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J. P. Girardeau-montaut - One of the best experts on this subject based on the ideXlab platform.
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Laser ablation threshold determination by Photoelectric Emission
Applied Physics A, 1999Co-Authors: Cs. Beleznai, J. P. Girardeau-montaut, D. Vouagner, C. Templier, H. GonnordAbstract:Laser-induced surface damage introduces a dramatic change in the Photoelectric properties of metallic and semiconductor substrates. Hence, by varying the applied laser intensity, ultra-short- pulsed laser-induced photoEmission (in the mono- or multiphotonic regime according to the applied wavelength) can be used to monitor in situ surface structural changes. Results for a model system (thin diamond-like carbon (DLC) layer on an Si carrier) are presented, where, after ablation of the DLC layer, we observed a rapid increase in the Photoelectric contribution from the underlying substrate. High-sensitivity measurements are presented for Au and W substrates where due to laser- induced damage within the escape depth of electrons and because of the apparition of ionized species upon ablation, the measured charge can indicate the onset of surface damage. Results are presented for various wavelengths (213 nm, 266 nm and 532 nm) and discussed in the light of previous results of threshold measurements obtained by optical methods.
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Simultaneous measurements of second-harmonic generation and two-photon Photoelectric Emission from Au
Applied Physics A: Materials Science & Processing, 1999Co-Authors: C. Tomas, E. Vinet, J. P. Girardeau-montautAbstract:Simultaneous measurements of the second-harmonic generation (SHG) and of the two-photon Photoelectric Emission (2PPE) responses induced from an Au target by the same incident picosecond laser beam at λ = 532 nm are performed. The effects of a dc electric field, applied between the sample (photocathode) and an anode in order to collect the photoelectrons, are investigated. The dependence on incident beam intensity and polarization of both 2PPE charge and SHG intensity is studied experimentally. Similar comportments are observed, however differences are found between SHG and photoEmission concerning their surface specificity and their sensitivity to the heat provided by the laser beam.
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Electron relaxation phenomena on a copper surface via nonlinear ultrashort single-photon Photoelectric Emission
Journal of Physics D: Applied Physics, 1997Co-Authors: N. Papadogiannis, S. D. Moustaïzis, J. P. Girardeau-montautAbstract:Time-resolved single-photon Photoelectric Emission measurements from polycrystalline copper, using an autocorrelation system of 450 fs duration at 248 nm laser pulses, are reported. This experimental technique makes possible the direct measurement of the electron energy relaxation time at the surface as well as the evaluation of the electron - phonon scattering time in metallic samples. A nonlinear increase of the electron photocurrent versus the laser intensity is observed. This nonlinearity is attributed to the non-thermal equilibrium between the electron gas and the lattice produced by the subpicosecond laser pulses and is related to the dynamics of energy relaxation between the electrons and the lattice. The influence of the non-thermal electrons on the photoEmission and their thermalization time is discussed. Our experimental results may be explained by a model based on the Fowler - Dubridge equation for photocurrent and on thermal-balance equations between electron and lattice subsystems.
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Aluminium electron-phonon relaxation-time measurement from subpicosecond nonlinear single-photon Photoelectric Emission at 248 nm
Applied Physics A, 1996Co-Authors: J. P. Girardeau-montaut, M. Afif, C. Girardeau-montaut, S. D. Moustaïzis, N. PapadogiannisAbstract:The sensitivity of Photoelectric Emission of polycrystalline aluminium, produced by 248 nm laser pulses with p-polarization and 450 fs duration, under incidence angles θ = 74–86°, has been measured. A nonlinear increase of photoEmission efficiency, as a function of the incident laser peak intensity in the range of 1–50 GW/cm^2, was displayed, which confirms earlier observations with gold and tungsten. This nonlinearity is consecutive to the non-thermal distribution of electron gas of laser-heated metal on the time scale of the electron-phonon relaxation time. Analysis of experimental data, using the model previously developed by us [1], gives a value of electron-phonon relaxation time ≈0.55 ± 0.11 ps.
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Enhancement of ultrashort Photoelectric Emission sensitivity of metals by alkaline ions implantation
Time-Resolved Electron and X-Ray Diffraction, 1995Co-Authors: J. P. Girardeau-montaut, M. Afif, C. Girardeau-montaut, Alain Perez, C. TomasAbstract:The production of high photoelectron densities from metallic photocathodes under ultrashort visible and UV-laser finds applications in various fields. Many workers tried, by the use of different techniques, to improve the Photoelectric performances of pure metals, essentially W and Mo, but all these prepared photocathodes were not able to withstand very high laser intensities, i.e., >= 1GW/cm2. We demonstrate that ion implantation is a valuable new tool to improve the Photoelectric Emission yield of pure metals. An enhancement of the sensitivity by a factor 5 to 50 was measured in ion potassium implanted tungsten irradiated by subpicosecond laser pulses with peak intensity of a few GW/cm2. Data on tungsten implanted by calcium and barium ions is also reported. An investigation of the chemical and physical properties at the origin of this enhancement are also reported. Optical and structural properties of these new materials were investigated by various techniques like reflectometry, ellipsometry, and grazing incidence x-ray diffraction, while the chemical structure of surfaces was determined by AES and XPS. The measurable changes on reflectivity and ellipsometric measurements can be interpreted both by the interface layer due to the radiation induced damage and by a modification of the dielectric function of W in the presence of ion-impurity.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
S. D. Moustaïzis - One of the best experts on this subject based on the ideXlab platform.
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Electron relaxation phenomena on a copper surface via nonlinear ultrashort single-photon Photoelectric Emission
Journal of Physics D: Applied Physics, 1997Co-Authors: N. Papadogiannis, S. D. Moustaïzis, J. P. Girardeau-montautAbstract:Time-resolved single-photon Photoelectric Emission measurements from polycrystalline copper, using an autocorrelation system of 450 fs duration at 248 nm laser pulses, are reported. This experimental technique makes possible the direct measurement of the electron energy relaxation time at the surface as well as the evaluation of the electron - phonon scattering time in metallic samples. A nonlinear increase of the electron photocurrent versus the laser intensity is observed. This nonlinearity is attributed to the non-thermal equilibrium between the electron gas and the lattice produced by the subpicosecond laser pulses and is related to the dynamics of energy relaxation between the electrons and the lattice. The influence of the non-thermal electrons on the photoEmission and their thermalization time is discussed. Our experimental results may be explained by a model based on the Fowler - Dubridge equation for photocurrent and on thermal-balance equations between electron and lattice subsystems.
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Aluminium electron-phonon relaxation-time measurement from subpicosecond nonlinear single-photon Photoelectric Emission at 248 nm
Applied Physics A, 1996Co-Authors: J. P. Girardeau-montaut, M. Afif, C. Girardeau-montaut, S. D. Moustaïzis, N. PapadogiannisAbstract:The sensitivity of Photoelectric Emission of polycrystalline aluminium, produced by 248 nm laser pulses with p-polarization and 450 fs duration, under incidence angles θ = 74–86°, has been measured. A nonlinear increase of photoEmission efficiency, as a function of the incident laser peak intensity in the range of 1–50 GW/cm^2, was displayed, which confirms earlier observations with gold and tungsten. This nonlinearity is consecutive to the non-thermal distribution of electron gas of laser-heated metal on the time scale of the electron-phonon relaxation time. Analysis of experimental data, using the model previously developed by us [1], gives a value of electron-phonon relaxation time ≈0.55 ± 0.11 ps.
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Enhancement of Photoelectric Emission sensitivity of tungsten by potassium ion implantation
Applied Physics Letters, 1995Co-Authors: J. P. Girardeau-montaut, M. Afif, C. Girardeau‐montaut, Alain Perez, S. D. MoustaïzisAbstract:Measurements of single‐photon Photoelectric Emission sensitivity of ion implanted polycrystalline tungsten surface by 3×1016 K+ ions/cm2 are reported. They are compared to the data previously obtained for pure tungsten tested under the same conditions. The enhancement of the Photoelectric sensitivity up to a factor of 50 was measured as a consequence of the change in the electronic properties of the tungsten surface, induced by the implanted alkali metal ions. Compared with other techniques used to reduce the work function of pure tungsten, the implanted surface exhibits a lower work function than the pure metal, and is capable of supporting high laser intensity for a long time. For these reasons it seems possible to consider the ion‐implantation technique as a suitable new method to significantly improve the Photoelectric performances of usual metals, under high laser intensity illuminations.
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Inversion of femtosecond single- and two-photon Photoelectric Emission sensitivities of tungsten
Journal of Physics D: Applied Physics, 1995Co-Authors: J. P. Girardeau-montaut, C. Girardeau‐montaut, S. D. MoustaïzisAbstract:We report the first measurements of two-photon Photoelectric Emission sensitivity of tungsten at 496 nm, using a p-polarized laser beam of 450 fs pulse duration under incidence angle theta =83 degrees . The beam was produced by an XeCl excimer pumped dye laser, with energy up to 45 mu J. As for gold, nonlinear growth of Photoelectric efficiency versus incident laser intensity is observed in the range 12-18 GW cm-2. Inversion of single- and two-photon sensitivities is also clearly demonstrated for laser peak intensity higher than 15 GW cm-2. Such effects are typical of subpicosecond metal behaviour and improve significantly the Photoelectric performances of metallic photocathodes.
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Femtosecond nonlinear single-photon Photoelectric Emission from tungsten at 248 nm
Journal of Physics D: Applied Physics, 1994Co-Authors: J. P. Girardeau-montaut, C. Girardeau‐montaut, S. D. MoustaïzisAbstract:The sensitivity of Photoelectric Emission of polycrystalline tungsten, produced by 248 nm laser pulses with 450 fs duration, has been measured. A nonlinear increase of photoEmission efficiency, as a function of laser peak intensity, was observed, which confirms earlier observations with gold. This nonlinear behaviour is a direct consequence of non-equilibrium between electron gas and lattice temperatures produced at the surface by the sub-picosecond laser pulses. The nonlinear multiphoton photoEmission order k was measured and shown to depend only on the laser intensity absorbed by the tungsten surface.
Mark A. Kasevich - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast Time-Resolved Photoelectric Emission.
Physical review letters, 2015Co-Authors: Thomas Juffmann, Brannon B. Klopfer, Gunnar E. Skulason, Catherine Kealhofer, Fan Xiao, Seth M. Foreman, Mark A. KasevichAbstract:The Emission times of laser-triggered electrons from a sharp tungsten tip are directly characterized under ultrafast, near-infrared laser excitation at Keldysh parameters of 6.6
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ultrafast time resolved Photoelectric Emission
Physical Review Letters, 2015Co-Authors: Thomas Juffmann, Brannon B. Klopfer, Gunnar E. Skulason, Catherine Kealhofer, Fan Xiao, Seth M. Foreman, Mark A. KasevichAbstract:The Emission times of laser-triggered electrons from a sharp tungsten tip are directly characterized under ultrafast, near-infrared laser excitation at Keldysh parameters of 6.6<γ<19.1. Emission delays up to 10 fs are observed, which are inferred from the energy gain of photoelectrons emitted into a synchronously driven microwave cavity. Few femtosecond timing resolution is achieved in a configuration capable of measuring timing shifts up to 55 ps. The technique can also be used to measure the microwave phase inside the cavity with a precision below 70 fs upon the energy resolved detection of a single electron.
C. Girardeau‐montaut - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of Photoelectric Emission sensitivity of tungsten by potassium ion implantation
Applied Physics Letters, 1995Co-Authors: J. P. Girardeau-montaut, M. Afif, C. Girardeau‐montaut, Alain Perez, S. D. MoustaïzisAbstract:Measurements of single‐photon Photoelectric Emission sensitivity of ion implanted polycrystalline tungsten surface by 3×1016 K+ ions/cm2 are reported. They are compared to the data previously obtained for pure tungsten tested under the same conditions. The enhancement of the Photoelectric sensitivity up to a factor of 50 was measured as a consequence of the change in the electronic properties of the tungsten surface, induced by the implanted alkali metal ions. Compared with other techniques used to reduce the work function of pure tungsten, the implanted surface exhibits a lower work function than the pure metal, and is capable of supporting high laser intensity for a long time. For these reasons it seems possible to consider the ion‐implantation technique as a suitable new method to significantly improve the Photoelectric performances of usual metals, under high laser intensity illuminations.
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Inversion of femtosecond single- and two-photon Photoelectric Emission sensitivities of tungsten
Journal of Physics D: Applied Physics, 1995Co-Authors: J. P. Girardeau-montaut, C. Girardeau‐montaut, S. D. MoustaïzisAbstract:We report the first measurements of two-photon Photoelectric Emission sensitivity of tungsten at 496 nm, using a p-polarized laser beam of 450 fs pulse duration under incidence angle theta =83 degrees . The beam was produced by an XeCl excimer pumped dye laser, with energy up to 45 mu J. As for gold, nonlinear growth of Photoelectric efficiency versus incident laser intensity is observed in the range 12-18 GW cm-2. Inversion of single- and two-photon sensitivities is also clearly demonstrated for laser peak intensity higher than 15 GW cm-2. Such effects are typical of subpicosecond metal behaviour and improve significantly the Photoelectric performances of metallic photocathodes.
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Femtosecond nonlinear single-photon Photoelectric Emission from tungsten at 248 nm
Journal of Physics D: Applied Physics, 1994Co-Authors: J. P. Girardeau-montaut, C. Girardeau‐montaut, S. D. MoustaïzisAbstract:The sensitivity of Photoelectric Emission of polycrystalline tungsten, produced by 248 nm laser pulses with 450 fs duration, has been measured. A nonlinear increase of photoEmission efficiency, as a function of laser peak intensity, was observed, which confirms earlier observations with gold. This nonlinear behaviour is a direct consequence of non-equilibrium between electron gas and lattice temperatures produced at the surface by the sub-picosecond laser pulses. The nonlinear multiphoton photoEmission order k was measured and shown to depend only on the laser intensity absorbed by the tungsten surface.
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High current density produced by femtosecond nonlinear single‐photon Photoelectric Emission from gold
Applied Physics Letters, 1993Co-Authors: J. P. Girardeau-montaut, S. D. Moustaïzis, C. Girardeau‐montaut, Costas FotakisAbstract:The sensitivity of single‐photon Photoelectric Emission of pure‐polycrystalline Au induced by a KrF excimer laser emitting at 248 nm pulses of 450 fs duration, has been measured. A nonlinear increase of Photoelectric efficiency as a function of the laser peak intensity has been observed. The threshold of this nonlinearity is estimated from the experimental data to be slightly less than 0.1 GW/cm2. This value is in good agreement with earlier observations for W and Zr. We demonstrate that this is the direct consequence of nonequilibrium electron and lattice temperatures produced at the surface by the subpicosecond laser pulses.
Thomas Juffmann - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast Time-Resolved Photoelectric Emission.
Physical review letters, 2015Co-Authors: Thomas Juffmann, Brannon B. Klopfer, Gunnar E. Skulason, Catherine Kealhofer, Fan Xiao, Seth M. Foreman, Mark A. KasevichAbstract:The Emission times of laser-triggered electrons from a sharp tungsten tip are directly characterized under ultrafast, near-infrared laser excitation at Keldysh parameters of 6.6
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ultrafast time resolved Photoelectric Emission
Physical Review Letters, 2015Co-Authors: Thomas Juffmann, Brannon B. Klopfer, Gunnar E. Skulason, Catherine Kealhofer, Fan Xiao, Seth M. Foreman, Mark A. KasevichAbstract:The Emission times of laser-triggered electrons from a sharp tungsten tip are directly characterized under ultrafast, near-infrared laser excitation at Keldysh parameters of 6.6<γ<19.1. Emission delays up to 10 fs are observed, which are inferred from the energy gain of photoelectrons emitted into a synchronously driven microwave cavity. Few femtosecond timing resolution is achieved in a configuration capable of measuring timing shifts up to 55 ps. The technique can also be used to measure the microwave phase inside the cavity with a precision below 70 fs upon the energy resolved detection of a single electron.