全正色散鎖模摻鐿光纖雷射之研究

Abstract

本實驗成功地架設了一套全正色散鎖模摻鐿光纖雷射，雷射腔內沒有使用實體的光學帶通濾波片，以偏振加波鎖模機制達到鎖模，並利用鎖相迴路技術使重複頻率達到穩頻。此雷射可產生重複率40 MHz、平均功率160 mW、半高寬12.8 ps的脈衝輸出。之後經過自製前向泵浦摻鐿光纖放大器，平均功率可達420 mW。利用中空光子晶體光纖做腔外色散補償，可將放大後的脈衝壓縮到300 fs。將壓縮後的脈衝耦合入光子晶體光纖，產生960 nm到1370 nm的連續光譜，也在344 nm、429 nm、502 nm等處產生可見光契倫科夫輻射。最後我們利用鎖相迴路控制使鎖模雷射的重複率達到穩頻，迴授圈外重複率的追蹤穩定度在1 秒鐘為 。

An ultrafast all-normal dispersion mode-locked ytterbium (Yb) doped fiber laser with no practical, optical bandpass filter is developed and the stabilization of its repetition frequency is achieved by using phase locked loop (PLL) technique. Polarization-additive pulse mode-locking (P-APM) method is employed to achieve mode-locking. The all-normal-dispersion ocsillator generates 12.8 ps (FWHM) laser pulses with 160 mW average power at 40 MHz repetition rate. Nearly triple power amplification (~ 420 mW) is achieved after forward pumped amplification and the pulsewidth of amplified pulses are externally compressed in the hollow-core photonic crystal fiber to 300 femtoseconds. The compressed laser pulses are sent into a solid core photonic crystal fiber (PCF) to generate supercontinuum (SC). The bandwidth of generated SC covers from 960 nm to 1370 nm and additionally, Cherenkov radiation at 344 nm, 429 nm, and 502 nm are observed. Finally, PLL technique is used to stabilize the repetition frequency of the mode-locked laser and the measured tracking stability of the out-of-loop repetition rate of our laser is at 1 s.