钬单掺双包层大芯径玻璃光纤的设计、制备及激光性能研究

Ho3+ doped fiber laser operating around ~2.1 micron can find a number of important applications in medicine, spectroscopy,remote sensing, eye-safe lidar, and next generation tele communication. However, the poor efficiency of ~2.1 micron fiber laser and the low output power,which are restricteded by pumping scheme,nonlinear effect and photodarkening, limit its practical applications. Comparing with Ho doped silica fiber, silicate glasses possess advantages such as low melting temprature, low cost, high rare earth solubility,low photodarkening effect, good beam quality with large core size,and so on. We propose to use silicate glass as the fiber matrix, design and fabricate large core double cladding fiber with high Ho doping concentration. The key techniques include developing the silicate glass, optimizing the Ho doping concentration by analysis of 1.95 micron absorption and ~2.1 micron emission properties;design of Numerial Aperture(NA) of the core and cladding glasses to achieve a large core fiber with good beam quality; investigating the performance of ~2.1 micron fiber laser by using a 1.9 micron in band pump scheme, and then optimize the fiber parameters. The purpose of this project is to build up know how on fabricating singly Ho doped, large core double cladding silicate glass fiber with low propagation loss, lay the first stone for the development and practical applications of ~2.1 micron fiber laser.

钬掺杂~2.1微米波段光纤激光器在生物医学、光谱学、遥感测量、激光雷达、下一代光通信等领域有着重要的应用前景。但是，受泵浦方式，非线性效应及光致暗化等因素影响，钬光纤激光的输出功率和效率不高，使实际应用受到限制。与传统掺Ho石英光纤相比，硅酸盐玻璃光纤具有低处理温度，低成本，高稀土离子溶解性，易于制备双包层光纤，光致暗化效应小，以及大芯径条件下输出光束质量好等优势。因此本项目以硅酸盐玻璃为光纤基质，设计、制备高浓度钬单掺大芯径双包层光纤，研究的核心问题包括优化硅酸盐玻璃成分，探索Ho3+掺杂浓度与1.95 微米吸收及~2.1微米发光性能之间的关系；设计大芯径光纤结构，掌握玻璃熔制，光纤预制棒制备及光纤拉制过程中去除OH基团等杂质的关键技术；用同带泵浦的方式研究单掺Ho大芯径光纤~2.1 微米激光输出性能，并优化光纤参数，为~2.1 微米光纤激光的开发和实用化打下基础。

开展玻璃光谱计算和成分优化工作，从玻璃形成理论和实验上对硅酸盐玻璃，锗酸盐玻璃，碲酸盐玻璃基质成分进行优化，初步确定了最优化基质玻璃配方。研究Ho离子在硅酸盐玻璃，碲酸盐玻璃，锗酸盐玻璃基质中的发射及吸收特性，初步确定最优化Ho离子掺杂浓度。制备了钬掺杂多组分玻璃光纤预制棒，并成功拉制光纤。进一步优化拉丝工艺，制备了大芯径掺Ho玻璃光纤，搭建了钬激光测试平台。成功制备了Ho3+单掺TWL双包层光纤，纤芯直径为14 μm，数值孔径为0.12。利用实验室自主搭建的1940 nm 掺Tm3+石英光纤激光器作为泵浦源，在一段9 cm长的Ho3+单掺TWL光纤中得到了最大功率34 mW的2040 nm激光输出，斜率效率约为3 %。这是迄今为止，唯一在碲酸盐氧化物玻璃中获得的Ho3+激光输出。