As the optical frequency standards based on cold atoms and ultra-stable cavity-stabilized laser continue to be improved, the demand of optical frequency combs that are used as clockwork is increasing as well. Recently, Matei et al. demonstrated a laser source with a record-breaking sub-Hz linewidth with very low frequency drift. Optical lattice clocks with Strontium atoms interrogated in a cryogenic environment have been demonstrated at 10-18 level of accuracy and stability. Moreover, the first Fermi-degenerate three-dimensional optical lattice frequency standard has also been reported, showing the potential to overridden the tradeoff between low quantum projection noise limit and density-dependent frequency shifts. Due to technical reasons the central frequency of the ultra-stable lasers is at approximately 194 THz, while the clock transition of neural Strontium atoms is centered around 429 THz. Here, we demonstrate a clockwork for spectral purity transfer from a 1542 nm reference laser to the interrogation wavelength of a Strontium clock at 698.44nm, paving the way for a novel level of instability and inaccuracy at 10-19 at 100 second for optical frequency measurement.

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Dr?Ronald?Holzwarth.pdf