微小化雙鏡式Yb3+:YAG環型固態雷射之研究

Abstract

以Yb3+:YAG作為增益介質，可利用其能階結構簡單、無受激態吸收及上轉換效應等寄生效應、僅8.6%的量子缺陷有利於高效率操作；吸收頻寬與放射頻寬皆寬、上能階生命期長等優點，而達成高效率雷射。雙鏡式環型共振腔由一組曲率半徑相同的平凹透鏡所組成，具有構造簡單、體積小、校準容易的特性。 結合Yb3+:YAG與雙鏡式環型共振腔的優點，並利用舊有之雙鏡式環型共振腔研究成果為基礎，成功的完成了微小化雙鏡式環形共振腔之初步研究與未來發展之評估。實驗方面，在鏡面曲率半徑為7.63 mm、體積僅為1.47 cm3之微小化雙鏡式環形共振腔結構中，實現幫浦功率閥值僅為0.7 W之立體8字型環型路徑；模擬方面，利用軟體輔助，對幫浦光在腔內聚焦尺寸及像散等特性做出模擬與分析，並與實驗結果做比較；同時，軟體輔助也應用於共振腔內雷射路徑解的模擬分析，驗證雷射路徑之理論計算；理論計算方面，在對稱雙鏡式環形共振腔架構之外，將探究與分析非對稱雙鏡式與拋物面雙鏡式環型共振腔之雷射路徑、穩定度等特性。 微小化雙鏡式環型共振腔的研究終極目標為發展出無須調整光路即可作用之環型雷射，我們將利用本研究所獲得之實驗、模擬以及理論計算等成果，做出合理之評估。

There are many merits of utilizing Yb3:YAG as laser gain medium for efficient operation and diode pumping, such as simple energy levels, no excited-state absorption, no upconversion , low quantum defect, broad absorption bandwidth, broad emission bandwidth, and long upper-state lifetime. Two identical spherical mirrors form the ring cavity which is simple, tiny and easy for alignment. With the advantages of Yb3:YAG and two-mirror ring cavity, and based on our previous effort on the two-mirror ring laser research, the initial research and evaluation of future development are accomplished. In experiment, a non-planar-8 laser path is achieved in a two-mirror ring cavity which is as small as 1.47 cm3 in volume and composed of two .7.63 mm radius-of-curvature spherical surfaces. In simulation, softwares are utilized to analyze the pumping beam size for mode matching and to simulate the laser path in cavity. In addition to the symmetric two-mirror ring cavity, asymmetric and paraboloidal structures are proposed and analyzed. The ultimate goal of two-mirror ring laser project is alignment-free two mirror ring laser. Based on the present experimental results, and theoretical analyses, a reasonable evaluation for alignment free laser is given.