Multiple lasers stabilization on a single three color optical cavity

We designed and implemented a simple and robust optical system for the frequency stabilization of lasers at different wavelength, used for the cooling and trapping of atoms in a Yb optical lattice clock. We used a single ultra-stable cavity to lock the frequency of three different lasers at 399 nm, 556 nm and 759 nm exploiting the offset sideband locking technique, derived from the common Pound-Drever-Hall method. A linewidth of less than 300Hz is obtained at 556 nm with a fractional frequency stability of 3 × 10−14 at 1s. At 759 nm we measured a long term drift less than 20kHz per day, which is sufficient to keep the lattice light shift fractional uncertainty under 1 × 10−18. The system was tested by simultaneously locking the three lasers to the cavity and operating the clock without any significant reduction in number of atoms.