| 摘要: | 鈮酸鋰具有良好的高非線性係數、電光係數、及鐵電姓質，因此我們可以利用這些特性讓一小片的sample距有多功能的能力。利用鐵電性質，我們可以發展出極化反轉的製程；利用非線性係數，我們可以製造出任何波段的雷射；利用電光係數，我們可以應用電光調置產生脈衝雷射。而為了減少光折變的效應，我們應用了鎂摻雜鈮酸鋰晶體來改進光折變的缺點。應用準相位匹配(Quasi-Phase Matching)的原理及極化反轉製程，再結合低損耗的光學波導的製作，我們可以達到良好的轉換效率，產生二倍頻(Second-Harmonic Generation)綠光雷射。 本研究成功的利用外加高壓電場法在5mol./%鎂摻雜鈮酸鋰基材上製作出18μm的極化反轉三階週期。使其反轉面積與全部面積比例為50%(DUTY)左右。 本論文以退火式質子交換波導(Anneal proton exchange, APE)、軟質子交換式波導(Soft Proton Exchange, SPE)及逆退火質子交換式波導(Reverse Proton Exchange, RPE)三種波導且以波導寬度為5、6、7μm做為比較。軟質子交換式波導的轉換效率約為20%W^(-1) cm^(-2)，退火式質子交換波導約為30%W^(-1) cm^(-2)。軟質子交換式波導因深度不夠的關係，所以造成耦合的效率降低，只要增加質子擴散時間，即可改善此缺點。其轉換效率預測會大於退火式質子交換波導。因為退火式質子交換波導在製程過程中會造成死層(dead layer)，使得非線性係數破壞，因此在相同的耦合條件下，軟質子交換式波導的效率會比退火式質子交換波導更好。而在量測過程中，因光纖耦合波導的效率不好，所以量測泵浦光時會量到其他雜散光，因此所量測出的效率會較低，若改善量測方法，相信可以達到更好的轉換效率。 逆退火式質子交換波導在製程過程中遇到晶格產生破壞的現象，推論是因為氫離子過度累積造成退火時應力過大所產生的破壞現象。所以本論文將會提出對於此製程可行的方法，以改善晶格破壞的情況。 LiNbO3 has higher nonlinear, electro-optic coefficient and ferroelectric property. We could fabricate a single chip with more capability. By using ferroelectric property and lithography, we can develop the periodically inverted domain, Using the nonlinear coefficient, we can generate any wavelength of laser. Using the electro-optic coefficient, we can produce Q-switched pulse laser. For reduce the effect of photorefractive, we choose MgO:LiNbO3 crystal to improve it. Appling the theory of quasi-phase matching and the fabrication of periodically poled, and combination with low loss optic waveguide, we can get high efficiency of second-harmonic generation (SHG) for green light laser. We successfully fabricate these 18 um 3rd period domain inverse with 5mol/% Mg-doped Linbo3 substrate, the duty cycle about 50%. This paper makes a comparison among three kind of waveguide, Anneal proton exchange, Soft proton exchange, Reverse proton exchange. Conversion efficiency of soft proton exchange waveguide is about 20%W^(-1) cm^(-2), anneal proton exchange waveguide is about 30%W^(-1) cm^(-2). Due to the depth of the soft proton exchange waveguide not quite enough, coupling efficiency become low. If we increase proton exchange time, can improve this situation.It is predicted that conversion efficiency of SPE waveguide would better than APE waveguide. There is a dead layer result in APE waveguide fabrication process, meanwhile destroy nonlinear coefficient. Due to the bad fiber to waveguide coupling efficiency, therefore scattering of fundamental light and noise were detected to reduce it in the measurement. we will have better result by improving the measurement. In fabrication the reverse proton exchange waveguide, it will cause the crystal-destroyed. We supposed that the more hydrogen ions accumulate the more crack will occur in crystal when the annealing processed therefore, we proposed some of new fabrication method to improve this situation |
