Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 7Citation - Scopus: 8Investigation of the Structural and Optical Properties of Copper-Titanium Oxide Thin Films Produced by Changing the Amount of Copper(Elsevier Ltd., 2019) Horzum, Şeyda; Gürakar, Sibel; Serin, TülayWe examine how the structural, morphological and optical properties of TiO2 thin films are changed with heavily copper (Cu) content. Variations in characteristic properties of the films with 0, 12.5, 25 and 50 wt% Cu contents, grown by sol-gel dip coating method, are observed by using X-ray diffraction (XRD), Raman scattering, atomic force microscopy, energy dispersive X-ray analysis and optical spectroscopy measurements. The XRD and Raman spectra indicate that pure TiO2 film forms in the anatase structure. At high Cu concentrations, XRD results also reveal the substitution of Ti with Cu and formation of extra compound Copper-Titanium oxide. Raman measurements also show that Cu is incorporated homogeneously into TiO2 matrix up to 12.5 wt% concentration and this uniformity is distorted at higher Cu contents. In addition, optical spectroscopy measurements show that the optical band gap energy decreases from 3.26 eV to 2.05 eV with increasing Cu concentration. Furthermore, it is observed that the refractive index values obtained by means of transmittance spectra at 550 nm wavelength; increases from 2.47 to 3.39 when the Cu concentration increases from 0 to 50 wt %.Article Citation - WoS: 2Citation - Scopus: 2Investigating the Experimental Limits of the Brewster’s Angle Method(Türkiye Klinikleri Journal of Medical Sciences, 2018) Sümer, Can; Kuştepeli, Alp; Dinleyici, Mehmet SalihWe present the method, analysis, and experimental results of the Brewster’s angle method commonly used for determining the refractive indices of optical films. We show the significance of the intersection of reflectance curves, in that the necessity for substrate refractive index and film layer thickness knowledge are both eliminated. We present the conditions for the existence of the second intersection of reflectance curves and introduce a method for determining the refractive index of the substrate layer by using the angular information alone. Analytical results reveal impressive practical sensitivity and accuracy limits for the method, where the experimental results also support the theoretical analysis.Article Citation - WoS: 7Citation - Scopus: 7Demonstration of Pulse Controlled All-Optical Switch/Modulator(The Optical Society, 2014) Akın, Osman; Dinleyici, Mehmet SalihAn all-optical pulse controlled switch/modulator based on evanescent coupling between a polymer slab waveguide and a single mode fiber is demonstrated. Very fast all-optical modulation/switching is achieved via Kerr effect of the nonlinear polymer placed in the evanescent region of the optical fiber. Local refractive index perturbation (δn = -1.45612 × 10 -5) on the thin film leads to 0.374 nW power modulation at the fiber output, which results in a switching efficiency of ≈1.5%.Conference Object Citation - WoS: 2Citation - Scopus: 2Fiber Optik Sensörler ile Sıvılarda Kırılma İndisi Ölçüm Yöntemlerinin Analizi(Institute of Electrical and Electronics Engineers Inc., 2017) İde, Cansu; Yüksel, KıvılcımRefractive index (RI) is one of the physical properties of material, such as boiling/melting point, density, and elasticity. As one of the distinctive features of the material, measurement of the RI is nowadays used in many areas including the food, oil and petroleum industry, biomedical applications, and environmental analysis. In recent years, fiber optic based refractometers become highly popular thanks to the advantages they provide compared to other methods used in the above mentioned fields. Two fiber optic refractive index sensors were investigated in this study: Fresnel reflection based-and long-period fiber grating (LPFG) based-refractometers. The former uses SMF fiber tip as sensing point interrogated by an OTDR from a distant location, where the latter examines the changes in the resonance wavelength. Experimental work realised on different concentrations of glucose-water and glycerol-water solutions successfully demonstrated the capability of the proposed sensor in measuring RI of liquid chemicals with a precision of 1.7×10-4 (Fresnel-based sensor) and maximum sensitivity of 193.42 nm/RIU (LPGF based sensor).Article Citation - WoS: 28Citation - Scopus: 30Optical Fiber Sensor System for Remote and Multi-Point Refractive Index Measurement(Elsevier Ltd., 2016) Yüksel, KıvılcımA Fresnel-reflection-based RI sensor using SMF fiber tips as sensing points interrogated by multi-wavelength OTDR from a distant location (up to several tens of kilometers) has been reported. The advantage of the system compared to previous work is that the distance between sensor points is not limited by the spatial resolution of OTDR. Experimental work demonstrated that the proposed sensor is capable of measuring refractive index of liquid chemicals with a precision of 1.7 × 10−4. This sensor prototype have strong conveniences (simple installation requirements, fast response and reliability in harsh environment) compared to previous Fresnel-based RI sensors which makes it a very good option for environmental monitoring systems. © 2016 Elsevier B.V.Article Citation - WoS: 195Optical Properties of Composites of Pmma and Surface-Modified Zincite Nanoparticles(American Chemical Society, 2007) Demir, Mustafa Muammer; Koynov, Kaloian; Akbey, Ümit; Bubeck, Christoph; Park, Insun; Lieberwirth, Ingo; Wegner, GerhardLocate full-text(opens in a new window)|Full Text(opens in a new window)|View at Publisher| Export | Download | Add to List | More... Macromolecules Volume 40, Issue 4, 20 February 2007, Pages 1089-1100 Optical properties of composites of PMMA and surface-modified zincite nanoparticles (Article) Demir, M.M.a, Koynov, K.a, Akbey, Ü.a, Bubeck, C.a, Park, I.ab, Lieberwirth, I.a, Wegner, G.a a Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany b Seoul National University, School of Chemistry, Korea, South Korea View references (65) Abstract Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO3H2) in situ by monolayer coverage. Particle size and graft density of -PO3H 2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (0) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerization was observed. Optical constants of the films ca. 2.0 μm including absorption and scattering efficiencies, indices of refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearly with ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm-1 and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguide propagation loss coefficients of the composite films were examined by prism coupling. A steep increase of the loss coefficient was found with a slope of 52 dB cm-1 vol %-1 as the volume fraction of the particle increases. The refractive index of the composites depends linearly on volume fraction of ZnO and varies from 1.487 to 1.507 (φ = 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy's formula.