Gruet, Florian

2022, Batori, Etienne, Affolderbach, Christoph, Pellaton, Matthieu, Gruet, Florian, Maddalena Violetti, Yuanyan Su, Anja K. Skrivervik, Mileti, Gaetano

2015-3-12, Kang, Songbai, Gharavipour, Mohammadreza, Affolderbach, Christoph, Gruet, Florian, Mileti, Gaetano

We demonstrate a high-performance pulsed optically pumped (POP) Rb vapor-cell clock based on a magnetron-type microwave cavity of only 44 cm3 external volume. Using optical detection, an unprecedented 35% contrast of the Ramsey signal has been obtained. Both the signal-to-noise ratio (of 30 000) and the estimated shot-noise limit of 1.7 × 10−14 τ−1/2 are at the same level as those found with a bigger cylindrical TE011 cavity (100 cm3 inner volume) and are sufficient for achieving excellent clock stability. Rabi oscillations are measured and indicate a sufficiently uniform microwave magnetic field distribution inside the cavity. The instability sources for the POP clock's performance are analyzed. A short-term stability of 2.1 × 10−13 τ−1/2 is demonstrated which is consistent with the noise budget.

2010, Di Francesco, Joab F., Gruet, Florian, Schori, Christian, Affolderbach, Christoph, Matthey-De-L'Endroit, Renaud, Mileti, Gaetano, Salvadé, Y., de Rooij, Nicolaas F., Petremand, Y.

We present our evaluation of a compact laser system made of a 795 nm VCSEL locked to the Rubidium absorption line of a micro-fabricated absorption cell. The spectrum of the VCSEL was characterised, including its RIN, FM noise and line-width. We optimised the signal-to-noise ratio and determined the frequency shifts versus the cell temperature and the incident optical power. The frequency stability of the laser (Allan deviation) was measured using a high-resolution wavemeter and an ECDL-based reference. Our results show that a fractional instability of ≥ ^10-9 may be reached at any timescale between 1 and 100'000 s. The MEMS cell was realised by dispensing the Rubidium in a glass-Silicon preform which was then, sealed by anodic bonding. The overall thickness of the reference cell is 1.5 mm. No buffer gas was added. The potential applications of this compact and low-consumption system range from optical interferometers to basic laser spectroscopy. It is particularly attractive for mobile and space instruments where stable and accurate wavelength references are needed.

, Almat, Nil, Gharavipour, Mohammadreza, Moreno, William, Gruet, Florian, Affolderbach, Christoph, Mileti, Gaetano

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 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.

2016-6-1, Gharavipour, Mohammadreza, Affolderbach, Christoph, Kang, Songbai, Pellaton, Matthieu, Mileti, Gaetano, Bandi Nagabhushan, Thejesh, Gruet, Florian

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.

2013-11-8, Gruet, Florian, Al-Samaneh, Ahmed, Kroemer, Eric, Bimboes, Laura, Miletic, Danijela, Affolderbach, Christoph, Wahl, Dietmar, Boudot, Rodolphe, Mileti, Gaetano, Michalzik, Rainer

, Matthey-De-L'Endroit, Renaud, Gruet, Florian, Schilt, Stephane, Mileti, Gaetano

Combining light modulation and frequency conversion techniques, a compact and simple frequency-stabilized optical frequency comb spanning over 45 nm in the 1.56- μm wavelength region is demonstrated. It benefits from the high-frequency stability achievable from rubidium atomic transitions at 780 nm probed in a saturation absorption scheme, which is transferred to the 1.56- μm spectral region via a second-harmonic generation process. The optical frequency comb is generated by an electro-optic modulator enclosed in a Fabry–Perot cavity that is injected by the fundamental frequency stabilized laser. Frequency stability better than 2 kHz has been demonstrated on time scales between 1000 s and 2 days both at 1560 nm, twice the rubidium wavelength, and for a comb line at 1557 nm.

2015-6-1, Matthey-De-L'Endroit, Renaud, Gruet, Florian, Schilt, Stephane, Mileti, Gaetano

Combining light modulation and frequency conversion techniques, a compact and simple frequency-stabilized optical frequency comb spanning over 45 nm in the 1.56-μm wavelength region is demonstrated. It benefits from the high-frequency stability achievable from rubidium atomic transitions at 780 nm probed in a saturation absorption scheme, which is transferred to the 1.56-μm spectral region via a second-harmonic generation process. The optical frequency comb is generated by an electro-optic modulator enclosed in a Fabry–Perot cavity that is injected by the fundamental frequency stabilized laser. Frequency stability better than 2 kHz has been demonstrated on time scales between 1000 s and 2 days both at 1560 nm, twice the rubidium wavelength, and for a comb line at 1557 nm.

2013-11-8, Gruet, Florian, Vecchio, Fabrizio, Affolderbach, Christoph, Pétremand, Yves, De Rooij, Nicolaas-F., Maeder, Thomas, Mileti, Gaetano

, Gruet, Florian, Al-Samaneh, Ahmed, Kroemer, Eric, Bimboes, Laura, Miletic, Danijela, Affolderbach, Christoph, Wahl, Dietmar, Boudot, Rodolphe, Mileti, Gaetano, Michalzik, Rainer

We report on the characterization and validation of custom-designed 894.6 nm vertical-cavity surface-emitting lasers (VCSELs), for use in miniature Cs atomic clocks based on coherent population trapping (CPT). The laser relative intensity noise (RIN) is measured to be 1×10⁻¹¹ Hz⁻¹ at 10 Hz Fourier frequency, for a laser power of 700 μW. The VCSEL frequency noise is 10¹³ ƒ ⁻¹ Hz²/Hz in the 10 Hz < ƒ < 10⁵ Hz range, which is in good agreement with the VCSEL’s measured fractional frequency instability (Allan deviation) of ≈ 1 × 10⁻⁸ at 1 s, and also is consistent with the VCSEL’s typical optical linewidth of 20–25 MHz. The VCSEL bias current can be directly modulated at 4.596 GHz with a microwave power of −6 to +6 dBm to generate optical sidebands for CPT excitation. With such a VCSEL, a 1.04 kHz linewidth CPT clock resonance signal is detected in a microfabricated Cs cell filled with Ne buffer gas. These results are compatible with state-of-the-art CPT-based miniature atomic clocks exhibiting a short-term frequency instability of 2–3×10⁻¹¹ at τ = 1 s and few 10⁻¹² at τ = 10⁴ s integration time.