臺灣博碩士論文加值系統

本論文在討論並研究及比較Nd:GdVO4 和 Nd:YVO4兩種晶體在二極體激發被動鎖模固態雷射中作為增益介質的輸出特性，在相同Nd離子濃度摻雜條件下，無論在連續波或是鎖模操作下，Nd:GdVO4都具有較高輸出功率、較大輸出轉換效率及較沒有輸出因熱效應造成之飽和現象。在鎖模特性比較上，Nd:GdVO4 也比Nd:YVO4 有較低的連續波鎖模臨界值(2cwth：2.7cwth)，而在低功率激發光源下（4.37 W），更展現較短脈衝(19.2ps：21.6ps)及較寬的頻寬(0.21nm:0.16nm)等特性，而在之後的二倍頻穩定度量測結果發現在高功率激發光源下，二倍頻訊號會因激發光源的提高而導致不穩定度跟隨提高，進而導致脈衝寬度變寬的現象，但在9.5 W 高激發光源下，所得到的脈衝寬度(30ps：38ps)與頻寬(0.24nm：0.18nm)結果仍舊以Nd:GdVO4有較佳的輸出特性，而在脈衝啟動時間的實驗結果中得知兩者最短的啟動時間皆落在100us左右，更發現其鬆弛震盪頻率（relaxation oscillation frequency）會隨激發光源的升高而增高的關係與理論預測符合，故歸納從所得到的結果和理論上都顯示具有較大頻寬、螢光散射截面及較佳熱傳導特性的Nd:GdVO4為一在1.06m波段很有潛力的的鎖模增益介質。

We characterize and compare the performance of cw and mode-locking operation between Diode-pumped passively mode-locked Nd:GdVO4 and Nd:YVO4 Lasers with a Saturable Bragg Reflector. With the same Nd ion doping in both gain media, higher output power, larger slope and conversion efficiency, and more unclear saturation due to thermal effect under high pumping condition were demonstrated in the Nd:GdVO4 laser gain medium compared to Nd:YVO4 both in cw and mode-locking operation. Furthermore, in mode-locking operation, lower cw mode-locking threshold (2 cwth：2.7cwth) was characterized. The shorter pulse width (19.2ps：21.6ps) and wider spectral bandwidth (0.21nm:0.16nm) also were demonstrated on low pumping power（4.37 W）. After characterization the SHG power fluctuation, we consider that pulse broadening was caused by the instability of SHG power as increasing pumping power. The shorter pulse width (30ps：38ps) and wider spectral bandwidth (0.24 nm:0.18nm) also were observed on high pumping power（9.5 W）. In the experiment of buildup dynamics of mode-locking Nd:GdVO4 and Nd:YVO4 lasers. We observed the shortest buildup time was also about 100us and the relaxation oscillation frequency will increasing as increasing pumping power. All the results obtained from Nd:GdVO4, were superior to those of Nd:YVO4, indicating that Nd:GdVO4 could be a promising gain media for Diode-pumped passively mode-locked solid state laser.

Content
Chinese abstract………………………………………………………………………..……..i
English abstract………………………………………………………………………………ii
Acknowledgement……………………………………………………….…………..………iii
Content…………………………………………………………….………………………... iii
Graphic content………………………………………………………………………………V
Chapter I Introduction and Motivation
1.1 Introduction………………………………………………………….…...………1
1.2 Motivation………………………………………………………....…....….……3
1.3 Organization of the thesis.……………….………………………..……...……...4
Chapter II Mode Locking of Lasers: Basic Principles and Mode Locked Mechanisms
2.1 Mode-locking……………..…………….………………………………………..5
2.1.1 Active mode-locking……………………………………………………...8
2.1.2 Passive mode-locking and the structure of SBR………………………….9
2.1.3 The etalon effect in mode-locking laser…………………………………15
2.1.4 Cavity configuration…………………………………………………….17
2.2 Pulse width Measurement………………………………………………………20
2.2.1 The interferometric autocorrelator………………………………………20
2.2.2 The intensity autocorrelator……………………………………………..22
Chapter III The characteristics of laser crystals Nd:GdVO4 and Nd:YVO4
3.1 Introduction………………………………………………………………..……23
3.2 The physical and optical properties of Nd:GdVO4 and Nd:YVO4 crystal……...23
3.3 Fluorescence spectra of Nd:GdVO4 and Nd:YVO4 crystal…………………….24
3.4 CW operation of Nd:GdVO4 and Nd:YVO4 laser……………..…….………….26
3.5 Discussion and conclusion………………………………………...……………29
Chapter IV The characterization of diode-pumped passively mode-locked Nd:GdVO4 and Nd:YVO4solid-state laser
4.1 Introduction……………………………………………………………………….30
4.2 The etalon effect in mode-locking Nd:GdVO4 laser……………………………...30
4.3 The effect of using cavity mirror…………………………………………………31
4.4 B-angle passively mode-locked Nd:GdVO4 and Nd:YdVO4 solid-state laser…...33
4.3.1 Comparison of mode-locking Nd:GdVO4 and Nd:YVO4 solid-state laser in low pumping power……………………………………………..…………33
4.3.2 Comparison of mode-locking of Nd:GdVO4 and Nd:YVO4 solid-state laser in high pumping power…………………………………………………….34
4.3.3 The power fluctuation of Nd:GdVO4 mode-locking and cw operation……36
4.3.4 Buildup dynamics of mode-locking Nd:GdVO4 and Nd:YVO4 laser…...…37
4.4 Discussion and conclusion………………………………………………..………38
Chapter V Conclusions and future works
5.1 Conclusions…………………………………….………………………..……..…40
5.2 Future works……………………………………….…………………..…………41
Reference.............................................................................................................76
Appendix..............................................................................................................79

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