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研究生： 游喬安
Yu, Chaio-An
論文名稱： 氦原子2S-3P飽和吸收光譜
Helium 2S-3P saturated absorption spectroscopy
指導教授： 崔祥辰
Chui, Hsiang-Chen
學位類別： 碩士
Master
系所名稱： 理學院 - 光電科學與工程學系
Department of Photonics
論文出版年： 2012
畢業學年度： 100
語文別： 英文
論文頁數： 63
中文關鍵詞： 氦原子 、飽和吸收光譜 、氣體放電
外文關鍵詞： helium, saturated absorption, gas discharge
相關次數： 點閱：81  下載：1 
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    • 都卜勒增寬效應經常在原子光譜的譜線上扮演著主要的增寬效應，尤其是在室溫原子的光譜中。為了要精確的量到原子譜線並且除去這些物理限制，光譜上免除都卜勒效應的技術被發展出來並應用在光譜學上，例如交錯原子束，雙光子光譜，飽和吸收光譜...等。在此篇碩士論文中的主題是以飽和吸收光譜為目標來觀測氦原子2S-3P的精細結構。我們首先用小型的氦原子氣體放電系統將基態1s2氦原子激發成1s2s激發態，密閉式的氦管壓力為300 mTorr ，管長為20 cm，接下來用1W波長為778 nm的紅光經由BIBO晶體倍頻成氦原子2S-3P共振頻率的389 nm紫光，使用都卜勒吸收的架構把紫光直接打過氦管將1s2s的氦原子激發到1s3p，並且成功的在388.94 nm尋找到其吸收譜線,其吸收訊號半高寬為4.6631 GHz，管內原子溫度經計算約為285°K

    Doppler broadening is usually the dominant contribution to the observed width of lines in atomic spectra, usually at room temperature. The techniques of Doppler-free laser spectroscopy overcome this limitation to give much higher resolution. There are some techniques used for this limitation to give much higher resolution. There are some techniques used for this purpose: the cross-beam method, two-photon spectroscopy and saturated absorption spectroscopy. In this thesis, we based on the saturated absorption spectroscopy for the target to observe the fine structure of 4He 2S-3P spectrum. At first, we use small size helium discharge system, which 4He cell is 20 cm long and 300 mTorr, to excite 1s2 state atoms to 1s2s state. Next, let 1 W, 778 nm laser beam pass through BIBO crystal to achieve frequency doubling which is resonant frequency of 4He 2S-3P transition. And we observe the Doppler broadened absorption signal at 388.94 nm, the FWHM of absorption signal is 4.6631 GHz and atoms temperature in cell is about 285°K.

    ABSTRACT I 論文摘要 II 致謝 III LIST OF FIGURES VI LIST OF TABLES IX CHAPTER 1 1 INTRODUCTION 1 1.1 RESEARCH BACKGROUND 1 1.2 HISTORY OF SATURATED ABSORPTION SPECTROSCOPY 2 1.3 OVERVIEW OF THE THESIS 2 CHAPTER 2 4 THEORETICAL BACKGROUND 4 2.1 INTRODUCTION OF HELIUM ATOMS 4 2.2 HELIUM ATOMIC FINE STRUCTURE 7 2.2-1 term state 7 2.2-2 Hamiltonian 9 2.3 DOPPLER-FREE SATURATED ABSORPTION SPECTROSCOPY 12 2.3-1 Basic laser absorption spectroscopy 12 2.3-2 Doppler Broadening 13 2.3-3 Saturated absorption 16 2.4 FREQUENCY DOUBLING BY PPLN 25 2.4-1 PPLN Technology 25 2.4-2 Nonlinear Polarization 28 2.4-3 Second Harmonic Generation (SHG), Frequency Mixing and Phase-matching 30 2.4-4 Quasi-Phase Matching (QPM) 34 2.5 HELIUM DISCHARGE SYSTEM 37 CHAPTER3 41 EXPERIMENTAL SETUP 41 3.1 HELIUM DISCHARGE SYSTEM 41 3.1-1 Radio Frequency Generator 43 3.1-2 Radio Frequency Amplifier 43 3.1-3 Helium Cell and Vacuum System 43 3.2 FREQUENCY DOUBLING SYSTEM 46 3.2-1 PPLN Waveguide 46 3.2-2 Heating Controller 47 3.3 EXPERIMENTAL SETUP 49 3.3-1 Experimental Setup for Rubidium 49 3.3-2 Experimental Setup for Helium 52 CHAPTER4 54 EXPERIMENTAL RESULTS AND FUTURE WORKS 54 4.1 RUBIDIUM SATURATED ABSORPTION 54 4.2 4HE SATURATED ABSORPTION 56 4.3 CONCLUSIONS AND FUTURE WORKS 61 REFERENCES 63

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