Christophe Gorecki

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

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Publications (155)91.39 Total impact

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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 · 3.53 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. http://authors.elsevier.com/a/1PNBe3IC9cin~9
    Sensors and Actuators A Physical 05/2014; 216:386-393. DOI:10.1016/j.sna.2014.05.003 · 1.94 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
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    ABSTRACT: We present a micro-optical system for ultraviolet/visible absorbance detection in silicon microfluidic channels, which consists of a micro-optical light coupler placed on top of the silicon fluidic channel to probe the molecules under test with laser light. We use nonsequential optical ray-tracing simulations to model the system and to optimize its performance with respect to optical efficiency and system complexity. Deep Proton Writing is used to prototype the plastic light coupler and its spacer baseplate which contains marks to align the micro-optics with respect to the microfluidic channel and which allows for an accurate control of the position of the micro-optics with respect to the excitation source. We demonstrate the proof of concept of this microfluidic light probe by measuring standard samples of coumarin 102 dye with concentrations between 0.6 µM and 6 mM. Calibrating the system yields a detection limit of 4.3 µM. To conclude, we show that the concept of this microfluidic detection system is generic in that it can be applied at different positions on different microfluidic channel configurations.
    Microfluidics and Nanofluidics 04/2014; 18(4). DOI:10.1007/s10404-014-1466-z · 2.67 Impact Factor
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    ABSTRACT: A process based on deep reactive ion etching (DRIE) has been developed and optimized for the fabrication of millimeter deep silicon cavities with smooth sidewalls. The process combines two approaches which involve an optimized etching process based on the classical Bosch process (Alcatel A601E equipment) followed by the use of an aqueous etchant solution of potassium hydroxide (KOH) to smooth the surface and remove the fluorocarbon contaminants remaining after the DRIE process. As DRIE highly depends on the opening size of the patterned etch mask, different opening sizes have been tested to completely etch through a 1.4 mm thick silicon wafer. Additionally, the effect of different etch-stop materials onto the sidewalls quality has also been characterized. Sidewall quality of etched-through cavities was characterized by scanning electron microscopy (SEM) and contact surface profilometry. This single-step DRIE etching followed by short exposure to KOH solution permits to smooth sidewalls and achieve a surface roughness as low as 50 nm, which is the roughness typically obtained with the Bosch process on standard depths.
    Sensors and Actuators A Physical 02/2014; 208. DOI:10.1016/j.sna.2013.12.031 · 1.94 Impact Factor
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    ABSTRACT: This letter reports on the development of an integrated micro-optical beam splitter that can be array-arranged. The proposed wafer-level fabrication, based on 45$^{circ}$ saw-dicing of glass substrates, allows rapid and low-cost processing. In particular, it leads to high compactness and possibility of wafer-level alignment/assembly, suitable for vertically integrated imaging micro-instruments. The device, including additional out-of plane reflection for extraction of sensing beam, can be as small as 1 ${rm mm}^{3}$.
    IEEE Photonics Technology Letters 01/2014; 26(1):100-103. DOI:10.1109/LPT.2013.2289981 · 2.18 Impact Factor
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    ABSTRACT: VIAMOS benefits from advanced MOEMS technologies, enabling a new generation of miniature instruments. The challenge is to provide hand-held, low-cost, fully parallel spectral domain miniature OCT devices adapted for early diagnosis of cutaneous pathologies. VIAMOS will lean on the experience and results fostered from a previous European collaborative project, diffusing the technology to medical diagnostic applications. The consequence will be a significant upgrade by adding new features such as heterodyne detection and integrated swept source.
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    ABSTRACT: The wafer-level integration technique of PageWafer® (SAES Getters' solution for getter film integration into wafer to wafer bonded devices) has been tested in hermetically 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.
    Journal of Micromechanics and Microengineering 04/2013; 23(5):055022. DOI:10.1088/0960-1317/23/5/055022 · 1.73 Impact Factor
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    ABSTRACT: We present the preliminary design, construction and technology of a microoptical, millimeter-size 3-D microlens scanner, which is a key-component for a number of optical on-chip microscopes with emphasis on the architecture of confocal microscope. The construction of the device relies on the vertical integration of micromachined building blocks: top glass lid, silicon electrostatic comb-drive X-Y and Z microactuators with integrated scanning microlenses, ceramic LTCC spacer, and bottom lid with focusing microlens. All components are connected on the wafer level only by sequential anodic bonding. The technology of through wafer vias is applied to create electrical connections through a stack of wafers. More generally, the presented bonding/connection technologies are also of a great importance for the development of various silicon-based devices based on vertical integration scheme. This approach offers a space-effective integration of complex MOEMS devices and an effective integration of various heterogeneous technologies.
    Proceedings of SPIE - The International Society for Optical Engineering 03/2013; DOI:10.1117/12.2002422 · 0.20 Impact Factor
  • Physical Review A 02/2013; 87(2). DOI:10.1103/PhysRevA.87.029903 · 2.99 Impact Factor
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    ABSTRACT: We report on a theoretical study and experimental characterization of coherent population trapping (CPT) resonances in buffer gas-filled vapor cells with push-pull optical pumping (PPOP) on Cs D1 line. We point out that the push-pull interaction scheme is identical to the so-called lin per lin polarization scheme. Expressions of the relevant dark states, as well as of absorption, are reported. The experimental setup is based on the combination of a distributed feedback (DFB) diode laser, a pigtailed intensity Mach-Zehnder electro-optic modulator (MZ EOM) for optical sidebands generation and a Michelson-like interferometer. A microwave technique to stabilize the transfer function operating point of the MZ EOM is implemented for proper operation. A CPT resonance contrast as high as 78% is reported in a cm-scale cell for the magnetic-field insensitive clock transition. The impact of the laser intensity on the CPT clock signal key parameters (linewidth - contrast - linewidth/contrast ratio) is reported for three different cells with various dimensions and buffer gas contents. The potential of the PPOP technique for the development of high-performance atomic vapor cell clocks is discussed.
    Physical Review A 02/2013; 87(1). DOI:10.1103/PhysRevA.87.013416 · 2.99 Impact Factor
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    ABSTRACT: This work presents the development of an integrated micro-optical beam splitter that can be arranged in array, and based on saw-dicing of glass substrates. The latter allows a rapid and rather low-cost processing, and in addition leads to high compactness and possibility of wafer level alignments, suitable for vertically integrated imaging microinstruments. The device allowing additional out-of plane reflection for extraction of sensing beam can be as small as 1mm3.
    Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS & EUROSENSORS XXVII), 2013 Transducers & Eurosensors XXVII: The 17th International Conference on; 01/2013
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    ABSTRACT: In this paper, we investigate the influence of different masking parameters onto the surface quality of the ${111}$ sidewalls in order to generate specifically deep cavities by wet-anisotropic-etching of bulk silicon, for optical sensors using cavity sidewalls as reflectors. Mask alignment with crystal planes prior to wet-etching is found to be essential in order to avoid the appearance of additional planes during long etching. Mask deposition processes have been also evaluated. Among the different employed mask materials, Cr/Au gives the best results. It is then shown that cavities as deep as 1 mm with low roughness sidewalls can be simply produced with potassium hydroxide solution with periodic piranha cleaning.
    Journal of Microelectromechanical Systems 01/2013; 23(3):585 - 591. DOI:10.1109/JMEMS.2013.2285575 · 1.92 Impact Factor
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    ABSTRACT: This paper reports on a compact table-top Cs clock based on coherent population trapping (CPT) with advanced frequency stability performance. The heart of the clock is a single buffer gas Cs-Ne microfabricated cell. Using a distributed feedback (DFB) laser resonant with the Cs D1 line, the contrast of the CPT signal is found to be maximized around 80°C, a value for which the temperature dependence of the Cs clock frequency is canceled. Advanced techniques are implemented to actively stabilize the clock operation on a zero-light-shift point. The clock frequency stability is measured to be 3.8 × 10¿(11) at 1 s and well below 10¿(11) until 50 000 s. These results demonstrate the possibility to develop highperformance chip-scale atomic clocks using vapor cells containing a single buffer gas.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 11/2012; 59(11):2584-7. DOI:10.1109/TUFFC.2012.2493 · 1.50 Impact Factor
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    ABSTRACT: We report on studies on the light-shift in caesium miniature atomic clocks based on coherent population trapping (CPT) using a micro-fabricated buffer-gas cell (MEMS cell). The CPT signal is observed on the Cs D1-line by coupling the two hyperfine ground-state Zeeman sublevels involved in the clock transition to a common excited state, using two coherent electromagnetic fields. These light fields are created with a distributed feedback laser and an electro-optical modulator. We study the light-shift phenomena at different cell temperatures and laser wavelengths around 894.6 nm. By adjusting the cell temperature, conditions are identified where a miniature CPT atomic clock can be operated with simultaneously low temperature coefficient and suppressed light-shift. The impact of the light-shift on the clock frequency stability is evaluated. These results are relevant for improving the long-term frequency stability of CPT-based Cs vapour-cell clocks.
    Applied Physics B 10/2012; 109(1). DOI:10.1007/s00340-012-5121-7 · 1.63 Impact Factor
  • Nicolas Passilly, Sylwester Bargiel, Christophe Gorecki
    07/2012; DOI:10.1051/photon/20126033

Publication Stats

490 Citations
91.39 Total Impact Points

Institutions

  • 2009–2014
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 1997–2013
    • 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
  • 1996–2008
    • Warsaw University of Technology
      • Institute of Micromechanics and Photonics
      Warszawa, Masovian Voivodeship, Poland
  • 2006
    • Vrije Universiteit Brussel
      • Applied Physics and Photonics (TONA)
      Bruxelles, Brussels Capital, Belgium
  • 1998–1999
    • The University of Tokyo
      • Laboratory for Integrated Micro Mechatronic Systems
      Tōkyō, Japan