WorldWideScience

Sample records for attosecond electron-hole dynamics

  1. 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.

  2. 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.

  3. 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.

  4. Electron-hole dynamics in CdTe tetrapods.

    Science.gov (United States)

    Malkmus, Stephan; Kudera, Stefan; Manna, Liberato; Parak, Wolfgang J; Braun, Markus

    2006-09-01

    We present transient absorption studies with femtosecond time resolution on the electron-hole dynamics in CdTe tetrapod nanostructures. Electron-hole pairs are generated by optical excitation in the visible spectral range, and an immediate bleach and induced absorption signal are observed. The relaxation dynamics to the lowest excitonic state is completed in about 6 ps. Experiments with polarized excitation pulses give information about the localization of the excited-state wave functions. The influence of the nanocrystal shape on the optical properties of CdTe nanoparticles is discussed. PMID:16942067

  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. 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.

  7. Ultrafast carrier dynamics in tetrahedral amorphous carbon: carrier trapping versus electron-hole recombination

    International Nuclear Information System (INIS)

    We report the investigation of the ultrafast carrier dynamics in thin tetrahedral amorphous carbon films by means of femtosecond time-resolved reflectivity. We estimated the electron-phonon relaxation time of a few hundred femtoseconds and we observed that under low optical excitation photo-generated carriers decay according to two distinct mechanisms attributed to trapping by defect states and direct electron-hole recombination. With high excitation, when photo-carrier and trap densities are comparable, a unique temporal evolution develops, as the time dependence of the trapping process becomes degenerate with the electron-hole recombination. This experimental evidence highlights the role of defects in the ultrafast electronic dynamics and is not specific to this particular form of carbon, but has general validity for amorphous and disordered semiconductors

  8. Spin dynamics and relaxation in graphene dictated by electron-hole puddles

    Science.gov (United States)

    van Tuan, Dinh; Ortmann, Frank; Cummings, Aron W.; Soriano, David; Roche, Stephan

    2016-02-01

    The understanding of spin dynamics and relaxation mechanisms in clean graphene, and the upper time and length scales on which spin devices can operate, are prerequisites to realizing graphene-based spintronic technologies. Here we theoretically reveal the nature of fundamental spin relaxation mechanisms in clean graphene on different substrates with Rashba spin-orbit fields as low as a few tens of μeV. Spin lifetimes ranging from 50 picoseconds up to several nanoseconds are found to be dictated by substrate-induced electron-hole characteristics. A crossover in the spin relaxation mechanism from a Dyakonov-Perel type for SiO2 substrates to a broadening-induced dephasing for hBN substrates is described. The energy dependence of spin lifetimes, their ratio for spins pointing out-of-plane and in-plane, and the scaling with disorder provide a global picture about spin dynamics and relaxation in ultraclean graphene in the presence of electron-hole puddles.

  9. 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.

  10. Femtosecond Dynamics and Nonlinear Effects of Electron-Hole Plasma in Semiconductor Doped Glasses.

    Science.gov (United States)

    Olbright, Gregory Richard

    The following is a comprehensive study of transient and steady-state nonlinear optical properties of semiconductor microcrystals embedded in a glass matrix (semiconductor doped glass). Transient thermal effects which give rise to longitudinal excitation discontinuities (i.e., kinks) that arise from partial sample switching in increasing absorption optical bistability are observed in a doped glass. The transient thermal effects occur on time scales of a few hundred milliseconds. Femtosecond and nanosecond laser pulses are employed to measure time-resolved and steady-state transmission and differential transmission spectra. The measured spectra reveal several beautiful effects which are attributed to the many-particle effects of electron-hole plasma. The spectra reveal: bandgap renormalization, broadening of the tail states and screening of the continuum states, state filling (spectral hole burning), thermalization of nonthermal carrier population distributions, band filling due to carrier relaxation of the thermal and nonthermal distributions, direct electron-hole recombination and long lived (>>100 ps) tail states which are attributed to electron trapping. Absorption edge dynamics discussed in this dissertation span 15 orders of magnitude.

  11. 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...

  12. 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.

  13. Correlated proton-electron hole dynamics in protonated water clusters upon extreme ultraviolet photoionization.

    Science.gov (United States)

    Li, Zheng; Vendrell, Oriol

    2016-07-01

    The ultrafast nuclear and electronic dynamics of protonated water clusters H(+)(H2O) n after extreme ultraviolet photoionization is investigated. In particular, we focus on cluster cations with n = 3, 6, and 21. Upon ionization, two positive charges are present in the cluster related to the excess proton and the missing electron, respectively. A correlation is found between the cluster's geometrical conformation and initial electronic energy with the size of the final fragments produced. For situations in which the electron hole and proton are initially spatially close, the two entities become correlated and separate in a time-scale of 20 to 40 fs driven by strong non-adiabatic effects. PMID:26798842

  14. 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

  15. 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

  16. Demonstration of attosecond ionization dynamics inside transparent solids

    Energy Technology Data Exchange (ETDEWEB)

    Gertsvolf, M; Corkum, P B [University of Ottawa, Ottawa, Ontario, K1N 6N5 (Canada); Spanner, M; Rayner, D M, E-mail: David.Rayner@nrc.gc.c, E-mail: Paul.Corkum@nrc.gc.c [National Research Council of Canada, Ottawa, Ontario, K1A 0R6 (Canada)

    2010-07-14

    Attosecond science has arisen from intense light pulses interacting with low density gases. We show that the initiating process-sub-cycle ionization-also survives in large band gap condensed media. Using fused SiO{sub 2} as an example, we measure the differential nonlinear absorption between the major and minor axis of elliptically polarized light. Through simulations that include ionization and light propagation, we confirm that changes in the ellipticity between the incident beam and the transmitted beam encode sub-cycle absorption dynamics. As the pulse duration is increased, we observe that sub-cycle ionization is masked by collisional processes. We propose a general class of methods for measuring attosecond dynamics in condensed media. (fast track communication)

  17. Exciton Mott transition in electron-hole systems: Dynamical mean-field theory for the continuous-space model

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Tomoya; Ohashi, Takuma; Asano, Kenichi; Ogawa, Tetsuo, E-mail: ueda@acty.phys.sci.osaka-u.ac.j [Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2009-02-01

    We study the exciton Mott transition in the three-dimensional electron-hole (e-h) system by means of an extension of the dynamical mean field theory (DMFT). In order to apply DMFT to the e-h system with the contact e-h attraction v, we construct DMFT for the continuous-space model by introducing the short wavelength cut-off. Using the generalized formulation of DMFT, we calculate the temperature dependence of the single-particle density of states and the exciton density. We demonstrate that the system crossovers from metal to insulator as v increases, and finally determine the phase diagram.

  18. Can strong-field ionization prepare attosecond dynamics?

    CERN Document Server

    Pabst, Stefan

    2015-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model for predicting the bandwidth of ionic states that can be coherently prepared by SFI. This bandwidth is given by the Fourier-transformed sub-cycle SFI rate and decreases considerably with increasing central wavelength of the ionizing pulse. Many-body calculations based on time-dependent configuration-interaction singles (TDCIS) quantitatively support this result and reveal an additional decrease of the bandwidth as a consequence of channel interactions and non-adiabatic dynamics. Our results further predict that multi-cycle femtosecond pulses can coherently prepare attosecond wave packets with higher selectivity and versatility compared to single-cycle pulses.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Attosecond dynamics and decoherence in neutron-H2 scattering

    Energy Technology Data Exchange (ETDEWEB)

    Dreismann, C. Aris [Institute of Chemistry, TU Berlin (Germany); Gray, Evan; Blach, Tom [Griffith University, School of Biomolecular and Physical Sciences, Brisbane (Australia)

    2011-07-01

    The standard theory of neutron scattering is based on time-dependent first order perturbation theory (Fermi's Golden Rule). However, the characteristic time-window of neutron Compton scattering (NCS) in the energy transfer range of 1-100 eV lies in the attosecond range, in which the applicability of the Golden Rule becomes questionable. It is argued that, in the NCS physical context, quantum entanglement and decoherence play a significant role. Results of current NCS experiments from H2 and D2 in the gas phase at T=41 K are reported, showing that the measured Compton profiles reveal new features of quantum dynamics which contradict conventional theoretical expectations. The non-unitary dynamical character of this ultrafast scattering experiments is discussed, and the specific role of decoherence is pointed out. The presented results indicate that the new effect under investigation may play a significant role also in other scattering experimental fields.

  4. Attosecond dynamical Franz-Keldysh effect in polycrystalline diamond.

    Science.gov (United States)

    Lucchini, M; Sato, S A; Ludwig, A; Herrmann, J; Volkov, M; Kasmi, L; Shinohara, Y; Yabana, K; Gallmann, L; Keller, U

    2016-08-26

    Short, intense laser pulses can be used to access the transition regime between classical and quantum optical responses in dielectrics. In this regime, the relative roles of inter- and intraband light-driven electronic transitions remain uncertain. We applied attosecond transient absorption spectroscopy to investigate the interaction between polycrystalline diamond and a few-femtosecond infrared pulse with intensity below the critical intensity of optical breakdown. Ab initio time-dependent density functional theory calculations, in tandem with a two-band parabolic model, accounted for the experimental results in the framework of the dynamical Franz-Keldysh effect and identified infrared induction of intraband currents as the main physical mechanism responsible for the observations. PMID:27563093

  5. 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.

  6. 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.

  7. Exact two-body quantum dynamics of an electron-hole pair in semiconductor coupled quantum wells: A time-dependent approach

    Science.gov (United States)

    Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido

    2016-05-01

    We simulate the time-dependent coherent dynamics of a spatially indirect exciton—an electron-hole pair with the two particles confined in different layers—in a GaAs coupled quantum well system. We use a unitary wave-packet propagation method taking into account in full the four degrees of freedom of the two particles in a two-dimensional system, including both the long-range Coulomb attraction and arbitrary two-dimensional electrostatic potentials affecting the electron and/or the hole separately. The method has been implemented for massively parallel architectures to cope with the huge numerical problem, showing good scaling properties and allowing evolution for tens of picoseconds. We have investigated both transient time phenomena and asymptotic time transmission and reflection coefficients for potential profiles consisting of (i) extended barriers and wells and (ii) a single-slit geometry. We found clear signatures of the internal two-body dynamics, with transient phenomena in the picosecond time scale which might be revealed by optical spectroscopy. Exact results have been compared with mean-field approaches which, neglecting dynamical correlations by construction, turn out to be inadequate to describe the electron-hole pair evolution in realistic experimental conditions.

  8. 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.

  9. Can strong-field ionization prepare attosecond dynamics?

    OpenAIRE

    Pabst, Stefan; Wörner, Hans Jakob

    2015-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model for predicting the bandwidth of ionic states that can be coherently prepared by SFI. This bandwidth is given by the Fourier-transformed sub-cycle SFI rate and decreases considerably with increasing central wavelength of the ionizing pulse. Many-body calculations based on time-dep...

  10. Attosecond physics

    International Nuclear Information System (INIS)

    , we show that such pulses are capable of stimulating measureable nuclear processes, which open the way for imaging attosecond dynamics of nuclear and atomic (e.g. core hole decay) processes. In conclusion, it should be emphasized that this idea unifies two of the most important fields in contemporary laser science - attosecond and ultra-intense science. (author)

  11. 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

  12. 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.

  13. Magnetic susceptibility from electron holes

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2013-07-01

    Full Text Available A recent theory of magnetic field amplification in electron holes is extended to derive the magnetic susceptibility of an electron-hole gas propagating in a magnetic flux tube along the ambient magnetic field. It is shown that the hole gas behaves diamagnetic adding some small amount to the well-known Landau susceptibility in the hole-carrying volume.

  14. 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)

  15. 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

  16. 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

  17. 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

  18. 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.

  19. Mapping of attosecond ionization dynamics by recollision-free higher-order harmonic generation

    Science.gov (United States)

    Verhoef, Aart J.; Mitrofanov, Alexander; Serebryannikov, Evgenii E.; Kartashov, Daniil V.; Zheltikov, Aleksei M.; Baltuska, Andrius

    2009-05-01

    In the presence of a high-intensity optical field, electrons are released from atoms on an attosecond time scale. Moreover, in the tunnelling regime, this process displays a strong sensitivity to the carrier-envelope phase (CEP) of a few-cycle light pulse. Tunnelling ionization - a fascinating quantum mechanical phenomenon - leads to a quasi-stepwise increase of free electron density and, as a consequence, of the refractive index of the medium. These steps of the refractive index, corresponding to half-cycles of the driving optical field, impose a transient attosecond phase mask. By scattering probe light off this mask we detect quasi-periodic higher-order harmonics, the spectrum of which, unlike that of the harmonics originating from intrinsic nonlinearity or driven by electron re-collisions, do not depend on the probe intensity and recollision dynamics. The implemented noncollinear pump-probe experimental technique allows optical harmonics generated due to a tunnelling-ionization-induced modulation of the electric current to be spatially separated from the harmonics originating from atomic and ionic nonlinear susceptibilities, enabling background-free time-resolved detection of electron-tunnelling-controlled harmonic spectra and offering an attractive solution for attosecond optical metrology of gases and bulk solids.

  20. Phase dynamics of non-equilibrium distributions of free electron-hole pairs in GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Bigot, J.Y.; Mycek, M.A.; Weiss, S.; Chemla, D.S.

    1994-05-01

    The authors resolve the phase and amplitude of the coherent emission of a non-equilibrium Fermi-Sea in four wave mixing experiments. It exhibits an ultrafast dynamical blue shift, due to Fermi-edge many-body effects.

  1. 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.

  2. 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)

  3. 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.

  4. Probing the Dynamics of Rydberg and Valence States of Molecular Nitrogen with Attosecond Transient Absorption Spectroscopy.

    Science.gov (United States)

    Warrick, Erika R; Cao, Wei; Neumark, Daniel M; Leone, Stephen R

    2016-05-19

    An attosecond pulse is used to create a wavepacket in molecular nitrogen composed of multiple bound and autoionizing electronic states of Rydberg and valence character between 12 and 16.7 eV. A time-delayed, few-femtosecond, near-infrared (NIR) laser pulse is used to couple individual states in the wavepacket to multiple neighboring states, resulting in time-dependent modification of the absorption spectrum and revealing both individual quantum beats of the wavepacket and the energy shifts of the excited states in the presence of the strong NIR field. The broad bandwidth of the attosecond pulse and high energy resolution of the extreme ultraviolet spectrometer allow the simultaneous observation of time-dependent dynamics for many individual vibrational levels in each electronic state. Quantum beating with periods from 1.3 to 12 fs and transient line shape changes are observed among vibrational levels of a progression of electronically autoionizing Rydberg states leading to the excited A (2)Πu N2(+) ion core. Vibrational levels in the valence b (1)Πu state exhibit 50 fs oscillation periods, revealing superpositions between individual vibrational levels within this state. Comparisons are made to previous studies of electronic wavepackets in atoms that highlight similarities to atomic behavior yet illustrate unique contributions of the diatomic molecular structure to the wavepacket, including the influence of different electronic potentials and vibrational-level-specific electronic dynamics. PMID:26862883

  5. 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.

  6. 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.

  7. 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.

  8. Attosecond dynamics of nuclear wavepackets induced by neutron Compton scattering

    International Nuclear Information System (INIS)

    For the first time, time-dependent nuclear wavepacket theory is applied to the experimental context of neutron Compton scattering (NCS). The derivation is analogous to the well-known expression of infrared laser absorption spectra (IR-LAS) in terms of autocorrelation functions of nuclear wavepackets moving on molecular potential energy surfaces in the electronic ground state. This analogy allows us to transfer the methods for nuclear wavepacket dynamics from IR-LAS to NCS. Systematic investigations for two model systems, HOD and C6D5H, demonstrate the effects of nuclear dynamics induced by NCS in the as (10-18 s) time domain on the NCS spectra. This is a consequence of the large momentum transfer from the neutron to the scattering atom and consequentially the ultrashort time for the nuclear wavepacket to travel the distance of its narrow width, followed by dissociation. This initial time evolution may be described approximately in terms of normal mode vibrations, together with additional excitations of translations and rotations which support depletion of any recurrences of the vibrational autocorrelation functions, also due to dissociation. In spite of the analogous derivation we predict some surprising, opposite trends in NCS i.e. in contrast to LAS. Thus, increasing the number of excited modes for polyatomic molecules, the resulting dynamics slow down for NCS and therefore, the spectral width narrows

  9. 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)).

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Mapping Ultrafast Dynamics of Highly Excited H2by Attosecond VUV-Radiation

    Science.gov (United States)

    Weber, Thorsten; Sturm, Felix; Wright, Travis; Ray, Dipanwita; Shivaram, Niranjan; Slaughter, Daniel; Bocharova, Irina; Ranitovic, Predrag; Belkacem, Ali

    2016-05-01

    We show how attosecond vacuum ultraviolet (VUV) and femtosecond infrared (IR) radiation can be used to excite and map dynamics of a highly excited neutral hydrogen molecule. By using time-delayed, strong laser pulses and ion imaging, we map the dynamics of highly-excited, bound states of hydrogen molecules. Due to the large stretching amplitude of the B electronic state, excited by the 9th harmonic of the fundamental laser frequency, the effective ionization potential of the hydrogen molecular ion changes substantially as the nuclear wave packet (NWP) vibrates in the bound, B potential energy curve. Therefore, the probability of ionizing the neutrally-excited hydrogen molecule by the IR probe pulse changes as the NWP evolves in the B potential. We probe this dynamics by ionizing the vibrating molecule by means of time-delayed IR radiation, and identify the dissociation channels with 3D-momentum ion imaging. Supported by DOE under Contract No. DE-AC02-05CH11231.

  16. Exciton Mott transition and pair condensation in the electron-hole system

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, Takuma; Ueda, Tomoya; Asano, Kenichi; Ogawa, Tetsuo, E-mail: ohashi@acty.phys.sci.osaka-u.ac.j [Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2009-02-01

    We investigate the exciton Mott transition and pair condensation in the spinless electron-hole Hubbard model by means of the dynamical mean field theory combined with the noncrossing approximation. By investigating the single-particle density of states, we find the crossover between the metallic electron-hole plasma and the exciton-like insulator. We also investigate the electron-hole pair condensation transition and the optical response, by calculation of the two-particle Green's function for the pair correlation with vertex corrections. It is shown that the excitonic peak in the optical response function gets strongly enhanced around the electron-hole pair condensation transition.

  17. 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

  18. 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.

  19. Observing the attosecond dynamics of nuclear wavepackets in molecules by using high harmonic generation in mixed gases

    International Nuclear Information System (INIS)

    We probe the attosecond dynamics of nuclear wavepackets in H2 and D2 molecules by measuring the relative phase of high harmonics generated in each molecule by using a novel method with a mixed gas of H2 and D2. We find that not only the single molecule responses but also the propagation effects of harmonics differ between the two isotopes and we conclude that in order to discuss the dynamics of molecules in the single molecule responses, the propagation effects need to be excluded from the raw harmonic signals. The measured relative phase as well as the intensity ratio are found to be monotonic functions of the harmonic order and are successfully reproduced by applying Feynman's path integral method fully to the dynamics of the nuclei and electrons in the molecules

  20. 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

  1. The picosecond dynamics of electron-hole pairs in graded and homogeneous CdS{sub x}Se{sub 1-x} semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hane, J.K.

    1995-05-01

    Wavelength and composition dependence of the time-resolved luminescence were examined. Effects of macroscopic composition gradient and microscopic alloy disorder on e{sup {minus}}-h{sup +} pair dynamics were probed. Materials with both increasing and decreasing S content with distance from the surface were examined, where 0{le} {times} {le}1 over the full range. In these graded materials, the band gap energy also varies with position. The graded semiconductor luminescence shows strong wavelength dependence, showing diffusion in both band gap and concentration gradients. A bottleneck in the diffusion is attributed to localization occurring primarily in the materials with greatest alloy disorder, i.e. around CdS{sub 0.5}Se{sub 0.50}. Homogeneous materials were studied for x = 0, 0.25, 0.50, 0.75, 1; the time-resolved luminescence depends strongly on the composition. The mixed compositions have longer decay constants than CdS and CdSe. Observed lifetimes agree with a picture of localized states induced by the alloy disorder. For a given homogeneous crystal, no wavelength dependence of the time decays was observed. Picosecond luminescence upconversion spectroscopy was used to study further the dependence of the luminescence on composition. Large nonexponential character in the decay functions was observed in the alloys; this long time tail can be attributed to a broad distribution of relaxation times as modeled by the Kohlrausch exponential.

  2. Geometries, Electronic Couplings, and Hole Dissociation Dynamics of Photoinduced Electron-Hole Pairs in Polyhexylthiophene-Fullerene Dyads Rigidly Linked by Oligophenylenes.

    Science.gov (United States)

    Miura, Taku; Tao, Ran; Shibata, Sho; Umeyama, Tomokazu; Tachikawa, Takashi; Imahori, Hiroshi; Kobori, Yasuhiro

    2016-05-11

    To shed a light on fundamental molecular functions of photoinduced charge conductions by organic photovoltaic materials, it is important to directly observe molecular geometries of the intermediate charges just after the photoinduced electron-transfer reactions. However, highly inhomogeneous molecular environments at the bulk heteojunction interfaces in the photoactive layers have prevented us from understanding the mechanism of the charge conductions. We have herein investigated orbital geometries, electronic couplings, and hole-dissociation dynamics of photoinduced charge-separated (CS) states in a series of poly(3-hexylthiophene)-fullerene linked dyads bridged by rigid oligo-p-phenylene spacers by using time-resolved EPR spectroscopy. It has been revealed that one-dimensional intramolecular hole-dissociations exothermically take place from localized holes in initial CS states, following bridge-mediated, photoinduced charge-separations via triplet exciton diffusions in the conjugated polymer-backbones. This molecular wire property of the photoinduced charges in solution at room temperature demonstrates the potential utility of the covalently bridged polymer molecules applied for the molecular devices. PMID:27082279

  3. 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

  4. 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...

  5. 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)

  6. 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.

  7. 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.

  8. High-harmonic generation in alpha-quartz by the electron-hole recombination

    CERN Document Server

    Otobe, T

    2016-01-01

    The first-principle calculation for the high-harmonic generation (HHG) in an alpha-quartz employing the time-dependent density-functional theory is reported. The photon energy is set to 1.55 eV, and the cutoff energy of the plateau region is found to be limited at the 19th harmonics (30 eV). The laser intensity dependence of HHG efficiency at the cutoff energy region is consistent with that of the hole density in the lowest-lying valence band. Numerical results indicate that the electron-hole recombination plays a crucial role in HHG in alpha-quartz. It is found that the 200 attosecond pulse train is generated utilizing HHG around the plateau cutoff energy.

  9. Analysis and simulation of BGK electron holes

    Directory of Open Access Journals (Sweden)

    L. Muschietti

    1999-01-01

    Full Text Available Recent observations from satellites crossing regions of magnetic-field-aligned electron streams reveal solitary potential structures that move at speeds much greater than the ion acoustic/thermal velocity. The structures appear as positive potential pulses rapidly drifting along the magnetic field, and are electrostatic in their rest frame. We interpret them as BGK electron holes supported by a drifting population of trapped electrons. Using Laplace transforms, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron distribution functions are self-consistent and compatible with the field and particle data associated with the observed pulses. In particular, the spatial width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulation code with open boundaries. We consider a strongly magnetized parameter regime in which the bounce frequency of the trapped electrons is much less than their gyrofrequency. Our investigation includes the influence of the ions, which in the frame of the hole appear as an incident beam, and impinge on the BGK potential with considerable energy. The nonlinear structure is remarkably resilient

  10. 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)

  11. Plasma electron-hole kinematics: momentum conservation

    CERN Document Server

    Hutchinson, I H

    2016-01-01

    We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, that behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside it, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

  12. 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...

  13. 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.

  14. 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.

  15. Attosecond science and the tunnelling time problem

    Energy Technology Data Exchange (ETDEWEB)

    Landsman, Alexandra S., E-mail: landsmanster@gmail.com; Keller, Ursula

    2015-01-05

    The question of how long it takes a particle to tunnel through a potential barrier has been a subject of intense theoretical debate for the last 80 years. In this decade of attosecond science, the answer to this question not only promises to deepen our understanding of fundamental quantum mechanics, but also has significant practical implications for how we interpret attosecond electron dynamics that underlie important phenomena in physics, chemistry and biology. Here we attempt to address this problem in the context of recent experimental measurements which use state-of-the-art ultrafast laser technology to resolve electron dynamics on the attosecond time-scale. This review therefore brings the theory of tunnelling time to the arena of ultrafast science, opening the door to improved resolution of, and cross-fertilization between, significant practical and fundamental questions in both fields.

  16. Terahertz Probes of Transient Conducting and Insulating Phases in Quasi-2D Electron-hole Gases

    International Nuclear Information System (INIS)

    We employ ultrafast terahertz (THz) pulses to study the dynamical interplay of optically-induced excitons and unbound electron-hole pairs in GaAs/AlGaAs quantum wells. A distinct low-energy oscillator appears upon resonant excitation of heavy-hole excitons, linked to transitions between their internal degrees of freedom. Time resolving changes in the THz conductivity, we can observe dynamical transitions between conducting and insulating phases as excitons form or ionize on ultrashort timescales

  17. Ultra-fast dynamics in atoms and molecules during photoionization: from attoseconds to femtoseconds

    OpenAIRE

    Månsson, Erik

    2014-01-01

    Treating the correlated behaviour of multiple particles is challenging for both theory and experiment. This thesis reports on a variety of experimental investigations aiming to advance the understanding of fundamental processes in atoms and molecules: double ionization, isomerization and dissociation. The emphasis lies on ultra-fast processes, where multiple electrons interact or nuclei move so rapidly that coupling between electronic and nuclear dynamics can not be neglected. Pulses ...

  18. Time-resolving Attosecond Chiral Dynamics in Molecules with High Harmonic Spectroscopy

    Science.gov (United States)

    Smirnova, O.; Cireasa, R.; Boguslavskiy, A.; Pons, B.; Wong, M. C. H.; Descamps, D.; Petit, S.; Ruf, H.; Thire, N.; Ferre, A.; Suarez, J.; Schmidt, B. E.; Higuet, J.; Alharbi, A. F.; Legare, F.; Blanchet, V.; Fabre, B.; Patchkovskii, S.; Mairesse, Y.; Bhardwaj, R.

    2015-05-01

    We demonstrate extreme chiral sensitivity of high harmonic generation from randomly oriented ensemble of chiral molecules in elliptical mid-infrared fields, and explain the physical mechanism underlying this very strong chiro-optical response. We also use the high harmonic spectra to follow the electronic chiral response with 0.1 femtosecond resolution. We studied two chiral molecules, epoxypropane and fenchone in 1.8 μm, 50 fs, mid-1013 W/cm2 pulses. Very small ellipticity of the incident light, about 1% in the field, is sufficient to induce several percent difference between the high harmonic response of left and right enantiomers. The origin of this effect lies in chiral-sensitive dynamics of the hole created by strong field ionization. Small differences in this dynamics between ionization and recombination are recorded and amplified by several orders of magnitude in high harmonic spectra. Using time-energy mapping we reconstruct sub-femtosecond chiral dynamics and show that the standard measure of the chiral signal is directly proportional to the recombination amplitude to the chiral-sensitive component of the hole wave-packet.

  19. 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.

  20. Correlated nuclear and electronic dynamics in photoionized systems studied by quantum and mixed quantum-classical approaches

    International Nuclear Information System (INIS)

    The advent of free electron lasers and high harmonic sources enables the investigation of electronic and nuclear dynamics of molecules and solids with atomic spatial resolution and femtosecond/attosecond time resolution, using bright and ultrashort laser pulses of frequency from terahertz to hard x-ray range. With the help of ultrashort laser pulses, the nuclear and electronic dynamics can be initiated, monitored and actively controlled at the typical time scale in the femtosecond to attosecond realm. Meanwhile, theoretical tools are required to describe the underlying mechanism. This doctoral thesis focuses on the development of theoretical tools based on full quantum mechanical multiconfiguration time-dependent Hartree (MCTDH) and mixed quantum classical approaches, which can be applied to describe the dynamical behavior of gas phase molecules and strongly correlated solids in the presence of ultrashort laser pulses. In the first part of this thesis, the focus is on the motion of electron holes in gas phase molecular ions created by extreme ultraviolet (XUV) photoionization and watched by spectroscopic approaches. The XUV photons create electron-hole in the valence orbitals of molecules by photoionization, the electron hole, as a positively charged quasi-particle, can then interact with the nuclei and the rest of electrons, leading to coupled non-Born-Oppenheimer dynamics. I present our study on electron-hole relaxation dynamics in valence ionized molecular ions of moderate size, using quantum wave packet and mixed quantum-classical approaches, using photoionized [H+(H2O)n]+ molecular ion as example. We have shown that the coupled motion of the electron-hole and the nuclei can be mapped out with femtosecond resolution by core-level x-ray transient absorption spectroscopy. Furthermore, in specific cases, the XUV photon can create a coherent electron hole, that can maintain its coherence to time scales of ∝ 1 picosecond. Employing XUV pump - IR probe spectroscopy

  1. Luminescence of nonlocalized electron-hole complexes in crystals

    International Nuclear Information System (INIS)

    The article deals with new spectral dependences of exciton molecules and other electron-hole formations in crystals with inversion center and big difference between effective masses of electrons and holes

  2. The origin of electron-hole asymmetry in graphite

    OpenAIRE

    Plochocka, P.; Solane, P. Y.; Nicholas, R. J.; Schneider, J. M.; Piot, B. A.; Maude, D. K.; Portugall, O.; Rikken, G.L.J.A.

    2011-01-01

    The electron hole asymmetry has been measured in natural graphite using magneto-optical absorption measurements. A splitting is observed for the transitions at both the $K$-point and the $H$-point of the Brillouin zone of graphite where the effect of trigonal warping vanishes. This result is fully consistent with the SWM Hamiltonian providing the free electron kinetic energy terms are taken into account. An identical electron-hole asymmetry should be present in graphene.

  3. 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.

  4. 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

  5. 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)

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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...

  11. 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...

  12. 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.

  13. Interaction between Electron Holes in a Strongly Magnetized Plasma

    DEFF Research Database (Denmark)

    Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans;

    1980-01-01

    The interaction between electron holes in a strongly magnetized, plasma-filled waveguide is investigated by means of computer simulation. Two holes may or may not coalesce, depending on their amplitudes and velocities. The interaction between holes and Trivelpiece-Gould solitons is demonstrated to...

  14. Entanglement discrimination in multi-rail electron-hole currents.

    Science.gov (United States)

    Baltanás, J P; Frustaglia, D

    2015-12-01

    We propose a quantum-Hall interferometer that integrates an electron-hole entangler with an analyzer working as an entanglement witness by implementing a multi-rail encoding. The witness has the ability to discriminate (and quantify) spatial-mode and occupancy entanglement. This represents a feasible alternative to limited approaches based on the violation of Bell-like inequalities. PMID:26569568

  15. Assembly and application of an instrument for attosecond-time-resolved ionization chronoscopy

    International Nuclear Information System (INIS)

    In the framework of this thesis a new setup for attosecond time-resolved measurements has been built and observations of ionization dynamics in rare gas atoms have been made. This new technique is entitled Ionization Chronoscopy and gives further evidence that time-resolved experiments in the attosecond regime will become a powerful tool for investigations in atomic physics. (orig.)

  16. 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

  17. Thermoelectric instability of electron-hole gas in semiconductors

    International Nuclear Information System (INIS)

    It is shown that thermoelectric instability is possible in a solid semiconductor in electron-hole gas by heating. The dissipation relaxation mechanism is capable of quenching the excitation. The anisotropy, corresponding to the high values of the gas characteristics in the direction concurrent with the heatup direction, facilitates the origination of cellular motion. The criteria of excitation and the cell dimensions ratios at the moment of its origination are defined. Possible experiments are considered and evaluations are carried out. 10 refs

  18. 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.

  19. 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)

  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. 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...

  2. 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.

  3. Electron Hole Plasma in Solids Induced by Ultrashort XUV Laser Pulses

    International Nuclear Information System (INIS)

    Irradiation of solids with ultrashort XUV laser pulses leads to an excitation of electrons from the valence band and deeper shells to the conduction band leading to a nonequilibrium highly energetic electron hole plasma. We investigate the transient electron dynamics in a solid semiconductor and metal (silicon and aluminum, respectively) under irradiation with a femtosecond VUV to XUV laser pulse as used in experiments with the Free Electron Laser FLASH at DESY in Hamburg, Germany. Applying the Asymptotical Trajectory Monte-Carlo technique, we obtain the transient energy distribution of the excited and ionized electrons within the solid. Photon absorption by electrons in different bands and secondary excitation and ionization processes are simulated event by event. The method was extended in order to take into account the electronic band structure and Pauli's principle for electrons in the conduction band. In this talk we review our results on the dynamics of the transient electron-hole plasma, in particular its transient density and energy distribution in dependence on laser and material parameters. For semiconductors we introduce the concept of an ''effective energy gap'' for collective electronic excitation, which can be applied to estimate the free electron density after high-intensity ultrashort XUV laser pulse irradiation. For aluminum we demonstrate that the electronic spectra depend on the relaxation kinetics of the excited electronic subsystem. Experimentally observed spectra of emitted photons from irradiated aluminum can be explained well with our results. (author)

  4. Attosecond streaking of photoelectron emission from disordered solids

    CERN Document Server

    Okell, W A; Fabris, D; Arrell, C A; Hengster, J; Ibrahimkutty, S; Seiler, A; Barthelmess, M; Stankov, S; Lei, D Y; Sonnefraud, Y; Rahmani, M; Uphues, Th; Maier, S A; Marangos, J P; Tisch, J W G

    2014-01-01

    Attosecond streaking of photoelectrons emitted by extreme ultraviolet light has begun to reveal how electrons behave during their transport within simple crystalline solids. Many sample types within nanoplasmonics, thin-film physics, and semiconductor physics, however, do not have a simple single crystal structure. The electron dynamics which underpin the optical response of plasmonic nanostructures and wide-bandgap semiconductors happen on an attosecond timescale. Measuring these dynamics using attosecond streaking will enable such systems to be specially tailored for applications in areas such as ultrafast opto-electronics. We show that streaking can be extended to this very general type of sample by presenting streaking measurements on an amorphous film of the wide-bandgap semiconductor tungsten trioxide, and on polycrystalline gold, a material that forms the basis of many nanoplasmonic devices. Our measurements reveal the near-field temporal structure at the sample surface, and photoelectron wavepacket te...

  5. 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.

  6. Introduction to attosecond delays in photoionization

    International Nuclear Information System (INIS)

    This tutorial presents an introduction to the interaction of light and matter on the attosecond timescale. Our aim is to detail the theoretical description of ultra-short time delays and to relate these to the phase of extreme ultraviolet (XUV) light pulses and to the asymptotic phaseshifts of photoelectron wave packets. Special emphasis is laid on time-delay experiments, where attosecond XUV pulses are used to photoionize target atoms at well-defined times, followed by a probing process in real time by a phase-locked, infrared laser field. In this way, the laser field serves as a ‘clock’ to monitor the ionization event, but the observable delays do not correspond directly to the delay associated with single-photon ionization. Instead, a significant part of the observed delay originates from a measurement induced process, which obscures the single-photon ionization dynamics. This artefact is traced back to a phaseshift of the above-threshold ionization transition matrix element, which we call the continuum-continuum phase. It arises due to the laser-stimulated transitions between Coulomb continuum states. As we shall show here, these measurement-induced effects can be separated from the single-photon ionization process, using analytical expressions of universal character, so that eventually the attosecond time delays in photoionization can be accessed.

  7. Radio Frequency Magnetic Field Effects on Electron-Hole Recombination

    International Nuclear Information System (INIS)

    We present measurements of the spectrum (1--80MHz) of the effect of a weak (∼500 μT ) radio frequency magnetic field on the electron-hole recombination of radical ion pairs in solution. Distinct spectra are observed for the pyrene anion/dimethylaniline cation radical pair in which one or both of the radicals are perdeuterated. The radical pair mechanism is developed theoretically and shown to account satisfactorily for both the magnetic field effect and the associated magnetic isotope effect

  8. Radio Frequency Magnetic Field Effects on Electron-Hole Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, J. R.; Timmel, C. R.; McLauchlan, K. A.; Hore, P. J.

    2001-08-13

    We present measurements of the spectrum (1--80MHz) of the effect of a weak ({approx}500 {mu}T ) radio frequency magnetic field on the electron-hole recombination of radical ion pairs in solution. Distinct spectra are observed for the pyrene anion/dimethylaniline cation radical pair in which one or both of the radicals are perdeuterated. The radical pair mechanism is developed theoretically and shown to account satisfactorily for both the magnetic field effect and the associated magnetic isotope effect.

  9. 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.

  10. 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

  11. Attosecond experiments on plasmonic nanostructures principles and experiments

    CERN Document Server

    Schötz, Johannes

    2016-01-01

    Johannes Schötz presents the first measurements of optical electro-magnetic near-fields around nanostructures with subcycle-resolution. The ability to measure and understand light-matter interactions on the nanoscale is an important component for the development of light-wave-electronics, the control and steering of electron dynamics with the frequency of light, which promises a speed-up by several orders of magnitude compared to conventional electronics. The experiments presented here on metallic nanotips, widely used in experiments and applications, do not only demonstrate the feasibility of attosecond streaking as a unique tool for fundamental studies of ultrafast nanophotonics but also represent a first important step towards this goal. Contents Electron Scattering in Solids Attosecond Streaking from Metal Nanotips Target Groups Lecturers and students of physics, especially in the area of nanophotonics and attosecond physics About the Author Johannes Schötz received his Master's degree in physics and cu...

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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

  17. Electron-hole asymmetry in two-terminal graphene devices

    Science.gov (United States)

    Hannes, W.-R.; Jonson, M.; Titov, M.

    2011-07-01

    A theoretical model is proposed to describe asymmetric gate-voltage dependence of conductance and noise in two-terminal ballistic graphene devices. The model is analyzed independently within the self-consistent Hartree and Thomas-Fermi approximations. Our results justify the prominent role of metal contacts in recent experiments with suspended graphene flakes. The contact-induced electrostatic potentials in graphene demonstrate a power-law decay, with the exponent varying from -1 to -0.5. Within our model we explain electron-hole asymmetry and strong Fabri-Perot oscillations of the conductance and noise with positive doping, which were observed in many experiments with submicrometer samples. Limitations of the Thomas-Fermi approximation in a vicinity of the Dirac point are discussed.

  18. 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.

  19. 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

  20. 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

  1. Many-particle correlations in quasi-two-dimensional electron-hole systems

    International Nuclear Information System (INIS)

    This thesis reports a theoretical investigation of many-particle correlation effects in semiconductor heterostructures containing quantum wells. Particular attention is paid towards quasi-particle pair correlations. Using the Green's function technique and the ladder approximation as a basis, the generalized mass action law, which describes the redistribution of particles between correlated and uncorrelated states in quasi-two-dimensional systems for different temperatures and total densities, is derived. The expression is valid beyond the low-density limit, which allows us to investigate the transition of the system from a dilute exciton gas to a dense electron-hole plasma. A generalized Levinson theorem, which takes k-space filling into account, is formulated. Screening in quasi-two-dimensional systems is analyzed rigorously. Firstly, the qualitatively new mechanism of static local screening by indirect excitons is studied using the simple Thomas-Fermi approximation. Then, a detailed many-body description suitable for a proper account of dynamic screening by a quasi-2D electron-hole plasma, and consistent with the previously derived mass action law, is provided. The generalized Lindhard approximation and excitonic plasmon-pole approximations are also derived. The theory is applied to single and double quantum wells. A self-consistent procedure is developed for numerical investigation of the ionization degree of an electron-hole plasma at different values of temperature/exciton Rydberg ratios. This procedure accounts for screening, k-space filling (exciton bleaching), and the formation of excitons. An abrupt jump in the value of the ionization degree that happens with an increase of the carrier density or temperature (Mott transition) is found in a certain density-temperature region. It has been found that the critical density of the Mott transition for indirect excitons may be much smaller than that for direct excitons. A suggestion has been made that some of the

  2. 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.

  3. 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.

  4. 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}.

  5. 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...

  6. Non-linear Plasma Wake Growth of Electron Holes

    CERN Document Server

    Hutchinson, I H; Zhou, C

    2015-01-01

    An object's wake in a plasma with small Debye length that drifts \\emph{across} the magnetic field is subject to electrostatic electron instabilities. Such situations include, for example, the moon in the solar wind wake and probes in magnetized laboratory plasmas. The instability drive mechanism can equivalently be considered drift down the potential-energy gradient or drift up the density-gradient. The gradients arise because the plasma wake has a region of depressed density and electrostatic potential into which ions are attracted along the field. The non-linear consequences of the instability are analysed in this paper. At physical ratios of electron to ion mass, neither linear nor quasilinear treatment can explain the observation of large-amplitude perturbations that disrupt the ion streams well before they become ion-ion unstable. We show here, however, that electron holes, once formed, continue to grow, driven by the drift mechanism, and if they remain in the wake may reach a maximum non-linearly stable...

  7. 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.

  8. 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.

  9. 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)

  10. 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.

  11. 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

  12. 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

  13. 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...

  14. Spectral Caustics in Attosecond Science

    Directory of Open Access Journals (Sweden)

    Dudovich N.

    2013-03-01

    Full Text Available A unique type of singularity common in wave phenomena, known as caustics, links processes observed in many different branches of physics [1]. We investigate the role of caustics in attosecond science and in particular the physical process behind high harmonic generation. By exploiting singularities of the three-step model that describes HHG, we can manipulate and enhance specific features in the emitted harmonic spectrum. This new level of control holds promises in both scientific and technological aspects of attosecond science, and provides a deeper insight into the basic mechanism underlying the high harmonic generation process.

  15. 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

  16. Molecular orbital imaging using attosecond pulses generated in N2

    International Nuclear Information System (INIS)

    a dynamical wavepacket serves as a test of feasibility for intra-molecular imaging with Angstroem spatial resolution and attosecond temporal resolution.

  17. 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

  18. 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.

  19. Anomalous Coulomb Drag in Electron-Hole Bilayers due to the Formation of Excitons

    Science.gov (United States)

    Efimkin, Dmitry K.; Galitski, Victor

    2016-01-01

    Several recent experiments have reported an anomalous temperature dependence of the Coulomb drag effect in electron-hole bilayers. Motivated by these puzzling data, we study theoretically a low-density electron-hole bilayer, where electrons and holes avoid quantum degeneracy by forming excitons. We describe the ionization-recombination crossover between the electron-hole plasma and exciton gas and calculate both the intralayer and drag resistivity as a function of temperature. The latter exhibits a minimum followed by a sharp upturn at low temperatures, in qualitative agreement with the experimental observations [see, e.g., J. A. Seamons et al., Phys. Rev. Lett. 102, 026804 (2009)]. Importantly, the drag resistivity in the proposed scenario is found to be rather insensitive to a mismatch in electron and hole concentrations, in sharp contrast to the scenario of electron-hole Cooper pairing.

  20. Ultrafast terahertz probes of transient conducting and insulating phases in an electron-hole gas

    Energy Technology Data Exchange (ETDEWEB)

    Kaindl, Robert A.; Carnahan, Marc A.; Hagele, Daniel; Lovenich, Reinhold; Chemla, Daniel S.

    2003-04-10

    Many-body systems in nature exhibit complexity and self-organization arising from seemingly simple laws. The long-range Coulomb interaction between electrical charges generates a plethora of bound states in matter, ranging from the hydrogen atom to complex biochemical structures. Semiconductors form an ideal laboratory for studying many-body interactions of quasi-particles among themselves and with lattice vibrations and light. Oppositely charged electron and hole quasi-particles can coexist in an ionized but correlated plasma, or form bound hydrogen-like pairs called excitons which strongly affect physical properties. The pathways between such states however remain elusive in near-visible optical experiments that detect a subset of excitons with vanishing center-of-mass momenta. In contrast, transitions between internal exciton levels which occur in the far-infrared at terahertz (10 s) frequencies are in dependent of this restriction suggesting their use as a novel pro be of pair dynamics. Here, we employ an ultrafast terahertz probe to directly investigate the dynamical interplay of optically-generated excitons and unbound electron-hole pairs in GaAs quantum wells. Our observations witness an unexpected quasi-instantaneous excitonic enhancement, reveal formation of insulating excitons on a hundred picosecond timescale and manifest conditions under which excitonic populations prevail.

  1. Probing scattering phase shifts by attosecond streaking

    OpenAIRE

    Pazourek, Renate; Nagele, Stefan; Doblhoff-Dier, Katharina; Feist, Johannes; Lemell, Christoph; Tökési, Karoly; Burgdörfer, Joachim

    2011-01-01

    Attosecond streaking is one of the most fundamental processes in attosecond science allowing for a mapping of temporal (i.e. phase) information on the energy domain. We show that on the single-particle level attosecond streaking time shifts contain spectral phase information associated with the Eisenbud-Wigner-Smith (EWS) time delay, provided the influence of the streaking infrared field is properly accounted for. While the streaking phase shifts for short-ranged potentials agree with the ass...

  2. Formation control of electron-hole droplets in diamond by a weak pulse injection

    Energy Technology Data Exchange (ETDEWEB)

    Omachi, J; Yoshioka, K; Kuwata-Gonokami, M [Department of Applied Physics, Graduate School of Engineering, University of Tokyo and CREST-JST, Tokyo 113-8656 (Japan); Naka, N, E-mail: gonokami@ap.t.u-tokyo.ac.j [Department of Physics, Kyoto University and PRESTO, JST, Kyoto 606-8502 (Japan)

    2009-02-01

    We demonstrate a formation control of electron-hole droplets (EHD) in diamond by a weak pulse injection. At high temperatures, we find a large enhancement of the luminescence signal from EHD. On the other hand, the enhancement decreases when we lower the temperature, indicating a decrease in the droplet size and the instability of EHD. In this region, electron-hole ensembles might form a new phase consisting of multi-excitonic clusters.

  3. 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.

  4. Modulating the Electron-Hole Interaction in a Hybrid Lead Halide Perovskite with an Electric Field.

    Science.gov (United States)

    Leijtens, Tomas; Srimath Kandada, Ajay Ram; Eperon, Giles E; Grancini, Giulia; D'Innocenzo, Valerio; Ball, James M; Stranks, Samuel D; Snaith, Henry J; Petrozza, Annamaria

    2015-12-16

    Despite rapid developments in both photovoltaic and light-emitting device performance, the understanding of the optoelectronic properties of hybrid lead halide perovskites is still incomplete. In particular, the polarizability of the material, the presence of molecular dipoles, and their influence on the dynamics of the photoexcitations remain an open issue to be clarified. Here, we investigate the effect of an applied external electric field on the photoexcited species of CH3NH3PbI3 thin films, both at room temperature and at low temperature, by monitoring the photoluminescence (PL) yield and PL decays. At room temperature we find evidence for electric-field-induced reduction of radiative bimolecular carrier recombination together with motion of charged defects that affects the nonradiative decay rate of the photoexcited species. At low temperature (190 K), we observe a field-induced enhancement of radiative free carrier recombination rates that lasts even after the removal of the field. We assign this to field-induced alignment of the molecular dipoles, which reduces the vibrational freedom of the lattice and the associated local screening and hence results in a stronger electron-hole interaction. PMID:26579724

  5. Nonlinear Electrostatic Instability and Electron Hole Growth in the Moon's Solar Wind Wake

    Science.gov (United States)

    Hutchinson, I. H.; Haakonsen, C. B.; Zhou, C.

    2015-11-01

    Velocity distribution function distortions and resulting instabilities arise in the interaction of unmagnetized bodies like the moon with the solar wind. To a good approximation the physics is dominated by cross-field drift (corresponding to the perpendicular-to-B wind speed relative to the moon) and free parallel electron and ion dynamics. Analytic calculations show that the electron velocity distribution in the wake becomes unstable because of a dimple formed by ``drift-deenergization'' analogous to the ``energization'' responsible for instability in the earth's bow shock. The much more extreme two-stream distortion of the ion distribution is stable until far downstream. However, high fidelity PIC calculations show that electron holes are spawned by the dimple, and while most accelerate out of the wake without growing much, a few remain at small speeds and grow eventually large enough to disrupt the ion distributions. The nonlinear hole growth mechanism is the same de-energization. It can be reinterpreted as drift into an increasing density region. We show how this growth can be understood analytically, and time permitting will discuss related phenomena concerning ion influence on hole speed and the forewake remnants of ``shadowing.'' Partially supported by the NSF/DOE Basic Plasma Science Partnership grant DE-SC0010491.

  6. 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)

  7. 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.

  8. Measurement and laser control of attosecond charge migration in ionized iodoacetylene.

    Science.gov (United States)

    Kraus, P M; Mignolet, B; Baykusheva, D; Rupenyan, A; Horný, L; Penka, E F; Grassi, G; Tolstikhin, O I; Schneider, J; Jensen, F; Madsen, L B; Bandrauk, A D; Remacle, F; Wörner, H J

    2015-11-13

    The ultrafast motion of electrons and holes after light-matter interaction is fundamental to a broad range of chemical and biophysical processes. We advanced high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately after ionization of iodoacetylene while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement and accurate theoretical description of both even and odd harmonic orders, enabled us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~100 attoseconds. We separately reconstructed quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determined the shape of the hole created by ionization. Our technique opens the prospect of laser control over electronic primary processes. PMID:26494175

  9. Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases

    Energy Technology Data Exchange (ETDEWEB)

    Kaindl, Robert A.; Hagele, D.; Carnahan, M. A.; Chemla, D. S.

    2008-09-11

    We report a comprehensive experimental study and detailed model analysis of the terahertz (THz) dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued THz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the THz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the THz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The THz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient THz spectroscopy of photoexcited quasi-2D electron-hole gases.

  10. 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...

  11. 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.

  12. Yield, variance and spatial distribution of electron-hole pairs in CsI

    Energy Technology Data Exchange (ETDEWEB)

    Gao, F., E-mail: fei.gao@pnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Xie, Y.; Kerisit, S.; Campbell, L.W. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Weber, W.J. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2011-10-01

    A Monte Carlo (MC) method previously developed has been applied to simulate the interaction of photons, with energies ranging from 50 eV to {approx}1 MeV, with CsI and the subsequent electron cascades. The MC model has been employed to compute nano-scale spatial distributions of electron-hole pairs and important intrinsic properties, including W, the mean energy per electron-hole pair, and the Fano factor, F. W exhibits discontinuities at the shell edges that follow the photoionization cross-sections and decreases with increase in photon energy (from {approx}19 to 15 eV), with an asymptotic value of 15.2 eV at high energy. This decrease may contribute to the initial rise in relative light yield with incident energy observed experimentally for CsI, thus suggesting that nonlinearity may be associated with intrinsic properties of the material at low energies. F is calculated to increase with increase in energy and has an asymptotic value of 0.28. A significant number of electron-hole pairs is produced through the different ionization channels of core shells and the corresponding relaxation processes, which may explain why F is larger for CsI than for Si or Ge. Finally, the calculated spatial distributions show that the electron-hole pairs are primarily distributed along fast electron tracks. These spatial distributions constitute important input for large-scale simulations of electron-hole pair transport.

  13. Yield, variance and spatial distribution of electron-hole pairs in CsI

    International Nuclear Information System (INIS)

    A Monte Carlo (MC) method previously developed has been applied to simulate the interaction of photons, with energies ranging from 50 eV to ∼1 MeV, with CsI and the subsequent electron cascades. The MC model has been employed to compute nano-scale spatial distributions of electron-hole pairs and important intrinsic properties, including W, the mean energy per electron-hole pair, and the Fano factor, F. W exhibits discontinuities at the shell edges that follow the photoionization cross-sections and decreases with increase in photon energy (from ∼19 to 15 eV), with an asymptotic value of 15.2 eV at high energy. This decrease may contribute to the initial rise in relative light yield with incident energy observed experimentally for CsI, thus suggesting that nonlinearity may be associated with intrinsic properties of the material at low energies. F is calculated to increase with increase in energy and has an asymptotic value of 0.28. A significant number of electron-hole pairs is produced through the different ionization channels of core shells and the corresponding relaxation processes, which may explain why F is larger for CsI than for Si or Ge. Finally, the calculated spatial distributions show that the electron-hole pairs are primarily distributed along fast electron tracks. These spatial distributions constitute important input for large-scale simulations of electron-hole pair transport.

  14. 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.

  15. Transient evolution of solitary electron holes in low pressure laboratory plasma

    CERN Document Server

    Choudhary, Mangilal; Mukherjee, Subroto

    2015-01-01

    Solitary electrons holes (SEHs) are localized electrostatic positive potential structures in collisionless plasmas. These are vortex-like structures in the electron phase space. Its existence is cause of distortion of the electron distribution in the resonant region. These are explained theoretically first time by Schamel et.al [Phys. Scr. 20, 336 (1979) and Phys. Plasmas 19, 020501 (2012)]. Propagating solitary electron holes can also be formed in a laboratory plasma when a fast rising high positive voltage pulse is applied to a metallic electrode [Kar et. al., Phys. Plasmas 17, 102113 (2010)] immersed in a low pressure plasma. The temporal evolution of these structures can be studied by measuring the transient electron distribution function (EDF). In the present work, transient EDF is measured after formation of a solitary electron hole in nearly uniform, unmagnetized, and collisionless plasma for applied pulse width and, where and are applied pulse width and inverse of ion plasma frequency respectively. Fo...

  16. Modulational instability of electrostatic acoustic waves in an electron-hole semiconductor quantum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yunliang, E-mail: ylwang@ustb.edu.cn; Lü, Xiaoxia [Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-02-15

    The modulational instability of quantum electrostatic acoustic waves in electron-hole quantum semiconductor plasmas is investigated using the quantum hydrodynamic model, from which a modified nonlinear Schrödinger equation with damping effects is derived using the reductive perturbation method. Here, we consider the combined effects of quantum recoil, quantum degenerate pressures, as well as the exchange-correlation effect standing for the electrons (holes) spin. The modulational instability for different semiconductors (GaAs, GaSb, and InP) is discussed. The collision between electron (hole) and phonon is also investigated. The permitted maximum time for modulational instability and the damping features of quantum envelope solitary wave are all determined by the collision. The approximate solitary solution with damping effects is presented in weak collision limit. The damping properties were discussed by numerical method.

  17. Modulational instability of electrostatic acoustic waves in an electron-hole semiconductor quantum plasma

    International Nuclear Information System (INIS)

    The modulational instability of quantum electrostatic acoustic waves in electron-hole quantum semiconductor plasmas is investigated using the quantum hydrodynamic model, from which a modified nonlinear Schrödinger equation with damping effects is derived using the reductive perturbation method. Here, we consider the combined effects of quantum recoil, quantum degenerate pressures, as well as the exchange-correlation effect standing for the electrons (holes) spin. The modulational instability for different semiconductors (GaAs, GaSb, and InP) is discussed. The collision between electron (hole) and phonon is also investigated. The permitted maximum time for modulational instability and the damping features of quantum envelope solitary wave are all determined by the collision. The approximate solitary solution with damping effects is presented in weak collision limit. The damping properties were discussed by numerical method

  18. Crossover between the dense electron-hole phase and the BCS excitonic phase in quantum dots

    International Nuclear Information System (INIS)

    Second order perturbation theory and a Lipkin-Nogami scheme combined with an exact Monte Carlo projection after variation are applied to compute the ground-state energy of 6 ≤ N ≤ 210 electron-hole pairs confined in a parabolic two-dimensional quantum dot. The energy shows nice scaling properties as N or the confinement strength is varied. A crossover from the high-density electron-hole phase to the BCS excitonic phase is found at a density which is roughly four times the close-packing density of excitons. (author)

  19. Crossover between the Dense Electron-Hole Phase and the BCS Excitonic Phase in Quantum Dots

    OpenAIRE

    Rodriguez, Boris A.; Gonzalez, Augusto; Quiroga, Luis; Capote, Roberto; Rodriguez, Ferney

    1998-01-01

    Second order perturbation theory and a Lipkin-Nogami scheme combined with an exact Monte Carlo projection after variation are applied to compute the ground-state energy of $6\\le N\\le 210$ electron-hole pairs confined in a parabolic two-dimensional quantum dot. The energy shows nice scaling properties as N or the confinement strength is varied. A crossover from the high-density electron-hole phase to the BCS excitonic phase is found at a density which is roughly four times the close-packing de...

  20. 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

  1. 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.

  2. Quantum interference in attosecond transient absorption of laser-dressed helium atoms

    CERN Document Server

    Chen, Shaohao; Gaarde, Mette B; Schafer, Kenneth J

    2013-01-01

    We calculate the transient absorption of an isolated attosecond pulse by helium atoms subject to a delayed infrared (\\ir) laser pulse. With the central frequency of the broad attosecond spectrum near the ionization threshold, the absorption spectrum is strongly modulated at the sub-\\ir-cycle level. Given that the absorption spectrum results from a time-integrated measurement, we investigate the extent to which the delay-dependence of the absorption yields information about the attosecond dynamics of the atom-field energy exchange. We find two configurations in which this is possible. The first involves multi photon transitions between bound states that result in interference between different excitation pathways. The other involves the modification of the bound state absorption lines by the IR field, which we find can result in a sub-cycle time dependence only when ionization limits the duration of the strong field interaction.

  3. 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....

  4. 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.

  5. 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.

  6. 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.

  7. 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...

  8. 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

  9. Ballistic phonon emission from electron-hole droplets: Application to the nuclear recoil problem

    International Nuclear Information System (INIS)

    The production of phonons after photoexcitation of Si is greatly influenced by electron-hole droplets. At moderate excitation densities droplets are formed and the process of quasidiffusion is bypassed by emission of ballistic phonons from droplets. The authors review these ideas and discuss the possibility of droplet formation in the course of plasma cooling which follows the ionization process of a nuclear recoil

  10. Large gap electron-hole superfluidity and shape resonances in coupled graphene nanoribbons

    Science.gov (United States)

    Zarenia, M.; Perali, A.; Peeters, F. M.; Neilson, D.

    2016-01-01

    We predict enhanced electron-hole superfluidity in two coupled electron-hole armchair-edge terminated graphene nanoribbons separated by a thin insulating barrier. In contrast to graphene monolayers, the multiple subbands of the nanoribbons are parabolic at low energy with a gap between the conduction and valence bands, and with lifted valley degeneracy. These properties make screening of the electron-hole interaction much weaker than for coupled electron-hole monolayers, thus boosting the pairing strength and enhancing the superfluid properties. The pairing strength is further boosted by the quasi one-dimensional quantum confinement of the carriers, as well as by the large density of states near the bottom of each subband. The latter magnifies superfluid shape resonances caused by the quantum confinement. Several superfluid partial condensates are present for finite-width nanoribbons with multiple subbands. We find that superfluidity is predominately in the strongly-coupled BEC and BCS-BEC crossover regimes, with large superfluid gaps up to 100 meV and beyond. When the gaps exceed the subband spacing, there is significant mixing of the subbands, a rounding of the shape resonances, and a resulting reduction in the one-dimensional nature of the system. PMID:27108968

  11. 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

  12. 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.

  13. 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

  14. Attosecond control of optical waveforms

    International Nuclear Information System (INIS)

    A new, monolithic scheme for stabilizing the phase between the carrier wave and the envelope (CE phase) in a train of few-cycle laser pulses is demonstrated. Self-phase modulation and second-harmonic generation or difference-frequency generation in a single periodically poled lithium niobate crystal, that transmits the main laser beam, allows for the CE-phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE-phase control, coupling into microstructured fibre, as well as separation and recombination of spectral components. As a result, the CE-phase error integrated over the spectral range of 0.2 mHz-35 MHz is as small as 0.016 x 2π rad. This implies that the phase of the field oscillations (λ ∼ 830 nm) with respect to the pulse peak is locked to within 44 attoseconds, resulting in optical waveform control with subhundred attosecond fidelity for the first time

  15. 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}_...

  16. 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.

  17. Far infrared spectroscopy of solids. I. Impurity states in Al2O3. II. Electron-hole droplets in Ge

    International Nuclear Information System (INIS)

    Far infrared Fourier transform spectroscopy was used to study the low lying vibronic states of Mn3+ in Al2O3 and the plasma absorption of electron-hole droplets in Ge. The transmission of Mn-doped samples of Al2O3 was measured in the frequency range from 3 to 30 cm-1 in applied magnetic fields up to 50 kG. Absorption lines were observed due to both ground and excited state transitions. Polarization measurements established that these absorption lines were due to electric dipole transitions. Temperature dependence measurements were used to derive a level diagram for the low lying states of Mn3+. A phenomenological model based on an electronic Hamiltonian was developed which successfully describes the data. The empirically determined trigonal field and spin-orbit quenching parameters of this model are 0.7 and 0.1 respectively. This quenching is attributed to the dynamic Jahn--Teller interaction. The plasma absorption of small (α) electron-hole drops in Ge was measured in the frequency range from 30 to 300 cm-1. The observed absorption is in good agreement with measurements by Vavilov and other workers. A theoretical model which includes both intraband and interband contributions to the dielectric constant in the Rayleigh limit of Mie theory is used to describe the observed lineshape. Measurements of plasma absorption of large (γ) drops in inhomogeneously stressed Ge were made in magnetic fields up to 50 kG. The lineshape at zero applied field was calculated in the large sphere limit of Mie theory including intraband terms and a zero-strain interband term. Qualitative agreement with experiment was obtained. The peak absorption shifted quadratically with applied magnetic field and the total plasma absorption increased. No oscillatory structure was observed in the field-dependence of the total absorption

  18. 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.

  19. 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.

  20. An ultrafast terahertz probe of the transient evolution of the charged and neutral phase of photo-excited electron-hole gas in a monolayer semiconductor

    Science.gov (United States)

    Liu, Xuefeng; Yu, Hongyi; Ji, Qingqing; Gao, Zhihan; Ge, Shaofeng; Qiu, Jun; Liu, Zhongfan; Zhang, Yanfeng; Sun, Dong

    2016-03-01

    We investigate the dynamical formation of an exciton from photo-excited electron-hole plasma and its subsequent decay dynamics in monolayer MoS2 grown by chemical vapor deposition (CVD) using ultrafast pump and terahertz probe spectroscopy. Different photo-excited electron-hole states are resolved based on their distinct responses to THz photon and decay lifetimes. The observed transient THz transmission can be fitted with two decay components: a fast component with a decay lifetime of 20 ps, which is attributed to the exciton lifetime, including its formation and subsequent intra-exciton relaxation; a slow component with an extremely long decay lifetime of several ns, possibly due to a long-lived dark exciton state. The relaxation dynamics are further supported by temperature and pump-fluence-dependent studies of the decay time constants. The sign of the transient THz observed in this experiment is the opposite of that measured in a recent parallel transient THz work on MoS2 [1]. The observed decay dynamics are also different, and the possible reasons for these discrepancies are discussed.

  1. Superconductivity of electron-hole pairs in a bilayer graphene system in a quantizing magnetic field

    Science.gov (United States)

    Fil', D. V.; Kravchenko, L. Yu.

    2009-08-01

    A state with spontaneous interlayer phase coherence in a bilayer quantum Hall system based on graphene is studied. This state can be regarded as a gas of superfluid electron-hole pairs whose components belong to different layers. A superfluid flow of such pairs is equivalent to two electric supercurrents in the layers. It is shown that in a graphene system a state with interlayer phase coherence arises if a definite unbalance of the filling factors of the Landau levels in neighboring layers is created. The temperature of the transition into a superfluid state, the maximum interlayer distance for which phase coherence is possible, and the critical values of the supercurrent are found. The advantages of using graphene systems instead of GaAs heterostructures to realize bilayer electron-hole superconductivity are discussed.

  2. Reversible electron-hole separation in a hot carrier solar cell

    OpenAIRE

    Limpert, Steven; Bremner, Stephen; Linke, Heiner

    2015-01-01

    Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the ...

  3. Observation and characterization of laser-driven Phase Space Electron Holes

    OpenAIRE

    Sarri, Gianluca; Dieckmann, Mark Eric; Brown, C. R. D.; Cecchetti, Carlo; Hoarty, D.J.; James, S.F.; Jung, R.; Kourakis, Ioannis; Schamel, H.; Willi, O.; Borghesi, Marco

    2010-01-01

    The direct observation and full characterization of a phase space electron hole (EH) generated during laser-matter interaction is presented. This structure, propagating in a tenuous, nonmagnetized plasma, has been detected via proton radiography during the irradiation with a ns laser pulse (I?2 ˜ 1014 W/cm2) of a gold hohlraum. This technique has allowed the simultaneous detection of propagation velocity, potential, and electron density spatial profile across the EH with fine spatial and temp...

  4. Superconductivity of electron-hole pairs in a bilayer graphene system in a quantizing magnetic field

    OpenAIRE

    Fil, D. V.; Kravchenko, L. Yu.

    2009-01-01

    The state with a spontaneous interlayer phase coherence in a graphene based bilayer quantum Hall system is studied. This state can be considered as a gas of superfluid electron-hole pairs with the components of the pair belonging to different layers. Superfluid flux of such pairs is equivalent to two electrical supercurrents in the layers. It is shown that the state with the interlayer phase coherence emerges in the graphene system if a certain imbalance of the Landau level filling factors of...

  5. Auto-solitons in electron-hole plasma/exciton system in silicon at 4.2 K

    International Nuclear Information System (INIS)

    Results of an experimental discovery and investigation of auto-oscillation for electron-hole plasma/excitons system in the Si at impact ionization of excitons in direct electric field are presented. It is shown that current auto-oscillations occur due to the destruction of homogeneous distribution of the electron-hole plasma density and the electron--hole plasma stratification caused by formation of strong nonequilibrium state of - auto-solitons. The microplasma breakdown of an inversely displaced Schottky barrier is the cause for the spontaneous excitation of auto-solitons

  6. Simulating gamma-ray energy resolution in scintillators due to electron-hole pair statistics

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, R.D., E-mail: rdnarayan@gmail.com [Arizona State University, Department of Physics, P.O. Box 871504, Tempe, AZ 85287-1504 (United States); Miranda, R., E-mail: ryan.miranda@asu.edu [Arizona State University, Department of Physics, P.O. Box 871504, Tempe, AZ 85287-1504 (United States); Rez, P., E-mail: peter.rez@asu.edu [Arizona State University, Department of Physics, P.O. Box 871504, Tempe, AZ 85287-1504 (United States)

    2011-11-15

    The best-possible limit to gamma-ray energy resolution in scintillators is given by the statistics of the number of electron-hole pairs produced by an incident gamma-ray, characterized by the Fano factor. The Fano factor is primarily controlled by the inelastic scattering during the electron cascade, which could be modeled by Monte Carlo simulation. Commonly used radiation transport codes do not follow the electrons to low enough energies to calculate electron-hole pair distributions. A Monte Carlo simulation for inelastic electron scattering is introduced based on cross-sections derived from data measured by Electron Energy-Loss Spectroscopy (EELS) for fast electrons. This inelastic scattering model was incorporated into the radiation transport code Penelope so that it could accurately count the number of electron-hole pairs produced by a gamma-ray. The Fano factor was calculated for the scintillators cerium fluoride (CeF{sub 3}) and lutetium oxyorthosilicate (Lu{sub 2}SiO{sub 5}).

  7. Simulating gamma-ray energy resolution in scintillators due to electron-hole pair statistics

    International Nuclear Information System (INIS)

    The best-possible limit to gamma-ray energy resolution in scintillators is given by the statistics of the number of electron-hole pairs produced by an incident gamma-ray, characterized by the Fano factor. The Fano factor is primarily controlled by the inelastic scattering during the electron cascade, which could be modeled by Monte Carlo simulation. Commonly used radiation transport codes do not follow the electrons to low enough energies to calculate electron-hole pair distributions. A Monte Carlo simulation for inelastic electron scattering is introduced based on cross-sections derived from data measured by Electron Energy-Loss Spectroscopy (EELS) for fast electrons. This inelastic scattering model was incorporated into the radiation transport code Penelope so that it could accurately count the number of electron-hole pairs produced by a gamma-ray. The Fano factor was calculated for the scintillators cerium fluoride (CeF3) and lutetium oxyorthosilicate (Lu2SiO5).

  8. Coherent electron - hole state and femtosecond cooperative emission in bulk GaAs

    International Nuclear Information System (INIS)

    The conditions for obtaining a collective coherent electron - hole state in semiconductors are discussed. The results of the experimental study of the regime of cooperative recombination of high-density electrons and holes (more than 3 x 1018 cm-3) in bulk GaAs at room temperature are presented. It is shown that the collective pairing of electrons and holes and their condensation cause the formation of a short-living coherent electron - hole BCS-like state, which exhibits radiative recombination in the form of high-power femtosecond optical pulses. It is experimentally demonstrated that almost all of the electrons and holes available are condensed at the very bottoms of the bands and are at the cooperative state. The average lifetime of this state is measured to be of about 300 fs. The dependences of the order parameter (the energy gap of the spectrum of electrons and holes) and the Fermi energy of the coherent BCS state on the electron - hole concentration are obtained. (special issue devoted to the 80th anniversary of academician n g basov's birth)

  9. Electron-cylotron maser radiation from electron holes: downward current region

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2012-01-01

    Full Text Available The electron-cyclotron maser emission theory from electron holes is applied to holes generated in the downward current region of the aurora. It is argued that the main background auroral kilometric radiation source may still be located in the upward current region electron-ring (horseshoe distribution while the fine structure is caused by electron holes predominantly in the downward current region. There the existence of electron holes is well established and electron densities are high enough for substantial maser growth rates. Trapping of radiation by the holes provides strong amplification. Upward motion of holes favours the escape of radiation both, from the holes and from the downward current region, into the upward current region. Since upward and downward current regions always exist simultaneously, they are acting in tandem in generating auroral kilometric radiation and its fine structure by the same mechanism though in different ways. This mechanism solves the long-standing problem of auroral kilometric radiation fine structure.

  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. Characterization of the size and position of electron-hole puddles at a graphene p-n junction

    Science.gov (United States)

    Milovanović, S. P.; Peeters, F. M.

    2016-03-01

    The effect of an electron-hole puddle on the electrical transport when governed by snake states in a bipolar graphene structure is investigated. Using numerical simulations we show that information on the size and position of the electron-hole puddle can be obtained using the dependence of the conductance on magnetic field and electron density of the gated region. The presence of the scatterer disrupts snake state transport which alters the conduction pattern. We obtain a simple analytical formula that connects the position of the electron-hole puddle with features observed in the conductance. The size of the electron-hole puddle is estimated from the magnetic field and gate potential that maximizes the effect of the puddle on the electrical transport.

  12. 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.

  13. 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.

  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. 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

  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. 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.

  18. Probing scattering phase shifts by attosecond streaking

    International Nuclear Information System (INIS)

    Attosecond streaking is one of the most fundamental processes in attosecond science allowing for a mapping of temporal (i.e. phase) information on the energy domain. We show that on the single-particle level attosecond streaking time shifts contain spectral phase information associated with the Eisenbud-Wigner-Smith (EWS) time delay, provided the infuence of the streaking infrared feld is properly accounted for. While the streaking phase shifts for short-ranged potentials agree with the associated EWS delays, Coulomb potentials require special care. We show that the interaction between the outgoing electron and the combined Coulomb and IR laser felds lead to a streaking phase shift that can be described classically.

  19. Probing scattering phase shifts by attosecond streaking

    CERN Document Server

    Pazourek, Renate; Doblhoff-Dier, Katharina; Feist, Johannes; Lemell, Christoph; Tökési, Karoly; Burgdörfer, Joachim

    2011-01-01

    Attosecond streaking is one of the most fundamental processes in attosecond science allowing for a mapping of temporal (i.e. phase) information on the energy domain. We show that on the single-particle level attosecond streaking time shifts contain spectral phase information associated with the Eisenbud-Wigner-Smith (EWS) time delay, provided the influence of the streaking infrared field is properly accounted for. While the streaking phase shifts for short-ranged potentials agree with the associated EWS delays, Coulomb potentials require special care. We show that the interaction between the outgoing electron and the combined Coulomb and IR laser fields lead to a streaking phase shift that can be described classically.

  20. Chlorine doping reduces electron-hole recombination in lead iodide perovskites: time-domain ab initio analysis.

    Science.gov (United States)

    Liu, Jin; Prezhdo, Oleg V

    2015-11-19

    Rapid development in lead halide perovskites has led to solution-processable thin film solar cells with power conversion efficiencies close to 20%. Nonradiative electron-hole recombination within perovskites has been identified as the main pathway of energy losses, competing with charge transport and limiting the efficiency. Using nonadiabatic (NA) molecular dynamics, combined with time-domain density functional theory, we show that nonradiative recombination happens faster than radiative recombination and long-range charge transfer to an acceptor material. Doping of lead iodide perovskites with chlorine atoms reduces charge recombination. On the one hand, chlorines decrease the NA coupling because they contribute little to the wave functions of the valence and conduction band edges. On the other hand, chlorines shorten coherence time because they are lighter than iodines and introduce high-frequency modes. Both factors favor longer excited-state lifetimes. The simulation shows good agreement with the available experimental data and contributes to the comprehensive understanding of electronic and vibrational dynamics in perovskites. The generated insights into design of higher-efficiency solar cells range from fundamental scientific principles, such as the role of electron-vibrational coupling and quantum coherence, to practical guidelines, such as specific suggestions for chemical doping. PMID:26505613

  1. 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.

  2. 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

  3. Attosecond nanoscale near-field sampling

    CERN Document Server

    Förg, Benjamin; Suessmann, Frederik; Foerster, Michael; Krueger, Michael; Ahn, Byung-Nam; Wintersperger, Karen; Zherebtsov, Sergey; Guggenmos, Alexander; Pervak, Vladimir; Kessel, Alexander; Trushin, Sergei; Azzeer, Abdallah; Stockman, Mark; Kim, Dong-Eon; Krausz, Ferenc; Hommelhoff, Peter; Kling, Matthias

    2015-01-01

    The promise of ultrafast light field driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical nearfields from light interaction with nanostructures with sub cycle resolution. Here, we experimentally demonstrate attosecond nearfield retrieval with a gold nanotip using streaking spectroscopy. By comparison of the results from gold nanotips to those obtained for a noble gas, the spectral response of the nanotip near field arising from laser excitation can be extracted. Monte Carlo MC trajectory simulations in near fields obtained with the macroscopic Maxwells equations elucidate the streaking mechanism on the nanoscale.

  4. 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.

  5. 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.

  6. 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

  7. The birth of attosecond physics and its coming of age

    Science.gov (United States)

    Krausz, Ferenc

    2016-06-01

    Classical electromagnetism allows the rapidity of light field oscillations to be inferred from measurement of the speed and wavelength of light. Quantum mechanics connects the rapidity of electronic motion with the energy spacing of the occupied quantum states, accessible by light absorption and emission. According to these indirect measurements, both dynamics, the oscillation of light waves as well as electron wavepackets, evolve within attoseconds. With the birth of attosecond metrology at the dawn of the new millennium, light waving and atomic-scale electronic motion, being mutually the cause of each other, became directly measurable. These elementary motions constitute the primary steps of any change in the physical, chemical, and biological properties of materials and living organisms. The capability of observing them is therefore relevant for the development of new materials and technologies, as well as understanding biological function and malfunction. Here, I look back at milestones along the rocky path to the emergence of this capability, with some details about those my group had the chance to make some contributions to. This is an attempt to show—from a personal perspective—how revolution in science or technology now relies on progress at a multitude of fronts, which—in turn—depend on the collaboration of researchers from disparate fields just as on their perseverance.

  8. 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...

  9. Light-matter interaction on the attosecond timescale

    CERN Document Server

    Dahlström, J M; Maquet, A

    2012-01-01

    This tutorial presents an introduction to the interaction of light and matter on the attosecond timescale. Our aim is to detail the theoretical description of ultra-short time-delays, and to relate these to the phase of extreme ultraviolet (XUV) light pulses and to the asymptotic phase-shifts of photoelectron wave packets. Special emphasis is laid on time-delay experiments, where attosecond XUV pulses are used to photoionize target atoms at well-defined times, followed by a probing process in real time by a phase-locked, infrared laser field. In this way, the laser field serves as a "clock" to monitor the ionization event, but the observable delays do not correspond directly to the delay associated with single-photon ionization. Instead, a significant part of the observed delay originates from a measurement induced process, which obscures the single-photon ionization dynamics. This artifact is traced back to a phase-shift of the above-threshold ionization transition matrix element, which we call the continuum...

  10. 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...

  11. Interband optical spectra of magnetoexcitons in semiconductor nanorings: Electron-hole spatial correlation

    Science.gov (United States)

    Citrin, D. S.; Maslov, A. V.

    2005-08-01

    An analytic model [R. A. Römer and M. E. Raikh, Phys. Rev. B 62, 7045 (2000); K. Moulopoulos and M. Constantinou, Phys. Rev. B 70, 235327 (2004)] for magnetoexcitons in nanoscale semiconductor rings is extended to calculate directly the linear optical properties. The spectroscopic properties exhibit pronounced Φ0=hc/e excitonic Aharonov-Bohm oscillations in the threading magnetic flux Φ when the ring radius R is less than the effective exciton Bohr radius a0 . The electron-hole spatial correlation induced by an optical field as a function of nanoring radius and threading magnetic flux is studied.

  12. 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.

  13. 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.

  14. Terahertz spectroscopy of two-dimensional electron-hole pairs: probing Mott physics of magneto-excitons

    Science.gov (United States)

    Zhang, Qi; Gao, Weilu; Watson, John; Manfra, Michael; Kono, Junichiro

    2015-03-01

    Density-dependent Coulomb interactions can drive electron-hole (e - h) pairs in semiconductors through an excitonic Mott transition from an excitonic gas into an e - h plasma. Theoretical studies suggest that these interactions can be strongly modified by an external magnetic field, including the absence of inter-exciton interactions in the high magnetic field limit in two dimensions, due to an e - h charge symmetry, which results in ultrastable magneto-excitons. Here, we present a systematic experimental study of e - h pairs in photo-excited undoped GaAs quantum wells in magnetic fields with ultrafast terahertz spectroscopy. We simultaneously monitored the dynamics of the intraexcitonic 1 s-2 p transition (which splits into 1 s-2p+ and 1 s-2p- transitions in a magnetic field) and the cyclotron resonance of unbound electrons and holes up to 10 Tesla. We found that the 1 s-2p- absorption feature is robust at high magnetic fields even under high excitation fluences, indicating magnetically enhanced stability of excitons. We will discuss the Mott physics of magneto-excitons as a function of temperature, e - h pair density, optical pump delay time, as well as magnetic field, and also compare two-dimensional excitons in GaAs quantum wells with three-dimensional excitons in bulk GaAs.

  15. Tuning of Near- and Far-Field Properties of All-dielectric Dimer Nanoantennas via Ultrafast Electron-Hole Plasma Photoexcitation

    CERN Document Server

    Baranov, Denis G; Krasnok, Alexander E; Belov, Pavel A; Alu, Andrea

    2016-01-01

    Achievement of all-optical ultrafast signal modulation and routing by a low-loss nanodevice is a crucial step towards an ultracompact optical chip with high performance. Here, we propose a specifically designed silicon dimer nanoantenna, which is tunable via photoexcitation of dense electron-hole plasma with ultrafast relaxation rate. Basing on this concept, we demonstrate the effect of beam steering up to 20 degrees via simple variation of incident intensity, being suitable for ultrafast light routing in an optical chip. The effect is demonstrated both in the visible and near-IR spectral regions for silicon and germanium based nanoantennas. We also reveal the effect of electron-hole plasma photoexcitation on local density of states (LDOS) in the dimer gap and find that the orientation averaged LDOS can be altered by 50\\%, whereas modification of the projected LDOS can be even more dramatic: almost 500\\% for transverse dipole orientation. Moreover, our analytical model sheds light on transient dynamics of the...

  16. Electron-hole asymmetry in high-Tc cuprates from theoretical viewpoints

    Directory of Open Access Journals (Sweden)

    T. Tohyama

    2006-09-01

    Full Text Available   Asymmetric features of various physical quantities in the normal and superconducting states between hole- and electron-doped cuprate high-temperature superconductors have been an issue of debate for a long time. Their exploration is very important for the understanding not only of the mechanism of high-Tc superconductivity but also of the nature of doped-Mott insulators. Presented in this review is the present status of theoretical understanding of the electronic states in hole- and electron-doped high- Tc cuprates as well as the origin of the electron-hole asymmetry of the electronic states. In particular, it is shown that numerically exact diagonalization calculations for small clusters in a t-J model with long-range hoppings, t and t nicely reproduce the electron-hole asymmetry observed experimentally in various quantities and thus make it possible to extract the physical origin of the asymmetry. These results give a deep insight on the asymmetric behaviors in hole- and electron-doped high-Tc cuprates and on the nature of doped Mott insulators.

  17. Interaction effects on the tunneling of electron-hole pairs in coupled quantum dots

    Science.gov (United States)

    Guerrero, Hector M.; Cocoletzi, Gregorio H.; Ulloa, Sergio E.

    2001-03-01

    The transit time of carriers is beginning to be an important parameter in the physical operation of semiconductor quantum dot `devices'. In the present work, we study the coherent propagation of electron-hole pairs in coupled self-assembled quantum dots in close proximity. These systems, achieved experimentally in a number of different geometries, have been recently implemented as a novel storage of optical information that may give rise to smart pixel technology in the near future [1]. Here, we apply an effective mass hamiltonian approach and solve numerically the time dependent Schroedinger equation of a system of photo-created electron-hole pairs in the dots. Our approach takes into account both Coulomb interactions and confinement effects. The time evolution is investigated in terms of the structural parameters for typical InAs-GaAs dots. Different initial conditions are considered, reflecting the basic processes that would take place in these experiments. We study the probabilities of finding the electron and hole in either the same or adjacent quantum dot, and study carefully the role of interactions in this behavior. [1] T. Lundstrom, W. Schoenfeld, H. Lee, and P. M. Petroff, Science 286, 2312 (1999).

  18. 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).

  19. Unravelling the Effects of Grain Boundary and Chemical Doping on Electron-Hole Recombination in CH3NH3PbI3 Perovskite by Time-Domain Atomistic Simulation.

    Science.gov (United States)

    Long, Run; Liu, Jin; Prezhdo, Oleg V

    2016-03-23

    Advancing organohalide perovskite solar cells requires understanding of carrier dynamics. Electron-hole recombination is a particularly important process because it constitutes a major pathway of energy and current losses. Grain boundaries (GBs) are common in methylammonium lead iodine CH3NH3PbI3 (MAPbI3) perovskite polycrystalline films. First-principles calculations have suggested that GBs have little effect on the recombination; however, experiments defy this prediction. Using nonadiabatic (NA) molecular dynamics combined with time-domain density functional theory, we show that GBs notably accelerate the electron-hole recombination in MAPbI3. First, GBs enhance the electron-phonon NA coupling by localizing and contributing to the electron and hole wave functions and by creating additional phonon modes that couple to the electronic degrees of freedom. Second, GBs decrease the MAPbI3 bandgap, reducing the number of vibrational quanta needed to accommodate the electronic energy loss. Third, the phonon-induced loss of electronic coherence remains largely unchanged and not accelerated, as one may expect from increased electron-phonon coupling. Further, replacing iodines by chlorines at GBs reduces the electron-hole recombination. By pushing the highest occupied molecular orbital (HOMO) density away from the boundary, chlorines restore the NA coupling close to the value observed in pristine MAPbI3. By introducing higher-frequency phonons and increasing fluctuation of the electronic gap, chlorines shorten electronic coherence. Both factors compete successfully with the reduced bandgap relative to pristine MAPbI3 and favor long excited-state lifetimes. The simulations show excellent agreement with experiment and characterize how GBs and chlorine dopants affect electron-hole recombination in perovskite solar cells. The simulations suggest a route to increased photon-to-electron conversion efficiencies through rational GB passivation. PMID:26930494

  20. Bandgap engineering of Magnéli phase TinO2n−1: Electron-hole self-compensation

    International Nuclear Information System (INIS)

    An electron-hole self-compensation effect is revealed and confirmed in nitrogen doped Magnéli phase TinO2n−1 (n = 7, 8, and 9) by using hybrid density functional theory calculations. We found that the self-compensation effect between the free electrons in Magnéli phase TinO2n−1 (n = 7, 8, and 9) and the holes induced by p-type nitrogen doping could not only prevent the recombination of photo-generated electron-hole pairs, but also lead to an effective bandgap reduction. This novel electron-hole self-compensation effect may provide a new approach for bandgap engineering of Magnéli phase metal suboxides

  1. Electron-hole excitations and optical spectra of bulk SrO from many-body perturbation theory

    International Nuclear Information System (INIS)

    This paper reports the quasiparticle band structure and the optical absorption spectrum of SrO, using many-body perturbation theory. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, electron-hole pair states and optical excitations are obtained by solving the Bethe-Salpeter equation for the electron-hole two-particle Green function. The calculated band gap for SrO is 6.0 eV, which is in good agreement with the corresponding experimental results. The theoretical result of optical absorption spectrum for SrO is also in close agreement with the experimental data. In particular, the calculated excitation energy for the lowest exciton peak in the optical absorption spectra of SrO reproduces very well the corresponding experimental result. (orig.)

  2. 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.

  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. 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.

  5. Second Harmonic Generation in h-BN and MoS$_2$ monolayers: the role of electron-hole interaction

    OpenAIRE

    Grüning, M; Attaccalite, C.

    2013-01-01

    We study second-harmonic generation in h-BN and MoS$_2$ monolayers using a novel \\emph{ab initio} approach based on Many-body theory. We show that electron-hole interaction doubles the signal intensity at the excitonic resonances with respect to the contribution from independent electronic transitions. This implies that electron-hole interaction is essential to describe second-harmonic generation in those materials. We argue that this finding is general for nonlinear optical properties in nan...

  6. The fate of electron-hole pairs in polymer:fullerene blends for organic photovoltaics.

    Science.gov (United States)

    Causa', Martina; De Jonghe-Risse, Jelissa; Scarongella, Mariateresa; Brauer, Jan C; Buchaca-Domingo, Ester; Moser, Jacques-E; Stingelin, Natalie; Banerji, Natalie

    2016-01-01

    There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs-whether they will dissociate to free charges or geminately recombine-is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%. PMID:27586309

  7. High-field autosolitons in p-Ge electron-hole plasma

    International Nuclear Information System (INIS)

    The processes of forming the high-field thermodiffusion autosolitons in the photogenerated electron-hole plasma (EHP), warmed up by the electric field, at T = 77 K in the p-Ge samples, oriented along the axis , are experimentally studied. Measurements of the volt-ampere characteristics (VAC), the electric field distributions along the samples and the IR-radiation within the range of the wave lengths λ = 1.65-10 μm showed, that the autosolitons generation is accompanied by appearance of the VAC N-shaped sections. The autosolitons are formed by the EHP concentrations of n ≥ 1 x 1014 cm-3 and field intensity E ≥ 500 V/cm and they are manifested in the form of static, moving and pulsing lateral strata with the field intensity of Eas = 1000-20000 V/cm and the carriers temperature of Tc ≥ 1000 K

  8. Electron and electron-hole quasiparticle states in a driven quantum contact

    Science.gov (United States)

    Vanević, Mihajlo; Gabelli, Julien; Belzig, Wolfgang; Reulet, Bertrand

    2016-01-01

    We study the many-body electronic state created by a time-dependent drive of a mesoscopic contact. The many-body state is expressed manifestly in terms of single-electron and electron-hole quasiparticle excitations with the amplitudes and probabilities of creation which depend on the details of the applied voltage. We experimentally probe the time dependence of the constituent electronic states by using an analog of the optical Hong-Ou-Mandel correlation experiment where electrons emitted from the terminals with a relative time delay collide at the contact. The electron wave packet overlap is directly related to the current noise power in the contact. We have confirmed the time dependence of the electronic states predicted theoretically by measurements of the current noise power in a tunnel junction under harmonic excitation.

  9. Electron-hole doping asymmetry of Fermi surface reconstructed in a simple Mott insulator.

    Science.gov (United States)

    Kawasugi, Yoshitaka; Seki, Kazuhiro; Edagawa, Yusuke; Sato, Yoshiaki; Pu, Jiang; Takenobu, Taishi; Yunoki, Seiji; Yamamoto, Hiroshi M; Kato, Reizo

    2016-01-01

    It is widely recognized that the effect of doping into a Mott insulator is complicated and unpredictable, as can be seen by examining the Hall coefficient in high Tc cuprates. The doping effect, including the electron-hole doping asymmetry, may be more straightforward in doped organic Mott insulators owing to their simple electronic structures. Here we investigate the doping asymmetry of an organic Mott insulator by carrying out electric-double-layer transistor measurements and using cluster perturbation theory. The calculations predict that strongly anisotropic suppression of the spectral weight results in the Fermi arc state under hole doping, while a relatively uniform spectral weight results in the emergence of a non-interacting-like Fermi surface (FS) in the electron-doped state. In accordance with the calculations, the experimentally observed Hall coefficients and resistivity anisotropy correspond to the pocket formed by the Fermi arcs under hole doping and to the non-interacting FS under electron doping. PMID:27492864

  10. Phonon-Induced Electron-Hole Excitation and ac Conductance in Molecular Junction

    Science.gov (United States)

    Ueda, Akiko; Utsumi, Yasuhiro; Imamura, Hiroshi; Tokura, Yasuhiro

    2016-04-01

    We investigate the linear ac conductance of molecular junctions under a fixed dc bias voltage in the presence of an interaction between a transporting electron and a single local phonon in a molecule with energy ω0. The electron-phonon interaction is treated by the perturbation expansion. The ac conductance as a function of the ac frequency ωac decreases or increases compared with the noninteracting case depending on the magnitude of the dc bias voltage. Furthermore, a dip emerges at ωac ˜ 2ω0. The dip originates from the modification of electron-hole excitation by the ac field, which cannot be obtained by treating the phonon in the linear regime of a classical forced oscillation.

  11. Characteristic lengths for three-carrier transport with spin-flip and electron-hole recombination

    Science.gov (United States)

    Krcmar, Maja; Saslow, Wayne M.

    2016-05-01

    The exact solution of the linearized, steady-state transport equation for three-carrier systems, such as can occur for semiconductors and ionic conductors, is constructed starting from the near-equilibrium entropy-production requirements of irreversible thermodynamics. Three characteristic modes are found, one associated with electrostatic screening (which is often neglected), and two modes associated with diffusion and "reactions." For a spintronics model with up and down electrons and unpolarized holes, the "reactions" are spin-flip and electron-hole recombination. We discuss how the variations in carrier density, diffusivity, recombination rate, and spin relaxation time affect the characteristic lengths. We apply these modes to study spin-polarized surface photoabsorption.

  12. Scanning photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated WS2 transistors

    International Nuclear Information System (INIS)

    We perform scanning photocurrent microscopy on WS2 ionic liquid-gated field effect transistors exhibiting high-quality ambipolar transport. By properly biasing the gate electrode, we can invert the sign of the photocurrent showing that the minority photocarriers are either electrons or holes. Both in the electron- and hole-doping regimes the photocurrent decays exponentially as a function of the distance between the illumination spot and the nearest contact, in agreement with a two-terminal Schottky-barrier device model. This allows us to compare the value and the doping dependence of the diffusion length of the minority electrons and holes on a same sample. Interestingly, the diffusion length of the minority carriers is several times larger in the hole accumulation regime than in the electron accumulation regime, pointing out an electron-hole asymmetry in WS2

  13. Interchain order and electron-hole photogeneration in trans-polyacetylene

    International Nuclear Information System (INIS)

    Two neighbouring trans-polyacetylene chains are modeled individually by the SSH Hamiltonian and coupled by an interchain electron transfer term. Geometrical considerations show that the interchain transfer integrals alternate in size and possibly even in sign. In the latter case parallel ordering of dimerization is favoured. Due to the bonding produced by the splitting of midgap levels for parallel ordering two neutral solitons on neighbouring chains are strongly bound. The binding energy is calculated in the continuum limit using the analogy to the solvable model of a diatomic polymer chain. The direct inter-chain photoproduction of electron-hole pairs is calculated for the two orderings and for polarization perpendicular to the chain axis. It is concluded that this contribution is generally smaller than the intra-chain optical absorption, but close to the threshold ω=2Δ the two contributions are comparable. (author). 15 refs, 3 figs

  14. 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

  15. 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.

  16. Reversible electron-hole separation in a hot carrier solar cell

    Science.gov (United States)

    Linke, Heiner

    Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the conditions under which electron-hole separation in hot-carrier solar cells can occur reversibly, that is, at maximum energy conversion efficiency. We find that, under specific conditions, the energy conversion efficiency of a hot-carrier solar cell can exceed the Carnot limit set by the intra-device temperature gradient alone, due to the additional contribution of the quasi-Fermi level splitting in the absorber. To achieve this, we consider a highly selective energy filter such as a quantum dot embedded into a one-dimensional conductor. We also establish that the open-circuit voltage of a hot-carrier solar cell is not limited by the band gap of the absorber, due to the additional thermoelectric contribution to the voltage. Additionally, we find that a hot-carrier solar cell can be operated in reverse as a thermally driven solid-state light emitter. In addition this theoretical analysis, I will also report on first experimental results in a nanowire-based energy filter device. Ref: S Limpert, S Bremner, and H Linke, New J. Phys 17, 095004 (2015)

  17. 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.

  18. Numerical simulation of attosecond nanoplasmonic streaking

    Energy Technology Data Exchange (ETDEWEB)

    Skopalova, E; Lei, D Y; Witting, T; Arrell, C; Frank, F; Sonnefraud, Y; Maier, S A; Tisch, J W G; Marangos, J P, E-mail: e.skopalova07@imperial.ac.uk [Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)

    2011-08-15

    The characterization of the temporal profile of plasmonic fields is important both from the fundamental point of view and for potential applications in ultrafast nanoplasmonics. It has been proposed by Stockman et al (2007 Nat. Photonics 1 539) that the plasmonic electric field can be directly measured by the attosecond streaking technique; however, streaking from nanoplasmonic fields differs from streaking in the gas phase because of the field localization on the nanoscale. To understand streaking in this new regime, we have performed numerical simulations of attosecond streaking from fields localized in nanoantennas. In this paper, we present simulated streaked spectra for realistic experimental conditions and discuss the plasmonic field reconstruction from these spectra. We show that under certain circumstances when spatial averaging is included, a robust electric field reconstruction is possible.

  19. 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.

  20. Attosecond Control in Photoionization of D2

    International Nuclear Information System (INIS)

    We study the dissociative photoionization of D2 by an attosecond pulse train (APT) in the presence of a near-infrared (IR) field. Strong oscillations in the D+ kinetic energy release spectrum with a half period of the optical cycle of the infrared field are observed and attributed to interferences between ionization pathways involving different harmonic orders of the APT due to the IR-induced coupling between the 1sσg and 2pσu ionization channels.

  1. 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.

  2. 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.

  3. Structural transformations in silicon under exposure by femtosecond laser pulse: role of electron-hole plasma and phonon-phonon anharmonism

    International Nuclear Information System (INIS)

    It is experimentally shown for the first time that by the effect of the feed-up laser pulse of 100 fs duration on the silicon target the consecutive structural transitions of the substance into the new crystalline and liquid metallic phase occur both during the laser pulse feed-up and after 0.1-103 ps, depending on the material excitation conditions. The thresholds of the observed structural transitions are determined and the phonon nodes, responsible for therefore, are identified. The structural transitions dynamics in the silicon by the 01.-103 ps times is described within the frames of the model of the phonon modes instability, originating due to the plasma electron-hole effect and also due to the intra- and intermode phonon-phonon anharmonic interactions

  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. Electronic hole localization in rutile and anatase TiO2 - Self-interaction correction in Delta-SCF DFT

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Jacobsen, Karsten Wedel; Rossmeisl, Jan

    2011-01-01

    We study electronic hole localization in rutile and anatase titanium dioxide by means of Δ-Self-Consistent Field Density Functional Theory. In order to compare stabilities of the localized and the delocalized hole states we introduce a simple correction to the wrong description of the localization...

  6. 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)

  7. Attosecond nonlinear polarization and light–matter energy transfer in solids

    Science.gov (United States)

    Sommer, A.; Bothschafter, E. M.; Sato, S. A.; Jakubeit, C.; Latka, T.; Razskazovskaya, O.; Fattahi, H.; Jobst, M.; Schweinberger, W.; Shirvanyan, V.; Yakovlev, V. S.; Kienberger, R.; Yabana, K.; Karpowicz, N.; Schultze, M.; Krausz, F.

    2016-06-01

    Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light–matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible–infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.

  8. 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...

  9. 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)

  10. Break the electron- hole balance and pressure induced superconductivity in Tungsten Ditelluride

    Science.gov (United States)

    Song, Fengqi; Pan, Xing-Chen

    Tungsten ditelluride has garnered immense interest due to the recent discovery of titanic unsaturated magnetoresistance up to 60 Tesla and its possible topological metal nature. The titanic unsaturated magnetoresistance is attributed to the perfect compensation between the opposite carriers in this material. Motivated by the small and sensitive Fermi surface of 5d electronic orbitals, we break the electron-hole balance by the application of high pressure. Superconductivity sharply appears at the pressure of 2.5 GPa, quickly reaching a maximum critical temperature of 7 K at around 16.8 GPa, and followed by a monotonic decrease in Tc with increasing pressure exhibiting the typical dome-shaped superconducting phase. What's more, linear magnetoresistance dominates the transport behavior under high pressure instead of semi-classical parabolic magnetoresistance, like in other topological metals. Refence: Nature Commun. 6, 7805 (2015), arXiv 1505, 07968. The authors would like to thank the National Key Projects for Basic Research in China, the National Natural Science Foundation of China , the NSF of Jiangsu Province, the PAPD project, and the Fundamental Research Funds for the Central Universities.

  11. Average Energy Expended Per Electron-Hole Pair in Germanium Detector for Dark Matter Searches

    Science.gov (United States)

    Wei, Wenzhao; Wang, Lu; Mei, Dongming; Cubed Collaboration

    2016-03-01

    The value of ɛ, the average energy expended per electron-hole pair, plays a critical role in determining the energy threshold of a bolometer detector with germanium in dark matter searches. We propose an independent method to estimate the value of ɛ down to milli-Kelvin range, which is the operating temperature for a SuperCDMS-like detector. A theoretical model and experimental analysis algorithm are developed in this work to estimate the value of ɛ based on the relationship between ɛ, detector energy resolution (Fano factor) and the primary phonon energy. We also investigated the energy threshold for a SuperCDMS-like detector with the value of ɛ calculated from our model. In this work, we present our theoretical calculation and show how to use experimental data to evaluate the value of ɛ. Subsequently, we report the temperature dependence of ɛ and its value at 50 milli-Kelvin. This work is supported by NSF in part by the NSF OIA 1434142, DOE Grant DE-FG02-10ER46709, and the State of South Dakota.

  12. Electron-hole capture in polymer heterojunction light-emitting diodes

    Science.gov (United States)

    Greenham, Neil

    2005-03-01

    Polymer light-emitting diodes based on blends of polyfluorene derivatives show very high efficiencies and low drive voltages. Electron-hole capture in these devices directly produces long-lived exciplex states where the electron and hole are predominantly localized on opposite sides of the heterojunction. The exciplex may then be thermally excited to form an intra-chain exciton, which can itself either emit, or be recycled to reform the exciplex. I will review the physics of exciplex formation and emission in these devices, and will show that exciplex formation rates are consistent with low free charge densities at the heterojunction. I will present evidence that the rate of charge transfer at polyfluorene heterojunctions can be modulated with an applied electric field, leading in some cases to an increase in photoluminescence efficiency with applied field. I will also present recent results showing enhanced triplet exciton formation after photoexcitation in polyfluorene blends, and will discuss the implications of the results for polymer light-emitting and photovoltaic devices.

  13. Calculation Method for Exciton Wavefunctions with Electron--Hole Exchange Interaction: Application to Carbon Nanotubes

    Science.gov (United States)

    Ajiki, Hiroshi

    2013-05-01

    A new method for calculating exciton wavefunctions in the presence of a long-range electron--hole (e--h) exchange interaction (EXI) is presented. The e--h EXI arises, for example, for cross-polarized excitons in a single-walled carbon nanotube (SWNT). Cross-polarized excitons have previously been calculated as an eigenvalue problem of a Bethe--Salpeter equation (BSE) within the Tamm--Dancoff-type approximation (TDA). The resulting wavefunctions provide quite different absorption spectra in comparison with those calculated in the self-consistent-field method [S. Uryu and T. Ando, J. Phys.: Conf. Ser. 302 (2011) 012004]. Although the self-consistent-field method is more reliable, exciton wavefunctions cannot be obtained from this method. A general method is derived here to obtain exciton wavefunctions that take the e--h EXI into account within the TDA, and the method is applied to the cross-polarized excitons of a SWNT. The absorption spectra calculated from the resulting exciton wavefunctions agree well with the spectra calculated from the self-consistent-field method within a rotating-wave approximation.

  14. Generating functional approach for spontaneous coherence in semiconductor electron-hole-photon systems

    Science.gov (United States)

    Yamaguchi, Makoto; Nii, Ryota; Kamide, Kenji; Ogawa, Tetsuo; Yamamoto, Yoshihisa

    2015-03-01

    Electrons, holes, and photons in semiconductors are interacting fermions and bosons. In this system, a variety of ordered coherent phases can be formed through the spontaneous phase symmetry breaking because of their interactions. The Bose-Einstein condensation (BEC) of excitons and polaritons is one of such coherent phases, which can potentially cross over into the Bardeen-Cooper-Schrieffer (BCS) type ordered phase at high densities under quasiequilibrium conditions, known as the BCS-BEC crossover. In contrast, one can find the semiconductor laser, superfluorescence (SF), and superradiance as relevant phenomena under nonequilibrium conditions. In this paper, we present a comprehensive generating functional theory that yields nonequilibrium Green's functions in a rigorous way. The theory gives us a starting point to discuss these phases in a unified view with a diagrammatic technique. Comprehensible time-dependent equations are derived within the Hartree-Fock approximation, which generalize the Maxwell-semiconductor-Bloch equations under the relaxation time approximation. With the help of this formalism, we clarify the relationship among these cooperative phenomena and we show theoretically that the Fermi-edge SF is directly connected to the e-h BCS phase. We also discuss the emission spectra as well as the gain-absorption spectra.

  15. Picosecond strain pulses generated by a supersonically expanding electron-hole plasma in GaAs

    Science.gov (United States)

    Young, E. S. K.; Akimov, A. V.; Campion, R. P.; Kent, A. J.; Gusev, V.

    2012-10-01

    Strain pulses with picosecond duration are generated directly in GaAs by optical excitation from a femtosecond laser. The photons are absorbed in a 15-nm layer near the surface, creating the electron-hole plasma, which diffusively expands into the bulk of the GaAs. At an early time, the drift velocity of the expanding plasma exceeds the speed of longitudinal sound, and the generated strain pulses cannot escape the plasma cloud. Such supersonic generation of strain pulses results in specific temporal and spatial shapes of the generated strain pulses, where the compression part has a much lower amplitude than the tensile part. This phenomenon is studied experimentally at low temperatures and analyzed theoretically based on the wave and diffusion equations for strain and plasma density, respectively. Two mechanisms, deformation potential and thermoelasticity, are responsible for the experimental observations. The relative contributions from these mechanisms are governed by the nonradiative recombination rate in the plasma and depend on the optical excitation density, inducing such nonlinear optoacoustic effects as shortening of the leading strain front and a superlinear/quadratic increase in its amplitude with the rise of pump laser fluence.

  16. 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.

  17. 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.

  18. 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

  19. 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...

  20. 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.

  1. 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

  2. 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.

  3. Spin-orbit interaction driven collective electron-hole excitations in a noncentrosymmetric nodal loop Weyl semimetal

    Science.gov (United States)

    Ahn, Kyo-Hoon; Lee, Kwan-Woo; Pickett, Warren E.

    2015-09-01

    NbP is one member of a new class of nodal loop semimetals characterized by the cooperative effects of spin-orbit coupling (SOC) and a lack of inversion center. Here transport and spectroscopic properties of NbP are evaluated using density functional theory methods. SOC together with the lack of inversion symmetry splits degeneracies, giving rise to "Russian doll nested" Fermi surfaces containing 4 ×10-4 electron (hole) carriers/f.u. Due to the modest SOC strength in Nb, the Fermi surfaces map out the Weyl nodal loops. Calculated structure around T*≈100 K in transport properties reproduces well the observed transport behavior only when SOC is included, attesting to the precision of the (delicate) calculations and the stoichiometry of the samples. Low-energy collective electron-hole excitations (plasmons) in the 20-60 meV range result from the nodal loop splitting.

  4. Superconductivity of electron-hole pairs in a double layer graphene system in a quantizing magnetic field

    International Nuclear Information System (INIS)

    The state with a spontaneous interlayer phase coherence in a graphene based bilayer quantum Hall system is studied. This state can be considered as a gas of superfluid electron-hole pairs with the components of the pair belonging to different layers. Superfluid flux of such pairs is equivalent to two electrical supercurrents in the layers. It is shown that the state with the interlayer phase coherence emerges in the graphene system if a certain imbalance of the Landau level filling factors of the layers is created. We obtain the temperature of transition into the superfluid state, the maximum interlayer distance at which the phase coherence is possible, and the critical values of the supercurrent. The advantages of use of graphene systems instead of GaAs heterostructures for the realization of the bilayer electron-hole superconductivity are discussed.

  5. 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

  6. Attosecond neutron scattering from open quantum systems

    Energy Technology Data Exchange (ETDEWEB)

    Dreismann, C.; Aris, C. [Institute of Chemistry, Technical University of Berlin (Germany)

    2010-07-01

    Neutron Compton scattering (NCS) from single nuclei of atoms in molecules, e.g. H{sub 2} (and/or single atoms, e.g. He) is effectuated in the attosecond timescale. The related scattering time is considered in detail, in relation with the Uncertainty Relations. It is shown that the entity scattering time gives a statistical measure of the length of the time interval during which an elementary neutron-nucleus collision may occur, in the same way that the spatial extent of a particle wavefunction (or wavepacket) gives a statistical measure of the extent of the region in which the particle may be found. Consequently, the elementary neutron-nucleus scattering process represents a time-interference phenomenon over the sub-femtosecond ''scattering time'' window. Moreover, the very short-range strong interaction of the neutron-nucleus collision implies that the scattering system (e.g. a proton partically dressed'' with electrons) must be considered as an open quantum system. Experimental results from H{sub 2}, D{sub 2} and HD are mentioned and their anomalous scattering property in the attosecond timescale is qualitatively discussed, also in connection with the Schulman-Gaveau effect.

  7. 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.

  8. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, I.; Huppert, M.; Wörner, H. J., E-mail: hwoerner@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich (Switzerland); Brown, M. A. [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich (Switzerland); Bokhoven, J. A. van [Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1, 8093 Zurich (Switzerland); Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, 5232 Villigen (Switzerland)

    2015-12-15

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  9. 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.

  10. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Science.gov (United States)

    Jordan, I.; Huppert, M.; Brown, M. A.; van Bokhoven, J. A.; Wörner, H. J.

    2015-12-01

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  11. 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.

  12. Disorder and magnetic-field induced breakdown of helical edge conduction in an inverted electron-hole bilayer

    OpenAIRE

    2014-01-01

    We calculate the conductance of a two-dimensional bilayer with inverted electron-hole bands, to study the sensitivity of the quantum spin Hall insulator (with helical edge conduction) to the combination of electrostatic disorder and a perpendicular magnetic field. The characteristic breakdown field for helical edge conduction splits into two fields with increasing disorder, a field $B_{c}$ for the transition into a quantum Hall insulator (supporting chiral edge conduction) and a smaller field...

  13. Influence of Interface Traps and Electron-Hole Puddles on Quantum Capacitance and Conductivity in Graphene Field-Effect Transistors

    OpenAIRE

    Zebrev, G. I.; Melnik, E. V.; Tselykovskiy, A. A.

    2010-01-01

    We study theoretically an influence of the near-interfacial insulator traps and electron-hole puddles on the small-signal capacitance and conductance characteristics of the gated graphene structures. Based on the self-consistent electrostatic consideration and taking into account the interface trap capacitance the explicit analytic expressions for charge carrier density and the quantum capacitance as functions of the gate voltage were obtained. This allows to extract the interface trap capaci...

  14. 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...

  15. 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}.

  16. Tunneling time in attosecond experiments, intrinsic-type of time. Keldysh, and Mandelstam–Tamm time

    Science.gov (United States)

    Kullie, Ossama

    2016-05-01

    Tunneling time in attosecond and strong-field experiments is one of the most controversial issues in current research, because of its importance to the theory of time, the time operator and the time–energy uncertainty relation in quantum mechanics. In Kullie (2015 Phys. Rev. A 92 052118) we derived an estimation of the (real) tunneling time, which shows an excellent agreement with the time measured in attosecond experiments, our derivation is found by utilizing the time–energy uncertainty relation, and it represents a quantum clock. In this work, we show different aspects of the tunneling time in attosecond experiments, we discuss and compare the different views and approaches, which are used to calculate the tunneling time, i.e. Keldysh time (as a real or imaginary quantity), Mandelstam–Tamm time, the classical view of the time measurement and our tunneling time relation(s). We draw some conclusions concerning the validity and the relation between the different types of the tunneling time with the hope that they will help to answer the question put forward by Orlando et al (2014 J. Phys. B 47 204002, 2014 Phys. Rev. A 89 014102): tunneling time, what does it mean? However, as we will see, the important question is a more general one: how to understand the time and the measurement of the time of a quantum system? In respect to our result, the time in quantum mechanics can be, in more general fashion, classified in two types, intrinsic dynamically connected, and external dynamically not connected to the system, and consequently (perhaps only) classical Newtonian time remains as a parametric type of time.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. Unified ab initio treatment of attosecond photoionization and Compton scattering

    International Nuclear Information System (INIS)

    We present a new theoretical approach to attosecond laser-assisted photo- and Compton ionization. Attosecond x-ray absorption and scattering are described by S-circumflex(1,2)-matrices, which are coherent superpositions of 'monochromatic' S-circumflex(1,2)-matrices in a laser-modified Furry representation. Besides refining the existing theory of the soft x-ray photoelectron attosecond streak camera and spectral phase interferometry (ASC and ASPI), we formulate a theory of hard x-ray photoelectron and Compton ASC and ASPI. The resulting scheme has a simple structure and leads to closed-form expressions for ionization amplitudes. We investigate Compton electron interference in the separable Coulomb-Volkov continuum with both Coulomb and laser fields treated non-perturbatively. We find that at laser-field intensities below 1013 Wcm-2 normalized Compton lines almost coincide with the lines obtained in the laser-free regime. At higher intensities, attosecond interferences survive integration over electron momenta, and feature prominently in the Compton lines themselves. We define a regime where the electron ground-state density can be measured with controllable accuracy in an attosecond time interval. The new theory provides a firm basis for extracting photo- and Compton electron phases and atomic and molecular wavefunctions from experimental data.

  3. 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.

  4. Exceptionally strong correlation-driven charge migration and attosecond transient absorption spectroscopy

    CERN Document Server

    Hollstein, Maximilian; Pfannkuche, Daniela

    2016-01-01

    We investigate theoretically charge migration following prompt double ionization of a polyatomic molecule (C$_2$H$_4$BrI) and find that for double ionization, correlation-driven charge migration appears to be particularly prominent, i.e., we observe exceptionally rich dynamics solely driven by the electron-electron interaction even in the situation when the electrons are emitted from outer-valence orbitals. These strongly correlated electron dynamics are witnessed in the theoretically determined time-resolved transient absorption cross section. Strikingly, features in the cross section can be traced back to electron hole populations and time-dependent partial charges and hence, can be interpreted with surprising ease. Remarkably, by taking advantage of element specific core-to-valence transitions, the hole population dynamics can be followed both in time and space. With this, not only do we report the high relevance of correlation-driven charge migration following double ionization but our findings also highl...

  5. 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.

  6. Isolated attosecond soft X-rays and water window XAFS

    Science.gov (United States)

    Biegert, Jens

    2016-05-01

    We demonstrate generation of isolated attosecond soft X-ray pulses with duration less than 350 as at the carbon K-edge at 284 eV. This reproducible and CEP stable attosecond soft X-ray continuum covers the entire water window from 200 eV to 550 eV with a flux of 7.3x 107 photons/s and corresponds to a pulse energy of 2.9 pJ. We demonstrate the utility of our table-top source through soft X-ray near-edge fine-structure spectroscopy at K-shell absorption edges in condensed matter and retrieve the specific absorption features corresponding to the binding orbitals. We believe that these results herald attosecond material science by bridging the gap between ultrafast temporal resolution and element specific probing at the fundamental absorption edges of matter.

  7. Multiphoton transitions for delay-zero calibration in attosecond spectroscopy

    CERN Document Server

    Herrmann, Jens; Chen, Shaohao; Wu, Mengxi; Ludwig, André; Kasmi, Lamia; Schafer, Kenneth J; Gallmann, Lukas; Gaarde, Mette B; Keller, Ursula

    2014-01-01

    The exact delay-zero calibration in an attosecond pump-probe experiment is important for the correct interpretation of experimental data. In attosecond transient absorption spectroscopy the determination of the delay-zero exclusively from the experimental results is not straightforward and may introduce significant errors. Here, we report the observation of quarter-laser-cycle (4{\\omega}) oscillations in a transient absorption experiment in helium using an attosecond pulse train overlapped with a precisely synchronized, moderately strong infrared pulse. We demonstrate how to extract and calibrate the delay-zero with the help of the highly nonlinear 4{\\omega} signal. A comparison with the solution of the time-dependent Schr\\"odinger equation is used to confirm the accuracy and validity of the approach. Moreover, we study the mechanisms behind the quarter-laser-cycle and the better-known half-laser-cycle oscillations as a function of experimental parameters. This investigation yields an indication of the robust...

  8. Attosecond streaking in a nano-plasmonic field

    Science.gov (United States)

    Kelkensberg, F.; Koenderink, A. F.; Vrakking, M. J. J.

    2012-09-01

    A theoretical study of the application of attosecond streaking spectroscopy to time-resolved studies of the plasmonic fields surrounding isolated, resonantly excited spherical nanoparticles is presented. A classification of the different regimes in attosecond streaking is proposed and identified in our results that are derived from Mie calculations of plasmon fields, coupled to classical electron trajectory simulations. It is shown that in an attosecond streaking experiment, the electrons are almost exclusively sensitive to the component of the field parallel to the direction in which they are detected. This allows one to probe the different components of the field individually by resolving the angle of emission of the electrons. Finally, simulations based on fields calculated by finite-difference time-domain (FDTD) are compared with the results obtained using Mie fields. The two are found to be in good agreement with each other, supporting the notion that FDTD methods can be used to reliably investigate non-spherical structures.

  9. 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.

  10. 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.

  11. 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

  12. Nonradiative Electron-Hole Recombination Rate Is Greatly Reduced by Defects in Monolayer Black Phosphorus: Ab Initio Time Domain Study.

    Science.gov (United States)

    Long, Run; Fang, Weihai; Akimov, Alexey V

    2016-02-18

    We report ab initio time-domain simulations of nonradiative electron-hole recombination and electronic dephasing in ideal and defect-containing monolayer black phosphorus (MBP). Our calculations predict that the presence of phosphorus divacancy in MBP (MBP-DV) substantially reduces the nonradiative recombination rate, with time scales on the order of 1.57 ns. The luminescence line width in ideal MBP of 150 meV is 2.5 times larger than MBP-DV at room temperature, and is in excellent agreement with experiment. We find that the electron-hole recombination in ideal MBP is driven by the 450 cm(-1) vibrational mode, whereas the recombination in the MBP-DV system is driven by a broad range of vibrational modes. The reduced electron-phonon coupling and increased bandgap in MBP-DV rationalize slower recombination in this material, suggesting that electron-phonon energy losses in MBP can be minimized by creating suitable defects in semiconductor device material. PMID:26821943

  13. 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...

  14. 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.

  15. 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

  16. 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

  17. 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

  18. 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...

  19. 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.

  20. 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.

  1. Theory of attosecond delays in laser-assisted photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Dahlström, J.M., E-mail: marcus.dahlstrom@fysik.su.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Atomic Physics, Fysikum, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Guénot, D.; Klünder, K.; Gisselbrecht, M.; Mauritsson, J. [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); L’Huillier, A., E-mail: anne.lhuillier@fysik.lth.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Maquet, A. [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France); Taïeb, R., E-mail: richard.taieb@upmc.fr [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France)

    2013-03-12

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself.

  2. Theory of attosecond delays in laser-assisted photoionization

    International Nuclear Information System (INIS)

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself

  3. Band-to-band tunneling distance analysis in the heterogate electron-hole bilayer tunnel field-effect transistor

    Science.gov (United States)

    Padilla, J. L.; Palomares, A.; Alper, C.; Gámiz, F.; Ionescu, A. M.

    2016-01-01

    In this work, we analyze the behavior of the band-to-band tunneling distance between electron and hole subbands resulting from field-induced quantum confinement in the heterogate electron-hole bilayer tunnel field-effect transistor. We show that, analogously to the explicit formula for the tunneling distance that can be easily obtained in the semiclassical framework where the conduction and valence band edges are allowed states, an equivalent analytical expression can be derived in the presence of field-induced quantum confinement for describing the dependence of the tunneling distance on the body thickness and material properties of the channel. This explicit expression accounting for quantum confinement holds valid provided that the potential wells for electrons and holes at the top and bottom of the channel can be approximated by triangular profiles. Analytical predictions are compared to simulation results showing very accurate agreement.

  4. Formation and Decay of Electron-Hole Plasma Clusters in a Direct-Gap Semiconductor CuCl

    Institute of Scientific and Technical Information of China (English)

    JIANG Lei(姜磊); WU Ming-Wei(吴明卫); M. Nagai; M. Kuwata-Gonokami

    2003-01-01

    The master equation for the cluster-size distribution function is solved numerically to investigate the electronhole droplet formation claimed to be discovered in the direct-gap CuCl excited by picosecond laser pulses [Nagai et al. Phys. Rev. Lett. 86 (2001)5795; J. Lumin. 100 (2002)233]. Our result shows that for the excitation in the experiment, the average number of pairs per cluster (ANPC) is only around 5.2, much smaller than that (106 typically for Ge) of the well studied electron-hole droplet in indirect-gap semiconductors such as Ge and Si.These results indicate that what measured in CuCl by Nagai et al. may not come from the EHD formed from exciton gas, instead possibly come from some bubbles of excitons in metallic liquid.

  5. Applications of Ultrafast Terahertz Pulses for Intra-ExcitonicSpectroscopy of Quasi-2D Electron-Hole Gases

    Energy Technology Data Exchange (ETDEWEB)

    Kaindl, Robert A.; Carnahan, Marc A.; Hagele, Daniel; Chemla, D.S.

    2006-09-02

    Excitons are of fundamental interest and of importance foropto-electronic applications of bulk and nano-structured semiconductors.This paper discusses the utilization of ultrafast terahertz (THz) pulsesfor the study of characteristic low-energy excitations of photoexcitedquasi 2D electron-hole (e-h) gases. Optical-pump THz-probe spectroscopyat 250-kHz repetition rate is employed to detect characteristic THzsignatures of excitons and unbound e-h pairs in GaAs quantum wells.Exciton and free-carrier densities are extracted from the data using atwo-component model. We report the detailed THz response and pairdensities for different photoexcitation energies resonant to heavy-holeexcitons, light-hole excitons, or the continuum of unbound pairs. Suchexperiments can provide quantitative insights into wavelength, time, andtemperature dependence of the low-energy response and composition ofoptically excited e-h gases in low-dimensionalsemiconductors.

  6. 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.

  7. Development of extreme ultraviolet and soft x-ray multilayer optics for scientific studies with femtosecond/attosecond sources

    Energy Technology Data Exchange (ETDEWEB)

    Aquila, Andrew Lee [Univ. of California, Berkeley, CA (United States)

    2009-05-21

    The development of multilayer optics for extreme ultraviolet (EUV) radiation has led to advancements in many areas of science and technology, including materials studies, EUV lithography, water window microscopy, plasma imaging, and orbiting solar physics imaging. Recent developments in femtosecond and attosecond EUV pulse generation from sources such as high harmonic generation lasers, combined with the elemental and chemical specificity provided by EUV radiation, are opening new opportunities to study fundamental dynamic processes in materials. Critical to these efforts is the design and fabrication of multilayer optics to transport, focus, shape and image these ultra-fast pulses This thesis describes the design, fabrication, characterization, and application of multilayer optics for EUV femtosecond and attosecond scientific studies. Multilayer mirrors for bandwidth control, pulse shaping and compression, tri-material multilayers, and multilayers for polarization control are described. Characterization of multilayer optics, including measurement of material optical constants, reflectivity of multilayer mirrors, and metrology of reflected phases of the multilayer, which is critical to maintaining pulse size and shape, were performed. Two applications of these multilayer mirrors are detailed in the thesis. In the first application, broad bandwidth multilayers were used to characterize and measure sub-100 attosecond pulses from a high harmonic generation source and was performed in collaboration with the Max-Planck institute for Quantum Optics and Ludwig- Maximilians University in Garching, Germany, with Professors Krausz and Kleineberg. In the second application, multilayer mirrors with polarization control are useful to study femtosecond spin dynamics in an ongoing collaboration with the T-REX group of Professor Parmigiani at Elettra in Trieste, Italy. As new ultrafast x-ray sources become available, for example free electron lasers, the multilayer designs

  8. 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

  9. 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.

  10. Direct extraction of intense-field-induced polarization in the continuum on the attosecond time scale from transient absorption

    Science.gov (United States)

    Li, X.; Haxton, D. J.; Gaarde, M. B.; Schafer, K. J.; McCurdy, C. W.

    2016-02-01

    A procedure is suggested for using transient absorption spectroscopy above the ionization threshold to measure the polarization of the continuum induced by an intense optical pulse. In this way transient absorption measurement can be used to probe subfemtosecond intense field dynamics in atoms and molecules. The method is based on an approximation to the dependence of these spectra on time delay between an attosecond XUV probe pulse and an intense pump pulse that is tested over a wide range of intensities and time delays by all-electrons-active calculations using the multiconfiguration time-dependent Hartree-Fock method in the case of neon.

  11. 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.

  12. AXSIS: Exploring the frontiers in attosecond X-ray science, imaging and spectroscopy

    Science.gov (United States)

    Kärtner, F. X.; Ahr, F.; Calendron, A.-L.; Çankaya, H.; Carbajo, S.; Chang, G.; Cirmi, G.; Dörner, K.; Dorda, U.; Fallahi, A.; Hartin, A.; Hemmer, M.; Hobbs, R.; Hua, Y.; Huang, W. R.; Letrun, R.; Matlis, N.; Mazalova, V.; Mücke, O. D.; Nanni, E.; Putnam, W.; Ravi, K.; Reichert, F.; Sarrou, I.; Wu, X.; Yahaghi, A.; Ye, H.; Zapata, L.; Zhang, D.; Zhou, C.; Miller, R. J. D.; Berggren, K. K.; Graafsma, H.; Meents, A.; Assmann, R. W.; Chapman, H. N.; Fromme, P.

    2016-09-01

    X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales. These have been studied with high time resolution primarily by optical spectroscopy, enabled by ultrafast laser technology, but they reduce the vast complexity of the process to a few reaction coordinates. In the AXSIS project at CFEL in Hamburg, funded by the European Research Council, we develop the new method of attosecond serial X-ray crystallography and spectroscopy, to give a full description of ultrafast processes atomically resolved in real space and on the electronic energy landscape, from co-measurement of X-ray and optical spectra, and X-ray diffraction. This technique will revolutionize our understanding of structure and function at the atomic and molecular level and thereby unravel fundamental processes in chemistry and biology like energy conversion processes. For that purpose, we develop a compact, fully coherent, THz-driven attosecond X-ray source based on coherent inverse Compton scattering off a free-electron crystal, to outrun radiation damage effects due to the necessary high X-ray irradiance required to acquire diffraction signals. This highly synergistic project starts from a completely clean slate rather than conforming to the specifications of a large free-electron laser (FEL) user facility, to optimize the entire instrumentation towards fundamental measurements of the mechanism of light absorption and excitation energy transfer. A multidisciplinary team formed by laser

  13. Research Update: Relativistic origin of slow electron-hole recombination in hybrid halide perovskite solar cells

    Science.gov (United States)

    Azarhoosh, Pooya; McKechnie, Scott; Frost, Jarvist M.; Walsh, Aron; van Schilfgaarde, Mark

    2016-09-01

    The hybrid perovskite CH3NH3PbI3 (MAPI) exhibits long minority-carrier lifetimes and diffusion lengths. We show that slow recombination originates from a spin-split indirect-gap. Large internal electric fields act on spin-orbit-coupled band extrema, shifting band-edges to inequivalent wavevectors, making the fundamental gap indirect. From a description of photoluminescence within the quasiparticle self-consistent GW approximation for MAPI, CdTe, and GaAs, we predict carrier lifetime as a function of light intensity and temperature. At operating conditions we find radiative recombination in MAPI is reduced by a factor of more than 350 compared to direct gap behavior. The indirect gap is retained with dynamic disorder.

  14. 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

  15. 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.

  16. Electron, Hole, Singlet, and Triplet Energy Transfer in Photoexcited Porphyrin-Naphthalenediimide Dyads.

    Science.gov (United States)

    Yushchenko, Oleksandr; Hangarge, Rahul V; Mosquera-Vazquez, Sandra; Boshale, Sheshanath V; Vauthey, Eric

    2015-06-18

    The excited-state dynamics of two molecular dyads, consisting of zinc (1) and free-base (2) porphyrin connected via a peptide linker to a core-substituted naphthalenediimide (NDI) have been investigated using optical spectroscopy. These dyads exhibit rich photophysics because of the large number of electronic excited states below 3 eV. In the case of 1 in apolar solvents, excitation energy transfer from the vibrationally hot singlet excited porphyrin to the NDI takes place with a 500 fs time constant. Electronic energy ends up in the NDI-localized triplet state, which decays to the ground state on a microsecond timescale. In polar solvents, ground-state recovery is faster by 5 orders of magnitude because of the occurrence of charge separation followed by recombination. On the other hand, excitation energy transfer in 2 takes place in the opposite direction, namely from the NDI to the porphyrin, which then undergoes intersystem crossing to the triplet state, followed by triplet energy transfer back to the NDI. Therefore, four distinct local electronic excited states are consecutively populated after excitation of the NDI unit of 2, with the energy shuttling between the two ends of the dyad. PMID:25418961

  17. 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.

  18. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  19. Attosecond Precision Multi-km Laser-Microwave Network

    CERN Document Server

    Xin, M; Peng, M Y; Kalaydzhyan, A; Wang, W; Muecke, O D; Kaertner, F X

    2016-01-01

    Synchronous laser-microwave networks consisting of many optical and microwave sources distributed over km-distances are crucial for scientific efforts requiring highest spatio-temporal resolution. However, present synchronization techniques limit these networks to 10-fs relative timing jitter between their sub-sources. Here, we present a novel 4.7 km laser-microwave network with attosecond precision for over tens of hours of continuous operation. It is achieved through new metrological devices and careful balancing of fiber nonlinearities and fundamental noise contributions. This work may enable next-generation attosecond photon-science facilities to revolutionize many research fields from structural biology to material science and chemistry to fundamental physics. It will also accelerate the development in other research areas requiring high spatio-temporal resolution such as geodesy, very-long-baseline interferometry, high-precision navigation and multi-telescope arrays.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Preparing attosecond coherences by strong-field ionization

    OpenAIRE

    Pabst, Stefan; Lein, Manfred; Wörner, Hans Jakob

    2016-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model, which is based on the Fourier transform of the subcycle SFI rate, for predicting the bandwidth of ionic states that can be coherently prepared by SFI. The coherent bandwidth decreases considerably with increasing central wavelength of the ionizing pulse but it is much less sensi...

  6. 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.

  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. 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)

  9. 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 %.

  10. 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.

  11. Dye-Sensitized Carbon Nano-Yarn Based Photovoltaic Cells with Enhanced Electron-Hole Separation and Barrier Characteristics

    Science.gov (United States)

    Moore, H. Justin; Leal, Miguel; Grissom, Glenn; Trad, Tarek; Islam, Nazmul; Touhami, Ahmed; Uddin, M. Jasim

    Over the last 30 years dye-sensitized solar cells have received considerable interest as an alternative energy source due to their low-cost, environmental sustainability, flexibility, and an abundant number of other practical applications. Flexible carbon nanotube-yarn based photo voltaic cells have shown considerable advantages over metal wire based solar cells or non-flexible substrates like indium-doped tin oxide glass. Carbon nanotubes are superior for photo voltaic cells due to their lower electrical resistance, excellent electrocatalytic activity, and high mechanical integrity. Here, we introduce the use of poly(3-hexylthiophene-2,5-diyl), [6.6] diphenyl C62 bis(butyric acid methyl ester), cadmium sulfide-cadmium selenide quantum dots, and ruthenium-based dye N719 to locally increase electron generation, decrease electron-hole pair recombination, as well as enhancing barrier characteristics. Our prototype 3-dimensional carbon nano-yarn based photovoltaic cells show an enhancement in photon to energy conversion efficiency (>6.5%). This along with prolonged environmental stability makes for a very promising solar cell. NIH, NSF, Welch Foundation.

  12. Determination of the electron-hole pair creation energy for semiconductors from the spectral responsivity of photodiodes

    CERN Document Server

    Scholze, F; Kuschnerus, P; Rabus, H; Richter, M; Ulm, G

    2000-01-01

    Ionizing radiation can be detected by the measurement of the charge carriers produced in a detector. The improved semiconductor technology now allows detectors operating near the physical limits of the detector materials to be designed. The mean energy required for producing an electron-hole pair, W, is a material property of the semiconductor. Here, the determination of W from the spectral responsivity of photodiodes is demonstrated. Using spectrally dispersed synchrotron radiation, different types of semiconductor photodiodes have been examined in the UV-, VUV-, and soft X-ray spectral range. Their spectral responsivity was determined with relative uncertainties between 0.4% and 1% using a cryogenic electrical-substitution radiometer as primary detector standard. Results are presented for silicon n-on-p junction photodiodes and for GaAsP/Au Schottky diodes at room temperature. The investigations for silicon covered the complete spectral range from 3 to 1500 eV, yielding a constant value W=(3.66+-0.03) eV fo...

  13. Magnetic Field Stabilized Electron-Hole Liquid in Indirect-Band-Gap AlxGa1-xAs

    Energy Technology Data Exchange (ETDEWEB)

    Alberi, Kristin; Fluegel, Brian; Crooker, Scott A.; Mascarenhas, Angelo

    2016-02-15

    An electron-hole liquid (EHL), a condensed liquidlike phase of free electrons and holes in a semiconductor, presents a unique system for exploring quantum many-body phenomena. While the behavior of EHLs is generally understood, less attention has been devoted to systematically varying the onset of their formation and resulting properties. We report on an experimental approach to tune the conditions of formation and characteristics using a combination of low excitation densities and high magnetic fields up to 90 T. Demonstration of this approach was carried out in indirect-band-gap Al0.387Ga0.613As. EHL droplets can be nucleated from one of two multiexciton complex states depending on the applied excitation density. Furthermore, the excitation density influences the carrier density of the EHL at high magnetic fields, where filling of successive Landau levels can be controlled. The ability to manipulate the formation pathway, temperature, and carrier density of the EHL phase under otherwise fixed experimental conditions makes our approach a powerful tool for studying condensed carrier phases in further detail.

  14. Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Alper, C.; Ionescu, A. M. [Nanoelectronic Devices Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015 (Switzerland); Medina-Bailón, C.; Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)

    2015-06-29

    We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I{sub ON} levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures.

  15. Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

    International Nuclear Information System (INIS)

    We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher ION levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures

  16. Effect of Electron-Hole Overlap and Exchange Interaction on Exciton Radiative Lifetimes of CdTe/CdSe Heteronanocrystals.

    Science.gov (United States)

    Granados Del Águila, Andrés; Groeneveld, Esther; Maan, Jan C; de Mello Donegá, Celso; Christianen, Peter C M

    2016-04-26

    Wave function engineering has become a powerful tool to tailor the optical properties of semiconductor colloidal nanocrystals. Core-shell systems allow to design the spatial extent of the electron (e) and hole (h) wave functions in the conduction- and valence bands, respectively. However, tuning the overlap between the e- and h-wave functions not only affects the oscillator strength of the coupled e-h pairs (excitons) that are responsible for the light emission, but also modifies the e-h exchange interaction, leading to an altered excitonic energy spectrum. Here, we present exciton lifetime measurements in a strong magnetic field to determine the strength of the e-h exchange interaction, independently of the e-h overlap that is deduced from lifetime measurements at room temperature. We use a set of CdTe/CdSe core/shell heteronanocrystals in which the electron-hole separation is systematically varied. We are able to unravel the separate effects of e-h overlap and e-h exchange on the exciton lifetimes, and we present a simple model that fully describes the recombination lifetimes of heteronanostructures (HNCs) as a function of core volume, shell volume, temperature, and magnetic fields. PMID:26982795

  17. Multiphoton transitions for delay-zero calibration in attosecond spectroscopy

    International Nuclear Information System (INIS)

    The exact delay-zero calibration in an attosecond pump-probe experiment is important for the correct interpretation of experimental data. In attosecond transient absorption spectroscopy the determination of the delay-zero exclusively from the experimental results is not straightforward and may introduce significant errors. Here, we report the observation of quarter-laser-cycle (4ω) oscillations in a transient absorption experiment in helium using an attosecond pulse train overlapped with a precisely synchronized, moderately strong infrared pulse. We demonstrate how to extract and calibrate the delay-zero with the help of the highly nonlinear 4ω signal. A comparison with the solution of the time-dependent Schrödinger equation is used to confirm the accuracy and validity of the approach. Moreover, we study the mechanisms behind the quarter-laser-cycle and the better-known half-laser-cycle oscillations as a function of experimental parameters. This investigation yields an indication of the robustness of our delay-zero calibration approach. (paper)

  18. Theory of attosecond delays in laser-assisted photoionization

    CERN Document Server

    Dahlström, J M; Klünder, K; Gisselbrecht, M; Mauritsson, J; L'Huillier, A; Maquet, A; Taïeb, R

    2011-01-01

    We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum--continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. This makes clear that the observed time-delays...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Energy relaxation and separation of a hot electron-hole pair in organic aggregates from a time-dependent wavepacket diffusion method

    International Nuclear Information System (INIS)

    The time-dependent wavepacket diffusive method [X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013)] is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling. The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with a central momentum. The results reveal that the hot electron energy relaxation is very well described by two rate processes with the fast rate much larger than the slow one, consistent with experimental observations, and an efficient electron-hole separation is accomplished accompanying the fast energy relaxation. Furthermore, although the extra energy indeed helps the separation by overcoming the Coulomb interaction, the width of initial wavepacket is much sensitive to the separation efficiency and the narrower wavepacket generates the more separated charges. This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation

  5. Quantum transport in chemically functionalized graphene at high magnetic field: Defect-Induced Critical States and Breakdown of Electron-Hole Symmetry

    OpenAIRE

    Leconte, Nicolas; Ortmann, Frank; Cresti, Alessandro; Charlier, Jean-Christophe; Roche, Stephan

    2014-01-01

    Unconventional magneto-transport fingerprints in the quantum Hall regime (with applied magnetic field from one to several tens of Tesla) in chemically functionalized graphene are reported. Upon chemical adsorption of monoatomic oxygen (from 0.5% to few percents), the electron-hole symmetry of Landau levels is broken, while a double-peaked conductivity develops at low-energy, resulting from the formation of critical states conveyed by the random network of defects-induced impurity states. Scal...

  6. 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.

  7. 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.

  8. 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.

  9. 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)

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Ultracold-atom quantum simulator for attosecond science

    CERN Document Server

    Sala, Simon; Saenz, Alejandro

    2013-01-01

    A quantum simulator based on ultracold optically trapped atoms for simulating the physics of atoms and molecules in ultrashort intense laser fields is introduced. The slowing down by about 13 orders of magnitude allows to watch in slow motion the tunneling and recollision processes that form the heart of attosecond science. The extreme flexibility of the simulator promises a deeper understanding of strong-field physics, especially for many-body systems beyond the reach of classical computers. The quantum simulator can experimentally straightforwardly be realized and is shown to recover the ionization characteristics of atoms in the different regimes of laser-matter interaction.

  20. 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.

  1. Attosecond Synchronization of High-Order Harmonics from Midinfrared Drivers

    International Nuclear Information System (INIS)

    The group delay dispersion, also known as the attochirp, of high-order harmonics generated in gases has been identified as the main intrinsic limitation to the duration of Fourier-synthesized attosecond pulses. Theory implies that the attochirp, which is inversely proportional to the laser wavelength, can be decreased at longer wavelength. Here we report the first measurement of the wavelength dependence of the attochirp using an all-optical, in situ method [N. Dudovich et al., Nature Phys. 2, 781 (2006)]. We show that a 2 μm driving wavelength reduces the attochirp with respect to 0.8 μm at comparable intensities

  2. 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

  3. 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.

  4. 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)

  5. 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.

  6. 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

  7. 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.

  8. 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.

  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. 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.

  12. 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

  13. 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

  14. Time-resolved photoemission by attosecond streaking: extraction of time information

    OpenAIRE

    Nagele, S; Pazourek, R; Feist, J.; Doblhoff-Dier, K; Lemell, C.; Tőkési, K; Burgdörfer, J.

    2011-01-01

    Attosecond streaking of atomic photoemission holds the promise to provide unprecedented information on the release time of the photoelectron. We show that attosecond streaking phase shifts indeed contain timing (or spectral phase) information associated with the Eisenbud-Wigner-Smith time delay matrix of quantum scattering. However, this is only accessible if the influence of the streaking infrared (IR) field on the emission process is properly accounted for. The IR probe field can strongly m...

  15. 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...

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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)

  2. 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.

  3. 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.

  4. Real-time evolution of a laser-dressed Helium atom: Attosecond-resolved two-color photoionization study

    CERN Document Server

    Shivaram, Niranjan; Tong, Xiao-Min; Sandhu, Arvinder S

    2011-01-01

    Using extreme-ultraviolet attosecond-pulse-trains, we investigate the photoionization dynamics of a Helium atom in the presence of moderately-strong (~10^12 W/cm^2) femtosecond laser pulses. The electronic structure of a laser-dressed atom is traced in real-time through precision measurements of ion-yields and photo-electron angular distributions. Quantum interferences between photo-excitation paths are interpreted using the Floquet formalism. As the laser pulse intensity ramps on femtosecond timescales, we observe transitions between ionization channels mediated by different atomic resonances. The quantum phase of interfering paths is extracted for each channel and compared with simulations. Our results elucidate photoionization mechanisms in strong-fields and open the doors for photo-absorption/ionization control schemes.

  5. Review of attosecond resolved measurement and control via carrier–envelope phase tagging with above-threshold ionization

    International Nuclear Information System (INIS)

    A precise, real-time, single-shot carrier–envelope phase (CEP) tagging technique for few-cycle pulses was developed and combined with cold-target recoil-ion momentum spectroscopy and velocity-map imaging to investigate and control CEP-dependent processes with attosecond resolution. The stability and precision of these new techniques have allowed for the study of intense, few-cycle, laser-matter dynamics with unprecedented detail. Moreover, the same stereo above-threshold ionization (ATI) measurement was expanded to multi-cycle pulses and allows for CEP locking and pulse-length determination. Here we review these techniques and their first applications to waveform characterization and control, non-sequential double ionization of argon, ATI of xenon and electron emission from SiO2 nanospheres. (invited review)

  6. 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.

  7. Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.

    Science.gov (United States)

    Luo, Kun; Roberts, Matthew R; Hao, Rong; Guerrini, Niccoló; Pickup, David M; Liu, Yi-Sheng; Edström, Kristina; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

    2016-07-01

    During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates. PMID:27325095

  8. Simulation of attosecond-resolved imaging of the plasmon electric field in metallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Prell, James S.; Borja, Lauren J. [Department of Chemistry, University of California, Berkeley, CA, 94720-1460 (United States); Neumark, Daniel M. [Department of Chemistry, University of California, Berkeley, CA, 94720-1460 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720 (United States); Leone, Stephen R. [Department of Chemistry, University of California, Berkeley, CA, 94720-1460 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720 (United States); Department of Physics, University of California, Berkeley, CA, 94720-1460 (United States)

    2013-02-15

    Sub-cycle photoelectron streaking from silver plasmonic nanospheres is simulated using few-cycle laser pulses tuned both on and off the plasmon resonance (376 nm vs 800 nm, respectively) to initiate the plasmon. Phase-locked, isolated attosecond XUV pulses induce photoemission from the nanospheres, and two different types of streaking of the photoelectrons occur simultaneously due to the laser and plasmon electric fields. Streaking is simulated over a wide range of excitation pulse intensities, and final velocity distributions for the photoelectrons emitted at different times are calculated. The resulting velocity distributions exhibit several characteristics attributable to the plasmon electric field. The dipole moment amplitude can be reconstructed using velocity map imaging or time-of-flight photoelectron velocity measurements without separate measurement of the laser electric field or deconvolution using an assumed streaking trace shape. These results indicate that photoelectron experiments in table-top set-ups can provide unprecedented spatio-temporal information about sub-cycle plasmon dynamics in metallic nanostructures. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. 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.

  10. Attosecond Coherent Control of Single and Double Photoionization in Argon.

    Science.gov (United States)

    Hogle, C W; Tong, X M; Martin, L; Murnane, M M; Kapteyn, H C; Ranitovic, P

    2015-10-23

    Ultrafast high harmonic beams provide new opportunities for coherently controlling excitation and ionization processes in atoms, molecules, and materials on attosecond time scales by employing multiphoton two-pathway electron-wave-packet quantum interferences. Here we use spectrally tailored and frequency tuned vacuum and extreme ultraviolet harmonic combs, together with two phase-locked infrared laser fields, to show how the total single and double photoionization yields of argon can be coherently modulated by controlling the relative phases of both optical and electronic-wave-packet quantum interferences. This Letter is the first to apply quantum control techniques to double photoionization, which is a fundamental process where a single, high-energy photon ionizes two electrons simultaneously from an atom. PMID:26551112

  11. 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.

  12. 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.

  13. High repetition rate plasma mirror device for attosecond science

    International Nuclear Information System (INIS)

    This report describes an active solid target positioning device for driving plasma mirrors with high repetition rate ultra-high intensity lasers. The position of the solid target surface with respect to the laser focus is optically monitored and mechanically controlled on the nm scale to ensure reproducible interaction conditions for each shot at arbitrary repetition rate. We demonstrate the target capabilities by driving high-order harmonic generation from plasma mirrors produced on glass targets with a near-relativistic intensity few-cycle pulse laser system operating at 1 kHz. During experiments, residual target surface motion can be actively stabilized down to 47 nm (root mean square), which ensures sub-300-as relative temporal stability of the plasma mirror as a secondary source of coherent attosecond extreme ultraviolet radiation in pump-probe experiments

  14. High repetition rate plasma mirror device for attosecond science

    Energy Technology Data Exchange (ETDEWEB)

    Borot, A.; Douillet, D.; Iaquaniello, G.; Lefrou, T.; Lopez-Martens, R. [Laboratoire d' Optique Appliquée, ENSTA-ParisTech, CNRS, Ecole Polytechnique, UMR 7639, 91761 Palaiseau (France); Audebert, P.; Geindre, J.-P. [Laboratoire pour l' Utilisation des Lasers Intenses, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex (France)

    2014-01-15

    This report describes an active solid target positioning device for driving plasma mirrors with high repetition rate ultra-high intensity lasers. The position of the solid target surface with respect to the laser focus is optically monitored and mechanically controlled on the nm scale to ensure reproducible interaction conditions for each shot at arbitrary repetition rate. We demonstrate the target capabilities by driving high-order harmonic generation from plasma mirrors produced on glass targets with a near-relativistic intensity few-cycle pulse laser system operating at 1 kHz. During experiments, residual target surface motion can be actively stabilized down to 47 nm (root mean square), which ensures sub-300-as relative temporal stability of the plasma mirror as a secondary source of coherent attosecond extreme ultraviolet radiation in pump-probe experiments.

  15. 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.

  16. 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)

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. The dynamics of electron and ion holes in a collisionless plasma

    Directory of Open Access Journals (Sweden)

    B. Eliasson

    2005-01-01

    Full Text Available We present a review of recent analytical and numerical studies of the dynamics of electron and ion holes in a collisionless plasma. The new results are based on the class of analytic solutions which were found by Schamel more than three decades ago, and which here work as initial conditions to numerical simulations of the dynamics of ion and electron holes and their interaction with radiation and the background plasma. Our analytic and numerical studies reveal that ion holes in an electron-ion plasma can trap Langmuir waves, due the local electron density depletion associated with the negative ion hole potential. Since the scale-length of the ion holes are on a relatively small Debye scale, the trapped Langmuir waves are Landau damped. We also find that colliding ion holes accelerate electron streams by the negative ion hole potentials, and that these streams of electrons excite Langmuir waves due to a streaming instability. In our Vlasov simulation of two colliding ion holes, the holes survive the collision and after the collision, the electron distribution becomes flat-topped between the two ion holes due to the ion hole potentials which work as potential barriers for low-energy electrons. Our study of the dynamics between electron holes and the ion background reveals that standing electron holes can be accelerated by the self-created ion cavity owing to the positive electron hole potential. Vlasov simulations show that electron holes are repelled by ion density minima and attracted by ion density maxima. We also present an extension of Schamel's theory to relativistically hot plasmas, where the relativistic mass increase of the accelerated electrons have a dramatic effect on the electron hole, with an increase in the electron hole potential and in the width of the electron hole. A study of the interaction between electromagnetic waves with relativistic electron holes shows that electromagnetic waves can be both linearly and nonlinearly

  3. Experimental determination of electron-hole pair creation energy in 4H-SiC epitaxial layer: An absolute calibration approach

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhuri, Sandeep K.; Zavalla, Kelvin J.; Mandal, Krishna C. [Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States)

    2013-01-21

    Electron-hole pair creation energy ({epsilon}) has been determined from alpha spectroscopy using 4H-SiC epitaxial layer Schottky detectors and a pulser calibration technique. We report an experimentally obtained {epsilon} value of 7.28 eV in 4H-SiC. The obtained {epsilon} value and theoretical models were used to calculate a Fano factor of 0.128 for 5.48 MeV alpha particles. The contributions of different factors to the ultimate alpha peak broadening in pulse-height spectra were determined using the calculated {epsilon} value and Monte-Carlo simulations. The determined {epsilon} value was verified using a drift-diffusion model of variation of charge collection efficiency with applied bias.

  4. Localized surface plasmon induced enhancement of electron-hole generation with silver metal island at n-Al:ZnO/p-Cu2O heterojunction

    International Nuclear Information System (INIS)

    Localized surface plasmon induced generation of electron-hole pairs with inclusion of metal islands of noble metal like Ag can enhance the photocurrent. A heterostructure of n-Al:ZnO/p-Cu2O with inclusion of Ag metalislands at the junction has been fabricated. I-V characteristic curve of these heterostructures shows a significant enhancement of photocurrent under the illumination (1.5 AMU). This enhancement of photocurrent is attributed to the supply of hot electrons generated in silver metal nanoislands. It has also been shown that inclusion of metal islands increases the absorption of solar spectrum in visible region at 500 nm. Enhancement of photocurrent may also be due to the direct resonance energy transfer from Localized Surface Plasmons of metal islands to Cu2O

  5. Investigation of the energy spectra and the electron-hole alignment of the InAs/GaAs quantum dots with an ultrathin cap layer

    Science.gov (United States)

    Gorshkov, Alexey P.; Volkova, Natalia S.; Istomin, Leonid A.; Zdoroveishev, Anton V.; Levichev, Sergey

    2016-08-01

    The effects of indium composition and the thickness of the combined InGaAs/GaAs thin cap layer on the energy spectra and relative electron-hole alignment of InAs quantum dots (QDs) grown by metal organic vapor phase epitaxy (MOVPE) are investigated by photoelectrical spectroscopy in a semiconductor/electrolyte system. In structures with InAs QDs and an InGaAs strain reducing layer, the shift of the hole's wave function to the QDs' top was revealed, which indicates In enrichment of the area near the top of QD'. In structures with an ultrathin GaAs cap layer a change of the sign of the built-in dipole moment was observed. This is explained by coupling effects of quantum-confined electrons with surface states.

  6. Electron-hole correlation effects in core-level spectroscopy probed by the resonant inelastic soft x-ray scattering map of C{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Weinhardt, L.; Fuchs, O.; Schoell, A.; Reinert, F. [Universitaet Wuerzburg, Experimentelle Physik VII, Am Hubland, 97074 Wuerzburg (Germany); Batchelor, D.; Umbach, E. [Karlsruhe Institute of Technology, D-76021 Karlsruhe (Germany); Baer, M. [Solar Energy Research, Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH (HZB), 14109 Berlin (Germany); Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154-4003 (United States); Blum, M. [Universitaet Wuerzburg, Experimentelle Physik VII, Am Hubland, 97074 Wuerzburg (Germany); Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154-4003 (United States); Denlinger, J. D.; Yang, W. [Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Heske, C. [Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154-4003 (United States)

    2011-09-14

    We have employed a unique spectroscopic approach, a resonant inelastic soft x-ray scattering (RIXS) map, to identify and separate electron-hole correlation effects in core-level spectroscopy. With this approach, we are able to derive a comprehensive picture of the electronic structure, separating ground state properties (such as the HOMO-LUMO separation) from excited state properties (such as the C 1s core-exciton binding energy of C{sub 60}). In particular, our approach allows us to determine the difference between core- and valence exciton binding energies in C{sub 60}[0.5 ({+-}0.2) eV]. Furthermore, the RIXS map gives detailed insight into the symmetries of the intermediate and final states of the RIXS process.

  7. Localized surface plasmon induced enhancement of electron-hole generation with silver metal island at n-Al:ZnO/p-Cu{sub 2}O heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Gurpreet, E-mail: physgk@gmail.com; Yadav, K. L.; Mitra, Anirban [High Power Laser Lab, Department of Physics, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand (India)

    2015-08-03

    Localized surface plasmon induced generation of electron-hole pairs with inclusion of metal islands of noble metal like Ag can enhance the photocurrent. A heterostructure of n-Al:ZnO/p-Cu{sub 2}O with inclusion of Ag metalislands at the junction has been fabricated. I-V characteristic curve of these heterostructures shows a significant enhancement of photocurrent under the illumination (1.5 AMU). This enhancement of photocurrent is attributed to the supply of hot electrons generated in silver metal nanoislands. It has also been shown that inclusion of metal islands increases the absorption of solar spectrum in visible region at 500 nm. Enhancement of photocurrent may also be due to the direct resonance energy transfer from Localized Surface Plasmons of metal islands to Cu{sub 2}O.

  8. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... enhanced in quantum confined lower-dimensional systems, where exciton and biexciton effects dominate the spectra even at room temperature. The coherent dynamics of excitons are at modest densities well described by the optical Bloch equations and a number of the dynamical effects known from atomic and...... as a tool to study the coherent exciton dynamics, and the importance of performing transform limited spectroscopy is demonstrated throughout....

  9. 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.

  10. Study of attosecond delays using perturbation diagrams and exterior complex scaling

    CERN Document Server

    Dahlström, J M

    2014-01-01

    We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange (RPAE). Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M -shell of argon atoms, where experiments have been carried out using the so-called RABITT technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon.

  11. Intensity dependence of laser-assisted atto-second photoionization spectra

    International Nuclear Information System (INIS)

    We study experimentally the influence of the intensity of the infrared (IR) probe field on atto-second pulse train (APT) phase measurements performed with the RABITT method (Reconstruction of atto-second Beating by Interference in Two-Photon Transitions). We find that if a strong IR field is applied, the atto-second 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. (authors)

  12. 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.

  13. 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.

  14. 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.

  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. 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.

  17. 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.”.

  18. 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}.

  19. 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.

  20. 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

  1. Imaging electron dynamics with time- and angle-resolved photoelectron spectroscopy

    CERN Document Server

    Popova-Gorelova, Daria; Santra, Robin

    2016-01-01

    We theoretically study how time- and angle-resolved photoemission spectroscopy can be applied for imaging coherent electron dynamics in molecules. We consider a process in which a pump pulse triggers coherent electronic dynamics in a molecule by creating a valence electron hole. An ultrashort extreme ultraviolet (XUV) probe pulse creates a second electron hole in the molecule. Information about the electron dynamics is accessed by analyzing angular distributions of photoemission probabilities at a fixed photoelectron energy. We demonstrate that a rigorous theoretical analysis, which takes into account the indistinguishability of transitions induced by the ultrashort, broadband probe pulse and electron hole correlation effects, is necessary for the interpretation of time- and angle-resolved photoelectron spectra. We show how a Fourier analysis of time- and angle-resolved photoelectron spectra from a molecule can be applied to follow its electron dynamics by considering photoelectron distributions from an indol...

  2. 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

  3. 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...

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Use of photoelectron laser phase determination method for attosecond measurements with quantum-mechanical calculations

    International Nuclear Information System (INIS)

    This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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)

  19. Attosecond Timing in Optical-to-Electrical Conversion

    CERN Document Server

    Baynes, Fred N; Fortier, Tara; Zhou, Qiugui; Beling, Andreas; Campbell, Joe C; Diddames, Scott A

    2014-01-01

    The most frequency-stable sources of electromagnetic radiation are produced optically, and optical frequency combs provide the means for high fidelity frequency transfer across hundreds of terahertz and into the microwave domain. A critical step in this photonic-based synthesis of microwave signals is the optical-to-electrical conversion process. Here we show that attosecond (as) timing stability can be preserved across the opto-electronic interface of a photodiode, despite an intrinsic temporal response that is more than six orders of magnitude slower. The excess timing noise in the photodetection of a periodic train of ultrashort optical pulses behaves as flicker noise (1/f) with amplitude of 4 as/Sqrt(Hz) at 1 Hz offset. The corresponding fractional frequency fluctuations are 1.4x10-17 at 1 second and 5.5x10-20 at 1000 seconds. These results demonstrate that direct photodetection, as part of frequency-comb-based microwave synthesis, can support the timing performance of the best optical frequency standards...

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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).

  6. Study of attosecond delays using perturbation diagrams and exterior complex scaling

    International Nuclear Information System (INIS)

    We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange. Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M-shell of argon atoms, where experiments have been carried out using the so-called reconstruction of attosecond beating by the two-photon interference transitions technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon. (paper)

  7. 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)

  8. 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)

  9. 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.

  10. 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.

  11. 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

  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. 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. 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)

  15. Columnar recombination for X-ray generated electron-holes in amorphous selenium and its significance in a-Se x-ray detectors

    Science.gov (United States)

    Bubon, O.; Jandieri, K.; Baranovskii, S. D.; Kasap, S. O.; Reznik, A.

    2016-03-01

    Although amorphous selenium (a-Se) has a long and successful history of application in optical and X-ray imaging, some of its fundamental properties are still puzzling. In particularly, the mechanism of carrier recombination following x-ray excitation and electric field and temperature dependences of the electron-hole pair creation energy (Wehp) remain unclear. Using the combination of X-ray photocurrent and pulse height spectroscopy measurements, we measure Wehp in a wide range of temperatures (218-320 K) and electric fields (10-100 V/µm) and show that the conventional columnar recombination model which assumes Langevin recombination within a column (a primary electron track) fails to explain experimental results in a wide range of electric fields and temperatures. The reason for the failure of the conventional model is revealed in this work, and the theory of the columnar recombination is modified to include the saturation of the recombination rate at high electric field in order to account for the experimental results in the entire range of fields and temperatures.

  16. Spatial separation of photo-generated electron-hole pairs in BiOBr/BiOI bilayer to facilitate water splitting.

    Science.gov (United States)

    Tang, Zhen-Kun; Yin, Wen-Jin; Le Zhang; Wen, Bo; Zhang, Deng-Yu; Liu, Li-Min; Lau, Woon-Ming

    2016-01-01

    The electronic structures and photocatalytic properties of bismuth oxyhalide bilayers (BiOX1/BiOX2, X1 and X2 are Cl, Br, I) are studied by density functional theory. Briefly, their compositionally tunable bandgaps range from 1.85 to 3.41 eV, suitable for sun-light absorption, and all bilayers have band-alignments good for photocatalytic water-splitting. Among them, heterogeneous BiOBr/BiOI bilayer is the best as it has the smallest bandgap. More importantly, photo-excitation of BiOBr/BiOI leads to electron supply to the conduction band minimum with localized states belonging mainly to bismuth of BiOBr where the H(+)/H2 half-reaction of water-splitting can be sustained. Meanwhile, holes generated by such photo-excitation are mainly derived from the iodine states of BiOI in the valence band maximum; thus, the O2/H2O half-reaction of water splitting is facilitated on BiOI. Detailed band-structure analysis also indicates that this intriguing spatial separation of photo-generated electron-hole pairs and the two half-reactions of water splitting are good for a wide photo-excitation spectrum from 2-5 eV; as such, BiOBr/BiOI bilayer can be an efficient photocatalyst for water-splitting, particularly with further optimization of its optical absorptivity. PMID:27585548

  17. Theoretical study on the effect of electron-hole pair excitations in resonant X-Ray emission spectroscopy for Ce intermetallic compounds

    International Nuclear Information System (INIS)

    We calculate Ce 4f→3d resonant X-Ray emission spectra (4f→3d RXES) of Ce intermetallic compounds on the basis of the impurity Anderson model. The calculation is based on the second-order optical formula and the excitation of electron-hole (e-h) pairs in the conduction band is taken into account. In the calculation of the first-order optical processes such as X-Ray photoemission spectroscopy (XPS) and X-Ray absorption spectroscopy (XAS) for rare earth systems, even if they are metallic ones, the effect of e-h pairs is usually neglected on the basis of the 1/Nf expansion. We will point out the importance of taking into account e-h pairs in RXES by showing the calculated results of 4f→3d RXES. In these spectra, the structures originating from e-h pairs newly appear, and the spectral weight transfer from the configuration without e-h pairs to that with e-h pairs is clearly observed. The reason why the effect of e-h pairs clearly appears in RXES is also discussed. (author)

  18. Electron magnetic resonance (EMR) study of electron-hole asymmetry in La1-x Ca x MnO3 manganites (x=0.2,0.8)

    International Nuclear Information System (INIS)

    X-band EMR measurements on powdered samples of single-crystalline La0.8Ca0.2MnO3 and polycrystalline La0.2Ca0.8MnO3 manganites were carried out at 120T500 K aiming to study the effect of the electron-hole doping asymmetry in La1-x Ca x MnO3 system. In the paramagnetic (PM) state both compounds differ in the nature of short-range magnetic orderings observed-clusters of double-exchange coupled Mn3+-Mn4+ ions and magneto-impurity-like clusters in the La0.8Ca0.2MnO3 and La0.2Ca0.8MnO3 compounds, respectively. Ferromagnetic ground state of La0.8Ca0.2MnO3 is characterized by the coexistence of orbitally ordered Mn3+ subsystem and Mn4+ with band-like carriers one, which are responsible for the multiline EMR spectra. Charge-ordered antiferromagnetic ground state of La0.2Ca0.8MnO3 causes a sharp decrease in intensity and then vanishing of the EMR signal observed in the PM region

  19. Direct View of Hot Carrier Dynamics in Graphene

    DEFF Research Database (Denmark)

    Johannsen, Jens Christian; Ulstrup, Søren; Cilento, Federico;

    2013-01-01

    The ultrafast dynamics of excited carriers in graphene is closely linked to the Dirac spectrum and plays a central role for many electronic and optoelectronic applications. Harvesting energy from excited electron-hole pairs, for instance, is only possible if these pairs can be separated before th...

  20. Ultrafast electronic dynamics in laser-excited crystalline bismuth

    Directory of Open Access Journals (Sweden)

    Chekalin S.

    2013-03-01

    Full Text Available Femtosecond spectroscopy was applied to capture complex dynamics of non equilibrium electrons in bismuth. Data analysis reveals significant wavevector dependence of electron-hole and electron-phonon coupling strength along the Γ-T direction of the Brillouin zone

  1. On the Attosecond charge migration in Cl.....N, Cl.....O, Br.....N and Br.....O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

    Indian Academy of Sciences (India)

    SANKHABRATA CHANDRA; MOHAMMED MUSTHAFA IQBAL; ATANU BHATTACHARYA

    2016-08-01

    The electron-electron relaxation and correlation-driven charge migration process, which features pure electronic aspect of ultrafast charge migration phenomenon, occurs on a very short timescale in ionized molecules and molecular clusters, prior to the onset of nuclear motion. In this article, we have presented natureof ultrafast pure electronic charge migration dynamics through Cl.....N, Cl.....O, Br.....N, and Br.....O halogen bonds, explored using density functional theory. We have explored the role of donor, acceptor, electron correlation, vibration and rotation in charge migration dynamics through these halogen bonds. For this work, we have selected ClF, Cl₂, ClOH, ClCN, BrF, BrCl, BrOH, and BrCN molecules paired with either NH₃ or H₂O. We have found that the timescale for pure electron-electron relaxation and correlation-driven charge migration through the Cl.....N, Br.....N, Cl.....O, and Br.....O halogen bonds falls in the range of 300–600 attosecond. The primary driving force behind the attosecond charge migration through the Cl.....N, Br.....N, Cl.....O, and Br.....O halogen bonds is the energy difference (∆E) between two stationary cationic orbitals (LUMO-β and HOMO-β), which together represents the initial hole density immediately following vertical ionization. We have also predicted that the strength of electron correlation has significant effect on the charge migration timescale in Cl.....N, Br.....N, Cl.....O, and Br.....O halogen bonded clusters. Vibration and rotation are also found to exhibit profound effect on attosecond charge migration dynamics through halogen bonds.

  2. Cluster dynamics transcending chemical dynamics toward nuclear fusion

    OpenAIRE

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-01-01

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 1015–1020 W·cm−2). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C4+(D+)4)n and (D+I22+)n at IM = 1018 W·cm−2, that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. Th...

  3. Time-resolved photoemission by attosecond streaking. Extraction of time information

    International Nuclear Information System (INIS)

    Complete text of publication follows. Attosecond streaking is one of the most spectacular applications within the emerging field of attoscience. Streaking is based on a variant of a pump-probe setting with an extreme ultraviolet (XUV) pulse of a few hundred attoseconds serving as a pump and a phase controlled few-cycle infrared (IR) pulse as a probe. Electrons emitted in the presence of an IR field are accelerated to different final momenta and energies depending on the value of the vector potential at the release time. Thus, time information is mapped onto the energy axis in analogy to conventional streaking. Attosecond streaking of atomic photoemission holds the promise to provide unprecedented information on the release time of the photoelectron. We have shown that attosecond streaking phase shifts indeed contain timing (or spectral phase) information associated with the Eisenbud - Wigner - Smith (EWS) time delay matrix of quantum scattering. We have identified on the one-electron (or independent particle) level considerable state dependent time shifts that can be observed in attosecond streaking and which are of quantum mechanical origin. We found a time delay between the hydrogenic 2s and 2p initial states in He+ exceeding 20 as for a wide range of IR intensities and XUV energies (see Fig. 1). In addition, we have identified large time shifts which result from the coupling between the IR streaking field and the Coulomb field which depend on the final energy of the free electron and can be accounted for classically. The EWS time shift (or energy variation of the scattering phase) is found to be accessible by streaking only if both initial-state-dependent entrance channel and final-state exit channel distortions are properly accounted for. For such a scenario we have shown that time delays on the single-digit attosecond scale due to short-ranged potentials are in reach. Acknowledgements This work was supported by the FWF-Austria, grant nos SFB016 and P21141-N16

  4. Study of recombination processes for 'electron-hole' pairs in germanium irradiated by γ rays from 60Co using the photovoltaic effect in P-N junctions

    International Nuclear Information System (INIS)

    Using the photo-voltaic effect in p-n junctions, we have studied, during bombardment, the mechanism of the recombination of 'electron-hole' pairs in the presence of structure defects produced in germanium of the N and P types by γ rays from a Co60 source. At 310 K the level of the recombination centres is situated 0.25 eV above the conduction band and the capture cross-sections of the holes and of the electrons have the respective values of: σp = 4 X 10-15 cm2 and σn = 3 X 10-15 cm2. The value of σn appears to be under-estimated because the number of defects in P-type samples appears to be lower than that in N-type samples. These results lead to the conclusion that the interstitials are responsible for the recombination. At 80 K it has been found that in N-type samples, a shallow level exists at O.05 eV below the conduction band with a capture cross-section for the holes of σp ≥ 10-14 cm2. We believe that in this case the recombination of charge carriers is controlled by the neighbouring 'defect-interstitial' pairs. In P-type samples at low temperature, the life-time is practically constant during irradiation. This fact is attributed to a spontaneous annealing of defects ol purely electrical origin. In the last part of the work the study of the photo-voltaic effect applied to the problem of gamma radiation dosimetry is considered. It is shown that such dosimeters, based on this principle, make it possible to measure the intensity of gamma rays over a very wide range. (author)

  5. 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)

  6. Attosecond delay of xenon $4d$ photoionization at the giant resonance and Cooper minimum

    CERN Document Server

    Magrakvelidze, Maia; Chakraborty, Himadri S

    2016-01-01

    A Kohn-Sham time-dependent local-density-functional scheme is utilized to predict attosecond time delays of xenon 4d photoionization that involves the 4d giant dipole resonance and Cooper minimum. The fundamental effect of electron correlations to uniquely determine the delay at both regions is demonstrated. In particular, for the giant dipole resonance, the delay underpins strong collective effect, emulating the recent prediction at C60 giant plasmon resonance [T. Barillot et al, Phys. Rev. A 91, 033413 (2015)]. For the Cooper minimum, a qualitative similarity with a photorecombination experiment near argon 3p minimum [S. B. Schoun et al, Phys. Rev. Lett. 112, 153001 (2014)] is found. The result should encourage attosecond measurements of Xe 4d photoemission.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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

  15. 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...

  16. 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.

  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, 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.

  18. 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.

  19. 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.

  20. 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.)

  1. 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.

  2. 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.

  3. 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)

  4. 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.

  5. 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

  6. 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.

  7. News and views from the attosecond generation, characterization and applications frontier

    International Nuclear Information System (INIS)

    Complete text of publication follows. We report on recent results in the generation, characterization and applications of energetic attosecond pulse trains and ultra-broad coherent XUV continua: 1) Generation: 1a) We report experimental results confirming contribution of both long and short trajectories in on-axis harmonic generation before, at and after an atomic gas jet, i.e. under three different phase matching conditions. The contribution of both trajectories is manifested through their interference leading to a modulated harmonic (and side band) yield as a function of the driving intensity. 1b) We report the generation of sub-fs pulse trains at the 40 μJ pulse energy level from laser surface plasma, measured through 2nd order intensity volume autocorrelation (2nd order IVAC). 2) Characterization: We present comparative studies between RABITT and 2nd order IVAC in on axis harmonic generation before, at and after an atomic gas jet. We find that the two techniques give fairly different results that are compatible with the differently weighted but unavoidable presence of the long and short trajectory in the generation process in all three phase matching conditions. We show that the relative contributions of the two trajectories can be estimated through RABITT measurements, while spatiotemporal mean pulse durations can be extracted from 2nd order IVAC traces. 3) Applications: 3a) We present time resolved VUV spectroscopy of ultrafast dynamics in molecular ethylene. 3b) We present time resolved XUV spectroscopy at the 1 fs temporal scale and ultra-broad band XUV Fourier Transform Spectroscopy in a manifold of doubly excited autoionizing and inner-shell Auger decaying states excited simultaneously through a coherent broadband XUV continuum. Acknowledgments. This work is supported in part by the European Community's Human Potential Program under contract MTKD-CT-2004-517145 (X-HOMES), the Ultraviolet Laser Facility (ULF) operating at FORTH-IESL (contract PHRI-CT-2001

  8. 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...

  9. 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.

  10. 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

  11. 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)

  12. 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.

  13. 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

  14. Tunneling time in attosecond experiments, Keldysh, Mandelstam-Tamm and intrinsic-type of time

    CERN Document Server

    Kullie, Ossama

    2015-01-01

    Tunneling time in attosecond and strong field experiments is one of the most controversial issues in today's research, because of its importance to the theory of time, the time operator and the time-energy uncertainty relation in quantum mechanics. In [1] we derived an estimation of the (real) tunneling time, which shows an excellent agreement with the time measured in attosecond experiments, our derivation is found by utilizing the time-energy uncertainty relation, and it represents a quantum clock. In this work, we show different aspects of the tunneling time in attosecond experiments, we discuss and compare the different views and approaches, which are used to calculate the tunneling time, i.e. Keldysh time (as a real or imaginary quantity), Mandelstam-Tamm time and our tunneling time relation(s). We draw some conclusion concerning the validity and the relation between the different types of the tunneling time with the hope, it will help to answer the the question put forward by Orlando et al [2] tunneling...

  15. 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.

  16. 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...

  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. 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.

  19. 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.

  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.