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基于8 wt.%铥离子掺杂的硅酸盐玻璃,采用管棒法制备光纤预制棒,并拉制出纤芯直径为7 μm、包层直径为125 μm的掺铥硅酸盐玻璃光纤,光纤端面如图5(a)所示。光纤的纤芯折射率为1.60486,包层折射率为1.59913,NA为0.135。选用Corning公司的SMF-28e+光纤作为掺铥硅酸盐光纤的匹配光纤,两种光纤的参数见表1。利用Vytran GPX-3400光纤熔接平台,采取非对称熔接的方法进行有源光纤与匹配光纤的熔接。图5(b)为利用光学显微镜观察的掺铥硅酸盐玻璃光纤与石英光纤的熔接效果图,图中右侧为掺铥光纤。在泵浦光作用下,熔接点处仅有少量的紫色上转换荧光泄露,说明熔接质量较好,通过进一步测试可知该熔接损耗约为0.6 dB。
Figure 5. (a) End face of Tm-doped silicate glass fiber and (b) the fusion splice of silica fiber and Tm-doped silicate fiber
Parameter Tm-doped silicate fiber SMF-28e+ silica fiber Core diameter/μm 7 8.2 Cladding diameter/μm 125 125 Numerical aperture 0.14 0.135 Effective group index of core refraction @1310 nm 1.4676 1.6049 Table 1. Parameters of silicate fiber and matched silica fiber
基于掺铥硅酸盐玻璃光纤与石英光纤的高质量熔接,搭建了掺铥光纤放大器测试新型光纤的增益性能。利用2 cm高掺铥硅酸盐玻璃光纤对功率为1 mW、中心波长为1950 nm的种子源进行放大。记录不同泵浦功率下输出的信号光功率相对于不加泵浦时输出信号光功率的比值,计算出光纤的增益系数为1.7 dB/cm。
Research of novel highly thulium-doped silicate glass fiber and related fiber lasers
doi: 10.3788/IRLA20200424
- Received Date: 2020-11-04
- Rev Recd Date: 2020-12-02
- Publish Date: 2021-09-23
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Key words:
- highly thulium-doped silicate glass fiber /
- emission cross section /
- fluorescence lifetime /
- linear-cavity fiber laser
Abstract: Active fiber with high rare earth ion doping concentration has always been the key component of high-performance single-frequency fiber lasers, and silicate glass can be used to fabricate highly doped active fibers with excellent unit gains. Here, highly doped silicate glass with the thulium ion doping concentration of 8 wt.% was prepared by a high-temperature melting process, and its spectral characteristics and fluorescence lifetime were measured. Based on McCumber theory, the emission cross section of the glass was calculated. By the method of rod-in-tube, fiber preforms were prepared, and then the highly thulium-doped silicate glass fiber of 7/125 μm was drawn. Based on low-loss specialty fiber fusion splicing, the fiber unit gain was measured, and linear-cavity fiber lasers based on 2 cm and 8 cm novel thulium-doped fibers were investigated, where 1950 nm laser output of hundred-milliwatt-level power was obtained. This work has shown that under such a high doping concentration of 8 wt.%, which is the highest thulium doping concentration to date, thulium ions still have good luminescence properties in this novel glass host. The homemade highly thulium-doped glass fiber in this paper can be used to fabricate high performance single-frequency fiber lasers.