Christophe Gorecki

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (209)123.7 Total impact

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    ABSTRACT: This paper presents a concept of an endomicroscope for an early detection of neoplastic lesions in the human stomach tissue, based on the swept source optical coherence tomography (SS-OCT) and a measurement probe with integrated Mirau micro interferometer. The system consists of pigtailed illumination and detection blocks, connected via a Gradient Index (GRIN) lens collimator to a micro-opto-electro-mechanical systems (MOEMS) measurement probe (4 mm $times $ 4 mm $times $ 20 mm). The technology of Mirau micro interferometer is based on vertical multi-wafer bonding approach. The MOEMS probe is intended to be mounted on a continuum robot arm to perform in vivo microscopy of stomach tissues. First, the optical design of the SS-OCT endomicroscope is described, including an analysis of sensitivity. Then, we focus on the fabrication technologies and optical characterization of a key component of the Mirau micro interferometer, i.e., monolithically integrated focusing glass lens. SS-OCT endomicroscope will provide a fast axial scanning of tissues with A-scan sweep rate of 110 kHz, offering the axial resolution of 5.2 $mu text{m}$ and the lateral resolution of 10.2 $mu text{m}$ .
    IEEE Sensors Journal 12/2015; 15(12):7061-7070. DOI:10.1109/JSEN.2015.2469547 · 1.76 Impact Factor
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    ABSTRACT: We report a simple method, based on intensity measurements, for the characterization of the wavefront and aberrations produced by micro-optical focusing elements. This method employs the setup presented earlier in [Opt. Express 22, 13202 (2014)] for measurements of the 3D point spread function, on which a basic phase-retrieval algorithm is applied. This combination allows for retrieval of the wavefront generated by the micro-optical element and, in addition, quantification of the optical aberrations through the wavefront decomposition with Zernike polynomials. The optical setup requires only an in-motion imaging system. The technique, adapted for the optimization of micro-optical component fabrication, is demonstrated by characterizing a plano-convex microlens.
    Applied Optics 11/2015; 54(31):9060. DOI:10.1364/AO.54.009060 · 1.78 Impact Factor

  • Journal of Micromechanics and Microengineering 11/2015; 25(11):115013. DOI:10.1088/0960-1317/25/11/115013 · 1.73 Impact Factor
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    ABSTRACT: This paper presents the optical design of a miniature 3D scanning system, which is fully compatible with the vertical integration technology of micro-opto-electro-mechanical systems (MOEMS). The constraints related to this integration strategy are considered, resulting in a simple three-element micro-optical setup based on an afocal scanning microlens doublet and a focusing microlens, which is tolerant to axial position inaccuracy. The 3D scanning is achieved by axial and lateral displacement of microlenses of the scanning doublet, realized by micro-electro-mechanical systems microactuators (the transmission scanning approach). Optical scanning performance of the system is determined analytically by use of the extended ray transfer matrix method, leading to two different optical configurations, relying either on a ball lens or plano-convex microlenses. The presented system is aimed to be a core component of miniature MOEMS-based optical devices, which require a 3D optical scanning function, e.g., miniature imaging systems (confocal or optical coherence microscopes) or optical tweezers.
    Applied Optics 09/2015; 54(22-22):6924-6934. DOI:10.1364/AO.54.006924 · 1.78 Impact Factor
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    ABSTRACT: 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.
    Scientific Reports 09/2015; 5:14001. DOI:10.1038/srep14001 · 5.58 Impact Factor
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    E Kroemer · M Abdel Hafiz · V Maurice · B Fouilland · C Gorecki · R Boudot ·
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    ABSTRACT: We report on the characterization of Cs vapor microfabricated cells filled with a Ne-He buffer gas mixture using coherent population trapping (CPT) spectroscopy. The temperature dependence of the Cs clock frequency is found to be canceled at the first order around a so-called inversion temperature higher than 80°C whose value depends on the buffer gas partial pressure ratio. This buffer gas mixture could be well-adapted for the development of miniature atomic clocks devoted to be used in specific applications such as defense and avionic systems with high operating temperature environment (typically higher than 85°C). This solution suggests an alternative to buffer gas mixtures generally used in optically-pumped vapor cell atomic clocks.
    Optics Express 07/2015; 23(14):18373-18380. DOI:10.1364/OE.23.018373 · 3.49 Impact Factor
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    ABSTRACT: We report the characterization using coherent population trapping (CPT) spectroscopy of an octadecyltrichlorosilane (OTS)-coated centimeter-scale Cs vapor cell. The linewidth of the narrow CPT resonance is compared to the linewidth of an evacuated Cs cell of similar size. The Cs-OTS adsorption energy is measured to be (0.42 ± 0.03) eV. A hyperfine population lifetime, T1 of 1.6 ms is reported, corresponding to about 37 useful bounces. Ramsey CPT fringes are detected using a pulsed CPT interrogation scheme.
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    ABSTRACT: We report the realization and characterization using coherent population trapping (CPT) spectroscopy of an octadecyltrichlorosilane (OTS)-coated centimeter-scale Cs vapor cell. The dual-structure of the resonance lineshape, with presence of a narrow structure line at the top of a Doppler-broadened structure, is clearly observed. The linewidth of the narrow resonance is compared to the linewidth of an evacuated Cs cell and of a buffer gas Cs cell of similar size. The Cs-OTS adsorption energy is measured to be (0.42 ± 0.03) eV, leading to a clock frequency shift rate of 2.7 × 10−9/K in fractional unit. A hyperfine population lifetime, T 1, and a microwave coherence lifetime, T 2, of 1.6 and 0.5 ms are reported, corresponding to about 37 and 12 useful bounces, respectively. Atomic-motion induced Ramsey narrowing of dark resonances is observed in Cs-OTS cells by reducing the optical beam diameter. Ramsey CPT fringes are detected using a pulsed CPT interrogation scheme. Potential applications of the Cs-OTS cell to the development of a vapor cell atomic clock are discussed.
    Journal of Applied Physics 05/2015; 117(18). DOI:10.1063/1.4919841 · 2.18 Impact Factor
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    ABSTRACT: We report the impact on imaging quality of mirror suspensions, referred to as spider legs, used to support the reference mirror in a Mirau micro-interferometer that requires the vertical alignment of lens, mirror, and beamsplitter. Because the light goes from the microlens to the beamsplitter through the mirror plane, the spider legs are a source of diffraction. This impact is studied as a function of different parameters of the spider legs design. Imaging criteria, such as the resolution as well as the symmetry of the imaging system, are determined using the point spread function and the modulation transfer function of the pupil. These imaging criteria are used to determine the optimum radius of curvature, thickness, and number of legs of the spider structure. We show that 3 curved legs give performances, with specific radius of curvature and thickness, similar to a suspension-free mirror.
    Optics Letters 05/2015; 40(10):2209-2212. DOI:10.1364/OL.40.002209 · 3.29 Impact Factor
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    ABSTRACT: 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.
    Optics Express 05/2015; 23(9). DOI:10.1364/OE.23.011702 · 3.49 Impact Factor
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    ABSTRACT: The paper presents the multi-wafer bonding technology as well as the integration of electrical connection to the zscanner wafer of the micromachined array-type Mirau interferometer. A Mirau interferometer, which is a key-component of optical coherence tomography (OCT) microsystem, consists of a microlens doublet, a MOEMS Z-scanner, a focusadjustment spacer and a beam splitter plate. For the integration of this MOEMS device heterogeneous bonding of Si, glass and SOI wafers is necessary. Previously, most of the existing methods for multilayer wafer bonding require annealing at high temperature, i.e., 1100°C. To be compatible with MEMS devices, bonding of different material stacks at temperatures lower than 400°C has also been investigated. However, if more components are involved, it becomes less effective due to the alignment accuracy or degradation of surface quality of the not-bonded side after each bonding operation. The proposed technology focuses on 3D integration of heterogeneous building blocks, where the assembly process is compatible with the materials of each wafer stack and with position accuracy which fits optical requirement. A demonstrator with up to 5 wafers bonded lower than 400°C is presented and bond interfaces are evaluated. To avoid the complexity of through wafer vias, a design which creates electrical connections along vertical direction by mounting a wafer stack on a flip chip PCB is proposed. The approach, which adopts vertically-stacked wafers along with electrical connection functionality, provides not only a space-effective integration of MOEMS device but also a design where the Mirau stack can be further integrated with other components of the OCT microsystem easily.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2015; 9375. DOI:10.1117/12.2077641 · 0.20 Impact Factor
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    ABSTRACT: The EU-funded project VIAMOS1 proposes an optical coherence tomography system (OCT) for skin cancer detection, which combines full-field and full-range swept-source OCT in a multi-channel sensor for parallel detection. One of the project objectives is the development of new fabrication technologies for micro-optics, which makes it compatible to Micro-Opto-Electromechanical System technology (MOEMS). The basic system concept is a wafer-based Mirau interferometer array with an actuated reference mirror, which enables phase shifted interferogram detection and therefore reconstruction of the complex phase information, resulting in a higher measurement range with reduced image artifacts. This paper presents an experimental one-channel on-bench OCT system with bulk optics, which serves as a proof-of-concept setup for the final VIAMOS micro-system. It is based on a Linnik interferometer with a wavelength tuning light source and a camera for parallel A-Scan detection. Phase shifting interferometry techniques (PSI) are used for the suppression of the complex conjugate artifact, whose suppression reaches 36 dB. The sensitivity of the system is constant over the full-field with a mean value of 97 dB. OCT images are presented of a thin membrane microlens and a biological tissue (onion) as a preliminary demonstration.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9529. DOI:10.1117/12.2189278 · 0.20 Impact Factor
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    ABSTRACT: We describe a technological platform developed for miniaturization of optical imaging instruments, such as laser scanning confocal microscopes or Optical Coherence Tomography devices. The platform employs multi-wafer vertical integration approach, combined with integrated glass-based micro-optics and heterogeneous bonding and interconnecting technologies. In this paper we focus on the unconventional fabrication methods of monolithic micro-optical structures and components in borosilicate glass (e.g. micro beamsplitters, refractive microlenses) for optical beam shaping and routing. In addition, we present hybrid laser-assisted integration of glass ball microlenses on the silicon MEMS actuators for transmissive beam scanning as well as methods of electrical signals distribution through thick glass substrates, based on HF etched via holes.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9375. DOI:10.1117/12.2078007 · 0.20 Impact Factor
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    ABSTRACT: Scientific articles focusing on fabrication of micro-components often evaluate their optical performances by techniques such as scanning electron microscopy or surface topography only. However, deriving the optical characteristics from the shape of the optical element requires using propagation algorithms. In this paper, we present a simple and intuitive method, based on the measurement of the intensity point spread function generated by the micro-component. The setup is less expensive than common systems and does not require heavy equipments, since it requires only a microscope objective, a CMOS camera and a displacement stage. This direct characterization method consists in scanning axially and recording sequentially the focal volume. Our system, in transmissive configuration, consists in the investigation of the focus generated by the microlens, allowing measuring the axial and lateral resolutions, estimating the Strehl ratio and calculating the numerical aperture of the microlens. The optical system can also be used in reflective configuration in order to characterize micro-reflective components such as molds. The fixed imaging configuration allows rapid estimation of quality and repeatability of fabricated micro-optical elements.
    SPIE Optical Engineering + Applications; 08/2014
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    ABSTRACT: We report the monolithic integration of glass membranes on a highly structured SOI wafer of electrostatic comb-drive actuator. The integration method combines glass micromachining techniques and non-standard processing of SOI, based on spray coating and projection photolithography. Proposed solution overcomes several basic difficulties of monolithic glass integration. We demonstrate its potential by fabrication of 4×4 matrix of reference mirrors on very thin (25 μm) and large (φ=2 mm) light-transparent glass membranes, which is of great importance for MOEMS-based phase-shift micro-interferometry systems.
    Optical MEMS and Nanophotonics (OMN), 2014 International Conference on, Glasgow; 08/2014
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    ABSTRACT: This paper presents a simple method based on the measurement of the 3D intensity point spread function for the quality evaluation of high numerical aperture micro-optical components. The different slices of the focal volume are imaged thanks to a microscope objective and a standard camera. Depending on the optical architecture, it allows characterizing both transmissive and reflective components, for which either the imaging part or the component itself are moved along the optical axis, respectively. This method can be used to measure focal length, Strehl ratio, resolution and overall wavefront RMS and to estimate optical aberrations. The measurement setup and its implementation are detailed and its advantages are demonstrated with micro-ball lenses and micro-mirrors. This intuitive method is adapted for optimization of micro-optical components fabrication processes, especially because heavy equipments and/or data analysis are not required.
    Optics Express 06/2014; 22(11):13202-13212. DOI:10.1364/OE.22.013202 · 3.49 Impact Factor
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    ABSTRACT: This paper reviews the progress made in the miniaturization of an isotropic space-qualified optically pumped magnetometer. Sensor isotropy is provided by a liquid crystal polarization rotator that sets the linear pumping beam polarization at 90◦ with respect to the ambient magnetic field. It allows a continuous polarization rotation from 0 to more than 300◦ with response times compatible with mobile or space applications. This rotator is nonmagnetic and can be easily integrated close to the gas cell. The miniature helium-4 sensor reaches a sensitivity of 10 pT/√Hz in a bandwidth from DC to 100 Hz.
    Sensors and Actuators A Physical 05/2014; 216:386-393. DOI:10.1016/j.sna.2014.05.003 · 1.90 Impact Factor
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    ABSTRACT: In this paper, we adapt a technique employed for glass microlenses fabrication in order to obtain matrices of millimeter size lenses for inspection applications. The use of microfabrication processes and Micro-Electro-Mechanical Systems (MEMS) compatible materials allow the integration of lenses larger than usual in microsystems. Since the presented lenses can have 2 mm in diameter or more, some aspects apparently irrelevant when diameters are lower than 500 μm must be reviewed and taken into account. Indeed, when the lenses are in the millimeter range, problems such as size nonuniformities within a matrix and asymmetric shapes of each lens are dependent on parameters as mask design, depth of the silicon cavities and enclosed vacuum control after anodic bonding, glass reflow temperature and even the position of the lenses on the substrate. Issues related to the fabrication flow-chart are addressed in this paper and solutions are proposed. First results are shown to prove the pertinence of this technique to fabricate MEMS-compatible millimetersized lenses to be integrated in miniature inspection systems. We also discuss some of the paths to follow that could help improving the performances.
    SPIE Photonics Europe; 05/2014
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    ABSTRACT: The presented paper shows the concept and optical design of an array-type Mirau-based OCT system for early diagnosis of skin cancer. The basic concept of the sensor is a full-field, full-range optical coherence tomography (OCT) sensor. The micro-optical interferometer array in Mirau configuration is a key element of the system allowing parallel imaging of multiple field of views (FOV). The optical design focuses on the imaging performance of a single channel of the interferometer array and the illumination design of the array. In addition a straylight analysis of this array sensor is given. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
    SPIE Optical Micro- and Nanometrology V, Brussels; 04/2014
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    ABSTRACT: High-resolution miniature imaging systems require high quality micro-optical elements. Therefore, it is essential to characterize their optical performances in order to optimize their fabrication. Usually, basic evaluation of micro-optical elements quality is based on the measurement of their topography since their optical properties are largely defined by their shape. However, optical characteristics have to be derived from the measured geometry. An alternative method is the direct measurement of their optical properties. Unlike topography measurement, it allows characterization of high numerical aperture components. Moreover, it can be applied to single elements but also to optical systems composed of several micro-optical components. In this work, we propose a simple method based on the measurement of the 3D intensity point spread function (IPSF). IPSF is defined by the 3D shape of the focal spot generated by the micro-element. The direct characterization of focusing response through the measurement of IPSF allows very precise estimation of micro-structures quality. The considered method consists in imaging different slices of the focal volume generated by the focusing component. It allows, depending on the configuration, characterizing both transmissive and reflective micro-optical components.
    Optical Micro- and Nanometrology V, Brussels; 04/2014

Publication Stats

775 Citations
123.70 Total Impact Points


  • 2009-2015
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2000-2015
    • University of Franche-Comté
      • Institut FEMTO-ST
      Becoinson, Franche-Comté, France
  • 2012
    • École Nationale Supérieure de Mécanique et des Microtechniques
      Becoinson, Franche-Comté, France
  • 2008
    • Nanyang Technological University
      • School of Mechanical and Aerospace Engineering (MAE)
      Tumasik, Singapore
  • 2006-2008
    • Warsaw University of Technology
      • Institute of Micromechanics and Photonics
      Warszawa, Masovian Voivodeship, Poland
    • Vrije Universiteit Brussel
      • Applied Physics and Photonics (TONA)
      Bruxelles, Brussels Capital, Belgium
    • INO - Istituto Nazionale di Ottica
      Florens, Tuscany, Italy
  • 1997-1999
    • The University of Tokyo
      • Laboratory for Integrated Micro Mechatronic Systems
      Tōkyō, Japan