Réalisation de micro-résonateurs organiques par procédés hybrides : Nouvelles perspectives en photonique intégrée

L’article consiste en une étude de micro-résonateurs (MRs) sphériques fabriqués à partir d’un matériau organique : le polymère NOA (Northland Optical Adhesive). Les auteurs présentent en un premier lieu le circuit micro fluidique spécialement adapté à la création de gouttes sphériques MRs.L’excitation des modes de galerie permet de déterminer les rayons des sphères. Dans une intégration photonique et pour un meilleur confinement, les sphères sont excitées en utilisant un guide d’onde réalisé par technique de « spin coating » à l’aide de polymère SU8 (bisphénol A d’éther glycide). Le couplage est réalisé à l’aide d’ondes évanescentes circulant du guide vers la sphère. La photographie des sphères excitées (pour deux configurations différentes all-pass ou add-drop) met en évidence les modes optiques situés à la surface des sphères synonymes de modes de galerie. L’analyse spectrale du signal à la sortie du guide met en évidence la présence de pics confirmant l’excitation de cette catégorie de modes au sein de la structure. Ces mesures, à l’aide de l’intervalle spectrale libre permettent de remonter aux diamètres des sphères. Les valeurs déterminées sont en bon accord avec celles mesurées à l’aide de la microscopie optique

About the Heisenberg's uncertainty principle and the determination of effective optical indices in integrated photonics at high sub-wavelength regime

International audienceWithin the Heisenberg’s uncertainty principle it is explicitly discussed the impact of these inequalities on the theory of integrated photonics at sub-wavelength regime. More especially, the uncertainty of the effective index values in nanophotonics at sub-wavelength regime, which is defined as the eigenvalue of the overall opto-geometric problems in integrated photonics, appears directly stemming from Heisenberg’s uncertainty. An apt formula is obtained allowing us to assume that the incertitude and the notion of eigenvalue called effective optical index or propagation constant is inversely proportional to the spatial dimensions of a given nanostructure yielding a transfer of the fuzziness on relevant senses of eigenvalues below a specific limit’s volume

L'effet Peltier appliqué à la conception et la réalisation d'un nouveau capteur de débit massique

The present paper deals with design and realization of a new mass flow sensor using the Peltier effect. The sensor, shaped as a bimetallic printed circuit includes three continuous parallel strips coated with a great deal of metal plated spots. In such a device, the central track performs as a classical thermoelectrical circuitry whose both plated and uncoated parts provide the thermopile junctions. The two outer strips are subjected to electrical currents so as to generate numerous small thermal gradients owing to the Peltier effect. Then, the resulting differences in temperature induce a Seebeck e.m.f. on to the close inner strip acting as a receiver. The thermal coupling between transmitters and receiver tracks depends on any variation of the surrounding environment heat transfert coefficient. Therefore, such a device allows us to detect any shift in physical properties related to the apparent thermal conductivity. In the special case of a steady state fluid, the induced e.m.f. in the receiving track hinges on the thermal conductivity. When the fluid is in relative motion along the sensor, the velocity can be read out as a function of voltage. As an application, the thermoelectric circuit is placed in a tube conducting a fluid flow, in order to design a new mass flowmeter. Experimental results show that when subjected to a steady mass flow rate the e.m.f. remains still, even though the pressure is allowed to vary through the pipe. Actually, the supplied information depends only on the mass flow rate. The main advantage of this measurement method, when compared with classical hot wire devices, is that any change in the surrounding environment average temperature does not induce any significant shift on the output voltage. On the other hand, when operated in a wide temperature range, easy compensating techniques can be used to provide accurate and reliable performance over large temperature variations.Le travail présenté est relatif à la conception et la réalisation d'un nouveau capteur de débit massique basé sur l'effet Peltier. Le capteur en forme de circuit imprimé bimétallique, comporte plusieurs pistes métalliques continues parallèles entre elles et partiellement recouvertes par un grand nombre de dépôts électrolytiques de nature différente. Un tel circuit se comporte comme un circuit thermoélectrique classique dans lequel les parties homogènes non recouvertes par le dépôt électrolytique constituent le premier conducteur du couple, les parties plaquées constituant le second conducteur. La méthode de mesure consiste à faire passer un courant électrique dans une ou plusieurs pistes constituant le circuit émetteur de façon à générer par effet Peltier des gradients thermiques qui seront détectés par un circuit détecteur identique placé à proximité. Dans le cas particulier d'un fluide au repos, la f.e.m. détectée par le circuit détecteur dépend de la conductivité thermique du fluide. Lorsque le fluide est en mouvement relatif par rapport au circuit, il est possible de détecter une f.e.m. dépendant en grandeur et en signe de la vitesse d'écoulement du fluide. A titre d'application un capteur de débit massique a été réalisé en plaçant les circuits thermoélectriques dans une canalisation parcourue par le fluide en mouvement

Experimental investigation of transient nonlinear phenomena in an annular thermoacoustic prime-mover: observation of a double-threshold effect

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Novel Antenna Structure for Early Breast Cancer Detection

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On the detection of nanoparticle cloud migration by a resonant photonic surface signal towards sedimentation velocity measurements

International audienceMigration and sedimentation of solid particles in a liquid are physical phenomena involving accumulation of soft matter or decantation of fragmented matter. A thorough understanding together with relevant measurements are prerequisites regarding many fields, including medicine, galenic pharmacology, food processing, and the cosmetics industry. In this paper, we investigate the feasibility of monitoring and detecting the migration of a nanoparticle cloud with a resonant light probe. For this purpose, hybrid silicon/silica/UV210 organic integrated photonic racetrack resonators were patterned by thin film processes to be used as sensors measuring the outcome of the impact of a cloud of nanoparticles, the dynamic migration plus sedimentation phenomenon of the nanoparticle cloud in water. A broadband superluminescent diode has been used for the excitation. Then, the spectral characteristics of the resonant guided modes have been analyzed, considering the observed changes while tracking the free spectral range of the transduced comb spectra as a function of time. The way to operate can be summarized as follows: Solutions based on spherical silica nanoparticles of fixed size are prepared and subjected to rheological measurements to obtain their respective viscosities. Next, a millimeter tank filled with water is conveniently placed on the active surface of the sensing chip, prior to the addition of one of the previously mentioned solutions. The series of spectra are acquired during the whole migration sequence and the transduced optical signal is then directly processed and treated by a specific code operated in real time by way of Lagrange interpolation polynomials. Collected data are then compared to a simple theoretical model describing the sedimentation of a spherical particle in water (Stokes' law). Eventually, the implementation of the device in a characterization platform and the development of a specific protocol allows a global treatment, whose description is followed by discussions on measurements and data. Consequently, after the impact of the drop containing the nanoparticles, the monitoring of a first phase regarding their fast cloud migration into the global study volume (with flow of matter plus vortex) eventually followed by their slow sedimentation, can be detected using such a resonant light probe. The overall duration of the first phase associated with sedimentation velocities is in the order of a few tens of µm/min for particles with submicron diameters (several hundreds of nanometers); a first attempt of comparison of this first phase with the results of the classic Stokes model would give a convergence of the values reaching between 9 and 19% for the sedimentation rates