| Summary: | 碩士 === 義守大學 === 電子工程學系碩士班 === 97 === For the generation of broadband tunability over 1.3 μm to 1.6 μm range in optical communications, Cr4+ ions have been demonstrated in a number of hosts including Cr4+:forsterite, Cr4+:Y2SiO5, and Cr4+:YAG. Since YAG is a cubic crystal with Ia-3d space group, its excellent thermal and optical properties has drawn extensive studies. However, a systematic study how the microstructure of Cr4+:YAG crystal fiber affects propagation loss is still lacking. Experimentally, the Cr4+:YAG crystal fiber was grown by the laser-heated pedestal growth (LHPG) method and Drawing Tower method which provides outstanding crystal quality and can easily change growth conditions, such as growth speed and core diameter. A double cladding technique was developed with pure YAG, silica/YAG mixture, and pure silica as the core, inner cladding, and outer cladding, respectively. The smallest core diameter we achieved is 10 μm. And improving Drawing Tower method by adding negative pressure control system to promote fiber’s quality and improve the true roundness of the single cladding crystal fiber. In order to understand the relation between the microstructure of Cr4+:YAG crystal fibers and the growth conditions, We also use the high-resolution transmission electron microscopy (HRTEM) to analysis Cr4+:YAG crystal fibers grown from the laser-heated pedestal growth (LHPG) method and add negative pressure’s Drawing Tower method, which reveal the nano-scale information in the core region, the interface of inner-outer cladding, and the influence of inter-diffusion process during growth.
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