臺灣博碩士論文加值系統

本論文的主題，在利用Z-scan技術研究簡單液體分子，甲醇和苯分子經由脈衝寬度28飛秒(fs)和波長 800 nm之雷射脈衝光照射下，產生的三階非線性光學特性。發現和使用皮秒(ps)和奈秒(ns)脈衝照射下，產生的三階非線性光學特性，截然不同。皮秒和奈秒下的呈現的是正透鏡效應，而在飛秒下的卻是負透鏡。經由擬合甲醇和苯的實驗數據，獲得其非線性折射率分別為n2 = -(8.0±0.1)×10-16 cm2/W和n2 = -(1.7±0.2) ×10-16 cm2/W。
首次嘗試提出其所產生的可能機制，由於短脈衝雷射場使分子產生偏極化，而短脈衝雷射場引發的電子響應，使得三階非共振的偏極化來不及反應，而引致次級波的產生。依據我們的分析，此因光場帶動液體分子電偶極矩所產生次級波，其相位比光場領先約180度，使得高斯光束的波前經過甲醇和苯時，猶如負透鏡的效果被扭曲。根據早先的實驗觀察，當雷射脈衝延展到皮秒時域，原子核鬆弛運動為主要貢獻，形成正透鏡的效果。因此，在超短次皮秒時域，此兩液體的非線性折射率為負值。

We present nonlinear refraction results for liquids methanol and benzene obtained with the Z-scan technique and 28 femtosecond (fs) 800 nm laser pulses. In contrast to the positive lensing effect obtained previously with picosecond and nanosecond laser pulses, a negative lensing effect is observed. The non-linear refractive index for methanol and benzene, obtained by fitting to their Z-scan curves, is determined to be n2=-(8.0±0.1)×10-16 cm2/W and n2=-(1.7±0.2) ×10-16 cm2/W respectively.
The associated mechanism is provided for the first time. Due to its extremely short duration the laser field interacts with valence electrons in the molecule. The third-order polarization arising from the non-resonant, delta-like response of valence electrons to the incident laser field and from the nuclear excitation which does not have time to relax within the pulse duration. The wave front distortion of the incident Gaussian laser beam is free of contributions from the nuclear motion and from resonances with the electronic motion. The manner the wave fronts are distorted by liquids methanol and benzene agrees with that done by a negative lens. As laser field lasts for much longer, say picoseconds, nuclear relaxation is expected to make significant contribution, leading to a positive nonlinear refraction as actually observed previously. From this we arrive at the conclusion, for the first time, that the nonlinear refractive indices of these two liquids are negative.

第一章 序論．．．．．．．．．．．．．．．．．．． 1
第二章 實驗裝置和實驗步驟．．．．．．．．．．．． 4
2.1實驗流程．．．．．．．．．．．．．．．．．．．． 4
2.2超短脈衝雷射．．．．．．．．．．．．．．．．． 6
2.3腔外色散補償．．．．．．．．．．．．．．．．． 9
2.4自相干儀及脈衝量測…………………………………… 14
2.5 Z-scan 實驗裝置架設和實驗步驟…………………… 17

第三章 非線性光學原理………………………………… 22
3.1非線性光學簡介………………………………… 22
3.2微觀態與巨觀態下的描述……………………… 23
3.2.1微觀態下的描述 ………………………… 23
3.2.2巨觀態下的描述………………………… 24
3.3線性與非線性吸收與折射效應………………… 27
3.4負透鏡效應的成因……………………………… 33

第四章 結果討論與未來展望…………………………… 36
4.1甲醇……………………………………………… 36
4.2苯………………………………………………… 42
4.3結論……………………………………………… 46
4.4使用Matlab程式擬和…………………………… 49
4.5未來工作與展望…………………………………… 53
參考資料…………………………………………………… 54
附錄
分子運動模型……………………………………………… 56

[1]M. Sheik-Bahae, A.A. Said, T.H. Wei, D.J. Hagan, and E.W. Van Stryland, IEEE J. Quantum Electron. QE-26 760 (1990)
[2]Audrea Gnoli, Luca Razzari, and Marcofabio Righini, “Z-scan measurements using high repetition rate lasers:how to manage thermal effects,” Optical Society of America, (2005).
[3]劉岱泯,國立中正大學碩士論文,”不同對稱性質的分子之非線性光學性質研究,” 國立中正大學 (2001).
[4]王志堅,國立中正大學碩士論文,”紫質分子在皮秒時域的非線性光學性質調查,”國立中正大學 (2002).
[5]R.L.Fork , O.E.Martinez, ”Negative dispersion using pair of prisms,” J.P.Gordon Opticcs letters,Vol. 9, No. 5, May (1984)
[6]C.Rulli re(Ed.), ”Femtosecond Laser Pulsers Principles and Experiments,” Spinger, (1998).
[7]陳震偉,國立中正大學碩士論文,”CS2與C2H4Cl2之量子干涉現象調查,” 國立中正大學 (2003).
[8]BAHAA E. A. SALEH,、MAVIN CARL TEICH, “Fundamentals of Photonics, ” New York , Wiley , (1991), Chap. 18 &19.
[9]Ralf Menzel, “Photonics,” (Linear and nonlinear interactions of laser light and matter) Springer , (2001), Chap. 4.
[10]Robert W. Boyd, “Nonlinear Optics,” Academic Press, New York, (1992), Chap. 9.
[11]M.Sheik-Bahae, A.A. Said, D.J. Hagan, T.H. Wei, J. Wang, J.Young, and E.W. Van Stryland, J. Opt. Soc. Am. B 9, 405 (1992).
[12]Richard P Feyman, Robert B. Leighton, and Matthew Sands, “The Feynman Lectures on Physics,” Addison-Wesley, Reading, Massachusetts, vol I, eq. (30.18), (1963).
[13]張耀文, 國立中正大學碩士論文,”探討不同雷射脈衝寬度下第三階非線性折射率異號的機制,” 國立中正大學 (2006).