Making optical atomic clocks more stable with $10^{-16}$ level laser stabilization

TL;DR

This paper presents a highly stable laser system with $10^{-16}$ fractional frequency instability, significantly enhancing the stability and performance of optical atomic clocks by enabling ultranarrow transition resolution.

Contribution

The authors develop a cavity-stabilized laser with reduced thermal noise, achieving unprecedented stability that improves optical clock performance and measurement precision.

Findings

Laser stability of $2 imes 10^{-16}$ fractional frequency instability.

Resolved ultranarrow 1 Hz transition linewidth in Yb optical lattice clock.

Achieved clock instability of $5 imes 10^{-16} / \sqrt{ au}$.

Abstract

The superb precision of an atomic clock is derived from its stability. Atomic clocks based on optical (rather than microwave) frequencies are attractive because of their potential for high stability, which scales with operational frequency. Nevertheless, optical clocks have not yet realized this vast potential, due in large part to limitations of the laser used to excite the atomic resonance. To address this problem, we demonstrate a cavity-stabilized laser system with a reduced thermal noise floor, exhibiting a fractional frequency instability of $2 \times 10^{-16}$. We use this laser as a stable optical source in a Yb optical lattice clock to resolve an ultranarrow 1 Hz transition linewidth. With the stable laser source and the signal to noise ratio (S/N) afforded by the Yb optical clock, we dramatically reduce key stability limitations of the clock, and make measurements consistent with a clock instability of $5 \times 10^{-16} / \sqrt{\tau}$.