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系統識別號 U0026-0107201514372100
論文名稱(中文) 氦原子的2S-3P躍遷的絕對頻率量測
論文名稱(英文) Absolute frequency measurement of Helium 2S-3P transitions
校院名稱 成功大學
系所名稱(中) 光電科學與工程學系
系所名稱(英) Department of Photonics
學年度 103
學期 2
出版年 104
研究生(中文) 陳嘉緯
研究生(英文) Chia-Wei Chen
學號 l76024014
學位類別 碩士
語文別 英文
論文頁數 50頁
口試委員 指導教授-崔祥辰
口試委員-蔡錦俊
口試委員-王立邦
中文關鍵字 絕對頻率量測  倍頻  光頻梳 
英文關鍵字 Absolute frequency measurement  second harmonic generation  optical frequency comb 
學科別分類
中文摘要 絕對頻率量測在物理常數的修正以及量子電動力學的理論驗證上有極大的幫助。不僅如此,氦原子在結構上是第二簡單的粒子,因此更是探討複雜原子分子模型的一項好題材。在這實驗當中,我們利用自製的ECDL以及MOPA系統架設一套穩定且窄線寬的778 nm光源,此外,更將雷射鎖在自製的穩定共振腔,減少雷射頻率的不穩定性。
此外,為了量測2S-3P的躍遷,我們更利用倍頻晶體搭配良好的溫控來獲得389nm的藍光,在先前的實驗中,因為PPLN波導對於雷射的抗損壞能力較差,即便其效率為bulk晶體的3倍以上,但輸出的藍光功率局限於5 mW,這樣的強度尚低於飽和強度強度許多. 因此,我們向Raicol購入PPKTP晶體,他有著高非線性係數,高損傷閥值的特性,我們的MOPA系統有著約950 mW的高輸出功率,期望能獲得至少15 mW的藍光。此外,我們也替PPKTP晶體設計新的溫控平台,提高藍光強度的穩定性。除了前述在雷射系統和倍頻溫控系統優化外,在磁場隔絕的部份也做了加強,在μ-metal內的量測結果約為0.002 Gauss,更降低塞曼效應的影響。
為了穩定雷射的頻率飄移,我們將外腔雷射鎖在我們自製的Fabry-Perot共振腔上,頻率不穩度於是被降低到僅211 kHz。接著,更將雷射頻率間接的穩定在光頻梳上,一但改變光頻梳的重複率,外腔雷射的頻率就會跟著擾動,以此法來量測出高精確度的飽和光譜譜線,也提高的頻率量測的準確度。
英文摘要 Absolute frequency measurement is really helpful in the correction of physical constant and the verification of quantum electrodynamics. Helium is the second simple atom in the universe, so it is a suitable sample for study of many-body atom structure. In this thesis, we use a homemade external cavity diode laser to construct a master oscillator power amplifier system with stable frequency, narrow linewidth and high-power output up to 950 mW.
In order to measure the 2S-3P transitions, we first use the PPLN waveguide for 778nm frequency doubling. Though its nonlinear efficiency is 3 times higher than bulk PPLN, but its damage threshold is low that limit its maximum output power. We additional bought PPKTP crystal for SHG from Raicol Crystals Corporation. With 1W fundamental input power, theoretically we can obtain at least 15 mW 389 nm power. Besides, we designed a new oven in order for the temperature stability of SHG system to get stable intensity of blue ray. To reduce the short-term frequency fluctuation, we lock our ECDL to a homemade reference cavity which finesse is near 120, and the frequency uncertainty is depressed to 211 kHz.
The magnetic isolation of helium tube is also improved to minimize the Zeeman effect. The measurement result of magnetic field inside the cover made in μ-metal is approximate 0.002 Gauss. In the experiment, we’ll stabilize the master laser to an optical frequency comb via offset lock and measure the absolute frequency of the saturated absorption dip with high accuracy.
論文目次 Abstract II
Contents V
Figure list VII
Table list IX

Chapter 1 Introduction
1.1 Motivation 1
1.2 Previous Experiment 3
1.3 Overview of this thesis 4
Chapter 2 Overview of Principle
2.1 Introduction of Helium atom 6
2.2 2(_^3)S-3(_^3)P Transition of Helium 7
2.3 Line broadening 8
2.4 saturation intensity 11
2.5 Saturated absorption spectroscopy 12
2.6 Optical cavity 14
2.7 PID control servo loop 16
2.8 Second harmonic generation 18
2.9 Zeeman Effect 20
2.10 Radio Frequency discharge 22
2.11 Optical Frequency Comb 22
2.12 Mode-lock fiber laser 23
Chapter 3 Experimental setup and result
3.1 389 nm Light Source diagram 25
3.2 778nm External Cavity Diode Laser 26
3.3 MOPA 28
3.4 Frequency stabilization and frequency tuning 29
3.5 Second Harmonic Generation 33
3.6 Discharge system and magnetic isolation 35
3.7 Absolute frequency measurement
3.7-1 Setup of Erbium-doped fiber comb 37
3.7-2 Methods for absolute frequency measurement 41
Chapter 4 Conclusion and future work
4.1 Conclusion 46
4.1 future work 48

Reference 49
參考文獻 1. F.S. Pavone, F. Marin, P. De Natale, and M. Inguscio, First Pure Frequency Measurement of an Optical Transition in Helium: Lamb Shift of the 23S1 Metastable Level. Physical Review Letters, Vol. 73(1), 42, 1994
2. F. Marin, F. Minardi, F. S. Pavone, and M. Inguscio, Precision measurement of the isotope shift of the 2Sto 3P transition in helium, physical Review A. Vol. 49(3), R1523, 1994
3. Chen Jian You, Helium 2S-3P saturated absorption transitions, Master diss. , National Cheng Kung University, 2014
4. Donald C. Morton, Q.W., and G.W.F. Drake, Energy levels for the stable isotopes of atomic helium (Helium-4 I and Helium-3 I). Can. J. Phys. 84, 83-105, 2006
5. Wolfgang Demtröder, Atoms, Molecules and Photons - An Introduction to Atomic-, Molecular- and Quantum Physics 2nd. Springer, 2011
6. Kerry Ann Neal, A CONFOCAL FABRY-PEROT INTERFEROMETER FOR USE IN LIDAR RECEIVERS, Master diss., MONTANA STATE UNIVERSITY, 2009
7. Bahaa E. A. Saleh, Malvin Carl Teich, Fundamentals of Photonics 2nd ed., Chap. 21, Nonlinear optics., Wiley-Interscience, 2007
8. W. Ubachs, NON LINEAR OPTICS, lecture notes, University of Amsterdam,Department of physics and astronomy,2007
9. Franz Schwabl, Quantum Mechanics, Springer, 2007
10. S. S. Hodgman, R.G.D., L. J. Byron, K. G. H. Baldwin, S. J. Buckman, and A. G. Truscott, Metastable Helium: A New Determination of the Longest Atomic Excited-State Lifetime. Phys. Rev. Lett., 103(5), 2009
11. Jun Ye, Steven T. Cundiff, Femtosecond Optical Frequency Comb: Principle, Operation and Applications. Springer, 2005
12. Guan, Yu-Chan., Multi-heterodyne Spectroscopy with Dual Fiber Combs Referenced to Microwave Frequency Standard. Master diss. , National Tsing Hua University, 2012.
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