# Compact Optical Atomic Clock Based on a Two-Photon Transition in Rubidium

## TL;DR

This paper presents a compact, manufacturable optical atomic clock using a two-photon transition in rubidium, achieving high stability suitable for practical applications like satellite navigation.

## Contribution

It introduces a simple, commercially-viable optical atomic clock architecture based on rubidium's two-photon transition with detailed stability analysis.

## Key findings

- Achieves fractional frequency instability of 3×10^{-13}/√τ for 1 to 10,000 seconds
- Identifies key sensitivities to magnetic fields, temperature, and laser power
- System constructed mainly from commercial components for easy deployment

## Abstract

Extra-laboratory atomic clocks are necessary for a wide array of applications (e.g. satellite-based navigation and communication). Building upon existing vapor cell and laser technologies, we describe an optical atomic clock, designed around a simple and manufacturable architecture, that utilizes the 778~nm two-photon transition in rubidium and yields fractional frequency instabilities of $3\times10^{-13}/\sqrt{\tau (s)}$ for $\tau$ from 1~s to 10000~s. We present a complete stability budget for this system and explore the required conditions under which a fractional frequency instability of $1\times 10^{-15}$ can be maintained on long timescales. We provide precise characterization of the leading sensitivities to external processes including magnetic fields and fluctuations of the vapor cell temperature and 778~nm laser power. The system is constructed primarily from commercially-available components, an attractive feature from the standpoint of commercialization and deployment of optical frequency standards.