Ultralow-Noise SiN Trampoline Resonators for Sensing and Optomechanics

In force sensing, optomechanics, and quantum motion experiments, it is typically advantageous to create lightweight, compliant mechanical elements with the lowest possible force noise. Here we report wafer-scale batch fabrication and characterization of high-aspect-ratio, nanogram-scale Si$_3$N$_4$ "trampolines" having quality factors above $4 \times 10^7$ and ringdown times exceeding five minutes (1 mHz linewidth). We measure a thermally limited force noise sensitivity of 16.2$\pm$0.8 aN/Hz$^{1/2}$ at room temperature, with a spring constant ($\sim$1 N/m) 2-5 orders of magnitude larger than those of competing technologies. We also characterize the suitability of these devices for high-finesse cavity readout and optomechanics applications, finding no evidence of surface or bulk optical losses from the processed nitride in a cavity achieving finesse 40,000. These parameters provide access to a single-photon cooperativity $C_0 \sim 8$ in the resolved-sideband limit, wherein a variety of outstanding optomechanics goals become feasible.Comment: 8 pages, 4 figures, 1 tabl

Transferts culturels et déclinaisons de la pédagogie européenne: le cas franco-romand au travers de l'itinéraire d'Alexandre Daguet (1816-1894)

Cette thèse vise à réévaluer la circulation des savoirs pédagogiques dans l’espace francosuisse. Méthodologiquement, nous nous proposons d’insister sur les modalités de passage de ces savoirs d’un contexte culturel à l’autre, en étudiant les acteurs, les vecteurs, ainsi que les inévitables transformations sémantiques qui accompagnent nécessairement ces échanges transnationaux. Cette recherche, articulée sous la forme d’une Gesellschaftsbiographie, prend pour guide le théoricien des idées éducatives, Alexandre Daguet (1816-1894). Il s’agit d’éclairer son rôle de médiateur privilégié dans le transfert de savoirs pédagogiques entre la Suisse romande et la France, en étudiant notamment son rôle de passeur via la revue L’Éducateur. Bien qu’il ait décliné l’appel de Ferdinand Buisson à édifier avec lui une « oeuvre internationale d’éducation », il n’en a pas pour le moins joué un rôle de « courtier » dans la diffusion de savoirs spécifiques, véhiculés notamment par les proscrits français réfugiés en Suisse romande dès 1852. Cette thèse permet de souligner comment les savoirs pédagogiques européens, élaborés de manière collective, sont diversement déclinés selon des spécificités locales. Dans ce sens, il s’agit de montrer qu’à mesure que les identités se solidifient, les spécificités nationales sont de plus en plus exaltées lors des Expositions universelles et les « exotismes » bientôt dévalorisés, voire même dissimulés au profit d’un certain génie national. Cette recherche souhaite donc contextualiser cette apparence trompeuse de Sonderfälle, pour mettre davantage de relief dans la construction collective d’une pédagogie européenne métissée. Mots clés : Alexandre Daguet, Suisse, transferts culturels, transformation sémantique, circulation des savoirs, histoire de la pédagogie, Ferdinand Buisson, Troisième RépubliqueThis thesis seeks to reassess the way in which pedagogical knowledge circulated between France and Switzerland. In terms of method, we have chosen to focus on the way in which this knowledge passed from one cultural context to another by studying the related actors and vectors, as well as the inevitable semantic transformations which, of necessity, accompany transnational exchanges of this nature. The research takes the form of a Gesellschaftsbiographie, with a guide in the person of educational theorist Alexandre Daguet (1816-1894). It aims to shed light on his role as a key mediator in the transfer of pedagogical expertise between French-speaking Switzerland and France, with a special emphasis on the way he used the review L’Éducateur to take this knowledge across borders. Although Daguet turned down the proposal by Ferdinand Buisson to work with the latter to create an “international treatise on education”, he nevertheless acted as a ‘broker’ in the trade of specific knowledge, passed on in particular by the French political exiles that took refuge in French-speaking Switzerland from 1852 onwards. The thesis also highlights the way in which European pedagogical knowledge, developed collectively, was applied in a variety of ways depending on local particularities. The issue here is to show the way in which, as identities became more firmly established, distinctive national features were increasingly honoured at Universal Expositions, while the various forms of “exoticism” soon fell out of favour, sometimes even to the point of being concealed in favour of national genius. This research therefore seeks to contextualise the deceptive semblance of Sonderfälle and provide a clearer picture of the collective emergence of a multifaceted European pedagogy. Key words : Alexandre Daguet, Switzerland, cultural transfer, semantic transformation, circulation of knowledge, history of pedagogy, Ferdinand Buisson, French Third Republi

Equality of the energy and group velocities of bulk acoustic waves in piezoelectric media

International audienceThe equality of the energy and group velocities of bulk acoustic waves in a lossless piezoelectric medium is demonstrated, with the energy velocity defined from the generalized energy density and the generalized Poynting vector

Attention an-archaïque : la tâche de traduire à l’ère séculière

[À l'origine dans / Was originally part of : Thèses et mémoires - FAS - Département de littérature comparée]L’époque actuelle se caractérise par un processus de sécularisation irrésolu. Les inconsistances de notre modernité relèvent à la fois d’une dissolution de l’hégémonie de la religion en occident et d’une diversification de régimes de valeurs, croyances et représentations ayant pour effet la persistance de différends idéologiques que le phénomène de globalisation à la fois accentue et résorbe sans les abolir. Cette thèse examine la pertinence de la traduction pour interroger les fondements littéraires des enjeux esthétiques et politiques de cette condition. En tant que procédé poïétique, modèle de subjectivité éthique et figure de pensée, la traduction constitue un dispositif littéraire intimement relié au problème de la sécularisation. Chacune des études qui composent la thèse cherche à approfondir, dans une perspective comparatiste, une intuition de base : le mode de dépossession inhérent au fait littéraire de traduire permet d’appréhender un certain ethos séculier dont le caractère historique ne serait pas totalement coupé d’un rapport à la transcendance dans le contexte de l’économie culturelle globale. Le problème de la traduction est abordé à partir de deux axes principaux : la distorsion de la tradition religieuse par la formation d’une religiosité d’ordre littéraire (un ethos séculier) et la distorsion d’un certain humanisme d’après l’expérience catastrophique et la manière dont cet ethos permet d’y survivre. Cette thèse vise à dégager de l’idée de traduction une capacité de régénérer un rapport éthique à autrui par la construction de liens inédits avec le passé et l’avenir ; une attention à la finitude humaine caractérisée par une disposition critique et affective face à ces artefacts humains que nous nommons littérature. Les écrits de la poète et traductrice Anne Carson jouent un rôle déterminant dans le cadre de cette recherche puisqu’ils exemplifient une capacité singulière de faire usage de la tradition qui permet d’envisager, ultimement, une régénération de la question du sens de l’humain, c’est-à-dire, d’une pensée sensible à l’inhumain entre nous.Our age is one fashioned by an unresolved and deeply problematic process of secularization. The waning of the hegemony of religion in the West and the reconfigurations of values, beliefs and representations in a global cultural economy calls for a certain mode of inquiry able to reflect changing social, political and aesthetic conditions of our discrepant contemporaneity. This thesis contends that translation embodies a relevant ethos for the humanities and a critical fulcrum to investigate an experience of incommensurability sustained in the tensions within secularization manifested through literary works and especially poetry. Secular imagination is bound to the problem and practice of translation that is framed here as a poïetic process, a model of ethical subjectivity and a figure of thought. This is exposed through a constellation of cultural inscriptions that reflect a sense of sundered transcendence in the midst of a secular world, most notably through the construction of a dislocated relationship to time. These inscriptions are examined along two lines of investigation that bring into focus a radical form of secular thought cultivated through an ambiguous relationship to a spiritual experience of fidelity deprived of a fixed, metaphysical, grounding: first, the emergence of a translational ethos from the distortion of the sacred/poetical economy of texts; second, the distortion of humanism in light of the untimely experience of catastrophe and how this ethos may be a way of working through it. This thesis aims to show how the task of translation shapes a certain critical attitude embedded in one’s affective dispossession that upholds the task of a return to the human. It fashions a mode of attention to radical human finitude that, in the end, does nothing more than expose its inhumanity. Anne Carson’s poetics of translation is exemplary of such an attention, of a daring spiritual disposition that may be a way to understand how literature and comparative literary inquiry can learn to regenerate the unresolved sense of secularization

Design of Computer Experiments: a powerful tool for the numerical design of BAW filters

We apply Design of Computer Experiments methods to the simulation of piezoelectric stacks and the design of BAW resonators and filters. Through the example of DCS filters with two different technologies (Iridium and Molybdenum electrodes), we show that the definition and the exploitation of a metamodel can accurately replace acoustic simulations and allows therefore a much faster material stack desig

Theoretical analysis of damping effects of guided elastic waves at solid/fluid interfaces

International audienceA theoretical description of ideal and viscous fluid media is proposed to address the problem of modeling damping effects of surface acoustic waves and more generally of any guided elastic waves at the interface between viscous fluids and solids. It is based on the Fahmy-Adler eigenvalue representation of the elastic propagation problem, adapted to provide Green's function of the considered media. It takes advantage of previous efforts developed to numerically stabilize Green's-function computation process. This function is used to compute a harmonic admittance according to the Blötekjaër approach. The influence of acoustic radiation and viscosity effects on different kinds of waves excited on various substrates is reported and discussed

Comparative myoanatomy of Tardigrada:new insights from the heterotardigrades <i>Actinarctus doryphorus</i> (Tanarctidae) and <i>Echiniscoides sigismundi</i> (Echiniscoididae)

Abstract Background Tardigrada is a group of microscopic invertebrates distributed worldwide in permanent and temporal aquatic habitats. Famous for their extreme stress tolerance, tardigrades are also of interest due to their close relationship with Arthropoda and Cycloneuralia. Despite recent efforts in analyzing the musculature of a number of tardigrade species, data on the class Heterotardigrada remain scarce. Aiming to expand the current morphological framework, and to promote the use of muscular body plans in elucidating tardigrade phylogeny, the myoanatomy of two heterotardigrades, Actinarctus doryphorus and Echiniscoides sigismundi, was analyzed by cytochemistry, scanning electron and confocal laser scanning microscopy and 3D imaging. We discuss our findings with reference to other tardigrades and internal phylogenetic relationships of the phylum. Results We focus our analyses on the somatic musculature, which in tardigrades includes muscle groups spanning dorsal, ventral, and lateral body regions, with the legs being musculated by fibers belonging to all three groups. A pronounced reduction of the trunk musculature is seen in the dorsoventrally compressed A. doryphorus, a species that generally has fewer cuticle attachment sites as compared to E. sigismundi and members of the class Eutardigrada. Interestingly, F-actin positive signals were found in the head appendages of A. doryphorus. Our analyses further indicate that cross-striation is a feature common to the somatic muscles of heterotardigrades and that E. sigismundi—as previously proposed for other echiniscoidean heterotardigrades—has relatively thick somatic muscle fibers. Conclusions We provide new insights into the myoanatomical differences that characterize distinct evolutionary lineages within Tardigrada, highlighting characters that potentially can be informative in future phylogenetic analyses. We focus our current analyses on the ventral trunk musculature. Our observations suggest that seven paired ventromedian attachment sites anchoring a large number of muscles can be regarded as part of the ground pattern of Tardigrada and that fusion and reduction of cuticular attachment sites is a derived condition. Specifically, the pattern of these sites differs in particular details between tardigrade taxa. In the future, a deeper understanding of the tardigrade myoanatomical ground pattern will require more investigations in order to include all major tardigrade lineages

Multiple Frequency Solidly Mounted BAW Filters

This paper reports the simultaneous fabrication of Receive and Transmit Bulk Acoustic Wave filters for the WCDMA standard on the same die. Both filters are based on Solidly Mounted Resonators using a common Bragg mirror, but with each having a specific piezoelectric film thickness. Electrical measurements reveal that the process steps required to provide the two different piezoelectric film thicknesses on the same die does not impact the electrical performances of resonators and filters and that this approach could thus be generalised to more than two filters

High overtone Bulk Acoustic Resonators: application to resonators, filters and sensors

International audienceAcoustelectric devices have been used now for several decade to stabilize oscillators, to filter radio-frequency signals or to allow for physical and even chemical detection and measures.Among all the structures that have been developed in that purpose, one has been revealing particularly interesting for the development of high quality factor resonator on an extended range of frequency. It is based on the generation of high overtones in bulk acoustic wave resonant structure and therefore are currently called HBARs. These devices may be fabricated along various approaches but they always consist of a thin (or thinned) piezoelectric layer deposited or bonded onto a high quality single crystal material. The spectral response of this kind of device exhibit a periodic comb of peaks modulated by the transducer response, yielding resonances on a very large spectrum with various characteristics and properties. We present here the basic principles of such devices, their remarquable properties, the etchnologies required to manufacture them and the various applications they can be applied for. A focus is partcularly dedicated to oscillator stabilization and to wirelss sensor development