Filters

2014 - 201844

More filters

201944
Reset filters

Settings

End date: 2019 × Start date: 2019 × End date: 2019 × Start date: 2011 × WGL Institute: IPHT ×

Search Results

Now showing 1 - 10 of 44
  • Thumbnail Image
    Item
    Giant faraday rotation through ultra-small Fe0n clusters in superparamagnetic FeO-SiO2 vitreous films
    (Hoboken : Wiley, 2017) Nakatsuka, Yuko; Pollok, Kilian; Wieduwilt, Torsten; Langenhorst, Falko; Schmidt, Markus A.; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa; Wondraczek, Lothar
    Magnetooptical (MO) glasses and, in particular, Faraday rotators are becoming key components in lasers and optical information processing, light switching, coding, filtering, and sensing. The common design of such Faraday rotator materials follows a simple path: high Faraday rotation is achieved by maximizing the concentration of paramagnetic ion species in a given matrix material. However, this approach has reached its limits in terms of MO performance; hence, glass‐based materials can presently not be used efficiently in thin film MO applications. Here, a novel strategy which overcomes this limitation is demonstrated. Using vitreous films of xFeO·(100 − x)SiO2, unusually large Faraday rotation has been obtained, beating the performance of any other glassy material by up to two orders of magnitude. It is shown that this is due to the incorporation of small, ferromagnetic clusters of atomic iron which are generated in line during laser deposition and rapid condensation of the thin film, generating superparamagnetism. The size of these clusters underbids the present record of metallic Fe incorporation and experimental verification in glass matrices.
  • Thumbnail Image
    Item
    Germania and alumina dopant diffusion and viscous flow effects at preparation of doped optical fibers
    (Ostrava : VSB - Technical University of Ostrava and University of Zilina Faculty of Electrical Engineering, 2017) Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Unger, Sonja; Schwuchow, Anka; Elsmann, Tino; Dellith, Jan; Aichele, Claudia; Fatobene Ando, Ron; Bartelt, Hartmut
    We report on germania and alumina dopant profile shift effects at preparation of compact optical fibers using packaging methods (Stack-and-Draw method, Rod-in-Tube (RiT) technique). The sintering of package hollow volume by viscous flow results in a shift of the core-pitch ratio in all-solid microstructured fibers. The ratio is increased by about 5% in the case of a hexagonal package. The shift by diffusion effects of both dopants is simulated for typical slow speed drawing parameters. Thermodynamic approximations of surface dissociation of germania doped silica suggest the need of an adequate undoped silica barrier layer to prevent an undesired bubble formation at fiber drawing. In contrast, alumina doping does not estimate critical dissociation effects with vaporous aluminium oxide components. We report guide values of diffusion length of germania and alumina for the drawing process by kinetic approximation. The germania diffusion involves a small core enlargement, typically in the sub-micrometer scale. Though, the alumina diffusion enlarges it by a few micrometers. A drawn pure alumina preform core rod transforms to an amorphous aluminosilicate core with a molar alumina concentration of only about 50% and a non-gaussian concentration profile.
  • Thumbnail Image
    Item
    Electric current-driven spectral tunability of surface plasmon polaritons in gold coated tapered fibers
    (College Park : American Institute of Physics, 2018) Lühder, Tilman; Wieduwilt, Torsten; Schneidewind, Henrik; Schmidt, Markus A.
    Here we introduce the concept of electrically tuning surface plasmon polaritons using current-driven heat dissipation, allowing controlling plasmonic properties via a straightforward-to-access quantity. The key idea is based on an electrical current flowing through the plasmonic layer, changing plasmon dispersion and phase-matching condition via a temperature-imposed modification of the refractive index of one of the dielectric media involved. This scheme was experimentally demonstrated on the example of an electrically connected plasmonic fiber taper that has sensitivities >50000 nm/RIU. By applying a current, dissipative heat generated inside metal film heats the surrounding liquid, reducing its refractive index correspondingly and thus modifying the phase-matching condition to the fundamental taper mode. We observed spectral shifts of the plasmonic resonance up to 300 nm towards shorter wavelength by an electrical power of ≤ 80 mW, clearly showing that our concept is important for applications that demand precise real-time and external control on plasmonic dispersion and resonance wavelengths.
  • Thumbnail Image
    Item
    Pseudo-HE images derived from CARS/TPEF/SHG multimodal imaging in combination with Raman-spectroscopy as a pathological screening tool
    (London : BioMed Central, 2016) Bocklitz, Thomas W.; Salah, Firas Subhi; Vogler, Nadine; Heuke, Sandro; Chernavskaia, Olga; Schmidt, Carsten; Waldner, Maximilian J.; Greten, Florian R.; Bräuer, Rolf; Schmitt, Michael; Stallmach, Andreas; Petersen, Iver; Popp, Jürgen
    Due to the steadily increasing number of cancer patients worldwide the early diagnosis and treatment of cancer is a major field of research. The diagnosis of cancer is mostly performed by an experienced pathologist via the visual inspection of histo-pathological stained tissue sections. To save valuable time, low quality cryosections are frequently analyzed with diagnostic accuracies that are below those of high quality embedded tissue sections. Thus, alternative means have to be found that enable for fast and accurate diagnosis as the basis of following clinical decision making.
  • Thumbnail Image
    Item
    Curcuminoid–BF2 complexes: Synthesis, fluorescence and optimization of BF2 group cleavage
    (Frankfurt a.M. : Beilstein-Institut, 2017) Weiß, Henning; Reichel, Jeannine; Görls, Helmar; Schneider, Kilian R.A.; Micheel, Mathias; Pröhl, Michael; Gottschaldt, Michael; Dietzek, Benjamin; Weigand, Wolfgang
    Eight difluoroboron complexes of curcumin derivatives carrying alkyne groups containing substituents have been synthesized following an optimised reaction pathway. The complexes were received in yields up to 98% and high purities. Their properties as fluorescent dyes have been investigated. Furthermore, a strategy for the hydrolysis of the BF2 group has been established using aqueous methanol and sodium hydroxide or triethylamine.
  • Thumbnail Image
    Item
    Interactive Dendrograms: The R Packages idendro and idendr0
    (Los Angeles : Foundation for Open Access Statistics, 2017) Sieger, Tomáš; Hurley, Catherine B.; Fiser, Karel; Beleites, Claudia
    Hierarchical cluster analysis is a valuable tool for exploring data by describing their structure using a dendrogram. However, proper visualization and interactive inspection of the dendrogram are needed to unlock the information in the data. We describe a new R package, idendro, that enables the user to inspect dendrograms interactively: to select and color clusters, to zoom and pan the dendrogram, and to visualize the clustered data not only in a built-in heat map, but also in any interactive plot implemented in the cranvas package. A lightweight version idendr0 with reduced dependencies is also available from the Comprehensive R Archive Network.
  • Thumbnail Image
    Item
    Interfacing optical fibers with plasmonic nanoconcentrators
    (Berlin : de Gruyter, 2018) Tuniz, Alessandro; Schmidt, Markus A.
    The concentration of light to deep-subwavelength dimensions plays a key role in nanophotonics and has the potential to bring major breakthroughs in fields demanding to understand and initiate interaction on nanoscale dimensions, including molecular disease diagnostics, DNA sequencing, single nanoparticle manipulation and characterization, and semiconductor inspection. Although planar metallic nanostructures provide a pathway to nanoconcentration of electromagnetic fields, the delivery/collection of light to/from such plasmonic nanostructures is often inefficient, narrow-band, and requires complicated excitations schemes, limiting widespread applications. Moreover, planar photonic devices reveal a reduced flexibility in terms of bringing the probe light to the sample. An ideal photonic-plasmonic device should combine (i) a high spatial resolution at the nanometre level beyond to what is state-of-the-art in near-field microscopy with (ii) flexible optical fibers to promote a straightforward integration into current near-field scanning microscopes. Here, we review the recent development and main achievements of nanoconcentrators interfacing optical fibers at their end-faces that reach entirely monolithic designs, including campanile probes, gold-coated fiber-taper nanotips, and fiber-integrated gold nanowires.
  • Thumbnail Image
    Item
    Influence of Sterilization and Preservation Procedures on the Integrity of Serum Protein-Coated Magnetic Nanoparticles
    (Basel : MDPI, 2017) Dutz, Silvio; Wojahn, Stephanie; Gräfe, Christine; Weidner, Andreas; Clement, Joachim H.
    Protein-coated magnetic nanoparticles are promising candidates for various medical applications. Prior to their application into a biological system, one has to guarantee that the particle dispersions are free from pathogens or any other microbiologic contamination. Furthermore, to find entrance into clinical routine, the nanoparticle dispersions have to be storable for several months. In this study, we tested several procedures for sterilization and preservation of nanoparticle containing liquids on their influence on the integrity of the protein coating on the surface of these particles. For this, samples were treated by freezing, autoclaving, lyophilization, and ultraviolet (UV) irradiation, and characterized by means of dynamic light scattering, determination of surface potential, and gel electrophoresis afterwards. We found that the UV sterilization followed by lyophilization under the addition of polyethylene glycol are the most promising procedures for the preparation of sterilized long-term durable protein-coated magnetic nanoparticles. Ongoing work is focused on the optimization of used protocols for UV sterilization and lyophilization for further improvement of the storage time.
  • Thumbnail Image
    Item
    Hybrid soliton dynamics in liquid-core fibres
    (Berlin : Nature Pulishing, 2017) Chemnitz, Mario; Gebhardt, Martin; Gaida, Christian; Stutzki, Fabian; Kobelke, Jens; Limpert, Jens; Tünnermann, Andreas; Schmidt, Markus A.
    The discovery of optical solitons being understood as temporally and spectrally stationary optical states has enabled numerous innovations among which, most notably, supercontinuum light sources have become widely used in both fundamental and applied sciences. Here, we report on experimental evidence for dynamics of hybrid solitons—a new type of solitary wave, which emerges as a result of a strong non-instantaneous nonlinear response in CS2-filled liquid-core optical fibres. Octave-spanning supercontinua in the mid-infrared region are observed when pumping the hybrid waveguide with a 460 fs laser (1.95 μm) in the anomalous dispersion regime at nanojoule-level pulse energies. A detailed numerical analysis well correlated with the experiment uncovers clear indicators of emerging hybrid solitons, revealing their impact on the bandwidth, onset energy and noise characteristics of the supercontinua. Our study highlights liquid-core fibres as a promising platform for fundamental optics and applications towards novel coherent and reconfigurable light sources.
  • Thumbnail Image
    Item
    Biomedical sensing and imaging with optical fibers—Innovation through convergence of science disciplines
    (College Park : American Institute of Physics, 2018) Li, Jiawen; Ebendorff-Heidepriem, Heike; Gibson, Brant C.; Greentree, Andrew D.; Hutchinson, Mark R.; Jia, Peipei; Kostecki, Roman; Liu, Guozhen; Orth, Antony; Ploschner, Martin; Schartner, Erik P.; Warren-Smith, Stephen C.; Zhang, Kaixin; Tsiminis, Georgios; Goldys, Ewa
    The probing of physiological processes in living organisms is a grand challenge that requires bespoke analytical tools. Optical fiber probes offer a minimally invasive approach to report physiological signals from specific locations inside the body. This perspective article discusses a wide range of such fiber probes developed at the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics. Our fiber platforms use a range of sensing modalities, including embedded nanodiamonds for magnetometry, interferometric fiber cavities for refractive index sensing, and tailored metal coatings for surface plasmon resonance sensing. Other fiber probes exploit molecularly sensitive Raman scattering or fluorescence where optical fibers have been combined with chemical and immunosensors. Fiber imaging probes based on interferometry and computational imaging are also discussed as emerging in vivo diagnostic devices. We provide examples to illustrate how the convergence of multiple scientific disciplines generates opportunities for the fiber probes to address key challenges in real-time in vivo diagnostics. These future fiber probes will enable the asking and answering of scientific questions that were never possible before.