Providing $10^{-16}$ Short-Term Stability of a 1.5-$\mu\hbox{m}$ Laser to Optical Clocks

We report on transferring 10
^-16
-level fractional frequency stability of a “master laser” operated at 1.5 μm to a “slave laser” operated at 698 nm, using a femtosecond fiber comb as transfer oscillator. With the 698-nm laser, the
¹
S
₀
-
³
P
₀
clock transition of
⁸⁷
Sr was resolved with a Fourier-limited linewidth of 1.5 Hz (before: 10 Hz). Potential noise sources contributed by the frequency comb are discussed in detail.