Near-100% Bragg reflectivity of X-rays

Journal name:
Nature Photonics
Volume:
5,
Pages:
539–542
Year published:
DOI:
doi:10.1038/nphoton.2011.197
Received
Accepted
Published online

Abstract

Ultrahigh-reflectance mirrors are essential optical elements of the most sophisticated optical instruments devised over the entire frequency spectrum. In the X-ray regime, super-polished mirrors with close to 100% reflectivity are routinely used at grazing angles of incidence. However, at large angles of incidence, and particularly at normal incidence, such high reflectivity has not yet been achieved. Here, we demonstrate by direct measurements that synthetic, nearly defect-free diamond crystals reflect more than 99% of hard X-ray photons backwards in Bragg diffraction, with a remarkably small variation in magnitude across the sample. This is a quantum leap in the largest reflectivity measured to date, which is at the limit of what is theoretically possible. This accomplishment is achieved under the most challenging conditions of normal incidence and with extremely hard X-ray photons.

At a glance

Figures

  1. X-ray Bragg diffraction diagram, X-ray Bragg reflectivity from a thick diamond crystal, and a colour map of averaged Bragg reflectivities for all allowed Bragg reflections and photon energies.
    Figure 1: X-ray Bragg diffraction diagram, X-ray Bragg reflectivity from a thick diamond crystal, and a colour map of averaged Bragg reflectivities for all allowed Bragg reflections and photon energies.

    a, X-ray Bragg reflectivity from a thick diamond crystal as a function of photon energy. Solid line: dynamical theory calculations20 of X-ray reflectivity RH(E) in Bragg backscattering (θ = 90°) for the H = (13 3 3) Bragg reflection with EH = 23.77 keV used in the experiment. Dashed line: calculations under assumption of zero photo-absorption. b, Colour map of reflectivities left fenceRHright fence of hard X-rays from thick diamond crystals averaged over the region of total Bragg reflection ΔEH. The averaged reflectivities are shown for all allowed Bragg reflections sorted by Bragg energies EH < 30 keV, and for the incident photon energies E > EH. White contour lines indicate equal values of incidence angle θ determined by Bragg's law, sin θ = EH/E.

  2. Reflectivity of X-rays as a function of photon energy E in Bragg backscattering from the (13 3 3) atomic planes in diamond (EH = 23.765 keV).
    Figure 2: Reflectivity of X-rays as a function of photon energy E in Bragg backscattering from the (13 3 3) atomic planes in diamond (EH = 23.765 keV).

    a, Filled circles indicate relative reflectivity measurements. Solid line indicates dynamical theory calculations for a 1-mm-thick crystal and incident X-rays with a 1 meV bandwidth. b, Same dependencies as in a, shown on a linear scale. c, Close up of peak reflectivity region in b. Dashed lines in b and c indicate calculations for perfectly monochromatic incident X-rays. d, Filled circles indicate absolute reflectivity measurements. Solid and dashed lines are the same theoretical curves as in a and b. There is no adjustment of the reflectivities of the experimental and theoretical curves except for the energy position of the reflectivity maximum. e, Close up of the peak reflectivity region in d.

  3. Absolute reflectivity.
    Figure 3: Absolute reflectivity.

    ac, Reflectivity of 13.9 keV X-rays from the (8 0 0) atomic planes of a diamond crystal in Bragg backscattering. d, X-ray Lang transmission topogram of the diamond crystal. Nearly defect-free diamond crystal reflects more than 99% of hard X-ray photons backwards in Bragg diffraction, with a remarkably small variation in magnitude across the sample. See text for more details.

  4. Scheme of the experimental set-up for reflectivity measurements with highly monochromatic X-rays.
    Figure 4: Scheme of the experimental set-up for reflectivity measurements with highly monochromatic X-rays.

    See Methods for details.

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Affiliations

  1. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

    • Yuri Shvyd'ko &
    • Stanislav Stoupin
  2. Technological Institute for Super-hard and Novel Carbon Materials, Troitsk, 142190, Russia

    • Vladimir Blank &
    • Sergey Terentyev

Contributions

Y.S. planned, organized, and performed the experiments, analysed the data and wrote the paper. S.S. built the 13.9 keV high-resolution monochromator, and performed reflectivity experiments and white beam topography studies of diamonds. V.B. and S.T. organized the manufacture of synthetic diamonds, and synthesized, processed and characterized the diamond crystals.

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The authors declare no competing financial interests.

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