Improve the Frequency Stabilization of Cs Fountain Clock’s Optical System with Modulation Transfer Spectroscopy

In view of the application of modulation transfer spectroscopy (MTS) in laser frequency stabilization can not only completely remove the Doppler background but also avoid extra frequency noise due to the frequency dither to laser in the normally used saturation absorption locking technique. Employ the nonlinear spectroscopy method of modulation transfer (MTS) replaces the saturated absorption for the cesium D 2 line transition to stabilize the laser frequency aims to improve the frequency stability of cesium atomic fountain clock’s optical system. We conducted two sets of modulation transfer spectroscopy apparatuses to stabilize two independent lasers, and the analysis of the beat signal between two independent laser systems has showed a frequency stability of $4.46\times 10^{-12}$ @ls, and a 3dB linewidth about 85KHz.