Frequency Calibration and Stabilization of the Cooling Laser of Ytterbium Lattice Clock with Molecular Iodine Spectroscopy

In order to apply the frequency comparison among the different optical clocks, transportable optical clocks (TOCs) is suggested as a valuable tool. For transportable clocks, the key technique is how to lock the lasers involved in the whole system. In this paper, we carry out a new way to calibrate and lock the second stage cooling laser of the ytterbium lattice clock with molecular iodine spectroscopy. The locking spectral width of 556 nm laser can be narrowed to 195 kHz, which can be used for frequency control and the stabilization of the second stage cooling. So the new method will make the transportable optical clocks more compact and robust in the future.