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    Fabrication of Multimode-Single Mode Polymer Fiber Tweezers for Single Cell Trapping and Identification with Improved Performance
    ( 2018) Rodrigues,SM ; Joana Isabel Paiva ; Ribeiro,RSR ; Soppera,O ; João Paulo Cunha ; Pedro Jorge ; 6260 ; 5864 ; 3565
    Optical fiber tweezers have been gaining prominence in several applications in Biology and Medicine. Due to their outstanding focusing abilities, they are able to trap and manipulate microparticles, including cells, needing any physical contact and with a low degree of invasiveness to the trapped cell. Recently, we proposed a fiber tweezer configuration based on a polymeric micro-lens on the top of a single mode fiber, obtained by a self-guided photopolymerization process. This configuration is able to both trap and identify the target through the analysis of short-term portions of the back-scattered signal. In this paper, we propose a variant of this fabrication method, capable of producing more robust fiber tips, which produce stronger trapping effects on targets by as much as two to ten fold. These novel lenses maintain the capability of distinguish the different classes of trapped particles based on the back-scattered signal. This novel fabrication method consists in the introduction of a multi mode fiber section on the tip of a single mode (SM) fiber. A detailed description of how relevant fabrication parameters such as the length of the multi mode section and the photopolymerization laser power can be tuned for different purposes (e.g., microparticles trapping only, simultaneous trapping and sensing) is also provided, based on both experimental and theoretical evidences.
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    The fiber connection method using a tapered silica fiber tip for microstructured polymer optical fibers
    ( 2018) Frazão,O ; Ferreira,M ; André Delgado Gomes ; Kowal,D ; Statkiewicz Barabach,G ; Mergo,P ; 6406
    In this work, an alternative method of coupling light into microstructured polymer fibers is presented. The solution consists in using a fiber taper fabricated with a CO2 laser. The connection is formed by inserting a tapered silica tip into the holes of a microstructured polymer fiber. This alternative method is duly characterized and the feasibility of such fiber connection to enable the polymer fiber as a displacement sensor is also demonstrated. © 2018 by the authors.
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    Multipath Interferometer Polished Microsphere for Enhanced Temperature Sensing
    ( 2018) André Delgado Gomes ; Karami,F ; Zibaii,MI ; Latifi,H ; Orlando Frazão ; 6406 ; 4061
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    Cleaved Silica Microsphere for Temperature Measurement
    ( 2018) André Delgado Gomes ; Beatriz Machado Silveira ; Dellith,J ; Becker,M ; Rothhard,M ; Bartelt,H ; Orlando Frazão ; 4061 ; 6406 ; 6684
    A sensing structure based on a cleaved silica microsphere is proposed for temperature sensing. The microsphere was cleaved using focused ion beam milling. The asymmetry in the structure introduced by the cut generates not only new cavities but also random interferometric reflections inside the microsphere. These two spectral components can be separated using low-pass and high-pass filters, respectively. The sensor response to temperature can be extracted from the cavities' component using a correlation method. The device achieved a temperature sensitivity of -10.8 +/- 0.2 pm/degrees C between 30 degrees C and 80 degrees C. The same effect is impossible to be obtained in a normal uncleaved microsphere. The random interferometric component did not provide any information on temperature using the same analysis. However, when changing the temperature, a new and completely distinct reflection spectrum with no apparent correlation with others at different temperatures was achieved.
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    Birefringence swap at the transition to hyperbolic dispersion in metamaterials
    ( 2012) J M Teixeira ; L M Sousa ; J P Araújo ; Paulo Vicente Marques ; J Ventura ; C T Sousa