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In this work, we present a fabrication process of a MOEMS endoscopic probe based on micro-assembly and local adhesive bonding of its four building blocks, i.e. a 2-D scanner, a Mirau micro-interferometer, a GRIN collimator and a flexible PCB. The complete assembly procedure consists of five steps and involves an active optical alignment between interferometer and collimator as well as electrical interconnecting of scanner with PCB. The assembly steps were performed in a cleanroom using semi-automatic chip-bonder equipment. The presented probe is a key component of a Swept-Source Optical Coherence Tomography (SS-OCT) system for endoscopic biomedical imaging.

International audience; Laser scanning based on Micro-Electro-Mechanical Systems (MEMS) scanners has become very attractive for biomedical endoscopic imaging, such as confocal microscopy or Optical Coherence Tomography (OCT). These scanners are required to be fast to achieve real-time image reconstruction while working at low actuation voltage to comply with medical standards. In this context, we report a 2-axis Micro-Electro-Mechanical Systems (MEMS) electrothermal micro-scanner capable of imaging large fields of view at high frame rates, e.g. from 10 to 80 frames per second. For this purpose, Lissajous scan parameters are chosen to provide the optimal image quality within the scanner capabilities and the sampling rate limit, resulting from the limited A-scan rate of typical swept-sources used for OCT. Images of 233 px × 203 px and 53 px × 53 px at 10 fps and 61 fps, respectively, are experimentally obtained and demonstrate the potential of this micro-scanner for high definition and high frame rate endoscopic Lissajous imaging.

International audience; In this paper, we present the construction and preliminary experimental results of a MOEMS fiber-based integrated probe for endoscopic optical imaging of stomach tissue using a Swept-Source Optical Coherence Tomography (SSOCT). The probe consists of a Mirau micro-interferometer, combined with a GRIN lens collimator and a micromirror scanner. We describe the building blocks of the probe, especially the monolithically integrated Mirau mirointerferometer, fabricated by wafer-level vertical stacking and anodic bonding of Si/glass components, and the electrothermal 2-axis MEMS microscanner allowing large swept angles (up to ±22°) at high frequencies (&gt kHz) for low driving voltages (

This work proposes a two-step phase-shifting algorithm as an improvement of fringe projection profilometry. Considering the working process of fringe projection, the captured fringe image is formulated with two variables, i.e. surface reflectivity and phase value. And a phase shift of 3π/2 is introduced to get the two-step phase-shifting. After appropriate variable substitution, expressions of two fringe images can be transformed into two equations corresponding to a line and a circle respectively. With this circle-line model, the characteristic of solution and the phase error due to non-zero ambient light are analyzed. Then the approach of error compensation is proposed based on estimation of the real fringe contrast and non-linear least square optimization. The validity of the proposed approach is demonstrated with both simulations and experiments.

In the past decade, rapid advances in silicon-based microelectromechanical (MEMS) technology have enabled the realization of a variety of novel functions in the micromechanical world similar to the functions performed by microelectronics. One motivation for developing MEMS is their small scale and the ease of integrating them with electronic circuits and sensors, resulting in miniaturized and smart microsystems with moving parts. The dimensional scale of MEMS devices is immediately compatible with the size of integrated optics (IO) and micro-optical devices such as optical fibers, laser diodes, channel waveguides, and diffractive or refractive microlenses. This scale (1 to 500 mm) is compatible with the size of optical beams, and is appropriate for controlling or manipulating optical radiation. MEMS technology exploits photolithographic techniques to fabricate microstructures with extremely high dimensional tolerances, precise positioning on the chip, and well-controlled microactuation. This potential is suitable for fabricating precision-defined optical components and offers relatively easy alignment procedures for optical parts. For all these reasons, MEMS technology has benefited from the integration of microstructures with free-space micro-optics and guided wave optics. This category of photonic devices constitutes a new extension of MEMS, called microoptoelectromechanical systems (MOEMS).Many novelMOEMS architectures, including micromirrors, microlenses, modulators and switches, microchoppers, microplatforms for integrated optics, fiber optics, scanners, optically driven actuators, integrated optical sensors, and other devices with optical functions have been developed. In this chapter we focus our attention on guided-waveMOEMS, combining micromachined structures and optical waveguides on silicon substrates. Since guided-wave MOEMS are fabricated by batch process, these devices are potentially low cost, and their monolithic structure improves their reliability. This approach of integrating optics with micromechanics has applications for integrated sensors, microactuators, and optical communication. A wide variety of fabrication technologies have been developed for optical waveguides on silicon. These include chemical vapor deposition (CVD), flame hydrolysis deposition (FHD), and spin-coating deposition of polymers. Waveguide structures are based on depositing silica layers for the cladding and doped silica, silicon nitride or silicon oxinitride, and polymers for the core layer, for example. The core layer is commonly structured by reactive ion etching (RIE). The waveguide-related structures include directional couplers, Y junctions, multiplexers, and possibly insertion of standard fiber optics via V-groove alignment procedures. Optical waveguides may be integrated with micromechanical deformable structures such as diaphragms, beams, bridges, and membranes. The micro-optomechanic element can serve as a sensor to detect a physical parameter of the mechanical deformation, as well as a microactuator, and also as an optical modulator or switch.

International audience; This contribution concerns the results of the European Collaborative Project MAC-TFC (MEMS Atomic Clocks for Timing, Frequency Control & Communications) aiming the developments of the European version of MEMS atomic clock presenting a short-term stability of 5x10-11 over 1 hour. MAC-TFC proposal (website: www.mac-tfc.eu) is 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). The goal is to develop and demonstrate all the necessary technologies to achieve an ultra-miniaturised, low-power caesium (Cs) atomic clock, using the principle of Coherent Population Trapping (CPT).

International audience; Nous présentons un système d’imagerie miniature basé sur une matrice d’interféromètres et réalisé à partir de technologies des microsystèmes opto-electromécaniques (MOEMS). En particulier, les composants des interféromètres sont fabriqués par des techniques collectives et assemblés par intégration verticale multisubstrats. La matrice d’interféromètres est ensuite intégrée au sein d’un système d’illumination et d’imagerie pour constituer un dispositif de tomographie à cohérence optique (OCT) dédié à l’analyse des pathologies de la peau. Le système repose sur une architecture matricielle d’interféromètres de Mirau, permettant une approche pleinchamp multicanaux. Cela lui confère des caractéristiques adaptées à l’imagerie de la peau comme un grand champ de vue latéral.

International audience; In this paper, we present construction, fabrication and characterization of an electrostatic MOEMS vertical microscannerfor generation of an optical phase shift in array-type interferometric microsystems. The microscanner employs asymmetriccomb-drives for a vertical displacement of a large 4x4 array of reference micromirrors and for in-situ position sensing.The device is designed to be fully compatible with Mirau configuration and with vertical integration strategy. This enablesfurther integration of the device within an “active” multi-channel Mirau micro-interferometer and implementation of thephase shifting interferometry (PSI) technique for imaging applications. The combination of micro-interferometer and PSIis particularly interesting in the swept-source optical coherence tomography, since it allows not only strong size reductionof a system but also improvement of its performance (sensitivity, removal of the image artefacts). The technology of deviceis based on double-side DRIE of SOI wafer and vapor HF releasing of the suspended platform. In the static mode, thedevice provides vertical displacement of micromirrors up to 2.8μm (0 - 40V), whereas at resonance (fo=500 Hz), it reaches0.7 μm for only 1VDC+1VAC. In both operation modes, the measured displacement is much more than required for PSIimplementation (352nm peak-to-peak). The presented device is a key component of array-type Mirau micro-interferometerthat enables the construction of portable, low-cost interferometric systems, e.g. for in vivo medical diagnostics.

National audience; Ce papier présente la conception et les briques d’un système OCT dédié au diagnostic de pathologies de la peau. Le système est basé sur une approche plein-champ multicanaux grâce à une architecture Mirau matricielle, combinant une source à balayage enlongueur d’onde réalisée par filtrage et de l’interférométrie à décalage de phase pour l’élimination des termes miroirs. L’interféromètre de Mirau, en particulier, est réalisé par des techniques de fabrication collective et d’intégration verticale multi-substrat, permettant une réduction significative de la taille et des coûts de fabrication du système.

International audience; This paper reports on an original architecture of microfabricated alkali vapor cell designed for miniature atomic clocks. The cell combines diffraction gratings with anisotropically etched single-crystalline silicon sidewalls to route a normally-incident beam in a cavity oriented along the substrate plane. Gratings have been specifically designed to diffract circularly polarized light in the first order, the latter having an angle of diffraction matching the (111) sidewalls orientation. Then, the length of the cavity where light interacts with alkali atoms can be extended. We demonstrate that a longer cell allows to reduce the beam diameter, while preserving the clock performances. As the cavity depth and the beam diameter are reduced, collimation can be performed in a tighter space. This solution relaxes the constraints on the device packaging and is suitable for wafer-level assembly. Several cells have been fabricated and characterized in a clock setup using coherent population trapping spectroscopy. The measured signals exhibit null power linewidths down to 2.23 kHz and high transmission contrasts up to 17%. A high contrast-to-linewidth ratio is found at a linewidth of 4.17 kHz and a contrast of 5.2% in a 7-mm-long cell despite a beam diameter reduced to 600 μm.

International audience; This paper presents the study of a fabrication technique of lenses arrays based on the reflow of glass inside cylindrical silicon cavities. Lenses whose sizes are out of the microfabrication standards are considered. In particular, the case of high fill factor arrays is discussed in detail since the proximity between lenses generates undesired effects. These effects, not experienced when lenses are sufficiently separated so that they can be considered as single items, are corrected by properly designing the silicon cavities. Complete topographic as well as optical characterizations are reported. The compatibility of materials with Micro-Opto-Electromechanical Systems (MOEMS) integration processes makes this technology attractive for the miniaturization of inspection systems, especially those devoted to imaging.