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Narrow-linewidth Brillouin laser for a two-photon rubidium frequency standard

Kyle W. Martin and River Beard

Andrei Isichenko, Kaikai Liu, and Daniel J. Blumenthal

Seth E. Erickson, Kaleb Campbell, and Sean Krzyzewski*

  • *Contact author: qst@afrl.af.mil
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Phys. Rev. Applied 26, 034046 – Published 21 September, 2026

DOI: https://doi.org/10.1103/vgf7-kjlg

Abstract

High-precision, portable, and deployable frequency standards are required for modern navigation and communication technologies. Optical frequency standards are attractive for their improved stability over their microwave counterparts; however, increased complexities have anchored them in the laboratory. Sacrificing the sensitivity of the most stable optical clocks has led to the recent development of deployable and portable optical frequency standards, leveraging hot atomic or molecular vapor. The short-term limit for a majority of previous reports on two-photon rubidium standards is either the shot-noise or intermodulation limit hindering the 1 s fractional frequency stability to around 1×10−13. The answer for the shot-noise limit is to increase optical power and collected fluorescence, while the intermodulation limit solution requires improvements in laser linewidth, stimulated Brillouin scattering (SBS) lasers are known to reduce frequency noise, suppressing noise of the pump laser. We investigate an optical frequency standard based on the two-photon transition in Rb87 probed with a narrow photonic integrated circuit SBS laser with a quality factor over 130 million and instantaneous linewidth <10  Hz. The use of a narrow clock laser coupled with operating at higher optical intensities yielded clock instabilities of 2×10−14 at 1 s, currently the best reported short-term stability for a two-photon rubidium optical frequency standard.

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Phys. Rev. Applied 26, 034046– Published 21 September, 2026
  • Received 2 March 2026
  • Accepted 14 July 2026
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