Two-photon light shift

Jörg Bialas, W. J. Firth, P. E. Toschek

Shira Jackson, Amar C. Vutha

We find a simple solution to the problem of probe laser light shifts in two-photon optical atomic clocks. We show that there exists a magic polarization at which the light shifts of the two atomic states involved in the clock transition are identical. We calculate the differential polarizability as a function of laser polarization for two-photon optical clocks based on neutral calcium and strontium, estimate the magic polarization angle for these clocks, and determine the extent to which probe laser light shifts can be suppressed. We show that the light shift and the two-photon excitation rate can be independently controlled using the probe laser polarization.

Hans Kleinpoppen

Roman Blum, Stefan Kundermann, Thibaud Ruelle +2 more

The rubidium two-photon optical atomic clock is a promising technology for applications that require a compact yet stable timekeeping device. However, its long-term frequency stability is often limited by the light shift (or AC Stark effect). In a rubidium two-photon frequency standard, we demonstrate in experiment that the light shift of the 778.1 nm wavelength probe beam can be mitigated with another, 1556.2 nm wavelength beam.

David S. Simon, Gregg S. Jaeger, Alexander V. Sergienko

Dou Li, Kangqi Liu, Pengfei Wang +1 more

two-photon transition optical frequency standard (2hν-OFS). 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 light 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 2hν-OFS 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.