  In this study, a dual-interrogation (DI) method was used to suppress the
light shift in the Rb 778 nm 5S1/2-5D5/2 two-photon transition (TPT) optical
frequency standard. The approach used an auxiliary system to calibrate the
light shift of the primary system in real time to mitigate the absolute light
shift and suppress the sensitivity of the system to the optical power. Results
show that after using the DI method, the absolute light shift and light-power
sensitivity of the system were reduced by a factor of 10. The proposed method
will improve the accuracy of the Rb 778 nm TPT optical frequency standard and
increase the mid- and long-term stability. The method can also be applied to
other vapor-cell atomic frequency standards that experience light shifts.
