Dick effect in a pulsed atomic clock using Coherent Population Trapping

The Dick effect can be a limitation of the achievable frequency stability of a passive atomic frequency standard when the ancillary frequency source is only periodically sampled. Here we analyze the Dick effect for a pulsed vapor cell clock using coherent population trapping (CPT). Due to its specific interrogation process without atomic preparation nor detection outside of the Ramsey pulses, it exhibits an original shape of the sensitivity function to phase noise of the oscillator. Numerical calculations using a three-level atom model are successfully compared with measurements; an approximate formula of the sensitivity function is given as an easy-to-use tool. A comparison of our CPT clock sensitivity to phase noise with a clock of the same duty cycle using a two-level system reveals a higher sensitivity in the CPT case. The influence of a free-evolution time variation and of a detection duration lengthening on this sensitivity is studied. Finally this study permitted to choose an adapted quartz oscillator and allowed an improvement of the clock fractional frequency stability at the level of 3.2x10-13 at 1

Comparaison des effets de trois modes de restitution de questionnaires d’intérêts: nomothétique, constructiviste et intégré

Plusieurs recherches ont été consacrées aux effets de restitution des tests psychologiques, mais peu d’entre elles ont confronté des approches innovantes. Cette recherche vise à comparer trois modes de restitution individuelle en les différenciant selon la conception de l’intervention: 1) nomothétique, qui met l’accent sur la restitution interactive d’un profil de résultats; 2) constructiviste, qui aide le participant à élaborer ses propres catégories d’interprétation; 3) intégrée, qui combine les deux approches précédentes. Les résultats (n = 86) montrent que la restitution constructiviste seule est moins bien évaluée et, chez les hommes, est associée à un moindre sentiment d’efficacité vocationnelle. La restitution intégrée présente les effets les plus favorables lorsqu’on analyse les productions qualitatives des répondants. Les implications pour la recherche et la pratique sont abordées dans la discussion.There have been studies targeting the effects of psychological test interpretation styles; however few of these studies deal with innovative approaches. This research study aims at comparing three styles of interpretation and differentiating them according to how the intervention was designed. There is the nomothetic interpretation, which means accentuating interactive interpretation of a results profile. There is also the constructivist interpretation, which means helping participants to elaborate their own categories of interpretation. The third style is called integrated interpretation and combines the two previous styles. The results (n = 86) show that the constructivist interpretation isn’t evaluated as positively as the other two; in addition the men in our sample associated it with a weak career-decision making self-efficacy. The integrated interpretation style presents the strongest effects when the qualitative productions of the subjects are analyzed. The implications for research and practice are dealt with in the discussion

Toward a typeface for the transcription of facial actions in sign languages

International audienceNon-manual actions, and more specifically facial actions (FA) can be found in all Sign Languages (SL). Those actions involve all the different facial parts and can have various and intricate linguistic relations with manual signs. Unlike in vocal languages, FA in SL provide more meaning than simple expressions of feelings and emotions. Yet non-manual parameters are among the most unknown formal features in SL studies. During the past 30 years, some studies have started questioning the meanings and linguistic values and the relations between manual and non-manual signs (Crashborn et al. 2008; Crashborn & Bank 2014); more recently, SL corpora have been analysed, segmented, and transcribed to help study FA (Vogst-Svenden 2008; Bergman et al. 2008; Sutton-Spence & Day 2008).Moreover, to fill the lack of an annotation system for FA, a few manual annotation systems have integrated facial glyphs, such as HamNoSys (Prillwitz et al. 1989) and SignWriting (Sutton 1995). On one hand, HamNoSys has been developed to describe all existing SLs at a phonetic level; it allows a formal, linear, highly detailed and searchable description of manual parameters. As for non-manual parameters, HamNoSys offers the replacement of hands by another articulators. Non-manual parameters can be written as “eyes” or “mouth” and described by the same symbols developed for hands (Hanke 2004). Unfortunately only a limited number of manual symbols can be translated into FA and the annotation system remains incomplete. On the other hand, SignWriting describes SL with iconic symbols placed in a 2D space representing the signer’s body. Facial expressions are divided into mouth, eyes, nose, eyebrows, etc., and are drawn in a circular “head” much like emoticons. SignWriting offers a detailed description of posture and actions of non-manual parameters, but does not ensure compatibility with the most common annotation software used by SL linguists (e.g., ELAN).Typannot, a interdisciplinary project led by linguists, designers, and developers, which aims to set up a complete transcription system for SL that includes every SL parameter (handshape, localisation, movement, FA), has developed a different methodologie. As mentioned earlier, FA have various linguistic values (mouthings, adverbial mouth gestures, semantically empty, enacting, whole face) and also include prosody and emotional meanings. In this regard, they can be more variable and signer-related than manual parameters. To offer the best annotation tool, Typannot’s approach has been to define facial parameters and all their possible tangible configurations. The goal is to set up the most efficient, simple, yet complete and universal formula to describe all possible FA.This formula is based on a 3 dimensional grid. Indeed all the different configurations of FA can be described by its X, Y, Z axis position. As a result, all FA can be described and encoded using a restricted list of 39 qualifiers. Based on this model and to help reduce the annotation process, a set of generic glyphs has been developed. Each qualifier has its own symbolic “generic” glyph. This methodical decomposition of all facial components enables a precise and accurate transcription of a complex FA using only a few glyphs.This formula and its generic glyphs have gone through a series of tests and revisions. Recently, an 18m20s long FA corpus of two deaf signers has been recorded using two different cameras. The first one, RGB HQ, is used to capture a high quality image and the second, infrared Kinect, is used to captured the depth. The latter was linked with Brekel Proface 2 (Leong et al. 2015), a 3D animation software that enables an automatic recognition of FA. This corpus has been fully annotated using Typannot’s generic glyphs. These annotations have enabled the validation of the general structure of Typannot FAformula and to identify some minor corrections to be made. For instance, it has been shown that the description of the air used to puff out or suck in cheeks is too restrictive and the description of the opening and closure of the eyelids is too unnecessarily precise.When those changes are implemented, our next task will be to develop a morphological glyphic system that will combine the different generic glyphs used for each facial parameter into one unique morphological glyph. This means that for any given FA, all the information contained in Typannot descriptive formula will be contained within one legible glyph. Some early research and work has already begun on this topic, but needs further development before providing a statement on its typographic structure. When this system is completed, it will be released with its own virtual keyboard (Typannot Keyboard, currently in development for handshapes) to help transcription and improve annotation processes.Bibliography :-Chételat-Pelé, E. (2010). Les Gestes Non Manuels en Langue des Signes Française ; Annotation, analyse et formalisation : application aux mouvements des sourcils et aux clignements des yeux. Université de Provence - Aix-Marseille I.-Crasborn, O., Van Der Kooij, E., Waters, D., Woll, B., & Mesch, J. (2008). Frequency distribution and spreading behavior of different types of mouth actions in three sign languages. Sign Language & Linguistics, 11(1), 45–67.-Crasborn, O. A., & Bank, R. (2014). An annotation scheme for the linguistic study of mouth actions in sign languages. http://repository.ubn.ru.nl/handle/2066/132960-Fontana, S. (2008). Mouth actions as gesture in sign language. Gesture, 8(1), 104‑123.-Hanke, T. (2004). HamNoSys—Representing sign language data in language resources and language processing contexts. In Workshop on the Representation and Processing of Sign Languages on the occasion of the Fourth International Conference on Language Resources and Evaluation (p. 1‑6).-Leong, C. W., Chen, L., Feng, G., Lee, C. M., & Mulholland, M. (2015). Utilizing depth sensors for analyzing multimodal presentations: Hardware, software and toolkits (p. 547‑556).Presented at Proceedings of the 2015 ACM on International Conference on Multimodal Interaction, ACM.-Prillwitz, S., Leven, R., Zienert, H., Hanke, T., & Henning, J. (1989). Hamburg notation system for sign languages: An introductory guide. Signum Press, Hamburg.-Sandler, W. (2009). Symbiotic symbolization by hand and mouth in sign language. Semiotica, 2009(174), 241‑275. http://doi.org/10.1515/semi.2009.035-Sutton, V. (1995). Lessons in Sign Writing: Textbook. DAC, La Jolla (CA).-Sutton-Spence, R., & Boyes-Braem, P. (2001). The hands are the head of the mouth: The mouth as articulator in sign languages. Signum Press, Hamburg

Tunable high-purity microwave signal generation from a dual-frequency VECSEL at 852 nm (orale)

International audienceWe demonstrate the dual-frequency emission of a diode-pumped vertical external-cavity semiconductor laser operating at 852 nm, dedicated to the coherent population trapping of cesium atoms for compact atomic frequency references. It is based on a single laser cavity sustaining the oscillation of two adjacent, cross-polarized, modes. The output power reaches 10 mW on each frequency. The frequency difference and the absolute laser frequencies are simultaneously precisely tuned and stabilized on external references, resulting in the generation of a high-purity optically-carried microwave signal. The laser design has focused on stability and compactness

Emission bifréquence d'un laser à semiconducteur en cavité externe à 852 nm pour les horloges atomiques a césium (orale)

National audienceNous décrivons l'émission simultanée en phase, sur deux fréquences optiques polarisées perpendiculairement, d'un laser à semiconducteur en cavité externe pompé optiquement. L'émission est accordable autour de la raie D2 du césium à 852,14 nm avec une puissance optique d'environ 13 mW sur chaque polarisation. La différence de fréquence est ajustée grâce à un modulateur électro-optique autour de 9,2 GHz. Nous évaluons la source réalisée en vue de son application au piégeage cohérent de population d'atomes de césium dans une horloge atomique

Evaluation of the noise properties of a dual-frequency VECSEL for compact Cs atomic clocks (Poster)

International audienceWe evaluate a dual-frequency and dual-polarization optically-pumped semiconductor laser emitting at 852 nm as a new laser source for compact atomic clocks based on the coherent population trapping (CPT) technique. The frequency difference between the laser modes is tunable to 9.2 GHz corresponding to the ground state hyperfine-split of Cs. Impact of the laser noise has been investigated. Laser relative intensity noise is limited by the pump-RIN transfer to a level of-110 dB/Hz. Laser frequency noise shows excess mechanical and technical noise resulting in a laser linewidth of 1 MHz at 1 s in lock operation. The noise performance and spectral properties of the laser are already adequate to realize CPT experiments and should result in Allan standard-deviation of the clock below 1 × 10-12 at 1 second

Two-cross-polarized-frequency VECSEL at 852nm for CPT-based Cs clocks (poster)

International audienceWe demonstrate a tunable high-purity microwave signal generation from a cross- polarized dual-frequency diode-pumped vertical external-cavity semiconductor laser operating at 852 nm for the coherent population trapping of cesium atoms in compact atomic frequency references

Low-noise dual-frequency laser for compact Cs atomic clocks

International audienceWe report the dual-frequency and dual-polarization emission of an optically-pumped vertical external-cavity semiconductor laser (OP-VECSEL). Our laser source provides a high-purity optically-carried RF signal tunable in the GHz range, and is specifically designed for the coherent population trapping (CPT) of Cs atoms in compact atomic clocks. The laser spectrum is stabilized onto a Cs atomic transition at 852.1 nm, and the frequency difference is locked to a local oscillator at 9.2 GHz. Special attention has been paid to the evaluation of the frequency, intensity and phase noise properties. A maximum phase noise of - 90 dBrad2/Hz has been measured. Finally, we estimate the contribution of the laser noise on the short-term frequency stability of a CPT atomic clock, and predict that a value below 3 × 10-13 over one second is a realistic target

Generation of high purity microwave signal from a dual-frequency OP-VECSEL (orale)

International audienceCoherent population trapping (CPT) is an interesting technique for the development of compact atomic frequency references. We describe an innovating laser source for the production of the two cross-polarized coherent laser fields which are necessary in CPT-based atomic clocks. It relies on the dual-frequency and dual-polarization operation of an optically-pumped vertical external-cavity semiconductor laser. This particular laser emission is induced by intracavity birefringent components which produce a controllable phase anisotropy within the laser cavity and force emission on two cross-polarized longitudinal modes. The laser emission is tuned at the Cs D2 line (λ = 852.14 nm), and the frequency difference ∆ν between the two laser modes is tunable in the microwave range. The laser line wavelength is stabilized onto an atomic hyperfine transition, and concurrently the frequency difference is locked to an ultra-low noise RF oscillator at 9.2 GHz. The high spectral purity of the optically-carried microwave signal resulting from the beatnote of the two cross-polarized laser lines is assessed through its narrow spectral linewidth (<30 Hz) as well as its low phase noise (≤ -100 dBrad2/Hz). The performance of this laser source is already adequate for the interrogation of atoms in a CPT atomic clock, and should result in an estimated relative stability of 3.10-13τ-1/2 - one order of magnitude better than commercial atomic clocks