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研究生:楊勝方
研究生(外文):Yang, Sheng-Fang
論文名稱:氦原子三重態的2S至3P精密光譜量測
論文名稱(外文):Precision Measurement of Helium Triplet 2S to 3P Transition
指導教授:王立邦王立邦引用關係
指導教授(外文):Wang, Li-Bang
口試委員:施宙聰劉怡維
口試委員(外文):Shy, Jow-TsongLiu, Yi- Wei
口試日期:2017-08-28
學位類別:碩士
校院名稱:國立清華大學
系所名稱:物理學系
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2017
畢業學年度:106
語文別:英文
論文頁數:45
中文關鍵詞:氦原子光譜三重態
外文關鍵詞:HeliumSpectroscopyTriplet
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本論文中,我們使用自製的外腔二極體雷射當作種子光源,其波長為778nm,經由一個Newport製造的Tapered amplifier放大其功率後,我們可以得到超過500mW的功率;我們把一部分的光打進一個波導式的PPLN,將778nm的雷射光倍頻成389nm的光源,然後利用此光源進行氦原子2 3S到3 3P的飽和吸收光譜;同時另一部份的光源和我們實驗室的光頻梳系統做拍頻,再利用offset lock的線路將我們的雷射鎖在光頻梳上,我們就可以精確的量測出雷射和譜線的頻率。我們得到的結果為,23S1→33P1的中心頻率是770724725.990(235) MHz,23S1→33P2的中心頻率是770724066.748(112) MHz,然而因為原子和光在低氣壓時的作用和我們預期的不一樣,所以我們還需要做更進一步的量測和理論分析,來確保中心頻率的準確性。
In this paper, we used a homemade external cavity diode laser (ECDL) as our seed laser and its wavelength was 778 nm. Then, we used a commercial tapered amplifier (Newport TA-7600) to boost our power up to more than 500 mW. After the tapered amplifier, the laser beam was split into two beams. One was sent to a waveguide PPLN to double the frequency of 778 nm and the other one was beaten with the optical fiber comb system in our lab. We used the beam at 389nm to perform the saturated absorption spectroscopy and measured the transition of helium atom from 2 3S to 3 3P. The absolute frequency was measured by the fiber comb system. We used the beat frequency between the ECDL and fiber comb system and an offset lock circuit to lock our laser on fiber comb system. Therefore, we could precisely know the absolute frequency of our laser and the targeted transition. The results of the transition frequencies were as follow: 23S1→33P1 f=770724725.990(235) MHz and 23S1→33P2 f=770724066.748(112) MHz. The precision of the results reached 〖10〗^(-10), but the accuracy of the absolute frequency had to be studied again and carefully because there were some effects between atoms and light, which could shift the center frequency of the transition.
Contents
摘要 i
Abstract ii
致謝 iii
Contents iv
List of Figures vi
List of Table x
Chapter 1 Introduction 1
Chapter 2 Basic Theories 3
2.1 Simple Simulation of Saturated Absorption Spectroscopy 3
2.1.1 Basic Model of Absorption Spectroscopy 3
2.1.2 Basic Model of Saturated Absorption Spectroscopy 6
2.2 Light-Pressure-Induced Frequency Shifts 8
2.3 Optical Fiber Comb 12
2.3.1 Brief History 12
2.3.2 Basic Theory 12
Chapter 3 Experimental Setup 15
3.1 Laser Source 16
3.1.1 778nm External Cavity Diode Laser 16
3.1.2 Second Harmonic Generation 19
3.2 Doppler-Free Spectroscopy 20
3.3 Fabry-Perot Interferometer 21
3.4 Optical Fiber Comb System 22
3.5 Beat Frequency and Offset Locking 24
3.5.1 Beat Frequency 24
3.5.2 Frequency Offset Locking System 26
Chapter 4 Data Analysis and Results 30
4.1 Effect of the Crossover Peak 31
4.2 Effect of Laser Power Change 32
4.3 Light-Pressure Effect 36
4.4 Our Results 38
4.5 Conclusion 41
References 45
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