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Optimization of Quantum Trajectories Driven by Strong-Field Waveforms

S. Haessler, T. Balčiunas, G. Fan, G. Andriukaitis, A. Pugžlys, A. Baltuška, T. Witting, R. Squibb, A. Zaïr, J. W. G. Tisch, J. P. Marangos, and L. E. Chipperfield
Phys. Rev. X 4, 021028 – Published 19 May 2014
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Abstract

Quasifree 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 extreme ultaviolet emission in the process of high-harmonic generation. The conventional sinusoidal driver fields set limitations on the maximum value of this energy transfer and the efficient return of the launched electron trajectories. It has been predicted that these limits can be significantly exceeded by an appropriately ramped-up cycle shape [L. E. Chipperfield et al., Phys. Rev. Lett. 102, 063003 (2009)]. Here, we present an experimental realization of similar cycle-shaped waveforms and demonstrate control of the high-harmonic generation process on the single-atom quantum level via attosecond steering of the electron trajectories. With our improved optical cycles, we boost the field ionization launching the electron trajectories, increase the subsequent field-to-electron energy transfer, and reduce the trajectory duration. We demonstrate, in realistic experimental conditions, 2 orders of magnitude enhancement of the generated extreme ultraviolet flux together with an increased spectral extension. This application, which is only one example of what can be achieved with cycle-shaped high-field light waves, has significant implications for attosecond spectroscopy and molecular self-probing.

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  • Received 17 January 2014

DOI:https://doi.org/10.1103/PhysRevX.4.021028

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

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Hiking Trails in Attosecond Landscapes

Published 19 May 2014

The frequency and intensity of attosecond light pulses can be increased by optimizing the optical pulses that drive a high-harmonic generation process.

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Authors & Affiliations

S. Haessler*, T. Balčiunas, G. Fan, G. Andriukaitis, A. Pugžlys, and A. Baltuška

  • Photonics Institute, Vienna University of Technology, Gußhausstraße 27/387, 1040 Vienna, Austria

T. Witting, R. Squibb, A. Zaïr, J. W. G. Tisch, and J. P. Marangos

  • Blackett Laboratory, Imperial College, London SW7 2AZ, United Kingdom

L. E. Chipperfield

  • Max Born Institute, Max-Born-Straße 2 A, 12489 Berlin, Germany

  • *Corresponding author. stefan.haessler@tuwien.ac.at
  • Present address: Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden.

Popular Summary

Ultrashort laser pulses can create powerful electric fields that pull on valence electrons as strongly as an atomic nucleus. Over the duration of a single laser lightwave oscillation cycle (lasting a few femtoseconds), an electron can be accordingly detached and steered along trajectories around its parent atom; these trajectories are governed by the time evolution of the lightwave cycles. The ability to shape the lightwave cycle thus yields control over single atoms on the quantum level on subfemtosecond time scales. In this study, we optimize lightwave-steered electron trajectories with more finesse than ever before. We are able to strongly enhance the generation of extreme-ultraviolet pulses that are emitted when the accelerated electron recollides with its parent atom; these pulses can be used for probing extremely fast (subfemtosecond) electron dynamics.

Previous theoretical studies have predicted that the typical sinusoidal waves created by lasers are not optimal for the generation of extreme-ultraviolet pulses. The primary challenge associated with creating optimized nonsinusoidal light waveforms in the laboratory is to phase lock several “color components” of the laser fields. For a long time, physicists were limited to using combinations of only two color components. Here, we demonstrate a technique to create phase-locked color components based on parametric amplification, splitting one photon of the fundamental laser into two photons of lower frequency. We are able to synthesize powerful light waveforms from three locked color components, providing the proof-of-concept for a technology scalable to many more components. The light waveforms that we create enhance the extreme-ultraviolet pulse-generation process, yielding a 100-fold increase in extreme-ultraviolet pulse flux.

This significant enhancement in pulse flux has applications in molecular self-probing and attosecond physics. We have tested photon energies up to 72 eV, although there is no obstacle, in principle, to scaling this technique to higher energies. Apart from extreme-ultraviolet pulse generation, our waveform-shaping technology will also have applications in other laser-driven processes, such as plasma heating or particle acceleration.

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Vol. 4, Iss. 2 — April - June 2014

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