近年來，超短脈衝雷射在眾多領域和應用上都具有非常重要的腳色。而將雷射脈衝壓縮和波長轉換同時間地在非線性晶體內進行的機制，便成為了非常受矚目的重要研究課題。舉例來說藥學分析、生物科技、材料處理、雷射加工、生物影像以及環境檢測等等，大多引入超短脈衝的設計。此項技術的發明，將帶給眾多領域的研究在技術成面上，擁有大幅度優越地進步提升和無庸置疑的影響。
在這篇論文裡，我將提出一種方法來產生超短脈衝。我是利用非線性光學中透過光參數產生和光參數放大的非線性機制，它不但可以有效的將脈衝轉換波長，同時也可以造成脈衝的壓縮。透過對這種非線性過程的電腦數學模擬結果，可以得到比轉換前之泵浦更高的訊號尖峰功率和超過九十倍的脈衝寬度壓縮成果。這項卓越的成果，是來自於脈衝在非線性晶體內的群速度分離效應和光參數增益隨著泵浦強度指數成長的效應。接著我更進一步模擬額外加輸入一組拍頻雷射的種子訊號，將光參數產生過程進化成光參數放大過程，更可由於側邊頻率的產生和鎖模效應產生更大的脈衝壓縮效應。
在這篇論文中，不僅提到電腦數學模擬的結果，更提出清楚的物理解釋說明以及簡短的自相關儀的設計，以便將來更進一步的完成實際的實驗架設。我誠摯的希望這篇論文可以為所有投入該項相關領域的研究者提供最大的幫助與資料提供，同時也真心地希望該項技術的延伸和應用可以帶給人類生活更大的進步。

Simultaneous laser pulse compression and frequency down conversion in nonlinear crystals is a topic that draws a particular attention nowadays. Laser sources with a femtosecond pulse width are important for a variety of applications in the fields of material processing, biotechnology, medicine, environmental monitoring, and ultra-fast chemistry. These techniques make a superior progress and a significant influence to a mass of researches.
Methods of ultra-short pulses generation through optical parametric generation and optical parametric amplification of a laser beat wave are described. Numerical simulation shows as much as 90 folds pulse compression in the generated signal laser pulse with a peak power exceeding the pump one. The group velocity mismatch effect and the exponential gain for the OPG process contributed to the pulse compression. The pulse width will be further compressing due to the phase locked side band generation in the beat wave OPA process.
Not only the simulation result is showed, but the clear physical concepts are also described in this dissertation. I hope sincerely this thesis will be contributive to the research in this field, and the expansions of my thesis will be conductive to the human life.

Table of Contents


CHAPTER 1 INTRODUCTION 1
1.1 MOTIVATION 1
1.2 QPM NONLINEAR FREQUENCY CONVERSION PROCESS 2
1.3 CONTRIBUTIONS OF THIS DISSERTATION 6
1.4 REFERENCES 6
CHAPTER 2 PULSE COMPRESSION MECHANISM OF OPTICAL PARAMETRIC GENERATION 7
2.1 INTRODUCTION 7
2.2 COUPLED WAVE EQUATIONS 7
2.3 SIMULATION RESULTS 9
2.4 SUMMARY 19
2.5 REFERENCE 20
CHAPTER 3 PULSE COMPRESSION MECHANISM OF BEAT WAVE OPTICAL PARAMETRIC AMPLIFICATION 21
3.1 INTRODUCTION 21
3.2 THEORY 22
3.3 SIMULATION RESULTS 25
3.4 SUMMARY 37
3.5 RERFERENCE 38
CHAPTER 4 FUTURE WORK 39
4.1 AUTO-CORRELATOR 39
4.2 CONCLUSION 43
4.3 RERFERENCE 44








List of Figures

Figure 1.1 The illustration of the OPG process 4
Figure 1.2 The coecept of GVM effect 5
Figure 2.1 The extraordinary refractive index of PPLN under 9
Figure 2.2 The relation of GVD parameter and wavelength for PPLN under 10
Figure 2.3 The compressed signal pulses under different pump power which pump is at 1064 nm and signal is at 1550 nm 13
Figure 2.4 The compressed signal pulses under different pump power which pump is at 1064 nm and signal is at 1550 nm 16
Figure 2.5 The compressed signal pulses under different pump power which pump is at 1064 nm and signal is at 1550 nm 16
Figure 2.6 The fitting curve of the three results described in this chapter 18
Figure 3.1 The spectral amplitude and the temporal amplitude of beat wave 23
Figure 3.2 The scheme of cascaded process for the beat wave seeding OPA. 24
Figure 3.3 The intensity distribution and the spectral amplitude of the pump for the case of continuous seeding sine wave 27
Figure 3.4 The intensity distribution and the spectral amplitude of the signal for the case of continuous seeding sine wave 27
Figure 3.5 The intensity distribution and the spectral amplitude of the signal for the case of seeding beat wave with frequency shift at 30GHz. 30
Figure 3.6 The intensity profile of the output signal and initial pump for the case of seeding beat wave with frequency shift at 30GHz. 30
Figure 3.7 The intensity distribution and the spectral amplitude of the signal for the case of seeding beat wave with frequency shift at 300GHz 32
Figure 3.8 The spectral amplitude and spectral phase of the output signal for the case of seeding beat wave with frequency shift at 300GHz 32
Figure 3.9 The intensity profile of the output signal and initial pump for the case of seeding beat wave with frequency shift at 300GHz. 33
Figure 3.10 The case with seeding beat cosine wave with frequency shift at 30 GHz. 34
Figure 3.11 The case with seeding beat cosine wave with frequency shift at 300 GHz 34
Figure 3.12 The case with seeding beat cosine wave with frequency shift at 250 GHz, and the seeding power is 100 mW 36
Figure 3.13 The case with seeding beat cosine wave with frequency shift at 30 GHz, and the seeding power is 200 mW 36
Figure 4.1 The relation between the wavelength and dispersion coefficient for CLN . 40
Figure 4.2 The refractive index versus wavelength for CLN @300K 41
Figure 4.3 The layout of autocorrelator 43


List of Tables


Table 2.1 The comparison of the three different cases in OPG process. 17

Table.3-1 The comparison of the two different cases in OPA process 37

Table 4.1 The comparison of three nonlinear crystals 40

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