| Item type |
学位論文 / Thesis or Dissertation(1) |
| 公開日 |
2010-02-22 |
| タイトル |
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タイトル |
Ultraviolet Laser Emission form a Micro-Pulling Down Method Grown Ce3+:LiCaAlF6 |
| タイトル |
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タイトル |
Ultraviolet Laser Emission form a Micro-Pulling Down Method Grown Ce3+:LiCaAlF6 |
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言語 |
en |
| 言語 |
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言語 |
eng |
| 資源タイプ |
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資源タイプ識別子 |
http://purl.org/coar/resource_type/c_46ec |
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資源タイプ |
thesis |
| 著者名 |
PHAM, MINH HONG
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| フリガナ |
パム, ミン ハウ
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| 著者 |
PHAM, MINH HONG
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| 学位授与機関 |
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学位授与機関名 |
総合研究大学院大学 |
| 学位名 |
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学位名 |
博士（学術） |
| 学位記番号 |
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内容記述タイプ |
Other |
|
内容記述 |
総研大甲第1187号 |
| 研究科 |
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値 |
物理科学研究科 |
| 専攻 |
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値 |
08 機能分子科学専攻 |
| 学位授与年月日 |
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学位授与年月日 |
2008-09-30 |
| 学位授与年度 |
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値 |
2008 |
| 要旨 |
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内容記述タイプ |
Other |
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内容記述 |
Recently，various new fluoride crystals have been developed as host for solid-state tunable UV lasers. Cerium（Ce）doped laser materials have been developed for use in the direct and efficient generation of tunable ultraviolet（UV）laser using a UV pump source．These have emerged as convenient and compact laser sources based on the electronically dipole-allowed interconfigurational 5d-4f transitions of Ce<sup>3＋</sup>ions in wide band-gap fluoride crystals. They are especially attractive for ultrashort-pulse generation and amplifications in the UV region．Among these crystal Ce<sup>3+</sup>;LiCaAIF<small>6</small>（Ce：LiCAF）which was first reported by M.A.Dubinskii et al in 1993，is the first known tunable UV laser directly pumped by the fourth harmonic of standard Nd：YAG laser. It proved to have sustained high output due to the absence of solarization effects therefore leading to efficient and sustained high power laser emission. This crystal is typically grown by the Bridgman and Czochralski（CZ）methods. Part of the difficulty in developing new materials is the high cost and difficulty in producing large crystals by standard crystal growth methods. To economically and efficiently grown a large crystal with laser quality，the micro-pulling down（μPD）method modified for fluoride crystal growth is advantageous. Owing to a fast growth speed，a high quality crystal can be grown at a shorter time and at a lower cost compared with other melt growth schemes. Moreover, μ-PD method has the capability to control the shape of the grown crystal to produce fiber; rod; tube, and so on .In this thesis, successful growth of a laser-quality Ce:LiCAF crystal using the micro-pulling down method is described. To improve the Ce:LicAF laser quality we also described the numerical simulation for optical properties of Ce:LiCAF. This is the first Ce:LiCAF crystal to be grown by the μ-PD method, thus its basic optical properties have to be investigated. Primarily, given specified experimental parameters, the goal was to determine the important optical parameters of the Ce:LiCAF sample in order to design the appropriate experimental conditions. The properties that were investigated using numerical methods were radius, absorption coefficient, and absorption profile for specified given values of optical pump beam diameter, pump energy and an assumed refractive index for Ce:LiCAF. One way of possibly increasing the laser output power for the Ce:LiCAF laser oscillator is to design a multiple side pumping scheme. In the experiment, the prismatic cell was applied for the first time in this work to a solid state laser system. It can offer an improved laser output beam quality due to more uniform electric field distribution in the crystal. It could also reduce the risk of damage in the crystal. Moreover multi-pass pumping will yield high power. This pumping geometry is similar in principle to a prismatic cell that was previously used in dye laser and was applied for the first time in this work to a solid-state laser system. This will be especially important in designing a high energy optically pump Ce:LiCAF laser. The quality of the Ce:LiCAF crystal as a laser material was then experimentally evaluated. A slope efficiency of 10% for the one, two-side, and multiple side pumping configurations were achieved. The experiment also showed that the slope efficiency improved from l0% to 23% when the sample's output windows were cut at Brewster angle. It should be noted that the samples that were studied in this work did not have polished sides, thus, explaining the relatively low slope efficiency values. Maximum output pulse energy of 1 mJ at 290 nm is achieved with an absorbed pump energy of 6 mJ with a slope efficiency of 23%. The lasing threshold is 2.5 mJ, which corresponds to a threshold fluence of 10 mJ/cm<sup>2</sup>. The emission at 290 nm has a pulse width of approximately 4 ns. This is the first demonstration of lasing in the ultraviolet region from a μ-PD method grown fluoride crystal. The flexibility and lower cost of this crystal growth scheme will drastically reduce the cost of crystal growth. This improvement will strongly enhance the applications of Ce:LiCAF laser itself. |
| 所蔵 |
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値 |
有 |
要旨・審査要旨 (273.8 kB)
