臺灣博碩士論文加值系統

本論文主要研究各種非線性光學材料之非線性光學係數來探討這些材料進行光參數產生過程(Optical Parametric Process)的特性，並且於頻率轉換後產生一窄頻寬、高功率雷射光源以做光譜學研究。
首先使用光波長1064nm、峰值功率4kWatt的Q-switch Nd3+ : YAG laser來泵浦產生有機非線性光學材料Urea、DAST、MHB、MBST與無機非線性光學材料LiNbO3等之Powder SHG，藉以找出高非線光學係數材料。 所得的結果依非性係數高到低排列依次為LiNbO3 ，MBST，MHB，Urea；而DAST只有在波長700nm產生線寬100nm的螢光，由於它是高非線光學係數材料，我們將持續投入研究其特性。
接著用光波長1064nm，峰值功率11kWatt的Q-switch Nd3+ : YAG pulsed-Laser來做光參數產生(OPG)與光參數放大(OPA)實驗。在OPG實驗裡，把晶格週期28-31μm的PPLN，其溫度從35oC到165oC，每10oC掃一次光譜，做了OPG實驗光譜分析；接著在OPA實驗中，把晶體溫度控制在70oC，利用晶格週期30μm之PPLN，藉以放大波長為1.561μm的光波，並且利用了單光儀原理來把放大的光波線寬變窄，實驗裡放大的1.561μm光波的線寬為4 。由於OPA雷射峰值功率高、線寬窄，若以後能用於光聲波法上對於解析度與偵測極限上有非常大的幫助。
最後，利用CO2 Laser進行光聲波法的低濃度氨氣體檢測，實驗中可量測濃度可達sub-ppm等級，將可應用在環境監測上。

In this dissertation, we study and measure the nonlinear optical coefficients of various nonlinear optical materials. The property and feasibility of these materials used in optical parametric process are discussed. These researches have been contributed to the optical parametric generation/amplification technique to obtain a narrow-band and high peak power laser for spectroscopy.
To investigate nonlinear coefficients of optical materials, we first use a Q-switched Nd3+： YAG laser of optical wavelength 1064nm and peak power 4kWatt to generate powder SHG signal of several organic nonlinear optical materials including Urea, DAST, MHB, and MBST, and inorganic nonlinear optical material LiNbO3. With the known characteristics of LiNbO3, we can conclude the high nonlinear optical coefficients of these probed samples. The powder SHG efficiency from high to low is found to be as LiNbO3 , MBST, MHB, and Urea. As for DAST, due to its strong absorption at the SHG signal, it mere generates fluorescent light of optical wavelength at 700nm with a line width of 100nm.
Next a Q-switched Nd3+： YAG laser of higher peak power 11kWatt is used for driving the optical parametric generation(OPG) and optical parametric amplifier(OPA) processes. In OPG experiment, by varying the operation temperatures from 35oC to 165oC in 10oC increments, we scan the OPG spectra with a monolithic PPLN having eight different grating periods from 28μm to 31μm in 0.5μm increments. In OPA experiment, a 1561nm laser diode is used as the seeding source to be amplified with a 30μm-grating-period PPLN at the phase matching temperature 70 oC. In order to narrow down the 1561nm laser diode linewidth, we use optical grating to disperse it down to 4 . Since OPA laser is characterized in high peak power and narrow-band linewidth, it is very helpful for achieving high-resolution and low-detection-limit photoacoustic spectroscopy.
Finally we investigate the photoacoustic spectroscopy for low concentration NH3 with CO2 laser, a detection limit of sub-ppm has been achieved. This method can certainly be contributed to environment sensing.

Abstract
摘要
誌謝
目錄
圖目錄
表目錄
Chapter 1 簡介
1.1 動機
1.2 光學參數過程(Optical Parametric Process )
1.3 光聲波光譜學(Photoacoustic Spectroscopy)
1.4 概觀整本論文
Chapter 2 非線性光學材料
2.1 二倍頻諧波產生(SHG)理論
2.2 非線性光學材料的需求條件
2.3 粉狀的二次諧波產生(Powder SHG)實驗
2.3.1 Urea, MHB, MBST, DAST化學結構式
2.3.2 實驗與結果
2.3.3 分析與討論
Chapter 3 光波長1.561μm的光參數產生器與光參數放大器
3.1 光參數參產生器的基本理論
3.1.1 耦合波方程式
3.1.2 增益與頻寬
3.1.3 晶格週期性極化與晶體溫度調變
3.2 波長1.561μm準相位匹配光參數產生器(OPG)與放大器(OPA)
3.2.1 相位匹配溫度
3.2.2 實驗設置
3.2.3 分析與討論
Chapter 4 有潛力的應用：光聲波光譜學. 用CO2雷射證明其可行性
4.1 光聲波理論
4.1.1 熱的產生
4.1.2 聲波產生
4.2 實驗結構
4.2.1 共振腔的設計
4.2.2 實驗設置
4.3 實驗結果與討論
4.3.1 NH3的吸收強度譜線
4.3.2 共振腔的共振頻率
4.3.3 聲光法光譜量測結果
4.3.4 分析與討論
Chapter 5 未來展望
References
Appendix A Matlab M-file to Solve Sellmeier Equation
Appendix B Matlab M-file to Plot Gain Curve
Appendix C Matlab M-file to Plot the Relation between Grating Period and Wavelength
Appendix D Lock-in Data Storage Program

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