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Affolderbach, Christoph
Nom
Affolderbach, Christoph
Affiliation principale
Fonction
Collaborateur scientifique
Email
christoph.affolderbach@unine.ch
Identifiants
Résultat de la recherche
Voici les éléments 1 - 10 sur 64
- PublicationAccès libreA cold-atom Ramsey clock with a low volume physics package(2024-01-09)
; ; ; - PublicationAccès libreAn additive-manufactured microwave cavity for a compact cold-atom clock(2023)
; ; We present an additive-manufactured microwave cavity for a Ramsey-type, double resonance, compact cold-atom clock. Atoms can be laser cooled inside the cavity using a grating magneto-optic trap with the cavity providing an excellent TE011-like mode while maintaining sufficient optical access for atomic detection. The cavity features a low Q-factor of 360 which conveniently reduces the cavity pulling of the future clock. Despite the potential porosity of the additive-manufacturing process, we demonstrate that the cavity is well-suited for vacuum. A preliminary clock setup using cold atoms allows for measuring the Zeeman spectrum and Rabi oscillations in the cavity which enables us to infer excellent field uniformity and homogeneity, respectively, across the volume accessed by the cold atoms. Ramsey spectroscopy is demonstrated, indicating that the cavity is suitable for clock applications. Finally, we discuss the limitations of the future clock. - PublicationAccès libreA Microcell Atomic Clock Based on a Double-Resonance Ramsey Scheme(2022)
; ; ; ; - PublicationAccès libreGNSS-grade space atomic frequency standards: Current status and ongoing developments(2021)
; ; ; We present an overview on the current state of Global Navigation Satellite Systems (GNSS)-grade or better space atomic frequency standards’ (SAFS) technologies and discuss their applications. We estimate that a total of more than 1000 such standards were sent to space so far, the vast majority consisting of rubidium-cell frequency standards, Cs atomic beam frequency standards, and passive hydrogen masers. Finally, we review a variety of ongoing developments in view of future new generations of GNSS-grade SAFSs. - PublicationAccès libreLong-Term Stability Analysis Towards <10-14 Level for a Highly Compact POP Rb Cell Atomic ClockLong-term frequency instabilities in vapor-cell clocks mainly arise from fluctuations of the experimental and environmental parameters that are converted to clock frequency fluctuations via various physical processes. Here, we discuss the frequency sensitivities and the resulting stability limitations at one-day timescale for a rubidium vapor-cell clock based on a compact magnetron-type cavity operated in air (no vacuum environment). Under ambient laboratory conditions, the external atmospheric pressure fluctuations may dominantly limit the clock stability via the barometric effect. We establish a complete longterm instability budget for our clock operated under stable pressure conditions. Where possible, the fluctuations of experimental parameters are measured via the atomic response. The measured clock instability of <2 × 10-14 at one day is limited by the intensity light-shift effect, which could further be reduced by active stabilization of the laser intensity or stronger optical pumping. The analyses reported here show the way toward simple, compact, and low-power vapor-cell atomic clocks with excellent long-term stabilities ≤10-14 at one day when operated in ambient laboratory conditions.
- PublicationAccès libreImpact of microwave-field inhomogeneity in an alkali vapour cell using Ramsey double-resonance spectroscopyWe numerically and experimentally evaluate the impact of the inhomogeneity of the microwave field in the cavity used to perform double-resonance (DR) Ramsey spectroscopy in a buffer gas alkali vapour cell. The Ramsey spectrum is numerically simulated using a simple theoretical model and taking into account the field distribution in a magnetron-type microwave resonator. An experimental evaluation is performed using a DR pulsed optically pumped (POP) atomic clock. It is shown that the sensitivity to the micro-wave power of the DR POP clock can be reproduced from the combination of two inhomogeneities across the vapour cell: microwave field inhomogeneity and atomic ground-state resonance frequency inhomogeneity. Finally, we present the existence of an optimum operation point for which the microwave power sensitivity of our DR POP clock is reduced by two orders of magnitude. It leads into a long-term frequency stability of 1 × 10-14.
- PublicationAccès libre3D printed microwave cavity for atomic clock applications: proof of concept(2018-6-7)
; ; ; - PublicationAccès libreRb vapor-cell clock demonstration with a frequency-doubled telecom laserWe employ a recently developed laser system, based on a low-noise telecom laser emitting around 1.56 μm, to evaluate its impact on the performance of an Rb vapor-cell clock in a continuous-wave double-resonance scheme. The achieved short-term clock instability below 2.5·10−13·τ−1∕2 demonstrates, for the first time, the suitability of a frequency-doubled telecom laser for this specific application. We measure and study quantitatively the impact of laser amplitude and frequency noises and of the ac Stark shift, which limit the clock frequency stability on short timescales. We also report on the detailed noise budgets and demonstrate experimentally that, under certain conditions, the short-term stability of the clock operated with the low-noise telecom laser is improved by a factor of three compared to clock operation using the direct 780-nm laser.
- PublicationAccès libreStudy of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications(2018)
; ; ; - PublicationAccès libreCharacterization of Frequency-Doubled 1.5-μm Lasers for High-Performance Rb ClocksWe report on the characterization of two fiber-coupled 1.5- μm diode lasers, frequency-doubled and stabilized to Rubidium (Rb) atomic resonances at 780 nm. Such laser systems are of interest in view of their implementation in Rb vaporcell atomic clocks, as an alternative to lasers emitting directly at 780 nm. The spectral properties and the instabilities of the frequency-doubled lasers are evaluated against a state-of-the-art compact Rb-stabilized laser system based on a distributed-feedback laser diode emitting at 780 nm. All three lasers are frequency stabilized using essentially identical Doppler-free spectroscopy schemes. The long-term optical power fluctuations at 780 nm are measured, simultaneously with the frequency instability measurements done by three beat notes established between the three lasers. One of the frequency-doubled laser systems shows at 780 nm excellent spectral properties. Its relative intensity noise <10−12 Hz−1 is one order of magnitude lower than the reference 780-nm laser, and the frequency noise <106 Hz2/Hz is limited by the laser current source. Its optical frequency instability is <4 × 10−12 at τ = 1 s, limited by the reference laser, and better than 1 × 10−11 at all timescales up to one day. We also evaluate the impact of the laser spectral properties and instabilities on the Rb atomic clock performance, in particular taking into account the light-shift effect. Optical power instabilities on long-term timescales, largely originating from the frequency-doubling stage, are identified as a limitation in view of high-performance Rb atomic clocks.