本論文之研究係在探討分佈式回授(DFB)結構於光參數震盪器之進展。由於 355 nm紫外光對於摻鎂鈮酸鋰能產生光折變效應而改變其折射係數，故使用此 355 nm之干涉儀寫入材料中使之產生週期性的折射係數改變(光柵結構)，再藉由532 nm泵浦光產生之OPG訊號去探測此週期性調製，並產生OPO之效果。

摻雜5%氧化鎂之鈮酸鋰，此材料相較於共熔(congruent)鈮酸鋰提供了更佳的光折變特性與更快的載子移動速度。此一材料，藉由Type-I的相位匹配之二階非線性光參數產生器於532 nm奈秒泵浦光，產生了寬廣之817.5 nm~1.52 μm之頻寬光源訊號。為了能達成可調式共振腔結構，即可調式週期性光柵結構，吾人研究發現透明導電薄膜 氧化銦錫，藉由三倍頻Nd:YAG之奈秒雷射照射後，可藉由雙光子吸收效應產生暫態光柵，而此光柵深度約為 135 nm，而根據本實驗結果，此光柵週期可從193.6 nm 調製到 766.7 nm，對應之共振波長為 890 nm~2.5 μm是一個非常廣泛並可實際應用的波段，此一發現成果，可用於未來DFBOPO於光波導之研究發展。最後，我們將現有實驗成果結合理論模擬，來去探討DFBOPO在摻鎂之鈮酸鋰之研究影響。

In the thesis, we have investigated on distributed feedback structure toward optical parametric oscillation. In order to fabricate a grating structure in the nonlinear gain medium such as MgO: LN, we used nano-second 355 nm UV pulse laser with interferometer technique to induce a periodical refractive index modulation (grating) structure, and this phenomenon is generated by photorefractive effect. Also, we demonstrated an optical parametric generation in MgO: LN which is used to detect the DFB structure.

In our knowledge, Mg-doped LiNbO3 is better than pure congruent LiNbO3 with low noise, fast photorefractive response time, higher photorefractive sensitivity and optical damage threshold. We demonstrated a type I phase matching optical parametric generation with pump 532 nm by changing the temperature of the crystal from 200.7 to 106.5℃. The results shows a wide tuning range of signal and idler from 817.5 to 1523 nm.

In order to design a tunable resonated cavity structure which means a tunable grating structure, we investigated on Indium Tin Oxide (ITO). In the experiment, when we pump a 355 nm UV with interferometer pattern, we discovered that there is a transient grating structure in the ITO by two-photon absorption. The maxima value of the refractive index change in ITO is ∆n=4.1×〖10〗^(-3). The tunable grating period in our interferometer setup is widely from 193.6 nm to 766.7 nm, which means the resonated wavelength is from 890nm to 2.5 μm. This particular transient grating result may give a chance on DFB OPO wave guide in future.

Furthermore, in theoretical simulation, we combined the coupled-wave theory with DFB theory to discuss the longitudinal mode selectivity and parametric threshold gain, also we modified the simulation with considering the absorption term completely. At last, we used the present experimental results and then combined it into the theory. To understand the physics and the opportunity for application.

Table of Contents
Abstract I
Abstract in Chinese III
Table of Contents V
List of Figures VIIII
Chapter 1: Introduction 1
1-1 Motivation 1
1-2 Nonlinear Optics 2
1.2.1 Material Excitation 2
1.2.1.1 Pyro-electric effect 5
1.2.1.2 Photorefractive effect 8
1.2.1.3 Directly laser induced Kerr effect 11
1-3 Grating 12
1.3.1 Types of the Gratings 12
1.3.2 Permanent and Transient gratings 13
1.3.3 Grating Creation 14
1.3.4 Grating Detection 17
Chapter 2: Optical Parametric Generation in 5% Magnesium-doped Lithium Niobate 22
2.1 Introduction 22
2.1.1 Sellmeier Equations 23
2.1.2 Phase Matching 25
2.2 Optical parametric generation 28
2.3 Experimental result and numerical calculation 30
2.3.1 Temperature and wavelength bandwidth 32
2.3.2 Measured spectrum of Type-I OPG conversion 36


Chapter 3: Transient grating in Indium Tin Oxide 37
3-1 Introduction 37
3-2 Two-photon absorption 37
3-3 Experimental setup and result 40
3.3.1 Analysis of Pump source in Michelson interferometer 41
3.3.2 Detection of interference pattern in photography process 43
3.3.3 Fabrication of Transient grating in Indium Tin Oxide thin film 47
3.3.4 Analysis of Transient grating in ITO 51
Chopper Technique 51
Polarization 54
The diffraction efficiency and refractive index change 56
Surface topography using Scanning Electron Microscopy (SEM) 59
3-4 Summary 63
Chapter 4: Coupled-wave theory and simulation result of distributed-feedback optical parametric oscillators 64
4.1 Coupled-wave theory 65
4.2 Simulation result 67
Chapter 5: Conclusions and Future work 74
5.1 Conclusions 74
5.2 Future work 75
Reference 76

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