Direct Phase Locking of a Ti:Sapphire Optical Frequency Comb to a Remote Optical Frequency Standard

TL;DR

This paper demonstrates ultralow noise transfer of a remote Sr optical clock laser to a Ti:Sapphire frequency comb via fiber, achieving stability comparable to the optical standard without a local cavity.

Contribution

It introduces a method for phase-locking a Ti:Sapphire comb to a remote optical standard through fiber, eliminating the need for a local high-finesse cavity.

Findings

Achieved fractional frequency instability of 6.7e-18 at 1s

Maintained high stability over 2.9 km fiber network

Enabled high-precision optical frequency transfer

Abstract

We report on an ultralow noise optical frequency transfer from a remotely located Sr optical lattice clock laser to a Ti:Sapphire optical frequency comb through telecom-wavelength optical fiber networks. The inherent narrow linewidth of the Ti:Sapphire optical frequency comb eliminates the need for a local reference high-finesse cavity. The relative fractional frequency instability of the optical frequency comb with respect to the remote optical reference was $6.7(1) \times 10^{-18}$ at 1 s and $1.05(3) \times 10^{-19}$ at 1,000 s including a 2.9 km-long fiber network. This ensured the optical frequency comb had the same precision as the optical standard. Our result paves the way for ultrahigh-precision spectroscopy and conversion of the highly precise optical frequency to radio frequencies in a simpler setup.