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A Rb microcell frequency reference based on two-photon transition at 778 nm

Martin Callejo, Andrei Mursa, Rémy Vicarini, Jacques Millo, Nicolas Passilly, Rodolphe Boudot

Published Jun 25, 2024• 0 citations
OpenAlex

Abstract

Modern communication and navigation systems can significantly benefit from the integration of compact atomic clocks. In this domain, microcell vapor cell optical clocks based on the Rb atom Doppler-free two photon absorption (TPA) at 778 nm are attractive candidates. Best prototypes have shown frequency stability levels of 1.8x10-13 at 1 s, averaging down to the 10-14 range1,2.

Related papers

Short-term stability of a microcell optical reference based on Rb atom two-photon transition at 778 nm

Martin Callejo, Andrei Mursa, Rémy Vicarini +5 more

We report on the development and short-term stability characterization of an optical frequency reference based on the spectroscopy of the rubidium two-photon transition at 778 nm in a microfabricated vapor cell. When compared against a 778 nm reference signal extracted from a frequency-doubled cavity-stabilized telecom laser, the short-term stability of the microcell frequency standard is 3.5 $\times$ 10$^{-13}$ $τ^{-1/2}$ until 200~s, in good agreement with a phase noise level of $+$ 43 dBrad$^2$/Hz at 1~Hz offset frequency. The two main contributions to the short-term stability of the microcell reference are currently the photon shot noise and the intermodulation effect induced by the laser frequency noise. With still a relevant margin of progress, these results show the interest of this spectroscopic approach for the demonstration of high-stability miniaturized optical vapor cell clocks. Such clocks are poised to be highly beneficial for applications in navigation, communications, and metrology.

arXiv:2407.00841•Jun 30, 2024•0 citations

Short-term stability of a microcell optical reference based on the Rb atom two-photon transition at 778 nm

Martin Callejo, Andrei Mursa, Rémy Vicarini +5 more

We report on the development and short-term stability characterization of an optical frequency reference based on the spectroscopy of the rubidium two-photon transition at 778 nm in a microfabricated vapor cell. When compared against a 778 nm reference signal extracted from a frequency-doubled cavity-stabilized telecom laser, the short-term stability of the microcell frequency standard is 3.5×10−13τ−1/2 until 200 s, in good agreement with a phase noise level of +43dBrad2/Hz at 1 Hz offset frequency. The two main contributions to the short-term stability of the microcell reference are currently the photon shot noise and the intermodulation effect induced by the laser frequency noise. Retaining a relevant margin of progress, these results show the interest of this spectroscopic approach for the demonstration of high-stability miniaturized optical vapor cell clocks. Such clocks are poised to be highly beneficial for applications in navigation, communications, and metrology.

Journal of the Optical Society of America B•Nov 22, 2024•14 citations

Rb microfabricated cells for a two-photon optical frequency reference

Martin Callejo, Rémy Vicarini, Andrei Mursa +4 more

Miniaturized vapor cell optical clocks based on the use of the two photon absorption transition (TPT) of the Rb atom at 778 nm have recently demonstrated remarkable stability results.

•Jun 18, 2023•0 citations

Microfabricated vapor cell atomic clocks at FEMTO-ST

Clément Carlé, Martin Callejo, Andrei Mursa +8 more

The convergence of atomic spectroscopy, MEMS cell technologies and integrated photonics has led to the deployment of high-precision chip-scale atomic devices [1]. In this talk, we will present in-progress studies at FEMTO-ST Institute, France, for the development of microcellbased microwave and optical atomic clocks, with enhanced stability performances. In the first part, we will talk about the demonstration of CPT-based microwave cell clocks with stability at 1 day in the low 10−12 range [2], made possible thanks to the combination of advanced Ramsey-based interrogation sequences [3] and cells built with low gas permeation windows [4-5]. In the second part, we will discuss the in-progress development of a microcell-based optical frequency reference based on the two-photon transition of Rb atom at 778 nm. An encouraging short-term stability of 3 × 10−13 at 1 s and 3 × 10−14 at 100 s has been recently achieved [6]. Future studies will be briefly discussed.

•Sep 30, 2024•1 citation

A Comprehensive Review of Rubidium Two-Photon Vapor Cell Optical Clock: Long-Term Performance Limitations and Potential Improvements

Asagwegbe C. Obaze-Adeleke, Bryan Semon, Thejesh Bandi

Two-photon vapor cell-based optical clocks are strong candidates for next-generation portable atomic standards, offering simplicity, compactness, and high performance. Their narrow clock transitions with counter-propagating beams enable first-order Doppler-free operation. However, systematic perturbations such as the AC Stark shift, temperature-induced shift, and drifts resulting from the laser system pose challenges cause instabilities to medium- to long-term performance. This paper provides a comprehensive overview of Rb two-photon vapor cell optical standards, focusing on the long-term performance-limiting effects and potential mitigation strategies, aiming for clock stabilities better than 1 × 10−15 over the averaging time of a day and beyond.

Photonics•May 20, 2025•10 citations

Compact 780-nm Rb optical clock

Zhendong Chen, Tianyu Liu, Ruoao Yang +9 more

We demonstrated a compact 780 nm rubidium optical clock, which includes an optical frequency standard and an optical frequency comb, with an optical volume of 11.6 liters. Unlike the 778 nm rubidium atomic clocks based on two-photon transition, here, the laser frequency is stabilized to the Rb D2 transition, using modulation transfer spectroscopy. This approach effectively eliminates Doppler background and provides a high signal to noise ratio and high sensitivity. A nearly 300 MHz microwave signal, whose phase exactly tracks that of the optical frequency standard, is generated via the optical frequency comb, yielding a frequency instability of 1.91 E-13 @1 s and 5.29 E-14 @1000 s in the electronic domain. To the best of our knowledge, this is the most precise frequency stabilization result for the first-excited-state transition of alkali metal atoms to date and represents the first optical clock based on this transition. These results offer a promising approach for the development of portable optical clocks.

arXiv:2501.01826•Physical Review Applied•Nov 24, 2025•4 citations
Modern communication and navigation systems can significantly benefit from the integration of compact atomic clocks. In this domain, microcell vapor cell optical clocks based on the Rb atom Doppler-free two photon absorption (TPA) at 778 nm are attractive candidates. Best prototypes have shown frequency stability levels of 1.8x10-13 at 1 s, averaging down to the 10-14 range1,2.
We report on the development and short-term stability characterization of an optical frequency reference based on the spectroscopy of the rubidium two-photon transition at 778 nm in a microfabricated vapor cell. When compared against a 778 nm reference signal extracted from a frequency-doubled cavity-stabilized telecom laser, the short-term stability of the microcell frequency standard is 3.5 ×\times× 10−13^{-13}−13 τ−1/2τ^{-1/2}τ−1/2 until 200~s, in good agreement with a phase noise level of +++ 43 dBrad2^22/Hz at 1~Hz offset frequency. The two main contributions to the short-term stability of the microcell reference are currently the photon shot noise and the intermodulation effect induced by the laser frequency noise. With still a relevant margin of progress, these results show the interest of this spectroscopic approach for the demonstration of high-stability miniaturized optical vapor cell clocks. Such clocks are poised to be highly beneficial for applications in navigation, communications, and metrology.
We report on the development and short-term stability characterization of an optical frequency reference based on the spectroscopy of the rubidium two-photon transition at 778 nm in a microfabricated vapor cell. When compared against a 778 nm reference signal extracted from a frequency-doubled cavity-stabilized telecom laser, the short-term stability of the microcell frequency standard is 3.5×10−13τ−1/2 until 200 s, in good agreement with a phase noise level of +43dBrad2/Hz at 1 Hz offset frequency. The two main contributions to the short-term stability of the microcell reference are currently the photon shot noise and the intermodulation effect induced by the laser frequency noise. Retaining a relevant margin of progress, these results show the interest of this spectroscopic approach for the demonstration of high-stability miniaturized optical vapor cell clocks. Such clocks are poised to be highly beneficial for applications in navigation, communications, and metrology.
The convergence of atomic spectroscopy, MEMS cell technologies and integrated photonics has led to the deployment of high-precision chip-scale atomic devices [1]. In this talk, we will present in-progress studies at FEMTO-ST Institute, France, for the development of microcellbased microwave and optical atomic clocks, with enhanced stability performances. In the first part, we will talk about the demonstration of CPT-based microwave cell clocks with stability at 1 day in the low 10−12 range [2], made possible thanks to the combination of advanced Ramsey-based interrogation sequences [3] and cells built with low gas permeation windows [4-5]. In the second part, we will discuss the in-progress development of a microcell-based optical frequency reference based on the two-photon transition of Rb atom at 778 nm. An encouraging short-term stability of 3 × 10−13 at 1 s and 3 × 10−14 at 100 s has been recently achieved [6]. Future studies will be briefly discussed.
Two-photon vapor cell-based optical clocks are strong candidates for next-generation portable atomic standards, offering simplicity, compactness, and high performance. Their narrow clock transitions with counter-propagating beams enable first-order Doppler-free operation. However, systematic perturbations such as the AC Stark shift, temperature-induced shift, and drifts resulting from the laser system pose challenges cause instabilities to medium- to long-term performance. This paper provides a comprehensive overview of Rb two-photon vapor cell optical standards, focusing on the long-term performance-limiting effects and potential mitigation strategies, aiming for clock stabilities better than 1 × 10−15 over the averaging time of a day and beyond.
We demonstrated a compact 780 nm rubidium optical clock, which includes an optical frequency standard and an optical frequency comb, with an optical volume of 11.6 liters. Unlike the 778 nm rubidium atomic clocks based on two-photon transition, here, the laser frequency is stabilized to the Rb D2 transition, using modulation transfer spectroscopy. This approach effectively eliminates Doppler background and provides a high signal to noise ratio and high sensitivity. A nearly 300 MHz microwave signal, whose phase exactly tracks that of the optical frequency standard, is generated via the optical frequency comb, yielding a frequency instability of 1.91 E-13 @1 s and 5.29 E-14 @1000 s in the electronic domain. To the best of our knowledge, this is the most precise frequency stabilization result for the first-excited-state transition of alkali metal atoms to date and represents the first optical clock based on this transition. These results offer a promising approach for the development of portable optical clocks.