Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
145 records were found.
Phosphate (P) and fluoride phosphate (FP) glasses are attractive materials for a wide range of photonic applications such as lasers, amplifiers, photosensitivity, optical storage and Faraday rotators. They demonstrate high W transmission, low linear and nonlinear refractive index, low viscosity and low melting temperatures, athermal behaviour. In addition, they are excellent host materials for active rare earth (RE) ions due to advantageous local structure effect and high RE ion solubility. The paper reviews the benefit of FP and P glass properties for different photonic applications. Base glass properties, local structure and its effect on RE ion properties are described for FP and P glasses studied by the author. The potential of the glasses for laser, amplifier and photosensitivity-based devices are demonstrated.
Results of direct UV-laser writing and of self-writing in glasses are surveyed comprehensively in terms of structure and evolution dynamics of the induced waveguides, absorption and geometry of the samples, and laser parameters applied in the experiments. In addition, the underlying mechanisms of photosensitivity that give rise to the observed refractive index changes are discussed.
A comprehensive survey of photosensitivity in glasses comprising permanent refractive index changes induced by laser exposure is reviewed. Progress, demands and remaining issues are discussed from various points of views such as pattern and properties of laser-written phase structures, assessment of glasses and dopants, characterisation and mechanisms of photosensitivity, benefits and potential applications, types and requirements of write lasers.
The Er broad band amplifier at 1.5 μm is of special interest.
Heike Ebendorff-Heidepriem
The study of radiation-induced defect formation in glasses is of growing interest for applications in optics and photonics. The influence of Tb3+ ions on X-ray-induced defects has been examined in glasses with different phosphate contents. The defects have been characterized by optical absorption and ESR spectroscopy. (Tb3+)+ ions are formed by X-ray irradiation. They exhibit a broad charge transfer band at 370 nm. The formation of (Tb3+)+ hole centres suppresses the formation of intrinsic phosphate-related hole centres, absorbing in the visible region. PO3 defects absorbing in the ultraviolet region contribute mainly to the electron centres corresponding to the (Tb3+)+ hole centres. Immediately after X-ray irradiation, 5–10% of the Tb3+ ions have been oxidized. The amount of (Tb3+)+ ions increases with increasing phosphate content. Th...
The study of radiation-induced defect formation in glasses is of growing interest for applications in optics and photonics. The influence of Eu3+ and Eu2+ ions on X-ray-induced defects has been examined in glasses with different phosphate contents. The defects have been characterized by optical absorption and ESR spectroscopy. X-ray irradiation induces the formation of both (Eu3+)− and (Eu2+)+ ions, whereby the amount of the latter one is considerably higher. Furthermore, the stability of both ions at room temperature is different. In the fluoride phosphate glass studied, the local environment of (Eu3+)− differs from that of Eu2+ which is chemically created. (Eu3+)− ions suppress the formation of intrinsic electron centers, whereas (Eu2+)+ ions suppress the formation of intrinsic hole centers. The amount and stability of (Eu3+)− depend...
The influence of Eu3+, Eu2+ and Tb3+ ions on x-ray and ultra violet laser induced defects is examined in a fluoride phosphate and an ultraphosphate glass. The defects are characterised by optical absorption, fluorescence and ESR spectroscopy Europium ions cause larger changes in the fluoride phosphate glass whereas terbium ions do in the ultraphosphate glass. Different mechanisms of defect formation are found for x-ray and ultraviolet excimer laser irradiation at 248 nm. X-ray irradiation induces valence changes of a part of the dopant ions into (Eu3+)-, (Eu2+)+ and (Tb3+)+ ions, respectively: By contrast, laser irradiation results in a very hst and complete photo-oxidation of Eu3+ but in a very slight photooxidation of Tb3+. Photoreduction of Eu3+ does not occur. Under x-ray irradiation, the dopants have a similar but small influence ...
