Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth
碩士 === 臺灣大學 === 光電工程學研究所 === 95 === Yttrium aluminum garnet (YAG) crystal doped with active ions has been widely used as laser gain medium. It is important to control the molten-zone properties well during the drawing process to enhance the performance of the output laser beam, because the laser qua...
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ndltd-TW-095NTU051240902015-10-13T13:55:55Z http://ndltd.ncl.edu.tw/handle/18971865043369472763 Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth 利用雷射加熱基座法生長掺釹釔鋁石榴石熔區特性之模擬分析 Yu-Ching Wu 吳育慶 碩士 臺灣大學 光電工程學研究所 95 Yttrium aluminum garnet (YAG) crystal doped with active ions has been widely used as laser gain medium. It is important to control the molten-zone properties well during the drawing process to enhance the performance of the output laser beam, because the laser quality is affected significantly by the species of active ions and its radial dopant concentration distribution in the gain medium. We have experimentally demonstrated the neodymium-doped YAG crystal fiber with the maximum central dopant concentration up to 2.4 atm.% with a fiber diameter of 220 μm by laser-heated-pedestal-growth technique when the rawing velocity is 1.25 mm per minute. The source rod was square with an end facet area of 480 μm by 480 μm and an uniform dopant concentration of 1.15 atm.%. To further understand the relation between the drawing parameters and the radial dopant concentration of the crystal fiber and compare with the experiment, we modified a 2-dimensional computational-fluid-dynamic (CFD) program, which was written by Lan et. al. for bulk materials. Simulation results agree with the experimental ones in size and shape of the molten zone for various CO2 laser input powers. Moreover, the radial dopant distribution of the crystal fiber in the simulations is similar to that in the experiments, but there are differences in the ariation of the maximum central concentration by changing the drawing speed. It is speculated that the crystal lattices are damaged due to the residual strain caused by high maximum central dopant concentration. Besides, the highest maximum central dopant concentration was about 1.5 atm.% in the simulations which is different from that in the experiments. We believe that it could be improved quantitatively by considering the surface tension coefficient as a function of both concentration and temperature in the simulation. Sheng-Lung Huang 黃升龍 2007 學位論文 ; thesis 68 zh-TW |
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碩士 === 臺灣大學 === 光電工程學研究所 === 95 === Yttrium aluminum garnet (YAG) crystal doped with active ions has been widely used as laser gain medium. It is important to control the molten-zone properties well during the drawing process to enhance the performance of the output laser beam, because the laser quality is affected significantly by the species of active ions and its radial dopant concentration distribution in the gain medium. We have experimentally demonstrated the neodymium-doped YAG crystal fiber with the maximum central dopant concentration up to 2.4 atm.% with a fiber diameter of 220 μm by laser-heated-pedestal-growth technique when the rawing velocity is 1.25 mm per minute. The source rod was square with an end facet area of 480 μm by 480 μm and an uniform dopant concentration of 1.15 atm.%.
To further understand the relation between the drawing parameters and the radial dopant concentration of the crystal fiber and compare with the experiment, we modified a 2-dimensional computational-fluid-dynamic (CFD) program, which was written by Lan et. al. for bulk materials. Simulation results agree with the experimental ones in size and shape of the molten zone for various CO2 laser input powers. Moreover, the radial dopant distribution of the crystal fiber in the simulations is similar to that in the experiments, but there are differences in the ariation of the maximum central concentration by changing the drawing speed. It is speculated that the crystal lattices are damaged due to the residual strain caused by high maximum central dopant concentration. Besides, the highest maximum central dopant concentration was about 1.5 atm.% in the simulations which is different from that in the experiments. We believe that it could be improved quantitatively by considering the surface tension coefficient as a function of both concentration and temperature in the simulation.
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author2 |
Sheng-Lung Huang |
author_facet |
Sheng-Lung Huang Yu-Ching Wu 吳育慶 |
author |
Yu-Ching Wu 吳育慶 |
spellingShingle |
Yu-Ching Wu 吳育慶 Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth |
author_sort |
Yu-Ching Wu |
title |
Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth |
title_short |
Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth |
title_full |
Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth |
title_fullStr |
Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth |
title_full_unstemmed |
Simulation of Molten-Zone Characteristics for Nd:YAG Crystal Using Laser-Heated Pedestal Growth |
title_sort |
simulation of molten-zone characteristics for nd:yag crystal using laser-heated pedestal growth |
publishDate |
2007 |
url |
http://ndltd.ncl.edu.tw/handle/18971865043369472763 |
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