摘要:玻璃光纖的發展使得跨洲、跨國、城市間乃至家庭到家庭之光通訊成為可能,它深深的影響了我們在教育、工作、個人通訊乃至娛樂時的生活型態。目前,玻璃光纖的主要功能在提供一個低耗損的傳輸介質,本人實驗室所發明的以玻璃披覆之摻鉻晶體光纖具有單晶之摻鉻纖心及玻璃包覆之外纖衣,這種創新的光纖提供了前所未有的大於270 nm之超寬頻近紅外光輻射。一方面而言,這種超寬頻光源是未來寬頻且無所不在的光通訊之核心技術;另一方面而言,它開啟了超高縱向解析度之生物檢測及影像、高效率可見光之產生乃至其他各種創新應用的可能。
過去10餘年來,光電科技可說是國內乃至全球成長最快速的領域之一。在台灣,光電產值已達US$43 billions(大約1兆3仟6佰億台幣),此項巨大的成功在可預見的將來,仍將持續的高速發展,因為,光電科技在國內已蔚為風潮,新的技術及應用不斷的被開發出來。
本計畫所將推動的玻璃披覆晶體光纖,到目前為止,已成功展示了它在(1)超高解析光學同調斷層掃瞄術;(2) 超低閥值的摻鉻YAG雷射;及(3) 寬頻可調波長藍/綠光等應用之潛力。欲進一步開發出其商業化應用之可能,有必要從元件面及系統面加以改良,尤其是光學增益的提昇上。根據我們數值模擬結果顯示,更長及更均勻的晶纖是必須的,因此本計劃將強化我們的晶纖生長系統,由更高度的自動化控制提昇晶纖長度及均勻度。就系統架構而言,我們將採雷射加熱基座生長法及光纖抽絲塔兩項技術同步進行;就商業化應用而言,如何提昇半導體雷射耦光進入雙纖衣光纖之效率,亦極為關鍵,子計畫三將負責結合台積電之電子束微影術,開發側向耦光技術。就生物檢測及影像而言,摻鉻之翠綠寶石晶纖,其1.24 m之中心波長非常適合,將於子計畫四開發此晶纖。
為了驗證此一摻鉻雙纖衣光纖技術,我們將以我們新近開發出之光學同調斷層掃描儀當各子計畫之測試平台,包括:光學轉換效率、光功率穩定性、增益頻寬、橫模品質、色散特性及縱向解析度都將加以評估。跨領域之整合是實現此一高增益光纖之關鍵,因此,本計畫除總計畫外,將分成四個子計畫,由臺大光電所的黃升龍教授主持計畫之整合,他及中山大學光電所的鄭木海教授、臺大光電所的黃鼎偉教授及台灣科技大學光電所的葉秉慧教授將分別主持其中一項子計畫。臺大的雷射加熱基座生長設備及中山大學的光纖抽絲塔將充分支持4個子計畫的需求,共同藉由晶纖元件、數值分析建構及儀器科技等跨領域技術之整合,以期達成計畫目標。黃升龍教授除負責整合各子計畫外,將持續改善其雷射加熱基底生長系統;鄭木海教授將改良摻鉻晶纖預型體之製作及光纖提拉;黃鼎偉教授將研製以側向光柵改善半導體雷射對雙纖衣光纖之耦合術;葉秉慧教授將開發摻鉻之翠綠寶石晶體光纖,以使寬頻光源之中心波長更適於生醫檢測及影像之應用。
Abstract: Glass fiber enables optical communication across continents, countries, cities, and even homes. It impacts our life style in terms of education, working, personal communication, entertainment, etc. The main function of a glass fiber is to provide a low-loss transmission medium. Our invention of glass-clad Chromium-doped crystal fiber is a novel type of fiber, which has a single crystalline core doped with Chromium ions and cladded by glass. Such innovative fibers provide special characteristics, i.e. > 270 nm broadband emission, which has never been obtained by rare-earth-ion doped glass fibers. On the one hand, the broadband emission is essential for future broadband and ubiquitous optical communications; on the other hand, crystal fibers open new windows for applications in ultra-high axial resolution bio-sensing/imaging, efficient visible light generation, as well as other novel functionalities.
Photonics has been one of the fastest growing industries during the last decade both in Taiwan and around the world. Vigorous pace of progress on photonic technologies generated a US$40-billion (i.e. NT$1,360,000,000,000.) revenue for Taiwan in 2006. This success can be expected to continue well into the new century as more people and more appliances continue to be connected by more bandwidth at more places.
Using our proprietary glass-clad crystal fiber technology, we have proved the concepts of (1) broadband amplified spontaneous emission (ASE) for ultra-high axial resolution optical coherence tomography (OCT), (2) record-low threshold Cr:YAG lasers, and (3) broadly tunable blue/green laser generation. To realize or commercialize the applications of this technology, improvement at system level as well as at component level are needed for sufficient optical gross gain of the crystal fibers. According to our simulation, longer fiber length with better core-diameter uniformity is crucial to achieve high gross gain. The purpose of this proposal is to enhance our present crystal fiber growth system so that more advanced apparatus can produce high gross gain. Two approaches will be attempted: one is to enhance our present co-drawing laser heated pedestal growth (LHPG) system; another is to use the rod-in-tube method by fiber drawing tower. In addition, efficient launching diode laser power to the double-clad fiber core is also crucial to the practical utilization of Cr doped fibers. Finally, we will also make an attempt to develop Cr doped forsterite fiber because of its eminently suitable center wavelength, i.e. 1.24 m, for bio sensing applications.
To justify the performance of the Cr doped double-clad fibers, our newly developed bench-top OCT system will serve as a test bed for all the fibers and power launching technique developed from each sub-project. The conversion efficiency, power stability, bandwidth, transverse mode quality, dispersion, and axial resolution will be evaluated. Interdisciplinary efforts are essential to put together all the required techniques and demonstrate the high gross- gain crystal fiber. Except the main project, we will have four sub-projects under the leadership of Professor Sheng-Lung Huang (Institute of Photonics and Optoelectronics, National Taiwan University). He and Professors Wood-Hi Cheng (Institute of Electro-Optical Engineering, National Sun Yat-Sen University), Ding-Wei Huang (Institute of Photonics and Optoelectronics, National Taiwan University), and Ping-Hui Yeh (Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology) will each lead a sub-project. The team will be well supported by the LHPG and fiber drawing tower facilities in National Taiwan University and National Sun Yat-Sen University, respectively. The works of the four sub-projects are tied together by a common theme of crystal fiber devices, analyzing algorithms, and instrumentation technologies that can enhance the gross gain. Professor S. L. Huang will coordinate the integration of the interdisciplinary research groups as well as enhance the LHPG system. Professor W. H. Cheng’s group will be on fiber drawing tower development. The focus of professor D. W. Huang’s group will be on developing side launching grating for coupling pump diode laser to the double-clad fibers. Professor P. H. Yeh will evaluate the performance of Cr:forsterite double-clad crystal fibers.