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Sample records for attosecond electron pulses

  1. Dispersion compensation for attosecond electron pulses

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Peter; Baumgarten, Cory; Batelaan, Herman; Centurion, Martin [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States)

    2012-08-20

    We propose a device to compensate for the dispersion of attosecond electron pulses. The device uses only static electric and magnetic fields and therefore does not require synchronization to the pulsed electron source. Analogous to the well-known optical dispersion compensator, an electron dispersion compensator separates paths by energy in space. Magnetic fields are used as the dispersing element, while a Wien filter is used for compensation of the electron arrival times. We analyze a device with a size of centimeters, which can be applied to ultrafast electron diffraction and microscopy, and fundamental studies.

  2. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses

    OpenAIRE

    Calegari, F; Ayuso, D.; A. Trabattoni; L. Belshaw; De Camillis, S.; Anumula, S.; Frassetto, F.; Poletto, L.; Palacios, A.; Decleva, P.; Greenwood, J. B.; Martin, F; Nisoli, M.

    2014-01-01

    In the last decade attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules and solids. Here we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine, and the subsequent detection of ultrafast dynamics on a sub-4.5-fs temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules repr...

  3. Use of Electron Correlation to Make Attosecond Measurements without Attosecond Pulses

    International Nuclear Information System (INIS)

    We describe how correlations between electrons can be used to trace the dynamics of correlated two-electron ionization with attosecond precision, without using attosecond pulses. The approach is illustrated using the example of Auger or Coster-Kronig decay triggered by photoionization with an extreme ultraviolet pulse. It requires correlated measurements of angle-resolved energy spectra of both the photo- and Auger electrons in the presence of a laser pulse. To reconstruct the dynamics, we use not only classical time and energy correlation, but also entanglement between the two electrons

  4. Reflected attosecond pulse radiation from moving electron layers

    CERN Document Server

    Cherednychek, Mykyta

    2015-01-01

    With the generation of high order harmonics (HHG) on the plasma surface it is possible to turn the laser pulse into a train of attosecond or even zeptosecond pulses in the back radiation. These attosecond pulses may have amplitude several orders of magnitude larger than that of the laser pulse under appropriate conditions. We study this process in detail, especially the nanobunching of the plasma electron density. We derive the analytical expression that describes the electron density profile and obtain a good agreement with particle-in-cell simulations. We investigate the most efficient case of HHG at moderate laser intensity (a0 = 10) on the over dense plasma slab with an exponential profile per-plasma. Subsequently we calculate the spectra of single attosecond pulses from back radiation using our expression for density shape in combination with the equation for spectrum of nanobunch radiation.

  5. Toward attosecond electron pulses using ultra-intense lasers

    Science.gov (United States)

    Varin, Charles; Fortin, Pierre-Louis; Piché, Michel

    2008-06-01

    In many countries around the world, ultra-intense laser facilities are being built. These state-of-the-art lasers are intended for innovative medical and technological applications, as well as for basic experiments at the frontiers of fundamental science. Laser particle acceleration is a promising new endeavor. Recently developed schemes using radially polarized beams could help in reaching unprecedentedly short electron pulse durations, well in the attosecond range and potentially in the subattosecond range.

  6. Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

    International Nuclear Information System (INIS)

    We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.

  7. Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

    Energy Technology Data Exchange (ETDEWEB)

    Mikkelsen, A.; Schwenke, J.; Fordell, T.; Luo, G.; Kluender, K.; Hilner, E.; Anttu, N.; Lundgren, E.; Mauritsson, J.; Andersen, J. N.; Xu, H. Q.; L' Huillier, A. [Department of Physics, Lund University, Box 118, 22100 Lund (Sweden); Zakharov, A. A. [MAX-lab, Lund University, Box 118, 22100 Lund (Sweden)

    2009-12-15

    We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.

  8. Relativistic attosecond electron pulses from cascaded acceleration using ultra-intense radially polarized laser beams

    Science.gov (United States)

    Varin, Charles; Fortin, Pierre-Louis; Piché, Michel

    Attosecond electron pulses with peak energy above 200 MeV could be produced with ultrafast 100-TW radially polarized laser beams in a two-stage configuration. Such electron beams would be collimated and potentially quasi-monoenergetic.

  9. Testing electron correlation in Helium using attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Camilo [Centro de Laseres Pulsados (CLPU), Plaza de la Merced s/n, Salamanca 37008 (Spain)

    2011-07-01

    Using a full quantum model beyond the one dimensional model, we are able to study the double correlated double ionization of Helium in several regimes. For example in the near IR, we have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a {lambda}=800 nm laser, with intensity I=4.5 x 10{sup 14} W/cm{sup 2}. We observe a finger-like structure in the correlated electron momentum distribution that can be interpreted as a signature of the microscopic dynamics in the recollision process. To study related process such as the excitation by recollision we make use of attosecond pulses to probe the dynamics of ionization. In this paper we introduce this novel technique to study the interaction that could lead increase the accuracy of the description of the correlated processes.

  10. Testing electron correlation in Helium using attosecond pulses

    International Nuclear Information System (INIS)

    Using a full quantum model beyond the one dimensional model, we are able to study the double correlated double ionization of Helium in several regimes. For example in the near IR, we have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a λ=800 nm laser, with intensity I=4.5 x 1014 W/cm2. We observe a finger-like structure in the correlated electron momentum distribution that can be interpreted as a signature of the microscopic dynamics in the recollision process. To study related process such as the excitation by recollision we make use of attosecond pulses to probe the dynamics of ionization. In this paper we introduce this novel technique to study the interaction that could lead increase the accuracy of the description of the correlated processes.

  11. Ramsey method for Auger-electron interference induced by an attosecond twin pulse

    OpenAIRE

    Buth, Christian; Schafer, Kenneth J.

    2010-01-01

    We examine the archetype of an interference experiment for Auger electrons: two electron wave packets are launched by inner-shell ionizing a krypton atom using two attosecond light pulses with a variable time delay. This setting is an attosecond realization of the Ramsey method of separated oscillatory fields. Interference of the two ejected Auger-electron wave packets is predicted, indicating that the coherence between the two pulses is passed to the Auger electrons. For the detection of the...

  12. Attosecond electron pulses from interference of above-threshold de Broglie waves

    CERN Document Server

    Varro, Sandor

    2007-01-01

    It is shown that the the interference of above-threshold electron de Broglie waves, generated by an intense laser pulse at a metal surface yields attosecond electron pulses. This inerference is an analogon of the superposition of high harmonics generated from rare gas atoms, resulting in trains of attosecond light pulses.Owing to the inherent kinematic dispersion, the propagation of attosecond de Broglie waves in vacuum is very different from that of attosecond light pulses, which propagate without changing shape. Above the metal surface there are "collaps bands" and "revival layers" of the electron current even at macroscopic distances. In the range of parameters considered, the maximum value of the current densities of such ultrashort electron pulses has been estimated to be of order of couple of tenths of milliamps per square centimeters.

  13. Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions

    International Nuclear Information System (INIS)

    We analyze carrier-envelope phase (CEP) effects on electron wave-packet momentum and energy spectra produced by one or two few-cycle attosecond xuv pulses. The few-cycle attosecond pulses are assumed to have arbitrary phases. We predict CEP effects on ionized electron wave-packet momentum distributions produced by attosecond pulses having durations comparable to those obtained by Sansone et al. [Science 314, 443 (2006)]. The onset of significant CEP effects is predicted to occur for attosecond pulse field strengths close to those possible with current experimental capabilities. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schroedinger equation including atomic potentials appropriate for the H and He atoms

  14. High harmonic attosecond pulse train amplification in a free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    McNeil, B.W.; Sheehy, B.; Thompson, N.R.; Dunning, D.J.

    2011-03-04

    It is shown using three-dimensional simulations that the temporal structure of an attosecond pulse train, such as that generated via high harmonic generation in noble gases, may be retained in a free electron laser amplifier through to saturation using a mode-locked optical klystron configuration. At wavelengths of {approx}12 nm, a train of attosecond pulses of widths {approx}300 as with peak powers in excess of 1 GW are predicted.

  15. High harmonic attosecond pulse train amplification in a free electron laser

    International Nuclear Information System (INIS)

    It is shown using three-dimensional simulations that the temporal structure of an attosecond pulse train, such as that generated via high harmonic generation in noble gases, may be retained in a free electron laser amplifier through to saturation using a mode-locked optical klystron configuration. At wavelengths of ∼12 nm, a train of attosecond pulses of widths ∼300 as with peak powers in excess of 1 GW are predicted.

  16. Optical attosecond pulses and tracking the nonlinear response of bound electrons

    Science.gov (United States)

    Hassan, M. Th.; Luu, T. T.; Moulet, A.; Raskazovskaya, O.; Zhokhov, P.; Garg, M.; Karpowicz, N.; Zheltikov, A. M.; Pervak, V.; Krausz, F.; Goulielmakis, E.

    2016-02-01

    The time it takes a bound electron to respond to the electromagnetic force of light sets a fundamental speed limit on the dynamic control of matter and electromagnetic signal processing. Time-integrated measurements of the nonlinear refractive index of matter indicate that the nonlinear response of bound electrons to optical fields is not instantaneous; however, a complete spectral characterization of the nonlinear susceptibility tensors—which is essential to deduce the temporal response of a medium to arbitrary driving forces using spectral measurements—has not yet been achieved. With the establishment of attosecond chronoscopy, the impulsive response of positive-energy electrons to electromagnetic fields has been explored through ionization of atoms and solids by an extreme-ultraviolet attosecond pulse or by strong near-infrared fields. However, none of the attosecond studies carried out so far have provided direct access to the nonlinear response of bound electrons. Here we demonstrate that intense optical attosecond pulses synthesized in the visible and nearby spectral ranges allow sub-femtosecond control and metrology of bound-electron dynamics. Vacuum ultraviolet spectra emanating from krypton atoms, exposed to intense waveform-controlled optical attosecond pulses, reveal a finite nonlinear response time of bound electrons of up to 115 attoseconds, which is sensitive to and controllable by the super-octave optical field. Our study could enable new spectroscopies of bound electrons in atomic, molecular or lattice potentials of solids, as well as light-based electronics operating on sub-femtosecond timescales and at petahertz rates.

  17. Feasibility analysis for attosecond X-ray pulses at FERMI and ELETTRA free electron laser

    International Nuclear Information System (INIS)

    We present preliminary analysis for the feasibility of the attosecond x-ray pulses at a proposed FERMI and ELETTRA free electron laser (FEL) [1]. In part 1 we restrict ourselves to minimal modifications to the proposed FEL and consider a scheme for attosecond x-ray production which can be qualified as a small add-on to a primary facility. We demonstrate that at 5-nm wavelength our scheme is capable for production of pulses with an approximate duration of 100 attoseconds at approximately 2 MW peak power and with an absolute temporal synchronization to a pump laser pulse. In part 2 we propose to use an FEL amplifier seeded by a VUV signal and to follow it by the scheme for attosecond x-ray production described in part 1

  18. Towards attosecond XUV pulses

    International Nuclear Information System (INIS)

    We are constructing a system for attosecond pulse generation via high-order harmonics generation in noble gases. To obtain a single attosecond pulse rather than a pulse train, we employ the regime of a few-cycle-pulse-driven harmonics generation. To achieve it, we are developing an external pulse compressor down to 7 - 10 fs using a gas-filled hollow fiber followed by chirped mirrors. We also proposed the method of high-energy attosecond pulse generation using high-order harmonics generated during the interaction of a relativistic-irradiance laser pulse with a thin foil. (author)

  19. New method for attosecond-terawatt pulse generation in X-ray free electron laser

    International Nuclear Information System (INIS)

    We propose a novel scheme for generating a terawatt-attosecond pulse from X-ray free-electron laser (XFEL), which is perfectly synchronized to the few cycle IR pulse. Our approach utilizes baseline configuration similar to PAL-XFEL, but adds a current enhanced self-amplified emission (ESASE) module inserted between the linac and the undulater that introduces only a few cycle energy and current modulation in the electron beam. Our scheme is compact and easy to implement and does not require a slotted foil, thereby leading to improved longitudinal coherence of the beam. We demonstrate the viability of our scheme with simulations using PAL-XFEL beam parameters. Attosecond science has emerged as an important research area of ultrafast phenomena during the past decade as it provides a direct access to capturing, measuring and controlling the electronic dynamics in atoms, molecules and condensed matters. However, high-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments spectroscopy are still lacking. Therefore, techniques are to be further developed to make a powerful isolated attosecond pulse in the x-ray range (1 keV and higher). Several techniques have been proposed to achieve attosecond pulses in a free electron laser (FEL). In this vein, we demonstrate in simulation a TW-attosecond pulse in FEL. In our scheme, it utilizes a laser-induced energy modulation to generate a few-cycle current modulation and small optical-delays between undulator modules for radiation alignment. In this work, we are able to show that an isolated 280 attosecond FWHM, 1 TW pulse at 1 keV (1.25 nm) photon energy and an 100 attosecond FWHM, 1 TW pulse at 12.4 keV (0.1 mn) can be generated. This scheme is simple and easy to implement and can be adapted to the existing FEL facilities. It is worthwhile to mention that in this scheme there is still a room for higher power even for shorter undulator lengths via tapering of the undulator or high

  20. Generation of subterawatt-attosecond pulses in a soft x-ray free-electron laser

    Science.gov (United States)

    Huang, Senlin; Ding, Yuantao; Huang, Zhirong; Marcus, Gabriel

    2016-08-01

    We propose a novel scheme to generate attosecond soft x rays in a self-seeded free-electron laser (FEL) suitable for enabling attosecond spectroscopic investigations. A time-energy chirped electron bunch with additional sinusoidal energy modulation is adopted to produce a short seed pulse through a self-seeding monochromator. This short seed pulse, together with high electron current spikes and a cascaded delay setup, enables a high-efficiency FEL with a fresh bunch scheme. Simulations show that using the Linac Coherent Light Source (LCLS) parameters, soft x-ray pulses with a FWHM of 260 attoseconds and a peak power of 0.5 TW can be obtained. This scheme also has the feature of providing a stable central wavelength determined by the self-seeding monochromator.

  1. Strong Field Acceleration of Attosecond Electron Pulses emitted by a Sharp Metallic Nanoprobe

    Directory of Open Access Journals (Sweden)

    Piglosiewicz B.

    2013-03-01

    Full Text Available We report on the observation of strong near-field acceleration of attosecond electron pulses emitted from a sharp nanometer-sized gold tip. Kinetic energy spectra extending over tens of eV and varying qualitatively with laser wavelength and intensity are explained in terms of the spatiotemporal electron dynamics in the strong field gradient at the tip apex.

  2. Obtaining attosecond X-ray pulses using a self-amplified spontaneous emission free electron laser

    International Nuclear Information System (INIS)

    We describe a technique for the generation of a solitary attosecond X-ray pulse in a free electron laser (FEL), via a process of self-amplified spontaneous emission. In this method, electrons experience an energy modulation upon interacting with laser pulses having a duration of a few cycles within single-period wiggler magnets. Two consecutive modulation sections, followed by compression in a dispersive section, are used to obtain a single, sub-femtosecond spike in the electron peak current. This region of the electron beam experiences an enhanced growth rate for FEL amplification. After propagation through a long undulator,this current spike emits a ∼250 attosecond X-ray pulse whose intensity dominates the X-ray emission from the rest of the electron bunch

  3. Tracing and controlling electronic dynamics in atoms and molecules by attosecond pulses

    International Nuclear Information System (INIS)

    In this review, we will focus on the theoretical aspects in observing and controlling the electronic dynamics in few-electron atoms and molecules by attosecond pulses in different circumstances. In particular, we will first review the main theoretical methods and concepts in strong field and attosecond physics, and then discuss a number of topics including generation of xuv light sources, the probe and steering of the electron motion in the combination of xuv and IR pulses, the photoionization time delay, the electron–electron correlation dynamics in multiple-electron atoms and molecules, etc. Although the present review mainly concentrates on the theoretical aspects, in each section we will also give a brief account of the related experimental implications and implementations for those which have been demonstrated so far or which will be experimentally feasible in the near future

  4. Tracing and controlling electronic dynamics in atoms and molecules by attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Liang-You, E-mail: liangyou.peng@pku.edu.cn [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Jiang, Wei-Chao; Geng, Ji-Wei; Xiong, Wei-Hao [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Gong, Qihuang, E-mail: qhgong@pku.edu.cn [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2015-04-18

    In this review, we will focus on the theoretical aspects in observing and controlling the electronic dynamics in few-electron atoms and molecules by attosecond pulses in different circumstances. In particular, we will first review the main theoretical methods and concepts in strong field and attosecond physics, and then discuss a number of topics including generation of xuv light sources, the probe and steering of the electron motion in the combination of xuv and IR pulses, the photoionization time delay, the electron–electron correlation dynamics in multiple-electron atoms and molecules, etc. Although the present review mainly concentrates on the theoretical aspects, in each section we will also give a brief account of the related experimental implications and implementations for those which have been demonstrated so far or which will be experimentally feasible in the near future.

  5. Exploring intense attosecond pulses

    Science.gov (United States)

    Charalambidis, D.; Tzallas, P.; Benis, E. P.; Skantzakis, E.; Maravelias, G.; Nikolopoulos, L. A. A.; Peralta Conde, A.; Tsakiris, G. D.

    2008-02-01

    After introducing the importance of non-linear processes in the extreme-ultra-violet (XUV) spectral regime to the attosecond (asec) pulse metrology and time domain applications, we present two successfully implemented techniques with excellent prospects in generating intense asec pulse trains and isolated asec pulses, respectively. For the generation of pulse trains two-color harmonic generation is exploited. The interferometric polarization gating technique appropriate for the generation of intense isolated asec pulses is discussed and compared to other relevant approaches.

  6. Generation of intense attosecond x-ray pulses using ultraviolet laser induced microbunching in electron beams

    Science.gov (United States)

    Xiang, D.; Huang, Z.; Stupakov, G.

    2009-06-01

    We propose a scheme that combines the echo-enabled harmonic generation technique with the bunch compression and allows one to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of an ultraviolet seed laser. A few-cycle intense laser is used to generate the required energy chirp in the beam for bunch compression and for selection of an attosecond x-ray pulse. Sending this beam through a short undulator results in an intense isolated attosecond x-ray pulse. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power of a few hundred MW and duration as short as 20 attoseconds (FWHM) can be generated from a 200 nm ultraviolet seed laser. The proposed scheme may enable the study of electronic dynamics with a resolution beyond the atomic unit of time (˜24 attoseconds) and may open a new regime of ultrafast sciences.

  7. Generation of Intense Attosecond X-Ray Pulses Using Ultraviolet Laser Induced Microbunching in Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.; Huang, Z.; Stupakov, G.; /SLAC

    2011-11-29

    We propose a scheme that combines the echo-enabled harmonic generation technique with the bunch compression and allows one to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of an ultraviolet seed laser. A few-cycle intense laser is used to generate the required energy chirp in the beam for bunch compression and for selection of an attosecond x-ray pulse. Sending this beam through a short undulator results in an intense isolated attosecond x-ray pulse. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power of a few hundred MW and duration as short as 20 attoseconds (FWHM) can be generated from a 200 nm ultraviolet seed laser. The proposed scheme may enable the study of electronic dynamics with a resolution beyond the atomic unit of time ({approx}24 attoseconds) and may open a new regime of ultrafast sciences.

  8. Signatures of attosecond electron tunneling dynamics in the evolution of intense few-cycle light pulses

    Science.gov (United States)

    Serebryannikov, E. E.; Verhoef, A. J.; Mitrofanov, A.; Baltuška, A.; Zheltikov, A. M.

    2009-11-01

    The sensitivity of electron tunneling to the phase of an ionizing light field is shown to manifest itself in detectable features in the spectral and temporal evolution of intense few-cycle light pulses in an ionizing medium. An ultrafast buildup of electron density in the regime of tunneling ionization gives rise to a modulation of a few-cycle field wave form and enhances the short-wavelength part of its spectrum. In a low-pressure gas, the signatures of electron tunneling in the evolution of few-cycle pulses can be isolated from the effects related to atomic nonlinear susceptibilities, giving an access to attosecond electron tunneling dynamics.

  9. Few-cycle attosecond pulse chirp effects on asymmetries in ionized electron momentum distributions

    International Nuclear Information System (INIS)

    The momentum distributions of electrons ionized from H atoms by chirped few-cycle attosecond pulses are investigated by numerically solving the time-dependent Schroedinger equation. The central carrier frequency of the pulse is chosen to be 25 eV, which is well above the ionization threshold. The asymmetry (or difference) in the yield of electrons ionized along and opposite to the direction of linear laser polarization is found to be very sensitive to the pulse chirp (for pulses with fixed carrier-envelope phase), both for a fixed electron energy and for the energy-integrated yield. In particular, the larger the pulse chirp, the larger the number of times the asymmetry changes sign as a function of ionized electron energy. For a fixed chirp, the ionized electron asymmetry is found to be sensitive also to the carrier-envelope phase of the few-cycle pulse.

  10. Electron dynamics triggered by double attosecond pulses: Simulations based on time-dependent density functional theory

    International Nuclear Information System (INIS)

    In order to observe the high-field effect, the external laser field must reach its peak intensity before the electron ionization. To this end, it is important to reduce pulse duration to typical attosecond timescale. In this paper, the interaction electron dynamics between attosecond pulses and dielectric is investigated within the time-dependent density functional theory. Taking the CaF2 crystal as an example, we give a comparison of electron dynamics response between single and double pulses. Moreover, the nonlinear energy absorption and electron excitation processes are simulated by adjusting the polarization direction of the sub-pulse. Present results demonstrate that the double pulses show lower electron excitation and energy absorption than the single pulse, which is in accordance with experimental higher ablation threshold and smaller heat-affected zones of the double pulses. In addition, the curves of final excited electron number and energy absorption exhibit the quasi-symmetry about the axis of 180°, which has not been reported yet.

  11. Electron dynamics triggered by double attosecond pulses: Simulations based on time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Yalong [School of Physics, Key Laboratory of Cluster Science of Ministry of Education, Beijing Institute of Technology, Beijing 100081 (China); Wang, Feng, E-mail: wangfeng01@tsinghua.org.cn [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Hong, Xuhai; Su, Wenyong [School of Physics, Key Laboratory of Cluster Science of Ministry of Education, Beijing Institute of Technology, Beijing 100081 (China); Zhang, Zhen [School of Software, Beijing Institute of Technology, Beijing 100081 (China)

    2014-01-10

    In order to observe the high-field effect, the external laser field must reach its peak intensity before the electron ionization. To this end, it is important to reduce pulse duration to typical attosecond timescale. In this paper, the interaction electron dynamics between attosecond pulses and dielectric is investigated within the time-dependent density functional theory. Taking the CaF{sub 2} crystal as an example, we give a comparison of electron dynamics response between single and double pulses. Moreover, the nonlinear energy absorption and electron excitation processes are simulated by adjusting the polarization direction of the sub-pulse. Present results demonstrate that the double pulses show lower electron excitation and energy absorption than the single pulse, which is in accordance with experimental higher ablation threshold and smaller heat-affected zones of the double pulses. In addition, the curves of final excited electron number and energy absorption exhibit the quasi-symmetry about the axis of 180°, which has not been reported yet.

  12. SASE FEL with energy-chirped electron beam and its application for generation of attosecond pulses

    International Nuclear Information System (INIS)

    Influence of a linear energy chirp in the electron beam on a SASE FEL operation is studied analytically and numerically using 1-D model. Explicit expressions for Green's functions and for output power of a SASE FEL are obtained for high-gain linear regime in the limits of small and large energy chirp parameter. Saturation length and power versus energy chirp parameter are calculated numerically. It is shown that the effect of linear energy chirp on FEL gain is equivalent to the linear undulator tapering (or linear energy variation along the undulator). A consequence of this fact is a possibility to perfectly compensate FEL gain degradation, caused by the energy chirp, by means of the undulator tapering independently of the value of the energy chirp parameter. An application of this effect for generation of attosecond pulses from a hard X-ray FEL is proposed. Strong energy modulation within a short slice of an electron bunch is produced by few-cycle optical laser pulse in a short undulator, placed in front of the main undulator. Gain degradation within this slice is compensated by an appropriate undulator taper while the rest of the bunch suffers from this taper and does not lase. Three-dimensional simulations predict that short (200 attoseconds) high-power (up to 100 GW) pulses can be produced in Angstroem wavelength range with a high degree of contrast. A possibility to reduce pulse duration to sub-100 attosecond scale is discussed. (Orig.)

  13. Probing Electron Correlation via Attosecond xuv Pulses in the Two-Photon Double Ionization of Helium

    International Nuclear Information System (INIS)

    Recent experimental developments of high-intensity, short-pulse extreme ultraviolet light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations to investigate the so-called 'sequential' regime ((ℎ/2π)ω>54.4 eV) in the two-photon double ionization of helium. We show that attosecond pulses allow us not only to probe but also to induce angular and energy correlations of the emitted electrons. The final momentum distribution reveals regions dominated by the Wannier ridge breakup scenario and by postcollision interaction.

  14. Secondary electron imaging of nanostructures using Extreme Ultra-Violet attosecond pulse trains and Infra-Red femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Maarsell, Erik; Arnold, Cord L.; Lorek, Eleonora; Guenot, Diego; Fordell, Thomas; Miranda, Miguel; Mauritsson, Johan; Xu, Hongxing; L' Huillier, Anne; Mikkelsen, Anders [Department of Physics, Lund University, Box 118, 221 00 Lund (Sweden)

    2013-02-15

    Surface electron dynamics unfold at time and length scales down to attoseconds and nanometres, making direct imaging with extreme spatiotemporal resolution highly desirable. However, this has turned out to be a major challenge even with the advent of reliable attosecond light sources. In this paper, photoelectrons from Ag nanowires and nanoparticles excited by extreme ultraviolet (XUV) attosecond pulse trains and infrared femtosecond pulses using a PhotoEmission Electron Microscope (PEEM) are imaged. In addition, the samples were investigated using Scanning Electron Microscopy (SEM) and synchrotron based X-ray photoelectron spectroscopy (XPS). To achieve contrast between the nanostructures and the substrate in the XUV images, three different substrate materials were investigated: Cr, ITO and Au. While plasmonic field enhancement can be observed on all three substrates, only on Au substrates do the Ag nanowires appear significantly brighter than the substrate in XUV-PEEM imaging. 3-photon photoemission imaging of plasmonic hot-spots was performed where the autocorrelation trace is observed in the interference signal between two femtosecond Infra-Red (IR) beams with sub-cycle precision. Finally, using Monte Carlo simulations, it is shown how the secondary electrons imaged in the XUV PEEM can potentially reveal information on the attosecond time scale from the near surface region of the nanostructures. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Combining attosecond XUV pulses with coincidence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sabbar, M., E-mail: msabbar@phys.ethz.ch; Heuser, S.; Boge, R.; Lucchini, M.; Cirelli, C.; Keller, U. [Department of Physics, ETH Zurich, 8093 Zurich (Switzerland); Gallmann, L. [Department of Physics, ETH Zurich, 8093 Zurich (Switzerland); Institute of Applied Physics, University of Bern, 3012 Bern (Switzerland)

    2014-10-15

    Here we present a successful combination of an attosecond beamline with a COLTRIMS apparatus, which we refer to as AttoCOLTRIMS. The setup provides either single attosecond pulses or attosecond pulse trains for extreme ultraviolet-infrared pump-probe experiments. We achieve full attosecond stability by using an active interferometer stabilization. The capability of the setup is demonstrated by means of two measurements, which lie at the heart of the COLTRIMS detector: firstly, we resolve the rotating electric field vector of an elliptically polarized few-cycle infrared laser field by attosecond streaking exploiting the access to the 3D momentum space of the charged particles. Secondly, we show streaking measurements on different atomic species obtained simultaneously in a single measurement making use of the advantage of measuring ions and electrons in coincidence. Both of these studies demonstrate the potential of the AttoCOLTRIMS for attosecond science.

  16. Ionization of atoms by chirped attosecond pulses

    International Nuclear Information System (INIS)

    We investigate the ionization dynamics of atoms by chirped attosecond pulses using the strong field approximation method. The pulse parameters are carefully chosen in the regime where the strong field approximation method is valid. We analyse the effects of the chirp of attosecond pulses on the energy distributions and the corresponding left-right asymmetry of the ionized electrons. For a single chirped attosecond pulse, the ionized electrons can be redistributed and the left-right asymmetry shows oscillations because of the introduction of the chirp. For time-delayed double attosecond pulses at different intensities with the weaker one chirped, exchanging the order of the two pulses shows a relative shift of the energy spectra, which can be explained by the different effective time delays of different frequency components because of the chirp. (atomic and molecular physics)

  17. Ab initio calculations of two-electron emission by attosecond pulses

    International Nuclear Information System (INIS)

    Recent experimental developments of high-intensity, short-pulse XUV light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations to investigate the so-called 'sequential' regime (hω > 54.4 eV) in the two-photon double ionization of helium. We show that attosecond pulses allow to not only probe but also to induce angular and energy correlations of the emitted electrons. Electron correlation induced by the time correlation between emission events manifests itself in the angular distribution of the ejected electrons. The final momentum distribution reveals regions dominated by the Wannier ridge break-up scenario and by post-collision interaction. In addition, we find evidence for an interference between direct (nonsequential) and indirect (sequential) double photo-ionization with intermediate shake-up states, the strength of which is controlled by the pulse duration.

  18. Simple Method to Generate Terawatt-Attosecond X-Ray Free-Electron-Laser Pulses.

    Science.gov (United States)

    Prat, Eduard; Reiche, Sven

    2015-06-19

    X-ray free-electron lasers (XFELs) are cutting-edge research tools that produce almost fully coherent radiation with high power and short-pulse length with applications in multiple science fields. There is a strong demand to achieve even shorter pulses and higher radiation powers than the ones obtained at state-of-the-art XFEL facilities. In this context we propose a novel method to generate terawatt-attosecond XFEL pulses, where an XFEL pulse is pushed through several short good-beam regions of the electron bunch. In addition to the elements of conventional XFEL facilities, the method uses only a multiple-slotted foil and small electron delays between undulator sections. Our scheme is thus simple, compact, and easy to implement both in already operating as well as future XFEL projects. We present numerical simulations that confirm the feasibility and validity of our proposal. PMID:26196979

  19. Attosecond intramolecular electron dynamics

    Directory of Open Access Journals (Sweden)

    Jaroń-Becker A.

    2013-03-01

    Full Text Available We present results of numerical simulations indicating a complex laser driven electron dynamics inside simple molecular systems on the attosecond time scale. This attosecond electron dynamics influences the instant of ionization of the molecule and the final electron momentum distributions.

  20. Strong-field ionization inducing multi-electron-hole coherence probed by attosecond pulses

    CERN Document Server

    Zhao, Jing; Zhao, Zengxiu

    2015-01-01

    We propose a new scenario to apply IR-pump-XUV-probe schemes to resolving strong field ionization induced and attosecond pulse driven electron-hole dynamics and coherence in real time. The coherent driving of both the infrared laser and the attoscond pulse correlates the dynamics of the core-hole and the valence-hole which leads to the otherwise forbidden absorption and emission of XUV photon. An analytical model is developed based on the strong-field approximation by taking into account of the essential multielectron configurations. The emission spectra from the core-valence transition and the core-hole recombination are found modulating strongly as functions of the time delay between the two pulses, which provides a unique insight into the instantaneous ionization and the interplay of the multi-electron-hole coherence.

  1. Electron correlation in two-photon double ionization of helium from attosecond to FEL pulses

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Lee [Los Alamos National Laboratory

    2009-01-01

    We investigate the role of electron correlation in the two-photon double ionization of helium for ultrashort pulses in the extreme ultraviolet (XUV) regime with durations ranging from a hundred attoseconds to a few femtoseconds. We perform time-dependent ab initio calculations for pulses with mean frequencies in the so-called 'sequential' regime ({Dirac_h}{omega} > 54.4 eV). Electron correlation induced by the time correlation between emission events manifests itself in the angular distribution of the ejected electrons, which strongly depends on the energy sharing between them. We show that for ultrashort pulses two-photon double ionization probabilities scale non-uniformly with pulse duration depending on the energy sharing between the electrons. Most interestingly we find evidence for an interference between direct ('nonsequential') and indirect ('sequential') double photoionization with intermediate shake-up states, the strength of which is controlled by the pulse duration. This observation may provide a route towards measuring the pulse duration of x-ray free-electron laser (XFEL) pulses.

  2. Electron correlation in two-photon double ionization of helium from attosecond to XFEL pulses

    International Nuclear Information System (INIS)

    We investigate the role of electron correlation in the two-photon double ionization of helium for ultrashort pulses in the extreme ultraviolet (XUV) regime with durations ranging from a hundred attoseconds to a few femtoseconds. We perform time-dependent ab initio calculations for pulses with mean frequencies in the so-called 'sequential' regime (ℎω > 54.4 eV). Electron correlation induced by the time correlation between emission events manifests itself in the angular distribution of the ejected electrons, which strongly depends on the energy sharing between them. We show that for ultrashort pulses two-photon double ionization probabilities scale non-uniformly with pulse duration depending on the energy sharing between the electrons. Most interestingly we find evidence for an interference between direct ('nonsequential') and indirect ('sequential') double photoionization with intermediate shake-up states, the strength of which is controlled by the pulse duration. This observation may provide a route towards measuring the pulse duration of x-ray free-electron laser (XFEL) pulses.

  3. Accessing properties of electron wave packets generated by attosecond pulse trains through time-dependent calculations

    International Nuclear Information System (INIS)

    We present a time-dependent method for calculating the energy-dependent atomic dipole phase that an electron acquires when it is ionized by the absorption of a single ultraviolet photon. Our approach exactly mirrors the method used to experimentally characterize a train of attosecond pulses. In both methods the total electron phase is measured (calculated) via a two-photon interference involving the absorption or emission of an additional infrared photon in the continuum. In our calculation we use a perfect (zero spectral phase) light field and so extract the atomic dipole phase directly from the electron wave packet. We calculate the atomic phase for argon, neon, and helium at low infrared intensities and compare them to previous perturbative calculations. At moderate infrared probe intensities, we find that that the dipole phase can still be reliably determined using two-photon interference, even when higher-order processes are non-negligible. We also show that a continuum structure, in this case a Cooper minimum in argon, significantly affects the probability for infrared absorption and emission over a range of energies around the minimum, even at low infrared intensities. We conclude that well-characterized attosecond pulse trains can be used to examine continuum structures in atoms and molecules

  4. Attosecond x-Ray Pulse Generation by Linear Thomson Scattering of Intense Laser Beam with Relativistic Electron

    Institute of Scientific and Technical Information of China (English)

    TIAN You-Wei; YU Wei; LU Pei-Xiang; Vinod Senecha; HE Feng; DENG De-Gang; XU Han

    2006-01-01

    Linear Thomson scattering of a short pulse laser by relativistic electron has been investigated using computer simulations. It is shown that scattering of an intense laser pulse of~33 fs full width at haff maximum, with an electron of γ0 = 10 initial energy, generates an ultrashort, pulsed radiation of 76 attoseconds with a photon wavelength of 2.5 nm in the backward direction. The scattered radiation generated by a highly relativistic electron has superior quality in terms of its pulse width and angular distribution in comparison to the one generated by lower relativistic energy electron.

  5. Attosecond x-Ray Pulse Generation by Linear Thomson Scattering of Intense Laser Beam with Relativistic Electron

    International Nuclear Information System (INIS)

    Linear Thomson scattering of a short pulse laser by relativistic electron has been investigated using computer simulations. It is shown that scattering of an intense laser pulse of ∼33 fs full width at half maximum, with an electron of γ0 = 10 initial energy, generates an ultrashort, pulsed radiation of 76 attoseconds with a photon wavelength of 2.5 nm in the backward direction. The scattered radiation generated by a highly relativistic electron has superior quality in terms of its pulse width and angular distribution in comparison to the one generated by lower relativistic energy electron.

  6. Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions: roles of frequency, intensity and an additional IR pulse

    Science.gov (United States)

    Peng, Liang-You; Pronin, Evgeny A.; Starace, Anthony F.

    2008-02-01

    The effects of the carrier-envelope phase (CEP) of a few-cycle attosecond pulse on ionized electron momentum and energy spectra are analyzed, both with and without an additional few-cycle IR pulse. In the absence of an IR pulse, the CEP-induced asymmetries in the ionized electron momentum distributions are shown to vary as the 3/2 power of the attosecond pulse intensity. These asymmetries are also found to satisfy an approximate scaling law involving the frequency and intensity of the attosecond pulse. In the presence of even a very weak IR pulse (having an intensity of the order of 1011 1012 W cm-2), the attosecond pulse CEP-induced asymmetries in the ionized electron momentum distributions are found to be significantly augmented. In addition, for higher IR laser intensities, we observe for low electron energies peaks separated by the IR photon energy in one electron momentum direction along the laser polarization axis; in the opposite direction, we find structured peaks that are spaced by twice the IR photon energy. Possible physical mechanisms for such asymmetric, low-energy structures in the ionized electron momentum distribution are proposed. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schrödinger equation including atomic potentials appropriate for the H and He atoms.

  7. Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions: roles of frequency, intensity and an additional IR pulse

    Energy Technology Data Exchange (ETDEWEB)

    Peng Liangyou; Pronin, Evgeny A; Starace, Anthony F [Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0111 (United States)], E-mail: astarace1@UNL.edu

    2008-02-15

    The effects of the carrier-envelope phase (CEP) of a few-cycle attosecond pulse on ionized electron momentum and energy spectra are analyzed, both with and without an additional few-cycle IR pulse. In the absence of an IR pulse, the CEP-induced asymmetries in the ionized electron momentum distributions are shown to vary as the 3/2 power of the attosecond pulse intensity. These asymmetries are also found to satisfy an approximate scaling law involving the frequency and intensity of the attosecond pulse. In the presence of even a very weak IR pulse (having an intensity of the order of 10{sup 11}-10{sup 12} W cm{sup -2}), the attosecond pulse CEP-induced asymmetries in the ionized electron momentum distributions are found to be significantly augmented. In addition, for higher IR laser intensities, we observe for low electron energies peaks separated by the IR photon energy in one electron momentum direction along the laser polarization axis; in the opposite direction, we find structured peaks that are spaced by twice the IR photon energy. Possible physical mechanisms for such asymmetric, low-energy structures in the ionized electron momentum distribution are proposed. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schroedinger equation including atomic potentials appropriate for the H and He atoms.

  8. Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions: roles of frequency, intensity and an additional IR pulse

    International Nuclear Information System (INIS)

    The effects of the carrier-envelope phase (CEP) of a few-cycle attosecond pulse on ionized electron momentum and energy spectra are analyzed, both with and without an additional few-cycle IR pulse. In the absence of an IR pulse, the CEP-induced asymmetries in the ionized electron momentum distributions are shown to vary as the 3/2 power of the attosecond pulse intensity. These asymmetries are also found to satisfy an approximate scaling law involving the frequency and intensity of the attosecond pulse. In the presence of even a very weak IR pulse (having an intensity of the order of 1011-1012 W cm-2), the attosecond pulse CEP-induced asymmetries in the ionized electron momentum distributions are found to be significantly augmented. In addition, for higher IR laser intensities, we observe for low electron energies peaks separated by the IR photon energy in one electron momentum direction along the laser polarization axis; in the opposite direction, we find structured peaks that are spaced by twice the IR photon energy. Possible physical mechanisms for such asymmetric, low-energy structures in the ionized electron momentum distribution are proposed. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schroedinger equation including atomic potentials appropriate for the H and He atoms

  9. Generation of Attosecond X-ray Pulses Beyond the Atomic Unit of Time Using Laser Induced Microbunching in Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.; Huang, Z.; Stupakov, G.; /SLAC

    2009-12-11

    Ever since the discovery of mode-locking, efforts have been devoted to reducing the duration of laser pulses since the ultrashort pulses are critical to explore the dynamics occurred on a ever-shorter timescale. In this paper we describe a scheme that's capable of generating intense attosecond x-ray pulses with duration beyond the atomic unit of time ({approx}24 attoseconds). The scheme combines the echo-enabled harmonic generation technique with the bunch compression which allows one to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of a UV seed laser. A few-cycle intense IR laser is used to generate the required energy chirp in the beam for bunch compression and for selection of an attosecond x-ray pulse. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power of a few hundred MW and duration as short as 20 attoseconds (FWHM) can be generated from a 200 nm UV seed laser. The proposed scheme may enable the study of electronic dynamics with a resolution beyond the atomic unit of time and may open a new regime of ultrafast sciences.

  10. Practical issues of retrieving isolated attosecond pulses

    International Nuclear Information System (INIS)

    The attosecond streaking technique is used for the characterization of isolated extreme ultraviolet (XUV) attosecond pulses. This type of measurement suffers from low photoelectron counts in the streaked spectrogram, and is thus susceptible to shot noise. For the retrieval of few- or mono-cycle attosecond pulses, high-intensity streaking laser fields are required, which cause the energy spectrum of above-threshold ionized (ATI) electrons to overlap with that of the streaked photoelectrons. It is found by using the principal component generalized projections algorithm that the XUV attosecond pulse can accurately be retrieved for simulated and experimental spectrograms with a peak value of 50 or more photoelectron counts. Also, the minimum streaking intensity is found to be more than 50 times smaller than that required by the classical streaking camera for retrieval of pulses with a spectral bandwidth supporting 90 as transform-limited pulse durations. Furthermore, spatial variation of the streaking laser intensity, collection angle of streaked electrons and time delay jitter between the XUV pulse and streaking field can degrade the quality of the streaked spectrogram. We find that even when the XUV and streaking laser focal spots are comparable in size, the streaking electrons are collected from a 4π solid angle, or the delay fluctuates by more than the attosecond pulse duration, the attosecond pulses can still be accurately retrieved. In order to explain the insusceptibility of the streaked spectrogram to these factors, the linearity of the streaked spectrogram with respect to the streaking field is derived under the saddle point approximation.

  11. Few-cycle isolated attosecond pulses

    International Nuclear Information System (INIS)

    Complete test of publication follows. In the last few years the field of attosecond science has shown impressive and rapid progress, mainly due to the introduction of novel experimental methods for the characterization of extreme ultraviolet (XUV) pulses and attosecond electron wave packets. This development has been also triggered by significant improvements in the control of the electric field of the driving infrared pulses. Particularly interesting for the applications is the generation of isolated attosecond XUV pulses using few-cycle driving pulses. In this case significant progresses have been achieved thanks to the stabilization of the carrier-envelope phase (CEP) of amplified light pulses. In this work we demonstrate that the polarization gating (PG) method with few-cycle phase-stabilized driving pulses allows one to generate few-cycle isolated attosecond pulses tunable on a very broad spectral region. The PG method is based on temporal modulation of the ellipticity of a light pulse, which confines the XUV emission in the temporal gate where the polarization is close to linear. The time-dependent polarization of phase-stabilized sub-6-fs pulses, generated by the hollow fiber technique, has been obtained using two birefringent plates. It is possible to create a linear polarization gate, whose position is imposed by the intensity profile of the pulse whilst the emission time is linked to the CEP of the electric field. The pulses have been analyzed by using a flat-field spectrometer. Continuous XUV spectra, corresponding to the production of isolated attosecond pulses, have been generated for particular CEP values. Upon changing the rotation of the first plate it was possible to tune the XUV emission in a broad spectra range. We have then achieved a complete temporal characterization of the generated isolated attosecond pulses using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG CRAB). The measured parabolic phase

  12. Attosecond X-ray free electron laser

    Directory of Open Access Journals (Sweden)

    Kim D. E.

    2013-03-01

    Full Text Available For a real, meaningful pump-probe experiment with attosecond temporal resolution, an isolated attosecond pulse is in demand. In this vein we report the generation of an isolated ~ 148 attosecond pulse duration radiation pulse at 0.1 angstrom wavelength using current enhanced self-amplified spontaneous emission free electron laser. We consider the 10-GeV PAL-XFEL e-beam for enhanced self-amplified spontaneous emission (ESASE scheme. In ESASE, X-ray SASE FEL is combined with a femtosecond laser system. An 800 nm wavelength, 5 fs FWHM carrier envelope phase stabilized laser was employed in ESASE scheme.

  13. Attosecond control of tunneling ionization and electron trajectories

    Energy Technology Data Exchange (ETDEWEB)

    Fiess, M; Horvath, B; Wittmann, T; Helml, W; Gagnon, J; Krausz, F; Kienberger, R [Max-Planck-Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, Garching (Germany); Cheng, Y; Zeng, B; Xu, Z [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai 201800 (China); Scrinzi, A, E-mail: markus.fiess@mpq.mpg.de [Ludwig-Maximilians-Universitaet Muenchen, Fakultaet fuer Physik, Theresienstrasse 37, 80333 Muenchen (Germany)

    2011-03-15

    We demonstrate the control of electron tunneling in the high-order harmonic generation process and subsequent positive-energy wavepacket propagation until recollision with the unprecedented precision of about 10 attoseconds. This is accomplished with waveforms synthesized from a few-cycle near-infrared pulse and its second harmonic. The presented attosecond control of few-cycle-driven high harmonics permits the generation of tunable isolated attosecond pulses, opening the prospects for a new class of attosecond pump-probe experiments.

  14. Generation of attosecond electron bunches

    International Nuclear Information System (INIS)

    Ultra-fast science is an important new research frontier that is driving the development of novel sources for generation of extremely short x-ray and electron pulses. Recent advances in femtosecond lasers have stimulated development of femtosecond x-ray sources that allow the study of matter at the time scale shorter than period of oscillations of atoms in molecules, ∼ 100 fs. The next breakthrough would be a source of electron pulses comparable with atomic periods ω-1 ∼ 100 attosecond (10-16 s), where ω is a transition frequency between atomic levels. This will open qualitatively new class of phenomena based on the interaction of atomic electrons in the medium with a collective electric field of electron pulses and not with their individual electrons. For example, one can expect coherent ionization losses that are proportional to a square number of electrons in the microbunch, phase synchronized excitation of medium followed by its relaxation with a radiation of a single-cycled optical pulse, excitation of entanglement states in the medium of atoms with few valence electrons, and possibly other new phenomena, yet to be identified. Simple estimation of coherent ionization losses shows that a 100 MeV, 100 attosecond electron pulse containing 105 electrons will lose its total energy after propagating only ∼ 200(micro)m through liquid hydrogen. This is approximately 104 times shorter stopping range than it is for a long (on atomic scale) electron bunch

  15. Circularly Polarized Attosecond Pulses and Molecular Atto-Magnetism

    CERN Document Server

    Bandrauk, Andre D

    2014-01-01

    Various schemes are presented for the generation of circularly polarized molecular high-order harmonic generation (MHOHG) from molecules. In particular it is shown that combinations of counter-rotating circularly polarized pulses produce the lowest frequency Coriolis forces with the highest frequency recollisions, thus generating new harmonics which are the source of circular polarized attosecond pulses (CPAPs). These can be used to generate circularly polarized electronic currents in molecular media on attosecond time scale. Molecular attosecond currents allow then for the generation of ultrashort magnetic field pulses on the attosecond time scale, new tools for molecular atto-magnetism (MOLAM).

  16. Creation and control of single attosecond XUV pulse by few-cycle intense laser pulse

    Science.gov (United States)

    Carrera, Juan J.; Tong, X. M.; Chu, Shih-I.

    2006-05-01

    We present a theoretical investigation of the mechanisms responsible for the production of single atto-second pulse by using few-cycle intense laser pulses. The atto-second XUV spectral is calculated by accurately integrating the time- dependent Schr"odinger equation. The detailed mechanism for the production of the XUV pulse are also corroborated by analyzing the classical trajectories of the electron. Our study shows that the first return of the rescattering electron is responsible for the high energy atto-second pulse. Furthermore, we can optimize the production of atto-second XUV pulses by modifying the trajectory of the rescattering electron by tuning the laser field envelope.

  17. XUV attosecond pulses: generation and measurement

    International Nuclear Information System (INIS)

    An overview is given of the state-of-the-art in optical attosecond pulse generation and measurements. The emission of ultrashort bursts of XUV radiation from a laser driven plasma is described and analysed in the framework of a semiclassical model that explains essential features of the emitted spectrum. While under most conditions, trains of XUV bursts, separated by the half-cycle time of the driving laser field are emitted, few-cycle laser pulses of a well-defined carrier-envelope phase can yield isolated XUV pulses of sub-femtosecond duration. A time resolving correlation technique that relies on the interaction of electrons with a strong laser light field allows the measurement of attosecond electron dynamics from systems excited by these ultrashort XUV pulses. (topical review)

  18. Complete temporal reconstruction of attosecond high-harmonic pulse trains

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Taec; Ko, Dong Hyuk; Park, Juyun; Tosa, Valer; Nam, Chang Hee, E-mail: chnam@kaist.ac.k [Department of Physics and Coherent X-ray Research Center, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-08-15

    The method of complete reconstruction of attosecond bursts has been demonstrated for attosecond high-harmonic pulse trains. The retrieved harmonic field provided detailed information about the envelope and the individual attosecond pulses contained in the attosecond pulse train. The time-frequency analysis revealed complicated spectral chirp structures and the contribution of different quantum paths to attosecond pulse formation.

  19. Lightwave control of attosecond pulse emission from plasma mirrors

    Directory of Open Access Journals (Sweden)

    Borot Antonin

    2013-08-01

    Full Text Available We demonstrate attosecond control of collective electron motion in plasmas driven by near-relativistic intensity laser fields of controlled waveform in both space and time. We were able to generate spatially isolated attosecond pulses from a plasma mirrors for the first time.

  20. Attosecond measurements without attosecond pulses: using particle correlation

    International Nuclear Information System (INIS)

    Full text: We describe how time and energy correlations between the electrons can be used to trace the dynamics of correlated two-electron ionization with sub-femtosecond precision, without using sub-femtosecond pulses. The approach is illustrated using the example of Auger or Coster-Kronig decay triggered by photo-ionization with an XUV pulse. It requires correlated measurements of angle-resolved energy spectra of both the photo- and Auger electrons in the presence of a laser pulse. Neither the XUV, nor the laser pulse have to be short compared to the decay time. We begin complete characterization of a process by reconstructing amplitude and phase of a correlated two-electron spectrum. Phase information is obtained in a manner similar to SPIDER reconstruction method of conventional ultrafast spectroscopy, where there is no fundamental limit to time resolution. Spectral phase is mapped onto amplitude modulation of spectral intensity by recording the interference of the original spectrum with its spectrally-shifted replica. Particle correlation also allows us to effectively solve the deconvolution problem, uncovering the fast component of the correlated process. One essential requirement, however, is temporal stability of the probe pulse relative to the pump: their relative jitter degrades time resolution. Fortunately, modem few-cycle infrared (IR) femtosecond pulses can be phase stabilized with incredible attosecond precision over very long times, naturally leading to attosecond stabilization of XUV pulses which they generate. Our approach can be used for any process resulting in the emission of two charged particles with fixed total energy. Examples are shake-off in one-photon two-electron ionization, photo-induced Auger or Coster-Kronig decay, etc. Ultrafast stages of such processes which can be time-resolved with our approach can also include Zeno and anti-Zeno stages of decay, core rearrangement, non-exponential decay due to structured continuum, etc. Ref. 1

  1. Attosecond-magnetic-field-pulse generation by intense few-cycle circularly polarized UV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2013-07-01

    Intense attosecond-magnetic-field pulses are predicted to be produced by intense few-cycle attosecond circularly polarized UV pulses. Numerical solutions of the time-dependent Schrödinger equation for H2+ are used to study the electronic dynamical process. Spinning attosecond circular electron wave packets are created on subnanometer molecular dimensions, thus generating attosecond magnetic fields of several tens of Teslas (105 G). Simulations show that the induced magnetic field is critically dependent on the pulse wavelength λ and pulse duration nτ (n is number of cycles) as predicted by a classical model. For ultrashort few-cycle circularly polarized attosecond pulses, molecular orientation influences the generation of the induced magnetic fields as a result of preferential ionization perpendicular to the molecular axis. The nonspherical asymmetry of molecules allows for efficient attosecond-magnetic-field-pulse generation.

  2. Methods of Attosecond X-Ray Pulse Generation

    International Nuclear Information System (INIS)

    We review several proposals for generation of solitary attosecond pulses using two types of free electron lasers which are envisioned as future light sources for studies of ultra-fast dynamics using soft and hard x-rays

  3. Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope

    CERN Document Server

    Mauritsson, J; Gustafsson, E; Swoboda, M; Ruchon, T; LHuillier, A; Schafer, K J

    2007-01-01

    The basic properties of atoms, molecules and solids are governed by electron dynamics which take place on extremely short time scales. To measure and control these dynamics therefore requires ultrafast sources of radiation combined with efficient detection techniques. The generation of extreme ultraviolet (XUV) attosecond (1 as = 10-18 s) pulses has, for the first time, made direct measurements of electron dynamics possible. Nevertheless, while various applications of attosecond pulses have been demonstrated experimentally, no one has yet captured or controlled the full three dimensional motion of an electron on an attosecond time scale. Here we demonstrate an attosecond quantum stroboscope capable of guiding and imaging electron motion on a sub-femtosecond (1 fs = 10-15 s) time scale. It is based on a sequence of identical attosecond pulses which are synchronized with a guiding laser field. The pulse to pulse separation in the train is tailored to exactly match an optical cycle of the laser field and the ele...

  4. Plasma effects in attosecond pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, T.J.M. [Centre for Theoretical Physics, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Ondarza-Rovira, R., E-mail: ricardo.ondarza@inin.gob.m [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Mexico 11801, Distrito Federal (Mexico)

    2010-03-29

    Particle-in-cell simulations have been used to explore further the role of plasma effects on the high harmonic spectrum generated in intense ultrarelativistic (UR) laser-plasma interactions. From a study of the electron dynamics during the laser-plasma interaction a strong correlation was established between the reflected laser pulses and plasma effects. The sources of intense attosecond pulses were found to originate within the plasma at sites of high electron density concentrations at which there is a correspondingly strong generation of electrostatic fields.

  5. Direct XUV Probing of Attosecond Electron Recollision

    International Nuclear Information System (INIS)

    We demonstrate that the recolliding electron wave packet, fundamental to many strong field phenomena, can be directly imaged with sub-A spatial and attosecond temporal resolution using attosecond extreme ultraviolet (XUV) pulses. When the recolliding electron revisits the parent ion, it can absorb an XUV photon yielding high energy electron and thereby providing a measurement of the electron energy at the moment of recollision. The full temporal evolution of the recollision wave packet can be reconstructed by measuring the photoelectron spectra for different time delays between the driving laser and the attosecond XUV probe. The strength of the photoelectron signal can be used to characterize the spatial distribution of the electron density in the longitudinal direction. Elliptical polarization can be used to characterize the electron probability in transversal direction

  6. Applications of Elliptically Polarized, Few-Cycle Attosecond Pulses

    Science.gov (United States)

    Starace, Anthony F.

    2016-05-01

    Use of elliptically-polarized light opens the possibility of investigating effects that are not accessible with linearly-polarized pulses. This talk presents two new physical effects that are predicted for ionization of the helium atom by few-cycle, elliptically polarized attosecond pulses. For double ionization of He by an intense elliptically polarized attosecond pulse, we predict a nonlinear dichroic effect (i.e., the difference of the two-electron angular distributions in the polarization plane for opposite helicities of the ionizing pulse) that is sensitive to the carrier-envelope phase, ellipticity, peak intensity I, and temporal duration of the pulse. For single ionization of He by two oppositely circularly polarized, time-delayed attosecond pulses we predict that the photoelectron momentum distributions in the polarization plane have helical vortex structures that are exquisitely sensitive to the time-delay between the pulses, their relative phase, and their handedness. Both of these effects manifest the ability to control the angular distributions of the ionized electrons by means of the attosecond pulse parameters. Our predictions are obtained numerically by solving the six-dimensional two-electron time-dependent Schrödinger equation for the case of elliptically polarized attosecond pulses. They are interpreted analytically by means of perturbation theory analyses of the two ionization processes. This work is supported in part by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Award No. DE-FG03-96ER14646.

  7. Generation of intense coherent attosecond X-ray pulses using relativistic electron mirrors

    Science.gov (United States)

    Kulagin, V. V.; Kornienko, V. N.; Cherepenin, Vladimir A.; Suk, Hyyong

    2013-05-01

    We analyse the steepening of the leading edge of femtosecond petawatt pulses with the use of plasma layers and show that, at an electron density several times higher than the critical one, an asymmetric (in time domain) pulse can be produced with an amplitude of the first half-wave differing little from the maximum pulse amplitude. Using numerical simulation, we have studied the interaction of such pulses with nanometre-thick films, including the generation of relativistic electron mirrors and the reflection of a counterpropagating probe pulse from such mirrors. The resulting coherent X-ray pulses have a duration of ~120 as and a power of ~600 GW at a wavelength of ~13 nm. Our results demonstrate that the reflectivity of a relativistic electron mirror situated in the accelerating pulse field is independent of the probe pulse amplitude when it increases up to the accelerating pulse amplitude.

  8. Generation of intense coherent attosecond X-ray pulses using relativistic electron mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Kulagin, V V; Kornienko, V N; Cherepenin, Vladimir A; Suk, Hyyong

    2013-05-31

    We analyse the steepening of the leading edge of femtosecond petawatt pulses with the use of plasma layers and show that, at an electron density several times higher than the critical one, an asymmetric (in time domain) pulse can be produced with an amplitude of the first half-wave differing little from the maximum pulse amplitude. Using numerical simulation, we have studied the interaction of such pulses with nanometre-thick films, including the generation of relativistic electron mirrors and the reflection of a counterpropagating probe pulse from such mirrors. The resulting coherent X-ray pulses have a duration of {approx}120 as and a power of {approx}600 GW at a wavelength of {approx}13 nm. Our results demonstrate that the reflectivity of a relativistic electron mirror situated in the accelerating pulse field is independent of the probe pulse amplitude when it increases up to the accelerating pulse amplitude. (interaction of laser radiation with matter. laser plasma)

  9. High-energy attosecond nanoplasmonic-based electron gun

    Science.gov (United States)

    Greig, S. R.; Elezzabi, A. Y.

    2016-03-01

    We present the design of an ultrafast conical lens based nanoplasmonic electron gun. Through excitation with a radially polarized laser pulse, and a combination of magnetostatic and spatial filtering, high energy electron packets with attosecond durations can be achieved.

  10. Efficient generation of an isolated single-cycle attosecond pulse

    CERN Document Server

    Lan, Pengfei; Cao, Wei; Wang, Xinlin

    2007-01-01

    A new method for efficiently generating an isolated single-cycle attosecond pulse is proposed. It is shown that the ultraviolet (UV) attosecond pulse can be utilized as a robust tool to control the dynamics of electron wave packets (EWPs). By adding a UV attosecond pulse to an infrared (IR) few-cycle pulse at a proper time, only one return of the EWP to the parent ion is selected to effectively contribute to the harmonics, then an isolated two-cycle 130-as pulse with a bandwidth of 45 eV is obtained. After complementing the chirp, an isolated single-cycle attosecond pulse with a duration less than 100 as seems achievable. In addition, the contribution of the quantum trajectories can be selected by adjusting the delay between the IR and UV fields. Using this method, the harmonic and attosecond pulse yields are efficiently enhanced in contrast to the scheme [G. Sansone {\\it et al.}, Science {\\bf314}, 443 (2006)] using a few-cycle IR pulse in combination with the polarization gating technique.

  11. Efficient generation of an isolated single-cycle attosecond pulse

    International Nuclear Information System (INIS)

    A method for efficiently generating an isolated single-cycle attosecond pulse is proposed. It is shown that the ultraviolet (UV) attosecond (as) pulse can be utilized as a robust tool to control the dynamics of electron wave packets (EWPs). By adding a UV attosecond pulse to an infrared (IR) few-cycle pulse at a proper time, only one return of the EWP to the parent ion is selected to effectively contribute to the harmonics; then, an isolated two-cycle 130-as pulse with a bandwidth of 45 eV is obtained. After complementing the chirp, an isolated single-cycle attosecond pulse with a duration less than 100 as seems achievable. In addition, the contribution of the quantum trajectories can be selected by adjusting the delay between the IR and UV fields. Using this method, the harmonic and attosecond pulse yields are efficiently enhanced in contrast to the scheme [G. Sansone et al., Science 314, 443 (2006)] using a few-cycle IR pulse in combination with the polarization gating technique

  12. Attosecond pulse shaping using partial phase matching

    OpenAIRE

    Austin, Dane R.; Biegert, Jens

    2014-01-01

    We propose a method for programmable shaping of the amplitude and phase of the XUV and x-ray attosecond pulses produced by high-order harmonic generation. It overcomes the bandwidth limitations of existing spectral filters and enables removal of the intrinsic attosecond chirp as well as the synthesis of pulse sequences. It is based on partial phase matching, such as quasi-phase matching, using a longitudinally addressable modulation.

  13. Above, around, and below threshold ionization using attosecond pulses

    International Nuclear Information System (INIS)

    Full text: Attosecond pulses offer a new route to produce temporally localized electron wave packets that can easily be tailored by altering the properties of the attosecond pulses. In this talk we will present three different experiments where attosecond pulses are used to inject electron wave packets into a continuum which is dressed by an infrared laser field. By tuning the central frequency of the attosecond pulses and/or changing the target gas, the initial energy of the wave packets is set to be either above, around, or below the ionization potential. To capture the motion of electron wave packets created above or around the ionization potential we have developed a quantum stroboscope to record the electron momentum distribution from a single ionization event. The quantum stroboscope is based on a sequence of identical attosecond pulses that are used to release electrons into a strong laser field exactly once per laser cycle. With this periodicity, the pulses create identical electron wave packets that add up coherently, with the result that the properties of an individual wave packet can be studied stroboscopically. We use this technique to study the coherent electron scattering of electrons that are driven back to the ion by the laser field. For electron wave packets created below the ionization potential we find that the ionization is greatly enhanced by the presence of the infrared laser field and that this enhancement strongly depends on the timing between the attosecond pulses and the laser field. We show that this effect can be attributed to interference between consecutive wave packets, which indicates that the wave packets stay in the vicinity of the ion over an extended time period. Using instead isolated attosecond pulses generated from an ultrashort, carrier-envelope- phase stabilized infrared laser with a time-dependent polarization we show that it is possible to also probe ultrafast bound electron dynamics. These attosecond pulses are broad

  14. Efficient attosecond control of electron dynamics in molecules

    Directory of Open Access Journals (Sweden)

    Wollenhaupt M.

    2013-03-01

    Full Text Available We demonstrate how the fast electron dynamics in molecules and hence the reaction of the system can be efficiently manipulated by controlling the temporal phase of an ultrashort laser pulse with attosecond precision.

  15. Isolated short attosecond pulse produced by using an intense few-cycle shaped laser and an ultraviolet attosecond pulse

    Science.gov (United States)

    Zhao, Song-Feng; Zhou, Xiao-Xin; Li, Peng-Cheng; Chen, Zhangjin

    2008-12-01

    An efficient method to generate a short attosecond pulse is presented by using intense few-cycle shaped infrared (ir) laser in combination with an ultraviolet (uv) attosecond (as) pulse. We show that high-order harmonic generation (HHG) plateau near the cutoff is enhanced by one order of magnitude compared with the shaped laser case and the HHG supercontinuum spectrum is generated by adding a uv attosecond pulse to the few-cycle shaped ir laser at a proper time. By enhancing the long quantum path and suppressing the short one corresponding to one major return, an isolated 57-as pulse with a bandwidth of 62eV is obtained directly. The time-frequency characteristics of the HHG are analyzed in detail by means of the wavelet transform of the time-dependent induced dipole acceleration. In addition, we also perform classical trajectory simulation of the strong-field electron dynamics and electron return map.

  16. Attosecond pulse shaping using partial phase matching

    International Nuclear Information System (INIS)

    We propose a method for programmable shaping of the amplitude and phase of the extreme ultraviolet and x-ray attosecond pulses produced by high-order harmonic generation. It overcomes the bandwidth limitations of existing spectral filters and enables removal of the intrinsic attosecond chirp as well as the synthesis of pulse sequences. It is based on partial phase matching using a longitudinally addressable modulation. Although the method is in principle applicable to any form of partial phase matching, we focus on quasi-phase matching using a counterpropagating pulse train. We present simulations of the production of isolated attosecond pulses at 250 eV, including a 31 as transform-limited pulse, tunably chirped pulses and double pulses. (paper)

  17. Multilayer Mirrors for Attosecond Pulse Shaping between 30 and 200 eV

    OpenAIRE

    Hofstetter, Michael

    2011-01-01

    Attosecond (as) physics has become a wide spreaded and still growing research field over the last decades. It allows for probing and controlling core- and outer shell electron dynamics with never before achieved temporal precision. High harmonic generation in gases in combination with advanced extreme ultraviolet (XUV ) optical components enable the generation of isolated attosecond pulses as required for absolute time measurements. But until recently, single attosecond pulse generation ha...

  18. Inconsistencies between two attosecond pulse metrology methods: A comparative study

    International Nuclear Information System (INIS)

    The two basic approaches underlying most of the metrology of attosecond pulse trains are compared in the spectral region ∼14-24 eV, that is, the second-order intensity volume autocorrelation and the resolution of attosecond beating by interference of two photon transitions (RABITT). They give rather dissimilar pulse durations. It is concluded that for the present experimental conditions RABITT may underestimate the duration under measurement, due to variations of the driving intensity, but in conjunction with theory allows an estimation of the relative contributions of two different electron trajectories to the extreme-ultraviolet (XUV) radiation.

  19. Terawatt-scale sub-10-fs laser technology - key to generation of GW-level attosecond pulses in X-ray free electron laser

    International Nuclear Information System (INIS)

    We propose a technique for the production of attosecond X-ray pulses which is based on the use of X-ray SASE FEL combined with a femtosecond laser system. A few-cycle optical pulse from a Ti:sapphire laser interacts with the electron beam in a two-period undulator resonant to 800 nm wavelength and produces energy modulation within a slice of the electron bunch. Following the energy modulator the electron beam enters the X-ray undulator and produces SASE radiation. Due to energy modulation the frequency is correlated to the longitudinal position within the few-cycle-driven slice of SASE radiation pulse. The largest frequency offset corresponds to a single-spike pulse in the time domain which is confined to one half-oscillation period near the central peak electron energy. The selection of single-spike pulses is achieved by using a crystal monochromator after the X-ray undulator. Our studies show that the proposed technique is capable to produce 300 attoseconds long single pulses with GW-level output power in the 0.1 nm wavelength range, and is applicable to the European X-ray Laser Project XFEL and the Linac Coherent Light Source at SLAC. (orig.)

  20. Attosecond laser pulse ionization of atoms and molecules

    International Nuclear Information System (INIS)

    Ionization dynamics of atoms and molecules under attosecond laser pulses with various photon energies and peak intensities have been investigated using the Time-Dependent Close-Coupling (TDCC) method. We predict the chirp effects on the triply differential probabilities for the ionized electrons of He produced by 450 and 135 asec pulses. In addition, we shall apply our generalized TDCC method to examine the four-body breakup dynamics of molecular hydrogen induced by these ultrashort pulses.

  1. Generation of atto-second pulses on relativistic mirror plasma

    International Nuclear Information System (INIS)

    When an ultra intense femtosecond laser (I > 1016 W.cm-2) with high contrast is focused on a solid target, the laser field at focus is high enough to completely ionize the target surface during the rising edge of the laser pulse and form a plasma. This plasma is so dense (the electron density is of the order of hundred times the critical density) that it completely reflects the incident laser beam in the specular direction: this is the so-called 'plasma mirror'. When laser intensity becomes very high, the non-linear response of the plasma mirror to the laser field periodically deforms the incident electric field leading to high harmonic generation in the reflected beam. In the temporal domain this harmonic spectrum is associated to a train of atto-second pulses. The goals of my work were to get a better comprehension of the properties of harmonic beams produced on plasma mirrors and design new methods to control theses properties, notably in order to produce isolated atto-second pulses instead of trains. Initially, we imagined and modeled the first realistic technique to generate isolated atto-second on plasma mirrors. This brand new approach is based on a totally new physical effect: 'the atto-second lighthouse effect'. Its principle consists in sending the atto-second pulses of the train in different directions and selects one of these pulses by putting a slit in the far field. Despite its simplicity, this technique is very general and applies to any high harmonic generation mechanism. Moreover, the atto-second lighthouse effect has many other applications (e.g in metrology). In particular, it paves the way to atto-second pump-probe experiments. Then, we studied the spatial properties of these harmonics, whose control and characterization are crucial if one wants to use this source in future application experiments. For instance, we need to control very precisely the harmonic beam divergence in order to achieve the atto-second lighthouse effect and get isolated

  2. Obtaining two attosecond pulses pulses for x-ray stimulated Raman spectroscopy

    International Nuclear Information System (INIS)

    Attosecond x-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft x-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each x-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 attoseconds. The carrier frequency of each x-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 attoseconds precision.

  3. Developing a High-Flux Isolated Attosecond Pulse Source

    Science.gov (United States)

    Kamalov, Andrei; Ware, Matthew; Bucksbaum, Philip; Cryan, James

    2016-05-01

    High harmonic based light sources have proven to be valuable experimental tools that facilitate studies of electron dynamics at their natural timescale, the attosecond regime. The nature of driving laser sources used in high harmonic generation make it difficult to attain attosecond pulses that are both isolated in time and of a high intensity. We present our progress in commissioning a beamline designed to produce high-flux isolated attosecond pulses. A multistep amplification process provides us with 30 mJ, 25 fs pulses centered around 800 nm with 100 Hz repetition rate. These pulses are spatially split and focused into a gas cell. A non-collinear optical gating scheme is used to produce a lighthouse source of high harmonic radiation wherein each beamlet is an isolated attosecond pulse. A variable-depth grazing-incidence stepped mirror is fabricated to extend the optical path length of the older beamlets and thus overlap the beamlets in time. The combined beam is tightly focused and ensuing mechanics will be studied with an electron spectrometer as well as a xuv photon spectrometer. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.

  4. Generation of short and intense attosecond pulses

    Science.gov (United States)

    Khan, Sabih Ud Din

    Extremely broad bandwidth attosecond pulses (which can support 16as pulses) have been demonstrated in our lab based on spectral measurements, however, compensation of intrinsic chirp and their characterization has been a major bottleneck. In this work, we developed an attosecond streak camera using a multi-layer Mo/Si mirror (bandwidth can support ˜100as pulses) and position sensitive time-of-flight detector, and the shortest measured pulse was 107.5as using DOG, which is close to the mirror bandwidth. We also developed a PCGPA based FROG-CRAB algorithm to characterize such short pulses, however, it uses the central momentum approximation and cannot be used for ultra-broad bandwidth pulses. To facilitate the characterization of such pulses, we developed PROOF using Fourier filtering and an evolutionary algorithm. We have demonstrated the characterization of pulses with a bandwidth corresponding to ˜20as using synthetic data. We also for the first time demonstrated single attosecond pulses (SAP) generated using GDOG with a narrow gate width from a multi-cycle driving laser without CE-phase lock, which opens the possibility of scaling attosecond photon flux by extending the technique to peta-watt class lasers. Further, we generated intense attosecond pulse trains (APT) from laser ablated carbon plasmas and demonstrated ˜9.5 times more intense pulses as compared to those from argon gas and for the first time demonstrated a broad continuum from a carbon plasma using DOG. Additionally, we demonstrated ˜100 times enhancement in APT from gases by switching to 400 nm (blue) driving pulses instead of 800 nm (red) pulses. We measured the ellipticity dependence of high harmonics from blue pulses in argon, neon and helium, and developed a simple theoretical model to numerically calculate the ellipticity dependence with good agreement with experiments. Based on the ellipticity dependence, we proposed a new scheme of blue GDOG which we predict can be employed to extract

  5. Direct observation of electron dynamics in the attosecond domain.

    Science.gov (United States)

    Föhlisch, A; Feulner, P; Hennies, F; Fink, A; Menzel, D; Sanchez-Portal, D; Echenique, P M; Wurth, W

    2005-07-21

    Dynamical processes are commonly investigated using laser pump-probe experiments, with a pump pulse exciting the system of interest and a second probe pulse tracking its temporal evolution as a function of the delay between the pulses. Because the time resolution attainable in such experiments depends on the temporal definition of the laser pulses, pulse compression to 200 attoseconds (1 as = 10(-18) s) is a promising recent development. These ultrafast pulses have been fully characterized, and used to directly measure light waves and electronic relaxation in free atoms. But attosecond pulses can only be realized in the extreme ultraviolet and X-ray regime; in contrast, the optical laser pulses typically used for experiments on complex systems last several femtoseconds (1 fs = 10(-15) s). Here we monitor the dynamics of ultrafast electron transfer--a process important in photo- and electrochemistry and used in solid-state solar cells, molecular electronics and single-electron devices--on attosecond timescales using core-hole spectroscopy. We push the method, which uses the lifetime of a core electron hole as an internal reference clock for following dynamic processes, into the attosecond regime by focusing on short-lived holes with initial and final states in the same electronic shell. This allows us to show that electron transfer from an adsorbed sulphur atom to a ruthenium surface proceeds in about 320 as. PMID:16034414

  6. Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope

    International Nuclear Information System (INIS)

    We demonstrate a quantum stroboscope based on a sequence of identical attosecond pulses that are used to release electrons into a strong infrared (IR) laser field exactly once per laser cycle. The resulting electron momentum distributions are recorded as a function of time delay between the IR laser and the attosecond pulse train using a velocity map imaging spectrometer. Because our train of attosecond pulses creates a train of identical electron wave packets, a single ionization event can be studied stroboscopically. This technique has enabled us to image the coherent electron scattering that takes place when the IR field is sufficiently strong to reverse the initial direction of the electron motion causing it to rescatter from its parent ion

  7. Atomic dynamics with attosecond VUV pulses

    International Nuclear Information System (INIS)

    Full text: Dynamical information on inner-shell processes was hitherto extracted from linewidths in the energy-domain. The recent realization of attosecond pulses with high photon energies now permits a time-based view of the extremely rapid relaxation processes that follow the creation of an atomic core hole. Extension of the pump-probe technique for this purpose requires i) ultrashort well isolated pulses of sufficiently high photon energy, and ii) a method for sampling the time of the emission of an electron with respect to the photoexcitation event. The exciting (pump) VUV pulses are generated as high harmonics of few-cycle (2-3 cycles of 2.5 fs) laser pulses (hv = 1.6 eV) in a neon medium at intensities exceeding 1014 W/cm2. Proper spectral filtering with dedicated multilayer reflectors at the harmonic cut-off results in VUV radiation bursts as short 250. The generated photon energies of about 100 eV are sufficiently energetic for creating vacancies in atoms, e.g. the M-shell of krypton, with the subsequent core-hole relaxation giving rise to emission of Auger electrons. A delayed (probe) laser ld acts as an ultrafast gate by exchanging momentum with the electron at the instant of its ejection, thus modulating the electrons kinetic energy. Analysis of the formed delay-dependent spectral sidebands reveals the evolution of the Auger wave packet. As the technique does not rely on particular transitions, a wide range of electron-emission processes following inner-shell photoexcitation will become accessible to time-resolved studies

  8. Multiple attosecond pulse generation in relativistically laser-driven overdense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Lavocat-Dubuis, X; Vidal, F; Matte, J-P; Kieffer, J-C; Ozaki, T, E-mail: xavier.lavocat-dubuis@polymtl.ca, E-mail: vidal@emt.inrs.ca [INRS-Centre Energie, Materiaux et Telecommunications, 1650 boulevard Lionel Boulet, Varennes, QC, J3X 1S2 (Canada)

    2011-02-15

    Using particle-in-cell simulations, we investigate the mechanisms that lead to attosecond pulses when an obliquely incident laser pulse interacts with an overdense plasma. We show that several attosecond pulses can be emitted per laser cycle as a result of the ejection of electron bunches associated with return currents within the plasma. The electron dynamics are investigated in phase space and with the help of the similarity parameter S=n{sub e}/a{sub 0}n{sub c}.

  9. Chromium/scandium multilayer mirrors for isolated attosecond pulses at 145  eV.

    Science.gov (United States)

    Guggenmos, Alexander; Jobst, Michael; Ossiander, Marcus; Radünz, Stefan; Riemensberger, Johann; Schäffer, Martin; Akil, Ayman; Jakubeit, Clemens; Böhm, Philip; Noever, Simon; Nickel, Bert; Kienberger, Reinhard; Kleineberg, Ulf

    2015-06-15

    Recent advances in the development of attosecond soft x-ray sources toward photon wavelengths below 10 nm are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. We demonstrate that current attosecond experiments in the sub-200-eV range benefit from these improved optics. We present our achievements in utilizing ion-beam-deposited chromium/scandium (Cr/Sc) multilayer mirrors, optimized by tailored material dependent deposition and interface polishing, for the generation of single attosecond pulses from a high-harmonic cut-off spectrum at a central energy of 145 eV. Isolated attosecond pulses have been measured by soft x-ray-pump/NIR-probe electron streaking experiments and characterized using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG/CRAB). The results demonstrate that Cr/Sc multilayer mirrors can be used as efficient attosecond optics for reflecting 600-attosecond pulses at a photon energy of 145 eV, which is a prerequisite for present and future attosecond experiments in this energy range. PMID:26076277

  10. Single attosecond pulse generation via continuum wave packet interference

    Science.gov (United States)

    Zhou, Shengpeng; Yang, Yujun; Ding, Dajun

    2016-07-01

    A single attosecond pulse generation via continuum-continuum interference is investigated theoretically by exposing a single-electron atom in a femtosecond laser field with the intensity in over-the-barrier ionization regime. We show that the ground state of the atom is depleted in such intense laser field and the high-order harmonics (HHG) via continuum to continuum coherence are generated. In a few-cycle monochromatic laser field (5 fs/800 nm, 1.2×1016 W cm-2), a single attosecond pulse with duration of 49 as is obtained from the HHG. With a two-color laser field combined by 1200 nm (8 fs/7.5×1015 W cm-2) and 800 nm (5 fs/1.0×1016 W cm-2), a shorter single pulse with duration of 29 as can further be produced by changing the relative carrier envelope phase of two laser pulses as a result of controlling the electronic quantum path in the intense electric field. Our results also show that a short single attosecond pulse can be generated in a wide range of the relative carrier envelope phase of the two laser pulses.

  11. Attosecond Hard X-ray Free Electron Laser

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar

    2013-03-01

    Full Text Available In this paper, several schemes of soft X-ray and hard X-ray free electron lasers (XFEL and their progress are reviewed. Self-amplified spontaneous emission (SASE schemes, the high gain harmonic generation (HGHG scheme and various enhancement schemes through seeding and beam manipulations are discussed, especially in view of the generation of attosecond X-ray pulses. Our recent work on the generation of attosecond hard X-ray pulses is also discussed. In our study, the enhanced SASE scheme is utilized, using electron beam parameters of an XFEL under construction at Pohang Accelerator Laboratory (PAL. Laser, chicane and electron beam parameters are optimized to generate an isolated attosecond hard X-ray pulse at 0.1 nm (12.4 keV. The simulations show that the manipulation of electron energy beam profile may lead to the generation of an isolated attosecond hard X-ray of 150 attosecond pulse at 0.1 nm.

  12. Attosecond Magnetic Field Pulse Generation by Intense Few Cycle Circularly Polarized UV Pulses

    CERN Document Server

    Yuan, Kai-Jun

    2013-01-01

    Intense attosecond magnetic field pulses are predicted to be produced by intense few cycle circularly polarized UV pulses. Numerical solutions of the time dependent Schr\\"{o}dinger equation for H$_2^+$ are used to study the dynamical process. Spiralling attosecond circular electron wave packets are created with nanometer molecular dimensions, thus generating magnetic fields of several tens of Teslas ($10^5$ Gauss). Simulations show that the induced magnetic field is critically dependent on the pulse wavelength $\\lambda$ and pulse duration $n\\tau$ ($n$ number of cycle) as predicted by a classical model. For ultrashort few cycle circularly polarized attosecond pulses, molecular orientation influences the generation of the induced magnetic fields as a result of preferential ionization perpendicular to the molecular axis.

  13. Attosecond Pulse Carrier-Envelope Phase Effects: Roles of Frequency, Intensity and an Additional IR Pulse

    Science.gov (United States)

    Pronin, Evgeny A.; Peng, Liang-You; Starace, Anthony F.

    2008-05-01

    The effects of the carrier-envelope phase (CEP) of a few-cycle attosecond pulse on ionized electron momentum and energy spectra are analyzed, both with and without an additional few-cycle IR pulse [1, 2]. In the absence of an IR pulse, the CEP-induced asymmetries in the ionized electron momentum distributions are shown to vary as the 3/2 power of the attosecond pulse intensity. These asymmetries are also found to satisfy an approximate scaling law involving the frequency and intensity of the attosecond pulse. In the presence of even a very weak IR pulse, the attosecond pulse CEP-induced asymmetries are found to be significantly augmented. In addition, for higher IR laser intensities, we observe for low electron energies peaks separated by the IR photon energy in one electron momentum direction along the laser polarization axis; in the opposite direction, we find structured peaks that are spaced by twice the IR photon energy. Possible physical mechanisms for such asymmetric, low-energy structures in the ionized electron momentum distribution are proposed. Our results are based on single-active-electron solutions of the 3D TDSE for H and He. [1] Peng LY, Pronin EA, and Starace AF, New J. Phys. 10, xxx (2008); [2] Peng LY, Starace AF, Phys. Rev. A 76, 043401 (2007)

  14. Molecular attosecond photoionization with few cycle XUV laser pulses

    International Nuclear Information System (INIS)

    We present molecular attosecond ionization with few cycle XUV laser pulses from numerical solutions of time dependent Schrodinger equations. Simulations performed on aligned H+2 exhibit signature of red-shifts in photoelectron energy spectra. This is shown to be critically sensitive to the the pulse duration and wavelength and is attributed to the broad spectral width of the ionizing pulses and diminishing electronic Franck-Condon factors with short pulses. We analyze the laser parameter dependence of the energy spectra by a perturbative model.

  15. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  16. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  17. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  18. Control of two-photon double ionization of helium with intense chirped attosecond laser pulses

    Science.gov (United States)

    Barmaki, S.; Lanteigne, P.; Laulan, S.

    2014-06-01

    We study the two-photon double-ionization process of the helium atom by solving numerically the nonrelativistic, time-dependent Schrödinger equation in its full dimensionality. We investigate with intense chirped attosecond laser pulses of 23.5-nm wavelength the two-photon absorption near and above the sequential threshold. We show how it is possible by adjusting the chirp parameter to control the electronic transitions inside the atom, thereby reinforcing or weakening the ionization process. Attosecond chirped laser pulses offer a promising way to probe and control the two-photon double ionization of helium when compared with attosecond transform-limited pulses.

  19. Route to intense single attosecond pulses

    Science.gov (United States)

    Tsakiris, George D.; Eidmann, Klaus; Meyer-ter-Vehn, Jürgen; Krausz, Ferenc

    2006-02-01

    A feasibility study is presented for the generation of single attosecond pulses using harmonics produced by planar targets irradiated at high intensities. The investigation focuses on the interaction of a few-optical cycles, carrier-envelope phase controlled, near-infrared laser pulse with an overdense plasma. The results obtained using an one-dimensional particle-in-cell code indicate that at laser intensities of 1020 W cm-2 a single sub-fs pulse can be generated in the 20 70 eV spectral range with an efficiency of a few per cent and with 10-3 to 10-4 for higher photon energies.

  20. Route to intense single attosecond pulses

    International Nuclear Information System (INIS)

    A feasibility study is presented for the generation of single attosecond pulses using harmonics produced by planar targets irradiated at high intensities. The investigation focuses on the interaction of a few-optical cycles, carrier-envelope phase controlled, near-infrared laser pulse with an overdense plasma. The results obtained using an one-dimensional particle-in-cell code indicate that at laser intensities of 1020 W cm-2 a single sub-fs pulse can be generated in the 20-70 eV spectral range with an efficiency of a few per cent and with 10-3 to 10-4 for higher photon energies

  1. Attosecond Strong-Field Interferometry of Electron Dynamics

    International Nuclear Information System (INIS)

    Interference effects arising during the highly nonlinear interaction of intense laser pulses with matter are presented for applications in attosecond spectroscopy and interferometry. In the first part we theoretically describe an approach to excite and measure bound electron wavepackets where temporal interference in the photoelectron momentum spectrum reveals the complete energy-level structure of an atom. In the second part we analyse and discuss experimentally observed interference patterns of few adjacent attosecond pulses generated in neon gas that can be controlled by varying experimental parameters such as carrier-envelope phase (CEP) or pressure.

  2. Double Ionization of Hydrogen Molecule by Intense Attosecond Laser Pulses

    Science.gov (United States)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-03-01

    Time-dependent close-coupling calculations within the fixed nuclei approximation are carried out for the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV. We consider here the two-photon absorption processes and examine the response of the ejected electrons, particularly the single- and the double-electron energy distributions, to linearly and circularly polarized pulse at laser intensities between 10^15 W/cm^2 and 10^16 W/cm^2. We find that, for both the linearly and circularly polarized pulses, sequential peaks and non-sequential wells appear in both the single- and double-electron energy distributions that are generally akin to the analogous two electrons photoemission processes in He atom driven by a linearly polarized intense attosecond pulse [1,2]. Furthermore, a clear signature of the sequential double-electron above threshold ionization process can be seen in the single- and double-electron energy distributions when a linearly polarized pulse is being used.[4pt] [1] I. F. Barna, J. Wang, and J. Burgdorfer, Phys. Rev. A. 73, 023402 (2006) [0pt] [2] T-G Lee, M. S. Pindzola and F. Robicheaux, Phys. Rev. A. 79, 053420 (2009)

  3. EEHG-assisted FEL schemes for attosecond X-ray pulses generation

    Energy Technology Data Exchange (ETDEWEB)

    Yan Jun [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Deng Haixiao, E-mail: denghaixiao@sinap.ac.c [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang Dong; Dai Zhimin [Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Shanghai 201800 (China)

    2010-09-21

    In this paper, the schemes of echo-enabled harmonic generation (EEHG) assisted free electron laser (FEL) for generating attosecond soft X-ray pulses are further investigated. We present brief analytical models and three-dimensional simulations for comparison studies of such schemes reported earlier. Moreover, on the basis of these analyses, a more compact and robust EEHG-assisted FEL scheme is proposed for pump-probe experiments using two-color attosecond X-ray pulses.

  4. Attosecond metrology: from electron capture to future signal processing

    Science.gov (United States)

    Krausz, Ferenc; Stockman, Mark I.

    2014-03-01

    The accurate measurement of time lies at the heart of experimental science, and is relevant to everyday life. Extending chronoscopy to ever shorter timescales has been the key to gaining real-time insights into microscopic phenomena, ranging from vital biological processes to the dynamics underlying high technologies. The generation of isolated attosecond pulses in 2001 allowed the fastest of all motions outside the nucleus -- electron dynamics in atomic systems -- to be captured. Attosecond metrology has provided access to several hitherto immeasurably fast electron phenomena in atoms, molecules and solids. The fundamental importance of electron processes for the physical and life sciences, technology and medicine has rendered the young field of attosecond science one of the most dynamically expanding research fields of the new millennium. Here, we review the basic concepts underlying attosecond measurement and control techniques. Among their many potential applications, we focus on the exploration of the fundamental speed limit of electronic signal processing. This endeavour relies on ultimate-speed electron metrology, as provided by attosecond technology.

  5. Generation of high-energy attosecond pulses by the relativistic-irradiance short laser pulse interacting with a thin foil

    International Nuclear Information System (INIS)

    When a thin foil target is irradiated by two laser pulses, or it is irradiated by one pulse under the condition when the charge separation electric field exceeds the laser field, the electron motion in the direction perpendicular to the target surface is suppressed. Electrons can only slide along the foil. Using an analytical model, we describe the new regime of attosecond pulse generation by the relativistic-irradiance short laser pulse interacting with the sliding mirror. Pulses with the duration of few hundred attoseconds can be generated with the conversion efficiency up to few percents

  6. Steering continuum electron dynamics by low-energy attosecond streaking

    Science.gov (United States)

    Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

    2016-08-01

    A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

  7. Towards attosecond X-ray pulses from the FEL

    International Nuclear Information System (INIS)

    The ability to study ultrafast phenomena has been recently advanced by the demonstrated production and measurement of a single, 650-attosecond (1018 sec), VUV x-ray pulse[1] and, latter, a 250-attosecond pulse[2]. The next frontier is a production of the x-ray pulses with shorter wavelengths and in a broader spectral range. Several techniques for a generation of an isolated, attosecond duration, short-wavelength x-ray pulse based upon the ponderomotive laser acceleration [3], SASE and harmonic cascade FELs ([4] - [6]) had been already proposed. In this paper we briefly review a technique proposed in [5] and present some new results

  8. Generation of an intense single isolated attosecond pulse by use of two-colour waveform control

    Science.gov (United States)

    Zeng, Bin; Yu, Yongli; Chu, Wei; Yao, Jinping; Fu, Yuxi; Xiong, Hui; Xu, Han; Cheng, Ya; Xu, Zhizhan

    2009-07-01

    We theoretically demonstrate the generation of an intense single attosecond pulse by superposing a weak sub-harmonic pulse upon a sine-waveform few-cycle driving pulse. By use of a sine-waveform few-cycle pulse instead of its traditionally used cosine waveform counterpart, we show that efficient tunnel ionization for generating electrons which can revisit their parent ion with high kinetic energy can occur only once in the few-cycle laser field, leading to an increase of efficiency by nearly two orders of magnitude in single attosecond pulse generation as compared with the use of a cosine-waveform field.

  9. Generation of an intense single isolated attosecond pulse by use of two-colour waveform control

    International Nuclear Information System (INIS)

    We theoretically demonstrate the generation of an intense single attosecond pulse by superposing a weak sub-harmonic pulse upon a sine-waveform few-cycle driving pulse. By use of a sine-waveform few-cycle pulse instead of its traditionally used cosine waveform counterpart, we show that efficient tunnel ionization for generating electrons which can revisit their parent ion with high kinetic energy can occur only once in the few-cycle laser field, leading to an increase of efficiency by nearly two orders of magnitude in single attosecond pulse generation as compared with the use of a cosine-waveform field.

  10. Double ionization of H2 by intense attosecond laser pulses

    Science.gov (United States)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-08-01

    We present calculations of the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV using the time-dependent close-coupling method within the fixed nuclei approximation. We focus on two-photon absorption processes and examine how the response of the ejected electrons, in particular the single- and the double-energy differential probabilities, is affected by linear and circular polarizations at laser-field intensities ranging from 10^{15}\\; \\rm W\\,cm^{-2} to 10^{16}\\; \\rm W\\,cm^{-2} . In general, we find that for both linearly and circularly polarized pulses, sequential peaks and non-sequential wells that appear in both the single- and double-energy differential probabilities are akin to the analogous two-electron photoemission processes in the helium atom driven by intense attosecond pulses. In addition, for the case of a linearly polarized pulse, a clear signature of the sequential double-electron above the threshold ionization process can be seen in these spectra.

  11. Double ionization of H2 by intense attosecond laser pulses

    International Nuclear Information System (INIS)

    We present calculations of the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV using the time-dependent close-coupling method within the fixed nuclei approximation. We focus on two-photon absorption processes and examine how the response of the ejected electrons, in particular the single- and the double-energy differential probabilities, is affected by linear and circular polarizations at laser-field intensities ranging from 1015 W cm-2 to 1016 W cm-2. In general, we find that for both linearly and circularly polarized pulses, sequential peaks and non-sequential wells that appear in both the single- and double-energy differential probabilities are akin to the analogous two-electron photoemission processes in the helium atom driven by intense attosecond pulses. In addition, for the case of a linearly polarized pulse, a clear signature of the sequential double-electron above the threshold ionization process can be seen in these spectra.

  12. Effect of Nuclear Motion on Molecular High-Order Harmonics and on Generation of Attosecond Pulses in Intense Laser Pulses

    Science.gov (United States)

    Bandrauk, André D.; Chelkowski, Szczepan; Kawai, Shinnosuke; Lu, Huizhong

    2008-10-01

    We calculate harmonic spectra and shapes of attosecond-pulse trains using numerical solutions of Non-Born-Oppenheimer time-dependent Shrödinger equation for 1D H2 molecules in an intense laser pulse. A very strong signature of nuclear motion is seen in the time profiles of high-order harmonics. In general the nuclear motion shortens the part of the attosecond-pulse train originating from the first electron contribution, but it may enhance the second electron contribution for longer pulses. The shape of time profiles of harmonics can thus be used for monitoring the nuclear motion.

  13. Gating attosecond pulse train generation using multicolor laser fields

    International Nuclear Information System (INIS)

    The process of high-order harmonic generation leads to the production of a train of attosecond-duration extreme ultraviolet (XUV) pulses, with one pulse emitted per optical half-cycle. For attosecond pump-probe experiments, a single, isolated attosecond pulse is preferable, requiring an almost continuous spectrum. We show experimentally and numerically that the addition of a second laser field, and later a third, at a noncommensurate frequency relative to the driving field can modify the subcycle shape of the electric field, leading to the appearance of additional spectral components between the usual odd harmonics and in some cases a quasicontinuum. We perform a parametric study of the frequency ratio between the two first laser fields, the result of which is in good agreement with theoretical selection rules. We also show numerically that using three laser frequencies from an optical parametric amplifier can achieve a single attosecond pulse from a 24-fs laser pulse.

  14. Effects of streaking laser intensity on the characterization of isolated attosecond pulses

    Science.gov (United States)

    Wang, He; Khan, Sabih; Chini, Michael; Chen, Shouyuan; Chang, Zenghu

    2009-05-01

    Single isolated attosecond extreme ultraviolet (XUV) pulses can be characterized by streaking photoelectrons using a near infrared (NIR) laser field. Classically, the streaking resolution is determined by the Rayleigh criterion, which requires the minimum NIR intensity of 5.5x10^13 W/cm^2 to resolve 90 as XUV pulses. Under such high NIR intensity, the electrons generated from multi-photon processes overlap with the streaked electrons in the spectrogram, which unavoidably introduces errors in the final XUV reconstruction. When the FROG-CRAB (Frequency-Resolved Optical Gating for Complete Reconstruction of Attosecond Bursts) technique is used to reconstruct the XUV pulses from the spectrogram, it was found that the minimum streaking intensity needed to resolve single attosecond pulses is dependent on the maximum count of the spectrogram. With a peak count of 100 in the spectrogram, chirped attosecond pulses with spectral bandwidth supporting 90-as transform limited pulse durations can be retrieved from the spectrogram with streaking intensity two orders of magnitude smaller than that derived from the Rayleigh criterion. Such low streaking field intensity is desirable to suppress the ATI background, which is important for the characterization of even shorter XUV attosecond pulses because it significantly reduces the intensity constraints on the experiments.

  15. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R.; Neumark, Daniel M.

    2016-05-01

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions.

  16. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy.

    Science.gov (United States)

    Ramasesha, Krupa; Leone, Stephen R; Neumark, Daniel M

    2016-05-27

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions. PMID:26980312

  17. Attosecond pulse trains as multi-color coherent control

    CERN Document Server

    Hernández, J V

    2009-01-01

    We present a general description of the interaction between multi-color laser pulses and atoms and molecules, focusing on the experimentally relevant example of infrared (IR) pulses overlapped with attosecond pulse trains (APTs). This formulation reveals explicitly and analytically the role of the delay between the IR pulse and APT as a coherent control parameter. Our formulation also shows the nearly equivalent roles of the delay and the carrier-envelope phase in controlling the interference between different multiphoton pathways. We illustrate these points by investigating the single ionization of He and introduce dressed adiabatic hyperspherical potentials to aid the discussion. We confirm the predictions with a full-dimensional, two-electron solution of the time-dependent Schr\\"odinger equation.

  18. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2011-08-01

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0×1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schrödinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  19. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    International Nuclear Information System (INIS)

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  20. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Kai-Jun; Bandrauk, Andre D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

    2011-08-15

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe{sup 2+} molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x10{sup 14} W/cm{sup 2}, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe{sup 2+}, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  1. The Simplest Method for Generation of an Attosecond Pulse Train

    Directory of Open Access Journals (Sweden)

    Katsuragawa Masayuki

    2013-03-01

    Full Text Available We report an extremely simple approach to generate an attosecond pulse train from more than octave-spanning discrete spectrum by only positioning transparent materials into the optical path without spatially dispersing the frequency components.

  2. Tailoring the amplification of attosecond pulse through detuned X-ray FEL undulator.

    Science.gov (United States)

    Kumar, Sandeep; Kang, Heung-Sik; Kim, Dong Eon

    2015-02-01

    We demonstrate that the amplification of attosecond pulse in X-ray free electron laser (FEL) undulator can be tailored. The characteristic of the amplification of an isolated attosecond pulse in the FEL undulator is investigated. An isolated 180 attoseconds full width half maximum (FWHM) pulse at 1.25 nm with a spectral bandwidth of 1% is injected into an undulator. The simulation results show that for a direct seeding of 3MW, the seed is amplified to the peak power of 106 GW (40 μJ, an output pulse-width of 383 attoseconds) in the presence of a detuning at FEL resonance condition in 100-m long undulator. We note that the introduction of detuning leads to the better performance compared to the case without detuning: shorter by 15.5% in a pulse-width and higher by 76.6% in an output power. Tapering yields a higher power (116% increases in the output power compared to the case without detuning) but a longer pulse (15.4% longer in the pulse-width). It was observed that ± Δλ(r)/8 (Δλ(r)/λ(r) ~1%) is the maximum degree of detuning, beyond which the amplification becomes poor: lower in the output power and longer in the pulse duration. The minimum power for a seed pulse needs to be higher than 1 MW for the successful amplification of an attosecond pulse at 1.25 nm. Also, the electron beam energy-spread must be less than 0.1% for a suitable propagation of attosecond pulse along the FEL undulator under this study. PMID:25836141

  3. Creation and control of a single coherent attosecond xuv pulse by few-cycle intense laser pulses

    Science.gov (United States)

    Carrera, Juan J.; Tong, X. M.; Chu, Shih-I.

    2006-08-01

    We present ab initio quantum and classical investigations on the production and control of a single attosecond pulse by using few-cycle intense laser pulses as the driving field. The high-harmonic-generation power spectrum is calculated by accurately and efficiently solving the time-dependent Schrödinger equation using the time-dependent generalized pseudospectral method. The time-frequency characteristics of the attosecond xuv pulse are analyzed in detail by means of the wavelet transform of the time-dependent induced dipole. To better understand the physical processes, we also perform classical trajectory simulation of the strong-field electron dynamics and electron returning energy map. We found that the quantum and classical results provide complementary and consistent information regarding the underlying mechanisms responsible for the production of the coherent attosecond pulse. For few-cycle (5fs) driving pulses, it is shown that the emission of the consecutive harmonics in the supercontinuum cutoff regime can be synchronized and locked in phase resulting in the production of a coherent attosecond pulse. Moreover, the time profile of the attosecond pulses can be controlled by tuning the carrier envelope phase.

  4. Molecular photoelectron momentum distributions by intense orthogonally polarized attosecond ultraviolet laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2015-10-01

    We study molecular photoelectron momentum distributions (MPMDs) of aligned H2+ by intense orthogonally polarized attosecond ultraviolet laser pulses. Photoionization is simulated by numerically solving corresponding three-dimensional time dependent Schrödinger equations with static nuclei. It is found that altering pulse phases ϕ varies the structure of MPMDs, which is attributed to the interference effect between orthogonal polarization ionizations. The phase ϕ dependent MPMDs are also a function of molecular alignment and pulse wavelengths. Altering the symmetry of initial electronic states offers the possibility of imaging molecular orbitals by orthogonal polarization attosecond MPMDs.

  5. Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented.

  6. Molecular photoelectron angular distributions with intense attosecond circularly polarized UV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2014-01-01

    We investigate effects of intermediate resonant electronic states on molecular photoelectron angular distributions (MPADs) by intense circularly polarized attosecond UV laser pulses. Simulations are performed on aligned H2+ by numerically solving the corresponding three dimensional time dependent Schrödinger equations. MPADs exhibit signature of rotations, which is shown to be critically sensitive to the symmetry of the intermediate resonant electronic state and the pulse intensity. This sensitivity is attributed to the coherent population transfer in the initial and intermediate resonant states, thus suggesting a method to control molecular photoionization on attosecond time scale.

  7. Asymmetries in production of He+(n=2) with an intense few-cycle attosecond pulse

    Science.gov (United States)

    Djiokap, J. M. Ngoko; Hu, S. X.; Jiang, Wei-Chao; Peng, Liang-You; Starace, Anthony F.

    2013-07-01

    By solving the two-electron time-dependent Schrödinger equation, we study carrier-envelope-phase (CEP) effects on ionization plus excitation of He to He+(n=2) states by a few-cycle attosecond pulse with a carrier frequency of 51 eV. For most CEPs the asymmetries in the photoelectron angular distributions with excitation of He+(2s) or He+(2p) have opposite signs and are two orders of magnitude larger than for ionization without excitation. These results indicate that attosecond pulse CEP effects may be significantly amplified in correlated two-electron ionization processes.

  8. Intensity Scalings of Attosecond Pulse Generation by the Relativistic-irradiance Laser Pulses

    Science.gov (United States)

    Pirozhkov, Alexander S.; Bulanov, Sergei V.; Esirkepov, Timur Zh.; Sagisaka, Akito; Tajima, Toshiki; Daido, Hiroyuki

    We present the theoretical comparative analysis of different attosecond pulse generation techniques in which the relativistic-irradiance driver pulses are used. In particular, we concentrate on the intensity scalings of the attosecond pulse duration, wavelength, and conversion efficiency. We also discuss the optimum conditions and the major implementation challenges.

  9. Towards efficient generation of attosecond pulses from overdense plasma targets

    International Nuclear Information System (INIS)

    Theoretical studies and computer simulations predict efficient generation of attosecond electromagnetic pulses from overdense plasma targets, driven by relativistically strong laser pulses. These predictions need to be validated in time resolved experiments in order to provide a route for applications. The first available femtosecond sources for these experiments are likely to be 10 fs pulses of a few millijoules, which could provide focal intensities at about the relativistic threshold. With particle-in-cell simulations, we demonstrate that the radiation resulting from interaction of such pulses with solid targets is expected to be attosecond trains with very high conversion efficiency as relativistic effects start to act

  10. Single attosecond pulse generation in He+ by controlling the instant ionization rate using attosecond pulse trains combined with an intense laser pulse

    International Nuclear Information System (INIS)

    High-order harmonics and single attosecond pulse generation by using an infrared laser pulse combined with attosecond pulse trains (APT) interacting with He+ have been investigated. We show that the ionization for different instant time intervals can be controlled by altering the time delay between the APT and the infrared pulse. Consequently, APT can be used as a tool to control the efficiency of high-order harmonics emitted at different times. By choosing appropriate APT and time delay, the driving pulse width for single attosecond pulse generation can be extended up to six optical cycles

  11. Single attosecond pulse generation in He+ by controlling the instant ionization rate using attosecond pulse trains combined with an intense laser pulse

    Science.gov (United States)

    He, Xinkui; Jia, T. Q.; Zhang, Jun; Suzuki, M.; Baba, M.; Ozaki, T.; Li, Ruxin; Xu, Zhizhan; Kuroda, Hiroto

    2007-08-01

    High-order harmonics and single attosecond pulse generation by using an infrared laser pulse combined with attosecond pulse trains (APT) interacting with He+ have been investigated. We show that the ionization for different instant time intervals can be controlled by altering the time delay between the APT and the infrared pulse. Consequently, APT can be used as a tool to control the efficiency of high-order harmonics emitted at different times. By choosing appropriate APT and time delay, the driving pulse width for single attosecond pulse generation can be extended up to six optical cycles.

  12. Multipass relativistic high-order-harmonic generation for intense attosecond pulses

    Science.gov (United States)

    Edwards, Matthew R.; Mikhailova, Julia M.

    2016-02-01

    We demonstrate that the total reflected field produced by the interaction of a moderately relativistic laser with dense plasma is itself an efficient driver of high-order-harmonic generation. A system of two or more successive interactions of an incident laser beam on solid targets may therefore be an experimentally realizable method of optimizing conversion of laser energy to high-order harmonics. Particle-in-cell simulations suggest that attosecond pulse intensity may be increased by up to four orders of magnitude in a multipass system, with decreased duration of the attosecond pulse train. We discuss high-order-harmonic wave-form engineering for enhanced attosecond pulse generation with an electron trajectory model, present the behavior of multipass systems over a range of parameters, and offer possible routes towards experimental implementation of a two-pass system.

  13. Generation of short and intense isolated Attosecond pulses by field-controlled excited states

    Science.gov (United States)

    Jooya, Hossein Z.; Li, Peng-Cheng; Liao, Sheng-Lun; Chu, Shih-I.

    2014-05-01

    A new mechanism for the coherent control of the generation of an isolated and ultrashort attosecond laser pulse with enhanced intensity is reported. Frequency and time delay of a weak high harmonics, added to a two color laser, are optimized to produce a 45 attosecond pulse with intensity of more than 70 times bigger than the original one. Resonance excitation and subsequent ionization are analyzed, along with electron trajectory investigation from wavelet time-frequency profile to explain the mechanism of the observed augmentation in this high-harmonic generation. This work is partially supported by DOE.

  14. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    International Nuclear Information System (INIS)

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation. (review article)

  15. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    Science.gov (United States)

    Okino, T.; Furukawa, Y.; Shimizu, T.; Nabekawa, Y.; Yamanouchi, K.; Midorikawa, K.

    2014-06-01

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation.

  16. Advances in laser technology for isolated attosecond pulse generation

    International Nuclear Information System (INIS)

    In this review we report on recent advances in laser technology, which have contributed to the fast development of attosecond science. In particular we will concentrate on two experimental methods for the generation of high-peak-power, few-optical-cycle laser pulses with controlled electric field, which are crucial for the generation of isolated attosecond pulses. The first method is the hollow-fiber compression technique, introduced in 1996 and now routinely used in several laboratories. So far, isolated attosecond pulses have been generated by using few-cycle pulses produced by such compression technique, in combination with active stabilization of the carrier-envelope phase. More recently, few-cycle pulses tunable in the infrared region have been generated by optical parametric amplification with passive stabilization of the carrier-envelope phase. Such parametric sources represent excellent drivers for the generation of harmonic radiation with an extended cutoff, and offer the possibility to extend attosecond science towards the soft-X rays region. Finally, we will briefly discuss the basic elements of attosecond metrology

  17. Attosecond control of electrons emitted from a nanoscale metal tip

    CERN Document Server

    Krüger, Michael; Hommelhoff, Peter; 10.1038/nature10196

    2011-01-01

    Attosecond science is based on steering of electrons with the electric field of well-controlled femtosecond laser pulses. It has led to, for example, the generation of XUV light pulses with a duration in the sub-100-attosecond regime, to the measurement of intra-molecular dynamics by diffraction of an electron taken from the molecule under scrutiny, and to novel ultrafast electron holography. All these effects have been observed with atoms or molecules in the gas phase. Although predicted to occur, a strong light-phase sensitivity of electrons liberated by few-cycle laser pulses from solids has hitherto been elusive. Here we show a carrier-envelope (C-E) phase-dependent current modulation of up to 100% recorded in spectra of electrons laser-emitted from a nanometric tungsten tip. Controlled by the C-E phase, electrons originate from either one or two sub-500as long instances within the 6-fs laser pulse, leading to the presence or absence of spectral interference. We also show that coherent elastic re-scatteri...

  18. Generation of coherent attosecond pulses from a nano-tube array illuminated by a high-power femtosecond laser

    International Nuclear Information System (INIS)

    A method to generate an isolated single-cycle attosecond pulse from the interaction of a high-power femtosecond laser pulse with a nano-tube array is demonstrated using a two-dimensional relativistic particle-in-cell simulation. The radiation mechanism is relativistic nonlinear Thomson scattering from the electrons in a target material. Coherent radiation is emitted in the direction of specular reflection for the incident laser pulse while the electrons make a bunch size smaller than a wavelength of the laser pulse. Maintaining the coherence of the radiation from the electrons is essential to get an intense attosecond duration, which is achieved by using a nano-tube array target and a sharply increasing laser pulse. Optimal conditions for attosecond pulse generation are investigated by parameter scanning over plasma density, target thickness and laser pulse duration. (paper)

  19. Theory of Attosecond Transient Absorption Spectroscopy of Krypton for Overlapping Pump and Probe Pulses

    OpenAIRE

    Pabst, Stefan; Sytcheva, Arina; Moulet, Antoine; Wirth, Adrian; Goulielmakis, Eleftherios; Santra, Robin

    2012-01-01

    We present the first fully ab initio calculations for attosecond transient absorption spectroscopy of atomic krypton with overlapping pump and probe pulses. Within the time-dependent configuration interaction singles (TDCIS) approach, we describe the pump step (strong-field ionization using a near-infrared pulse) as well as the probe step (resonant electron excitation using an extreme- ultraviolet pulse) from first principles. We extent our TDCIS model and account for the spin-orbit splitting...

  20. Obtaining two attosecond pulses for X-ray stimulated Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Penn, G., E-mail: gepenn@lbl.go [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2010-01-01

    Attosecond X-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft X-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each X-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 as. The carrier frequency of each X-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 as precision.

  1. Obtaining two attosecond pulses for X-ray stimulated Raman spectroscopy

    International Nuclear Information System (INIS)

    Attosecond X-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft X-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each X-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 as. The carrier frequency of each X-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 as precision.

  2. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    Science.gov (United States)

    Ma, Guangjin; Dallari, William; Borot, Antonin; Krausz, Ferenc; Yu, Wei; Tsakiris, George D.; Veisz, Laszlo

    2015-03-01

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ˜100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  3. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Guangjin, E-mail: guangjin.ma@mpq.mpg.de [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Krausz, Ferenc [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Department für Physik, Ludwig-Maximilians-Universität, D-85748 Garching (Germany); Yu, Wei [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2015-03-15

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  4. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    International Nuclear Information System (INIS)

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

  5. Perturbation-theory analysis of ionization by a chirped few-cycle attosecond pulse

    Energy Technology Data Exchange (ETDEWEB)

    Pronin, E. A.; Starace, Anthony F.; Peng Liangyou [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299 (United States); State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

    2011-07-15

    The angular distribution of electrons ionized from an atom by a chirped few-cycle attosecond pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. The dependence of the asymmetry in the ionized electron distributions on both the chirp and the carrier-envelope phase (CEP) of the pulse are explained using a simple analytical formula that approximates the exact PT result. This approximate formula (in which the chirp dependence is explicit) reproduces reasonably well the chirp-dependent oscillations of the electron angular distribution asymmetries found numerically by Peng et al. [Phys. Rev. A 80, 013407 (2009)]. It can also be used to determine the chirp rate of the attosecond pulse from the measured electron angular distribution asymmetry.

  6. Generation of high-energy isolated attosecond pulses

    International Nuclear Information System (INIS)

    Complete text of publication follows. Since the first experimental demonstration of the generation of isolated attosecond pulses, the attosecond technology has become an important branch of ultrafast science. So far, the reported applications of isolated attosecond pulses have been limited by the low photon flux of the available sources. We demonstrate a technique for the generation of isolated attosecond pulses with energy up to 2.1 nJ. The key elements are: the use of few-optical-cycle driving pulses with stable carrier-envelope phase (CEP), linear polarization and peak intensity beyond the saturation intensity of the gas use for HHG; and the optimization of the interaction geometry in terms of gas pressure, position and thickness of the gas cell. We used 5-fs driving pulses with stable CEP to generate XUV radiation by HHG in a 2.5-mm-long cell filled with xenon at static pressure (2.5-3 torr) at a peak intensity I = (2.3±0.3) x 1015 W/cm2. The XUV spectra display an evolution from a continuous behavior to a modulated one by changing the CEP value. The energy of the XUV pulses in the case of continuous spectra was 2.1 nJ, after a 100-nm-thick aluminium filter used to block the fundamental radiation and the low order harmonics. We have also used argon, krypton and neon as generating media: also in such cases clear transition between modulated and continuous XUV spectra were observed upon changing the CEP of the driving pulses. We have measured the temporal characteristics of the attosecond pulses by using the FROGCRAB method. Figure 1 a shows a portion of the FROGCRAB trace; in the reconstructed temporal intensity profile of the XUV pulses, the pulse duration was 155±5 as (the transform limit was ∼ 120 as). The physical mechanism at the basis of this method is related to the ionization dynamics in the generating medium. We used a nonadiabatic three-dimensional numerical model. In agreement with experimental results, the calculated XUV spectra display an

  7. Conditions for the reliable production of isolated attosecond pulses

    International Nuclear Information System (INIS)

    Full text: We outline a simple approach for determining plateau positions in harmonic spectra that demonstrates very clearly the requirement for carrier-envelope phase and intensity stabilisation in the IR laser pulse for reliable attosecond pulse production. Neglecting the phase and intensity characteristics of the laser pulse will lead to large variations in the duration and number of sub-fs pulses produced via high harmonics cut-off windowing. (author)

  8. Control and dynamics of attosecond electron wave packets in strong laser fields

    International Nuclear Information System (INIS)

    Full text: Trains of attosecond pulses, emerging from the phase-locking of high-order harmonics generated in a strong laser field are now being routinely produced and characterized in a few laser laboratories. Attosecond pulse trains (APTs) are flexible attosecond sources, since the amplitude and relative phase of the spectral components (the harmonics) can be tailored, allowing us to vary both the duration and the carrier frequency of the pulses. Attosecond pulses interacting with a gas of atoms generate electron wave packets (EWPs), which are temporally localized with approximately the same duration as the attosecond pulses. In contrast to the tunneling electron wave packets giving rise to processes such as high-order harmonic generation and above-threshold-ionization (ATI), the properties of these EWPs are inherited from the attosecond pulses through the single-photon ionization step. Thus the energy and temporal characteristics of the EWPs can be varied independently of the process under investigation, by controlling the properties of the attosecond pulses. This talk will describe two recent experiments done in Lund. First we report on the generation, compression and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. The APT is synthesized from the 13th to 35th harmonics of a 35 fs Ti:sapphire laser. The harmonics are generated by focusing the laser beam into a window-less gas cell, filled with argon. To achieve the required on-target attosecond pulses, the harmonics are filtered spatially, using a fixed aperture, and spectrally using aluminum filters. The aluminum filters also serve the purpose of compressing the attosecond pulses, using the negative group-delay dispersion of aluminum to compensate for the intrinsic positive chirp of the attosecond pulses. This experiment demonstrates a practical method for the synthesis and control of attosecond waveforms, and in this case the production of pulses of

  9. Probing attosecond pulse structures by XUV-induced hole dynamics

    CERN Document Server

    You, Jhih-An; Dahlström, Jan Marcus

    2015-01-01

    We investigate a two-photon ionization process in neon by an isolated attosecond pump pulse and two coherent extreme ultraviolet probe fields. The probe fields, tuned to the 2s-2p transition in the residual ion, allow for coherent control of the photoelectron via indirect interactions with the hole. We show that the photoelectron-ion coincidence signal contains an interference pattern that can be used to reconstruct the temporal structure of attosecond pump pulses. Our results are supported by simulations based on time-dependent configuration-interaction singles and lowest-order perturbation theory within second quantization.

  10. Amplitude and phase control of attosecond light pulses

    International Nuclear Information System (INIS)

    We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms

  11. Attosecond dynamics of electrons in molecules and liquids

    Science.gov (United States)

    Woerner, Hans Jakob

    2016-05-01

    The ultrafast motion of electrons and holes following light-matter interaction is fundamental to a broad range of chemical and biophysical processes. In this lecture, I will discuss two recent experiments carried out in our group that measure the atomic-scale motion of charge with attosecond temporal resolution (1 as = 10-18 s). The first experiment is carried out on isolated, spatially oriented molecules in the gas phase. We advance high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately following ionization of iodoacetylene, while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement of both even and odd harmonic orders, enables us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~ 100 as. We separately reconstruct quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determine the shape of the hole created by ionization. The second experiment is carried out on a free-flowing microjet of liquid water. We use an attosecond pulse train synchronized with a near-infrared laser pulse to temporally resolve the process of photoemission from liquid water using the RABBIT technique. We measure a delay on the order of 50 as between electrons emitted from the HOMO of liquid water compared to that of gas-phase water and a substantially reduced modulation contrast of the corresponding sidebands. Since our measurements on solvated water molecules are referenced to isolated ones, the measured delays reflect (i) the photoionization delays caused by electron transport through the aqueous environment and (ii) the effect of solvation on the parent molecule. The relative modulation contrast, in turn, contains information on (iii) the modification of transition amplitudes and (iv) dephasing processes. These experiments make the liquid phase and its fascinating

  12. The two-electron attosecond streak camera for time-resolving intra-atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Emmanouilidou, A [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Staudte, A; Corkum, P B, E-mail: a.emmanouilidou@ucl.ac.u [Joint Laboratory for Attosecond Science, University of Ottawa and National Research Council, 100 Sussex Drive, Ottawa, ON, K1A 0R6 (Canada)

    2010-10-15

    We generalize the one-electron attosecond streak camera to time-resolve the correlated two-electron escape dynamics during a collision process involving a deep core electron. The collision process is triggered by an extreme ultraviolet (XUV) attosecond pulse (single-photon absorption) and probed by a weak infrared field. The principle of our two-electron streak camera is that by placing the maximum of the vector potential of the probing field at the time of collision, we get the maximum splitting of the inter-electronic angle of escape. We thereby determine the time of collision.

  13. Single Circularly Polarized Attosecond Pulse Generation by Intense Few Cycle Elliptically Polarized Laser Pulses and Terahertz Fields from Molecular Media

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2013-01-01

    We present a method for producing a single circularly polarized attosecond pulse by an intense few cycle elliptically polarized laser pulse combined with a terahertz field from numerical solutions of the time-dependent Schrödinger equation for the molecular ion H2+. It is found that in the presence of a 62.5 THz (λ=4800nm) field at an intensity of ˜1014W/cm2, a single circularly polarized 114 as pulse can be generated by an elliptical polarized laser pulse at a wavelength of 400 nm with an ellipticity of ɛ=0.59. The efficiency of circular polarization attosecond pulse generation is interpreted based on a classical model of single electron recollision with the parent ion.

  14. Temporal Characterization of individual Harmonics of an attosecond pulse train by THz Streaking

    CERN Document Server

    Ardana-Lamas, F; Stepanov, A; Gorgisyan, I; Juranic, P; Abela, R; Hauri, C P

    2015-01-01

    We report on the global temporal pulse characteristics of individual harmonics in an attosecond pulse train by means of photo-electron streaking in a strong low-frequency transient. The scheme allows direct retrieval of pulse durations and first order chirp of individual harmonics without the need of temporal scanning. The measurements were performed using an intense THz field generated by tilted phase front technique in LiNbO_3 . Pulse properties for harmonics of order 23, 25 and 27 show that the individual pulse durations and linear chirp are decreasing by the harmonic order.

  15. Investigation of the Newly Proposed Carrier-Envelope-Phase Stable Attosecond Pulse Source

    CERN Document Server

    Tibai, Z; Nagy-Csiha, Zs; Fülöp, J A; Almási, G; Hebling, J

    2016-01-01

    Practical aspects of the robust method we recently proposed for producing few-cycle attosecond pulses with arbitrary waveform in the extreme ultraviolet spectral range are studied numerically. It is based on the undulator radiation of relativistic ultrathin electron layers produced by inverse free-electron laser process. Optimal conditions for nanobunching are given; attosecond pulse energy and waveform, and their stability are studied. For K=0.8 undulator parameter, carrier-envelope-phase stable pulses with >45 nJ energy and 80 as duration at 20 nm, and >250 nJ energy and 240 as duration at 60 nm are predicted with 31 mrad and 13 mrad phase stability, respectively.

  16. Attosecond correlation dynamics during electron tunnelling from molecules

    Energy Technology Data Exchange (ETDEWEB)

    Walters, Zachary B; Smirnova, Olga, E-mail: zwalters@gmail.co, E-mail: Olga.Smirnova@mbi-berlin.d [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin (Germany)

    2010-08-28

    In this communication, we present an analytical theory of strong-field ionization of molecules, which takes into account the rearrangement of multiple interacting electrons during the ionization process. We show that such rearrangement offers an alternative pathway to the ionization of orbitals more deeply bound than the highest occupied molecular orbital. This pathway is not subject to the full exponential suppression characteristic of direct tunnel ionization from the deeper orbitals. The departing electron produces an 'attosecond correlation pulse' which controls the rearrangement during the tunnelling process. The shape and duration of this pulse are determined by the electronic structure of the relevant states, molecular orientation and laser parameters. (fast track communication)

  17. Generation of an isolated sub-100 attosecond pulse in the water-window spectral region

    International Nuclear Information System (INIS)

    We propose a scheme to generate isolated attosecond pulses in the water-window spectral region. Based on the numerical solutions of the single active electron model, we investigate high-order harmonic generation in helium atoms driven by a multi-cycle two-colour optical field synthesized by an intense 2000 nm, 20 fs pulse and its frequency-doubled pulse. When the latter is slightly detuned and properly phase shifted with respect to the fundamental laser pulse, an ultra-broad extreme ultraviolet supercontinuum with a spectral width of 130 eV can be generated in the 270–400 eV spectral regions. A supercontinuum from 280–340 eV in the water window can be selected to yield an isolated 67 attosecond pulse without employing any phase compensation. This water window coherent x-ray pulse with less than 100 attosecond duration is a potential tool for studying the ultrafast electronic dynamics of biological samples in water. (geophysics, astronomy and astrophysics)

  18. Attosecond pulse shaping around a Cooper minimum

    CERN Document Server

    Schoun, S B; Wheeler, J; Roedig, C; Agostini, P; DiMauro, L F; Schafer, K J; Gaarde, M B

    2013-01-01

    High harmonic generation (HHG) is used to measure the spectral phase of the recombination dipole matrix element (RDM) in argon over a broad frequency range that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well with predictions based on the scattering phases and amplitudes of the interfering s- and d-channel contributions to the complementary photoionization process. The reconstructed attosecond bursts that underlie the HHG process show that the derivative of the RDM spectral phase, the group delay, does not have a straight-forward interpretation as an emission time, in contrast to the usual attochirp group delay. Instead, the rapid RDM phase variation caused by the CM reshapes the attosecond bursts.

  19. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Frassetto, F.; Poletto, L., E-mail: poletto@dei.unipd.it [National Research Council, Institute of Photonics and Nanotechnologies, via Trasea 7, 35131 Padova (Italy); Trabattoni, A.; Anumula, S.; Sansone, G. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); Calegari, F. [National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy); Nisoli, M. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy)

    2014-10-15

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10{sup 11} W/cm{sup 2}.

  20. 4D attosecond imaging with free electrons: Diffraction methods and potential applications

    Energy Technology Data Exchange (ETDEWEB)

    Baum, Peter, E-mail: peter.baum@lmu.de [Max-Planck-Institute of Quantum Optics, and Ludwig-Maximilians-Universitaet Muenchen, Am Coulombwall 1, 85748 Garching (Germany); Zewail, Ahmed H., E-mail: zewail@caltech.edu [Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125 (United States)

    2009-12-10

    We consider here the extension of four-dimensional (4D) electron imaging methodology to the attosecond time domain. Specifically, we discuss the generation of attosecond electron pulses and the in situ probing with electron diffraction. The free electron pulses have a de Broglie wavelength on the order of picometers and a high degree of monochromaticity ({Delta}E/E{sub 0} {approx} 10{sup -4}); attosecond optical pulses have typically a wavelength of 20 nm and {Delta}E/E{sub 0} {approx} 0.5, where E{sub 0} is the central energy and {Delta}E is the energy bandwidth. Diffraction, and tilting of the electron pulses/specimen, permit the direct investigation of electron density changes in molecules and condensed matter. We predict the relevant changes in diffraction caused by electron density motion and give two examples as prototype applications, one that involves matter-field interaction, and the other is that of change in bonding order. This 4D imaging on the attosecond time scale is a pump-probe approach in free space and with free electrons.

  1. Attosecond dynamics of electron correlation in doubly excited atomic states

    International Nuclear Information System (INIS)

    We have solved the time-dependent Schroedinger equation describing the simultaneous interaction of the He 1s2s 1S state with two laser-generated pulses of trapezoidal or Gaussian shape, of duration 86 fs and of frequencies ω1=1.453 au and ω2=1.781 au. The system is excited to the energy region of two strongly correlated doubly excited states, chosen for this study according to specific criteria. It is demonstrated quantitatively that, provided one focuses on the dynamics occurring within the attosecond timescale, the corresponding orbital configurations, 2s2p and 2p3d 1P0, exist as nonstationary states, with occupation probabilities that are oscillating as the states decay exponentially into the 1sεp continuum, during and after the laser-atom interaction. It follows that it is feasible to probe by attosecond pulses the motion of configurations of electrons as they correlate via the total Hamiltonian. For the particular system studied here, the probe pulses could register the oscillating doubly excited configurations by de-exciting to the He 1s3d 1D state, which emits at 6680 A. (author). Letter-to-the-editor

  2. Generation of a Super Strong Attosecond Pulse from an Atomic Superposition State Irradiated by a Shape-Optimized Short Pulse

    International Nuclear Information System (INIS)

    Using a linearly polarized, phase-stabilized 3-fs driving pulse of 800 nm central wavelength shape-optimized on its ascending edge by its an amplitude-reduced pulse irradiating on a superposition state of the helium atom, we demonstrate theoretically the generation of a super strong isolated 176-attosecond pulse in the spectral region of 93–124 eV. The unusually high intensity of this attosecond pulse is marked by the Rabi-like oscillations emerging in the time-dependent populations of the ground state and the continuum during the occurrence of the electron recombination, which is for the first time observed in this work. (atomic and molecular physics)

  3. A three-colour scheme to generate isolated attosecond pulses

    International Nuclear Information System (INIS)

    We propose a new scheme to produce isolated attosecond pulses, involving the use of three laser pulses: a fundamental laser field of intensity I = 3.5 x 1014 W cm-2 and of wavelength λ = 820 nm, and two properly chosen weak lasers with wavelengths 1.5λ and 0.5λ. The three lasers have a Gaussian envelope of 36 fs full width at half maximum. The resulting total field is an asymmetric electric field with an isolated peak. We show that a model atom, interacting with the above-defined total field, generates an isolated attosecond pulse as short as 1/10 of a laser period, i.e. approximately 270 as.

  4. A three-colour scheme to generate isolated attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Orlando, G; Corso, P P; Fiordilino, E; Persico, F, E-mail: orlando@fisica.unipa.i [Dipartimento di Scienze Fisiche ed Astronomiche, Via Archirafi 36, 90123 Palermo (Italy)

    2010-01-28

    We propose a new scheme to produce isolated attosecond pulses, involving the use of three laser pulses: a fundamental laser field of intensity I = 3.5 x 10{sup 14} W cm{sup -2} and of wavelength {lambda} = 820 nm, and two properly chosen weak lasers with wavelengths 1.5{lambda} and 0.5{lambda}. The three lasers have a Gaussian envelope of 36 fs full width at half maximum. The resulting total field is an asymmetric electric field with an isolated peak. We show that a model atom, interacting with the above-defined total field, generates an isolated attosecond pulse as short as 1/10 of a laser period, i.e. approximately 270 as.

  5. Attosecond pulse characterization with coherent Rydberg wavepackets

    CERN Document Server

    Pabst, Stefan

    2016-01-01

    We propose a new technique to fully characterize the temporal structure of extreme ultraviolet pulses by ionizing a bound coherent electronic wavepacket. The populated energy levels make it possible to interfere different spectral components leading to quantum beats in the photoelectron spectrum as a function of the delay between ionization and initiation of the wavepacket. The influence of the dipole phase, which is the main obstacle for state-of-the-art pulse characterization schemes, can be eliminated by angle integration of the photoelectron spectrum. We show that particularly atomic Rydberg wavepackets are ideal and that wavepackets involving multiple electronic states provide redundant information which can be used to cross-check the consistency of the phase reconstruction.

  6. Attosecond electronic and nuclear quantum photodynamics of the ozone molecule

    Energy Technology Data Exchange (ETDEWEB)

    Halász, G. J. [Department of Information Technology, University of Debrecen, H-4010 Debrecen, PO Box 12 (Hungary); Perveaux, A.; Lasorne, B.; Gatti, F. [CTMM, Institut Charles Gerhardt Montpellier, F-34095 Montpellier Cedex 5 (France); Robb, M. A. [Imperial College London, Department of Chemistry, London SW7 2AZ (United Kingdom); Vibók, Á. [Department of Theoretical Physics, University of Debrecen, H-40410 Debrecen, PO Box 5 (Hungary)

    2013-11-13

    Coupled electron-nuclear dynamics simulations are investigated for the ozone molecule on the attosecond time scale. The initial wavepacket is pumped as a coherent superposition of two or three electronic states.

  7. Isolated attosecond pulse generation from atom radiated by a three-color laser pulse

    International Nuclear Information System (INIS)

    We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 10 fs/800 nm Ti-sapphire laser and a two-color field consisting of 30 fs/532 nm and 30 fs/1330 nm pulses. Compared with harmonic spectrum generated by a monochromatic field, the harmonics generated from the synthesized three-color field show a supercontinuum spectrum with a bandwidth of 235 eV, ranging from the 154th to the 306th order harmonic. This phenomenon can be attributed to the fact that the ionization of atoms as well as motion of ionized electron can be effectively controlled in the three-color field. Therefore, an isolated 46-as pulse can be generated by superposing supercontinuum from the 160th to the 210th order harmonics. (atomic and molecular physics)

  8. Klein-Gordon Equation with Casimir Potential for Attosecond Laser Pulse Interaction with Matter

    CERN Document Server

    Kozlovskii, Miroslaw P; Kozlowski, Miroslaw; Marciak-Kozlowska, Janina

    2005-01-01

    In this paper the Klein-Gordon equation (K-GE) is solved for the interaction of attosecond laser pulses with medium in which Casimir force operates. It is shown that for nanoscale structures, NEMS and MEMS, the attosecond laser pulses can be used as the tool for the investigation of the role played by Casimir force on the nanoscale. Key words: Casimir force; NEMS, MEMS, Attosecond laser pulses.

  9. Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

    OpenAIRE

    Haessler, Stefan; Balčiūnas, T.; Fan, G.; Chipperfield, L.; Baltuska, A.

    2014-01-01

    Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the attosecond time scale. The applicability of these IAP would be widened drastically by increasing their energy. Here we analyze the potential of using multi-colour driving pulses for temporally gating the attosecond pulse generation process. We devise how this approach can enable the generation of IAP with the available high-energy kHz-repetition-rate Ytterb...

  10. Coherent hard x rays from attosecond pulse train-assisted harmonic generation.

    Science.gov (United States)

    Klaiber, Michael; Hatsagortsyan, Karen Z; Müller, Carsten; Keitel, Christoph H

    2008-02-15

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond pulse train of soft x rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift, which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. This way, short pulses of coherent hard x rays of up to 40 keV energy can be generated. PMID:18278127

  11. Spectral shaping of attosecond pulses using two-colour laser fields

    International Nuclear Information System (INIS)

    We use a strong two-colour laser field composed of the fundamental (800 nm) and the second harmonic (400 nm) of an infrared (IR) laser field to generate attosecond pulses with controlled spectral and temporal properties. With a second-harmonic intensity equal to 15% of the IR intensity the second-harmonic field is strong enough to significantly alter and control the electron trajectories in the generation process. This enables us to tune the central photon energy of the attosecond pulses by changing the phase difference between the IR and the second-harmonic fields. In the time domain the radiation is emitted as a sequence of pulses separated by a full IR cycle. We also perform calculations showing that the effect of even stronger second-harmonic fields leads to an extended tunable range under conditions that are experimentally feasible

  12. Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)

  13. Harmonic and attosecond pulse enhancement in the presence of noise

    International Nuclear Information System (INIS)

    In this paper, we theoretically investigate the effect of noise on the photoionization, the generation of the high-order harmonic and the attosecond pulse irradiated from a model He+ ion. It shows that by properly adding noise fields, such as Gaussian white noise, random light or colored noise, both the ionization probabilities (IPs) and the harmonic yields can be enhanced by several orders of magnitude. Further, by tuning the noise intensity, a stochastic resonance-like curve is observed, showing the existence of an optimal noise in the ionization enhancement process. Finally, by superposing a properly selected harmonic, an intense attosecond pulse with a duration of 67 as is directly generated. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  14. Harmonic and attosecond pulse enhancement in the presence of noise

    Institute of Scientific and Technical Information of China (English)

    Feng Li-Qiang; Chu Tian-Shu

    2012-01-01

    In this paper,we theoretically investigate the effect of noise on the photoionization,the generation of the high-order harmonic and the attosecond pulse irradiated from a model He+ ion.It shows that by properly adding noise fields,such as Gaussian white noise,random light or colored noise,both the ionization probabilities (IPs) and the harmonic yields can be enhanced by several orders of magnitude.Further,by tuning the noise intensity,a stochastic resonance-like curve is observed,showing the existence of an optimal noise in the ionization enhancement process.Finally,by superposing a properly selected harmonic,an intense attosecond pulse with a duration of 67 as is directly generated.

  15. Enhanced dense attosecond electron bunch generation by irradiating an intense laser on a cone target

    Science.gov (United States)

    Hu, Li-Xiang; Yu, Tong-Pu; Shao, Fu-Qiu; Zou, De-Bin; Yin, Yan

    2015-03-01

    By using two-dimensional particle-in-cell simulations, we demonstrate enhanced spatially periodic attosecond electron bunches generation with an average density of about 10nc and cut-off energy up to 380 MeV. These bunches are acquired from the interaction of an ultra-short ultra-intense laser pulse with a cone target. The laser oscillating field pulls out the cone surface electrons periodically and accelerates them forward via laser pondermotive force. The inner cone wall can effectively guide these bunches and lead to their stable propagation in the cone, resulting in overdense energetic attosecond electron generation. We also consider the influence of laser and cone target parameters on the bunch properties. It indicates that the attosecond electron bunch acceleration and propagation could be significantly enhanced without evident divergency by attaching a plasma capillary to the original cone tip.

  16. Enhanced dense attosecond electron bunch generation by irradiating an intense laser on a cone target

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Li-Xiang; Yu, Tong-Pu, E-mail: tongpu@nudt.edu.cn; Shao, Fu-Qiu; Zou, De-Bin; Yin, Yan [College of Science, National University of Defense Technology, Changsha 410073 (China)

    2015-03-15

    By using two-dimensional particle-in-cell simulations, we demonstrate enhanced spatially periodic attosecond electron bunches generation with an average density of about 10n{sub c} and cut-off energy up to 380 MeV. These bunches are acquired from the interaction of an ultra-short ultra-intense laser pulse with a cone target. The laser oscillating field pulls out the cone surface electrons periodically and accelerates them forward via laser pondermotive force. The inner cone wall can effectively guide these bunches and lead to their stable propagation in the cone, resulting in overdense energetic attosecond electron generation. We also consider the influence of laser and cone target parameters on the bunch properties. It indicates that the attosecond electron bunch acceleration and propagation could be significantly enhanced without evident divergency by attaching a plasma capillary to the original cone tip.

  17. Attosecond control of collective electron motion in plasmas

    OpenAIRE

    Borot, Antonin; Malvache, Arnaud; Chen, Xiaowei; Jullien, Aurélie; Geindre, Jean-Paul; Audebert, Patrick; Mourou, Gérard; Quéré, Fabien; Lopez-Martens, Rodrigo

    2012-01-01

    Today, light fields of controlled and measured waveform can be used to guide electron motion in atoms and molecules with attosecond precision. Here, we demonstrate attosecond control of collective electron motion in plasmas driven by extreme intensity (≈1018 W cm−2) light fields. Controlled few-cycle near-infrared waves are tightly focused at the interface between vacuum and a solid-density plasma, where they launch and guide subcycle motion of electrons from the plasma with characteristic en...

  18. Molecular orbital imaging using attosecond pulses generated in N2

    International Nuclear Information System (INIS)

    Complete text of publication follows. The strong interaction of a molecule with a laser field frees by tunnel ionization an attosecond electron wave packet that probes its bound state half a laser cycle later as it re-collides with the core. Rich information on ths (possibly transient) electronic and nuclear configuration is encoded in the attosecond XUV burst emitted during recombination, a process called high-order harmonic generation (HHG). Complete characterization (intensity, phase and polarization) of this observable gives access to the transition dipole moment over a large momentum span. This transition dipole may allow direct imaging of the radiating molecular orbital using a tomographic procedure. For the first time we succeeded to characterize the intensity, phase and polarization of the XUV emission in aligned N2 molecules. Our measurements evidence multi-orbital contributions to the attosecond emission and also reveal the ellipticity of the harmonics. Recent experimental and theoretical studies have revealed that molecules could be tunnel ionized from several orbitals simultaneously. These different orbitals lead to interfering contributions in the attosecond emission. We were able to separate these contributions and by using the tomographic molecular orbital reconstruction technique, HOMO and HOMO-1 orbitals were reconstructed in N2. These reconstructions show remarkable agreement with theoretical simulations and also provide us with the sign changes in the orbital wave functions. An investigation was addressed to the validity of the plane wave approximation in our calculation. The coherent superposition of the HOMO and HOMO-1 orbitals provides time-resolved experimental images of the wave packet ('hole') left empty after coherent tunnel ionization from both orbitals. The recombining electron wave packet probes the 'hole' at the instant of recombination providing information about the electronic structure of the molecule at that moment. This imaging of

  19. Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

    International Nuclear Information System (INIS)

    We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (∼20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes

  20. Single X-Ray Attosecond Pulse Generation by Using Combined Pulses Irradiating on a United Two-Atom System

    Institute of Scientific and Technical Information of China (English)

    CHEN Ji-Gen; LI Chen; CHI Fang-Ping; YANG Yu-Jun

    2007-01-01

    @@ A scheme of a single x-ray attosecond pulse generation from a two-atom system exposed to the combined laser pulses is proposed. Our numerical results show that a single x-ray attosecond pulse rather than a train one can be produced by modulation of ionization.

  1. Attosecond pulse generation by a two-color field

    International Nuclear Information System (INIS)

    A method for the generation of attosecond electromagnetic pulses is suggested. The key idea of the method consists in using a two-color laser pump for high-order harmonic generation composed of a low-frequency linearly polarized field and a high-frequency elliptically polarized field. Such a two-color pump can provide for the return of photoelectrons (after atom ionization) to the vicinity of the parent ion with high kinetic energy and their recombination for only specific ionization moments t0. The range of these moments, δt0, is defined by the velocity of electron wave-packet spreading and the time that the photoelectron spent in the continuum (before the recombination). Conditions were found that minimize the range δt0. For the specific parameters of a two-color pump, the duration of recombination emission, τg, can be in the range of 1-10 as. With an increase of pump intensity, the duration τg decreases and can be reduced to the subattosecond scale

  2. Attosecond physics

    International Nuclear Information System (INIS)

    The first part of the thesis is dealing with issues related to the problem of extending time-resolved spectroscopy into attosecond time domain. Despite of first experimental successes, the technique of generating attosecond light pulses is still in its infancy. As a result, important problems and questions remain unanswered. The purpose of this chapter is the temporal and spatial characterization of harmonic attosecond pulses by theoretical means. Here, an ab-initio numerical model is presented, which gives us detailed, quantitative information on the generation and characterization of such pulses. The topic of the second part is the relativistic ionization. Here we introduce the analytic single-electron-response theory of tunnel ionization of hydrogenlike ions in ultrahigh intensity laser fields. Since the problem of relativistic ionization is intrinsically three-dimensional, ionization rates are obtained from a quasi-classical solution of the three-dimensional Klein-Gordon and Dirac equations. This presents the first quantitative determination of tunneling in atomic ions in the relativistic regime. Such a theory opens the possibility to study strong laser field processes with highly charged ions, where relativistic ionization plays a dominant role. An actual example of such a process, where relativistic tunneling plays an essential role, is given in third part of this thesis. Here we make use of two key properties of relativistic ionization: on the one hand, due to the high nonlinearity of the tunneling process, ionized electrons appear in form of free electron pulses with attosecond pulse duration. On the other hand, since the kinetic energy of a laser-accelerated electrons increases with rising intensity, these attosecond electron pulses gain energy in MeV-range in a relativistic laser field. Based on these two facts, we introduce a method to refocus such energetic attosecond electron pulses to the parent nucleus immediately following ionization. Furthermore

  3. Coherent hard x-rays from attosecond pulse train-assisted harmonic generation

    OpenAIRE

    Klaiber, Michael; Hatsagortsyan, Karen Z.; Müller, Carsten; Christoph H. Keitel

    2007-01-01

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond-pulse train of soft x-rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. I...

  4. Quantum interference in laser-assisted photoionization and analytical methods for the measurement of an attosecond xuv pulse

    International Nuclear Information System (INIS)

    Investigations of the quantum interference in laser-assisted photoionization by an attosecond extreme ultraviolet (xuv) pulse shows an approximately constant value for the total photoionizations for different laser intensities. The square of the full width at half maximum of a photoelectron energy spectrum (PES) linearly depends on the laser intensity. By determining the laser-related phase of each streaked electron and using a transfer equation with linear corrections, an analytically quick method is proposed for precisely reconstructing the xuv pulse intensity (chirp) from one (two) measured PES(s) with a theoretical root-mean-square temporal (energy) difference of less than 1 attosecond (0.1 eV).

  5. Quantum interference in laser-assisted photoionization and analytical methods for the measurement of an attosecond xuv pulse

    Energy Technology Data Exchange (ETDEWEB)

    Ge Yucheng; He Haiping [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)

    2011-08-15

    Investigations of the quantum interference in laser-assisted photoionization by an attosecond extreme ultraviolet (xuv) pulse shows an approximately constant value for the total photoionizations for different laser intensities. The square of the full width at half maximum of a photoelectron energy spectrum (PES) linearly depends on the laser intensity. By determining the laser-related phase of each streaked electron and using a transfer equation with linear corrections, an analytically quick method is proposed for precisely reconstructing the xuv pulse intensity (chirp) from one (two) measured PES(s) with a theoretical root-mean-square temporal (energy) difference of less than 1 attosecond (0.1 eV).

  6. Double Ionization of He by an Intense Elliptically-Polarized, Few-Cycle Attosecond Pulse

    Science.gov (United States)

    Ngoko Djiokap, Jean Marcel; Manakov, Nikolai M.; Meremianin, Alexei V.; Hu, Suxing; Madsen, Lars B.; Starace, Anthony F.

    2015-05-01

    By solving the six-dimensional two-electron, time-dependent Schrödinger equation for He interacting with an arbitrarily-polarized intense attosecond XUV pulse, we demonstrate numerically the control of He double ionization by means of the pulse polarization and its carrier-envelope phase (CEP). Using perturbation theory (PT), we predict a new type of CEP-sensitive polarization asymmetry that is normally absent in single photon double ionization of He, but does occur for an elliptically-polarized, few-cycle attosecond XUV pulse. We call this new effect nonlinear dichroism, which is sensitive not only to the ellipticity, peak intensity I, and temporal duration of the pulse, but also to the energy-sharing. This dichroic effect (i.e., the difference of the two-electron angular distributions for opposite helicities of the ionizing XUV pulse) originates from interference of first- and second-order PT amplitudes, allowing one to investigate and control S- and D-wave channels of the two-electron continuum. Nonlinear dichroism probes electron correlation on its natural timescale since it vanishes for long pulses. Research supported in part by DOE, BES, Chem. Sciences, Geosciences, and Biosciences Div., Grant No. DEFG03-96ER14646.

  7. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    International Nuclear Information System (INIS)

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  8. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Balogh, Emeric [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); Kovacs, Katalin [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Dombi, Peter; Farkas, Gyozo [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Fulop, Jozsef A.; Hebling, Janos [Department of Experimental Physics, University of Pecs, H-7624 Pecs (Hungary); Tosa, Valer [National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Varju, Katalin [HAS Research Group on Laser Physics, University of Szeged, H-6701 Szeged (Hungary)

    2011-08-15

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  9. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    CERN Document Server

    Balogh, Emeric; Dombi, Peter; Fulop, Jozsef A; Farkas, Gyozo; Hebling, Janos; Tosa, Valer; Varju, Katalin; 10.1103/PhysRevA.84.023806

    2011-01-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half-cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single atom response yields an attosecond pulse train.

  10. A case study for terahertz-assisted single attosecond pulse generation

    CERN Document Server

    Balogh, Emeric; Tosa, Valer; Varjú, Katalin

    2014-01-01

    We numerically investigate the use of strong THz radiation in assisting single attosecond pulse generation by few-cycle, 800 nm laser pulses. We optimize focusing conditions to generate short and powerful single attosecond pulses of high-energy photons by keeping the parameters of the THz field within the limits achieved experimentally. We show that using optimal focusing geometry isolated attosecond pulses shorter than 100 as can be obtained even in the absence of further gating or XUV compression techniques, using an 8 fs generating pulse. Furthermore, quantum path control of short- and long-trajectory components is demonstrated by varying the delay between the THz and IR pulses.

  11. Attosecond Thomson-scattering x-ray source driven by laser-based electron acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Luo, W. [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China); College of Science, National University of Defense Technology, Changsha 410073 (China); Zhuo, H. B.; Yu, T. P. [College of Science, National University of Defense Technology, Changsha 410073 (China); Ma, Y. Y. [College of Science, National University of Defense Technology, Changsha 410073 (China); Applied Ion Beam Physics Laboratory, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Song, Y. M.; Zhu, Z. C. [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Theoretical Physics I, Ruhr University, D-44801 Bochum (Germany)

    2013-10-21

    The possibility of producing attosecond x-rays through Thomson scattering of laser light off laser-driven relativistic electron beams is investigated. For a ≤200-as, tens-MeV electron bunch produced with laser ponderomotive-force acceleration in a plasma wire, exceeding 10{sup 6} photons/s in the form of ∼160 as pulses in the range of 3–300 keV are predicted, with a peak brightness of ≥5 × 10{sup 20} photons/(s mm{sup 2} mrad{sup 2} 0.1% bandwidth). Our study suggests that the physical scheme discussed in this work can be used for an ultrafast (attosecond) x-ray source, which is the most beneficial for time-resolved atomic physics, dubbed “attosecond physics.”.

  12. Generation of Attosecond X-Ray Pulse through Coherent Relativistic Nonlinear Thomson Scattering

    CERN Document Server

    Lee, K; Jeong, Y U; Lee, B C; Park, S H

    2005-01-01

    In contrast to some recent experimental results, which state that the Nonlinear Thomson Scattered (NTS) radiation is incoherent, a coherent condition under which the scattered radiation of an incident laser pulse by a bunch of electrons can be coherently superposed has been investigated. The Coherent Relativistic Nonlinear Thomson Scattered (C-RNTS) radiation makes it possible utilizing the ultra-short pulse nature of NTS radiation with a bunch of electrons, such as plasma or electron beams. A numerical simulation shows that a 25 attosecond X-ray pulse can be generated by irradiating an ultra-intense laser pulse of 4x10(19) W/cm2 on an ultra-thin solid target of 50 nm thickness, which is commercially available. The coherent condition can be easily extended to an electron beam from accelerators. Different from the solid target, much narrower electron beam is required for the generation of an attosecond pulse. Instead, this condition could be applied for the generation of intense Compton scattered X-rays with a...

  13. Comparison of RABITT and FROG measurements in the temporal characterization of attosecond pulse trains

    CERN Document Server

    Kim, Kyung Taec; Park, Mi Na; Imran, Tayyab; Umesh, G; Nam, Chang Hee

    2007-01-01

    The attosecond high harmonic pulses obtained from a long Ar-filled gas cell were characterized by two techniques - the reconstruction of attosecond beating by interference of two-photon transition (RABITT) and frequency-resolved optical gating (FROG) methods. The pulse durations obtained by RABITT and FROG methods agreed within 10 %.

  14. Attosecond control of orbital parity mix interferences and the relative phase of even and odd harmonics in an attosecond pulse train.

    Science.gov (United States)

    Laurent, G; Cao, W; Li, H; Wang, Z; Ben-Itzhak, I; Cocke, C L

    2012-08-24

    We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train. PMID:23002742

  15. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    Directory of Open Access Journals (Sweden)

    Jianqiang Zhu

    2012-01-01

    Full Text Available We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA. The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about 10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments.

  16. Optical-induced electrical current in diamond switched by femtosecond–attosecond laser pulses by ab initio simulations

    International Nuclear Information System (INIS)

    The electric current has been switched in diamond by a dual-laser field with an attosecond pulse train and a femtosecond laser, respectively serving to excite and drive electrons. The optical-induced current is simulated by the developed method based on the time-dependent density functional theory. The electric current is induced within several attoseconds with the diamond’s conductivity increased by 16∼23 orders of magnitude. Our work opens the way to extending electronic signal processing from the present gigahertz domain into the exahertz domain. (paper)

  17. Single attosecond burst generation during ionization of excited atoms by intense ultrashort laser pulses

    Science.gov (United States)

    Emelin, M. Yu.; Ryabikin, M. Yu.; Sergeev, A. M.

    2008-02-01

    We develop an analytical approach to describing the generation of a single attosecond burst during barrier-suppression ionization of a hydrogen atom by an intense laser pulse. We derive analytical expressions that describe the evolution of the electron wave packet in the time interval between the detachment from the atom and the collision with the parent ion for an arbitrary initial atomic state by assuming the atom to be fully ionized in one laser-field half-period. For various s-states, we derive expressions for the profile of the attosecond burst generated when the electron packet collides with the ion and analyze the dependence of its generation efficiency on the principal quantum number n of the initial atomic state. The results obtained are compared with the results of three-dimensional numerical calculations. We show that the attosecond pulse generation efficiency can be several orders of magnitude higher than that in the case of ionization from the ground state when pre-excited atomic states are used.

  18. Control of high order harmonic emission using attosecond pulse trains

    International Nuclear Information System (INIS)

    Full text: We show that attosecond pulse trains (APTs) are a natural tool for controlling strong field processes such as high order harmonic generation. When used in combination with an intense infrared laser field, the timing of the APT with respect to the infrared (IR) laser field can be used to microscopically select a single quantum path contribution to a process that would otherwise consist of many interfering components. It is through this timing that we predict control over the release of the electron into the continuum, its excursion inside the continuum and consequently influence the yield and coherence properties of the harmonics. Since our initial calculation was based on the time-dependent Schroedinger equation, only single atom effects could be predicted. We have carried out an initial experiment in which we generate the APT from harmonic generation in a xenon fiber target, and focus the APT together with the remaining IR field with an Ag mirror into an He gas jet. The photon spectrum for a fixed time delay between APT and IR field is shown: a clear enhancement of the harmonic spectrum at the cutoff region is seen only when both the APT and the IR field are present. We have predicted control over quantum paths of electron wavepackets using a combination of APT and an IR field, manifesting in the harmonic photon spectrum as order-of-magnitude enhancement of the harmonic yield and spectral cleanup. First experimental results, for a fixed time delay, clearly confirm the enhancement and spectral control, whereas in a future experiment we plan to vary the time delay. Refs. 3 (author)

  19. State-of-the-art attosecond metrology

    International Nuclear Information System (INIS)

    Research highlights: → We present a complete setup for investigations with attosecond temporal resoultion. → Few-cycle visible laser pulses are used to generate xray pulses approaching the atomic unit of time. → Attosecond XUV pulses explore ultrafast electronic dynamics in atoms. - Abstract: Tracking and controlling electron dynamics in the interior of atoms, molecules as well as in solids is at the forefront of modern ultrafast science . Time-resolved studies of these dynamics require attosecond temporal resolution that is provided by an ensemble of techniques consolidated under the term 'attosecond metrology'. This work reports the development and commissioning of what we refer to as next-generation attosecond beamline technology: the AS-1 attosecond beamline at the Max-Planck Institute of Quantum Optics. It consists of a phase-stabilized few-cycle laser system, for the generation of XUV radiation, and modules tailored for the spectral filtering and isolation of attosecond pulses as well as for their temporal characterization. The setup produces the shortest attosecond pulses demonstrated to date and combines them with advanced spectroscopic instrumentation (electron-, ion- and XUV-spectrometers). These pulses serve as temporally confined trigger events (attosecond streaking and tunneling spectroscopy) or probe pulses (attosecond absorption and photoelectron spectroscopy) enabling attosecond chronoscopy to be applied to a broad range of systems belonging to the microcosm.

  20. State-of-the-art attosecond metrology

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, M., E-mail: martin.schultze@mpq.mpg.de [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Wirth, A.; Grguras, I.; Uiberacker, M.; Uphues, T.; Verhoef, A.J.; Gagnon, J. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Hofstetter, M.; Kleineberg, U. [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Goulielmakis, E. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Krausz, F. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany)

    2011-04-15

    Research highlights: {yields} We present a complete setup for investigations with attosecond temporal resoultion. {yields} Few-cycle visible laser pulses are used to generate xray pulses approaching the atomic unit of time. {yields} Attosecond XUV pulses explore ultrafast electronic dynamics in atoms. - Abstract: Tracking and controlling electron dynamics in the interior of atoms, molecules as well as in solids is at the forefront of modern ultrafast science . Time-resolved studies of these dynamics require attosecond temporal resolution that is provided by an ensemble of techniques consolidated under the term 'attosecond metrology'. This work reports the development and commissioning of what we refer to as next-generation attosecond beamline technology: the AS-1 attosecond beamline at the Max-Planck Institute of Quantum Optics. It consists of a phase-stabilized few-cycle laser system, for the generation of XUV radiation, and modules tailored for the spectral filtering and isolation of attosecond pulses as well as for their temporal characterization. The setup produces the shortest attosecond pulses demonstrated to date and combines them with advanced spectroscopic instrumentation (electron-, ion- and XUV-spectrometers). These pulses serve as temporally confined trigger events (attosecond streaking and tunneling spectroscopy) or probe pulses (attosecond absorption and photoelectron spectroscopy) enabling attosecond chronoscopy to be applied to a broad range of systems belonging to the microcosm.

  1. Nonlinear Interaction of Intense Attosecond XUV Pulses with Atoms and Molecules

    Science.gov (United States)

    Midorikawa, K.; Shimizu, T.; Nabekawa, Y.

    We have observed nonlinear optical processes such as two-photon double ionization and above threshold ionization of rare gases in the xuv region with intense high-order harmonics. Using two-photon double ionization in He, the pulse width of the 27th (42 eV) harmonic was measured by an autocorrelation technique, and found it to be 8 ns. A train of attosecond pulses was also characterized directly by the energy-resolved autocorrelation of the above threshold ionized electrons.

  2. Attosecond chirp compensation over broadband high-order harmonics to generate near transform-limited 63 as pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Dong Hyuk; Kim, Kyung Taec; Park, Juyun; Lee, Jae-hwan; Nam, Chang Hee, E-mail: chnam@kaist.ac.k [Department of Physics and Coherent X-ray Research Center, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-06-15

    By generating broadband high-harmonic pulses from neon and compensating for attosecond chirp by the material dispersion of argon, the generation of near transform-limited 63 as pulses was achieved. The spectral phase analysis showed that, without proper compensation, the attosecond chirp of the broadband harmonics caused splitting of attosecond high-harmonic pulses in addition to pulse broadening. Although it was attained only within a limited spectral range, the attosecond chirp compensation was successful in bringing out pulse compression over broad harmonics, which signifies the effectiveness of the attosecond chirp compensation by material dispersion.

  3. Generation of high harmonics and attosecond pulses with ultrashort laser pulse filaments and conical waves

    Indian Academy of Sciences (India)

    A Couairon; A Lotti; D Faccio; P Di Trapani; D S Steingrube; E Schulz; T Binhammer; U Morgner; M Kovacev; M B Gaarde

    2014-08-01

    Results illustrating the nonlinear dynamics of ultrashort laser pulse filamentation in gases are presented, with particular emphasis on the filament properties useful for developing attosecond light sources. Two aspects of ultrashort pulse filaments are specifically discussed: (i) numerical simulation results on pulse self-compression by filamentation in a gas cell filled with noble gas. Measurements of high harmonics generated by the pulse extracted from the filament allows for the detection of intensity spikes and subcycle pulses generated within the filament. (ii) Simulation results on the spontaneous formation of conical wavepackets during filamentation in gases, which in turn can be used as efficient driving pulses for the generation of high harmonics and isolated attosecond pulses.

  4. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    Science.gov (United States)

    Chen, Zi-Yu; Li, Xiao-Ya; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-06-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. It is also shown that XUV pulse of peak field strength up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$ can be produced. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  5. Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses

    CERN Document Server

    Chen, Zi-Yu; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

    2014-01-01

    A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. In addition, the peak electric field of the pulse is up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

  6. Secondary-electron cascade in attosecond photoelectron spectroscopy from metals

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    an analytical model based on an approximate solution to Boltzmann's transport equation to account for the amount and energy distribution of these secondary electrons. Our theory is in good agreement with the electron spectrum found in a recent attosecond streaking experiment. To suppress the......Attosecond spectroscopy is currently restricted to photon energies around 100 eV. We show that under these conditions, electron-electron scatterings, as the photoelectrons leave the metal, give rise to a tail of secondary electrons with lower energies and hence a significant background. We develop...

  7. Nonlinear Optics of Intense Attosecond Light Pulses

    Science.gov (United States)

    Nazarkin, Alexander

    2006-10-01

    The interaction of an intense light pulse of "subatomic" duration with a system of multiple discrete quantum states is analyzed. The nonperturbative character of the response to the pulse field leading to an efficient conversion into high order harmonics is predicted. The spatial-temporal evolution of the field is shown to obey a generalized nonlinear wave equation of the double-sine-Gordon type. In addition to the solitary wave structures, it predicts a nontrivial regime of pulse amplification accompanied by extreme temporal self-contraction of the amplified field.

  8. Two attosecond pulse transient absorption spectroscopy and extraction of the instantaneous AC Stark shift in helium

    Science.gov (United States)

    Bækhøj, Jens E.; Bojer Madsen, Lars

    2016-07-01

    In two attosecond pulse absorption spectroscopy (TAPAS) the use of two attosecond XUV pulses allows the extraction of atomic and molecular quantum mechanical dipole phases from spectroscopic measurements. TAPAS relies on interference between processes that individually only include a single XUV photon, and therefore does not rely on high intensity attosecond pulses. To show the usefulness and limitations of the TAPAS method we investigate its capability of capturing the instantaneous AC Stark shift induced by a midinfrared 3200 nm pulse in the | 1{{s}}2{{p}}> state of helium.

  9. Intense single attosecond pulses from surface harmonics using the polarization gating technique

    Science.gov (United States)

    Rykovanov, S. G.; Geissler, M.; Meyer-ter-Vehn, J.; Tsakiris, G. D.

    2008-02-01

    Harmonics generated at solid surfaces interacting with relativistically strong laser pulses are a promising route towards intense attosecond pulses. In order to obtain single attosecond pulses one can use few-cycle laser pulses with carrier-envelope phase stabilization. However, it appears feasible to use longer pulses using polarization gating—the technique known for a long time from gas harmonics. In this paper, we investigate in detail a specific approach to this technique on the basis of one-dimensional-particle-in-cell (1D PIC) simulations, applied to surface harmonics. We show that under realistic conditions polarization gating results in significant temporal confinement of the harmonics emission allowing thus the generation of intense single attosecond pulses. We study the parameters needed for gating only one attosecond pulse and show that this technique is applicable to both normal and oblique incidence geometry.

  10. Few-Cycle Driven Relativistically Oscillating Plasma Mirrors: A Source of Intense Isolated Attosecond Pulses

    Science.gov (United States)

    Heissler, P.; Hörlein, R.; Mikhailova, J. M.; Waldecker, L.; Tzallas, P.; Buck, A.; Schmid, K.; Sears, C. M. S.; Krausz, F.; Veisz, L.; Zepf, M.; Tsakiris, G. D.

    2012-06-01

    The conditions required for the production of isolated attosecond pulses from relativistically oscillating mirrors (ROM) are investigated numerically and experimentally. In simulations, carrier-envelope-phase-stabilized three-cycle pulses are found to be sufficient to produce isolated attosecond pulses, while two-cycle pulses will predominantly lead to isolated attosecond pulses even in the absence of carrier-envelope stabilization. Using a state-of-the-art laser system delivering three-cycle pulses at multiple-terawatt level, we have generated higher harmonics up to 70 eV photon energy via the ROM mechanism. The observed spectra are in agreement with theoretical expectations and highlight the potential of few-cycle-driven ROM harmonics for intense isolated attosecond pulse generation for performing extreme ultraviolet-pump extreme ultraviolet-probe experiments.

  11. Spectral signature of short attosecond pulse trains

    CERN Document Server

    Mansten, E; Mauritsson, J; Ruchon, T; LHuillier, A; Tate, J; Gaarde, M B; Eckle, P; Guandalini, A; Holler, M; Schapper, F; Gallmann, L; Keller, U

    2008-01-01

    We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.

  12. Molecular above-threshold-ionization angular distributions with intense circularly polarized attosecond XUV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2012-05-01

    Photoionization of aligned and fixed nuclei three-dimensional H2+ and two-dimensional H2 by intense circularly polarized attosecond extreme ultraviolet laser pulses is investigated from numerical solutions of the time-dependent Schrödinger equation. Molecular above-threshold-ionization angular distributions are found to be rotated with respect to the two laser perpendicular polarizations or, equivalently the symmetry axes of the molecule. The angle of rotation is critically sensitive to laser wavelength λ, photoelectron energy Een, and molecular internuclear distance R. The correlated interaction of the two electrons in H2 is shown to also influence such angular distribution rotations in different electronic states.

  13. Double ionization of H{sub 2} by intense attosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Teck-Ghee; Pindzola, M S; Robicheaux, F, E-mail: tg10002@auburn.ed [Department of Physics, Auburn University, Auburn, AL 36849 (United States)

    2010-08-28

    We present calculations of the double ionization of H{sub 2} induced by an intense attosecond laser pulse at a photon energy of 40 eV using the time-dependent close-coupling method within the fixed nuclei approximation. We focus on two-photon absorption processes and examine how the response of the ejected electrons, in particular the single- and the double-energy differential probabilities, is affected by linear and circular polarizations at laser-field intensities ranging from 10{sup 15} W cm{sup -2} to 10{sup 16} W cm{sup -2}. In general, we find that for both linearly and circularly polarized pulses, sequential peaks and non-sequential wells that appear in both the single- and double-energy differential probabilities are akin to the analogous two-electron photoemission processes in the helium atom driven by intense attosecond pulses. In addition, for the case of a linearly polarized pulse, a clear signature of the sequential double-electron above the threshold ionization process can be seen in these spectra.

  14. Real time tracing of valence-shell electronic coherences with attosecond transient absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wirth, A. [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany); Santra, R. [Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Department of Physics, University of Hamburg, Jungiusstrasse 9, 20355 Hamburg (Germany); Goulielmakis, E., E-mail: elgo@mpq.mpg.de [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany)

    2013-03-12

    Highlights: ► Detailing the technique of attosecond transient absorption spectroscopy. ► Tracing the charge state time-resolved ionization of atoms. ► Real-time observation and reconstruction of valence electron motion in Kr{sup +} ions. ► Observation of coherences in correlated multi-hole systems: Kr{sup 2+} and xenon ions. - Abstract: The chemical properties of atoms, molecules and of more complex systems such as clusters, nanoparticles or condensed matter systems are determined by valence electrons. Real-time control of these properties requires the capability of tracing as well as of driving valence electrons on their native temporal scale of motion, that is, within tens to thousands of attoseconds. Here we detail the technique of attosecond transient absorption spectroscopy. It combines the extreme sensitivity of core-level spectroscopy with the unprecedented temporal resolution offered by the tools of attosecond technology. We use the technique to demonstrate real-time tracing and complete characterization of coherent electron motion triggered by single, double or multiple ionization of atoms exposed to intense, few-cycle pulses. Our work opens the door to high fidelity, time-domain studies and control of electron dynamics in the microcosm.

  15. Effects of Laser Intensities and Target Shapes on Attosecond Pulse Generation from Irradiated Solid Surfaces

    Science.gov (United States)

    Zheng, Jun; Sheng, Zheng-Ming; Zhang, Jie; Chen, Min; Ma, Yan-Yun

    2006-02-01

    Single attosecond pulses can be generated when an intense laser pulse focused in a volume of a few cubic wavelengths (λ3) is reflected from a solid plasma surface. With relativistic two-dimensional particle-in-cell simulations, we investigate the effects of the incident laser intensity and the target surface profiles on attosecond pulse generation. Usually the width of the reflected attosecond pulse decreases and its electromagnetic energy density increases with increasing laser intensity, while the energy conversion efficiency to the attoseond pulse decreases. By changing the target surface profile, such as using a convex surface or adding proper preplasma, one can further shorten the attosecond pulse duration and meanwhile increase its energy density.

  16. Towards intense attosecond pulses: using two beams for high order harmonic generation from solid targets

    Science.gov (United States)

    Tarasevitch, A. P.; Kohn, R.; von der Linde, D.

    2009-07-01

    The advantages of using two beam high order harmonic generation (HOHG) from solids are discussed. The two-pulse technique allows additional control of the parameters essential for the attosecond pulse generation. We show that spectral filtering is not necessary for the generation of attosecond pulses. The simple oscillating mirror model is in qualitative agreement with the computer simulations. We present the results of first experiments using two beams for HOHG.

  17. Effects of pressure and gas-jet thickness on the generation of attosecond pulse

    International Nuclear Information System (INIS)

    We investigate how the intensity and duration of an attosecond pulse generated from high-order harmonic generation are affected by the pressure and thickness of the gas jet by taking into account the macroscopic propagation of both fundamental and harmonic fields. Our simulations show that, limited by the propagation effects, especially the absorption of harmonics, the intensity of an attosecond pulse cannot be improved by just independently increasing the gas pressure or the medium length. On the other hand, due to good phase-matching conditions, the duration of a generated attosecond pulse can be improved by changing the gas pressure. (atomic and molecular physics)

  18. Genetic optimization of attosecond pulse generation in light-field synthesizers

    CERN Document Server

    Balogh, E; Tosa, V; Goulielmakis, E; Varjú, K; Dombi, P

    2014-01-01

    We demonstrate control over attosecond pulse generation and shaping by numerically optimizing the synthesis of few-cycle to sub-cycle driver waveforms. The optical waveform synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort single and double attosecond pulse production (with tunable separation) revealing the potentials of the light wave synthesizer device demonstrated by Wirth et al. [Science 334, 195 (2011)]. The results are also analyzed with respect to attosecond pulse propagation phenomena.

  19. Genetic optimization of attosecond-pulse generation in light-field synthesizers

    Science.gov (United States)

    Balogh, E.; Bódi, B.; Tosa, V.; Goulielmakis, E.; Varjú, K.; Dombi, P.

    2014-08-01

    We demonstrate control over attosecond-pulse generation and shaping by numerically optimizing the synthesis of few-cycle to subcycle driver wave forms. The optical wave-form synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort single- and double-attosecond-pulse production (with tunable separation), revealing the potentials of the light wave synthesizer device demonstrated by A. Wirth et al. [Science 334, 195 (2011), 10.1126/science.1210268]. The robustness of the results are also analyzed with respect to attosecond-pulse propagation phenomena.

  20. Probing sub-cycle strong field ionization dynamics with an attosecond XUV pulse

    International Nuclear Information System (INIS)

    Full text: The dynamics of ionization in a strong laser field with wavelength around 800 nm (corresponding to an optical field cycle of ∼ 2.6 fs) can be investigated by using 250 attosecond extreme ultraviolet (XUV) pulse as a probe (1 attosecond = 10-18 s). Such pulses are now available in the laboratory and can be precisely timed relative to the laser pulse. The sub-laser-cycle ionization dynamics can be inferred by studying the XUV ionization yield with different time delays between the XUV pulse and the laser pulse. The XUV ionization yield as a function of delay reflects both, the ground state depletion as well as sub-cycle dynamical features of ionization. We present a theoretical investigation of the process. Simulations on one spatial dimension (1-d) show that the sub-cycle features may be attributed to the distortions of the ground state by the strong laser field. However, distortion of the ground state is expected to be larger in 1-d than in 3-d. Therefore we numerically solve the time-dependent Schroedinger equation in 3-d using cylindrical coordinates. We employ a hybrid discretization using finite elements and finite difference techniques. Total XUV ionization yields and electron spectra as a function of delay will be presented and the importance of adiabatic bound state distortion and of dynamical effects will be discussed. (author)

  1. Coherence revival during the attosecond electronic and nuclear quantum photodynamics of the ozone molecule

    CERN Document Server

    Halász, Gábor J; Lasorne, Benjamin; Robb, Mike A; Gatti, Fabien; Vibók, Ágnes

    2013-01-01

    A coherent superposition of two electronic states of ozone (ground and Hartley B) is prepared with a UV pump pulse. Using the multiconfiguration time-dependent Hartree approach, we calculate the subsequent time evolution of the two corresponding nuclear wave packets and the coherence between them. The resulting wave packet shows an oscillation between the two chemical bonds. Even more interesting, the coherence between the two electronics states reappears after the laser pulse is switched off, which could be observed experimentally with an attosecond probe pulse.

  2. Monitoring the Birth of an Electronic Wavepacket in a Neutral Molecule with Attosecond Time-Resolved Photoelectron Spectroscopy

    CERN Document Server

    Perveaux, Aurelie; Gatti, Fabien; Halasz, Gabor; Vibok, Agnes; Lasorne, Benjamin

    2014-01-01

    Numerical simulations are presented to validate the possible use of cutting-edge attosecond time- resolved photoelectron spectroscopy to observe in real time the creation of an electronic wavepacket and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds.

  3. Attosecond gamma-ray pulses via nonlinear Compton scattering in the radiation dominated regime

    CERN Document Server

    Li, Jian-Xing; Galow, Benjamin J; Keitel, Christoph H

    2015-01-01

    The interaction of a relativistic electron bunch with a counter-propagating tightly-focused laser beam is investigated for intensities when the dynamics is strongly affected by its own radiation. The Compton scattering spectra of gamma-radiation are evaluated employing a semiclassical description for the laser-driven electron dynamics and a quantum electrodynamical description for the photon emissions. We show for laser facilities under construction that gamma-ray bursts of few hundred attoseconds and dozens of megaelectronvolt photon energies may be detected in the near-backwards direction of the initial electron motion. Tight focussing of the laser beam and radiation reaction are demonstrated to be jointly responsible for such short gamma-ray bursts which are independent of both duration of electron bunch and laser pulse. Furthermore, the stochastic nature of the gamma-photon emission features signatures in the resulting gamma-ray comb in the case of the application of a multi-cycle laser pulse.

  4. Plasma Approach for Generating Ultra-Intense Single Attosecond Pulse

    International Nuclear Information System (INIS)

    In our previous work, a plasma approach for single attosecond pulse (AP) generation was proposed. A few-cycle relativistic circularly polarized laser pulse will induce a single drastic oscillation of plasma boundary, from which high-order harmonics and furthermore an ultra-intense single AP can be generated naturally after it is reflected. Analytical model and simulations both demonstrate that the process is mostly efficient as the pulse duration is close to the plasma responding time. The effects of plasma density ramp are analyzed here, suggesting that the proposal is still quite efficient with appropriate density gradient in the ramp. At last, a combined approach is employed to obtain single AP with 30 fs incident laser. The relatively large-duration pulse is firstly shortened by a density dropping thin foil, and then reflected from an overdense plasma target. One-dimensional simulation shows that a 600 as single light pulse is generated with peak intensity of 3×1020 W/cm2. (cai awardee's article)

  5. Attosecond pulse generation by applying a weak static electric field to a few-cycle pulse

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Guangjiu; Guo Xiaolv [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Shao Tianjiao [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Xue Kang, E-mail: gjzhao@dicp.ac.cn [School of Physics, Northeast Normal University, Changchun 130024 (China)

    2011-09-15

    The high-order harmonic generation process under the combination of a few-cycle pulse and a static electric field was investigated in this work. A linear harmonic cutoff extension was observed with its dependence on the relative strength ratio of the static electric field with respect to a single-color, 2.5 optical cycle (oc), 800 nm, 1.4x10{sup 15} W cm{sup -2} few-cycle pulse as the fundamental driving field. Exploiting the relative strength ratio tuning from 0 to 0.1, a linear continuum width extending on the XUV spectrum up to 191 eV, which supports the creation of an 18 attosecond isolated attosecond pulse, was generated. Moreover, classical trajectory calculation and time-frequency analyses for explaining the mechanism are also presented.

  6. Molecular above-threshold-ionization angular distributions with attosecond bichromatic intense XUV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2012-01-01

    Angular distributions of molecular above-threshold ionization (MATI) in bichromatic attosecond extreme ultraviolet (XUV) linear polarization laser pulses have been theoretically investigated. Multiphoton ionization in a prealigned molecular ion H2+ produces clear MATI spectra which show a forward-backward asymmetry in angular and momentum distributions which is critically sensitive to the carrier envelope phase (CEP) φ, the time delay Δτ between the two laser pulses, and the photoelectron kinetic energies Ee. The features of the asymmetry in MATI angular distributions are described well by multiphoton perturbative ionization models. Phase differences of continuum electron wave functions can be extracted from the CEP φ and time delay Δτ dependent ionization asymmetry ratio created by interfering multiphoton ionization pathways. At large internuclear distances MATI angular distributions exhibit more complex features due to laser-induced electron diffraction where continuum electron wavelengths are less than the internuclear distance.

  7. Tracing attosecond electron motion inside a molecule by interferences from photoelectron emission

    Energy Technology Data Exchange (ETDEWEB)

    Xu Minghui; Peng Liangyou; Zhang Zheng; Gong Qihuang, E-mail: liangyou.peng@pku.edu.cn, E-mail: qhgong@pku.edu.cn [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

    2011-01-28

    We present a theoretical study of photoelectron emission of a homonuclear molecule by an attosecond xuv pulse, which can be regarded as a natural double-slit experiment. We show that attosecond electron motion inside the molecule opens one to two 'slits' for photoionization. Interference fringes in the angle-resolved photoelectron momentum distributions exhibit varying visibility (V), depending on the degree of which-path information (P). The complementarity relation, P{sup 2} + V{sup 2} {<=} 1, is verified in the time-dependent molecule double-slit experiment. Hence, the electron motion can be easily mapped out by measuring the interference visibility. This opens up the prospect of employing interferometric techniques to probe ultrafast intramolecular electronic motions. (fast track communication)

  8. Signatures of nuclear motion in molecular high-order harmonics and in the generation of attosecond pulse trains by ultrashort intense laser pulses

    Science.gov (United States)

    Bandrauk, André D.; Chelkowski, Szczepan; Lu, Huizhong

    2009-04-01

    Non-Born-Oppenheimer time-dependent Shrödinger equation numerical simulations of the nonlinear nonperturbative response of 1D H2, H+2 molecules (and their isotopes) in few cycle intense 800 nm laser pulses are presented to study the effect of nuclear motion on molecular high-order harmonic generation. A time-frequency analysis is used to identify electron recollision and recombination times responsible for the generation of attosecond pulse trains during the nuclear motion. A very strong signature of nuclear motion is seen in the time profiles of high-order harmonics. In the case of high laser intensity (I sime 1015 W cm-2) the nuclear motion shortens the part of the attosecond pulse train originating from the first electron contribution and may enhance the onset of the second electron contribution for longer pulses. Molecular motion thus can act as an important 'time-gating' for controlling the length of generated attosecond pulses. The shape of time profiles of harmonics can thus be used for monitoring the nuclear motion. In the case of lower laser intensity, I sime 4 × 1014 W cm-2, we also find in time profiles a clear signature of electron excitation due to recollision of the returning electron.

  9. Signatures of nuclear motion in molecular high-order harmonics and in the generation of attosecond pulse trains by ultrashort intense laser pulses

    International Nuclear Information System (INIS)

    Non-Born-Oppenheimer time-dependent Schroedinger equation numerical simulations of the nonlinear nonperturbative response of 1D H2, H+2 molecules (and their isotopes) in few cycle intense 800 nm laser pulses are presented to study the effect of nuclear motion on molecular high-order harmonic generation. A time-frequency analysis is used to identify electron recollision and recombination times responsible for the generation of attosecond pulse trains during the nuclear motion. A very strong signature of nuclear motion is seen in the time profiles of high-order harmonics. In the case of high laser intensity (I ≅ 1015 W cm-2) the nuclear motion shortens the part of the attosecond pulse train originating from the first electron contribution and may enhance the onset of the second electron contribution for longer pulses. Molecular motion thus can act as an important 'time-gating' for controlling the length of generated attosecond pulses. The shape of time profiles of harmonics can thus be used for monitoring the nuclear motion. In the case of lower laser intensity, I ≅ 4 x 1014 W cm-2, we also find in time profiles a clear signature of electron excitation due to recollision of the returning electron.

  10. Efficient Attosecond Phenomena in the Relativistic λ3 Regime

    International Nuclear Information System (INIS)

    Particle-in-cell simulations of relativistically strong laser pulses interacting with overdense plasma targets predict that coherent motion of electrons leads to the efficient generation of strong attosecond electromagnetic pulses and dense attosecond electron bunches. The optimal conditions for these attosecond phenomena are achieved in the λ3 regime, when few-cycle laser pulses are focused to a wavelength-limited spot, producing maximal intensity and maximal gradients with a given energy. The natural synchronism of these attosecond phenomena should enable a kind of relativistic attosecond optoelectronics

  11. Generation and Characterization of Attosecond Pulses. Final report

    International Nuclear Information System (INIS)

    The research undertaken in this project has been directed toward the area of attoscience, in particular the problem of attosecond metrology. That is, the accurate determination of the electric field of attosecond XUV radiation. This outstanding problem has been identified as a critical technology for further development of the field, and our research adds to the area by providing the first method for characterization using the harmonic radiation itself as a tool. The technical effectiveness of this approach is very high, since it is vastly easier to detect XUV radiation directly than via the spectrum of photoelectrons liberated from atoms by it. This means that the experimental data rate can be much higher in principle using all-optical detection that electron detection, which will greatly aid the utility of harmonic XUV sources in attoscience applications. There are as yet no direct public benefits from this area of scientific research, though access to material structural dynamics on unprecedented brief timescales are expected to yield significant benefits for the future

  12. Rotations of molecular photoelectron angular distributions with intense ultrashort circularly polarized attosecond laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2013-04-01

    Molecular photoelectron angular distributions (MPADs) by intense (I0 ⩾ 1014 W/cm2) circularly polarized ultrashort, few cycle (attosecond) ultraviolet laser pulses are presented from numerical solutions of time dependent Schrödinger equations. For the aligned molecular ion H_2^+, the MPADs exhibit rotations with respect to the polarization and molecular symmetry axes which are determined by the symmetry of the initial electronics states. It is also found that the rotation angle of MPADs is insensitive to the pulse intensity. We attribute these effects to the asymmetry between the parallel and perpendicular (to the molecular axis) polarization photoionization. Influence of the molecular alignment and ionizing pulse ellipticity on the rotation of MPADs is also shown to allow control of the nonsymmetric ionization.

  13. Ponderomotive Laser Acceleration and Focusing in Vacuum: Application for Attosecond Electron Bunches

    International Nuclear Information System (INIS)

    A novel approach for the generation of ultrabright attosecond electron bunches is proposed, based on acceleration in vacuum by a short laser pulse. The laser pulse profiles is tailored such that the electrons are both focused and accelerated by the ponderomotive force of the light. Using time-averaged equations of motion analytical criteria for optimal regime of acceleration are found. It is shown that for realistic laser parameters a beam with up to 106 particles and normalized transverse and longitudinal emittances -8 m can be produced

  14. Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

    CERN Document Server

    Haessler, Stefan; Fan, Guangyu; Chipperfield, Luke E; Baltuška, Andrius

    2014-01-01

    Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the attosecond time scale. The applicability of these IAP would be widened drastically by increasing their energy. Here we analyze the potential of using multi-colour driving pulses for temporally gating the attosecond pulse generation process. We devise how this approach can enable the generation of IAP with the available high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering 180-fs, 1030-nm pulses). We show theoretically that this requires a three-colour field composed of the fundamental and its second harmonic as well as a lower-frequency auxiliary component. We present pulse characterization measurements of such auxiliary pulses generated directly by white-light seeded OPA with the required significantly shorter pulse duration than the that of the fundamental. This, combined with our recent experimental results on three-colour waveform synthesis [Phys....

  15. Infrared Two-Color Multicycle Laser Field Synthesis for Generating an Intense Attosecond Pulse

    Science.gov (United States)

    Takahashi, Eiji J.; Lan, Pengfei; Mücke, Oliver D.; Nabekawa, Yasuo; Midorikawa, Katsumi

    2010-06-01

    We propose and demonstrate the generation of a continuum high-order harmonic spectrum by mixing multicycle two-color (TC) laser fields with the aim of obtaining an intense isolated attosecond pulse. By optimizing the wavelength of a supplementary infrared pulse in a TC field, a continuum harmonic spectrum was created around the cutoff region without carrier-envelope phase stabilization. The obtained harmonic spectra clearly show the possibility of generating isolated attosecond pulses from a multicycle TC laser field, which is generated by an 800 nm, 30 fs pulse mixed with a 1300 nm, 40 fs pulse. Our proposed method enables us not only to relax the requirements for the pump pulse duration but also to reduce ionization of the harmonic medium. This concept opens the door to create an intense isolated attosecond pulse using a conventional femtosecond laser system.

  16. Resonant enhancement of a single attosecond pulse in a gas medium by a time-delayed control field

    International Nuclear Information System (INIS)

    An optical coherent control scheme has been proposed and theoretically investigated where an extreme ultraviolet single attosecond pulse (SAP) propagates through dense helium gas dressed by a time-delayed femtosecond laser pulse. The laser pulse couples the 2s2p(1P) and 2s2(1S) autoionizing states when the SAP excites the 2s2p state. After going through the gas, the spectral and temporal profiles of the SAP are strongly distorted. A narrowed but enhanced spike in the spectrum shows up for specific intensities and time delays of the laser, which exemplifies the control of a broadband photon wave packet by an ultrashort dressing field for the first time. We analyse the photon and electron dynamics and determine the dressing condition that maximizes this enhancement. The result demonstrates new possibilities of attosecond optical control.

  17. Isolated attosecond pulses from ionization gating of high-harmonic emission

    Energy Technology Data Exchange (ETDEWEB)

    Abel, Mark J., E-mail: abelm@berkeley.edu [Departments of Chemistry and Physics, University of California, Berkeley, CA 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Pfeifer, Thomas; Nagel, Phillip M.; Boutu, Willem; Bell, M. Justine; Steiner, Colby P.; Neumark, Daniel M. [Departments of Chemistry and Physics, University of California, Berkeley, CA 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Leone, Stephen R., E-mail: srl@berkeley.edu [Departments of Chemistry and Physics, University of California, Berkeley, CA 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2009-12-10

    Combining results from several techniques of attosecond spectroscopy, we show that ionization gating of high-harmonic emission on the leading edge of the driving pulse produces isolated attosecond pulses with a contrast ratio (the energy in the main pulse normalized to the energy in adjacent satellite pulses) c=3.3{+-}0.2. Half-cycle cutoff analysis confirms that harmonic generation proceeds in the ionization-gated regime. The attosecond pulse contrast is measured using the technique of carrier-envelope phase (CEP)-scanning, recently developed by our group, in which photoelectrons generated from Ne atoms by the harmonic pulse are streaked as a function of CEP. Streaking of photoelectrons as a function of attosecond time delay also confirms the isolated nature of the harmonic pulse, which is measured to have a duration of 430{+-}15 as, limited by the bandwidth of the reflective X-ray optics employed. The combined measurements imply that the experimental advantages of the ionization gating technique-tunable X-ray emission, relaxed sensitivity to the CEP and scalability to longer driver pulses-are also conferred on isolated attosecond pulse production.

  18. Relativistic generation of isolated attosecond pulses in a λ3 focal volume

    International Nuclear Information System (INIS)

    Lasers that provide an energy encompassed in a focal volume of a few cubic wavelengths (λ3) can create relativistic intensity with maximal gradients, using minimal energy. With particle-in-cell simulations we found, that single 200 attosecond pulses could be produced efficiently in a λ3 laser pulse reflection, via deflection and compression from the relativistic plasma mirror created by the pulse itself. An analytical model of coherent radiation from a charged layer confirms the pulse compression and is in good agreement with simulations. The novel technique is efficient (∼10%) and can produce single attosecond pulses from the millijoule to the joule level

  19. Single-attosecond pulse generation with an intense multicycle driving pulse

    Science.gov (United States)

    Cao, Wei; Lu, Peixiang; Lan, Pengfei; Wang, Xinlin; Yang, Guang

    2006-12-01

    Higher-order harmonic generation from strong laser-atom interaction in the multicycle regime is investigated using the Lewenstein model. While the peak intensity of the driving laser is oversaturated, the atom will be ionized completely during a few half optical cycles. The harmonic spectrum then reveals a continuous multiplateau structure in the cutoff region because of the ground state depletion. Each subplateau can be superposed to generate single attosecond pulse. Since the intensity of high-order harmonics from ion is comparable to that from atom if the peak intensity is super-intense, appropriate subplateau should be selected for single attosecond pulse generation. It is also shown that the nonadiabatic effect plays a crucial role in tuning the bandwidth of the subplateau.

  20. Single-attosecond pulse generation with an intense multicycle driving pulse

    International Nuclear Information System (INIS)

    Higher-order harmonic generation from strong laser-atom interaction in the multicycle regime is investigated using the Lewenstein model. While the peak intensity of the driving laser is oversaturated, the atom will be ionized completely during a few half optical cycles. The harmonic spectrum then reveals a continuous multiplateau structure in the cutoff region because of the ground state depletion. Each subplateau can be superposed to generate single attosecond pulse. Since the intensity of high-order harmonics from ion is comparable to that from atom if the peak intensity is super-intense, appropriate subplateau should be selected for single attosecond pulse generation. It is also shown that the nonadiabatic effect plays a crucial role in tuning the bandwidth of the subplateau

  1. Two-center interference in molecular photoelectron energy spectra with intense attosecond circularly polarized XUV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bian, Xue-Bin; Bandrauk, André D.

    2014-08-01

    We study two-center electron interference in molecular photoionization processes by intense attosecond circularly polarized extreme ultraviolet (XUV) laser pulses in both symmetric H2+ and nonsymmetric HHe2+ one-electron diatomic systems. Simulations from numerical solutions of time-dependent Schrödinger equations for the oriented symmetric molecular ion H2+ exhibit a signature of interference with double peaks (minima) in molecular attosecond photoelectron energy spectra (MAPES) at critical angles ϑc between the continuum electron momentum pe and the molecular internuclear R axis. The interference patterns are shown to be influenced by the molecular Coulomb potential, leading to a shift of the critical angle ϑc. Dependence of the two-center interference on the pulse ellipticity is also investigated. Furthermore, it is found that the interference phenomena are critically sensitive to the molecular orbital symmetry. For the nonsymmetric molecular ion HHe2+, such double peaks in MAPES also occur, thus suggesting a method for imaging orbitals in molecules by intense ultrashort circularly polarized XUV pulses on the attosecond time scale.

  2. A bright attosecond x-ray pulse train generation in a double-laser-driven cone target

    Science.gov (United States)

    Hu, Li-Xiang; Yu, Tong-Pu; Shao, Fu-Qiu; Luo, Wen; Yin, Yan

    2016-06-01

    By using full three-dimensional particle-in-cell and Monte Carlo simulations, we investigate the generation of a high-brightness attosecond x-ray pulse train in a double-laser-driven cone target. The scheme makes use of two lasers: the first high-intensity laser with a laser peak intensity 1.37 × 1020 W/cm2 irradiates the cone and produces overdense attosecond electron bunches; the second counterpropagating weakly relativistic laser with a laser peak intensity 4.932 × 1017 W/cm2 interacts with the produced electron bunches and a bright x-ray pulse train is generated by Thomson backscattering of the second laser off the attosecond electron bunches. It is shown that the photon flux rises by 5 times using the cone target as compared with a normal channel. Meanwhile, the x-ray peak brightness increases significantly from 1.4 × 1021/(s mm2 mrad2 0.1 keV) to 6.0 × 1021/(s mm2 mrad2 0.1 keV), which is much higher than that of the Thomson x-ray source generated from traditional accelerators. We also discuss the influence of the laser and target parameters on the x-ray pulse properties. This compact bright x-ray source may have diverse applications, e.g., the study of electric dynamics and harmonics emission in the atomic scale.

  3. Intense Isolated Ultrashort Attosecond Pulse Generation in a Multi-Cycle Three-Colour Laser Field

    Science.gov (United States)

    Zhang, Gang-Tai

    2014-12-01

    An efficient method for generating an intense isolated ultrashort attosecond pulse is presented theoretically. By adding a 267 nm controlling pulse to a multi-cycle two-colour field, not only the spectral cutoff and the yields of the harmonic spectrum are evidently enhanced, but also the selection of the single quantum path is realised. Then a high-efficiency supercontinuum with a 504 eV bandwidth and smooth structure is obtained, which enables the production of an intense isolated 30 as pulse. In addition, the influences of the laser parameters on the supercontinuum and isolated attosecond pulse are investigated.

  4. Ultra-intense single attosecond pulse generated from circularly polarized laser interacting with overdense plasma

    Science.gov (United States)

    Ji, Liangliang; Shen, Baifei; Zhang, Xiaomei; Wen, Meng; Xia, Changquan; Wang, Wenpeng; Xu, Jiancai; Yu, Yahong; Yu, Mingyang; Xu, Zhizhan

    2011-08-01

    Few-cycle relativistic circularly polarized (CP) laser pulse reflected from overdense plasma is investigated by analysis and particle-in-cell simulations. It is found that through the laser-induced one-time drastic oscillation of the plasma boundary, an ultra-intense single attosecond light pulse can be generated naturally. An analytical model is proposed to describe the interaction and it agrees well with simulation results. They both indicate that peak intensity of the generated attosecond pulse is higher when the plasma density is closer to the relativistic transparency threshold and/or the pulse duration is closer to plasma oscillating period. Two dimensional simulation shows that a two-cycle 1021 W/cm2 CP laser can generate a single 230 attosecond 2 × 1021 W/cm2 pulse of light at a conversion efficiency greater than 10-2.

  5. Ultra-intense single attosecond pulse generated from circularly polarized laser interacting with overdense plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ji Liangliang; Shen Baifei; Zhang Xiaomei; Wen Meng; Xia Changquan; Wang Wenpeng; Xu Jiancai; Yu Yahong; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P. O. Box 800-211, Shanghai 201800 (China); Yu Mingyang [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)

    2011-08-15

    Few-cycle relativistic circularly polarized (CP) laser pulse reflected from overdense plasma is investigated by analysis and particle-in-cell simulations. It is found that through the laser-induced one-time drastic oscillation of the plasma boundary, an ultra-intense single attosecond light pulse can be generated naturally. An analytical model is proposed to describe the interaction and it agrees well with simulation results. They both indicate that peak intensity of the generated attosecond pulse is higher when the plasma density is closer to the relativistic transparency threshold and/or the pulse duration is closer to plasma oscillating period. Two dimensional simulation shows that a two-cycle 10{sup 21} W/cm{sup 2} CP laser can generate a single 230 attosecond 2 x 10{sup 21} W/cm{sup 2} pulse of light at a conversion efficiency greater than 10{sup -2}.

  6. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    CERN Document Server

    Kowalewski, Markus; Rouxel, Jérémy R; Mukamel, Shaul

    2016-01-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry an additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences and demonstrate how it offers a novel tool to monitor non-adiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can enhance the time resolution and provide direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  7. Investigation of novel shape-controlled linearly and circularly polarized attosecond pulse sources

    Science.gov (United States)

    Tóth, György; Tibai, Zoltán; Nagy-Csiha, Zsuzsanna; Márton, Zsuzsanna; Almási, Gábor; Hebling, János

    2016-02-01

    In this article, we investigate the temporal shape of one- or few-cycle, 20-180 nm central wavelength attosecond pulses that are produced in a scheme based on coherent undulator radiation. It is demonstrated, that the carrier-envelope phase (CEP) of the radiated electric field can be chosen arbitrarily by shaping the magnetic field of the radiator undulator appropriately. It is shown that the temporal shape and the spectrum of the generated electric field are influenced by the spatial shape and amplitude of the magnetic field of the radiator undulator for different central wavelength pulses, while both are practically independent of the energy of the initial electron bunch. Shape distortions at high K undulator parameters are also discussed.

  8. Technique for the Generation of Attosecond X-Ray Pulses Using an FEL

    International Nuclear Information System (INIS)

    We describe a technique for the generation of an isolated burst of X-ray radiation with a duration of ∼ 100 attoseconds in a free electron laser (FEL) employing self-amplified spontaneous emission. Our scheme relies on an initial interaction of the electron beam with an ultra-short laser pulse in a one-period wiggler followed by compression in a dispersive section. The result of this interaction is to create a sub-femtosecond slice of the electron beam with enhanced growth rates for FEL amplification. After many gain lengths through the FEL undulator, the X-ray output from this slice dominates the radiation of the entire bunch. We consider the impact of various effects on the efficiency of this technique. Different configurations are considered in order to realize various timing structures for the resulting radiation

  9. Optical vortices discern attosecond time delay in electron emission from magnetic sublevels

    CERN Document Server

    Wätzel, Jonas

    2016-01-01

    Photoionization from energetically distinct electronic states may have a relative time delay of tens of attoseconds. Here we demonstrate that pulses of optical vortices allow measuring such attoseconds delays from magnetic sublevels, even from a spherically symmetric target. The di?erence in the time delay is substantial and exhibits a strong angular dependence. Furthermore, we find an atomic scale variation in the time delays depending on the target orbital position in the laser spot. The findings o?er thus a qualitatively new way for a spatio-temporal sensing of the magnetic states from which the photoelectrons originate, with a spatial resolution way below the di?raction limit of the vortex beam. Our conclusions follow from analytical considerations based on symmetry, complemented and confirmed with full numerical simulations of the quantum dynamics.

  10. Isolated sub-10 attosecond pulse generation by a 6-fs driving pulse and a 5-fs subharmonic controlling pulse

    Directory of Open Access Journals (Sweden)

    Yunhui Wang

    2012-06-01

    Full Text Available We theoretically study high-order harmonic generation by quantum path control in a special two-color laser field, which is synthesized by a 6 fs/800 nm fundamental pulse and a weaker 5 fs/1600 nm subharmonic controlling pulse. Single quantum path is selected without optimizing any carrier phase, which not only broadens the harmonic bandwidth to 400 eV, but also enhances the harmonic conversion efficiency in comparison with the short-plus-long scheme, which is based on 5 fs/800 nm driving pulse and 6 fs/1600 nm control pulse. An isolated 8-attosecond pulse is produced with currently available ultrafast laser sources.

  11. Generation of a single attosecond pulse from an overdense plasma surface driven by a laser pulse with time-dependent polarization

    International Nuclear Information System (INIS)

    The influence of time-dependent polarization on attosecond pulse generation from an overdense plasma surface driven by laser pulse is discussed analytically and numerically. The results show that the frequency of controlling pulse controls the number and interval of the generated attosecond pulse, that the generation moment of the attosecond pulse is dominated by the phase difference between the controlling and driving pulses, and that the amplitude of the controlling pulse affects the intensity of the attosecond pulse. Using the method of time-dependent polarization, a “single” ultra-strong attosecond pulse with duration τ ≈ 8.6 as and intensity I ≈ 3.08 × 1020 W·cm−2 can be generated. (physics of gases, plasmas, and electric discharges)

  12. Observation and analysis of an interferometric autocorrelation trace of an attosecond pulse train

    International Nuclear Information System (INIS)

    We report the direct observation of phase locking between adjacent pulses in an attosecond pulse train (APT) via interferometric autocorrelation (IAC). In this measurement, the Coulomb explosion of N2 caused by two-photon absorption is utilized as correlated signals between two replicas of the APT that are the outcome of the spatial division of the APT in the interferometer. The analysis of IAC by the spatial division of the APT is consistent with the experimental trace of the IAC, and yields the duration of the pulse in the APT of 320 attoseconds, which corresponds to a 1.3 cycle period of the carrier frequency of the harmonic field

  13. Spectral phase measurement of a Fano resonance using tunable attosecond pulses

    Science.gov (United States)

    Kotur, M.; Guénot, D.; Jiménez-Galán, Á.; Kroon, D.; Larsen, E. W.; Louisy, M.; Bengtsson, S.; Miranda, M.; Mauritsson, J.; Arnold, C. L.; Canton, S. E.; Gisselbrecht, M.; Carette, T.; Dahlström, J. M.; Lindroth, E.; Maquet, A.; Argenti, L.; Martín, F.; L'Huillier, A.

    2016-02-01

    Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.

  14. Attosecond-resolved electron dynamics around the 1st ionization threshold of helium measured by multidimensional absorption spectroscopy

    International Nuclear Information System (INIS)

    We recently developed a transient-coupling measurement scheme, which we employed to uncover coherent laser-induced coupling of doubly-excited helium states to continuum states. Here, we apply this measurement scheme to study in detail the coherent electron dynamics and general absorption phenomena arising for single-excitation of helium around 24 eV with attosecond-pulsed VUV light fields. Exploiting a multidimensional control by (a) varying the time delay between the attosecond and a coupling laser pulse, (b) tuning the coupling laser intensity and (c) analyzing the propagation direction of the transmitted VUV attosecond pulse we observe the transformation of the original (Lorentzian) resonance shapes into Fano line shapes. To understand the mechanism behind this quantum control we performed numerical simulations to model our experimental results, which include the attosecond-pulsed excitation and laser coupling of multiple excited states. These simulations allowed us to identify the ponderomotive dressing of the states in the laser field as a key component for understanding the control of several line shapes of the observed absorption spectra.

  15. Attosecond-resolved electron dynamics around the 1st ionization threshold of helium measured by multidimensional absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kaldun, Andreas; Ott, Christian; Stooss, Veit; Raith, Philipp; Meyer, Kristina; Laux, Martin; Blaettermann, Alexander; Ding, Thomas; Pfeifer, Thomas [Max-Planck Institut f. Kernphysik, Heidelberg (Germany)

    2013-07-01

    We recently developed a transient-coupling measurement scheme, which we employed to uncover coherent laser-induced coupling of doubly-excited helium states to continuum states. Here, we apply this measurement scheme to study in detail the coherent electron dynamics and general absorption phenomena arising for single-excitation of helium around 24 eV with attosecond-pulsed VUV light fields. Exploiting a multidimensional control by (a) varying the time delay between the attosecond and a coupling laser pulse, (b) tuning the coupling laser intensity and (c) analyzing the propagation direction of the transmitted VUV attosecond pulse we observe the transformation of the original (Lorentzian) resonance shapes into Fano line shapes. To understand the mechanism behind this quantum control we performed numerical simulations to model our experimental results, which include the attosecond-pulsed excitation and laser coupling of multiple excited states. These simulations allowed us to identify the ponderomotive dressing of the states in the laser field as a key component for understanding the control of several line shapes of the observed absorption spectra.

  16. Generation of Attosecond x-ray pulse using Coherent Relativistic Nonlinear Thomson Scattering

    International Nuclear Information System (INIS)

    Relativistic plasma, a new regime in physics, has been opened due to the development in ultra-intense laser technology during the past decade. Not only the fundamental aspect of relativistic plasma are attractive but also its potential application seems to be significant especially in the area of the generation of high energy particles such as electrons, ions, positrons, and γ-rays. The generation of x-ray radiation with a pulse width of sub-femtoseconds presently draws much attention because such a radiation allows one to explore ultra-fast dynamics of electrons and nucleons. Several schemes have been proposed and/or demonstrated to generate an ultra-short x-ray pulse: the relativistic Doppler shift of a backscattered laser pulse by a relativistic electron beam, the harmonic frequency upshift of a laser pulse by relativistic nonlinear motion of electrons, high order harmonic generation in the interaction of intense laser pulse with noble gases and solids The train of a few 100 attosecond pulses has been observed in the case of laser-noble gas interaction. When a low-intensity laser pulse is irradiated on an electron, the electron undergoes a harmonic oscillatory motion and generates a dipole radiation with the same frequency as the incident laser pulse, which is called Thomson scattering. As the laser intensity increases, the oscillatory motion of the electron becomes relativistically nonlinear, which leads to the generation of harmonic radiations, referred to as Relativistic Nonlinear Thomson Scattered (RNTS) radiation. The motion of the electron begins to be relativistic as the following normalized vector potential approaches to unity: a0=8.5 x 10-10 λΙ1/2 , (1) where λ is the laser wavelength in μm and I the laser intensity in W/cm2 The RNTS radiation has been investigated in analytical ways. Recently, indebted to the development of the ultra-intense laser pulse, experiments on RNTS radiation have been carried out by irradiating a laser pulse of 1018

  17. Control of the two-Photon Double Ionization of Helium with Intense Chirped Attosecond Laser Pulses

    Science.gov (United States)

    Barmaki, Samira; Laulan, Stephane

    2014-05-01

    We study the two-photon double ionization process of the helium atom by solving numerically the nonrelativistic time-dependent Schrödinger equation in its full dimensionality. We investigate with an intense chirped attosecond laser pulse of central carrier frequency that corresponds to the 29th harmonic of a Ti-sapphire laser the direct and sequential processes in helium. We show how it is possible by adjusting the chirp parameter to control the dominance of one process over the other within the atom. Attosecond chirped laser pulses offer a promising way to probe and control the two-photon double ionization of helium when compared with attosecond transform-limited pulses.

  18. Isolated atto-second pulse generated by spatial shaping of femtosecond laser beam

    International Nuclear Information System (INIS)

    We study numerically the time-dependent HHG phase-matching in the laser beam having a flat-top radial intensity profile. A flat-top profile is the key to produce similar ionization degree at the axis and at the periphery and thus to achieve simultaneous phase-matched generation. Such a profile can be obtained experimentally by using two concentric phase plates that introduce a specific phase shift between the central and the outer part of a focused Gaussian beam. We find realistic laser field parameters and medium density that allow obtaining (after spectral filtering) single atto-second pulse using 10 fs driving laser pulse. Our technique provides isolated atto-second pulse emission almost insensitive on the CEP of the laser pulse. Moreover, the technique is effective both for the mid-plateau and the cut-off spectral range. In particular, the XUV from Ar target in the cut-off spectral range (compatible with the Zr filter) provides isolated atto-second pulse with 185 as duration at a central energy of 92 eV. Using achievable multi mJ 10 fs laser pulses this technique could provide atto-second pulses approaching the μJ energy range. (authors)

  19. Development of the Schrodinger equation for attosecond laser pulse interaction with Planck gas

    CERN Document Server

    Kozlowski, M; Pilsudski, Josef

    2011-01-01

    The creation of the new particles by the interaction of the ultrarelativistic ions,from Large Hadron Collider(LHC), and attosecond laser pulse open new possibilities for laser physicists community .In this paper we propose the hyperbolic Schr\\"odinger equation (HSE) for gas of the "classical" particles "i.e. particles with mass= Planck mass We discuss the inclusion of the gravity to the HSE The solution of the HSE for a particle in a box is obtained. It is shown that for particles with m greater than Mp the energy spectrum is independent of the mass of particle. Key words: attosecond laser pulses, Schrodinger equation, Planck particles, thermal processes

  20. Effect of the carrier-envelope phase of the driving laser field on the high-order harmonic attosecond pulse

    International Nuclear Information System (INIS)

    The effect of the carrier-envelope phase of a few-cycle driving laser field on the generation and measurement of high-order harmonic attosecond pulses is investigated theoretically. We find that the position of the generated attosecond soft-x-ray pulse in the cutoff region is locked to the oscillation of the driving laser field, but not to the envelope of the laser pulse. This property ensures the success of the width measurement of an attosecond soft-x-ray pulse based on the cross correlation between the attosecond pulse and its driving laser pulse [M. Hentschel et al., Nature (London) 414, 509 (2001)]. However, there still exists a timing jitter of the order of tens of attoseconds between the attosecond pulse and its driving laser field. We also propose a method to detect the carrier-envelope phase of the driving laser field by measuring the spatial distribution of the photoelectrons induced by the attosecond soft-x-ray pulse and its driving laser pulse

  1. Angular distribution in two-photon double ionization of helium by intense attosecond soft X-ray pulses

    CERN Document Server

    Barna, I F; Wang, J

    2006-01-01

    We investigate two-photon double ionization of helium by intense ($10^{15} W/cm^2$) ultrashort ($\\approx 300$ as) soft X-ray pulses (E = 91.6 eV). The time-dependent two-electron Schr\\"odinger equation is solved using a coupled channel method. We show that for ultrashort pulses the angular distribution of ejected electrons depends on the pulse duration and provides novel insights into the role of electron correlations in the two-electron photoemission process. The angular distribution at energies near the ``independent electron'' peaks is close to dipolar while it acquires in the ``valley'' of correlated emission a significant quadrupolar component within a few hundred attoseconds.

  2. Quantum path control using attosecond pulse trains via UV-assisted resonance enhance ionization

    Institute of Scientific and Technical Information of China (English)

    李芳; 魏来; 何志聪

    2015-01-01

    We theoretically investigate the quantum path selection in an ultraviolet (UV)-assisted near-infrared field with an UV energy below the ionization threshold. By calculating the ionization probability with different assistant UV frequencies, we find that a resonance-enhanced ionization peak emerges in the region Euvattosecond pulse train (APT) centered in the resonance region, we show that the short quantum path can be well selected in the continuum case. By performing the electron trajectory analysis, we have further explained the physical mechanism of the quantum path selection. Moreover, we also demonstrate that in the resonance region, the harmonic emission from the selected paths is more efficient than that with the APT energy above the ionization threshold.

  3. Simulation of Intense Isolated Attosecond Pulse Generation with a Two-color Laser Field

    Science.gov (United States)

    Eilanlou, Abdolreza Amani; Ishikawa, Kenichi L.; Nabekawa, Yasuo; Takahashi, Hiroyuki; Midorikawa, Katsumi

    A numerical analysis by solving the time-dependent Schrödinger equation on a neon atom within the single-active electron approximation shows that a two-color laser field synthesized from a sub-12-fs fundamental field and a detuned second harmonic field with a wavelength shorter than 380nm is suitable for generating an intense isolated attosecond pulse (IAP). We have also investigated the effects of carrier-envelope phase variation on the obtained IAP and have compared the results to those obtained from a 5-fs fundamental field alone with the same peak field amplitude to show that a more intense IAP can be generated by the two-color laser field which is useful for nonlinear experiments in the extreme ultraviolet spectral range.

  4. Asymmetries in Production of He^+(n=2) with an Intense Few-Cycle Attosecond Pulse

    Science.gov (United States)

    Marcel Ngoko Djiokap, Jean; Hu, Suxing X.; Starace, Anthony F.

    2012-06-01

    By solving the two-active-electron time-dependent Schr"odinger equation (in its full dimensionality) in an intense few-cycle attosecond pulse, we investigate the carrier-envelope-phase (CEP) induced asymmetries in the differential probability for ionization plus excitation of He to the He^+(n=2) states. Owing to the broad bandwidth of the intense pulse, substantial asymmetries in the differential probability for ionization of an electron along the positive and negative polarization direction of the pulse are found. Such asymmetry involves prominent interference between direct and indirect ionization pathways seen simultaneously in the partial photoelectron spectra. Electron correlations are probed by comparing projections of the wave packet onto the field-free highly correlated Jacobi matrix wave function [E. Foumouo et al., Phys. Rev. A 74, 063409 (2006)] and uncorrelated Coulomb states. The CEP-effect found along the z-axis in the total asymmetry seems to be consistent with perturbation theory [E. A. Pronin et al., Phys. Rev. A 80, 063403 (2009)].

  5. Attosecond quantum stroboscope.

    Science.gov (United States)

    Paulus, Gerhard G; Stania, Gernot

    2009-04-14

    Electron disco: A "quantum stroboscope" for capturing the electron motion on a subfemtosecond timescale for a particular class of problems is highlighted. The picture shows a diffraction pattern caused by wave packets obtained by synchronizing attosecond UV pulses to a near-IR field and ionizing rare-gas atoms. PMID:19294685

  6. Angular distribution in two-photon double ionization of helium by intense attosecond soft-x-ray pulses

    Science.gov (United States)

    Barna, Imre F.; Wang, Jianyi; Burgdörfer, Joachim

    2006-02-01

    We investigate two-photon double ionization of helium by intense (≈1015W/cm2) ultrashort (≈300as) soft-x-ray pulses (E=91.6eV) . The time-dependent two-electron Schrödinger equation is solved using a coupled channel method. We show that for ultrashort pulses the angular distribution of ejected electrons depends on the pulse duration and provides insight into the role of electron correlations in the two-electron photoemission process. The angular distribution at energies near the “independent-electron” peaks is close to dipolar while it acquires in the “valley” of correlated emission a significant quadrupolar component within a few hundred attoseconds.

  7. Attosecond Steering of Electrons with Optimised Strong Field Waveforms

    CERN Document Server

    Haessler, S; Fan, G; Witting, T; Squibb, R; Chipperfield, L; Zaïr, A; Andriukaitis, G; Pugžlys, A; Tisch, J W G; Marangos, J P; Baltuška, A

    2013-01-01

    Quasi-free field driven electron trajectories are a key element of strong-field dynamics. Upon recollision with the parent ion, the energy transferred from the field to the electron may be released as attosecond duration XUV emission1,2 in the process of high harmonic generation (HHG). The conventional sinusoidal driver fields set limitations on the maximum value of this energy transfer, and it has been predicted that this limit can be significantly exceeded by an appropriately ramped-up cycle-shape3.Here, we present an experimental realization of such cycle-shaped waveforms and demonstrate control of the HHG process on the single-atom quantum level via attosecond steering of the electron trajectories. With our optimized optical cycles, we boost the field-ionization launching the electron trajectories, increase the subsequent field-to-electron energy transfer, and reduce the trajectory duration, to obtain greatly enhanced HHG efficiency as well as spectral extension compared to sinusoidal drivers. This applic...

  8. Intensity improvement in the attosecond pulse generation with the coherent superposition initial state

    International Nuclear Information System (INIS)

    We investigate the coherent superposition initial state effect and found that when the initial active electron state is prepared in the coherent superposition of the 1s and 2s states of the He+ ion and the chirp parameter of the fundamental field in the two-color scheme is chosen to be β=0.3, the harmonic cutoff energy is remarkably extended and the harmonic yield is enhanced by at least 6 orders of magnitude compared with the case of the single 1s ground state with chirp-free pulse. An ultrabroad supercontinuum with a 458 eV bandwidth is formed, directly producing an intense isolated 34 as pulse. -- Highlights: ► Simulating the HHG process irradiated from a model He+ ion in a two-color field. ► Preparing the initial active electronic state in the 1s and 2s superposition state. ► Finding the optimized chirp parameter of β=0.3 for the fundamental field. ► Observing the intensity enhancement in HHG with more than 6 orders of magnitude improvement. ► Generating a 34 as isolated attosecond pulse with similar intensity enhancement.

  9. Intensity improvement in the attosecond pulse generation with the coherent superposition initial state

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Chu, Tianshu, E-mail: tschu@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

    2012-03-26

    We investigate the coherent superposition initial state effect and found that when the initial active electron state is prepared in the coherent superposition of the 1s and 2s states of the He{sup +} ion and the chirp parameter of the fundamental field in the two-color scheme is chosen to be β=0.3, the harmonic cutoff energy is remarkably extended and the harmonic yield is enhanced by at least 6 orders of magnitude compared with the case of the single 1s ground state with chirp-free pulse. An ultrabroad supercontinuum with a 458 eV bandwidth is formed, directly producing an intense isolated 34 as pulse. -- Highlights: ► Simulating the HHG process irradiated from a model He{sup +} ion in a two-color field. ► Preparing the initial active electronic state in the 1s and 2s superposition state. ► Finding the optimized chirp parameter of β=0.3 for the fundamental field. ► Observing the intensity enhancement in HHG with more than 6 orders of magnitude improvement. ► Generating a 34 as isolated attosecond pulse with similar intensity enhancement.

  10. Propagation of attosecond electron bunches along the cone-and-channel target

    International Nuclear Information System (INIS)

    Generation and propagation of attosecond electron bunches along a cone-and-channel target are investigated by particle-in-cell simulation. The target electrons are pulled out by the oscillating electric field of an intense laser pulse irradiating a cone target and accelerated forward along the cone walls. It is shown that the energetic electrons can be further guided and confined by a channel attached to the cone tip. The propagation of these electrons along the channel induces a strong quasistatic magnetic field as well as a sheath electric field since a part of the energetic electrons expands into the surrounding vacuum. The electromagnetic field in turn confines the surface currents. With the cone-and-channel target the energetic electrons can be much better collimated and propagate much farther than that from the classical cone target.

  11. Generation of isolated attosecond pulses with a specific waveform two-color laser field

    Institute of Scientific and Technical Information of China (English)

    Jinping Yao; Yao Li; Ya Cheng

    2011-01-01

    We theorotically propose a new methed for generating intense isolated attosceond pulses during high-order harmonic generation (HHG) process by accurately controlling electron motion with a two-color laser field,which consists of an, 8O0-nm, 4-fs elliptically pollarized laser field and a 1400-nm, ~43-fs linearly polarized laser field. With this method, the supercontinua with a spectral width above 200 eV are obtained, which call support a ~15-as isolated pulse after phase compensation Classical and quantum analyses explain the controlling effects well. In particular, when the pules duration of the 800-nm laser field increases to 20- fs,sub-1O0-as isolated pules can be obtained even without any phase compensation%@@ We theoretically propo8e a new method for generating intense isolated attosecond pulses during high-order harmonic generation (HHG) process by accurately controlling electron motion with a two-color laser field,which consists of an 800-nm, 4-fs elliptically polarized laser field and a 1400-nm, ~43-fs linearly polarized laser field.With this method, the supercontinua with a spectral width above 200 eV are obtained, which can support a ~15-as isolated pulse after phase compensation.Classical and quantum analyses explain the controlling effects well.In particular, when the puLse duration of the 800-nm laser field increases to 20-fs, sub-lOO-as isolated pulses can be obtained even without any phase compensation.

  12. EDITORIAL: Focus on Attosecond Physics

    Science.gov (United States)

    Bandrauk, André D.; Krausz, Ferenc; Starace, Anthony F.

    2008-02-01

    Investigations of light-matter interactions and motion in the microcosm have entered a new temporal regime, the regime of attosecond physics. It is a main 'spin-off' of strong field (i.e., intense laser) physics, in which nonperturbative effects are fundamental. Attosecond pulses open up new avenues for time-domain studies of multi-electron dynamics in atoms, molecules, plasmas, and solids on their natural, quantum mechanical time scale and at dimensions shorter than molecular and even atomic scales. These capabilities promise a revolution in our microscopic knowledge and understanding of matter. The recent development of intense, phase-stabilized femtosecond (10-15 s) lasers has allowed unparalleled temporal control of electrons from ionizing atoms, permitting for the first time the generation and measurement of isolated light pulses as well as trains of pulses on the attosecond (1 as = 10-18 s) time scale, the natural time scale of the electron itself (e.g., the orbital period of an electron in the ground state of the H atom is 152 as). This development is facilitating (and even catalyzing) a new class of ultrashort time domain studies in photobiology, photochemistry, and photophysics. These new coherent, sub-fs pulses carried at frequencies in the extreme ultraviolet and soft-x-ray spectral regions, along with their intense, synchronized near-infrared driver waveforms and novel metrology based on sub-fs control of electron-light interactions, are spawning the new science of attosecond physics, whose aims are to monitor, to visualize, and, ultimately, to control electrons on their own time and spatial scales, i.e., the attosecond time scale and the sub-nanometre (Ångstrom) spatial scale typical of atoms and molecules. Additional goals for experiment are to advance the enabling technologies for producing attosecond pulses at higher intensities and shorter durations. According to theoretical predictions, novel methods for intense attosecond pulse generation may in

  13. Laser plasma as a source of intense attosecond pulses via high-order harmonic generation

    International Nuclear Information System (INIS)

    The incredible progress in ultrafast laser technology and Ti:sapphire lasers have lead to many important applications, one of them being high-order harmonic generation (HHG). HHG is a source of coherent extreme ultraviolet (XUV) radiation, which has opened new frontiers in science by extending nonlinear optics and time-resolved spectroscopy to the XUV region, and pushing ultrafast science to the attosecond domain. Progress in attosecond science has revealed many new phenomena that have not been seen with femtosecond pulses. Clearly, the next frontier is to study nonlinear effects at the attosecond timescale and in the XUV. However, a problem with present-day attosecond pulses is that they are just too weak to induce measurable nonlinearities, which severely limits the application of this source. While HHG from solid targets has shown promise for higher conversion efficiency, there is no experiment so far that demonstrates isolated attosecond pulse generation. The generation of isolated, several 100-as pulses with few-µJ energy will enable us to enter a completely new phase in attoscience. In past works, we have demonstrated that high-order harmonics from lowly ionized plasma is a highly efficient method to generate coherent XUV pulses. For example, indium plasma has been shown to generate intense 13th harmonic of the Ti:sapphire laser, with conversion efficiency of 10-4. However, the quasi-monochromatic nature of indium harmonics would make it difficult to generate attosecond pulses. We have also demonstrated that one could increase the harmonic yield by using nanoparticle targets. Specifically, we showed that by using indium oxide nanoparticles or C60 film, we could obtain intense harmonics between wavelengths of 50 to 90 nm. The energy in each of these harmonic orders was measured to be a few µJ, which is sufficient for many applications. However, the problem of using nanoparticle or film targets is the rapid decrease in the harmonic intensity, due to the rapid

  14. Collective energy loss of attosecond electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Ogata, A., E-mail: ogata@post.kek.jp [Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Kondoh, T.; Norizawa, K.; Yang, J.; Yoshida, Y.; Kashiwagi, S. [Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Kaneko, T. [Department of Applied Physics, Okayama University of Science, Ridai-cho, Kita-ku, Okayama 700-0005 (Japan)

    2011-05-01

    In this study, we have analytically shown that if the electron bunch length is in the 100-as range, the energy loss of the bunch is proportional to the square of the number of electrons in the bunch. If the number of electrons is large, the collective loss introduces a high-energy-density state in the target. The results were verified by carrying out 2D PIC simulations.

  15. Collective energy loss of attosecond electron bunches

    International Nuclear Information System (INIS)

    In this study, we have analytically shown that if the electron bunch length is in the 100-as range, the energy loss of the bunch is proportional to the square of the number of electrons in the bunch. If the number of electrons is large, the collective loss introduces a high-energy-density state in the target. The results were verified by carrying out 2D PIC simulations.

  16. Attosecond keV x-ray pulses driven by Thomson scattering in a tight focus regime

    International Nuclear Information System (INIS)

    The radiation of a relativistic electron interacting with a co-propagating tightly focused high-power laser is investigated. High-order fields (HOFs) existing in a tight focus (a few micrometers or so) affect the dynamics of electrons rather significantly so as to enhance radiation intensity by several orders of magnitude. In the case of a co-propagating interaction geometry, the second-order field plays an important role in radiation enhancement. It is demonstrated that when HOFs are included, the radiation efficiency is increased by a factor of up to 100 000 for w0 = 2 and 5 μm, with a laser intensity of 2.2x1020 W cm-2, compared with that when HOFs are not included. The enhancement is larger for smaller electron energies and laser beam waists. It has also been shown that when an electron bunch interacts with a high-intensity tightly-focused femtosecond laser pulse in a co-propagation geometry, attosecond (∼300 as) x-ray pulses can be produced. The photon energy can reach about 40 keV for an electron energy of 2 GeV. The physical scheme investigated in this work can be used for an ultrafast (attosecond or femtosecond) x-ray source in the range of 10-100 keV.

  17. Single sub-50-attosecond pulse generation from chirp-compensated harmonic radiation using material dispersion

    International Nuclear Information System (INIS)

    A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization and hence experience a large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with a duration less than 50 as

  18. Single sub-50-attosecond pulse generation from chirp-compensated harmonic radiation using material dispersion

    International Nuclear Information System (INIS)

    A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization, experiencing large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with the duration less than 50 as.

  19. Isolated attosecond pulse generation with the chirped two-color laser field

    Science.gov (United States)

    Tai, Huiqin; Li, Fang; Wang, Zhe

    2016-07-01

    We propose a scheme to generate isolated attosecond pulse using a linearly chirped two-color laser field, which includes a fundamental laser field and a weak infrared control laser field in the multicycle regime. The fundamental laser field consists of one linearly up-chirped and one linearly down-chirped pulses. The control pulse is chirped free. We compare the attosecond pulse generated in the chirped two-color field and the chirp-free field. It is found that an IAP can be generated even without carrier envelop phase stabilization in the chirped two-color laser field with a duration of 40 fs. We also discuss the influence of the relative intensity, relative phase, time delay, and chirping parameters on the generation of IAPs.

  20. Ionization of helium in the attosecond equivalent light pulse of 1 GeV/u U92+ projectiles

    International Nuclear Information System (INIS)

    Single and double ionization of helium by 1 GeV/u U92+ impact was explored in a kinematically complete experiment. The relativistic ion generates a sub-attosecond (10-18 s) superintense (I>1019 W/cm2) electromagnetic pulse, which is interpreted as a field of equivalent photons (Weizsaecker-Williams method). Cross sections, the emission characteristics of ions and electrons as well as momentum balances are quantitatively discussed in terms of photoionization of the atom in this broadband, ultra-short virtual photon field. (orig.)

  1. Spatial shaping of intense femtosecond beams for the generation of high-energy attosecond pulses

    Science.gov (United States)

    Constant, E.; Dubrouil, A.; Hort, O.; Petit, S.; Descamps, D.; Mével, E.

    2012-04-01

    We generate high-order harmonics with a spatially shaped TW laser beam. We present and analyse in detail a new approach for shaping an intense laser field to a flat-top intensity profile near focus. We show that this approach is well adapted for high harmonic generation with high-energy fundamental pulses and highlight the possibilities for generating high-energy attosecond pulses.

  2. Spatial shaping of intense femtosecond beams for the generation of high-energy attosecond pulses

    International Nuclear Information System (INIS)

    We generate high-order harmonics with a spatially shaped TW laser beam. We present and analyse in detail a new approach for shaping an intense laser field to a flat-top intensity profile near focus. We show that this approach is well adapted for high harmonic generation with high-energy fundamental pulses and highlight the possibilities for generating high-energy attosecond pulses. (paper)

  3. Temporal structure of attosecond pulses from intense laser-atom interactions

    International Nuclear Information System (INIS)

    We find that the high harmonics have a power-law spectrum Iω∼ω-3.3±0.25 in a wide frequency domain starting at the ionization potential Ip and down to the plateau beginning. Our spectrotemporal analysis of the emitted radiation displays clear bowlike structures in the (t,ω) plane. These 'bows' correspond to Corkum's reencounters of the freed electron with the atom. We find that the bows are not filled and thus cannot be due to any bremsstrahlung. Rather, it is a resonant process that we call stimulated recombination (SR). It occurs when an electron with momentum p reencounters the incompletely ionized atom, and interferes with itself still remaining in the ground state. The SR leads to a highly efficient resonant emission at (ℎ/2π)ω=p2/2m+Ip in the form of attosecond pulses. The SR relies on a low level of ionization and strongly benefits from the use of few-cycle laser pulses

  4. EDITORIAL: Attosecond and x-ray free-electron laser physics Attosecond and x-ray free-electron laser physics

    Science.gov (United States)

    Moshammer, R.; Ullrich, J.

    2009-07-01

    Currently, we are witnessing a revolution in photon science, driven by the vision to time-resolve ultra-fast electronic motion in atoms, molecules, and solids as well as by the quest for the characterization of time-dependent structural changes in large molecules and solids. Quantum jumps in the development of light sources are the key technologies for this emerging field of research. Thus, high harmonic radiation bursts now penetrate the attosecond (10-18 s) regime and free-electron lasers (FELs) deliver ultra-brilliant femtosecond, coherent VUV and x-ray pulses. This special issue presents a snapshot of this ongoing revolution and brings together, for the first time, pioneering results in both of these fields that are expected to evolve synergetically in the future. The volume is based on the spirit of the International Conference on Multi-Photon Processes, ICOMP08, which was held at the Max Planck Institute for Nuclear Physics in Heidelberg in summer 2008. The first contributions include articles that envision tracing electronic motion on an attosecond time scale and its relation to nuclear motion. After more technical papers on the generation of attosecond pulses via high harmonic generation (HHG), molecular and two-electron atomic dynamics in strong optical fields at a typical wavelength of 800 nm are presented pointing to sub-cycle, attosecond features. Making the transition to shorter wavelengths, nonlinear dynamics in atoms and molecules is explored via experimental and theoretical methods, where the present measurements are nearly exclusively performed at FEL sources. A substantial number of articles focus on the investigation of the most simple many- (few-) photon two-electron processes in double ionization of helium at optical and VUV wavelengths, with the goal of characterizing this fundamental reaction, not yet consistently solved theoretically, in spite of huge efforts. Finally, the behaviour of more complex nanoscaled systems, i.e. clusters, is

  5. A-periodic multilayer development for attosecond pulses in the 300-500 eV photon energy range

    Energy Technology Data Exchange (ETDEWEB)

    Guggenmos, Alexander; Hofstetter, Michael; Kleineberg, Ulf [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Garching (Germany); Max-Planck-Institut fuer Quantenoptik, Garching (Germany); Rauhut, Roman [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Garching (Germany)

    2011-07-01

    The development of ultrafast X-ray pulses in the sub-femtosecond time regime is a cutting edge technology for studying electron dynamics in atoms, molecules or solid surfaces/nanostructures by means of pump/probe electron spectroscopy. XUV elements as multilayer mirrors and thin metal filters are used to filter and shape attosecond bursts from high harmonic radiation. One near future goal is to extend the current technology to higher photon energies, reaching the water window range around 300-500 eV, where the in-vitro investigation of bio-materials on ultra-short time scales becomes possible. Following the ideas of nowadays experimental setups, both the spectral and the temporal resolution can be determined and guided by means of periodic and a-periodic multilayer mirrors, allowing for spectral and temporal soft X-ray pulse shaping. We will present first investigations of periodic and a-periodic multilayer XUV optics in that energy range of 300-400 eV and discuss their applications for filtering single attosecond pulses from High Harmonic radiation. Simulations and optimizations of various binary and ternary multilayer material systems as well as first experimental results achieved by Ion Beam Deposition and in-situ ellipsometry of the deposited nanolayers are demonstrated.

  6. A-periodic multilayer development for attosecond pulses in the 300-500 eV photon energy range

    International Nuclear Information System (INIS)

    The development of ultrafast X-ray pulses in the sub-femtosecond time regime is a cutting edge technology for studying electron dynamics in atoms, molecules or solid surfaces/nanostructures by means of pump/probe electron spectroscopy. XUV elements as multilayer mirrors and thin metal filters are used to filter and shape attosecond bursts from high harmonic radiation. One near future goal is to extend the current technology to higher photon energies, reaching the water window range around 300-500 eV, where the in-vitro investigation of bio-materials on ultra-short time scales becomes possible. Following the ideas of nowadays experimental setups, both the spectral and the temporal resolution can be determined and guided by means of periodic and a-periodic multilayer mirrors, allowing for spectral and temporal soft X-ray pulse shaping. We will present first investigations of periodic and a-periodic multilayer XUV optics in that energy range of 300-400 eV and discuss their applications for filtering single attosecond pulses from High Harmonic radiation. Simulations and optimizations of various binary and ternary multilayer material systems as well as first experimental results achieved by Ion Beam Deposition and in-situ ellipsometry of the deposited nanolayers are demonstrated.

  7. Single Ultrashort Attosecond Pulse Generation via Combination of Chirped Fundamental Laser and an Ultraviolet Controlling Pulse

    International Nuclear Information System (INIS)

    We theoretically study the high-order harmonic generation (HHG) from a hydrogen atom in an intense few-cycle chirped fundamental laser in combination with an ultraviolet (uv) controlling pulse. The high-order harmonic spectrum is calculated by solving the time-dependent Schroedinger equation using the split-operator method. In our calculation, we present the difference of the high-order harmonic spectrum from one-dimensional (1D) model hydrogen atom and three-dimensional (3D) real hydrogen atom. We found that the plateau of the high-order harmonic generation from the 1D case and 3D case are all extended effectively to Ip + 35Up due to the presence of the chirped laser pulse and the HHG supercontinuum spectrum is generated by adding an ultraviolet controlling pulse at a proper time, but the efficiency of the HHG for 3D case is more higher at the near cut-off region than the 1D case. Therefore, the generation of the attosecond pulse by synthesizing the harmonics near cut-off region have some slight differences between 1D and 3D simulations. As a real 3D case study, we show that an isolated 18 as pulse with a bandwidth of 232.5 eV is generated directly by optmizing the combination laser fields. (atomic and molecular physics)

  8. Efficient generation of isolated attosecond pulses with high beam-quality by two-color Bessel-Gauss beams

    CERN Document Server

    Wang, Zhe; Zhang, Qingbin; Wang, Shaoyi; Lu, Peixiang

    2011-01-01

    The generation of isolated attosecond pulses with high efficiency and high beam quality is essential for attosec- ond spectroscopy. We numerically investigate the supercontinuum generation in a neutral rare-gas medium driven by a two-color Bessel-Gauss beam. The results show that an efficient smooth supercontinuum in the plateau is obtained after propagation, and the spatial profile of the generated attosecond pulse is Gaussian-like with the divergence angle of 0.1 degree in the far field. This bright source with high beam quality is beneficial for detecting and controlling the microscopic processes on attosecond time scale.

  9. Attosecond angle-resolved photoelectron spectroscopy

    International Nuclear Information System (INIS)

    We report experiments on the characterization of a train of attosecond pulses obtained by high-harmonic generation, using mixed-color (XUV+IR) atomic two-photon ionization and electron detection on a velocity map imaging detector. We demonstrate that the relative phase of the harmonics is encoded both in the photoelectron yield and the angular distribution as a function of XUV-IR time delay, thus making the technique suitable for the detection of single attosecond pulses. The timing of the attosecond pulse with respect to the field oscillation of the driving laser critically depends on the target gas used to generate the harmonics

  10. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    Science.gov (United States)

    Jiménez-Galán, Álvaro; Martín, Fernando; Argenti, Luca

    2016-02-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate ab initio calculations or be extracted from a few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N =2 threshold for the RABITT (reconstruction of attosecond beating by interference of two-photon transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association with a weak IR probe, obtaining results in quantitative agreement with those from accurate ab initio simulations. In particular, we show that (i) the use of finite pulses results in a homogeneous redshift of the RABITT beating frequency, as well as a resonant modulation of the beating frequency in proximity to intermediate autoionizing states; (ii) the phase of resonant two-photon amplitudes generally experiences a continuous excursion as a function of the intermediate detuning, with either zero or 2 π overall variation.

  11. Two-photon finite-pulse model for resonant transitions in attosecond experiments

    CERN Document Server

    Galán, Álvaro Jiménez; Argenti, Luca

    2015-01-01

    We present an analytical model capable of describing two-photon ionization of atoms with attosecond pulses in the presence of intermediate and final isolated autoionizing states. The model is based on the finite-pulse formulation of second-order time-dependent perturbation theory. It approximates the intermediate and final states with Fano's theory for resonant continua, and it depends on a small set of atomic parameters that can either be obtained from separate \\emph{ab initio} calculations, or be extracted from few selected experiments. We use the model to compute the two-photon resonant photoelectron spectrum of helium below the N=2 threshold for the RABITT (Reconstruction of Attosecond Beating by Interference of Two-photon Transitions) pump-probe scheme, in which an XUV attosecond pulse train is used in association to a weak IR probe, obtaining results in quantitative agreement with those from accurate \\emph{ab initio} simulations. In particular, we show that: i) Use of finite pulses results in a homogene...

  12. Controlling high-order harmonic generation from the stretched diatom molecules subject to an attosecond pulse

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Gao; Lin, Jing-Quan [Changchun University of Science and Technology, Changchun (China); Yang, Yu-Jun [Jilin University, Changchun (China)

    2011-04-15

    We investigate the influence of an attosecond pulse on the high-order harmonic spectra generated from a stretched diatom molecule subjected to a mid-infrared femtosecond pulse by numerically solving the one-dimensional time-dependent Schroedinger equation. We show that, by adding a 750 attosecond pulse with wavelength of 76 nm to a five-cycle mid-infrared femtosecond pulses with wavelength of 1600 nm, the harmonic efficiencies are effectively enhanced compared with the case of only one mid-infrared femtosecond pulse; meanwhile, the enhanced harmonic efficiencies exhibit an obvious feature of a relative phase dependence between the two pulses. The harmonic efficiencies are enhanced overall by 2 - 3 orders of magnitude when the relative phase of the two pulses is set as {phi} = 2T + 0.3T (T is the oscillation period of the mid-infrared pulse), and the harmonic efficiencies near the second cutoff position of I{sub p} + 5.6U{sub p} are enhanced over 4 orders of magnitude when the relative phase is set as {phi} = 2T. This result indicates that frequency-selected enhancement can be realized by adjusting the relative phase of the two pulses. The reason for relative-phase-dependent structure of the spectra is discussed in detail by using the four main mechanisms of harmonic generation in molecules and the property of atomic ionization.

  13. Ultrarelativistic nanoplasmonics as a new route towards extreme intensity attosecond pulses

    CERN Document Server

    Gonoskov, Arkady A; Kim, Arkady V; Marklund, Mattias; Sergeev, Aleksander M

    2011-01-01

    The generation of ultra-strong attosecond pulses through laser-plasma interactions offers the opportunity to surpass the intensity of any known laboratory radiation source, giving rise to new experimental possibilities, such as quantum electrodynamical tests and matter probing at extremely short scales. Here we demonstrate that a laser irradiated plasma surface can act as an efficient converter from the femto- to the attosecond range, giving a dramatic rise in pulse intensity. Although seemingly similar schemes have been presented in the literature, the present setup deviates significantly from previous attempts. We present a new model describing the nonlinear process of relativistic laser-plasma interaction. This model, which is applicable to a multitude of phenomena, is shown to be in excellent agreement with particle-in-cell simulations. We provide, through our model, the necessary details for an experiment to be performed. The possibility to reach intensities above 10^26 W/cm^2, using upcoming 10 petawatt...

  14. Broadband multilayer mirror and diffractive optics for attosecond pulse shaping in the 280-500 eV photon energy range

    Directory of Open Access Journals (Sweden)

    Schmidt J.

    2013-03-01

    Full Text Available Chirped broadband multilayer mirrors are key components to shape attosecond pulses in the XUV range. Compressing high harmonic pulses to their Fourier limit is the major goal for attosecond physics utilizing short pulse pump-probe experiments. Here, we report about the first implementation of multilayers and diffractive optics fulfilling these requirements in the “water-window” spectral range.

  15. Attosecond xuv pulses for complete mapping of the time-dependent wave packets of D2+

    International Nuclear Information System (INIS)

    We have shown that the whole time-dependent vibrational wave packet of D2+ ions can be reconstructed from the kinetic energy release of the D+ ion pairs when it is probed with an attosecond xuv pulse. Such a full interrogation of the wave packet will pave the way for controlling the generation of tailor-designed wave packets for favorable chemical reaction paths, as well as for probing the time evolution of their interaction with the medium

  16. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  17. Ultrarelativistic nanoplasmonics as a route towards extreme-intensity attosecond pulses

    Science.gov (United States)

    Gonoskov, A. A.; Korzhimanov, A. V.; Kim, A. V.; Marklund, M.; Sergeev, A. M.

    2011-10-01

    The generation of ultrastrong attosecond pulses through laser-plasma interactions offers the opportunity to surpass the intensity of any known laboratory radiation source, giving rise to new experimental possibilities, such as quantum electrodynamical tests and matter probing at extremely short scales. Here we demonstrate that a laser irradiated plasma surface can act as an efficient converter from the femto- to the attosecond range, giving a dramatic rise in pulse intensity. Although seemingly similar schemes have been described in the literature, the present setup differs significantly from the previous attempts. We present a model describing the nonlinear process of relativistic laser-plasma interaction. This model, which is applicable to a multitude of phenomena, is shown to be in excellent agreement with particle-in-cell simulations. The model makes it possible to determine a parameter region where the energy conversion from the femto- to the attosecond regime is maximal. Based on the study we propose a concept of laser pulse interaction with a target having a groove-shaped surface, which opens up the potential to exceed an intensity level of 1026 W/cm2 and observe effects due to nonlinear quantum electrodynamics with upcoming laser sources.

  18. Ultrarelativistic nanoplasmonics as a route towards extreme-intensity attosecond pulses

    International Nuclear Information System (INIS)

    The generation of ultrastrong attosecond pulses through laser-plasma interactions offers the opportunity to surpass the intensity of any known laboratory radiation source, giving rise to new experimental possibilities, such as quantum electrodynamical tests and matter probing at extremely short scales. Here we demonstrate that a laser irradiated plasma surface can act as an efficient converter from the femto- to the attosecond range, giving a dramatic rise in pulse intensity. Although seemingly similar schemes have been described in the literature, the present setup differs significantly from the previous attempts. We present a model describing the nonlinear process of relativistic laser-plasma interaction. This model, which is applicable to a multitude of phenomena, is shown to be in excellent agreement with particle-in-cell simulations. The model makes it possible to determine a parameter region where the energy conversion from the femto- to the attosecond regime is maximal. Based on the study we propose a concept of laser pulse interaction with a target having a groove-shaped surface, which opens up the potential to exceed an intensity level of 1026 W/cm2 and observe effects due to nonlinear quantum electrodynamics with upcoming laser sources.

  19. Breaking the Attosecond, Angstrom and TV/M Field Barriers with Ultra-Fast Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Rosenzweig, James; Andonian, Gerard; Fukasawa, Atsushi; Hemsing, Erik; Marcus, Gabriel; Marinelli, Agostino; Musumeci, Pietro; O' Shea, Brendan; O' Shea, Finn; Pellegrini, Claudio; Schiller, David; Travish, Gil; /UCLA; Bucksbaum, Philip; Hogan, Mark; Krejcik, Patrick; /SLAC; Ferrario, Massimo; /INFN, Rome; Full, Steven; /Penn State U.; Muggli, Patric; /Southern California U.

    2012-06-22

    Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This use of very low Q beams may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the LCLS have produced {approx}2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments in cryogenic undulator technology, to create compact accelerator-undulator systems that can lase below 0.15 {angstrom}, or be used to permit 1.5 {angstrom} operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.

  20. The role of absolute phase of few-cycle laser field in the generation and measurement of attosecond high-order harmonic pulses

    International Nuclear Information System (INIS)

    The effect of the absolute phase of the few-cycle driving laser pulse on the generation and measurement of high-order harmonic attosecond pulses is investigated theoretically. We find that the position of the generated attosecond soft-x-ray pulse in cutoff region is locked to the oscillations of the driving laser field, but not to the envelope of the laser pulse. This property ensures the success [M. Hentschel et al. Nature vol. 414, 509 (2001)] of the width measurement of attosecond soft-x-ray pulse based on the cross-correlation between the attosecond pulse and its driving laser pulse. However, there is a timing jitter of the order of tens of attoseconds between the attosecond pulse and the driving laser field. This sets a limit for the measurement with the shorter attosecond pulses if we cannot control the absolute phase of the few-cycle laser field. Also, we propose a novel method to detect the absolute phase of the driving laser field by measuring the spatial distribution of the photoelectrons induced by the attosecond soft-x-ray pulse and its driving laser pulse

  1. Theory of attosecond pulse train control of strong field processes

    International Nuclear Information System (INIS)

    Full text: We present both single atom and macroscopic propagation calculations which demonstrate that attosec and pulse trains (APTs) are natural tools for controlling strong field processes driven by an infrared (IR) laser. This control originates in the short duration of the APTs and their periodicity, which is half the IR laser period. This allows us to fix the ionization to a particular point in each IR half cycle and to select which quantum paths are available for the ionized electron to follow. In this talk we will discuss the use of APTs to control and probe strong field processes such as above threshold ionization and harmonic generation. Solutions of the time-dependent Schroedinger equation (TDSE) for a helium atom subject to a combined APT/IR field show that both the yield and the coherence properties of the harmonics are improved when the APT is timed to launch the electron along the shortest quantum path, which exhibits a slow phase dependence and therefore gives rise to well behaved harmonics. Recently, we have carried out non-adiabatic phase matching calculations of helium atoms exposed to the combination of a strong IR laser pulse and an APT. We find that there are phase matching conditions where the single atom quantum path selection has a very large impact on the generated harmonics. Additionally, we find that for optimal delays between the APT and IR driving pulses the harmonic yield can be enhanced by two to four orders of magnitude over most of the harmonic spectrum. This is a much larger enhancement than that of the single atom response and is due both to a change in the IR intensity dependence of the harmonic strength and phase due to the presence of the APT, and to improved phase matching. Refs. 2 (author)

  2. Circularly polarized attosecond pulses from molecular high-order harmonic generation by ultrashort intense bichromatic circularly and linearly polarized laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2012-04-01

    We describe the generation of high-order elliptically and circularly polarized harmonic spectra in an aligned H+2 molecule ion by a combination of two-colour ultrashort intense laser fields from numerical solutions of the corresponding time-dependent Schrödinger equation (TDSE). In intense bichromatic circularly and linearly or circularly polarized laser pulses with intensity I0 and angular frequencies ω0 and 2ω0, it is found that maximum molecular high-order harmonic generation (MHOHG) energies are functions of the molecular internuclear distance. Based on a classical model of laser-induced electron collisions with neighbouring ions, the optimal values of the pulse relative carrier envelope phase phi, the molecular internuclear distance R and the angle thetav of molecular alignment to the laser polarization axis are obtained for efficiently producing MHOHG spectra with the maximum harmonic energy Ip + 13.5Up, where Ip is the ionization potential of the molecule and Up = I0/4meω20 is the ponderomotive energy of the continuum electron at intensity I0 and frequency ω0 of the laser pulse. The results have been confirmed from corresponding TDSE nonperturbative numerical simulations. The polarization property of the generated harmonics is also presented. The mechanism of MHOHG is further characterized with a Gabor time frequency analysis. It is confirmed that a single collision trajectory of the continuum electron with neighbouring ions dominates in the MHOHG processes. The high efficiency of the proposed MHOHG scheme provides a possible source for production of elliptically and/or circularly polarized attosecond extreme ultraviolet pulses. Circularly polarized attosecond pulses can also be generated by using intense ultrashort circularly polarized laser pulses in combination with static electric fields of comparable intensity for H+2 at equilibrium. A time frequency analysis also confirms the role of single recollisions as the dominant mechanism of the generation

  3. Circularly polarized attosecond pulses from molecular high-order harmonic generation by ultrashort intense bichromatic circularly and linearly polarized laser pulses

    International Nuclear Information System (INIS)

    We describe the generation of high-order elliptically and circularly polarized harmonic spectra in an aligned H+2 molecule ion by a combination of two-colour ultrashort intense laser fields from numerical solutions of the corresponding time-dependent Schrödinger equation (TDSE). In intense bichromatic circularly and linearly or circularly polarized laser pulses with intensity I0 and angular frequencies ω0 and 2ω0, it is found that maximum molecular high-order harmonic generation (MHOHG) energies are functions of the molecular internuclear distance. Based on a classical model of laser-induced electron collisions with neighbouring ions, the optimal values of the pulse relative carrier envelope phase φ, the molecular internuclear distance R and the angle thetav of molecular alignment to the laser polarization axis are obtained for efficiently producing MHOHG spectra with the maximum harmonic energy Ip + 13.5Up, where Ip is the ionization potential of the molecule and Up = I0/4meω20 is the ponderomotive energy of the continuum electron at intensity I0 and frequency ω0 of the laser pulse. The results have been confirmed from corresponding TDSE nonperturbative numerical simulations. The polarization property of the generated harmonics is also presented. The mechanism of MHOHG is further characterized with a Gabor time frequency analysis. It is confirmed that a single collision trajectory of the continuum electron with neighbouring ions dominates in the MHOHG processes. The high efficiency of the proposed MHOHG scheme provides a possible source for production of elliptically and/or circularly polarized attosecond extreme ultraviolet pulses. Circularly polarized attosecond pulses can also be generated by using intense ultrashort circularly polarized laser pulses in combination with static electric fields of comparable intensity for H+2 at equilibrium. A time frequency analysis also confirms the role of single recollisions as the dominant mechanism of the generation

  4. Simultaneous VUV and XUV pulse generation and characterization for attosecond pump probe experiments

    CERN Document Server

    Fabris, D; Walke, D; Witting, T; Marangos, J P; Tisch, J W G

    2013-01-01

    We report the generation and characterization of isolated attosecond XUV and VUV pulses generated simultaneously via HHG driven by few-cycle pulses using an in-line dual gas target system. One gas jet target was operated with Kr gas that optimized HHG in the 15-25 eV photon energy range (VUV), whilst the second gas jet target was operated in Ne gas to optimize the high harmonic generation around 90 eV (XUV). Appropriate filters were used to isolate the required spectral components to synthesize isolated pulses. Sn and In filters were used for the VUV region while a Zr filter was used for the XUV. We characterized both the XUV and VUV pulses independently using the attosecond streaking technique and the LSGPA retrieval algorithm obtaining a 1.7$\\pm$0.2 fs pulse using the In filter and a 616$\\pm$50 as pulse using Sn, while preserving a 266$\\pm$10 as isolated XUV pulse.

  5. Laser Phase Determination and Transfer Function to Directly Measure the Temporal Structure of a Narrow Bandwidth Attosecond EUV Pulse

    Institute of Scientific and Technical Information of China (English)

    GE Yu-Cheng

    2006-01-01

    A laser phase determination method and a transfer function that includes a proportional term of a measured photoelectron energy spectrum are presented to directly measure the detailed temporal structure of a narrow bandwidth attosecond extreme-ultraviolet (EUV) pulse. The method is based on the spectrum measurement of an electron generated by EUV photo-ionization interacting with a femtosecond laser field. The results of the study suggest that measurements should be taken at 0° or 180° with respect to the linear laser polarization. The method has a temporal measurement range of about half a laser oscillation period. The temporal resolution also depends on the jitter and control precision of the laser and EUV pulses.

  6. Generation of isolated attosecond pulses in the far field by spatial filtering with an intense few-cycle mid-infrared laser

    CERN Document Server

    Jin, Cheng; Trallero-Herrero, Carlos A; Lin, C D

    2011-01-01

    We report theoretical calculations of high-order harmonic generation (HHG) of Xe with the inclusion of multi-electron effects and macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. By using the time-frequency analysis we show that the reshaping of the fundamental laser field is responsible for the continuum structure in the HHG spectra. We further suggest a method for obtaining an isolated attosecond pulse (IAP) by using a filter centered on axis to select the harmonics in the far field with different divergence. We also discuss the carrier-envelope-phase dependence of an IAP and the possibility to optimize the yield of the IAP. With the intense few-cycle mid-infrared lasers, this offers a possible method for generating isolated attosecond pulses.

  7. Generation of High-Order Harmonic Continuum Supporting Single Attosecond Pulse in Argon Driven by Intense 7 fs Laser Pulse

    Science.gov (United States)

    Zheng, Y. H.; Xiong, H.; Peng, Y.; Xu, H.; Yang, X.; Zeng, Z. N.; Chen, X. W.; Li, R. X.; Zeng, H. P.; Xu, Z. Z.

    High-order harmonic continuum in the cutoff is demonstrated with an argon gas cell driven by 0.4 mJ/7 fs (FWHM) ultrashort intense laser pulse. We find that the spectral structure, the modulation depth and the continuum bandwidth of the high-order harmonic spectra vary when the carrier-envelope phase (CEP) of driving laser pulse is stabilized at different values. At some CEP values, a continuous spectrum of <17% modulation depth and 10 eV continuum bandwidth is achieved, supporting a transform-limited 300 attosecond single pulse in time domain.

  8. Attosecond control of electron-ion recollision in high harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Gademann, G; Kelkensberg, F; Siu, W K; Vrakking, M J J [FOM-Institute for Atomic and Molecular Physics (AMOLF), Science Park 104, 1098 XG Amsterdam (Netherlands); Johnsson, P [Department of Physics, Lund University, PO Box 118, SE-22100 Lund (Sweden); Gaarde, M B; Schafer, K J, E-mail: g.gademann@amolf.nl [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)

    2011-03-15

    We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.

  9. Attosecond control of electron-ion recollision in high harmonic generation

    Science.gov (United States)

    Gademann, G.; Kelkensberg, F.; Siu, W. K.; Johnsson, P.; Gaarde, M. B.; Schafer, K. J.; Vrakking, M. J. J.

    2011-03-01

    We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.

  10. High-order harmonic generation spectra and isolated attosecond pulse generation with a two-color time delayed pulse

    Energy Technology Data Exchange (ETDEWEB)

    Feng Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China); Chu Tianshu, E-mail: tschu@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Investigation of HHG spectra and single isolated attosecond pulse generation. Black-Right-Pointing-Pointer Irradiation from a model Ne atom by two-color time delayed pulse. Black-Right-Pointing-Pointer Observation of time delay effect and relative phase effect. Black-Right-Pointing-Pointer Revelation of the optimal condition for generating isolated attosecond pulse. Black-Right-Pointing-Pointer Generation of a single isolated attosecond pulse of 45as. - Abstract: In this paper, we theoretically investigate the delay time effect on the high-order harmonic generation (HHG) when a model Ne atom is exposed to a two-color time delayed pulse, consisting of a 5fs/800 nm fundamental field and a 20fs/2000 nm controlling field. It shows that the HHG spectra are strongly sensitive to the delay time between the two laser fields, in particular, for the zero carrier-envelope phase (CEP) {phi} case (corresponding to the 800 nm fundamental field), the maximum cutoff energy has been achieved at zero delay time. However, with the introduction of the CEP ({phi} = 180 Degree-Sign ), the delay effect on HHG is changed, exhibiting a 'U' structure harmonic emission from -1 T to 1 T. In addition, the combinations of different controlling pulse frequencies and pulse intensities have also been considered, showing the similar results as the original controlling field case, but with some characteristics. Finally, by properly superposing the optimal harmonic spectrum, an isolated 45as pulse is generated without phase compensation.

  11. The soft-photon approximation in infrared-laser-assisted atomic ionization by extreme-ultraviolet attosecond-pulse trains

    International Nuclear Information System (INIS)

    We use the soft-photon approximation, formulated for finite pulses, to investigate the effects of the dressing pulse duration and intensity on simulated attosecond pump–probe experiments employing trains of attosecond extreme-ultraviolet pulses in conjunction with an IR probe pulse. We illustrate the validity of the approximation by comparing the modelled photoelectron distributions for the helium atom, in the photon energy region close to the N = 2 threshold, to the results from the direct solution of the time-dependent Schrödinger equation for two active electrons. Even in the presence of autoionizing states, the model accurately reproduces most of the background features of the ab initio photoelectron spectrum in the 1s channel. A splitting of the photoelectron harmonic signal along the polarization axis, in particular, is attributed to the finite duration of the probe pulse. Furthermore, we study the dependence of the sideband integrated signal on the pump–probe time delay for increasing IR field strengths. Starting at IR intensities of the order of  ∼ 1 TW cm−2, overtones in the sideband oscillations due to the exchange of three or more IR photons start to appear. We derive an analytical expression in the frequency-comb limit of the soft-photon model for the amplitude of all the sideband frequency components and show that these amplitudes oscillate as a function of the intensity of the IR field. In particular, we predict that the amplitude of the fundamental component with frequency 2ωIR, on which the rabitt optical reconstruction technique is based, changes sign periodically. (paper)

  12. Photoionization dynamics in the presence of attosecond pulse trains and strong fields

    International Nuclear Information System (INIS)

    Highlights: ► We study two-color ionization atoms with attosecond pulse trains and strong fields. ► Floquet formalism is used to explain interferences in ionization. ► We discuss the control of photoionization with use of strong fields. - Abstract: We present experimental results and a theoretical framework for understanding the ionization dynamics in atoms exposed to XUV attosecond pulse trains and strong multi-cycle infrared (IR) fields. We invoke the Floquet formalism to model dressed atomic states as a manifold of Fourier components spaced by the laser frequency. In XUV-IR pump–probe measurements, we observe that the ionization yield oscillates due to quantum interference between photo-excitation paths to a Floquet state. We show that the intensity-dependent shifts of atomic structure modify the ionization channels and the associated interference phase. We extract this phase variation and compare it with simulations. These results provide a comprehensive description of the two-color ionization process and enable new schemes for control of attosecond ionization and fragmentation dynamics

  13. Lanthanum-molybdenum multilayer mirrors for attosecond pulses between 80 and 130 eV

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, M; Schultze, M; Guggenmos, A; Gagnon, J; Yakovlev, V S; Krausz, F; Kleineberg, U [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Am Coulombwall 1, 85748 Garching (Germany); Aquila, A; Yang, S; Gullikson, E [Center for X-Ray Optics, Lawrence Berkeley National Laboratory, 2-400, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Huth, M; Nickel, B [Center for NanoScience (CeNS), Ludwig-Maximilians-Universitaet Muenchen, Schellingstrasse 4, 80799 Munich (Germany); Goulielmakis, E, E-mail: michael.hofstetter@mpq.mpg.de [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)

    2011-06-15

    A novel multilayer material system consisting of lanthanum and molybdenum nano-layers for both broadband and highly reflecting multilayer mirrors in the energy range between 80 and 130 eV is presented. The simulation and design of these multilayers were based on an improved set of optical constants, which were recorded by extreme ultraviolet (XUV)/soft-x-ray absorption measurements on freestanding lanthanum nano-films between 30 eV and 1.3 keV. Lanthanum-molybdenum (La/Mo) multilayer mirrors were produced by ion-beam sputtering and characterized through both x-ray and XUV reflectivity measurements. We demonstrate the ability to precisely simulate and realize aperiodic stacks. Their stability against ambient air conditions is demonstrated. Finally, the La/Mo mirrors were used in the generation of single attosecond pulses from high-harmonic cut-off spectra above 100 eV. Isolated 200 attosecond-long pulses were measured by XUV-pump/IR-probe streaking experiments and characterized using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG/CRAB) analyses.

  14. Photoionization dynamics in the presence of attosecond pulse trains and strong fields

    Energy Technology Data Exchange (ETDEWEB)

    Shivaram, Niranjan; Timmers, Henry [Department of Physics and College of Optical Sciences, University of Arizona, Tucson, AZ 85721 (United States); Tong, Xiao-Min [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8573 (Japan); Sandhu, Arvinder, E-mail: sandhu@physics.arizona.edu [Department of Physics and College of Optical Sciences, University of Arizona, Tucson, AZ 85721 (United States)

    2013-03-12

    Highlights: ► We study two-color ionization atoms with attosecond pulse trains and strong fields. ► Floquet formalism is used to explain interferences in ionization. ► We discuss the control of photoionization with use of strong fields. - Abstract: We present experimental results and a theoretical framework for understanding the ionization dynamics in atoms exposed to XUV attosecond pulse trains and strong multi-cycle infrared (IR) fields. We invoke the Floquet formalism to model dressed atomic states as a manifold of Fourier components spaced by the laser frequency. In XUV-IR pump–probe measurements, we observe that the ionization yield oscillates due to quantum interference between photo-excitation paths to a Floquet state. We show that the intensity-dependent shifts of atomic structure modify the ionization channels and the associated interference phase. We extract this phase variation and compare it with simulations. These results provide a comprehensive description of the two-color ionization process and enable new schemes for control of attosecond ionization and fragmentation dynamics.

  15. Optimization of infrared two-color multicycle field synthesis for intense-isolated-attosecond-pulse generation

    Science.gov (United States)

    Lan, Pengfei; Takahashi, Eiji J.; Midorikawa, Katsumi

    2010-11-01

    We present the optimization of the two-color synthesis method for generating an intense isolated attosecond pulse (IAP) in the multicycle regime. By mixing an infrared assistant pulse with a Ti:sapphire main pulse, we show that an IAP can be produced using a multicycle two-color pulse with a duration longer than 30 fs. We also discuss the influence of the carrier-envelope phase (CEP) and the relative intensity on the generation of IAPs. By optimizing the wavelength of the assistant field, IAP generation becomes insensitive to the CEP slip. Therefore, the optimized two-color method enables us to relax the requirements of pulse duration and easily produce the IAP with a conventional multicycle laser pulse. In addition, it enables us to markedly suppress the ionization of the harmonic medium. This is a major advantage for efficiently generating intense IAPs from a neutral medium by applying the appropriate phase-matching and energy-scaling techniques.

  16. Enhanced asymmetry in few-cycle attosecond pulse ionization of He in the vicinity of autoionizing resonances

    International Nuclear Information System (INIS)

    By solving the two-active-electron, time-dependent Schrödinger equation in its full dimensionality, we investigate the carrier-envelope phase (CEP) dependence of single ionization of He to the He+(1s) state triggered by an intense few-cycle attosecond pulse with carrier frequency ω corresponding to the energy ℏω = 36 eV. Effects of electron correlations are probed by comparing projections of the final state of the two-electron wave packet onto field-free highly correlated Jacobi matrix wave functions with projections onto uncorrelated Coulomb wave functions. Significant differences are found in the vicinity of autoionizing resonances. Owing to the broad bandwidths of our 115 and 230 as pulses and their high intensities (1–2 PW cm−2), asymmetries are found in the differential probability for ionization of electrons parallel and antiparallel to the linear polarization axis of the laser pulse. These asymmetries stem from interference of the one- and two-photon ionization amplitudes for producing electrons with the same momentum along the linear polarization axis. Whereas these asymmetries generally decrease with increasing ionized electron kinetic energy, we find a large enhancement of the asymmetry in the vicinity of two-electron doubly excited (autoionizing) states on an energy scale comparable to the widths of the autoionizing states. The CEP dependence of the energy-integrated asymmetry agrees very well with the predictions of time-dependent perturbation theory (Pronin et al 2009 Phys. Rev. A 80 063403). (paper)

  17. Generation of an isolated few-attosecond pulse in optimized inhomogeneous two-color fields

    Science.gov (United States)

    Chou, Yi; Li, Peng-Cheng; Ho, Tak-San; Chu, Shih-I.

    2015-08-01

    We present a numerical study for optimization of ultrabroad supercontinuum spectrum by controlling the waveforms of laser fields, with the ultimate goal to generate isolated ultrashort attosecond pulses. Specifically, we extend a derivative-free nonconvex optimization algorithm for maximization of the supercontinnum power spectrum near the high-order harmonic generation (HHG) cutoff. It is found that optimally shaped inhomogeneous two-color mid-infrared laser fields can greatly enhance and extend the high-order harmonic generation plateau. Wavelet time-frequency analysis and classical simulations show that the superposition of resulting hydrogen HHG supercontinuum effectively gives rise to a robust isolated 5-as pulse.

  18. Attosecond streaking of shake-up and Auger electrons in xenon

    Directory of Open Access Journals (Sweden)

    Drescher M.

    2013-03-01

    Full Text Available We present first results of simultaneous attosecond streaking measurements of shake-up electrons and Auger electrons emitted from xenon. We extract relative photo-emission delays for electrons emitted from the 4d, 5s and 5p subshell, as well as for the 5p−25d correlation satellite (shake-up electrons.

  19. Attosecond streaking of shake-up and Auger electrons in xenon

    Science.gov (United States)

    Verhoef, A. J.; Mitrofanov, A.; Krikunova, M.; Kabachnik, N. M.; Drescher, M.; Baltuska, A.

    2013-03-01

    We present first results of simultaneous attosecond streaking measurements of shake-up electrons and Auger electrons emitted from xenon. We extract relative photo-emission delays for electrons emitted from the 4d, 5s and 5p subshell, as well as for the 5p-25d correlation satellite (shake-up electrons).

  20. Intense attosecond pulse generated from a molecular harmonic plateau of H2+ in mid-infrared laser fields

    Science.gov (United States)

    Yu, Chao; He, Haixiang; Wang, Yunhui; Shi, Qi; Zhang, Yadong; Lu, Ruifeng

    2014-03-01

    High-order harmonic generation from the molecular ion H2+ exposed to intense laser fields is investigated by the time-dependent quantum wave packet method. Molecular and atomic plateaus of harmonic spectra are effectively distinguished at large internuclear distances, where the harmonic efficiency of the molecular plateau is several orders of magnitude higher than that of the latter. We report on a physical model of the origin of the molecular supercontinua and reveal that the creation of this plateau directly results from the interference of the intramolecular electronic wave packet localized in two potential wells following the laser field. This is our first effort in utilizing the efficient molecular plateau to generate intense isolated attosecond pulses by controlling the dynamics of the nucleus and electrons with a mid-infrared laser. Further, we show that the harmonic plateau is enhanced at the macroscopic level by solving the Maxwell wave equation coupled with the Schrödinger equation.

  1. Conditions for the reliable production of attosecond pulses using ultra-short laser generated high harmonics

    International Nuclear Information System (INIS)

    Full text: We outline some of the theoretical tools available for calculating high harmonic structures generated by the interaction of short IR laser pulses with target gases. We demonstrate a simple approach for determining plateau positions in harmonic spectra, and use that to outline the stringent requirements for carrier-envelope phase and intensity stabilization in the laser pulse for reliable attosecond pulse production. Neglecting the phase and intensity characteristics of the laser pulse will lead to large variations in the duration and number of sub-is pulses produced via high harmonics cut-off windowing. We go on to discuss macroscopic influences, such as the effect of positioning and geometry of the laser focus within the gas jet. (author)

  2. Charge migration induced by attosecond pulses in bio-relevant molecules

    Science.gov (United States)

    Calegari, Francesca; Trabattoni, Andrea; Palacios, Alicia; Ayuso, David; Castrovilli, Mattea C.; Greenwood, Jason B.; Decleva, Piero; Martín, Fernando; Nisoli, Mauro

    2016-07-01

    After sudden ionization of a large molecule, the positive charge can migrate throughout the system on a sub-femtosecond time scale, purely guided by electronic coherences. The possibility to actively explore the role of the electron dynamics in the photo-chemistry of bio-relevant molecules is of fundamental interest for understanding, and perhaps ultimately controlling, the processes leading to damage, mutation and, more generally, to the alteration of the biological functions of the macromolecule. Attosecond laser sources can provide the extreme time resolution required to follow this ultrafast charge flow. In this review we will present recent advances in attosecond molecular science: after a brief description of the results obtained for small molecules, recent experimental and theoretical findings on charge migration in bio-relevant molecules will be discussed.

  3. Towards optical attosecond pulses: broadband phase coherence between an ultrafast laser and OPO using lock-tozero CEO stabilization

    Science.gov (United States)

    McCracken, R. A.; Sun, J.; Leburn, C. G.; Reid, D. T.

    2013-03-01

    The carrier-envelope-offset frequencies of the pump, signal, idler and related sum-frequency mixing pulses have been locked to 0 Hz in a 20-fs-Ti:sapphire-pumped optical parametric oscillator, satisfying a critical prerequisite for optical attosecond pulse synthesis.

  4. Towards optical attosecond pulses: broadband phase coherence between an ultrafast laser and OPO using lock-tozero CEO stabilization

    Directory of Open Access Journals (Sweden)

    Reid D. T.

    2013-03-01

    Full Text Available The carrier-envelope-offset frequencies of the pump, signal, idler and related sum-frequency mixing pulses have been locked to 0 Hz in a 20-fs-Ti:sapphire-pumped optical parametric oscillator, satisfying a critical prerequisite for optical attosecond pulse synthesis.

  5. Robust generation of isolated attosecond pulse against the variation of carrier envelope phase of driving laser pulses

    International Nuclear Information System (INIS)

    We propose a scheme for generating isolated attosecond pulse (IAP) via high-order harmonic generation in gases using a chirped two-color laser field of multicycle duration. In contrast to previous techniques where the stable carrier-envelope phase (CEP) of the driving laser pulses is a prerequisite for IAP generation, the proposed scheme is robust against the large variation of CEP. We show the generation of IAP with an intensity fluctuation less than 50% and an intensity contrast ratio higher than 5:1 when the CEP shift is as large as 1.35π.

  6. Optimization of single attosecond x-ray pulses by genetic algorithm control of the chirp and initial phase of 5 fs laser pulses

    International Nuclear Information System (INIS)

    We show that the peak intensity of single attosecond x-ray pulses is enhanced by 1 or 2 orders of magnitude, the pulse duration is greatly compressed, and the optimal propagation distance is shortened by genetic algorithm optimization of the chirp and initial phase of 5 fs laser pulses. However, as the laser intensity increases, more efficient nonadiabatic self-phase matching can lead to a dramatically enhanced harmonic yield, and the efficiency of optimization decreases in the enhancement and compression of the generated attosecond pulses

  7. Attosecond lighthouses from plasma mirrors

    OpenAIRE

    A. Wheeler, Jonathan; Borot, Antonin; Monchocé, Sylvain; Vincenti, Henri; Ricci, Aurélien; Malvache, Arnaud; Lopez-Martens, Rodrigo B.; Quéré, Fabien

    2012-01-01

    International audience The nonlinear interaction of an intense femtosecond laser pulse with matter can lead to the emission of a train of sub-laser-cycle--attosecond--bursts of short-wavelength radiation1, 2. Much effort has been devoted to producing isolated attosecond pulses, as these are better suited to real-time imaging of fundamental electronic processes3, 4, 5, 6. Successful methods developed so far rely on confining the nonlinear interaction to a single sub-cycle event7, 8, 9. Here...

  8. Temporal characterization of individual harmonics of an attosecond pulse train by THz streaking

    Science.gov (United States)

    Ardana-Lamas, F.; Erny, C.; Stepanov, A. G.; Gorgisyan, I.; Juranić, P.; Abela, R.; Hauri, C. P.

    2016-04-01

    We report on the temporal pulse characteristics of individual harmonics in an attosecond pulse train by means of photoelectron streaking in a strong low-frequency transient. The scheme allows one to retrieve the pulse durations and first-order chirp of individual harmonics without the need for temporal scanning. The measurements were performed using an intense THz field generated by a tilted phase front technique in LiNbO3. We compared the performance of Xe clusters and atomic He as a detection medium and retrieved the temporal properties for harmonics of order 19, 21, 23, 25, and 27. Our measurements confirm that the individual pulse durations and linear chirp decrease by harmonic order.

  9. Generation of an isolated sub-30 attosecond pulse in a two-color laser field and a static electric field

    International Nuclear Information System (INIS)

    We theoretically investigate high-order harmonic generation (HHG) from a helium ion model in a two-color laser field, which is synthesized by a fundamental pulse and its second harmonic pulse. It is shown that a supercontinuum spectrum can be generated in the two-color field. However, the spectral intensity is very low, limiting the application of the generated attosecond (as) pulse. By adding a static electric field to the synthesized two-color field, not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased, but also the quantum paths of the HHG can be significantly modulated. As a result, the extension and enhancement of the supercontinuum spectrum are achieved, producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV. In particular, we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  10. Quantum mechanical approach to probing the birth of attosecond pulses using a two-color field

    CERN Document Server

    Dahlström, J M; Mauritsson, J

    2011-01-01

    We investigate the generation of even and odd harmonics using an intense laser and a weak second harmonic field. Our theoretical approach is based on solving the saddle-point equations within the Strong Field Approximation. The phase of the even harmonic oscillation as a function of the delay between fundamental and second harmonic field is calculated and its variation with energy is found to be in good agreement with recent experimental results. We also find that the relationship between this phase variation and the group delay of the attosecond pulses, depends on the intensity and wavelength of the fundamental field as well as the ionization potential of the atom.

  11. Development of the Schrodinger equation for attosecond laser pulse interaction with Planck gas

    OpenAIRE

    Kozlowski, M; Marciak-Kozlowska, J; Pilsudski, Josef

    2011-01-01

    The creation of the new particles by the interaction of the ultrarelativistic ions,from Large Hadron Collider(LHC), and attosecond laser pulse open new possibilities for laser physicists community .In this paper we propose the hyperbolic Schr\\"odinger equation (HSE) for gas of the "classical" particles "i.e. particles with mass= Planck mass We discuss the inclusion of the gravity to the HSE The solution of the HSE for a particle in a box is obtained. It is shown that for particles with m grea...

  12. Quantum mechanical approach to probing the birth of attosecond pulses using a two-colour field

    Energy Technology Data Exchange (ETDEWEB)

    Dahlstroem, J M; L' Huillier, A; Mauritsson, J, E-mail: Anne.LHuillier@fysik.lth.se [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden)

    2011-05-14

    We investigate the generation of even and odd harmonics using an intense laser and a weak second harmonic field. Our theoretical approach is based on solving the saddle-point equations within the strong field approximation. The phase of the even harmonic oscillation as a function of the delay between the fundamental and second harmonic field is calculated and its variation with energy is found to be in good agreement with recent experimental results. We also find that the relationship between this phase variation and the group delay of the attosecond pulses depends on the intensity and wavelength of the fundamental field as well as the ionization potential of the atom.

  13. Quantum mechanical approach to probing the birth of attosecond pulses using a two-colour field

    International Nuclear Information System (INIS)

    We investigate the generation of even and odd harmonics using an intense laser and a weak second harmonic field. Our theoretical approach is based on solving the saddle-point equations within the strong field approximation. The phase of the even harmonic oscillation as a function of the delay between the fundamental and second harmonic field is calculated and its variation with energy is found to be in good agreement with recent experimental results. We also find that the relationship between this phase variation and the group delay of the attosecond pulses depends on the intensity and wavelength of the fundamental field as well as the ionization potential of the atom.

  14. Isolated attosecond pulse by optimize the parameters of two-color combined field

    International Nuclear Information System (INIS)

    Based on the classical theory, in this paper we optimize the intensity ratio of basic frequency field and low frequency field in the combined field. Then solving time-dependent Schrodinger equation of one-dimensional model helium atom driven by the optimized combined field, we find that high-order harmonic generation cut-off position of helium atom is extended. In addition, taking into account the initial phase of the basic frequency field, we obtain an isolated sub-37 attosecond pulse from the high-order harmonic generation of Helium atom driven by the combined field. (authors)

  15. Optical concept of a compressor for XUV pulses in the attosecond domain.

    Science.gov (United States)

    Frassetto, Fabio; Villoresi, Paolo; Poletto, Luca

    2008-04-28

    We discuss the phase properties of a double-grating compressor with grazing-incidence gratings in the off-plane mount, designed for the temporal compression of XUV attosecond pulses produced with the technique of high-order harmonic generation. Its purpose is to introduce a negative chirp that compensates for the intrinsic chirp of the pulse. The study is based on the path lengths of the rays at different wavelengths, and their control in order to achieve either positive or negative group-delay dispersion. We demonstrate that the sign and the amount of the dispersion introduced is controlled by a linear translation of a grating. Beside the instrument is expected to present a high throughput, constant along the spectrum of interest. The compressor can be designed for any spectral region in the XUV and soft X-ray domain. As a test case, the applications to the compression of attosecond pulses centered at 70 eV and at 160 eV are discussed. PMID:18545369

  16. Controls for the generation of high-order harmonics and attosecond pulses by an infrared laser field combined with a low-frequency pulse

    International Nuclear Information System (INIS)

    We investigate high-order harmonic generations by controlling various quantum paths of harmonics in an infrared laser field which combines a low-frequency pulse. Both classical theory and the quantum wavelet transform method are used to understand the physics of harmonics. By adjusting the carrier envelope phase of the fundamental field, the intensities of harmonic spectra increase and the harmonics in the plateau become regular. Attosecond pulses each with a duration of 58 as are obtained directly by compressing the harmonics, and with phase compensation an isolated attosecond pulse less than 30 as can be generated. (general)

  17. Energy and angular differential probabilities for photoionization of He using chirped attosecond soft-x-ray pulses

    International Nuclear Information System (INIS)

    Based on the time-dependent close-coupling method, energy and angular differential probabilities for various ionization processes of He atoms subjected to intense attosecond soft-x-ray pulses with a photon energy of 91.6 eV and a peak intensity of 1015 W/cm2 are calculated to explore their dependence on the duration and the chirp of the pulse. It is found that the single and the double electron energy distributions for two-photon double ionization are rather sensitive to chirps. That is, both the magnitudes and locations of the sequential peaks in the single electron energy distributions vary strongly with chirps and the two-electron energy distributions being broadened and stretched along the equal energy sharing direction as opposed to the usual total excess energy direction for the case of zero chirp. In addition, our calculation also reveals an unexpected structure formed between the two sequential peaks. In order to better understand the chirp effects on both independent-electron and correlated electron emissions and their relations to the origin of the structure, we analyzed the corresponding probability differential in energy and angle.

  18. Large enhancement of macroscopic yield in attosecond pulse train assisted harmonic generation

    Science.gov (United States)

    Gaarde, Mette B.; Schafer, Kenneth J.; Heinrich, Arne; Biegert, Jens; Keller, Ursula

    2005-07-01

    Attosecond pulse trains (APT) are natural tools for controlling strong field processes, due to their periodicity and short duration. Here we present nonadiabatic calculations of the macroscopic harmonic signal created by a gas of helium atoms exposed to a strong infrared (IR) pulse in combination with an APT. We find that the harmonic yield can be enhanced by two to four orders of magnitude for the optimal delays between the IR and the APT pulses. The large enhancement is due to the change in the IR-intensity dependence of both the harmonic strength and phase caused by the presence and timing of the APT. This leads to enhancement of the harmonic yield and improved phase matching conditions over a large volume.

  19. Large enhancement of macroscopic yield in attosecond pulse train-assisted harmonic generation

    International Nuclear Information System (INIS)

    Attosecond pulse trains (APT) are natural tools for controlling strong field processes, due to their periodicity and short duration. Here we present nonadiabatic calculations of the macroscopic harmonic signal created by a gas of helium atoms exposed to a strong infrared (IR) pulse in combination with an APT. We find that the harmonic yield can be enhanced by two to four orders of magnitude for the optimal delays between the IR and the APT pulses. The large enhancement is due to the change in the IR-intensity dependence of both the harmonic strength and phase caused by the presence and timing of the APT. This leads to enhancement of the harmonic yield and improved phase matching conditions over a large volume

  20. Monitoring attosecond dynamics of coherent electron-nuclear wave packets by molecular high-order-harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Bredtmann, Timm [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada); Institut fuer Chemie und Biochemie, Freie Universitaet Berlin, Takustrasse 3, D-14195 Berlin (Germany); Chelkowski, Szczepan; Bandrauk, Andre D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

    2011-08-15

    A pump-probe scheme for preparing and monitoring electron-nuclear motion in a dissociative coherent electron-nuclear wave packet is explored from numerical solutions of a non-Born-Oppenheimer time-dependent Schroedinger equation. A mid-ir intense few-cycle probe pulse is used to generate molecular high-order-harmonic generation (MHOHG) from a coherent superposition of two or more dissociative coherent electronic-nuclear wave packets, prepared by a femtosecond uv pump pulse. Varying the time delay between the intense ir probe pulse and the uv pump pulse by a few hundreds of attoseconds, the MHOHG signal intensity is shown to vary by orders of magnitude, thus showing the high sensitivity to electron-nuclear dynamics in coherent electron-nuclear wave packets. We relate this high sensitivity of MHOHG spectra to opposing electron velocities (fluxes) in the electron wave packets of the recombining (recolliding) ionized electron and of the bound electron in the initial coherent superposition of two electronic states.

  1. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    OpenAIRE

    Jianqiang Zhu; Xinglong Xie; Meizhi Sun; Qunyu Bi; Jun Kang

    2012-01-01

    We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the K...

  2. Attosecond physics at the nanoscale

    CERN Document Server

    Ciappina, M F; Landsman, A S; Okell, W; Zherebtsov, S; Förg, B; Schötz, J; Seiffert, J L; Fennel, T; Shaaran, T; Zimmermann, T; Chacón, A; Guichard, R; Zaïr, A; Tisch, J W G; Marangos, J P; Witting, T; Braun, A; Maier, S A; Roso, L; Krüger, M; Hommelhoff, P; Kling, M F; Krausz, F; Lewenstein, M

    2016-01-01

    Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this article we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spati...

  3. Two-photon double ionization of neon using an intense attosecond pulse train

    CERN Document Server

    Manschwetus, B; Campi, F; Maclot, S; Coudert-Alteirac, H; Lahl, J; Wikmark, H; Rudawski, P; Heyl, C M; Farkas, B; Mohamed, T; L'Huillier, A; Johnsson, P

    2016-01-01

    We present the first demonstration of two-photon double ionization of neon using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a photon energy regime where both direct and sequential mechanisms are allowed. For an APT generated through high-order harmonic generation (HHG) in argon we achieve a total pulse energy close to 1 $\\mu$J, a central energy of 35 eV and a total bandwidth of $\\sim30$ eV. The APT is focused by broadband optics in a neon gas target to an intensity of $3\\cdot10^{12} $W$\\cdot$cm$^{-2}$. By tuning the photon energy across the threshold for the sequential process the double ionization signal can be turned on and off, indicating that the two-photon double ionization predominantly occurs through a sequential process. The demonstrated performance opens up possibilities for future XUV-XUV pump-probe experiments with attosecond temporal resolution in a photon energy range where it is possible to unravel the dynamics behind direct vs. sequential double ionization and the asso...

  4. Generation of Bright Isolated Attosecond Soft X-Ray Pulses Driven by Multi-Cycle Mid-Infrared Lasers

    CERN Document Server

    Chen, M -C; Mancuso, C; Dollar, F; Galloway, B; Popmintchev, D; Huang, P -C; Walker, B; Plaja, L; Jaron-Becker, A; Becker, A; Popmintchev, T; Murnane, M M; Kapteyn, H C

    2014-01-01

    High harmonic generation driven by femtosecond lasers makes it possible to capture the fastest dynamics in molecules and materials. However, to date the shortest attosecond (as) pulses have been produced only in the extreme ultraviolet (EUV) region of the spectrum below 100 eV, which limits the range of materials and molecular systems that can be explored. Here we use advanced experiment and theory to demonstrate a remarkable convergence of physics: when mid-infrared lasers are used to drive the high harmonic generation process, the conditions for optimal bright soft X-ray generation naturally coincide with the generation of isolated attosecond pulses. The temporal window over which phase matching occurs shrinks rapidly with increasing driving laser wavelength, to the extent that bright isolated attosecond pulses are the norm for 2 \\mu m driving lasers. Harnessing this realization, we demonstrate the generation of isolated soft X-ray attosecond pulses at photon energies up to 180 eV for the first time, that e...

  5. High-Order Harmonic Extension and Generation of Single Isolated Attosecond Pulse in Hydrogen Gas by Using Plasmonic Field Enhancement

    Directory of Open Access Journals (Sweden)

    Mojtaba Taghipour Kaffash, Neda Anvari, Saeed Batebi

    2014-01-01

    Full Text Available Recent advances in laser technology have enabled the full control of few-cycle optical fields, which have key applications including the production of isolated, attosecond (1as=10 -18s extreme ultraviolet (XUV pulses via high-harmonic generation (HHG [i] and the study of nanosystems in the ultrafast regime[ii,iii].

  6. Theoretical methods for attosecond electron and nuclear dynamics: applications to the H2 molecule

    Science.gov (United States)

    Palacios, Alicia; Sanz-Vicario, José Luis; Martín, Fernando

    2015-12-01

    Attosecond science, born at the beginning of this century with the generation of the first bursts of light with durations shorter than a femtosecond, has opened the way to look at electron dynamics in atoms and molecules at its natural timescale. Thus controlling chemical reactions at the electronic level or obtaining time-resolved images of the electronic motion has become a goal for many physics and chemistry laboratories all over the world. The new experimental capabilities have spurred the development of sophisticated theoretical methods that can accurately predict phenomena occurring in the sub-fs timescale. This review provides an overview of the capabilities of existing theoretical tools to describe electron and nuclear dynamics resulting from the interaction of femto- and attosecond UV/XUV radiation with simple molecular targets. We describe one of these methods in more detail, the time-dependent Feshbach close-coupling (TDFCC) formalism, which has been used successfully over the years to investigate various attosecond phenomena in the hydrogen molecule and can easily be extended to other diatomics. In addition to describing the details of the method and discussing its advantages and limitations, we also provide examples of the new physics that one can learn by applying it to different problems: from the study of the autoionization decay that follows attosecond UV excitation to the imaging of the coupled electron and nuclear dynamics in H2 using different UV-pump/IR-probe and UV-pump/UV-probe schemes.

  7. Quantum path control and isolated attosecond pulse generation in the combination of near-infrared and terahertz pulses

    Science.gov (United States)

    Zhong, Hui-Ying; Guo, Jing; Zhang, Hong-Dan; Du, Hui; Liu, Xue-Shen

    2015-07-01

    We present an efficient and realizable scheme for the generation of an ultrashort single attosecond (as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz (THz) field. The high-order harmonic generation (HHG) can be obtained by solving the time-dependent Schrödinger equation accurately and efficiently with time-dependent generalized pseudo-spectral (TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time-frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174108, 11104108, and 11271158).

  8. Characterization of electron-deficient chemical bonding of diborane with attosecond electron wavepacket dynamics and laser response

    Energy Technology Data Exchange (ETDEWEB)

    Yonehara, Takehiro, E-mail: yota@mns2.c.u-tokyo.ac.jp [Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba 153-8902, Tokyo (Japan); Takatsuka, Kazuo, E-mail: kaztak@mns2.c.u-tokyo.ac.jp [Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba 153-8902, Tokyo (Japan)

    2009-12-10

    We report a theoretical study of non-adiabatic electrons-nuclei coupled dynamics of diborane H{sub 2}BH{sub 2}BH{sub 2} under several types of short pulse lasers. This molecule is known to have particularly interesting geometrical and electronic structures, which originate from the electron-deficient chemical bondings. We revisit the chemical bonding of diborane from the view point of electron wavepacket dynamics coupled with nuclear motions, and attempt to probe the characteristics of it by examining its response to intense laser fields. We study in the following three aspects, (i) bond formation of diborane by collision between two monoboranes, (ii) attosecond electron wavepacket dynamics in the ground state and first excited state by circularly polarized laser pulse, and (iii) induced fragmentation back to monoborane molecules by linearly polarized laser. The wave lengths of two types of laser field employed are 200 nm (in UV range) and 800 nm (in IR range), and we track the dynamics from hundreds of attoseconds up to few tens of femtoseconds. To this end, we apply the ab initio semiclassical Ehrenfest theory, into which the classical vector potential of a laser field is introduced. Basic features of the non-adiabatic response of electrons to the laser fields is elucidated in this scheme. To analyze the electronic wavepackets thus obtained, we figure out bond order density that is a spatial distribution of the bond order and bond order flux density arising only from the bonding regions, and so on. Main findings in this work are: (i) dimerization of monoboranes to diborane is so efficient that even intense laser is hard to prevent it; (ii) collective motions of electron flux emerge in the central BHHB bonding area in response to the circularly polarized laser fields; (iii) laser polarization with the direction of central two BH bonding vector is efficient for the cleavage of BH{sub 3}-BH{sub 3}; and (iv) nuclear derivative coupling plays a critical role in the

  9. High-order harmonics extension and isolated attosecond pulse generation in three-color field: Controlling factors

    International Nuclear Information System (INIS)

    In the present Letter, we theoretically discuss the optimum conditions for generating ultrashort attosecond pulse in three-color field with a model He exposed to the intense 5 fs, 800 nm fundamental field and the two weak control fields of 25 fs, 400 nm and 25 fs, 1600 nm. Through investigating the controlling factors in HHG spectra generation via manipulating the laser parameters of the three fields, we demonstrate that properly increasing the pulse intensity of 800 nm and 1600 nm fields at the same time with zero phase effects is an effective way to generate short attosecond pulses. Finally, an isolated pulse of 7 as is predicted by Fourier transforming an ultrabroad XUV continuum of 393 eV with phase compensation. -- Highlights: → Single isolated attosecond pulse generation in three-color scheme. → A synthesized field of an intense 5 fs/800 nm and two weak 25 fs/400 nm and 25 fs/1600 nm pulses. → Solution of time-dependent Schroedinger equation for He interacting with external laser filed. → Properly increase of the intensities of 800 nm and 400 nm pulses and zero phase effect. → Generation of 7 as pulse under the optimized conditions of the laser parameters.

  10. High-order harmonics extension and isolated attosecond pulse generation in three-color field: Controlling factors

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Chu, Tianshu, E-mail: tschu@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

    2011-09-26

    In the present Letter, we theoretically discuss the optimum conditions for generating ultrashort attosecond pulse in three-color field with a model He exposed to the intense 5 fs, 800 nm fundamental field and the two weak control fields of 25 fs, 400 nm and 25 fs, 1600 nm. Through investigating the controlling factors in HHG spectra generation via manipulating the laser parameters of the three fields, we demonstrate that properly increasing the pulse intensity of 800 nm and 1600 nm fields at the same time with zero phase effects is an effective way to generate short attosecond pulses. Finally, an isolated pulse of 7 as is predicted by Fourier transforming an ultrabroad XUV continuum of 393 eV with phase compensation. -- Highlights: → Single isolated attosecond pulse generation in three-color scheme. → A synthesized field of an intense 5 fs/800 nm and two weak 25 fs/400 nm and 25 fs/1600 nm pulses. → Solution of time-dependent Schroedinger equation for He interacting with external laser filed. → Properly increase of the intensities of 800 nm and 400 nm pulses and zero phase effect. → Generation of 7 as pulse under the optimized conditions of the laser parameters.

  11. Design of broadband transmission quarter-wave plates for polarization control of isolated attosecond pulses

    International Nuclear Information System (INIS)

    Using a standard Levenberg–Marquardt algorithm, broadband quarter-wave plates (QWPs) with bandwidth from 3 to 18 eV in the extreme ultraviolet (EUV) region were designed using aperiodic Mo/Si multilayers. By analyzing the design results of the Mo/Si multiayers with different bilayer numbers, we found that a Mo/Si multilayer with more bilayers can achieve broader phase control, but suffers from lower total throughput and a degree of circular polarization. In addition, the pulse broadenings caused by the group delay dispersions of the designed broadband QWPs were studied, and their layer distributions were investigated. The oscillating distribution of bilayer thickness in optimized multilayers was observed, which is considered to be the reason for forming the broadband phase control. Such broadband QWPs can be applied to generate a circularly polarized broadband EUV source, such as isolated attosecond pulse, directly from a linearly polarized source. (paper)

  12. High-order harmonic and attosecond pulse generation on plasma mirrors: basic mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Thaury, C; Quere, F, E-mail: fabien.quere@cea.f [Service des Photons, Atomes et Molecules, Commissariat l' Energie Atomique, DSM/IRAMIS, CEA Saclay, 91191 Gif sur Yvette (France)

    2010-11-14

    When an intense femtosecond laser pulse hits an optically polished surface, it generates a dense plasma that itself acts as a mirror, known as the plasma mirror. As this mirror reflects the high-intensity laser field, its nonlinear temporal response can lead to a periodic temporal distortion of the reflected wave, associated with a train of attosecond light pulses, and, in the frequency domain, to the generation of high-order harmonics of the laser. This tutorial presents detailed theoretical and numerical analysis of the two dominant harmonic generation mechanisms identified so far, coherent wake emission and the relativistic oscillating mirror. Parametric studies of the emission efficiency are presented for these two regimes, and the phase properties of the corresponding harmonics are discussed. This theoretical study is complemented by a synthesis of recent experimental results, which establishes that these two mechanisms indeed dominate harmonic generation on plasma mirrors. (phd tutorial)

  13. High-order harmonic and attosecond pulse generation on plasma mirrors: basic mechanisms

    International Nuclear Information System (INIS)

    When an intense femtosecond laser pulse hits an optically polished surface, it generates a dense plasma that itself acts as a mirror, known as the plasma mirror. As this mirror reflects the high-intensity laser field, its nonlinear temporal response can lead to a periodic temporal distortion of the reflected wave, associated with a train of attosecond light pulses, and, in the frequency domain, to the generation of high-order harmonics of the laser. This tutorial presents detailed theoretical and numerical analysis of the two dominant harmonic generation mechanisms identified so far, coherent wake emission and the relativistic oscillating mirror. Parametric studies of the emission efficiency are presented for these two regimes, and the phase properties of the corresponding harmonics are discussed. This theoretical study is complemented by a synthesis of recent experimental results, which establishes that these two mechanisms indeed dominate harmonic generation on plasma mirrors. (phd tutorial)

  14. Quantum Path Selection and Isolated-Attosecond-Pulse Generation of H2+ with an Intense Laser Pulse and a Static Field

    Science.gov (United States)

    Miao, Xiang-Yang; Liu, Sha-Sha

    2015-01-01

    We theoretically investigate the high-order-harmonic generation from the H2+ molecular ion exposed to the combination of an intense trapezoidal laser and a static field. The results show that the harmonic spectrum is obviously extended and the short quantum path is selected to contribute to the spectrum, because the corresponding long path is seriously suppressed. Then the combined Coulomb and laser field potentials and the time-dependent electron wave packet distributions are applied to illustrate the physical mechanism of high-order harmonic generation. Finally, by adjusting the intensity of the static field and superposing a properly selected range of the HHG spectrum, a 90-as isolated attosecond pulse is straightforwardly obtained.

  15. Attosecond Quantum-Beat Spectroscopy in Helium

    CERN Document Server

    Shivaram, Niranjan; Timmers, Henry; Sandhu, Arvinder

    2015-01-01

    The evolution of electron wavepackets determines the course of many physical and chemical phenomena and attosecond spectroscopy aims to measure and control such dynamics in real-time. Here, we investigate radial electron wavepacket motion in Helium by using an XUV attosecond pulse train to prepare a coherent superposition of excited states and a delayed femtosecond IR pulse to ionize them. Quantum beat signals observed in the high resolution photoelectron spectrogram allow us to follow the field-free evolution of the bound electron wavepacket and determine the time-dependent ionization dynamics of the low-lying 2p state.

  16. Attosecond Double-Slit Experiment

    International Nuclear Information System (INIS)

    A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (slits) of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are measured. A situation in which one and the same electron encounters a single and a double slit at the same time is observed. The investigation of the fringes makes possible interferometry on the attosecond time scale. From the number of visible fringes, for example, one derives that the slits are extended over about 500 as

  17. Attosecond double-slit experiment.

    Science.gov (United States)

    Lindner, F; Schätzel, M G; Walther, H; Baltuska, A; Goulielmakis, E; Krausz, F; Milosević, D B; Bauer, D; Becker, W; Paulus, G G

    2005-07-22

    A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (slits) of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are measured. A situation in which one and the same electron encounters a single and a double slit at the same time is observed. The investigation of the fringes makes possible interferometry on the attosecond time scale. From the number of visible fringes, for example, one derives that the slits are extended over about 500 as. PMID:16090782

  18. Attosecond electron-electron collision dynamics of the four-electron escape in Be close to threshold

    CERN Document Server

    Emmanouilidou, A

    2012-01-01

    We explore the escape geometry of four electrons a few eV above threshold following single-photon absorption from the ground state of Be. We find that the four electrons leave the atom on the vertices of a pyramid instead of a previously-predicted tetrahedron. To illustrate the physical mechanisms of quadruple ionization we use a momentum transferring attosecond collision scheme which we show to be in accord with the pyramid break-up pattern.

  19. Attosecond ionization dynamics

    International Nuclear Information System (INIS)

    Complete test of publication follows. In the interaction between light and matter, the central energy and bandwidth of the radiation, in relation to the energy structure of the studied atoms or molecules, are important parameters. Extreme ultraviolet attosecond pulses, produced through high-order harmonic generation, have during the last years been increasingly used for such studies, particularly in combination with intense infrared (IR) fields, for time-resolved studies of strong field processes. Attosecond experiments have so far utilized pulses with high central energies, in excess of the ionization, potentials of the studied species. When these pulses interact with matter they induce single-photon ionization, creating electron wave packets with a significant initial energy. In the present work, we have generated attosecond pulse trains in xenon, with individual pulse durations of 370 as. Their central energy is 23 eV, which is above the ionization potential of argon (15.8 eV) and neon (21.6 eV), but below that of helium (24.6 eV). We let these pulses interact with the target gas in the presence of a strong IR laser pulse, and measure the on yield as a function of the phase of the IR field at the time of arrival of the pulse. For helium, where the central energy of the pulses is below the ionization threshold, we find a significant enhancement of the ion yield when the IR field is present. In addition, the ion yield exhibits a sub-cycle modulation as a function of the IR phase. The origin of these effects can be understood through the measured photoelectron momentum distributions, and is confirmed by theoretical calculations based on the integration of the time-dependent Schroedinger equation.

  20. Multiple ionization of atoms with xuv attosecond pulses: Two-photon double ionization of helium with 50 eV photons

    Energy Technology Data Exchange (ETDEWEB)

    Bachau, H [Centre Lasers Intenses et Applications, Universite Bordeaux I-CNRS-CEA, 33405 Talence Cedex (France); Foumouo, E; Antoine, Ph; Piraux, B [Laboratoire de Physique Atomique, Moleculaire et Optique, unite PAMO, Universite Catholique de Louvain, 2 chemin du cyclotron, B-1348 Louvain-la-Neuve (Belgium); Chuluunbaatar, O [Joint Institute for Nuclear Research, Dubna, Moscow region, 141980 (Russian Federation); Popov, Y [Nuclear Physics Institute, Moscow State University, Moscow, 119991 (Russian Federation); Shakeshaft, R, E-mail: bachau@celia.u-bordeaux1.f [Physics Department, University of Southern California, Los Angeles, CA 90089-0484 (United States)

    2010-02-01

    We consider two-photon double ionization of helium by two xuv photons in the region around the sequential ionization threshold. We show that, on the attosecond timescale, the mechanism for double ionization is dominated by the absorption of one photon by each electron in the fundamental state He(1s{sup 2}). We examine the dynamics of two-photon double ionization of helium for an averaged photon energy {omega} = 50 eV, with a pulse duration of two optical cycles. The double ionization rate, energy and angular distributions are calculated by solving the time-dependent Schroedinger equation. Results are discussed on the basis of a model.

  1. Multiple ionization of atoms with xuv attosecond pulses: Two-photon double ionization of helium with 50 eV photons

    International Nuclear Information System (INIS)

    We consider two-photon double ionization of helium by two xuv photons in the region around the sequential ionization threshold. We show that, on the attosecond timescale, the mechanism for double ionization is dominated by the absorption of one photon by each electron in the fundamental state He(1s2). We examine the dynamics of two-photon double ionization of helium for an averaged photon energy ω = 50 eV, with a pulse duration of two optical cycles. The double ionization rate, energy and angular distributions are calculated by solving the time-dependent Schroedinger equation. Results are discussed on the basis of a model.

  2. Theoretical description of atomic photoionization by an attosecond XUV pulse in a strong laser field: effects of rescattering and orbital polarization

    International Nuclear Information System (INIS)

    A theoretical description of atomic photoionization by attosecond pulses in the presence of an intense laser pulse is presented. It is based on the numerical solving of the non-stationary Schroedinger equation which includes on an equal footing the realistic atomic potential and the electric fields of both pulses. The calculated energy spectra and angular distributions of photoelectrons are compared with those obtained using a simple approximate model based on the strong-field approximation. The agreement is excellent for large energy of photoelectrons. When the energy is small, the rescattering of electrons by the ionic core affects the cross section considerably making the strong-field approximation inadequate. Influence of the electron orbital polarization on the ionization cross section is investigated

  3. Temporal characterization of attosecond pulses emitted from solid-density plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hoerlein, R; Nomura, Y; Rykovanov, S G; Osterhoff, J; Major, Zs; Karsch, S; Veisz, L; Krausz, F; Tsakiris, G D [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Tzallas, P; Charalambidis, D [Foundation for Research and Technology-Hellas, Institute for Electronic Structure and Laser, PO Box 1527, GR-71110 Heraklion, Crete (Greece); Dromey, B; Zepf, M, E-mail: george.tsakiris@mpq.mpg.d [Department of Physics and Astronomy, Queens University, Belfast BT7 1NN (United Kingdom)

    2010-04-15

    The generation of high harmonics from solid-density plasmas promises the production of attosecond (as) pulses orders of magnitude brighter than those from conventional rare gas sources. However, while spatial and spectral emission of surface harmonics has been characterized in detail in many experiments proof that the harmonic emission is indeed phase locked and thus bunched in as-pulses has only been delivered recently (Nomura et al 2009 Nat. Phys. 5 124-8). In this paper, we discuss the experimental setup of our extreme ultraviolet (XUV) autocorrelation (AC) device in detail and show the first two-photon ionization and subsequent AC experiment using solid target harmonics. In addition, we describe a simple analytical model to estimate the chirp between the individual generated harmonics in the sub- and mildly relativistic regime and validate it using particle-in-cell (PIC) simulations. Finally, we propose several methods applicable to surface harmonics to extend the temporal pulse characterization to higher photon energies and for the reconstruction of the spectral phase between the individual harmonics. The experiments described in this paper prove unambiguously that harmonic emission from solid-density plasmas indeed occurs as a train of sub-femtosecond pulses and thus fulfills the most important property for a next-generation as-pulse source of unprecedented brightness.

  4. Attosecond Dynamics of Electron Wave Packets in Intense Laser Fields

    Science.gov (United States)

    Varjú, K.; Johnsson, P.; Mauritsson, J.; López-Martens, R.; Gustafsson, E.; Remetter, T.; L'huillier, A.

    The continuous progress in the performances of light sources as well as detection techniques allows us to investigate and control the states of matter in even finer details. Light sources, ranging from the infrared (IR) to the extreme ultraviolet (XUV), are becoming increasingly coherent, intense, well characterized, and controlled. The shortest available light pulses are now significantly shorter than 1 fs [1]-[4], thus offering unique promise for studies of ultrafast electron dynamics.

  5. Attosecond-correlated dynamics of two electrons in argon

    Indian Academy of Sciences (India)

    V Sharma; N Camus; B Fischer; M Kremer; A Rudenko; B Bergues; M Kuebel; N G Johnson; M F Kling; T Pfeifer; J Ullrich; R Moshammer

    2014-01-01

    In this work we explored strong field-induced decay of doubly excited transient Coulomb complex Ar** → Ar2++2. We measured the correlated two-electron emission as a function of carrier envelop phase (CEP) of 6 fs pulses in the non-sequential double ionization (NSDI) of argon. Classical model calculations suggest that the intermediate doubly excited Coulomb complex loses memory of its formation dynamics. We estimated the ionization time difference between the two electrons from NSDI of argon and it is 200 ± 100 as (N Camus et al, Phys. Rev. Lett. 108, 073003 (2012)).

  6. On the Generation of Intense Isolated Attosecond Pulses by Many-Cycle Laser Fields

    Science.gov (United States)

    Tzallas, Paris; Skantzakis, Emmanouil; Kruse, Jann E.; Charalambidis, Dimitrios

    Real-time observation of ultrafast dynamics in all states of matter requires temporal resolution on the atomic unit of time (24.189 asec) (1 asec = 1{0}^{-18} s). Tools for tracking such ultrafast dynamics are ultrashort light pulses. During the last decade, continuous efforts in ultrashort pulse engineering led to the development of light pulses width duration close to the atomic unit of time. Attosecond (asec) pulses have been synthesized by broadband coherent extreme ultraviolet (XUV) radiation generated by the interaction of gases or solids with an intense IR fs pulse. Asec pulse trains can be generated when the medium interacts with many-cycle driving IR fs laser fields. In this case, a broadband XUV frequency comb is emitted from the medium. The Fourier synthesis of a part of the comb results in an asec pulse train. Isolated asec pulses are generated when the medium is forced to emit XUV radiation only during few cycles of the driving laser field. This leads to the emission of a broadband quasicontinuum XUV radiation. The Fourier synthesis of the continuum part of the spectrum results in an isolated asec pulse. For the realization of studies of ultrafast dynamics, intense asec pulses are preferable. If the pulses are intense enough to induce a nonlinear process in a target system, they can be used for ultrafast dynamic studies in an XUV pump-probe configuration. Although trains of intense asec pulses are commonly produced nowadays, the generation of intense isolated asec pulses remains a challenge. Here, we review a recently developed approach for the generation of intense asec pulses using high-peak-power many-cycle laser fields. The approach is based on controlling, with asec precession, the response of the atomic dipole to an external many-cycle driving field in such a way as to emit an isolated asec XUV burst. This approach has been implemented by using the inteferometric polarization gating (IPG) technique. The bandwidth of the generated XUV radiation is

  7. Mechanisms of infrared-laser-assisted atomic ionization by attosecond pulses

    International Nuclear Information System (INIS)

    We propose a mechanism to understand the infrared (IR) laser assisted atomic ionization by attosecond pulses (AP). Atomic structures in an IR laser field are described by Floquet states and atoms can be ionized to a Floquet state by a single AP through different Floquet components. The interference of ionization through different Floquet components results in the oscillation of the ionization yield as a function of the arriving time of the AP. The proposed mechanism explains the recent experimental observations [Johnsson et al., Phys. Rev. Lett. 99, 233001 (2007)]. Furthermore, we find that, for a specified photoelectron energy, the ionization yield always oscillates as a function of the relative phase between the AP and the IR laser for both He and Ar atoms.

  8. Phase measurement of a Fano window resonance using tunable attosecond pulses

    CERN Document Server

    Kotur, M; Jimenez-Galan, A; Kroon, D; Larsen, E W; Louisy, M; Bengtsson, S; Miranda, M; Mauritsson, J; Arnold, C L; Canton, S E; Gisselbrecht, M; Carette, T; Dahlstrom, J M; Lindroth, E; Maquet, A; Argenti, L; Martin, F; L'Huillier, A

    2015-01-01

    We study the photoionization of argon atoms close to the 3s$^2$3p$^6$ $\\rightarrow$ 3s$^1$3p$^6$4p $\\leftrightarrow$ 3s$^2$3p$^5$ $\\varepsilon \\ell$, $\\ell$=s,d Fano window resonance. An interferometric technique using an attosecond pulse train, i.e. a frequency comb in the extreme ultraviolet range, and a weak infrared probe field allows us to study both amplitude and phase of the photoionization probability amplitude as a function of photon energy. A theoretical calculation of the ionization process accounting for several continuum channels and bandwidth effects reproduces well the experimental observations and shows that the phase variation of the resonant two-photon amplitude depends on the interaction between the channels involved in the autoionization process.

  9. Generation of isolated attosecond extreme ultraviolet pulses employing nanoplasmonic field enhancement: optimization of coupled ellipsoids

    Energy Technology Data Exchange (ETDEWEB)

    Stebbings, S L; Suessmann, F; Yang, Y-Y; Kling, M F [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strass e 1, 85748 Garching (Germany); Scrinzi, A [Ludwig-Maximilians-Universitaet Muenchen, Theresienstrasse 37, 80333 Muenchen (Germany); Durach, M; Rusina, A; Stockman, M I, E-mail: sarah.stebbings@mpq.mpg.de, E-mail: mstockman@gsu.edu, E-mail: matthias.kling@mpq.mpg.de [Department of Physics and Astronomy, Georgia State University, 29 Peachtree Center Avenue, Atlanta, GA 30303 (United States)

    2011-07-15

    The production of extreme ultraviolet (XUV) radiation via nanoplasmonic field-enhanced high-harmonic generation (HHG) in gold nanostructures at MHz repetition rates is investigated theoretically in this paper. Analytical and numerical calculations are employed and compared in order to determine the plasmonic fields in gold ellipsoidal nanoparticles. The comparison indicates that numerical calculations can accurately predict the field enhancement and plasmonic decay, but may encounter difficulties when attempting to predict the oscillatory behavior of the plasmonic field. Numerical calculations for coupled symmetric and asymmetric ellipsoids for different carrier-envelope phases (CEPs) of the driving laser field are combined with time-dependent Schroedinger equation simulations to predict the resulting HHG spectra. The studies reveal that the plasmonic field oscillations, which are controlled by the CEP of the driving laser field, play a more important role than the nanostructure configuration in finding the optimal conditions for the generation of isolated attosecond XUV pulses via nanoplasmonic field enhancement.

  10. Attosecond XUV probing of strong field ionization dynamics from one- and two-electron 1D atoms

    International Nuclear Information System (INIS)

    Full text: The probing of strong field ionization dynamics by a 250 attosecond XUV pulse is considered, first, for a one-electron 1D atom, and second, for a two-electron 1D atom. In the one-electron case, the XUV ionization yield as a function of time delay between the laser pulse and the XUV pulse is seen to reflect the time-dependence of the field-dressed neutral atomic population. The depletion of the ground state, and hence the dynamics of strong field ionization, can be inferred on sub-cycle timescales. Furthermore, it is suggested that this XUV probing also reveals the sub-cycle distortions of the atomic ground state near the peaks of the strong laser field. In the two electron case, both the neutral and singly-ionized populations in the strong field can be probed by the XUV pulse. The time-dependent yield of XUV ionization from the ionic population reflects the time-dependence of the ionization from the strong laser field. This shows directly the strong field ionization dynamics on sub-cycle timescales. (author)

  11. A flexible apparatus for attosecond photoelectron spectroscopy of solids and surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, E.; Stanislawski, M.; Uphues, Th. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Neppl, S.; Barth, J. V.; Menzel, D.; Feulner, P. [Physik Department E20, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Cavalieri, A. L. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Max-Planck Research Department for Structural Dynamics, Universitaet Hamburg, Notkestrasse 85, 22607 Hamburg (Germany); Bothschafter, E. M.; Ernstorfer, R.; Kienberger, R. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Physik Department E11, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Hofstetter, M.; Kleineberg, U.; Krausz, F. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, Fakultaet fuer Physik, Am Coulombwall 1, 85748 Garching (Germany)

    2011-06-15

    We describe an apparatus for attosecond photoelectron spectroscopy of solids and surfaces, which combines the generation of isolated attosecond extreme-ultraviolet (XUV) laser pulses by high harmonic generation in gases with time-resolved photoelectron detection and surface science techniques in an ultrahigh vacuum environment. This versatile setup provides isolated attosecond pulses with photon energies of up to 140 eV and few-cycle near infrared pulses for studying ultrafast electron dynamics in a large variety of surfaces and interfaces. The samples can be prepared and characterized on an atomic scale in a dedicated flexible surface science end station. The extensive possibilities offered by this apparatus are demonstrated by applying attosecond XUV pulses with a central photon energy of {approx}125 eV in an attosecond streaking experiment of a xenon multilayer grown on a Re(0001) substrate.

  12. Laser-assisted-autoionization dynamics of helium resonances with single attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Wei-Chun; Lin, C. D. [J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Zhao Songfeng [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2011-09-15

    The strong coupling between two autoionizing states in helium is studied theoretically with the pump-probe scheme. An isolated 100-as XUV pulse is used to excite helium near the 2s2p({sup 1} P) resonance state in the presence of an intense infrared (IR) laser. The laser field introduces strong coupling between 2s2p({sup 1} P) and 2p{sup 2}({sup 1} S) states. The IR also can ionize helium from both autoionizing states. By changing the time delay between the XUV and the IR pulses, we investigated the photoelectron spectra near the two resonances. The results are used to explain the recent experiment by Gilbertson et al.[Phys. Rev. Lett. 105, 263003 (2010)]. Using the same isolated attosecond pulse and a 540-nm laser, we also investigate the strong coupling between 2s2p({sup 1} P) and 2s{sup 2}({sup 1} S) by examining how the photoelectron spectra are modified versus the time delay and the possibility of observing Autler-Townes doublet in such experiments.

  13. Influence of vibrational states on high-order-harmonic generation and an isolated attosecond pulse from a N2 molecule

    Science.gov (United States)

    Guo, Jing; Ge, Xin-Lei; Zhong, Huiying; Zhao, Xi; Zhang, Meixia; Jiang, Yuanfei; Liu, Xue-Shen

    2014-11-01

    The high-order-harmonic generation (HHG) from the N2 molecule in an intense laser field is investigated by applying the Lewenstein method. The initial state is constructed as a linear combination of the highest occupied molecular orbital (HOMO) and the lower-lying orbital below the HOMO, which is well described by a Gaussian wave packet generated by using the gamess-uk package. The HHG with different vibrational states of N2 are calculated and our results show that the harmonic intensity can be enhanced by higher vibrational states, which can be explained by the ionization probability. We also compared the cases with a different full width at half maximum of laser fields together, which can be well understood by the time-frequency analysis and the three-step model. Finally, the attosecond pulse generation is studied with different vibrational states, where a series of attosecond pulses can be produced with the shortest being 91 as.

  14. Wavebreaking-induced Transmitted Emission of Attosecond Extreme-ultraviolet Pulses from Laser-driven Overdense Plasmas

    CERN Document Server

    Chen, Zi-Yu; Pukhov, Alexander

    2015-01-01

    We present a new mechanism of attosecond extreme-ultraviolet (XUV) pulses generation from a relativistic laser-driven overdense plasma surfaces. Unlike high-order harmonic generation by reflection of a laser from the front target surface, the emission is in the transmitted direction with frequencies of local plasma frequency and its harmonics. Through simulations and analysis, we demonstrate that the ultrashort XUV emission is predominantly due to the strong plasma- density oscillation in the front skin layer induced by wavebreaking. This mechanism provides new insights into the senarios of harmonic generation from solid surfaces and the dynamics of laser- plasma interactions. It also offers a new method of attosecond XUV pulses generation which may find extensive applications in a number of fields.

  15. High resolution electron spectrometers for characterizing the contrast of isolated 25 as pulses

    International Nuclear Information System (INIS)

    Highlights: • The accuracy of characterizing the contrast of an isolated 25 attosecond pulse is highly dependent on the energy resolution of the electron energy spectrometer. • Magnetic-bottle electron energy spectrometer has insufficient resolution for accurate contrast measurement. • New design in the magnetic-bottle spectrometer improved the resolution by restricting the acceptance angle with a small pinhole. • The satellite pulse of the isolated 25 attosecond can be characterized with less than 10 percent error by the new magnetic-bottle spectrometer design. - Abstract: We quantify the effects of the energy resolution of a magnetic bottle electron spectrometer in an attosecond streak camera on the accuracy of measuring the relative amplitudes of satellite pulses around the main attosecond pulse. Our numerical simulations show that the spectral resolution can be significantly improved by restricting the acceptance angle using a pinhole located near the source of the photoelectrons. The intensity of the pre- and post-pulses which are 1% and 10% of a main 25 as pulse can potentially be measured with less than 10% error by two practical time-of-flight spectrometer designs

  16. Generation of Broadband Attosecond Pulse via Controlling Quantum Path by Two Color Field in Long Wavelength Driving Regime

    International Nuclear Information System (INIS)

    In this paper, we have investigated theoretically the high harmonic generation form helium atom in long wavelength driving regime at 2000 nm through solving time-dependent Schroedinger equation. By adding a second harmonic pulse (1000 nm) and a UV attosecond pulse (200 nm) to the driving field, an efficient method for picking out and enhancing ionization path to generate high-yield supercontinuum harmonics is realized, and then an isolated sub-100 as pulse with a bandwidth of 190 eV is significantly obtained. (atomic and molecular physics)

  17. MeV femtosecond electron pulses from direct-field acceleration in low density atomic gases

    CERN Document Server

    Varin, Charles; Hogan-Lamarre, Pascal; Fennel, Thomas; Piché, Michel; Brabec, Thomas

    2015-01-01

    Using three-dimensional particle-in-cell simulations, we show that few-MeV electrons can be produced by focusing tightly few-cycle radially-polarized laser pulses in a low-density atomic gas. In particular, it is observed that for the few-TW laser power needed to reach relativistic electron energies, longitudinal attosecond microbunching occurs naturally, resulting in femtosecond structures with high-contrast attosecond density modulations. The three-dimensional particle-in-cell simulations show that in the relativistic regime the leading pulse of these attosecond substructures survives to propagation over extended distances, suggesting that it could be delivered to a distant target, with the help of a properly designed transport beamline.

  18. Generation of isolated ultra-short attosecond pulses by coherent control of the population of excited states

    Science.gov (United States)

    Jooya, Hossein Z.; Li, Peng-Cheng; Liao, Sheng-Lun; Chu, Shih-I.

    2016-01-01

    We present an ab-initio theoretical investigation of the enhancement of ultra-broad super-continuum harmonic spectra by coherently controlling the electron quantum paths of the helium atom and He+ ion. The time-dependent Schrödinger equation is solved by means of the time-dependent generalized pseudo-spectral method, allowing non-uniform and optimal spatial grid discretization and accurate and efficient propagation of the wave function in space and time. The population of the first two low-lying excited states of He+ is selectively controlled by adding low intensity, high frequency laser pulses to a two color mid-infrared laser field. Although the intensity of the added field is weak, its high frequency makes the subsequent ionization probability from excited states become much larger than for the case of many photons (mid-IR filed), even though the intensity is smaller. We found that the intensity of the attosecond pulse generated by superposing a range of synchronized high harmonics is significantly enhanced by 20 orders of magnitude. Similar calculations have been performed for the neutral He atoms. We found that an intense and ultra-short isolated 18 as can be generated directly. To understand the underlying mechanism of such dramatic enhancement and the role of electron quantum paths, we perform wavelet time-frequency transform of high harmonic spectra. The results show that we can selectively control the domination of the two distinct long and short electron trajectories by controlling the population of different excited states.

  19. Interferometric autocorrelation of an attosecond pulse train calculated using feasible formulae

    International Nuclear Information System (INIS)

    The autocorrelation trace of an attosecond pulse train (APT) directly revealed the pulse envelope in our recent experiment on measuring the two-photon Coulomb explosion of a nitrogen molecule as a correlation signal. Although the spatial overlap of the two replicas of the APT in the correlation measurement was only achieved near the focal region owing to the spatial split of the measured APT field, which is a situation quite different from that of the correlation measurement using a Michelson interferometer, the interference fringes clearly appeared on the correlation envelope and provedthe odd symmetry of the electric field to the time translation with a half-period of the driving laser field. In this paper, we show a simple and practical analysis for the propagation and the nonlinear interaction of an APT to simulate the experimental result of the interferometric autocorrelation of the spatially split APT. The spatial convolution of the focused electric field is essential for obtaining the fringes. We also discuss how the autocorrelation should be described in the context of the second-order perturbation theory within a dipole approximation

  20. A new technique to generate 100 GW-level attosecond X-ray pulses from the X-ray SASE FELs

    International Nuclear Information System (INIS)

    We propose a scheme for generation of single 100 GW 300-as pulse in the X-ray free electron laser with the use of a few cycles optical pulse from Ti:sapphire laser system. Femtosecond optical pulse interacts with the electron beam in the two-period undulator resonant to 800 nm wavelength and produces energy modulation within a slice of the electron bunch. Following the energy modulator the electron beam enters the first part of the baseline gap-adjustable X-ray undulator and produces SASE radiation with 100 MW-level power. Due to energy modulation the frequency is correlated to the longitudinal position within the few-cycle-driven slice of the SASE radiation pulse. The largest frequency offset corresponds to a single-spike pulse in the time domain which is confined to one half-oscillation period near the central peak electron energy. After the first undulator the electron beam is guided through a magnetic delay which we use to position the X-ray spike with the largest frequency offset at the ''fresh'' part of the electron bunch. After the chicane the electron beam and the radiation produced in the first undulator enter the second undulator which is resonant with the offset frequency. In the second undulator the seed radiation at reference frequency plays no role, and only a single (300 as duration) spike grows rapidly. The final part of the undulator is a tapered section allowing to achieve maximum output power 100-150 GW in 0.15 nm wavelength range. Attosecond X-ray pulse is naturally synchronized with its fs optical pulse which reveals unique perspective for pump-probe experiments with sub-femtosecond resolution. (orig.)

  1. Above-threshold double ionization of helium with attosecond intense soft x-ray pulses

    International Nuclear Information System (INIS)

    We theoretically study a process in which helium is doubly ionized by absorbing two soft x-ray (91.45 eV) photons from attosecond, intense high-order harmonic sources. We directly solve the time-dependent Schroedinger equation and obtain electron energy distribution in the double continuum. Our results show that between the two peaks in electron energy spectra, expected for usual sequential ionization, an additional component (anomalous component) is present. The total two photon above-threshold double ionization yield including the anomalous component is explained by sequential processes: the two electrons are ejected one by one, absorbing a single photon each. This observation rejects the intuition that nonsequential double ionization would be responsible for the anomalous component. With the help of simple semiclassical stochastic models, we discuss two possible origins of the anomalous component, namely, postionization energy exchange and second ionization during core relaxation, of which the latter is more plausible: the ionization interval is so short that the second electron is ejected while the two electrons are still exchanging energy

  2. Relativistic attosecond physics

    International Nuclear Information System (INIS)

    Full text: Few-cycle laser pulses focused to a λ3 volume can produce relativistic intensities with only millijoules of energy. Relativistic intensity is achieved when the dimensionless field strength a0 ≥ 1, where a0 = eE0/meωc (for λ = 800 nm, a0 = 1 corresponds to I = 2x1018 W/cm2). In the relativistic λ3 regime, isolated attosecond pulses are efficiently formed through relativistic reflection, deflection, and compression. Particle-in-cell (PIC) simulations show that attosecond pulses are formed for a variety of plasma profiles, and the compressed pulse durations can scale inversely with driving field strength. The extreme spatial and temporal gradients achieved through λ3 focusing provides the strongest slopes in the plasma density, deflecting subsequent half-cycles of the driving radiation into unique non-specular directions. The same coherent motion of the critical surface that provides relativistic deflection also provides relativistic Doppler compression, generating attosecond pulses with conversion efficiency ∼ 10-1 under optimal conditions. Previously, isolated attosecond pulses have been generated using high harmonic generation in gases with conversion efficiency ∼ 10-6. Simulations indicate that the dense relativistic electron sheets can be extracted when the driving laser is incident on a sharp plasma boundary at large angles of incidence. Electrons are ejected from the plasma at locations of minimal pressure and are accelerated by the electromagnetic field. In turn, these electrons deflect and compress the radiation into a train of attosecond electromagnetic pulses. The electron bunches inherit a chirped energy structure with sub-cycle duration; -2x108 electrons per bunch are observed for specific simulation parameters. Relativistic deflection and compression is expected whenever relativistic intensity laser pulses interact with a critically dense plasma. For τ 30 fs laser pulses, we observe relativistic deflection and spectral broadening

  3. Rotations of molecular photoelectron angular distributions in above threshold ionization of H2+ by intense circularly polarized attosecond UV laser pulses

    International Nuclear Information System (INIS)

    We present molecular photoelectron angular distributions (MPADs) in multi-photon ionization processes by circularly polarized attosecond UV laser pulses. Simulations are performed on the single electron aligned molecular ion H2+ by solving corresponding 3D time-dependent Schrödinger equations. Numerical results of molecular above threshold ionization (MATI) show that rotations of MPADs with respect to the molecular and polarization axes depend on pulse intensities and photoelectron kinetic energies. We attribute the rotation to Γ, the difference between parallel and perpendicular ionization probabilities. It is found that in a resonant ionization process, the rotation angle is also a function of the symmetry of intermediate electronic states. The coherent population transfer between the initial and the resonant electronic states is controlled by pulse intensities. Such dependence of rotations on the pulse intensity is absent in Rydberg resonant ionizations as well as in MATI at large energy photons ℏω > Ip, where ω is angular frequency of photons and Ip is the molecular ionization potential. We describe these processes by a multi-photon perturbation theory model. Effects of molecular alignment and pulse ellipticities on rotations are investigated, confirming the essence of the ionization parameter Γ in rotations of MPADs. (paper)

  4. Rotations of molecular photoelectron angular distributions in above threshold ionization of H2+ by intense circularly polarized attosecond UV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2014-10-01

    We present molecular photoelectron angular distributions (MPADs) in multi-photon ionization processes by circularly polarized attosecond UV laser pulses. Simulations are performed on the single electron aligned molecular ion H_2^+ by solving corresponding 3D time-dependent Schrödinger equations. Numerical results of molecular above threshold ionization (MATI) show that rotations of MPADs with respect to the molecular and polarization axes depend on pulse intensities and photoelectron kinetic energies. We attribute the rotation to Γ, the difference between parallel and perpendicular ionization probabilities. It is found that in a resonant ionization process, the rotation angle is also a function of the symmetry of intermediate electronic states. The coherent population transfer between the initial and the resonant electronic states is controlled by pulse intensities. Such dependence of rotations on the pulse intensity is absent in Rydberg resonant ionizations as well as in MATI at large energy photons ℏω > Ip, where ω is angular frequency of photons and Ip is the molecular ionization potential. We describe these processes by a multi-photon perturbation theory model. Effects of molecular alignment and pulse ellipticities on rotations are investigated, confirming the essence of the ionization parameter Γ in rotations of MPADs.

  5. Diagrammatic approach to attosecond delays in photoionization

    CERN Document Server

    Dahlström, J M; Lindroth, E

    2012-01-01

    We study laser-assisted photoionization by attosecond pulses using a time-independent formalism based on diagrammatic many-body perturbation theory. Our aim is to provide an ab inito route to the "delays" for this above-threshold ionization process, which is essential for a quantitative understanding of attosecond metrology. We present correction curves for characterization schemes of attosecond pulses, such as "streaking", that account for the delayed atomic response in ionization from neon and argon. We also verify that photoelectron delays from many-electron atoms can be measured using similar schemes if, instead, the so-called continuum--continuum delay is subtracted. Our method is general and it can be extended also to more complex systems and additional correlation effects can be introduced systematically.

  6. Production of intense attosecond vector beam pulse trains based on harmonics

    Science.gov (United States)

    Han, Yu-Jing; Liao, Guo-Qian; Chen, Li-Ming; Li, Yu-Tong; Wang, Wei-Min; Zhang, Jie

    2015-11-01

    We provide the first report on the harmonics generated by an intense femtosecond vector beam that is normally incident on a solid target. By using 2D particle-in-cell (PIC) codes, we observe the third and the fifth harmonic signals with the same vector structure as the driving beam, and obtain an attosecond vector beam pulse train. We also show that the conversion efficiencies of the third and the fifth harmonics reach their maxima for a plasma density of four times the critical density due to the plasma resonating with the driving force. This method provides a new means of generating intense extreme ultraviolet (XUV) vector beams via ultra-intense laser-driven harmonics. Project supported by the National Basic Research Program of China (Grant Nos. 2013CBA01501 and 2013CBA01504), the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2012YQ120047), Chinese Academy of Science Key Program, the National Natural Science of China (Grant Nos. 11135012 and 11375262), and the Project of Shandong Province Higher Educational Science and Technology Program, China (Grant No. J11LA52).

  7. Isolated sub-30-attosecond pulse generation using a multicycle two-color chirped laser and a static electric field

    International Nuclear Information System (INIS)

    We present a theoretical investigation of high-order harmonic generation in a chirped two-color laser field, which is synthesized by a 10-fs/800-nm fundamental chirped pulse and a 10-fs/1760-nm subharmonic pulse. It is shown that a supercontinuum can be produced using the multicycle two-color chirped field. However, the supercontinuum reveals a strong modulation structure, which is not good for the generation of an isolated attosecond pulse. By adding a static electric field to the multicycle two-color chirped field, not only the harmonic cutoff is extended remarkably, but also the quantum paths of the high-order harmonic generation (HHG) are modified significantly. As a result, both the extension of the supercontinuum and the selection of a single quantum path are achieved, producing an isolated 23-as pulse with a bandwidth of about 170.6 eV. Furthermore, the influences of the laser intensities on the supercontinuum and isolated attosecond pulse generation are investigated. (atomic and molecular physics)

  8. Time-and-energy-resolved measurement of Auger cascades following Kr 3d excitation by attosecond pulses

    International Nuclear Information System (INIS)

    We show that attosecond metrology has evolved from proof-of-principle experiments to a level where complex processes can be resolved in time that cannot be accessed using any other existing technique. The cascaded Auger decay following ionization and excitation of the 3d-subshell in Kr with subfemtosecond 94 eV soft x-ray pulses has been energy- and time-resolved in an x-ray pump-infrared probe experiment. This Auger cascade reveals rich multi-electron dynamics, which despite the fact that there are many experimental and theoretical data available, is not yet fully understood. We present time-resolved data showing the sequence of the temporal dynamics in the cascaded Auger decay. The decay time of several groups of lines has been measured, including the lines at the low-energy part of the spectrum, which are predominantly produced by the second-step Auger transitions. Our experimental data reveal long lifetimes (up to 70 fs) of the subvalence excited ionic (intermediate) states in the cascaded resonant Auger decay. Extensive theoretical calculations within the multiconfiguration Dirac-Fock (MCDF) approach show that the observed long lifetime may be attributed to the second-step Auger decay of the resonantly excited 3d-1np states with n = 6,7. Furthermore, our experimental data show that the electrons with a kinetic energy around 25 eV (generally assigned as M4,5N1N1 1S0 normal Auger lines) have a component corresponding to the second-step Auger decay of the ion after resonant Auger transition 3d-1np → 4s2 4p3 4dnp → 4s2 4p4 with a lifetime of 26 ± 4 fs. (paper)

  9. Attosecond Nonlinear Optics

    International Nuclear Information System (INIS)

    We report nonlinear multiphoton processes in atoms and molecules by intense high harmonics and their applications to attosecond pulse characterization. Phase matched high harmonics by a loosely focusing geometry produce highly focusable intensity with fully spatiotemporal coherence, which is sufficient to induce nonlinear optical phenomena in the extreme ultraviolet and soft x-ray (XUV) region. With this XUV coherent light source, two-photon double ionization in He is demonstrated with 42-eV high harmonic photons. On the other hand, when intense high harmonics around 20 eV is subjected to N2 molecules, occurrence of Coulomb explosion following to two-photon double ionization is observed in attosecond temporal precision. Taking advantage of larger cross section of two-photon ionization in molecules, we successfully perform the interferometric autocorrelation of an attosecond pulse train with the ion signals produced by Coulomb explosion of nitrogen molecules. The result reveals the phase relation between attosecond pulses in the train.

  10. Attosecond and zeptosecond x-ray pulses via nonlinear Thomson backscattering

    International Nuclear Information System (INIS)

    Nonlinear Thomson backscattering of an intense circularly polarized laser by a counterpropagating energetic electron is investigated. The results show that in the scattering of a non-tightly-focused laser pulse with an intensity around 1019 W/cm2 and a pulse duration of 100 fs full width at half maximum by a counterpropagating electron with an initial energy of 10 MeV, a crescent-shaped pulse with a pulse duration of 469 as and the photon energy ranging from 230 eV to 2.5 keV is generated in the backward direction. It is shown that the radiated pulse shape and monochromaticity can be modified by changing the laser beam waist, while in the case of a tightly focused laser field, a single peak pulse with a shorter duration and better monochromaticity can be obtained. With increase of the electron initial energy, the peak power of the radiated pulse increases and the pulse duration decreases. An isolated powerful zeptosecond (10-21 s) pulse with a peak power of about 1010 W/rad2 and photon energy up to several MeV can be obtained with a 250 MeV electron

  11. Formation of Attosecond XUV Pulses via Resonance with Hydrogen-Like Atoms Irradiated by Intense Laser Field

    Science.gov (United States)

    Polovinkin, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga; Ryabikin, M. Yu.

    We show the possibility to produce a short bunch of few nearly bandwidth-limited few-cycle attosecond pulses via the time-dependent resonant interaction of an incident radiation pulse with the bound states of hydrogenlike atoms. Time-dependence of the resonant interaction is based on time-dependent tunnel ionization from the excited states and temporal adiabatic Stark splitting of the excited energy levels, provided by far-off-resonant laser pulse whose intensity is much below the atomic ionization threshold. Without external synchronization of the spectral components it is possible to produce pulses of XUV radiation with duration up to 80 as at the carrier wavelength 13.5 nm in Li2 +-plasma.

  12. Propagation effects of isolated attosecond pulse generation with a multicycle chirped and chirped-free two-color field

    Energy Technology Data Exchange (ETDEWEB)

    Du Hongchuan; Hu Bitao [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2011-08-15

    We present a theoretical study of isolated attosecond pulse generation with a multicycle chirped and chirped-free two-color field. We show that the bandwidth of the extreme ultraviolet supercontinuum can be extended by combining a multicycle chirped pulse and a multicycle chirped-free pulse. Also, the broadband supercontinuum can still be generated when the macroscopic effects are included. Furthermore, the macroscopic effects can ameliorate the temporal characteristic of the broadband supercontinuum of the single atom, and eliminate the modulations of the broadband supercontinuum. Thus a very smooth broadband supercontinuum and a pure isolated 102-as pulse can be directly obtained. Moreover, the structure of the broadband supercontinuum can be steadily maintained for a relative long distance after a certain distance.

  13. Single attosecond pulse generation by nonlinear Thomson scattering in a tightly focused intense laser beam

    International Nuclear Information System (INIS)

    The relativistic nonlinear Thomson scattering of a tightly focused intense laser pulse by an electron is investigated, and the temporal and spectral characters of the radiation are discussed. In a tightly focused laser pulse with an intensity of approximately 1020 W/cm2 and a pulse duration of 20 fs, the electron is scattered away from the focus quickly by the ponderomotive force and therefore the radiation emitted at the focus is much higher than that at other regions. As a result, a single ultrashort pulse of 3.8 as is generated and its corresponding spectrum is broadened to 200 orders of the frequency of the driving laser. With increasing the laser intensity, the signal-to-noise of the radiated pulse increases, and the pulse duration decreases. Moreover, the phase behavior of the spectral components and the dependence of the radiated power on the laser intensity are discussed

  14. Towards Zeptosecond-Scale Pulses from X-Ray Free-Electron Lasers

    CERN Document Server

    Dunning, D J; Thompson, N R

    2013-01-01

    The short wavelength and high peak power of the present generation of free-electron lasers (FELs) opens the possibility of ultra-short pulses even surpassing the present (tens to hundreds of attoseconds) capabilities of other light sources - but only if x-ray FELs can be made to generate pulses consisting of just a few optical cycles. For hard x-ray operation (~0.1nm), this corresponds to durations of approximately a single attosecond, and below into the zeptosecond scale. This talk will describe a novel method to generate trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL facilities by using a relatively short 'afterburner'. Such pulses would enhance research opportunity in atomic dynamics and push capability towards the investigation of electronic-nuclear and nuclear dynamics. The corresponding multi-colour spectral output, with a bandwidth envelope increased by up to two orders of magnitudes over SASE, also has potential applications.

  15. Intense attosecond radiation from an X-ray FEL - extended version

    International Nuclear Information System (INIS)

    We propose the use of a ultra-relativistic electron beam interacting with a feW--cycle, intense laser pulse and an intense pulse of the coherent x-rays to produce a multi-MW intensity, x-ray pulses ∼100 attoseconds in duration. Due to a naturally-occurring frequency chirp, these pulses can be further temporally compressed

  16. Attosecond timing jitter pulse trains from semiconductor saturable absorber mode-locked Cr:LiSAF lasers

    OpenAIRE

    Sennaroğlu, Alphan; Li, Duo; Demirbaş, Ümit; Benedick, Andrew; Fujimoto, James G.; Kaertner, Franz X.

    2012-01-01

    The timing jitter of optical pulse trains from diode-pumped, semiconductor saturable absorber mode-locked femtosecond Cr:LiSAF lasers is characterized by a single-crystal balanced optical cross-correlator with an equivalent sensitivity in phase noise of -235 dBc/Hz. The RMS timing jitter is 30 attoseconds integrated from 10 kHz to 50 MHz, the Nyquist frequency of the 100 MHz repetition rate oscillator. The AM-to-PM conversion induced excess phase noise is calculated and compared with experime...

  17. Wavebreaking-associated transmitted emission of attosecond extreme-ultraviolet pulses from laser-driven overdense plasmas

    Science.gov (United States)

    Chen, Zi-Yu; Cherednychek, Mykyta; Pukhov, Alexander

    2016-06-01

    We present a new mechanism of attosecond extreme-ultraviolet (XUV) pulses generation from a relativistic laser-driven overdense plasma surfaces in the wavebreaking regime. Through particle-in-cell simulations and analysis, we demonstrate that the observed ultrashort XUV emission for the parameters we considered is predominantly due to a strong plasma-density oscillation subsequent to wavebreaking. The coupling of the strong density variation and the transverse fields in the front surface layer gives rise to the transmitted emission with frequencies mainly around the local plasma frequency. This mechanism provides new insights into the scenarios of XUV generation from solid surfaces and the dynamics of laser–plasma interactions.

  18. Electron dynamics in strong laser pulse illumination of large rare gas clusters

    Science.gov (United States)

    Saalmann, U.; Rost, J. M.

    2005-11-01

    We analyze the dynamics of up to 105 electrons resulting from illuminating a xenon cluster with 9093 atoms with intense laser pulses of different length and peak intensity. Interesting details of electron motion are identified which can be probed with a time resolution of 100 attoseconds. Corresponding experiments would shed light on unexplored territory in complex electronic systems such as clusters and they would also permit to critically access the present theoretical description of this dynamics.

  19. Fundamentals of attosecond optics

    CERN Document Server

    Chang, Zenghu

    2011-01-01

    Attosecond optical pulse generation, along with the related process of high-order harmonic generation, is redefining ultrafast physics and chemistry. A practical understanding of attosecond optics requires significant background information and foundational theory to make full use of these cutting-edge lasers and advance the technology toward the next generation of ultrafast lasers. Fundamentals of Attosecond Optics provides the first focused introduction to the field. The author presents the underlying concepts and techniques required to enter the field, as well as recent research advances th

  20. Generation of broad XUV continuous high harmonic spectra and isolated attosecond pulses with intense mid-infrared lasers

    Science.gov (United States)

    Trallero-Herrero, C.; Jin, Cheng; Schmidt, B. E.; Shiner, A. D.; Kieffer, J.-C.; Corkum, P. B.; Villeneuve, D. M.; Lin, C. D.; Légaré, F.; Le, A. T.

    2012-01-01

    We present experimental results showing the appearance of a near-continuum in the high-order harmonic generation spectra of atomic and molecular species as the driving laser intensity of a mid-infrared pulse increases. Detailed macroscopic simulations reveal that these near-continuum spectra are capable of producing isolated attosecond pulses (IAPs) in the far field if a proper spatial filter is applied. Further, our simulations show that the near-continuum spectra and the IAPs are a product of the strong temporal and spatial reshaping (blue shift and defocusing) of the driving field. This offers a possibility of producing IAPs with a broad range of photon energy, including plateau harmonics, by mid-IR laser pulses even without carrier-envelope phase stabilization.

  1. Generation of broad XUV continuous high harmonic spectra and isolated attosecond pulses with intense mid-infrared lasers

    International Nuclear Information System (INIS)

    We present experimental results showing the appearance of a near-continuum in the high-order harmonic generation spectra of atomic and molecular species as the driving laser intensity of a mid-infrared pulse increases. Detailed macroscopic simulations reveal that these near-continuum spectra are capable of producing isolated attosecond pulses (IAPs) in the far field if a proper spatial filter is applied. Further, our simulations show that the near-continuum spectra and the IAPs are a product of the strong temporal and spatial reshaping (blue shift and defocusing) of the driving field. This offers a possibility of producing IAPs with a broad range of photon energy, including plateau harmonics, by mid-IR laser pulses even without carrier-envelope phase stabilization. (fast track communication)

  2. Attosecond-resolution two-electron harmonic emission

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [College of Science, Liaoning University of Technology, Jinzhou 121000 (China); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Li, Wenliang; Yuan, Minghu [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Duan, Yunbo [Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Chu, Tianshu, E-mail: tschu008@163.com [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

    2015-04-17

    Highlights: • A two-electron time-dependent Schrödinger equation analysis. • Harmonic emission spectrum from the neutral He atom in intense laser field. • An extended harmonic plateau with many new harmonic cutoffs. • A propose model of double recombination arising from electron correlation effect. • A general characteristic of double recombination in the two-electron system. - Abstract: Two-electron harmonic emission from the He atom has been investigated by solving the two-electron time-dependent Schrödinger equation (TDSE), which exhibits an extended plateau and many new harmonic cutoffs beyond the classical single-electron harmonic cutoff. Theoretical analyses show that these extended new cutoffs are caused by the sequential double recombination and the nonsequential double recombination of the two electrons, which is a general characteristic for the two-electron harmonic emission and which is revealed through the investigation on laser parameter effects. Moreover, from analyzing the time-dependent wave functions, the motions of the two electrons and the single and double ionization time have been described.

  3. Attosecond-resolution two-electron harmonic emission

    International Nuclear Information System (INIS)

    Highlights: • A two-electron time-dependent Schrödinger equation analysis. • Harmonic emission spectrum from the neutral He atom in intense laser field. • An extended harmonic plateau with many new harmonic cutoffs. • A propose model of double recombination arising from electron correlation effect. • A general characteristic of double recombination in the two-electron system. - Abstract: Two-electron harmonic emission from the He atom has been investigated by solving the two-electron time-dependent Schrödinger equation (TDSE), which exhibits an extended plateau and many new harmonic cutoffs beyond the classical single-electron harmonic cutoff. Theoretical analyses show that these extended new cutoffs are caused by the sequential double recombination and the nonsequential double recombination of the two electrons, which is a general characteristic for the two-electron harmonic emission and which is revealed through the investigation on laser parameter effects. Moreover, from analyzing the time-dependent wave functions, the motions of the two electrons and the single and double ionization time have been described

  4. Complex Spectra Structure of an Attosecond Pulse Train Driven by Sub-5-fs Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    YUN Chen-Xia; TENG Hao; ZHANG Wei; WANG Li-Feng; ZHAN Min-Jie; HE Xin-Kui; WANG Bing-Bing; WEI Zhi-Yi

    2011-01-01

    We present the observation of the additional spectral components between the odd order harmonics in the harmonic spectrum generated from argon gas driven by sub-5-fs laser pulses.The theoretical analysis shows that the asymmetric laser field in both spatial and temporal domains leads to this complicated spectrum structure of high order harmonics.

  5. Energy Sharing in the 2-Electron Attosecond Streak Camera

    CERN Document Server

    Price, H; Emmanouilidou, A

    2011-01-01

    Using the recently developed concept of the 2-electron streak camera (see NJP 12, 103024 (2010)), we have studied the energy-sharing between the two ionizing electrons in single-photon double ionization of He(1s2s). We find that the most symmetric and asymmetric energy sharings correspond to different ionization dynamics with the ion's Coulomb potential significantly influencing the latter. This different dynamics for the two extreme energy sharings gives rise to different patterns in asymptotic observables and different time-delays between the emission of the two electrons. We show that the 2-electron streak camera resolves the time-delays between the emission of the two electrons for different energy sharings.

  6. Energy sharing in the two-electron attosecond streak camera

    International Nuclear Information System (INIS)

    Using the recently developed concept of the two-electron streak camera (see Emmanouilidou et al 2010 New J. Phys. 12 103024), we studied the energy sharing between the two ionizing electrons in single-photon double ionization of He(1s2s). We found that the most symmetric and asymmetric energy sharings correspond to different ionization dynamics with the ion's Coulomb potential significantly influencing the latter. This different dynamics for the two extreme energy sharings gives rise to different patterns in asymptotic observables and different time delays between the emission of the two electrons. We show that the two-electron streak camera resolves the time delays between the emission of the two electrons for different energy sharings.

  7. Energy sharing in the two-electron attosecond streak camera

    Energy Technology Data Exchange (ETDEWEB)

    Price, H; Emmanouilidou, A [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Staudte, A, E-mail: a.emmanouilidou@ucl.ac.uk [Joint Laboratory for Attosecond Science, University of Ottawa and National Research Council, 100 Sussex Drive, Ottawa, ON K1A 0R6 (Canada)

    2011-09-15

    Using the recently developed concept of the two-electron streak camera (see Emmanouilidou et al 2010 New J. Phys. 12 103024), we studied the energy sharing between the two ionizing electrons in single-photon double ionization of He(1s2s). We found that the most symmetric and asymmetric energy sharings correspond to different ionization dynamics with the ion's Coulomb potential significantly influencing the latter. This different dynamics for the two extreme energy sharings gives rise to different patterns in asymptotic observables and different time delays between the emission of the two electrons. We show that the two-electron streak camera resolves the time delays between the emission of the two electrons for different energy sharings.

  8. Swarm of ultra-high intensity attosecond pulses from laser-plasma interaction

    Energy Technology Data Exchange (ETDEWEB)

    Bulanov, S S; Krushelnick, K; Maksimchuk, A [FOCUS Center and Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Bychenkov, V Y U [Institute of Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Popov, K I; Rozmus, W [Theoretical Physics Institute, University of Alberta, Edmonton T6G 2J1, Alberta (Canada)

    2010-08-01

    We report on the realistic scheme of intense X-rays and {gamma}-radiation generation in a laser interaction with thin foils. It is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. A series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of a swarm of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  9. Swarm of ultra-high intensity attosecond pulses from laser-plasma interaction

    International Nuclear Information System (INIS)

    We report on the realistic scheme of intense X-rays and γ-radiation generation in a laser interaction with thin foils. It is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. A series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of a swarm of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  10. Ensemble of ultra-high intensity attosecond pulses from laser-plasma interaction

    Science.gov (United States)

    Bulanov, S. S.; Maksimchuk, A.; Krushelnick, K.; Popov, K. I.; Bychenkov, V. Yu.; Rozmus, W.

    2010-01-01

    The efficient generation of intense X-rays and γ-radiation is studied. The scheme is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. In the proposed scheme a series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of an ensemble of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  11. Ensemble of ultra-high intensity attosecond pulses from laser-plasma interaction

    International Nuclear Information System (INIS)

    The efficient generation of intense X-rays and γ-radiation is studied. The scheme is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. In the proposed scheme a series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of an ensemble of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  12. Ensemble of ultra-high intensity attosecond pulses from laser-plasma interaction

    Energy Technology Data Exchange (ETDEWEB)

    Bulanov, S.S., E-mail: sbulanov@eecs.umich.ed [FOCUS Center and Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109 (United States); Institute of Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Maksimchuk, A.; Krushelnick, K. [FOCUS Center and Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109 (United States); Popov, K.I. [Theoretical Physics Institute, University of Alberta, Edmonton T6G 2J1, Alberta (Canada); Bychenkov, V.Yu. [Theoretical Physics Institute, University of Alberta, Edmonton T6G 2J1, Alberta (Canada); P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow 119991 (Russian Federation); Rozmus, W. [Theoretical Physics Institute, University of Alberta, Edmonton T6G 2J1, Alberta (Canada)

    2010-01-04

    The efficient generation of intense X-rays and gamma-radiation is studied. The scheme is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. In the proposed scheme a series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of an ensemble of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  13. Swarm of ultra-high intensity attosecond pulses from laser-plasma interaction

    Science.gov (United States)

    Bulanov, S. S.; Bychenkov, V. Y. U.; Krushelnick, K.; Maksimchuk, A.; Popov, K. I.; Rozmus, W.

    2010-08-01

    We report on the realistic scheme of intense X-rays and γ-radiation generation in a laser interaction with thin foils. It is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. A series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of a swarm of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  14. Ensemble of ultra-high intensity attosecond pulses from laser-plasma interaction

    CERN Document Server

    Bulanov, S S; Krushelnick, K; Popov, K I; Bychenkov, V Yu; Rozmus, W

    2009-01-01

    The efficient generation of intense X-rays and $\\gamma$-radiation is studied. The scheme is based on the relativistic mirror concept, {\\it i.e.}, a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. In the proposed scheme a series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of an ensemble of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.

  15. Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules

    Science.gov (United States)

    Sturm, Felix; Ray, Dipanwita; Wright, Travis; Shivaram, Niranjan; Bocharova, Irina; Slaughter, Daniel; Ranitovic, Predrag; Belkacem, Ali; Weber, Thorsten

    2016-05-01

    Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O2+and the O+ ion yields with attosecond precision. Supported by DOE under Contract No. DE-AC02-05CH11231.

  16. Eliminating the dipole phase in attosecond pulse characterization using Rydberg wave packets

    Science.gov (United States)

    Pabst, Stefan; Dahlström, Jan Marcus

    2016-07-01

    We propose a technique to fully characterize the temporal structure of extreme ultraviolet pulses by ionizing a bound coherent electronic wave packet. The influence of the dipole phase, which is the main obstacle for state-of-the-art pulse characterization schemes, can be eliminated by angle integration of the photoelectron spectrum. We show that in particular, atomic Rydberg wave packets are ideal and that wave packets involving multiple electronic states provide redundant information that can be used to cross-check the consistency of the phase reconstruction.

  17. Interaction of relativistic electrons with an intense laser pulse: High-order harmonic generation based on Thomson scattering

    Science.gov (United States)

    Hack, Szabolcs; Varró, Sándor; Czirják, Attila

    2016-02-01

    We investigate nonlinear Thomson scattering as a source of high-order harmonic radiation with the potential to enable attosecond light pulse generation. We present a new analytic solution of the electron's relativistic equations of motion in the case of a short laser pulse with a sine-squared envelope. Based on the single electron emission, we compute and analyze the radiated amplitude and phase spectrum for a realistic electron bunch, with special attention to the correct initial values. These results show that the radiation spectrum of an electron bunch in head-on collision with a sufficiently strong laser pulse of sine-squared envelope has a smooth frequency dependence to allow for the synthesis of attosecond light pulses.

  18. IR-assisted ionization of helium by attosecond extreme ultraviolet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ranitovic, P; Gramkow, B; De, S; DePaola, B; Singh, K P; Cao, W; Magrakvelidze, M; Ray, D; Bocharova, I; Mashiko, H; Litvinyuk, I; Cocke, C L [J R Macdonald Lab, Physics Department, Kansas State University, Manhattan, KS 66506 (United States); Tong, X M [Institute of Materials Science and Center for Computational Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Sandhu, A; Gagnon, E; Murnane, M M; Kapteyn, HC [JILA and Department of Physics, University of Colorado and NIST, Boulder, CO 80309-0440 (United States)], E-mail: predragr@jila.colorado.edu, E-mail: tong@ims.tsukuba.ac.jp, E-mail: cocke@phys.ksu.edu

    2010-01-15

    Attosecond science has opened up the possibility of manipulating electrons on their fundamental timescales. Here, we use both theory and experiment to investigate ionization dynamics in helium on the attosecond timescale by simultaneously irradiating the atom with a soft x-ray attosecond pulse train (APT) and an ultrafast laser pulse. Because the APT has resolution in both energy and time, we observe processes that could not be observed without resolution in both domains simultaneously. We show that resonant absorption is important in the excitation of helium and that small changes in energies of harmonics that comprise the APT can result in large changes in the ionization process. With the help of theory, ionization pathways for the infrared-assisted excitation and ionization of helium by extreme ultraviolet (XUV) attosecond pulses have been identified and simple model interpretations have been developed that should be of general applicability to more complex systems (Zewail A 2000 J. Phys. Chem. A 104 5660-94)

  19. Attosecond Interference Induced by Coulomb-Field-Driven Transverse Backward-Scattering Electron Wave-Packets

    CERN Document Server

    Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Yu, Xianhuan; Yang, Weifeng; Hu, Shilin; Chen, Jing; Xu, SongPo; Chen, YongJu; Quan, Wei; Liu, XiaoJun

    2016-01-01

    A novel and universal interference structure is found in the photoelectron momentum distribution of atoms in intense infrared laser field. Theoretical analysis shows that this structure can be attributed to a new form of Coulomb-field-driven backward-scattering of photoelectrons in the direction perpendicular to the laser field, in contrast to the conventional rescattering along the laser polarization direction. This transverse backward-scattering process is closely related to a family of photoelectrons initially ionized within a time interval of less than 200 attosecond around the crest of the laser electric field. Those electrons, acquiring near-zero return energy in the laser field, will be pulled back solely by the ionic Coulomb field and backscattered in the transverse direction. Moreover, this rescattering process mainly occurs at the first or the second return times, giving rise to different phases of the photoelectrons. The interference between these photoelectrons leads to unique curved interference ...

  20. Attosecond signatures in photodissociation by an intense Ti:Sapphire pulse

    CERN Document Server

    McCann, J F; Williams, I D; Peng, Liang-You

    2005-01-01

    In our model the electron dynamics are described by a two-state approximation. This might appear a rough approximation since it neglects coupling through excited electronic states and ionization channels. However at high intensity (laser fields equivalent to the Coulomb force) and long wavelength (photon energy much lower than the ionization potential) the dissociation process occurs by adiabatic polarization involving the lowest electronic states. For the experiment in question, with intensities above 10x14 W cm-2 and photon energies of 1.5eV, such an approach is well justified. More contentious is the neglect of rotational heating (that is molecular realignment) during the pulse. However, this process is essentially an internal relaxation and for a 50fs pulse it has a small effect. To calculate the dissociation spectrum, we have applied discretization methods developed for photoionization of molecules4) to solve the quantum equations in a dual configuration and momentum space. Technical details are discusse...

  1. Intensity improvement in the attosecond pulse generation with the coherent superposition initial state

    Science.gov (United States)

    Feng, Liqiang; Chu, Tianshu

    2012-03-01

    We investigate the coherent superposition initial state effect and found that when the initial active electron state is prepared in the coherent superposition of the 1s and 2s states of the He+ ion and the chirp parameter of the fundamental field in the two-color scheme is chosen to be β=0.3, the harmonic cutoff energy is remarkably extended and the harmonic yield is enhanced by at least 6 orders of magnitude compared with the case of the single 1s ground state with chirp-free pulse. An ultrabroad supercontinuum with a 458 eV bandwidth is formed, directly producing an intense isolated 34 as pulse.

  2. Frequency-resolved optical gating for complete reconstruction of attosecond bursts : FROG CRAB

    International Nuclear Information System (INIS)

    Full text: We will show that when an atom is ionized by an XUV pulse in the presence of a low frequency laser field, this laser field acts as an ultrafast electron phase modulator on the electron wave-packet generated in the continuum. This phase modulator has a very large bandwidth and enables to transpose the most efficient techniques used for the temporal characterization of femtosecond pulses - such as SPIDER, FROG, or chronocyclic tomography - to attosecond fields, via continuum electron wave-packets replicas of these fields. We will then detail some of the attosecond metrology techniques derived from this general principle. We will especially insist on a recently proposed technique, FROG CRAB, which allows the complete temporal characterization of arbitrarily complex attosecond fields. FROG CRAB is direct transposition of Frequency-Resolved Optical Gating to attosecond electron wave-packets, using a femtosecond laser pulse as a phase gate. All the experimental tools for the implementation of CRAB are available. Besides its technical interest, CRAB establishes a direct connection between the main attosecond characterization techniques demonstrated experimentally so far, and considerably extends their scope, thus providing a general perspective on attosecond metrology. Refs. 2 (author)

  3. Attosecond physics at a nanoscale metal tip

    Directory of Open Access Journals (Sweden)

    Lemell Christoph

    2013-03-01

    Full Text Available With few-cycle laser oscillator pulses at 800 nm we observe strong-field and attosecond physics phenomena in electron spectra recorded at a nanoscale tungsten tip. We observe the rescattering plateau as well as a strong carrier-envelope phase dependence of the spectra. We model the results with the semiclassical three-step model as well as with time-dependent density functional theory.

  4. Attosecond double-slit experiment

    OpenAIRE

    Lindner, F.; Schaetzel, M. G.; Walther, H.; Baltuska, A.; Goulielmakis, E.; Krausz, F.; Milosevic, D. B; BAUER, D; Becker, W.; Paulus, G G

    2005-01-01

    A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (``slits'') of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are observed. A situation in which one and the same electron encounters a single and a double slit at the same time is discussed. The investigation of the fringes makes possible interfe...

  5. Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: towards chiral attosecond pulses

    Science.gov (United States)

    Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Fleischer, Avner; Bordo, Eliyahu; Fan, Tingting; Popmintchev, Dimitar; Popmintchev, Tenio; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2016-06-01

    Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching. We find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. This feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments.

  6. Attosecond Electro-Magnetic Forces Acting on Metal Nanospheres Induced By Relativistic Electrons

    Science.gov (United States)

    Lagos, M. J.; Batson, P. E.; Reyes-Coronado, A.; Echenique, P. M.; Aizpurua, J.

    2014-03-01

    Swift electron scattering near nanoscale materials provides information about light-matter behavior, including induced forces. We calculate time-dependent electromagnetic forces acting on 1-1.5 nm metal nanospheres induced by passing swift electrons, finding both impulse-like and oscillatory response forces. Initially, impulse-like forces are generated by a competition between attractive electric forces and repulsive magnetic forces, lasting a few attoseconds (5-10 as). Oscillatory, plasmonic response forces take place later in time, last a few femtoseconds (1- 5 fs), and apparently rely on photon emission by decay of the electron-induced surface plasmons. A comparison of the strength of these two forces suggests that the impulse-like behavior dominates the process, and can transfer significant linear momentum to the sphere. Our results advance understanding of the physics behind the observation of both attractive and repulsive behavior of gold nano-particles induced by electron beams in aberration-corrected electron microscopy. Work supported under DOE, Award # DE-SC0005132, Basque Gov. project ETORTEK inano, Spanish Ministerio de Ciencia e Innovacion, No. FIS2010-19609-C02-01.

  7. Attosecond probing of state-resolved ionization and superpositions of atoms and molecules

    Science.gov (United States)

    Leone, Stephen

    2016-05-01

    Isolated attosecond pulses in the extreme ultraviolet are used to probe strong field ionization and to initiate electronic and vibrational superpositions in atoms and small molecules. Few-cycle 800 nm pulses produce strong-field ionization of Xe atoms, and the attosecond probe is used to measure the risetimes of the two spin orbit states of the ion on the 4d inner shell transitions to the 5p vacancies in the valence shell. Step-like features in the risetimes due to the subcycles of the 800 nm pulse are observed and compared with theory to elucidate the instantaneous and effective hole dynamics. Isolated attosecond pulses create massive superpositions of electronic states in Ar and nitrogen as well as vibrational superpositions among electronic states in nitrogen. An 800 nm pulse manipulates the superpositions, and specific subcycle interferences, level shifting, and quantum beats are imprinted onto the attosecond pulse as a function of time delay. Detailed outcomes are compared to theory for measurements of time-dynamic superpositions by attosecond transient absorption. Supported by DOE, NSF, ARO, AFOSR, and DARPA.

  8. Production and Characterization of Attosecond Bunch Trains

    Energy Technology Data Exchange (ETDEWEB)

    Sears, Christopher M.S.; Colby, Eric; Ischebeck, Rasmus; McGuinness , Christopher; Nelson, Janice; Noble, Robert; Siemann, Robert H.; Spencer, James; Walz, Dieter; /SLAC; Plettner, Tomas; Byer, Robert L.; /Stanford U.

    2008-06-02

    We report the production of optically spaced attosecond microbunches produced by the inverse Free Electron Laser (IFEL) process. The IFEL is driven by a Ti:sapphire laser synchronized with the electron beam. The IFEL is followed by a magnetic chicane that converts the energy modulation into the longitudinal microbunch structure. The microbunch train is characterized by observing Coherent Optical Transition Radiation (COTR) at multiple harmonics of the bunching. The experimental results are compared with 1D analytic theory showing good agreement. Estimates of the bunching factors are given and correspond to a microbunch length of 350as fwhm. The formation of stable attosecond electron pulse trains marks an important step towards direct laser acceleration.

  9. Generation of isolated attosecond pulses in the far field by spatial filtering with an intense few-cycle mid-infrared laser

    International Nuclear Information System (INIS)

    We report theoretical calculations of high-order harmonic generation (HHG) of Xe with the inclusion of multielectron effects and macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. By using the time-frequency analysis we show that the reshaping of the fundamental laser field is responsible for the continuum structure in the HHG spectra. We further suggest a method for obtaining an isolated attosecond pulse (IAP) by using a filter centered on axis to select the harmonics in the far field with different divergence. We also discuss the carrier-envelope-phase dependence of an IAP and the possibility to optimize the yield of the IAP. With intense few-cycle mid-infrared lasers, this offers a possible method for generating isolated attosecond pulses.

  10. Generation of isolated attosecond pulses in the far field by spatial filtering with an intense few-cycle mid-infrared laser

    Science.gov (United States)

    Jin, Cheng; Le, Anh-Thu; Trallero-Herrero, Carlos A.; Lin, C. D.

    2011-10-01

    We report theoretical calculations of high-order harmonic generation (HHG) of Xe with the inclusion of multielectron effects and macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. By using the time-frequency analysis we show that the reshaping of the fundamental laser field is responsible for the continuum structure in the HHG spectra. We further suggest a method for obtaining an isolated attosecond pulse (IAP) by using a filter centered on axis to select the harmonics in the far field with different divergence. We also discuss the carrier-envelope-phase dependence of an IAP and the possibility to optimize the yield of the IAP. With intense few-cycle mid-infrared lasers, this offers a possible method for generating isolated attosecond pulses.

  11. Generation of isolated attosecond pulses in the far field by spatial filtering with an intense few-cycle mid-infrared laser

    Energy Technology Data Exchange (ETDEWEB)

    Jin Cheng; Le, Anh-Thu; Trallero-Herrero, Carlos A.; Lin, C. D. [J. R. Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506-2604 (United States)

    2011-10-15

    We report theoretical calculations of high-order harmonic generation (HHG) of Xe with the inclusion of multielectron effects and macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. By using the time-frequency analysis we show that the reshaping of the fundamental laser field is responsible for the continuum structure in the HHG spectra. We further suggest a method for obtaining an isolated attosecond pulse (IAP) by using a filter centered on axis to select the harmonics in the far field with different divergence. We also discuss the carrier-envelope-phase dependence of an IAP and the possibility to optimize the yield of the IAP. With intense few-cycle mid-infrared lasers, this offers a possible method for generating isolated attosecond pulses.

  12. Relativistic laser-matter interaction: from attosecond pulse generation to fast ignition

    International Nuclear Information System (INIS)

    The field of laser-matter interaction has branched out in two main directions. The first, motivated by laser inertial confinement fusion, warm-dense-matter, fast ignition and astrophysics in laboratory, and the second driven by ultra-high intensity, exotic physics, high-energy particle, photon beam generation and time-resolved attosecond (zeptosecond) science. The degree of maturity from both experimental and theoretical stand-points is such that a large European infrastructure for each branch is contemplated as part of the European Roadmap. The first one, HiPER-PETAL will be dedicated to fast ignition with the aim of obtaining a thermonuclear gain of 100, whereas the second, Extreme Light Infrastructure (ELI) could go beyond the relativistic regime to foray into the ultra-relativistic domain >1024 W cm-2. In this paper we highlight the intriguing perspectives that these two projects will offer

  13. Photoelectron Angular Distribution and Phase in Two-Photon Single Ionization of H and He by a Femtosecond and Attosecond Extreme-Ultraviolet Pulse

    Directory of Open Access Journals (Sweden)

    Kenichi L. Ishikawa

    2013-03-01

    Full Text Available We theoretically study the photoelectron angular distribution (PAD from the two-photon single ionization of H and He by femtosecond and attosecond extreme-ultraviolet pulses, based on the time-dependent perturbation theory and simulations with the full time-dependent Schrodinger equation. The PAD is formed by the interference of the s and d continuum wave packets, and, thus, contains the information on the relative phase and amplitude ratio between them. We find that, when a spectrally broadened femtosecond pulse is resonant with an excited level, the PAD substantially changes with pulse width, since the competition between resonant and nonresonant ionization paths, leading to distinct from the scattering phase shift difference, changes with it. In contrast, when the Rydberg manifold is excited, and for the case of above-threshold two-photon ionization, and the PAD do not depend much on pulse width, except for the attosecond region. Thus, the Rydberg manifold and the continuum behave similarly in this respect. For a high-harmonic pulse composed of multiple harmonic orders, while the value is different from that for a single-component pulse, the PAD still rapidly varies with pulse width. The present results illustrate a new way to tailor the continuum wave packet.

  14. Theory of attosecond absorption spectroscopy in krypton

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Lindroth, Eva; Madsen, Lars Bojer

    2012-01-01

    A theory for time-domain attosecond pump–attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies and...... Auger widths, as well as wave functions and dipole coupling matrix elements, are determined by accurate many-body structure calculations. We create a hole in a valence shell by an attosecond pump, couple an inner-shell electron to the hole by an attosecond probe, and then monitor the formation of the...

  15. 0.5 keV soft X-ray attosecond continua

    CERN Document Server

    Teichmann, S M; Cousin, S L; Hemmer, M; Biegert, J

    2016-01-01

    Attosecond light pulses in the extreme ultraviolet have drawn a great deal of attention due to their ability to interrogate electronic dynamics in real time. Nevertheless, to follow charge dynamics and excitations in materials, element selectivity is a prerequisite, which demands such pulses in the soft X-ray region, above 200 eV, to simultaneously cover several fundamental absorption edges of the constituents of the materials. Here, we experimentally demonstrate the exploitation of a transient phase matching regime to generate carrier envelope controlled soft X-ray supercontinua with pulse energies up to 2.9 +/- 0.1 pJ and a flux of (7.3 +/- 0.1)x10^7 photons/s across the entire water window and attosecond pulses with 13 as transform limit. Our results herald attosecond science at the fundamental absorption edges of matter by bridging the gap between ultrafast temporal resolution and element specific probing.

  16. Absorption and emission of single attosecond light pulses in an autoionizing gaseous medium dressed by a time-delayed control field

    OpenAIRE

    Chu, Wei-Chun; C. D. Lin

    2012-01-01

    An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the 2s2p(1P) autoionizing state, which is coupled to the 2s2(1S) autoionizing state by a femtosecond infrared laser with the intensity in the order of 10^{12} W/cm2. The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for ...

  17. Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

    Science.gov (United States)

    Cheng, Yan; Chini, Michael; Wang, Xiaowei; González-Castrillo, Alberto; Palacios, Alicia; Argenti, Luca; Martín, Fernando; Chang, Zenghu

    2016-08-01

    Attosecond science promises to allow new forms of quantum control in which a broadband isolated attosecond pulse excites a molecular wave packet consisting of a coherent superposition of multiple excited electronic states. This electronic excitation triggers nuclear motion on the molecular manifold of potential energy surfaces and can result in permanent rearrangement of the constituent atoms. Here, we demonstrate attosecond transient absorption spectroscopy (ATAS) as a viable probe of the electronic and nuclear dynamics initiated in excited states of a neutral molecule by a broadband vacuum ultraviolet pulse. Owing to the high spectral and temporal resolution of ATAS, we are able to reconstruct the time evolution of a vibrational wave packet within the excited B'Σ1u+ electronic state of H2 via the laser-perturbed transient absorption spectrum.

  18. Tracing non-equilibrium plasma dynamics on the attosecond timescale in small clusters

    International Nuclear Information System (INIS)

    It is shown by microscopic calculations that the energy absorption of a rare-gas cluster from a vacuum-ultraviolet (VUV) pulse can be traced with time-delayed extreme-ultraviolet (XUV) attosecond probe pulses by measuring the kinetic energy of the electrons detached by the probe pulse. By means of this scheme we demonstrate that, for pump pulses as short as one femtosecond, the charging of the cluster proceeds during the formation of an electronic nano-plasma inside the cluster. Using moderate harmonics for the VUV and high harmonics for the XUV pulse from the same near-infrared laser source, this scheme with well defined time delays between pump and probe pulses should be experimentally realizable. Going to even shorter pulse durations we predict that pump and probe pulses of about 250 attoseconds can induce and monitor non-equilibrium dynamics of the nano-plasma

  19. Time-energy properties of an attosecond extreme ultra-violet pulse

    International Nuclear Information System (INIS)

    The time-energy properties of high-order harmonic generation (HHG) are calculated for a linearly polarized 7-fs laser pulse with different carrier-envelope phases (CEPs). The quantum trajectory paths that contribute to an as (1 as=10−18 s) pulse in HHG are identified. The laser-duration dependence and the CEP dependence of HHG energy property are investigated. The study shows that an as extreme ultra-violet (XUV) pulse can be selected from HHG spectrum near cut-off energy with a bandpass optical filter. The theoretical prediction of the pulse duration is proportional to bandwidth. Analysis suggests that a measured narrowband as XUV pulse may consist of instantaneous shorter pulses each dependent on laser pulse duration, intensity, and CEP. These information can be used as references for producing, selecting, improving and manipulating (timing) as pulses. (atomic and molecular physics)

  20. Theory of strong-field attosecond transient absorption

    Science.gov (United States)

    Wu, Mengxi; Chen, Shaohao; Camp, Seth; Schafer, Kenneth J.; Gaarde, Mette B.

    2016-03-01

    Attosecond transient absorption is one of the promising new techniques being developed to exploit the availability of sub-femtosecond extreme ultraviolet (XUV) pulses to study the dynamics of the electron on its natural time scale. The temporal resolution in a transient absorption setup comes from the control of the relative delay and coherence between pump and probe pulses, while the spectral resolution comes from the characteristic width of the features that are being probed. In this review we focus on transient absorption scenarios where an attosecond pulse of XUV radiation creates a broadband excitation that is subsequently probed by a few cycle infrared (IR) laser. Because the attosecond XUV pulses are locked to the IR field cycle, the exchange of energy in the laser-matter interaction can be studied with unprecedented precision. We focus on the transient absorption by helium atoms of XUV radiation around the first ionization threshold, where we can simultaneoulsy solve the time-dependent Schrödinger equation for the single atom response and the Maxwell wave equation for the collective response of the nonlinear medium. We use a time-domain method that allows us to treat on an equal footing all the different linear and nonlinear processes by which the medium can exchange energy with the fields. We present several simple models, based on a few-level system interacting with a strong IR field, to explain many of the novel features found in attosecond transient absorption spectrograms. These include the presence of light-induced states, which demonstrate the ability to probe the dressed states of the atom. We also present a time-domain interpretation of the resonant pulse propagation features that appear in absorption spectra in dense, macroscopic media. We close by reviewing several recent experimental results that can be explained in terms of the models we discuss. Our aim is to present a road map for understanding future attosecond transient absorption

  1. Exploring single-photon ionization on the attosecond time scale

    International Nuclear Information System (INIS)

    One of the fundamental processes in nature is the photoelectric effect in which an electron is ripped away from its atom via the interaction with a photon. This process was long believed to be instantaneous but with the development of attosecond pulses (1 as 10−18 s) we can finally get an insight into its dynamic. Here we measure a delay in ionization time between two differently bound electrons. The outgoing electrons are created via ionization with a train of attosecond pulses and we probe their relative delay with a synchronized infrared laser. We demonstrate how this probe field influences the measured delays and show that this contribution can be estimated with a universal formula, which allows us to extract field free atomic data.

  2. Probing scattering phase shifts by attosecond streaking

    International Nuclear Information System (INIS)

    Complete text of publication follows. The emerging field of attoscience enables the investigation of electron dynamics as well as timing information of photoionization processes. Attosecond streaking has developed into a powerful tool to achieve temporal resolution on the sub-100 attosecond time scale. It is based on a pump-probe setting with an extreme ultraviolet (XUV) pulse of a few hundred attoseconds duration serving as pump and a phase-controlled few-cycle infrared (IR) pulse as probe. Temporal information about the photoionization process can thus be mapped onto the energy axis in analogy to conventional streaking. We studied attosecond streaking of the release time of electrons in atomic photoemission by solving the time-dependent Schroedinger equation (TDSE) for effective one-electron systems. We presented calculations also employing a restricted ionization model (RIM) in the TDSE. We verified that the trajectory effects on the time shift resulting from the interaction between the outgoing electron and the combined Coulomb and IR laser fields can be described classically. We have shown that Eisenbud-Wigner-Smith (EWS) time shifts (or energy variation of the scattering phase) for short-ranged potentials become accessible by attosecond streaking provided both initial-state dependent entrance channel and final-state exit channel distortions are properly accounted for. For Coulomb potentials the coupling between the IR streaking field and the Coulomb field which depends on the final energy of the free electron dominates the extracted streaking time shift but can be accounted for classically. In addition we have identified considerable state dependent time shifts for easily polarizable initial states which are of quantum mechanical origin. Accounting for polarization of the initial state, the remaining difference of time delays between ionization from states with different angular momentum can be related to the EWS delay of the centrifugal potential

  3. Generation of intense circularly polarized attosecond light bursts from relativistic laser plasmas

    CERN Document Server

    Ma, Guangjin; Yu, M Y; Shen, Baifei; Veisz, Laszlo

    2016-01-01

    We have investigated the polarization of attosecond light bursts generated by nanobunches of electrons from relativistic few-cycle laser pulse interaction with the surface of overdense plasmas. Particle-in-cell simulation shows that the polarization state of the generated attosecond burst depends on the incident-pulse polarization, duration, carrier envelope phase, as well as the plasma scale length. Through laser and plasma parameter control, without compromise of generation efficiency, a linearly polarized laser pulse with azimuth $\\theta^i=10^\\circ$ can generate an elliptically polarized attosecond burst with azimuth $|\\theta^r_{\\rm atto}|\\approx61^\\circ$ and ellipticity $\\sigma^r_{\\rm atto}\\approx0.27$; while an elliptically polarized laser pulse with $\\sigma^i\\approx0.36$ can generate an almost circularly polarized attosecond burst with $\\sigma^r_{\\rm atto}\\approx0.95$. The results propose a new way to a table-top circularly polarized XUV source as a probe with attosecond scale time resolution for many a...

  4. Autler-Townes effects in attosecond circular polarization molecular photoionization

    International Nuclear Information System (INIS)

    We present molecular photoionization simulations by intense (I ∼ 1016 W/cm2) few cycle circularly polarized attosecond extreme ultraviolet laser pulses for aligned H2+ from numerical solutions of the corresponding time-dependent Schrodinger equation. With appropriate laser pulse parameters, circular attosecond coherent electron wave packets (CEWPs) are created in excited Rydberg states. Such CEWPs are spatially localized during ionization processes, thus resulting in sufficient population oscillations between the resonant excited Rydberg states and the initial ground state. Consequently Autler-Townes splitting in circular polarization energy spectra is predicted, which is shown to be critically sensitive to the pulse intensity, duration, and polarization. The resulting photoelectron angular distributions are rotated with respect to the molecular axis due to the nonspherical Coulomb potential of the molecule, resulting in different ionization rates at different laser polarization-molecular angles.

  5. Theoretical exploration of harmonic emission and attosecond pulse generation from H2+ in the presence of terahertz pulse

    Science.gov (United States)

    Liu, Hang; Feng, Liqiang

    2016-06-01

    Harmonic generation spectra from H2+ molecule ion driven by the chirped pulse combined with a terahertz (THz) pulse have been theoretically investigated by numerically solving the non-Born-Oppenheimer time-dependent Schrödinger equation (NBO-TDSE). The results show that with the introduction of the chirp, the harmonic cutoff is extended, resulting in a smooth supercontinuum. Further, when the initial vibrational state is prepared as v = 3, and by properly adding a THz controlling pulse, the harmonic yield is enhanced by almost six orders of magnitude compared with the single chirped pulse case. Quantum analyses are shown to explain the harmonic extension and enhancement. Furthermore, through the investigation of the isotopic effect, we find that more intense harmonics are generated in the lighter nucleus. Finally, by properly superposing the harmonics, a series of intense 35 as XUV pulses can be obtained, which are almost six orders of magnitude improvement in comparison with the single chirped pulse case.

  6. Decoherence in Attosecond Photoionization

    OpenAIRE

    Pabst, Stefan; Greenman, L.; Ho, P; Mazziotti, D.; Santra, Robin

    2011-01-01

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion...

  7. Entangled valence electron-hole dynamics revealed by stimulated attosecond x-ray Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Healion, Daniel; Zhang, Yu; Biggs, Jason D.; Govind, Niranjan; Mukamel, Shaul

    2012-09-06

    We show that broadband x-ray pulses can create wavepackets of valence electrons and holes localized in the vicinity of a selected atom (nitrogen, oxygen or sulfur in cysteine) by resonant stimulated Raman scattering. The subsequent dynamics reveals highly correlated motions of entangled electrons and hole quasiparticles. This information goes beyond the time-dependent total charge density derived from x-ray diffraction.

  8. Attosecond Streaking in the Low-Energy Region

    International Nuclear Information System (INIS)

    The low-energy photonelectron (PEs) ionized by a single attosecond pulse can be controlled by a moderately intense infrared field (IR). The electric field of the IR pulse can drive part of the PEs back to the parent ion and induce multiple rescattering of the electrons. Interesting interference patterns are observed in the photoelectron momentum distributions, which are formed by the rescattered electrons and the directly ionized PEs. By analyzing the interference patterns with a simple semiclassical model, which considers the particular PE trajectories incorporating the rescattering with the core, we demonstrate that the low-energy attosecond streaking offers a promising method of holographic imaging of atomic and molecular potential. In addition, we show that neither strong field approximation (SFA) or Coulomb-Volkov approximation (CVA) is able to reproduce these interesting structures at the low energy region

  9. The Raman effect in femto- and attosecond physics

    Energy Technology Data Exchange (ETDEWEB)

    Zheltikov, Aleksei M [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2011-01-31

    The interaction of ultrashort light pulses with matter is accompanied by a variety of new phenomena involving Raman scattering due to vibrational and rotational modes of molecules, electronic states of atoms and ions, and phonons in solids. These effects offer unique opportunities for an all-optical detection of ultrafast processes on the femto- and attosecond time scales, efficient spectral and temporal transformation of ultrashort field waveforms, and highly sensitive microscopy of physical, chemical, and biological objects. (reviews of topical problems)

  10. Atomic and molecular phases through attosecond streaking

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2011-01-01

    In attosecond streaking, an electron is released by a short xuv pulse into a strong near infrared laser field. If the laser couples two states in the target, the streaking technique, which allows for a complete determination of the driving field, also gives an accurate measurement of the relative...... phase of the atomic or molecular ionization matrix elements from the two states through the interference from the two channels. The interference may change the phase of the photoelectron streaking signal within the envelope of the infrared field, an effect to be accounted for when reconstructing short...

  11. Generation and characterization of atto second pulses

    International Nuclear Information System (INIS)

    Atto-second pulse trains in the extreme ultraviolet range can be produced by high-order harmonic generation, by focusing an intense femtosecond pulse in a rare gas jet. In this thesis, we present a temporal characterization of this radiation on the femtosecond and atto-second timescales. By transposing a spectral interferometry technique commonly used in the infrared range (SPIDER), we make a complete single-shot characterization of the temporal profile of individual harmonics, on the femtosecond timescale. In a second part, we study experimentally the atto-second structure of the harmonic radiation, and demonstrate a temporal drift in the emission: the lowest harmonics are emitted before the highest ones. This chirp, which is directly related to the electron dynamics in the generation process, imposes a lower limit to the duration that can be achieved by increasing the spectral range. We show how generating conditions can be optimized in order to enhance the synchronization in the emission, and how atto-second pulses can be re-compressed. Last, we propose a new technique for the complete characterization of arbitrary atto-second pulses: FROGCRAB. This method would allow simultaneous measurements of the femtosecond and atto-second structures of the radiation, and thus a complete knowledge of the atto-second light source in the perspective of applications. (author)

  12. 极紫外阿秒脉冲产生过程的本征原子相位分析%Analysis of intrinsic atomic phase in process of extreme ultraviolet attosecond pulse generation

    Institute of Scientific and Technical Information of China (English)

    王超; 刘虎林; 田进寿; 徐向晏; 曹希斌; 温文龙; 王俊锋

    2012-01-01

    In order to analyze the phase matching of extreme ultraviolet high harmonics in the process of attosecond pulses generation, the analytic expressions were achieved based on the three-step analysis model for optical field ionization high-harmonic generation (HHG) , and the harmonic spectral phase in the process of altosecund pulse generation was analyzed. It was found that, except the highest order harmonic, the spectral phase contribution of each harmonic consists of two sources of long trajectory electrons and short ones, and that, unlike the generated harmonics by the former, the spectral phase of those harmonics from the latter has regular phase relation among each other. The final conclusion is drawn that supprebsing the long trajectory electrons can reduce the pulse width of attosecond pulses, which is of great significance to the issue of high harmonic phase matching in generation of allosecond pulses.%为了研究高次谐波极紫外阿秒脉冲产生过程中的谐波相位匹配问题,基于光场电离高次谐波产生过程3步分析模型得出了高次谐波产生过程的理论描述解析式,并以此分析了阿秒脉冲产生过程中的高次谐波本征原子相位.由研究可知,除最高阶谐波外,对同一阶高次谐波产生有贡献的电子均有两类——长轨迹电子和短轨迹电子,各高次谐波长轨迹电子产生的谐波谱相之间几乎不存在线性关系,而短轨迹电子产生的高次谐波谱相之间则存在着良好的线性关系.结果表明,抑制各谐波长轨迹电子有助于产生更小脉宽阿秒脉冲.此结果对极紫外阿秒脉冲产生实验中的高次谐波相位匹配有重要的参考价值.

  13. On the possibility of the emission of attosecond pulses owing to the interaction of counterpropagating relativistically intense laser pulses with a thin layer of a diluted plasma

    Science.gov (United States)

    Platonenko, V. T.; Sterzhantov, A. F.

    2010-01-01

    A numerical experiment in which two relativistically intense laser pulses are normally incident on a layer of a diluted plasma from two opposite sides is described. The period of Langmuir plasma oscillations is much larger than the pulse duration and the product of this period by the speed of light is much larger than the thickness of the layer. A pulse propagating to the right is incident on the layer earlier than the counter pulse and carries a significant fraction of electrons or all of the electrons from the plasma. Under certain conditions, electrons form a bunch, which contains most of the electrons and has a thickness much smaller than the wavelength of light. The counter pulse perturbs the motion of the bunch and initiates the emission of a short few-cycle pulse, which propagates in the positive direction (to the right), significantly differs in structure from the counter pulse, and has a duration much smaller than the field period in laser pulses.

  14. All-fibre photonic signal generator for attosecond timing and ultralow-noise microwave

    OpenAIRE

    Kwangyun Jung; Jungwon Kim

    2015-01-01

    High-impact frequency comb applications that are critically dependent on precise pulse timing (i.e., repetition rate) have recently emerged and include the synchronization of X-ray free-electron lasers, photonic analogue-to-digital conversion and photonic radar systems. These applications have used attosecond-level timing jitter of free-running mode-locked lasers on a fast time scale within ~100 μs. Maintaining attosecond-level absolute jitter over a significantly longer time scale can dramat...

  15. Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Weijie Hua

    2016-03-01

    Full Text Available Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns. We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

  16. The attosecond facility of the extreme light infrastructure in Hungary

    International Nuclear Information System (INIS)

    Complete text of publication follows. The Extreme Light Infrastructure (ELI) project is a joint European effort to form an integrated laser infrastructure comprised of three sites. The ELI Beamlines Facility (Czech Republic) will mainly focus on particle acceleration and X-ray generation, while the ELI Nuclear Physics Facility (Romania) will be dealing with laser-based nuclear physics and high-field physics. Here, we report on the ELI Attosecond Light Pulse Source (ALPS) to be built in the city of Szeged, Hungary. The frontiers of modern photonics are defined by the characteristics of available photon sources. Synchrotrons and X-ray free electron lasers offer Angstroem wavelengths combined with high flux and brilliance, providing unique opportunities to explore the structure of matter with sub-atomic resolution. Laser-driven high harmonic sources, on the other hand, deliver flashes of extreme ultraviolet and soft X-ray light with durations below 100 asec, allowing direct time-domain insight into both structural and electronic motion, i.e. any dynamics taking place outside the atomic core. ELI-ALPS will combine these characteristics of modern photon sources: the short-wavelength and high flux of third-generation synchrotron sources with the incomparable pulse duration of laser-driven harmonic sources. Thus, ALPS' energetic attosecond X-ray pulses will enable recording freeze-frame images of the dynamical electronic-structural behaviour of complex atomic, molecular and condensed matter systems, with attosecond-picometer resolution. In addition, these attosecond XUV/X-ray pulses will come in synchronism with waveform-controlled light pulses all the way from THz (far infrared) to PHz (ultraviolet) frequencies. The main technological backbone of ELI-ALPS will be optical parametric chirped-pulse amplification (OPCPA). Pumped by dedicated all-solid-state short-pulse lasers and their (low-order) harmonics, this approach will be competitive with conventional (Ti

  17. Versatile attosecond beamline in a two-foci configuration for simultaneous time-resolved measurements

    Energy Technology Data Exchange (ETDEWEB)

    Locher, R.; Lucchini, M., E-mail: mlucchini@phys.ethz.ch; Herrmann, J.; Sabbar, M.; Weger, M.; Ludwig, A.; Gallmann, L.; Keller, U. [Department of Physics, ETH Zurich, CH-8093 Zürich (Switzerland); Castiglioni, L.; Greif, M.; Hengsberger, M. [Institute of Physics, University of Zurich, CH-8057 Zürich (Switzerland)

    2014-01-15

    We present our attoline which is a versatile attosecond beamline at the Ultrafast Laser Physics Group at ETH Zurich for attosecond spectroscopy in a variety of targets. High-harmonic generation (HHG) in noble gases with an infrared (IR) driving field is employed to generate pulses in the extreme ultraviolet (XUV) spectral regime for XUV-IR cross-correlation measurements. The IR pulse driving the HHG and the pulse involved in the measurements are used in a non-collinear set-up that gives independent access to the different beams. Single attosecond pulses are generated with the polarization gating technique and temporally characterized with attosecond streaking. This attoline contains two target chambers that can be operated simultaneously. A toroidal mirror relay-images the focus from the first chamber into the second one. In the first interaction region a dedicated double-target allows for a simple change between photoelectron/photoion measurements with a time-of-flight spectrometer and transient absorption experiments. Any end station can occupy the second interaction chamber. A surface analysis chamber containing a hemispherical electron analyzer was employed to demonstrate successful operation. Simultaneous RABBITT measurements in two argon jets were recorded for this purpose.

  18. Attosecond interferometry: techniques and spectroscopy

    OpenAIRE

    Kroon, David

    2016-01-01

    The interaction between an intense laser pulse and a gas medium leads to the emission of coherent bursts of light in the extreme ultraviolet range. This process, known as high-order harmonic generation, has today, almost three decades after its discovery, developed into a reliable source of extremely short (on the order of 100 as) pulses of electromagnetic radiation, with a wide range of applications in the atomic, molecular and optical sciences. The access to radiation with attosecond durati...

  19. Light field driven streak-camera for single-shot measurements of the temporal profile of XUV-pulses from a free-electron laser

    International Nuclear Information System (INIS)

    The Free Electron Laser in Hamburg (FLASH) is a source for highly intense ultra short extreme ultraviolet (XUV) light pulses with pulse durations of a few femtoseconds. Due to the stochastic nature of the light generation scheme based on self amplified spontaneous emission (SASE), the duration and temporal profile of the XUV pulses fluctuate from shot to shot. In this thesis, a THz-field driven streak-camera capable of single pulse measurements of the XUV pulse-profile has been realized. In a first XUV-THz pump-probe experiment at FLASH, the XUV-pulses are overlapped in a gas target with synchronized THz-pulses generated by a new THz-undulator. The electromagnetic field of the THz light accelerates photoelectrons produced by the XUV-pulses with the resulting change of the photoelectron momenta depending on the phase of the THz field at the time of ionisation. This technique is intensively used in attosecond metrology where near infrared streaking fields are employed for the temporal characterisation of attosecond XUV-Pulses. Here, it is adapted for the analysis of pulse durations in the few femtosecond range by choosing a hundred times longer far infrared streaking wavelengths. Thus, the gap between conventional streak cameras with typical resolutions of hundreds of femtoseconds and techniques with attosecond resolution is filled. Using the THz-streak camera, the time dependent electric field of the THz-pulses was sampled in great detail while on the other hand the duration and even details of the time structure of the XUV-pulses were characterized. (orig.)

  20. Attosecond Time-Resolved Autoionization of Argon

    International Nuclear Information System (INIS)

    Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape of the 3s3p6np 1P Fano resonance series (26.6-29.2 eV) were modified by intense few-cycle near infrared laser pulses, while the delay between the attosecond pulse and the laser pulse was changed by a few femtoseconds. Numerical simulations revealed that the experimentally observed splitting of the 3s3p64p 1P line is caused by the coupling between two short-lived highly excited states in the strong laser field.

  1. Ultrashort and coherent single-electron pulses for diffraction at ultimate resolutions

    International Nuclear Information System (INIS)

    energies of tens of keV which extends the attosecond streaking methodology to freely propagating electrons. We study the laser streaking effect in detail both experimentally and by numerical simulations and reveal its potential for characterizing electron pulses with durations down to the sub-femtosecond regime. In addition, the method enables the determination of the energy bandwidth and the chirp of the electrons. Finally, we developed a microspectrometer for the characterization of samples for ultrafast electron diffraction. These samples have a typical thickness of tens of nanometers and are often only a few hundred micrometers in diameter.

  2. Attosecond clocking of scattering dynamics in dielectrics

    Science.gov (United States)

    Kling, Matthias

    2016-05-01

    In the past few years electronic-device scaling has progressed rapidly and miniaturization has reached physical gate lengths below 100 nm, heralding the age of nanoelectronics. Besides the effort in size scaling of integrated circuits, tremendous progress has recently been made in increasing the switching speed where strong-field-based ``dielectric-electronics'' may push it towards the petahertz frontier. In this contest, the investigation of the electronic collisional dynamics occurring in a dielectric material is of primary importance to fully understand the transport properties of such future devices. Here, we demonstrate attosecond chronoscopy of electron collisions in SiO2. In our experiment, a stream of isolated aerodynamically focused SiO2 nanoparticles of 50 nm diameter was delivered into the laser interaction region. Photoemission is initiated by an isolated 250 as pulse at 35 eV and the electron dynamics is traced by attosecond streaking using a delayed few-cycle laser pulse at 700 nm. Electrons were detected by a kilohertz, single-shot velocity-map imaging spectrometer, permitting to separate frames containing nanoparticle signals from frames containing the response of the reference gas only. We find that the nanoparticle photoemission exhibits a positive temporal shift with respect to the reference. In order to understand the physical origin of the shift we performed semi-classical Monte-Carlo trajectory simulations taking into account the near-field distributions in- and outside the nanoparticles as obtained from Mie theory. The simulations indicate a pronounced dependence of the streaking time shift near the highest measured electron energies on the inelastic scattering time, while elastic scattering only shows a small influence on the streaking time shift for typical dielectric materials. We envision our approach to provide direct time-domain access to inelastic scattering for a wide range of dielectrics.

  3. Design of multi-pulsed electron source

    International Nuclear Information System (INIS)

    A multi-pulsed electron source is introduced, including the design and the first experimental results. The multi- pulsed electron source can generate multi-pulsed intense electron beams with energy of 2 to 3 MeV and beam intensity of 2.5 kA. The pulse interval is adjustable from 100 ns to 1000 ns without special step. An inductive adder with multi-pulsed driving source is chosen to generate pulsed vacuum diode voltage and both velvet cathode and large-emission-area thermionic dispenser cathode are adopted to generate multi-pulsed intense electron beams. In order to adopt the two different cathodes, two different diodes with the same interface are adopted. The first experimental results indicate that the source runs stably. The multi-pulsed diode voltage is now up to 2. 7 MV and the beam intensity is more than 1.6 kA both near the anode hole with Faraday cup and near the exit of the source with B-dot. The experimental results also indicate that using velvet as cathode the cathode plasma is inevitable and beam intensities become much bigger from pulse to pulse; when the larger-emission-area thermionic dispenser cathode is used, there is few cathode plasma and beam intensities are almost the same for-m pulse to pulse. (authors)

  4. Ticking terahertz wave generation in attoseconds

    CERN Document Server

    Zhang, Dongwen; Meng, Chao; Du, Xiyu; Zhou, Zhaoyan; Zhao, Zengxiu; Yuan, Jianmin

    2012-01-01

    We perform a joint measurement of terahertz waves and high-order harmonics generated from noble atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase-delay of the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft-collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in HHG processes, dominant THz wave generation as well but in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.

  5. Control of electron localization in the dissociation of H2+ using orthogonally polarized two-color sequential laser pulses

    International Nuclear Information System (INIS)

    Orthogonally polarized two-color sequential laser pulses are used to control the electron localization in the dissociation of H2+. The first single attosecond pulse, whose polarization axis is perpendicular to the molecular axis, excites H2+ from 1sσg to 2pσu, and the time-delayed infrared pulse, whose polarization axis is parallel to the molecular axis, steers the electron between two nuclei. The simulation of the time-dependent Schrödinger equation predicts the control degree of the electron localization can be up to 90% with the current laser technology. To the best of our knowledge, we first reveal that the new mechanism for this asymmetric localization is due to the mixture of 2pπg and 2pπu, instead of 1sσg and 2pσu in the previous studies.

  6. Semiclassical model for attosecond angular streaking.

    Science.gov (United States)

    Smolarski, M; Eckle, P; Keller, U; Dörner, R

    2010-08-16

    Attosecond angular streaking is a new technique to achieve unsurpassed time accuracy of only a few attoseconds. Recently this has been successfully used to set an upper limit on the electron tunneling delay time in strong laser field ionization. The measurement technique can be modeled with either the time-dependent Schrödinger equation (TDSE) or a more simple semiclassical approach that describes the process in two steps in analogy to the three-step model in high harmonic generation (HHG): step one is the tunnel ionization and step two is the classical motion in the strong laser field. Here we describe in detail a semiclassical model which is based on the ADK theory for the tunneling step, with subsequent classical propagation of the electron in the laser field. We take into account different ellipticities of the laser field and a possible wavelength-dependent ellipticity that is typically observed for pulses in the two-optical-cycle regime. This semiclassical model shows excellent agreement with the experimental result. PMID:20721150

  7. Nonlinear pulse evolution in seeded free-electron laser amplifiers and in free-electron laser cascades

    International Nuclear Information System (INIS)

    The advances in laser technology have made available very short and intense laser pulses which can be used to seed a high-gain single-pass free-electron laser (FEL) amplifier. With these seed pulses, a regime of the FEL interaction where the radiation evolution is simultaneously dominated by nonlinear effects (saturation) and time-dependent effects (slippage) can be explored. This regime is characterized by the propagation of a solitary wavelike pulse where the power of the optical wave grows quadratically with time, its pulse length decreases and the spectral bandwidth increases. We analyze the interplay between the field and particle dynamics of this propagation regime which was studied before and termed super-radiance. Furthermore we analyze the properties of the strong higher-order harmonic emission from this wave and its behavior when propagating in a cascade FEL. The super-radiant pulse is indeed capable of passing through the stages of a cascade FEL and to regenerate itself at the wavelength of the higher-order harmonic. The optical pulse obtained is shorter than a cooperation length and is strongly chirped in frequency, thus allowing further longitudinal compression down to the attosecond time scale

  8. Theoretical description of atomic photoionization by attosecond XUV pulses in a strong laser field: the case of p-shell ionization

    International Nuclear Information System (INIS)

    A theoretical description of attosecond photoionization in the presence of a strong laser field, based on the numerical solution of the Schroedinger equation, is extended to the case of p-shell ionization. In particular, Ar(3p) photoionization is considered. The main difference between this case and the previously considered case of s-shell ionization stems from the interference of the two dipole allowed channels of p-shell photoionization, which determines the angular distribution of photoelectrons in the absence of the laser field. The latter additionally distorts the angular distributions. We also extend to the initial p-shell case the model based on the strong-field approximation (SFA), which has been suggested earlier. At high photoelectron energy and low laser intensity both calculations give similar results. However, at low electron energy the SFA is inadequate. The dependence of the angular distribution on the carrier-envelope phase and the effects of orbital polarization are considered

  9. Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

    Directory of Open Access Journals (Sweden)

    J. Szlachetko

    2014-03-01

    Full Text Available Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s to femtoseconds (10−15 s and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS, we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

  10. Decoherence in attosecond photoionization.

    Science.gov (United States)

    Pabst, Stefan; Greenman, Loren; Ho, Phay J; Mazziotti, David A; Santra, Robin

    2011-02-01

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy. PMID:21405393

  11. Attosecond physics: facing the wave-particle duality

    International Nuclear Information System (INIS)

    Recent progress in generation and control of intense optical fields has given rise to isolated soft x-ray pulses with durations significantly below 1 fs. These constitute a tool of unprecedented temporal definition for attosecond physics-the study and manipulation of electronic motion on a time scale approaching the atomic unit of time. A key mechanism in such experiments is the well-defined momentum transfer between a quasi-free electron, released from an atom following irradiation by a short x-ray pulse, and a precisely controlled strong visible light field. The electrons' final kinetic energy thus sensitively depends on the timing of electron release with respect to the field oscillations and reveals the ejected electrons' confinement in time with sub-cycle, i.e. attosecond, resolution. Experiments resulting in electron emission of different durations can be interpreted in terms of a particle-like or wave-like electron, depending on whether the emission duration is considerably shorter or longer than the wave period of the probing light

  12. Attosecond strong-field interferometry in graphene: Chirality, singularity, and Berry phase

    Science.gov (United States)

    Kelardeh, Hamed Koochaki; Apalkov, Vadym; Stockman, Mark I.

    2016-04-01

    We propose an interferometry in graphene's reciprocal space without a magnetic field, employing strong ultrafast circularly polarized optical pulses. The reciprocal space interferograms contain information on the electronic spectra and topological properties of graphene and on the waveform and circular polarization of the excitation optical pulses. These can be measured using angle-resolved photoemission spectroscopy (ARPES) with attosecond ultraviolet pulses. The predicted effects provide unique opportunities in fundamental studies of two-dimensional topological materials and in applications to future petahertz light-wave-driven electronics.

  13. Probing single-photon ionization on the attosecond time scale

    CERN Document Server

    Klünder, K; Gisselbrecht, M; Fordell, T; Swoboda, M; Guénot, D; Johnsson, P; Caillat, J; Mauritsson, J; Maquet, A; Taïeb, R; L'Huillier, A

    2010-01-01

    We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the $3s^2$ and from the $3p^6$ shell, at different excitation energies ranging from 32 to 42 eV. The determination of single photoemission time delays requires to take into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using an universal formula and is found to account for a substantial fraction of the measured delay.

  14. Electron trajectories in pulsed radiation fields

    International Nuclear Information System (INIS)

    The work reported here analyzes the dynamical behavior of an electron, initially at rest, when subjected to a radiation pulse of arbitrary, but integrable, shape. This is done by a general integration procedure that has been programmed in VAXIMA. Upon choosing a specific shape for the pulse, VAXIMA finds both the space-time trajectory and the four-momentum of the electron. These are obtained in analytic or numerical form - or both - at the choice of the user. Several examples of analytical and numerical solutions, for different pulse shapes, are given

  15. Generation of Femtosecond Electron and Photon Pulses

    CERN Document Server

    Thongbai, Chitrlada; Kangrang, Nopadol; Kusoljariyakul, Keerati; Rhodes, Michael W; Rimjaem, Sakhorn; Saisut, Jatuporn; Vilaithong, Thiraphat; Wichaisirimongkol, Pathom; Wiedemann, Helmut

    2005-01-01

    Femtosecond electron and photon pulses become a tool of interesting important to study dynamics at molecular or atomic levels. Such short pulses can be generated from a system consisting of an RF-gun with a thermionic cathode, an alpha magnet as a magnetic bunch compressor, and a linear accelerator. The femtosecond electron pulses can be used directly or used as sources to produce electromagnetic radiation of equally short pulses by choosing certain kind of radiation pruduction processes. At the Fast Neutron Research Facility (Thailand), we are especially interested in production of radiation in Far-infrared and X-ray regime. In the far-infrared wavelengths which are longer than the femtosecond pulse length, the radiation is emitted coherently producing intense radiation. In the X-ray regime, development of femtosecond X-ray source is crucial for application in ultrafast science.

  16. Conservation laws, bilinear forms and solitons for a fifth-order nonlinear Schrödinger equation for the attosecond pulses in an optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Jun; Tian, Bo, E-mail: tian_bupt@163.com; Zhen, Hui-Ling; Sun, Wen-Rong

    2015-08-15

    Under investigation in this paper is a fifth-order nonlinear Schrödinger equation, which describes the propagation of attosecond pulses in an optical fiber. Based on the Lax pair, infinitely-many conservation laws are derived. With the aid of auxiliary functions, bilinear forms, one-, two- and three-soliton solutions in analytic forms are generated via the Hirota method and symbolic computation. Soliton velocity varies linearly with the coefficients of the high-order terms. Head-on interaction between the bidirectional two solitons and overtaking interaction between the unidirectional two solitons as well as the bound state are depicted. For the interactions among the three solitons, two head-on and one overtaking interactions, three overtaking interactions, an interaction between a bound state and a single soliton and the bound state are displayed. Graphical analysis shows that the interactions between the two solitons are elastic, and interactions among the three solitons are pairwise elastic. Stability analysis yields the modulation instability condition for the soliton solutions.

  17. Conservation laws, bilinear forms and solitons for a fifth-order nonlinear Schrödinger equation for the attosecond pulses in an optical fiber

    International Nuclear Information System (INIS)

    Under investigation in this paper is a fifth-order nonlinear Schrödinger equation, which describes the propagation of attosecond pulses in an optical fiber. Based on the Lax pair, infinitely-many conservation laws are derived. With the aid of auxiliary functions, bilinear forms, one-, two- and three-soliton solutions in analytic forms are generated via the Hirota method and symbolic computation. Soliton velocity varies linearly with the coefficients of the high-order terms. Head-on interaction between the bidirectional two solitons and overtaking interaction between the unidirectional two solitons as well as the bound state are depicted. For the interactions among the three solitons, two head-on and one overtaking interactions, three overtaking interactions, an interaction between a bound state and a single soliton and the bound state are displayed. Graphical analysis shows that the interactions between the two solitons are elastic, and interactions among the three solitons are pairwise elastic. Stability analysis yields the modulation instability condition for the soliton solutions

  18. Observation of molecular dipole excitations by attosecond self-streaking

    CERN Document Server

    Wachter, Georg; Sato, Shunsuke A; Pazourek, Renate; Wais, Michael; Lemell, Christoph; Tong, Xiao-Min; Yabana, Kazuhiro; Burgdörfer, Joachim

    2015-01-01

    We propose a protocol to probe the ultrafast evolution and dephasing of coherent electronic excitation in molecules in the time domain by the intrinsic streaking field generated by the molecule itself. Coherent electronic motion in the endohedral fullerene \\Necsixty~is initiated by a moderately intense femtosecond UV-VIS pulse leading to coherent oscillations of the molecular dipole moment that persist after the end of the laser pulse. The resulting time-dependent molecular near-field is probed through the momentum modulation of photoemission from the central neon atom by a time-delayed attosecond XUV pulse. Our ab-initio time-dependent density functional theory and classical trajectory simulations predict that this self-streaking signal accurately traces the molecular dipole oscillations in real time. We discuss the underlying processes and give an analytical model that captures the essence of our ab-initio simulations.

  19. Time-resolved photoemission using attosecond streaking

    CERN Document Server

    Nagele, Stefan; Wais, Michael; Wachter, Georg; Burgdörfer, Joachim

    2014-01-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric effect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the field-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for effective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes $A$@$\\text{C}_{60}$ and discuss how streaking time shifts are modified due to the interaction of the $\\text{C}_...

  20. Attosecond time delays in the nuclear dynamics of strong-field molecular dissociation

    Science.gov (United States)

    Armstrong, Greg; Ultrafast Molecular Physics Group Collaboration

    2016-05-01

    The relative time delay in the photoemission from neighboring atomic valence sub-shells has become an area of considerable recent interest, with delays of tens of attoseconds reported in pump-probe experiments for a number of atomic targets. Such delays may be extracted, for example, from phase differences in the photoelectron energy spectra for the different sub-shells as a function of delay between pump and probe pulses. The focus of such experiments has, to date, been atomic targets, on the assumption that only electronic motion can lead to delays on the attosecond scale.We investigate the molecular analogue of such studies by calculating the kinetic-energy release (KER) spectrum for neighboring vibrational states as a function of pump-probe delay time. In particular, we focus on molecular targets where electronic excitation is negligible, and show that attosecond time delays are also possible for purely nuclear motion. We will present evidence of these attosecond delays derived from both numerical solutions of the time-dependent Schrödinger equation and experiment. We analyze and understand the observed shifts using the photon-phase formalism. G.S.J. Armstrong, J. McKenna, B. Gaire, M. Zohrabi, B. Berry, B. Jochim, Kanaka Raju, P., P. Feizollah, K.D. Carnes, Ben-Itzhak, B.D. Esry.

  1. Intensity Dependence of Laser-Assisted Attosecond Photoionization Spectra

    CERN Document Server

    Swoboda, M; Ruchon, T; Johnsson, P; Mauritsson, J; Schafer, K J; L'Huillier, A

    2009-01-01

    We study experimentally the influence of the intensity of the infrared (IR) probe field on attosecond pulse train (APT) phase measurements performed with the RABITT method (Reconstruction of Attosecond Beating by Interference in Two-Photon Transitions). We find that if a strong IR field is applied, the attosecond pulses will appear to have lower-than-actual chirp rates. We also observe the onset of the streaking regime in the breakdown of the weak-field RABITT conditions. We perform a Fourier-analysis of harmonic and sideband continuum states and show that the mutual phase relation of the harmonics can be extracted from higher Fourier components.

  2. Intensity dependence of laser-assisted attosecond photoionization spectra

    Science.gov (United States)

    Swoboda, M.; Dahlström, J. M.; Ruchon, T.; Johnsson, P.; Mauritsson, J.; L'Huillier, A.; Schafer, K. J.

    2009-08-01

    We study experimentally the influence of the intensity of the infrared (IR) probe field on attosecond pulse train (APT) phase measurements performed with the RABITT method (Reconstruction of Attosecond Beating by Interference in Two-Photon Transitions). We find that if a strong IR field is applied, the attosecond pulses will appear to have lower-than-actual chirp rates. We also observe the onset of the streaking regime in the breakdown of the weak-field RABITT conditions. We perform a Fourier-analysis of harmonic and sideband continuum states and show that the mutual phase relation of the harmonics can be extracted from higher Fourier components.

  3. Electron photodetachment by short laser pulse

    NARCIS (Netherlands)

    Golovinski, P. A.; Drobyshev, A. A.

    2012-01-01

    Expressions are derived for calculations of the total probabilities and electron spectra for the photodetachment of electrons from negative ions with filled valence s shells by ultrashort laser pulses. Particular calculations have been performed for two negative ions (H- and Li-) and titanium-sapphi

  4. Attosecond imaging of XUV-induced atomic photoemission and Auger decay in strong laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Zherebtsov, S; Wirth, A; Uphues, T; Znakovskaya, I; Herrwerth, O; Gagnon, J; Korbman, M; Yakovlev, V S; Kling, M F [Max-Planck Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching (Germany); Vrakking, M J J [FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam (Netherlands); Drescher, M, E-mail: matthias.kling@mpq.mpg.de [Fachbereich fuer Physik, Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany)

    2011-05-28

    Velocity-map imaging has been employed to study the photoemission in Ne and N{sub 4,5}OO Auger decay in Xe induced by an isolated 85 eV extreme ultraviolet (XUV) pulse in the presence of a strong few-cycle near-infrared (NIR) laser field. Full three-dimensional momentum information about the released electrons was obtained. The NIR and XUV pulse parameters were extracted from the measured Ne streaking traces using a FROG CRAB retrieval algorithm. The attosecond measurements of the Auger decay in Xe show pronounced broadening of the Auger lines corresponding to the formation of sidebands. The temporal evolution of the sideband signals and their asymmetry along the laser polarization axis exhibit oscillations similar to those known from attosecond streaking measurements. The experimental results are in good agreement with model calculations based on an analytical solution of the Schroedinger equation within the strong field approximation.

  5. Generation of multi-color attosecond x-ray radiation through modulation compression

    Energy Technology Data Exchange (ETDEWEB)

    Qiang Ji [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Wu Juhao [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2011-08-22

    In this paper, we propose a scheme to generate tunable multi-color attosecond coherent x-ray radiation. This scheme uses a modulation compression method to generate a multi-spike prebunched kilo-ampere peak current electron beam from a few tens ampere electron beam out of a linac. Such a beam transporting through a series of undulator radiators and bunch compressors generates multi-color coherent x-ray radiation. As an illustration, we present an example to generate two attosecond pulses with 2.2 nm and 3 nm coherent x-ray radiation wavelength and more than 200 MW peak power using a 50 A 200 nm laser seeded electron beam.

  6. Pulsed electron beams in transient plasmas

    International Nuclear Information System (INIS)

    In the present work a large variety of experimental investigation is reviewed, having in common pulsed electron beams in transient plasmas. The simulation of nuclear pumping of plasma recombination lasers using pulsed electron beams led to the optimization of a coaxial discharge geometry which allowed lasing at the 585.3 nm transition in Ne I, Ne-H2 mixtures. In a detailed investigation of the cathode sheaths by superposition of two discharges, a simple and accurate method to measure the sheath width has been worked out and a new way of pulsed electron beam generation has been discovered. The electron beam (280 A peak current, 10 ns pulse duration, diameter less than 100 μm over a few centimeters length) is produced in a pseudospark-like discharge without inner diaphragms by the synergy of two discharges. Its parameters can be efficiently controlled by the preionization discharge. The exceptional radial stability of this beam along the discharge tube access opens the possibility to use the device as a pulsed high-density ion trap. The extension of this research helped to discover and to explain the (Cruise) effect, namely the capture and guiding of the electron beam by dielectric fibres. (author) 10 figs., 64 refs

  7. 0.5-keV Soft X-ray attosecond continua.

    Science.gov (United States)

    Teichmann, S M; Silva, F; Cousin, S L; Hemmer, M; Biegert, J

    2016-01-01

    Attosecond light pulses in the extreme ultraviolet have drawn a great deal of attention due to their ability to interrogate electronic dynamics in real time. Nevertheless, to follow charge dynamics and excitations in materials, element selectivity is a prerequisite, which demands such pulses in the soft X-ray region, above 200 eV, to simultaneously cover several fundamental absorption edges of the constituents of the materials. Here, we experimentally demonstrate the exploitation of a transient phase matching regime to generate carrier envelope controlled soft X-ray supercontinua with pulse energies up to 2.9±0.1 pJ and a flux of (7.3±0.1) × 10(7) photons per second across the entire water window and attosecond pulses with 13 as transform limit. Our results herald attosecond science at the fundamental absorption edges of matter by bridging the gap between ultrafast temporal resolution and element specific probing. PMID:27167525

  8. π-Electron rotations in chiral aromatic molecules induced by ultashort laser pulses

    International Nuclear Information System (INIS)

    π Electron play an important role in formation of the molecular structures and reactivity of aromatic molecules. In recent years, research fields of electron dynamics in atoms and molecules have attracted considerable attention with rapid progress in laser science and technology in femtosecond to attosecond time regimes [1]. This is a new branch of femtosecond chemistry. In this talk, we present the results of our recent works on control of π-electron rotation in photo-induced chiral aromatic molecules [2-4]. Control of π-electron rotation has potential utility to next-generation ultrafast switching devices. After a short introduction, the principle of generation of unidirectional π-electron rotation in aromatic molecules induced by a linearly polarized UV laser pulse is described. Next, the results of control simulations of π-electron rotations and those of the π- electron ring currents are presented for two representative chiral aromatic molecules; one is 2,5-dichlor[n] (3,6) pyrazinophane with one aromatic pyrzine ring [2], and the other is (P)-2,2’-biphenol with two aromatic rings [3,4]. Finally, the summary of the π-electron rotations and perspectives of ultrashort quantum switching investigations are described. (author)

  9. The post-Born-Oppenheimer regime: dynamics of electronic motion in molecules by attosecond few-cycle spectroscopy

    International Nuclear Information System (INIS)

    Dynamics of electronic motion when the nuclei are clamped is discussed and shown to be always described as a superposition of adiabatic electronic states. These states are stationary when the nuclei are clamped but their superposition leads to multiply periodic motion where the natural frequencies are the differences in the energies of the adiabatic electronic states. When one or more of the frequencies are low and the atoms are allowed to move, the electronic rearrangement is commensurate with the motion of the nuclei. This is the usual breakdown of the Born-Oppenheimer approximation. But when the electronic frequencies are higher there is an electronic motion before the nuclei move. The motion can be demonstrated through expectation values such as the multipole moments of the charge distribution. Such superposition states will be excited when the laser pulse width in energy exceeds the spacings of the states. For low-lying valence excited or low Rydberg states this requires a femtosecond or shorter laser pulse. Since the carrier frequency has to be comparable to the excitation energy, the required laser pulses must span only a few cycles.

  10. Attosecond electronic and nuclear quantum photodynamics of ozone: time-dependent Dyson orbitals and dipole

    CERN Document Server

    Perveaux, A; Lasorne, B; Gatti, F; Robb, M A; Halász, G J; Vibók, Á

    2014-01-01

    A nonadiabatic scheme for the description of the coupled electron and nuclear motions in the ozone molecule was proposed recently. An initial coherent nonstationary state was prepared as a superposition of the ground state and the excited Hartley band. In this situation neither the electrons nor the nuclei are in a stationary state. The multiconfiguration time dependent Hartree method was used to solve the coupled nuclear quantum dynamics in the framework of the adiabatic separation of the time-dependent Schr\\"odinger equation. The resulting wave packet shows an oscillation of the electron density between the two chemical bonds. As a first step for probing the electronic motion we computed the time-dependent molecular dipole and the Dyson orbitals. The latter play an important role in the explanation of the photoelectron angular distribution. Calculations of the Dyson orbitals are presented both for the time-independent as well as the time-dependent situations. We limited our description of the electronic mot...

  11. Long pulse electron gun for laser applications

    International Nuclear Information System (INIS)

    This paper reports on large-area electron guns that are critical components in many high-energy gas laser systems. The secondary emission electron (SEE) gun offers an attractive option for pulsed laser applications. With this type of cold cathode gun, a dc voltage is applied to the cathode and the electron beam is generated by secondary emission due to ion bombardment processes. The gun is controlled by modulating the source of ions which resides at ground potential. This design greatly simplifies the electron gun power system. SEE-gun systems have been developed which provide 150-220 keV beams at current densities exceeding 25 mA/cm2 with current density uniformities of approximately ±10% over areas of up to 5 x 150 cm2. Pulse lengths have ranged from 30 μs to 20 ms at repetition rates from single-pulse to 30 Hz. It is expected that the SEE-gun can be scaled to beam voltages of greater than 300 kV, beam areas greater than 1 m2, peak current densities exceeding 1 A/cm2, time-averaged current densities approx-gt 0.5 mA/cm2, pulse lengths of 0.1 μs to dc, and pulse repetition rates >1 kHz with good uniformity, high reliability and long life. Furthermore, the inherent simplicity of the SEE-gun results in low cost and a compact, light-weight system

  12. Attosecond streaking of molecules in the low-energy region studied by a wavefunction splitting scheme

    International Nuclear Information System (INIS)

    We present a theoretical study of the low-energy photoelectron spectra of hydrogen molecular ion generated by a single attosecond pulse in the presence of an infrared (IR) laser field. In order to investigate this type of attosecond streaking of molecules, we developed a very efficient grid-based numerical method to solve the two-centre time-dependent Schrödinger equation (TDSE) in the prolate spheroidal coordinates. Specifically, the radial coordinate is discretized with the finite-element discrete variable representation (FE-DVR) for easy parallel computation and the angular coordinate with the usual DVR. A wavefunction splitting scheme is utilized to reduce the demanding requirement of the computational resource to solve the corresponding TDSE when an IR field is present. After verification of the accuracy and efficiency of our method, we then apply it to investigate the attosecond streaking spectra of H+2 in the low-energy region. In contrast to the usual attosecond streaking in the high-energy region, part of the low-energy electrons may be driven back to rescatter with the residual two-centre core. Very interesting interference structures are present in the low-energy region. When the internuclear distance is small, they are very similar to what we have recently observed in the atomic case. (paper)

  13. Ionization and transient absorption control with a resonant attosecond clock

    International Nuclear Information System (INIS)

    Metastable states are important actors in the ionisation of atoms and molecules. Sub-femtosecond extreme ultraviolet pulses can coherently populate several transiently bound states at once, thus starting the attosecond clocks which are required to monitor and control ultrafast electronic evolution above the ionisation threshold. Here we illustrate, from a theoretical point of view, the effects coherent superpositions of 1Po doubly excited states in the helium atom have on channel-resolved photoelectron spectra as well as on the transient absorption spectrum of the atom in the extreme ultraviolet region, when they are created by a single-attosecond pulse in the presence of a strong few-cycle near-infrared/visible pulse which acts as a probe. Interference fringes varying rapidly with the pump-probe time delay are visible in both photoelectron and transient absorption spectra. From such fringes, the wave packet itself can conceivably be reconstructed. Conversely, all observables are modulated by the characteristic beating periods of the wave packet, so that control of partial ionisation yields, branching ratios, and light absorption or amplification can be achieved

  14. Light field driven streak-camera for single-shot measurements of the temporal profile of XUV-pulses from a free-electron laser; Lichtfeld getriebene Streak-Kamera zur Einzelschuss Zeitstrukturmessung der XUV-Pulse eines Freie-Elektronen Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Fruehling, Ulrike

    2009-10-15

    The Free Electron Laser in Hamburg (FLASH) is a source for highly intense ultra short extreme ultraviolet (XUV) light pulses with pulse durations of a few femtoseconds. Due to the stochastic nature of the light generation scheme based on self amplified spontaneous emission (SASE), the duration and temporal profile of the XUV pulses fluctuate from shot to shot. In this thesis, a THz-field driven streak-camera capable of single pulse measurements of the XUV pulse-profile has been realized. In a first XUV-THz pump-probe experiment at FLASH, the XUV-pulses are overlapped in a gas target with synchronized THz-pulses generated by a new THz-undulator. The electromagnetic field of the THz light accelerates photoelectrons produced by the XUV-pulses with the resulting change of the photoelectron momenta depending on the phase of the THz field at the time of ionisation. This technique is intensively used in attosecond metrology where near infrared streaking fields are employed for the temporal characterisation of attosecond XUV-Pulses. Here, it is adapted for the analysis of pulse durations in the few femtosecond range by choosing a hundred times longer far infrared streaking wavelengths. Thus, the gap between conventional streak cameras with typical resolutions of hundreds of femtoseconds and techniques with attosecond resolution is filled. Using the THz-streak camera, the time dependent electric field of the THz-pulses was sampled in great detail while on the other hand the duration and even details of the time structure of the XUV-pulses were characterized. (orig.)

  15. Strong-field-induced attosecond dynamics in SiO2

    Directory of Open Access Journals (Sweden)

    Kienberger R.

    2013-03-01

    Full Text Available Striking field-induced changes in the absorption near the Si L-edge of SiO2 exposed to a near-infrared laser field of several V/Å delivered by a few-cycle pulse are observed with sub-100 attosecond extreme ultraviolet pulses by means of attosecond transient absorption.

  16. Attosecond delays in molecular photoionization

    CERN Document Server

    Huppert, Martin; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-01-01

    We report measurements of energy-dependent attosecond photoionization delays between the two outer-most valence shells of N$_2$O and H$_2$O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N$_2$O, whereas the delays in H$_2$O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N$_2$O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to $\\sim$110 as. The unstructured continua of H$_2$O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.

  17. Attosecond physics attosecond measurements and control of physical systems

    CERN Document Server

    Torres, Ricardo; Zaïr, Amelle

    2013-01-01

    Attophysics is an emerging field in physics devoted to the study and characterization of matter dynamics in the sub-femtosecond time scale. This book gives coverage of a broad set of selected topics in this field, exciting by their novelty and their potential impact. The book is written review-like. It also includes fundamental chapters as introduction to the field for non-specialist physicists. The book is structured in four sections: basics, attosecond pulse technology, applications to measurements and control of physical processes and future perspectives. It is a valuable reference tool for researchers in the field as well as a concise introduction to non-specialist readers.

  18. Pulse shaper for electron gun control

    International Nuclear Information System (INIS)

    Modulation of electron gun of spectrometer for surface diagnostics allows to proceed to recording of N(E) from recording of the first derivative of secondary-emitted electron energy redistribution, dN/dE(E) with minimal modernization of the available modernization of the available receiving channel of spectrometer. Circuit with inductive bond ensures galvanic decoupling of the former by inlet and outlet. Irial spectra of characteristical losses in N(E) form obtained at modulation of the electron primary beam using the developed pulse former, and in dN/dE(E) form-using modulation of braking potential, are presented. 9 refs.; 2 figs

  19. Double ionization of helium by intense near-infrared and VUV laser pulses

    International Nuclear Information System (INIS)

    We investigate the dynamics of double ionization of He atom by an intense near-infrared and an attosecond vacuum ultraviolet (VUV) laser pulse, which are either applied in sequence or at the same time. To this end we solve the time-dependent Schroedinger equation for a two-electron model atom interacting with the two fields. We compare the double-ionization yields and probability density distributions, with and without the application of the attosecond pulse, for the different scenarios. The results of our numerical simulations show how ionization or excitation of the neutral atom by a preceding or simultaneously applied VUV pulse affects the double-ionization dynamics driven by the near-infrared laser pulse. The findings provide insights regarding the question if attosecond technology can be used to temporally resolve mechanisms of correlated emission of electrons in a strong laser field.

  20. Generation of broad XUV continuous high harmonic spectra and isolated attosecond pulses with intense mid-infrared lasers

    CERN Document Server

    Trallero-Herrero, C; Schmidt, B E; Shiner, A D; Kieffer, J-C; Corkum, P B; Villeneuve, D M; Lin, C D; Légaré, F; Le, A-T

    2011-01-01

    We present experimental results showing the appearance of a near-continuum in the high-order harmonic generation (HHG) spectra of atomic and molecular species as the driving laser intensity of an infrared pulse increases. Detailed macroscopic simulations reveal that these near-continuum spectra are capable of producing IAPs in the far field if a proper spatial filter is applied. Further, our simulations show that the near-continuum spectra and the IAPs are a product of strong temporal and spatial reshaping (blue shift and defocusing) of the driving field. This offers a possibility of producing IAPs with a broad range of photon energy, including plateau harmonics, by mid-IR laser pulses even without carrier-envelope phase stabilization.