Compact and ultrastable photonic microwave oscillator

M. Giunta1,2, J. Yu1,5, M. Lessing1, M. Fischer1, M. Lezius1, X. Xie3,6, G. Santarelli4, Y. Le Coq3, & R. Holzwarth1,2

1Menlo Systems GmbH, Germany
2Max Planck Institute of Quantum Optics, Germany
3LNE-SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Francey
4Laboratoire Photonique, Numérique et Nanosciences (LP2N), IOGS-CNRS-Universités de Bordeaux, France
5Current address: Physikalisch-Technische Bundesanstalt (PTB), Germany
6Current address: State Key Laboratory of Advanced Optical Communication Systems and Networks, Peking University, China

Optics Letters Vol. 45, p. 1140 (2020); doi:

Frequency comb synthesized microwaves have been so far realized with tabletop systems, operated in well-controlled environments. Here, we demonstrate state-of-the-art ultrastable microwave synthesis with a compact rack-mountable apparatus. We present absolute phase noise characterization of a 12 GHz signal using an ultrastable laser at 194 THz and an Er:fiber comb divider, obtaining -83 dBc/Hz at 1 Hz and <-166 dBc/Hz for offsets greater than 5 kHz. Employing semiconductor coating mirrors for the same
type of transportable optical frequency reference, we show that -105 dBc/Hz at 1 Hz is supported by demonstrating a residual noise limit of division and detection process of -115 dBc/Hz at 1 Hz. This level of fidelity paves the way for the deployment of ultrastable photonic microwave oscillators and for operating transportable optical clocks.