Laser hosts

Oxyhalide Glasses. Many glasses contain both oxide and haUde anions. The introduction of haUdes into an oxide glass typically serves to reduce the glass-transition temperature, T, and to increase the coefficient of thermal expansion. Oxyfluorophosphates have been investigated as laser host... 

By the sol-gel-process, inorganic glassy and hybrid polymeric materials are accessible at comparatively low temperatures [1], Therefore, organic molecules or dyes can easily be incorporated into the oxide matrix. This combination is especially attractive for the development of the following devices optical filters, solid-state lasers, optical switches, nonlinear optical laser hosts, optical data storage media, and photoconductive devices and films [2]. 

Garnets are important gems, abrasives, microwave systems components, magnetic bubble memories, and laser hosts. For the latter, yttrium aluminum garnet is the most important. It also plays an important role in aircraft turbines where it forms a protective coating on the turbine blades. 

Among the best-known garnets Y3Fe2Fe3012 (Y3Fe5012 yttrium-iron garnet YIG) for its magnetic properties and applications, Y3A15012 (YAG, important laser host material). 

Because the mineral scheelite and the related pyrochlore (Section 6.3.9) are important laser host materials for rare earth metal ions, many such compounds and their doped crystals have been investigated intensively. Compounds with the scheelite structure are given in Table 6.8. 

Table 1 Uses of Alumina Solid alumina Furnace components Catalyst substrates Electronics substrates Electrical insulators Cutting tools Bearings Spark Plugs Arc lamp tubes Laser hosts Gem stones Alumina powders Abrasives Catalyst pellets Alumina coatings Oxidation protection of aluminum and aluminum alloys Capacitors Transisitors Bioceramics Alumina fibers Thermal insulators Fire retardation Alumina as a component of...

Dense alumina can also be made by melting, but the high-melting temperature of 2,054°C makes this process expensive and difficult to control. High-value materials such as gem stones and laser hosts can be made by adding various colorants such as chromium, titanium, iron, cobalt, and vanadium to the melt. 

Ceramics in aluminate systems are usually formed from cubic crystal systems and this includes spinel and garnet. Rare earth aluminate garnets include the phase YAG (yttrium aluminium garnet), which is an important laser host when doped with Nd(III) and more recently Yb(III). Associated applications include applications as scintillators and phosphors. 

Rare earth aluminates are also important commercially as ceramics and ceramic composites for scintillation applications. The importance of the optical properties of rare earth aluminates is underscored by the used of Nd-doped YAG as a laser host. 

Another approach in apatite structure laser hosts is that by Scott et al. (1997) using... 

Leverenz HW (1968) An Introduction to Luminescence of Solids. Dover Publications, New York Louis-Achille V, DeWindt L, Defranceschi M (2000) Electronic structure of minerals The apatite group as a relevant example. Inti J Quantum Chem. 77 991-1006 Loutts GB, Hong P, Chai BHT (1994) Comparison of neodymium laser hosts based on a fluoro-apatite structure. Mater Res Soc 1994 45-49... 

L. Seijo and Z. Barandiaran, in Computational Chemistry Reviews of Current Trends, J. Leszczynski (ed.). World Scientific, Singapore, 1999, Vol. 4, pp. 55-152. C. A. Morrison, Crystal Fields for Transition-Metal Ions in Laser Host Materials, Springer-Verlag, Berlin/Heidelberg, 1992. 

The optical properties of rare-earth doped yttrium oxide and other rare-earth oxides have been studied extensively for several years, since the oxides are excellent laser host materials. Laser action of EurYjOs has been observed at 0.6113/xm (Chang, 1963) Nd Y203 has also been studied as a laser crystal (Hoskins and Softer, 1964 Holloway et al., 1%6). Recently, a Nd tYjOs crystal was used as a room-temperature frequency converter laser output was observed at 1.07 /Lim and at 1.31 /i,m when the crystal was pumped by a Kr c.w. laser (Stone and Burrus, 1978). The possibility of an X-ray pumped laser using various rare-earth ions in Y2O3 has also been discussed (Ratinen, 1971). Other applications of Y2O3 such as thermionic emission (Kul varskaya, 1976) and electroluminescence (Tanaka et al., 1976) have also been described. 

Rare-earth sesquioxides are of interest as laser host materials in addition to other practical applications. Neodymium is known to exhibit laser action in several rare-earth oxides including La203 (Hoskins and Softer, 1965) and Gd203 (Softer and Hoskins, 1964). Laser action in crystals of the form R R203 has also been observed, particularly Ho Er203 (Softer and Hoskins, 1966) and Tm Er203 (Softer and Hoskins, 1965). The possibility of obtaining stimulated emission from crystals of the latter form has spurred much of the fundamental spectroscopic research on the sesquioxides. 

Advanced ceramics include newer materials such as laser host materials, piezoelectric ceramics, ceramics for dynamic random access memories (DRAMs), etc., often produced in small quantities with higher prices. 

Yttrium aluminum garnet (YAG) single crystals are the most widely used laser host, with over 100,000 YAG lasers... 

---