Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Optical Characterization of Nanoscale Dielectric Films on Curved Surfaces Using Near Field Diffraction Method(Izmir Institute of Technology, 2019) Ataç, Enes; Dinleyici, Mehmet Salih; Dinleyici, Mehmet Salih; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyDemand on the high-quality optical thin films has increased because of the importance in the optical sensor technologies. The thicknesses of such films are usually shorter than the wavelength of visible light. Therefore, the optical characterization of these films is not a routine procedure especially on curved surfaces such as optical fiber. Besides, the methods in the literature and commercially available systems are either expensive, destructive or non-real time. In this thesis, it is aimed to propose a simple, inexpensive and non-destructive optical characterization method of nano-scale dielectric films on curved surfaces. The methodology of that approach can be described as the near field wavefront tracing diffraction by using structured light. In this way, it has been shown that sub-wavelength film thicknesses can be estimated. The proposed diffraction method is organized in four main stages. These are the coating of optical fibers, generation of structured light, determination of wave propagation via the near field Huygens-Fresnel wave-front tracing and sensing and processing of signal from the sensor array. Layer by layer assembly technique is used in coating process to keep under control the thickness of transparent film. Selection of various source types is about to changing of point spread function of applied field and observe the effects on intensity pattern. Using near field diffraction technique, sub-wavelength thickness of thin films can be predicted by taking the higher order components of diffraction pattern by recording at very close proximity to object. In this way, determination of thickness beyond the diffraction limits can be realized. Furthermore, the resolution of sensor array in sensing part is important since pixel size of the sensor array determines your detection limits to catch all variations on diffraction pattern. The whole process has a mathematical model with numerical analysis methods. This dissertation is about the proposing a mathematical estimation model for the optical properties of nano-scale dielectric films coated on curved surfaces. The experimental results show that near field Huygens-Fresnel wave-front tracing method by using structured light is a powerful technique.Master Thesis Polarization and Phase Characterization of Side-Polished Optical Fibers(Izmir Institute of Technology, 2018) Karataş, Yunus Emre; Dinleyici, Mehmet Salih; Dinleyici, Mehmet Salih; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this thesis, the polarization and phase properties of the side-polished optical fiber (SPOF) are aimed to characterize. The Linearly Polarized (LP) modes of standard optical fibers have been affected by the side-polished geometry which breaking symmetry. At the side-polished area guided modes couple to non-symmetric modes and phase shift occurs due to the birefringent property of the SPOF. That kind of structure has an excellent usage potential as a portable optical sensor or optical fiber communication device. It was primarily concentrated on the LP modes of the standard optical fiber. LP mode field solutions extracted from Maxwell Equations were calculated with MATLAB, and mode intensity distributions were constructed accordingly. The calculated intensity distributions were utilized for figuring out the mode content of the outputs of the twomode experiment. The recorded CCD Camera images were matched with the calculated intensity distributions, and then the best-matched LP mode combination was selected as output mode content. In the single-mode experiment at the side-polished area, quasi-degenerate fundamental modes occur. According to the state of polarization of the modes, they suffer attenuation and phase shift in different levels. Therefore, after the side-polished area, degenerate fundamental modes propagate together with a particular phase difference. This situation composes elliptical polarization at the output. Various modal polarization rotation and phase shifts were observed, and then polarization ellipses were obtained with MATLAB. The resultant ellipses demonstrate that the effect of SPOF on guided modes varies with the angle of input polarization.