Graded-index characteristics in single-crystal fibers.
TL;DR: Single-crystal fibers of Ti(3+):Al(2)O (3) have been grown by the laser-heated pedestal growth technique and shown to exhibit radial refractive-index gradients and can be fitted with a parabolic model.
Abstract: Single-crystal fibers of Ti3+:Al2O3 have been grown by the laser-heated pedestal growth technique and shown to exhibit radial refractive-index gradients. A refractive-index increase of approximately 12% in the fiber core with respect to the fiber sidewalls has been measured. The index profile can be fitted with a parabolic model. Postgrowth treatment of Cr3+:Gd3Sc2Al3O12 fibers has been shown to produce a uniform cladding region with a graded-index core. The core index is some 12.5% larger than the cladding region, with an index profile shape that is approximately parabolic in nature.
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TL;DR: In this article, the axial and radial dopant distribution was measured by electron probe microanalysis for micro-pulling-down growth of solid solutions and it was shown that axial segregation corresponds to the bend interface.
33 citations
TL;DR: In this article, a double cladding structure of a pure silica multimode step-index fiber with a 100/110 μm core/cladding diameter reached a length of approximately 9∼10 mm from the input surface of the optical fiber with the diameters ranging from 5 to 8 μm at input intensities more than 1.5×10 12 W/cm 2.
29 citations
TL;DR: In this paper, the authors discuss the technique of LHPG, various SC fiber optics that have been grown for both active and passive applications, and methods that may be used to clad the fibers.
Abstract: Single-crystal (SC) fiber optics have been grown for many years for use as passive fibers for the delivery of IR laser radiation and as active fibers useful as minirod lasers. Most of the early work on SC fiber optics involved the growth of unclad sapphire fibers for the transmission of Er:YAG laser radiation at 2.94 μm. More recently there has been a renewed interest in rare-earth (RE) doped oxide crystal fibers for use as high power fiber lasers. By analogy with RE doped-bulk laser crystals it is expected that pure YAG and other crystalline SC fibers should be capable of transmitting extremely high laser energies. SC oxide fibers have some distinct advantages over conventional glass fibers including higher thermal conductivity and low stimulated Brillouin scattering (SBS) gain coefficients. The latter can limit the ultimate power output of glass fiber lasers. To date most of the investigators have used the technique of Laser Heated Pedestal Growth (LHPG) to grow unclad SC fibers with diameters ranging from 30 to 350 μm and in lengths as long as 5 m. The loss for SC sapphire fibers at 2.94 μm has been measured as low as 0.3 dB/m. In this review we discuss the technique of LHPG, the various SC fiber optics that have been grown for both active and passive applications, and methods that may be used to clad the fibers.
27 citations
01 Jan 2010
TL;DR: In this paper, the authors describe the background history, theoretical fundamentals, and how the features of the pedestal growth process affect the growth of oxide fibers, and present a list of materials processed by laser heating in recent decades.
Abstract: The laser-heated pedestal growth (LHPG) technique, when compared with conventional growth methods, presents many advantages, such as high pulling rates, a crucible-free process, and growth of high and low melting point materials. These special features make the LHPG technique a powerful material research tool. We describe the background history, theoretical fundamentals, and how the features of LHPG affect the growth of oxide fibers. We also present a list of materials processed by laser heating in recent decades, such as LiNbO3, Sr–Ba–Nb–O, Bi12TiO20, Sr2RuO4, Bi–Sr–Ca–Cu–O, ZrO2:Y2O3, LaAlO3, and also the eutectic fibers of Al2O3:GdAlO3, Al2O3:Y2O3, and ZrO2:Al2O3.
23 citations
Dissertation•
21 Dec 2009
TL;DR: In this article, the authors propose two concepts differents to depasser les principalaux ecueils des systemes emettant dans le proche infrarouge (1 μm).
Abstract: Le nombre croissant d‟applications des sources lasers de puissance favorise le developpement de solutions techniques innovantes afin d‟atteindre des performances inedites. Pour y parvenir, la technologie des lasers solides beneficie des progres considerables realises pour l‟integration et la montee en puissance des diodes lasers utilisees pour le pompage. Les milieux a gain doivent alors permettre une conversion efficace du rayonnement de pompage en rayonnement laser tout en limitant les phenomenes thermiques et les effets induits par la puissance crete. Au cours de cette these, nous proposons d‟etudier deux concepts differents afin de depasser les principaux ecueils des systemes emettant dans le proche infrarouge (1 μm). Dans le cadre d‟une collaboration regroupant le Laboratoire de Physico-Chimie des Materiaux Luminescents, le Laboratoire Charles Fabry de l‟Institut d‟Optique et l‟entreprise Fibercryst, nous avons developpe et caracterise des fibres cristallines dopees Ytterbium elaborees par la technique de croissance micro-pulling down. Cette geometrie combinant les proprietes des cristaux massifs et les avantages des fibres en verre nous a permis d‟obtenir des performances laser prometteuses pour la realisation de systemes alliant forte energie, forte puissance moyenne et forte puissance crete. La seconde partie de ce travail de these est consacree a l‟etude du concept de pompage direct de cristaux dopes Neodyme dans les niveaux emetteurs. Cette voie, permettant de reduire a l‟extreme l‟echauffement dans le milieu, est fortement prometteuse pour l‟amelioration des performances des systemes laser utilisant des cristaux dopes Neodyme.
10 citations
References
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TL;DR: In this paper, the surface tension driven flow in a cylindrical melt suspended between two rods was investigated by numerical solution of the steady state differential equations for heat and momentum transfer.
172 citations
TL;DR: The first successful growth of Ba(Mg1/3Ta2/3)O3 (BMT) single crystals by the laser heated pedestal growth technique (LHPG) is reported in this paper.
Abstract: The preparation of Ba(Mg1/3Ta2/3)O3 (BMT) ceramics and the first successful growth of BMT single crystals by the laser heated pedestal growth technique (LHPG) is reported. The single crystal has a simple cubic perovskite structure in comparison to the ordered hexagonal structure normally found in ceramics of the same phase. The dielectric properties of single crystals are examined, the dielectric Q value increases with the increase in B‐site ordering, while the dielectric constant κ is relatively independent of ordering. Our results also show that BMT is a candidate substrate for high Tc superconductor thin films as it has one of the highest Q values known for the oxide perovskite family, along with its matching thermal expansion coefficient α=9.0×10−6/ °C and twin‐free cubic perovskite structure with a=4.0877 A. BMT single crystals grown by the LHPG technique are probably the highest melting oxide compounds grown to date.
82 citations
TL;DR: In this paper, a method for measuring the refractive index profile of optical glass fibres is described, which simply monitors the reflection of a focused laser beam from a polished fibre end face.
Abstract: A new method for measuring the refractive index profile of optical glass fibres is described. This simply monitors the reflection of a focused laser beam from a polished fibre end face. Detailed tests on the accuracy and resolution of the method are described and the index profiles of several fibres are given as an example of its feasibility.
55 citations
TL;DR: In this paper, single-crystal Cr-doped Al2O3 fibers are grown by a floating zone technique from small source rods locally melted at the end by a CO2 laser.
Abstract: Single‐crystal Cr‐doped Al2O3 fibers can be grown by a floating‐zone technique from small source rods locally melted at the end by a CO2 laser. By using the same laser to melt and regrow only the surface of the fiber, the Cr concentration in this surface layer can be reduced by a factor of 100 or more by selective evaporation.
55 citations
TL;DR: The laser-heated pedestal growth method has been shown to be one of the most versatile techniques for growing device quality single-crystal fibers of uniform diameter as mentioned in this paper, which can combine the light-guiding properties of fibers with the diverse range of properties available in singlecrystal materials.
Abstract: Single-crystal fibers represent a virtually untapped source of opportunity for both materials and device research. These quasi-one-dimensional materials which can be used individually or in fiber bundles can combine the light-guiding properties of fibers with the diverse range of properties available in single-crystal materials. Light guiding can be enhanced with the use of refractive-index-matched claddings. In recent years the laser-heated pedestal growth method has been shown to be one of the most versatile techniques for growing device quality single-crystal fibers of uniform diameter. The method may be the easiest and the fastest method known for producing small single crystals for property analysis, and its use for this purpose has been growing. This paper discusses some of the interesting opportunities available for single-crystal fiber materials and device research.
54 citations