Ultra-stable laser with average fractional frequency drift rate below $5\times10^{-19}/\mathrm{s}$

TL;DR

This paper demonstrates an ultra-stable laser stabilized to a cryogenic silicon cavity with an extremely low fractional frequency drift below 5×10⁻¹⁹/s, surpassing many existing standards in stability and drift performance.

Contribution

The study presents a cryogenic silicon cavity-based laser achieving unprecedented fractional frequency drift below 5×10⁻¹⁹/s, with stability surpassing microwave standards without atomic references.

Findings

Fractional frequency instability of ≤2×10⁻¹⁶ at 60-1000s

Stability comparable to the best hydrogen masers over one day

Fractional frequency drift below 5×10⁻¹⁹/s

Abstract

Cryogenic single-crystal optical cavities have the potential to provide highest dimensional stability. We have investigated the long-term performance of an ultra-stable laser system which is stabilized to a single-crystal silicon cavity operated at 124 K. Utilizing a frequency comb, the laser is compared to a hydrogen maser that is referenced to a primary caesium fountain standard and to the $^{87}\mathrm{Sr}$ optical lattice clock at PTB. With fractional frequency instabilities of $\sigma_y(\tau)\leq2\times10^{-16}$ for averaging times of $\tau=60\mathrm{~s}$ to $1000\mathrm{~s}$ and $\sigma_y(1 \mathrm{d})\leq 2\times10^{-15}$ the stability of this laser, without any aid from an atomic reference, surpasses the best microwave standards for short averaging times and is competitive with the best hydrogen masers for longer times of one day. The comparison of modeled thermal response of the cavity with measured data indicates a fractional frequency drift below $5\times 10^{-19}/\mathrm{s}$, which we do not expect to be a fundamental limit.