Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Optical Characterization of Dielectric Films on Curved Surfaces Using Diffraction Method(Izmir Institute of Technology, 2016) Ekici, Çağın; Dinleyici, Mehmet Salih; Ekici, Çağın; Dinleyici, Mehmet Salih; 01. Izmir Institute of Technology; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of EngineeringIn this thesis, we aim to characterize optical properties of thin dielectric films coated on curved surfaces. Indeed, optical thin films attract a great deal of attention especially the ones coated on silica based optical waveguides used as sensor system. Therefore, the step index optical fiber is used in the thesis as a substrate due to the fact that the sensor technology tends towards to fiber optic based platforms. In the thesis, a step index optical fiber is coated with polyvinyl alcohol (PVA), then its thickness is mathematically estimated exploiting Fresnel scalar diffraction method. Phase front of the laser light wave comes across with a phase object (fiber optic), transmits through of it and diffracts. Whole process is modeled by using numerical analysis methods and compared to experimental results to obtain desired parameters in MATLAB. The conventional least-squares method is used for comparison purpose. Although the emphasis is on optical thin film characterization, we demonstrate the application area of diffraction from fiber optic as sensor. It is used to detect adulteration of olive oil that is big concern for the food industry. The refractive index of various mixture of olive oil and sunflower oil is measured with intend to detect adulteration. This feature makes it a good candidate for fiber optic based refractive index sensor and it may bring practicability and precision to the sensing process. This dissertation gives detailed information about diffraction from fiber optic both theoretically and experimentally. The experiments were realized by using 632.8 nm continuous wave laser. Both of the experimental results demonstrate that phase diffraction method is a powerful technique to characterize optical thin films and to sense refractive index of the surrounding medium.Master Thesis Reflection Properties of a Gaussian Laser Beam From Multilayer Dielectric Films(Izmir Institute of Technology, 2010) Şen, Taner; Dinleyici, Mehmet Salih; Dinleyici, Mehmet Salih; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyA laser microphone is a surveillance device that uses a laser beam to detect sound vibrations in a distant object. The object is typically inside a room where a conversation is taking place, and can be anything that can vibrate (for example, picture or window) in response to the sound waves of the conversation. The object preferably has a smooth surface. The laser beam is directed into the room through a window, reflected off the object and returned to a receiver that converts the beam to audio signal. The beam is mostly bounced off the window itself. Usually these kinds of devices are used by surveillance intelligence in some parts of governments and these kinds of weapons analyze the laser beam which reflects from window. In this thesis a countermeasure to the detection of laser beam is analyzed. In order to make this possible, the reflection from dielectric stratified surfaces of a Gaussian laser beam needs to be described. The reflected beam profile of electromagnetic radiation exposes to various effects different from reflected plane waves. Gaussian beams which reflect from a dielectric slab experience in a shifting maximum point in one direction; lateral shift, focal shift and angular divergence are the shift and distortion of the beam profile. The Gaussian beam propagates in z direction and broadens in transverse plane, in two dimensions and is decomposed into plane wave components. Upon analyzing the reflection coefficient and beam profile, reduction of beam power after reflection from stratified films is described.Master Thesis Polarization Effects of Nonspherical Scatterers in Dielectric Optical Film(Izmir Institute of Technology, 2007) Yunus, Nasrettin; Dinleyici, Mehmet Salih; Dinleyici, Mehmet Salih; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyPolarization enhancement in liquid crystal display (LCD) backlighting systems comprises important part of works on improvement of the brightness. Optical films containing scatterer particles are used in these systems. Therefore, dielectric scatterer particles are greatly needed to be analyzed for their optical scattering properties, and especially for polarizing effects. Depending on the sizes relative to the wavelength and the shape of the particles various computation approaches have been developed based on electromagnetic scattering theories such as Mie scattering, T-matrix methods etc... Simulation programs of these approaches have been examined and applied for spherical and nonspherical particles. In general, for the particles those a few times large in size compared to the incident wavelength, the polarization differentiation is insignificant for a spherical particle compared to a spheroid one. And, the prolate spheroids with higher aspect ratio have been able to produce most significant differentiating figures. Polarization measurements have been carried on commercially available dielectric optical films of two different set and also on the films with/without nonspherical zeolite particles prepared in the laboratory. Since the commercial films consist of spherical scatters, they show no polarization discrimination at all. On the other hand existence of zeolite particles in the film resulted in significant polarization discrimination at forward scattering angle. The results for polarization discrimination properties of the prolate spheroid particles have been compared with the spherical ones. Consequently, the discrepancy induced on the polarization that way has a good potential to be used in improvement of the brightness.