Home About us Contact
|
Home About us Contact | ||
|
|
||
Sapphire
Kinds of Sapphire Terms modified by Sapphire Selected AbstractsTrap states in n-GaN grown on AlN/sapphire template by MOVPEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008T. Ito Abstract Using epitaxial AlN/sapphire templates, high crystalline quality GaN films are grown on them by metal organic chemical vapour deposition. The electron traps behaviour of these GaN films were observed by deep level transient spectroscopy (DLTS). Four distinct trap levels were ob-served in both n-GaN grown on AlN/sapphire template and on conventional low temperature buffer layer (LT-BL)/sapphire. The magnitude the of the DLTS signal E1 and E2 were almost same. It suggests that E1 is not only associate with dislocation density but also other defect. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical properties of InN grown on Si(111) substratePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010E. Sakalauskas Abstract A comprehensive characterization of the optical properties of wurtzite InN films grown by molecular beam epitaxy on Si(111) substrates is presented. Two types of films are investigated in this work: InN on AlN/Si(111) and InN on GaN/AlN/Si(111). Their properties are compared to a layer deposited on GaN/sapphire substrate. The dielectric function (DF) is obtained from spectroscopic ellipsometry (SE). The infrared studies yield the plasma frequency and thus the electron density, while the interband absorption is probed between 0.56 and 9.8,eV. For InN grown on Si(111) substrate, the absorption onset is slightly shifted to higher energies with respect to the InN film grown on GaN/sapphire which can be attributed to higher electron concentrations. Despite this, strongly pronounced optical transitions due to critical points of the band structure are found in the high-energy part of the DF. It emphasizes the already promising quality of the InN films on silicon. Band-gap renormalization (BGR), band filling, and strain are taken into account in order to estimate the intrinsic band gap of wurtzite InN. For the InN layers on silicon, we get a band gap between 0.66 and 0.685,eV. [source] Fabrication study of AlN solar-blind (<280,nm) MSM photodetectors grown by low-temperature depositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010Meei-Ru Chen Abstract AlN, an important semiconductor with the widest band gap among III-nitrides, was employed to construct solar blind metal,semiconductor,metal photodetectors (MSM-PDs). MSM-PDs were fabricated on AlN epitaxial thin films deposited on GaN/sapphire using a helicon sputtering system at a low temperature of 300,°C. The dark current of the device is as low as 200,fA at 20,V and the photocurrent illuminated by a D2 lamp increases more than two orders of magnitude. The photocurrent increases almost linearly with the incident optical power at the wavelength of 200,nm. The results show that the low temperature grown AlN MSM device is suitable for the application of deep UV detection. [source] Structural evaluation of GaN/sapphire grown by epitaxial lateral overgrowth by X-ray microdiffractionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006M. Drakopoulos The cover picture from the article [1] depicts the geometry of X-ray diffraction on a GaN/sapphire structure made by a two-step epitaxial lateral overgrowth (2S-ELO) process. Below, the X-ray rocking curve as a function of the vertical beam position in 2S-ELO GaN/sapphire is shown. A low intensity line diverging from the main peak position (arrow) may be interpreted as the disappearance of a winged crystal region due to dislocation curvature. This paper is a presentation from the 6th International Conference on Nitride Semiconductors held in Bremen, Germany, in 2005. Further articles from ICNS-6 are also being published in phys. stat. sol. (a) 203, No. 7 (2006) and phys. stat. sol. (c) 3, No. 6 (2006). [source] Monocrystalline ZnO films grown by atomic layer epitaxy , growth and characterizationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004K. Kopalko Abstract We report successful growth of thin films of ZnO by atomic layer epitaxy (ALE). Properties of the ZnO films grown by ALE on GaN/sapphire are described in relation to those grown by the same sequential procedure on uncoated sapphire and glass substrates. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sapphire: copying garbage collection without stopping the worldCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 3-5 2003Richard L. Hudson Abstract The growing use in concurrent systems of languages that require garbage collection (GC), such as Java, is raising practical interest in concurrent GC. Sapphire is a new algorithm for concurrent copying GC for Java. It stresses minimizing the amount of time any given application thread may need to block to support the collector. In particular, Sapphire is intended to work well in the presence of a large number of application threads, on small- to medium-scale shared memory multiprocessors. Sapphire extends previous concurrent copying algorithms, and is most closely related to replicating copying collection, a GC technique in which application threads observe and update primarily the old copies of objects. The key innovations of Sapphire are: (1) the ability to ,flip' one thread at a time (changing the thread's view from the old copies of objects to the new copies), as opposed to needing to stop all threads and flip them at the same time; (2) exploiting Java semantics and assuming any data races occur on volatile fields, to avoid a barrier on reads of non-volatile fields; and (3) working in concert with virtually any underlying (non-concurrent) copying collection algorithm. Copyright © 2003 John Wiley & Sons, Ltd. [source] Nanowire-Templated Epitaxial Growth: Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane Sapphire (Adv. Mater.ADVANCED MATERIALS, Issue 23 200923/2009) George Wang and co-workers report on p. 2416 that low dislocation density a -plane GaN films can be grown by the coalescence of vertically-aligned, single-crystalline GaN nanowires on lattice-mismatched r -plane sapphire. In this technique, shown by the artists' rendering on the inside cover, the nanowires facilitate dramatic strain relaxation in the suspended GaN film, leading to a large reduction in defects. [source] Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane SapphireADVANCED MATERIALS, Issue 23 2009Qiming Li Coalescence of a vertically aligned GaN nanowire array on r -plane sapphire, a technique called nanowire-templated lateral epitaxial growth, is used to grow low-dislocation density a -plane GaN. The resulting film is connected to the lattice-mismatched substrate by nanowires, which facilitates dramatic strain relaxation and leads to a significant reduction in defects. [source] Direct Observation of Inversion Domain Boundaries of GaN on c -Sapphire at Sub-ångstrom Resolution,ADVANCED MATERIALS, Issue 11 2008Fude Liu Inversion domain boundaries (IDBs) of GaN are studied by a high-resolution technique. The IDB separates adjacent domains of opposite polarity. The image shows a GaN IDB in the [bar;2110] projection. The theoretical IDB structure fits the experimentally obtained structure well. The inset is an image acquired from a very thin region on the right side of the IDB. It can indicate the polarity of GaN directly. [source] Use of confocal and multiphoton microscopy for the evaluation of micro-optical components and emittersMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2004J.M. Girkin Abstract We report on the application of confocal and multiphoton microscopic techniques for the evaluation of the latest generation of micro optical components. The optical emitting characteristics of arrays of matrix addressable GaN micrometer-sized light emitting diodes (micro-LEDs) have been measured using a commercial confocal microscope utilising the LEDs' own emission along with reflection confocal microscopy to determine the surface structure. Multiphoton induced luminescence from the 10,20-micron diameter emitters has also been used to examine the structure of the device and we compare this with electrically induced emission. In related work, the optical properties of micro lens arrays (10,100-micron diameter) fabricated in SiC, Sapphire, and Diamond have been determined using transmission confocal microscopy. Such optical microscopy techniques offer a simple, non-destructive method to determine the structure and performance of such novel devices. Microsc. Res. Tech. 64:293,296, 2004. © 2004 Wiley-Liss, Inc. [source] Competition of Epitaxy and Ion Beam Irradiation-Determined Texture during Ion Beam-Assisted Deposition of Gallium Nitride Films on r-Plane SapphirePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003J.W. Gerlach Abstract The nitrogen ion beam-assisted growth of wurtzitic gallium nitride thin films on the r -plane of sapphire is investigated. X-ray diffraction and electron microscopy reveal that the crystallographic texture of the films is very sensitive to the ion beam parameters. By carefully choosing these parameters it is possible to direct intentionally the orientation of the GaN films. [source] Rule based processing of the CD4000, CD3200 and CD Sapphire analyser output using the Cerner Discern Expert ModuleINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 6 2009P. BURGESS Summary The latest version of our Laboratory Information System haematology laboratory expert system that handles the output of Abbott Cell-Dyn Sapphires, CD4000s and a CD3200 full blood count analyser in three high-volume haematology laboratories is described. The three hospital laboratories use Cerner Millennium Version 2007.02 software and the expert system uses Cerner Millennium Discern Expert rules and some small Cerner Command Language in-house programs. The entire expert system is totally integrated with the area-wide database and has been built and maintained by haematology staff members, as has the haematology database. Using patient demographic data, analyser numeric results, analyser error and morphology flags and previous results for the patient, this expert system decides whether to validate the main full blood count indices and white cell differential, or if the analyser results warrant further operator intervention/investigation before verifying, whether a blood film is required for microscopic review and if abnormal results require phoning to the staff treating the patient. The principles of this expert system can be generalized to different haematology analysers and haematology laboratories that have different workflows and different software. [source] In the Wake of Things: Speculating in and about Sapphires in Northern MadagascarAMERICAN ANTHROPOLOGIST, Issue 2 2004ANDREW WALSH ABSTRACT This article discusses the interrelatedness of two sorts of speculation undertaken by Malagasy sapphire miners and traders involved in the northern Malagasy sapphire trade: first, the speculating that these people do in sapphires, and, second, the speculating that they do about the uses to which sapphires are put by foreigners. Although Malagasy people involved in the local trade know a great deal about how sapphires might be profitably traded, most of them do not know why foreigners are so interested in these stones. Dubious of foreign traders' assurances that sapphires are used in the production of jewelry, they speculate a variety of alternate, secret uses for them. In this article, it is argued that these speculations emerge out of a variety of locally developed assumptions about how the sapphire trade works, and specifically, the significant roles that deception and knowledge differentials play in its operation. [source] Optical investigations on the existence of phase transition in ZnO:Li thin films prepared by DC sputtering methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2008A. Abu EL-Fadl Abstract We investigated the effect of temperature on the absorption spectra of Zn0.8Li0.2O thin films (ZnO:Li), deposited at 573 K, in the wavelength range 190-800 nm. The films were deposited on sapphire, MgO or quartz substrates by DC sputtering method. The results show a shift of the optical energy gap (Eg), with direct allowed transition type near the fundamental edge, to lower wavelengths as the temperature increases. The temperature rate of Eg changes considerably showing an anomaly around 320 K depending on type of substrate. The founded results indicated that replacement of Zn ions with Li ions induces a ferroelectric phase in the ZnO wurtzite-type semiconductor. The exponential dependence of the absorption coefficient on the incident photon energy suggests the validity of the Urbach rule. (© 2007 WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of InN metalorganic vapor phase epitaxy using in-situ spectroscopic ellipsometryCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005M. Drago Abstract Metalorganic vapor phase epitaxy of InN layers on sapphire was studied in-situ by spectroscopic ellipsometry (SE), ex-situ atomic force microscopy and optical microscopy. Surface morphology has been largely improved by using nitrogen instead of hydrogen as carrier gas during sapphire nitridation. Using the sensitivity of in-situ SE with respect to roughness we established a new growth procedure with low V/III ratio (104) at high temperature (580 °C) and growth rates as high as 350 nm/h, leading to improved electronic layer properties and allowing for growth of comparably thick layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Laser Hair Removal with Alexandrite versus Diode Laser Using Four Treatment Sessions: 1-Year ResultsDERMATOLOGIC SURGERY, Issue 11 2001Sorin Eremia MD Background. Laser hair removal is the treatment of choice for hypertrichosis. The two most commonly used hair removal lasers are compared. Objective. To present the results of a comparative study examining the role of wavelength, fluence, spot size, pulse width, and cooling systems on long-term results after a series of four laser hair removal treatments using the 755 nm alexandrite and 800,810 nm diode lasers. Methods. The axillae of 15 untanned, type I,V patients were treated side by side four times at 4- to 6-week intervals with a 755 nm, 3-msec pulse width, cryogen spray-equipped alexandrite laser and an 800 nm, variable pulse width, cooled sapphire window-equipped diode laser. Each patient was pretested and treated with the maximum fluence tolerated at the largest spot size available for each laser (12 mm round/113 mm2 for the alexandrite and 9 mm for the diode). Results. Evaluations were done at 3, 6, 9, and 12 months after the last treatment. Twelve-month results with the alexandrite and diode lasers achieved 85% versus 84% hair reduction. The fact that tan avoidance was strictly followed permitted the use of relatively high fluences (25,30+ J/cm2) even in type IV patients. For most patients, four treatment sessions using high fluences (30,40 J/cm2) with relatively large spot sizes (12 mm round for the 755 nm alexandrite and 9 mm for the 800 nm diode) resulted in 12-month hair reductions in the 90% range. Conclusion. Both the alexandrite and diode lasers in this 12-month study produced excellent long-term hair reductions. [source] Development of 230,270 nm AlGaN-based deep-UV LEDsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2010Hideki Hirayama Abstract We demonstrated AlGaN multi-quantum well (MQW) deep-ultraviolet (UV) light-emitting diodes (LEDs) with wavelengths in the range of 227.5 to 273 nm fabricated on high-quality AlN buffers on sapphire substrates grown by metal-organic chemical vapor deposition (MOCVD). We realized crack-free, thick AlN buffers on sapphire with a low threading dislocation density (TDD) and an atomically flat surface by using the ammonia (NH3) pulse-flow multilayer (ML) growth technique. We obtained single-peaked operation of an AlGaN-MQW LED with a wavelength of 227.5 nm, which is the shortest wavelength of AlGaN-based LED on sapphire. The maximum output power and the external quantum efficiency (EQE) of the 261- and 227.5-nm LEDs were 1.65 mW and 0.23% in room-temperature (RT) continuous-wave (CW) operation, and 0.15 mW and 0.2% in RT pulsed operation, respectively. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(3): 24,33, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10197 [source] Recent Progress in GaN-Based Light-Emitting DiodesADVANCED MATERIALS, Issue 45 2009Haiqiang Jia Abstract In the last few years the GaN-based white light-emitting diode (LED) has been remarkable as a commercially available solid-state light source. To increase the luminescence power, we studied GaN LED epitaxial materials. First, a special maskless V-grooved c -plane sapphire was fabricated, a GaN lateral epitaxial overgrowth method on this substrate was developed, and consequently GaN films are obtained with low dislocation densities and an increased light-emitting efficiency (because of the enhanced reflection from the V-grooved plane). Furthermore, anomalous tunneling-assisted carrier transfer in an asymmetrically coupled InGaN/GaN quantum well structure was studied. A new quantum well structure using this effect is designed to enhance the luminescent efficiency of the LED to ,72%. Finally, a single-chip phosphor-free white LED is fabricated, a stable white light is emitted for currents from 20 to 60,mA, which makes the LED chip suitable for lighting applications. [source] Nanowire-Templated Epitaxial Growth: Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane Sapphire (Adv. Mater.ADVANCED MATERIALS, Issue 23 200923/2009) George Wang and co-workers report on p. 2416 that low dislocation density a -plane GaN films can be grown by the coalescence of vertically-aligned, single-crystalline GaN nanowires on lattice-mismatched r -plane sapphire. In this technique, shown by the artists' rendering on the inside cover, the nanowires facilitate dramatic strain relaxation in the suspended GaN film, leading to a large reduction in defects. [source] Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane SapphireADVANCED MATERIALS, Issue 23 2009Qiming Li Coalescence of a vertically aligned GaN nanowire array on r -plane sapphire, a technique called nanowire-templated lateral epitaxial growth, is used to grow low-dislocation density a -plane GaN. The resulting film is connected to the lattice-mismatched substrate by nanowires, which facilitates dramatic strain relaxation and leads to a significant reduction in defects. [source] Nanofacet Lithography: A New Bottom-Up Approach to Nanopatterning and Nanofabrication by Soft Replication of Spontaneously Faceted Crystal Surfaces,ADVANCED MATERIALS, Issue 10 2007R. Gabai The faceting of unstable crystal surfaces provides self-assembling templates for soft lithography, enabling the facile generation of a variety of periodic nanopatterned monolayers, nanowires, nanogrooves, nanogrids, and nanowaffles of Au and Si (the figure shows the replication of faceted sapphire to an elastomeric stamp, and then to a patterned self-assembled monolayer). [source] Threading dislocations in domain-matching epitaxial films of ZnOJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2007W.-R. Liu The structures of high-quality ZnO epitaxial films grown by pulsed-laser deposition on sapphire (0001) without an oxygen gas flow were investigated by X-ray diffraction and transmission electron microscopy. The great disparity of X-ray diffraction line widths between the normal and in-plane reflections reveals the specific threading dislocation geometry of ZnO. Most threading dislocations are pure edge dislocations. From a combination of scattering and microscopic results, it is found that threading dislocations are not uniformly distributed in the ZnO films, but the films consist of columnar epitaxial cores surrounded by annular regions of edge threading dislocations in large density. The local surface morphology and capacitance signal obtained from atomic force and scanning capacitance microscopes indicate that the aggregation of threading dislocations leads to high interface traps at the annular regions. [source] Diamond as pressure sensor in high-pressure Raman spectroscopy using sapphire and other gem anvil cellsJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2003Valentín García Baonza Abstract We propose a new Raman pressure scale based on the shift with pressure of the fundamental Raman band of micrometer-sized diamonds. First, we confirmed that the pressure slope of the triply degenerate diamond phonon behaves in a similar fashion to that of the bulk. Our measurements were calibrated Raman against the Sm:YAG fluorescence pressure scale up to 5 GPa using a gasketed sapphire anvil cell. The most relevant features regarding the design of the anvil cell are briefly outlined. Measurements were performed under hydrostatic conditions using 4 : 1 methanol,ethanol as pressure-transmitting medium. The calibration pressures according to the relationship p(GPa) = 0.356[,(cm,1) , 1332.3] are considered to be accurate within about 0.1 GPa. The convenience of using micrometer-sized diamonds as pressure sensors in Raman studies using gem anvil devices is demonstrated with several examples. Copyright © 2003 John Wiley & Sons, Ltd. [source] Preparation of Highly Dense PZN,PZT Thick Films by the Aerosol Deposition Method Using Excess-PbO PowderJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Jong-Jin Choi Lead zinc niobate,lead zirconate titanate thick films with a thickness of 50,100 ,m were deposited on silicon and alumina substrates using the aerosol deposition method. The effects of excess lead oxide (PbO) on stress relaxation during postannealing were studied. Excess PbO content was varied from 0 to 5 mol%. The as-deposited film had a fairly dense microstructure with nanosized grains. The films deposited on silicon were annealed at temperatures of 700°C, and the films deposited on sapphire were annealed at 900°C in an electrical furnace. The annealed film was detached and cracks were generated due to the high residual compressive stress and thermal stress induced by thermal expansion coefficient mismatch. However, the film deposited using powder containing 2% of excess PbO showed no cracking or detachment from the substrate after the postannealing process. The PbO evaporation at elevated temperature during the postannealing process seemed to have reduced the residual compressive stress. The remanent polarization and relative dielectric constant of the 50 ,m thick films annealed at 900°C were 43.1 ,C/cm2 and 1400, respectively, which were comparable with the values of a bulk specimen prepared by a powder sintering process. [source] Determination of the Thermal Resistance of the Polymer,Ceramic Interface of Alumina-Filled Polymer CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004Richard F. Hill To model the thermal conductivity of polymer composites that are filled with ceramic powders, the conductivity of each component as well as the interfacial resistance at each ceramic,polymer boundary must be known. An indirect method to determine this interfacial boundary resistance is proposed by preparing large-scale "macromodel" simulations of the polymer,ceramic interface. Macromodels, prepared by spin-coating a polymer layer onto sapphire wafers, were formed in a sapphire,polymer,sapphire sandwich type structure. The interfacial boundary thermal resistance was calculated from thermal resistance measurements made on the macromodels. [source] Alumina Volatility in Water Vapor at Elevated TemperaturesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2004Elizabeth J. Opila The volatility of alumina in high-temperature water vapor was determined by a weight loss technique. Sapphire coupons were exposed at temperatures between 1250° and 1500°C, water partial pressures between 0.15 and 0.68 atm in oxygen, a total pressure of 1 atm, and flowing gas velocities of 4.4 cm/s. The water vapor pressure dependence of sapphire volatility was consistent with Al(OH)3(g) formation. The enthalpy of reaction to form Al(OH)3(g) from sapphire and water vapor was determined to be 210 ± 20 kJ/mol, comparing favorably to other studies. Microstructural examination of tested sapphire coupons revealed surface rearrangement consistent with a volatilization process. [source] Solid Solubility and Precipitation in a Single-Crystal Alumina,Zirconia SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Matthew A. Stough Solid solubility was examined in Zr-doped sapphire and Al-doped yttria-stabilized zirconia (YSZ) single crystals from 1200° to 1600°C. Specimens were fabricated via ion implantation of single crystals, followed by annealing in air. Secondary ion mass spectroscopy (SIMS) was used to quantify solute redistribution during annealing. Comparison of SIMS results with analytical electron microscopy (AEM) revealed an alumina solubility of 0.2,0.3 wt% in zirconia, and a zirconia solubility of 0.004,0.027 wt% in alumina. Direct imaging of zirconia precipitates revealed that tetragonal zirconia precipitates from supersaturated sapphire with the following orientation relationship: (100)tetragonal, (0001)sapphire and [01¯1]tetragonal, [12¯10]sapphire. [source] Transparent Polycrystalline Alumina Ceramic with Sub-Micrometre Microstructure by Means of Electrophoretic DepositionMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2006A. Braun Abstract The optical quality attainable in coarse-grained polycrystalline alumina is severely limited by grain-boundary scattering, which is inherent to non-cubic materials. The optical properties of sub-micrometre polycrystalline alumina are of growing interest triggered by the fact that a decrease in the grain sizes of the final sintered material yields an improvement in the optical quality while the scattering mechanism changes as the grain size becomes comparable with the wavelength of light. To achieve transparent alumina ceramics with a fine-grained microstructure, however, porosity and other defects must be avoided. This necessitates the optimization of processing and sintering procedures. Electrophoretic deposition (EPD) is a colloidal process in which ceramic bodies are directly shaped from a stable suspension by application of an electric field. Electrophoretic deposition enables the formation of homogeneous, uniform green microstructures with high density, which can be sintered to transparency. It is a simple and precise technique to synthesize not only monoliths, but also composites with complex geometries [1]. Alumina green bodies were deposited from stabilized aqueous suspensions with and without doping. Green alumina compacts were evaluated based on their pore size distribution and density. Densification behaviour was characterized by dilatometric studies conducted at constant heating rate. Samples were sintered at different temperatures with subsequent post-densification by hot isostatic pressing. Transparency was evaluated by means of spectroscopic measurements. The measured in-line transmission of the samples at 645 nm was more than 50,% and that is 58,% of the value of sapphire. The influence of dopings on transparency was investigated. The mechanical properties of the samples were tested. [source] Single-mode pumping scheme for EDFA with high-power conversion efficiency using a 980-NM Ti:S laserMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2006M. A. Mahdi Abstract In this paper, we demonstrate a high-power erbium-doped fiber amplifier pumped by single-mode titanium sapphire (Ti:S) laser at 980 nm. The highest output power of 22.6 dBm is measured at 1549 nm with an input signal power of 4 dBm and a pump power of 300 mW. This corresponds to power-conversion efficiency (PCE) of 60%, providing 95% quantum efficiency. The experimental results show the feasibility of using a single-mode laser from a high-power semiconductor chip to produce high-efficiency booster amplifiers. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 71,74, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21264 [source] Femtosecond laser-assisted formation of channels in sapphire using KOH solutionPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2008Saulius Juodkazis Abstract We report on wet etching of photomodified regions in crystalline sapphire using KOH solution. Tightly focused femtosecond laser pulses (150 fs at 800 nm wavelength) were used to create void structures enclosed in an amorphised sapphire shell inside the bulk of a crystalline host. The diameter of the amorphous regions can be controlled by pulse energy and was typically 0.5,1.5 µm. The etching rate depends on the distance between adjacent irradiation spots, pulse energy, concentration of etchant and ultrasonic agitation. Amorphised sapphire is etched out in KOH solution. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||||||||