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arXiv · 1004.5110

Extreme ultraviolet frequency comb metrology

Dominik Z. Kandula·Christoph Gohle·Tjeerd J. Pinkert·Wim Ubachs·Kjeld S. E. Eikema
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Abstract

The remarkable precision of frequency comb (FC) lasers is transferred to the extreme ultraviolet (XUV, wavelengths shorter than 100 nm), a frequency region previously not accessable to these devices. A frequency comb at XUV wavelengths near 51 nm is generated by amplification and coherent upconversion of a pair of pulses originating from a near-infrared femtosecond FC laser. The phase coherence of the source in the XUV is demonstrated using Helium atoms as a ruler and phase detector. Signals in the form of stable Ramsey-like fringes with high contrast are observed when the FC laser is scanned over P states of Helium, from which the absolute transition frequency in the XUV can be extracted. This procedure yields a 4He ionization energy at h 5945204212(6) MHz, improved by nearly an order of magnitude in accuracy, thus challenging QED calculations of this two-electron system.

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Dominik Z. Kandula, Christoph Gohle, Tjeerd J. Pinkert, Wim Ubachs, Kjeld S. E. Eikema. 2010-05-10. Extreme ultraviolet frequency comb metrology. https://doi.org/10.1103/physrevlett.105.063001

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