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標題: | 外腔式摻鉻釔鋁石榴石雙纖衣晶體光纖雷射 External cavity Cr4+:YAG double-clad crystal fiber laser |
作者: | Ying-Jie Chen 陳英傑 |
指導教授: | 黃升龍 |
關鍵字: | 頻域光學同調斷層掃描技術(FDOCT),外腔式摻鉻釔鋁石榴石雙纖衣晶體光纖雷射, Frequency domain optical coherence tomography (FDOCT),External cavity Cr4+:YAG double-clad crystal fiber laser, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 頻域光學同調斷層掃描技術,(frequency domain optical coherence tomography; FDOCT )具高速掃描、高解析度以及掃描深度不再受限於光程改變之範圍等優點,FDOCT已成為現今之生醫光電領域與醫學研究已成為極重要之三維成像技術,而該技術所使用的光源為寬頻光源或是可調波長雷射,本論文以摻鉻釔鋁石榴石晶體光纖作為增益介質所研製出的晶纖雷射具備體積小、低閥值功率等優點,具有極高的潛力發展成FDOCT的系統光源。
我們藉由光學鍍膜技術於晶纖兩端鍍上高反射薄膜作為共振腔而產生雷射輸出,雷射的閥值功率為61.9 mW,是Cr4+:YAG雷射文獻中最低的七分之ㄧ,斜線效率可以達到7.75%,為了在腔內插出調頻元件,更近一步將系統共振腔拉長成為外腔式雷射系統並以球面鏡來作為輸出耦合透鏡,雷射輸出的斜線效率亦可達到6.65%,雷射的閥值功率為102.35 mW,同時以實驗來分析驗證雷射系統的損耗與傳輸模態,並透過雷射效率的模擬程式來計算出外腔式雷射系統的往返損耗,計算的結果為0.465 dB,系統可以額外承受的損耗為0.295 dB。 本論文提出兩種調頻雷射的架構,分別是V型外部共振腔調頻雷射系統與線型外部共振腔雷射系統。我們透過模擬分析來計算系統的往返損耗,評估哪一個架構較適合以實驗來驗證。V型外部共振腔調頻雷射系統的往返損耗為0.959 dB,若採用此系統晶纖長度至少要大於4 cm才可以產生雷射輸出;線型外部共振腔雷射系統往返損耗為0.755 dB,若採用此系統晶纖長度只要大於2.7 cm就可以產生雷射輸出,此外,線型共振腔系統架構也較簡單,所以實驗上採用線型架構作來產生可調波長雷射輸出。 Frequency domain optical coherence tomography (FDOCT) has many advantages such as high sweep rate, high axial resolution, and the scanning depth of system is no longer confined by reference arm movement range, therefore, it has become an important scanning technique in the bio photonics realm and medical research. The light source of FDOCT system can be broadband light source or tunable laser, in this thesis, we use Cr4+:YAG double-clad crystal fiber as gain medium to fabricate fiber laser is equipped with advantages of low threshold and compact system structure, so it has considerable potential to develop as light source of FDOCT system. By using coating technology, we have HR coating in the end face of fiber to build laser cavity. Threshold of laser system is 61.9 mW which is one seventh lower than literature and slope efficiency is 7.75%, respectively. In order to insert tuning component in laser cavity, external cavity laser system is achieved. Slope efficiency of system is also as high as 6.65%, and threshold becomes 102.35 mW, we also analyze both round trip loss and mode composition in laser cavity by experiment and simulation program. The round trip loss in external cavity laser system is 0.465 dB, and the system tolerance in loss is 0.295 dB. There are two tunable laser system proposed in this thesis, and it is V-shape cavity tunable laser system and Linear cavity tunable laser system. In order to assess which one is suitable for tunable laser system, we utilize simulation program to calculate round trip loss in laser system, respectively. Round trip loss in V-shape cavity tunable laser system is 0.959 dB. The length of fiber in system should be longer than 4 cm to generate laser output, and the alignment of system is difficult; round trip loss in Linear cavity tunable laser system is 0.755 dB. The length of fiber in this system should be longer than just 2.7 cm to generate laser output, and the alignment of system is easy, so we decide to adopt Linear cavity tunable laser system. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/25163 |
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顯示於系所單位: | 光電工程學研究所 |
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