P. Dziuban

Coherent population trapping resonances in Cs–Ne vapor microcells for miniature clocks applications

We report the characterization of dark line resonances observed in Cs vapor microcells filled with a unique neon (Ne) buffer gas. The impact on the coherent population trapping (CPT) resonance of some critical external parameters such as laser intensity, cell temperature, and microwave power is studied. We show the suppression of the first-order light shift by proper choice of the microwave power. The temperature dependence of the Cs ground state hyperfine resonance frequency is shown to be canceled in the 77–80 °C range for various Ne buffer gas pressures. The necessity to adjust the Ne buffer gas pressure or the cell dimensions to optimize the CPT signal height at the frequency inversion temperature is pointed out. Based on such Cs–Ne microcells, we preliminary demonstrate a 852 nm vertical cavity surface emitted laser (VCSEL)-modulated based CPT atomic clock exhibiting a short term fractional frequency instability σy(τ)=1.5×10−10τ−1/2 until 30 s. These results, similar to those published in the literat...

First-order cancellation of the Cs clock frequency temperature-dependence in Ne-Ar buffer gas mixture

Through the detection of Coherent Population Trapping (CPT) resonances, we demonstrate the temperature-dependence cancellation of the Cs clock frequency in microfabricated vapor cells filled with a mixture of Ne and Ar. The inversion temperature at which the Cs clock frequency temperature sensitivity is greatly reduced only depends on the partial pressure of buffer gases and is measured to be lower than 80°C as expected with simple theoretical calculations. These results are important for the development of state-of-the-art Cs vapor cell clocks with improved long-term frequency stability.

Towards the realization of the first European MEMS atomic clock

This paper presents the preliminary results of developments of the European version of MEMS atomic clock presenting a short-term stability of 5×10−11 over 1 hour while operating with less than 200 mW power consumption. The frame of such developments is the European proposal MAC-TFC (www.mac-tfc.eu), bringing together a consortium made of five major academic institutions (University of Besançon, University of Neuchâtel, EPFL-Lausanne, Technological University of Wroclaw, University of Ulm); two research institutes (VTT and CEA/Léti) and three industrial partners (SAES Getters, SWATCH R&D and Oscilloquartz).

Microfabrication and thermal behavior of miniature cesium-vapor cells for atomic clock operations

We report on the microfabrication and packaging of Cs-vapor cells filled with Ne or Ar for micro atomic clocks (MACs) based on the coherent population trapping (CPT). We present a two-step anodic bonding process to control the cell atmosphere for long-term operation of MACs. Furthermore, the results of thermal analysis of a cell embedded in the physical package are shown in order to discuss the optimal design of the package for the thermal management of the MAC.

Fabrication of wall-coated Cs vapor cells for a chip-scale atomic clock

Cesium vapor microcells incorporating a Cs dispenser were fabricated. An organosilane monolayer was successfully applied to the microcell walls as an anti-relaxation coating to improve the relaxation time of Cs atoms.

Dark line resonances in Cs-Ne vapor microcells for chip scale atomic clocks

We report the characterization of Coherent Population Trapping (CPT) resonances in Cs vapor microcells filled with Neon (Ne) buffer gas. The impact on the atomic hyperfine resonance of some external parameters such as laser intensity and cell temperature is studied. We show the suppression of the first-order light shift by proper choice of the microwave power. The temperature dependence of the Cs ground state hyperfine resonance frequency is shown to be canceled in the 77–80°C range for various Ne buffer gas pressures. We preliminary demonstrate a 852 nm VCSEL-modulated based CPT atomic clock exhibiting a short term fractional frequency instability σ<inf>y</inf>(τ) = 1.5×10⁻¹⁰ τ^−1/2 until 200 s.

Cs collisional frequency shift measurements in microcells filled with a Ne-Ar buffer gas mixture

We report on the measurement of the dependence on temperature of the Cs clock frequency in microfabricated vapor cells filled with a mixture of Ne and Ar through the detection of Coherent Population Trapping (CPT) resonances. The temperature-dependence reduction of the Cs clock frequency is demonstrated in various cells. The inversion temperature at which the Cs clock frequency sensitivity is greatly reduced is found to be only dependent on the partial pressure of buffer gases and is measured to be lower than 80°C as expected with simple theoretical calculations.

Fabrication and spectroscopy of Cs vapor cells with buffer gas for miniature atomic clock

In this communication we discuss the fabrication and spectroscopic characterization of original micro-fabricated Cs cells filled with buffer gas in view of applications in miniature atomic clocks. The influence of several experimental parameters on CPT resonances in such micro cells is studied. We observed a quadratic temperature dependence of the clock frequency in a micro-fabricated cell filled with Cs and pure Ne buffer gas. This results in a low temperature coefficient around the inversion temperature, and relaxes the stability requirements on the cell temperature and should improve the clocks long term stability. The possibility to achieve such low temperature coefficient using a single type of buffer gas can noticeably simplify the technique of the cell production. Indeed, the control of the buffer-gas represents a difficult challenge in micro-fabricated cells production. Finally we report on preliminary short term clock stability measurements. A stability of 5x10-10 τ-1/2 @ 1s is obtained. This value is in good agreement with the signal-tonoise stability prediction but remains to be improved.