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標題: | 短波長摻鐿光纖雷射及其倍頻之研究 Study of short wavelength Ytterbium-doped fiber laser and its frequency doubling |
作者: | You-Wei Fan 范祐維 |
指導教授: | 黃升龍(Sheng-Lung Huang) |
關鍵字: | 光纖雷射,摻鐿光纖雷射,纖心幫浦,倍頻,藍光雷射, fiber laser,Ytterbium-doped fiber laser,core pumping,frequency-doubling,blue laser, |
出版年 : | 2010 |
學位: | 碩士 |
摘要: | 光纖雷射比傳統雷射有輕、薄、短、小及散熱佳的優點,在各領域都有相當大的應用潛力。摻鐿光纖雷射利用雙纖衣結構,可達到70% 以上之斜率效率,因而有因低維修、低營運成本及極佳的光束品質,在光通訊的幫浦雷射光源、倍頻綠光雷射及倍頻黃光醫療用雷射等各波長目前均有利用。摻鐿光纖雷射與放大器在980 nm 以上的波長已有不少研究與開發,唯短於980 nm 波長則尚未有所突破;由於摻鐿光纖雷射之傳輸損耗低,因此有機會利用摻鐿光纖研製出短波長之雷射並倍頻得到高效率之藍光雷射,其應用如雷射電視之藍光背光源、儲存謀體、高解析度印刷等的市場將不可限量。
本論文討論了摻鐿光纖雷射之理論,深入研究長度、溫度、反射率對雷射輸出功率的影響,並預測了此準三階雷射在高溫時反而效率會提升,迥異於一般準三階雷射的特殊現象。實驗方面討驗證了光纖長度和端面角度對輸出頻譜間的波長轉換之關係,並成功地令從未有文獻報導的960 nm 波長之摻鐿光雷射達成出光,量測到雷射在高溫時效率確實較佳,攝氏101 度時的雷射閥值約107 mW,斜率效率約8.6%。我們以軟體研究實驗和模擬的誤差原因,討論了摻雜濃度、吸收與放射截面積、光纖纖心和內纖衣之折射率差、腔內損耗、螢光生命期、摻雜半徑與雷射系統間的物理關係,使用方程式限制並預測物理參數範圍,修正螢光生命期約為0.95 ~ 0.98 ms,腔內損耗約0.7 ~ 0.94 dB,並設計實驗證實共振腔因增益光纖與被動式光纖間的模場不相稱而使得熔接損耗高達0.82 dB。最後我們使用此960 nm 輸出之摻鐿光纖雷射配以LBO 非線性倍頻晶體做腔外倍頻得到波長480 nm 的藍光雷射。 Compared to traditional lasers, fiber laser has the advantages of more compact and better heat dissipation. Therefore, it plays an important role in several fields. The Ytterbium-doped fiber laser (YDFL) achieves slope efficiency higher than 70 % by using the structure of double-cladding fiber, therefore, it has a good beam quality with lower operating costs and maintenance fee. It can be used to be the source of Erbium-doped fiber laser (EDFL) in optical communication, the gain medium of frequency-doubled green and yellow lasers. For YDFL, laser of wavelengths above 980 nm has been developed, but not surmounted yet for shorter wavelengths. Due to the low propagation loss of Yb-doped fiber, it is possible to use the YDFL to produce a laser at the low gain and short wavelength region for obtaining a frequency-doubled blue laser, which is good for many industries, such as the source of blue light of laser TV, storage media, and high resolution printer, etc. In this thesis, we study the theory of fiber laser, including the effects of fiber length, temperature, and reflection on the laser output power. It is predicted that the laser can have a better efficiency at higher fiber temperature, which is quite different form typical quasi-three level lasers. We clarify the relation of the length and facet angle of fiber on the spectra experimentally, and let the 960 nm-YDFL lase successfully, for the first time.The efficiency was better in higher temperature as predicted. The threshold pump power was 107 mW and the slope efficiency was 8.6% at 101 oC. Computer software was used to evaluate the experimental error, and discuss the physical relations of concentration, absorption and emission cross-sections, the difference of refractive index between fiber core and inner cladding, fluorescence lifetime, intra-cavity loss, and doping radius. The fluorescence lifetime and intra-cavity loss were modified to be 0.95 ~ 0.98 ms and 0.7 ~ 0.94 dB, so that the simulation and experiment can have good agreement. And then we designed an experiment to prove that the splicing loss between gain fiber and passive fiber was 0.82 dB due to the mode mismatching caused from different mode field diameters. Finally, we used this 960 nm-YDFL and LBO to obtain a frequency-doubled blue laser externally. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/22261 |
全文授權: | 未授權 |
顯示於系所單位: | 光電工程學研究所 |
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