Polarization conversion by dielectric subwavelength gratings in conical mounting

Subwavelength dielectric gratings are examined in total-internal-reflection configuration. It is demonstrated experimentally that such elements, fabricated in TiO2, can perform full polarization conversion from incident TE to TM with nearly 100% efficiency. The dependence of the polarization conversion on the angle of incidence is analyzed. Rigorous diffraction theory is used to cross check the experimental results

Matrixes of unconventional micro-optical components molded with etched silicon

This paper reports on a process to create microlenses characterized by unconventional footprints, spherical profiles and a wide range of sizes. Fabricated shapes such as squares, rectangles, ellipses, triangles and hexagons are tested alone as well as in matrix with high fulfill factors. The technique is based on molds from which microlenses are fabricated by UV-molding replication. The molds are produced by silicon wet isotropic etching in an acid solution. The process is mainly steered by temperature and etching concentration. The use of the proposed technology opens a wide range of geometries allowing the fabrication of microlenses matrices with high fulfill factors as well as microlenses for beam-shaping

Reduction of helium permeation in microfabricated cells using aluminosilicate glass substrates and Al2_2O3_3 coatings

The stability and accuracy of atomic devices can be degraded by the evolution of their cell inner atmosphere. Hence, the undesired entrance or leakage of background or buffer gas, respectively, that can permeate through the cell walls, should be slowed down. In this work, we investigate helium permeation in microfabricated alkali vapor cells filled with He and whose windows are made of borosilicate glass (BSG) or aluminosilicate glass (ASG). The permeation is then derived from routine measurements of the pressure-shifted hyperfine transition frequency of an atomic clock. We first confirm that ASG reduces He permeation rate by more than two orders of magnitude, in comparison with BSG. In addition, we demonstrate that Al$_2$O$_3$ thin-film coatings, known to avoid alkali consumption in vapor cells, can also significantly reduce He permeation. The permeation through BSG is thereby reduced by a factor 110 whereas the one through ASG is decreased by a factor up to 5.8 compared to uncoated substrates. These results may contribute to the development of miniaturized atomic clocks and sensors with improved long-term stability or sensitivity.Comment: 7 pages, 5 figure

La brillance des faisceaux lasers diffractés

Nous montrons que la troncature d'un faisceau de Laguerre-Gauss symétrique d'ordre élevé par un diaphragme circulaire centré réduit son facteur $M^2$ et peut améliorer sa brillance malgré les pertes introduites

Optique binaire pour la mise en forme spatiale de faisceaux laser IR, visible et UV

Nous montrons les possibilités de mises en forme d'amplitude et de polarisation des faisceaux laser qu'offrent quelques Eléments Optiques Diffractifs binaires simples

Effects of getters on hermetically sealed micromachined cesium-neon cells for atomic clocks

International audienceThe wafer-level integration technique of PageWafer R (SAES Getters' solution for getter film integration into wafer to wafer bonded devices) has been tested in fermetically sealed miniature glass-Si-glass cells filled with Cs and Ne, e.g. for microelectromechanical systems (MEMS) atomic clock applications. Getter effects on the cell atmosphere are analyzed by quadruple mass spectroscopy and coherent population trapping (CPT) spectroscopy. The quadruple mass spectroscopy revealed that the residual gases (H2, O2, N2 and CO2) that are attributed to anodic bonding process are drastically reduced by the getter films while desirable gases such as Ne seem to remain unaffected. The impurity pressure in the getter-integrated cells was measured to be less than 4 × 10−2 mbar, i.e. pressure 50 times lower than the one measured in the cells without getter (2 mbar). Consequently, the atmosphere of the getter-integrated cells is much more pure than that of the getter-free cells. CPT signals obtained from the getter-integrated cells are stable and are, in addition, similar to each other within a cell batch, suggesting the strong potential of applications of this getter film and especially for its wafer-level integration to MEMS atomic clocks and magnetometers

Mesure d'un effet de lentille de population dans un cristal de Cr3+^{3+}:LiSAF par la technique du Z-scan

Nous avons réalisé une expérience permettant de mesurer la variation de la polarisabilité des ions Cr$^{3+}$ dans le LiSAF lorsqu'ils passent de l'état fondamental $^{4}$A$_{2}$ à l'état excité $^{4}$T$_{2}$. Cette variation de polarisabilité est à l'origine d'un effet de lentille de population non-linéaire dépendant du temps

Towards the Realization of the First European MEMS Atomic Clock

International audienceThis paper presents the preliminary results of developments of the European version of MEMS atomic clock presenting a short-term stability of 5x10-11 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)