Idris Kabalci

Spectroscopic properties of Tm 3+ :TeO 2 -PbF 2 glasses in the near infrared

Tm3+-doped glasses have two emission bands that peak around 1470 nm and 1800 nm in the near infrared, making them potentially important in the development of fiber-optic amplifiers and fiber lasers. The relative strength and the quantum efficiency of these bands depend on the glass composition as well as the active ion concentration. In this study, we have investigated the variation of the luminescence strengths as a function of glass composition and Tm3+ ion concentration in a new type of Tm3+-doped tellurite glass. In the experiments, two sets of samples with the host composition (1-x)TeO2-(x)PbF2 were prepared. In the first set, the active ion concentration was constant (1 mol. % Tm3+) and x=10, 15, 17, 20, 22 and 25 mol. %. The second set had samples with x=10 mol. % and the active ion concentration varied from 0.2 to 1 mol. %. In the experiments, absorption measurements were first made to determine the spontaneous emission probabilities of the 4f-4f transitions of the Tm3+ ions. The calculations were made by using the Judd-Ofelt theory. The samples were then excited with a 785-nm diode to measure the relative emission strengths of the 1470-nm and 1800-nm bands. Our results show that as the Tm3+ ion concentration increases from 0.2 mol. % to 1 mol. %, the ratio of the 1470-nm intensity decreases from 0.98 to 0.18 relative to that of the 1800-nm band.

Ultra-Wideband Positioning System Using TWR and Lateration Methods

Indoor wireless positioning systems enables location based applications to work properly inside buildings. Since GPS technology could not supply desired precision in indoor environment, there has been many positioning systems developed based on different technologies to solve localization problem. In this paper, indoor navigation system based on Ultra-Wideband technology has been proposed. Then, ranging model of the tracking system is established. Trilateration, Least Square Estimation and Centroid Method positioning algorithms are applied to provide a realistic comparison between them. Results are analyzed to compare the accuracy between different algorithms and the ideas are shared to improve the current study.

Hardness and Structural Properties of Yb 3+ Doped B 2 O 3 -ZnO-TiO 2 Glasses

In this study, the main thermal, structural and mechanical properties of optical glass materials were investigated by conventional glass melting method. The thermal properties of optical glass materials are important in that they constitute the first steps towards the investigation of other physical and chemical properties. According to the thermal properties of the material, the glass transition temperature, Tg, increases for different glass compositions. The XRD, XRF, FT-IR and hardness properties of the obtained optical glass materials were determined experimentally in terms of their structural and mechanical properties for their suitability for potential applications. XRD spectra obtained without heat treatment of glass materials show that the material structure is amorphous. In the same way, Vicker’s hardness values of the glassware increase relative to the different glass compositions, resulting in a result that the material is influenced by the bonds between the constituents of the chemical components.

Mechanical, Structural and Thermal Properties of Transparent Bi2O3-Al2O3-ZnO-TeO2 Glass System

Oxide based optical glass materials has important potential material in many applications from fiber optic to sensor due to the high transparency and amourphous structures. The objective of this study is to synthesize the novel optical glass materials based on the bismuth and aluminum contents to be able to determine the physical, chemical and mechanical properties by considering the systematic experimental steps. In this study, Bi2O3–Al2O3 based tellurite optical glasses have been prepared by using conventional melt quenching method as a function of the both Bi2O3 and Al2O3 compositions. There is a strong interactions between the glass former and modifier ions that might effect on the structure and mechanical properties. During the experimental steps, thermal, structural and mechanical properties of the prepared glass materials have been determined considering the DTA/DSC, FT-IR spectroscopy, SEM and Vicker’s hardness techniques, respectively. Thermal parameters, like glass transition, Tg, onset, Tx, crystallization, Tp, and melting, Tm, temperatures were obtained by using DTA scan.

Er3+ doped chalcogenide glasses and sputtered thin films: Structural and spectroscopic characterization

In this research, we report Er3+ doped chalcogenide based glasses, well known for infrared transparency with various applications in the photonics and optoelectronics. Er3+ doped chalcogenide glasses were prepared by using vertical furnace with an argon gas atmosphere. For the structural and spectroscopic measurements, thin films at about 460nm thicknesses were deposited by using radio-frequency (RF) magnetron sputtering technique. Er3+ deposited thin films were annealed at different temperature as 450, 500, 550, and 600°C in the tube furnace and rapid thermal annealer (RTA) at 2°C/min, and 10°C/min heating rate, respectively. As a result, absorptions, luminescence, and structural properties of the Er3+ ion doped GLS thin films were affected from different annealing process.

Thermal analysis and linear optical properties of (1−x)TeO 2 -(x)ZnCl 2 optical glasses for photonic applications

The investigation covers the thermal and linear optical properties of binary TeO2-ZnCl2 optical glass systems contain different ZnCl2 compositions ranging from 10 to 40mol%. Preparation of the glass systems were realized by melting the mixture of TeO2 and ZnCl2 chemicals in a platinum crucible at 850°C for 60 min in air. In the experiments, thermal analysis was performed to determine the thermal characteristics such as, glass transition (Tg), crystallization (Tp), and melting (Tm) temperatures for different heating rates (B=10, 20, 30 and 40 °C/min) by using the differential thermal analysis (DTA) plot. By considering the DTA plots, the crystallization activation energies were determined by using the Ozawa and modified Kissinger equations. Finally, thermal analysis show that the crystallization activation energies were 487.6kJ/mol, 215.8kJ/mol, 392.kJ/mol, and 273.3kJ/mol for the x=10, 20, 30, and 40mol% ZnCl2 contents, respectively. Optical band gaps (direct and indirect) and Urbach energies of the glass samples were estimated from the absorption spectra measured between 300 and 800nm. The direct band gap energies decrease from 3.65 eV to 3.35 eV, and indirect band gap energies also decrease from 3.59 eV to 3.30 eV by increasing the ZnCl2 content from 10 to 40 mol%, respectively.

Preparation Of Co, Mn, Nd Doped SiO2 Thin Films And Investigation The Microstructural Propoerties

MxOy(M:Co, Mn, Nd)‐doped SiO2 thin films were prepared by sol‐gel method on glass substrates using Si(OC2H5)4 (tetraethylorthosilicate, TEOS,) as starting material. Si(OC2H5)4 was dissolved in ethanol and thus, precursor solution was prepared. Various layers of coatings were obtained at room temperature by sol‐gel dip‐coating process at a withdrawal speed of 10 cm/min. The coated substrates were exposed to heat treatment at 650° C. Structural and optical properties of the films were examined by UV‐VIS (Lamda 2S Spectrophotometer), AFM (Atomic Force Microscopy) and SE (Spectroscopic Ellipsometry)