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Mileti, Gaetano
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Mileti, Gaetano
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gaetano.mileti@unine.ch
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Voici les éléments 1 - 10 sur 40
- PublicationMétadonnées seulementLong-Term Stability Analysis Towards < 10-14 Level for a Highly Compact POP Rb Cell Atomic Clock(2019-4-14)
; ; ; ; Long-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 long-term 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·E10.14 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 towards 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. - PublicationMétadonnées seulementBarometric Effect in Vapor-Cell Atomic Clocks(2018-6-4)
; ; ; Vapor-cell atomic clocks are compact and high-performance frequency references employed in various appli-cations ranging from telecommunication to global positioningsystems. Environmental sensitivities are often the main sourcesof long-term instabilities of the clock frequency. Among thesesensitivities, the environmental pressure shift describes the clockfrequency change with respect to the environmental pressurevariations. We report here on our theoretical and experimentalanalysis of the environmental pressure shift on rubidium atomicfrequency standards (RAFSs) operated under open atmosphere.By using an unsealed high-performance laser-pumped rubidiumstandard, we demonstrate that the deformation of the vapor-cell volume induced by the environmental pressure changes(i.e., barometric effect) is the dominant environmental pressureshift in a standard laboratory environment. An experimentalbarometric coefficient of 8.2×10−14/hPa is derived, in goodagreement with theory and with previously reported measure-ments of frequency shifts of RAFS operated when transiting tovacuum. - PublicationMétadonnées seulementDesign of atomic clock cavity based on aloop-gap geometry and modified boundaryconditions(2017-6-27)
; ; - PublicationMétadonnées seulementOptically-detected spin-echo method for relaxation times measurements in a Rb atomic vapor(2017-6-26)
; ; ; ; - PublicationMétadonnées seulementDouble-resonance spectroscopy in Rubidium vapour-cells for high performance and miniature atomic clocks(2017-2-16)
; ; ; Kang, SWe report our studies on using microwave-optical double-resonance (DR) spectroscopy for a high-performance Rb vapour-cell atomic clock in view of future industrial applications. The clock physics package is very compact with a total volume of only 0.8 dm3. It contains a recently in-house developed magnetron-type cavity and a Rb vapour cell. A homed-made frequency-stabilized laser system with an integrated acousto-optical-modulator (AOM) – for switching and controlling the light output power– is used as an optical source in a laser head (LH). The LH has the overall volume of 2.5 dm3 including the laser diode, optical elements, AOM and electronics. In our Rb atomic clock two schemes of continuous-wave DR and Ramsey-DR schemes are used, where the latter one strongly reduces the light-shift effect by separation of the interaction of light and microwave. Applications of the DR clock approach to more radically miniaturized atomic clocks are discussed. - PublicationMétadonnées seulementInterferometric measurements beyond the coherence length of the laser source(2016-9-19)
; ; ; ; Polster, AlbertInterferometric measurements beyond the coherence length of the laser are investigated theoretically and experimentally in this paper. Thanks to a high-bandwidth detection, high-speed digitizers and a fast digital signal processing, we have demonstrated that the limit of the coherence length can be overcome. Theoretically, the maximal measurable displacement is infinite provided that the sampling rate is sufficiently short to prevent any phase unwrapping error. We could verify experimentally this concept using a miniature interferometer prototype, based on a frequency stabilized vertical cavity surface emitting laser. Displacement measurements at optical path differences up to 36 m could be realized with a relative stability better than 0.1 ppm, although the coherence length estimated from the linewidth and frequency noise measurements do not exceed 6.6 m. - PublicationMétadonnées seulementRb-stabilized laser at 1572 nm for CO2 monitoring(2016-7-4)
; ; ; ; ; We have developed a compact rubidium-stabilized laser system to serve as optical frequency reference in the 1.55-m wavelength region, in particular for CO2 monitoring at 1572 nm. The light of a fiber-pigtailed distributed feedback (DFB) laser emitting at 1560 nm is frequency-doubled and locked to a sub-Doppler rubidium transition at 780 nm using a 2-cm long vapor glass cell. Part of the DFB laser light is modulated with an electro-optical modula-tor enclosed in a Fabry-Perot cavity, generating an optical frequency comb with spectral cover-age extending from 1540 nm to 1580 nm. A second slave DFB laser emitting at 1572 nm and offset-locked to one line of the frequency comb shows a relative frequency stability of 1·10-11at 1 s averaging time and <4·10-12 from 1 hour up to 3 days. - PublicationMétadonnées seulementDFB-ridge laser diodes at 894 nm for Cesium atomic clocks(2016-2-13)
; ; Time and frequency applications are in need of high accuracy and high stability clocks. Optically pumped compact industrial Cesium atomic clocks are a promising approach that could satisfy these demands. However, the stability of these clocks relies, among others, on the performances of the laser diodes that are used. This issue has led the III-V Lab to commit to the European Euripides-LAMA project that aims to provide competitive compact optical Cesium clocks for ground applications. This work will provide key experience for further space technology qualification. III-V Lab is in charge of the design, fabrication and reliability of Distributed-Feedback diodes (DFB) at 894 nm (D1 line of Cesium) and 852 nm (D2 line). LTF-Unine is in charge of their spectral characterisation. The use of D1 line for pumping will provide simplified clock architecture compared to the D2 line pumping thanks to simpler atomic transitions and a larger spectral separation between lines in the 894 nm case. Also, D1 line pumping overcomes the issue of unpumped “idle states” that occur with D2 line. The modules should provide narrow linewidth (<1 MHz), very good reliability in time and, crucially, be less sensitive to optical feedback. The development of the 894 nm wavelength is grounded on III-V Lab results for 852 nm DFB. We show here results from Al-free active region with InGaAsP quantum well Ridge DFB lasers. We obtain the D1 Cs line (894.4 nm) at 67°C and 165 mA (optical power of 40 mW) with a high side mode suppression ratio. The wavelength evolution with temperature and current are respectively 0.06 nm/K and 0.003 nm/mA. The laser linewidth is less than 1 MHz. The Relative Intensity Noise (RIN) and the frequency noise are respectively less than 10-12 Hz-1 @ f ≥ 10 Hz and 109 Hz2/Hz @ f ≥ 10 Hz. - PublicationMétadonnées seulementStability limitations from optical detection in Ramsey-type vapour-cell atomic clocks(2015-10-29)
; ; ; In today's state of the art compact vapour-cell atomic clocks relying on the pulsed Ramsey-type interrogation, optical detection noise is a major limitation to the achievable short-term stability. In this communication, the influence of the optical detection time on the clock's short-term stability is investigated and a new analytical expression is developed to precisely predict the stability performance, taking into account the details of the optical detection phase of a Ramsey-type atomic clock. The theory is in good agreement with the experimental results. It is applied for evaluating the clock's shot-noise limit. - PublicationMétadonnées seulementHigh performance vapour-cell frequency standards(: Journal of Physics: Conference Series 723, 2015-10-27)
; ; ; ; ; ; We report our investigations on a compact high-performance rubidium (Rb) vapour-cell clock based on microwave-optical double-resonance (DR). These studies are done in both DR continuous-wave (CW) and Ramsey schemes using the same Physics Package (PP), with the same Rb vapour cell and a magnetron-type cavity with only 45 cm3 external volume. In the CW-DR scheme, we demonstrate a DR signal with a contrast of 26% and a linewidth of 334 Hz; in Ramsey-DR mode Ramsey signals with higher contrast up to 35% and a linewidth of 160 Hz have been demonstrated. Short-term stabilities of 1.4×10^-13 τ^-1/2 and 2.4×10^-13 τ^-1/2 are measured for CW-DR and Ramsey-DR schemes, respectively. In the Ramsey-DR operation, thanks to the separation of light and microwave interactions in time, the light-shift effect has been suppressed which allows improving the long-term clock stability as compared to CW-DR operation. Implementations in miniature atomic clocks are considered.