Browsing by Subject "Mie scattering"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Fabrication of novel core-shell nanostructures for photonics applications
    (2013) Khudiyev, Tural
    Developments in nanoscale fabrication and characterization techniques have led to fundamental changes in the scientific understanding of many fields, and novel nanostructures have been utilized to investigate the conceptual underpinnings behind a diverse array of natural phenomena. However, nanofabrication methods are frequently hindered by issues such as misalignment, small batch sizes, high production costs and constraints in material choice or nanostructure diversity, which decrease their potential utility and prevent their widespread application in nanoscale optics and photonics. In this work, a new top-down nanofabrication method is described, which is called Iterative Size Reduction (ISR), where step-by-step reduction is utilized to decrease structure dimensions from macro- to nanosizes and produce indefinitely long one-dimensional core-shell nanostructures with properties highly suitable for use in optical applications. Plateau-Rayleigh instabilities are then utilized to thermally degrade ISR-produced nanowire arrays into complex core-shell schemes, which are produced successively in a hitherto-undescribed transitory region between core-shell nanowires and core-shell nanospheres. A diverse array of optical phenomena have been observed on fabricated novel core-shell nano-platforms, which are utilized in the design of novel nanostructures for emerging photonics applications. Briefly, (a) the resonant Mie scattering behavior is characterized on glass-polymer nanostructures and these nanostructures are designed for large-area structural coloration, (b) a novel non-resonant Mie scattering regime responsible for the scattering characteristics exhibited by all-polymer core-shell nanowires is described, (c) a nanoscale analogue to the thin film interference phenomenon is demonstrated that occurs on the core-shell boundary of ISR-produced micro- and nanostructures, (d) an unusual photonic crystal structure observed in the neck feathers of mallard drakes is investigated and imitated, (e) a series of all-polymer core-shell nanowires to function as novel light-trapping platforms and sensors are engineered and (f) the generation of supercontinuum light in well-ordered arrays of As2Se3 nanowires is reported.
  • Thumbnail Image
    ItemOpen Access
    Light scattering from core-shell nano-structures : structural coloration
    (2013) Dolaş, Muhammet Halit
    In this work, we produced kilometer-long semiconducting cylindrical nanostructures by using a top-to-bottom nano-fabrication technique which was recently developed in our research group. Comparison of commonly used methods of producing nano-structures such as electrospinning and nano-imprint lithography versus iterative thermal size reduction (ISR) is done in terms of uniformity, geometry control, multi-material compatibility, yield and device integrability. While the others cannot fulfil all requirements, ISR shows impressive results in all aspects. From very beginning to end, all steps of production and characterization of nano-wires produced by ISR, the design, chalcogenide glass production, preform preparation, fiber drawing, iterative size reduction, chemical etching and imaging are explained in details. In addition, production and characterization of nanospheres by in-fiber fluid instability which is based on Plateau-Rayleigh instability is also demonstrated. Theoretical study on scattering from small particles, Mie scattering, which is one of the mechanisms for structural coloration together with thin film interference, multilayer interference, diffraction grating and photonic crystals is done. Structural coloration due to scattering from small particles is simulated using Finite Domain Time Difference (FDTD) method and compared with theoretical results estimated for nano-wire and nano-sphere cases. Results are confirmed with observation of structural coloration by taking dark field optical microscopy images of the final products of ISR and in-fiber fluid instability processes