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Glasses
Published in Marvin J. Weber, and TECHNOLOGY, 2020
Patricia A. Morris Hotsenpiller
Tables 18.1.1 through 18.1.3 contain data regarding the fabrication and properties of crystalline waveguides produced in the dielectric oxides: LiNb03, LiTaG3, KTiPOs (KTP), KNbQ3, and Nd:Y2Al5Q12 (Nd:YAG). LiNbG3, LiTaO,, KTP, and KNbG3 are nonlinear optical materials with large second-order nonlinearities. Nd: YAG is a solid-state laser material. Table 18.1.4 summarizes the indices of refraction of the bulk crystals for comparison with the Δn and n values listed. Tables 18.1.1 through 18.1.3 contain a comprehensive summary of the data, so only a few brief comments are made here.
Optical Properties of Solids
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
Phosphors are solids that absorb energy and re-emit it as light. As in the lasers that we have just described, the emitter is usually an impurity ion in a host lattice. However, for the general uses of phosphors, it is not necessary to produce intense, coherent beams of light, and the emitting process is spontaneous rather than induced. There are many applications of phosphors, for example, the colours of plasma television screens are produced by phosphors that are bombarded with electrons from a beam. Phosphors are also used to produce white light in LED bulbs. The light emitting diode in white light LED bulbs actually produces radiation in the blue/violet region. Some of this radiation is absorbed by the phosphor coating and re-emitted as yellow, green, or red light to produce a white light. The yellow, red, or green light is produced by an impurity ion, often a lanthanoid ion, in a host lattice. Host lattices include alkaline earth aluminates, yttrium aluminium garnet (YAG), nitrides, and silicates. Ce3+-doped YAG, for example, is a common phosphor producing a broad band of light due to a transition from 5d to 4f centered in the yellow region of the spectrum. The light from the LED is absorbed by an electron in a 4f orbital which is excited to an excited vibrational state of a 5d level. The electron then loses energy, moving to the vibrational ground state of the 5d level. From there it emits yellow and green light and returns to the 4f level (Figure 8.6).
Basic Postulates of Crystal Field Theory
Published in Mikhail G. Brik, Chong-Geng Ma, Theoretical Spectroscopy of Transition Metal and Rare Earth Ions, 2019
Mikhail G. Brik, Chong-Geng Ma
The YAG structure is cubic and is described by the Ia-3d space group (No. 230) with the lattice constant a = 12.0062 Å.52 There are two Al sites in this structure: four- and six-fold coordinated. The Y ions are eight-fold coordinated. Comparing the ionic radii of the host cations (Al3+—0.39 Å for the four-fold coordination and 0.535 Å for the six-fold coordination, Y3+—1.019 Å for the eight-fold coordination) with that one for the Cr4+ ions (0.41 Å for the four-fold coordination and 0.55 Å for the six-fold coordination)53 and taking into account preference of the Cr4+ ions to occupy the tetrahedral sites, it is clear that the four-fold coordinated aluminum ions will be replaced by the dopants. Of course, the dopant concentration is very small—not more than 1–2% only. If only the nearest four ligands around the tetrahedral Al ion are considered, then the local site symmetry is D2d.39Table 8.7 collects the Cartesian coordinates of the oxygen ions in the AlO4 tetrahedral cluster obtained from Ref. 46, whereas Fig. 8.14 shows the nearest environment around the Cr4+ ion in the system of reference corresponding to the data from Table 8.7 (the z axis is directed from the plane of figure towards the reader). All Cr-0 distances in this complex are 1.75378 Å.
Laboratory spray drying of materials for batteries, lasers, and bioceramics
Published in Drying Technology, 2019
C. Arpagaus, A. Collenberg, D. Rütti
In solid-state lasers, yttrium aluminum garnet (YAG, Y3Al5O12) is commonly used as host material. Rare earth elements such as ytterbium (Yb), erbium (Er), praseodymium (Pr), or neodymium (Nd) are doped into YAG as active laser ions, which determine the light absorption and emission profiles. For example, Nd:YAG emits infrared light at a wavelength of 1,064 nm and provides output power levels up to the kW range.[23] Yb:YAG lasers emit at 1,030 nm and are good substitutes for Nd:YAG in high-power applications. Er:YAG is lasing at 2,940 nm and couples well into water and body fluids making this laser especially useful for medicine and dentistry uses.[25] In comparison, Pr:YAG lasers offer interesting perspectives for applications in optics and photonics, for example, in the field of scintillator materials, to count the energy and intensity of ionizing radiation.[20]
Use of lasers in minimally invasive spine surgery
Published in Expert Review of Medical Devices, 2018
Neodymium-doped yttrium-aluminum-garnet (Nd:YAG) lasers are the most widely used laser systems in a variety of medical fields. The absorption of 1064- and 1318-nm wavelengths by biological tissue is relatively low, and thus, the scattering effect is high. The penetration depth in cartilaginous tissue reaches up to 6 mm with powers 20–40 W and pulse 0.05–0.1 s. The coagulation zone can be reduced to 0.6 mm with a contact laser probe. It has been proven to be effective for ablation and coagulation of disc tissues in both experimental and clinical studies [25,26]. Nd:YAG laser has benefits of fiber-optic delivery, applicability in dry and aqueous media, and hemostatic effect. However, it is a hot laser, which generates and transmits heat through the tissues.
A review of bio-fuelled LHR engines
Published in International Journal of Ambient Energy, 2020
Krishna Kumar Pandey, S. Murugan
Garnet ceramics, with a composition of Y3AlxFex-5O12 (x = 0, 0.7, 1.4 and 5), can be considered a TBS material (Ghosh 2015). In particular, YAG (Y3Al5O12) has an excellent phase and thermal stability up to the melting point of 2243 K, higher temperature mechanical properties. The oxygen resistance of YAG is higher and offers improved protection to the bond coat because the oxygen diffusivity in YAG is around 10 orders of magnitude lower than zirconia.