Browsing by Subject "Core-shell nanowires"

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    All-chalcogenide core-shell fibers for nonlinear applications
    (2015-11) Türedi, Bekir
    The extreme spectral broadening phenomenon called as Supercontinuum generation is considered as one of the most striking phenomenon in nonlinear optics. Due to their broad spectra and uniformly distributed power over the spectra supercontinuum sources have found wide range of applications in areas such as spectroscopy, frequency metrology, optical coherence tomography, microscopy and telecommunications. In this thesis, we propose a new method to fabricate multicore fibers made of chalcogenide glasses for the use of high power Supercontinuum generation. We designed and fabricated a new seven-core-structured fiber with chalcogenide core /chalcogenide cladding step-index fiber embedded in polymer matrix. After three successful iterative steps we fabricated seven-core chalcogenide glasses fiber which has diameter around 1.35 μm which is engineered to be approximately zero dispersion. The refractive indices of these two materials at 1550 nm are 2.73 and 2.61; as a result the NA is engineered to 0.8 at this wavelength. The step index structure of the fiber provides the very well-confinement of light to the core of the fibers. This enables the more interaction of light with the highly nonlinear part of the fiber and preserves light to be absorbed by the polymer jacket which has high absorbance at IR region. By using split step Fourier method we showed the potential of our fiber to generate supercontinuum covering from 1 μm to 3.5 μm.
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    Structural coloring in large scale core-shell nanowires
    (American Chemical Society, 2011) Khudiyev, T.; Ozgur E.; Yaman, M.; Bayındır, Mehmet
    We demonstrated two complementary size-dependent structural coloring mechanisms, interference and scattering, in indefinitely long core-shell nanowire arrays. The unusual nanostructures are comprised of an amorphous semiconducting core and a polymer shell layer with disparate refractive indices but with similar thermomechanical properties. Core-shell nanowires are mass produced from a macroscopic semiconductor rod by using a new top-to-bottom fabrication approach based on thermal size reduction. Nanostructures with diameters from 30 to 200 nm result in coloration that spans the whole visible spectrum via resonant Mie scattering. Nanoshell coloration based on thin film interference is proposed as a structural coloration mechanism which becomes dominant for nanowires having 700-1200 nm diameter. Controlled color generation in any part of visible and infrared spectral regions can be achieved by the simple scaling down procedure. Spectral color generation in mass-produced uniform core-shell nanowire arrays paves the way for applications such as spectral authentication at nanoscale, light-scattering ingredients in paints and cosmetics, large-area devices, and infrared shielding. © 2011 American Chemical Society.