Polarization and particle size dependence of radiative forces on small metallic particles in evanescent optical fields. Evidences for either repulsive or attractive gradient forces

International audienceWe have observed the motion of metallic particles above various optical waveguides injected by 1064nm radiation. Small gold particles (250nm diameter) are attracted towards the waveguide where the intensity of the optical field is maximum, and are propelled at high velocity (up to 350µm/s) along the waveguide due to radiation pressure. The behaviour of larger metallic particles (diameter >600nm) depends on the polarization of the evanescent field: for TM polarization they are attracted above the waveguide and propelled by the radiation pressure; for TE polarization they are expelled on the side of the waveguide and propelled at much smaller velocity. This is consistent with calculations of radiative forces on metallic particles by Nieto-Vesperinas et al. 3D-finite element method calculations carried out for our experimental situations confirm the observed dependence with the polarization of the field and the size of the particles

Polarization effects on the manipulation of micropoarticles in the evanescent field of an optical waveguide

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Curved sensors for compact high-resolution wide field designs: prototype demonstration and optical characterization

International audienceOver the recent years, a huge interest has grown for curved electronics, particularly for opto-electronics systems. Curved sensors help the correction of off-axis aberrations, such as Petzval Field Curvature, astigmatism, and bring significant optical and size benefits for imaging systems. In this paper, we first describe advantages of curved sensor and associated packaging process applied on a 1/1.8'' format 1.3Mpx global shutter CMOS sensor (Teledyne EV76C560) into its standard ceramic package with a spherical radius of curvature Rc=65mm and 55mm. The mechanical limits of the die are discussed (Finite Element Modelling and experimental), and electro-optical performances are investigated. Then, based on the monocentric optical architecture, we proposed a new design, compact and with a high resolution, developed specifically for a curved image sensor including optical optimization, tolerances, assembly and optical tests. Finally, a functional prototype is presented through a benchmark approach and compared to an existing standard optical system with same performances and a x2.5 reduction of length. The finality of this work was a functional prototype demonstration on the CEA-LETI during Photonics West 2018 conference. All these experiments and optical results demonstrate the feasibility and high performances of systems with curved sensors

A methodology to design optical systems with curved sensors

International audienceCurved sensors are a suitable technological solution to enhance the vast majority of optical systems. In this work, we show the entire process to create curved sensor-based optical systems and the possibilities they offer. This paper defines the boundaries of the reachable curvatures for a full range of monolithic sensors. We discuss how the curved focal plane shape is related to the imaged scenes and optical parameters. Two camera prototypes are designed, realized and tested, demonstrating a new compact optical architecture for a 40 degree compact objective, as well as a wide field fisheye zoom objective using a convex sensor to image a 180 degree field of view

Methodology to design optical systems with curved sensors

Curved sensors are a suitable technological solution to enhance the vast majority of optical systems. In this work, we show the entire process to create curved sensor-based optical systems and the possibilities they offer. This paper defines the boundaries of the reachable curvatures for a full range of monolithic sensors. We discuss how the curved focal plane shape is related to the imaged scenes and optical parameters. Two camera prototypes are designed, realized, and tested, demonstrating a new compact optical architecture for a 40 deg compact objective as well as a wide-field fisheye zoom objective using a convex sensor to image a 180 deg field of view

Time-lapse contact microscopy of cell cultures based on non-coherent illumination

International audienceVideo microscopy offers outstanding capabilities to investigate the dynamics of biological and pathological mechanisms in optimal culture conditions. Contact imaging is one of the simplest imaging architectures to digitally record images of cells due to the absence of any objective between the sample and the image sensor. However, in the framework of in-line holography, other optical components, e.g., an optical filter or a pinhole, are placed underneath the light source in order to illuminate the cells with a coherent or quasi-coherent incident light. In this study, we demonstrate that contact imaging with an incident light of both limited temporal and spatial coherences can be achieved with sufficiently high quality for most applications in cell biology, including monitoring of cell sedimentation, rolling, adhesion, spreading, proliferation, motility, death and detachment. Patterns of cells were recorded at various distances between 0 and 1000 μm from the pixel array of the image sensors. Cells in suspension, just deposited or at mitosis focalise light into photonic nanojets which can be visualised by contact imaging. Light refraction by cells significantly varies during the adhesion process, the cell cycle and among the cell population in connection with every modification in the tridimensional morphology of a cell