| Summary: | 博士 === 輔仁大學 === 應用科學與工程研究所博士班 === 100 === Abstract
In this thesis, the main approaches was using Czochralski growth method for high temperature single crystal growth. Due to yttrium aluminum garnet being an excellent laser host crystal and suitable lattice structure arrangement, it can be used for laser active ion filler. Therefore, by choosing iron, chromium, and ytterbium as doping elements, we have investigated the growth and physical properties of yttrium aluminum garnet crystal doped with different concentration of the above-mentioned ions.
We have grown pure yttrium aluminum garnet crystal and doped it with different concentrations of iron and chromium. Due to the difficulties in growing and controlling parameters with high concentration of iron and chromium doping, we could only grow 1 inch of diameter sample doped with low concentration. The doping concentrations are as followings: (1) YAG mixed with Fe3+ ion concentration of 0.2, 1 and 4 at.%. (2)YAG mixed with Cr3+ ion concentration of 0.1, 0.5 and 1 at.%. As for growing with ytterbium doping, we could use various different concentrations. Doping Yb3+ concentrations of 3, 10, 15, 20, 50 and 80 at.% and pure ytterbium aluminum garnet crystals were grown. We have developed an automatic growth control system to grow 2 inches crystal.
From XRD measurements, the variances of lattice constant are smaller than 1 % for the samples doping with different concentrations, which are Fe : YAG, Cr: YAG, and Yb :YAG respectively. There are no prominent change in lattice structure, it still maintains to cubic structure. As for Raman measurements, we obeserved the external lattice vibration mode for Fe : YAG. On the other hand, for Cr : YAG and Yb :YAG there are two kinds of vibration mode : external lattice vibration mode and internal extension vibration mode. From the transmittance spectra, we found that when the dopant was iron ion, there were two absorption peaks at 408 and 416nm when the concentrations of iron were 1% and 4%, respectively. On the other hand, for doped with chromium and ytterbium, distinct absorption peaks and broad bands of absorption were found. From the Stark levels of these two crystals, the interchanges of its energy levels were observed clearly. It makes these two materials have broad applications on laser elements.
KEYWORDS : YAG; XRD spectra; Raman spectra; transmittance spectra
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