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To miniaturize the double-resonance (DR) rubidium (Rb) vapor-cell atomic clocks, a new type of micro-loop-gap microwave resonator (mu-LGR) is proposed for TE011-like mode where the magnetic field inside the cavity is homogeneous and oriented along its longitudinal axis over a large volume. It provides more design degrees of freedom by elaborating the printed pattern in the middle layer, while the mechanical strength of the cavity is strong. It also possesses a wider tuning range of the resonances in order to compensate the fabrication tolerances on such miniature precision devices. A theoretical analysis of the general mu-LGR without tuning is presented first, serving as the basic guideline to design the tunable mu-LGR. To demonstrate the wide tuning mechanism, an equivalent circuit model and different tuning schemes are discussed. The measured results show that the proposed tunable mu-LGR can operate at 6.835 GHz by properly adjusting the tuning screw position. Compared to the existing mu-LGRs, this new design can achieve a 40% volume reduction (572 mm(3), approaching the physical limit) and a comparable magnetic field quality, and enlarges the frequency tuning range to 260 MHz (twofold) in measurement. Thus, the proposed compact tunable mu-LGR has a high potential in miniature vapor-cell atomic frequency standards.

International audience; Recent developments in quantum technology have resulted in a new generation of sensors for measuring inertial quantities, such as acceleration and rotation. These sensors can exhibit unprecedented sensitivity and accuracy when operated in space, where the free-fall interrogation time can be extended at will and where the environment noise is minimal. European laboratories have played a leading role in this field by developing concepts and tools to operate these quantum sensors in relevant environment, such as parabolic flights, free-fall towers, or sounding rockets. With the recent achievement of Bose–Einstein condensation on the International Space Station, the challenge is now to reach a technology readiness level sufficiently high at both component and system levels to provide “off the shelf” payload for future generations of space missions in geodesy or fundamental physics. In this roadmap, we provide an extensive review on the status of all common parts, needs, and subsystems for the application of atom-based interferometers in space, in order to push for the development of generic technology components.

We 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 microwave 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.

We present a prospective experimental study on double-resonance Ramsey spectroscopy in a micro fabricated Rb vapor cell, in view of future miniature atomic clocks with improved stability performance. Ramsey signals with a narrow central fringe width of 1.5 kHz combined with a competitive contrast of > 5 % are observed, resulting in a clock short-term stability of approximate to 1x10(-11) tau(-1/2). The employed pulsed optical pumping (POP) scheme bears promise for reduced light-shift effects and thus for improved clock stability on medium- to long-term timescales.

In this communication, we give an overview of the field of space atomic clocks and motivate the need for novel types of space atomic clocks, notably based on laser technology. We outline the development status of our pulsed laser-pumped Rb clock in view of combined state-of-the-art stability (~10−14 @ 1 day) and small volume (< 5L). The frequency and intensity stability of a custom made compact pulsed laser source is discussed in view of its implementation in the pulsed laser-pumped clock. Finally, we analyze spectral aging data for a DFB laser diode accumulated over several years and discuss new lines of atomic clock development.

The authors present the realisation and characterisation of an additively manufactured (AM) microwave resonator cavity for double-resonance (DR) vapour-cell atomic clocks. The design of the compact microwave cavity is based on the loop-gap resonator approach, previously demonstrated for conventionally-machined aluminium components. In the present study, the resonator is fabricated by AM using a metal-coated polymer. A resonance frequency at the desired 6.835 GHz rubidium atomic frequency is obtained. When employed in an atomic clock setup, the AM cavity enables a DR signal of

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 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

Laser-cooled atoms and coherent population trapping (CPT) are promising tools for realizing a compact microwave frequency reference with excellent stability. To realize a high performance device, it is necessary to understand and minimize all sources of technical noise. Here, we investigate the role of laser frequency noise in cold-atom CPT with an apparatus based on the grating magneto-optical trap (GMOT). We compare the performance of our setup with an external cavity diode laser (ECDL) and a distributed feedback diode laser (DFB). With the DFB, laser frequency noise is one of the dominant noise sources in our system. With the ECDL, it is significantly reduced. We also report frequency stability measurements of our apparatus with a short-term Allan deviation $\sigma_{y}(\tau) \approx 3 \times 10^{-11} / \sqrt{\tau}$ up to $\tau =10\mathrm{s}$.

We analyze the main effects that limit the frequency stability of a high-performance compact Rb vapor-cell atomic clock on medium- to long-term timescales up to one day, in view of identifying the fundamental clock stability limits. The clock is operated in a pressure-stabilized environment to reduce the impact of atmospheric pressure fluctuations to below 10-14 which allows the evaluation of the other limiting effects at this level. The current clock stability reaches 1 × 10-14 at 104 s averaging time, with light intensity fluctuations at the vapor cell input identified as the main contribution to the instability.

We employ a three-level Bloch vector model to simulate Ramsey fringes of our Rb vapor-cell atomic clock. The residual inhomogeneity of the microwave magnetic field across the buffer-gas cell is a key ingredient for correctly modelling the behavior at high microwave powers (pulse area > π/2. We add to this model different position-dependent frequency shifts that arise from external fields, and we identify inhomogeneous light-shifts as the dominant contribution for reproducing the measured clock frequency shifts as a function of microwave power. Other frequency shifts give negligible contributions.

Vapor-cell atomic clocks are compact and high-performance frequency references employed in various applications ranging from telecommunication to global positioning systems. Environmental sensitivities are often the main sources of long-term instabilities of the clock frequency. Among these sensitivities, the environmental pressure shift describes the clock frequency change with respect to the environmental pressure variations. We report here on our theoretical and experimental analysis of the environmental pressure shift on rubidium atomic frequency standards (RAFSs) operated under open atmosphere. By using an unsealed high-performance laser-pumped rubidium standard, we demonstrate that the deformation of the vapor-cell volume induced by the environmental pressure changes (i.e., barometric effect) is the dominant environmental pressure shift in a standard laboratory environment. An experimental barometric coefficient of $8.2\times 10^{-14}$ /hPa is derived, in good agreement with theory and with previously reported measurements of frequency shifts of RAFS operated when transiting to vacuum.

We 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.

We report on the characterization of two fiber-coupled 1.5- $\mu \text{m}$ 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 vapor-cell 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 $ at $\tau = 1$ s, limited by the reference laser, and better than $1 \times 10^{-11}$ 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.

In this communication, we report on our recent investigations related to the development of a compact high performance laser-pumped vapor cell Rubidium atomic clock. These studies include the evaluation of alternative technologies for key components of the clock such as the laser source and the microwave cavity. We also present new spectroscopic and metrological investigations aiming to improve the medium and long-term frequency stability (microwave power shift, light shift and environmental effects).

We demonstrate operation of a Ramey-mode Rb vapor-cell atomic clock based on a microwave cavity realized by additive manufacturing (3D-printing). The cavity design is based on a loop-gap approach and its critical electrode structure is realized in one monolithic piece by stereolithography of a polymer which simplifies the assembly of the cavity. The microwave magnetic field in the cavity shows excellent uniformity and high homogeneity across the Rb cell, which results in high-contrast Ramsey fringes observed on the clock transition. A measured clock stability of 2.2∗10−13 τ−1/2 demonstrates the feasibility of the approach. We discuss aging studies performed on 3D-printed test samples that are of relevance for long-term operation of the clock.

We present our ongoing development of a compact (

We present the first steps executed to space qualify an assembly technique for miniaturized optical components that already demonstrated its maturity for the ground segment. Two different types of demonstrators have been manufactured and submitted to various tests: endurance demonstrators placed in simulated environment reproducing strong space environmental constraints that may potentially destroy the devices under test, and a functional demonstrator put in operational conditions as typically found in a satellite environment. The technology, the realized demonstrators and the results of the tests are reported.

We present the development and complete spectral characterization of our compact and frequency-stabilized laser heads, to be used for rubidium atomic clocks and basic spectroscopy. The light source is a Distributed Feed-Back (DFB) laser diode emitting at 780 nm or 795 nm. The laser frequency is stabilized on a sub-Doppler absorption peak of the 87Rb atom, obtained from an evacuated rubidium cell. These laser heads, including the electronics for the light signals detection, have an overall volume of 0.63 liters. We also present a variant of the laser head into which is integrated an Acousto-Optical Modulator (AOM) that precisely detunes the laser frequency in order to minimize the AC Stark shift in Rb atomic clocks.

Today laser diodes are extensively used in numerous research fields and applications, due to their simplicity of handling and control, frequency agility, single-mode frequency ability, reliability, low power consumption and compactness.

We report on a narrow-linewidth diode laser source emitting at 780 nm, based on frequency doubling from 1.56 μm, which is frequency stabilized on the D2 transition line of Rubidium (Rb). This compact laser source shows a frequency stability of 2·10−12 at 1 s and < 5·10−12 for τ up to 104 s. This laser source is evaluated in a modular four-laser setup to identify and locate the sources of instabilities. In view of the lasers' applications to vapor-cell Rb atomic clocks, we also studied the various light-shift coefficients in a pulsed optically-pumped Rb clock. Finally, we evaluate the impact of the frequency and intensity instabilities of the frequency-doubled optical sources on the clock stability.

We apply an innovative method called Optically-Detected Spin-Echo to measure the intrinsic coherence relaxation time in the buffer-gas vapor cell of a Rb atomic clock [1]. This method suppresses the influence of static-magnetic-field-gradients across the cell which is a source of relaxation processes. Such studies are of interest for high-performance Rb atomic clocks, where both intrinsic population and coherence relaxation times (T 1 and T 2 , respectively) of the “clock transition” (52S 1/2 |F g = 1, m F = 0〉 ↔ |F g = 2, m F = 0〉) are relevant.

We present our studies on a compact high-performance continuous wave (CW) double-resonance (DR) rubidium frequency standard in view of future portable applications. Our clock exhibits a short-term stability of 1.4 × 10 -13 τ -1/2 , consistent with the short-term noise budget for an optimized DR signal. The metrological studies on the medium- to longterm stability of our Rb standard with measured stabilities are presented. The dependence of microwave power shift on light intensity, and the possibility to suppress the microwave power shift is demonstrated. The instabilities arising from the vapor cell geometric effect are evaluated, and are found to act on two different time scales (fast and slow stem effects). The resulting medium- to long-term stability limit is around 5.5 × 10 -14 . Further required improvements, particularly focusing on medium- to long-term clock performance, are discussed.

Interferometric 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.

In vapor cell atomic clocks the atom-field interaction is typically obtained inside a microwave cavity resonator in which the microwave driving field together with a static magnetic field and an optical field are applied to excite the atoms. These fields are generally well-controlled, mutually aligned to a common quantization axis. Since the exploited atomic transition is sensitive to any potential axis misalignment, the performance of the clock can also be affected. We study the effect of such misalignment for the case of a cylindrical cavity used in vapor-cell atomic clocks, taking into account the misalignments of the optical detection field and the static magnetic field required for the atomic transition. Both the geometry of the cavity and the factors contributing to losses can play role in the degradation of the signal and are taken into account in the misalignment problem discussed.

In the frame of an optical reference laser system, a frequency-stabilized optical frequency comb was generated from the radiation of a 1560-nm DFB laser, which was frequency-doubled and stabilized to a rubidium transition in a sub-Doppler absorption scheme using a 2-cm long vapor glass cell. A DFB laser emitting at 1572 nm was then offset-locked to an appropriate line of the comb. At 1572 nm, a relative frequency stability of 110−11 at 1 s has been obtained, reaching < 410−12 from 3,000 s up to 3 days.

Optical pumping on the cesium (Cs) D1 transition at 894 nm, as compared to the Cs D2 line at 852 nm, can present advantages for e.g. Cs thermal beam atomic clocks or other atom-based sensors and instrumentation, due to its simpler hyperfine structure, larger atomic level splitting, and absence of cycling transitions. Here we report on the realisation and spectral characterisation of custom-made narrow-band DFB laser diodes emitting at 894 nm.

In the framework of an on-board optical reference system, a 1560-nm DFB laser frequency-doubled and locked onto the D2 line of 87Rb using a 2-cm long vapour glass cell is used to generate an optical frequency comb. A second DFB laser operating at 1572 nm, a wavelength corresponding to a CO2 transition is offset-locked to one mode of the comb. At 1572 nm, a relative frequency stability of 1·10−11 at 1 s was obtained, reaching less than 4·10−12 from 3,000 s up to at least 3 days. Limitations arising from the 1560-nm stabilized laser are discussed.

In this study we aim at improving the homogeneity of the magnetic field inside a microwave resonator cavity designed in line with the development of a novel, high-performance frequency standard. We study the effect of modified boundary conditions applied to a cavity based on a loop-gap geometry, and demonstrate the high potential of this cavity to improve the frequency stability. Our concept is suitable for the future generation of compact, high-precision frequency standards based on vapor cells and pulsed optical pumping regime (POP atomic clocks). These novel clocks are excellent candidate for future applications in space or mobile applications where highly compact instruments are required.

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 ( -12 Hz -1 @ f ≥ 10 Hz and 109 Hz 2 /Hz @ f ≥ 10 Hz.

International audience; We report on studies on the light-shift in caesium miniature atomic clocks based on coherent population trapping (CPT) using a micro-fabricated buffer-gas cell (MEMS cell). The CPT signal is observed on the Cs D1-line by coupling the two hyperfine ground-state Zeeman sublevels involved in the clock transition to a common excited state, using two coherent electromagnetic fields. These light fields are created with a distributed feedback laser and an electro-optical modulator. We study the light-shift phenomena at different cell temperatures and laser wavelengths around 894.6 nm. By adjusting the cell temperature, conditions are identified where a miniature CPT atomic clock can be operated with simultaneously low temperature coefficient and suppressed light-shift. The impact of the light-shift on the clock frequency stability is evaluated. These results are relevant for improving the long-term frequency stability of CPT-based Cs vapour-cell clocks.

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.

International audience; INRIM demonstrated a Rb vapour cell clock based on pulsed optical pumping (POP) with unprecedented frequency stability performances, both in the short and in the medium-long term period. In the frame of a EMRP project, we are developing a new clock based on the same POP principle but adopting solutions aimed at reducing the noise sources affecting the INRIM clock.At the same time, concerning possible technological applications, particular care are devoted in the project to reduce the size and the weight of the clock, still keeping the excellent stability of the INRIM clock. The paper resumes the main results of this activity.

We report on the experimental measurement of the DC and microwave magnetic field distributions inside a recently-developed compact magnetron-type microwave cavity, mounted inside the physics package of a high-performance vapor-cell atomic frequency standard. Images of the microwave field distribution with sub-100 $\mu$m lateral spatial resolution are obtained by pulsed optical-microwave Rabi measurements, using the Rb atoms inside the cell as field probes and detecting with a CCD camera. Asymmetries observed in the microwave field images can be attributed to the precise practical realization of the cavity and the Rb vapor cell. Similar spatially-resolved images of the DC magnetic field distribution are obtained by Ramsey-type measurements. The T2 relaxation time in the Rb vapor cell is found to be position dependent, and correlates with the gradient of the DC magnetic field. The presented method is highly useful for experimental in-situ characterization of DC magnetic fields and resonant microwave structures, for atomic clocks or other atom-based sensors and instrumentation., Comment: 23 pages, 9 Figures in IEEE Transactions on Instrumentation and Measurement, 2015

We report an aging study on micro-fabricated alkali vapor cells using neon as a buffer gas. An experimental atomic clock setup is used to measure the cell’s intrinsic frequency, by recording the clock frequency shift at different light intensities and extrapolating to zero intensity. We find a drift of the cell’s intrinsic frequency of (-5.2 ± 0.6) × 10-11/day and quantify deterministic variations in sources of clock frequency shifts due to the major physical effects to identify the most probable cause of the drift. The measured drift is one order of magnitude stronger than the total frequency variations expected from clock parameter variations and corresponds to a slow reduction of buffer gas pressure inside the cell, which is compatible with the hypothesis of loss of Ne gas from the cell due to its permeation through the cell windows. A negative drift on the intrinsic cell frequency is reproducible for another cell of the same type. Based on the Ne permeation model and the measured cell frequency drift, we determine the permeation constant of Ne through borosilicate glass as (5.7 ± 0.7) × 10-22 m2 s-1 Pa-1 at 81 °C. We propose this method based on frequency metrology in an alkali vapor cell atomic clock setup based on coherent population trapping for measuring permeation constants of inert gases.

Simultaneous self-induced transparency and a dark line resonance are observed inside a mode-locked laser. The circulating pulse, tuned to the 795-nm optical resonance of rubidium, has sufficient intensity to create at each passage a population inversion-return to ground state, typical of self-induced transparency. A drop in fluorescence (dark line resonance), is observed as the repetition rate is tuned to a submultiple of the hyperfine ground-state splitting.

We present a novel scheme for reducing the AC Stark effect in optical-microwave double-resonance spectroscopy and its application for efficient suppression of the light-shift-related instabilities in laser-pumped gas-cell atomic clocks. The method uses a multi-frequency pump light field that can be easily produced by frequency modulation of the single-frequency pump laser. We show theoretically that variations of the light shift with both laser frequency and light intensity can be strongly suppressed with properly chosen pump light spectra. Suitable modulation parameters can be found for both the case of pure frequency modulation as well as for pump light spectra showing amplitude-modulation contributions, as usually found for current modulation of diode lasers. We experimentally demonstrate the method for a Rb atomic clock using a frequency-modulated distributed Bragg-reflector laser diode as pump light source.

We introduce and demonstrate an experimental method, optically-detected spin-echo (ODSE), to measure ground-state relaxation times of a rubidium (Rb) atomic vapor held in a glass cell with buffer-gas. The work is motivated by our studies on high-performance Rb atomic clocks, where both population and coherence relaxation times ( T1 and T2 , respectively ) of the ‘ clock transition ’ (52 S1/2 ∣ Fg = 1, mF = 0⟩ ↔ ∣ Fg = 2, mF = 0⟩) are relevant. Our ODSE method is inspired by classical nuclear magnetic resonance spin-echo method, combined with optical detection. In contrast to other existing methods, like continuous-wave double-resonance ( CW-DR ) and Ramsey-DR, principles of the ODSE method allow suppression of decoherence arising from the inhomogeneity of the static magnetic field across the vapor cell, thus enabling measurements of intrinsic relaxation rates, as properties of the cell alone. Our experimental result for the coherence relaxation time, specific for the clock transition, measured with the ODSE method is in good agreement with the theoretical prediction, and the ODSE results are validated by comparison to those obtained with Franzen, CW-DR and Ramsey-DR methods. The method is of interest for a wide variety of quantum optics experiments with optical signal readout.

We present our studies on a compact high-performance continuous wave (CW) double-resonance (DR) rubidium frequency standard in view of future portable applications. Our clock exhibits a short-term stability of 1.4 × 10(-13) τ(-1/2), consistent with the short-term noise budget for an optimized DR signal. The metrological studies on the medium- to longterm stability of our Rb standard with measured stabilities are presented. The dependence of microwave power shift on light intensity, and the possibility to suppress the microwave power shift is demonstrated. The instabilities arising from the vapor cell geometric effect are evaluated, and are found to act on two different time scales (fast and slow stem effects). The resulting medium- to long-term stability limit is around 5.5 × 10(-14). Further required improvements, particularly focusing on medium- to long-term clock performance, are discussed.

In this paper, we present the design, fabrication, and electrical characterization of a low-power microwave source for interrogation of cesium atomic hyperfine transition frequency using the coherent population trapping (CPT) technique. The 4.6-GHz frequency generation and signal buffering is performed by a single-chip frequency synthesizer ASIC with a frequency tuning resolution of 1 x 10-13 and a programmable RF output power from -10 to 0 dBm. The circuit was used to modulate the current of a vertical-cavity surface-emitting laser through a dedicated impedance matching network and low thermal conductivity transmission line. Strong modulation sidebands with > 60% of carrier amplitude were obtained with an ASIC power consumption of 12 mW. The system was used as optical source for atomic interrogation in an experimental cesium CPT clock. The measured clock stability of 5 x 10-11 at τ = 1 s, going down to 4.5x10-12 at τ = 200 s, is limited by the signal-to-noise ratio of the detected CPT signal.

The 2014 edition of the European Frequency and Time Forum (EFTF), being held in Neuchatel, Switzerland from June 23-26, 2014. This edition marks the 28th in a series of successful meetings that started in 1987. The Local Organising Committee of EFTF-2014 includes representatives from the University of Neuchatel, Spectratime Orolia, Fondation Suisse pour la Recherche en Microtechnique (FSRM) and the Centre Suisse d'Electronique et de Microtechnique (CSEM). We acknowledge also the strong support from the numerous institutional and industrial sponsors that is essential for an event that will gather over 300 persons around scientific, social and friendly meetings during the whole week. The Scientific Committee of EFTF-2014 is glad to propose a rich scientific program resulting from the record number of 318 submitted abstracts. The schedule includes three parallel sessions of lectures (approximately 90 talks in 24 sessions), a poster session every day and a short presentation from each exhibitor on Thursday morning. This year, the Wednesday morning plenary talks will be given by Prof. Serge Haroche (ENS, Paris, and Nobel Prize in Physics in 2012) and Dr. John Kitching (NIST, Boulder, chipscale atomic devices). The student poster finalists will be displayed during the whole duration of the conference.