Operation of atomic-clock transitions by twisted light modes*

During the last decade, a considerable interest has been paid to the production and application of twisted (or vortex) light beams. These structured beams, that possess a helical phase front and also carry orbital angular momentum (OAM), were found to be a valuable tool for a great variety of studies in atomic, molecular and optical physics. Of particular interest here is interrogation of trapped atoms and ions with vortex light. The use of OAM light allows significant suppression of the AC-Stark shift of transition frequencies if an atom is located near the center of photon beam. Together with the efficient excitation of higher-multipole (dipole-forbidden) channels, this cancellation of the AC-Stark shift makes twisted light promising for studying and employing atomic clock transitions. In this contribution we will discuss recent experimental and theoretical advances in spectroscopy of the clock transitions with the help of OAM light beams [1]. Special attention will be placed the $^2S_{1/2} (F = 0) \to {}^2F_{7/2}(F =3 M_F = 0)$ electric octupole (E3) transition in a single trapped ${}^{171}Yb^{+}$ ion, which attracts currently much attention as a candidate for a novel frequency standard. We will show how the topological charge and polarization of incident twisted light can be used to control this transition and will discuss the potential of development of ``OAM-based atomic clocks’’.     

 

[1] S. A.-L. Schulz \textit{et al.}, Phys. Rev. A {\bf 102} (2020) 012812