Attosecond photon sources: the first decade and beyond [Invited]

Chang, Zenghu; Corkum, P. B.

doi:10.1364/josab.27.0000b9

Cited by 133 publications

(101 citation statements)

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“…Ideally, the probing pulse would be another attosecond XUV pulse of comparable duration. While considerable progress has been made towards developing attosecond XUV sources of sufficient intensity and timing control (Takahashi et al, 2010;Lan et al, 2011;Gilbertson et al, 2010b;Chang and Corkum, 2010;Tzallas et al, 2011), such XUV-pump-XUV-probe settings have not yet been implemented for attosecond chronoscopy. Instead, IR laser pulses for which exquisite phase-and thus subcycle timing control has been achieved (see e.g., Hentschel et al, 2001;Baltuska et al, 2003;Chang, 2011, and references therein) are used to interrogate the time evolution.…”

Section: )mentioning

confidence: 99%

Attosecond chronoscopy of photoemission

2015

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Recent advances in the generation of well characterized sub-femtosecond laser pulses have opened up unpredicted opportunities for the real-time observation of ultrafast electronic dynamics in matter. Such attosecond chronoscopy allows a novel look at a wide range of fundamental photophysical and photochemical processes in the time domain, including Auger and autoionization processes, photoemission from atoms, molecules, and surfaces, complementing conventional energy-domain spectroscopy. Attosecond chronoscopy raises fundamental conceptual and theoretical questions as which novel information becomes accessible and which dynamical processes can be controlled and steered. These questions are currently a matter of lively debate which we address in this review. We will focus on one prototypical case, the chronoscopy of the photoelectric effect by attosecond streaking. Is photoionization instantaneous or is there a finite response time of the electronic wavefunction to the photoabsorption event? Answers to this question turn out to be far more complex and multi-faceted than initially thought. They touch upon fundamental issues of time and time delay as observables in quantum theory. We review recent progress of our understanding of time-resolved photoemission from atoms, molecules, and solids. We will highlight the unresolved and open questions and we point to future directions aiming at the observation and control of electronic motion in more complex nanoscale structures and in condensed matter.

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confidence: 99%

Attosecond chronoscopy of photoemission

2015

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Attoclock reveals natural coordinates of the laser-induced tunnelling current flow in atoms

et al. 2011

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In the research area of strong-laser-field interactions and attosecond science 1 , tunnelling of an electron through the barrier formed by the electric field of the laser and the atomic potential is typically assumed to be the initial key process that triggers subsequent dynamics [1][2][3] . Here we use the attoclock technique 4 to obtain experimental information about the electron tunnelling geometry (the natural coordinates of the tunnelling current flow) and exit point. We confirm vanishing tunnelling delay time, show the importance of the inclusion of Stark shifts 5,6 and report on multi-electron effects clearly identified by comparing results in argon and helium atoms. Our combined theory and experiment allows us to single out the geometry of the inherently one-dimensional tunnelling problem, through an asymptotic separation of the full three-dimensional problem. Our findings have implications for laser tunnel ionization in all atoms and in particular in larger molecular systems with correspondingly larger dipoles and polarizabilities.One of the most striking manifestations of the rules of quantum mechanics is the possibility for a particle to move from one side of a potential barrier to the other regardless of the energy height of that barrier. This includes the classically forbidden case, referred to as tunnelling, where the potential energy of the barrier is higher than the energy of the particle (Fig. 1a). In linearly polarized laser fields, electron tunnelling is expected to eventually lead to above-threshold ionization, enhanced double ionization and coherent emission up to the X-ray regime with high-order harmonic generation [7][8][9][10] . Therefore, a detailed understanding of the tunnelling step is of paramount importance for attosecond science, including generation of attosecond pulses 11,12 and attosecond measurement techniques 4,13,14 . The attoclock 4 is an attosecond streaking technique 13 . The rotating electric field vector of a close-to-circularly polarized laser field gives the time reference, in a manner similar to the hands of a clock, and the time is measured by counting fractions of cycles with the exact angular position of the rotating electric field. In this way it is possible to obtain attosecond time resolution by employing a femtosecond pulse. The attoclock was used to set an upper limit to the tunnelling delay time during the tunnel ionization process in helium 15 , and to measure the ionization times in double ionization of argon 16,17 . For the attoclock, a very short few-femtosecond pulse is used to both ionize an atom and to provide the time reference. The pulse duration is kept sufficiently short such that the ionization event is limited to within one optical cycle around the peak of the pulse. As a result of the close-to-circular polarization, re-scattering of the liberated electron with the parent ion is mostly suppressed. Assuming classical 1 Physics Department, ETH Zurich, 8093 Zurich, Switzerland, 2 Lundbeck Foundation Theoretical Center for Quantum System Research, De...

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“…In the last decade, attosecond (as) science and ultrafast technology has grown quickly into one of the most exciting scientific new frontiers in the 21st century [1][2][3][4]. In particular, it has been experimentally demonstrated that single and multiple attosecond laser pulses can be produced by means of the process of high-order harmonic generation (HHG) in rare gases [5,6].…”

Section: Introductionmentioning

confidence: 99%

Effects of macroscopic propagation on spectra of broadband supercontinuum harmonics and isolated-attosecond-pulse generation: Coherent control of the electron quantum trajectories in two-color laser fields

Chu

2012

Phys. Rev. A

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Recently it was shown that broadband supercontinuum harmonics can be produced from the long-trajectory electrons in the single-atom response by the coherent control of the electron trajectories through optimized two-color laser fields. Such supercontinuum harmonics can be superposed to generate an isolated sub-30-attosecond (as) pulse [Liu et al., Phys. Rev. A 84, 033414 (2011)]. In this paper, we investigate the effect of macroscopic propagation on the supercontinuum harmonic spectra and the subsequent attosecond-pulse generation of atomic hydrogen. The time-dependent Schrödinger equation is solved accurately and efficiently by means of the time-dependent generalized pseudospectral method. The effects of macroscopic propagation are investigated in near and far field by solving Maxwell's equation. The results show that the contribution of short-trajectory electron emission is increased when the macroscopic propagation is considered. However, the characteristics of the dominant long-trajectory electron emission (in the single-atom response case) are not changed, and an isolated 53 as pulse can be generated in the near field. Moreover, in the far field, the contribution of long-trajectory electron emission is still dominant for both on-axis and off-axis cases. As a result, an isolated 42 as pulse can be generated directly. Similar results are obtained when the atomic target position is changed. Therefore, the proposed method for the single ultrashort attosecond-pulse generation can be realized by means of the coherent control of the electron quantum paths in appropriately optimized two-color laser fields.

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Attosecond photon sources: the first decade and beyond [Invited]

Cited by 133 publications

References 68 publications

Attosecond chronoscopy of photoemission

Attosecond chronoscopy of photoemission

Attoclock reveals natural coordinates of the laser-induced tunnelling current flow in atoms

Effects of macroscopic propagation on spectra of broadband supercontinuum harmonics and isolated-attosecond-pulse generation: Coherent control of the electron quantum trajectories in two-color laser fields

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