Doppler Shift Mitigation in a Chip-Scale Atomic Beam Clock

TL;DR

This paper presents a chip-scale atomic beam clock that mitigates Doppler and light shift sensitivities by exploiting their competition, achieving stable operation with minimal laser frequency dependence.

Contribution

It introduces a novel approach to suppress laser frequency sensitivity in a chip-scale atomic beam clock by leveraging the interplay between Doppler and resonant light shifts.

Findings

Clock operates with zero sensitivity to laser frequency variation.

Achieved white-noise-limited frequency averaging over 1000 seconds.

Demonstrated suppression of common shifts limiting chip-scale atomic clocks.

Abstract

Chip-scale microwave atomic systems based on thermal atomic beams offer a promising approach to realize low-power and low-drift clocks for timing holdover applications. Miniature beam clocks are expected to suppress many of the shifts that commonly limit existing chip-scale atomic clocks based on coherent population trapping, including collisional shifts and some light shifts. However, the beam geometry can amplify some challenges such as Doppler shifts, which generate a strong sensitivity to laser frequency variation. Using a cm-scale 87Rb atom beam clock, we identify a surprisingly strong competition between Doppler shifts and resonant light shifts arising from asymmetric decay in the clock spectroscopy {\Lambda}-system. Leveraging this competition between Doppler and resonant light shifts, we demonstrate clock operation at specific, convenient experimental parameters consistent with zero sensitivity to laser frequency variation and white-noise-limited clock frequency averaging for 1000 s of integration.