Phd Degree / Doktora

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Access Right: Open AccessSubject: search.filters.subject.Photonic crystals

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  • Doctoral Thesis
    The Fabrication of Plasmonic/Photonic Nanostructures in Polymers: Mechanical Sensor Applications
    (Izmir Institute of Technology, 2019) Topçu, Gökhan; Demir, Mustafa Muammer; Eanes, Mehtap
    Functional polymer nanocomposites offer futuristic properties by the association of inorganic additive micro-/nanostructures into the polymers. With the growing knowledge of the physical fundamentals, stimuli-responsive polymeric composites enable detection of chemical, thermal, and mechanical changes by optical sensors and probes. Since the accurate real-time detection of the change in mechanical loading is vital for construction and industrial fields, the use of colorimetric pressure elements in a static body is important for the prediction of catastrophic failures. In this thesis, strain/pressure responsive colorimetric films were produced. A number of polymer nanocomposite-based mechanical sensors are presented. By transferring the optical activity (coherent reflection and plasmonic coupling) of the additives into various polymeric matrices having different mechanical features, the strain and pressure sensors are developed for practical applications. There are two approaches used for the fabrication of polymeric mechanical sensors: i) PDMS/SiO2 composites, ii) PAAm/Au NP composites. The coherent reflectivity of SiO2 colloidal particle arrays was used to develop strain sensors while controllable localized surface plasmon resonance of Au NPs was employed for pressure sensors. These optical systems were separately associated with viscoelastic and elastic polymeric systems, and sensor properties were discussed.
  • Doctoral Thesis
    Photonic Crystal Based Spectral Filter Devices for Optical Communication
    (Izmir Institute of Technology, 2015) Karakılınç, Özgür Önder; Dinleyici, Mehmet Salih; Dinleyici, Mehmet Salih
    It is already foreseen that future integrated photonic circuits for ultra fast alloptical signal processing will require various types of functional elements that include spectral managements. Consequently, dynamical manipulations of the photonic crystals play an important role in order to route the optical signal between waveguide channels or may be among layers. Hence, in this study, photonic crystal based spectral filters are proposed for all-optical communication applications. Firstly, grating structures composed with Gaussian beam interference equation and stimulated by nonlinearity phenomenon in photonic crystal are studied. The grating structure exhibiting special features on transmission characteristics are shown. After that, idea is expanded with applying a realistic Gaussian beam source, and transient grating in nonlinear photonic crystal structure is considered. At this point, light wave interaction with nonlinear response time plays a significant role on the signal manipulation. So, the behavior of pulse propagation in the medium having the response of instantaneous nonlinearity (Kerr) is summarized. As a second aspect of this work, the optical resonator, which is essential functional block for filtering, modulating, buffering, switching in integrated optical circuits systems, is presented. Photonic crystal microcavity based dual-mode dual-band bandpass filter is designed and its transmission characteristics are investigated for various configurations. Photonic crystal resonator structure is formed by a point defect microcavity that is constituted with a large and three smaller auxiliary perturbation rods. Degenerate modes at each band may also be excited by changing the structure properties of the perturbation. The proposed photonic crystal spectral filters structure can effectively be used for optical communication applications.
  • Doctoral Thesis
    Mathematical Modelling of Light Propagation in Pohotonic Crystal Waveguides
    (Izmir Institute of Technology, 2014) Eti, Neslihan; Sözüer, Hüseyin Sami
    Photonic crystals are artificially engineered materials where the dielectric constant varies periodically. A photonic band gap can be created by scattering at the dielectric interfaces, which forbids propagation of light in a certain frequency range of light. This property enables us to control light, which is normally impossible with conventional optics. Moreover, by placing a linear defect into the photonic crystal, one can construct a waveguide, which keeps light inside the waveguide in the desired direction. Thus, by using photonic crystal waveguides one can control light propagation in integrated circuit devices. The goal of this work is to provide a comprehensive understanding of how to bend light using photonic crystal waveguides. The purpose is to create a 90◦ bend for line defect photonic crystal assisted waveguides and present fully three-dimensional calculations with optimized geometrical parameters that minimize the bending loss. The scheme uses one-dimensional photonic crystal slab waveguides for straight sections, and a corner element that employs a square photonic crystal with a band gap at the operating frequency.. The two different structures, with either silicon-silica or with silicon-air are used in the guiding photonic crystal layer. Furthermore, the guiding layer is sandwiched between either air on both top and bottom, or between air on top and silica substrate at the bottom, to serve as the ”cladding” medium. Calculations are presented for the transmission values of TE-like modes where the electric field is strongly transverse to the direction of propagation, with and without the photonic crystal corner element for comparison. We find that the bending loss can be reduced to under 2%.