Abstract
摘要:双纖衣掺鐿(ytterbium)光纖的快速發展可說是雷射及光纖領域的一大突破,它使得高功率的光纖雷射和高功率的光放大器成為可能。以往1012 W/m2等級之光強度,祇可靠大型且須水冷之脈衝雷射,才可能達成,如今以掺鐿雙纖衣光纖雷射,可以做在小如筆記型電腦的體積內,這將使得高強度雷射,可更為廣泛的應用於精密材料加工及非線性光學等領域,尤其掺鐿雙纖衣光纖雷射光具有極佳之光轉換效率及光束品質,因此,其高強度之光輸出及低散熱須求,將比目前所有雷射技術在高功率領域,都具有明顯之優勢。
目前耦合高功率半導體雷射至雙纖衣光纖分兩大技術主流,一是以側向光纖熔燒,達成多模光纖對多模光纖之耦光,此一技術雖相對成熟,但其價格較高;另一可能之解決方案為光纖側邊 V 形切口之耦光,此一技術架構可有效降低量產成本,本計畫將與貿隆機械公司及工業技術研究院南部分院規劃之雷射應用科技中心合作,共同開發一創新之側向光柵光激發之高強度雷射技術,以研製由單模光纖產生大於100 W等級輸出功率之掺鐿雙纖衣光纖雷射。我們亦將從速率方程出發,以波長為975 nm的雷射激發掺Yb3+光纖雷射進行數值模擬,全面分析雷射閥值功率、雷射輸出功率、增益等重要参數與激發功率、光纖長度、腔鏡反射率、掺雜濃度等参數之間的關係,採用高濃度掺Yb3+光纖與模擬所得結果比較以驗証模型。
總結來說,成功研發出高強度掺鐿光纖雷射技術,可實現高附加價值之微米等級精細加工技術,廣泛應用於國內已有相當基礎之平面顯示、通訊及軟性電子等產業,不僅可以提昇產業競爭力,並可促進光、機、電之整合,擴展高功率雷射之應用領域。
Abstract: The rapid development of double-clad Yb:fiber is a breakthrough in laser and fiber areas. It enables 1012 W/m2-level fiber lasers and optical amplifiers, which, in the past, only large and water-cooled pulsed lasers can produce such a high intensity light source. In addition, it can be arranged in a size similar to a standard notebook PC, and can be widely used in precision material processing and nonlinear optics. The optical conversion efficiency of the double-clad Yb:fiber laser is close to 80% with nearly transform limited beam quality, which results in apparent advantage compared to existing high power laser technologies.
So far, there are two main approaches for the coupling between pump laser diode to the double-clad fiber, one is using side pumping by multi-mode fiber to multi-mode fiber fusion; the other is V-groove on the perimeter of the double-clad fiber. The former technique is well established, but its fabrication cost is high. The latter is under development, but has the potential to lower the cost. This proposal is to develop a novel side coupling scheme using fiber grating. We will collaborate with SYSCO Machinery Corporation and the Laser Technology Center of the South Branch of ITRI. The goal is a 100-W high power Yb:fiber laser with single mode output. Numerical simulation on the rate equations of the laser dynamics will be employed to study the dependence of laser threshold, output power, and gain coefficient on pump power, fiber length, mirror reflectance, and doping concentration. Experimental verification will be performed to justify the numerical model.
In summary, the successful development of high intensity Yb:fiber laser can speed up the realization of high value-added micron-level precision machinery to be used in flat panel display, optical communications, and soft-electronics industries. It will strengthen the industry competence as well as facilitate the integration of optics, mechanics, and electronics to extend the applications of high power lasers.
Keyword(s)
光纖雷射
掺
鐿光纖
精密加工
fiber laser
Ytterbium doped fiber
Precision machining