Compact 780 nm Rb Optical Clock

TL;DR

This paper presents a compact 780 nm rubidium optical clock with high stability and precision, utilizing a novel stabilization method to achieve the most accurate frequency stabilization for the first-excited-state transition of alkali atoms.

Contribution

The development of a compact rubidium optical clock stabilized to the Rb D2 transition using modulation transfer spectroscopy, achieving record stability for this atomic transition.

Findings

Frequency instability of 1.91 E-13 @1 s

Most precise stabilization for alkali first-excited-state transition

First optical clock based on this transition

Abstract

We demonstrated a compact 780 nm rubidium optical clock, which includes an optical frequency standard and an optical frequency comb, with an optical volume of 11.6 liters. Unlike the 778 nm rubidium atomic clocks based on two-photon transition, here, the laser frequency is stabilized to the Rb D2 transition, using modulation transfer spectroscopy. This approach effectively eliminates Doppler background and provides a high signal to noise ratio and high sensitivity. A nearly 300 MHz microwave signal, whose phase exactly tracks that of the optical frequency standard, is generated via the optical frequency comb, yielding a frequency instability of 1.91 E-13 @1 s and 5.29 E-14 @1000 s in the electronic domain. To the best of our knowledge, this is the most precise frequency stabilization result for the first-excited-state transition of alkali metal atoms to date and represents the first optical clock based on this transition. These results offer a promising approach for the development of portable optical clocks.