Fluorescence endomicroscopy with structured illumination

Author(s): Nenad Bozinovic, Cathie Ventalon, Tim Ford, and Jerome Mertz

Abstract:

“We present an endomicroscope apparatus that utilizes structured illumination to produce high resolution (~ 2.6µm) optically sectioned fluorescence images over a field of view of about 240µm. The endomicroscope is based on the use of a flexible imaging fiber bundle with a miniaturized objective. We also present a strategy to largely suppress structured illumination artifacts that arise when imaging in thick tissue that exhibits significant out-of-focus background. To establish the potential of our endomicroscope for preclinical or clinical applications, we provide images of BCECF-AM labeled rat colonic mucosa.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 11, pp. 8016-8025
DOI: 10.1364/OE.16.008016

Applying SLODAR to measure aberrations in the eye

Author(s): Andrew Lambert, Benjamin J. Birt, David A. Atchison, and Huanqing Guo

Abstract:

“As a proof of concept we apply a technique called SLODAR as implemented in astronomy to the human eye. The technique uses single exposures of angularly separated “stars” on a Hartmann-Shack sensor to determine a profile of aberration strength localised in altitude in astronomy, or path length into the eye in our application. We report on the success of this process with both model and real human eyes. There are similarities and significant differences between the astronomy and vision applications.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 16, Issue 10, pp. 7309-7322, 2008
DOI: 10.1364/OE.16.007309

Oscillations and interactions of dark and dark–bright solitons in Bose–Einstein condensates

Author(s): Christoph Becker, Simon Stellmer, Parvis Soltan-Panahi, Sören Dörscher, Mathis Baumert, Eva-Maria Richter, Jochen Kronjäger, Kai Bongs & Klaus Sengstock

Abstract:

“Solitons are among the most distinguishing fundamental excitations in a wide range of nonlinear systems such as water in narrow channels, high-speed optical communication, molecular biology and astrophysics. Stabilized by a balance between spreading and focusing, solitons are wave packets that share some exceptional generic features such as form stability and particle-like properties. Ultracold quantum gases represent very pure and well-controlled nonlinear systems, therefore offering unique possibilities to study soliton dynamics. Here, we report on the observation of long-lived dark and dark–bright solitons with lifetimes of up to several seconds as well as their dynamics in highly stable optically trapped 87Rb Bose–Einstein condensates. In particular, our detailed studies of dark and dark–bright soliton oscillations reveal the particle-like nature of these collective excitations for the first time. In addition, we discuss the collision between these two types of solitary excitation in Bose–Einstein condensates.”

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Publication: Nature Physics
Issue/Year: Nature Physics 4, 496 – 501 (2008)
DOI: 10.1038/nphys962

Application of an interferometric phase contrast method to fabricate arbitrary diffractive optical elements

Author(s): Marcel Teschke, Robert Heyer, Marco Fritzsche, Sebastian Stoebenau, Stefan Sinzinger

Abstract:

“A novel approach for the fabrication of diffractive optical elements is described. This approach is based on an interferometric phase contrast method that transforms a complex object wavefront into an intensity pattern. The resulting intensity pattern is used to expose a photoresist layer on a substrate. After development, a diffractive phase object with an on-axis diffraction pattern is achieved. We show that the interferometric phase contrast method allows a precise control of the resulting intensity pattern. An array of blazed Fresnel lenses is realized in photoresist by using kinoform or detour-phase computer holograms for the interferometric phase contrast setup.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 47, Issue 14, pp. 2550-2556 (2008)
DOI: 10.1364/AO.47.002550

Optically driven pumps and flow sensors for microfluidic systems

Author(s): H Mushfique, J Leach, R Di Leonardo, M J Padgett, J M Cooper

Abstract:

“This paper describes techniques for generating and measuring fluid flow in microfluidic devices. The first technique is for the multi-point measurement of fluid flow in microscopic geometries. The flow sensing method uses an array of optically trapped microprobe sensors to map out the fluid flow. The optical traps are alternately turned on and off such that the probe particles are displaced by the flow of the surrounding fluid and then retrapped. The particles’ displacements are monitored by digital video microscopy and directly converted into velocity field values. The second is a method for generating flow within a microfluidic channel using an optically driven pump. The optically driven pump consists of two counter-rotating birefringent vaterite particles trapped within a microfluidic channel and driven using optical tweezers. The transfer of spin angular momentum from a circularly polarized laser beam causes the particles to rotate at up to 10 Hz. The pump is shown to be able to displace fluid in microchannels, with flow rates of up to 200 m-3 s-1 (200 fL s-1). In addition a flow sensing method, based upon the technique mentioned above, is incorporated into the system in order to map the magnitude and direction of fluid flow within the channel.”

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Publication: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
Issue/Year: Journal of Mechanical Engineering Science, Volume 222, Number 5 / 2008, Pages 829-837
DOI: 10.1243/09544062JMES760