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Ultra-precise measurement of optical frequency ratios

Jörn Stenger·Harald Schnatz·Christian Tamm·Harald R. Telle
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Abstract

We developed a novel technique for frequency measurement and synthesis, based on the operation of a femtosecond comb generator as transfer oscillator. The technique can be used to measure frequency ratios of any optical signals throughout the visible and near-infrared part of the spectrum. Relative uncertainties of $10^{-18}$ for averaging times of 100 s are possible. Using a Nd:YAG laser in combination with a nonlinear crystal we measured the frequency ratio of the second harmonic $ν_{SH}$ at 532 nm to the fundamental $ν_0$ at 1064 nm, $ν_{SH}/ν_0 = 2.000 000 000 000 000 001 \times (1 \pm 7 \times 10^{-19})$.

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Jörn Stenger, Harald Schnatz, Christian Tamm, Harald R. Telle. 2001-09-24. Ultra-precise measurement of optical frequency ratios. https://doi.org/10.1103/physrevlett.88.073601

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