Radio Frequency from Optical with Instabilities below 10^−15 - Generation and Measurement

Published

August 8, 2025

Author(s)

Archita Hati, Marco Pomponio, Nicholas Nardelli, Tanner Grogan, Kyungtae Kim, Dahyeon Lee, Jun Ye, Tara Fortier, Andrew Ludlow, Craig Nelson

Abstract

This paper presents a frequency synthesis that achieved exceptional stability by transferring optical signals to the RF domain at 100 MHz. These systems employ a cryogenic silicon cavity-stabilized laser at 1542 nm and an ultra-low expansion (ULE) glass cavity at 1157 nm, both converted to 10 GHz signals via Ti:Sapphire and Er/Yb:glass optical frequency combs (OFCs). The 10 GHz microwave outputs are further divided down to 100 MHz using a commercial microwave prescaler, which exhibits a residual frequency instability of σy(1 s) < 10^−15 and low 10^−18 level at a few thousand seconds. Measurements are performed using a newly developed custom ultra-low-noise digital measurement system. The new system enables high-sensitivity evaluation across the entire synthesis chain, from the optical and microwave heterodynes as well as the direct RF signals. Results show an absolute instability of σy(1 s) ≈ 4.7 × 10^−16 at 100 MHz. This represents the first demonstration of such low instability at 100 MHz, corresponding to a phase noise of -140 dBc/Hz at a 1 Hz offset and significantly surpassing earlier systems. These advancements open new opportunities for precision metrology and timing systems.

Citation

IEEE Open Journal of Ultrasonics, Ferroelectrics, and Frequency Control

Volume

5

Pub Type

Journals

Download Paper

https://doi.org/10.1109/OJUFFC.2025.3596866

Local Download

Keywords

Allan Deviation, Digital Measurement System, Frequency Instability, Phase Noise, Prescaler, Optical Clocks, Optical Frequency Divider, Stability Transfer

Citation

Hati, A. , Pomponio, M. , Nardelli, N. , Grogan, T. , Kim, K. , Lee, D. , Ye, J. , Fortier, T. , Ludlow, A. and Nelson, C. (2025), Radio Frequency from Optical with Instabilities below 10^&#8722;15 - Generation and Measurement, IEEE Open Journal of Ultrasonics, Ferroelectrics, and Frequency Control, [online], https://doi.org/10.1109/OJUFFC.2025.3596866, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959625 (Accessed October 9, 2025)