基於非線性光纖環與主動相位調變之偏振保持鎖模摻鉺光纖雷射

Abstract

在此論文裡我們主要研究基於非線性光纖環之偏振保持鎖模摻鉺光纖雷射，由於起始架構之被動鎖模雷射僅能產生類雜訊脈衝鎖模，所以我們在非線性光纖環裡加入相位調變器，藉由改變相位調變器的調變振幅來調變非線性光纖環的相位偏壓點，從而也能來調變非線性光纖環的穿透率偏壓點，成功產生單一脈衝鎖模。為了最佳化鎖模品質，我們進一步移除主迴路的帶通濾波器，同時也藉由改變相位調變器的調變頻率及調變振幅來產生不同的鎖模狀態。我們可以在這個雷射上觀察到2、4、6、8、10以及12 GHz的諧波鎖模和2、5、10 GHz的約分諧波鎖模。此外我們也可觀察到透過調變頻率的些微改變，雷射的中心波長會跟著平移，利用調變頻率與波長移動的相對比率我們可以推估出光纖雷射的整體色散值，然後利用加入適當色散補償光纖成功獲得接近ps的最短脈衝寬度。

In this thesis work we mainly study the polarization maintaining mode-locked Er-doped fiber laser based on a nonlinear fiber loop. Since the initial passive mode-locked laser setup can only generate noise-like pulses, we insert a phase modulator in the nonlinear fiber loop to adjust the nonlinear fiber loop transmission by tuning the modulation amplitude of the phase modulator. Single pulse mode-locking is successfully achieved. To further improve the mode-locking performance and to increase the possible mode-locking states, we remove the optical band-pass filter in the main fiber loop. After this change, we can observe the harmonic mode-locking at 2, 4, 6, 8, 10 and 12 GHz, and the rational harmonic mode-locking at 2, 5 and 10 GHz. We can also observe that the center lasing wavelength will be shifted if the modulation frequency is slight tuned. The relative ratio between the wavelength tuning range and the modulation frequency tuning range can be used to estimate the net dispersion in the fiber laser cavity. By inserting a suitable section of dispersion compensation fibers, we finally achieve the shortest ps pulse width from the studied fiber laser setup.