Science.gov

Sample records for picosecond plasma issledovanie

  1. Picosecond resolution soft x-ray laser plasma interferometry

    SciTech Connect

    Moon, S; Nilsen, J; Ng, A; Shlyaptsev, V; Dunn, J; Hunter, J; Keenan, R; Marconi, M; Filevich, J; Rocca, J; Smith, R

    2003-12-01

    We describe a soft x-ray laser interferometry technique that allows two-dimensional diagnosis of plasma electron density with picosecond time resolution. It consists of the combination of a robust high throughput amplitude division interferometer and a 14.7 nm transient inversion soft x-ray laser that produces {approx} 5 ps pulses. Due to its picosecond resolution and short wavelength scalability, this technique has potential for extending the high inherent precision of soft x-ray laser interferometry to the study of very dense plasmas of significant fundamental and practical interest, such as those investigated for inertial confined fusion. Results of its use in the diagnostics of dense large scale laser-created plasmas are presented.

  2. Picosecond imaging of low-density plasmas by electron deflectometry.

    PubMed

    Centurion, M; Reckenthaeler, P; Krausz, F; Fill, E E

    2009-02-15

    We have imaged optical-field ionized plasmas with electron densities as low as 10(13) cm(-3) on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons.

  3. Picosecond time-resolved measurements of dense plasma line shifts

    DOE PAGES

    Stillman, C. R.; Nilson, P. M.; Ivancic, S. T.; ...

    2017-06-13

    Picosecond time-resolved x-ray spectroscopy is used to measure the spectral line shift of the 1s2p–1s2 transition in He-like Al ions as a function of the instantaneous plasma conditions. The plasma temperature and density are inferred from the Al Heα complex using a nonlocal-thermodynamic-equilibrium atomic physics model. The experimental spectra show a linearly increasing red shift for electron densities of 1 to 5 × 1023 cm–3. Furthermore, the measured line shifts are broadly consistent with a generalized analytic line-shift model based on calculations of a self-consistent field ion sphere model.

  4. Picosecond time-resolved measurements of dense plasma line shifts

    NASA Astrophysics Data System (ADS)

    Stillman, C. R.; Nilson, P. M.; Ivancic, S. T.; Golovkin, I. E.; Mileham, C.; Begishev, I. A.; Froula, D. H.

    2017-06-01

    Picosecond time-resolved x-ray spectroscopy is used to measure the spectral line shift of the 1 s 2 p -1 s2 transition in He-like Al ions as a function of the instantaneous plasma conditions. The plasma temperature and density are inferred from the Al H eα complex using a nonlocal-thermodynamic-equilibrium atomic physics model. The experimental spectra show a linearly increasing redshift for electron densities of 1 -5 ×1023c m-3 . The measured line shifts are broadly consistent with a generalized analytic line-shift model based on calculations of a self-consistent field ion-sphere model.

  5. Use of extended laser plasma for generation of high-order harmonics of picosecond duration

    SciTech Connect

    Ganeev, R A; Boltaev, G S; Reyimbaev, Sh; Sherniyozov, Kh; Usmanov, T

    2015-07-31

    We report the results of experimental investigations on the generation of picosecond radiation harmonics in extended laser plasma produced on the surface of different metal targets. The effect of plasma length, heating pulse duration and delay between the heating and transformable pulses on the efficiency of conversion to higher harmonics is studied. The λ = 1064 nm radiation conversion to a short-wavelength (down to 50 nm, 21st harmonic) range in extended plasma of several metals is demonstrated. (interaction of laser radiation with matter. laser plasma)

  6. Proton Radiography of Laser-Plasma Interactions with Picosecond Time Resolution

    SciTech Connect

    Mackinnon, A J; Patel, P K; Town, R J; Hatchett, S P; Hicks, D; Phillips, T H; Wilks, S C; Price, D; Key, M H; Lasinski, B; Langdon, B; Borghesi, M; Romagnani, L; Kar, S

    2005-02-10

    Radiography of laser-produced plasmas with MeV protons has the potential to provide new information on plasma conditions in extreme states of matter. Protons with energies up to many hundreds MeV, produced by large scale accelerators have been recently been used to obtain mass density radiographs of the behavior of large samples which have been shocked on microsecond timescales with approximately mm spatial resolution. The recent discovery of laminar proton beams accelerated to multi-MeV energies by picosecond duration laser beams has provided the opportunity to probe dense plasmas with hitherto unparalleled temporal and spatial resolution.

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

    SciTech Connect

    Lopez-Arias, M.; Oujja, M.; Sanz, M.; Castillejo, M.; Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T.

    2012-02-15

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

  8. Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

    SciTech Connect

    Tamura, Jun; Kumaki, Masafumi; Kondo, Kotaro; Kanesue, Takeshi; Okamura, Masahiro

    2016-02-15

    We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe{sup 21+}) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe{sup 19+}). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

  9. Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

    NASA Astrophysics Data System (ADS)

    Tamura, Jun; Kumaki, Masafumi; Kondo, Kotaro; Kanesue, Takeshi; Okamura, Masahiro

    2016-02-01

    We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe21+) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe19+). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

  10. Study of plasma pressure evolution driven by strong picosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Li, M.; Wang, J. X.; Xu, Y. X.; Zhu, W. J.

    2017-01-01

    Through one dimensional relativistic particle-in-cell simulation of strong laser interaction with the solid-density plasma, the evolution of the plasma impact pressure behind a thin foil has been investigated in details. An energy-compression mechanism has been proposed to help optimizing the laser and plasma parameters. It has been found that by using a picosecond laser with intensity 1015 W cm-2, an impact pressure as high as several hundreds of GPa order of magnitude can be obtained. The numerical analysis demonstrates that the peak pressure is mainly resulted from the ion contribution. These results are of potential application to the laser loading upon solids in order to study the material properties under extra-high dynamic pressure.

  11. Temporal structure of X-ray radiation pulses of picosecond laser plasma

    SciTech Connect

    Belyaev, V S; Kovkov, D V; Matafonov, A P; Karabadzhak, G F; Raikunov, G G; Faenov, A Ya; Pikuz, S A; Skobelev, I Yu; Pikuz, T A; Fokin, D A; Fortov, V E; Ignat'ev, G N; Kapitanov, S V; Krapiva, P S; Korotkov, K E

    2013-09-30

    The shape of the X-ray pulse generated by picosecond laser plasma is experimentally studied. The unusual phenomenon was experimentally observed for the first time for targets made of moderate-heavy chemical elements, namely, the pulse of hard X-ray radiation generated by laser plasma at the laser radiation flux of ∼10{sup 18} W cm{sup -2} had a longer duration than the pulse of softer X-ray radiation. A simple kinetic model is suggested for explaining this fact. We have suggested a method for controlling the temporal shape of X-ray pulse emitted by laser plasma by varying the contrast of laser pulse. (interaction of laser radiation with matter)

  12. Picosecond X-ray Laser Interferometry for Probing Dense Laser-Produced Plasmas

    NASA Astrophysics Data System (ADS)

    Dunn, James; Smith, Raymond F.; Filevich, Jorge; Rocca, Jorge J.; Moon, Stephen J.; Nilsen, Joseph; Shlyaptsev, Vyacheslav N.; Keenan, Roisin; Ng, Andrew; Hunter, James R.; Marconi, Mario. C.

    2003-10-01

    The development of compact, x-ray laser (XRL) sources has great potential to advance interferometric techniques to shorter wavelengths for probing dense, rapidly changing, laser-heated plasmas. The use of soft x-rays has many advantages over optical or UV wavelength probes including greatly reduced refraction and lower absorption within the plasma. Another advantage when coupled with a short probe pulse duration, is the achievement of sub-micron spatial resolution close to the target surface to make precise measurements in the highest density region with negligible plasma motion blurring. This makes x-ray laser interferometry a unique tool for studying high density plasmas giving new information about the underlying physical processes and allowing the study of new plasma regimes. We describe precision interferometric characterization experiments using the picosecond, 14.7 nm x-ray laser source generated on the Compact Multipulse Terawatt (COMET) laser facilty at LLNL together with the Mach-Zehnder type Diffraction Grating Interferometer (DGI) designed and built at Colorado State University. A review of the results from dense, mm-scale line focus plasma experiments will be described with detailed comparisons to 1-, 1.5- and 2-D hydrodynamic simulations. Ongoing experiments on smaller spot focus high intensity plasmas will be discussed.

  13. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: X-ray spectral diagnostics of plasmas heated by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Bryunetkin, B. A.; Skobelev, I. Yu; Faenov, A. Ya; Khakhalin, S. Ya; Kalashnikov, M. P.; Nickles, P. V.; Schnürer, M.

    1993-06-01

    The properties of a magnesium plasma heated by picosecond laser pulses have been determined by x-ray spectral methods. Experiments were carried out at a laser power density ~ 1.5 · 1018 W/cm2. The x-ray spectra were detected by spectrographs with a plane CsAP crystal and a mica crystal bent into part of a spherical surface 10 cm in radius. The experimental data are compared with predictions of a calculation on the time-varying kinetics of multiply charged magnesium ions.

  14. Electric Field Measurements in Non-Equilibrium Electric Discharge Plasmas Using Picosecond Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Goldberg, Benjamin M.

    This dissertation presents the results of development of a picosecond four wave mixing technique and its use for electric field measurements in nanosecond pulse discharges. This technique is similar to coherent anti-Stokes Raman spectroscopy and is well suited for electric field measurements in high pressure plasmas with high spatial and temporal resolution. The results show that the signal intensity scales proportionally to the square of the electric field, the signal is emitted as a coherent beam, and is polarized parallel to the electric field vector, making possible electric field vector component measurements. The signal is generated when a collinear pair of pump and Stokes beams, which are generated in a stimulated Raman shifting cell (SRS), generate coherent excitation of molecules into a higher energy level, hydrogen for the present work. The coherent excitation mixes with a dipole moment induced by an external electric field. The mixing of these three "waves'" allows the molecules to radiate at their Raman frequency, producing a fourth, signal, wave which is proportional to the square of the electric field. The time resolution of this technique is limited by the coherence decay time of the molecules, which is a few hundred picoseconds.

  15. Fast ion acceleration in a foil plasma heated by a multi-picosecond high intensity laser

    NASA Astrophysics Data System (ADS)

    Iwata, Natsumi; Mima, Kunioki; Sentoku, Yasuhiko; Yogo, Akifumi; Nagatomo, Hideo; Nishimura, Hiroaki; Azechi, Hiroshi

    2017-07-01

    We study the one-dimensional expansion of a thin foil plasma irradiated by a high intensity laser with multi-picosecond (ps) pulse durations by using particle-in-cell simulation. Electrons are found to recirculate around the expanding plasma for many times, which results in stochastic heating leading to increase of the electron temperature in the multi-ps time scale beyond the ponderomotive scaling. The conventional isothermal model cannot describe such an expansion of plasmas in the long time scale. We here developed a non-isothermal plasma expansion theory that takes the time dependence of electron temperature into account for describing the multi-ps interactions in one-dimensional geometry. By assuming that the time scale of electron temperature evolution is slow compared with the plasma expansion time scale, we derived a non-self-similar solution. The time evolution of ion maximum energy obtained by the non-isothermal theory explains the details of that observed in the simulation.

  16. Picosecond LIBS diagnostics for Tokamak in situ plasma facing materials chemical analysis

    NASA Astrophysics Data System (ADS)

    Morel, Vincent; Pérès, Bastien; Bultel, Arnaud; Hideur, Ammar; Grisolia, Christian

    2016-02-01

    First results are presented in relation with experimental and theoretical studies performed at the CORIA laboratory in the general framework of the determination of the chemical analysis of Tokamak plasma facing materials by laser-induced breakdown spectroscopy (LIBS) in picosecond regime. Experiments are performed on W in a specific chamber. This chamber is equipped with a UV-visible-near IR spectroscopic device. Boltzmann plots are derived for typical laser characteristics. We show that the initial excitation temperature is close to 12 000 K followed by a quasi steady value close to 8500 K. The ECHREM (Euler code for CHemically REactive Multicomponent laser-induced plasmas) code is developed to reproduce the laser-induced plasmas. This code is based on the implementation of a Collisional-Radiative model in which the different excited states are considered as full species. This state-to-state approach is relevant to theoretically assess the departure from excitation and chemical equilibrium. Tested on aluminum, the model shows that the plasma remains close to excitation equilibrium.

  17. Picosecond imaging of inertial confinement fusion plasmas using electron pulse-dilation

    NASA Astrophysics Data System (ADS)

    Hilsabeck, T. J.; Nagel, S. R.; Hares, J. D.; Kilkenny, J. D.; Bell, P. M.; Bradley, D. K.; Dymoke-Bradshaw, A. K. L.; Piston, K.; Chung, T. M.

    2017-02-01

    Laser driven inertial confinement fusion (ICF) plasmas typically have burn durations on the order of 100 ps. Time resolved imaging of the x-ray self emission during the hot spot formation is an important diagnostic tool which gives information on implosion symmetry, transient features and stagnation time. Traditional x-ray gated imagers for ICF use microchannel plate detectors to obtain gate widths of 40-100 ps. The development of electron pulse-dilation imaging has enabled a 10X improvement in temporal resolution over legacy instruments. In this technique, the incoming x-ray image is converted to electrons at a photocathode. The electrons are accelerated with a time-varying potential that leads to temporal expansion as the electron signal transits the tube. This expanded signal is recorded with a gated detector and the effective temporal resolution of the composite system can be as low as several picoseconds. An instrument based on this principle, known as the Dilation X-ray Imager (DIXI) has been constructed and fielded at the National Ignition Facility. Design features and experimental results from DIXI will be presented.

  18. Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using 66Zn/63Cu, 208Pb/238U, 232Th/238U, 66Zn/232Th and 66Zn/208Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%).

  19. Tomographic reconstruction of high-energy-density plasmas with picosecond temporal resolution.

    PubMed

    Baker, K L

    2006-03-15

    Three-dimensional reconstruction of the electron density in a plasma can be obtained by passing multiple beams at different field angles simultaneously through a plasma and performing a tomographic reconstruction of the measured field-dependent phase profiles. A relatively simple experimental setup is proposed and simulations are carried out to verify the technique. The plasma distribution is modeled as a discrete number of phase screens, and a Zernike polynomial representation of the phase screens is used to reconstruct the plasma profile.

  20. Comments on "Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma"

    NASA Astrophysics Data System (ADS)

    Zaytsev, Sergey M.; Popov, Andrey M.; Zorov, Nikita B.; Labutin, Timur A.

    2016-04-01

    In the paper "Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma" by Syahrun Nur Abdulmadjid, Nasrullah Idris, Marincan Pardede, Eric Jobiliong, Rinda Hedwig, Zener Sukra Lie, Hery Suyanto, May On Tjia, Koo Hendrik Kurniawan and Kiichiro Kagawa [Spectrochim. Acta Part B 114 (2015) 1-6], the authors presented experimental study to demonstrate the sensitive detection of C, Cr and Si in low-alloy steels under low pressure He atmosphere. Although the use of only UV-VIS spectral range for determination of these elements seems to be a beneficial, the point that needs to be commented is the result of carbon determination with the use of C I 247.856 nm line. Thermodynamic modeling based on the NIST and R. Kurucz data for the different excitation conditions in plasma demonstrates that it is hardly possible to distinguish any carbon signal due to significantly intensive iron line Fe II 247.857 nm. Authors are kindly requested to re-consider this part of their study.

  1. Tomographic reconstruction of high energy density plasmas with picosecond temporal resolution

    SciTech Connect

    Baker, K L

    2005-09-20

    Three-dimensional reconstruction of the electron density in a plasma can be obtained by passing multiple beams at different field angles simultaneously through a plasma and performing a tomographic reconstruction of the measured field-dependent phase profiles. In this letter, a relatively simple experimental setup is proposed and simulations are carried out to verify the technique. The plasma distribution is modeled as a discreet number of phase screens and a Zernike polynomial representation of the phase screens is used to reconstruct the plasma profile. Using a subpicosecond laser, the complete three-dimensional electron density of the plasma can be obtained with a time resolution limited only by the transit time of the probe through the plasma.

  2. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: High-resolution x-ray spectroscopy of a plasma produced by an intense picosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Bryunetkin, B. A.; Skobelev, I. Yu; Faenov, A. Ya; Kalashnikov, M. P.; Nickles, P. V.; Schnürer, M.; Pikuz, S. A.

    1993-04-01

    It has been shown experimentally that a source based on a plasma produced by a picosecond laser is extremely promising for systematic research on the satellite structures of multiply charged ions which have electrons in L or M shells. The combination of the unique characteristics of this source and the particular measurement apparatus used (with a spectral resolution Δλ/λ~10-4) has made it possible to refine the wavelengths of several transitions of Mg IX and X ions which had been identified previously, to identify for the first time ten spectral lines due to 1s2p4l → 1s24l and 1s2p3l → 1s23l transitions of the Mg X ion, and to measure the wavelengths of 47 spectral lines which have tentatively been attributed to the Be-like ion Mg IX.

  3. X-ray streak camera diagnostics of picosecond laser-plasma interactions

    SciTech Connect

    Cobble, J.A.; Fulton, R.D.; Jones, L.A.; Kyrala, G.A.; Schappert, G.T.; Taylor, A.J.; Wahlin, E.K.

    1992-05-01

    An x-ray streak camera is used to diagnose a laser-produced Al plasma with time resolution of {approximately}10 ps. A streak record of filtered emission and a time-integrated transmission grating spectrum reveal that the plasma radiation is dominated by emission from He- and H-like resonance lines. 11 refs.

  4. X-ray streak camera diagnostics of picosecond laser-plasma interactions

    SciTech Connect

    Cobble, J.A.; Fulton, R.D.; Jones, L.A.; Kyrala, G.A.; Schappert, G.T.; Taylor, A.J.; Wahlin, E.K.

    1992-01-01

    An x-ray streak camera is used to diagnose a laser-produced Al plasma with time resolution of {approximately}10 ps. A streak record of filtered emission and a time-integrated transmission grating spectrum reveal that the plasma radiation is dominated by emission from He- and H-like resonance lines. 11 refs.

  5. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: Identification of transitions from the 1s2l2l'3l'' autoionizing levels of the Be-like Mg IX ion in a plasma heated by a picosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Abdallah, J.; Clark, R. E.; Bryunetkin, B. A.; Skobelev, I. Yu; Faenov, A. Ya; Kalashnikov, M. P.; Nickles, P. V.; Schnurer, M.; Pikuz, S. A.

    1993-12-01

    The x-ray emission spectrum of a magnesium plasma produced by a picosecond laser has been studied. Dielectronic satellites of the resonance line of the He-like Mg XI ion have been identified for the first time. These satellites result from radiative transitions from 1s2l2l'3l'' autoionizing levels of the Be-like Mg IX ion.

  6. Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma

    NASA Astrophysics Data System (ADS)

    Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Lie, Zener Sukra; Suyanto, Hery; Tjia, May On; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

    2015-12-01

    An experimental study has been performed on the gas pressure and laser energy dependent variations of plasma emission intensities in Ar, He and N2 ambient gases induced by picosecond (ps) Nd-YAG laser irradiation on low alloy steel (JSS) samples. The study is aimed to demonstrate distinct advantage of using low pressure He ambient gas in combination with ps laser for the sensitive ppm level detection of C, Si and Cr emission lines in the UV-VIS spectral region. The much shorter pulses of ps laser are chosen for the effective ablation at much lower energy and for the benefit of reducing the undesirable long heating of the sample surface. It is found that the C I 247.8 nm, Fe I 253.5 nm, and Si I 251.4 nm emission lines induced by the ps laser at 15 mJ are readily detected with He ambient gas of 2.6 kPA, featuring generally sharp spectral signals with very low background. The following experimental results using samples with various concentrations of C, Si and Cr impurities are shown to produce for each of those elements a linear calibration line with extrapolated zero intercept, demonstrating the applicability for their quantitative analyses, with a preliminary estimated detection limits of 20 μg/g, 15 μg/g, and 5 μg/g, for C, Si, and Cr, respectively. The possibility of applying the same setup for concentration depth profiling is also demonstrated.

  7. Effect of plasma density scale length on the properties of bremsstrahlung x-ray sources created by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Courtois, C.; Compant La Fontaine, A.; Landoas, O.; Lidove, G.; Méot, V.; Morel, P.; Nuter, R.; Lefebvre, E.; Boscheron, A.; Grenier, J.; Aléonard, M. M.; Gerbaux, M.; Gobet, F.; Hannachi, F.; Malka, G.; Scheurer, J. N.; Tarisien, M.

    2009-01-01

    Results of an experimental study of multi-MeV bremsstrahlung x-ray sources created by picosecond laser pulses are presented. The x-ray source is created by focusing the short pulse in an expanding plasma obtained by heating a solid target with a time-delayed nanosecond laser beam. The high-energy part of the x-ray spectrum and emission lobe are inferred from photonuclear activation techniques. The x-ray dose is measured with silicon diodes. Two-dimensional images of the source are reconstructed from a penumbral imaging technique. These results indicate the creation of a relatively small source, below 200μm diameter, delivering doses up to 12mrad in air at 1m with x-ray temperature up to 2.8MeV. The diagnostics used give access to a whole set of coherent experimental results on the x-ray source properties which are compared to extensive numerical simulations. X-ray intensity and temperature are found to increase with the size of the preplasma.

  8. Effect of plasma density scale length on the properties of bremsstrahlung x-ray sources created by picosecond laser pulses

    SciTech Connect

    Courtois, C.; Compant La Fontaine, A.; Landoas, O.; Lidove, G.; Meot, V.; Morel, P.; Nuter, R.; Lefebvre, E.; Boscheron, A.; Grenier, J.; Aleonard, M. M.; Gerbaux, M.; Gobet, F.; Hannachi, F.; Malka, G.; Scheurer, J. N.; Tarisien, M.

    2009-01-15

    Results of an experimental study of multi-MeV bremsstrahlung x-ray sources created by picosecond laser pulses are presented. The x-ray source is created by focusing the short pulse in an expanding plasma obtained by heating a solid target with a time-delayed nanosecond laser beam. The high-energy part of the x-ray spectrum and emission lobe are inferred from photonuclear activation techniques. The x-ray dose is measured with silicon diodes. Two-dimensional images of the source are reconstructed from a penumbral imaging technique. These results indicate the creation of a relatively small source, below 200 {mu}m diameter, delivering doses up to 12 mrad in air at 1 m with x-ray temperature up to 2.8 MeV. The diagnostics used give access to a whole set of coherent experimental results on the x-ray source properties which are compared to extensive numerical simulations. X-ray intensity and temperature are found to increase with the size of the preplasma.

  9. Picosecond soft-x-ray pulses from a high-intensity laser-plasma source.

    PubMed

    Pelletier, J F; Chaker, M; Kieffer, J C

    1996-07-15

    We report time-resolved spectroscopic analysis of laser-produced plasma x-ray sources. Plasmas produced by a 400-fs 1-TW tabletop laser are characterized with a transmission grating spectrometer coupled to a soft-x-ray streak camera. Soft-x-ray radiation in the 1-6-nm range with durations of 2-7 ps is observed for copper and tantalum plasmas. The effect of incident laser energy on the x-ray pulse duration is also investigated.

  10. Picosecond laser filamentation in air

    NASA Astrophysics Data System (ADS)

    Schmitt-Sody, Andreas; Kurz, Heiko G.; Bergé, Luc; Skupin, Stefan; Polynkin, Pavel

    2016-09-01

    The propagation of intense picosecond laser pulses in air in the presence of strong nonlinear self-action effects and air ionization is investigated experimentally and numerically. The model used for numerical analysis is based on the nonlinear propagator for the optical field coupled to the rate equations for the production of various ionic species and plasma temperature. Our results show that the phenomenon of plasma-driven intensity clamping, which has been paramount in femtosecond laser filamentation, holds for picosecond pulses. Furthermore, the temporal pulse distortions in the picosecond regime are limited and the pulse fluence is also clamped. In focused propagation geometry, a unique feature of picosecond filamentation is the production of a broad, fully ionized air channel, continuous both longitudinally and transversely, which may be instrumental for many applications including laser-guided electrical breakdown of air, channeling microwave beams and air lasing.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  12. Picosecond Streaked K-Shell Spectroscopy of Near Solid-Density Aluminum Plasmas

    NASA Astrophysics Data System (ADS)

    Stillman, C. R.; Nilson, P. M.; Ivancic, S. T.; Mileham, C.; Froula, D. H.; Golovkin, I. E.

    2016-10-01

    The thermal x-ray emission from rapidly heated solid targets containing a buried-aluminum layer was measured. The targets were driven by high-contrast 1 ω or 2 ω laser pulses at focused intensities up to 1 ×1019W/Wcm2 cm2 . A streaked x-ray spectrometer recorded the Al Heα and lithium-like satellite lines with 2-ps temporal resolution and moderate resolving power (E/E ΔE 700). Time-integrated measurements over the same spectral range were used to correct the streaked data for variations in photocathode sensitivity. Line widths and intensity ratios from the streaked data were interpreted using a collisional radiative atomic model to provide the average plasma conditions in the buried layer as a function of time. It was observed that the resonance line tends toward lower photon energies at high electron densities. The measured shifts will be compared to predicted shifts from Stark-operator calculations at the inferred plasma conditions. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944, the office of Fusion Energy Sciences Award Number DE-SC0012317, and the Stewardship Science Graduate Fellowship Grant Number DE-NA0002135.

  13. Picosecond-TALIF and VUV absorption measurements of absolute atomic nitrogen densities from an RF atmospheric pressure plasma jet with He/O2/N2 gas mixtures

    NASA Astrophysics Data System (ADS)

    West, Andrew; Niemi, Kari; Schröter, Sandra; Bredin, Jerome; Gans, Timo; Wagenaars, Erik

    2015-09-01

    Reactive Oxygen and Nitrogen species (RONS) from RF atmospheric pressure plasma jets (APPJs) are important in biomedical applications as well as industrial plasma processing such as surface modification. Atomic oxygen has been well studied, whereas, despite its importance in the plasma chemistry, atomic nitrogen has been somewhat neglected due to its difficulty of measurement. We present absolute densities of atomic nitrogen in APPJs operating with He/O2/N2 gas mixtures in open air, using picosecond Two-photon Absorption Laser Induced Fluorescence (ps-TALIF) and vacuum ultra-violet (VUV) absorption spectroscopy. In order to apply the TALIF technique in complex, He/O2/N2 mixtures, we needed to directly measure the collisional quenching effects using picosecond pulse widths (32ps). Traditional calculated quenching corrections, used in nanosecond TALIF, are inadequate due to a lack of quenching data for complex mixtures. Absolute values for the densities were found by calibrating against a known density of Krypton. The VUV absorption experiments were conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Atomic nitrogen densities were on the order of 1020 m-3 with good agreement between TALIF and VUV absorption. UK EPSRC grant EP/K018388/1.

  14. Effects of picosecond terawatt UV laser beam filamentation and a repetitive pulse train on creation of prolonged plasma channels in atmospheric air

    NASA Astrophysics Data System (ADS)

    Zvorykin, V. D.; Ionin, A. A.; Levchenko, A. O.; Seleznev, L. V.; Shutov, A. V.; Sinitsyn, D. V.; Smetanin, I. V.; Ustinovskii, N. N.

    2013-08-01

    Amplitude-modulated UV laser pulse of up to 30 J energy was produced at hybrid Ti:Sapphire/KrF GARPUN-MTW laser facility when a preliminary amplified train of short pulses was injected into unstable resonator cavity of the main e-beam-pumped KrF amplifier. The combined radiation consisted of regeneratively amplified picosecond pulses with subTW peak power overlapped with 100-ns pulse of a free-running lasing. The advantages of combined radiation for production of long-lived prolonged plasma channels in air and HV discharge triggering were demonstrated: photocurrent sustained by modulated pulse is two orders of magnitude higher and HV breakdown distance is twice longer than for a smooth UV pulse. It was found that in contrast to IR radiation multiple filamentation of high-power UV laser beam does not produce extended nonlinear focusing of UV radiation.

  15. A comparative study of pressure-dependent emission characteristics in different gas plasmas induced by nanosecond and picosecond neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers.

    PubMed

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

    2013-11-01

    An experimental study has been performed on the pressure-dependent plasma emission intensities in Ar, He, and N2 surrounding gases with the plasma induced by either nanosecond (ns) or picosecond (ps) yttrium aluminum garnet laser. The study focused on emission lines of light elements such as H, C, O, and a moderately heavy element of Ca from an agate target. The result shows widely different pressure effects among the different emission lines, which further vary with the surrounding gases used and also with the different ablation laser employed. It was found that most of the maximum emission intensities can be achieved in Ar gas plasma generated by ps laser at low gas pressure of around 5 Torr. This experimental condition is particularly useful for spectrochemical analysis of light elements such as H, C, and O, which are known to suffer from intensity diminution at higher gas pressures. Further measurements of the spatial distribution and time profiles of the emission intensities of H I 656.2 nm and Ca II 396.8 nm reveal the similar role of shock wave excitation for the emission in both ns and ps laser-induced plasmas, while an additional early spike is observed in the plasma generated by the ps laser. The suggested preference of Ar surrounding gas and ps laser was further demonstrated by outperforming the ns laser in their applications to depth profiling of the H emission intensity and offering the prospect for the development of three-dimensional analysis of a light element such as H and C.

  16. A comparative study of emission efficiencies in low-pressure argon plasmas induced by picosecond and nanosecond Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Mangasi Marpaung, Alion; Ramli, Muliadi; Idroes, Rinaldi; Suyanto, Hery; Lahna, Kurnia; Nur Abdulmadjid, Syahrun; Idris, Nasrullah; Pardede, Marincan; Hedwig, Rinda; Sukra Lie, Zener; Putra Kurniawan, Davy; Hendrik Kurniawan, Koo; Jie Lie, Tjung; Tjia, May On; Kagawa, Kiichiro

    2016-11-01

    An experimental study is performed on the comparative advantages of nanosecond (ns) and picosecond (ps) lasers in laser-induced breakdown spectroscopy (LIBS) analysis. The experiment focused on the relative efficiencies of the plasma emission induced by the two lasers in low-pressure Ar ambient gas for samples of various hardnesses. It is shown that the emission intensities are consistenly reduced when the ns laser is replaced by the ps laser. This is explained as the consequence of the increased power density delivered by the ps laser, which results in a time mismatch between the passage of the ablated atoms and the formation of the shock wave. The time mismatch in turn leads to less effective thermal excitation by the shock wave plasma and the hence reduced emission intensity. Furthermore, this adverse effect is found to worsen for softer samples due to the slower formation of the shock wave. These results are obtained with the same volumes of craters produced by the two lasers on the same sample, which implies that ns laser irradiation has higher emission efficiency than ps laser irradiation.

  17. Excitation mechanisms in 1 mJ picosecond laser induced low pressure He plasma and the resulting spectral quality enhancement

    SciTech Connect

    Idris, Nasrullah; Lahna, Kurnia; Abdulmadjid, Syahrun Nur; Ramli, Muliadi; Suyanto, Hery; Marpaung, Alion Mangasi; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Lie, Zener Sukra; Lie, Tjung Jie; Kurniawan, Koo Hendrik; Tjia, May On

    2015-06-14

    We report in this paper the results of an experimental study on the spectral and dynamical characteristics of plasma emission induced by 1 mJ picoseconds (ps) Nd-YAG laser using spatially resolved imaging and time resolved measurement of the emission intensities of copper sample. This study has provided the experimental evidence concerning the dynamical characteristics of the excitation mechanisms in various stages of the plasma formation, which largely consolidate the basic scenarios of excitation processes commonly accepted so far. However, it is also clearly shown that the duration of the shock wave excitation process induced by ps laser pulses is much shorter than those observed in laser induced breakdown spectroscopy employing nanosecond laser at higher output energy. This allows the detection of atomic emission due exclusively to He assisted excitation in low pressure He plasma by proper gating of the detection time. Furthermore, the triplet excited state associated with He I 587.6 nm is shown to be the one most likely involved in the process responsible for the excellent spectral quality as evidenced by its application to spectrochemical analysis of a number of samples. The use of very low energy laser pulses also leads to minimal destructive effect marked by the resulted craters of merely about 10 μm diameter and only 10 nm deep. It is especially noteworthy that the excellent emission spectrum of deuterium detected from D-doped titanium sample is free of spectral interference from the undesirable ubiquitous water molecules without a precleaning procedure as applied previously and yielding an impressive detection limit of less than 10 μg/g. Finally, the result of this study also shows a promising application to depth profiling of impurity distribution in the sample investigated.

  18. Picosecond Chemical and Biological Events.

    ERIC Educational Resources Information Center

    Rentzepis, P. M.

    1978-01-01

    Describes a currently used picosecond spectroscopy system capable of reliably recording picosecond events. Two areas of picosecond research are discussed: one concerns the interaction of electrons in fluids; the second, the primary events in vision. (Author/HM)

  19. Picosecond Laser Pulse Interactions with Metallic and Semiconductor Surfaces.

    DTIC Science & Technology

    1984-11-01

    between the hot, dense carrier plasma and the lattice vibrations of less than two picoseconds. A careful observation and analysis of the photoelectric...photoelectric effect, an emission proportional to the square of the intensity. This is due to photoemis- Ssion from the hot, dense carrier plasma created...by the same pulse, or by a preceding picosecond pulse. The lifetime of this plasma surface layer is lim- ited by diffusion of the hot carriers out of

  20. Picosecond optoelectronic devices

    SciTech Connect

    Lee, C.L.

    1984-01-01

    Ever since the invention of picosecond lasers, scientists and electronic engineers have been dreaming of inventing electronic devices that can record in real time the physical and electronic events that take place on picosecond time scales. With the exception of the expensive streak camera, this dream has been largely unfullfilled. Today, a real-time oscilloscope with picosecond time resolution is still not available. To fill the need for even better time resolution, researchers have turned to optical pulses and thus a hybrid technology has emerged-picosecond optoelectronics. This technology, based on bulk photoconductors, has had a slow start. However, because of the simplicity, scaleability, and jitterfree nature of the devices, the technology has recently experienced a rapid growth. This volume reviews the major developments in the field of picosecond optoelectronics over the past decade.

  1. Laser induced breakdown spectroscopy with picosecond pulse train

    NASA Astrophysics Data System (ADS)

    Lednev, Vasily N.; Pershin, Sergey M.; Sdvizhenskii, Pavel A.; Grishin, Mikhail Ya; Davydov, Mikhail A.; Stavertiy, Anton Ya; Tretyakov, Roman S.

    2017-02-01

    Picosecond pulse train and nanosecond pulse were compared for laser ablation and laser induced breakdown spectroscopy (LIBS) measurements. A detailed study revealed that the picosecond pulse train ablation improved the quality of laser craters (symmetric crater walls and the absence of large redeposited droplets), which was explained by a smaller heat affected zone and suppression of melt splash. Greater plasma dimensions and brighter plasma emission were observed by gated imaging for picosecond pulse train compared to nanosecond pulse ablation. Increased intensity of atomic and ionic lines in gated and time integrated spectra provided better signal-to-noise ratio for picosecond pulse train sampling. Higher temperature and electron density were detected during first microsecond for the plasma induced by the picosecond pulse train. Improved shot-to-shot reproducibility for atomic/ionic line intensity in the case of picosecond pulse train LIBS was explained by more effective atomization of target material in plasma and better quality of laser craters. Improved precision and limits of detections were determined for picosecond pulse train LIBS due to better reproducibility of laser sampling and increased signal-to-noise ratio.

  2. Picosecond beam monitor

    DOEpatents

    Schutt, D.W.; Beck, G.O.

    1974-01-01

    The current in the beam of a particle accelerator is monitored with picosecond resolution by causing the beam to impinge upon the center conductor of a coaxial line, generating a pulse of electromagnetic energy in response thereto. This pulse is detected by means such as a sampling oscilloscope. (Official Gazette)

  3. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Investigation of the energy balance components for a plane target irradiated with a picosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Borodin, V. G.; Il'in, V. V.; Komarov, V. M.; Malinov, V. A.; Migel', V. M.; Nikitin, N. V.; Charukhchev, Aleksandr V.; Chernov, V. N.

    2000-01-01

    The scattering and absorption of a high-power picosecond laser pulse by a solid target were investigated experimentally making use of the 'Progress-P' Nd:glass laser facility (λ = 1053 nm, τ = 1.4 ps) at radiation intensities I = 1016 — 1019 W cm-2 on the target surface. It was found that, for I <= 1017 W cm-2, more than 30% of the intensity of the scattered light was contained in the specularly reflected component. The absorption coefficient of the laser radiation with intensities ranging from 1018 to 1019 W cm-2 was higher for targets made of materials with higher atomic numbers.

  4. Parametric instabilities in picosecond time scales

    SciTech Connect

    Baldis, H.A.; Rozmus, W.; Labaune, C.; Mounaix, Ph.; Pesme, D.; Baton, S.; Tikhonchuk, V.T.

    1993-03-01

    The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studied for many years because of their importance to ICF; with laser pulses with duration of approximately a nanosecond, and laser intensities in the range 10{sup 14}--10{sup 15}W/cm{sup 2} these instabilities are of crucial concern because of a number of detrimental effects. Although the laser pulse duration of interest for these studies are relatively long, it has been evident in the past years that to reach an understanding of these instabilities requires their characterization and analysis in picosecond time scales. At the laser intensities of interest, the growth rate for stimulated Brillouin scattering (SBS) is of the order of picoseconds, and of an order of magnitude shorter for stimulated Raman scattering (SRS). In this paper the authors discuss SBS and SRS in the context of their evolution in picosecond time scales. They describe the fundamental concepts associated with their growth and saturation, and recent work on the nonlinear treatment required for the modeling of these instabilities at high laser intensities.

  5. Picosecond Spin Caloritronics

    NASA Astrophysics Data System (ADS)

    Cahill, David G.

    The coupling of spin and heat, i.e., spin caloritronics, gives rise to new physical phenomena in nanoscale spin devices and new ways to manipulate local magnetization. Our work in this field takes advantage of recent advances in the measurement and understanding of heat transport at the nanoscale using ultrafast lasers. We use a picosecond duration pump laser pulses as a source of heat and picosecond duration probe laser pulses to detect changes in temperature, spin accumulation, and spin transfer torque using a combination of time-domain thermoreflectance and time-resolved magneto-optic Kerr effect Our pump-probe optical methods enable us to change the temperature of ferromagnetic layers on a picosecond time-scale and generate enormous heat fluxes on the order of 100 GW m-2 that persist for ~ 30 ps. Thermally-driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The spin-dependent Seebeck effect of a perpendicular ferromagnetic layer converts a heat current into spin current, which in turn can be used to exert a spin transfer torque (STT) on a second ferromagnetic layer with in-plane magnetization. Using a [Co,Ni] multilayer as the source of spin, an energy fluence of ~ 4 J m-2 creates thermal STT sufficient to induce ~ 1 % tilting of the magnetization of a 2 nm-thick CoFeB layer.

  6. Picosecond Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T.; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G.

    2017-02-01

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal /Y3Fe5 O12 bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal /Y3Fe5 O12 interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 108 A m-2 K-1 .

  7. Picosecond measurements using photoacoustic detection

    NASA Technical Reports Server (NTRS)

    Heritier, J.-M.; Siegman, A. E.

    1983-01-01

    A report is presented of experimental results on picosecond time-resolved photoacoustic measurements of excited-state lifetimes, cross sections, and polarization properties for organic dye molecules in solution, using a new technique in which the total photoacoustic impulse produced by two ultrashort optical pulses with variable time delay between them is detected. The picosecond photoacoustic detection technique reported here appears to be a promising new way to observe weak excited-state cross sections and to perform picosecond lifetime measurements in a large variety of weakly absorbing and/or nonfluorescing atomic and molecular systems.

  8. Synchronization of sub-picosecond electron and laser pulses

    SciTech Connect

    Rosenzweig, J.B.; Le Sage, G.P.

    1999-07-01

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is sub-picosecond, with tens of femtosecond synchronization implied for next generation experiments. The design of a microwave timing modulator system is now being investigated in more detail. (AIP) {copyright} {ital 1999 American Institute of Physics.}

  9. Synchronization of sub-picosecond electron and laser pulses

    SciTech Connect

    Rosenzweig, J. B.; Le Sage, G. P.

    1999-07-12

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is sub-picosecond, with tens of femtosecond synchronization implied for next generation experiments. The design of a microwave timing modulator system is now being investigated in more detail.

  10. Picosecond Spin Seebeck Effect.

    PubMed

    Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G

    2017-02-03

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal/Y_{3}Fe_{5}O_{12} bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal/Y_{3}Fe_{5}O_{12} interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 10^{8}  A m^{-2} K^{-1}.

  11. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Feasibility of generation of picosecond and subpicosecond x-ray pulses in thin films

    NASA Astrophysics Data System (ADS)

    Gordienko, Vyacheslav M.; Dzhidzhoev, M. S.; Kolchin, V. V.; Magnitskiy, Sergey A.; Platonenko, Viktor T.; Savel'ev, Andrei B.; Tarasevitch, A. P.

    1995-02-01

    The characteristics of a femtosecond laser plasma, formed by irradiation of a thin freely suspended carbon film, are investigated numerically. It is shown that the use of thin films can increase considerably the electron temperature of a femtosecond laser plasma and make it possible to generate x-rays of shorter wavelengths. This method can also be used to increase the efficiency of conversion of the energy of laser pulses into the radiation emitted by hydrogen-like carbon ions without a significant increase in the duration of x-ray pulses.

  12. High brightness picosecond electron gun

    SciTech Connect

    Merano, M.; Collin, S.; Renucci, P.; Gatri, M.; Sonderegger, S.; Crottini, A.; Ganiere, J.D.; Deveaud, B.

    2005-08-15

    We have developed a high brightness picosecond electron gun. We have used it to replace the thermionic electron gun of a commercial scanning electron microscope (SEM) in order to perform time-resolved cathodoluminescence experiments. Picosecond electron pulses are produced, at a repetition rate of 80.7 MHz, by femtosecond mode-locked laser pulses focused on a metal photocathode. This system has a normalized axial brightness of 93 A/cm{sup 2} sr kV, allowing for a spatial resolution of 50 nm in the secondary electron imaging mode of the SEM. The temporal width of the electron pulse is 12 ps.

  13. Picosecond spectroscopy of dihydro biliverdin

    NASA Astrophysics Data System (ADS)

    Ditto, Manfred; Brunner, Harald; Lippitsch, Max E.

    1991-10-01

    Picosecond time-resolved fluorescence and absorption spectroscopy was performed on dihydro biliverdin, a model for the chromophore in the plant pigment phytochrome, a chromoprotein governing plant growth. Close agreement between the model compound and the native chromophore proves the importance of the saturated pyrrol ring for the decay kinetics and renders chromophore protonation in phytochrome unlikely.

  14. Picosecond Fresnel transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Schliep, Karl B.; Quarterman, P.; Wang, Jian-Ping; Flannigan, David J.

    2017-05-01

    We report the demonstration of picosecond Fresnel imaging with an ultrafast transmission electron microscope (UEM). By operating with a low instrument repetition rate (5 kHz) and without objective-lens excitation, the picosecond demagnetization of an FePt film, via in situ, femtosecond laser excitation, is directly imaged. The dynamics are quantified and monitored as a time-dependent change in the degree of electron coherence within the magnetic domain walls. The relative coherence of conventional (thermionic) Fresnel transmission electron microscopy is also directly compared to that of Fresnel UEM through the domain-wall size. Further, the robustness and reversibility of the domain-wall dynamics are illustrated by repeating the picosecond image scans at defocus values having the same magnitude but different signs (e.g., +25 mm vs. -25 mm). Control experiments and approaches to identifying and isolating systematic errors and sources of artifacts are also described. This work, and continued future developments also described here, opens the way to direct correlation of transient structure, morphology, and magnetic dynamics in magnetic thin films and spintronic devices.

  15. Boosting laser-ion acceleration with multi-picosecond pulses

    NASA Astrophysics Data System (ADS)

    Yogo, A.; Mima, K.; Iwata, N.; Tosaki, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Johzaki, T.; Sentoku, Y.; Nishimura, H.; Sagisaka, A.; Matsuo, K.; Kamitsukasa, N.; Kojima, S.; Nagatomo, H.; Nakai, M.; Shiraga, H.; Murakami, M.; Tokita, S.; Kawanaka, J.; Miyanaga, N.; Yamanoi, K.; Norimatsu, T.; Sakagami, H.; Bulanov, S. V.; Kondo, K.; Azechi, H.

    2017-02-01

    Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 1018 W cm-2, the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines.

  16. Boosting laser-ion acceleration with multi-picosecond pulses

    PubMed Central

    Yogo, A.; Mima, K.; Iwata, N.; Tosaki, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Johzaki, T.; Sentoku, Y.; Nishimura, H.; Sagisaka, A.; Matsuo, K.; Kamitsukasa, N.; Kojima, S.; Nagatomo, H.; Nakai, M.; Shiraga, H.; Murakami, M.; Tokita, S.; Kawanaka, J.; Miyanaga, N.; Yamanoi, K.; Norimatsu, T.; Sakagami, H.; Bulanov, S. V.; Kondo, K.; Azechi, H.

    2017-01-01

    Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 1018 W cm−2, the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines. PMID:28211913

  17. Picosecond X-ray streak camera dynamic range measurement

    SciTech Connect

    Zuber, C. Bazzoli, S.; Brunel, P.; Gontier, D.; Raimbourg, J.; Rubbelynck, C.; Trosseille, C.; Fronty, J.-P.; Goulmy, C.

    2016-09-15

    Streak cameras are widely used to record the spatio-temporal evolution of laser-induced plasma. A prototype of picosecond X-ray streak camera has been developed and tested by Commissariat à l’Énergie Atomique et aux Énergies Alternatives to answer the Laser MegaJoule specific needs. The dynamic range of this instrument is measured with picosecond X-ray pulses generated by the interaction of a laser beam and a copper target. The required value of 100 is reached only in the configurations combining the slowest sweeping speed and optimization of the streak tube electron throughput by an appropriate choice of high voltages applied to its electrodes.

  18. The use of picosecond lasers beyond tattoos.

    PubMed

    Forbat, E; Al-Niaimi, F

    2016-10-01

    Picosecond lasers are a novel laser with the ability to create a pulse of less than one nanosecond. They have been available in the clinical context since 2012. Dermatologists are now using picosecond lasers regularly for the treatment of blue and green pigment tattoo removal. This article reviews the use of picosecond lasers beyond tattoo removal. The overall consensus for the use of picosecond lasers beyond tattoo treatment is positive. With examples of this in the treatment of nevus of Ota, minocycline-induced pigmentation, acne scarring, and rhytides.

  19. Broadly tunable picosecond ir source

    DOEpatents

    Campillo, A.J.; Hyer, R.C.; Shapiro, S.L.

    1980-04-23

    A picosecond traveling-wave parametric device capable of controlled spectral bandwidth and wavelength in the infrared is reported. Intense 1.064 ..mu..m picosecond pulses (1) pass through a 4.5 cm long LiNbO/sub 3/ optical parametric oscillator crystal (2) set at its degeneracy angle. A broad band emerges, and a simple grating (3) and mirror (4) arrangement is used to inject a selected narrow-band into a 2 cm long LiNbO/sub 3/ optical parametric amplifier crystal (5) along a second pump line. Typical input energies at 1.064 ..mu..m along both pump lines are 6 to 8 mJ for the oscillator and 10 mJ for the amplifier. This yields 1 mJ of tunable output in the range 1.98 to 2.38 ..mu..m which when down-converted in a 1 cm long CdSe crystal mixer (6) gives 2 ..mu..J of tunable radiation over the 14.8 to 18.5 ..mu..m region. The bandwidth and wavelength of both the 2 and 16 ..mu..m radiation output are controlled solely by the diffraction grating.

  20. Broadly tunable picosecond IR source

    DOEpatents

    Campillo, Anthony J.; Hyer, Ronald C.; Shapiro, Stanley J.

    1982-01-01

    A picosecond traveling-wave parametric device capable of controlled spectral bandwidth and wavelength in the infrared is reported. Intense 1.064 .mu.m picosecond pulses (1) pass through a 4.5 cm long LiNbO.sub.3 optical parametric oscillator crystal (2) set at its degeneracy angle. A broad band emerges, and a simple grating (3) and mirror (4) arrangement is used to inject a selected narrow-band into a 2 cm long LiNbO.sub.3 optical parametric amplifier crystal (5) along a second pump line. Typical input energies at 1.064 .mu.m along both pump lines are 6-8 mJ for the oscillator and 10 mJ for the amplifier. This yields 1 mJ of tunable output in the range 1.98 to 2.38 .mu.m which when down-converted in a 1 cm long CdSe crystal mixer (6) gives 2 .mu.J of tunable radiation over the 14.8 to 18.5 .mu.m region. The bandwidth and wavelength of both the 2 and 16 .mu.m radiation output are controlled solely by the diffraction grating.

  1. Reactor for boron fusion with picosecond ultrahigh power laser pulses and ultrahigh magnetic field trapping

    NASA Astrophysics Data System (ADS)

    Miley, G. H.; Hora, H.; Kirchhoff, G.

    2016-05-01

    Compared with the deuterium tritium (DT) fusion, the environmentally clean fusion of protons with 11B is extremely difficult. When instead of nanosecond laser pulses for thermal-ablating driven ignition, picosecond pulses are used, a drastic change by nonlinearity results in ultrahigh acceleration of plasma blocks. This radically changes to economic boron fusion by a measured new avalanche ignition.

  2. Applications using a Picosecond 14.7 nm X-Ray Laser

    SciTech Connect

    Dunn, J; Smith, R F; Nilsen, J; Shlyaptsev, V N; Filevich, J; Rocca, J J; Marconi, M C

    2001-09-21

    We report recent application experiments on the LLNL COMET tabletop facility using the picosecond, 14.7 nm Ni-like Pd x-ray laser. This work includes measurements of a laser-produced plasma density profile with a diffraction grating interferometer.

  3. Production of Picosecond, Kilojoule, and Petawatt Laser Pulses via Raman Amplification of Nanosecond Pulses

    SciTech Connect

    Trines, R. M. G. M.; Bingham, R.; Norreys, P. A.; Fiuza, F.; Fonseca, R. A.; Silva, L. O.

    2011-09-02

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion.

  4. Fundamentals of picosecond laser ultrasonics.

    PubMed

    Matsuda, Osamu; Larciprete, Maria Cristina; Li Voti, Roberto; Wright, Oliver B

    2015-02-01

    The aim of this article is to provide an introduction to picosecond laser ultrasonics, a means by which gigahertz-terahertz ultrasonic waves can be generated and detected by ultrashort light pulses. This method can be used to characterize materials with nanometer spatial resolution. With reference to key experiments, we first review the theoretical background for normal-incidence optical detection of longitudinal acoustic waves in opaque single-layer isotropic thin films. The theory is extended to handle isotropic multilayer samples, and is again compared to experiment. We then review applications to anisotropic samples, including oblique-incidence optical probing, and treat the generation and detection of shear waves. Solids including metals and semiconductors are mainly discussed, although liquids are briefly mentioned.

  5. Ablation of steel using picosecond laser pulses in burst mode

    NASA Astrophysics Data System (ADS)

    Lickschat, Peter; Demba, Alexander; Weissmantel, Steffen

    2017-02-01

    Results obtained in picosecond laser processing of steel applying the burst mode are presented. Using the burst mode, pulse trains, i.e., bursts, consisting of a number of picosecond pulses with an inter-pulse delay of 12.5 ns and 10 ps pulse duration are applied for material processing. Small cavities with sizes in the range of the laser beam diameter made by single-burst ablation are compared to quadratic cavities of 0.5 × 0.5 mm² produced by multiburst ablation and simultaneous scanning of the laser beam across the steel sample surface. The ablated volume per pulse within the burst was calculated either from the ablated volume per burst or from the ablation depth of the quadratic cavities. With the second to fourth pulses in the bursts, a reduction of the ablated volume per pulse in comparison with the first pulse in the bursts (i.e., to the use of single pulses) was found for both single- and multiburst ablation, which is assumed to be due to plasma shielding. By contrast, the ablated volume per pulse within the bursts increases for the fifth to eighth pulses. Heat accumulation effect and the influence of the heated plasma can be assumed to be the reason for these higher ablation rates. SEM micrographs also show that there is a higher melt ejection out of the laser processed area. This is indicated by the formation of bulges about the ablated area.

  6. Lidar receivers for picosecond remote sensing

    NASA Technical Reports Server (NTRS)

    Stoyanov, D. V.; Dreischuh, T. N.

    1992-01-01

    The lidars of picosecond resolution are an attractive tool for remote probing of some highly dynamic objects like sea subsurface waters, small-scale turbulences in the atmosphere, etc. The picosecond lasers are suitable illuminating sources, but the main restrictions are due to the lack of proper receiving methods, combining the both high temporal and amplitude resolution, good sensitivity, short integration time, and wide dynamic range. The methods for short pulse measurements are not suitable for picosecond lidars, operating at low level, with highly dynamic signals. The streak-cameras are of high cost, lower sensitivity, and lower dynamic range (approximately 10(exp 3)). Because of the background, the single quantum regime in photomultipliers (PMT) is ineffective. The sampling of highly dynamic optical signals with resolution less than or equal to 1ns is a serious problem, limiting the application of the high speed PMT-MCP (microchannel plate) in the picosecond lidar systems. The goal of this work is to describe the use of a new photodetection technique which combines the picosecond resolution with the high amplitude resolution, dynamic range, and sensitivity.

  7. Lidar receivers for picosecond remote sensing

    NASA Astrophysics Data System (ADS)

    Stoyanov, D. V.; Dreischuh, T. N.

    1992-07-01

    The lidars of picosecond resolution are an attractive tool for remote probing of some highly dynamic objects like sea subsurface waters, small-scale turbulences in the atmosphere, etc. The picosecond lasers are suitable illuminating sources, but the main restrictions are due to the lack of proper receiving methods, combining the both high temporal and amplitude resolution, good sensitivity, short integration time, and wide dynamic range. The methods for short pulse measurements are not suitable for picosecond lidars, operating at low level, with highly dynamic signals. The streak-cameras are of high cost, lower sensitivity, and lower dynamic range (approximately 10(exp 3)). Because of the background, the single quantum regime in photomultipliers (PMT) is ineffective. The sampling of highly dynamic optical signals with resolution less than or equal to 1ns is a serious problem, limiting the application of the high speed PMT-MCP (microchannel plate) in the picosecond lidar systems. The goal of this work is to describe the use of a new photodetection technique which combines the picosecond resolution with the high amplitude resolution, dynamic range, and sensitivity.

  8. Analysis of Picosecond Pulsed Laser Melted Graphite

    DOE R&D Accomplishments Database

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

    1986-12-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

  9. Subpicosecond and picosecond laser ablation of dental enamel: comparative analysis

    NASA Astrophysics Data System (ADS)

    Rode, Andrei V.; Madsen, Nathan R.; Kolev, Vesselin Z.; Gamaly, Eugene G.; Luther-Davies, Barry; Dawes, Judith M.; Chan, A.

    2004-06-01

    We report the use of sub-picosecond near-IR and ps UV pulsed lasers for precision ablation of freshly extracted human teeth. The sub-picosecond laser wavelength was ~800nm, with pulsewidth 150 fs and pulse repetition rate of 1kHz; the UV laser produced 10 ps pulses at 266 nm with pulse rate of ~1.2x105 pulses/s; both lasers produced ~1 W of output energy, and the laser fluence was kept at the same level of 10-25 J/cm2. Laser radiation from both laser were effectively absorbed in the teeth enamel, but the mechanisms of absorption were radically different: the near-IR laser energy was absorbed in a plasma layer formed through the optical breakdown mechanism initiated by multiphoton absorption, while the UV-radiation was absorbed due to molecular photodissociation of the enamel and conventional thermal deposition. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain low with subpicosecond laser pulses, but risen up to 30°C, well above the 5°C pain level with the UV-laser. This study demonstrates the potential for ultra-short-pulsed lasers to precision and painless ablation of dental enamel, and indicated the optimal combination of laser parameters in terms of pulse energy, duration, intensity, and repetition rate, required for the laser ablation rates comparable to that of mechanical drill.

  10. Picosecond lasers with the dynamical operation control

    NASA Astrophysics Data System (ADS)

    Mikheev, N. G.; Morozov, V. B.; Olenin, A. N.; Yakovlev, D. V.

    2016-04-01

    Numerical model for simulation of generation process in advanced pulse-periodic high-peak-power picosecond diode-pumped Nd:YAG and Nd:YLF lasers has been developed. The model adequately describes picosecond pulse formation governed by active and passive mode-locking, negative feedback and adjustable loss level in the oscillator cavity. Optical jitter of output pulses attributed to laser generation development from spontaneous noise level was evaluated using statistical analysis of calculation results. In the presented laser scheme, minimal jitter value on the level ~40 ps was estimated.

  11. A Picosecond 14.7 nm X-Ray Laser for Probing Matter Undergoing Rapid Changes

    SciTech Connect

    Dunn, J; Smith, R F; Nilsen, J; Nelson, A J; Van Buuren, T W; Moon, S J; Hunter, J R; Filevich, J; Rocca, J J; Marconi, M C; Shlyaptsev, V N

    2002-10-07

    With laser-driven tabletop x-ray lasers now operating in the efficient saturation regime, the source characteristics of high photon flux, high monochromaticity, picosecond pulse duration, and coherence are well-matched to many applications involving the probing of matter undergoing rapid changes. We give an overview of recent experiments at the Lawrence Livermore National Laboratory (LLNL) Compact Multipulse Terawatt (COMET) laser using the picosecond 14.7 nm x-ray laser as a compact, ultrafast probe for surface analysis and for interferometry of laser-produced plasmas. The plasma density measurements for known laser conditions allow us to reliably and precisely benchmark hydrodynamics codes. In the former case, the x-ray laser ejects photo-electrons, from the valence band or shallow core-levels of the material, and are measured in a time-of-flight analyzer. Therefore, the electronic structure can be studied directly to determine the physical properties of materials undergoing rapid phase changes.

  12. BRIEF COMMUNICATIONS: Picosecond spectroscopy of pyrrol pigments

    NASA Astrophysics Data System (ADS)

    Lippitsch, M. E.; Leitner, A.; Riegler, M.; Aussenegg, F. R.

    1982-05-01

    Picosecond fluorescence and absorption spectroscopy methods were used to study pyrromethenone, pyrromethene, and biliverdin. These methods made it possible to determine some details of the kinetics of various relaxation mechanisms. The results obtained provided a better understanding of the biological action of pyrrol pigments.

  13. Tomographic reconstruction of picosecond acoustic strain propagation

    NASA Astrophysics Data System (ADS)

    Tomoda, Motonobu; Matsuda, Osamu; Wright, Oliver B.; Li Voti, Roberto

    2007-01-01

    By means of an ultrafast optical technique, picosecond acoustic strain pulses in a transparent medium are tomographically visualized. The authors reconstruct strain pulses in Au-coated glass from time-domain reflectivity changes as a function of the optical angle of incidence, with ˜1ps temporal and ˜100nm spatial resolutions.

  14. Flexible pulse delay control up to picosecond for high-intensity twin electron bunches

    DOE PAGES

    Zhang, Zhen; Ding, Yuantao; Emma, Paul; ...

    2015-09-10

    Two closely spaced electron bunches have attracted strong interest due to their applications in two color X-ray free-electron lasers as well as witness bunch acceleration in plasmas and dielectric structures. In this paper, we propose a new scheme of delay system to vary the time delay up to several picoseconds while not affecting the bunch compression. Numerical simulations based on the Linac Coherent Light Source are performed to demonstrate the feasibility of this method.

  15. Interaction of intense multi-picosecond laser pulses with matter

    NASA Astrophysics Data System (ADS)

    Kemp, Andreas; Divol, Laurent; Cohen, Bruce

    2011-10-01

    We present new results on the two- and three-dimensional kinetic modeling of short-pulse laser-matter interaction of Petawatt pulses at the spatial and temporal scales relevant to current experiments. We address key questions such as characterizing the multi-picosecond evolution of the laser energy conversion into hot electrons, i.e., conversion efficiency as well as angular- and energy distribution; the impact of return currents on the laser-plasma interaction; and the effect of self-generated electric and magnetic fields on electron transport. We will report applications to current experiments at LLNL's Titan laser and Omega EP, and to a Fast-Ignition point design. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. Picosecond laser welding of similar and dissimilar materials.

    PubMed

    Carter, Richard M; Chen, Jianyong; Shephard, Jonathan D; Thomson, Robert R; Hand, Duncan P

    2014-07-01

    We report picosecond laser welding of similar and dissimilar materials based on plasma formation induced by a tightly focused beam from a 1030 nm, 10 ps, 400 kHz laser system. Specifically, we demonstrate the welding of fused silica, borosilicate, and sapphire to a range of materials including borosilicate, fused silica, silicon, copper, aluminum, and stainless steel. Dissimilar material welding of glass to aluminum and stainless steel has not been previously reported. Analysis of the borosilicate-to-borosilicate weld strength compares well to those obtained using similar welding systems based on femtosecond lasers. There is, however, a strong requirement to prepare surfaces to a high (10-60 nm Ra) flatness to ensure a successful weld.

  17. Picosecond ionization dynamics in femtosecond filaments at high pressures

    NASA Astrophysics Data System (ADS)

    Gao, Xiaohui; Patwardhan, Gauri; Schrauth, Samuel; Zhu, Daiwei; Popmintchev, Tenio; Kapteyn, Henry C.; Murnane, Margaret M.; Romanov, Dmitri A.; Levis, Robert J.; Gaeta, Alexander L.

    2017-01-01

    We investigate the plasma dynamics inside a femtosecond-pulse-induced filament generated in an argon gas for a wide range of pressures up to 60 bar. At higher pressures, we observe ionization immediately following a pulse, with up to a threefold increase in the electron density within 30 ps after the filamentary propagation of a femtosecond pulse. Our study suggests that this picosecond evolution can be attributed to collisional ionization including Penning and associative ionizations and electron-impact ionization of excited atoms generated during the pulse. The dominance of excited atoms over ionized atoms at the end of the pulse also indicates an intrapulse inhibition of avalanche ionization. This delayed ionization dynamics provides evidence for diagnosing atomic and molecular excitation and ionization in intense laser interaction with high-pressure gases.

  18. Monolithic millimeter-wave and picosecond electronic technologies

    SciTech Connect

    Talley, W.K.; Luhmann, N.C.

    1996-03-12

    Theoretical and experimental studies into monolithic millimeter-wave and picosecond electronic technologies have been undertaken as a collaborative project between the Lawrence Livermore National Laboratory (LLNL) and the University of California Department of Applied Science Coherent Millimeter-Wave Group under the auspices of the Laboratory Directed Research and Development Program at LLNL. The work involves the design and fabrication of monolithic frequency multiplier, beam control, and imaging arrays for millimeter-wave imaging and radar, as well as the development of high speed nonlinear transmission lines for ultra-wideband radar imaging, time domain materials characterization and magnetic fusion plasma applications. In addition, the Coherent Millimeter-Wave Group is involved in the fabrication of a state-of-the-art X-band ({approximately}8-11 GHz) RF photoinjector source aimed at producing psec high brightness electron bunches for advanced accelerator and coherent radiation generation studies.

  19. Analysis of efficient ion acceleration with multi-picosecond LFEX laser

    NASA Astrophysics Data System (ADS)

    Iwata, Natsumi; Yogo, Akifumi; Mima, Kunioki; Tosaki, Shota; Koga, Keisuke; Nagatomo, Hideo; Kishimoto, Yasuaki; Nishimura, Hiroaki; Azechi, Horishi

    2016-10-01

    We demonstrate an efficient proton acceleration reaching 30 MeV by using high contrast, kilojoule, picosecond laser LFEX at the peak intensity of 2.3 ×1018 W/cm2. Owing to the large spot size of 70 μm FWHM, the target foil expands one-dimensionally during the multi-picosecond pulse duration time, which yields the electron heating beyond the ponderomotive scaling observed in the experiment. We present by a 1D PIC simulation that the electron temperature evolves in time while the electrons recirculate between the front and rear surfaces of the expanding plasma. A theoretical calculation for the ion maximum energy that takes the temperature evolution into account agrees with the experimental result quantitatively. Being supported by the experiment and simulation, our theoretical model for the non-isothermal plasma expansion dynamics will provide an important basis for understanding the multi-picosecond high intensity laser-plasma interactions and for various applications such as energetic ion beam generation for medical applications and fast ignition-based laser fusion.

  20. Picosecond pulsed diode ring laser gyroscope

    SciTech Connect

    Rosker, M.J.; Christian, W.R.; McMichael, I.C.

    1994-12-31

    An external ring cavity containing as its active medium a pair of InGaAsP diodes is modelocked to produce picosecond pulses. In such a laser, a small frequency difference proportional to the nonreciprocal phase shift (resulting from, e.g., the Sagnac effect) can be observed by beating together the counter propagating laser arms; the device therefore acts as a rotating sensor. In contrast to a conventional (cw) ring laser gyroscope, the pulsed gyroscope can avoid gain competition, thereby enabling the use of homogeneously broadened gain media like semiconductor diodes. Temporal separation of the pulses within the cavity also discriminates against frequency locking of the lasers. The picosecond pulsed diode ring laser gyroscope is reviewed. Both active and passive modelocking are discussed.

  1. High-power picosecond laser pulse recirculation.

    PubMed

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P J

    2010-07-01

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  2. High Power Picosecond Laser Pulse Recirculation

    SciTech Connect

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  3. The picosecond laser for tattoo removal.

    PubMed

    Hsu, Vincent M; Aldahan, Adam S; Mlacker, Stephanie; Shah, Vidhi V; Nouri, Keyvan

    2016-11-01

    The prevalence of tattoos continues to grow as modern society's stigma towards this form of body art shifts towards greater acceptance. Approximately one third of Americans aged 18-25 and 40 % of Americans aged 26-40 are tattooed. As tattoos continue to rise in popularity, so has the demand for an effective method of tattoo removal such as lasers. The various colors of tattoo inks render them ideal targets for specific lasers using the principle of selective photothermolysis. Traditional laser modalities employed for tattoo removal operate on pulse durations in the nanosecond domain. However, this pulse duration range is still too long to effectively break ink into small enough particles. Picosecond (10(-12)) lasers have emerged at the forefront of laser tattoo removal due to their shorter pulse lengths, leading to quicker heating of the target chromophores, and consequently, more effective tattoo clearance. Recent studies have cited more effective treatment outcomes using picosecond lasers. Future comparative studies between picosecond lasers of various settings are necessary to determine optimal laser parameters for tattoo clearance.

  4. A picosecond high pressure gas switch

    SciTech Connect

    Cravey, W.R.; Poulsen, P.P.; Pincosy, P.A.

    1992-06-01

    Work is being done to develop a high pressure gas switch (HPGS) with picosecond risetimes for UWB applications. Pulse risetimes on the order of 200 picoseconds have been observed at 1 kHz prf and 1 atmosphere. Calculations show that switching closure times on the order of tens of picoseconds can be achieved at high pressures and higher electric fields. A voltage hold-off of 1 MV/cm has been measured at 10 atmospheres and several MV/cm appears possible with the HPGS. With these high electric field levels, energy storage of tens of Joules in a reasonably sized package is achievable. Initial HPGS performance has been characterized on the WASP pulse generator at LLNL. A detailed description of the switch used for initial testing is given. Switch recovery times of 1-ms have been measured at 1 atmosphere. Data on the switching uniformity, voltage hold-off recovery, and pulse repeatability, is presented. In addition, a physics switch model is described and results are compared with lab data.

  5. Synchronization of Sub-Picosecond Electron and Laser Pulses

    SciTech Connect

    Rosenzweig, J.B.; Le Sage G.P.

    2000-08-15

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is subpicosecond, with tens of femtosecond synchronization implied for next-generation experiments. Typically, an RF electron accelerator is synchronized to a short pulse laser system by detecting the repetition signal of a laser oscillator, adjusted to an exact subharmonic of the linac RF frequency, and multiplying or phase locking this signal to produce the master RF clock. Pulse-to-pulse jitter characteristic of self-mode-locked laser oscillators represents a direct contribution to the ultimate timing jitter between a high intensity laser focus and electron beam at the interaction point, or a photocathode drive laser in an RF photoinjector. This timing jitter problem has been addressed most seriously in the context of the RF photoinjector, where the electron beam properties are sensitive functions of relative timing jitter. The timing jitter achieved in synchronized photocathode drive laser systems is near, or slightly below one picosecond. The ultimate time of arrival jitter of the beam at the photoinjector exit is typically a bit smaller than the photocathode drive-laser jitter due to velocity compression effects in the first RF cell of the gun. This tendency of the timing of the electron beam arrival at a given spatial point to lock to the RF lock is strongly reinforced by use of magnetic compression.

  6. Filamentation and supercontinuum generation in solid-state dielectric media with picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Galinis, J.; Tamošauskas, G.; GražulevičiÅ«tÄ--, I.; KeblytÄ--, E.; Jukna, V.; Dubietis, A.

    2015-09-01

    Filamentation and supercontinuum generation with 1.3-ps, 1055-nm laser pulses in YAG crystal is investigated numerically and experimentally. Numerical simulations based on solving the unidirectional nonparaxial propagation equation uncover that the self-focusing dynamics of a picosecond laser pulse markedly differs from that observed in a femtosecond filamentation regime. We show that spatiotemporal transformation of the picosecond pulse is governed by the free electron plasma, which defocuses and absorbs its rear part, resulting in the formation of several subpulses of femtosecond duration, which thereafter undergo peculiar spatiotemporal dynamics and have different contributions to spectral superbroadening. The numerical findings are confirmed experimentally by measuring the spatiotemporal intensity profiles of the wave packet at various stages of propagation where relevant events of the spectral broadening occur.

  7. Measurement of Sub-Picosecond Electron Bunches via Electro-Optic Sampling of Coherent Transition Radiation

    SciTech Connect

    Maxwell, Timothy John

    2012-01-01

    Future collider applications as well as present high-gradient laser plasma wakefield accelerators and free-electron lasers operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. We present results on the single-shot electro-optic spectral decoding of coherent transition radiation from bunches generated at the Fermilab A0 photoinjector laboratory. A longitudinal double-pulse modulation of the electron beam is also realized by transverse beam masking followed by a transverse-to-longitudinal phase-space exchange beamline. Live profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of the coherent transition radiation.

  8. Formation of a fine-dispersed liquid-metal target under the action of femto- and picosecond laser pulses for a laser-plasma radiation source in the extreme ultraviolet range

    SciTech Connect

    Vinokhodov, A Yu; Krivokorytov, M S; Koshelev, K N; Krivtsun, V M; Sidelnikov, Yu V; Medvedev, V V; Kompanets, V O; Melnikov, A A; Chekalin, S V

    2016-01-31

    We report the results of studying the dynamics of deformation and fragmentation of liquid-metal droplets under the action of ultrashort laser pulses. The experiments have been performed to optimise the shape of the droplet target used in extreme ultraviolet (EUV) radiation sources based on the laser-produced plasma using the pre-pulse technology. The pre-pulse is generated by a system incorporating a master Ti : sapphire oscillator and a regenerative amplifier, allowing one to vary the pulse duration from 50 fs to 50 ps. The power density of laser radiation at the droplet target, averaged over the pulse duration and spatial coordinates, has reached 3 × 10{sup 15} W cm{sup -2}. The production of liquid-metal droplets has been implemented by means of a droplet generator based on a nozzle with a ring piezoceramic actuator. The droplet material is the eutectic indium – tin alloy. The droplet generator could operate in the droplet and jet regime with a maximal rate of stable operation 5 and 150 kHz, respectively. The spatial stability of droplet position σ = 1% – 2% of its diameter is achieved. The size of the droplets varied within 30 – 70 μm, their velocity was 2 – 8 m s{sup -1} depending on the operation regime. (interaction of laser radiation with matter. laser plasma)

  9. Picosecond x-ray streak cameras

    NASA Astrophysics Data System (ADS)

    Averin, V. I.; Bryukhnevich, Gennadii I.; Kolesov, G. V.; Lebedev, Vitaly B.; Miller, V. A.; Saulevich, S. V.; Shulika, A. N.

    1991-04-01

    The first multistage image converter with an X-ray photocathode (UMI-93 SR) was designed in VNIIOFI in 1974 [1]. The experiments carried out in IOFAN pointed out that X-ray electron-optical cameras using the tube provided temporal resolution up to 12 picoseconds [2]. The later work has developed into the creation of the separate streak and intensifying tubes. Thus, PV-003R tube has been built on base of UMI-93SR design, fibre optically connected to PMU-2V image intensifier carrying microchannel plate.

  10. Relativistically strong CO{sub 2} laser driver for plasma-channeled particle acceleration

    SciTech Connect

    Pogorelsky, I.V.

    1995-12-31

    Long-wavelength, short-duration laser pulses are desirable for plasma wakefield particle acceleration and plasma waveguiding. The first picosecond terawatt CO{sub 2} laser is under development to test laser-driven electron acceleration schemes.

  11. Picosecond High Pressure Gas Switch experiment

    SciTech Connect

    Cravey, W.R.; Freytag, E.K.; Goerz, D.A.; Poulsen, P.; Pincosy, P.A.

    1993-08-01

    A high Pressure Gas Switch has been developed and tested at LLNL. Risetimes on the order of 200 picoseconds have been observed at 1 kHz prf and 1 atmosphere pressures. Calculations show that switching closure times on the order of tens of picoseconds can be achieved at higher pressures and electric fields. A voltage hold-off of 1 MV/cm has been measured at 10 atmospheres and several MV/cm appears possible with the HPGS. With such high electric field levels, energy storage of tens of Joules in a reasonably sized package is achievable. Initial HPGS performance has been characterized using the WASP pulse generator at LLNL. A detailed description of the switch used for initial testing is given. Switch recovery times of 1-ms have been measured at 1 atmosphere. Data on the switching uniformity, voltage hold-off recovery, and pulse repeatability, is presented. In addition, a physics switch model is described and results are compared with experimental data. Modifications made to the WASP HV pulser in order to drive the HPGS will also be discussed. Recovery times of less than 1 ms were recorded without gas flow in the switch chambers. Low pressure synthetic air was used as the switch dielectric. Longer recovery times were required when it was necessary to over-voltage the switch.

  12. Picosecond laser ablation of porcine sclera

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  13. Picosecond time-resolved imaging using SPAD cameras

    NASA Astrophysics Data System (ADS)

    Gariepy, Genevieve; Leach, Jonathan; Warburton, Ryan; Chan, Susan; Henderson, Robert; Faccio, Daniele

    2016-10-01

    The recent development of 2D arrays of single-photon avalanche diodes (SPAD) has driven the development of applications based on the ability to capture light in motion. Such arrays are composed typically of 32x32 SPAD detectors, each having the ability to detect single photons and measure their time of arrival with a resolution of about 100 ps. Thanks to the single-photon sensitivity and the high temporal resolution of these detectors, it is now possible to image light as it is travelling on a centimetre scale. This opens the door for the direct observation and study of dynamics evolving over picoseconds and nanoseconds timescales such as laser propagation in air, laser-induced plasma and laser propagation in optical fibres. Another interesting application enabled by the ability to image light in motion is the detection of objects hidden from view, based on the recording of scattered waves originating from objects hidden by an obstacle. Similarly to LIDAR systems, the temporal information acquired at every pixel of a SPAD array, combined with the spatial information it provides, allows to pinpoint the position of an object located outside the line-of-sight of the detector. A non-line-of-sight tracking can be a valuable asset in many scenarios, including for search and rescue mission and safer autonomous driving.

  14. Picosecond adsorbate dynamics at condensed phase interfaces

    SciTech Connect

    Scott, T.W.; Chang, Y.J.; Martorell, J.

    1993-12-31

    Picosecond surface second harmonic generation has been used to probe a variety of elementary adsorbate reactions at liquid-solid interfaces. Electron transfer reactions at semiconductor-liquid junctions, geminate recombination of photogenerated free radical pairs and the orientational dynamics of dipolar adsorbates have all been explored in varying degrees of detail. These kinetic studies have led to a detailed analysis of adsorbate detection on the surface of non-centrosymmetric substrates as well as the use of total internal reflection geometries for signal enhancement from optically absorbing liquids. Particular emphasis has been placed on the static and dynamic characterization of adsorbate orientational distribution functions and how these are determined from the torque exerted on adsorbates by the angular part of the molecule-surface interaction potential.

  15. Timing Characteristics of Large Area Picosecond Photodetectors

    SciTech Connect

    Adams, Bernhard W.; Elagin, Andrey L.; Frisch, H.; Obaid, Razib; Oberla, E; Vostrikov, Alexander; Wagner, Robert G.; Wang, Jingbo; Wetstein, Matthew J.; Northrop, R

    2015-09-21

    The LAPPD Collaboration was formed to develop ultralast large-area imaging photodetectors based on new methods for fabricating microchannel plates (MCPs). In this paper we characterize the time response using a pulsed, sub picosecond laser. We observe single photoelectron time resolutions of a 20 cm x 20 cm MCP consistently below 70 ps, spatial resolutions of roughly 500 pm, and median gains higher than 10(7). The RMS measured at one particular point on an LAPPD detector is 58 ps, with in of 47 ps. The differential time resolution between the signal reaching the two ends of the delay line anode is measured to be 5.1 ps for large signals, with an asymptotic limit falling below 2 ps as noise-over-signal approaches zero.

  16. 100 W all fiber picosecond MOPA laser.

    PubMed

    Chen, Sheng-Ping; Chen, Hong-Wei; Hou, Jing; Liu, Ze-Jin

    2009-12-21

    A high power picosecond laser is constructed in an all fiber master oscillator power amplifier (MOPA) configuration. The seed source is an ytterbium-doped single mode fiber laser passively mode-locked by a semiconductor saturable absorber mirror (SESAM). It produces 20 mW average power with 13 ps pulse width and 59.8 MHz repetition rate. A direct amplification of this seed source encounters obvious nonlinear effects hence serious spectral broadening at only ten watt power level. To avoid these nonlinear effects, we octupled the repetition rate to about 478 MHz though a self-made all fiber device before amplification. The ultimate output laser exhibits an average power of 96 W, a pulse width of 16 ps, a beam quality M2 of less than 1.5, and an optical conversion efficiency of 61.5%.

  17. Patterning of ITO with picosecond lasers

    NASA Astrophysics Data System (ADS)

    Račiukaitis, Gediminas; Brikas, Marijus; Gedvilas, Mindaugas; Darčianovas, Gediminas

    2007-02-01

    Indium-tin oxide (ITO) is the main material for making transparent electrodes in electronic devices and flat panel displays. Laser-direct-write technology has been widely used for patterning ITO. The well defined edges and good electrical isolation at a short separation are required for the modern OLED and RFID devices of high packing density. High repetition rate lasers with a short, picosecond pulse width offer new possibilities for high efficiency structuring of transparent conductors on glass and other substrates. The results of patterning the ITO film on glass with picosecond lasers at various wavelengths are presented. Laser radiation initiated ablation of the material, forming trenches in ITO. Profile of the trenches was analyzed with a phase contrast optical microscope, a stylus type profiler, SEM and AFM. Clean removal of the ITO layer was achieved with the 266 nm radiation when laser fluence was above the threshold at 0.20 J/cm2, while for the 355 nm radiation the threshold was higher, above 0.46 J/cm2. The glass substrate was damaged in the area where the fluence was higher than 1.55 J/cm2. The 532 nm radiation allowed getting well defined trenches, but a lot of residues in the form of dust were generated on the surface. UV radiation at the 266 nm provided the widest working window for ITO ablation without damage of the substrate. Use of UV laser radiation with fluences close to the ablation threshold made it possible to minimize surface contamination and the recast ridge formation during the process.

  18. Investigation of picosecond blue laser emission from chlorophyll molecules

    SciTech Connect

    Liu Yixian; Wang Yagang; Zhu Wei; Li Fuming; Yang Shanyuan; Zhou Peilin

    1988-03-01

    Results on picosecond blue laser emission from a chlorophyll (chl) dye laser with an ultrashort cavity are reported. The laser mechanism involves intermolecular energy transfer from excited coumarin (co) molecules to chlorophyll a and b pigment molecules.

  19. Rapid scanning autocorrelator for measurements of picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Harde, H.; Burggraf, H.

    1981-08-01

    A rapid scanning autocorrelation interferometer for measurements of picosecond laser pulses is described which uses a rotating prism as scanning device in one arm of the interferometer to permit continuous display of autocorrelation traces at audio frequencies on an oscilloscope. Scan widths of more than 500 ps with high linearity can be achieved. Autocorrelation measurements of picosecond pulses from a synchronously pumped mode-locked dye laser are presented.

  20. Electric field measurements in a nanosecond pulse discharge by picosecond CARS/4-wave mixing

    NASA Astrophysics Data System (ADS)

    Goldberg, Ben; Shkurenkov, Ivan; Adamovich, Igor; Lempert, Walter

    2014-10-01

    Time-resolved electric field measurements in hydrogen by picosecond CARS/4-wave mixing are presented. Measurements are carried out in a high voltage nanosecond pulse discharge in hydrogen in plane-to-plane geometry, at pressures of up to several hundred Torr, and with a time resolution of 0.2 ns. Absolute calibration of the diagnostics is done using a sub-breakdown high voltage pulse of 12 kV/cm. A diffuse discharge is obtained by applying a peak high voltage pulse of 40 kV/cm between the electrodes. It is found that breakdown occurs at a lower field, 15--20 kV/cm, after which the field in the plasma is reduced rapidly due to plasma self shielding The experimental results are compared with kinetic modeling calculations, showing good agreement between the measured and the predicted electric field.

  1. Picosecond dynamics from lanthanide chloride melts

    NASA Astrophysics Data System (ADS)

    Kalampounias, Angelos G.

    2012-12-01

    The picosecond dynamics of molten lanthanide chlorides is studied by means of vibrational spectroscopy. Polarized Raman spectra of molten LaCl3, NdCl3, GdCl3, DyCl3, HoCl3 and YCl3 are fitted to a model enabling to obtain the times of vibrational dephasing, tν and vibrational frequency modulation tω. Our aim is to find possible sensitive indicators of short-time dynamics. It has been found that all lanthanide chlorides exhibit qualitative similarities in the vibrational relaxation and frequency modulation times in the molten state. It appears that the vibrational correlation functions of all melts comply with the Rothschild approach assuming that the environmental modulation is described by a stretched exponential decay. The evolution of the dispersion parameter α indicates the deviation of the melts from the model simple liquid and the similar local environment in which the oscillator is placed and with which it is coupled. The "packing" of the anions around central La3+ cation seems to be the key factor for the structure and the dynamics of the melts. The results are discussed in the framework of the current phenomenological status of the field.

  2. Picosecond runaway electron beams in air

    SciTech Connect

    Mesyats, G. A.; Yalandin, M. I.; Reutova, A. G.; Sharypov, K. A.; Shpak, V. G.; Shunailov, S. A.

    2012-01-15

    Experimental data on the generation of picosecond runaway electron beams in an air gap with an inhomogeneous electric field at a cathode voltage of up to 500 kV are presented. The methods and equipment developed for these experiments made it possible to measure the beam characteristics with a time resolution of better than 10{sup -11} s, determine the voltage range and the beam formation time in the breakdown delay stage, and demonstrate the influence of the state of the cathode surface on the stability of runaway electron generation. It is demonstrated that the critical electron runaway field in air agrees with the classical concepts and that the accelerated beam can be compressed to {approx}20 ps. It is unlikely that, under these conditions, the beam duration is limited due to the transition of field emission from the cathode to a microexplosion of inhomogeneities. The maximum energy acquired by runaway electrons in the course of acceleration does not exceed the value corresponding to the electrode voltage.

  3. Photoacoustic generation by multiple picosecond pulse excitation.

    PubMed

    Liu, Tan; Wang, Jing; Petrov, Georgi I; Yakovlev, Vladislav V; Zhang, Hao F

    2010-04-01

    The purpose of this work is to demonstrate that higher amplitude of ultrashort laser induced photoacoustic signal can be achieved by multiple-pulse excitation when the temporal duration of the pulse train is less than the minimum of the medium's thermal relaxation time and stress relaxation time. Thus, improved signal-to-noise ratio can thus be attained through multiple-pulse excitation while minimizing the energy of each pulse. The authors used a Michelson interferometer together with a picoseconds laser system to introduce two 6 ps pulses separated by a controllable delay by introducing a path length difference between the two arms of the interferometer. The authors then employed a series of three interferometers to create a pulse train consisting of eight pulses. The average pulse energy was 11 nJ and the temporal span of the pulse train was less than 1 ns. The detected peak-to-peak amplitude of the multiple-pulse induced photoacoustic waves were linearly dependent on the number of pulses in the pulse train and such a linearity held for different optical absorption coefficients. The signal-to-noise ratio improved when the number of pulses increased. Moreover, nonlinear effects were not detected and no photoacoustic saturation effect was observed. The authors have shown that multiple-pulse excitation improves the signal-to-noise ratio through an accumulated energy deposition effect. This method is invaluable for photoacoustic measurements that require ultrashort laser pulses with minimized pulse energy to avoid laser damage.

  4. Picosecond laser ablation of polyamide electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Götze, Marco; Krimig, Olaf; Kürbitz, Tobias; Henning, Sven; Heilmann, Andreas; Hillrichs, Georg

    2017-02-01

    Electrospun nanofibers mats have a great potential in tissue engineering and regenerative medicine. Their high porosity and enormous volume to surface ratio stimulate the growth and adhesion of mammalian cells and serve as a stable support structure. These suitable properties can be further optimized by structuring of the nanofibers. Ultrashort pulsed lasers can be used for modifying of the electrospun nanofibers without significant heat exposure. It seems also possible to generate very fine cuts from the fiber mats. In this study, polyamide electrospun nanofibers samples were processed with picosecond UV-laser irradiation (λ = 355 nm, τ = 15 ps). The samples were processed in dry, wet and immersed condition. To optimize cutting and structuring of nanofiber tissue flakes, the influence of different laser parameters on line widths, edge quality, heat-affected zone (HAZ) and the contamination of the fibers by ablated particles (debris) were examined. One additional aim was the minimization of the flake size. It was possible to generate nanofiber flakes in the sub-millimeter range. The quality of the nanofiber flakes could be improved by ablation near the ablation threshold of the material. For cutting under wet conditions shrinking of the flakes has to be taken into account.

  5. Dielectric breakdown induced by picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

    1976-01-01

    The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.

  6. Mitotic spindle studied using picosecond laser scissors

    NASA Astrophysics Data System (ADS)

    Baker, N. M.; Botvinick, E. L.; Shi, Linda; Berns, M. B.; Wu, George

    2006-08-01

    In previous studies we have shown that the second harmonic 532 nm, from a picosecond frequency doubled Nd:YAG laser, can cleanly and selectively disrupt spindle fiber microtubules in live cells (Botvinick et al 2004, Biophys. J. 87:4303-4212). In the present study we have ablated different locations and amounts of the metaphase mitotic spindle, and followed the cells in order to observe the fate of the irradiated spindle and the ability of the cell to continue through mitosis. Cells of the rat kangaroo line (PTK2) were stably transfected by ECFP-tubulin and, using fluorescent microscopy and the automated RoboLase microscope, (Botvinick and Berns, 2005, Micros. Res. Tech. 68:65-74) brightly fluorescent individual cells in metaphase were irradiated with 0.2447 nJ/micropulse corresponding to an irradiance of 1.4496*10^7 J/(ps*cm^2) . Upon irradiation the exposed part of the mitotic spindle immediately lost fluorescence and the following events were observed in the cells over time: (1) immediate contraction of the spindle pole towards the cut, (2) recovery of connection between pole and cut microtubule, (3) completion of mitosis. This system should be very useful in studying internal cellular dynamics of the mitotic spindle.

  7. The histology of skin treated with a picosecond alexandrite laser and a fractional lens array.

    PubMed

    Tanghetti, Emil A

    2016-09-01

    The treatment of acne scars and wrinkles with a picosecond Alexandrite laser was recently FDA cleared. In 2014 we presented our initial histologic findings with this device on in vivo and ex vivo skin. This current study expands on the 2014 pilot study with an investigation of different energy settings using histology and the confocal microscope to describe the changes observed in the skin. We used a 755 nm picosecond Alexandrite laser with a fractional optic with three different energy settings to treat in vivo. After treatment, the patients and skin samples were also evaluated with a confocal microscope followed by biopsies which were evaluated histologically. Histology revealed unique intra-epidermal cavities. The number, density, and the size of these cavities were dependent on the melanin index and delivered energy when evaluated with histopathology and the confocal microscope. These localized zones of injury appear to form microscopic epidermal injury zones which are exfoliated over a 3-week period. These intra-epidermal cavities result from areas of laser-induced optical breakdown (LIOB). This injury is most consistent with a localized plasma formation in the epidermis initiated by the melanin absorption of the high energy picosecond light. It appears that treatments with this device and optic result in improvements in dyspigmentation and acne scars with new collagen, elastic tissue, and mucin. The production of this LIOB could directly stimulate an epidermal repair mechanism that results in these clinical findings. Lasers Surg. Med. 48:646-652, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  8. Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor

    DOE PAGES

    Hora, H.; Korn, G.; Eliezer, S.; ...

    2016-10-11

    Measured highly elevated gains of proton–boron (HB11) fusion (Picciottoet al., Phys. Rev. X4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousiset al., Laser Part. Beams 32, 409 (2014); Horaet al., Laser Part. Beams33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh accelerationabovemore » $$10^{20}~\\text{cm}~\\text{s}^{-2}$$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora,Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas3, 4712 (1996)) in exact agreement (Horaet al., Phys. Plasmas14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $$f_{\\text{NL}}$$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. Finally, this is supported also by other experiments with very high HB11 reactions under different conditions (Labauneet al., Nature Commun.4, 2506 (2013)).« less

  9. Fiber-delivered picosecond source for coherent Raman scattering imaging

    PubMed Central

    Wang, Ke; Xu, Chris

    2013-01-01

    We demonstrate a two-color, fiber-delivered picosecond source for coherent Raman scattering (CRS) imaging. The wavelength-tunable picosecond pump is generated by nonlinear spectral compression of a prechirped femtosecond pulse from a mode-locked titanium:sapphire (Ti:S) laser. The 1064 nm picosecond Stokes pulse is generated by an all-fiber time-lens source that is synchronized to the Ti:S laser. The pump and Stokes beams are combined in an optical fiber coupler, which serves not only as the delivery fiber but also as the nonlinear medium for spectral compression of the femtosecond pulse. CRS imaging of mouse skin is performed to demonstrate the practicality of this source. PMID:22048375

  10. Optothermal response of plasmonic nanofocusing lens under picosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Du, Z.; Chen, C.; Traverso, L.; Xu, X.; Pan, L.; Chao, I.-H.; Lavine, A. S.

    2014-03-01

    This work studied the optothermal response of plasmonic nanofocusing structures under picosecond pulsed laser irradiation. The surface plasmon polariton is simulated to calculate the optical energy dissipation as the Joule heating source and the thermal transport process is studied using a two temperature model (TTM). At the picosecond time scale that we are interested in, the Fourier heat equation is used to study the electron thermal transport and the hyperbolic heat equation is used to study the lattice thermal transport. For comparison, the single temperature model (STM) is also studied. The difference between TTM and STM indicates that TTM provides more accurate estimates in the picosecond time scale and the STM results are only reliable when the local electron and lattice temperature difference is negligible.

  11. Picosecond time resolved conductance measurements of redox molecular junctions

    NASA Astrophysics Data System (ADS)

    Arielly, Rani; Nachman, Nirit; Zelinskyy, Yaroslav; May, Volkhard; Selzer, Yoram

    2017-03-01

    Due to bandwidth limitations of state of the art electronics, the transient transport properties of molecular junctions are experimentally a terra incognita, which can only be explored if novel picosecond current-probing techniques are developed. Here we demonstrate one such approach: the laser pulse-pair sequence scheme. The method is used to monitor in picosecond resolution the oxidation state of a redox molecule, 6-ferrocenyl-1-hexanethiol, within a junction and to quantify its redox rate constant, which is found to be (80 ps)-1.

  12. An All-Optical Picosecond Switch in Polydiacetylene

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Frazier, Donald O.; Paley, Mark S.

    2002-01-01

    Polydiacetylene derivative of 2-methyl-4-nitroaniline (PDAMNA) showed a picosecond switching property. This phenomenon was demonstrated by wave guiding a cw He-Ne laser collinearly with a mode-locked picosecond Nd:YAG laser at 532 nm through a hollow fiber coated on the inside with a thin film of PDAMNA. The z-scan investigations of PDAMNA thin film revealed that the PDAMNA system is a three level system and the switching is caused by excited state absorption of the He-Ne beam.

  13. Molecular collision processes in the presence of picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Lee, H. W.; George, T. F.

    1979-01-01

    Radiative transitions in molecular collision processes taking place in the presence of picosecond pulses are studied within a semiclassical formalism. An expression for adiabatic potential surfaces in the electronic-field representation is obtained, which directly leads to the evaluation of transition probabilities. Calculations with a Landau-Zener-type model indicate that picosecond pulses can be much more effective in inducing transitions than a single long pulse of the same intensity and the same total energy, if the intensity is sufficiently high that the perturbation treatment is not valid.

  14. On the generation and disruption of a picosecond runaway electron beam during the breakdown of an atmospheric-pressure gas gap

    SciTech Connect

    Barengolts, S. A.; Mesyats, G. A.; Tsventoukh, M. M.; Uimanov, I. V.

    2012-03-26

    The generation and disruption of the picosecond runaway electron beam in atmospheric pressure strongly overvolted gas gap is considered with emphasis on the runaway kinetics, the increase in emission current and plasma density, and beam instabilities. It has been shown that a few-nanosecond ten-kV prepulse gives rise to a streamer. Application of the main pulse ({approx}2 MV/ns) results in the runaway electron beam generation with the streamer electrons involved in the acceleration, and in increase of the electron emission from the cathode and the plasma density. At the high enough plasma density, fast beam instability disrupts the runaway electron beam.

  15. Proposal for Cherenkov Time of Flight Technique with Picosecond Resolution

    SciTech Connect

    S. Majewski; A. Margaryan; L. Tang

    2005-08-05

    A new particle identification device for Jlab 12 GeV program is proposed. It is based on the measurement of time information obtained by means of a new photon detector and time measuring concept. The expected time measurement precision for the Cherenkov time-of-flight detector is about or less than 10 picosecond for Cherenkov radiators with lengths less than 50 cm.

  16. Picosecond lasers for tattoo removal: a systematic review.

    PubMed

    Reiter, Ofer; Atzmony, Lihi; Akerman, Lehavit; Levi, Assi; Kershenovich, Ruben; Lapidoth, Moshe; Mimouni, Daniel

    2016-09-01

    Given that the pigment particles in tattoos have a relaxation time of <10 ns, picosecond lasers would be expected to be more effective than nanosecond lasers in tattoo removal. To systematically review the evidence regarding the effectiveness and safety of picosecond lasers for tattoo removal, Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, and reference lists were searched for relevant trials. The primary outcome was >70 % clearance of tattoo pigment. Secondary outcomes were 90-100 % clearance of tattoo pigment, number of laser sessions required, and adverse effects. Eight trials were included, six with human participants (160 participants) and 2 with animal models. Seven of the eight trials explored the usage of either 755, 758, 795, 1064, or 1064/532-nm picosecond lasers for black and blue ink tattoos. In the human trials, 69-100 % of tattoos showed over 70 % clearance of pigment after 1-10 laser treatments. Reported side effects included pain, hyperpigmentation and hypopigmentation, blister formation and transient erythema, edema, and pinpoint bleeding. Included articles varied in type of laser investigated, mostly non-comparative studies and with a medium to high risk of bias. There is sparse evidence that picosecond lasers are more effective than their nanosecond counterparts for mainly black and blue ink tattoo removal, with minor side effects.

  17. A simple technique for individual picosecond laser pulse duration measurements

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.

    1976-01-01

    We describe here a simple nonlinear optic technique for the measurement of the duration of individual picosecond pulses. The accuracy and relative simplicity of the technique increase with the number of pulses measured. An experimental test of the basis of the technique is described.

  18. Picosecond photoconductive devices for 10 Gbit/s optoelectronic switching

    NASA Astrophysics Data System (ADS)

    Veith, G.

    1985-03-01

    Semiconductor materials with a high density of recombination and trapping centers exhibit extremely short carrier lifetimes in the order of 1 to 100 ps and have been the base for the development of high speed optoelectronic switches. These devices are activated by picosecond laser pulses and can be driven nearly free of jitter with respect to the optical excitation pulses. They show some unique properties as picosecond risetimes and response times and can be operated within a relatively high dynamical range (10-5 to 10 sub 4 V) (0.00001 to 0.0001 V). A review is given on the wide field of possible applications of the ultrafast photoconductive switches. They can be used as photodetectors for picosecond light pulses as well as sampling gates for the characterization of high speed electronic and optoelectronic devices. In some experiments which are discussed more in detail the author demonstrates the capability of this type of photoconductive switches for the generation of picosecond infrared pulse trains in laser diodes and for the generation of high-bit rate electrical codes for use in Gbit/s optical communication and sensing systems, for logical switching and for testing purposes of high speed electronic instrumentations.

  19. Picosecond lasers: the next generation of short-pulsed lasers.

    PubMed

    Freedman, Joshua R; Kaufman, Joely; Metelitsa, Andrea I; Green, Jeremy B

    2014-12-01

    Selective photothermolysis, first discussed in the context of targeted microsurgery in 1983, proposed that the optimal parameters for specific thermal damage rely critically on the duration over which energy is delivered to the tissue. At that time, nonspecific thermal damage had been an intrinsic limitation of all commercially available lasers, despite efforts to mitigate this by a variety of compensatory cooling mechanisms. Fifteen years later, experimental picosecond lasers were first reported in the dermatological literature to demonstrate greater efficacy over their nanosecond predecessors in the context of targeted destruction of tattoo ink. Within the last 4 years, more than a decade after those experiments, the first commercially available cutaneous picosecond laser unit became available (Cynosure, Westford, Massachusetts), and several pilot studies have demonstrated its utility in tattoo removal. An experimental picosecond infrared laser has also recently demonstrated a nonthermal tissue ablative capability in soft tissue, bone, and dentin. In this article, we review the published data pertaining to dermatology on picosecond lasers from their initial reports to the present as well as discuss forthcoming technology.

  20. Transverse spatial coherence of a transient nickellike silver soft-x-ray laser pumped by a single picosecond laser pulse.

    PubMed

    Lucianetti, A; Janulewicz, K A; Kroemer, R; Priebe, G; Tümmler, J; Sandner, W; Nickles, P V; Redkorechev, V I

    2004-04-15

    The degree of spatial coherence in the direction perpendicular to the target surface is reported for a transient nickellike silver x-ray laser at 13.9 nm. An x-ray laser plasma column was produced by irradiating a slab silver target with a single shaped picosecond laser pulse with energy less than 3 J. Young's double-slit method was applied to measure the fringe visibility as a function of the slit separation for different target lengths. The diameter of the equivalent incoherent source and the coherence radius of the output radiation were determined as well.

  1. Picosecond and nanosecond laser annealing and simulation of amorphous silicon thin films for solar cell applications

    NASA Astrophysics Data System (ADS)

    Theodorakos, I.; Zergioti, I.; Vamvakas, V.; Tsoukalas, D.; Raptis, Y. S.

    2014-01-01

    In this work, a picosecond diode pumped solid state laser and a nanosecond Nd:YAG laser have been used for the annealing and the partial nano-crystallization of an amorphous silicon layer. These experiments were conducted as an alternative/complementary to plasma-enhanced chemical vapor deposition method for fabrication of micromorph tandem solar cell. The laser experimental work was combined with simulations of the annealing process, in terms of temperature distribution evolution, in order to predetermine the optimum annealing conditions. The annealed material was studied, as a function of several annealing parameters (wavelength, pulse duration, fluence), as far as it concerns its structural properties, by X-ray diffraction, SEM, and micro-Raman techniques.

  2. The fast decay of ionized nitrogen molecules in laser filamentation investigated by a picosecond streak camera

    NASA Astrophysics Data System (ADS)

    Lei, Mingwei; Wu, Chengyin; Liang, Qingqing; Zhang, An; Li, Yu; Cheng, Qian; Wang, Shufeng; Yang, Hong; Gong, Qihuang; Jiang, Hongbing

    2017-07-01

    A column of bright filament is generated when a strong 800 nm femtosecond laser propagates in pure nitrogen gas, from which some fluorescence emission lines are observed. These emission lines can be assigned to the transitions of {{{{N}}}2}+ ({{{B}}}2{{{{Σ }}}{{u}}}+\\to {{{X}}}2{{{{Σ }}}{{g}}}+) and N2 (C3Πu → B3Πg). By using a picosecond streak camera, we investigated the fluorescence decay dynamics of {{{{N}}}2}+ ({{{B}}}2{{{{Σ }}}{{u}}}+\\to {{{X}}}2{{{{Σ }}}{{g}}}+). It was found that the decay time is in the sub-nanosecond range when the gas pressure is several millibar, more than two orders magnitude shorter than its spontaneous emission lifetime. Through monitoring the population evolution of {{{{N}}}2}+ ({{{B}}}2{{{{Σ }}}{{u}}}+) as a function of free electron density, we concluded that the fast decay originates from the collision between {{{{N}}}2}+ ({{{B}}}2{{{{Σ }}}{{u}}}+) and free electrons in the plasma filament.

  3. Picosecond Optical Studies of Semiconductor Dynamics

    NASA Astrophysics Data System (ADS)

    McLean, Daniel Garth

    An investigation of the recombination dynamics of a photoexcited electron-hole plasma is reported. The experiment performed is a pump-probe type utilizing time -of-flight delay techniques to extract the time dependence of a relaxing plasma. Polarization techniques are utilized to eliminate background reflection. The pulses utilized are 15 psec in width at (lamda) = 630nm and excitation energy densities vary between 1-5mJ/cm('2). The theory describing the reflectivity change due to the presence of the plasma and to lattice temperature changes is derived. The theory for the recombination dynamics includes the process of Auger recombination, bimolecular recombination, and linear recombination. The predictions made by the theory within its limitations are compared to the data obtained. Analysis shows that the dynamics predicted are accurate for part of the energy range available, however, at the high energies the limitations placed on the theory are violated and the dynamics observed no longer agree with the predictions. The result is that investigations at these energy densities must account for the lattice temperature rise and its secondary effects. Also this work points out the necessity of an accurate description of the pump energy absorption dynamics in order to fully explain the initial conditions required for and accurate description of the relaxation process.

  4. Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor

    SciTech Connect

    Hora, H.; Korn, G.; Eliezer, S.; Nissim, N.; Lalousis, P.; Giuffrida, L.; Margarone, D.; Picciotto, A.; Miley, G. H.; Moustaizis, S.; Martinez-Val, J. -M.; Barty, C. P. J.; Kirchhoff, G. J.

    2016-10-11

    Measured highly elevated gains of proton–boron (HB11) fusion (Picciottoet al., Phys. Rev. X4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousiset al., Laser Part. Beams 32, 409 (2014); Horaet al., Laser Part. Beams33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh accelerationabove$10^{20}~\\text{cm}~\\text{s}^{-2}$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora,Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas3, 4712 (1996)) in exact agreement (Horaet al., Phys. Plasmas14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $f_{\\text{NL}}$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. Finally, this is supported also by other experiments with very high HB11 reactions under different conditions (Labauneet al., Nature Commun.4, 2506 (2013)).

  5. Picosecond optical vortex pulse illumination forms a monocrystalline silicon needle.

    PubMed

    Takahashi, Fuyuto; Miyamoto, Katsuhiko; Hidai, Hirofumi; Yamane, Keisaku; Morita, Ryuji; Omatsu, Takashige

    2016-02-24

    The formation of a monocrystalline silicon needle by picosecond optical vortex pulse illumination was demonstrated for the first time in this study. The dynamics of this silicon needle formation was further revealed by employing an ultrahigh-speed camera. The melted silicon was collected through picosecond pulse deposition to the dark core of the optical vortex, forming the silicon needle on a submicrosecond time scale. The needle was composed of monocrystalline silicon with the same lattice index (100) as that of the silicon substrate, and had a height of approximately 14 μm and a thickness of approximately 3 μm. Overlaid vortex pulses allowed the needle to be shaped with a height of approximately 40 μm without any changes to the crystalline properties. Such a monocrystalline silicon needle can be applied to devices in many fields, such as core-shell structures for silicon photonics and photovoltaic devices as well as nano- or microelectromechanical systems.

  6. New and Advanced Picosecond Lasers for Tattoo Removal.

    PubMed

    Adatto, Maurice A; Amir, Ruthie; Bhawalkar, Jayant; Sierra, Rafael; Bankowski, Richard; Rozen, Doran; Dierickx, Christine; Lapidoth, Moshe

    2017-01-01

    Early methods of tattoo removal ultimately resulted in unacceptable cosmetic outcomes. While the introduction of laser technology was an improvement over the existing chemical, mechanical, and surgical procedures, the use of nonselective tattoo removal with carbon dioxide and argon lasers led to scarring. Q-switched lasers with nanosecond (10-9) pulse domains were considered to have revolutionized tattoo treatment, by selectively heating the tattoo particles, while reducing the adverse sequelae to adjacent normal skin. Theoretical considerations of restricting pulse duration, to heat tattoo particles to higher temperatures, proposed the use of sub-nanosecond pulses to target particles with thermal relaxation times lower than the nanosecond pulses in Q-switched lasers. Initial studies demonstrated that picosecond (10-12) pulses were more effective than nanosecond pulses in clearing black tattoos. Advances in picosecond technology led to the development of commercially available lasers, incorporating several different wavelengths, to further refine pigment targeting.

  7. Polydiacetylene as an all-optical picosecond Switch

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin A.; Frazier, D. O.; Paley, M. S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Polydiacetylene derivative of 2-methyl-4-nitroaniline (PDAMNA) shows a picosecond switching property, which illustrated a partial all-optical picosecond NAND logic gate. The switching phenomenon was demonstrated by waveguiding two collinear beams at 633 nm and 532 nm through a hollow fiber of 50 micrometers diameter, coated from inside with a thin film of PDAMNA. A Z-scan investigations of a PDAMNA thin film on quartz substrate revealed that the switching effect was attributed to an excited state absorption in the systems. The studies also showed that the polymer suffers a photo-oxidation beyond an intensity level of 2.9 x 10(exp 6) w/square cm. The photo-oxidized film has different physical properties that are different from the original film before oxidation. The life time of both excited states before and after oxidation as well as their absorption coefficients were estimated by fitting a three level system model to the experimental results.

  8. Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement.

    PubMed

    Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; Long, Cary; Huang, Chunning; Takeda, Yasuhiro; Liu, Yun

    2014-11-01

    A compact multifunctional optical correlator system for pulse width measurement of ultrashort ultraviolet (UV) pulses has been designed and experimentally demonstrated. Both autocorrelation and cross-correlation functions are measured using a single nonlinear crystal, and the switching between two measurements requires no adjustment of phase matching and detector. The system can measure UV pulse widths from sub-picoseconds to 100 ps, and it involves no auxiliary pulse in the measurement. The measurement results on a burst-mode picosecond UV laser show a high-quality performance on speed, accuracy, resolution, and dynamic range. The proposed correlator can be applied to measure any ultrashort UV pulses produced through sum-frequency generation or second-harmonic generation.

  9. Recent progress in picosecond pulse generation from semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Auyeung, J. C.; Johnston, A. R.

    1982-01-01

    This paper reviews the recent progress in producing picosecond optical pulses from semiconductor laser diodes. The discussion concentrates on the mode-locking of a semiconductor laser diode in an external resonator. Transform-limited optical pulses ranging from several picoseconds to subpicosecond durations have been observed with active and passive mode-locking. Even though continuing research on the influence of impurities and defects on the mode-locking process is still needed, this technique has good promise for being utilized in fiber-optic communication systems. Alternative methods of direct electrical and optical excitation to produce ultrashort laser pulses are also described. They can generate pulses of similar widths to those obtained by mode-locking. The pulses generated will find applications in laser ranging and detector response measurement.

  10. Surfaces and thin films studied by picosecond ultrasonics

    SciTech Connect

    Maris, J.H.; Tauc, J.

    1992-05-01

    This research is the study of thin films and interfaces via the use of the picosecond ultrasonic technique. In these experiments ultrasonic waves are excited in a structure by means of a picosecond light pulse ( pump pulse''). The propagation of these waves is detected through the use of a probe light pulse that is time-delayed relative to the pump. This probe pulse measures the change {Delta}R(t) in the optical reflectivity of the structure that occurs because the ultrasonic wave changes the optical properties of the structure. This technique make possible the study of the attenuation and velocity of ultrasonic waves up to much higher frequencies than was previously possible (up to least 500 GHz). In addition, the excellent time-resolution of the method makes it possible to study nanostructures of linear dimensions down to 100 {Angstrom} or less by ultrasonic pulse-echo techniques. 25 refs.

  11. Recent progress in picosecond pulse generation from semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Auyeung, J. C.; Johnston, A. R.

    1982-01-01

    This paper reviews the recent progress in producing picosecond optical pulses from semiconductor laser diodes. The discussion concentrates on the mode-locking of a semiconductor laser diode in an external resonator. Transform-limited optical pulses ranging from several picoseconds to subpicosecond durations have been observed with active and passive mode-locking. Even though continuing research on the influence of impurities and defects on the mode-locking process is still needed, this technique has good promise for being utilized in fiber-optic communication systems. Alternative methods of direct electrical and optical excitation to produce ultrashort laser pulses are also described. They can generate pulses of similar widths to those obtained by mode-locking. The pulses generated will find applications in laser ranging and detector response measurement.

  12. Picosecond transient absorption study of photodissociated carboxy hemoglobin and myoglobin

    SciTech Connect

    Janes, S.M.; Dalickas, G.A.; Eaton, W.A.; Hochstrasser, R.M.

    1988-09-01

    The optical transient absorption spectra at 30 ps and 6.5 ns after photolysis are compared for both carboxy hemoglobin (HbCO) and carboxy myoglobin (MbCO). Both 355- and 532-nm excitation pulses were used. In all cases the shapes of the optical difference spectra thus generated are stationary over the complete time-scale studied. The photolysis spectra for MbCO are not significantly different from the equilibrium difference spectra generated on the same picosecond spectrometer when measured to an accuracy of +/- 0.5 nm. In addition, spectral parameters for delegated HbCO generated on the same spectrometer but detected by two different techniques, either by a Vidicon detector or point by point with photomultiplier tubes, are reported; the results are different from some of the previously reported picosecond experiments.

  13. Picoseconds-Laser Modification of Thin Films

    SciTech Connect

    Gakovic, Biljana; Trtica, Milan; Batani, Dimitri; Desai, Tara; Redaelli, Renato

    2006-04-07

    The interaction of a Nd:YAG laser, pulse duration of 40 ps, with a titanium nitride (TiN) and tungsten-titanium (W-Ti) thin films deposited at silicon was studied. The peak intensity on targets was up to 1012 W/cm2. Results have shown that the TiN surface was modified, by the laser beam, with energy density of {>=}0.18 J/cm2 ({lambda}laser= 532 nm) as well as of 30.0 J/cm2 ({lambda}laser= 1064 nm). The W-Ti was surface modified with energy density of 5.0 J/cm2 ({lambda}laser= 532 nm). The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects such as melting, vaporization of molten materials, dissociation and ionization of the vaporized material, appearance of plasma, etc. The following morphological changes of both targets were observed: (i) The appearance of periodic microstructures, in the central zone of the irradiated area, for laser irradiation at 532 nm. Accumulation of great number of laser pulses caused film ablation and silicon modification. (ii) Hole formation on the titanium nitride/silicon target was registered at 1064 nm. The process of the Nd:YAG laser interaction with both targets was accompanied by plasma formation above the target.

  14. High average power ultraviolet picosecond optical vortex generation

    NASA Astrophysics Data System (ADS)

    Sasaki, Yuta; Kowa, Maya; Yamaguchi, Koki; Shibakawa, Jun; Miyamoto, Katsuhiko; Omatsu, Takashige

    2017-04-01

    We reported on high average power ultraviolet (UV) picosecond optical vortex generation without any spatial separation of the phase singularity due to the walk-off effect by employing a pair of β-BaB2O4 and reversed β-BaB2O4 crystals. The UV vortex output power was measured to be 1.76 W, corresponding to the optical-optical conversion efficiency of 17 %.

  15. Characterization of Copper Line Array Erosion with Picosecond Ultrasonics

    NASA Astrophysics Data System (ADS)

    Pic, Nicolas; Bennedine, Karim; Tas, Guray; Alliata, Dario; Clerico, Jana

    2007-09-01

    Chemical mechanical planarization (CMP) is a critical process for creating high performance interconnected structures. If line structures are under polished, residual copper or barrier will short out the circuitry resulting in defective dies. However, over polishing increases the line resistance, negatively impacting both the speed and performance of devices. To maintain high yield, it is thus critical to maintain the copper lines at the desired thickness. This requires strict process control. Several metrology techniques are used to monitor CMP processes including optical techniques that measure dielectric polishing and high resolution profilometry (HRP™) that can measure the relative step height differences between structures such as interlayer dielectric pads, copper pads, and line arrays. In contrast, the picosecond ultrasonic laser sonar method (PULSE™) measures the copper thickness and therefore directly measures the parameter of interest for CMP process monitoring. The picosecond ultrasonic technique is well established for measuring on solid copper structures such as pads. However, in the dense narrow line arrays that are required for current and next generation devices, the measurement spot size, while only approximately 10 μm in diameter, may cover hundreds of copper line/dielectric pairs. Therefore a new detector was developed that is insensitive to the dielectric signal. The capabilities of picosecond ultrasonic laser method to measure both copper pads and 0.6 μm line arrays were recently tested at STMicroelectronics (STM). The results were compared against Scanning Electron Microscopy (SEM). The samples included different products and six different metal layers. This paper will further describe the picosecond ultrasonic method, its use at STM, and detailed results for the various samples.

  16. OSA Proceedings on Picosecond Electronics and Optoelectronics. Volume 4

    DTIC Science & Technology

    1989-01-01

    3 shows PL decay time and the time integrated PL intensity of QWI and QW2 of three samples as a function of Va. The physical interpretations are...Picosecond Pulse Generation and Sampling with GaAs Monolithic Integrated Circuits .6........................................ R. A. Marsland, C. . Madden...73 K L. HaIl,_E.Jt?. Ippen, J. Mark, and G. Eisenstein rSpread-Spectrum- Integrated Optic Modulators ....................... 76 David W

  17. X-ray production with sub-picosecond laser pulses

    SciTech Connect

    Schappert, G.T.; Cobble, J.A.; Fulton, R.D.; Kyrala, G.A.

    1993-12-31

    The interaction of intense, sub-picosecond laser pulses with solid targets produces intense picosecond x-ray pulses. With focused laser pulses of several 10 {sup 18} W/cm{sup 2}, He-like and H-like line radiation from targets such as aluminum and silicon has been produced. The energy conversion efficiency from the laser pulse energy to the 1--2 keV line x-rays is nearly one percent. The duration of the line x-ray radiation is of the order of ten picoseconds, although this may be an upper estimate because of the temporal resolution of the x-ray streak camera. The spatial extent of the x-ray source region is only slightly larger than the laser focal spot, or about 10 {mu}m in diameter. With these characteristics, such x-ray sources emit an intensity of nearly 10{sup 14} W/cm{sup 2}. Experiments and modeling which led to the above conclusions will be discussed.

  18. The first picosecond terawatt CO{sub 2} laser at the Brookhaven Accelerator Test Facility

    SciTech Connect

    Pogorelsky, I.V.; Ben-Zvi, I.; Babzien, M.

    1998-02-01

    The first terawatt picosecond CO{sub 2} laser will be brought to operation at the Brookhaven Accelerator Test Facility in 1998. System consists of a single-mode TEA oscillator, picosecond semiconductor optical switch, multi-atmosphere. The authors report on design, simulation, and performance tests of the 10 atm final amplifier that allows for direct multi-joule energy extraction in a picosecond laser pulse.

  19. Picosecond pulsed laser ablation and micromachining of 4H-SiC wafers

    NASA Astrophysics Data System (ADS)

    Molian, Pal; Pecholt, Ben; Gupta, Saurabh

    2009-02-01

    Ultra-short pulsed laser ablation and micromachining of n-type, 4H-SiC wafer was performed using a 1552 nm wavelength, 2 ps pulse, 5 μJ pulse energy erbium-doped fiber laser with an objective of rapid etching of diaphragms for pressure sensors. Ablation rate, studied as a function of energy fluence, reached a maximum of 20 nm per pulse at 10 mJ/cm 2, which is much higher than that achievable by the femtosecond laser for the equivalent energy fluence. Ablation threshold was determined as 2 mJ/cm 2. Scanning electron microscope images supported the Coulomb explosion (CE) mechanism by revealing very fine particulates, smooth surfaces and absence of thermal effects including melt layer formation. It is hypothesized that defect-activated absorption and multiphoton absorption mechanisms gave rise to a charge density in the surface layers required for CE and enabled material expulsion in the form of nanoparticles. Trenches and holes micromachined by the picosecond laser exhibited clean and smooth edges and non-thermal ablation mode for pulse repetition rates less than 250 kHz. However carbonaceous material and recast layer were noted in the machined region when the pulse repetition rate was increased 500 kHz that could be attributed to the interaction between air plasma and micro/nanoparticles. A comparison with femtosecond pulsed lasers shows the promise that picosecond lasers are more efficient and cost effective tools for creating sensor diaphragms and via holes in 4H-SiC.

  20. A semiconductor injection-switched high-pressure sub-10-picosecond carbon dioxide laser amplifier

    NASA Astrophysics Data System (ADS)

    Hughes, Michael Kon Yew

    A multiatmospheric-pressure-broadened CO2 laser amplifier was constructed to amplify sub-10-picosecond pulses generated with semiconductor switching. High-intensity, mid-infrared, amplified pulses have many applications: especially in fields such as non-linear optics, laser-plasma interaction, and laser particle acceleration. The injected pulses are produced by exciting GaAs (or an engineered, fast-recombination time semiconductor) with an ultrafast visible laser pulse to induce transient free carriers with sufficient density to reflect a co-incident hybrid-CO2 laser pulse. The short pulse is injected directly into the regenerative amplifier cavity from an intra-cavity semiconductor switch. The CO2-gas-mix amplifier is operated at 1.24 MPa which is sufficient to collisionally broaden the individual rotational spectral lines so that they merge to produce a gain spectrum wide enough to support pulses less than 10 ps long. After sufficient amplification, the pulse is switched out with another semiconductor switch pumped with a synchronized visible-laser pulse. This system is demonstrated and analysed spectrally and temporally. The pulse-train spectral analysis is done for a GaAs-GaAs double-switch arrangement using a standard spectrometer and two HgCdTe detectors; one of which is used for a reference signal. An infrared autocorrelator was designed and constructed to temporally analyse the pulse trains emerging from the amplifier. Interpretation of the results was aided by the development of a computer model for short-pulse amplification which incorporated saturation effects, rotational- and vibrational-mode energy redistribution between pulse round trips, and the gain enhancement due to one sequence band. The results show that a sub-10-picosecond pulse is injected into the cavity and that it is amplified with some trailing pulses at 18 ps intervals generated by coherent effects. The energy level reached, estimated through modelling, was >100 mJ/cm2.

  1. Nonlinear guiding of picosecond CO2 laser pulses in atmosphere(Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tochitsky, Sergei

    2017-05-01

    During the last 20 years much attention has been given to the study of propagation of short intense laser pulses for which the peak power exceeds the critical power of self-focusing, Pcr. For a laser power P < Pcr, a dynamic equilibrium between the Kerr self-focusing, diffraction and defocusing caused by laser-ionized plasma result in the production of a high intensity laser filament in air within which a variety of nonlinear optical phenomena are observed. However, research in the 0.8-1 μm range so far has shown a fundamental limitation of guided energy to a few mJ transported within an 100 μm single channel. A long-wavelength, 0 10 μm CO2 laser is a promising candidate for nonlinear guiding because expected high Pcr values according to the modeling should allow for the increase of energy (and therefore power) in a self-guided beam from mJ (GW) to few Joules (TW). During the last decade a significant progress has been achieved in amplification of picosecond pulses to terawatt and recently to <10 TW power level at UCLA and ATF BNL. Such powerful 10 μm lasers open possibility for nonlinear propagation studies in an atmospheric window with high transmission. As a natural first step in a our program on picosecond CO2 laser filamentation, we have made first measurements of Kerr coefficients of air and air constituents around 10 μm. We also undertook direct measurements of n2 of air by analyzing nonlinear self-focusing in air using a 3 ps, 600 GW pulses of the BNL CO2 laser.

  2. Picosecond laser bonding of highly dissimilar materials

    NASA Astrophysics Data System (ADS)

    Carter, Richard M.; Troughton, Michael; Chen, Jianyong; Elder, Ian; Thomson, Robert R.; Lamb, Robert A.; Esser, M. J. Daniel; Hand, Duncan P.

    2016-10-01

    We report on recent progress in developing an industrially relevant, robust technique to bond dissimilar materials through ultra-fast microwelding. This technique is based on the use of a 5.9ps, 400kHz Trumpf laser operating at 1030nm. Tight focusing of the laser radiation at, or around, the interface between two materials allows for simultaneous absorption in both. This absorption rapidly, and locally, heats the material forming plasma from both materials. With suitable surface preparation this plasma can be confined to the interface region where it mixes, cools and forms a weld between the two materials. The use of ps pulses results in a short interaction time. This enables a bond to form whilst limiting the heat affected zone (HAZ) to a region of only a few hundred micrometres across. This small scale allows for the bonding of materials with highly dissimilar thermal properties, and in particular coefficients of thermal expansion e.g. glass-metal bonding. We report on our results for a range of material combinations including, Al-Bk7, Al-SiO2 and Nd:YAG-AlSi. Emphasis will be laid on the technical requirements for bonding including the required surface preparation of the two materials and on the laser parameters required. The quality of the resultant bonds are characterized through shear force measurements (where strengths equal to and exceeding equivalent adhesives will be presented). The lifetime of the welds is also discussed, paying particular attention to the results of thermal cycling tests.

  3. Observation of Betatron X-Ray Radiation in a Self-Modulated Laser Wakefield Accelerator Driven with Picosecond Laser Pulses

    DOE PAGES

    Albert, F.; Lemos, N.; Shaw, J. L.; ...

    2017-03-31

    We investigate a new regime for betatron x-ray emission that utilizes kilojoule-class picosecond lasers to drive wakes in plasmas. When such laser pulses with intensities of ~ 5 × 1 0 18 W / cm 2 are focused into plasmas with electron densities of ~ 1 × 1 0 19 cm - 3 , they undergo self-modulation and channeling, which accelerates electrons up to 200 MeV energies and causes those electrons to emit x rays. The measured x-ray spectra are fit with a synchrotron spectrum with a critical energy of 10–20 keV, and 2D particle-in-cell simulations were used to modelmore » the acceleration and radiation of the electrons in our experimental conditions« less

  4. Observation of Betatron X-Ray Radiation in a Self-Modulated Laser Wakefield Accelerator Driven with Picosecond Laser Pulses.

    PubMed

    Albert, F; Lemos, N; Shaw, J L; Pollock, B B; Goyon, C; Schumaker, W; Saunders, A M; Marsh, K A; Pak, A; Ralph, J E; Martins, J L; Amorim, L D; Falcone, R W; Glenzer, S H; Moody, J D; Joshi, C

    2017-03-31

    We investigate a new regime for betatron x-ray emission that utilizes kilojoule-class picosecond lasers to drive wakes in plasmas. When such laser pulses with intensities of ∼5×10^{18}  W/cm^{2} are focused into plasmas with electron densities of ∼1×10^{19}  cm^{-3}, they undergo self-modulation and channeling, which accelerates electrons up to 200 MeV energies and causes those electrons to emit x rays. The measured x-ray spectra are fit with a synchrotron spectrum with a critical energy of 10-20 keV, and 2D particle-in-cell simulations were used to model the acceleration and radiation of the electrons in our experimental conditions.

  5. Temporal Characterization of a Picosecond Laser-Pumped X-ray Laser (for Applications)

    SciTech Connect

    Dunn, J; Nilsen, J; Shepherd, R; Shlyaptsev, V; Booth, R; Smith, R; Hunter, J

    2003-11-25

    Compact soft x-ray laser sources are now used routinely for various applications primarily because of their high repetition rate, high photon fluence and short pulse duration characteristics. For some of these applications, for example interferometry of high density laser-produced plasmas, longer optical drive pulses, 6-13 ps (FWHM), have been implemented to maximize the x-ray output and coherence. It is therefore important to know the x-ray laser pulse length, shape and repeatability for these specific experiments as a baseline measurement but also to better understand the temporal behavior as a function of the pumping conditions in general. We report a detailed temporal characterization of the picosecond-driven 14.7 nm Ni-like Pd ion x-ray laser on the Compact Multipulse Terawatt (COMET) laser at LLNL using an ultrafast x-ray streak camera measurement of a horizontal slice of the near-field x-ray laser pattern. This is measured as a function of the chirped pulse amplification pumping laser conditions, including varying the pump pulse from 0.5-27 ps (FWHM), varying the plasma column length as well as investigating traveling wave (TW) and non-TW irradiation conditions.

  6. Demonstration of a 1 Joule, 500 W average power picosecond laser

    NASA Astrophysics Data System (ADS)

    Reagan, Brendan A.; Baumgarten, Cory M.; Pedicone, Michael A.; Bravo, Herman; Yin, Liang; Wang, Hanchen; Menoni, Carmen S.; Rocca, Jorge J.

    2017-02-01

    We report the demonstration of a chirped pulse amplification laser system that produces 1.5 J pulses at 0.5 kHz repetition rate and 0.75 kW average power. These pulses are subsequently compressed resulting 1 J, 5 ps duration pulses at 500 Hz repetition rate. The 8-pass main amplifier consists of two diode-pumped, cryogenic-temperature Yb:YAG active mirrors cooled by a thermally efficient, high capacity cryogenic-cooling system. This amplifier operates with an opticalto- optical efficiency of 37%. The amplified pulses have excellent beam quality with a measured M2 factor of 1.3. Over 30 minutes of continuous operation, we measured a shot-to-shot pulse energy fluctuation of only 0.75% RMS over the nearly 1 million shots fired. This laser was employed to make the first demonstration of a compact, plasma-based EUV/soft x-ray laser operating at a repletion rate of 400 Hz. In this proof-of-principle demonstration, shaped 1 J pulses of picosecond duration were focused onto a rotating molybdenum target at grazing incidence. The resulting plasma is collisionally ionized to the Ni-like ionic stage where a large, transient population inversion results in production of bright λ = 18.9 nm laser pulses.

  7. Temporal characterization of a picosecond-laser-pumped x-ray laser for applications

    NASA Astrophysics Data System (ADS)

    Dunn, James; Smith, Raymond F.; Shepherd, Ronnie; Booth, Rex; Nilsen, Joseph; Hunter, James R.; Shlyaptsev, Vyacheslav N.

    2003-12-01

    Compact soft x-ray laser sources are now used routinely for various applications primarily because of their high repetition rate, high photon fluence and short pulse duration characteristics. For some of these applications, for example interferometry of high density laser-produced plasmas, longer optical drive pulses, 6 13 ps (FWHM), have been implemented to maximize the x-ray output and coherence. It is therefore important to know the x-ray laser pulse length, shape and repeatability for these specific experiments as a baseline measurement but also to better understand the temporal behavior as a function of the pumping conditions in general. We report a detailed temporal characterization of the picosecond-driven 14.7 nm Ni-like Pd ion x-ray laser on the Compact Multipulse Terawatt (COMET) laser at LLNL using an ultrafast x-ray streak camera measurement of a horizontal slice of the near-field x-ray laser pattern. This is measured as a function of the chirped pulse amplification pumping laser conditions, including varying the pump pulse from 0.5 27 ps (FWHM), varying the plasma column length as well as investigating traveling wave (TW) and non-TW irradiation conditions.

  8. High power picosecond vortex laser based on a large-mode-area fiber amplifier.

    PubMed

    Tanaka, Yuichi; Okida, Masahito; Miyamoto, Katsuhiko; Omatsu, Takashige

    2009-08-03

    We present the production of picosecond vortex pulses from a stressed large-mode-area fiber amplifier for the first time. 8.5 W picosecond output with a peak power of approximately 12.5 kW was obtained at a pump power of 29 W. 2009 Optical Society of America.

  9. Pilot Production of Large Area Microchannel Plates and Picosecond Photodetectors

    NASA Astrophysics Data System (ADS)

    Minot, M.; Adams, B.; Abiles, M.; Bond, J.; Craven, C.; Cremer, T.; Foley, M.; Lyashenko, A.; Popecki, M.; Stochaj, M.; Worstell, W.; Elam, J.; Mane, A.; Siegmund, O.; Ertley, C.

    2016-09-01

    Pilot production performance is reported for large area atomic layer deposition (ALD) coated microchannel plates (ALD-GCA-MCPs) and for Large Area Picosecond Photodetectors (LAPPD™) which incorporate them. "Hollowcore" glass capillary array (GCA) substrates are coated with ALD resistive and emissive layers to form the ALDGCA- MCPs, an approach that facilitates independent selection of glass substrates that are mechanically stronger and that have lower levels of radioactive alkali elements compared to conventional MCP lead glass, reducing background noise[1,2,3,4]. ALD-GCA-MCPs have competitive gain ( 104 each or 107 for a chevron pair ), enhanced lifetime and gain stability (7 C cm-2 of charge extraction), reduced background levels (0.028 events cm-2 sec-1) and low gamma-ray detection efficiency. They can be fabricated in large area (20cm X 20 cm) planar and curved formats suitable for use in high radiation environment applications, including astronomy, space instrumentation, and remote night time sensing. The LAPPD™ photodetector incorporates these ALD-GCA-MCPs in an all-glass hermetic package with top and bottom plates and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na2KSb photocathode, amplified with a stacked chevron pair of ALD-GCA-MCPs. Signals are collected on RF strip-line anodes integrated into to the bottom plates which exit the detector via pin-free hermetic seals under the side walls [5]. Tests show that LAPPDTMs have electron gains greater than 107, submillimeter spatial resolution for large (multiphoton) pulses and several mm for single photons, time resolution less than 50 picoseconds for single photons, predicted resolution less than 5 picoseconds for large pulses, high stability versus charge extraction[6], and good uniformity for applications including astrophysics, neutron detection, high energy physics Cherenkov light detection, and quantum-optical photon-correlation experiments.

  10. Picosecond flash spectroscopic studies on ultraviolet stabilizers and stabilized polymers

    NASA Technical Reports Server (NTRS)

    Scott, G. W.

    1982-01-01

    Spectroscopic and excited state decay kinetics are reported for monomeric and polymeric forms of ultraviolet stabilizers in the 2-(2'-hydroxyphenyl)-benzotriazole and 2-hydroxybenzophenone classes. For some of these molecules in various solvents at room temperature, (1) ground state absorption spectra, (2) emission spectra, (3) picosecond time-resolved transient absorption spectra, (4) ground state absorption recovery kinetics, (5) emission kinetics, and (6) transient absorption kinetics are reported. In the solid state at low temperatures, emission spectra and their temperature dependent kinetics up to approximately 200K as well as, in one case, the 12K excitation spectra of the observed dual emission are also reported.

  11. Picosecond Laser Pulse Interactions with Metallic and Semiconducting Surfaces

    DTIC Science & Technology

    1990-01-31

    205. C.A. MacDonald, A.M. Malvezzi and F. Spaepen, "Picosecond Time- Resolved Measurements of Crystallization in Noble Metals," Journal of Applied...Permanent address: Istituto di Fisica Applicata, Pavia, Italy 2. J.M. Liu, H. Kurz and N. Bloembergen. Appl. Phys. Lett., 41, 643 (1982) 3. P.M. Fauchet and...classical theory by: r* 2C (9) which, for the nucleation example above is 17 . The rate of evaporation can be estimated from the kinetic theory of gases

  12. In Vitro picosecond ultrasonics in a single cell

    NASA Astrophysics Data System (ADS)

    Rossignol, C.; Chigarev, N.; Ducousso, M.; Audoin, B.; Forget, G.; Guillemot, F.; Durrieu, M. C.

    2008-09-01

    Ultrasonics signals at frequencies 5.7±0.1 and 6.8±0.1GHz are measured in two organelles of a single vegetal cell in vitro with a picosecond ultrasonic technique. Using standard values for cell optical index, ultrasound velocities of 1.6±0.1 and 2.0±0.1μm/ns are measured from several signals recorded in the vacuole and in the nucleus of a single Allium cepa cell, respectively. A 1μm lateral and 0.25μm depth resolution is attained.

  13. Picosecond imaging of signal propagation in integrated circuits

    NASA Astrophysics Data System (ADS)

    Frohmann, Sven; Dietz, Enrico; Dittrich, Helmar; Hübers, Heinz-Wilhelm

    2017-04-01

    Optical analysis of integrated circuits (IC) is a powerful tool for analyzing security functions that are implemented in an IC. We present a photon emission microscope for picosecond imaging of hot carrier luminescence in ICs in the near-infrared spectral range from 900 to 1700 nm. It allows for a semi-invasive signal tracking in fully operational ICs on the gate or transistor level with a timing precision of approximately 6 ps. The capabilities of the microscope are demonstrated by imaging the operation of two ICs made by 180 and 60 nm process technology.

  14. Mechanical Properties of Nuclear Fuel Surrogates using Picosecond Laser Ultrasonics

    SciTech Connect

    David Hurley; Marat Khafizov; Farhad Farzbod; Eric Burgett

    2013-05-01

    Detailed understanding between microstructure evolution and mechanical properties is important for designing new high burnup nuclear fuels. In this presentation we discuss the use of picosecond ultrasonics to measure localize changes in mechanical properties of fuel surrogates. We develop measurement techniques that can be applied to investigate heterogeneous elastic properties caused by localize changes in chemistry, grain microstructure caused by recrystallization, and mechanical properties of small samples prepared using focused ion beam sample preparation. Emphasis is placed on understanding the relationship between microstructure and mechanical properties

  15. Efficient second harmonic generation of picosecond laser pulses.

    NASA Technical Reports Server (NTRS)

    Rabson, T. A.; Ruiz, H. J.; Shah, P. L.; Tittel, F. K.

    1972-01-01

    Efficient conversion to the second harmonic (SH) using KD2PO4 and CsH2AsO4 crystals inside a folded cavity of a high-power-dye mode-locked neodymium-glass laser is reported. For the first time, frequency-doubled picosecond light pulses have been obtained in CsH2AsO4 with peak powers of the order of 1 GW/sq cm at 0.531 micron for an effective pump power density of 4 GW/sq cm.

  16. High-power picosecond fiber source for coherent Raman microscopy.

    PubMed

    Kieu, Khanh; Saar, Brian G; Holtom, Gary R; Xie, X Sunney; Wise, Frank W

    2009-07-01

    We report a high-power picosecond fiber pump laser system for coherent Raman microscopy (CRM). The fiber laser system generates 3.5 ps pulses with 6 W average power at 1030 nm. Frequency doubling yields more than 2 W of green light, which can be used to pump an optical parametric oscillator to produce the pump and the Stokes beams for CRM. Detailed performance data on the laser and the various wavelength conversion steps are discussed, together with representative CRM images of fresh animal tissue obtained with the new source.

  17. Stimulated parametric fluorescence induced by picosecond pump pulses.

    NASA Technical Reports Server (NTRS)

    Rabson, T. A.; Ruiz, H. J.; Shah, P. L.; Tittel, F. K.

    1972-01-01

    Stimulated parametric fluorescence emission tunable over the range from 0.96 to 1.16 microns has been obtained using a barium sodium niobate crystal pumped by a frequency-doubled and mode-locked neodymium:glass laser. The pump radiation in the form of a train of picosecond pulses produced infrared parametric fluorescence pulses, less than 10 psec in duration and with average peak powers on the order of 300 W when pumped with a power density of 300 MW/sq cm.

  18. Picosecond optical vortex pulse illumination forms a monocrystalline silicon needle

    PubMed Central

    Takahashi, Fuyuto; Miyamoto, Katsuhiko; Hidai, Hirofumi; Yamane, Keisaku; Morita, Ryuji; Omatsu, Takashige

    2016-01-01

    The formation of a monocrystalline silicon needle by picosecond optical vortex pulse illumination was demonstrated for the first time in this study. The dynamics of this silicon needle formation was further revealed by employing an ultrahigh-speed camera. The melted silicon was collected through picosecond pulse deposition to the dark core of the optical vortex, forming the silicon needle on a submicrosecond time scale. The needle was composed of monocrystalline silicon with the same lattice index (100) as that of the silicon substrate, and had a height of approximately 14 μm and a thickness of approximately 3 μm. Overlaid vortex pulses allowed the needle to be shaped with a height of approximately 40 μm without any changes to the crystalline properties. Such a monocrystalline silicon needle can be applied to devices in many fields, such as core–shell structures for silicon photonics and photovoltaic devices as well as nano- or microelectromechanical systems. PMID:26907639

  19. Subsurface imaging of grain microstructure using picosecond ultrasonics

    DOE PAGES

    Khafizov, M.; Pakarinen, J.; He, L.; ...

    2016-04-21

    We report on imaging subsurface grain microstructure using picosecond ultrasonics. This approach relies on elastic anisotropy of crystalline materials where ultrasonic velocity depends on propagation direction relative to the crystal axes. Picosecond duration ultrasonic pulses are generated and detected using ultrashort light pulses. In materials that are transparent or semitransparent to the probe wavelength, the probe monitors GHz Brillouin oscillations. The frequency of these oscillations is related to the ultrasonic velocity and the optical index of refraction. Ultrasonic waves propagating across a grain boundary experience a change in velocity due to a change in crystallographic orientation relative to the ultrasonicmore » propagation direction. This change in velocity is manifested as a change in the Brillouin oscillation frequency. Using the ultrasonic propagation velocity, the depth of the interface can be determined from the location in time of the transition in oscillation frequency. An image of the grain boundary is obtained by scanning the beam along the surface. We demonstrate this volumetric imaging capability using a polycrystalline UO2 sample. As a result, cross section liftout analysis of the grain boundaries using electron microscopy were used to verify our imaging results.« less

  20. Tunable picosecond spectroscopy for detection of nitric oxide

    NASA Astrophysics Data System (ADS)

    Tanjaroon, Chakree; Lue, Christopher J.; Reeve, Scott W.; Johnson, J. Bruce; Allen, Susan D.

    2013-05-01

    Nitric oxide (NO) is a major chemical byproduct of many photochemically active nitrogen-containing compounds. As a prototypical free radical with a very well characterized high-resolution spectrum, NO provides a standard spectroscopic fingerprint for indirect quantitative analysis and detection of a number of low vapor pressure nitroaromatic compounds in air through either direct photochemical decomposition of a parent molecule or from its relatively high vapor pressure chemical constituents. In this paper, we will discuss applications of picosecond laser spectroscopy for measurements and detection of NO and the nascent NO generated from photolysis of nitrobenzene. We will give a general overview of our tunable picosecond laser and detection system that we routinely use for probing and exciting the NO gamma band. This broad wavelength tuning capability of our laser allows us to set up pump-probe type experiments for detecting blue shifted rovibronic bands and probing the relative population distribution for NO. In all cases, experiments were performed using UV laser pulses of duration less than 20 ps. Also, we studied the effect of N2 collisions on the photoframentation spectrum of nitrobenzene in 1000 mbar of N2 buffer gas.

  1. Wavelength scaling of silicon laser ablation in picosecond regime

    NASA Astrophysics Data System (ADS)

    Sikora, A.; Grojo, D.; Sentis, M.

    2017-07-01

    Single pulse laser ablation of silicon has been investigated at 343, 515, and 1030 nm using a laser pulse duration of 50 ps. In this large spectral range, ablation thresholds of silicon vary from 0.01 to 0.83 J/cm2, confirming a strong dependence on the wavelength. By solving the free-carrier density rate equation at threshold conditions, we show that band-to-band linear absorption dominates energy deposition at 343 and 515 nm, whereas at 1030 nm, the energy leading to ablation is primarily absorbed by the generated free-carriers. This allows us to determine the relevant criteria to derive a simple model predicting the wavelength dependence of the ablation threshold in this regime. We obtain an excellent agreement between experimental measurements and calculations by simply considering an averaged energy density required in the absorption depth for surface ablation and accounting for the laser-induced variations of the important thermophysical parameters. On the basis of this analysis, we discuss the optimal wavelength and fluence conditions for maximum removal rate, ablation efficiency, and accuracy. Despite the difference in mechanisms at the different wavelengths, we find that the maximal efficiency remains at around 7 times the ablation threshold fluence for all investigated wavelengths. This work provides guidelines for high-quality and efficient micromachining of silicon in the scarcely explored picosecond regime, while new picosecond sources offer numerous advantages for real throughput industrial applications.

  2. Picosecond lidar techniques in laboratory and field diagnostics

    NASA Astrophysics Data System (ADS)

    Goulard, R.

    1984-12-01

    The availability of picosecond laser systems opens a new potential in the field of diagnostics. It is now possible to observe chemical events over time intervals as short as 10 to the minus 9th power sec (e.g., fluorescence, bond-selective chemistry,...) without overlap with the much shorter 10 to the minus 12th power sec triggering signal. In addition, two specific effects are of special interest to real industrial flame diagnostics. One is the elimination of background noise, since the picosecond time-gating of the detector will collect the whole signal of interest but only a tiny fraction of the time-spread noise background (e.g., soot, walls,...). The other is related to the very short length of these pulses (similar to mm): it is the possibility to use the lidar/radar principle to convert the time history of the measured back scattered signals into a millimeter-resolved space distribution along the beam. In this fashion, Raman and other techniques can yield a detailed map of concentrations and temperatures in three-dimensional space, even in sooty combustors background, with the need of only one single porthole.

  3. Picosecond and femtosecond laser ablation of hard tissues

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexander A.; Makropoulou, Mersini I.; Kar, Ajoy K.; Khabbaz, Marouan

    1996-12-01

    In this study, the interaction of picosecond and femtosecond pulsed laser radiation with human dental tissue was investigated experimentally, as this unexplored field is expected to be a potential alternative in powerful laser processing of biomedical structures. Dentin ablation rate experiments were performed by using teeth sections of different thickness. Dental tissue samples were irradiated in air with i) a regenerative amplifier laser at 1064 nm, pulse duration 110 ps, ii) the second harmonic laser at 532 nm, pulse duration 100 ps, and iii) a picosecond tunable dye amplifier at 595 nm, pulse width 800 fs. In all the experiments the pulse repetition rate was 10 Hz. The ablation rate per pulse at different energy fluence settings was calculated by measuring the time needed for the perforation of the whole dental sample thickness. Short laser pulses can confine thermal energy within the optical zone, which maximizes photothermal and photomechanical mechanisms of interaction. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage.

  4. Subsurface imaging of grain microstructure using picosecond ultrasonics

    SciTech Connect

    Khafizov, M.; Pakarinen, J.; He, L.; Henderson, H. B.; Manuel, M. V.; Nelson, A. T.; Jaques, B. J.; Butt, D. P.; Hurley, David H.

    2016-04-21

    We report on imaging subsurface grain microstructure using picosecond ultrasonics. This approach relies on elastic anisotropy of crystalline materials where ultrasonic velocity depends on propagation direction relative to the crystal axes. Picosecond duration ultrasonic pulses are generated and detected using ultrashort light pulses. In materials that are transparent or semitransparent to the probe wavelength, the probe monitors GHz Brillouin oscillations. The frequency of these oscillations is related to the ultrasonic velocity and the optical index of refraction. Ultrasonic waves propagating across a grain boundary experience a change in velocity due to a change in crystallographic orientation relative to the ultrasonic propagation direction. This change in velocity is manifested as a change in the Brillouin oscillation frequency. Using the ultrasonic propagation velocity, the depth of the interface can be determined from the location in time of the transition in oscillation frequency. An image of the grain boundary is obtained by scanning the beam along the surface. We demonstrate this volumetric imaging capability using a polycrystalline UO2 sample. As a result, cross section liftout analysis of the grain boundaries using electron microscopy were used to verify our imaging results.

  5. Studies on laser material processing with nanosecond and sub-nanosecond and picosecond and sub-picosecond pulses

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Tao, Sha; Wang, Brian; Zhao, Jay

    2016-03-01

    In this paper, laser ablation of widely used metal (Al, Cu. stainless-steel), semiconductor (Si), transparent material (glass, sapphire), ceramic (Al2O3, AlN) and polymer (PI, PMMA) in industry were systematically studied with pulse width from nanosecond (5-100ns), picosecond (6-10ps) to sub-picosecond (0.8-0.95ps). A critical damage zone (CDZ) of up to 100um with ns laser, <=50um with ps laser, and <=20um with sub-ps laser, respectively was observed as a criteria of selecting the laser pulse width. The effects of laser processing parameters on speed and efficiency were also investigated. This is to explore how to provide industry users the best laser solution for device micro-fabrication with best price. Our studies of cutting and drilling with ns, ps, and sub-ps lasers indicate that it is feasible to achieve user accepted quality and speed with cost-effective and reliable laser by optimizing processing conditions.

  6. Picosecond-petawatt laser-block ignition for avalanche fusion of boron by ultrahigh acceleration and ultrahigh magnetic fields

    NASA Astrophysics Data System (ADS)

    Hora, H.; Lalousis, P.; Giuffrida, L.; Margarone, D.; Korn, G.; Eliezer, S.; Miley, G. H.; Moustaizis, S.; Mourou, G.; Barty, C. P. J.

    2016-05-01

    Fusion energy from reacting hydrogen (protons) with the boron isotope 11 (HB11) resulting in three stable helium nuclei, is without problem of nuclear radiation in contrast to DT fusion. But the HB11 reaction driven by nanosecond laser pulses with thermal compression and ignition by lasers is extremely difficult. This changed radically when irradiation with picosecond laser pulses produces a non-thermal plasma block ignition with ultrahigh acceleration. This uses the nonlinear (ponderomotive) force to surprizingly resulting in same thresholds as DT fusion even under pessimistic assumption of binary reactions. After evaluation of reactions trapped cylindrically by kilotesla magnetic fields and using the measured highly increased HB11 fusion gains for the proof of an avalanche of the three alphas in secondary reactions, possibilities for an absolutely clean energy source at comptitive costs were concluded.

  7. Simultaneous High-Resolution 2-Dimensional Spatial and 1-Dimensional Picosecond Streaked X-ray Pinhole Imaging

    SciTech Connect

    Steel, A B; Nagel, S R; Dunn, J; Baldis, H A

    2012-05-03

    A Kentech x-ray streak camera was run at the LLNL Compact Multipulse Terawatt (COMET) laser to record simultaneous space- and time-resolved measurements of picosecond laser-produced plasmas. Four different x-ray energy channels were monitored using broad-band filters to record the time history of Cu targets heated at irradiances of 10{sup 16} - 10{sup 19} W/cm{sup 2}. Through the Cu filter channel, a time-resolution below 3ps was obtained. Additionally, an array of 10 {micro}m diameter pinholes was placed in front of the camera to produce multiple time-resolved x-ray images on the photocathode and time-integrated images on the phosphor with 10 and 15 times magnification, respectively, with spatial resolution of <13 {micro}m.

  8. Picosecond excitonic absorption recovery of 100 nm GaAs/AlGaAs narrow multiple quantum-well wires

    NASA Astrophysics Data System (ADS)

    Tackeuchi, Atsushi; Kitada, Hideki; Arimoto, Hiroshi; Sugiyama, Yoshihiro; Endoh, Akira; Nakata, Yoshiaki; Inata, Tsuguo; Muto, Shunichi

    1991-08-01

    We report the time-resolved absorption measurement of narrow multiple quantum-well (MQW) wires to investigate their fast recoveries from excitonic absorption bleaching. Wires down to 130 nm were fabricated from MQWs using focused ion beam lithography and electron cyclotron-resonance chlorine-plasma etching. In this structure, the photoexcited carriers diffuse toward the sidewalls and recombine on the surface of the sidewalls. We show that the strong optical nonlinearity of excitons is preserved, even in wires of 130 nm width, and having a fast recovery time in the picosecond region. We also briefly discuss the possibility of making quantum wires which have a faster recovery time and larger optical nonlinearity.

  9. Simultaneous picosecond and femtosecond solitons delivered from a nanotube-mode-locked all-fiber laser.

    PubMed

    Han, D D; Liu, X M; Cui, Y D; Wang, G X; Zeng, C; Yun, L

    2014-03-15

    We propose a compact nanotube-mode-locked all-fiber laser that can simultaneously generate picosecond and femtosecond solitons at different wavelengths. The pulse durations of picosecond and femtosecond solitons are measured to be ∼10.6  ps and ∼466  fs, respectively. Numerical results agree well with the experimental observations and clearly reveal that the dynamic evolutions of the picosecond and femtosecond solitons are qualitatively distinct in the intracavity. Our study presents a simple, stable, low-cost, and dual-scale ultrafast-pulsed laser source suitable for practical applications in optical communications.

  10. Optimally shaped narrowband picosecond pulses for femtosecond stimulated Raman spectroscopy.

    PubMed

    Hoffman, David P; Valley, David; Ellis, Scott R; Creelman, Mark; Mathies, Richard A

    2013-09-09

    A comparison between a Fabry-Pérot etalon filter and a conventional grating filter for producing the picosecond (ps) Raman pump pulses for femtosecond stimulated Raman spectroscopy (FSRS) is presented. It is shown that for pulses of equal energy the etalon filter produces Raman signals twice as large as that of the grating filter while suppressing the electronically resonant background signal. The time asymmetric profile of the etalon-generated pulse is shown to be responsible for both of these observations. A theoretical discussion is presented which quantitatively supports this hypothesis. It is concluded that etalons are the ideal method for the generation of narrowband ps pulses for FSRS because of the optical simplicity, efficiency, improved FSRS intensity and reduced backgrounds.

  11. Ultrahigh speed photography of picosecond light pulses and echoes.

    PubMed

    Duguay, M A; Mattick, A T

    1971-09-01

    Three new results have been obtained with a recently developed camera of 10-psec framing time: (1) The effect of the finite speed of light in photographing relativistic objects is experimentally demonstrated, by photographing a dumbbell-like entity formed by two packets of light. In contrast to material objects, which, theory predicts, should appear rotated, the light dumbbell appears sheared. (2) Photographs of the mode-locked Nd: glass laser radiation show numerous subsidiary pulses accompanying the main ultrashort pulses in the train. The latter have durations ranging from 7 psec to 15 psec. (3) The technique of gated picture ranging, previously used with nanosecond pulses, is extended to the picosecond range where a resolution of 1 cm is demonstrated. Some potentially useful applications are proposed.

  12. Picosecond pulse radiolysis of the liquid diethyl carbonate.

    PubMed

    Torche, Fayçal; El Omar, Abdel Karim; Babilotte, Philippe; Sorgues, Sébastien; Schmidhammer, Uli; Marignier, Jean-Louis; Mostafavi, Mehran; Belloni, Jacqueline

    2013-10-24

    The diethyl carbonate, DEC, is an ester that is used as a solvent in Li-ion batteries, but its behavior under ionizing radiation was unknown. The transient optical absorption spectra, the decay kinetics, and the influence of various scavengers have been studied by using the picosecond laser-triggered electron accelerator ELYSE. In neat DEC, the intense near-IR (NIR) absorption spectrum is assigned to the solvated electron. It is overlapped in the visible range by another transient but longer-lived and less intense band that is assigned to the oxidized radical DEC(-H). The solvated electron molar absorption coefficients and radiolytic yield evolution from 25 ps, the geminate recombination kinetics, and the rate constants of electron transfer reactions to scavengers are determined. The radiolytic mechanism, indicating a certain radioresistance of DEC, is compared with that for other solvents.

  13. Picosecond Control of Quantum Dot Laser Emission by Coherent Phonons

    NASA Astrophysics Data System (ADS)

    Czerniuk, T.; Wigger, D.; Akimov, A. V.; Schneider, C.; Kamp, M.; Höfling, S.; Yakovlev, D. R.; Kuhn, T.; Reiter, D. E.; Bayer, M.

    2017-03-01

    A picosecond acoustic pulse can be used to control the lasing emission from semiconductor nanostructures by shifting their electronic transitions. When the active medium, here an ensemble of (In,Ga)As quantum dots, is shifted into or out of resonance with the cavity mode, a large enhancement or suppression of the lasing emission can dynamically be achieved. Most interesting, even in the case when gain medium and cavity mode are in resonance, we observe an enhancement of the lasing due to shaking by coherent phonons. In order to understand the interactions of the nonlinearly coupled photon-exciton-phonon subsystems, we develop a semiclassical model and find an excellent agreement between theory and experiment.

  14. Sub-Picosecond, High Flux, Thomson X-Ray Sources

    SciTech Connect

    James Boyce; David Douglas; Hiroyuki Toyokawa; Winthrop J. Brown; Fred Hartemann

    2003-05-12

    With the advent of high average power FELs, the idea of using such a device to produce x-rays via the Thomson scattering process is appealing, if sufficient flux and/or brightness can be generated. Such x-rays are produced simultaneously with FEL light, offering unprecedented opportunities for pump-probe studies. We discuss non-invasive modifications to the Jefferson Lab's FEL that would meet the criteria of high flux, sub-picosecond, x-ray source. One allows proof-of-principle experiments, is relatively inexpensive, but is not conducive as a ''User-facility.'' Another is a User facility configuration but requires FEL facility modifications. For all sources, we present Thomson scattering flux calculations and potential applications.

  15. Picosecond amorphization of SiO2 stishovite under tension

    PubMed Central

    Misawa, Masaaki; Ryuo, Emina; Yoshida, Kimiko; Kalia, Rajiv K.; Nakano, Aiichiro; Nishiyama, Norimasa; Shimojo, Fuyuki; Vashishta, Priya; Wakai, Fumihiro

    2017-01-01

    It is extremely difficult to realize two conflicting properties—high hardness and toughness—in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested “high-density glass polymorphs” before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids. PMID:28508056

  16. Picosecond amorphization of SiO2 stishovite under tension.

    PubMed

    Misawa, Masaaki; Ryuo, Emina; Yoshida, Kimiko; Kalia, Rajiv K; Nakano, Aiichiro; Nishiyama, Norimasa; Shimojo, Fuyuki; Vashishta, Priya; Wakai, Fumihiro

    2017-05-01

    It is extremely difficult to realize two conflicting properties-high hardness and toughness-in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested "high-density glass polymorphs" before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids.

  17. Picosecond pulse generated supercontinuum as a stable seed for OPCPA.

    PubMed

    Indra, Lukáš; Batysta, František; Hříbek, Petr; Novák, Jakub; Hubka, Zbyněk; Green, Jonathan T; Antipenkov, Roman; Boge, Robert; Naylon, Jack A; Bakule, Pavel; Rus, Bedřich

    2017-02-15

    We present a stable supercontinuum (SC) generated in a bulk YAG crystal, pumped by 3 ps chirped pulses at 1030 nm. The SC is generated in a loose focus geometry in a 13 cm long YAG crystal, allowing for stable and robust single-filament generation. The SC energy stability exceeds that of the pump laser by almost a factor of 3. Additionally, we show that the SC spectrum has long-term stability and that the SC is coherent and compressible by compressing the portions of SC spectra close to the corresponding Fourier limit. This makes the picosecond-pulse-driven SC a suitable stable seed for OPCPA amplifiers.

  18. Optical limiting and picosecond relaxation of carbocyanines upper electronic states

    NASA Astrophysics Data System (ADS)

    Oulianov, D. A.; Dvornikov, A. S.; Rentzepis, P. M.

    2002-05-01

    Nonlinear absorption, anomalous fluorescence and relaxation of high-lying electronic states in six carbocyanine dyes, including cryptocyanine (DCI), DDI, DTDCI, DTTCI, DOTCI and HDIDCI, in solution and in polymer, were studied by means of picosecond transient absorption spectroscopy and nonlinear transmission experiments. Absorption cross-sections of the S 1→S n transition, and decay rates of the second singlet excited state, S 2, were measured. All dyes showed strong reverse saturable absorption in the 450-600 nm region with large excited to ground state absorption cross-section ratios. For DTDCI this ratio, at 470 nm, was measured to be 350, which is the largest ever reported. All molecules have shown strong optical limiting effect. However, in all molecules except DCI a saturation of the optical limiting process was observed as expected, owing to relatively long, up to 17.5 ps, lifetime of the S 2 state. The S 2 state fluorescence quantum yields were also measured.

  19. Picosecond laser-induced water condensation in a cloud chamber.

    PubMed

    Sun, Haiyi; Liu, Yonghong; Ju, Jingjing; Tian, Ye; Bai, Yafeng; Liu, Yaoxiang; Du, Shengzhe; Wang, Cheng; Wang, Tiejun; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2016-09-05

    We investigated water condensation in a laboratory cloud chamber induced by picosecond (ps) laser pulses at ~350 ps (800 nm/1-1000 Hz) with a maximum peak power of ~25 MW. The peak power was much lower than the critical power for self-focusing in air (~3-10 GW depending on the pulse duration). Sparks, airflow and snow formation were observed under different laser energies or repetition rates. It was found that weaker ps laser pulses can also induce water condensation by exploding and breaking down ice crystals and/or water droplets into tiny particles although there was no formation of laser filament. These tiny particles would grow until precipitation in a super-saturation zone due to laser-induced airflow in a cold region with a large temperature gradient.

  20. Picosecond pulse measurements using the active laser medium

    NASA Technical Reports Server (NTRS)

    Bernardin, James P.; Lawandy, N. M.

    1990-01-01

    A simple method for measuring the pulse lengths of synchronously pumped dye lasers which does not require the use of an external nonlinear medium, such as a doubling crystal or two-photon fluorescence cell, to autocorrelate the pulses is discussed. The technique involves feeding the laser pulses back into the dye jet, thus correlating the output pulses with the intracavity pulses to obtain pulse length signatures in the resulting time-averaged laser power. Experimental measurements were performed using a rhodamine 6G dye laser pumped by a mode-locked frequency-doubled Nd:YAG laser. The results agree well with numerical computations, and the method proves effective in determining lengths of picosecond laser pulses.

  1. 157 W all-fiber high-power picosecond laser.

    PubMed

    Song, Rui; Hou, Jing; Chen, Shengping; Yang, Weiqiang; Lu, Qisheng

    2012-05-01

    An all-fiber high-power picosecond laser is constructed in a master oscillator power amplifier configuration. The self-constructed fiber laser seed is passively mode locked by a semiconductor saturable absorber mirror. Average output power of 157 W is obtained after three stages of amplification at a fundamental repetition rate of 60 MHz. A short length of ytterbium double-clad fiber with a high doping level is used to suppress nonlinear effects. However, a stimulated Raman scattering (SRS) effect occurs owing to the 78 kW high peak power. A self-made all-fiber repetition rate increasing system is used to octuple the repetition rate and decrease the high peak power. Average output power of 156.6 W is obtained without SRS under the same pump power at a 480 MHz repetition rate with 0.6 nm line width.

  2. Picosecond energy transfer in Porphyridium cruentum and Anacystis nidulans.

    PubMed Central

    Brody, S S; Treadwell, C; Barber, J

    1981-01-01

    Picosecond energy transfer is measured in Anacystis nidulans and Porphyridium cruentum. Fluorescence is sensitized by a 6-ps laser flash, at 530 nm. The time dependence of fluorescence is measured with reference to the laser pulse. Fluorescence is recorded from phycoerythrin (576 nm), R-phycocyanin (640 nm), allophycocyanin (666 nm), Photosystem II chlorophyll (690 nm) and long wave length chlorophyll (715 nm). Energy transfer measurements are made at 37 degrees C, 23 degrees C, and 0 degrees C, and 77 degrees K. It is shown that the rate of energy transfer can be varied with temperature. In both A. nidulans and P. cruentum there is a sequential transfer of excitation energy from phycoerythrin to phycocyanin to allophycocyan to Photosystem II chlorophyll fluorescence. The long wavelength chlorophyll fluorescence at 715 nm, however, does not always follow a sequential transfer of excitation energy. Depending on the temperature, fluorescence at 715 nm can precede fluorescence from phycocyanin. PMID:6788106

  3. Generation and detection of incoherent phonons in picosecond ultrasonics.

    PubMed

    Perrin, B; Péronne, E; Belliard, L

    2006-12-22

    In picosecond ultrasonics experiments the absorption of a femtosecond laser pulse in a thin metallic transducer is used to generate very short acoustic pulses. These pulses are made of coherent longitudinal waves with a frequency spectrum that can reach 100-200 GHz. The laser pulse absorption gives rise to a heating of the film of a few Kelvin within a typical time of 1 ps. Later on, the heat goes in the substrate through an interface thermal resistance and is diffused by thermal conduction. At very low temperature and in pure crystals the thermal phonons emitted by the heated metallic film can propagate ballistically over large distances and produce a so-called heat pulse. We report on the experimental evidence of the coexistence of the coherent acoustic pulse and the incoherent heat pulse generated and detected by laser ultrasonics.

  4. Picosecond Acoustic Measurement of Anisotropic Properties of Thin Films

    SciTech Connect

    Perton, M.; Rossignol, C.; Chigarev, N.; Audoin, B.

    2007-03-21

    Properties of thin metallic films have been studied extensively by means of laser-picosecond ultrasonics. Generation of longitudinal and shear waves via thermoelastic mechanism and large source has been only demonstrated for waves vectors along the normal to the interface. However, such measurements cannot provide complete information about elastic properties of films. As it has been already shown for nanosecond ultrasonics, the knowledge of group or phase velocities in several directions for sources with small lateral size allows determining the stiffness tensor coefficients of a sample. The experimental set-up was prepared to obtain the thinnest size for the source to achieve acoustic diffraction. The identification of the stiffness tensor components, based on the inversion of the bulk waves phase velocities, is applied to signals simulated and experimentally recorded for a material with hexagonal properties. First estimation of stiffness tensor coefficients for thin metallic film 2.1 {mu}m has been performed.

  5. Plasmon-driven sub-picosecond breathing of metal nanoparticles.

    PubMed

    Bonafé, Franco P; Aradi, Bálint; Guan, Mengxue; Douglas-Gallardo, Oscar A; Lian, Chao; Meng, Sheng; Frauenheim, Thomas; Sánchez, Cristián G

    2017-08-31

    We present the first real-time atomistic simulation on the quantum dynamics of icosahedral silver nanoparticles under strong laser pulses, using time dependent density functional theory (TDDFT) molecular dynamics. We identify the emergence of sub-picosecond breathing-like radial oscillations starting immediately after laser pulse excitation, with increasing amplitude as the field intensity increases. The ultrafast dynamic response of nanoparticles to laser excitation points to a new mechanism other than equilibrium electron-phonon scattering previously assumed, which takes a much longer timescale. A sharp weakening of all bonds during laser excitation is observed, thanks to plasmon damping into excited electrons in anti-bonding states. This sudden weakening of bonds leads to a uniform expansion of the nanoparticles and launches coherent breathing oscillations.

  6. Femtosecond stimulated Raman scattering picosecond molecular thermometry in condensed phases.

    PubMed

    Dang, N C; Bolme, C A; Moore, D S; McGrane, S D

    2011-07-22

    We demonstrate the capability of femtosecond stimulated Raman scattering (FSRS) data to measure the temperature of condensed matter at the molecular vibrational level. We report the temperature dependence of Raman loss to Raman gain ratios for low frequency modes (<300  cm(-1)) in a CaCO3 single crystal from cryogenic to room temperature, which is shown to be in agreement with theoretical predictions. We also report the measurements of nonequilibrium time evolution of mode specific vibrational temperatures in the CaCO3 single crystal to demonstrate that FSRS can measure temperature on picosecond time scales. Finally, we point out the unique origin of this temperature dependent anti-Stokes to Stokes ratio in stimulated Raman, which is not present in other coherent Raman spectroscopies. These measurements require no material dependent parameters or prior calibration.

  7. Three-dimensional imaging of biological cells with picosecond ultrasonics

    NASA Astrophysics Data System (ADS)

    Danworaphong, Sorasak; Tomoda, Motonobu; Matsumoto, Yuki; Matsuda, Osamu; Ohashi, Toshiro; Watanabe, Hiromu; Nagayama, Masafumi; Gohara, Kazutoshi; Otsuka, Paul H.; Wright, Oliver B.

    2015-04-01

    We use picosecond ultrasonics to image animal cells in vitro—a bovine aortic endothelial cell and a mouse adipose cell—fixed to Ti-coated sapphire. Tightly focused ultrashort laser pulses generate and detect GHz acoustic pulses, allowing three-dimensional imaging (x, y, and t) of the ultrasonic propagation in the cells with ˜1 μm lateral and ˜150 nm depth resolutions. Time-frequency representations of the continuous-wavelet-transform amplitude of the optical reflectivity variations inside and outside the cells show GHz Brillouin oscillations, allowing the average sound velocities of the cells and their ultrasonic attenuation to be obtained as well as the average bulk moduli.

  8. Semiconductor Characterization with Acoustic and Thermal waves on Picosecond Timescales

    NASA Astrophysics Data System (ADS)

    Wright, Oliver B.

    1997-03-01

    Ultrafast optical techniques for semiconductor characterization can probe the dynamics of photoexcited carriers, leading to applications in, for example, in-line monitoring of semiconductor processing and optimization of materials for sub-picosecond electronic switches or for nanoscale electronic devices.(Semiconductors Probed by Ultrafast Laser Spectroscopy, edited by R. R. Alfano (Academic, New York, 1984).) Picosecond or femtosecond optical pulses excite electrons to higher electronic bands, producing a nonequilibrium electron-hole distribution. Various physical effects result from the relaxation of this distribution. Luminescence or photoelectron emission are examples. In the present study the focus is on acoustic and thermal effects. The change in electron and hole occupation probabilities induces an electronic stress distributed throughout the carrier penetration depth. A temperature change of the lattice and an associated thermal stress are also produced. The combined stress distribution launches a strain pulse that propagates into the sample as a longitudinally polarized acoustic wave in the present experiments. Its reflection from sub-surface boundaries, interfaces or defects can be detected at the surface by another, weaker optical probe pulse. During this time the temperature distribution in the semiconductor also changes due to thermal wave propagation,(Photoacoustic and Thermal Wave Phenomena in Semiconductors, edited by Andreas Mandelis (North Holland, New York, 1987).) and this simultaneously influences the optical probe pulse. Both reflectance modulation and beam deflection methods for probing were used to investigate crystalline and amorphous silicon samples.(O. B. Wright, U. Zammit, M. Marinelli, and V. Gusev, Appl. Phys. Lett. 69, 553 (1996).) (O. B. Wright and V. E. Gusev, Appl. Phys. Lett. 66, 1190 (1995).) (O. B. Wright and K. Kawashima, Phonon Scattering in Condensed Matter VII, edited by R. O. Pohl and M. Meissner, Springer Verlag, Berlin

  9. Ultrafast Optical Beam Deflection in a Planar Waveguide for High Dynamic Range Recording at Picosecond Resolution

    SciTech Connect

    Sarantos, C H; Heebner, J E

    2008-07-02

    We report the latest performance of an ultrafast, all-optical beam deflector based on a prism array imprinted in a planar waveguide. The deflector enables single-shot, high dynamic range optical recording with picosecond resolution.

  10. Comparative shock wave analysis during corneal ablation with an excimer laser, picosecond laser, and femtosecond laser

    NASA Astrophysics Data System (ADS)

    Krueger, Ronald R.; Juhasz, Tibor

    1995-05-01

    With the event of topographic steep central islands following excimer laser surgery and the potential damage to the corneal endothelium, shock waves are playing an increasingly important role in laser refractive surgery. With this in mind, we performed a comparative shock wave analysis in corneal tissue using an excimer laser, picosecond laser, and femtosecond laser. We used a Lambda Physik excimer laser at 308 nm wavelength, a Nd:YLF picosecond laser at 1053 nm wavelength and a synchronously pumped linear cavity femtosecond laser at 630 nm wavelength. The pulse widths of the corresponding lasers were 8 ns, 18 ps, 150 fs, respectively. The energy density of irradiation was 2.5 to 8 times the threshold level being 2 J/cm2 (excimer laser), 86 J/cm2 (picosecond laser) and 10.3 J/cm2 (femtosecond laser). Shock wave dynamics were analyzed using time-resolved photography on a nanosecond time scale using the picosecond laser in corneal tissue, water and air. Shock wave dynamics using the femtosecond laser were studied in water only while the excimer laser induced shock wave during corneal ablation was studied in air only. We found the dynamics of shock waves to be similar in water and corneal tissue indicating that water is a good model to investigate shock wave effects in the cornea. The magnitude of the shock wave velocity and pressure decays over time to that of a sound wave. The distance over which it decays is 3 mm in air with the excimer laser and 600 - 700 micrometers in air with the picosecond laser. In water, the picosecond laser shock wave decays over a distance of 150 micrometers compared to the femtosecond laser shock wave which decays over a distance of 30 micrometers . Overall the excimer laser shock wave propagates 5 times further than that of the picosecond laser and the picosecond laser shock wave propagates 5 times further than that of the femtosecond laser. In this preliminary comparison, the time and distance for shock wave decay appears to be directly

  11. Direct observation of the orientational Kerr effect in the self-focusing of picosecond pulses.

    NASA Technical Reports Server (NTRS)

    Reintjes, J.; Carman, R. L.

    1972-01-01

    Direct measurements of the relaxation time of the birefringence within the self-focusing region of mode-locked laser pulses in several anisotropic liquids establish the importance of the orientational Kerr effect in the picosecond time regime. This result leads to some speculation as to the origin of the high degree of symmetry in the phase-modulated filament spectra observed with picosecond pulses.

  12. Synthesis of picosecond pulses by spectral compression and shaping of femtosecond pulses in engineered quadratic nonlinear media.

    PubMed

    Marangoni, M; Brida, D; Conforti, M; Capobianco, A D; Manzoni, C; Baronio, F; Nalesso, G F; De Angelis, C; Ramponi, R; Cerullo, G

    2009-02-01

    Narrow-bandwidth picosecond pulses of predetermined spectral and temporal shapes are generated with high efficiency by frequency conversion of femtosecond pulses in lithium tantalate crystals with engineered quasi-phase-matching structures. We give examples of the synthesis of Gaussian and super-Gaussian picosecond pulses and also of a pair of synchronized phase-coherent picosecond pulses with a predetermined carrier-frequency difference.

  13. Oscillations of absorption of a probe picosecond light pulse caused by its interaction with stimulated picosecond emission of GaAs

    SciTech Connect

    Ageeva, N. N.; Bronevoi, I. L. Zabegaev, D. N.; Krivonosov, A. N.

    2015-04-15

    The self-modulation of absorption of a picosecond light pulse was observed earlier [1] in a thin (∼1-μm thick) GaAs layer pumped by a high-power picosecond pulse. Analysis of the characteristics of this self-modulation predicted [5] that the dependences of the probe pulse absorption on the pump pulse energy and picosecond delay between pump and probe pulses should be self-modulated by oscillations. Such self-modulation was experimentally observed in this work. Under certain conditions, absorption oscillations proved to be a function of part of the energy of picosecond stimulated emission of GaAs lying above a certain threshold in the region where the emission front overlapped the probe pulse front. Absorption oscillations are similar to self-modulation of the GaAs emission characteristics observed earlier [4]. This suggests that the self-modulation of absorption and emission is determined by the same type of interaction of light pulses in the active medium, the physical mechanism of which has yet to be determined.

  14. Micromachining with picosecond double pulses on silicon and aluminium

    NASA Astrophysics Data System (ADS)

    Wojakowski, B.; Suttmann, O.; Klug, U.; Kling, R.

    2009-02-01

    Laser double pulses offer interesting opportunities to increase the ablation performance of ultra short laser pulses. In recent published and performed experiments we have presented an optical setup that covers delay times from some picosecond up to 20 ns as well as first experimental results of ablating aluminium and silicon. In this paper we present further results of especially interesting time domains for both materials. The ablation efficiency on silicon with inter pulse delays from 6.3 ns to 15 ns was investigated. In this range the double pulse effect was mainly depending on the fluency. The double pulse efficiency increase is connected with a higher thermal impact on the work piece. The change of delay and repetition rate has no influence on the ablation efficiency for both single and double pulses. The experiments on aluminium concentrated on the pulse delays of 50 ps to 400 ps. The ablation depth per pulse is lower than for single pulse ablation in this range. Double pulse efficiency decreases up to a pulse delay of 150 ps.

  15. Advantages offered by high average power picosecond lasers

    NASA Astrophysics Data System (ADS)

    Moorhouse, C.

    2011-03-01

    As electronic devices shrink in size to reduce material costs, device size and weight, thinner material thicknesses are also utilized. Feature sizes are also decreasing, which is pushing manufacturers towards single step laser direct write process as an attractive alternative to conventional, multiple step photolithography processes by eliminating process steps and the cost of chemicals. The fragile nature of these thin materials makes them difficult to machine either mechanically or with conventional nanosecond pulsewidth, Diode Pumped Solids State (DPSS) lasers. Picosecond laser pulses can cut materials with reduced damage regions and selectively remove thin films due to the reduced thermal effects of the shorter pulsewidth. Also, the high repetition rate allows high speed processing for industrial applications. Selective removal of thin films for OLED patterning, silicon solar cells and flat panel displays is discussed, as well as laser cutting of transparent materials with low melting point such as Polyethylene Terephthalate (PET). For many of these thin film applications, where low pulse energy and high repetition rate are required, throughput can be increased by the use of a novel technique to using multiple beams from a single laser source is outlined.

  16. The lartge-area picosecond photo-detector (LAPPD) project

    NASA Astrophysics Data System (ADS)

    Varner, Gary

    2012-03-01

    The technological revolution that replaced the bulky Cathode Ray Tube with a wide variety of thin, reduced-cost display technologies, has yet to be realized for photosensors. Such a low-cost, robust and flexible photon detector, capable of efficient single photon measurement with good spatial and temporal resolution, would have numerous scientific, medical and industrial applications. To address the significant technological challenges of realizing such a disruptive technology, the Large Area Picosecond Photo-Detector (LAPPD) collaboration was formed, and has been strongly supported by the Department of Energy. This group leverages the inter-disciplinary capabilities and facilities at Argonne National Laboratory, the Berkeley Space Sciences Laboratory (SSL), electronics expertise at the Universities of Chicago and Hawaii, and close work with industrial partners to extend the known technologies. Advances in theory-inspired design and in-situ photocathode characterization during growth, Atomic Layer Deposition (ALD) for revolutionizing micro-channel plate fabrication, and compact, wave-form sampling CMOS ASIC readout of micro striplines are key tools toward realizing a viable LAPPD device. Progress toward a first 8" x 8" demonstrator module will be presented.

  17. Picosecond laser photolysis studies of DMA DMPP in solution

    NASA Astrophysics Data System (ADS)

    Miyasaka, Hiroshi; Itaya, Akira; Rotkiewicz, Krystyna; Rechthaler, Karl

    1999-07-01

    Picosecond transient absorption spectra of: 4-(4'- N,N-dimethylaminophenyl)-3,5-dimethyl-1,7-diphenyl-bis-pyrazolo-[3,4-b;4',3'-e]-pyridine (DMA-DMPP), 3,5-dimethyl-1,7-diphenyl-bis-pyrazolo-[3,4-b;4',3'-e]-pyridine (BPP) and 3,5-dimethyl-1,4,7-triphenyl-bis-pyrazolo-[3,4-b;4',3'-e]-pyridine (H-DMPP) were measured in solvents of different polarity. The results revealed the previously postulated change of the character of the fluorescing state from a primary excited, low polar state in non-polar solvents to a CT state in highly polar ones. Transient absorption spectra in the equilibrium fluorescent state of DMA-DMPP in polar solvents comprised the band ascribable to the cation radical of the DMA moiety. The charge transfer process is fastest in methanol and acetonitrile; in the former it is not controlled by a dynamic Stokes shift.

  18. Sub-picosecond Resolution Time-to-Digital Converter

    SciTech Connect

    Ph D, Vladimir Bratov; Ph D, Vladimir Katzman; MS EE, Jeb Binkley

    2006-03-30

    Time-to-digital converters with sub-picosecond resolutions are needed to satisfy the requirements of time-on-flight measurements of the next generation of high energy and nuclear physics experiments. The converters must be highly integrated, power effective, low cost, and feature plug-and-play capabilities to handle the increasing number of channels (up to hundreds of millions) in future Department of Energy experiments. Current state-off-the-art time-to-digital converter integrated circuits do not have the sufficient degree of integration and flexibility to fulfill all the described requirements. During Phase I, the Advanced Science and Novel Technology Company in cooperation with the nuclear physics division of the Oak Ridge National Laboratory has developed the architecture of a novel time-to-digital converter with multiple channels connected to an external processor through a special interfacing block and synchronized by clock signals generated by an internal phase-locked loop. The critical blocks of the system including signal delay lines and delay-locked loops with proprietary differential delay cells, as well as the required digital code converter and the clock period counter have been designed and simulated using the advanced SiGe120 BiCMOS technological process. The results of investigations demonstrate a possibility to achieve the digitization accuracy within 1ps. ADSANTEC has demonstrated the feasibility of the proposed concept in computer simulations. The proposed system will be a critical component for the next generation of NEP experiments.

  19. A Sub-Picosecond Photon Pulse Facility for SLAC

    SciTech Connect

    Cornacchia, Max

    2001-08-28

    It is possible to generate very bright sub-picosecond pulses of spontaneous x-ray radiation utilizing the electron beam from the SLAC linear accelerator and an undulator. The present injection-damping ring system used to inject into the PEP-II B-Factory can be used for this purpose, without any modification to the linear accelerator except for a sequence of 4 bending magnets to compress the electron bunch. With a charge of 3.4 nC per bunch accelerated to 28 GeV and a 10 m long undulator it is quite feasible to generate pulses of x-rays of 8.3 kV energy (in a spectrum extending to over 1 MeV), 80 fsec long (full-width-half-maximum), with a peak brightness of the order of 10{sup 25} photons/(sec x mm{sup 2} x mrad{sup 2} x 0.1% bandwidth), and 10{sup 8} photons per pulse in a 0.1% bandwidth. This facility could be built and operated ahead of the LCLS schedule and would provide both a powerful tool for research in its own right, as well as a way to conduct critical accelerator and x-ray optics R and D for the LCLS.

  20. Direct fluorescence characterisation of a picosecond seeded optical parametric amplifier

    NASA Astrophysics Data System (ADS)

    Stuart, N. H.; Bigourd, D.; Hill, R. W.; Robinson, T. S.; Mecseki, K.; Patankar, S.; New, G. H. C.; Smith, R. A.

    2015-02-01

    The temporal intensity contrast of high-power lasers based on optical parametric amplification (OPA) can be limited by parametric fluorescence from the non-linear gain stages. Here we present a spectroscopic method for direct measurement of unwanted parametric fluorescence widely applicable from unseeded to fully seeded and saturated OPA operation. Our technique employs simultaneous spectroscopy of fluorescence photons slightly outside the seed bandwidth and strongly attenuated light at the seed central wavelength. To demonstrate its applicability we have characterised the performance of a two-stage picosecond OPA pre-amplifier with 2.8×105 gain, delivering 335 μJ pulses at 1054 nm. We show that fluorescence from a strongly seeded OPA is reduced by ~500× from the undepleted to full pump depletion regimes. We also determine the vacuum fluctuation driven noise term seeding this OPA fluorescence to be 0.7±0.4 photons ps-1 nm-1 bandwidth. The resulting shot-to-shot statistics highlights a 1.5% probability of a five-fold and 0.3% probability of a ten-fold increase of fluorescence above the average value. Finally, we show that OPA fluorescence can be limited to a few-ps pedestal with 3×10-9 temporal intensity contrast 1.3 ps ahead of an intense laser pulse, a level highly attractive for large scale chirped-pulse OPA laser systems.

  1. Picosecond infrared laser (PIRL): an ideal phonomicrosurgical laser?

    PubMed

    Hess, Markus; Hildebrandt, Michael Dominik; Müller, Frank; Kruber, Sebastian; Kroetz, Peter; Schumacher, Udo; Reimer, Rudolph; Kammal, Michael; Püschel, Klaus; Wöllmer, Wolfgang; Miller, Dwayne

    2013-11-01

    A comparison of tissue cutting effects in excised cadaver human vocal folds after incisions with three different instruments [scalpel, CO2 laser and the picosecond infrared laser-(PIRL)] was performed. In total, 15 larynges were taken from human cadavers shortly after death. After deep freezing and thawing for the experiment, the vocal folds suspended in the hemilarynx were incised. Histology and environmental scanning electron microscopy (ESEM) analyses were performed. Damage zones after cold instrument cuts ranged from 51 to 135 μm, as compared to 9-28 μm after cutting with the PIRL. It was shown that PIRL incision had smaller zones of tissue coagulation and tissue destruction, when compared with scalpel and CO2 laser cuts. The PIRL technology provides an (almost) atraumatic laser, which offers a quantum jump towards realistic 'micro'-phonosurgery on a factual cellular dimension, almost entirely avoiding coagulation, carbonization, or other ways of major tissue destruction in the vicinity of the intervention area. Although not available for clinical use yet, the new technique appears promising for future clinical applications, so that technical and methodological characteristics as well as tissue experiments seem worthwhile to be communicated at this stage of development.

  2. Plasmonic coloring of noble metals rendered by picosecond laser exposure

    NASA Astrophysics Data System (ADS)

    Guay, J.-M.; CalaLesina, A.; Gordon, P. G.; Baxter, J.; Barry, S. T.; Ramunno, L.; Berini, P.; Weck, A.

    2017-02-01

    We show the angle-independent coloring of metals in air arising from nanoparticle distributions on metal surfaces created via picosecond laser processing. Each of the colors is linked to a unique total accumulated fluence, rendering the process compatible with industry. We report the coating of the colored metal surfaces using atomic layer deposition which is shown to preserve colors and provide mechanical and chemical protection Laser bursts are composed of closely time-spaced pulses separated by 12.8 ns. The coloring of silver using burst versus non-burst is shown to increase the Chroma, or color saturation, by 50% and broaden the color Lightness range by up to 60%. The increase in Chroma and Lightness are accompanied by the creation of 3 kinds of different laser-induced periodic surface structures (LIPSS). One of these structures is measured to be 10 times the wavelength of light and are not yet explained by conventional theories. Two temperature model simulations of laser bursts interacting with the metal surface show a significant increase in the electron-phonon coupling responsible for the well-defined LIPSS observed on the surface of silver. Finite-difference time-domain simulations of nanoparticles distributed on the high-spatial frequency LIPSS (HSFL) explain the increase in color saturation (i.e. Chroma of the colors) by the enhanced absorption and enriched plasmon resonances.

  3. Upconversion imaging using short-wave infrared picosecond pulses.

    PubMed

    Mathez, Morgan; Rodrigo, Peter John; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2017-02-01

    To the best of our knowledge, we present the first demonstration of short-wavelength infrared image upconversion that employs intense picosecond signal and pump beams. We use a fiber laser that emits a signal beam at 1877 nm and a pump beam at 1550 nm-both with a pulse width of 1 ps and a pulse repetition rate of 21.7 MHz. Due to synchronization of high peak-power pulses, efficient upconversion is achieved in a single-pass setup that employs a bulk lithium niobate crystal. Optimizing the temporal overlap of the pulses for high upconversion efficiency enables us to exploit a relatively large pump beam diameter to upconvert a wider range of signal spatial frequencies in the crystal. The 1877 nm signal is converted into 849 nm-enabling an image to be acquired by a silicon CCD camera. The measured size of the smallest resolvable element of this imaging system is consistent with the value predicted by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination.

  4. Sub-picosecond optical switching with a negative index metamaterial

    SciTech Connect

    Dani, Keshav M; Upadhya, Prashant C; Zahyum, Ku

    2009-01-01

    Development of all-optical signal processing, eliminating the performance and cost penalties of optical-electrical-optical conversion, is important for continu,ing advances in Terabits/sec (Tb/s) communications.' Optical nonlinearities are generally weak, traditionally requiring long-path, large-area devicesl,2 or very high-Q, narrow-band resonator structures.3 Optical metamaterials offer unique capabilities for optical-optical interactions. Here we report 600 femtosecond (fs) all-optical modulation using a fIShnet (2D-perforated metallamorphous-Si (a-Si)/metal film stack) negative-index meta material with a structurally tunable broad-band response near 1.2 {micro}m. Over 20% modulation (experimentally limited) is achieved in a path length of only 116 nm by photo-excitation of carriers in the a-Si layer. This has the potential for Tb/s aU-optical communication and will lead to other novel, compact, tunable sub-picosecond (ps) photonic devices.

  5. Picosecond Pulse Radiolysis of Highly Concentrated Carbonate Solutions.

    PubMed

    Ghalei, Mohammad; Ma, Jun; Schmidhammer, Uli; Vandenborre, Johan; Fattahi, Massoud; Mostafavi, Mehran

    2016-03-10

    Highly concentrated potassium carbonate aqueous solutions are studied by picosecond pulse radiolysis with the purpose of exploring the formation processes of carbonate radical CO3(•-). The transient absorption band of solvated electron produced by ionizing is markedly shifted from 715 to 600 nm when the solute concentration of K2CO3 is 5 mol L(-1). This spectral shift is even more important than that observed for the solvated electron in 10 mol L(-1) KOH solutions. The broad absorption band of solvated electron in K2CO3 solutions overlaps with that of carbonate radical CO3(•-) formed at ultrashort time. Nitrate ion is used to scavenge the solvated electron and to observe the contribution of carbonate radical CO3(•-). The analysis of the amplitude and the kinetics of carbonate radical formation in highly concentrated solutions shows that CO3(•-) is formed within the electron pulse (7 ps) by two parallel mechanisms: a direct effect on the solute and the oxidation of the solute by water radical hole H2O(•+). These two mechanisms are followed by an additional one, by reaction between the solute and OH(•) radical especially in lower concentration. The radiolytic yield of each process is discussed.

  6. Picosecond laser ablation of nickel-based superalloy C263

    NASA Astrophysics Data System (ADS)

    Semaltianos, N. G.; Perrie, W.; Cheng, J.; French, P.; Sharp, M.; Dearden, G.; Watkins, K. G.

    2010-02-01

    Picosecond laser (10.4 ps, 1064 nm) ablation of the nickel-based superalloy C263 is investigated at different pulse repetition rates (5, 10, 20, and 50 kHz). The two ablation regimes corresponding to ablation dominated by the optical penetration depth at low fluences and of the electron thermal diffusion length at high fluences are clearly identified from the change of the surface morphology of single pulse ablated craters (dimples) with fluence. The two corresponding thresholds were measured as F {th(D1)/1}=0.68±0.02 J/cm2 and F {th(D2)/1}=2.64±0.27 J/cm2 from data of the crater diameters D 1,2 versus peak fluence. The surface morphology of macroscopic areas processed with a scanning laser beam at different fluences is characterised by ripples at low fluences. As the fluence increases, randomly distributed areas among the ripples are formed which appear featureless due to melting and joining of the ripples while at high fluences the whole irradiated surface becomes grainy due to melting, splashing of the melt and subsequent resolidification. The throughput of ablation becomes maximal when machining at high pulse repetition rates and with a relatively low fluence, while at the same time the surface roughness is kept low.

  7. Probing single-cell mechanics with picosecond ultrasonics.

    PubMed

    Dehoux, Thomas; Abi Ghanem, Maroun; Zouani, Omar F; Ducousso, Mathieu; Chigarev, Nikolay; Rossignol, Clément; Tsapis, Nicolas; Durrieu, Marie-Christine; Audoin, Bertrand

    2015-02-01

    The mechanical properties of cells play a key role in several fundamental biological processes, such as migration, proliferation, differentiation and tissue morphogenesis. The complexity of the inner cell composition and the intricate meshwork formed by transmembrane cell-substrate interactions demands a non-invasive technique to probe cell mechanics and cell adhesion at a subcell scale. In this paper we review the use of laser-generated GHz acoustic waves--a technique called picosecond ultrasonics (PU)--to probe the mechanical properties of single cells. We first describe applications to vegetal cells and biomimetic systems. We show how these systems can be used as simple models to understand more complex animal cells. We then present an opto-acoustic bio-transducer designed for in vivo measurements in physiological conditions. We illustrate the use of this transducer through the simultaneous probing of the density and compressibility of Allium cepa cells. Finally, we demonstrate that this technique can quantify animal-cell adhesion on metallic surfaces by analyzing the acoustic pulses reflected off the cell-metal interface. This innovative approach allows investigating quantitatively cell mechanics without fluorescent labels or mechanical contact to the cell.

  8. Effect of defocusing on picosecond laser-coupling into gold cones

    SciTech Connect

    Bush, I. A. Pasley, J.; Thomas, A. G. R.; Gartside, L.; Sarfraz, S.; Wagenaars, E.; Green, J. S.; Notley, M.; Lowe, H.; Spindloe, C.; Winstone, T.; Robinson, A. P. L.; Clarke, R.; Ma, T.; Yabuuchi, T.; Wei, M.; Beg, F. N.; Stephens, R. B.; MacPhee, A.; MacKinnon, A. J.; and others

    2014-01-15

    Here, we show that defocusing of the laser in the interaction of a picosecond duration, 1.053 μm wavelength, high energy pulse with a cone-wire target does not significantly affect the laser energy coupling efficiency, but does result in a drop in the fast electron effective temperature. This may be beneficial for fast ignition, since not only were more electrons with lower energies seen in the experiment but also the lower prepulse intensity will reduce the amount of preplasma present on arrival of the main pulse, reducing the distance the hot electrons have to travel. We used the Vulcan Petawatt Laser at the Rutherford Appleton Laboratory and gold cone targets with approximately 1 mm long, 40 μm diameter copper wires attached to their tip. Diagnostics included a quartz crystal imager, a pair of highly oriented pyrolytic graphite crystal spectrometers and a calibrated CCD operating in the single photon counting regime, all of which looked at the copper K{sub α} emission from the wire. A short pulse optical probe, delayed 400 ps relative to the main pulse was employed to diagnose the extent of plasma expansion around the wire. A ray-tracing code modeled the change in intensity on the interior surface of the cone with laser defocusing. Using a model for the wire copper K{sub α} emission coupled to a hybrid Vlasov-Fokker-Planck code, we ran a series of simulations, holding the total energy in electrons constant whilst varying the electron temperature, which support the experimental conclusions.

  9. Laser-to-hot-electron conversion limitations in relativistic laser matter interactions due to multi-picosecond dynamics

    DOE PAGES

    Schollmeier, Marius; Sefkow, Adam B.; Geissel, Matthias; ...

    2015-04-20

    High-energy short-pulse lasers are pushing the limits of plasma-based particle acceleration, x-ray generation, and high-harmonic generation by creating strong electromagnetic fields at the laser focus where electrons are being accelerated to relativistic velocities. Understanding the relativistic electron dynamics is key for an accurate interpretation of measurements. We present a unified and self-consistent modeling approach in quantitative agreement with measurements and differing trends across multiple target types acquired from two separate laser systems, which differ only in their nanosecond to picosecond-scale rising edge. Insights from high-fidelity modeling of laser-plasma interaction demonstrate that the ps-scale, orders of magnitude weaker rising edge ofmore » the main pulse measurably alters target evolution and relativistic electron generation compared to idealized pulse shapes. This can lead for instance to the experimentally observed difference between 45 MeV and 75 MeV maximum energy protons for two nominally identical laser shots, due to ps-scale prepulse variations. Our results indicate that the realistic inclusion of temporal laser pulse profiles in modeling efforts is required if predictive capability and extrapolation are sought for future target and laser designs or for other relativistic laser ion acceleration schemes.« less

  10. Laser-to-hot-electron conversion limitations in relativistic laser matter interactions due to multi-picosecond dynamics

    SciTech Connect

    Schollmeier, M.; Sefkow, A. B.; Geissel, M.; Kimmel, M. W.; Rambo, P. K.; Schwarz, J.; Arefiev, A. V.; Flippo, K. A.; Johnson, R. P.; Shimada, T.; Gaillard, S. A.; Offermann, D. T.

    2015-04-15

    High-energy short-pulse lasers are pushing the limits of plasma-based particle acceleration, x-ray generation, and high-harmonic generation by creating strong electromagnetic fields at the laser focus where electrons are being accelerated to relativistic velocities. Understanding the relativistic electron dynamics is key for an accurate interpretation of measurements. We present a unified and self-consistent modeling approach in quantitative agreement with measurements and differing trends across multiple target types acquired from two separate laser systems, which differ only in their nanosecond to picosecond-scale rising edge. Insights from high-fidelity modeling of laser-plasma interaction demonstrate that the ps-scale, orders of magnitude weaker rising edge of the main pulse measurably alters target evolution and relativistic electron generation compared to idealized pulse shapes. This can lead for instance to the experimentally observed difference between 45 MeV and 75 MeV maximum energy protons for two nominally identical laser shots, due to ps-scale prepulse variations. Our results show that the realistic inclusion of temporal laser pulse profiles in modeling efforts is required if predictive capability and extrapolation are sought for future target and laser designs or for other relativistic laser ion acceleration schemes.

  11. Laser-to-hot-electron conversion limitations in relativistic laser matter interactions due to multi-picosecond dynamics

    SciTech Connect

    Schollmeier, Marius; Sefkow, Adam B.; Geissel, Matthias; Arefiev, Alexey V.; Flippo, Kirk A.; Gaillard, Sandrine A.; Johnson, Randy P.; Kimmel, Mark W.; Offermann, Dustin T.; Rambo, Patrick K.; Schwarz, Jens; Shimada, Tom

    2015-04-20

    High-energy short-pulse lasers are pushing the limits of plasma-based particle acceleration, x-ray generation, and high-harmonic generation by creating strong electromagnetic fields at the laser focus where electrons are being accelerated to relativistic velocities. Understanding the relativistic electron dynamics is key for an accurate interpretation of measurements. We present a unified and self-consistent modeling approach in quantitative agreement with measurements and differing trends across multiple target types acquired from two separate laser systems, which differ only in their nanosecond to picosecond-scale rising edge. Insights from high-fidelity modeling of laser-plasma interaction demonstrate that the ps-scale, orders of magnitude weaker rising edge of the main pulse measurably alters target evolution and relativistic electron generation compared to idealized pulse shapes. This can lead for instance to the experimentally observed difference between 45 MeV and 75 MeV maximum energy protons for two nominally identical laser shots, due to ps-scale prepulse variations. Our results indicate that the realistic inclusion of temporal laser pulse profiles in modeling efforts is required if predictive capability and extrapolation are sought for future target and laser designs or for other relativistic laser ion acceleration schemes.

  12. Laser ablation of iron: A comparison between femtosecond and picosecond laser pulses

    SciTech Connect

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

    2013-08-28

    In this study, a comparison between femtosecond (fs) and picosecond (ps) laser ablation of electrolytic iron was carried out in ambient air. Experiments were conducted using a Ti:sapphire laser that emits radiation at 785 nm and at pulse widths of 110 ps and 130 fs, before and after pulse compression, respectively. Ablation rates were calculated from the depth of craters produced by multiple laser pulses incident normally to the target surface. Optical and scanning electron microscopy showed that picosecond laser pulses create craters that are deeper than those created by the same number of femtosecond laser pulses at the same fluence. Most of the ablated material was ejected from the ablation site in the form of large particles (few microns in size) in the case of picosecond laser ablation, while small particles (few hundred nanometers) were produced in femtosecond laser ablation. Thermal effects were apparent at high fluence in both femtosecond and picosecond laser ablation, but were less prevalent at low fluence, closer to the ablation threshold of the material. The quality of craters produced by femtosecond laser ablation at low fluence is better than those created at high fluence or using picosecond laser pulses.

  13. EXPERIMENTS ON LASER AND E-BEAM TRANSPORT AND INTERACTION IN A PLASMA CHANNEL.

    SciTech Connect

    POGORELSKY,I.V.; PAVLISHIN,I.V.; BEN-ZVI,I.; ET AL.

    2004-09-15

    An ablative capillary discharge is installed into a linac beamline and serves as a plasma source for generating and characterizing wakefields. Simultaneously, the electron beam is used as a tool for plasma diagnostics. A high-energy picosecond CO{sub 2} laser channeled within the same capillary strongly affects a counterpropagating electron beam. These observations, supported with simulations, suggest the possibility of manipulating relativistic electron beams by steep plasma channels ponderomotively produced by a laser.

  14. High-brightness picosecond ion beam source based on BNL Terawatt CO2 laser: Proof-of-principle experiments

    SciTech Connect

    Shkolnikov, Peter

    2012-10-04

    Under the continuing DOE support, we have: o assembled the basic experiment setup and then continued expanding it to include diverse diagnostics and to accommodate gas jet targets in addition to metal foils; o conducted an extensive study of our novel laser, significantly enhanced laser beam diagnostics, and improved relevant laser parameters; o turned our experiments into a truly international endeavor with active collaboration of close to 20 researchers in US, UK, and Germany; o conducted the first ever experiments with proton and ion acceleration by lasers interacting with overcritical plasma of gas jets; o for the first time directly observed radiation pressure acceleration of protons, including quasi-monoenergetic spectra promising for future applications; o for the first time directly observed quasi-stable, bubble-like plasma structures that likely evolved from relativistic laser-plasma solitons (post-solitons). Thus, we have confirmed a strong potential of a picosecond TW CO2 laser as a research tool in laser-plasma science and as a promising vehicle for future applications of laser ion acceleration. This has led to apparent increase of the interest in mid-IR laser ion acceleration. In particular, another major research group began extensive proton acceleration experiments with their own CO2 laser at UCLA. As a result, the mechanisms responsible for laser proton acceleration in gas jets have become somewhat clearer. It is also important to note that modest DOE funding played the role of a seed support ensuring the formation of a multinational research team, whose members contributed its time and equipment with value well in excess of that seed amount.

  15. Enhancement of terahertz wave generation from laser induced plasma

    SciTech Connect

    Xie Xu; Xu Jingzhou; Dai Jianming; Zhang, X.-C.

    2007-04-02

    It is well known that air plasma induced by ultrashort laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the laser induced plasma where there is a preexisting plasma background. When a laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another laser beam creating a plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.

  16. Picosecond laser cutting and drilling of thin flex glass

    NASA Astrophysics Data System (ADS)

    Wlodarczyk, Krystian L.; Brunton, Adam; Rumsby, Phil; Hand, Duncan P.

    2016-03-01

    We investigate the feasibility of cutting and drilling thin flex glass (TFG) substrates using a picosecond laser operating at wavelengths of 1030 nm, 515 nm and 343 nm. 50 μm and 100 μm thick AF32®Eco Thin Glass (Schott AG) sheets are used. The laser processing parameters such as the wavelength, pulse energy, pulse repetition frequency, scan speed and the number of laser passes which are necessary to perform through a cut or to drill a borehole in the TFG substrate are studied in detail. Our results show that the highest effective cutting speeds (220 mm/s for a 50 μm thick TFG substrate and 74 mm/s for a 100 μm thick TFG substrate) are obtained with the 1030 nm wavelength, whereas the 343 nm wavelength provides the best quality cuts. The 515 nm wavelength, meanwhile, can be used to provide relatively good laser cut quality with heat affected zones (HAZ) of <25 μm for 50 μm TFG and <40 μm for 100 μm TFG with cutting speeds of 100 mm/s and 28.5 mm/s, respectively. The 343 nm and 515 nm wavelengths can also be used for drilling micro-holes (with inlet diameters of ⩽75 μm) in the 100 μm TFG substrate with speeds of up to 2 holes per second (using 343 nm) and 8 holes per second (using 515 nm). Optical microscope and SEM images of the cuts and micro-holes are presented.

  17. Cell stimulation and calcium mobilization by picosecond electric pulses

    PubMed Central

    Semenov, Iurii; Xiao, Shu; Kang, Dongkoo; Schoenbach, Karl H.; Pakhomov, Andrei G.

    2015-01-01

    We tested if picosecond electric pulses (psEP; 190 kV/cm, 500 ps at 50% height), which are much shorter than channel activation time, can activate voltage-gated (VG) channels. Cytosolic Ca2+ was monitored by Fura-2 ratiometric imaging in GH3 and NG108 cells (which express multiple types of VG calcium channels, VGCC), and in CHO cells (which express no VGCC). Trains of up to 100 psEP at 1 kHz elicited no response in CHO cells. However, even a single psEP significantly increased Ca2+ in both GH3 (by 114+/−48 nM) and NG108 cells (by 6 +/−1.1 nM). Trains of 100 psEP amplified the response to 379+/−33 nM and 719+/−315 nM, respectively. Ca2+ responses peaked within 2–15 s and recovered for over 100 s; they were 80–100% inhibited by verapamil and ω-conotoxin, but not by the substitution of Na+ with N-methyl-D-glucamine. There was no response to psEP in Ca2+-free medium, but adding external Ca2+ even 10 s later evoked Ca2+ response. We conclude that electrical stimuli as short as 500 ps can cause long-lasting opening of VGCC by a mechanism which does not involve conventional electroporation, heating (which was under 0.06 °K per psEP), or membrane depolarization by opening of VG Na+ channels. PMID:26011130

  18. Multi-channel picosecond photon timing with microchannel plate detectors

    NASA Astrophysics Data System (ADS)

    Lapington, J. S.; Conneely, T.

    2011-08-01

    Microchannel plate-based detectors have the capability to photon-count at time resolutions which outperform solid-state devices such as the APD or SiPM, and have a geometry that lends itself to pixelated readouts. We describe a multi-channel, photon-counting microchannel plate detector optimised for photon timing in the picosecond regime. The detector was originally developed for application to time-resolved spectroscopy in the life sciences, however its performance characteristics make it suitable for applications where high time resolution and multi-channel photon-counting are required including Cherenkov light detection in nuclear physics, particle physics, and astroparticle astronomy.We describe the prototype detector, a sealed tube device comprising an optical photocathode proximity focussed to a small pore microchannel plate stack. Event charge is collected on a multi-channel readout comprising an 8×8 pixel array, manufactured on a multilayer ceramic, which provides vacuum integrity for the detector enclosure and a multi-way electrical feedthrough for the readout array. Each pixel addresses one channel of a NINO ASIC, a multi-channel preamplifier-discriminator device. The discriminator outputs are timed to 25 ps by the HPTDC time-to-digital converter ASIC, which uses a time-over-threshold technique for amplitude walk correction. We present performance measurements using a pulsed laser of the 64 channel prototype system comprising a 25 mm detector, NINO front-end, and a CAEN V1290A VME module utilising HPTDC. We discuss the next phase in the project—design and manufacture of a 40 mm detector with a 16×16 pixel2 readout coupled to custom NINO/HPTDC electronics constructed as a series of 64 channel modules, expandable to even larger channel densities.

  19. Cell stimulation and calcium mobilization by picosecond electric pulses.

    PubMed

    Semenov, Iurii; Xiao, Shu; Kang, Dongkoo; Schoenbach, Karl H; Pakhomov, Andrei G

    2015-10-01

    We tested if picosecond electric pulses (psEP; 190 kV/cm, 500 ps at 50% height), which are much shorter than channel activation time, can activate voltage-gated (VG) channels. Cytosolic Ca(2+) was monitored by Fura-2 ratiometric imaging in GH3 and NG108 cells (which express multiple types of VG calcium channels, VGCC), and in CHO cells (which express no VGCC). Trains of up to 100 psEP at 1 kHz elicited no response in CHO cells. However, even a single psEP significantly increased Ca(2+) in both GH3 (by 114 ± 48 nM) and NG108 cells (by 6 ± 1.1 nM). Trains of 100 psEP amplified the response to 379 ± 33 nM and 719 ± 315 nM, respectively. Ca(2+) responses peaked within 2-15s and recovered for over 100 s; they were 80-100% inhibited by verapamil and ω-conotoxin, but not by the substitution of Na(+) with N-methyl-D-glucamine. There was no response to psEP in Ca(2+)-free medium, but adding external Ca(2+) even 10s later evoked Ca(2+) response. We conclude that electrical stimuli as short as 500 ps can cause long-lasting opening of VGCC by a mechanism which does not involve conventional electroporation, heating (which was under 0.06 K per psEP), or membrane depolarization by opening of VG Na(+) channels.

  20. The Application Of Picosecond-Resolved Fluorescence Spectroscopy In The Study Of Flavins And Flavoproteins

    NASA Astrophysics Data System (ADS)

    Visser, Antonie J.; van Hoek, Arie

    1988-06-01

    Picosecond relaxation processes of flavins and flavoproteins were investigated with mode-locked and synchronously pumped lasers as source of excitation and time-correlated single photon counting in detection. Free flavin rotational correlation times of 80-150 ps (values depending on the flavin derivative used) could be precisely determined. Picosecond-resolved fluorescence of the flavin bound in the electron-carrier protein flavodoxin from Desulfovibrio vulgaris yields a fluorescence lifetime component of 30 ps in the fluorescence decay. Time-resolved tryptophan fluorescence in flavodoxin exhibits a short lifetime component, which is attributed in part to energy transfer from tryptophan to flavin. Three-dimensional fluorescence spectroscopy and fluorescence anisotropy decay analysis of the two tryptophan residues in flavodoxin provide new evidence for specific flavin-tryptophan interaction. Finally, picosecond-resolved spectroscopy enables the direct measurement of energy transfer between two different chromophores in a protein, from which topographical details can be inferred.

  1. An investigation on the hole quality during picosecond laser helical drilling of stainless steel 304

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyu; Di, Jianke; Zhou, Ming; Yan, Yu; Wang, Rong

    2015-05-01

    Precision drilling with ultra-short pulse lasers (e.g., picosecond and femtosecond) has been advocated to significantly improve the quality of the micro-holes with reduced recast layer thickness and no heat-affected zone. However, a combination of high-power picosecond laser with helical drilling strategy in laser drilling has rarely been reported in previous studies. In the present study, a series of micro-holes with circular, triangular, rectangular, and rhombic shapes (diameter 0.6 mm) were manufactured on stainless steel 304 using a newly developed laser drilling system which incorporated a picosecond laser and a high-speed laser beam rotation apparatus into a five-axis positioning platform. The quality of the helical drilled holes, e.g., recast layer, micro-crack, circularity, and conicity, were evaluated using an optical microscope, an optical interferometer, and a scanning electron microscope. In addition, the microstructure of the samples was investigated following etching treatment. It was demonstrated that the entrance ends, the exit ends, and the side walls of the micro-holes were quite smooth without accumulation of spattering material and formation of recast layer and micro-crack. No tapering phenomenon was observed, and the circularity of the holes was fairly good. There was no distinctive difference with regard to the microstructure between the edges of the holes and the bulk material. Picosecond laser helical drilling can be an effective technique for manufacturing of micro-holes with very high quality. The development of high-power picosecond laser would promote picosecond laser drilling to be more industrial relevance in the future.

  2. Time-resolved study of formate on Ni( 1 1 1 ) by picosecond SFG spectroscopy

    NASA Astrophysics Data System (ADS)

    Kusafuka, K.; Noguchi, H.; Onda, K.; Kubota, J.; Domen, K.; Hirose, C.; Wada, A.

    2002-04-01

    Time-resolved vibrational measurements were carried out on formate (HCOO) adsorbed on Ni(1 1 1) surface by combining the sum-frequency generation method and picosecond laser system (time resolution of 6 ps). Rapid intensity decrease (within the time resolution) followed by intensity recovery (time constant of several tens of ps) of CH stretching signal was observed when picosecond 800 nm pulse was irradiated on the sample surface. From the results of temperature and pump fluence dependences of temporal behaviour of signal intensity, we concluded that the observed intensity change was induced by non-thermal process. Mechanism of the temporal intensity change was discussed.

  3. Picosecond supercontinuum laser with consistent emission parameters over variable repetition rates from 1 to 40 MHz

    NASA Astrophysics Data System (ADS)

    Schönau, Thomas; Siebert, Torsten; Härtel, Romano; Klemme, Dietmar; Lauritsen, Kristian; Erdmann, Rainer

    2013-02-01

    An freely triggerable picosecond visible supercontinuum laser source is presented that allows for a uniform spectral profile and equivalent pulse characteristics over variable repetition rates from 1 to 40MHz. The system features PM Yb3+-doped fiber amplification of a picosecond gain-switched seed diode at 1062 nm. The pump power in the multi-stage amplifier is actively adjusted by a microcontroller for a consistent peak power of the amplified signal in the full range of repetition rates. The length of the PCF is scaled to deliver a homogeneous spectrum and minimized distortion of the temporal pulse shape.

  4. Relativistic theory for picosecond time transfer in the vicinity of Earth

    NASA Technical Reports Server (NTRS)

    Petit, G.; Wolf, P.

    1994-01-01

    The problem of light propagation is treated in a geocentric reference system with the goal of ensuring picosecond accuracy for time transfer techniques using electromagnetic signals in the vicinity of the Earth. We give an explicit formula for a one way time transfer, to be applied when the spatial coordinates of the time transfer stations are known in a geocentric reference system rotating with the Earth. This expression is extended, at the same accuracy level of one picosecond, to the special cases of two way and LASSO time transfers via geostationary satellites.

  5. Sub-surface channels in sapphire made by ultraviolet picosecond laser irradiation and selective etching.

    PubMed

    Moser, Rüdiger; Ojha, Nirdesh; Kunzer, Michael; Schwarz, Ulrich T

    2011-11-21

    We demonstrate the realization of sub-surface channels in sapphire prepared by ultraviolet picosecond laser irradiation and subsequent selective wet etching. By optimizing the pulse energy and the separation between individual laser pulses, an optimization of channel length can be achieved with an aspect ratio as high as 3200. Due to strong variation in channel length, further investigation was done to improve the reproducibility. By multiple irradiations the standard deviation of the channel length could be reduced to 2.2%. The achieved channel length together with the high reproducibility and the use of a commercial picosecond laser system makes the process attractive for industrial application.

  6. Simulation of picosecond pulse propagation in fibre-based radiation shaping units

    NASA Astrophysics Data System (ADS)

    Kuptsov, G. V.; Petrov, V. V.; Laptev, A. V.; Petrov, V. A.; Pestryakov, E. V.

    2016-09-01

    We have performed a numerical simulation of picosecond pulse propagation in a combined stretcher consisting of a segment of a telecommunication fibre and diffraction holographic gratings. The process of supercontinuum generation in a nonlinear photoniccrystal fibre pumped by picosecond pulses is simulated by solving numerically the generalised nonlinear Schrödinger equation; spectral and temporal pulse parameters are determined. Experimental data are in good agreement with simulation results. The obtained results are used to design a high-power femtosecond laser system with a pulse repetition rate of 1 kHz.

  7. Picosecond anti-Stokes generation in a photonic-crystal fiber for interferometric CARS microscopy.

    PubMed

    Andresen, Esben Ravn; Keiding, Søren Rud; Potma, Eric Olaf

    2006-08-07

    We generate tunable picosecond anti-Stokes pulses by four-wave mixing of two picosecond pump and Stokes pulse trains in a photonic-crystal fiber. The visible, spectrally narrow anti-Stokes pulses with shifts over 150 nm are generated without generating other spectral features. As a demonstration, we employ the generated anti-Stokes pulses as reference pulses in an interferometric coherent anti-Stokes Raman scattering imaging experiment showing that interpulse coherence among the pump, Stokes and anti-Stokes beams is retained.

  8. Highly efficient picosecond degenerate four-wave mixing in a tellurite microstructured optical fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Hoang Tuan, Tong; Kawamura, Harutaka; Nagasaka, Kenshiro; Suzuki, Takenobu; Ohishi, Yasutake

    2016-06-01

    Wavelength-tunable picosecond degenerate four-wave mixing was demonstrated in a tellurite microstructured optical fiber (TMOF). The zero-dispersion wavelength of the TMOF was shifted to 1570 nm by introducing a single ring of air holes in the cladding. The anti-Stokes signal sideband can be generated from 1490 to 1500 nm, and the Stokes idler sideband can emit from 1595 to 1645 nm. Because of the high nonlinearity of the TMOF and the large peak power of the picosecond pump, a maximal signal gain of 31.2 dB and an idler conversion efficiency of +35 dB were achieved.

  9. Picosecond intersubband hole relaxation in p-type quantum wells

    SciTech Connect

    Xu, Z.; Fauchet, P.M.; Rella, C.W.; Schwettman, H.A.

    1995-12-31

    We report the first direct measurement of the relaxation time of holes in p-type quantum wells using tunable, subpicosecond mid-infrared laser pulses in a pump-probe arrangement. The QW layers consisted of 50 In{sub 0.5}Ga{sub 0.5}As/Al{sub 0.5}Ga{sub 0.5}As periods. The In{sub 0.5}Ga{sub 0.5}As well was 4 nm wide and the Al{sub 0.5}Ga{sub 0.5}As barrier was 8 nm wide. The dopant concentration was 10{sup 19} CM{sup -3} which corresponds to a sheet density of 1.2 x 10{sup 13} CM{sup -2}. The room temperature IR spectrum showed a 50 meV wide absorption peak at 5.25 {mu}m (220 meV). This energy agrees with the calculated n=1 heavy hole to n=1 light hole transition energy of 240 meV (150 meV for strain and 90 meV for confinement). The large absorption width results from hole-hole scattering and the difference in dispersion relations between the two subbands. The equal-wavelength pump-probe transmission measurements were performed using the Stanford free electron laser (FEL). The FEL pulses were tuned between 4 and 6 {mu} m and their duration was less than 1 ps. The measurements were performed as a function of temperature, pump wavelength and intensity (from 0.3 to 10 GW/cm{sup 2}). In all our experiments, we find an increase of transmission (decrease of absorption or bleaching) following photopumping, which recovers as a single exponential with a time constant (relaxation time) of the order of 1 picosecond. The maximum change in transmission is linear with pump 2 intensity below 1 GW/cm{sup 2} and saturates to {approximately}3% with a saturation intensity I{sub sat} of 3 GW/cm{sup 2}. As the saturation regime is entered, the relaxation time increases from 0.8 ps to 1.8 ps. This relaxation time depends on the temperature T: it increases from 0.8 ps to 1.3 ps as T decreases from 300 K to 77 K. Finally, when we tune the laser through the absorption band, the magnitude of the signal changes but its temporal behavior does not change, within the accuracy of the measurements.

  10. Nanosecond X-ray diffraction from biological samples with a laser-produced plasma source.

    PubMed

    Frankel, R D; Forsyth, J M

    1979-05-11

    By using 4.45-angstrom radiation generated by Cl+15 ions in a laser plasma and nanosecond exposures, low-angle x-ray diffraction patterns were obtained from dried rat spinal nerves and a powder of cholesterol. Three to four 400-picosecond, 45-joule pulses were required for the exposure. This new technique should have wide application in structural kinetic studies.

  11. Electronics for a Picosecond Time-of-flight Measurement

    SciTech Connect

    Brandt, Andrew Gerhart; Rijssenbeek, Michael

    2014-11-03

    TITLE: Electronics for a Picosecond Time-of-flight Measurement ABSTRACT: Time-of-flight (TOF) detectors have historically been used as part of the particle identification capability of multi-purpose particle physics detectors. An accurate time measurement, combined with a momentum measurement based on the curvature of the track in a magnetic field, is often sufficient to determine the particle's mass, and thus its identity. Such detectors typically have measured the particle flight time extremely precisely, with an uncertainty of one hundred trillionths of a second (also referred to as 100 picoseconds). To put this in perspective it would be like counting all the people on the Earth and getting it right within 1 person! Another use of TOFs is to measure the vertex of the event, which is the location along the beam line where the incoming particles (typically protons) collide. This vertex positon is a well measured quantity for events where the protons collide “head on” as the outgoing particles produced when you blast the proton apart can be used to trace back to a vertex point from which they originated. More frequently the protons just strike a glancing blow and remain intact—in this case they are nearly parallel to the beam and you cannot tell their vertex without this ability to precisely measure the time of flight of the protons. Occasionally both happen in the same event, that is, a central system and two protons are produced. But are they from the same collision, or just a boring background where more than one collision in the same bunch crossing conspire to fake the signal of interest? That’s where the timing of the protons comes into play. The main idea is to measure the time it takes for the two protons to reach TOF detectors positioned equidistant from the center of the main detector. If the vertex is displaced to one side than that detector will measure a shorter time while the other side detector will measure a correspondingly longer time

  12. Development of a picosecond CO2 laser system for a high-repetition γ-source

    SciTech Connect

    Polyanskiy, M.N.; Pogorelsky, I.V.; Yakimenko, V.E.; Platonenko, V.T.

    2009-04-17

    The concept of a high-repetition-rate, high-average power {gamma}-source is based on Compton backscattering from the relativistic electron beam inside a picosecond CO{sub 2} laser cavity. Proof-of-principle experiments combined with computer simulations allow evaluating the promise of this approach for novel applications in science and technology.

  13. PS-1/S1 picosecond streak camera application for multichannel laser system diagnostics

    SciTech Connect

    Garanin, S G; Bel'kov, S A; Rogozhnikov, G S; Rukavishnikov, N N; Romanov, V V; Voronich, I N; Vorob'ev, N S; Gornostaev, P B; Lozovoi, V I; Shchelev, M Ya

    2014-08-31

    A PS-1/S1 picosecond image-tube streak camera (ITSC) with slit scan (streak camera), developed and manufactured at the General Physics Institute RAS, has been used to measure the spatiotemporal characteristics of ultrashort laser pulses generated by a petawatt-power laser installation 'FEMTO' at the Institute of Laser Physics Research in Sarov. It is found that such a camera is suitable for measuring the spatial and temporal parameters of single laser pulses with an accuracy of about one picosecond. It is shown that the intensity time profile of a train of picosecond pulses may be precisely defined for the pulses separated in time by a few picoseconds. The camera allows the contrast of radiation to be determined with a high (no less than 10{sup 3}) accuracy; spatial distribution of the laser pulses can be measured with an accuracy of tens of microns, and the temporal separation of single laser pulses can be identified with an accuracy of 1 – 1.5 ps. (extreme light fields and their applications)

  14. Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser

    NASA Technical Reports Server (NTRS)

    Auyeung, J.

    1981-01-01

    We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.

  15. Picosecond time-space holographic interferograms stored by persistent spectral hole burning

    NASA Astrophysics Data System (ADS)

    Rebane, A.; Ollikainen, O.

    1990-09-01

    A novel approach to interferometric processing of ultrafast optical signals is demonstrated by using hologram storage in persistent spectral hole burning media. Multiple time-space holographic images of ultrafast scenes are interferometrically compared by using read-out with a frequency-tunable narrow band laser. The feasibility of simultaneous detection of spatial and spectral phase distortions of picosecond wavefronts is demonstrated.

  16. Expansion dynamics of supercritical water probed by picosecond time-resolved photoelectron spectroscopy.

    PubMed

    Gladytz, Thomas; Abel, Bernd; Siefermann, Katrin R

    2015-02-21

    Vibrational excitation of liquid water with femtosecond laser pulses can create extreme states of water. Yet, the dynamics directly after initial sub-picosecond delocalization of molecular vibrations remain largely unclear. We study the ultrafast expansion dynamics of an accordingly prepared supercritical water phase with a picosecond time resolution. Our experimental setup combines vacuum-compatible liquid micro-jet technology and a table top High Harmonic light source driven by a femtosecond laser system. An ultrashort laser pulse centered at a wavelength of 2900 nm excites the OH-stretch vibration of water molecules in the liquid. The deposited energy corresponds to a supercritical phase with a temperature of about 1000 K and a pressure of more than 1 GPa. We use a time-delayed extreme ultraviolet pulse centered at 38.6 eV, and obtained via High Harmonic generation (HHG), to record valence band photoelectron spectra of the expanding water sample. The series of photoelectron spectra is analyzed with noise-corrected target transform fitting (cTTF), a specifically developed multivariate method. Together with a simple fluid dynamics simulation, the following picture emerges: when a supercritical phase of water expands into vacuum, temperature and density of the first few nanometers of the expanding phase drop below the critical values within a few picoseconds. This results in a supersaturated phase, in which condensation seeds form and grow from small clusters to large clusters on a 100 picosecond timescale.

  17. Stimulated backward Raman scattering excited in the picosecond range: high efficiency conversions

    NASA Astrophysics Data System (ADS)

    Chevalier, R.; Sokolovskaia, A.; Tcherniega, N.; Rivoire, G.

    1991-04-01

    Stimulated backward Raman scattering (SBRS) excited by picosecond laser pulses is produced with high efficiency conversion in materials displaying large Raman gain and small Kerr constants. A constant energy efficiency of 40% is obtained in aceton for a wide range of the exciting laser energy. The spatial, spectral and temporal structure of the backscattering beam is studied.

  18. Surface displacement measured by beam distortion detection technique: Application to picosecond ultrasonics

    SciTech Connect

    Chigarev, N.; Rossignol, C.; Audoin, B.

    2006-11-15

    A sensitive technique of surface displacement measurement without interferometry is proposed for the goals of picosecond ultrasonics. Simple description of detection mechanism is provided on the basis of paraxial approximation of light diffraction. Test experiments with gold and tungsten layers have been performed and analyzed. The efficiency of the technique is compared with interferometry and reflectometry methods.

  19. Effects of picosecond laser repetition rate on ablation of Cr12MoV cold work mold steel

    NASA Astrophysics Data System (ADS)

    Wu, Baoye; Deng, Leimin; Liu, Peng; Zhang, Fei; Duan, Jun; Zeng, Xiaoyan

    2017-07-01

    In this paper, the effects of pulse repetition rate on ablation efficiency and quality of Cr12MoV cold work mold steel have been studied using a picosecond (ps) pulse Nd:YVO4 laser system at λ= 1064 nm. The experimental results of area ablation on target surface reveal that laser repetition rate plays a significant role in controlling ablation efficiency and quality. Increasing the laser repetition rate, while keeping a constant mean power improves the ablation efficiency and quality. For each laser mean power, there is an optimal repetition rate to achieve a higher laser ablation efficiency with low surface roughness. A high ablation efficiency of 42.29, 44.11 and 47.52 μm3/mJ, with surface roughness of 0.476, 0.463 and 0.706 μm could be achieved at laser repetition rate of 10 MHz, for laser mean power of 15, 17 and 19 W, respectively. Scanning electron microcopy images revels that the surface morphology evolves from rough with numerous craters, to flat without pores when we increased the laser repetition rate. The effects of laser repetition rate on the heat accumulation, plasma shield and ablation threshold were analyzed by numerical simulation, spectral analysis and multi-laser shot, respectively. The synergetic effects of laser repetition rate on laser ablation rate and machining quality were analyzed and discussed systemically in this paper.

  20. Monochromatic x-ray radiography of laser-driven spherical targets using high-energy, picoseconds LFEX laser

    NASA Astrophysics Data System (ADS)

    Sawada, Hiroshi; Fujioka, S.; Lee, S.; Arikawa, Y.; Shigemori, K.; Nagatomo, H.; Nishimura, H.; Sunahara, A.; Theobald, W.; Perez, F.; Patel, P. K.; Beg, F. N.

    2015-11-01

    Formation of a high density fusion fuel is essential in both conventional and advanced Inertial Confinement Fusion (ICF) schemes for the self-sustaining fusion process. In cone-guided Fast Ignition (FI), a metal cone is attached to a spherical target to maintain the path for the injection of an intense short-pulse ignition laser from blow-off plasma created when nanoseconds compression lasers drive the target. We have measured a temporal evolution of a compressed deuterated carbon (CD) sphere using 4.5 keV K-alpha radiography with the Kilo-Joule, picosecond LFEX laser at the Institute of Laser Engineering. A 200 μm CD sphere attached to the tip of a Au cone was directly driven by 9 Gekko XII beams with 300 J/beam in a 1.3 ns Gaussian pulse. The LFEX laser irradiated on a Ti foil to generate 4.51 Ti K-alpha x-ray. By varying the delay between the compression and backlighter lasers, the measured radiograph images show an increase of the areal density of the imploded target. The detail of the quantitative analyses to infer the areal density and comparisons to hydrodynamics simulations will be presented. This work was performed with the support and under the auspices of the NIFS Collaboration Research program (NIFS13KUGK072). H.S. was supported by the UNR's International Activities Grant program.

  1. Application of picosecond laser-induced breakdown spectroscopy to quantitative analysis of boron in meatballs and other biological samples.

    PubMed

    Hedwig, Rinda; Lahna, Kurnia; Lie, Zener Sukra; Pardede, Marincan; Kurniawan, Koo Hendrik; Tjia, May On; Kagawa, Kiichiro

    2016-11-10

    This report presents the results of laser-induced breakdown spectroscopy (LIBS) study on biological and food samples of high water content using a picosecond (ps) laser at low output energy of 10 mJ and low-pressure helium ambient gas at 2 kPa. Evidence of excellent emission spectra of various analyte elements with very low background is demonstrated for a variety of samples without the need of sample pretreatment. Specifically, limits of detection in the range of sub-ppm are obtained for hazardous Pb and B impurities in carrots and meatballs. This study also shows the inferior performance of LIBS using a nanosecond laser and atmospheric ambient air for a soft sample of high water content and thereby explains its less successful applications in previous attempts. The present result has instead demonstrated the feasibility and favorable results of employing LIBS with a ps laser and low-pressure helium ambient gas as a less costly and more practical alternative to inductively coupled plasma for regular high sensitive inspection of harmful food preservatives and environmental pollutants.

  2. A Comparison in laser precision drilling of stainless steel 304 with nanosecond and picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyu; Di, Jianke; Zhou, Ming; Yan, Yu

    2014-09-01

    Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected zone. However, a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous research. In the present study, a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system, respectively. The quality of the micro-holes, e.g., recast layer, micro-crack, circularity, and conicity, etc, is evaluated by employing an optical microscope, an optical interferometer, and a scanning electron microscope. Additionally, the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching treatment. The researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled micro-holes. The formation of a recast layer with a thickness of ˜25 μm is detected on the side walls, associated with initiation of micro-cracks. Tapering phenomenon is also observed and the circularity of the micro-holes is rather poor. With regard to the micro-holes drilled by picosecond laser, the entrance ends, the exit ends, and the side walls are quite smooth without accumulation of spattering material, formation of recast layer and micro-cracks. The circularity of the micro-holes is fairly good without observation of tapering phenomenon. Furthermore, there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent material. This study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.

  3. Comparison of responses of tattoos to picosecond and nanosecond Q-switched neodymium: YAG lasers.

    PubMed

    Ross, V; Naseef, G; Lin, G; Kelly, M; Michaud, N; Flotte, T J; Raythen, J; Anderson, R R

    1998-02-01

    To test the hypothesis that picosecond laser pulses are more effective than nanosecond domain pulses in clearing of tattoos. Intratattoo comparison trial of 2 laser treatment modalities. A large interdisciplinary biomedical laser laboratory on the campus of a tertiary medical center. Consecutive patients with black tattoos were enrolled; all 16 patients completed the study. We treated designated parts of the same tattoo with 35-picosecond and 10-nanosecond pulses from 2 neodymium:YAG lasers. Patients received a total of 4 treatments at 4-week intervals. All laser pulse parameters were held constant except pulse duration. Radiation exposure was 0.65 J/cm2 at the skin surface. Biopsies were performed for routine microscopic and electron microscopic analysis at the initial treatment session and 4 weeks after the final treatment in 8 consenting patients. Also, ink samples were irradiated in vitro. In vivo, on the completion of treatment, a panel of dermatologists not associated with the study (and blinded to the treatment type) evaluated photographs to assess tattoo lightening. Formalin-fixed specimens were examined for qualitative epidermal and dermal changes as well as depth of pigment alteration. Electron micrographs were examined for particle electron density and size changes (in vivo and in vitro). The gross in vitro optical density changes were measured. In 12 of 16 tattoos, there was significant lightening in the picosecond-treated areas compared with those treated with nanosecond pulses. Mean depth of pigment alteration was greater for picosecond pulses, but the difference was not significant. In vivo biopsy specimens showed similar electron-lucent changes for both pulse durations. In vitro results were similar for both pulse durations, showing increases in particle sizes and decreased electron density as well as gross ink lightening. Picosecond pulses are more efficient than nanosecond pulses in clearing black tattoos. Black tattoos clear principally by laser

  4. Picosecond excite-and-probe absorption measurement of the 4T2 state nonradiative lifetime in ruby

    NASA Technical Reports Server (NTRS)

    Gayen, S. K.; Wang, W. B.; Petricevic, V.; Dorsinville, R.; Alfano, R. R.

    1985-01-01

    In a picosecond excite-and-probe absorption measurement, a 527-nm picosecond pulse excites the 4T2 state of the Cr(3+) ion in ruby and a 3.4-micron picosecond probe pulse monitors the growth and decay of population in the 2E state as a function of pump-probe delay. From the growth of population in the metastable 2E state, an upper limit of 7 ps for the nonradiative lifetime of the 4T2 state is determined.

  5. Laser-electron Compton interaction in plasma channels

    SciTech Connect

    Pogorelsky, I.V.; Ben-Zvi, I.; Hirose, T.

    1998-10-01

    A concept of high intensity femtosecond laser synchrotron source (LSS) is based on Compton backscattering of focused electron and laser beams. The short Rayleigh length of the focused laser beam limits the length of interaction to a few picoseconds. However, the technology of the high repetition rate high-average power picosecond lasers required for high put through LSS applications is not developed yet. Another problem associated with the picosecond laser pulses is undesirable nonlinear effects occurring when the laser photons are concentrated in a short time interval. To avoid the nonlinear Compton scattering, the laser beam has to be split, and the required hard radiation flux is accumulated over a number of consecutive interactions that complicates the LSS design. In order to relieve the technological constraints and achieve a practically feasible high-power laser synchrotron source, the authors propose to confine the laser-electron interaction region in the extended plasma channel. This approach permits to use nanosecond laser pulses instead of the picosecond pulses. That helps to avoid the nonlinear Compton scattering regime and allows to utilize already existing technology of the high-repetition rate TEA CO{sub 2} lasers operating at the atmospheric pressure. They demonstrate the advantages of the channeled LSS approach by the example of the prospective polarized positron source for Japan Linear Collider.

  6. Note: electronic circuit for two-way time transfer via a single coaxial cable with picosecond accuracy and precision.

    PubMed

    Prochazka, Ivan; Kodet, Jan; Panek, Petr

    2012-11-01

    We have designed, constructed, and tested the overall performance of the electronic circuit for the two-way time transfer between two timing devices over modest distances with sub-picosecond precision and a systematic error of a few picoseconds. The concept of the electronic circuit enables to carry out time tagging of pulses of interest in parallel to the comparison of the time scales of these timing devices. The key timing parameters of the circuit are: temperature change of the delay is below 100 fs/K, timing stability time deviation better than 8 fs for averaging time from minutes to hours, sub-picosecond time transfer precision, and a few picoseconds time transfer accuracy.

  7. Recording the synchrotron radiation by a picosecond streak camera for bunch diagnostics in cyclic accelerators

    NASA Astrophysics Data System (ADS)

    Vereshchagin, A. K.; Vorob'ev, N. S.; Gornostaev, P. B.; Dorokhov, V. L.; Kryukov, S. S.; Lozovoi, V. I.; Meshkov, O. I.; Nikiforov, D. A.; Smirnov, A. V.; Shashkov, E. V.; Schelev, M. Ya

    2016-02-01

    A PS-1/S1 picosecond streak camera with a linear sweep is used to measure temporal characteristics of synchrotron radiation pulses on a damping ring (DR) at the Budker Institute of Nuclear Physics (BINP) of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk). The data obtained allow a conclusion as to the formation processes of electron bunches and their 'quality' in the DR after injection from the linear accelerator. The expediency of employing the streak camera as a part of an optical diagnostic accelerator complex for adjusting the injection from a linear accelerator is shown. Discussed is the issue of designing a new-generation dissector with a time resolution up to a few picoseconds, which would allow implementation of a continuous bunch monitoring in the DR during mutual work with the electron-positron colliders at the BINP.

  8. Tracing temperature in a nanometer size region in a picosecond time period.

    PubMed

    Nakajima, Kaoru; Kitayama, Takumi; Hayashi, Hiroaki; Matsuda, Makoto; Sataka, Masao; Tsujimoto, Masahiko; Toulemonde, Marcel; Bouffard, Serge; Kimura, Kenji

    2015-08-21

    Irradiation of materials with either swift heavy ions or slow highly charged ions leads to ultrafast heating on a timescale of several picosecond in a region of several nanometer. This ultrafast local heating result in formation of nanostructures, which provide a number of potential applications in nanotechnologies. These nanostructures are believed to be formed when the local temperature rises beyond the melting or boiling point of the material. Conventional techniques, however, are not applicable to measure temperature in such a localized region in a short time period. Here, we propose a novel method for tracing temperature in a nanometer region in a picosecond time period by utilizing desorption of gold nanoparticles around the ion impact position. The feasibility is examined by comparing with the temperature evolution predicted by a theoretical model.

  9. Amplification of picosecond pulses in a 140-GHz gyrotron-traveling wave tube.

    PubMed

    Kim, H J; Nanni, E A; Shapiro, M A; Sirigiri, J R; Woskov, P P; Temkin, R J

    2010-09-24

    An experimental study of picosecond pulse amplification in a gyrotron-traveling wave tube (gyro-TWT) has been carried out. The gyro-TWT operates with 30 dB of small signal gain near 140 GHz in the HE₀₆ mode of a confocal waveguide. Picosecond pulses show broadening and transit time delay due to two distinct effects: the frequency dependence of the group velocity near cutoff and gain narrowing by the finite gain bandwidth of 1.2 GHz. Experimental results taken over a wide range of parameters show good agreement with a theoretical model in the small signal gain regime. These results show that in order to limit the pulse broadening effect in gyrotron amplifiers, it is crucial to both choose an operating frequency at least several percent above the cutoff of the waveguide circuit and operate at the center of the gain spectrum with sufficient gain bandwidth.

  10. In-line monitoring of advanced copper CMP processes with picosecond ultrasonic metrology

    NASA Astrophysics Data System (ADS)

    Hsieh, Ming Hsun; Yeh, J. H.; Tsai, Mingsheng; Yang, Chan Lon; Tan, John; Leary, Sean Patrick

    2006-03-01

    Chemical mechanical planarization (CMP) is a challenging process step for manufacturers implementing dualdamascene architectures at the 65 nm technology node. The polishing rate can vary significantly from wafer-to-wafer, across a single wafer, and across a single die, depending on factors including electroplate profile, slurry chemistry, pad wear, and underlying structure. The process is further complicated by the introduction of low-k dielectrics that have significantly different mechanical properties than the harder SiO II they replace. Picosecond ultrasonics is a nondestructive, small-spot method that can be used for in-line on-product monitoring of metal processes including copper CMP. In this paper we will present gauge-capable picosecond ultrasonic results on copper erosion test structures that also demonstrate excellent correlation with electrical test measurements and TEM results on 65 nm products.

  11. Raman linewidth measurements using time-resolved hybrid picosecond/nanosecond rotational CARS.

    PubMed

    Nordström, Emil; Hosseinnia, Ali; Brackmann, Christian; Bood, Joakim; Bengtsson, Per-Erik

    2015-12-15

    We report an innovative approach for time-domain measurements of S-branch Raman linewidths using hybrid picosecond/nanosecond pure-rotational coherent anti-Stokes Raman spectroscopy (RCARS). The Raman coherences are created by two picosecond excitation pulses and are probed using a narrow-band nanosecond pulse at 532 nm. The generated RCARS signal contains the entire coherence decay in a single pulse. By extracting the decay times of the individual transitions, the J-dependent Raman linewidths can be calculated. Self-broadened S-branch linewidths for nitrogen and oxygen at 293 K and ambient pressure are in good agreement with previous time-domain measurements. Experimental considerations of the approach are discussed along with its merits and limitations. The approach can be extended to a wide range of pressures and temperatures and has potential for simultaneous single-shot thermometry and linewidth determination.

  12. Picosecond Acoustics in Single Quantum Wells of Cubic GaN /(Al ,Ga )N

    NASA Astrophysics Data System (ADS)

    Czerniuk, T.; Ehrlich, T.; Wecker, T.; As, D. J.; Yakovlev, D. R.; Akimov, A. V.; Bayer, M.

    2017-01-01

    A picosecond acoustic pulse is used to study the photoelastic interaction in single zinc-blende GaN /AlxGa1 -x N quantum wells. We use an optical time-resolved pump-probe setup and demonstrate that tuning the photon energy to the quantum well's lowest electron-hole transition makes the experiment sensitive to the quantum well only. Because of the small width, its temporal and spatial resolution allows us to track the few-picosecond-long transit of the acoustic pulse. We further deploy a model to analyze the unknown photoelastic coupling strength of the quantum well for different photon energies and find good agreement with the experiments.

  13. Recording the synchrotron radiation by a picosecond streak camera for bunch diagnostics in cyclic accelerators

    SciTech Connect

    Vereshchagin, A K; Vorob'ev, N S; Gornostaev, P B; Kryukov, S S; Lozovoi, V I; Smirnov, A V; Shashkov, E V; Schelev, M Ya; Dorokhov, V L; Meshkov, O I; Nikiforov, D A

    2016-02-28

    A PS-1/S1 picosecond streak camera with a linear sweep is used to measure temporal characteristics of synchrotron radiation pulses on a damping ring (DR) at the Budker Institute of Nuclear Physics (BINP) of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk). The data obtained allow a conclusion as to the formation processes of electron bunches and their 'quality' in the DR after injection from the linear accelerator. The expediency of employing the streak camera as a part of an optical diagnostic accelerator complex for adjusting the injection from a linear accelerator is shown. Discussed is the issue of designing a new-generation dissector with a time resolution up to a few picoseconds, which would allow implementation of a continuous bunch monitoring in the DR during mutual work with the electron-positron colliders at the BINP. (acoustooptics)

  14. High-voltage picosecond photoconductor switch based on low-temperature-grown GaAs

    NASA Technical Reports Server (NTRS)

    Frankel, Michael Y.; Whitaker, John F.; Mourou, Gerard A.; Smith, Frank W.; Calawa, Arthur R.

    1990-01-01

    A GaAs material grown by molecular beam epitaxy at a low substrate temperature was used to fabricate a photoconductor switch that produces 6-V picosecond electrical pulses. The pulses were produced on a microwave coplanar-strip transmission line lithographically patterned on the low-temperature (LT) GaAs. A 150-fs laser pulse was used to generate carriers in the LT GaAs gap between the metal strips, partially shorting a high DC voltage placed across the lines. The 6-V magnitude of the electrical pulses obtained is believed to be limited by the laser pulse power and not by the properties of the LT GaAs. Experiments were also performed on a picosecond photoconductor switch fabricated on a conventional ion-damaged silicon-on-sapphire substrate. Although comparable pulse durations were obtained, the highest pulse voltage achieved with the latter device was 0.6 V.

  15. Tracing temperature in a nanometer size region in a picosecond time period

    PubMed Central

    Nakajima, Kaoru; Kitayama, Takumi; Hayashi, Hiroaki; Matsuda, Makoto; Sataka, Masao; Tsujimoto, Masahiko; Toulemonde, Marcel; Bouffard, Serge; Kimura, Kenji

    2015-01-01

    Irradiation of materials with either swift heavy ions or slow highly charged ions leads to ultrafast heating on a timescale of several picosecond in a region of several nanometer. This ultrafast local heating result in formation of nanostructures, which provide a number of potential applications in nanotechnologies. These nanostructures are believed to be formed when the local temperature rises beyond the melting or boiling point of the material. Conventional techniques, however, are not applicable to measure temperature in such a localized region in a short time period. Here, we propose a novel method for tracing temperature in a nanometer region in a picosecond time period by utilizing desorption of gold nanoparticles around the ion impact position. The feasibility is examined by comparing with the temperature evolution predicted by a theoretical model. PMID:26293488

  16. High-power picosecond laser drilling/machining of carbon fibre-reinforced polymer (CFRP) composites

    NASA Astrophysics Data System (ADS)

    Salama, A.; Li, L.; Mativenga, P.; Sabli, A.

    2016-02-01

    The large differences in physical and thermal properties of the carbon fibre-reinforced polymer (CFRP) composite constituents make laser machining of this material challenging. An extended heat-affected zone (HAZ) often occurs. The availability of ultrashort laser pulse sources such as picosecond lasers makes it possible to improve the laser machining quality of these materials. This paper reports an investigation on the drilling and machining of CFRP composites using a state-of-the-art 400 W picosecond laser system. Small HAZs (<25 µm) were obtained on the entry side of 6-mm-diameter hole drilled on sample of 6 mm thickness, whereas no HAZ was seen below the top surface on the cut surfaces. Multiple ring material removal strategy was used. Furthermore, the effect of laser processing parameters such as laser power, scanning speed and repetition rate on HAZ sizes and ablation depth was investigated.

  17. Femtoseconds-picoseconds nonlinear optics with nearly-mm thick cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Khoo, I. C.; Chen, Chun-Wei; Ho, Tsung-Jui; Lin, Tsung-Hsien

    2017-02-01

    We have succeeded in fabricating unusually thick (up to 550 microns), well aligned cholesteric liquid crystals that possess low scattering loss, large operating temperature range and well-defined photonic bandgap in the visible - near infrared regime. These CLC's possess sufficiently large ultrafast (sub-picosecond) electronic optical nonlinearity needed for direct compression, stretching and recompression of femtoseconds-picoseconds laser pulses without additional optics, as demonstrated by theory and experiments. Despite such world-record setting thickness, these CLC's are extremely compact in comparison to other state-of-the-art materials/devices used for similar operations. They are therefore highly promising for miniaturization and reduced complexity of photonic platform/systems for ultrafast pulse modulations.

  18. Surfaces and thin films studied by picosecond ultrasonics. Progress report, December 1, 1989--November 30, 1992

    SciTech Connect

    Maris, J.H.; Tauc, J.

    1992-05-01

    This research is the study of thin films and interfaces via the use of the picosecond ultrasonic technique. In these experiments ultrasonic waves are excited in a structure by means of a picosecond light pulse (``pump pulse``). The propagation of these waves is detected through the use of a probe light pulse that is time-delayed relative to the pump. This probe pulse measures the change {Delta}R(t) in the optical reflectivity of the structure that occurs because the ultrasonic wave changes the optical properties of the structure. This technique make possible the study of the attenuation and velocity of ultrasonic waves up to much higher frequencies than was previously possible (up to least 500 GHz). In addition, the excellent time-resolution of the method makes it possible to study nanostructures of linear dimensions down to 100 {Angstrom} or less by ultrasonic pulse-echo techniques. 25 refs.

  19. Delivery of picosecond lasers in multimode fibers for coherent anti-Stokes Raman scattering imaging.

    PubMed

    Wang, Zhiyong; Yang, Yaliang; Luo, Pengfei; Gao, Liang; Wong, Kelvin K; Wong, Stephen T C

    2010-06-07

    We investigated the possibility of using standard commercial multimode fibers (MMF), Corning SMF28 fibers, to deliver picosecond excitation lasers for coherent anti-Stokes Raman scattering (CARS) imaging. We theoretically and/or experimentally analyzed issues associated with the fiber delivery, such as dispersion length, walk-off length, nonlinear length, average threshold power for self-phase modulations, and four-wave mixing (FWM). These analyses can also be applied to other types of fibers. We found that FWM signals are generated in MMF, but they can be filtered out using a long-pass filter for CARS imaging. Finally, we demonstrated that MMF can be used for delivery of picosecond excitation lasers in the CARS imaging system without any degradation of image quality.

  20. Picosecond laser-induced breakdown at 5321 and 5347 A - Observation of frequency-dependent behavior

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

    1977-01-01

    A study is presented of picosecond laser-induced breakdown at 3547 and 5321 A of several materials. The thresholds obtained for breakdown at 5321 A are compared to previous results obtained at 1.064 microns using the same laser system. This comparison illustrates the transition of bulk laser-induced breakdown as it becomes increasingly frequency dependent. UV picosecond pulses are obtained by mixing 5321 A and 1.064 micron pulses in a KH2PO4 crystal. Upper and lower bounds on the 3547 A breakdown threshold are defined, although some effects of walk-off distortion and self-focusing are observed. The results are discussed with reference to models for the intrinsic processes involved in the breakdown, i.e., avalanche and multiphoton ionization.

  1. Picosecond fiber MOPA pumped supercontinuum source with 39 W output power.

    PubMed

    Chen, Kang Kang; Alam, Shaif-Ul; Price, Jonathan H V; Hayes, John R; Lin, Dejiao; Malinowski, Andrew; Codemard, Christophe; Ghosh, Debashri; Pal, Mrinmay; Bhadra, Shyamal K; Richardson, David J

    2010-03-15

    We report a picosecond fiber MOPA pumped supercontinuum source with 39 W output, spanning at least 0.4-2.25 microm at a repetition rate of 114.8 MHz. The 2m long PCF had a large, 4.4 microm diameter core and a high-delta design which led to an 80% coupling efficiency, high damage threshold and rapid generation of visible continuum generation from the picosecond input pulses. The high and relatively uniform power density across the visible spectral region was approximately 31.7 mW/nm corresponding to peak power density of approximately 12.5 W/nm for the 21 ps input pulses. The peak power density was increased to 26.9 W/nm by reducing the repetition rate to 28 MHz. This represents an increase in both average and peak power compared to previously reported visible supercontinuum sources from either CW pumped or pulsed-systems.

  2. Tracing temperature in a nanometer size region in a picosecond time period

    NASA Astrophysics Data System (ADS)

    Nakajima, Kaoru; Kitayama, Takumi; Hayashi, Hiroaki; Matsuda, Makoto; Sataka, Masao; Tsujimoto, Masahiko; Toulemonde, Marcel; Bouffard, Serge; Kimura, Kenji

    2015-08-01

    Irradiation of materials with either swift heavy ions or slow highly charged ions leads to ultrafast heating on a timescale of several picosecond in a region of several nanometer. This ultrafast local heating result in formation of nanostructures, which provide a number of potential applications in nanotechnologies. These nanostructures are believed to be formed when the local temperature rises beyond the melting or boiling point of the material. Conventional techniques, however, are not applicable to measure temperature in such a localized region in a short time period. Here, we propose a novel method for tracing temperature in a nanometer region in a picosecond time period by utilizing desorption of gold nanoparticles around the ion impact position. The feasibility is examined by comparing with the temperature evolution predicted by a theoretical model.

  3. Picosecond x-ray diagnostics for third and fourth generation synchrotron sources

    SciTech Connect

    DeCamp, Matthew

    2016-03-30

    In the DOE-EPSCoR State/National Laboratory partnership grant ``Picosecond x-ray diagnostics for third and fourth generation synchrotron sources'' Dr. DeCamp set forth a partnership between the University of Delaware and Argonne National Laboratory. This proposal aimed to design and implement a series of experiments utilizing, or improving upon, existing time-domain hard x-ray spectroscopies at a third generation synchrotron source. Specifically, the PI put forth three experimental projects to be explored in the grant cycle: 1) implementing a picosecond ``x-ray Bragg switch'' using a laser excited nano-structured metallic film, 2) designing a robust x-ray optical delay stage for x-ray pump-probe studies at a hard x-ray synchrotron source, and 3) building/installing a laser based x-ray source at the Advanced Photon Source for two-color x-ray pump-probe studies.

  4. Picosecond spectral coherent anti-Stokes Raman scattering imaging with principal component analysis of meibomian glands

    PubMed Central

    Lin, Chia-Yu; Suhalim, Jeffrey L.; Nien, Chyong Ly; Miljković, Miloš D.; Diem, Max; Jester, James V.; Potma, Eric. O.

    2011-01-01

    The lipid distribution in the mouse meibomian gland was examined with picosecond spectral anti-Stokes Raman scattering (CARS) imaging. Spectral CARS data sets were generated by imaging specific localized regions of the gland within tissue sections at consecutive Raman shifts in the CH2 stretching vibrational range. Spectral differences between the location specific CARS spectra obtained in the lipid-rich regions of the acinus and the central duct were observed, which were confirmed with a Raman microspectroscopic analysis, and attributed to meibum lipid modifications within the gland. A principal component analysis of the spectral data set reveals changes in the CARS spectrum when transitioning from the acini to the central duct. These results demonstrate the utility of picosecond spectral CARS imaging combined with multivariate analysis for assessing differences in the distribution and composition of lipids in tissues. PMID:21361667

  5. Coherent Smith-Purcell radiation as a diagnostic for sub-picosecond electron bunch length

    SciTech Connect

    Nguyen, D.C.

    1996-10-01

    We suggest a novel technique of measuring sub-picosecond electron bunch length base on coherent Smith-Purcell radiation (SPR) emitted when electrons pass close to the surface of a metal grating. With electron bunch lengths comparable to the grating period, we predict that coherent SPR will be emitted at large angles with respect to direction of beam propagation. As the bunch length shortens, the coherent SPR will be enhanced over the incoherent component that is normally observed at small angles. Furthermore, the angular distribution of the coherent SPR will be shifted toward smaller angles as the bunch length becomes much smaller than the grating period. By measuring the angular distribution of the coherent SPR, one can determine the bunch length of sub-picosecond electron pulses. This new technique is easy to implement and appears capable of measuring femtosecond electron bunch lengths.

  6. Localized Control of Ligand Binding in Hemoglobin: Effect of Tertiary Structure on Picosecond Geminate Recombination

    NASA Astrophysics Data System (ADS)

    Friedman, J. M.; Scott, T. W.; Fisanick, G. J.; Simon, S. R.; Findsen, E. W.; Ondrias, M. R.; MacDonald, V. W.

    1985-07-01

    The picosecond geminate rebinding of molecular oxygen was monitored in a variety of different human, reptilian, and fish hemoglobins. The fast (100 to 200 picoseconds) component of the rebinding is highly sensitive to protein structure. Both proximal and distal perturbations of the heme affect this rebinding process. The rebinding yield for the fast process correlates with the frequency of the stretching motion of the iron-proximal histidine mode (vFe-His) observed in the transient Raman spectra of photodissociated ligated hemoglobins. The high-affinity R-state species exhibit the highest values for vFe-His and the highest yields for fast rebinding, whereas low affinity R-state species and T-state species exhibit lower values of vFe-His and correspondingly reduced yields for this geminate process. These findings link protein control of ligand binding with events at the heme.

  7. Experimental investigation of picosecond dynamics following interactions between laser accelerated protons and water

    NASA Astrophysics Data System (ADS)

    Senje, L.; Coughlan, M.; Jung, D.; Taylor, M.; Nersisyan, G.; Riley, D.; Lewis, C. L. S.; Lundh, O.; Wahlström, C.-G.; Zepf, M.; Dromey, B.

    2017-03-01

    We report direct experimental measurements with picosecond time resolution of how high energy protons interact with water at extreme dose levels (kGy), delivered in a single pulse with the duration of less than 80 ps. The unique synchronisation possibilities of laser accelerated protons with an optical probe pulse were utilized to investigate the energy deposition of fast protons in water on a time scale down to only a few picoseconds. This was measured using absorbance changes in the water, induced by a population of solvated electrons created in the tracks of the high energy protons. Our results indicate that for sufficiently high doses delivered in short pulses, intertrack effects will affect the yield of solvated electrons. The experimental scheme allows for investigation of the ultrafast mechanisms occurring in proton water radiolysis, an area of physics especially important due to its relevance in biology and for proton therapy.

  8. Solitary surface acoustic waves and bulk solitons in nanosecond and picosecond laser ultrasonics.

    PubMed

    Hess, Peter; Lomonosov, Alexey M

    2010-02-01

    Recent achievements of nonlinear acoustics concerning the realization of solitons and solitary waves in crystals and their surfaces attained by nanosecond and picosecond laser ultrasonics are discussed and compared. The corresponding pump-probe setups are described, which allow an all-optical contact-free excitation and detection of short strain pulses in the broad frequency range between 10 MHz and about 300 GHz. The formation of solitons in the propagating longitudinal strain pulses is investigated for nonlinear media with intrinsic lattice-based dispersion. The excitation of solitary surface acoustic waves is realized by a geometric film-based dispersion effect. Future developments and potential applications of nonlinear nanosecond and picosecond ultrasonics are discussed.

  9. Dynamics in protein powders on the nanosecond-picosecond time scale are dominated by localized motions.

    PubMed

    Nickels, Jonathan D; García Sakai, Victoria; Sokolov, Alexei P

    2013-10-03

    We present analysis of nanosecond-picosecond dynamics of Green Fluorescence Protein (GFP) using neutron scattering data obtained on three spectrometers. GFP has a β-barrel structure that differs significantly from the structure of other globular proteins and is thought to result in a more rigid local environment. Despite this difference, our analysis reveals that the dynamics of GFP are similar to dynamics of other globular proteins such as lysozyme and myoglobin. We suggest that the same general concept of protein dynamics may be applicable to all these proteins. The dynamics of dry protein are dominated by methyl group rotations, while hydration facilitates localized diffusion-like motions in the protein. The latter has an extremely broad relaxation spectrum. The nanosecond-picosecond dynamics of both dry and hydrated GFP are localized to distances of ∼1-3.5 Å, in contrast to the longer range diffusion of hydration water.

  10. Excitation of wakefields in a relativistically hot plasma created by dying non-linear plasma wakefields

    SciTech Connect

    Sahai, A. A.; Katsouleas, T. C.; Gessner, S.; Hogan, M.; Joshi, C.; Mori, W. B.

    2012-12-21

    We study the various physical processes and their timescales involved in the excitation of wakefields in relativistically hot plasma. This has relevance to the design of a high repetition-rate plasma wakefield collider in which the plasma has not had time to cool between bunches in addition to understanding the physics of cosmic jets in relativistically hot astrophysical plasmas. When the plasma is relativistically hot (plasma temperature near m{sub e}c{sup 2}), the thermal pressure competes with the restoring force of ion space charge and can reduce or even eliminate the accelerating field of a wake. We will investigate explicitly the case where the hot plasma is created by a preceding Wakefield drive bunch 10's of picoseconds to many nanoseconds ahead of the next drive bunch. The relativistically hot plasma is created when the excess energy (not coupled to the driven e{sup -} bunch) in the wake driven by the drive e{sup -} bunch is eventually converted into thermal energy on 10's of picosecond timescale. We will investigate the thermalization and diffusion processes of this non-equilibrium plasma on longer time scales, including the effects of ambi-polar diffusion of ions driven by hot electron expansion, possible Columbic explosion of ions producing higher ionization states and ionization of surrounding neutral atoms via collisions with hot electrons. Preliminary results of the transverse and longitudinal wakefields at different timescales of separation between a first and second bunch are presented and a possible experiment to study this topic at the FACET facility is described.

  11. Magnetic vortex dynamics on a picosecond timescale in a hexagonal permalloy pattern

    SciTech Connect

    Shim, J.-H.; Kim, D.-H.; Mesler, B.; Moon, J.-H.; Lee, K.-J.; Anderson, E. H.; Fischer, P.

    2009-12-02

    We have observed a motion of magnetic vortex core in a hexagonal Permalloy pattern by means of Soft X-ray microscopy. Pump-probe stroboscopic observation on a picosecond timescale has been carried out after exciting a ground state vortex structure by an external field pulse of 1 ns duration. Vortex core is excited off from the center position of the hexagonal pattern but the analysis of the core trajectory reveals that the motion is nongyrotropic.

  12. Semiconductors Investigated by Time Resolved Raman Absorption and Photoluminescence Spectroscopy Using Femtosecond and Picosecond Laser Techniques.

    DTIC Science & Technology

    1983-05-05

    if necessary and identify by block number) Picosecond Lasers, Femtosecond Lasers, Ring Cavity, Mode Locked Dye and Glass Lasers, Time-resolved...conductor processes. In addition, we have improved the stabil ity and shortened the pulse duration emitted from a mode - locked glass laser by at...pulse duration emitted from a mode -locked glass laser by at least a factor of two, by using heptamethine pyrylium #5 - a new saturable absorber. In the

  13. Electronic Raman scattering from terbium gallium garnet excited with a picosecond laser

    NASA Astrophysics Data System (ADS)

    Koningstein, J. A.; Lemaire, H.; Atkinson, G. H.

    1987-09-01

    The electronic Raman (ER) spectrum of terbium gallium garnet, recorded using picosecond radiation from the frequency-doubled output of a Nd:YAG laser is reported. The observed spectral bands with frequency shifts up to 6000 cm-1 are the result of the effect of a strong crystal field which causes J-mixing between the 7F 6,5,....,0 states. The site symmetry of Tb 3+ in the garnet can be confirmed from this spectroscopy.

  14. Applications of infrared free electron lasers in picosecond and nonlinear spectroscopy

    NASA Astrophysics Data System (ADS)

    Fann, W. S.; Benson, S. V.; Madey, J. M. J.; Etemad, S.; Baker, G. L.; Rothberg, L.; Roberson, M.; Austin, R. H.

    1990-10-01

    In this paper we describe two different types of spectroscopic experiments that exploit the characteristics of the infrared FEL, Mark III, for studies of condensed matter: - the spectrum of χ(3)(-3ω; ω, ω, ω) in polyacetylene: an application of the free electron laser in nonlinear optical spectroscopy, and - a dynamical test of Davydov-like solitons in acetanilide using a picosecond free electron laser. These two studies highlight the unique contributions FELs can make to condensed-matter spectroscopy.

  15. Generation of picosecond laser pulses at 1030 nm with gigahertz range continuously tunable repetition rate.

    PubMed

    Aubourg, Adrien; Lhermite, Jérôme; Hocquet, Steve; Cormier, Eric; Santarelli, Giorgio

    2015-12-01

    We report on a watt range laser system generating picosecond pulses using electro-optical modulation of a 1030 nm single frequency low noise laser diode. Its repetition rate is continuously tunable between 11 and 18 GHz. Over this range, output spectra and pulse characteristics are measured and compared with a numerical simulation. Finally, amplitude and residual phase noise measurements of the source are also presented.

  16. Power scaling of a picosecond vortex laser based on a stressed Yb-doped fiber amplifier.

    PubMed

    Koyama, Mio; Hirose, Tetsuya; Okida, Masahito; Miyamoto, Katsuhiko; Omatsu, Takashige

    2011-01-17

    Power scaling of a picosecond vortex laser based on a stressed Yb-doped fiber amplifier is analyzed. An output power of 25 W was obtained for 53 W of pumping, with a peak power of 37 kW. Frequency doubling of the vortex output was demonstrated using a nonlinear PPSLT crystal. A second-harmonic output power of up to 1.5 W was measured at a fundamental power of 11.2 W.

  17. High-average-power and high-beam-quality Innoslab picosecond laser amplifier.

    PubMed

    Xu, Liu; Zhang, Hengli; Mao, Yefei; Yan, Ying; Fan, Zhongwei; Xin, Jianguo

    2012-09-20

    We demonstrated a laser-diode, end-pumped picosecond amplifier. With effective shaping of the seed laser, we achieved 73 W amplified laser output at the pump power of 255 W, and the optical-optical efficiency was about 28%. The beam propagation factors M(2) measured at the output power of 60 W in the horizontal direction and the vertical direction were 1.5 and 1.4, respectively.

  18. Spontaneous picosecond pulse generation in a diode-pumped Nd:YAP laser.

    PubMed

    Chen, Weidong; Li, Yanying; Zhang, Ge; Huang, Yihui; Chen, Zhenqiang

    2013-10-21

    We present the first observation, to the best of our knowledge, the spontaneous generation of picoseconds pulse trains in a diode-pumped Nd:YAP laser with gigahertz repetition rate. Spatially dependent temporal dynamics were experimentally observed. After theoretically reconstruct the experimental temporal-resolved patterns, we verify that the complicated spatially-dependent temporal dynamics were originated from simultaneous coherent locking combination of fundamental and several additional higher-order transverse modes.

  19. Observation of coherent undulator radiation from sub-picosecond electron pulses

    SciTech Connect

    Bocek, D.; Hernandez, M.; Kung, P.; Lihn, Hung-chi; Settakorn, C.; Wiedemann, H.

    1995-09-01

    The generation and observation of high power, coherent, far-infrared undulator radiation from sub-picosecond electron bunches at the SUNSHINE facility is reported. Coherent undulator radiation tunable from 50 to 200 microns wavelength is demonstrated. Measurements of the energy (up to 1.7 mJ per 1 microsecs macropulse), frequency spectrum, and spatial distribution of the radiation are reported. Apparent exponential growth of the radiated energy as a function of undulator length is observed.

  20. Shaping pulses using frequency conversion with a modulated picosecond free electron laser

    SciTech Connect

    Hooper, B.A.; Madey, J.M.J.

    1995-12-31

    Computer simulations and experiments indicate that we can shape the infrared picosecond pulses of the Mark III FEL in amplitude, frequency, and phase. Strongly modulated fundamental and second harmonic pulses have been generated by operating the Mark III FEL in the regime of strong sideband growth. In this paper, we present the results of simulations and experiments for second harmonic generation with fundamental inputs from 2 to 3 {mu}m.

  1. Toward picosecond time-resolved X-ray absorption studies of interfacial photochemistry

    NASA Astrophysics Data System (ADS)

    Gessner, Oliver; Mahl, Johannes; Neppl, Stefan

    2016-05-01

    We report on the progress toward developing a novel picosecond time-resolved transient X-ray absorption spectroscopy (TRXAS) capability for time-domain studies of interfacial photochemistry. The technique is based on the combination of a high repetition rate picosecond laser system with a time-resolved X-ray fluorescent yield setup that may be used for the study of radiation sensitive materials and X-ray spectroscopy compatible photoelectrochemical (PEC) cells. The mobile system is currently deployed at the Advanced Light Source (ALS) and may be used in all operating modes (two-bunch and multi-bunch) of the synchrotron. The use of a time-stamping technique enables the simultaneous recording of TRXAS spectra with delays between the exciting laser pulses and the probing X-ray pulses spanning picosecond to nanosecond temporal scales. First results are discussed that demonstrate the viability of the method to study photoinduced dynamics in transition metal-oxide semiconductor (SC) samples under high vacuum conditions and at SC-liquid electrolyte interfaces during photoelectrochemical water splitting. Opportunities and challenges are outlined to capture crucial short-lived intermediates of photochemical processes with the technique. This work was supported by the Department of Energy Office of Science Early Career Research Program.

  2. Clearance of yellow tattoo ink with a novel 532-nm picosecond laser.

    PubMed

    Alabdulrazzaq, Hamad; Brauer, Jeremy A; Bae, Yoon-Soo; Geronemus, Roy G

    2015-04-01

    Although technology and tattoo removal methods continue to evolve, yellow pigment clearance continues to be challenging and usually unsuccessful. We describe a case series of six tattoos containing yellow ink, successfully treated with a frequency-doubled Nd:YAG 532-nm picosecond laser. Case series with six subjects participating for the treatment of multicolored tattoos that contain yellow pigment. Treatments performed with a frequency-doubled Nd:YAG 532-nm picosecond laser at 6-8 week intervals. One subject achieved complete clearance of the treated site after one session, and five subjects required 2-4 treatments to achieve over 75% clearance. Minimal downtime was experienced, and no scarring or textural skin changes were observed in any of the treated sites. This is the first case series that demonstrates effective and consistent reduction of yellow tattoo ink using a frequency doubled Nd:YAG 532-nm laser with a picosecond pulse duration. Treatments were well tolerated and subjects had positive outcomes. This is a small observational case series from an ongoing clinical trial, and studies with a larger sample size and comparative group are needed in the future. © 2015 Wiley Periodicals, Inc.

  3. Laser Treatment of Professional Tattoos With a 1064/532-nm Dual-Wavelength Picosecond Laser.

    PubMed

    Kauvar, Arielle N B; Keaney, Terrence C; Alster, Tina

    2017-09-19

    Picosecond-domain laser pulses improve the photomechanical disruption of tattoos. This study evaluates the efficacy and safety of a novel, dual-wavelength, 1,064/532-nm, picosecond-domain laser for tattoo clearance. This was a prospective, self-controlled, clinical study of 34 subjects with 39 tattoos treated at 2 sites with an interval of 4.8 ± 1.6 weeks and up to 10 treatments (mean, 7.5). Blinded evaluation and investigator assessment of serial digital images was performed to evaluate treatment efficacy in the 36 tattoos that received at least 3 treatments. Investigators also assessed efficacy before each treatment visit up to 10 treatments. Safety and tolerability was evaluated for all 39 tattoos that underwent at least 1 treatment. Blinded evaluation demonstrated that lightening of tattoos was achieved in all subjects, with 86% (31 of 36 tattoos) showing at least a 50% clearance after 3 treatments. Adverse events were few and transient in nature. Patient satisfaction and treatment tolerability were high. Treatment of single-colored and multicolored tattoos with this novel 1,064/532-nm picosecond laser is highly safe and effective.

  4. Detection of nonlinear picosecond acoustic pulses by time-resolved Brillouin scattering

    SciTech Connect

    Gusev, Vitalyi E.

    2014-08-14

    In time-resolved Brillouin scattering (also called picosecond ultrasonic interferometry), the time evolution of the spatial Fourier component of an optically excited acoustic strain distribution is monitored. The wave number is determined by the momentum conservation in photon-phonon interaction. For linear acoustic waves propagating in a homogeneous medium, the detected time-domain signal of the optical probe transient reflectivity shows a sinusoidal oscillation at a constant frequency known as the Brillouin frequency. This oscillation is a result of heterodyning the constant reflection from the sample surface with the Brillouin-scattered field. Here, we present an analytical theory for the nonlinear reshaping of a propagating, finite amplitude picosecond acoustic pulse, which results in a time-dependence of the observed frequency. In particular, we examine the conditions under which this information can be used to study the time-evolution of the weak-shock front speed. Depending on the initial strain pulse parameters and the time interval of its nonlinear transformation, our theory predicts the detected frequency to either be monotonically decreasing or oscillating in time. We support these theoretical predictions by comparison with available experimental data. In general, we find that picosecond ultrasonic interferometry of nonlinear acoustic pulses provides access to the nonlinear acoustic properties of a medium spanning most of the GHz frequency range.

  5. A low timing jitter picosecond microchip laser pumped by pulsed LD

    NASA Astrophysics Data System (ADS)

    Wang, Sha; Wang, Yan-biao; Feng, Guoying; Zhou, Shou-huan

    2016-07-01

    SESAM passively Q-switched microchip laser is a very promising instrument to replace mode locked lasers to obtain picosecond pulses. The biggest drawback of a passively Q-switched microchip laser is its un-avoided large timing jitter, especially when the pump intensity is low, i.e. at low laser repetition rate range. In order to obtain a low timing jitter passively Q-switched picosecond microchip laser in the whole laser repetition rate range, a 1000 kHz pulsed narrow bandwidth Fiber Bragg Grating (FBG) stablized laser diode was used as the pump source. By tuning the pump intensity, we could control the output laser frequency. In this way, we achieved a very low timing jitter passively Q-switched picosecond laser at 2.13 mW, 111.1 kHz. The relative timing jitter was only 0.0315%, which was around 100 times smaller compared with a cw LD pumped microchip working at hundred kilohertz repetition rate frequency range.

  6. A study of transient stimulated Raman scattering and self-focusing in the picosecond time regime

    NASA Technical Reports Server (NTRS)

    Reintjes, J. F.

    1971-01-01

    Two third order processes, stimulated Raman scattering and self-focusing, with picosecond pulses are studied. In the case of transient stimulated scattering, the gain is reduced from the steady state value, and qualitatively new features, such as shortening and delay of the Stokes pulse relative to the laser pulse, appear. These predictions are extended to realistic laser pulses, and experiments confirm all of the theoretical predictions. The self-focusing and frequency broadening of picosecond pulses is studied in the absence of stimulated Raman scattering in several materials with large orientational Kerr constants. Measurements of the relaxation time indicate that the orientational Kerr effect is important in the self-focusing of picosecond pulses. Self-focused filaments are observed to propagate with constant diameters over a distance greater than 10 cm, but disappear before the end of a 20 cm cell. The filaments radiate light continuously along their path and the spectrum of the light shows that the frequency content extends symmetrically for several hundred wave numbers on either side of the laser frequency.

  7. Few-femtosecond timing jitter from a picosecond all-polarization-maintaining Yb-fiber laser.

    PubMed

    Chen, Wei; Song, Youjian; Jung, Kwangyun; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

    2016-01-25

    We characterize the timing jitter of a picosecond all-polarization-maintaining (all-PM) Yb-fiber laser using the optical cross-correlation method. For the 10 MHz all-normal dispersion mode-locked laser with ~0.5 nm spectral bandwidth, the measured high-frequency jitter is as low as 5.9 fs (RMS) when integrated from 10 kHz to the Nyquist frequency of 5 MHz. A complete numerical model with ASE noise is built to simulate the timing jitter characteristics in consideration of intracavity pulse evolution. The mutual comparison among simulation result, analytical model and experiment data indicate that the few femtosecond timing jitter from the picosecond fiber laser is attributed to the complete elimination of Gordon-Haus jitter by narrow bandpass filtering by a fiber Bragg grating (FBG). The low level of timing jitter from this compact and maintenance-free PM picosecond fiber laser source at a low MHz repetition rate is promising to advance a number of femtosecond-precision timing and synchronization applications.

  8. Stretching of Picosecond Laser Pulses with Uniform Reflecting Volume Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Mokhov, Sergiy

    It is shown that a uniform reflecting volume Bragg grating (VBG) can be used as a compact monolithic stretcher of high-power picosecond laser pulses in cases when chirped Bragg gratings with an appropriate chirp rate are difficult to fabricate. A chirp-free reflected stretched pulse is generated of almost rectangular shape when incident short pulse propagates along a grating and experiences local Bragg diffraction. The increase in duration of the reflected pulse is approximately equal to twice the propagation times along the grating. We derived the analytic expression for diffraction efficiency, which incorporates incident pulse duration, grating thickness, and amplitude of refractive index modulation, enabling an optimum selection of the grating for pulse stretching. The typical expected theoretical value of diffraction efficiency is about 10% after taking into account the spectral narrowing of the reflected emission. We believe that the relatively low energy efficiency of the proposed method is more than offset by a number of advantages, which are chirp-free spectrum of a stretched pulse, compactness, robustness, preservation of setup alignment and beam quality, and tolerance to high power. Obtained pulses of several tens of picoseconds can be amplified by standard methods which are not requiring special measures to avoid undesirable non-linear effects. We propose a simple and reliable method to control the temporal parameters of the high-power picosecond pulses using the same laser source and the VGB of variable thickness that can significantly simplify the experiments requiring different pulse durations.

  9. Picosecond-time-resolved studies of nonradiative relaxation in ruby and alexandrite

    SciTech Connect

    Gayen, S.K.; Wang, W.B.; Petricevic, V.; Alfano, R.R.

    1985-01-01

    Dynamics of the nonradiative transitions between the /sup 4/T/sub 2/ pump band and the /sup 2/E storage level of the Cr/sup 3 +/ ion in ruby and alexandrite crystals is studied using the picosecond excite-and-probe absorption technique. A 527-nm picosecond pulse excites the /sup 4/T/sub 2/ state of the Cr/sup 3 +/ ion, and an infrared picosecond probe pulse monitors the subsequent growth and decay of population in the excited states as a function of pump-probe delay. An upper limit of 7 ps is determined for the nonradiative lifetime of the /sup 4/T/sub 2/ state in ruby. A vibrational relaxation time of 25 ps for the /sup 4/T/sub 2/ band in alexandrite is estimated. The time to attain thermal equilibrium population between the /sup 2/E and /sup 4/T/sub 2/ levels of alexandrite following excitation of /sup 4/T/sub 2/ band is estimated to be approx. 100 ps.

  10. Refractive index, sound velocity and thickness of thin transparent films from multiple angles picosecond ultrasonics

    SciTech Connect

    Cote, R.; Devos, A.

    2005-05-15

    We present a method for refractive indices and longitudinal sound velocity measurements from picosecond ultrasonic experiments made at different probe incidence angles. For transparent or semitransparent materials such as dielectrics or semiconductors, picosecond ultrasonic experiments can lead to oscillations in the reflectivity curves whose frequency depends on the refractive indices, the sound velocity and the experiments angle. From these data we establish a simple method for the calculation of the refractive indices and verify it on a GaAs sample. We show on fluorinated silica glass and aluminum nitride practical applications of this method on thin films. From two experiments we measure the refraction index and the sound velocity of these materials, with no assumption on the materials properties or on the sample layers' thicknesses. Here the materials are buried under a thin aluminum film. It illustrates the fact that the method can be applied to multilayers. From the same experiments we then derive the thickness of the layers. It shows that this method can render picosecond ultrasonic experiments independent from other characterization means.

  11. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Temporal and thermodynamic characteristics of plasma formation

    NASA Astrophysics Data System (ADS)

    Ignatavichyus, M. V.; Kazakyavichyus, É.; Orshevski, G.; Danyunas, V.

    1991-11-01

    An investigation was made of plasma formation accompanying the interaction with aluminum, iron, and VK-6 alloy targets of nanosecond radiation from a YAG:Nd3+ laser (Emax = 50 mJ, τ = 3-8 ns). The duration of the plasma formation process depended weakly on the laser radiation parameters [the power density was varied in the range 1-3 GW/cm2, the pulse rise time in the range 2-8 ns, or the rate of rise of the power density in the range (1-8) × 108 W · cm - 2 · ns -1]. A study was made of the establishment of a local thermodynamic equilibrium in a plasma jet excited by radiation from nanosecond and picosecond (E = 30 mJ, τ = 40 ps) lasers. The maximum of the luminescence from an aluminum plasma excited by picosecond laser radiation was found to correspond to a local thermodynamic equilibrium. A local thermodynamic equilibrium could be absent in the case of excitation by nanosecond laser radiation.

  12. Picosecond laser welding of optical to metal components

    NASA Astrophysics Data System (ADS)

    Carter, Richard M.; Troughton, Michael; Chen, Jinanyong; Elder, Ian; Thomson, Robert R.; Lamb, Robert A.; Esser, M. J. Daniel; Hand, Duncan P.

    2016-03-01

    We report on practical, industrially relevant, welding of optical components to themselves and aluminum alloy components. Weld formation is achieved through the tight focusing of a 5.9ps, 400kHz Trumpf laser operating at 1030nm. By selecting suitable surface preparation, clamping and laser parameters, the plasma can be confined, even with comparatively rough surfaces, by exploiting the melt properties of the glass. The short interaction time allows for a permanent weld to form between the two materials with heating limited to a region ~300 µm across. Practical application of these weld structures is typically limited due to the induced stress within the glass and, critically, the issues surrounding post-weld thermal expansion. We report on the measured strength of the weld, with a particular emphasis on laser parameters and surface preparation.

  13. Laser-driven plasma photonic crystals for high-power lasers

    NASA Astrophysics Data System (ADS)

    Lehmann, G.; Spatschek, K. H.

    2017-05-01

    Laser-driven plasma density gratings in underdense plasma are shown to act as photonic crystals for high power lasers. The gratings are created by counterpropagating laser beams that trap electrons, followed by ballistic ion motion. This leads to strong periodic plasma density modulations with a lifetime on the order of picoseconds. The grating structure is interpreted as a plasma photonic crystal time-dependent property, e.g., the photonic band gap width. In Maxwell-Vlasov and particle-in-cell simulations it is demonstrated that the photonic crystals may act as a frequency filter and mirror for ultra-short high-power laser pulses.

  14. PRIMARY TESTS OF LASER / E BEAM INTERACTION IN A PLASMA CHANNEL.

    SciTech Connect

    POGORELSKY,I.V.; BEN ZVI,I.; HIROSE,T.; YAKIMENKO,V.; KUSCHE,K.; SIDDONS,P.; ET AL

    2002-06-23

    A high-energy CO{sub 2} laser is channeled in a capillary discharge. Plasma dynamic simulations confirm occurrence of guiding conditions at the relatively low axial plasma density 1 {divided_by} 4 x 10{sup 17} cm{sup -3}. A relativistic electron beam transmitted through the capillary changes its properties depending upon the plasma density. We observe focusing, defocusing or steering of the e-beam. Counter-propagation of the electron and laser beams in the plasma channel results in generation of intense picosecond x-ray pulses.

  15. Comoving acceleration of overdense electron-positron plasma by colliding ultra-intense laser pulses

    SciTech Connect

    Liang, Edison

    2006-06-15

    Particle-in-cell (PIC) simulation results of sustained acceleration of electron-positron (e+e-) plasmas by comoving electromagnetic (EM) pulses are presented. When a thin slab of overdense e+e- plasma is irradiated with linear-polarized ultra-intense short laser pulses from both sides, the pulses are transmitted when the plasma is compressed to thinner than {approx}2 relativistic skin depths. A fraction of the plasma is then captured and efficiently accelerated by self-induced JxB forces. For 1 {mu}m laser and 10{sup 21} W cm{sup -2} intensity, the maximum energy exceeds GeV in a picosecond.

  16. Picosecond Raman Study of Vibrational Cooling and Protein Dynamics in the Primary Photochemistry of Rhodopsin

    NASA Astrophysics Data System (ADS)

    Kim, Judy; Mathies, Richard

    2003-03-01

    Picosecond Stokes and anti-Stokes Raman spectra are used to probe the structural dynamics and reactive energy flow of both the chromophore and binding pocket residues in the primary cis-to-trans isomerization reaction of rhodopsin. The appearance of characteristic ethylenic, hydrogen out-of-plane (HOOP) and low-wavenumber photoproduct bands in the Stokes Raman spectra of the chromophore is instrument-response limited, consistent with a sub-picosecond product appearance time (1,2). Intense high and low-frequency anti-Stokes chromophore peaks demonstrate that the all-trans photoproduct, photorhodopsin, is produced vibrationally hot on the ground-state surface (2). Specifically, the low-frequency modes at 282, 350 and 477 cm-1 are highly vibrationally excited (T > 2000 K) immediately following isomerization, revealing that these low-frequency motions directly participate in the reactive curve-crossing process. The anti-Stokes modes are characterized by a ˜2.5 ps temporal decay that coincides with the conversion of photorhodopsin to bathorhodopsin. This correspondence shows that the photo-to-batho transition is a ground-state cooling process, and that energy storage in the primary visual photoproduct is complete on the picosecond time scale. The remarkable similarity between the room-temperature picosecond vibrational structure of photo- and bathorhodopsin and that of the low-temperature trapped primary photoproduct suggests that chromophore isomerization impulsively excites and drives changes in nearby protein residues. These amino acid changes within the binding pocket are probed by picosecond UV Raman spectroscopy of aromatic residues (3). Difference spectra reveal that at least one tryptophan (trp265) and one tyrosine (tyr191, 268 and/or 178) residue undergoes structural changes in < 5 ps, presumably due to steric interaction with the isomerizing chromophore as well as energy flow from chromophore to the binding pocket. This result indicates that the protein

  17. Interaction physics of multipicosecond Petawatt laser pulses with overdense plasma.

    PubMed

    Kemp, A J; Divol, L

    2012-11-09

    We study the interaction of intense petawatt laser pulses with overdense plasma over several picoseconds, using two- and three-dimensional kinetic particle simulations. Sustained irradiation with non-diffraction-limited pulses at relativistic intensities yields conditions that differ qualitatively from what is experimentally available today. Nonlinear saturation of laser-driven density perturbations at the target surface causes recurrent emissions of plasma, which stabilize the surface and keep absorption continuously high. This dynamics leads to the acceleration of three distinct groups of electrons up to energies many times the laser ponderomotive potential. We discuss their energy distribution for applications like the fast-ignition approach to inertial confinement fusion.

  18. Picosecond laser ablation of nano-sized WTi thin film

    NASA Astrophysics Data System (ADS)

    Petrović, S.; Gaković, B.; Peruško, D.; Desai, T.; Batani, D.; Čekada, M.; Radak, B.; Trtica, M.

    2009-08-01

    Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm2 were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma.

  19. Effects of laser polarization in the expansion of plasma waveguides

    NASA Astrophysics Data System (ADS)

    Lemos, N.; Grismayer, T.; Cardoso, L.; Geada, J.; Figueira, G.; Dias, J. M.

    2013-10-01

    We experimentally demonstrate that a column of hydrogen plasma generated by an ultra-short (sub-picosecond), moderate intensity (˜1015-16 W.cm-2) laser, radially expands at a higher velocity when using a circularly polarized laser beam instead of a linearly polarized beam. Interferometry shows that after 1 ns there is a clear shock structure formed, that can be approximated to a cylindrical blast wave. The shock velocity was measured for plasmas created with linearly and circularly polarized laser beams, indicating an approximately 20% higher velocity for plasmas generated with a circularly polarized laser beam, thus implying a higher plasma electron temperature. The heating mechanism was determined to be the Above Threshold Ionization effect. The calculated electrum energy spectrum for a circularly polarized laser beam was broader when compared to the one generated by a linearly polarized laser beam, leading to a higher plasma temperature.

  20. Pressure Gradient Effects On Two-Dimensional Plasma Expansion

    SciTech Connect

    Moon, S; Smith, R F; Dunn, J; Keenan, R; Nilsen, J; Hunter, J R; Filevich, J; Rocca, J J; Marconi, M C; Shlyaptsev, V N

    2004-10-05

    Recent advances in interferometry has allowed for the characterization of the electron density expansion within a laser produced plasma to within 10 {micro}m of the target surface and over picosecond timescales. This technique employs the high brightness output of the transient gain Ni-like Pd collisional x-ray laser at 14.7 nm to construct an effective moving picture of the two-dimensional (2-D) expansion of the plasma. We present experimentally measured density profiles of an expanding Al plasma generated through laser irradiation in a 14mm line focus geometry. Significant lateral expansion was observed at all times as well as a pronounced on-axis electron density dip. Detailed modeling with a 2-D plasma physics code gives good agreement to experimental observations. Large pressure gradients associated with the tight focal spot conditions are calculated to dominate in shaping the plasma density profile.

  1. Picosecond dynamics of photochemical systems. Final report, 1/1/79-6/30/80. [(Ketone) fluorenone; 1,4-diazobicyclooctane (amine)

    SciTech Connect

    Peters, K.S.

    1980-11-17

    The mechanism of the photoreduction of aromatic ketones by amines has been investigated using picosecond absorption spectroscopy. The experiments reveal that the process involves complete electron transfer occurring within a half-life of 20 picoseconds for benzophenone/Dabco and fluorenone/Dabco.

  2. Measurements of absolute radical densities in atmospheric pressure plasmas with complex gas mixtures

    NASA Astrophysics Data System (ADS)

    O'Connell, Deborah

    2015-05-01

    Low temperature plasmas are emerging as an exciting development for therapeutics. Non-equilibrium plasmas, operated at ambient atmospheric pressure and temperature, are very efficient sources for highly reactive neutral particles, including reactive oxygen and nitrogen species (RONS), which are known to play a crucial role in biological systems and existing therapeutics. Transport of these plasma components to the target is complex. In order to understand the chemical kinetics and plasma-liquid-biological interaction mechanisms measurements of the relevant RONS are key. Under atmospheric pressure these are challenging, primarily due to the multi-phase and highly collisional environment, requiring extremely high temporal (picosecond to nanosecond) and spatial (microns) resolution. Absolute measurements of radical densities (including O and OH) using picosecond two-photon absorption laser induced fluorescence (ps-TALIF), UV and high-resolution synchrotron VUV absorption spectroscopy will be presented. Fluorescence lifetime measurements of the laser-excited radicals are possible with picosecond resolution and this provides us with information about collisional quenching partners and thus collision kinetics with the surrounding environment. The authors acknowledge support by the UK EPSRC EP/H003797 and EP/K018388.

  3. Pilot production and advanced development of large-area picosecond photodetectors

    NASA Astrophysics Data System (ADS)

    Minot, Michael J.; Adams, Bernhard W.; Aviles, Melvin; Bond, Justin L.; Craven, Christopher A.; Cremer, Till; Foley, Michael R.; Lyashenko, Alexey; Popecki, Mark A.; Stochaj, Michael E.; Worstell, William A.; Mane, Anil U.; Elam, Jeffrey W.; Siegmund, Oswald H. W.; Ertley, Camden; Frisch, Henry; Elagin, Andrey

    2016-09-01

    We report pilot production and advanced development performance results achieved for Large Area Picosecond Photodetectors (LAPPD). The LAPPD is a microchannel plate (MCP) based photodetector, capable of imaging with single-photon sensitivity at high spatial and temporal resolutions in a hermetic package with an active area of 400 square centimeters. In December 2015, Incom Inc. completed installation of equipment and facilities for demonstration of early stage pilot production of LAPPD. Initial fabrication trials commenced in January 2016. The "baseline" LAPPD employs an all-glass hermetic package with top and bottom plates and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na2KSb photocathode and amplified with a stacked chevron pair of "next generation" MCPs produced by applying resistive and emissive atomic layer deposition coatings to borosilicate glass capillary array (GCA) substrates. Signals are collected on RF strip-line anodes applied to the bottom plates which exit the detector via pinfree hermetic seals under the side walls. Prior tests show that LAPPDs have electron gains greater than 107, submillimeter space resolution for large pulses and several mm for single photons, time resolutions of 50 picoseconds for single photons, predicted resolution of less than 5 picoseconds for large pulses, high stability versus charge extraction, and good uniformity. LAPPD performance results for product produced during the first half of 2016 will be reviewed. Recent advances in the development of LAPPD will also be reviewed, as the baseline design is adapted to meet the requirements for a wide range of emerging application. These include a novel ceramic package design, ALD coated MCPs optimized to have a low temperature coefficient of resistance (TCR) and further advances to adapt the LAPPD for cryogenic applications using Liquid Argon (LAr). These developments will meet the needs for DOE-supported RD for the Deep Underground Neutrino

  4. Nonlinear optical properties of GaAs at 1. 06 micron, picosecond pulse investigation and applications

    SciTech Connect

    Cui, A.G.

    1992-01-01

    The author explores absorptive and refractive optical nonlinearities at 1.06 [mu]m in bulk, semi-insulating, undoped GaAs with a particular emphasis on the influence of the native deep-level defect known as EL2. Picosecond pump-probe experimental technique is used to study the speed, magnitude, and origin of the absorptive and refractive optical nonlinearities and to characterize the dynamics of the optical excitation of EL2 in three distinctly different undoped, semi-insulating GaAs samples. Intense optical excitation of these materials leads to the redistribution of charge among the EL2 states resulting in an absorptive nonlinearity due to different cross sections for electron and hole generation through this level. This absorptive nonlinearity is used in conjunction with the linear optical properties of the material and independent information regarding the EL2 concentration to extract the cross section ratio [sigma][sub p]/[sigma][sub e] [approx equal]0.8, where [sigma][sub p](e) is the absorption cross section for hole (electron) generation from EL2[sup +] (EL2[sup 0]). The picosecond pump-probe technique can be used to determine that EL2/EL2[sup +]density ratio in an arbitrary undoped, semi-insulating GaAs sample. The author describes the use of complementary picosecond pump-probe techniques that are designed to isolate and quantify cumulative and instantaneous absorptive and refractive nonlinear processes. Numerical simulations of the measurements are achieved by solving Maxwell equations with the material equations in a self-consistent manner. The numerical analysis together with the experimental data allows extraction of a set of macroscopic nonlinear optical parameters in undoped GaAs. The nonlinearities in this material have been used to construct three proof-of-principle nonlinear optical devices for use at 1.06 [mu]m: (1) a weak beam amplifier, (2) a polarization rotation optical switch, and (3) optical limiters.

  5. Picosecond pulse duration laser treatment for dermal melanocytosis in Asians : A retrospective review.

    PubMed

    Ohshiro, Takafumi; Ohshiro, Toshio; Sasaki, Katsumi; Kishi, Kazuo

    2016-06-29

    Background and aims: Recently novel picosecond duration lasers (ps-lasers) have been developed for the treatment of multicolored and recalcitrant tattoos, and safety and efficacy have been reported. We therefore hypothesized that the ps-laser could be an alternative treatment for dermal pigmented lesions and performed a retrospective review to evaluate the efficacy and safety of the ps-laser. Subjects and methods: A retrospective photographic review of 10 patients with dermal pigmented lesions was performed (ages from 4 months to 52 yr), 6 nevus of Ota, 3 ectopic Mongolian spots and 1 Mongolian spots. The patients were treated in the Ohshiro Clinic with picosecond 755 nm alexandrite laser (ps-Alex laser) and picosecond 1064 nm Nd:YAG laser (ps-Nd:YAG laser) from April 2014 to December 2015 (ps-Alex laser, 7 patients; ps-Nd:YAG laser, 3 patients, 1 to 3 treatment sessions). Improvement was evaluated as percentage of pigmentation clearance comparing the baseline findings with those at 3 months after the final treatment using a five category grading scale: Poor, 0-24%; Fair, 25-49%; Good, 50-74%; Excellent, 75-94%; and Complete, 95-100% improvement. Adverse events were also assessed. Results: All ten patients obtained clinical improvement ranging from fair to excellent. Treatment with the ps-Alex laser caused transient hyperpigmentation followed by improvement to complete resolution at 3 months follow-up. The ps-Nd:YAG laser caused severe transient erythema and swelling but no post-inflammatory hyperpigmentation. Conclusions: Our results suggest that the 755 nm and 1064 nm ps-lasers are efficacious for the treatment of dermal pigment lesions, with minimum adverse events.

  6. Picosecond pulse duration laser treatment for dermal melanocytosis in Asians : A retrospective review

    PubMed Central

    Ohshiro, Toshio; Sasaki, Katsumi; Kishi, Kazuo

    2016-01-01

    Background and aims: Recently novel picosecond duration lasers (ps-lasers) have been developed for the treatment of multicolored and recalcitrant tattoos, and safety and efficacy have been reported. We therefore hypothesized that the ps-laser could be an alternative treatment for dermal pigmented lesions and performed a retrospective review to evaluate the efficacy and safety of the ps-laser. Subjects and methods: A retrospective photographic review of 10 patients with dermal pigmented lesions was performed (ages from 4 months to 52 yr), 6 nevus of Ota, 3 ectopic Mongolian spots and 1 Mongolian spots. The patients were treated in the Ohshiro Clinic with picosecond 755 nm alexandrite laser (ps-Alex laser) and picosecond 1064 nm Nd:YAG laser (ps-Nd:YAG laser) from April 2014 to December 2015 (ps-Alex laser, 7 patients; ps-Nd:YAG laser, 3 patients, 1 to 3 treatment sessions). Improvement was evaluated as percentage of pigmentation clearance comparing the baseline findings with those at 3 months after the final treatment using a five category grading scale: Poor, 0–24%; Fair, 25–49%; Good, 50–74%; Excellent, 75–94%; and Complete, 95–100% improvement. Adverse events were also assessed. Results: All ten patients obtained clinical improvement ranging from fair to excellent. Treatment with the ps-Alex laser caused transient hyperpigmentation followed by improvement to complete resolution at 3 months follow-up. The ps-Nd:YAG laser caused severe transient erythema and swelling but no post-inflammatory hyperpigmentation. Conclusions: Our results suggest that the 755 nm and 1064 nm ps-lasers are efficacious for the treatment of dermal pigment lesions, with minimum adverse events. PMID:27721561

  7. A picosecond laser FAIMS analyzer for detecting ultralow quantities of explosives

    NASA Astrophysics Data System (ADS)

    Chistyakov, Alexander A.; Kotkovskii, Gennadii E.; Sychev, Alexey V.; Odulo, Ivan P.; Bogdanov, Artem S.; Perederiy, Anatoly N.; Spitsyn, Evgeny M.; Shestakov, Alexander V.

    2014-10-01

    A method for detecting ultralow quantities of explosives in air and explosive traces using a state-of-the-art picosecond chip Nd3+:YAG laser has been elaborated. The method combines field asymmetric ion mobility spectrometry (FAIMS) with laser ionization of air samples and laser desorption of analyzed molecules from examined surfaces. Radiation of the fourth harmonic (λ = 266 nm, τpulse = 300 ps, Epulse = 20-150 μJ, ν = 20-300 Hz) was used. The ionization efficiencies for trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), and glyceryl trinitrate (NG) were investigated. The dependences on frequency, pulse energy, peak intensity, and average power for TNT and RDX were determined. It was shown that the optimal peak intensity should be no less than 2•106 W/cm2; at lower peak intensities, the increase of the average laser power in the interval 5-15 mW enhanced the ion signal. The results of detection of TNT, RDX, and NG vapors under these conditions were compared with the results obtained using nanosecond laser excitation. The detected ion signals for all explosives were shown to be two- to threefold higher in the case of picosecond excitation. The FAIMS laser desorption regime was developed where a laser beam exiting the detector after removal of a special plug was used. The results of TNT and RDX detection are presented. The chip Nd3+:YAG laser has a small emitter and a consumed electric power of 25 W. The estimated detection threshold of the prototype picosecond laser FAIMS analyzer of explosives is (1-3)•10-15g/cm3 for TNT vapors.

  8. Picosecond transient absorption spectroscopy in the blue spectral region of photosystem I.

    PubMed

    Mi, D; Lin, S; Blankenship, R E

    1999-11-16

    Picosecond transient absorption difference spectroscopy in the blue wavelength region (380-500 nm) was used to study the early electron acceptors in photosystem I. Samples were photosystem I core particles with about 100 chlorophylls per reaction center isolated from the cyanobacterium Synechocystis sp. PCC 6803. After excitation at 590 nm at room temperature, decay-associated spectra (DAS) were determined from global analysis in the blue region, yielding two transient components and one nondecaying component. A 3 ps decay phase is interpreted as primarily due to antenna excited-state redistribution. A 28 ps decay phase is interpreted as due to overall excited-state decay by electron transfer. The nondecaying component is ascribed to the difference spectrum of P(700) and the quinone or A(1) electron acceptor (P(700)(+)A(1)(-) - P(700)A(1)). Decay curves on the millisecond time scale at different wavelengths were measured with an autoxidizable artificial electron acceptor, benzyl viologen, and the (P(700)(+) - P(700)) difference spectrum was constructed. The (A(1)(-) - A(1)) difference spectrum was obtained by taking the difference between the above two difference spectra. A parallel picosecond experiment under strongly reducing conditions was also done as a control experiment. These conditions stabilize the electron on an earlier acceptor, A(0). The nondecaying component of the DAS at low potential was assigned to (P(700)(+)A(0)(-) - P(700)A(0)) since the electron-transfer pathway from A(0) to A(1) was blocked. The [(P(700)(+)A(0)(-) - P(700)A(0)) - (P(700)(+) - P(700))] subtraction gives a spectrum, interpreted as the (A(0)(-) - A(0)) difference spectrum of a chlorophyll a molecule, consistent with previous studies. The (A(1)(-) - A(1)) spectrum resolved on the picosecond time scale shows significant differences with similar spectra measured on longer time scales. These differences may be due to electrochromic effects and spectral evolution.

  9. 130-W picosecond green laser based on a frequency-doubled hybrid cryogenic Yb:YAG amplifier.

    PubMed

    Hong, Kyung-Han; Lai, Chien-Jen; Siddiqui, Aleem; Kärtner, Franz X

    2009-09-14

    130-W average-power picosecond green laser pulses at 514.5 nm are generated from a frequency-doubled hybrid cryogenic Yb:YAG laser. A second-harmonic conversion efficiency of 54% is achieved with a 15-mm-long noncritically phase-matched lithium triborate (LBO) crystal from a 240-W 8-ps 78-MHz pulse train at 1029 nm. The high-average-power hybrid laser system consists of a picosecond fiber chirped-pulse amplification seed source and a cryogenically-cooled double-pass Yb:YAG amplifier. The M(2) value of 2.7, measured at 77 W of second-harmonic power, demonstrates a good focusing quality. A thermal analysis shows that the longitudinal temperature gradient can be the main limiting factor in the second-harmonic efficiency. To our best knowledge, this is the highest-average-power green laser source generating picosecond pulses.

  10. Picosecond and nanosecond pulse delivery through a hollow-core Negative Curvature Fiber for micro-machining applications.

    PubMed

    Jaworski, Piotr; Yu, Fei; Maier, Robert R J; Wadsworth, William J; Knight, Jonathan C; Shephard, Jonathan D; Hand, Duncan P

    2013-09-23

    We present high average power picosecond and nanosecond pulse delivery at 1030 nm and 1064 nm wavelengths respectively through a novel hollow-core Negative Curvature Fiber (NCF) for high-precision micro-machining applications. Picosecond pulses with an average power above 36 W and energies of 92 µJ, corresponding to a peak power density of 1.5 TWcm⁻² have been transmitted through the fiber without introducing any damage to the input and output fiber end-faces. High-energy nanosecond pulses (>1 mJ), which are ideal for micro-machining have been successfully delivered through the NCF with a coupling efficiency of 92%. Picosecond and nanosecond pulse delivery have been demonstrated in fiber-based laser micro-machining of fused silica, aluminum and titanium.

  11. Femtosecond fiber CPA system based on picosecond master oscillator and power amplifier with CCC fiber.

    PubMed

    Želudevičius, J; Danilevičius, R; Viskontas, K; Rusteika, N; Regelskis, K

    2013-03-11

    Results of numerical and experimental investigations of the simple fiber CPA system seeded by nearly bandwidth-limited pulses from the picosecond oscillator are presented. We utilized self-phase modulation in a stretcher fiber to broaden the pulse spectrum and dispersion of the fiber to stretch pulses in time. During amplification in the ytterbium-doped CCC fiber, gain-shaping and self-phase modulation effects were observed, which improved pulse compression with a bulk diffraction grating compressor. After compression with spectral filtering, pulses with the duration of 400 fs and energy as high as 50 µJ were achieved, and the output beam quality was nearly diffraction-limited.

  12. High-accuracy picosecond characterization of gain-switched laser diodes

    SciTech Connect

    Cova, S.; Lacaita, A.; Ghioni, M.; Ripamonti, G. )

    1989-12-15

    A unique combination of the time-correlated photon-counting technique and single-photon avalanche diode detectors gives an accurate characterization of gain-switched semiconductor lasers with picosecond resolution. The high sensitivity and the clean shape of the time response reveal even small features (reflections and relaxation oscillations), making a true optimization of the laser-diode operation possible. The technique outperforms the standard characterization with ultrafast p-i-n photodiodes and a sampling oscilloscope. In addition, compared with other methods, it has favorable features that greatly simplify the measurement.

  13. Electromagnetically induced transparency in a cascade-type quantum well subband system under intense picosecond excitation

    NASA Astrophysics Data System (ADS)

    Hanna, S.; Eichenberg, B.; Firsov, D. A.; Vorobjev, L. E.; Ustinov, V. M.; Seilmeier, A.

    2016-01-01

    The coherent light-matter interaction in a 4-level cascade-type subband system of an asymmetric GaAs/AlGaAs quantum well structure is studied in pump-probe transmission experiments with picosecond (ps) time resolution. Coupling two excited subbands by an intense mid-infrared laser pulse at low sample temperatures is found to result in a substantially increased transparency of the fundamental e1-e2 transition. We find a reduction of the absorption coefficient by ~80%, which is one of the most pronounced electromagnetically induced transparency in solid state systems observed so far.

  14. Generation of energetic, picosecond seed pulses for CO2 laser using Raman shifter

    NASA Astrophysics Data System (ADS)

    Welch, Eric; Tochitsky, Sergei; Joshi, Chan

    2017-03-01

    We present a new concept for generating 3 ps seed pulses for a high-power CO2 laser amplifier that are multiple orders more energetic than seed pulses generated by slicing from a nanosecond CO2 laser pulse. We propose to send a 1 µm picosecond laser through a C6D6 Raman shifter and mix both the pump and shifted components in a DFG crystal to produce pulses at 10.6 µm. Preliminary results of a proof-of-principle experiment are presented.

  15. Simulating picosecond X-ray diffraction from crystals using FFT methods on MD output

    SciTech Connect

    Kimminau, Giles; Nagler, Bob; Higginbotham, Andrew; Murphy, William; Wark, Justin; Park, Nigel; Hawreliak, James; Kalantar, Dan; Lorenzana, Hector; Remington, Bruce

    2007-12-12

    Multi-million atom non-equilibrium molecular dynamics (MD) simulations give significant insight into the transient processes that occur under shock compression. Picosecond X-ray diffraction enables the probing of materials on a timescale fast enough to test such effects. In order to simulate diffraction patterns, Fourier methods are required to gain a picture of reciprocal lattice space. We present here results of fast Fourier transforms of atomic coordinates of shocked crystals simulated by MD, and comment on the computing power required as a function of problem size. The relationship between reciprocal space and particular experimental geometries is discussed.

  16. Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Athanasopoulos, G. I.; Giapintzakis, J.

    2013-08-01

    One-step growth of n-doped Si nanostructures by picosecond ultra fast pulsed laser deposition at 1064 nm is reported for the first time. The structure and morphology of the Si nanostructures were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Transmission electron microscopy studies revealed that the shape of the Si nanostructures depends on the ambient argon pressure. Fibrous networks, cauliflower formations and Si rectangular crystals grew when argon pressure of 300 Pa, 30 Pa and vacuum (10-3 Pa) conditions were used, respectively. In addition, the electrical resistance of the vacuum made material was investigated.

  17. A New Technology for Applanation Free Corneal Trephination: The Picosecond Infrared Laser (PIRL)

    PubMed Central

    Linke, Stephan J.; Frings, Andreas; Ren, Ling; Gomolka, Amadeus; Schumacher, Udo; Reimer, Rudolph; Hansen, Nils-Owe; Jowett, Nathan; Richard, Gisbert; Miller, R. J. Dwayne

    2015-01-01

    The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas. PMID:25781907

  18. High-energy picosecond hybrid fiber/crystal laser for thin films solar cells micromachining

    NASA Astrophysics Data System (ADS)

    Lecourt, Jean-Bernard; Boivinet, Simon; Bertrand, Anthony; Lekime, Didier; Hernandez, Yves

    2015-05-01

    We report on an hybrid fiber/crystal ultra-short pulsed laser delivering high pulse energy and high peak power in the picosecond regime. The laser is composed of a mode-lock fiber oscillator, a pulse picker and subsequent fiber amplifiers. The last stage of the laser is a single pass Nd:YVO4 solid-state amplifier. We believe that this combination of both technologies is a very promising approach for making efficient, compact and low cost lasers compatible with industrial requirements.

  19. Wavelength dependence of picosecond laser-induced periodic surface structures on copper

    NASA Astrophysics Data System (ADS)

    Maragkaki, Stella; Derrien, Thibault J.-Y.; Levy, Yoann; Bulgakova, Nadezhda M.; Ostendorf, Andreas; Gurevich, Evgeny L.

    2017-09-01

    The physical mechanisms of the laser-induced periodic surface structures (LIPSS) formation are studied in this paper for single-pulse irradiation regimes. The change in the LIPSS period with wavelength of incident laser radiation is investigated experimentally, using a picosecond laser system, which provides 7-ps pulses in near-IR, visible, and UV spectral ranges. The experimental results are compared with predictions made under the assumption that the surface-scattered waves are involved in the LIPSS formation. Considerable disagreement suggests that hydrodynamic mechanisms can be responsible for the observed pattern periodicity.

  20. Fluorescence properties of dyes adsorbed to silver islands, investigated by picosecond techniques

    NASA Astrophysics Data System (ADS)

    Leitner, A.; Lippitsch, M. E.; Draxler, S.; Riegler, M.; Aussenegg, F. R.

    1985-02-01

    The fluorescence properties of dye molecules (rhodamine 6G and erythrosin) adsorbed on pure glass surfaces and on silver islands films are investigated by cw and picosecond time-resolved methods. On pure glass surfaces we observe concentration quenching below a critical intermolecular distance (reduction of the fluorescence power per molecule as well as shortened and non-exponential fluorescence decay). On silver islands films the shortening in fluorescence lifetime is more drastic and is nearly independent of the intermolecular distance. This behavior suggests an electrodynamic interaction between dye monomers and plasmons in the metal particles, modified by a damping influence of dye dimers.

  1. Polarized multiplex coherent anti-Stokes Raman scattering using a picosecond laser and a fiber supercontinuum

    NASA Astrophysics Data System (ADS)

    Michel, Sébastien; Courjaud, Antoine; Mottay, Eric; Finot, Christophe; Dudley, John; Rigneault, Hervé

    2011-02-01

    We perform multiplex coherent anti-Stokes Raman scattering (CARS) micro-spectroscopy with a picosecond pulsed laser and a broadband supercontinuum (SC) generated in photonic crystal fiber. CARS signal stability is achieved using an active fiber coupler that avoids thermal and mechanical drifts. We obtain multiplex CARS spectra for test liquids in the 600-2000 cm-1 spectral range. In addition we investigate the polarization dependence of the CARS spectra when rotating the pump beam linear polarization state relative to the linearly polarized broad stokes SC. From these polarization measurements we deduce the Raman depolarization ratio, the resonant versus nonresonant contribution, the Raman resonance frequency, and the linewidth.

  2. Two-frequency picosecond laser based on composite vanadate crystals with {sigma}-polarised radiation

    SciTech Connect

    Sirotkin, A A; Sadovskiy, S P; Garnov, Sergei V

    2013-07-31

    A two-frequency picosecond laser based on {alpha}-cut Nd:YVO{sub 4}-YVO{sub 4} composite vanadate crystals is experimentally studied for the s-polarised radiation at the {sup 4}F{sub 3/2} - {sup 4}I{sub 11/2} transition with frequency tuning using Fabry-Perot etalons of different thickness. The difference between the radiation wavelengths was tuned within the range of 1.2-4.4 nm. In the mode-locking regime, the two-frequency radiation power was 280 mW at an absorbed pump power of 12 W. (lasers)

  3. Dynamical test of Davydov-type solitons in acetanilide using a picosecond free-electron laser

    NASA Astrophysics Data System (ADS)

    Fann, Wunshain; Rothberg, Lewis; Roberson, Mark; Benson, Steve; Madey, John; Etemad, Shahab; Austin, Robert

    1990-01-01

    Picosecond infrared excitation experiments on acetanilide, an α-helix protein analog, indicate that the anomalous 1650-cm-1 band which appears on cooling of acetanilide crystals persists for at least several microseconds following rapid pulsed heating. The ground-state recovery time is 15+/-5 psec, consistent with a conventional mode strongly coupled to the phonon bath. We therefore suggest that the unusual temperature-dependent spectroscopy of acetanilide can be accounted for by slightly nondegenerate hydrogen atom configurations in the crystal.

  4. Detection of electronic excited states in conjugated polymers by picosecond transient strain spectroscopy

    SciTech Connect

    Kanner, G.S.; Frolov, S.; Vardeny, Z.V. Physics Department, University of Utah, Salt Lake City, Utah 84112 )

    1995-02-27

    We describe a new type of spectroscopy based on picosecond transient strain in absorption photomodulation that can be used to detect and identify both allowed and forbidden optical transitions in solid thin films. We have applied the new spectroscopy to a variety of conducting polymer films such as polythiophene, [ital trans] and [ital cis] polyacetylene, and poly(diethynyl-silane), in which we measured energy levels of various excitonic states with odd and even symmetry that are, respectively, allowed and forbidden in the optical absorption.

  5. Femtosecond and picosecond laser drilling of metals at high repetition rates and average powers.

    PubMed

    Ancona, A; Döring, S; Jauregui, C; Röser, F; Limpert, J; Nolte, S; Tünnermann, A

    2009-11-01

    The influence of pulse duration on the laser drilling of metals at repetition rates of up to 1 MHz and average powers of up to 70 W has been experimentally investigated using an ytterbium-doped-fiber chirped-pulse amplification system with pulses from 800 fs to 19 ps. At a few hundred kilohertz particle shielding causes an increase in the number of pulses for breakthrough, depending on the pulse energy and duration. At higher repetition rates, the heat accumulation effect overbalances particle shielding, but significant melt ejection affects the hole quality. Using femtosecond pulses, heat accumulation starts at higher repetition rates, and the ablation efficiency is higher compared with picosecond pulses.

  6. Sub-picosecond ultra-low frequency passively mode-locked fiber laser

    NASA Astrophysics Data System (ADS)

    Cuadrado-Laborde, Christian; Cruz, José L.; Díez, Antonio; Andrés, Miguel V.

    2016-11-01

    We developed a nonlinear polarization rotation all-fiber mode-locked erbium-doped fiber laser, with the purpose to reach a sub-picosecond and sub-megahertz light pulse emission. In the process, we observed three different emission regimes as the net birefringence is changed, namely high-power dissipative soliton resonance, low-power soliton regime, and a mixed combination of both. In the pure solitonic regime, a 0.961 MHz train of chirp-free Gaussian pulses was obtained, with a time width of 0.919 ps at 1564.3 nm.

  7. Two-photon photoemission from metals induced by picosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Bechtel, J. H.; Smith, W. L.; Bloembergen, N.

    1977-01-01

    We have measured the two-photon photoemission current density from tungsten, tantalum, and molybdenum when irradiated by 532-nm wavelength radiation. This wavelength was produced by the second-harmonic radiation of single picosecond laser pulses from a mode-locked neodymium-doped yttrium-aluminum-garnet laser. The results are interpreted in terms of both a simple temperature-independent two-photon photoemission effect and a generalization of the Fowler-DuBridge theory of photoemission. The laser polarization dependence of the emitted current is also reported.

  8. Polarized multiplex coherent anti-Stokes Raman scattering using a picosecond laser and a fiber supercontinuum.

    PubMed

    Michel, Sébastien; Courjaud, Antoine; Mottay, Eric; Finot, Christophe; Dudley, John; Rigneault, Hervé

    2011-02-01

    We perform multiplex coherent anti-Stokes Raman scattering (CARS) micro-spectroscopy with a picosecond pulsed laser and a broadband supercontinuum (SC) generated in photonic crystal fiber. CARS signal stability is achieved using an active fiber coupler that avoids thermal and mechanical drifts. We obtain multiplex CARS spectra for test liquids in the 600-2000 cm(-1) spectral range. In addition we investigate the polarization dependence of the CARS spectra when rotating the pump beam linear polarization state relative to the linearly polarized broad stokes SC. From these polarization measurements we deduce the Raman depolarization ratio, the resonant versus nonresonant contribution, the Raman resonance frequency, and the linewidth.

  9. Spatiospectral and picosecond spatiotemporal properties of a broad area operating channeled-substrate-planar laser array

    NASA Technical Reports Server (NTRS)

    Yu, NU; Defreez, Richard K.; Bossert, David J.; Wilson, Geoffrey A.; Elliott, Richard A.

    1991-01-01

    Spatiospectral and spatiotemporal properties of an eight-element channeled-substrate-planar laser array are investigated in both CW and pulsed operating conditions. The closely spaced CSP array with strong optical coupling between array elements is characterized by a broad area laserlike operation determined by its spatial mode spectra. The spatiotemporal evolution of the near and far field exhibits complex dynamic behavior in the picosecond to nanosecond domain. Operating parameters for the laser device have been experimentally determined. These results provide important information for the evaluation of the dynamic behavior of coherent semiconductor laser arrays.

  10. GHz high power Yb-doped picosecond fiber laser and supercontinuum generation.

    PubMed

    Gao, Jing; Ge, Tingwu; Li, Wuyi; Kuang, Hongshen; Wang, Zhiyong

    2014-12-20

    We demonstrated a 97 W all-fiber picosecond master oscillator power amplifier seeding by an actively harmonic mode-locked Yb-doped fiber laser. The laser seed pulse duration was 7.7 ps at a 1.223 GHz repetition rate with a central wavelength of 1062 nm. In addition, by launching the amplified pulses into a 5 m long photonic crystal fiber, we obtained a 41.8 W supercontinuum covering the wavelength from 600 to 1700 nm with a 10 dB bandwidth of 1040 nm.

  11. 1016nm all fiber picosecond MOPA laser with 50W output.

    PubMed

    Qi, Xue; Chen, Sheng-Ping; Sun, Hai-Yue; Yang, Bing-Ke; Hou, Jing

    2016-07-25

    This paper presents an all fiber high power picosecond laser at 1016 nm in master oscillator power amplifier (MOPA) configuration. A direct amplification of this seed source encounters obvious gain competition with amplified spontaneous emission (ASE) at ~1030 nm, leading to a seriously reduced amplification efficiency. To suppress the ASE and improve the amplification efficiency, we experimentally investigate the influence of the gain fiber length and the residual ASE on the perforemance of the 1016 nm amplifier. The optimized 1016 nm MOPA laser exhibits an average power of 50 W and an optical conversion efficiency of 53%.

  12. On-Chip Picosecond Pulse Detection and Generation Using Graphene Photoconductive Switches

    PubMed Central

    2015-01-01

    We report on the use of graphene for room temperature on-chip detection and generation of pulsed terahertz (THz) frequency radiation, exploiting the fast carrier dynamics of light-generated hot carriers, and compare our results with conventional low-temperature-grown gallium arsenide (LT-GaAs) photoconductive (PC) switches. Coupling of picosecond-duration pulses from a biased graphene PC switch into Goubau line waveguides is also demonstrated. A Drude transport model based on the transient photoconductance of graphene is used to describe the mechanism for both detection and generation of THz radiation. PMID:25710079

  13. Picosecond time scale modification of forward scattered light induced by absorption inside particles.

    PubMed

    Kervella, Myriam; d'Abzac, Françoix-Xavier; Hache, François; Hespel, Laurent; Dartigalongue, Thibault

    2012-01-02

    The aim of this work is to evaluate the influence of absorption processes on the Time Of Flight (TOF) of the light scattered out of a thick medium in the forward direction. We use a Monte-Carlo simulation with temporal phase function and Debye modes. The main result of our study is that absorption inside the particle induces a decrease of the TOF on a picosecond time scale, measurable with a femtosecond laser apparatus. This decrease, which exhibits a neat sensitivity to the absorption coefficient of particles, could provide an efficient way to measure this absorption.

  14. Picosecond kinetics and Sn <-- S1 absorption spectra of retinoids and carotenoids

    NASA Astrophysics Data System (ADS)

    Bondarev, Stanislav L.; Tikhomirov, S. A.; Bachilo, Sergei M.

    1991-05-01

    Light energy absorption, as well as the subsequent photochemical and photophysical processes of cis -+trans isomerisation (vision and bacteriorhodopsin photosynthesis) and energy transfer (photosynthesis in green plants and micro organisms) take place in a pigment-protein complex including polyene chromophors, retinoids and carotenoids. Picosecond and subpicosecond studies of the spectral and kinetic characteristics of these processes are carried out in both complex photoreceptor and photosynthetic ms'2 and model systems with the use of solutions of retinoids and carotenoids.36 The lifetimes of the lower singlet-exited states S (21A; ) ofsome carotenoids in toluene at room temperature have been measured by the method of picosecond photolysis and amount to 8.6+/- 0.5 for all-trans-fl -carotene1 and 5.2 0.6 PS for canthaxanthin.5 /3 -carotene fluorescence at room temperature is practically absent, its yield being less than iO (Ref. 7). /1 -carotene fluorescence at 77 and 4.2 K in isopentane discovered by us8 is characterized by yields of (4+/-2) .iO and (8+/-3) . i0- and lifetimes of(4+/-2) .iO' and (8+/-3) .iO' and is due to the transitions from the higher S(1' B) state. The picosecond transient S -S absorption of/I - carotene in different solvents at 293 K is characterized by spectra in the 550-600 nm range.8 For retinoids, there is one work (Ref. 4) which gives the S, +-Si absorption spectrum of the Schiff base (aldimine) of retinal with amaz 465 mn in n-hexane at 290 K. The duration of transient absorption was 21 5 ps, although the fluorescence kinetics measured in this work (Ref. 4) at 298 K were characterized by two-component decay with r1 = 22 and r2 = 265 ps. The transient picosecond absorption spectra for retinal are absent in the literature and the lifetimes of its singlet-excited state at room temperature, measured by absorption and fluorescence, amount to 20+/-10 Ps in n-hexane3 and 17 Ps in ethanol,'9 respectively.

  15. Simulating Picosecond X-ray Diffraction from shocked crystals by Post-processing Molecular Dynamics Calculations

    SciTech Connect

    Kimminau, G; Nagler, B; Higginbotham, A; Murphy, W; Park, N; Hawreliak, J; Kadau, K; Germann, T C; Bringa, E M; Kalantar, D; Lorenzana, H; Remington, B; Wark, J

    2008-06-19

    Calculations of the x-ray diffraction patterns from shocked crystals derived from the results of Non-Equilibrium-Molecular-Dynamics (NEMD) simulations are presented. The atomic coordinates predicted by the NEMD simulations combined with atomic form factors are used to generate a discrete distribution of electron density. A Fast-Fourier-Transform (FFT) of this distribution provides an image of the crystal in reciprocal space, which can be further processed to produce quantitative simulated data for direct comparison with experiments that employ picosecond x-ray diffraction from laser-irradiated crystalline targets.

  16. A new technology for applanation free corneal trephination: the picosecond infrared laser (PIRL).

    PubMed

    Linke, Stephan J; Frings, Andreas; Ren, Ling; Gomolka, Amadeus; Schumacher, Udo; Reimer, Rudolph; Hansen, Nils-Owe; Jowett, Nathan; Richard, Gisbert; Miller, R J Dwayne

    2015-01-01

    The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas.

  17. Picosecond Electronics and Optoelectronics Held at Incline Village, Nevada on 13-15 March 1985.

    DTIC Science & Technology

    1986-02-04

    effect in reflection mode, is *rmqtes for very’ high speed electronic measurements of presented. This technique is well suited for the future devi( e...speed Tr:LiNbO, optical wave- -- a:.’.--’ rnt:-tir km effect , and sub. guide switch/modulators as well as the use of such - r:: s ,-irc rioded...psec and . ’ ,.,-, - : "’, 8:15 PM ThC3 Picosecond Optoelectronic Diagnostics of Field Effect Transistors. [oin a’I - tr ,pac( C(o,oraitlon 10:45 AM ThB

  18. Picosecond laser ultrasonics for imaging of transparent polycrystalline materials compressed to megabar pressures.

    PubMed

    Kuriakose, Maju; Raetz, Samuel; Chigarev, Nikolay; Nikitin, Sergey M; Bulou, Alain; Gasteau, Damien; Tournat, Vincent; Castagnede, Bernard; Zerr, Andreas; Gusev, Vitalyi E

    2016-07-01

    Picosecond laser ultrasonics is an all-optical experimental technique based on ultrafast high repetition rate lasers applied for the generation and detection of nanometric in length coherent acoustic pulses. In optically transparent materials these pulses can be detected not only on their arrival at the sample surfaces but also all along their propagation path inside the sample providing opportunity for imaging of the sample material spatial inhomogeneities traversed by the acoustic pulse. Application of this imaging technique to polycrystalline elastically anisotropic transparent materials subject to high pressures in a diamond anvil cell reveals their significant texturing/structuring at the spatial scales exceeding dimensions of the individual crystallites.

  19. Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

    SciTech Connect

    Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G.; Sharples, Steve D.

    2010-02-15

    This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

  20. Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector.

    PubMed

    Smith, Richard J; Light, Roger A; Sharples, Steve D; Johnston, Nicholas S; Pitter, Mark C; Somekh, Mike G

    2010-02-01

    This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

  1. High-visibility two-photon interference at a telecom wavelength using picosecond-regime separated sources

    SciTech Connect

    Aboussouan, Pierre; Alibart, Olivier; Ostrowsky, Daniel B.; Baldi, Pascal; Tanzilli, Sebastien

    2010-02-15

    We report on a two-photon interference experiment in a quantum relay configuration using two picosecond regime periodically poled lithium niobate (PPLN) waveguide based sources emitting paired photons at 1550 nm. The results show that the picosecond regime associated with a guided-wave scheme should have important repercussions for quantum relay implementations in real conditions, essential for improving both the working distance and the efficiency of quantum cryptography and networking systems. In contrast to already reported regimes, namely, femtosecond and CW, it allows achieving a 99% net visibility two-photon interference while maintaining a high effective photon pair rate using only standard telecom components and detectors.

  2. DOE-HEP Final Report for 2013-2016: Studies of plasma wakefields for high repetition-rate plasma collider, and Theoretical study of laser-plasma proton and ion acceleration

    SciTech Connect

    Katsouleas, Thomas C.; Sahai, Aakash A.

    2016-08-08

    There were two goals for this funded project: 1. Studies of plasma wakefields for high repetition-rate plasma collider, and 2. Theoretical study of laser-plasma proton and ion acceleration. For goal 1, an analytical model was developed to determine the ion-motion resulting from the interaction of non-linear “blow-out” wakefields excited by beam-plasma and laser-plasma interactions. This is key to understanding the state of the plasma at timescales of 1 picosecond to a few 10s of picoseconds behind the driver-energy pulse. More information can be found in the document. For goal 2, we analytically and computationally analyzed the longitudinal instabilities of the laser-plasma interactions at the critical layer. Specifically, the process of “Doppler-shifted Ponderomotive bunching” is significant to eliminate the very high-energy spread and understand the importance of chirping the laser pulse frequency. We intend to publish the results of the mixing process in 2-D. We intend to publish Chirp-induced transparency. More information can be found in the document.

  3. Dynamic high pressure generation through plasma implosion driven by an intense laser pulse

    NASA Astrophysics Data System (ADS)

    Li, M.; Wang, J. X.; Yuan, T.; Xu, Y. X.; Zhu, W. J.

    2017-03-01

    When an intense laser pulse is loaded upon solids, very high impact pressure can be generated on the surface. In this letter, we simulate this process through one-dimensional particle-in-cell simulation and find that the pressure as high as 0.13 TPa can be generated after the laser pulse with intensity 1015 W/cm2 and 5 picosecond duration is injected upon a nanometer solid-density plasma. The peak pressure is shown to be resulted from an energetic high-density plasma bunch, produced through plasma implosion under extremely high light pressure.

  4. Equation-of-State Measurement of Dense Plasmas Heated With Fast Protons

    SciTech Connect

    Dyer, G. M.; Bernstein, A. C.; Cho, B. I.; Osterholz, J.; Grigsby, W.; Dalton, A.; Ditmire, T.; Shepherd, R.; Ping, Y.; Chen, H.; Widmann, K.

    2008-07-04

    Using an ultrafast pulse of mega-electron-volt energy protons accelerated from a laser-irradiated foil, we have heated solid density aluminum plasmas to temperatures in excess of 15 eV. By measuring the temperature and the expansion rate of the heated Al plasma simultaneously and with picosecond time resolution we have found the predictions of the SESAME Livermore equation-of-state (LEOS) tables to be accurate to within 18%, in this dense plasma regime, where there have been few previous experimental measurements.

  5. Equation-of-State Measurement of Dense Plasmas Heated With Fast Protons

    NASA Astrophysics Data System (ADS)

    Dyer, G. M.; Bernstein, A. C.; Cho, B. I.; Osterholz, J.; Grigsby, W.; Dalton, A.; Shepherd, R.; Ping, Y.; Chen, H.; Widmann, K.; Ditmire, T.

    2008-07-01

    Using an ultrafast pulse of mega-electron-volt energy protons accelerated from a laser-irradiated foil, we have heated solid density aluminum plasmas to temperatures in excess of 15 eV. By measuring the temperature and the expansion rate of the heated Al plasma simultaneously and with picosecond time resolution we have found the predictions of the SESAME Livermore equation-of-state (LEOS) tables to be accurate to within 18%, in this dense plasma regime, where there have been few previous experimental measurements.

  6. Equation-of-state measurement of dense plasmas heated with fast protons.

    PubMed

    Dyer, G M; Bernstein, A C; Cho, B I; Osterholz, J; Grigsby, W; Dalton, A; Shepherd, R; Ping, Y; Chen, H; Widmann, K; Ditmire, T

    2008-07-04

    Using an ultrafast pulse of mega-electron-volt energy protons accelerated from a laser-irradiated foil, we have heated solid density aluminum plasmas to temperatures in excess of 15 eV. By measuring the temperature and the expansion rate of the heated Al plasma simultaneously and with picosecond time resolution we have found the predictions of the SESAME Livermore equation-of-state (LEOS) tables to be accurate to within 18%, in this dense plasma regime, where there have been few previous experimental measurements.

  7. Picosecond laser micromachining prior to FIB milling for electronic microscopy sample preparation

    NASA Astrophysics Data System (ADS)

    Sikora, Aurélien; Fares, Lahouari; Adrian, Jérôme; Goubier, Vincent; Delobbe, Anne; Corbin, Antoine; Sentis, Marc; Sarnet, Thierry

    2017-10-01

    In order to check the manufacturing quality of electronic components using electron microscopy, the area of interest must be exposed. This requires the removal of a large quantity of matter without damaging the surrounding area. This step can be accomplished using ion milling but the processing can last a few hours. In order to accelerate the preparation of the samples, picosecond laser micromachining prior to Focused Ion Beam polishing is envisioned. Laser ablation allows the fast removal of matter but induces damages around the ablated area. Therefore the process has to be optimized in order to limit the size of both the heat affected zone and induced dislocation zone. For this purpose, cavities have been engraved in silicon and in electronic components, using a linearly polarized picosecond laser (∼50 ps) at three different wavelengths (343, 515 and 1030 nm). Results showed that the cross sectional shapes and the surface topologies can be tuned by the laser fluence and the number of pulses. Clear cross sections of bumps and cavity openings, exposing multilayer interfaces, are demonstrated. The silicon removal rates, tuned by the applied energy density, have been measured. Removal rates achieved at 200 kHz were typically hundred times higher than those achieved by ion milling and the best efficiency was obtained at 343 nm.

  8. Droplet distribution during sub-picosecond laser deposition of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Gontad, Francisco; Cesaria, Maura; Klini, Argyro; Manousaki, Aleka; Perrone, Alessio; Caricato, Anna Paola

    2017-10-01

    Even if it has been recently assessed that sub-picosecond ablation is not a ;melting-free; process, a systematic investigation of the issue of droplets is still lacking. In this paper we discuss the effects of fluence (F = 0.3, 1, 3 J/cm2), target-substrate distance (dTS = 5, 6, 7, 8, 9 cm) and number of laser pulses per site (Np/s = 2, 12, 22, 36, 96) on the morphology in terms of droplets and plasmonic response of gold nanoparticles deposited by sub-picosecond pulsed laser ablation. Among metals, gold is an ideal candidate to study the occurrence of droplets due to its low electron-phonon coupling that favors the appearance of heat affected zones. Our findings demonstrate that Np/s affects the production of large droplets more intensely than F and dTS. In fact, increasing Np/s produced much larger droplets than the ones obtained by tuning the fluence and an increment in the droplet density of 10 times. On the other hand, while the maximum density of small droplets (average diameter ≤ 0.15 μm) occurs at F = 1 J/cm2 (with respect to 0.3 J/cm2 and 3 J/cm2), the total droplet density exhibits a minimum at such fluence.

  9. A Brief Technical History of the Large-Area Picosecond Photodetector (LAPPD) Collaboration

    SciTech Connect

    Adams, B.W.; et al.

    2016-03-06

    The Large Area Picosecond PhotoDetector (LAPPD) Collaboration was formed in 2009 to develop large-area photodetectors capable of time resolutions measured in pico-seconds, with accompanying sub-millimeter spatial resolution. During the next three and one-half years the Collaboration developed the LAPPD design of 20 x 20 cm modules with gains greater than $10^7$ and non-uniformity less than $15\\%$, time resolution less than 50 psec for single photons and spatial resolution of 700~microns in both lateral dimensions. We describe the R\\&D performed to develop large-area micro-channel plate glass substrates, resistive and secondary-emitting coatings, large-area bialkali photocathodes, and RF-capable hermetic packaging. In addition, the Collaboration developed the necessary electronics for large systems capable of precise timing, built up from a custom low-power 15-GigaSample/sec waveform sampling 6-channel integrated circuit and supported by a two-level modular data acquisition system based on Field-Programmable Gate Arrays for local control, data-sparcification, and triggering. We discuss the formation, organization, and technical successes and short-comings of the Collaboration. The Collaboration ended in December 2012 with a transition from R\\&D to commercialization.

  10. Low-loss Type II waveguide writing in fused silica with single picosecond laser pulses.

    PubMed

    Zhang, Haibin; Eaton, Shane M; Herman, Peter R

    2006-05-29

    A new domain of rapid waveguide writing with non-overlapping pulses of a 1-kHz ultrashort laser is demonstrated to produce low loss waveguides in fused silica glass. This new regime is distinguishable in two ways from traditional approaches in laser waveguide writing. First, an examination of a wide 50-fs to 5-ps range of pulse duration shows the lowest loss waveguides to form in a narrow 1.0 +/- 0.2 ps window that significantly exceeds the 50 - 200 fs duration reported as optimal in other studies. Second, an unusually high scan speed of 1.0 +/- 0.2 mm/s points to a novel Type-II photosensitivity mechanism for generating low-loss refractive index structures. The waveguides comprise of an array of nearly isolated single-pulse interaction volumes that sharply contrast with the high exposures of tens to thousands of overlapping laser pulses typically applied along a slowly moving focal volume. A minimum propagation loss of ~0.2 dB/cm and a slightly asymmetric mode diameter of ~9 mum is reported for 633-nm light. The low loss waveguides fabricated with picosecond pulses enables 3-D photonics circuit fabrication with simpler and lower cost picosecond laser systems.

  11. Picosecond spin relaxation in low-temperature-grown GaAs

    SciTech Connect

    Uemura, M.; Honda, K.; Yasue, Y.; Tackeuchi, A.; Lu, S. L.; Dai, P.

    2014-03-24

    The spin relaxation process of low-temperature-grown GaAs is investigated by spin-dependent pump and probe reflectance measurements with a sub-picosecond time resolution. Two very short carrier lifetimes of 2.0 ps and 28 ps, which can be attributed to nonradiative recombinations related to defects, are observed at 10 K. The observed spin polarization shows double exponential decay with spin relaxation times of 46.2 ps (8.0 ps) and 509 ps (60 ps) at 10 K (200 K). The observed picosecond spin relaxation, which is considerably shorter than that of conventional GaAs, indicates the strong relevance of the Elliott-Yafet process as the spin relaxation mechanism. For the first (second) spin relaxation component, the temperature and carrier density dependences of the spin relaxation time indicate that the Bir-Aronov-Pikus process is also effective at temperatures between 10 K and 77 K, and that the D'yakonov-Perel’ process is effective between 125 K (77 K) and 200 K.

  12. Selective Ablation of Thin Films with Picosecond-Pulsed Lasers for Solar Cells

    NASA Astrophysics Data System (ADS)

    Račiukaitis, G.; Gečys, P.; Gedvilas, M.; Regelskis, K.; Voisiat, B.

    2010-10-01

    Functional thin-films are of high importance in modern electronics for flat panel displays, photovoltaics, flexible and organic electronics. Versatile technologies are required for patterning thin-film materials on rigid and flexible substrates. The large-area applications of thin films such as photovoltaics need high speed and simple to use techniques. Ultra-short laser processing with its flexibility is one of the ways to achieve high quality material etching but optimization of the processes is required to meet specific needs of the applications. Lasers with picosecond pulse duration were applied in selective ablation of conducting, semi-conducting and isolating films in the complex multilayered thin-film solar cells based on amorphous Si and CuInxGa(1-x)Se2 (CIGS) deposited on glass and polymer substrates. Modeling of energy transition between the layers and temperature evolution was performed to understand the processes. Selection of the right laser wavelength was important to keep the energy coupling in a well defined volume at the interlayer interface. Ultra-short pulses ensured high energy input rate into absorbing material permitting peeling of the layers with no influence on the remaining material. Use of high repetition rate lasers with picosecond pulse duration offers new possibilities for high quality and efficiency patterning of advanced materials for thin-film electronics.

  13. Germanium Sub-Microspheres Synthesized by Picosecond Pulsed Laser Melting in Liquids: Educt Size Effects

    NASA Astrophysics Data System (ADS)

    Zhang, Dongshi; Lau, Marcus; Lu, Suwei; Barcikowski, Stephan; Gökce, Bilal

    2017-01-01

    Pulsed laser melting in liquid (PLML) has emerged as a facile approach to synthesize submicron spheres (SMSs) for various applications. Typically lasers with long pulse durations in the nanosecond regime are used. However, recent findings show that during melting the energy absorbed by the particle will be dissipated promptly after laser-matter interaction following the temperature decrease within tens of nanoseconds and hence limiting the efficiency of longer pulse widths. Here, the feasibility to utilize a picosecond laser to synthesize Ge SMSs (200~1000 nm in diameter) is demonstrated by irradiating polydisperse Ge powders in water and isopropanol. Through analyzing the educt size dependent SMSs formation mechanism, we find that Ge powders (200~1000 nm) are directly transformed into SMSs during PLML via reshaping, while comparatively larger powders (1000~2000 nm) are split into daughter SMSs via liquid droplet bisection. Furthermore, the contribution of powders larger than 2000 nm and smaller than 200 nm to form SMSs is discussed. This work shows that compared to nanosecond lasers, picosecond lasers are also suitable to produce SMSs if the pulse duration is longer than the material electron-phonon coupling period to allow thermal relaxation.

  14. Picosecond pulsed infrared laser tuned to amide I band dissociates polyglutamine fibrils in cells.

    PubMed

    Kawasaki, Takayasu; Ohori, Gaku; Chiba, Tomoyuki; Tsukiyama, Koichi; Nakamura, Kazuhiro

    2016-09-01

    Amyloid fibrils are causal substances for serious neurodegenerative disorders and amyloidosis. Among them, polyglutamine fibrils seen in multiple polyglutamine diseases are toxic to neurons. Although much efforts have been made to explore the treatments of polyglutamine diseases, there are no effective drugs to block progression of the diseases. We recently found that a free electron laser (FEL), which has an oscillation wavelength at the amide I band (C = O stretch vibration mode) and picosecond pulse width, was effective for conversion of the fibril forms of insulin, lysozyme, and calcitonin peptide into their monomer forms. However, it is not known if that is also the case in polyglutamine fibrils in cells. We found in this study that the fibril-specific β-sheet conformation of polyglutamine peptide was converted into nonfibril form, as evidenced by the infrared microscopy and scanning-electron microscopy after the irradiation tuned to 6.08 μm. Furthermore, irradiation at this wavelength also changed polyglutamine fibrils to their nonfibril state in cultured cells, as shown by infrared mapping image of protein secondary structure. Notably, infrared thermography analysis showed that temperature increase of the cells during the irradiation was within 1 K, excluding thermal damage of cells. These results indicate that the picosecond pulsed infrared laser can safely reduce amyloid fibril structure to the nonfibril form even in cells.

  15. Generation of flat-top picosecond pulses by means of a two-stage birefringent filter

    NASA Astrophysics Data System (ADS)

    Will, Ingo

    2008-09-01

    We describe the type of pulse shaper for production of flat-top pulses that is used at the Photo Injector Test Facility (PITZ) at DESY. This shaper consists of a two-stage birefringent filter. Using a simple model, this pulse shaper can be regarded as a system that splits the Gaussian input pulse into four mutually delayed replicas and stacks them in a phase-coherent way. Although a variety of different pulse shapes can be generated by this method, the system is particularly suited for the generation of flat-top output pulses with duration between 10 and 100 ps. When operating in combination with an actively modelocked Nd:YLF oscillator, it can shape picosecond pulses arranged in long trains, as required for photocathode lasers for the TESLA-type linear accelerators. Using trains of equally shaped picosecond pulses has an additional benefit: It permits measuring the shape of these pulses by cross-correlation in real-time using a so-called optical sampling system. Such a system is employed as a measurement tool for appropriate alignment of the individual components of the pulse shaper.

  16. Compact, high-pulse-energy, high-power, picosecond master oscillator power amplifier.

    PubMed

    Chan, Ho-Yin; Alam, Shaif-Ul; Xu, Lin; Bateman, James; Richardson, David J; Shepherd, David P

    2014-09-08

    We report a compact, stable, gain-switched-diode-seeded master oscillator power amplifier (MOPA), employing direct amplification via conventional Yb(3+)-doped fibers, to generate picosecond pulses with energy of 17.7 μJ and 97-W average output power (excluding amplified spontaneous emission) at 5.47-MHz repetition frequency in a diffraction-limited and single-polarization beam. A maximum peak power of 197 kW is demonstrated. Such a high-energy, high-power, MHz, picosecond MOPA is of great interest for high-throughput material processing. With 13.8-μJ pulse energy confined in the 0.87-nm 3-dB spectral bandwidth, this MOPA is also a promising source for nonlinear frequency conversion to generate high-energy pulses in other spectral regions. We have explored the pulse energy scaling until the stimulated Raman Scattering (SRS) becomes significant (i.e. spectral peak intensity exceeds 1% of that of the signal).

  17. Picosecond and nanosecond studies of the photoreduction of benzophenone by N,N-diethylaniline and triethylamine

    SciTech Connect

    Devadoss, C.; Fessenden, R.W. )

    1991-09-19

    The photoreduction of benzophenone by N,N-diethylaniline and triethylamine has been examined in a number of solvents by both nano- and picosecond laser photolysis. With diethylaniline, electron transfer is the primary step and the spectrum of the ion pair has been detected even in nonpolar solvents such as benzene and cyclohexane. Rapid proton transfer then takes place to form a high yield of the ketyl radical. The lifetime of the ion pair in benzene is about 900 ps. In acetonitrile, the ion pair dissociated into individual ions which then decay by back electron transfer and proton transfer. A spectral shift to the red occurs over 100 ps as the contact ion pair dissociated. In acidic alcohols such as methanol and trifluoroethanol, proton transfer from the alcohol occurs to produce the ketyl radical. In the case of triethylamine, no distinct absorption band for benzophenone anion was seen in picosecond experiments but difference spectra, which removed much of the spectrum of benzophenone triplet, clearly showed some contribution from the anion. For this compound, it is likely that electron transfer occurs first followed by very fast proton transfer.

  18. Picosecond Pulsed Laser Ablation for the Surface Preparation of Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Palmieri, Frank; Ledesma, Rodolfo; Fulton, Tayler; Arthur, Alexandria; Eldridge, Keishara; Thibeault, Sheila; Lin, Yi; Wohl, Chris; Connell, John

    2017-01-01

    As part of a technical challenge under the Advanced Composites Program, methods for improving pre-bond process control for aerospace composite surface treatments and inspections, in conjunction with Federal Aviation Administration guidelines, are under investigation. The overall goal is to demonstrate high fidelity, rapid and reproducible surface treatment and surface characterization methods to reduce uncertainty associated with the bonding process. The desired outcomes are reliable bonded airframe structure, and reduced timeline to certification. In this work, laser ablation was conducted using a q-switched Nd:YVO4 laser capable of nominal pulse durations of 8 picoseconds (ps). Aerospace structural carbon fiber reinforced composites with an epoxy resin matrix were laser treated, characterized, processed into bonded assemblies and mechanically tested. The characterization of ablated surfaces were conducted using scanning electron microscopy (SEM), water contact angle (WCA) goniometry, micro laser induced breakdown spectroscopy (uLIBS), and electron spin resonance (ESR). The bond performance was assessed using a double cantilever beam (DCB) test with an epoxy adhesive. The surface characteristics and bond performance obtained from picosecond ablated carbon fiber reinforced plastics (CFRPs) are presented herein.

  19. Ligation-Dependent Picosecond Dynamics in Human Hemoglobin As Revealed by Quasielastic Neutron Scattering.

    PubMed

    Fujiwara, Satoru; Chatake, Toshiyuki; Matsuo, Tatsuhito; Kono, Fumiaki; Tominaga, Taiki; Shibata, Kaoru; Sato-Tomita, Ayana; Shibayama, Naoya

    2017-08-31

    Hemoglobin, the vital O2 carrier in red blood cells, has long served as a classic example of an allosteric protein. Although high-resolution X-ray structural models are currently available for both the deoxy tense (T) and fully liganded relaxed (R) states of hemoglobin, much less is known about their dynamics, especially on the picosecond to subnanosecond time scales. Here, we investigate the picosecond dynamics of the deoxy and CO forms of human hemoglobin using quasielastic neutron scattering under near physiological conditions in order to extract the dynamics changes upon ligation. From the analysis of the global motions, we found that whereas the apparent diffusion coefficients of the deoxy form can be described by assuming translational and rotational diffusion of a rigid body, those of the CO form need to involve an additional contribution of internal large-scale motions. We also found that the local dynamics in the deoxy and CO forms are very similar in amplitude but are slightly lower in frequency in the former than in the latter. Our results reveal the presence of rapid large-scale motions in hemoglobin and further demonstrate that this internal mobility is governed allosterically by the ligation state of the heme group.

  20. Machining parameter optimization of C/SiC composites using high power picosecond laser

    NASA Astrophysics Data System (ADS)

    Zhang, Ruoheng; Li, Weinan; Liu, Yongsheng; Wang, Chunhui; Wang, Jing; Yang, Xiaojun; Cheng, Laifei

    2015-03-01

    Picosecond laser is an important machining technology for high hardness materials. In this paper, high power picosecond laser was utilized to drill micro-holes in C/SiC composites, and the effects of different processing parameters including the helical line width and spacing, machining time and scanning speed were discussed. To characterize the qualities of machined holes, scanning electron microscope (SEM) was used to analyze the surface morphology, energy dispersive spectroscopy (EDS) and X-ray photoelectric spectroscopy (XPS) were employed to describe the element composition change between the untreated and laser-treated area. The experimental results indicated that all parameters mentioned above had remarkable effects on the qualities of micro-holes such as shape and depth. Additionally, the debris consisted of C, Si and O was observed on the machined surface. The Sisbnd C bonds of the SiC matrix transformed into Sisbnd O bonds after machined. Furthermore, the physical process responsible for the mechanism of debris formation was discussed as well.

  1. Picosecond laser micromachining of nitinol and platinum-iridium alloy for coronary stent applications

    NASA Astrophysics Data System (ADS)

    Muhammad, N.; Whitehead, D.; Boor, A.; Oppenlander, W.; Liu, Z.; Li, L.

    2012-03-01

    The demand for micromachining of coronary stents by means of industrial lasers rises quickly for treating coronary artery diseases, which cause more than one million deaths each year. The most widely used types of laser for stent manufacturing are Nd:YAG laser systems with a wavelength of 1064 nm with pulse lengths of 10-3-10-2 seconds. Considerable post-processing is required to remove heat-affected zones (HAZ), and to improve surface finishes and geometry. Using a third harmonic laser radiation of picosecond laser (6×10-12 s pulse duration) in UV range, the capability of the picosecond laser micromachining of nitinol and platinum-iridium alloy for coronary stent applications are presented. In this study dross-free cut of nitinol and platinum-iridium alloy tubes are demonstrated and topography analysis of the cut surface is carried out. The HAZ characteristics have been investigated by means of microscopic examinations and measurement of micro-hardness distribution near the cut zones.

  2. Fast spectral coherent anti-Stokes Raman scattering microscopy with high-speed tunable picosecond laser.

    PubMed

    Cahyadi, Harsono; Iwatsuka, Junichi; Minamikawa, Takeo; Niioka, Hirohiko; Araki, Tsutomu; Hashimoto, Mamoru

    2013-09-01

    We develop a coherent anti-Stokes Raman scattering (CARS) microscopy system equipped with a tunable picosecond laser for high-speed wavelength scanning. An acousto-optic tunable filter (AOTF) is integrated in the laser cavity to enable wavelength scanning by varying the radio frequency waves applied to the AOTF crystal. An end mirror attached on a piezoelectric actuator and a pair of parallel plates driven by galvanometer motors are also introduced into the cavity to compensate for changes in the cavity length during wavelength scanning to allow synchronization with another picosecond laser. We demonstrate fast spectral imaging of 3T3-L1 adipocytes every 5  cm-1 in the Raman spectral region around 2850  cm-1 with an image acquisition time of 120 ms. We also demonstrate fast switching of Raman shifts between 2100 and 2850  cm-1, corresponding to CD2 symmetric stretching and CH2 symmetric stretching vibrations, respectively. The fast-switching CARS images reveal different locations of recrystallized deuterated and nondeuterated stearic acid.

  3. Pulsed picosecond and nanosecond discharge development in liquids with various dielectric permittivity constants

    NASA Astrophysics Data System (ADS)

    Starikovskiy, Andrey

    2016-09-01

    The dynamics of pulsed picosecond and nanosecond discharge development in liquid water, ethanol and hexane were investigated experimentally. It is shown that the dynamics of discharge formation fundamentally differ between liquids with low and high dielectric permittivity coefficients. The difference in the nanosecond discharge development in liquid dielectrics may be explained by the formation of micro-discontinuities in the media during the electrostriction compression/rarefaction stage in liquids with high dielectric permittivity. Three possible mechanisms for the propagation of discharge in liquids play a different role depending on the pulse duration. The first is the formation of low density channels in liquid. In the second case the electrostatic forces support the expansion of nanoscale voids behind the front of the ionization wave; in the wave front the extreme electric field provides a strong negative pressure in the dielectric fluid due to the presence of electrostriction forces, forming the initial micro-voids in the continuous medium. Finally, in the third case, when a picosecond electric pulse is utilized, the ionization in the liquid phase occurs as a result of direct electron impact without undergoing a phase transition.

  4. Structuring of functional thin films and surfaces with picosecond-pulsed lasers

    NASA Astrophysics Data System (ADS)

    Raciukaitis, G.; Gecys, P.; Gedvilas, M.; Voisiat, B.

    2012-03-01

    During the recent few years picosecond lasers have been proved as a reliable tool for microfabrication of diverse materials. We present results of our research on structuring of thin films and surfaces using the direct laser writing and the laser beam interference ablation techniques. The processes of micro-pattering were developed for metallic, dielectric films as well as complex multi-layer structures of thin-film solar cells as a way to manufacture frequency-selective surfaces, fine optical components and integrated series interconnects for photovoltaics. Technologies of nano-structuring of surfaces of advanced technical materials such as tungsten carbide were developed using picosecond lasers as well. Experimental work was supported by modeling and simulation of energy coupling and dissipation inside the layers. Selectiveness of the ablation process is defined by optical and mechanical properties of the materials, and selection of the laser wavelength facilitated control of the structuring process. Implementation of the technologies required fine adjustment of spatial distribution of laser irradiation, therefore both techniques are benefiting from shaping the laser beam with diffractive optical elements. Utilization of the whole laser energy included beam splitting and multi-beam processing.

  5. Germanium Sub-Microspheres Synthesized by Picosecond Pulsed Laser Melting in Liquids: Educt Size Effects.

    PubMed

    Zhang, Dongshi; Lau, Marcus; Lu, Suwei; Barcikowski, Stephan; Gökce, Bilal

    2017-01-13

    Pulsed laser melting in liquid (PLML) has emerged as a facile approach to synthesize submicron spheres (SMSs) for various applications. Typically lasers with long pulse durations in the nanosecond regime are used. However, recent findings show that during melting the energy absorbed by the particle will be dissipated promptly after laser-matter interaction following the temperature decrease within tens of nanoseconds and hence limiting the efficiency of longer pulse widths. Here, the feasibility to utilize a picosecond laser to synthesize Ge SMSs (200~1000 nm in diameter) is demonstrated by irradiating polydisperse Ge powders in water and isopropanol. Through analyzing the educt size dependent SMSs formation mechanism, we find that Ge powders (200~1000 nm) are directly transformed into SMSs during PLML via reshaping, while comparatively larger powders (1000~2000 nm) are split into daughter SMSs via liquid droplet bisection. Furthermore, the contribution of powders larger than 2000 nm and smaller than 200 nm to form SMSs is discussed. This work shows that compared to nanosecond lasers, picosecond lasers are also suitable to produce SMSs if the pulse duration is longer than the material electron-phonon coupling period to allow thermal relaxation.

  6. Superhydrophilicity to superhydrophobicity transition of picosecond laser microstructured aluminum in ambient air.

    PubMed

    Long, Jiangyou; Zhong, Minlin; Zhang, Hongjun; Fan, Peixun

    2015-03-01

    Studies regarding the wettability transition of micro- and nano-structured metal surfaces over time are frequently reported, but there seems to be no generally accepted theory that explains this phenomenon. In this paper, we aim to clarify the mechanism underlying the transition of picosecond laser microstructured aluminum surfaces from a superhydrophilic nature to a superhydrophobic one under ambient conditions. The aluminum surface studied exhibited superhydrophilicity immediately after being irradiated by a picosecond laser. However, the contact angles on the surface increased over time, eventually becoming large enough to classify the surface as superhydrophobic. The storage conditions significantly affected this process. When the samples were stored in CO2, O2 and N2 atmospheres, the wettability transition was restrained. However, the transition was accelerated in atmosphere that was rich with organic compounds. Moreover, the superhydrophobic surface could recover their original superhydrophilicity by low temperature annealing. A detailed XPS analysis indicated that this wettability transition process was mainly caused by the adsorption of organic compounds from the surrounding atmosphere onto the oxide surface.

  7. High average power picosecond pulse generation from a thulium-doped all-fiber MOPA system.

    PubMed

    Liu, Jiang; Wang, Qian; Wang, Pu

    2012-09-24

    We report a stable highly-integrated high power picosecond thulium-doped all-fiber MOPA system without using conventional chirped pulse amplification technique. The master oscillator was passively mode-locked by a SESAM to generate average power of 15 mW at a fundamental repetition rate of 103 MHz in a short linear cavity, and a uniform narrow bandwidth FBG is employed to stabilize the passively mode-locked laser operation. Two-stage double-clad thulium-doped all-fiber amplifiers were used directly to boost average power to 20.7 W. The laser center wavelength was 1962.8 nm and the pulse width was 18 ps. The single pulse energy and peak-power after the amplication were 200 nJ and 11.2 kW respectively. To the best of our knowledge, this is the highest average power ever reported for a picosecond thulium-doped all-fiber MOPA system.

  8. High-power transverse-mode-switchable all-fiber picosecond MOPA.

    PubMed

    Liu, Tong; Chen, Shengping; Qi, Xue; Hou, Jing

    2016-11-28

    A high-power transverse-mode-switchable all-fiber picosecond laser in a master-oscillator power-amplifier (MOPA) configuration is demonstrated. The master oscillator is a gain-switched laser diode delivering picosecond pulses with 25 MHz repetition rate at the wavelength of 1.06 μm. After multi-stage amplification in ytterbium-doped fibers, the average output power is scaled to 117 W. A mechanical long-period grating is employed as a fiber mode convertor to achieve controllable conversion from the fundamental (LP01) to the second-order (LP11) mode. Efficient mode conversion is demonstrated and the output characteristics for both modes are investigated. It is shown that LP01 and LP11 modes have nearly identical optical-to-optical conversion efficiency during amplification, but the nonlinear spectral degradation is significantly alleviated for LP11 mode operation. Owing to the compact all-fiber architecture, this high-power transverse-mode-switchable fiber laser is reliable during long-term operation and thus promising for many practical applications, e.g. high-resolution laser micro-processing.

  9. Fiber laser pumped high power mid-infrared laser with picosecond pulse bunch output.

    PubMed

    Wei, Kaihua; Chen, Tao; Jiang, Peipei; Yang, Dingzhong; Wu, Bo; Shen, Yonghang

    2013-10-21

    We report a novel quasi-synchronously pumped PPMgLN-based high power mid-infrared (MIR) laser with picosecond pulse bunch output. The pump laser is a linearly polarized MOPA structured all fiberized Yb fiber laser with picosecond pulse bunch output. The output from a mode-locked seed fiber laser was directed to pass through a FBG reflector via a circulator to narrow the pulse duration from 800 ps to less than 50 ps and the spectral FWHM from 9 nm to 0.15 nm. The narrowed pulses were further directed to pass through a novel pulse multiplier through which each pulse was made to become a pulse bunch composing of 13 sub-pulses with pulse to pulse time interval of 1.26 ns. The pulses were then amplified via two stage Yb fiber amplifiers to obtain a linearly polarized high average power output up to 85 W, which were then directed to pass through an isolator and to pump a PPMgLN-based optical parametric oscillator via quasi-synchronization pump scheme for ps pulse bunch MIR output. High MIR output with average power up to 4 W was obtained at 3.45 micron showing the feasibility of such pump scheme for ps pulse bunch MIR output.

  10. Folding and unfolding of a photoswitchable peptide from picoseconds to microseconds.

    PubMed

    Ihalainen, Janne A; Bredenbeck, Jens; Pfister, Rolf; Helbing, Jan; Chi, Lei; van Stokkum, Ivo H M; Woolley, G Andrew; Hamm, Peter

    2007-03-27

    Using time-resolved IR spectroscopy, we monitored the kinetics of folding and unfolding processes of a photoswitchable 16-residue alanine-based alpha-helical peptide on a timescale from few picoseconds to almost 40 micros and over a large temperature range (279-318 K). The folding and unfolding processes were triggered by an ultrafast laser pulse that isomerized the cross linker within a few picoseconds. The main folding and unfolding times (700 ns and 150 ns, respectively, at room temperature) are in line with previous T-jump experiments obtained from similar peptides. However, both processes show complex, strongly temperature-dependent spectral kinetics that deviate clearly from a single-exponential behavior. Whereas in the unfolding experiment the ensemble starts from a well defined folded state, the starting ensemble in the folding experiment is more heterogeneous, which leads to distinctly different kinetics of the experiments, because they are sensitive to different regions of the energy surface. A qualitative agreement with the experimental data-set can be obtained by a model where the unfolded states act as a hub connected to several separated "misfolded" states with a distribution of rates. We conclude that a rather large spread of rates (k(1) : k(n) approximately 9) is needed to explain the experimentally observed stretched exponential response with stretching factor beta = 0.8 at 279 K.

  11. Wavelength conversion through soliton self-frequency shift in tellurite microstructured fiber with picosecond pump pulse

    NASA Astrophysics Data System (ADS)

    Bi, Wanjun; Li, Xia; Xing, Zhaojun; Zhou, Qinling; Fang, Yongzheng; Gao, Weiqing; Xiong, Liangming; Hu, Lili; Liao, Meisong

    2016-01-01

    Wavelength conversion to the wavelength range that is not covered by commercially available lasers could be accomplished through the soliton self-frequency shift (SSFS) effect. In this study, the phenomenon of SSFS pumped by a picosecond-order pulse in a tellurite microstructured fiber is investigated both theoretically and experimentally. The balance between the dispersion and the nonlinearity achieved by a 1958 nm pump laser induces a distinct SSFS effect. Attributed to the large spectral distance between the pump pulse and the fiber zero-dispersion wavelength, the SSFS is not cancelled due to energy shedding from the soliton to the dispersive wave. Details about the physical mechanisms behind this phenomenon and the variations of the wavelength shift, the conversion efficiency are revealed based on numerical simulations. Owing to the large soliton number N, the pulse width of the first split fundamental soliton is approximately 40 fs, producing a pulse compression factor of ˜38, much higher than that pumped by a femtosecond pulse. Experiments were also conducted to confirm the validity of the simulation results. By varying the pump power, a continuous soliton shift from 1990 nm to 2264 nm was generated. The generation of SSFS in tellurite microstructured fibers with picosecond pump pulse can provide a new approach for wavelength conversion in the mid-infrared range and could be useful in medical and some other areas.

  12. Insights into the photochemical disproportionation of transition metal dimers on the picosecond time scale.

    PubMed

    Lomont, Justin P; Nguyen, Son C; Harris, Charles B

    2013-05-09

    The reactivity of five transition metal dimers toward photochemical, in-solvent-cage disproportionation has been investigated using picosecond time-resolved infrared spectroscopy. Previous ultrafast studies on [CpW(CO)3]2 established the role of an in-cage disproportionation mechanism involving electron transfer between 17- and 19-electron radicals prior to diffusion out of the solvent cage. New results from time-resolved infrared studies reveal that the identity of the transition metal complex dictates whether the in-cage disproportionation mechanism can take place, as well as the more fundamental issue of whether 19-electron intermediates are able to form on the picosecond time scale. Significantly, the in-cage disproportionation mechanism observed previously for the tungsten dimer does not characterize the reactivity of four out of the five transition metal dimers in this study. The differences in the ability to form 19-electron intermediates are interpreted either in terms of differences in the 17/19-electron equilibrium or of differences in an energetic barrier to associative coordination of a Lewis base, whereas the case for the in-cage vs diffusive disproportionation mechanisms depends on whether the 19-electron reducing agent is genuinely characterized by 19-electron configuration at the metal center or if it is better described as an 18 + δ complex. These results help to better understand the factors that dictate mechanisms of radical disproportionation and carry implications for radical chain mechanisms.

  13. Germanium Sub-Microspheres Synthesized by Picosecond Pulsed Laser Melting in Liquids: Educt Size Effects

    PubMed Central

    Zhang, Dongshi; Lau, Marcus; Lu, Suwei; Barcikowski, Stephan; Gökce, Bilal

    2017-01-01

    Pulsed laser melting in liquid (PLML) has emerged as a facile approach to synthesize submicron spheres (SMSs) for various applications. Typically lasers with long pulse durations in the nanosecond regime are used. However, recent findings show that during melting the energy absorbed by the particle will be dissipated promptly after laser-matter interaction following the temperature decrease within tens of nanoseconds and hence limiting the efficiency of longer pulse widths. Here, the feasibility to utilize a picosecond laser to synthesize Ge SMSs (200~1000 nm in diameter) is demonstrated by irradiating polydisperse Ge powders in water and isopropanol. Through analyzing the educt size dependent SMSs formation mechanism, we find that Ge powders (200~1000 nm) are directly transformed into SMSs during PLML via reshaping, while comparatively larger powders (1000~2000 nm) are split into daughter SMSs via liquid droplet bisection. Furthermore, the contribution of powders larger than 2000 nm and smaller than 200 nm to form SMSs is discussed. This work shows that compared to nanosecond lasers, picosecond lasers are also suitable to produce SMSs if the pulse duration is longer than the material electron-phonon coupling period to allow thermal relaxation. PMID:28084408

  14. Stretching of picosecond laser pulses with uniform reflecting volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Mokhov, Sergiy; Spiro, Alexander; Smirnov, Vadim; Kaim, Sergiy; Zeldovich, Boris; Glebov, Leonid

    2017-08-01

    This study shows that a uniform reflecting volume Bragg grating (VBG) can be used as a compact monolithic stretcher of high-power picosecond laser pulses, which is important for cases in which chirped Bragg gratings with the required chirp rate are difficult to fabricate. When an incident short pulse propagates along a grating and experiences local Bragg diffraction, a chirp-free reflected stretched pulse with an almost rectangular shape is generated. The increase in the duration of the reflected pulse is approximately equal to twice the propagation time along the grating. We derive an analytic expression for the diffraction efficiency, which incorporates the incident pulse duration, grating thickness, and amplitude of the refractive index modulation, enabling selection of the optimum grating for pulse stretching. Theoretical models of the extended pulse profiles are found to be in good agreement with experimental autocorrelation measurements. We also propose a simple and reliable method to control the temporal parameters of high-power picosecond pulses using the same laser source and a VBG of variable thickness, which can simplify experiments requiring different pulse durations significantly.

  15. 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°.

  16. Electrolytes Ageing in Lithium-ion Batteries: A Mechanistic Study from Picosecond to Long Timescales.

    PubMed

    Ortiz, Daniel; Jiménez Gordon, Isabel; Baltaze, Jean-Pierre; Hernandez-Alba, Oscar; Legand, Solène; Dauvois, Vincent; Si Larbi, Gregory; Schmidhammer, Uli; Marignier, Jean-Louis; Martin, Jean-Frédéric; Belloni, Jacqueline; Mostafavi, Mehran; Le Caër, Sophie

    2015-11-01

    The ageing phenomena occurring in various diethyl carbonate/LiPF6 solutions are studied using gamma and pulse radiolysis as a tool to generate similar species as the ones occurring in electrolysis of Li-ion batteries (LIBs). According to picosecond pulse radiolysis experiments, the reaction of the electron with (Li(+), PF6(-)) is ultrafast, leading to the formation of fluoride anions that can then precipitate into LiF(s). Moreover, direct radiation-matter interaction with the salt produces reactive fluorine atoms forming HF(g) and C2H5F(g). The strong Lewis acid PF5 is also formed. This species then forms various R(1)R(2)R(3) P=O molecules, where R is mainly -F, -OH, and -OC2H5. Substitution reactions take place and oligomers are slowly formed. Similar results were obtained in the ageing of an electrochemical cell filled with the same model solution. This study demonstrates that radiolysis enables a description of the reactivity in LIBs from the picosecond timescale until a few days.

  17. Time-resolved fluorescence polarization spectroscopy of visible and near infrared dyes in picosecond dynamics

    NASA Astrophysics Data System (ADS)

    Pu, Yang; Alfano, Robert R.

    2015-03-01

    Near-infrared (NIR) dyes absorb and emit light within the range from 700 to 900 nm have several benefits in biological studies for one- and/or two-photon excitation for deeper penetration of tissues. These molecules undergo vibrational and rotational motion in the relaxation of the excited electronic states, Due to the less than ideal anisotropy behavior of NIR dyes stemming from the fluorophores elongated structures and short fluorescence lifetime in picosecond range, no significant efforts have been made to recognize the theory of these dyes in time-resolved polarization dynamics. In this study, the depolarization of the fluorescence due to emission from rotational deactivation in solution will be measured with the excitation of a linearly polarized femtosecond laser pulse and a streak camera. The theory, experiment and application of the ultrafast fluorescence polarization dynamics and anisotropy are illustrated with examples of two of the most important medical based dyes. One is NIR dye, namely Indocyanine Green (ICG) and is compared with Fluorescein which is in visible range with much longer lifetime. A set of first-order linear differential equations was developed to model fluorescence polarization dynamics of NIR dye in picosecond range. Using this model, the important parameters of ultrafast polarization spectroscopy were identified: risetime, initial time, fluorescence lifetime, and rotation times.

  18. Electric-field-assisted gain control in a high-power picosecond laser diode

    NASA Astrophysics Data System (ADS)

    Vainshtein, Sergey N.; Yuferev, Valentin; Kostamovaara, Juha T.

    2003-03-01

    A laser diode structure has lately been reported that is capable of generating high-power picosecond optical pulses (~ 50 W / 20 ps) in the near-infrared range for laser radars and other applications. The physical idea consists of achieving fast gain control through the effect of a transverse electric field on the carrier distribution across the active region, which controls the local gain and local absorption at each instant. The mechanism of field-assisted gain control, which has so far been formulated only as a qualitative idea, is justified in this work by simulations of the carrier transport and laser response using the semiconductor device simulator "Atlas" (Silvaco Inc.). A simplified approach is adopted which replaces photon-assisted carrier transport with carrier penetration over the lowered potential barrier. This points to reasonably good agreement between the experimental and simulation results for picosecond pulse generation, provided that the carrier mobilities are assumed to be higher than those in the heavily doped semiconductor structure by a factor of ~ 4. One important conclusion is that comprehensive modelling of the operation of the experimental laser diode is not possible without considering photon-assisted carrier transport, which has not been studied so far at very high carrier densities (exceeding the transparency concentration).

  19. Experimental and modelling investigations into the laser ablation with picosecond pulses at second harmonics

    NASA Astrophysics Data System (ADS)

    Boerner, Paul; Zandonadi, Germana; Eberle, Gregory; Wegener, Konrad

    2015-03-01

    Ablation threshold experiments on various materials are carried out using a picosecond laser generating second harmonic radiation in air at atmospheric pressure. Various materials are investigated which vary according to their different electronic band gap structure and include: silicon, fine grain polycrystalline diamond, copper, steel and tungsten carbide. Through the use of scanning electron microscopy and 3D confocal microscopy, the crater depth and diameter are determined and a correlation is found. The ablation thresholds are given for the aforementioned materials and compared with recent literature results. Picosecond laser-material interactions are modelled using the two-temperature model, simulated and compared with experimental results for metallic materials. An extension of the two-temperature model to semiconducting and insulating materials is discussed. This alternative model uses multiple rate equations to describe the transient free electron density. Additionally, a set of coupled ordinary differential equations describes the processes of multiphoton excitation, inverse bremsstrahlung, and collisional excitation. The resulting electron density distribution can be used as an input for an electron density dependent twotemperature model. This multiple rate equation model is a generic and fast model, which provides important information like ablation threshold, ablation depth and optical properties.

  20. Nonequilibrium evolution of strong-field anisotropic ionized electrons towards a delayed plasma-state.

    PubMed

    Pasenow, B; Moloney, J V; Koch, S W; Chen, S H; Becker, A; Jaroń-Becker, A

    2012-01-30

    Rigorous quantum calculations of the femtosecond ionization of hydrogen atoms in air lead to highly anisotropic electron and ion angular (momentum) distributions. A quantum Monte-Carlo analysis of the subsequent many-body dynamics reveals two distinct relaxation steps, first to a nearly isotropic hot nonequilibrium and then to a quasi-equilibrium configuration. The collective isotropic plasma state is reached on a picosecond timescale well after the ultrashort ionizing pulse has passed.

  1. Clustered gases as a medium for efficient plasma waveguide generation.

    PubMed

    Milchberg, H M; Kim, K Y; Kumarappan, V; Layer, B D; Sheng, H

    2006-03-15

    Clustered gas jets are shown to be an efficient means for plasma waveguide generation, for both femtosecond and picosecond generation pulses. These waveguides enable significantly lower on-axis plasma density (less than 10(18) cm(-3)) than in conventional hydrodynamic plasma waveguides generated in unclustered gases. Using femtosecond pump pulses, self-guided propagation and strong absorption (more than 70%) are used to produce long centimetre scale channels in an argon cluster jet, and a subsequent intense pulse is coupled into the guide with 50% efficiency and guided at above 10(17)W cm(-2) intensity over 40 Rayleigh lengths. We also demonstrate efficient generation of waveguides using 100 ps axicon-generated Bessel-beam pump pulses. Despite the expected sub-picosecond cluster disassembly time, we observe long pulse absorption efficiencies up to a maximum of 35%. Simulations show that in the far leading edge of the long laser pulse, the volume of heated clusters evolves to a locally uniform and cool plasma already near ionization saturation, which is then efficiently heated by the remainder of the pulse.

  2. Interferometric Diagnosis of Two-Dimensional Plasma Expansion

    SciTech Connect

    Smith, R F; Moon, S; Dunn, J; Nilsen, J; Shlyaptsev, V N; Hunter, J R; Rocca, J; Filevich, J; Marconi, M C

    2002-07-31

    Recent advances in interferometry has allowed for the characterization of the electron density expansion within a laser produced plasma to within 10 {micro}m of the target surface and over picosecond timescales. This technique employs the high brightness output of the transient gain Ni-like Pd collisional x-ray laser at 14.7 nm to construct an effective moving picture of the two-dimensional (2-D) expansion within the plasma. In this paper we present experimentally measured density profiles from an Al plasma and make comparisons with 1.5-D and 2-D code simulations. The results are discussed along with an analysis of the underlying mechanisms driving the plasma expansion.

  3. Effect of preformed plasma on terahertz-wave emission from the plasma generated by two-color laser pulses

    SciTech Connect

    Minami, Yasuo; Nakajima, Makoto; Suemoto, Tohru

    2011-02-15

    We introduced a weak prepulse 0-2 ns before the main pulse in the formation of a terahertz (THz) wave in air plasma by laser pulses composed of fundamental and second-harmonic waves. The prepulse suppressed the THz wave generated by the main pulse. We analyzed the suppression factor as a function of the time interval between the prepulse and the main pulse and found that the THz wave from the main pulse decreases immediately after the prepulse, recovers partially within several hundred picoseconds, and then recovers slowly. This suppression is attributed to the dense plasma, which absorbs and screens the generated THz wave, since the relaxation time is close to the lifetime of the fluorescence from the plasma. The results support the idea that the major mechanism of THz wave generation is explained by the plasma current model.

  4. A novel dual-wavelength, Nd:YAG, picosecond-domain laser safely and effectively removes multicolor tattoos.

    PubMed

    Bernstein, Eric F; Schomacker, Kevin T; Basilavecchio, Lisa D; Plugis, Jessica M; Bhawalkar, Jayant D

    2015-07-14

    Although nanosecond-domain lasers have been the mainstay of laser tattoo removal for decades, recent disruptive innovations in laser design have introduced a new class of commercial Q-switched lasers that generate picosecond-domain pulses. A picosecond-domain, Nd:YAG laser with a KTP frequency-doubling crystal was used to treat 31 decorative tattoos in 21 subjects. Safety and effectiveness were determined by blinded evaluation of digital images in this prospective clinical study. The average clearance overall as evaluated by blinded observers evaluating randomized digital photographs was 79 ± 0.9% (mean ± sem) after an average of 6.5 treatments. Of the 31 tattoos completing treatment, 6 had evidence of mild hyper- or hypo-pigmentation by evaluation of photographs. The 350 picosecond, 532 nm, and 450 picosecond 1,064 nm Nd:YAG laser is safe and effective for removing decorative tattoos. Lasers Surg. Med. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

  5. Peak power tunable mid-infrared oscillator pumped by a high power picosecond pulsed fiber amplifier with bunch output

    NASA Astrophysics Data System (ADS)

    Wei, Kaihua; Guo, Yan; Lai, Xiaomin; Fan, Shanhui

    2016-07-01

    A high power mid-infrared optical parametric oscillator (OPO) with picosecond pulse bunch output is experimentally demonstrated. The pump source was a high power master oscillation power amplifier (MOPA) picosecond pulsed fiber amplifier. The seed of the MOPA was a gain-switched distributed Bragg reflector (DBR) laser diode (LD) with picosecond pulse operation at a high repetition rate. The seed laser was amplified to 50 W by two-stage pre-amplifiers and a large mode area (LMA) Yb fiber based power-amplifier. A fiber-pigtailed acousto-optic modulator with the first order diffraction transmission was inserted into the second pre-amplifier to form a picosecond pulse bunch train and to change the peak power simultaneously. The power-amplified pulse bunches were focused to pump a wavelength-tunable OPO for emitting high power mid-infrared laser. By adjusting the OPO cavity length, the maximum average idler powers obtained at 3.1, 3.3 and 3.5 μm were 7, 6.6 and 6.4 W respectively.

  6. Use of multiple picosecond high-mass molecular dynamics simulations to predict crystallographic B-factors of folded globular proteins.

    PubMed

    Pang, Yuan-Ping

    2016-09-01

    Predicting crystallographic B-factors of a protein from a conventional molecular dynamics simulation is challenging, in part because the B-factors calculated through sampling the atomic positional fluctuations in a picosecond molecular dynamics simulation are unreliable, and the sampling of a longer simulation yields overly large root mean square deviations between calculated and experimental B-factors. This article reports improved B-factor prediction achieved by sampling the atomic positional fluctuations in multiple picosecond molecular dynamics simulations that use uniformly increased atomic masses by 100-fold to increase time resolution. Using the third immunoglobulin-binding domain of protein G, bovine pancreatic trypsin inhibitor, ubiquitin, and lysozyme as model systems, the B-factor root mean square deviations (mean ± standard error) of these proteins were 3.1 ± 0.2-9 ± 1 Å(2) for Cα and 7.3 ± 0.9-9.6 ± 0.2 Å(2) for Cγ, when the sampling was done for each of these proteins over 20 distinct, independent, and 50-picosecond high-mass molecular dynamics simulations with AMBER forcefield FF12MC or FF14SB. These results suggest that sampling the atomic positional fluctuations in multiple picosecond high-mass molecular dynamics simulations may be conducive to a priori prediction of crystallographic B-factors of a folded globular protein.

  7. [Surfaces and thin films studied by picosecond ultrasonics]. Annual progress report, [December 1, 1993--November 30, 1994

    SciTech Connect

    Maris, H.J.

    1994-10-01

    We are using picosecond optics techniques to perform ultrasonic and thermal transport measurements on thin films and nanostructures. We are investigating the basic physics of sound and phonon propagation in solids, and also attempting to develop practical techniques for the ultrasonic evaluation of thin-film nanostructures.

  8. Comparison of two picosecond lasers to a nanosecond laser for treating tattoos: a prospective randomized study on 49 patients.

    PubMed

    Lorgeou, A; Perrillat, Y; Gral, N; Lagrange, S; Lacour, J-P; Passeron, T

    2017-07-31

    Q-switched nanosecond lasers demonstrated their efficacy in treating most types of tattoos, but complete disappearance is not always achieved even after performing numerous laser sessions. Picosecond lasers are supposed to be more efficient in clearing tattoos than nanosecond lasers, but prospective comparative data remain limited. To compare on different types of tattoos the efficacy of a nanosecond laser with two types of picosecond lasers. We conducted a prospective randomized study performed from December 2014 to June 2016 on adult patients with all types of tattoos. The tattoos were divided into two halves of equal size. After randomization, half of the tattoo was treated with a picosecond laser and the other half with a nanosecond laser. The evaluation was performed on standardized pictures performed before treatment and 2 months after the last session, by two physicians, not involved in the treatment, blinded on the type of treatments received. The main end point was a clearance above 75% of the tattoos. A total of 49 patients were included. Professional tattoos represented 85.7%, permanent make-up 8.2% and non-professional tattoo 6.1%. The majority were black or blue and 10.2% were polychromatic. No patient was lost during follow-up. A reduction of 75% or more of the colour intensity was obtained for 33% of the tattoos treated with the picosecond lasers compared to 14% with the nanosecond laser (P = 0.008). An improvement superior to 75% was obtained in 34% monochromic black or blue tattoos with the picosecond lasers compared to 9% for the nanosecond laser. Only one of the five polychromic tattoos achieved more than 75% of improvement with the two types of laser. Our results show a statistically significant superiority of the picosecond lasers compared to the nanosecond laser for tattoo clearance. However, they do not show better efficacy for polychromic tattoos and the difference in terms of side-effects was also minimal with a tendency of picosecond

  9. Understanding Plasmas with a High Degree of Correlation Through Modeling: From Rydberg and Fermionic Plasmas to Penning Plasmas

    NASA Astrophysics Data System (ADS)

    Christlieb, Andrew

    2015-09-01

    Ultra cold neutral plasmas have gained attention over the past 15 years as being a unique environment for studying moderately to strongly coupled neutral systems. The first ultra cold neutral plasmas were generated by ionizing a Bose Einstein condensate, generating a plasma with .1K ions and 2-4K electrons. These neutral plasmas have the unique property that the ratio of their potential energy to their kinetic energy, (Γ = PE / KE), can greatly exceed 1, leading to a strongly correlated system. The high degree of correlation means that everything from wave propagation through collision dynamics behaves quite differently from their counterpart in traditional neutral plasmas. Currently, a range of gases and different methods for cooling have been used to generate these plasmas from supersonic expansion, through penning trap configurations (reference Tom, Jake and Ed). These systems have time scales form picoseconds to milliseconds have a particle numbers from 105 to 109. These systems present a unique environment for studying the physics of correlation due to their low particle number and small size. We start by reviewing ultra cold plasmas and the current sate of the art in generating these correlated systems. Then we introduce the methods we will use for exploring these systems through direct simulation of Molecular Dynamics models; Momentum Dependent Potentials, Treecodes and Particle-Particle Particle-Mesh methods. We use these tools to look at two key areas of ultra cold plasmas; development of methods to generate a plasma with a Γ >> 1 and the impact of correlation of collisional relaxation. Our eventual goal is to use what we learn to develop models that can simulate correlation in large plasma systems that are outside of the scope of Molecular Dynamics models. In collaboration with Gautham Dharmuman, Mayur Jain, Michael Murillo and John Verboncoeur. This work it supposed by Air Force Office of Scientific Research.

  10. Competition reactions of H2O•+ radical in concentrated Cl- aqueous solutions: picosecond pulse radiolysis study.

    PubMed

    El Omar, Abdel Karim; Schmidhammer, Uli; Rousseau, Bernard; LaVerne, Jay; Mostafavi, Mehran

    2012-11-29

    Picosecond pulse-probe radiolysis measurements of highly concentrated Cl(-) aqueous solutions are used to probe the oxidation mechanism of the Cl(-). The transient absorption spectra are measured from 340 to 710 nm in the picosecond range for the ultrafast electron pulse radiolysis of halide solutions at different concentrations up to 8 M. The amount of Cl(2)(•-) formation within the electron pulse increases notably with increasing Cl(-) concentration. Kinetic measurements reveal that the direct ionization of Cl(-) cannot solely explain the significant amount of fast Cl(2)(•-) formation within the electron pulse. The results suggest that Cl(-) reacts with the precursor of the OH(•) radical, i.e., H(2)O(•+) radical, to form Cl(•) atom within the electron pulse and the Cl(•) atom reacts subsequently with Cl(-) to form Cl(2)(•-) on very short time scales. The proton transfer reaction between H(2)O(•+) and the water molecule competes with the electron transfer reaction between Cl(-) and H(2)O(•+). Molecular dynamics simulations show that number of water molecules in close proximity decreases with increasing concentration of the salt (NaCl), confirming that for highly concentrated solutions the proton transfer reaction between H(2)O(•+) and a water molecule becomes less efficient. Diffusion-kinetic simulations of spur reactions including the direct ionization of Cl(-) and hole scavenging by Cl(-) show that up to 30% of the H(2)O(•+) produced by the irradiation could be scavenged for solutions containing 5.5 M Cl(-). This process decreases the yield of OH(•) radical in solution on the picosecond time scale. The experimental results for the same concentration of Cl(-) at a given absorbed dose show that the radiation energy absorbed by counterions is transferred to Cl(-) or water molecules and the effect of the countercation such as Li(+), K(+), Na(+), and Mg(2+) on the oxidation yield of Cl(-) is negligible.

  11. Photoluminescent zinc oxide polymer nanocomposites fabricated using picosecond laser ablation in an organic solvent

    NASA Astrophysics Data System (ADS)

    Wagener, Philipp; Faramarzi, Shamsolzaman; Schwenke, Andreas; Rosenfeld, Rupert; Barcikowski, Stephan

    2011-06-01

    Nanocomposites made of ZnO nanoparticles dispersed in thermoplastic polyurethane were synthesized using picosecond laser ablation of zinc in a polymer-doped solution of tetrahydrofuran. The pre-added polymer stabilizes the ZnO nanoparticles in situ during laser ablation by forming a polymer shell around the nanoparticles. This close-contact polymer shell has a layer thickness up to 30 nm. Analysis of ZnO polyurethane nanocomposites using optical spectroscopy, high resolution transmission electron microscopy and X-ray diffraction revealed that oxidized and crystalline ZnO nanoparticles were produced. Those nanocomposites showed a green photoluminescence emission centred at 538 nm after excitation at 350 nm, which should be attributed to oxygen defects generated during the laser formation mechanism of the monocrystalline nanoparticles. Further, the influence of pulse energy and polymer concentration on the production rate, laser fluence and energy-specific mass productivity was investigated.

  12. generation of picosecond pulses in solid-state lasers using new active media

    SciTech Connect

    Lisitsyn, V.N.; Matrosov, V.N.; Pestryakov, E.V.; Trunov, V.I.

    1986-07-01

    Results are reported of investigations aimed at generating nanosecond radiation pulses in solid-state lasers using new active media having broad gain lines. Passive mode locking is accomplished for the first time in a BeLa:Nd/sup 3/ laser at a wavelength 1.354 microm, and in a YAG:Nd/sup 3/ laser on a 1.32-microm transition. The free lasing and mode-locking regimes were investigated in an alexandrite (BeA1/sub 2/O/sub 4/:Cr/sup 3/) laser in the 0.72-0.78-microm range and in a synchronously pumped laser on F/sub 2//sup -/ centers in LiF in the 1.12-1.24-microm region. The features of nonlinear perception of IR radiation by the eye, using a developed picosecond laser on F/sub 2//sup -/ centers, are investigated for the first time.

  13. Towards a table-top microscope for nanoscale magnetic imaging using picosecond thermal gradients

    PubMed Central

    Bartell, J. M.; Ngai, D. H.; Leng, Z.; Fuchs, G. D.

    2015-01-01

    Research advancement in magnetoelectronics is challenged by the lack of a table-top magnetic measurement technique with the simultaneous temporal and spatial resolution necessary for characterizing magnetization dynamics in devices of interest, such as magnetic memory and spin torque oscillators. Although magneto-optical microscopy provides superb temporal resolution, its spatial resolution is fundamentally limited by optical diffraction. To address this challenge, we study heat rather than light as a vehicle to stroboscopically transduce a local magnetic moment into an electrical signal while retaining picosecond temporal resolution. Using this concept, we demonstrate spatiotemporal magnetic microscopy using the time-resolved anomalous Nernst effect (TRANE). Experimentally and with supporting numerical calculations, we find that TRANE microscopy has temporal resolution below 30 ps and spatial resolution determined by the area of thermal excitation. Based on these findings, we suggest a route to exceed the limits imposed by far-field optical diffraction. PMID:26419515

  14. 355, 532, and 1064 nm picosecond laser interaction with grass tissues

    NASA Astrophysics Data System (ADS)

    Kim, Jaehun; Ki, Hyungson

    2012-12-01

    In this article, we investigate how 355, 532, and 1064 nm picosecond lasers interact with grass tissues. We have identified five interaction regimes, and based on this classification, interaction maps have been constructed from a systematic experiment. The optical properties of light absorbing grass constituents are studied theoretically in order to understand how and how much light is absorbed by grass tissues. Scanning electron microscopy and optical microscopy are employed for observing morphological and structural changes of grass tissues. To the best of the authors' knowledge, this is the first investigation into laser interaction with plant leaves and reveals some fundamental findings regarding how a laser interacts with grass tissues and how plant leaves can be processed using lasers.

  15. Modification of anodised aluminium surfaces using a picosecond fibre laser for printing applications.

    PubMed

    Ansari, I A; Watkins, K G; Sharp, M C; Hutchinson, R A; Potts, R M; Clowes, J

    2012-06-01

    The use of an ultrafast fibre laser at a wavelength of 1064 nm has allowed the surface modification of anodised aluminium plates coated with a 2 micron thick anodised layer for potential industrial applications. The micro- and nano-scale structuring of the anodised aluminium using picosecond pulses of approximately 25 ps duration at 200 kHz repetition rate was investigated. The interaction of the laser with the substrate created a hydrophilic surface, giving a contact angle of less than 10 degrees. On examination under a Scanning Electron Microscope (SEM), a morphology created due to laser induced spallation was observed. It has been found that these laser processed hydrophilic surfaces revert to a hydrophobic state with time. This has potential for application in the printing industry and offers reusability and sustainability of the process materials. This has been confirmed in initial trials.

  16. Fast phosphor picosecond streak tube for ultrafast laser diagnostics in repetitive mode

    NASA Astrophysics Data System (ADS)

    Ageeva, N. V.; Gornostaev, P. B.; Ivanova, S. R.; Kulechenkova, T. P.; Levina, G. P.; Lozovoi, V. I.; Makushina, V. A.; Schelev, M. Ya; Shashkov, E. V.; Scaballanovich, T. A.; Smirnov, A. V.; Vereschagin, A. K.; Vereschagin, K. A.; Vorobiev, N. S.

    2015-08-01

    The well-established PIF-01/S1/P43 picosecond streak tube, designed 30 years ago and still manufactured at the A.M. Prokhorov General Physics Institute, was modified by replacing its traditional P43 phosphor screen with a P47 one having approximately three orders of magnitude shorter decay time. The experimental measurements of this decay time were provided by PIF-01/S1/P47 image tube photocathode irradiation either with a single or a train of 8 ps laser pulses separated by 8 ns from each other at a 1.08 μm wavelength. The results of our preliminary measurements of P47-BH phosphor (manufactured by Phosphor Technology Ltd) indicate the possibility of employing the PIF-01/S1/P47 streak tube for synchrotron diagnostics at a units megahertz repetition rate without the negative influence of ‘ghost images’ from the previous streak records.

  17. UV photolysis of nitromethane studied by sub-picosecond time-resolved CARS experiments

    SciTech Connect

    Rajchenbach, C.; Jonusauskas, G.; Rulliere, C.

    1996-04-01

    Using sub-picosecond CARS experiment we observed direct photolysis of liquid nitromethane after pulse excitation at 299 nm. We measured the dynamics behavior under excitation of three main ground state Raman lines: the {nu} (CN) mode at 917 cm{sup -1}, the {nu}s(NO2) and {delta}s(CH3) modes near 1400 cm{sup -1} and the {nu}s(CH3) mode at 2968 cm{sup -1}. From the evolution of these modes we deduced that the excited state disappears with a lifetime of 1.1{+-}0.3 ps and we measured a photolysis quantum yield at 299 nm of 24%{+-}5%. Important and fast non-radiative desexcitation channel from excited to ground states has been observed.

  18. Investigation of Carbon Fiber Reinforced Plastics Machining Using 355 nm Picosecond Pulsed Laser

    NASA Astrophysics Data System (ADS)

    Hu, Jun; Zhu, Dezhi

    2017-08-01

    Carbon fiber reinforced plastics (CFRP) has been widely used in the aircraft industry and automobile industry owing to its superior properties. In this paper, a Nd:YVO4 picosecond pulsed system emitting at 355 nm has been used for CFRP machining experiments to determine optimum milling conditions. Milling parameters including laser power, milling speed and hatch distance were optimized by using box-behnken design of response surface methodology (RSM). Material removal rate was influenced by laser beam overlap ratio which affects mechanical denudation. The results in heat affected zones (HAZ) and milling quality were discussed through the machined surface observed with scanning electron microscope. A re-focusing technique based on the experiment with different focal planes was proposed and milling mechanism was also analyzed in details.

  19. Magnetic vortex-antivortex dynamics on a picosecond timescale in a rectangular Permalloy pattern

    SciTech Connect

    Kim, D.-H.; Mesler-Lai, B.; Anderson, E.; Fischer, P.; Moon, J.-H.; Lee, K.-J.

    2009-06-25

    We report our experimental finding that there exists a pair of magnetic vortex and antivortex generated during an excited motion of a magnetic vortex core. Two vortices structure in 2 x 4 {micro}m{sup 2} rectangular Permalloy pattern is excited by an external field pulse of 1-ns duration, where each vortex is excited and followed by the vortex core splitting. X-ray microscopy with high spatiotemporal resolution enables us to observe a linking domain between two temporarily generated pairs of vortex-antivortex cores only surviving for several hundreds of picoseconds. The linking domain structure is found to depend on the combinational configuration of two original vortex cores, which is supported by micromagnetic simulations with a very good agreement.

  20. Light-induced picosecond rotational disordering of the inorganic sublattice in hybrid perovskites

    DOE PAGES

    Wu, Xiaoxi; Tan, Liang Z.; Shen, Xiaozhe; ...

    2017-07-26

    Femtosecond resolution electron scattering techniques are applied to resolve the first atomic-scale steps following absorption of a photon in the prototypical hybrid perovskite methylammonium lead iodide. Following above-gap photoexcitation, we directly resolve the transfer of energy from hot carriers to the lattice by recording changes in the mean square atomic displacements on 10-ps time scales. Measurements of the time-dependent pair distribution function show an unexpected broadening of the iodine-iodine correlation function while preserving the Pb-I distance. This indicates the formation of a rotationally disordered halide octahedral structure developing on picosecond time scales. Here, this work shows the important role ofmore » light-induced structural deformations within the inorganic sublattice in elucidating the unique optoelectronic functionality exhibited by hybrid perovskites and provides new understanding of hot carrier-lattice interactions, which fundamentally determine solar cell efficiencies.« less

  1. Laser diagnostics in combustion: Elastic scattering and picosecond laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Ossler, Frederik E.

    Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of submicron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz-Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were smaller than one micrometer in diameter. The LM theory was also used to characterize different size groups in a burning spray. A 3-D technique based on a picosecond laser and a streak camera was demonstrated for measurements of fast and turbulent biphase flows. The entire 3-D information was obtained within a time-span of less than 15 nanoseconds. A 2-D technique for lifetime measurements based on a picosecond laser and a streak camera has been demonstrated on static objects. An analysis indicates that the technique may be applied to measurements of lifetimes around or below one picosecond employing femtosecond lasers and femtosecond streak-cameras. The technique may in principle be used to study dynamic systems when two detectors are used. Fluorescence lifetime measurements on hydrogen and oxygen atoms in flames at atmospheric pressure demonstrate the need of lasers with suiting spectral properties such as jitter and linewidth and the need of detectors with high sensitivity in the near IR in the case of oxygen atoms. The fluorescence lifetimes of gas phase acetone and 3- pentanone at 266 nm excitation wavelength have been measured for mixtures with nitrogen and air at temperatures between 323 and 723 K and pressures between 0.01 and 10

  2. Rotational reorientation dynamics of C60 in various solvents. Picosecond transient grating experiments

    NASA Astrophysics Data System (ADS)

    Rubtsov, I. V.; Khudiakov, D. V.; Nadtochenko, V. A.; Lobach, A. S.; Moravskii, A. P.

    1994-11-01

    The picosecond transient grating technique has been used to study the rotational reorientation of C60 in various solvents: in toluene 7 +/- 1.5 ps, o-dichlorobenzene 10.3 +/- 1.5 ps, o-xylene 13 +/- 2 ps and in decalin 3.5 +/- 1.5 ps. The data obtained cannot be described by hydrodynamic Debye theory. Rough-sphere fluid theory predicts the correct values for C60 rotation in toluene, o-dichlorobenzene and in decalin. The deviations for o-xylene are probably connected with the specifics of the local solvent structure or with the stronger interaction of C60 with solvent molecules. The rotation of C60 in decalin is rapid and approaches the rotation in the gas phase determined by inertia.

  3. Picosecond ultrasonic study of surface acoustic waves on titanium nitride nanostructures

    SciTech Connect

    Bjornsson, M. M.; Connolly, A. B.; Mahat, S.; Rachmilowitz, B. E.; Daly, B. C.; Antonelli, G. A.; Myers, A.; Singh, K. J.; Yoo, H. J.; King, S. W.

    2015-03-07

    We have measured surface acoustic waves on nanostructured TiN wires overlaid on multiple thin films on a silicon substrate using the ultrafast pump-probe technique known as picosecond ultrasonics. We find a prominent oscillation in the range of 11–54 GHz for samples with varying pitch ranging from 420 nm down to 168 nm. We find that the observed oscillation increases monotonically in frequency with decrease in pitch, but that the increase is not linear. By comparing our data to two-dimensional mechanical simulations of the nanostructures, we find that the type of surface oscillation to which we are sensitive changes depending on the pitch of the sample. Surface waves on substrates that are loaded by thin films can take multiple forms, including Rayleigh-like waves, Sezawa waves, and radiative (leaky) surface waves. We describe evidence for detection of modes that display characteristics of these three surface wave types.

  4. A Novel Low-Ringing Monocycle Picosecond Pulse Generator Based on Step Recovery Diode

    PubMed Central

    Zhou, Jianming; Yang, Xiao; Lu, Qiuyuan; Liu, Fan

    2015-01-01

    This paper presents a high-performance low-ringing ultra-wideband monocycle picosecond pulse generator, formed using a step recovery diode (SRD), simulated in ADS software and generated through experimentation. The pulse generator comprises three parts, a step recovery diode, a field-effect transistor and a Schottky diode, used to eliminate the positive and negative ringing of pulse. Simulated results validate the design. Measured results indicate an output waveform of 1.88 peak-to-peak amplitude and 307ps pulse duration with a minimal ringing of -22.5 dB, providing good symmetry and low level of ringing. A high degree of coordination between the simulated and measured results is achieved. PMID:26308450

  5. Picosecond laser structuration under high pressures: Observation of boron nitride nanorods

    SciTech Connect

    Museur, Luc; Petitet, Jean-Pierre; Kanaev, Andrei V.; Michel, Jean-Pierre; Marine, Wladimir; Anglos, Demetrios; Fotakis, Costas

    2008-11-01

    We report on picosecond UV-laser processing of hexagonal boron nitride (BN) at moderately high pressures above 500 bar. The main effect is specific to the ambient gas and laser pulse duration in the ablation regime: when samples are irradiated by 5 or 0.45 ps laser pulses in nitrogen gas environment, multiple nucleation of a new crystalline product-BN nanorods-takes place. This process is triggered on structural defects, which number density strongly decreases upon recrystallization. Nonlinear photon absorption by adsorbed nitrogen molecules is suggested to mediate the nucleation growth. High pressure is responsible for the confinement and strong backscattering of ablation products. A strong surface structuring also appears at longer 150 ps laser irradiation in similar experimental conditions. However, the transformed product in this case is amorphous strongly contaminated by boron suboxides B{sub x}O{sub y}.

  6. Directly driven source of multi-gigahertz, sub-picosecond optical pulses

    DOEpatents

    Messerly, Michael J.; Dawson, Jay W.; Barty, Christopher P.J.; Gibson, David J.; Prantil, Matthew A.; Cormier, Eric

    2015-10-20

    A robust, compact optical pulse train source is described, with the capability of generating sub-picosecond micro-pulse sequences, which can be periodic as well as non-periodic, and at repetition rates tunable over decades of baseline frequencies, from MHz to multi-GHz regimes. The micro-pulses can be precisely controlled and formatted to be in the range of many ps in duration to as short as several fs in duration. The system output can be comprised of a continuous wave train of optical micro-pulses or can be programmed to provide gated bursts of macro-pulses, with each macro-pulse consisting of a specific number of micro-pulses or a single pulse picked from the higher frequency train at a repetition rate lower than the baseline frequency. These pulses could then be amplified in energy anywhere from the nJ to MJ range.

  7. Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses.

    PubMed

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

    2013-04-08

    This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps.

  8. A Novel Low-Ringing Monocycle Picosecond Pulse Generator Based on Step Recovery Diode.

    PubMed

    Zhou, Jianming; Yang, Xiao; Lu, Qiuyuan; Liu, Fan

    2015-01-01

    This paper presents a high-performance low-ringing ultra-wideband monocycle picosecond pulse generator, formed using a step recovery diode (SRD), simulated in ADS software and generated through experimentation. The pulse generator comprises three parts, a step recovery diode, a field-effect transistor and a Schottky diode, used to eliminate the positive and negative ringing of pulse. Simulated results validate the design. Measured results indicate an output waveform of 1.88 peak-to-peak amplitude and 307ps pulse duration with a minimal ringing of -22.5 dB, providing good symmetry and low level of ringing. A high degree of coordination between the simulated and measured results is achieved.

  9. A theoretical study of the stress relaxation in HMX on the picosecond time scale

    NASA Astrophysics Data System (ADS)

    Long, Yao; Chen, Jun

    2015-12-01

    The stress relaxation model of β-HMX on the picosecond time scale is studied by a theoretical approach. The relaxation of normal stress is contributed by lattice vibration, and the relaxation of shear stress is contributed by molecular rotation. Based on this model, the energy dissipation rule of the elastic wave and the profile of the shock wave are investigated. We find at low frequency the dissipation rate of the elastic wave is proportional to the power function of frequency, and under high speed shock loading the width of the stress relaxation zone is less than 0.3 μm there is a pressure peak with a height of 14 GPa near the wave front.

  10. NO binding kinetics in myoglobin investigated by picosecond Fe K-edge absorption spectroscopy

    PubMed Central

    Silatani, Mahsa; Lima, Frederico A.; Penfold, Thomas J.; Rittmann, Jochen; Reinhard, Marco E.; Rittmann-Frank, Hannelore M.; Borca, Camelia; Grolimund, Daniel; Milne, Christopher J.; Chergui, Majed

    2015-01-01

    Diatomic ligands in hemoproteins and the way they bind to the active center are central to the protein’s function. Using picosecond Fe K-edge X-ray absorption spectroscopy, we probe the NO-heme recombination kinetics with direct sensitivity to the Fe-NO binding after 532-nm photoexcitation of nitrosylmyoglobin (MbNO) in physiological solutions. The transients at 70 and 300 ps are identical, but they deviate from the difference between the static spectra of deoxymyoglobin and MbNO, showing the formation of an intermediate species. We propose the latter to be a six-coordinated domed species that is populated on a timescale of ∼200 ps by recombination with NO ligands. This work shows the feasibility of ultrafast pump–probe X-ray spectroscopic studies of proteins in physiological media, delivering insight into the electronic and geometric structure of the active center. PMID:26438842

  11. Compact picosecond mode-locked and cavity-dumped Nd:YVO4 laser.

    PubMed

    Wegner, U; Meier, J; Lederer, M J

    2009-12-07

    We report on a diode pumped, semiconductor saturable absorber mirror mode-locked picosecond Nd:YVO(4) oscillator with cavity-dumping. In pure cw-mode-locking this laser produced up to 17W of average power at a pulse repetition rate of 9.7MHz, corresponding to a pulse energy of 1.7microJ. Using an electro-optic cavity dumper, we achieved average powers up to 7.8W at 500kHz and 10W at 1MHz dumping rate. With corresponding pulse energies of 15.6microJ and 10microJ respectively and pulsewidths around 10ps, this laser could become a compact source for materials processing applications, alternative to more complex schemes such as regenerative amplifiers or ultra-long resonator oscillators.

  12. High-power, high repetition-rate, green-pumped, picosecond LBO optical parametric oscillator.

    PubMed

    Kienle, Florian; Teh, Peh Siong; Lin, Dejiao; Alam, Shaif-Ul; Price, Jonathan H V; Hanna, D C; Richardson, David J; Shepherd, David P

    2012-03-26

    We report on a picosecond, green-pumped, lithium triborate optical parametric oscillator with record-high output power. It was synchronously pumped by a frequency-doubled (530 nm), pulse-compressed (4.4 ps), high-repetition-rate (230 MHz), fiber-amplified gain-switched laser diode. For a pump power of 17 W, a maximum signal and idler power of 3.7 W and 1.8 W was obtained from the optical parametric oscillator. A signal pulse duration of ~3.2 ps was measured and wide tunability from 651 nm to 1040 nm for the signal and from 1081 nm to 2851 nm for the idler was achieved.

  13. Picosecond charge transport in rutile at high carrier densities studied by transient terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Zajac, V.; Němec, H.; Kužel, P.

    2016-09-01

    We study terahertz photoconductivity of a rutile single crystal between 10 and 300 K under strong photoexcitation by femtosecond pulses at 266 nm. A marked dependence of the carrier mobility on the carrier density is observed leading to highly complex transport phenomena on a picosecond time scale. We develop a general model of carrier photoconductive response in the case of time dependent inhomogeneous distribution of carrier density and mobility. This allows us to assess an important role of both electrons and holes in the response of photoexcited rutile. At low temperatures, the carrier mobility is initially reduced due to the electron-hole scattering and increases by one order of magnitude upon ambipolar diffusion of the carriers into deeper regions of the sample. At room temperature, contributions of transient hot optical phonons and/or of midinfrared polaron excitations with charge-density-dependent dielectric strength emerge in the photoconductivity spectra.

  14. Sub-picosecond double-clad photonic crystal fiber oscillator and amplifier system

    NASA Astrophysics Data System (ADS)

    Li, Pingxue; Zhang, Mengmeng; Liang, Boxing; Chi, Junjie

    2015-08-01

    A ytterbium-doped large mode area PCF sub-picosecond laser oscillator and amplifier system is experimentally studied. The oscillator which combines NPE and SESAM is operating on the all-normal-dispersion regime and the LMA PCF is used as the gain medium. In the CW mode-locking regime, the oscillator directly generates the pulse at the repetition rate of 83.7 MHz while the pulse duration is 960 fs. The double-clad fiber amplifier system directly generates a high average power of 12.53 W with a pulse duration of 4.1 ps corresponding to the pulse energy of 150 nJ and peak power of 36.6 KW after about 3 m ytterbium doped double clad fiber amplification.

  15. Investigation on Soft X-Ray Lasers with a Picosecond-Laser-Irradiated Gas Puff Target

    SciTech Connect

    Fiedorowiez, H; Bartnik, A; Jarocki, R; Rakowski, R; Dunn, J; Smith, R F; Hunter, J; Hilsen, J; Shlyaptsev, V N

    2002-10-09

    We present results of experimental studies on transient gain soft x-ray lasers with a picosecond-laser-irradiated gas puff target. The target in a form of an elongated gas sheet is formed by pulsed injection of gas through a slit nozzle using a high-pressure electromagnetic valve developed and characterized at the Institute of Optoelectronics. The x-ray laser experiments were performed at the Lawrence Livermore National Laboratory using the tabletop Compact Multipulse Terawatt (COMET) laser to irradiate argon, krypton or xenon gas puff targets. Soft x-ray lasing in neon-like argon on the 3p-3s transition at 46.9 nm and the 3d-3p transition at 45.1 nm have been demonstrated, however, no amplification for nickel-like krypton or xenon was observed. Results of the experiments are presented and discussed.

  16. Degradation of picosecond temporal contrast of Ti:sapphire lasers with coherent pedestals.

    PubMed

    Khodakovskiy, Nikita; Kalashnikov, Mikhail; Gontier, Emilien; Falcoz, Franck; Paul, Pierre-Mary

    2016-10-01

    Recompressed pulses from Ti:sapphire chirped-pulse lasers are accompanied by a slowly decaying post-pulse pedestal that is coherent with the main pulse. The pedestal typically consists of numerous pulses with temporal separation in the picosecond range. The source of this artifact lies in the Ti:sapphire active medium itself, both in the Kerr-lens mode-locked oscillator and in subsequent amplifiers. In the presence of substantial self-phase modulation, after recompression the post-pedestal generates a mirror-symmetric pre-pulse pedestal. This pedestal severely degrades the leading edge of the output pulse. This degradation is far more limiting than the original post-pedestal and severely lowers the achievable temporal contrast.

  17. Picosecond laser damage performance assessment of multilayer dielectric gratings in vacuum.

    PubMed

    Alessi, David A; Carr, C Wren; Hackel, Richard P; Negres, Raluca A; Stanion, Kenneth; Fair, James E; Cross, David A; Nissen, James; Luthi, Ronald; Guss, Gabe; Britten, Jerald A; Gourdin, William H; Haefner, Constantin

    2015-06-15

    Precise assessment of the high fluence performance of pulse compressor gratings is necessary to determine the safe operational limits of short-pulse high energy lasers. We have measured the picosecond laser damage behavior of multilayer dielectric (MLD) diffraction gratings used in the compression of chirped pulses on the Advanced Radiographic Capability (ARC) kilojoule petawatt laser system at the Lawrence Livermore National Laboratory (LLNL). We present optical damage density measurements of MLD gratings using the raster scan method in order to estimate operational performance. We also report results of R-on-1 tests performed with varying pulse duration (1-30 ps) in air, and clean vacuum. Measurements were also performed in vacuum with controlled exposure to organic contamination to simulate the grating use environment. Results show sparse defects with lower damage resistance which were not detected by small-area damage test methods.

  18. Multi-gigahertz picosecond optical parametric oscillator pumped by 80-MHz Yb-fiber laser.

    PubMed

    Kimmelma, Ossi; Chaitanya Kumar, S; Esteban-Martin, Adolfo; Ebrahim-Zadeh, M

    2013-11-15

    We report a multi-gigahertz (GHz) repetition-rate picosecond optical parametric oscillator (OPO) based on MgO:PPLN, synchronously pumped by a Yb-fiber laser operating at 80 MHz, where the multiplication of repetition frequency is achieved using fractional increment in the OPO cavity length. Using this simple technique, we achieve OPO operation up to the 88th harmonic of the pump laser frequency, corresponding to a repetition rate as high as 7 GHz. Deploying a 5% output coupler, we are able to extract up to 960 mW of average signal power at the fundamental with 600 mW at the 88th harmonic (7 GHz), using a pump power of 5.6 W. The measured relative standard deviations of the fundamental and fifth harmonic signal power are recorded to be 1.6% and 3.5%, respectively, while the fundamental signal pulse duration is measured to be 18.4 ps.

  19. Study of self-focusing and self-phase-modulation in the picosecond-time regime.

    NASA Technical Reports Server (NTRS)

    Reintjes, J.; Carman, R. L.; Shimizu, F.

    1973-01-01

    Study of the propagation of a single picosecond pulse of a mode-locked Nd-glass laser in CS2 nitrobenzene and toluene by observations of the birefringence and spectral changes in self-focused laser light. Multiple second-harmonic probing beams are used for birefringence measurements in a single IR pulse in various portions of the active cell. The orientational Kerr effect is found to be the prime factor of induced birefringence in nitrobenzene and toluene. The results for CS2 are also consistent with this mechanism and show that the duration of an IR pulse in the focal volume is less than that of the incident pulse. The properties of beams which are focused within the cell by an external lens are also investigated.

  20. Measurement of transient atomic displacements in thin films with picosecond and femtometer resolution.

    PubMed

    Kozina, M; Hu, T; Wittenberg, J S; Szilagyi, E; Trigo, M; Miller, T A; Uher, C; Damodaran, A; Martin, L; Mehta, A; Corbett, J; Safranek, J; Reis, D A; Lindenberg, A M

    2014-05-01

    We report measurements of the transient structural response of weakly photo-excited thin films of BiFeO3, Pb(Zr,Ti)O3, and Bi and time-scales for interfacial thermal transport. Utilizing picosecond x-ray diffraction at a 1.28 MHz repetition rate with time resolution extending down to 15 ps, transient changes in the diffraction angle are recorded. These changes are associated with photo-induced lattice strains within nanolayer thin films, resolved at the part-per-million level, corresponding to a shift in the scattering angle three orders of magnitude smaller than the rocking curve width and changes in the interlayer lattice spacing of fractions of a femtometer. The combination of high brightness, repetition rate, and stability of the synchrotron, in conjunction with high time resolution, represents a novel means to probe atomic-scale, near-equilibrium dynamics.

  1. Ultrafast electron diffraction: determination of radical structure with picosecond time resolution

    NASA Astrophysics Data System (ADS)

    Cao, J.; Ihee, H.; Zewail, A. H.

    1998-06-01

    Using ultrafast electron diffraction (UED) with the temporal diffraction-difference method recently developed in this laboratory, we report accurate determination of the radical (CF 2) structure in the dissociation of diiododifluoromethane (CF 2I 2) with picosecond time resolution. Time-zero was clocked accurately within 2 ps and both iodine atoms were found to be liberated in less than 4 ps. The structure, absolute fraction, and electronic state of the radical were determined. The CF 2 radical was found to be in X1A1 ground state with C-F and F⋯F distances of 1.30(±0.02) Å and 2.06(±0.06) Å, respectively.

  2. Picosecond ultrasonic study of surface acoustic waves on titanium nitride nanostructures

    NASA Astrophysics Data System (ADS)

    Bjornsson, M. M.; Connolly, A. B.; Mahat, S.; Rachmilowitz, B. E.; Daly, B. C.; Antonelli, G. A.; Myers, A.; Singh, K. J.; Yoo, H. J.; King, S. W.

    2015-03-01

    We have measured surface acoustic waves on nanostructured TiN wires overlaid on multiple thin films on a silicon substrate using the ultrafast pump-probe technique known as picosecond ultrasonics. We find a prominent oscillation in the range of 11-54 GHz for samples with varying pitch ranging from 420 nm down to 168 nm. We find that the observed oscillation increases monotonically in frequency with decrease in pitch, but that the increase is not linear. By comparing our data to two-dimensional mechanical simulations of the nanostructures, we find that the type of surface oscillation to which we are sensitive changes depending on the pitch of the sample. Surface waves on substrates that are loaded by thin films can take multiple forms, including Rayleigh-like waves, Sezawa waves, and radiative (leaky) surface waves. We describe evidence for detection of modes that display characteristics of these three surface wave types.

  3. Development of picoseconds Time of Flight systems in Meson Test Beam Facility at Fermilab

    SciTech Connect

    Ronzhin, A.; Albrow, M.; Demarteau, M.; Los, S.; Malik, S.; Pronko, S.; Ramberg, E.; Zatserklyaniy, A.; /Puerto Rico U., Mayaguez

    2010-11-01

    The goal of the work is to develop time of flight (TOF) system with about 10 picosecond time resolution in real beam line when start and stop counters separated by some distance. We name the distance as 'base' for the TOF. This 'real' TOF setup is different from another one when start and stop counters located next to each other. The real TOF is sensitive to beam momentum spread, beam divergence, etc. Anyway some preliminary measurements are useful with close placement of start and stop counter. We name it 'close geometry'. The work started about 2 years ago at Fermilab Meson Test Beam Facility (MTBF). The devices tested in 'close geometry' were Microchannel Plate Photomultipliers (MCP PMT) with Cherenkov radiators. TOF counters based on Silicon Photomultipliers (SiPms) with Cherenkov radiators also in 'close geometry' were tested. We report here new results obtained with the counters in the MTBF at Fermilab, including beam line data.

  4. Broadband amplification by picosecond OPCPA in DKDP pumped at 515 nm.

    PubMed

    Skrobol, Christoph; Ahmad, Izhar; Klingebiel, Sandro; Wandt, Christoph; Trushin, Sergei A; Major, Zsuzsanna; Krausz, Ferenc; Karsch, Stefan

    2012-02-13

    On the quest towards reaching petawatt-scale peak power light pulses with few-cycle duration, optical parametric chirped pulse amplification (OPCPA) pumped on a time scale of a few picoseconds represents a very promising route. Here we present an experimental demonstration of few-ps OPCPA in DKDP, in order to experimentally verify the feasibility of the scheme. Broadband amplification was observed in the wavelength range of 830-1310 nm. The amplified spectrum supports two optical cycle pulses, at a central wavelength of ~920 nm, with a pulse duration of 6.1 fs (FWHM). The comparison of the experimental results with our numerical calculations of the OPCPA process showed good agreement. These findings confirm the reliability of our theoretical modelling, in particular with respect to the design for further amplification stages, scaling the output peak powers to the petawatt scale.

  5. Nanosurgery with near-infrared 12-femtosecond and picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Uchugonova, Aisada; Zhang, Huijing; Lemke, Cornelius; König, Karsten

    2011-03-01

    Laser-assisted surgery based on multiphoton absorption of NIR laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. Here we apply femtosecond laser scanning microscopes for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) with an in situ pulse duration at the target ranging from 12 femtoseconds up to 3 picoseconds was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy (AFM) and electron microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery.

  6. Picosecond nonlinear optical studies of gold nanoparticles synthesised using coriander leaves (Coriandrum sativum)

    NASA Astrophysics Data System (ADS)

    Venugopal Rao, S.

    2011-07-01

    The results are presented from the experimental picosecond nonlinear optical (NLO) studies of gold nanoparticles synthesised using coriander leaf (Coriandrum sativum) extract. Nanoparticles with an average size of ∼30 nm (distribution of 5-70 nm) were synthesised according to the procedure reported by Narayanan et al. [Mater. Lett. 2008, 62, 4588-4591]. NLO studies were carried out using the Z-scan technique using 2 ps pulses near 800 nm. Open-aperture data suggested saturation absorption as the nonlinear absorption mechanism, whereas closed-aperture data suggested a positive nonlinearity. The magnitude of third-order nonlinearity was estimated to be (3.3 ± 0.6) × 10-13 esu. A solvent contribution to the nonlinearity was also identified and estimated. A comparison is attempted with some recently reported NLO studies of similar gold nanostructures.

  7. Stimulated Raman adiabatic passage in sodium vapor with picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Hicks, Jim L.; Tanjaroon, Chakree; Allen, Susan D.; Tilley, Matt; Hoke, Steven; Johnson, J. Bruce

    2017-08-01

    Experimental measurements and calculations of stimulated Raman adiabatic passage transfer efficiencies were made on a sodium gas starting from the 3 2S1 /2 electronic ground state, passing through the 3 2P1 /2 and/or the 3 2P3 /2 to the 5 2S1 /2 state. The lasers used in the experiments had a pulse width of several picoseconds and were close to the Fourier transform limit. Although the linewidth of the laser was much smaller than the spin orbit splitting between the 3 P 1 /2 2 and 3 P 3 /2 2 states, Experiments and calculations reveal that both 3p states play a role in the transfer efficiency when the lasers are tuned to resonance through the 3 2P1 /2 state, revealing evidence of quantum interference between the competing pathways.

  8. Quartz Crystal Microbalances for quantitative picosecond laser-material-interaction investigations - Part I: Technical considerations

    NASA Astrophysics Data System (ADS)

    Gierse, N.; Schildt, T.; Esser, H. G.; Sergienko, G.; Brezinsek, S.; Freisinger, M.; Zhao, D.; Ding, H.; Terra, A.; Samm, U.; Linsmeier, Ch.

    2016-12-01

    In this work the technical suitability of Quartz Crystal Microbalances (QMBs) for in situ, pulse resolved mass removal measurements is demonstrated for picosecond laser ablation of magnetron sputtered coatings. The QMBs show a linear characteristic of the sensitivity for layer thickness of different metals up to several microns. Laser pulse resolved measurements of the mass ablated from the metal layer were performed. About 400 ng of chromium was ablated during the first laser pulse while in subsequent pulses < 220 ng were removed. This is compared with previous findings. The sensitivity for ablation of the QMBs is found to be larger than for deposition, which is explained by the radial sensitivity of the QMBs. Future refinements of the setup and the benefits of the pulse resolved mass loss measurements for laser based methods like LIBS and LIAS are discussed and will be presented in part II currently in preparation.

  9. Modeling of multi-burst mode pico-second laser ablation for improved material removal rate

    NASA Astrophysics Data System (ADS)

    Hu, Wenqian; Shin, Yung C.; King, Galen

    2010-02-01

    This paper deals with the unique phenomena occurring during the multi-burst mode picosecond (ps) laser ablation of metals through modeling and experimental studies. The two-temperature model (TTM) is used and expanded to calculate the ablation depth in the multi-burst mode. A nonlinear increment of ablation volume is found during the multi-burst laser ablation. The deactivation of ablated material and the application of temperature-dependent electron-phonon coupling are demonstrated to be important to provide reliable results. The simulation results based on this expanded laser ablation model are experimentally validated. A significant increase of ablation rate is found in the multi-burst mode, compared with the single-pulse mode under the same total fluence. This numerical model provides a physical perspective into the energy transport process during multi-burst laser ablation and can be used to study the pulse-to-pulse separation time effect on the ablation rate.

  10. Ultra-flat supercontinuum generated from high-power, picosecond telecommunication fiber laser source.

    PubMed

    Liao, Ruoyu; Song, Youjian; Zhou, Xiaokang; Chai, Lu; Wang, Chingyue; Hu, Minglie

    2016-11-20

    An ultra-flat, high-power supercontinuum generated from a picosecond telecommunication fiber laser was presented. The pulse from a carbon nanotube mode-locked oscillator was amplified using an Er-Yb codoped fiber amplifier. The output of the system achieved an average power of 2.7 W, with the center wavelength at 1564 nm and a FWHM of 6 nm in the spectral domain. By passing this amplified high-power pulse through a 4.6 m highly nonlinear photonic crystal fiber, an ultra-flat supercontinuum spanning 1600-2180 nm is generated. And the average power of the supercontinuum achieves 1 W.

  11. Controlling the spins angular momentum in ferromagnets with sequences of picosecond acoustic pulses.

    PubMed

    Kim, Ji-Wan; Vomir, Mircea; Bigot, Jean-Yves

    2015-02-17

    Controlling the angular momentum of spins with very short external perturbations is a key issue in modern magnetism. For example it allows manipulating the magnetization for recording purposes or for inducing high frequency spin torque oscillations. Towards that purpose it is essential to modify and control the angular momentum of the magnetization which precesses around the resultant effective magnetic field. That can be achieved with very short external magnetic field pulses or using intrinsically coupled magnetic structures, resulting in a transfer of spin torque. Here we show that using picosecond acoustic pulses is a versatile and efficient way of controlling the spin angular momentum in ferromagnets. Two or three acoustic pulses, generated by femtosecond laser pulses, allow suppressing or enhancing the magnetic precession at any arbitrary time by precisely controlling the delays and amplitudes of the optical pulses. A formal analogy with a two dimensional pendulum allows us explaining the complex trajectory of the magnetic vector perturbed by the acoustic pulses.

  12. Picosecond Diffraction at the ESRF: How Far Have We Come and Where Are We Going?

    SciTech Connect

    Wulff, Michael; Kong Qingyu; Cammarata, Marco; Lo Russo, Manuela; Anfinrud, Philip; Schotte, Friedrich; Lorenc, Maciej; Ihee, Hyotcherl; Kim, Tae Kyu; Plech, Anton

    2007-01-19

    The realization of solution phase pump-probe diffraction experiments on beamline ID09B is described. The pink beam from a low-K in-vacuum undulator is used to study the structural dynamics of small molecules in solution to 100 picosecond time resolution and at atomic resolution. The X-ray chopper and the associated timing modes of the synchrotron are described. The dissociation of molecular iodine in liquid CCl4 is studied by single pulse diffraction. The data probe not only the iodine structures but also the solvent structure as the latter is thermally excited by the flow of energy from recombining iodine atoms. The low-q part of the diffraction spectra is a sensitive probe of the hydrodynamics of the solvent as a function of time.

  13. Sub-picosecond streak camera measurements at LLNL: From IR to x-rays

    SciTech Connect

    Kuba, J; Shepherd, R; Booth, R; Steward, R; Lee, E W; Cross, R R; Springer, P T

    2003-12-21

    An ultra fast, sub-picosecond resolution streak camera has been recently developed at the LLNL. The camera is a versatile instrument with a wide operating wavelength range. The temporal resolution of up to 300 fs can be achieved, with routine operation at 500 fs. The streak camera has been operated in a wide wavelength range from IR to x-rays up to 2 keV. In this paper we briefly review the main design features that result in the unique properties of the streak camera and present its several scientific applications: (1) Streak camera characterization using a Michelson interferometer in visible range, (2) temporally resolved study of a transient x-ray laser at 14.7 nm, which enabled us to vary the x-ray laser pulse duration from {approx}2-6 ps by changing the pump laser parameters, and (3) an example of a time-resolved spectroscopy experiment with the streak camera.

  14. Picosecond Z-scan measurements on bulk GaN crystals

    SciTech Connect

    Pacebutas, V.; Stalnionis, A.; Krotkus, A.; Suski, T.; Perlin, P.; Leszczynski, M.

    2001-06-25

    Bulk GaN crystals were characterized by using picosecond laser pulses at {lambda}=0.527{mu}m and Z-scan techniques. The role of the free-carrier absorption was evaluated by a dynamical, pump-and-probe-type transmitivity measurement. The values of two-photon absorption coefficient (17{endash}20 cm/GW) and refractive index changes at high optical irradiances due to bound (n{sub 2}={minus}4{times}10{sup {minus}12}esu) and free ({sigma}{sub r}={minus}1.0{times}10{sup {minus}20}cm{sup 3}) electrons in that material were determined. {copyright} 2001 American Institute of Physics.

  15. Surface Functionalization of AISI 316 Steel by Laser Texturing of Shaped Microcavities with Picosecond Pulses

    NASA Astrophysics Data System (ADS)

    Sampedro, J.; Ferre, R.; Fernández, E.; Pérez, I.; Cárcel, B.; Molina, T.; Ramos, J. A.

    Surface texturing is gaining interest in the field of surface engineering. Enhancements can be obtained by carefully creating textures with arrangement of 3D-cavities; such textures retain lubricant and enhancing the hydrodynamic effect, reducing therefore the friction coefficient and wear of sliding contact surfaces 3D-cavities may have flat or curved shapes. In this investigation a picosecond pulsed laser with 1030 nm and 343 nm has been used to develop precise surface textures with triangular and flat shaped profiles. Tribological essays showed improvements in the tribological behavior of textured surfaces, triangular profile cavities obtained a friction coefficient < 0.03 doubling the wear resistance compared to reference surface without texture.

  16. Laser Processing of Coarse Grain Polycrystalline Diamond (PCD) Cutting Tool Inserts using Picosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Dold, C.; Henerichs, M.; Gilgen, P.; Wegener, K.

    Manufacturing of cutting edges in PCD cutting tool inserts (CTI) using picosecond pulsewidth laser sources is presented. Cutting edge radii of redge = 5 to 6 μm are achieved. Validation experiments are carried out on a turning lathe using lasered and ground CTI on machining carbon fibre reinforced plastics (CFRP) which is mainly used for aircraft structures. Experiments are done on fine and coarse grain PCD structures (average grain sizes are 2-4 μm and 25 μm resepectively) which are not economical in the latter case if manufactured conventionally, e.g. using grinding processes. Wear resistance, tool lifetime and process forces can be improved if laser processed coarse grain cutting tools are employed.

  17. Light-induced picosecond rotational disordering of the inorganic sublattice in hybrid perovskites

    PubMed Central

    Wu, Xiaoxi; Tan, Liang Z.; Shen, Xiaozhe; Hu, Te; Miyata, Kiyoshi; Trinh, M. Tuan; Li, Renkai; Coffee, Ryan; Liu, Shi; Egger, David A.; Makasyuk, Igor; Zheng, Qiang; Fry, Alan; Robinson, Joseph S.; Smith, Matthew D.; Guzelturk, Burak; Karunadasa, Hemamala I.; Wang, Xijie; Zhu, Xiaoyang; Kronik, Leeor; Rappe, Andrew M.; Lindenberg, Aaron M.

    2017-01-01

    Femtosecond resolution electron scattering techniques are applied to resolve the first atomic-scale steps following absorption of a photon in the prototypical hybrid perovskite methylammonium lead iodide. Following above-gap photoexcitation, we directly resolve the transfer of energy from hot carriers to the lattice by recording changes in the mean square atomic displacements on 10-ps time scales. Measurements of the time-dependent pair distribution function show an unexpected broadening of the iodine-iodine correlation function while preserving the Pb–I distance. This indicates the formation of a rotationally disordered halide octahedral structure developing on picosecond time scales. This work shows the important role of light-induced structural deformations within the inorganic sublattice in elucidating the unique optoelectronic functionality exhibited by hybrid perovskites and provides new understanding of hot carrier—lattice interactions, which fundamentally determine solar cell efficiencies. PMID:28782016

  18. Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials

    NASA Astrophysics Data System (ADS)

    Zalden, Peter; Shu, Michael J.; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W.; Wong, H.-S. Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M.

    2016-08-01

    Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag4In3Sb67Te26 . Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales—faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.

  19. Picosecond Pulse Radiolysis of Propylene Carbonate as a Solute in Water and as a Solvent.

    PubMed

    Marignier, Jean-Louis; Torche, Fayçal; Le Caër, Sophie; Mostafavi, Mehran; Belloni, Jacqueline

    2016-03-10

    The ester propylene carbonate (PC) is a solvent with a high static dielectric constant where the charges generated by ionizing radiation are expected to be long-lived at room temperature. Time-resolved optical absorption spectroscopy after picosecond electron pulses reveals the formation of a UV band, within less than two nanoseconds, that is assigned to the radical anion PC(-•), arising from a fast attachment reaction of electrons onto PC. Assignment and reactivity of PC(-•) in neat solvent and solutions are discussed in relation with data obtained in solutions of PC in water under reducing or oxidizing conditions and in solutions in PC of aromatic scavengers with various reduction potentials. The fate of the electrons and the ionization yield in PC are compared with those of other solvents.

  20. Magnetic reversal dynamics of a quantum system on a picosecond timescale.

    PubMed

    Klenov, Nikolay V; Kuznetsov, Alexey V; Soloviev, Igor I; Bakurskiy, Sergey V; Tikhonova, Olga V

    2015-01-01

    We present our approach for a consistent, fully quantum mechanical description of the magnetization reversal process in natural and artificial atomic systems by means of short magnetic pulses. In terms of the simplest model of a two-level system with a magnetic moment, we analyze the possibility of a fast magnetization reversal on the picosecond timescale induced by oscillating or short unipolar magnetic pulses. We demonstrate the possibility of selective magnetization reversal of a superconducting flux qubit using a single flux quantum-based pulse and suggest a promising, rapid Λ-scheme for resonant implementation of this process. In addition, the magnetization reversal treatment is fulfilled within the framework of the macroscopic theory of the magnetic moment, which allows for the comparison and explanation of the quantum and classical behavior.

  1. High-speed laser-assisted cutting of strong transparent materials using picosecond Bessel beams

    NASA Astrophysics Data System (ADS)

    Bhuyan, M. K.; Jedrkiewicz, O.; Sabonis, V.; Mikutis, M.; Recchia, S.; Aprea, A.; Bollani, M.; Trapani, P. Di

    2015-08-01

    We report single-pass cutting of strong transparent glass materials of 700 μm thickness with a speed up to 270 mm/s using single-shot nanostructuring technique exploiting picosecond, zero-order Bessel beams at laser wavelength of 1030 nm. Particularly, we present results of a systematic study of cutting of tempered glass which has high resistance to thermal and mechanical shocks due to the inhomogeneous material properties along its thickness, and homogeneous glass that identify a unique focusing geometry and a finite pitch dependency, for which cutting with high quality and high reproducibility can be achieved. These results represent a significant advancement in the field of high-speed cutting of technologically important transparent materials.

  2. Individual and collective vibrational modes of nanostructures studied by picosecond ultrasonics.

    PubMed

    Bienville, T; Robillard, J F; Belliard, L; Roch-Jeune, I; Devos, A; Perrin, B

    2006-12-22

    We report on picosecond ultrasonic measurements obtained on aluminum and platinum nanostructures with variable dot size and lateral periodicity which realized a 2D phononic crystal. Performing investigations at different resolution scales, we have identified individual modes of vibration depending on the dot size, and mode of vibration strongly correlated with the bi-dimensional organization. The platinum dots sputtered on an aluminum layer have shown a behavior of isolated oscillators without any coupling between neighbor elements in this phononic crystal. The frequency of such normal modes, extracted from time resolved measurements are in good agreement with 3D finite element simulations. In contrast, with aluminum dot systems where the coupling is more efficient we observe a complex spectrum of vibrational modes related to the band structure induced by the bi-dimensional patterning.

  3. Patterned graphene ablation and two-photon functionalization by picosecond laser pulses in ambient conditions

    SciTech Connect

    Bobrinetskiy, I. I. Otero, N.; Romero, P. M.; Emelianov, A. V.

    2015-07-27

    Direct laser writing is a technology with excellent prospects for mask-less processing of carbon-based nanomaterials, because of the wide range of photoinduced reactions that can be performed on large surfaces with submicron resolution. In this paper, we demonstrate the use of picoseconds laser pulses for one-step ablation and functionalization of graphene. Varying the parameters of power, pulse frequency, and speed, we demonstrated the ablation down to 2 μm width and up to mm-long lines as well as functionalization with spatial resolution less than 1 μm with linear speeds in the range of 1 m/s. Raman and atomic-force microscopy studies were used to indicate the difference in modified graphene states and correlation to the changes in optical properties.

  4. Directed fast electron beams in ultraintense picosecond laser irradiated solid targets

    SciTech Connect

    Ge, X. L.; Lin, X. X.; Yuan, X. H. E-mail: ytli@iphy.ac.cn; Sheng, Z. M.; Carroll, D. C.; Neely, D.; Gray, R. J.; Tresca, O.; McKenna, P.; Yu, T. P.; Chen, M.; Liu, F.; Zhuo, H. B.; Zielbauer, B.; and others

    2015-08-31

    We report on fast electron transport and emission patterns from solid targets irradiated by s-polarized, relativistically intense, picosecond laser pulses. A beam of multi-MeV electrons is found to be transported along the target surface in the laser polarization direction. The spatial-intensity and energy distributions of this beam are compared with the beam produced along the laser propagation axis. It is shown that even for peak laser intensities an order of magnitude higher than the relativistic threshold, laser polarization still plays an important role in electron energy transport. Results from 3D particle-in-cell simulations confirm the findings. The characterization of directional beam emission is important for applications requiring efficient energy transfer, including secondary photon and ion source development.

  5. Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials.

    PubMed

    Zalden, Peter; Shu, Michael J; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W; Wong, H-S Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M

    2016-08-05

    Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag_{4}In_{3}Sb_{67}Te_{26}. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales-faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.

  6. Measurements of Electron Transport in Foils Irradiated with a Picosecond Time Scale Laser Pulse

    SciTech Connect

    Brown, C. R. D.; Hoarty, D. J.; James, S. F.; Swatton, D.; Hughes, S. J.; Morton, J. W.; Guymer, T. M.; Hill, M. P.; Chapman, D. A.; Andrew, J. E.; Comley, A. J.; Shepherd, R.; Dunn, J.; Chen, H.; Schneider, M.; Brown, G.; Beiersdorfer, P.; Emig, J.

    2011-05-06

    The heating of solid foils by a picosecond time scale laser pulse has been studied by using x-ray emission spectroscopy. The target material was plastic foil with a buried layer of a spectroscopic tracer material. The laser pulse length was either 0.5 or 2 ps, which resulted in a laser irradiance that varied over the range 10{sup 16}-10{sup 19} W/cm{sup 2}. Time-resolved measurements of the buried layer emission spectra using an ultrafast x-ray streak camera were used to infer the density and temperature conditions as a function of laser parameters and depth of the buried layer. Comparison of the data to different models of electron transport showed that they are consistent with a model of electron transport that predicts the bulk of the target heating is due to return currents.

  7. Generation of 180 W average green power from a frequency-doubled picosecond rod fiber amplifier

    DOE PAGES

    Zhao, Zhi; Sheehy, Brian; Minty, Michiko

    2017-03-29

    Here, we report on the generation of 180 W average green power from a frequency-doubled picosecond rod fiber amplifier. In an Yb-doped fiber master-oscillator-power-amplifier system, 2.3-ps 704 MHz pulses are first amplified in small-core fibers and then in large-mode-area rod fibers to produce 270 W average infrared power with a high polarization extinction ratio and diffraction-limited beam quality. By carrying out frequency doubling in a lithium triborate (LBO) crystal, 180 W average green power is generated. To the best of our knowledge, this is the highest average green power achieved in fiber-based laser systems.

  8. Precise Control of the Number of Layers of Graphene by Picosecond Laser Thinning

    PubMed Central

    Lin, Zhe; Ye, Xiaohui; Han, Jinpeng; Chen, Qiao; Fan, Peixun; Zhang, Hongjun; Xie, Dan; Zhu, Hongwei; Zhong, Minlin

    2015-01-01

    The properties of graphene can vary as a function of the number of layers (NOL). Controlling the NOL in large area graphene is still challenging. In this work, we demonstrate a picosecond (ps) laser thinning removal of graphene layers from multi-layered graphene to obtain desired NOL when appropriate pulse threshold energy is adopted. The thinning process is conducted in atmosphere without any coating and it is applicable for graphene films on arbitrary substrates. This method provides many advantages such as one-step process, non-contact operation, substrate and environment-friendly, and patternable, which will enable its potential applications in the manufacturing of graphene-based electronic devices. PMID:26111758

  9. Treatment of tattoos with a picosecond alexandrite laser: a prospective trial.

    PubMed

    Saedi, Nazanin; Metelitsa, Andrei; Petrell, Kathleen; Arndt, Kenneth A; Dover, Jeffrey S

    2012-12-01

    OBJECTIVE To study a picosecond 755-nm alexandrite laser for the removal of tattoos to confirm the efficacy of this therapy, focusing on the effect of therapy on the target lesion as well as the surrounding tissues and quantifying the number of necessary treatments. DESIGN Fifteen patients with tattoos were enrolled. Treatments were scheduled approximately 6 ± 2 weeks apart. Standard photographs using 2-dimensional imaging were taken at baseline, before each treatment, and 1 month and 3 months after the last treatment. SETTING Dermatology clinic at SkinCare Physicians in Chestnut Hill, Massachusetts. PATIENTS Fifteen patients with darkly pigmented tattoos. MAIN OUTCOME MEASURES Treatment efficacy was assessed by the level of tattoo clearance in standard photographs. These photographs were assessed by a blinded physician evaluator and based on a 4-point scale. Efficacy was also assessed based on physician and patient satisfaction measured on a 4-point scale. RESULTS Twelve of 15 patients with tattoos (80%) completed the study. All 12 patients obtained greater than 75% clearance. Nine patients (75%) obtained greater than 75% clearance after having 2 to 4 treatments. The average number of treatment sessions needed to obtain this level of clearance was 4.25. All 12 patients (100%) were satisfied or extremely satisfied with the treatment. Adverse effects included pain, swelling, and blistering. Pain resolved immediately after therapy, while the swelling and blistering resolved within 1 week. Hypopigmentation and hyperpigmentation were reported at the 3-month follow-up. CONCLUSION The picosecond 755-nm alexandrite laser is a safe and very effective procedure for removing tattoo pigment.

  10. Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for gas-phase temperature measurements

    NASA Astrophysics Data System (ADS)

    Miller, Joseph Daniel

    Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is employed for quantitative gas-phase temperature measurements in combustion processes and heated flows. In this approach, ultrafast 100-fs laser pulses are used to induce vibrational and rotational transitions in N2 and O2, while a third spectrally narrowed picosecond pulse is used to probe the molecular response. Temporal suppression of the nonresonant contribution and elimination of collisional effects are achieved by delay of the probe pulse, while sufficient spectral resolution is maintained for frequency-domain detection and thermometry. A theoretical framework is developed to model experimental spectra by phenomenologically describing the temporal evolution of the vibrational and rotational wavepackets as a function of temperature and pressure. Interference-free, single-shot vibrational fs/ps CARS thermometry is demonstrated at 1-kHz from 1400-2400 K in a H2-air flame, with accuracy better than 3%. A time-asymmetric exponential pulse shape is introduced to optimize nonresonant suppression with a 103 reduction at a probe delay of 0.31 ps. Low-temperature single-shot thermometry (300-700 K) with better than 1.5% accuracy is demonstrated using a fully degenerate rotational fs/ps CARS scheme, and the influence of collision energy transfer on thermometry error is quantified at atmospheric pressure. Interference-free thermometry, without nonresonant contributions and collision-induced error, is demonstrated for the first time using rotational fs/ps CARS at room temperature and pressures from 1-15 atm. Finally, the temporal and spectral resolution of fs/ps CARS is exploited for transition-resolved time-domain measurements of N2 and O2 self-broadened S-branch Raman linewidths at pressures of 1-20 atm.

  11. A compact picosecond pulsed laser source using a fully integrated CMOS driver circuit

    NASA Astrophysics Data System (ADS)

    He, Yuting; Li, Yuhua; Yadid-Pecht, Orly

    2016-03-01

    Picosecond pulsed laser source have applications in areas such as optical communications, biomedical imaging and supercontinuum generation. Direct modulation of a laser diode with ultrashort current pulses offers a compact and efficient approach to generate picosecond laser pulses. A fully integrated complementary metaloxide- semiconductor (CMOS) driver circuit is designed and applied to operate a 4 GHz distributed feedback laser (DFB). The CMOS driver circuit combines sub-circuits including a voltage-controlled ring oscillator, a voltagecontrolled delay line, an exclusive-or (XOR) circuit and a current source circuit. Ultrashort current pulses are generated by the XOR circuit when the delayed square wave is XOR'ed with the original square wave from the on-chip oscillator. Circuit post-layout simulation shows that output current pulses injected into an equivalent circuit load of the laser have a pulse full width at half maximum (FWHM) of 200 ps, a peak current of 80 mA and a repetition rate of 5.8 MHz. This driver circuit is designed in a 0.13 μm CMOS process and taped out on a 0.3 mm2 chip area. This CMOS chip is packaged and interconnected with the laser diode on a printed circuit board (PCB). The optical output waveform from the laser source is captured by a 5 GHz bandwidth photodiode and an 8 GHz bandwidth oscilloscope. Measured results show that the proposed laser source can output light pulses with a pulse FWHM of 151 ps, a peak power of 6.4 mW (55 mA laser peak forward current) and a repetition rate of 5.3 MHz.

  12. Energy transfer in LHCII monomers at 77K studied by sub-picosecond transient absorption spectroscopy.

    PubMed

    Kleima, F J; Gradinaru, C C; Calkoen, F; van Stokkum, I H; van Grondelle, R; van Amerongen, H

    1997-12-09

    Energy transfer from chlorophyll b (Chl b) to chlorophyll a (Chl a) in monomeric preparations of light-harvesting complex II (LHCII) from spinach was studied at 77 K using pump-probe experiments. Sub-picosecond excitation pulses centered at 650 nm were used to excite preferentially Chl b and difference absorption spectra were detected from 630 to 700 nm. Two distinct Chl b to Chl a transfer times, approximately 200 fs and 3 ps, were found. A clearly distinguishable energy transfer process between Chl a molecules occurred with a time constant of 18 ps. The LHCII monomer data are compared to previously obtained LHCII trimer data, and both data sets are fitted simultaneously using a global analysis fitting routine. Both sets could be described with the following time constants: 140 fs, 600 fs, 8 ps, 20 ps, and 2.9 ns. In both monomers and trimers 50% of the Chl b to Chl a transfer is ultrafast (<200 fs). However, for monomers this transfer occurs to Chl a molecules that absorb significantly more toward shorter wavelengths than for trimers. Part of the transfer from Chl b to Chl a that occurs with a time constant of 600 fs in trimers is slowed down to several picoseconds in monomers. However, it is argued that observed differences between monomers and trimers should be ascribed to the loss of some Chl a upon monomerization or a shift of the absorption maximum of one or several Chl a molecules. It is concluded that Chl b to Chl a transfer occurs only within monomeric subunits of the trimers and not between different subunits.

  13. Picosecond excitation energy transfer of allophycocyanin studied in solution and in crystals.

    PubMed

    Ranjbar Choubeh, Reza; Sonani, Ravi R; Madamwar, Datta; Struik, Paul C; Bader, Arjen N; Robert, Bruno; van Amerongen, Herbert

    2017-07-28

    Cyanobacteria perform photosynthesis with the use of large light-harvesting antennae called phycobilisomes (PBSs). These hemispherical PBSs contain hundreds of open-chain tetrapyrrole chromophores bound to different peptides, providing an arrangement in which excitation energy is funnelled towards the PBS core from where it can be transferred to photosystem I and/or photosystem II. In the PBS core, many allophycocyanin (APC) trimers are present, red-light-absorbing phycobiliproteins that covalently bind phycocyanobilin (PCB) chromophores. APC trimers were amongst the first light-harvesting complexes to be crystallized. APC trimers have two spectrally different PCBs per monomer, a high- and a low-energy pigment. The crystal structure of the APC trimer reveals the close distance (~21 Å) between those two chromophores (the distance within one monomer is ~51 Å) and this explains the ultrafast (~1 ps) excitation energy transfer (EET) between them. Both chromophores adopt a somewhat different structure, which is held responsible for their spectral difference. Here we used spectrally resolved picosecond fluorescence to study EET in these APC trimers both in crystallized and in solubilized form. We found that not all closely spaced pigment couples consist of a low- and a high-energy pigment. In ~10% of the cases, a couple consists of two high-energy pigments. EET to a low-energy pigment, which can spectrally be resolved, occurs on a time scale of tens of picoseconds. This transfer turns out to be three times faster in the crystal than in the solution. The spectral characteristics and the time scale of this transfer component are similar to what have been observed in the whole cells of Synechocystis sp. PCC 6803, for which it was ascribed to EET from C-phycocyanin to APC. The present results thus demonstrate that part of this transfer should probably also be ascribed to EET within APC trimers.

  14. Picosecond pulse radiolysis of direct and indirect radiolytic effects in highly concentrated halide aqueous solutions.

    PubMed

    Balcerzyk, Anna; Schmidhammer, Uli; El Omar, Abdel Karim; Jeunesse, Pierre; Larbre, Jean-Philippe; Mostafavi, Mehran

    2011-08-25

    Recently we measured the amount of the single product, Br(3)(-), of steady-state radiolysis of highly concentrated Br(-) aqueous solutions, and we showed the effect of the direct ionization of Br(-) on the yield of Br(3)(-). Here, we report the first picosecond pulse-probe radiolysis measurements of ionization of highly concentrated Br(-) and Cl(-) aqueous solutions to describe the oxidation mechanism of the halide anions. The transient absorption spectra are reported from 350 to 750 nm on the picosecond range for halide solutions at different concentrations. In the highly concentrated halide solutions, we observed that, due to the presence of Na(+), the absorption band of the solvated electron is shifted to shorter wavelengths, but its decay, taking place during the spur reactions, is not affected within the first 4 ns. The kinetic measurements in the UV reveal the direct ionization of halide ions. The analysis of pulse-probe measurements show that after the electron pulse, the main reactions in solutions containing 1 M of Cl(-) and 2 M of Br(-) are the formation of ClOH(-•) and BrOH(-•), respectively. In contrast, in highly concentrated halide solutions, containing 5 M of Cl(-) and 6 M of Br(-), mainly Cl(2)(-•) and Br(2)(-•) are formed within the electron pulse without formation of ClOH(-•) and BrOH(-•). The results suggest that, not only Br(-) and Cl(-) are directly ionized into Br(•) and Cl(•) by the electron pulse, the halide atoms can also be rapidly generated through the reactions initiated by excitation and ionization of water, such as the prompt oxidation by the hole, H(2)O(+•), generated in the coordination sphere of the anion. © 2011 American Chemical Society

  15. Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

    NASA Astrophysics Data System (ADS)

    Berg, Christopher Michael

    An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock

  16. Hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering at flame temperatures using a second-harmonic bandwidth-compressed probe.

    PubMed

    Kearney, Sean P; Scoglietti, Daniel J

    2013-03-15

    We demonstrate an approach for picosecond probe-beam generation that enables hybrid femtosecond/picosecond pure-rotational coherent anti-Stokes Raman scattering (CARS) measurements in flames. Sum-frequency generation of bandwidth-compressed picosecond radiation from femtosecond pumps with phase-conjugate chirps provides probe pulses with energies in excess of 1 mJ that are temporally locked to the femtosecond pump/Stokes preparation. This method overcomes previous limitations on hybrid femtosecond/picosecond rotational CARS techniques, which have relied upon less efficient bandwidth-reduction processes that have generally resulted in prohibitively low probe energy for flame measurements. We provide the details of the second-harmonic approach and demonstrate the technique in near-adiabatic hydrogen/air flames.

  17. A retrospective analysis on the management of pigmented lesions using a picosecond 755-nm alexandrite laser in Asians.

    PubMed

    Chan, Johnny Chun-yin; Shek, Samantha Yee-nam; Kono, Taro; Yeung, Chi Keung; Chan, Henry Hin-lee

    2016-01-01

    Photo-aging in Chinese often presents with benign pigmentary lesions. Q-switched lasers for pigmentary lesions in Asians had reported a risk of post-inflammatory hyperpigmentation (PIH) up to 25%. Longer pulse widths in the millisecond domains were advocated with reduced risk of PIH. Recently, picosecond lasers of various wavelengths were introduced with proven efficacy in tattoo removal. The objective of this study is to assess the efficacy and safety of a novel picosecond 755-nm alexandrite laser for the treatment of benign pigmented lesions in Asians retrospectively. A list of all patients who received picosecond 755-nm alexandrite laser treatment at a private dermatology center in Hong Kong was included. Those who had any other laser or topical treatment during the period of picosecond laser treatment were excluded. The age, skin phototype, type of pigmentary lesion, number of treatments performed was recorded. The baseline and most recent standardized photographs were assessed by trained physicians for comparison. A score of 0-4, representing poor 0-24%, fair 25-49%, good 50-74%, excellent 75-95%, and complete 95%+ improvement was given. Adverse events associated with the laser treatment were also recorded. All patients were followed up until 6 months after the last laser session. A total of 13 subjects were included in the present study. The number of treatment sessions received ranged from one to seven. The benign pigmentary lesions consist of Nevus of Ota, café-au-lait patches, lentigines, Becker's nevus, Hori's macules, and nevus spilus. Among patients with Nevus of Ota, one patient achieved complete clearance after four treatments and two other patients had excellent clearance after three and four sessions, respectively. Patients with café-au-lait had fair to good clearance after one to seven treatment sessions. One patient who has Hori's macules was resistant to laser treatments and a fair response was achieved after eight treatments. In the present

  18. Generation of a 2.2 nJ picosecond optical pulse with blue-violet wavelength using a GaInN master oscillator power amplifier

    NASA Astrophysics Data System (ADS)

    Koda, Rintaro; Takiguchi, Yoshiro; Kono, Shunsuke; Watanabe, Hideki; Hanzawa, Yasunari; Nakajima, Hiroshi; Shiozaki, Masaki; Sugawara, Nobuhiro; Kuramoto, Masaru; Narui, Hironobu

    2015-07-01

    We report the generation of a picosecond optical pulse with 2.2 nJ pulse energy at blue-violet wavelengths using a GaN-based mode-locked laser diode (MLLD) and a semiconductor optical amplifier (SOA). The picosecond optical pulse generated by MLLD at a frequency of 812 MHz was amplified effectively by SOA. We optimized SOA with a widely flared waveguide structure to generate a high optical pulse energy.

  19. PLASMA GENERATOR

    DOEpatents

    Foster, J.S. Jr.

    1958-03-11

    This patent describes apparatus for producing an electricity neutral ionized gas discharge, termed a plasma, substantially free from contamination with neutral gas particles. The plasma generator of the present invention comprises a plasma chamber wherein gas introduced into the chamber is ionized by a radiofrequency source. A magnetic field is used to focus the plasma in line with an exit. This magnetic field cooperates with a differential pressure created across the exit to draw a uniform and uncontaminated plasma from the plasma chamber.

  20. Analysis of incidence of bulla formation after tattoo treatment using the combination of the picosecond Alexandrite laser and fractionated CO2 ablation.

    PubMed

    Au, Sonoa; Liolios, Ana M; Goldman, Mitchel P

    2015-02-01

    The picosecond Alexandrite laser has shown increased efficacy in tattoo removal in comparison to Q-switched lasers. However, bulla formation is a well-known and expected side effect of this novel treatment and causes patient discomfort. To analyze the incidence of bulla formation after tattoo treatment using the combination of the picosecond Alexandrite laser and fractionated CO2 ablation. This is a retrospective chart review to determine the incidence of bulla formation after laser tattoo removal in 95 patients who were treated with either with the picosecond Alexandrite laser alone or in combination with fractional CO2 ablation. Twenty-six patients (32%) treated with the picosecond laser alone experienced blistering, whereas none of the patients treated with the combination of the picosecond laser and fractionated CO2 ablation experienced blistering. The difference in incidence of bulla formation between the 2 groups was found to be statistically significant (p < .05). This study shows a significant decrease in bulla formation associated with tattoo treatment when fractionated CO2 ablation is added to the picosecond Alexandrite laser, which is consistent with observations from a previous case series. This is important because decreasing extensive blistering likely results in increased patient satisfaction and willingness to return for future treatments.

  1. Ultrashort electron pulses as a four-dimensional diagnosis of plasma dynamics.

    PubMed

    Zhu, P F; Zhang, Z C; Chen, L; Li, R Z; Li, J J; Wang, X; Cao, J M; Sheng, Z M; Zhang, J

    2010-10-01

    We report an ultrafast electron imaging system for real-time examination of ultrafast plasma dynamics in four dimensions. It consists of a femtosecond pulsed electron gun and a two-dimensional single electron detector. The device has an unprecedented capability of acquiring a high-quality shadowgraph image with a single ultrashort electron pulse, thus permitting the measurement of irreversible processes using a single-shot scheme. In a prototype experiment of laser-induced plasma of a metal target under moderate pump intensity, we demonstrated its unique capability of acquiring high-quality shadowgraph images on a micron scale with a-few-picosecond time resolution.

  2. Equation of State Measurements of Dense Plasmas Heated by Laser Accelerated MeV Protons

    NASA Astrophysics Data System (ADS)

    Dyer, Gilliss; Bernstein, Aaron; Cho, Byoung-Ick; Grigsby, Will; Dalton, Allen; Shepherd, Ronnie; Ping, Yuan; Chen, Hui; Widmann, Klaus; Ozterhoz, Jens; Ditmire, Todd

    2008-04-01

    Using a fast proton beam generated with an ultra intense laser we have generated and measured the equation of state of solid density plasma at temperatures near 20 eV, a regime in which there have been few previous experimental measurements. The laser accelerated a directional, short pulse of MeV protons, which isochorically heated a solid slab of aluminum. Using two simultaneous, temporally resolved measurements we observed the thermal emission and expansion of the heated foil with picosecond time resolution. With these data we were able to confirm, to within 10%, the SESAME equation-of-state table in this dense plasma region.

  3. Narrow-bandwidth Tunable Picosecond Pulses in the Visible Produced by Noncollinear optical parametric Amplification with a Chirped Blue Pump

    SciTech Connect

    Co, Dick T.; Lockard, Jenny V.; McCamant, David W.; Wasielewski, Michael R.

    2010-03-26

    Narrow-bandwidth ( ~27 cm-1 ) tunable picosecond pulses from 480 nm–780 nm were generated from the output of a 1 kHz femtosecond titanium:sapphire laser system using a type I noncollinear optical parametric amplifier (NOPA) with chirped second-harmonic generation (SHG) pumping. Unlike a femto second NOPA, this system utilizes a broadband pump beam, the chirped 400 nm SHG of the Ti:sapphire fundamental, to amplify a monochromatic signal beam (spectrally-filtered output of a type II collinear OPA). Optimum geometric conditions for simultaneous phase- and group-velocity matching were calculated in the visible spectrum. This design is an efficient and simple method for generating tunable visible picosecond pulses that are synchronized to the femtosecond pulses.

  4. Demonstration of an ultraviolet stimulated Brillouin scattering pulse compressed hundred picosecond laser in LiB3O5 crystals

    NASA Astrophysics Data System (ADS)

    Bai, Zhenxu; Wang, Yulei; Lu, Zhiwei; Jiang, Li; Yuan, Hang; Liu, Zhaohong

    2017-08-01

    A hundred picosecond ultraviolet (UV) laser is demonstrated with a pulse duration of less than 200 ps and peak power of 0.6 GW. With a hundred picosecond stimulated Brillouin scattering compressed pulse as the fundamental light, the UV output at 355 nm is obtained by extra-cavity sum-frequency-mixing in two LiB3O5 crystals. Maximum UV energy was 100 mJ when the incident energy was 280 mJ, yielding an optical-to-optical efficiency of 35.7%. This result is of interest for the generation of high energy sub-nanosecond UV lasers which finds applications in shock ignition and industrial processing.

  5. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Donin, V. I.; Yakovin, D. V.; Gribanov, A. V.

    2015-12-01

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses.

  6. Generation and Propagation of a Picosecond Acoustic Pulse at a Buried Interface: Time-Resolved X-Ray Diffraction Measurements

    SciTech Connect

    Lee, S.H.; Cavalieri, A.L.; Fritz, D.M.; Swan, M.C.; Reis, D.A.; Hegde, R.S.; Reason, M.; Goldman, R.S.

    2005-12-09

    We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al{sub 0.3}Ga{sub 0.7}As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.

  7. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    SciTech Connect

    Donin, V I; Yakovin, D V; Gribanov, A V

    2015-12-31

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses. (control of laser radiation parameters)

  8. Quasi CW mode, regular and chaotic dynamics in picosecond Nd:YAG laser with millisecond pumping under optoelectronic feedback control

    NASA Astrophysics Data System (ADS)

    Gorbunkov, M. V.; Maslova, Yu. Ya.; Petukhov, V. A.; Semenov, M. A.; Shabalin, Yu. V.; Vinogradov, A. V.

    2007-06-01

    We propose and study both numerically and experimentally a laser system controlled by the combination of positive and negative feedbacks capable to generate a long picosecond pulse train of stable amplitude as well as regular pulsation with sub-microsecond period. The proper combination of feedbacks is realized in a Nd:YAG laser with millisecond pumping by means of a single optoelectronic negative feedback which utilizes signal reflected from an intracavity Pockels cell polarizer. Regular pulsation (microgroups of picosecond pulses) with controlled period from 25 to 75 resonator round trips is obtained. The development of chaotic dynamics displayed by the system at higher pumping level differs from the Feigenbaum scenario. The regular pulsation regime has a great potential in a laser-electron X-ray generator design and other applications.

  9. Picosecond time-resolved adsorbate response to substrate heating: Spectroscopy and dynamics of CO/Cu(100)

    NASA Astrophysics Data System (ADS)

    Germer, T. A.; Stephenson, J. C.; Heilweil, E. J.; Cavanagh, R. R.

    1994-07-01

    The response of the molecular stretch mode of CO/Cu(100) near 2086 cm-1 (ν1) to resonant infrared, and nonresonant visible and ultraviolet pumping is measured on a picosecond time scale. Fourier transform infrared measurements establish that ν1 is anharmonically coupled to the frustrated translation near 32 cm-1 (ν4), so that transient shifts in ν1 indicate population changes in ν4. The ν1 response to visible and ultraviolet pumping is characterized by a spectral shift near zero delay time, which decays with a ≊2 ps time constant to an intermediate value, which then decays on a ≊200 ps time scale. The data agree well with a model whereby ν4 couples to both the photogenerated hot electrons and to the heated phonons. The characteristic coupling times to these two heat baths are found to both be a few picoseconds.

  10. 201 W picosecond green laser using a mode-locked fiber laser driven cryogenic Yb:YAG amplifier system.

    PubMed

    Kowalewski, Katie; Zembek, Jason; Envid, Victoria; Brown, David C

    2012-11-15

    We have generated 201 W of green (514.5 nm) average power from a frequency-doubled picosecond cryogenic Yb:YAG laser system driven by a 50 MHz, 12.4 ps mode-locked Yb fiber laser producing 430 W of average power at 1029 nm, using direct pulse amplification. The fundamental beam produced was near-diffraction-limited (M(2)<1.3). Second-harmonic-generation is achieved using a 20 mm long noncritically phase-matched Lithium triborate (LiB3O5) crystal; conversion efficiencies as high as 58% have been observed. At 100 W of 514.5 nm output power, the average M(2) value was 1.35. To the best of our knowledge, this is the highest average power picosecond green pulsed laser.

  11. Seedless velocimetry at 100  kHz with picosecond-laser electronic-excitation tagging.

    PubMed

    Jiang, Naibo; Mance, Jason G; Slipchenko, Mikhail N; Felver, Josef J; Stauffer, Hans U; Yi, Tongxun; Danehy, Paul M; Roy, Sukesh

    2017-01-15

    Picosecond-laser electronic-excitation tagging (PLEET), a seedless picosecond-laser-based velocimetry technique, is demonstrated in non-reactive flows at a repetition rate of 100 kHz with a 1064 nm, 100 ps burst-mode laser. The fluorescence lifetime of the PLEET signal was measured in nitrogen, and the laser heating effects were analyzed. PLEET experiments with a free jet of nitrogen show the ability to measure multi-point flow velocity fluctuations at a 100 kHz detection rate or higher. Both spectral and dynamic mode decomposition analyses of velocity on a Ma=0.8 free jet show two dominant Strouhal numbers around 0.24 and 0.48, respectively, well within the shear-layer flapping frequencies of the free jets. This technique increases the laser-tagging repetition rate for velocimetry to hundreds of kilohertz. PLEET is suitable for subsonic through supersonic laminar- and turbulent-flow velocity measurements.

  12. High-power linearly-polarized picosecond thulium-doped all-fiber master-oscillator power-amplifier.

    PubMed

    Liu, Jiang; Liu, Chen; Shi, Hongxing; Wang, Pu

    2016-06-27

    We demonstrated a linearly-polarized picosecond thulium-doped all-fiber-integrated master-oscillator power-amplifier system, which yielded 240 W of average output power at 127 MHz repetition rate. The seed source is a passively mode-locked polarization-maintaining thulium-doped all-fiber oscillator with a nearly transform-limited pulse duration of 10 ps. In combination with a pre-chirp fiber having a positive group velocity dispersion and a three stage polarization-maintaining thulium-doped all-fiber amplifier, output pulse energies up to 1.89 µJ with 42 kW pulse peak power are obtained without the need of complex free-space stretcher or compressor setups. To the best of our knowledge, this is the highest average output power ever reported for a picosecond all-fiber-integrated laser at 2 µm wavelength region.

  13. Narrow-bandwidth tunable picosecond pulses in the visible produced by noncollinear optical parametric amplification with a chirped blue pump.

    PubMed

    Co, Dick T; Lockard, Jenny V; McCamant, David W; Wasielewski, Michael R

    2010-04-01

    Narrow-bandwidth (approximately 27 cm(-1)) tunable picosecond pulses from 480 nm-780 nm were generated from the output of a 1 kHz femtosecond titanium:sapphire laser system using a type I noncollinear optical parametric amplifier (NOPA) with chirped second-harmonic generation (SHG) pumping. Unlike a femtosecond NOPA, this system utilizes a broadband pump beam, the chirped 400 nm SHG of the Ti:sapphire fundamental, to amplify a monochromatic signal beam (spectrally-filtered output of a type II collinear OPA). Optimum geometric conditions for simultaneous phase- and group-velocity matching were calculated in the visible spectrum. This design is an efficient and simple method for generating tunable visible picosecond pulses that are synchronized to the femtosecond pulses.

  14. Picosecond to femtosecond pulses from high power self mode-locked ytterbium rod-type fiber laser.

    PubMed

    Deslandes, Pierre; Perrin, Mathias; Saby, Julien; Sangla, Damien; Salin, François; Freysz, Eric

    2013-05-06

    We have designed an ytterbium rod-type fiber laser oscillator with tunable pulse duration. This system that delivers more than 10 W of average power is self mode-locked. It yields femtosecond to picosecond laser pulses at a repetition rate of 74 MHz. The pulse duration is adjusted by changing the spectral width of a band pass filter that is inserted in the laser cavity. Using volume Bragg gratings of 0.9 nm and 0.07 nm spectrum bandwidth, this oscillator delivers nearly Fourier limited 2.8 ps and 18.5 ps pulses, respectively. With a 4 nm interference filter, one obtains picosecond pulses that have been externally dechirped down to 130 fs.

  15. 26 nJ picosecond solitons from thulium-doped single-mode master oscillator power fiber amplifier.

    PubMed

    Renard, William; Canat, Guillaume; Bourdon, Pierre

    2012-02-01

    We report on an all single-mode master oscillator power fiber amplifier delivering high energy picosecond solitons at 1960 nm. The Bragg stabilized and self-starting oscillator delivers 62 pJ transform-limited pulses at 11.2 MHz pulse repetition frequency. Solitons are amplified in a core-pumped single-mode heavily thulium-doped fiber up to 26 nJ. The average and peak power are 291 mW and 7.4 kW, respectively. Pulses remain transform limited without significant self-phase-modulation distortion. We discuss the limitations of picosecond pulse amplification in a core-pumped single-mode fiber amplifier.

  16. The study of 3.2 mJ picosecond regenerative amplifier at 2 kHz

    NASA Astrophysics Data System (ADS)

    Bai, Zhen-ao; Fan, Zhong-wei; Lian, Fu-qiang; Bai, Zhen-xu; Kan, Zhi-jun; Zhang, Jing; Wang, Jia-zan

    2014-12-01

    We report on a high energy laser diode (LD) side-continuous-pumped Nd:YAG (yttrium aluminum garnet) picosecond regenerative amplifier. The mode-locking picosecond oscillator is used as seed source with 31.3 ps pulse width, 150 mW average power and 1064.4 nm center wavelengths at the repetition frequency of 86 MHz. For the amplifier system, average output power of 6.4 W and 10.8 W are achieved at repetition frequency of 2 kHz and 4.5 kHz, which corresponds to output pulse energy of 3.2 mJ and 2.4 mJ respectively. The regenerative amplifier designed has high compact and high stability.

  17. Doubly-Resonant Fabry-Perot Cavity for Power Enhancement of Burst-Mode Picosecond Ultraviolet Pulses

    SciTech Connect

    Abudureyimu, Reheman; Huang, Chunning; Liu, Yun

    2015-01-01

    We report on a first experimental demonstration of locking a doubly-resonant Fabry-Perot cavity to burst-mode picosecond ultraviolet (UV) pulses by using a temperature controlled dispersion compensation method. This technique will eventually enable the intra cavity power enhancement of burst-mode 402.5MHz/50ps UV laser pulses with a MW level peak power required for the laser assisted H- beam stripping experiment at the Spallation Neutron Source.

  18. Supercontinuum generation from 2 to 20 μm in GaAs pumped by picosecond CO₂ laser pulses.

    PubMed

    Pigeon, J J; Tochitsky, S Ya; Gong, C; Joshi, C

    2014-06-01

    We report on the generation of supercontinuum radiation from 2 to 20 μm in a 67 mm long GaAs crystal pumped by a train of 3 ps CO2 laser pulses. Temporal measurements indicate that sub-picosecond pulse splitting is involved in the production of such wide-bandwidth radiation in GaAs. The results show that the observed spectral broadening is heavily influenced by four-wave mixing and stimulated Raman scattering.

  19. Microviscosity in polyacrylamide gels with pendant triphenyl-methane leuco derivatives: picosecond time-resolved fluorescence study

    NASA Astrophysics Data System (ADS)

    Tamai, Naoto; Ishikawa, Masazumi; Kitamura, Noboru; Masuhara, Hiroshi

    1991-10-01

    Picosecond fluorescence dynamics of triphenylmethane dyes bonded to polyacrylamide gels before and after swelling was studied by a single-photon timing technique. Microviscosity in the gels after swelling was estimated to be 10-11 cP by examining the viscosity dependence of fluorescence dynamics of malachite green in various alcohols. The results were interpreted in terms of structured stiff water in a microcavity of the gels.

  20. ULTRA-BRIGHT X-RAY GENERATION USING INVERSE COMPTON SCATTERING OF PICOSECOND CO(2) LASER PLUSES.

    SciTech Connect

    TSUNEMI,A.; ENDO,A.; POGORELSKY,I.; BEN-ZVI,I.; KUSCHE,K.; SKARITKA,J.; YAKIMENKO,V.; HIROSE,T.; URAKAWA,J.; OMORI,T.; WASHIO,M.; LIU,Y.; HE,P.; CLINE,D.

    1999-03-01

    Laser-Compton scattering with picosecond CO{sub 2} laser pulses is proposed for generation of high-brightness x-rays. The interaction chamber has been developed and the experiment is scheduled for the generation of the x-rays of 4.7 keV, 10{sup 7} photons in 10-ps pulse width using 50-MeV, 0.5-nC relativistic electron bunches and 6 GW CO{sub 2} laser.

  1. Terahertz acoustics in hot dense laser plasmas.

    PubMed

    Adak, Amitava; Robinson, A P L; Singh, Prashant Kumar; Chatterjee, Gourab; Lad, Amit D; Pasley, John; Kumar, G Ravindra

    2015-03-20

    We present a hitherto unobserved facet of hydrodynamics, namely the generation of an ultrahigh frequency acoustic disturbance in the terahertz frequency range, whose origins are purely hydrodynamic in nature. The disturbance is caused by differential flow velocities down a density gradient in a plasma created by a 30 fs, 800 nm high-intensity laser (∼5×10(16)  W/cm(2)). The picosecond scale observations enable us to capture these high frequency oscillations (1.9±0.6  THz) which are generated as a consequence of the rapid heating of the medium by the laser. Adoption of two complementary techniques, namely pump-probe reflectometry and pump-probe Doppler spectrometry provides unambiguous identification of this terahertz acoustic disturbance. Hydrodynamic simulations well reproduce the observations, offering insight into this process.

  2. Rapid micromachining of high aspect ratio holes in fused silica glass by high repetition rate picosecond laser

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Abolghasemi, Ladan; Herman, Peter R.

    2014-01-01

    We present multiple methods of high aspect ratio hole drilling in fused silica glass, taking advantage of high power and high repetition rate picosecond lasers and flexible beam delivery methods to excise deep holes with minimal collateral damage. Combinations of static and synchronous scanning of laser focus were explored over a range of laser repetition rates and burst-train profiles that dramatically vary laser plume interaction dynamics, heat-affected zone, and heat accumulation physics. Chemically assisted etching of picosecond laser modification tracks are also presented as an extension from femtosecond laser writing of volume nanograting to form high aspect ratio (77) channels. Processing windows are identified for the various beam delivery methods that optimize the laser exposure over energy, wavelength, and repetition rate to reduce microcracking and deleterious heating effects. The results show the benefits of femtosecond laser interactions in glass extend into the picosecond domain, where the attributes of higher power further yield wide processing windows and significantly faster fabrication speed. High aspect ratio holes of 400 μm depth were formed over widely varying rates of 333 holes per second for mildly cracked holes in static-focal positioning through to one hole per second for low-damage and taper free holes in synchronous scanning.

  3. Picosecond pulses compression at 1053-nm center wavelength by using a gas-filled hollow-core fiber compressor

    NASA Astrophysics Data System (ADS)

    Huang, Zhi-Yuan; Wang, Ding; Leng, Yu-Xin; Dai, Ye

    2015-01-01

    We theoretically study the nonlinear compression of picosecond pulses with 10-mJ of input energy at the 1053-nm center wavelength by using a one-meter-long gas-filled hollow-core fiber (HCF) compressor and considering the third-order dispersion (TOD) effect. It is found that when the input pulse is about 1 ps/10 mJ, it can be compressed down to less than 20 fs with a high transmission efficiency. The gas for optimal compression is krypton gas which is filled in a HCF with a 400-μm inner diameter. When the input pulse duration is increased to 5 ps, it can also be compressed down to less than 100 fs efficiently under proper conditions. The results show that the TOD effect has little impact on picosecond pulse compression and the HCF compressor can be applied on compressing picosecond pulses efficiently with a high compression ratio, which will benefit the research of high-field laser physics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204328, 61221064, 61078037, 11127901, and 11134010), the National Basic Research Program of China (Grant No. 2011CB808101), the Commission of Science and Technology of Shanghai, China (Grant No. 12dz1100700), the Natural Science Foundation of Shanghai, China (Grant No. 13ZR1414800), and the International Science and Technology Cooperation Program of China (Grant No. 2011DFA11300).

  4. Narrow bandwidth passively mode locked picosecond Erbium doped fiber laser using a 45° tilted fiber grating device.

    PubMed

    Wang, Tianxing; Yan, Zhijun; Mou, Chengbo; Liu, Zuyao; Liu, Yunqi; Zhou, Kaiming; Zhang, Lin

    2017-07-10

    An all-fiber passively picosecond mode locked Erbium doped laser using a 45° tilted fiber grating (45° TFG) and a fiber Bragg grating (FBG) is reported in this work. Due to the strong polarization dependent loss (PDL) of 45° TFG and narrow 3-dB bandwidth of FBG, the Erbium doped fiber laser (EDFL) can generate picosecond mode locked pulse based on the nonlinear polarization rotation (NPR) effect. The laser features a repetition rate of 9.67 MHz, a pulse duration of 33 ps, a signal-to-noise ratio (SNR) of 70 dB, an average output power of 1.2 mW, and a single pulse energy of 124 pJ under the pump power of 102 mW. Besides, the central wavelength of the laser can be continuously adjusted from 1550.65 nm to 1551.44 nm. The technique of using a 45° TFG to generate picosecond pulses can be readily extended to other wavelength such as mid-infrared (mid-IR) where fiber polarizing components are either expensive or not available. To the best of our knowledge, the spectral width is the narrowest among all-fiber passively mode locked Erbium-doped laser based on NPR.

  5. High-power picosecond 355 nm laser based on La₂CaB₁₀O₁₉ crystal.

    PubMed

    Li, Kai; Zhang, Ling; Xu, Degang; Zhang, Guochun; Yu, Haijuan; Wang, Yuye; Shan, Faxian; Wang, Lirong; Yan, Chao; Wu, Yicheng; Lin, Xuechun; Yao, Jianquan

    2014-06-01

    Third harmonic generation experiments were performed on a type-I phase-matching La2CaB10O19 crystal cut at θ=49.4° and φ=0.0° with dimensions of 4.0  mm×4.0  mm×17.6  mm. A 1064 nm laser with a maximum average power of 35.2 W was employed as the fundamental light source, which has a pulse width of 10 picoseconds and a pulse repetition rate of 80 MHz. A type-I noncritical phase-matching LBO crystal was used to generate 532 nm lasers. By investigating a series of focusing lens combinations, a picosecond 355 nm laser of 5.3 W was obtained, which is the highest power of picosecond 355 nm laser based on a La2CaB10O19 crystal so far. The total conversion efficiency from 1064 to 355 nm was up to 15.1%.

  6. A method for detecting ultra-low quantities of explosives with use a picosecond laser FAIMS analyzer

    NASA Astrophysics Data System (ADS)

    Chistyakov, Alexander A.; Kotkovskii, Gennadii E.; Odulo, Ivan P.; Sychev, Alexey V.; Bogdanov, Artem S.; Perederiy, Anatoly N.; Spitsyn, Evgeny M.; Shestakov, Alexander V.

    2015-05-01

    A method for detecting ultralow quantities of explosives in air with use a state-of-the-art picosecond chip Nd3+:YAG laser has been developed. The method combines field asymmetric ion mobility spectrometry (FAIMS) with laser ionization of examined air samples. Radiation of λ = 266nm, τpulse = 300ps, Epulse = 30-150μJ, ν = 20-300Hz was used. Processes in the ion source for the use both picosecond and nanosecond ionization modes were analyzed. Parameters of the laser ion source have been specially optimized. The dependences on frequency, pulse energy, peak intensity, and average power for trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) were obtained. It was shown that the optimal peak intensity should be no less 3·106 W/cm2. The detected ion signals for all explosives were shown to be threefold higher for picosecond excitation in comparison with use a nanosecond laser of the same average power. The estimated detection threshold of the prototype equals 1. 10-15 g/cm3. The results are promising for the development of a highly sensitive, portable laser explosive detector.

  7. Sub-picosecond chirped return-to-zero nonlinear optical pulse propagating in dense dispersion-managed fibre

    NASA Astrophysics Data System (ADS)

    Guo, Shuqin; Le, Zichun; Quan, Bisheng

    2006-01-01

    By numerical simulation, we show that the fourth-order dispersion (FOD) makes sub-picosecond optical pulse broaden as second-order dispersion (SOD), makes optical pulse oscillate simultaneously as third-order dispersion (TOD). Based on above two reasons, sub-picosecond optical pulse will be widely broaden and lead to emission of continuum radiation during propagation. Here, resemble to two- and third-order dispersion compensation, fourth-order dispersion compensation is also suggested in a dispersion-managed optical fiber link, which is realized by arranging two kinds of fiber with opposite dispersion sign in each compensation cell. For sake of avoiding excessively broadening, ultra short scale dispersion compensation cell is required in ultra high speed optical communication system. In a full dispersion compensation optical fiber system which path average dispersion is zero about SOD, TOD, and FOD, even suffering from affection of high order nonlinear like self-steep effect and self-frequency shift, 200 fs gauss optical pulse can stable propagate over 1000 km with an optimal initial chirp. When space between neighboring optical pulse is only 2 picoseconds corresponding to 500 Gbit/s transmitting capacity, eye diagram is very clarity after 1000 km. The results demonstrate that ultra short scale dispersion compensation including FOD is need and effective in ultra-high speed optical communication.

  8. An automatic robotic system for three-dimensional tooth crown preparation using a picosecond laser.

    PubMed

    Wang, Lei; Wang, Dangxiao; Zhang, Yuru; Ma, Lei; Sun, Yuchun; Lv, Peijun

    2014-09-01

    Laser techniques have been introduced into dentistry to overcome the drawbacks of traditional treatment methods. The existing methods in dental clinical operations for tooth crown preparation have several drawbacks which affect the long-term success of the dental treatment. To develop an improved robotic system to manipulate the laser beam to achieve safe and accurate three-dimensional (3D) tooth ablation, and thus to realize automatic tooth crown preparation in clinical operations. We present an automatic laser ablation system for tooth crown preparation in dental restorative operations. The system, combining robotics and laser technology, is developed to control the laser focus in three-dimensional motion aiming for high speed and accuracy crown preparation. The system consists of an end-effector, a real-time monitor and a tooth fixture. A layer-by-layer ablation method is developed to control the laser focus during the crown preparation. Experiments are carried out with picosecond laser on wax resin and teeth. The accuracy of the system is satisfying, achieving the average linear errors of 0.06 mm for wax resin and 0.05 mm for dentin. The angle errors are 4.33° for wax resin and 0.5° for dentin. The depth errors for wax resin and dentin are both within 0.1 mm. The ablation time is 1.5 hours for wax resin and 3.5 hours for dentin. The ablation experimental results show that the movement range and the resolution of the robotic system can meet the requirements of typical dental operations for tooth crown preparation. Also, the errors of tooth shape and preparation angle are able to satisfy the requirements of clinical crown preparation. Although the experimental results illustrate the potential of using picosecond lasers for 3D tooth crown preparation, many research issues still need to be studied before the system can be applied to clinical operations. © 2014 Wiley Periodicals, Inc.

  9. Rattling in the cage: ions as probes of sub-picosecond water network dynamics.

    PubMed

    Schmidt, Diedrich A; Birer, Ozgür; Funkner, Stefan; Born, Benjamin P; Gnanasekaran, Ramachandran; Schwaab, Gerhard W; Leitner, David M; Havenith, Martina

    2009-12-30

    We present terahertz (THz) measurements of salt solutions that shed new light on the controversy over whether salts act as kosmotropes (structure makers) or chaotropes (structure breakers), which enhance or reduce the solvent order, respectively. We have carried out precise measurements of the concentration-dependent THz absorption coefficient of 15 solvated alkali halide salts around 85 cm(-1) (2.5 THz). In addition, we recorded overview spectra between 30 and 300 cm(-1) using a THz Fourier transform spectrometer for six alkali halides. For all solutions we found a linear increase of THz absorption compared to pure water (THz excess) with increasing solute concentration. These results suggest that the ions may be treated as simple defects in an H-bond network. They therefore cannot be characterized as either kosmotropes or chaotropes. Below 200 cm(-1), the observed THz excess of all salts can be described by a linear superposition of the water absorption and an additional absorption that is attributed to a rattling motion of the ions within the water network. By providing a comprehensive set of data for different salt solutions, we find that the solutions can all be very well described by a model that includes damped harmonic oscillations of the anions and cations within the water network. We find this model predicts the main features of THz spectra for a variety of salt solutions. The assumption of the existence of these ion rattling motions on sub-picosecond time scales is supported by THz Fourier transform spectroscopy of six alkali halides. Above 200 cm(-1) the excess is interpreted in terms of a change in the wing of the water network librational mode. Accompanying molecular dynamics simulations using the TIP3P water model support our conclusion and show that the fast sub-picosecond motions of the ions and their surroundings are almost decoupled. These findings provide a complete description of the solute-induced changes in the THz solvation dynamics for the

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

    SciTech Connect

    BULLOCK, A B

    1999-05-26

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

  11. Soft x-ray plasma-based seeded multistage amplification chain.

    PubMed

    Oliva, Eduardo; Fajardo, Marta; Li, Lu; Sebban, Stephane; Ros, David; Zeitoun, Philippe

    2012-10-15

    To date, plasma-based soft x-ray lasers have demonstrated experimentally 1 μJ, 1 ps (1 MW) pulses. This Letter reports extensive study using time-dependant Maxwell-Bloch code of seeding millimeter scale plasmas that store more than 100 mJ in population inversion. Direct seeding of these plasmas has to overcome very strong amplified spontaneous emission (ASE) as well as prevent wake-field amplification. Below 100 nJ injected energy, seed produces pulses with picosecond duration. To overcome this limitation, a new scheme has been studied, taking advantage of a plasma preamplifier that dramatically increases the seed energy prior to entering the main plasma amplifier leading to ASE and wake-free, fully coherent 21.6 μJ, 80 fs pulses (0.27 GW).

  12. Pattern analysis of laser-tattoo interactions for picosecond- and nanosecond-domain 1,064-nm neodymium-doped yttrium-aluminum-garnet lasers in tissue-mimicking phantom.

    PubMed

    Ahn, Keun Jae; Zheng, Zhenlong; Kwon, Tae Rin; Kim, Beom Joon; Lee, Hye Sun; Cho, Sung Bin

    2017-05-08

    During laser treatment for tattoo removal, pigment chromophores absorb laser energy, resulting in fragmentation of the ink particles via selective photothermolysis. The present study aimed to outline macroscopic laser-tattoo interactions in tissue-mimicking (TM) phantoms treated with picosecond- and nanosecond-domain lasers. Additionally, high-speed cinematographs were captured to visualize time-dependent tattoo-tissue interactions, from laser irradiation to the formation of photothermal and photoacoustic injury zones (PIZs). In all experimental settings using the nanosecond or picosecond laser, tattoo pigments fragmented into coarse particles after a single laser pulse, and further disintegrated into smaller particles that dispersed toward the boundaries of PIZs after repetitive delivery of laser energy. Particles fractured by picosecond treatment were more evenly dispersed throughout PIZs than those fractured by nanosecond treatment. Additionally, picosecond-then-picosecond laser treatment (5-pass-picosecond treatment + 5-pass-picosecond treatment) induced greater disintegration of tattoo particles within PIZs than picosecond-then-nanosecond laser treatment (5-pass-picosecond treatment + 5-pass-nanosecond treatment). High-speed cinematography recorded the formation of PIZs after repeated reflection and propagation of acoustic waves over hundreds of microseconds to a few milliseconds. The present data may be of use in predicting three-dimensional laser-tattoo interactions and associated reactions in surrounding tissue.

  13. Evaluation of Homogeneity and Elastic Properties of Solid Argon at High Pressures Using Picosecond Laser Ultrasonic Interferometry

    NASA Astrophysics Data System (ADS)

    Zerr, A.; Kuriakose, M.; Raetz, S.; Chigarev, N.; Nikitin, S. M.; Gasteau, D.; Tournat, V.; Bulou, A.; Castagnede, B.; Gusev, V. E.; Lomonosov, A.

    2015-12-01

    In picosecond ultrasonic interferometry [1], femto- or picosecond pump laser pulses are first used to generate acoustic pulses ranging from several to a few tens of nanometres length, thanks to the optoacoustic transduction in a light absorbing generator. Time-delayed femto- or picosecond probe laser pulses are then used to follow the propagation of these ultrashort acoustic pulses through a transparent medium that is in contact with the generator surface. The transient signal thus contains, at each moment in time, information on the local elastic, optical and elasto-optical properties of the tested material at the position where the laser-generated picosecond acoustic pulse is located during its propagation in the sample depth. Hence, the technique allows evaluation of sound velocities and elastic anisotropy of micro-crystallites composing a transparent material compressed to high pressures in a diamond anvil cell (DAC). This interferometry technique also helps to understand the micro-crystallite orientations in a case of elastically anisotropic material. Here we report the preliminary results of picosecond ultrasonic interferometry applied to the evaluation of homogeneities and elastic properties of polycrystalline solid argon compressed to 10 GPa and 15 GPa. In comparison with the earlier reported experiments on H2O ice at Mbar pressures [2], more efforts were spent to the evaluation of the lateral microstructure of the sample at high pressures, i.e., to inhomogeneities along the surface of the optoacoustic generator, rather than to the in-depth imaging along the axis of the DAC. The lateral imaging is performed over a distance of 60 - 90 µm, nearly corresponding to the complete sample diameter. In addition to the presence of expected lateral inhomogeneities the obtained results demonstrate important changes in their distribution upon pressure increase from 10 to 15 GPa. On the basis of the analysis of the statistic probability in the detection of differently

  14. Note: Space qualified photon counting detector for laser time transfer with picosecond precision and stability

    NASA Astrophysics Data System (ADS)

    Prochazka, Ivan; Kodet, Jan; Blazej, Josef

    2016-05-01

    The laser time transfer link is under construction for the European Space Agency in the frame of Atomic Clock Ensemble in Space. We have developed and tested the flying unit of the photon counting detector optimized for this space mission. The results are summarized in this Note. An extreme challenge was to build a detector package, which is rugged, small and which provides long term detection delay stability on picosecond level. The device passed successfully all the tests required for space missions on the low Earth orbits. The detector is extremely rugged and compact. Its long term detection delay stability is excellent, it is better than ±1 ps/day, in a sense of time deviation it is better than 0.5 ps for averaging times of 2000 s to several hours. The device is capable to operate in a temperature range of -55 °C up to +60 °C, the change of the detection delay with temperature is +0.5 ps/K. The device is ready for integration into the space structure now.

  15. Probing Transient Valence Orbital Changes with Picosecond Valence-to-Core X-ray Emission Spectroscopy

    DOE PAGES

    March, Anne Marie; Assefa, Tadesse A.; Boemer, Christina; ...

    2017-01-17

    Here we probe the dynamics of valence electrons in photoexcited [Fe(terpy)2]2+ in solution to gain deeper insight into the Fe-ligand bond changes. We use hard X-ray emission spectroscopy (XES), which combines element specificity and high penetration with sensitivity to orbital structure, making it a powerful technique for molecular studies in a wide variety of environments. A picosecond-time-resolved measurement of the complete Is X-ray emission spectrum captures the transient photoinduced changes and includes the weak valence-to-core (vtc) emission lines that correspond to transitions from occupied valence orbitals to the nascent core-hole. Vtc-XES offers particular insight into the molecular orbitals directly involvedmore » in the light-driven dynamics; a change in the metal-ligand orbital overlap results in an intensity reduction and a blue energy shift in agreement with our theoretical calculations and more subtle features at the highest energies reflect changes in the frontier orbital populations.« less

  16. Picosecond infrared study of carbonmonoxy cytochrome c oxidase: Ligand transfer dynamics and binding orientations

    SciTech Connect

    Peterson, K.A.; Stoutland, P.O.; Dyer, R.B.; Woodruff, W.H.

    1991-01-01

    Cytochrome c oxidase (CcO), an enzyme which catalyzes the reduction of dioxygen to water in the terminal step of the respiratory chain, combines several fundamental chemical processes in performing its function. The coordination chemistry and ligation dynamics of the cytochrome {alpha}{sub 3}-Cu{sub B} site, where O{sub 2} and other small molecules such as CO, NO and isocyanates can bind, are essential to the function of the enzyme. Recent time-resolved infrared (TRIR) and visible absorption measurements have shown that coordination to Cu{sub B}{sup +} is an obligatory mechanistic step for CO entering the cytochrome {alpha}{sub 3} heme site and departing the protein after photodissociation. The timescale (> 10{sup {minus}7} s) of the TRIR measurements precluded observation of the ligation dynamics immediately following photodissociation. Here we report a picosecond timescale TRIR study of these events. The results reveal that the photoinitiated ligand transfer of CO from Fe{sub a3}{sup 2+} to Cu{sub B}{sup +}, which are believed to lie 4--5 {Angstrom} apart, occurs within 1 ps. 9 refs., 2 figs.

  17. The Boersch effect in a picosecond pulsed electron beam emitted from a semiconductor photocathode

    NASA Astrophysics Data System (ADS)

    Kuwahara, Makoto; Nambo, Yoshito; Aoki, Kota; Sameshima, Kensuke; Jin, Xiuguang; Ujihara, Toru; Asano, Hidefumi; Saitoh, Koh; Takeda, Yoshikazu; Tanaka, Nobuo

    2016-07-01

    The space charge effect has been clearly observed in the energy distributions of picosecond pulse beams from a spin-polarized electron microscope, and was found to depend upon the quantity of charge per pulse. The non-linear phenomena associated with this effect have also been replicated in beam simulations that take into account of a three-dimensional space charge. The results show that a charge of 500 aC/pulse provides the highest brightness with a 16-ps pulse duration, a 30-keV beam energy, and an emission spot of 1.8 μm. Furthermore, the degeneracy of the wave packet of the pulsed electron beam has been evaluated to be 1.6 × 10-5 with a charge of 100 aC/pulse, which is higher than that for a continuously emitted electron beam despite the low beam energy of 30 keV. The high degeneracy and high brightness contribute to the realization of high temporal and energy resolutions in low-voltage electron microscopy, which will serve to reduce radiolysis damage and enhance scattering contrast.

  18. Low viscosity in the aqueous domain of cell cytoplasm measured by picosecond polarization microfluorimetry

    PubMed Central

    1991-01-01

    Information about the rheological characteristics of the aqueous cytoplasm can be provided by analysis of the rotational motion of small polar molecules introduced into the cell. To determine fluid-phase cytoplasmic viscosity in intact cells, a polarization microscope was constructed for measurement of picosecond anisotropy decay of fluorescent probes in the cell cytoplasm. We found that the rotational correlation time (tc) of the probes, 2,7-bis-(2-carboxyethyl)-5-(and-6- )carboxyfluorescein (BCECF), 6-carboxyfluorescein, and 8-hydroxypyrene- 1,3,6-trisulfonic acid (HPTS) provided a direct measure of fluid-phase cytoplasmic viscosity that was independent of probe binding. In quiescent Swiss 3T3 fibroblasts, tc values were 20-40% longer than those in water, indicating that the fluid-phase cytoplasm is only 1.2- 1.4 times as viscous as water. The activation energy of fluid-phase cytoplasmic viscosity was 4 kcal/mol, which is similar to that of water. Fluid-phase cytoplasmic viscosity was altered by less than 10% upon addition of sucrose to decrease cell volume, cytochalasin B to disrupt cell cytoskeleton, and vasopressin to activate phospholipase C. Nucleoplasmic and peripheral cytoplasmic viscosities were not different. Our results establish a novel method to measure fluid-phase cytoplasmic viscosity, and indicate that fluid-phase cytoplasmic viscosity in fibroblasts is similar to that of free water. PMID:1993739

  19. Ultrafast graphene and carbon nanotube film patterning by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Bobrinetskiy, Ivan I.; Emelianov, Alexey V.; Otero, Nerea; Romero, Pablo M.

    2016-03-01

    Carbon nanomaterials is among the most promising technologies for advanced electronic applications, due to their extraordinary chemical and physical properties. Nonetheless, after more than two decades of intensive research, the application of carbon-based nanostructures in real electronic and optoelectronic devices is still a big challenge due to lack of scalable integration in microelectronic manufacturing. Laser processing is an attractive tool for graphene device manufacturing, providing a large variety of processes through direct and indirect interaction of laser beams with graphene lattice: functionalization, oxidation, reduction, etching and ablation, growth, etc. with resolution down to the nanoscale. Focused laser radiation allows freeform processing, enabling fully mask-less fabrication of devices from graphene and carbon nanotube films. This concept is attractive to reduce costs, improve flexibility, and reduce alignment operations, by producing fully functional devices in single direct-write operations. In this paper, a picosecond laser with a wavelength of 515 nm and pulse width of 30 ps is used to pattern carbon nanostructures in two ways: ablation and chemical functionalization. The light absorption leads to thermal ablation of graphene and carbon nanotube film under the fluence 60-90 J/cm2 with scanning speed up to 2 m/s. Just under the ablation energy, the two-photon absorption leads to add functional groups to the carbon lattice which change the optical properties of graphene. This paper shows the results of controlled modification of geometrical configuration and the physical and chemical properties of carbon based nanostructures, by laser direct writing.

  20. Photooxidation and photoaquation of iron hexacyanide in aqueous solution: A picosecond X-ray absorption study

    PubMed Central

    Reinhard, M.; Penfold, T. J.; Lima, F. A.; Rittmann, J.; Rittmann-Frank, M. H.; Abela, R.; Tavernelli, I.; Rothlisberger, U.; Milne, C. J.; Chergui, M.

    2014-01-01

    We present a picosecond Fe K-edge absorption study of photoexcited ferrous and ferric hexacyanide in water under 355 and 266 nm excitation. Following 355 nm excitation, the transient spectra for the ferrous and ferric complexes exhibit a red shift of the edge reflecting an increased electron density at the Fe atom. For the former, an enhanced pre-edge transition is also observed. These observations are attributed to the aquated [Fe(CN)5OH2]3− species, based on quantum chemical calculations which also provide structural parameters. Upon 266 nm excitation of the ferric complex, a transient reminiscent of the aquated species is observed (appearance of a pre-edge feature and red shift of the edge) but it is different from that obtained under 355 nm excitation. This points to a new reaction channel occurring through an intermediate state lying between these two excitation energies. Finally, 266 nm excitation of the ferrous species is dominated by the photooxidation channel with formation of the ferric complex as main photoproduct. However, we observe an additional minor photoproduct, which is identical to the 266 nm generated photoproduct of the ferric species, suggesting that under our experimental conditions, the pump pulse photooxidises the ferrous complex and re-excites the primary ferric photoproduct. PMID:26798775