle, Robert A.; Wilson, Lloyd G.

    2008-01-01

    Under the Propulsion Discipline of NASA s Fundamental Aeronautics Program s Hypersonics Project, a test apparatus, for testing a scramjet isolator model, is being constructed at NASA's Langley Research Center. The test apparatus will incorporate a 1-inch by 2-inch by 15-inch-long scramjet isolator model supplied with 2.1 lbm/sec of unheated dry air through a Mach 2.5 converging-diverging nozzle. The planned research will incorporate progressively more challenging measurement techniques to characterize the flow field within the isolator, concluding with the application of the Laser-Induced Thermal Acoustic (LITA) measurement technique. The primary goal of this research is to use the data acquired to validate Computational Fluid Dynamics (CFD) models employed to characterize the complex flow field of a scramjet isolator. This paper describes the test apparatus being constructed, pre-test CFD simulations, and the LITA measurement technique.

  13. Screening and characterization of biopharmaceuticals by high-performance capillary electrophoresis with laser-induced native fluorescence detection.

    PubMed

    Lee, T T; Lillard, S J; Yeung, E S

    1993-01-01

    High-performance capillary electrophoresis (HPCE) with laser-induced native fluorescence (LIF) detection is used to address significant problems in the quality control of biopharmaceuticals. All of the biopharmaceuticals studied can be detected at subnanomolar levels with linear dynamic ranges of at least 3 orders of magnitude. HPCE/LIF can determine impurities in "purified" biopharmaceuticals present in amounts less than 0.01% (i.e., at 4 x 10(-11) M) that of the major component. With HPCE/LIF, detection sensitivity is thus no longer a concern in the assaying of active ingredients in biopharmaceutical dosage formulations. The peptide mapping of biopharmaceuticals present at 1 x 10(-7) M (or an injected limit of detection of 60 amol) is presented. Also, kinetic information on the reaction of a recombinant enzyme-drug with its substrate present at the micromolar level has been extracted from electropherograms acquired in real-time. PMID:8354226

  14. Laser induced fluorescence spectroscopy of various carbon nanostructures (GO, G and nanodiamond) in Rd6G solution

    PubMed Central

    Bavali, A.; Parvin, P.; Mortazavi, S. Z.; Nourazar, S. S.

    2015-01-01

    The effect of carbon nanostructures such as graphene (G), graphene oxide (GO) and nanodiamond (ND) on the spectral properties of Rhodamine 6G (Rd6G) emission due to the laser induced fluorescence (LIF) was investigated. It is shown that the addition of carbon nano- structures lead to sensible Red/Blue shifts which depend on the optical properties and surface functionality of nanoparticles. The current theories such as resonance energy transfer (RET), fluorescence quenching and photon propagation in scattering media support the experimental findings. Stern-Volmer curves for dynamic and static quenching of Rd6G molecules embedded with G, GO and nanodiamond are correlated with spectral shifts. Furthermore, time evolution of the spectral shift contributes to determine loading/release rates of fluorescent species with large S-parameter on the given nano-carriers. PMID:26137372

  15. Time-Resolved Aluminum Monoxide Emission Measurements in Laser-Induced Plasma

    NASA Astrophysics Data System (ADS)

    Surmick, David; Parigger, Christian

    2014-03-01

    Laser-induced plasmas are useful for diagnostic applications in a wide variety of fields. One application is the creation of laser-induced plasmas on the surface of an aluminum sample to simulate an aluminized flame. In this study, aluminum monoxide emissions are measured to characterize the temperature along the laser-induced plasma as a function of time delay following laser-induced optical breakdown. The breakdown event is achieved by focusing 1064 nanometer laser radiation from an Nd:YAG laser onto the surface of an aluminum sample. Light from the plasma is dispersed with the use of a Czerny-Turner spectrograph, and time resolved emission spectra are recorded with an intensified, gated detector. Temperatures are inferred from the diatomic molecular emissions by fitting the experimentally collected to theoretically calculated spectra using a Nelder-Mead algorithm. For computation of synthetic spectra we utilize accurate line strengths for selected AlO molecular bands. Atomic emissions from aluminum are also investigated in our study of laser-induced plasma.

  16. Laser-Induced Breakdown Spectroscopy (LIBS) in Geochemical Analysis

    NASA Astrophysics Data System (ADS)

    McMillan, N. J.

    2012-12-01

    Laser-Induced Breakdown Spectroscopy (LIBS) analysis is being applied to an increasing number of geochemical problems, including mineral and rock analysis on the Mars rover Curiosity, elemental concentrations in ore minerals, identification of ore minerals, provenance determination of gems and other conflict minerals, geochemical mapping, correlation of rock units, and sample screening. LIBS is a laser ablation technique in which the photons emitted from electron transitions in the cooling plasma are diffracted and recorded as a spectrum. LIBS has several characteristics that set it apart from traditional, lab-based techniques. First, LIBS is relatively simple and requires no sample preparation, resulting in analysis that is portable, in situ, real-time, rapid, and inexpensive (in terms of equipment purchase, maintenance, and operating personnel). Second, each LIBS spectrum contains an enormous amount of information about the material. Most elements emit photons in the typical LIBS spectral range (200-1000 nm). Spectral interferences for which corrections are necessary in traditional techniques are additional, useful information in the LIBS spectrum, and recent work has demonstrated that some isotopic ratios can be measured with LIBS data. Thus, LIBS spectra are detailed chemical fingerprints of materials and the use of multivariate analysis can resolve issues that have been untouchable using traditional techniques. A good example is determination of country of origin for rubies and sapphires. Concentrations of key trace elements, as analyzed by LA-ICP-MS, have been used with marginal success to demonstrate that different deposits yield rubies or sapphires with unique, identifiable compositions. However, the fields for each deposit overlap in the 2- or 3-component diagrams commonly used. In contrast, it is possible to determine country of origin with greater than 90% accuracy using LIBS data, in which the intensities of 13,700 wavelengths are used as variables in multivariate analysis. Because LIBS spectra can accurately compare materials to each other, LIBS has great potential for rapid, field-based correlation, chemical mapping, and screening samples for further analysis. It also has potential for analytical situations in which we currently use high-precision data to ask the question "Are these materials the same or different?" For instance, trace element concentrations are used to identify sub-populations within detrital zircons of the same age. LIBS data may more easily distinguish such sub-populations.

  17. Bioanalytical and photophysical applications of sensitive nonlinear wave-mixing spectroscopy based on laser-induced gratings

    NASA Astrophysics Data System (ADS)

    Knittle, James Eugene

    Nonlinear degenerate four-wave mixing is presented as a sensitive optical absorption-based detection and measurement technique for condensed-phase systems. By taking advantage of the inherent properties of this method, one can design a measurement system offering minimal optical path lengths (less than 100 mum) and miniscule probe volumes (often approaching just a few pico liters) using a single laser. This is possible because the laser output is split into two or more beams which are then redirected and focused to intersect at or near the focused waist of the beams. This ultra small probe volume makes this method inherently compatible with capillary flow systems and thin films. It also offers the additional benefit of minimizing the amount of sample required for study. This is particularly advantageous when the sample is difficult to obtain or may be dangerous to work with such as an enzyme, forensic sample or toxin. This method can also be used to study samples which themselves do not strongly absorb the light energy. Indirect detection is performed by measuring the effect the analyte of interest has on a co-solvated species which itself directly absorbs the laser light. By measuring the changes in the physical and chemical properties of this visualization agent, the presence of the analyte can be measured indirectly. The main effect giving rise to the degenerate four-wave mixing signal in liquid and other condensed-based systems is the conversion of light energy to heat by the absorbing medium. The subsequent temperature change induces an inhomogeneous change in the refractive index of the medium which diffracts the input beams to generate the signal beams. Because wave mixing is an optical absorption-based technique, it can be used simultaneously with other methods such as fluorescence to effectively measure the physical and chemical properties of an analyte.

  18. Laser-induced fluorescence of fused silica irradiated by ArF excimer laser

    SciTech Connect

    Zhang Haibo [Shanghai Key Laboratory of All Solid-state Laser and Applied Techniques, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); Graduate University of Chinese Academy of Science, Beijing 100049 (China); Yuan Zhijun; Zhou Jun; Dong Jingxing; Wei Yunrong; Lou Qihong [Shanghai Key Laboratory of All Solid-state Laser and Applied Techniques, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China)

    2011-07-01

    Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

  19. Laser-induced breakdown spectroscopy detection of heavy metal in water based on graphite conch method

    NASA Astrophysics Data System (ADS)

    Wang, Chunlong; Liu, Jianguo; Zhao, Nanjing; Shi, Huan; Liu, Lituo; Ma, Mingjun; Zhang, Wei; Chen, Dong; Liu, Jing; Zhang, Yujun; Liu, Wenqing

    2012-10-01

    The laser-induced breakdown spectroscopy emission characteristics of trace heavy metal lead in water is studied based on graphite conch method, with a 1064nm wavelength Nd: YAG laser as excitation source, the echelle spectrometer and ICCD detector are used for spectral separation and high sensitive detection with high resolution and wide spectral range. The delay time 900ns and gate time 1600ns are determined in the experiment. The calibration curve of Pb is plotted based on the different concentration measurement results, and a limit of detection of 0.0138mg / L is obtained for Pb in water. Graphite conch method effectively overcomes the current problems on laser-induced breakdown spectroscopy detection of heavy metal in water. The detection limits and stability are improved. The reference data is provided for further study on the fast measurement of trace heavy metals in water by laser induced breakdown spectroscopy technique.

  20. Photophysics of Laser Dye-Doped Polymer Membranes for Laser-Induced Fluorescence Photogrammetry

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Laser-induced fluorescence target generation in dye-doped polymer films has recently been introduced as a promising alternative to more traditional photogrammetric targeting techniques for surface profiling of highly transparent or reflective membrane structures. We investigate the photophysics of these dye-doped polymers to help determine their long-term durability and suitability for laser-induced fluorescence photogrammetric targeting. These investigations included experimental analysis of the fluorescence emission pattern, spectral content, temporal lifetime, linearity, and half-life. Results are presented that reveal an emission pattern wider than normal Lambertian diffuse surface scatter, a fluorescence time constant of 6.6 ns, a pump saturation level of approximately 20 micro J/mm(exp 2), and a useful lifetime of more than 300,000 measurements. Furthermore, two demonstrations of photogrammetric measurements by laser-induced fluorescence targeting are presented, showing agreement between photogrammetric and physically measured dimensions within the measurement scatter of 100 micron.

  1. Emission tomography of laser induced plasmas with large acceptance angle apertures

    E-print Network

    Shabanov, Sergei

    2010-01-01

    It is proposed to use apertures with large acceptance angles to reduce the integration time when studying the emissivity of laser induced plasmas by means of the Abel inversion method. The spatial resolution lost due to contributions of angled lines of sight to the intensity data collected along the plasma plume diameter is restored by a special numerical data processing. The procedure is meant for the laser induced plasma diagnostics and tomography when the integration time needed to achieve a reasonable signal to noise ratio exceeds a characteristic time scale of the plasma state variations which is short especially at early stages of the plasma evolution.

  2. Evolution of femtosecond laser-induced damage in doped GaN thin films

    NASA Astrophysics Data System (ADS)

    Grinys, Tomas; Dmukauskas, Mantas; Š?iuka, Mindaugas; Nargelas, Saulius; Melninkaitis, Andrius

    2014-02-01

    Mg- and Si-doped GaN layers deposited by metalorganic chemical vapor deposition method were irradiated with femtosecond pulse duration laser of three different wavelengths 1,030, 515 and 343 nm. Both single and multiple shot laser induced damage thresholds of doped GaN layers were evaluated and discussed. The scanning electron microscopy employed with electron beam induced current and energy dispersive X-ray techniques were used to study laser damage morphology. It was observed that ablated area and laser-induced damage increased with irradiation fluence. The mechanism of damage generation by Gaussian beam profile laser was considered.

  3. Study of concentric iridescent ring around the laser-induced pits on the solar cell surface

    NASA Astrophysics Data System (ADS)

    Zhu, Rongzhen; Cheng, Xiang-ai; Wang, Rui; Xu, Zhongjie

    2015-05-01

    The laser-induced damage on the surface of monocrystalline silicon (m-Si) solar cells and GaAs/Gesingle heterojunction solar cells are investigated. The solar cells were irradiated by a continuous wave laser at the wavelength of 532 nm. Concentric iridescent ring appeared on the damaged surfaces when observed with an optical microscope (OM) of broad spectrum. The damaged surface film was characterized by X-ray photoelectron spectroscopy (XPS) and the Contour Meter. The laser-induced temperature in silicon was calculated. The formation mechanism of the film and the cause of the concentric iridescent ring were analyzed.

  4. Detection of Broadband Terahertz Waves with a Laser-Induced Plasma in Gases

    SciTech Connect

    Dai Jianming; Xie Xu; Zhang, X.-C. [Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2006-09-08

    We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) waves via electric-field-induced second-harmonic generation in laser-induced air plasma with ultrashort laser pulses. By introducing the second-harmonic component of the white light in the laser-induced plasma as a local oscillator, coherent detection of broadband THz waves with ambient air is demonstrated for the first time. Our results show that, depending on the probe intensity, detection of THz waves in air can be categorized as incoherent, hybrid, and coherent detection. Coherent detection is achieved only when the tunnel ionization process dominates in gases.

  5. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    SciTech Connect

    Chen, Anmin [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China) [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China); Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Ding, Dajun [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)] [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Shao, Junfeng; Wang, Tingfeng [State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)] [State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Huang, Xuri [Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China)] [Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China); Jin, Mingxing [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China) [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2013-10-15

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  6. Single-Walled Carbon Nanotubes, Carbon Nanofibers and Laser-Induced Incandescence

    NASA Technical Reports Server (NTRS)

    Schubert, Kathy (Technical Monitor); VanderWal, Randy L.; Ticich, Thomas M.; Berger, Gordon M.; Patel, Premal D.

    2004-01-01

    Laser induced incandescence applied to a heterogeneous, multi-element reacting flows is characterized by a) temporally resolved emission spectra, time-resolved emission at selected detection wavelengths and fluence dependence. Laser fluences above 0.6 Joules per square centimeter at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence beyond this value lead to a super-heated plasma, well above the vaporization of temperature of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solid-like structures.

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

    NASA Astrophysics Data System (ADS)

    Wood, R. M.

    1998-04-01

    The commonly used units of measurement for laser induced damage are those of peak energy or power density. However, the laser induced damage thresholds, LIDT, of all materials are well known to be absorption, wavelength, spot size and pulse length dependent. As workers using these values become divorced from the theory it becomes increasingly important to use the correct units and to understand the correct scaling factors. This paper summarizes the theory and highlights the danger of using the wrong LIDT units in the context of potentially hazardous materials, laser safety eyewear and laser safety screens.

  8. Laser-induced synthesis and decay of Tritium under exposure of solid targets in heavy water

    E-print Network

    Barmina, E V; Timashev, S F; Shafeev, G A

    2013-01-01

    The processes of laser-assisted synthesis of Tritium nuclei and their laser-induced decay in cold plasma in the vicinity of solid targets (Au, Ti, Se, etc.) immersed into heavy water are experimentally realized at peak laser intensity of 10E10-10E13 Watts per square centimeter. Initial stages of Tritium synthesis and their laser-induced beta-decay are interpreted on the basis of non-elastic interaction of plasma electrons having kinetic energy of 5-10 eV with nuclei of Deuterium and Tritium, respectively.

  9. Laser-induced synthesis and decay of Tritium under exposure of solid targets in heavy water

    E-print Network

    E. V. Barmina; P. G. Kuzmin; S. F. Timashev; G. A. Shafeev

    2013-06-03

    The processes of laser-assisted synthesis of Tritium nuclei and their laser-induced decay in cold plasma in the vicinity of solid targets (Au, Ti, Se, etc.) immersed into heavy water are experimentally realized at peak laser intensity of 10E10-10E13 Watts per square centimeter. Initial stages of Tritium synthesis and their laser-induced beta-decay are interpreted on the basis of non-elastic interaction of plasma electrons having kinetic energy of 5-10 eV with nuclei of Deuterium and Tritium, respectively.

  10. Online compositional analysis in coal gasification environment using laser-induced plasma technology

    NASA Astrophysics Data System (ADS)

    Deng, Kung-Li; Wu, Juntao; Wang, Zhe; Lee, Boon; Guida, Renato

    2006-08-01

    Integrated Gasification Combined Cycle (IGCC) power plants have great potential for future clean-coal power generation. Today, the quality of coal is measured by sampling coal using various offline methods, and the syn-gas composition is determined by taking samples downstream of the gasifier and measured by gas chromatograph (GC). Laser induced plasma technology has demonstrated high sensitivity for elementary detection. The capability of free space transmission and focusing of laser beam makes laser induced plasma a unique technology for online compositional analysis in coal gasification environment and optimization control.

  11. Transition probabilities of Ni II spectral lines measured by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Manrique, J.; Aguilera, J. A.; Aragón, C.

    2013-05-01

    Experimental transition probabilities for 48 lines of the transition array 3d84s-3d84p of Ni II have been obtained by laser induced breakdown spectroscopy. A procedure based on the measurement and fitting of curves of growth that avoids the systematic error due to self-absorption has been used. The laser induced plasmas are generated using a Nd:YAG laser from a set of Ni-Cu alloys with different Ni concentrations. A comparison is made of our results with the available experimental and theoretical values.

  12. Development of brain tumor demarcation technique using two-color laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Matsumoto, Maki; Saeki, Souichi; Kajiwara, Koji; Ishihara, Hideyuki; Amano, Takayuki; Nishizaki, Takafumi; Saito, Takashi; Suzuki, Michiyasu

    2005-11-01

    In the field of neurosurgery for brain tumor, it is crucially important to remove almost totally certain brain tumors because of patients' quality of life. However, there has been few effective means of determining the boundaries between tumor tissue and surrounding normal brain parenchyma, making tumor resection totally dependent on the experiencing judgment of surgeons. Therefore, it is quite desirable to construct a real-time and highly sensitive monitoring system to detect tumor margins during surgery. In this study, proposed is the novel photo-dynamic diagnosis method for glioma-surgery. Using excited fluorescence from an oncotropic luminophore dye generally used in PDT and auto-fluorescence from some intracellular enzymes, e.g. NADH (Reduced Nicotinamide Adenine Dinucleotide), the ratio-metric technique in two-color laser-induced fluorescence was experimentally applied to brain tumor detection. The experiment was conducted using brain tumor rat models. An oncotoropic fluorescent dye, NPe6 (mono-L-aspartyl chlorin e6), was injected intravenously and then two fluorescence images were taken with irradiation of violet light, The fluorescence intensities of intracellular enzymes and NPe6 were found to decrease and increase in tumor lesions, respectively. Fluorescence intensity ratio could quantitatively identify tumor margins. Undesirable fluorescence variation could be reduced, which was dependent on inhomogeneous irradiation intensity distribution due to brain surface shape and illuminating light source itself. Thus, the ratio image could achieve higher contrast enhancement in tumor boundaries than single-color PDD. Furthermore, the histological examination provided correlation with ratio-image enhanced area. Consequently, the present method was clarified to be effective to brain tumor monitoring and quantitative tumor boundary demarcation.

  13. Describing Autophagy via Analysis of Individual Organelles by Capillary Electrophoresis with Laser Induced Fluorescence Detection

    PubMed Central

    Satori, Chad P.

    2013-01-01

    Autophagy is a cellular process responsible for the degradation of intracellular cargo. Its dynamic nature and the multiple types of autophagy organelles present at a given time make current measurements, such as those done by Western blotting, insufficient to understand autophagy and its roles in aging and disease. Capillary electrophoresis coupled to laser induced fluorescence detection (CE-LIF) has been used previously to count and determine properties of individual organelles, but has never been used on autophagy organelles or for determination of changes of such properties. Here we used autophagy organelles isolated from L6 cells expressing GFP-LC3, which is an autophagy marker, to develop a CE-LIF method for the determination of the number of autophagy organelles, their individual GFP-LC3 fluorescence intensities, and their individual electrophoretic mobilities. These properties were compared under basal and rapamycin-driven autophagy, which showed differences in the number of detected organelles and electrophoretic mobility distributions of autophagy organelles. Vinblastine treatment was also used to halt autophagy and further characterize changes and provide additional insight on the nature of autophagy organelles. This approach revealed dramatic and opposite directions in changes of organelle numbers, GFP-LC3 contents, and electrophoretic mobilities during the duration of the vinblastine treatment. These trends suggested the identity of organelle types being detected. These observations demonstrate that individual organelle analysis by CE-LIF is a powerful technology to investigate the complexity and nature of autophagy, a process that plays critical roles in response to drug treatments, aging, and disease. PMID:24164243

  14. Time-domain laser-induced fluorescence spectroscopy apparatus for clinical diagnostics

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin; Papaioannou, Thanassis; Jo, Javier A.; Vaitha, Russel; Shastry, Kumar; Marcu, Laura

    2004-01-01

    We report the design and development of a compact optical fiber-based apparatus for in situ time-resolved laser-induced fluorescence spectroscopy (tr-LIFS) of biological systems. The apparatus is modular, optically robust, and compatible with the clinical environment. It incorporates a dual output imaging spectrograph, a gated multichannel plate photomultiplier (MCP-PMT), an intensified charge-coupled-device (ICCD) camera, and a fast digitizer. It can accommodate various types of light sources and optical fiber probes for selective excitation and remote light delivery/collection as required by different applications. The apparatus allows direct recording of the entire fluorescence decay with high sensitivity (nM range fluorescein dye concentration with signal-to-noise ratio of 46) and with four decades dynamic range. It is capable of resolving a broad range of fluorescence lifetimes from hundreds of picoseconds (as low as 300 ps) using the MCP-PMT coupled to the digitizer to milliseconds using the ICCD. The data acquisition and analysis process is fully automated, enabling fast recording of fluorescence intensity decay across the entire emission spectrum (0.8 s per wavelength or ˜40 s for a 200 nm wavelength range at 5 nm increments). The spectral and temporal responses of the apparatus were calibrated and its performance was validated using fluorescence lifetime standard dyes (Rhodamin B, 9-cyanoanthracene, and rose Bengal) and tissue endogenous fluorophores (elastin, collagen, nicotinamide adenine dinucleotide, and flavin adenine dinucleotide). Fluorescence decay lifetimes and emission spectra of all tested compounds measured with the current tr-LIFS apparatus were found in good agreement with the values reported in the literature. The design and performance of tr-LIFS apparatus have enabled in vivo studies of atherosclerotic plaques and brain tumors.

  15. Measuring total soil carbon with laser-induced breakdown spectroscopy (LIBS).

    PubMed

    Cremers, D A; Ebinger, M H; Breshears, D D; Unkefer, P J; Kammerdiener, S A; Ferris, M J; Catlett, K M; Brown, J R

    2001-01-01

    Improving estimates of carbon inventories in soils is currently hindered by lack of a rapid analysis method for total soil carbon. A rapid, accurate, and precise method that could be used in the field would be a significant benefit to researchers investigating carbon cycling in soils and dynamics of soil carbon in global change processes. We tested a new analysis method for predicting total soil carbon using laser-induced breakdown spectroscopy (LIBS). We determined appropriate spectral signatures and calibrated the method using measurements from dry combustion of a Mollisol from a cultivated plot. From this calibration curve we predicted carbon concentrations in additional samples from the same soil and from an Alfisol collected in a semiarid woodland and compared these predictions with additional dry combustion measurements. Our initial tests suggest that the LIBS method rapidly and efficiently measures soil carbon with excellent detection limits (approximately 300 mg/kg), precision (4-5%), and accuracy (3-14%). Initial testing shows that LIBS measurements and dry combustion analyses are highly correlated (adjusted r2 = 0.96) for soils of distinct morphology, and that a sample can be analyzed by LIBS in less than one minute. The LIBS method is readily adaptable to a field-portable instrument, and this attribute--in combination with rapid and accurate sample analysis--suggests that this new method offers promise for improving measurement of total soil carbon. Additional testing of LIBS is required to understand the effects of soil properties such as texture, moisture content, and mineralogical composition (i.e., silicon content) on LIBS measurements. PMID:11790033

  16. Mechanisms of Laser-Induced Dissection and Transport of Histologic Specimens

    PubMed Central

    Vogel, Alfred; Lorenz, Kathrin; Horneffer, Verena; Hüttmann, Gereon; von Smolinski, Dorthe; Gebert, Andreas

    2007-01-01

    Rapid contact- and contamination-free procurement of histologic material for proteomic and genomic analysis can be achieved by laser microdissection of the sample of interest followed by laser-induced transport (laser pressure catapulting). The dynamics of laser microdissection and laser pressure catapulting of histologic samples of 80 ?m diameter was investigated by means of time-resolved photography. The working mechanism of microdissection was found to be plasma-mediated ablation initiated by linear absorption. Catapulting was driven by plasma formation when tightly focused pulses were used, and by photothermal ablation at the bottom of the sample when defocused pulses producing laser spot diameters larger than 35 ?m were used. With focused pulses, driving pressures of several hundred MPa accelerated the specimen to initial velocities of 100–300 m/s before they were rapidly slowed down by air friction. When the laser spot was increased to a size comparable to or larger than the sample diameter, both driving pressure and flight velocity decreased considerably. Based on a characterization of the thermal and optical properties of the histologic specimens and supporting materials used, we calculated the evolution of the heat distribution in the sample. Selected catapulted samples were examined by scanning electron microscopy or analyzed by real-time reverse-transcriptase polymerase chain reaction. We found that catapulting of dissected samples results in little collateral damage when the laser pulses are either tightly focused or when the laser spot size is comparable to the specimen size. By contrast, moderate defocusing with spot sizes up to one-third of the specimen diameter may involve significant heat and ultraviolet exposure. Potential side effects are maximal when samples are catapulted directly from a glass slide without a supporting polymer foil. PMID:17766336

  17. Erasure and formation of femtosecond laser-induced nanostructures

    NASA Astrophysics Data System (ADS)

    Zimmermann, F.; Plech, A.; Richter, Sören; Tünnermann, A.; Nolte, S.

    2015-03-01

    The local inscription of strong birefringence by ultrashort laser pulses facilitates the fabrication of manifold photonic devices, such as data storage devices. One intriguing feature of these nanograting-based data units is to delete and rewrite new nanograting voxels by changing the laser polarization orientation during inscription. However, up to now no comprehensive picture of this complex physical process exists. Thus we performed optical retardance measurements as well as microscopic analyses, such as small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) to address this issue. Our results reveal that only few laser pulses already lead to an erasure of nanometric pores which is mapped by the total (X-ray) scattering volume as well as by the strong reduction of the initial form birefringence. Simultaneously, new nanostructures form which arrange in individual grating planes with ongoing irradiation. However, since the rewrite process is no ideal mechanism some of the old sheets remain, which perturb the quality of the new nanograting. When rewriting multiple times the glass becomes even more porous due to repetitive annealing and quenching. This promotes the formation of new inhomogeneities and in turn leads to an increase in optical retardance.

  18. Thermomechanical modification of diffraction gratings

    NASA Astrophysics Data System (ADS)

    Sumetsky, M.; Dulashko, Y.; Fleming, J. W.; Kortan, A.; Reyes, P. I.; Westbrook, P. S.

    2004-06-01

    The most accurate approaches to fabrication of diffraction gratings are known to be the lithographic and holographic methods. The lithographic methods allow fabrication of arbitrarily chirped gratings whose performance, however, is degraded by stitching errors. The holographic methods are free from stitching errors; however, they are limited in the achievable spatial variations of their grating periods. We suggest a method of diffraction grating modification by nonuniform heating and stretching that is much more flexible than the holographic approach and does not suffer from the problem of stitching error. We demonstrate our approach for quartz phase masks that have a characteristic grating period of 1 µm and a length of several centimeters. Our approach allows the grating periods of the phase masks to vary in a range from a few picometers to a few nanometers and a spatial resolution of a few millimeters. It is shown that the grating period can be modified with a negligible effect on the profile of the gratings.

  19. Time-integrated laser-induced plasma spectroscopy in the vacuum ultraviolet for the quantitative elemental characterization of steel alloys

    NASA Astrophysics Data System (ADS)

    Khater, M. A.; van Kampen, P.; Costello, J. T.; Mosnier, J.-P.; Kennedy, E. T.

    2000-09-01

    This paper demonstrates that time-integrated space-resolved laser-induced plasma spectroscopy (TISR-LIPS) is a useful technique in the vacuum ultraviolet (VUV) for the quantitative determination of the carbon content in steels. The standard reference samples used were carbon-iron alloys containing a relatively wide concentration range of carbon (0.041-1.32%). In the experiments the output of a Q-switched Nd:YAG (1064 nm) laser, with approximately a 1 J maximum output pulse energy and approximately a 12 ns temporal pulse width, was focused onto the surface of each sample (under vacuum) in order to produce the emitting plasma. A fore-slit mounted in the target chamber allowed spatially-resolved spectral measurements in the axial direction of the plasma and provided emission lines that were almost free of the background continuum. A 1 m normal incidence vacuum spectrometer, equipped with a 1200 grooves mm-1 concave grating and a micro-channel plate/photodiode array detector combination, was used as the detection system. A particularly interesting feature of this work is the demonstration that VUV spectroscopy allows ionic lines to be used and linear calibration curves were obtained for the five carbon spectral lines (from C+ and C2+) under investigation. The limits of detection for all lines were determined; the lowest detection limit (87+/-10 ppm) was obtained from the C2+ 97.70 nm line, which compares favourably with the only available value in the literature of 100 ppm.

  20. 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.

  1. Circular Fibonacci gratings.

    PubMed

    Gao, Nan; Zhang, Yuchao; Xie, Changqing

    2011-11-01

    We introduce circular Fibonacci gratings (CFGs) that combine the concept of circular gratings and Fibonacci structures. Theoretical analysis shows that the diffraction pattern of CFGs is composed of fractal distributions of impulse rings. Numerical simulations are performed with two-dimensional fast Fourier transform to reveal the fractal behavior of the diffraction rings. Experimental results are also presented and agree well with the numerical results. The fractal nature of the diffraction field should be of great theoretical interest, and shows potential to be further developed into practical applications, such as in laser measurement with wideband illumination. PMID:22086040

  2. Compact slanted grating couplers

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Jiang, Jianhua; Nordin, Gregory P.

    2004-07-01

    We present a compact and efficient design for slanted grating couplers (SLGC's) to vertically connect fibers and planar waveguides without intermediate optics. The proposed SLGC employs a strong index modulated slanted grating. With the help of a genetic algorithm-based rigorous design tool, a 20 ?m-long SLGC with 80.1% input coupling efficiency has been optimized. A rigorous mode analysis reveals that the phase-matching condition and Bragg condition are satisfied simultaneously with respect to the fundamental leaky mode supported by the optimized SLGC.

  3. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B. (Shoreham, NY)

    1986-01-01

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

  4. Use of laser-induced ionization to detect soot inception in premixed flames

    SciTech Connect

    Manzello, Samuel L.; Lee, Eui Ju; Mulholland, George W

    2005-08-20

    Experimental measurements of laser-induced ionization were performed for ethene-air premixed flames operated near the soot inception point. Soot was ionized with a pulsed laser operated at 532 nm. The ionization signal was collected with a tungsten electrode located in the postflame region. Ionization signals were collected by use of both single-electrode and dual-electrode configurations. Earlier laser-induced- ionization studies focused on the use of a single biased electrode to generate the electric field, with the burner head serving as the path to ground. In many practical combustion systems, a path to ground is not readily available. To apply the laser-induced- ionization diagnostic to these geometries, a dual-electrode geometry must be employed. The influence of electrode configuration, flame equivalence ratio, and flame height on ionization signal detection was determined. The efficacy of the laser-induced-ionization diagnostic in detecting soot inception in the postflame region of a premixed flame by use of a dual-electrode configuration was investigated. Of the dual-electrode configurations tested, the dual-electrode geometry oriented parallel to the laser beam was observed to be most sensitive for detecting the soot inception point in a premixed flame.

  5. Capillary electrophoresis with laser-induced fluorescence detection for fast and reliable apolipoprotein E genotyping

    Microsoft Academic Search

    G. W Somsen; H. T. M. E Welten; F. Ph Mulder; C. W Swart; I. P Kema; G. J de Jong

    2002-01-01

    The use of capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection for the rapid determination of apolipoprotein E (apoE) genotypes was studied. High resolution and sensitive detection of the concerned DNA restriction fragments was achieved using CE buffers with hydroxypropylmethylcellulose (HPMC) as sieving polymer and ethidium bromide (EB) as fluorescent intercalating agent. In order to achieve adequate resolutions in short

  6. An Analysis of Signal Intensity Affected by The Light Spot With Laser Induced Fluorescence Detection

    Microsoft Academic Search

    Wang Jie; Wang Li-qiang; Shi Yan; Zheng Hua; Lu Zu-kang

    2006-01-01

    The experiment of capillary electrophoresis (CE) is put up with the laser induced fluorescence detection (LIFD) system made by ourselves. The model same as the actual system is set up in the software of optical simulation. In order to heighten the fluorescence signals intensity, increase the light spot which illuminate in the detection window of capillary instead of the traditional

  7. DETECTION OF CONTAMINANTS ON POULTRY PROCESSING PLANT EQUIPMENT USING LASER-INDUCED FLUORESCENCE IMAGING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fluorescence techniques have demonstrated great potential for detection of the presence of fecal and other biological substances that can harbor pathogens. We used a recently developed laser-induced fluorescence imaging system (LIFIS) to demonstrate the potential use of fluorescence techniques for d...

  8. Scanning delay generator for measurement of kinetic decays using laser-induced fluorescence techniques

    NASA Technical Reports Server (NTRS)

    Halpern, J. B.; Towns, T. G.

    1982-01-01

    An electronic device is described which generates a delayed pulse, where the delay is increased in a step-like manner. This device finds application in the measurement of kinetic decays, particularly when laser-induced fluorescent (LIF) detection of the decaying species is used. The circuit uses 15 low-power Schottky TTL chips and is contained within a dual width NIM module.

  9. Growth of carbon nanotubes by open-air laser-induced chemical vapor deposition

    Microsoft Academic Search

    Kinghong Kwok; Wilson K. S. Chiu

    2005-01-01

    Carbon nanotubes have remarkable mechanical, electronic and electrochemical properties, but the full potential for application will be realized only if the growth of high quantity and quality carbon nanotubes can be optimized and well controlled. In this study, carbon nanotubes have been successfully grown on fused quartz rods by a novel open-air laser-induced chemical vapor deposition (LCVD) technique with gold

  10. Detection of fecal residue on poultry carcasses by laser induced fluorescence imaging techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential use of laser-induced fluorescence imaging techniques was investigated for the detection of diluted fecal matters from various parts of the digestive tract, including colon, ceca, small intestine, and duodenum, on poultry carcasses. One of the challenges for using fluorescence imaging f...

  11. Evidence of laser induced decomposition of triaminotrinitrobenzene from surface enhanced Raman spectroscopy

    Microsoft Academic Search

    F. J. Owens

    2011-01-01

    It is observed that the focused 632 nm laser of the confocal micro-Raman spectrometer decomposes triaminotrinitrobenzene (TATB). The temperature generated in the laser spot determined by measuring the ratio of the intensities of the anti-Stokes to Stokes spectra is too low to cause thermal decomposition. The observed decomposition is suggested to be a result of laser induced electronic excitation. The

  12. PAPER www.rsc.org/loc | Lab on a Chip Laser-induced cavitation based micropump

    E-print Network

    Ohl, Claus-Dieter

    PAPER www.rsc.org/loc | Lab on a Chip Laser-induced cavitation based micropump Rory Dijkinka as versatile and robust pumping techniques. Here, we present a cavitation based technique, which is able cavitation event is created by focusing a laser pulse in a conventional PDMS microfluidic chip close

  13. Laser induced fluorescence in Ar and He plasmas with a tunable diode laser

    Microsoft Academic Search

    R. F. Boivin; E. E. Scime

    2003-01-01

    A diode laser based laser induced fluorescence (LIF) diagnostic that uses an inexpensive diode laser system is described. This LIF diagnostic has been developed on the hot helicon experiment (HELIX) plasma device. The same diode laser is used to alternatively pump Ar II and He I transitions to obtain argon ion and atomic helium temperatures, respectively. The 1.5 MHz bandwidth

  14. Application of laser-induced breakdown spectroscopy for detecting leakage of boric acid

    Microsoft Academic Search

    Yong-Il Kim; Dong-Jin Yoon; Seung-Seok Lee; Yun Hee Lee; Ki-Bok Kim

    2011-01-01

    Recently, many studies have been conducted on developing on-line leak detection techniques in the reactor vessel head of nuclear power plants. One of them, laser-induced breakdown spectroscopy (LIBS), an effective technique of leak detection, which is a kind of atomic emission spectroscopy that uses a highly energetic laser pulse as the excitation source, has been of interest due to the

  15. Confirmation of an Electron Avalanche Causing Laser-induced Bulk Damage at 106 µm

    Microsoft Academic Search

    D. W. Fradin; Eli Yablonovitch; Michael Bass

    1973-01-01

    laser-induced breakdown,1 may be described by the following sequence of steps: First, absorption occurs at microscopic absorbing inclusions 2 or by means of an intrinsic nonlinear absorption process such as multiphoton absorption or electron avalanche break- down. Second, the energy absorbed from the beam heats the medium. Finally, a thermally induced frac- ture or a phase change occurs that in

  16. Key factors in achieving ultra-broadband THz emission from a laser-induced gas plasma

    Microsoft Academic Search

    Volker Blank; Mark D. Thomson; Hartmut G. Roskos

    2011-01-01

    We demonstrate how the observed emission of ultra-broadband THz pulses (>100 THz) from a two-color (?-2?) laser-induced gas plasma is strongly dictated by the precise spectral and temporal characteristics of the input optical fields. OCIS codes: (190.4380) Nonlinear optics, four-wave mixing; (300.6495) Spectroscopy, terahertz

  17. Experimental evaluation of strategies for quantitative laser-induced-fluorescence imaging of nitric oxide

    E-print Network

    Lee, Tonghun

    Engineering Department, Stanford University, Stanford, CA 94305, USA Abstract Nitric oxide laser. All rights reserved. Keywords: Nitric oxide; Laser-induced fluorescence; NO reburn; Combustion,2]. A species of par- ticular concern for its harmful impact on the envi- ronment is nitric oxide (NO), whose

  18. Analysis of laser induced acoustic pulse probing of charge distributions in dielectrics

    E-print Network

    Boyer, Edmond

    L-171 Analysis of laser induced acoustic pulse probing of charge distributions in dielectrics C pulse method for the determination ofelectric field or charge distributions in dielectrics are analysed years, new approaches to the study of charge storage and transport phenomena in dielectrics have been

  19. Vibrational temperature measurements in a shock layer using laser induced predissociation fluorescence

    Microsoft Academic Search

    D. J. Sutton; A. F. P. Houwing; P. C. Palma; R. I. Sandeman

    1993-01-01

    Single shot spatially and spectrally resolved laser induced predissociation fluorescence measurements in a shock layer around a cylinder in a pulsed supersonic free stream are presented. Fluoresence signals were produced using the tuned output of an argon fluoride excimer laser to excite a mixture of rovibrational transitions in molecular oxygen. The signals produced along a line inside the shock layer

  20. Analysis of protein-based binding media found in paintings using laser induced fluorescence spectroscopy

    Microsoft Academic Search

    Austin Nevin; Sharon Cather; Demetrios Anglos; Costas Fotakis

    2006-01-01

    Laser induced fluorescence (LIF) spectroscopy of intrinsic fluorophores from organic media found in paintings (casein, animal glue and egg proteins) provides novel non-invasive means of characterisation of general classes of media on the basis of fluorescence emission arising from the presence of certain amino acids and their degradation byproducts. Proteins from traditionally employed binding media include collagen, casein, albumin and