A Two-Photon E1-M1 Optical Clock

TL;DR

This paper proposes a novel two-photon E1-M1 excitation method for optical clocks that simplifies setup, enhances portability, and offers Doppler-free excitation, with potential for use in hot vapor cell standards.

Contribution

It introduces an E1-M1 excitation scheme for optical clocks that does not require hyperfine mixing or magnetic fields, enabling more portable and accessible frequency standards.

Findings

Neutral Hg has ideal properties for a hot, portable frequency standard.

The method provides Doppler-free excitation without hyperfine mixing.

Optimal parameters are identified for multiple group II atoms.

Abstract

An allowed E1-M1 excitation scheme creates optical access to the ${^1S_0} \rightarrow {^3P_0}$ clock transition in group II type atoms. This method does not require the hyperfine mixing or application of an external magnetic field of other optical clock systems. The advantages of this technique include a Doppler-free excitation scheme and increased portability with the use of vapor cells. We will discuss technical mechanisms of a monochromatic excitation scheme for a hot E1-M1 clock and briefly discuss a bichromatic scheme to eliminate light shifts. We determine the optimal experimental parameters for Hg, Yb, Ra, Sr, Ba, Ca, Mg, and Be and calculate that neutral Hg has ideal properties for a hot, portable frequency standard.