Abstract

Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.

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Acknowledgements

This work was supported by the USA–Israel Binational Science Foundation (BSF). The Technion group was supported by the Israel Science Foundation (grant no. 1225/14) and the Israeli Center of Research Excellence ‘circle of light’ supported by the I-CORE Program of the Planning and Budgeting Committee and The Israel Science Foundation. The experiment was carried out in JILA. O.K. and O.C acknowledge the warm hospitality in JILA. The JILA and NIST authors acknowledge funding from the US Department of Energy Office of Basic Energy Sciences (award no. DE-SC0002002). JILA also acknowledges funding from the Physics Frontiers Center Program and from an AFOSR DURIP award for the laser system used for this work. P.G. acknowledges support from the Deutsche Forschungsgemeinschaft (no. GR 4234/1-1). R.K. acknowledges the Swedish Research Council (VR) for financial support.

Author information

Affiliations

  1. Solid State Institute and Physics Department, Technion, Haifa 32000, Israel

    • Ofer Kfir
    • , Avner Fleischer
    •  & Oren Cohen
  2. Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA

    • Patrik Grychtol
    • , Emrah Turgut
    • , Ronny Knut
    • , Dmitriy Zusin
    • , Dimitar Popmintchev
    • , Tenio Popmintchev
    • , Hans Nembach
    • , Henry Kapteyn
    •  & Margaret Murnane
  3. Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA

    • Ronny Knut
    • , Hans Nembach
    •  & Justin M. Shaw
  4. Department of Physics and Optical Engineering, Ort Braude College, Karmiel 21982, Israel

    • Avner Fleischer

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Contributions

O.C., M.M. and H.K. conceived and supervised the project. O.K., P.G., E.T. and A.F. designed the experimental set-up. O.K., P.G., E.T., R.K., D.Z., T.P. and D.P. constructed the experimental set-up and conducted the experiment. O.K. and P.G. analysed the data with input from other authors. O.K. developed the theory and carried out the numerical simulations. O.K., P.G. and O.C. wrote the manuscript with input from all other authors.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Ofer Kfir or Oren Cohen.

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DOI

https://doi.org/10.1038/nphoton.2014.293

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