Doppler-free optical clocks
Optical atomic clocks have transformed precision timekeeping, offering superior stability and accuracy compared to their microwave-based counterparts. A key challenge in achieving their exceptional performance is mitigating the Doppler shift caused by the thermal motion of atoms, which limits the achievable spectroscopic resolution. Conventionally, this shift is suppressed by tightly confining atoms, as in optical lattice and ion clocks. An emerging alternative is Doppler-free excitation via multi-photon processes, where the Doppler shifts of the individual laser beams cancel out. In this talk, I will explore the advantages and limitations of this Doppler-free approach and highlight recent developments in two- and three-photon optical clocks. These systems promise to rival or surpass microwave clocks in performance while maintaining their simplicity and robustness.

