1,721,247 research outputs found
Optical fiber meta-tips
No full textWe report on the first demonstration of a proof-of-principle optical fiber 'meta-tip', which integrates a phase-gradient plasmonic metasurface on the fiber tip. For illustration and validation purposes, we present numerical and experimental results pertaining to various prototypes implementing generalized forms of the Snell's transmission/reflection laws at near-infrared wavelengths. In particular, we demonstrate several examples of beam steering and coupling with surface waves, in fairly good agreement with theory. Our results constitute a first step toward the integration of unprecedented (metasurface-enabled) light-manipulation capabilities in optical-fiber technology. By further enriching the emergent 'lab-on-fiber' framework, this may pave the way for the widespread diffusion of optical metasurfaces in real-world applications to communications, signal processing, imaging and sensing. © The Author(s) 2017
Microgel assisted Lab-on-Fiber Optrode
No full textPrecision medicine is continuously demanding for novel point of care systems, potentially exploitable also for in-vivo analysis. Biosensing probes based on Lab-On-Fiber Technology have been recently developed to meet these challenges. However, devices exploiting standard label-free approaches (based on ligand/target molecule interaction) suffer from low sensitivity in all cases where the detection of small molecules at low concentrations is needed. Here we report on a platform developed through the combination of Lab-On-Fiber probes with microgels, which are directly integrated onto the resonant plasmonic nanostructure realized on the fiber tip. In response to binding events, the microgel network concentrates the target molecule and amplifies the optical response, leading to remarkable sensitivity enhancement. Moreover, by acting on the microgel degrees of freedom such as concentration and operating temperature, it is possible to control the limit of detection, tune the working range as well as the response time of the probe. These unique characteristics pave the way for advanced label-free biosensing platforms, suitably reconfigurable depending on the specific application. © 2017 The Author(s)
Divertiamoci con l’Arte, giochiamo con la Scienza Il centro commerciale come “nuovo” Agorà
No full textLa necessità di qualificare aree urbane ha guidato alla costruzione di una esperienza di Arte e divulgazione scientifica al Centro Commerciale, ridefinendolo come “Agora” per divulgare la cultura, rivitalizzare il tessuto sociale di un territorio e connettere la periferia al Centro, coinvolgendo gli studenti delle scuol
Optical fiber tip templating using direct focused ion beam milling
No full textWe report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a 'double-layer' photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology
Fiber-Tip Coupling of Bloch Surface Waves
No full textWe experimentally demonstrate the excitation of Bloch surface waves on the tip of single-mode optical fibers via a grating-coupled mechanism. In spite of unavoidable fabrication-related tolerances, we evaluate sensing performances in line with state-of-the-art plasmonic benchmarks, paving the way for the development of advanced 'all-dielectric' lab-on-fiber optrodes. © 2018 IEEE
Confinement-sensitive optical response of cholesteric liquid crystals in electrospun fibers
No full textSoft self-assembling photonic materials such as cholesteric liquid crystals are attractive due to their multiple unique and useful properties, in particular, an optical band gap that can be continuously and dynamically tuned in response to weak external influences, easy device integration, compatibility with flexible architectures, and, as shown here, potential for submicrometer optical applications. We study such a system formed by a short-pitch cholesteric confined in the core of polymer fibers produced by coaxial electrospinning, showing that the selective reflection arising from the helical photonic structure of the liquid crystal is present even when its confining cavity is well below a micrometer in thickness, allowing as little as just half a turn of the helix to develop. At this scale, small height variations result in a dramatic change in the reflected color, in striking difference to the bulk behavior. These conclusions are made possible by combining focused ion beam (FIB) dissection and imaging of the internal fiber morphology with optical microscopy. The FIB dissection further reveals that the cross section of the cavity within the fiber can have a shape that is quite different from that of the outside fiber. This is critical for the photonic behavior of the composite fiber because different optical textures are generated not only by change in thickness but also by the shape of the cavity. Our results provide insights into the behavior of cholesterics in submicrometer cavities and demonstrate their potential at such dimensions. © 2013 American Chemical Society
Optical fiber meta-tips
No full textWe realize the first optical-fiber "meta-tips" implementing in the near-infrared the beam-steering with increasing angles, up to the limit case of surface-waves excitation. We also explore their capability to work as local refractive index sensor. © OSA 2016
Focused ion beam for studying cholesteric liquid crystals under submicrometer confinement
No full textWe have visualized the internal structure of electrospun polymer fibers, having liquid crystals in the core, using focused ion beam milling. In this way we were able to correlate observed selective reflection and optical texture, in a specific fiber location, with the corresponding cavity dimensions and shape. It was found that cholesteric liquid crystals exhibit peculiar optical behavior, distinctively different from the one in bulk, when they are confined in sub-micrometer cavities. Because of the reduced dimensions, the pitch of the helix has to change even for tiny variations in cavity size, resulting in changes in the wavelength of the selective reflection. The ion beam milling is a destructive process and it is relevant to consider possible side effects and consequences on the polymer sheath and thus on the revealed cavities. We analyze the heating due to the ion beam exposure calculating the subsequent temperature increase in the polymer and at a polymer-liquid crystal interface. The derived increase of temperature is very small and is not expected to induce any notable change in the polymer cavities. © 2014 SPIE
Optical fiber meta-tips
No full textWe report on the first example of a "meta-tip" configuration that integrates a metasurface on the tip of an optical fiber. Our proposed design is based on an inverted-Babinet plasmonic metasurface obtained by patterning (via focused ion beam) a thin gold film deposited on the tip of an optical fiber, so as to realize an array of rectangular aperture nanoantennas with spatially modulated sizes. By properly tuning the resonances of the aperture nanoantennas, abrupt variations can be impressed in the field wavefront and polarization. We fabricated and characterized several proof-of-principle prototypes operating an near-infrared wavelengths, and implementing the beam-steering (with various angles) of the cross-polarized component, as well as the excitation of surface waves. Our results pave the way to the integration of the exceptional field-manipulation capabilities enabled by metasurfaces with the versatility and ubiquity of fiber-optics technological platforms. © 2016 SPIE
Meta-tips for lab-on-fiber optrodes
No full textWe realize the first optical-fiber "meta-tip" that integrates a metasurface on the tip of an optical fiber. In our proposed configuration a Babinet-inverted plasmonic metasurface is fabricated by patterning (via focused-ion-beam) an array of rectangular aperture nanoantennas in a thin gold film. Via spatial modulation of the nanoantennas size, we properly tune their resonances so as to impress abrupt arbitrary phase variations in the transmitted field wavefront. As a proof-of-principle, we fabricate and characterize several prototypes implementing in the near-infrared the beam-steering with various angles. We also explore the limit case where surface waves are excited, and its capability to work as refractive index sensors. Notably, its sensitivity overwhelms that of the corresponding gradient-free plasmonic array, thus paving the way to the use of metasurfaces for label-free chemical and biological sensing. Our experimental results, in fairly good agreement with numerical predictions, demonstrate the practical feasibility of the meta-tip concept, and set the stage for the integration of metasurfaces, and their exceptional capabilities to manipulate light, in fiber-optics technological platforms, within the emerging "lab-on-fiber" paradigm. © 2016 SPIE
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