鎖模摻鉺光纖雷射中的光固子現象

Abstract

本論文探討在鎖模摻鉺光纖雷射中的主要光固子現象，一方面可以利用光固子效應來實現高脈衝重複率、飛秒級的鎖模摻鉺光纖雷射，另一方面，也可以將鎖模摻鉺光纖雷射當作一個新的實驗平台，用來觀測和探討如光固子結合態之類的光固子現象。 在產生高重複率、超短脈衝序列這部分，被動諧波鎖模和非同步光固子鎖模都可以用來提高飛秒級鎖模摻鉺光纖雷射的脈衝重複率。尤其是利用非同步光固子鎖模的方式，可以從鎖模摻鉺光纖雷射直接產生重複率10 GHz、脈寬816 fs、超模抑制比高達70 dB以上的脈衝序列。而且利用非同步鎖模特有的偏移頻率之取出和鎖定，我們發展出一個簡單且經濟的方法來維持非同步鎖模雷射的長期穩定。利用此長期穩定雷射共振腔長的方法，GHz、飛秒等級的非同步鎖模摻鉺光纖雷射將具有經濟上的優勢。 在探索新的光固子現象這方面，光固子結合態可在被動或混和式頻率調變鎖模摻鉺光纖雷射中觀察到。尤其是在混和式頻率調變鎖模摻鉺光纖雷射中，我們能夠產生重複率高達10 GHz的新型穩定結合光固子對，並且相當於有1177個光固子對同時存在於雷射共振腔中。我們也已在理論上探討此光固子對的形成和穩定機制，所獲得的結果與實驗上的觀測相當符合。

The dissertation investigates the important soliton phenomena in mode-locked Er-fiber lasers. On one hand, the soliton effects can be employed to demonstrate sub-ps mode-locked Er-fiber lasers at high repetition rates. On the other hand, the mode-locked Er-fiber lasers can be used as a handy platform for investigating new types of soliton phenomena, including the soliton bound states. In the regard of demonstrating high-repetition-rate ultrashort pulses, passive harmonic mode-locking and asynchronous soliton mode-locking both show the ability to increase the pulse repetition rate of sub-ps mode-locked Er-fiber lasers. In particular, the 10 GHz 0.8 ps SMSR > 70 dB pulse train has been directly generated from an asynchronously mode-locked (ASM) Er-fiber soliton laser. We have also developed a simple and economic long-term stabilization method based on the deviation-frequency extraction and locking. With the scheme, sub-ps ASM Er-fiber soliton lasers with GHz repetition rates can have economic advantages for practical applications. In the regard of demonstrating new types of soliton phenomena, the soliton bound states have been observed both in the passively mode-locked and the hybrid FM mode-locked Er-fiber lasers. Most importantly, for the first time new stable bound soliton pairs at the 10 GHz repetition rate are observed experimentally in a hybrid FM mode-locked Er-fiber laser, in which there are 1177 soliton pairs simultaneously circulating in the laser cavity. The corresponding mechanisms for explaining the formation as well as the superior stability of these closely bound soliton pairs are theoretically investigated and experimentally examined.