Spectral purity transfer between optical wavelengths at the 10−18 level

We present an optical frequency comb-based scheme that transfers 4.5 × 10
⁻¹⁶
fractional frequency stability from a 1062 nm wavelength laser to a 1542 nm laser. We demonstrate that this scheme does not hinder the transfer down to 3 × 10
⁻¹⁸
at 1 s, one order of magnitude better than previous reported result. This exceeds, by more than one order of magnitude, the stability of any optical oscillator demonstrated to date, and satisfies the stability requirement for quantum projection noise-limited optical lattice clocks. We will finally describe our latest efforts to apply this technique for improving the performance the LNE-SYRTE Sr-based optical lattice clocks.