利用光子晶體光纖製造長週期光纖光柵與超連續光譜

Abstract

在此篇論文，我們研究兩個主題: 第一，我們使用兩種鋸齒狀元件在光子晶體光纖上產生易變、可調的長週期光纖光柵。長週期光柵的中心波長、截止頻帶和穿透損失可以被大範圍的調整。我們在啾頻的長周期光柵上觀察到不等間距的干涉條紋，干涉條紋與交互作用的長度和長周期光柵兩端啾頻的程度有關，干涉條紋可以被消除，當我們減小交互作用的長度和啾頻的量。藉著利用這可調的長週期光柵，我們也對摻鉺光纖放大器作增益平坦化，並且也被證實。第二，我們也研究不同起始穿透率摻鉻釔鋁石榴石之摻釹釩酸釓固態激發的Q-開關 (Q-switched) 鎖模雷射。在輸出偶合鏡反射率R = 60%，飽和吸收體穿透率 T0 = 40%，並且激發功率15瓦時，有最大的Q-開關波包脈衝能量大約0.096 毫焦耳。最後，我們藉由高脈衝能量的Q-開關鎖模雷射耦合至光子晶體光纖，產生了950 nm至1450 nm寬的超連續光譜。

In the thesis, we investigate two topics: First, we report a method for generating versatile tunable long-period gratings (LPGs) in photonic crystal fibers (PCFs) by using two kind of corrugated devices. The central wavelength and rejection bandwidth of LPGs can be tuned over a broad spectral range with adjustable transmission loss. Spectral fringes with uneven spacing wre observed in chirped LPGs, depending on the interaction length and the amount of chirping between the two ends of the LPG, and can be removed by reducing interaction length and chirping. By utilizing a stress-induced LPG, gain flattening of an erbium-doped fiber amplifier has also been demonstrated. Second, We investigated the Q-switched and mode-locked operation in a diode-pumped Nd:GdVO4 laser by the permutation of initial transmittance T0 of Cr4+:YAG crystal. The highest pulse energy of Q-switched envelope about 0.096 mJ with output coupler of R = 60% and initial transmission T0 = 40% of a Cr:YAG saturable absorber can be obtained at the 15 W pump power. Finally, supercontinuum is generated by using a Q-switched mode-locked laser coupling into photonic crystal fiber.