Sub-100 attoseconds optics-to-microwave synchronization

TL;DR

This paper demonstrates optical-to-microwave synchronization with residual phase noise as low as -120 dBc/Hz at 1 Hz offset and rms time deviation below 100 attoseconds over 1000 seconds, using fiber-based femtosecond frequency combs.

Contribution

It introduces a novel synchronization method achieving sub-100 attoseconds timing precision with low-noise fiber-based frequency combs and advanced noise reduction techniques.

Findings

Residual phase noise as low as -120 dBc/Hz at 1 Hz offset

Fractional frequency instability of 1.1E-16 at 1 s

RMS time deviation below 100 attoseconds up to 1000 s

Abstract

We use two fiber-based femtosecond frequency combs and a low-noise carrier suppression phase detection system to characterize the optical to microwave synchronization achievable with such frequency divider systems. By applying specific noise reduction strategies, a residual phase noise as low as -120 dBc/Hz at 1 Hz offset frequency from a 11.55 GHz carrier is measured. The fractional frequency instability from a single optical-to-frequency divider is 1.1E-16 at 1 s averaging down to below 2E-19 after only 1000 s. The corresponding rms time deviation is lower than 100 attoseconds up to 1000 s averaging duration.