Browsing by Author "Kendir, Esra"
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Item Open Access Effect of temperature and wavelength on the refractive index of water : a fiber-optic sensor application(Springer (India) Private Ltd., 2021-03-25) Kendir, Esra; Yaltkaya, Ş.The refractive index n(λ,T) is a basic optical property of materials. The refractive index and the thermo-optic coefficient (dn/dT) are significant parameters of liquids for optically controlled systems, such as the direct measurement of liquid solution concentrations and optical paths. In this study, the variation in the refractive index of water in the liquid phase with temperature was measured with our self-designed fiber optic-based refractive index sensor and dn/dT values were obtained with a full-width half-maximum method at wavelengths of 980, 1426, and 1550 nm, respectively. Water is the most abundant and life-critical substance in the world, and its optical properties pose challenging scientific problems that require knowledge of the refractive index to be resolved. The results indicate that the experimental refractive index values are compatible with both the theoretical and experimental data in the literature. We also tested the refraction index results with two theoretical models and obtained good agreement between the calculated and experimental values. The resolution of the fiber optic-based refractive index sensor was 10−5. Our designed sensor could measure the refractive index of liquids with temperature with accuracy.Item Open Access Fabrication of biaxial polarization-maintaining optical fiber with ultra-low bending-dependent polarization extinction ratio deterioration(Academic Press, 2022-02-07) Karatutlu, Ali; Yapar Yıldırım, Elif; Midilli, Yakup; Akçimen, Samet; Ortaç, Bülend; Kendir, EsraDifferent applications, including interferometers, gyroscopes, and frequency combs, require a single polarized light transmission by maintaining this property against the environmental perturbation. As a new type of polarization-maintaining (PM) fiber, a biaxial PM fiber was fabricated over 30 dB of high polarization extinction ratio (PER) values among two orthogonal axes over a fiber length of 110 m. The PM fiber was manufactured with a combination of an elliptical core and Panda-type geometries. The PER values were demonstrated to be preserved at harsh temperature conditions from −55 °C to +85 °C. The bending loss measurements indicate the biaxial PM fiber has ultra-low bending dependent PER deterioration (<0.5 %) at various bending diameters from 12 mm to 5 mm. The biaxial PM property was also confirmed by the group beat length measurements and found to be less than 1.5 mm at 1550 nm. The optical time-domain reflectometer (OTDR) measurements show that the optical loss of the biaxial PM fiber was below 1.5 dB/km over 3 km length. The mode-field diameter (MFD) and the numerical aperture (NA) values were also reported along two polarized axes. This novel PM fiber offers a single solution for the elliptical and Panda-type PM fibers utilized for integrated fiber-based sensors and instruments.Item Open Access Production of biaxial polarization-maintaining optical fiber with panda-type and elliptical-core geometry(IEEE, 2021-09-30) Karatutlu, Ali; Yıldırım, Elif Yapar; Kendir, Esra; Ortaç, BülendPolarization Maintaining (PM) fibers can be produced in different ways in terms of their stress-birefringent geometric structures such as Panda-type, bow-tie and elliptical core [1] . These designs in principal function in the same way causing internal stress on the core and creating birefringence between two orthogonal (slow and fast) axes. In the typical Panda-type PM fibers, polarization extinction ratio (PER) is preserved over 30 dB along the slow axis and there is over ~ 10 dB difference between the fast and slow axes (Region 1 and Region 2, respectively, Fig. 1.b .). On the other hand, elliptical core PM fibers can be produced without boron-doped stress rods and thus they are easier to manufacture than the other two PM fibers with compatible birefringence values. Some of the applications require utilizing PM fiber components in order to developed environmentally-stable laser systems [2] , [3] . For these reasons, a specialty PM fiber structure may be needed in which the properties of both Panda-type and elliptical core geometry PM fibers can be used together.Item Open Access Structural, optical and magnetic properties of α-Fe2O3-SiO2 and Dy2O3-SiO2 composites produced by a Facile method(Springer, 2020) Kendir, Esra; Tekgül, A.; Küçük, İ.; Yaltkaya, Ş.We prepared SiO2, Fe2O3-SiO2, and Dy2O3-SiO2 composites by an enhanced method and reported the result of their structural, optical and magnetic properties. In the x-ray diffraction results of the Fe2O3-SiO2, Fe2O3 and the SiO2 it is evident that these composites are crystallized in rhombohedral and trigonal structures, respectively. In theDy2O3-SiO2 composite, SiO2 transforms into a trigonal structure with the addition of Dy. The absorption bands belong to Fe2O3, and Dy2O3 were obtained using the Fourier transform infrared spectra. In ultraviolet–visible spectra, the photocatalytic properties of Fe2O3-SiO2 and Dy2O3-SiO2 were determined as a function of time at room temperature. Maximum transmittance change at 800 nm was 75% and 40% for composites Fe2O3-SiO2, and Dy2O3-SiO2, respectively. The photocatalytic property of Dy2O3-SiO2 composite increases gradually from short to long in the wavelength region where it exhibits a maximum value in the visible region. In magnetic measurements, a weak ferromagnetic behavior was observed in the Fe2O3-SiO2, while Dy2O3-SiO2 exhibited paramagnetic behavior as expected. The saturation and coercivity values for Fe2O3-SiO2 were found to be 0.15 Am2kg−1 and 40 mT, respectively.