摘要
光纤激光器是大功率激光、空间激光通信、引力波探测、地球磁力探测等国家安全与科学前沿领域的迫切和重大需求.稀土离子掺杂的高增益玻璃光纤是光纤激光器的核心工作介质.氟硫磷酸盐(fluoro-sulfo-phosphate,FSP)激光玻璃具有稀土溶解度高、受激发射截面大、光学光谱性质优异等特点,是高增益激光光纤的潜在候选.本文从玻璃形成区、玻璃结构与性质关系、掺稀土玻璃发光与激光角度系统研究了Al F_(3)-R_(2)SO_(4)-RPO_(3)/Zn(PO_(3))_(2)(R=Li、Na、K)系列新型FSP玻璃.结果表明,热力学方法有助于简便快速地确定玻璃形成区,为该类新型激光玻璃设计提供指导.通过固体核磁共振谱、拉曼光谱、差示扫描量热分析、耐久性实验等揭示了Zn(PO_(3))_(2)能够提高FSP玻璃的结构聚合度和阴阳离子相互作用强度,从而增强玻璃的抗析晶稳定性和化学耐久性等,为大尺寸玻璃制备和光纤拉制奠定基础.Er^(3+)/Yb^(3+)共掺FSP激光玻璃典型的Er^(3+):^(4)I_(13/2)→^(4)I_(15/2)跃迁(~1.5μm)的荧光寿命为5.9~7.5 ms,发射截面为8.5×10^(–21)~9.0×10^(–21)cm^(2),光谱品质因子最高为6.4×10^(–23)cm^(2)s,饱和强度最低为1.0×10^(7)W/m^(2),优于部分掺铒磷酸盐、氟磷酸盐激光玻璃.通过组分优化,本文制备了Er^(3+)/Yb^(3+)共掺FSP单模光纤,峰值增益达4.7 d B/cm@1535 nm.基于该光纤实现了阈值约为50 m W、斜率效率为11.3%的光纤激光.
Fiber lasers (FLs) with excellent beam quality,high reliability and compact structure are urgently demanded in the fields of national security and scientific research,such as high-power laser,free-space optical communication,and gravitational wave detection.These applications rely on rare-earth-doped high-gain glass fibers,which play critical roles in FLs.However,the rare earth solubility of commercial silica glass (~10;ions/cm^(2)) is restricted by its rigid structures.Thus,the active fiber fabricated by silica glass typically has low gain,which becomes a challenge for developing high-performance FLs.Phosphate-based glass is a promising candidate because it has higher solubility of rare earth (~10^(19)ions/cm^(3)) and larger emission cross-section compared with silica glass.By incorporating fluoride and sulfate into phosphate matrix,the fluoro-sulfo-phosphate (FSP) glass that combines the favorable spectroscopic properties of fluoride and sulfate glasses with the advantages of phosphate glass can be derived.The addition of fluoride reduces the linear and nonlinear refractive indices of phosphate glass,which is advantageous for operating FLs.The maximum phonon energies of fluoride(~500 cm^(2)) and sulfate (~990 cm^(2)) are lower than that of phosphate (~1200 cm^(2)).Therefore,sulfate and fluoride ions can tailor the local structures of rare earth and enhance radiative transition probability,leading to increased optical gain.Herein,this work systemically investigated the FSP glasses with the compositions of Al F_(3)-R_(2)SO_(4)-RPO_(3)/Zn(PO_(3))_(2)(R=Li,Na,K).Their glass-forming regions were determined under the guidance of thermodynamic calculation method.The dependence of properties on structure of the FSP glass was analyzed by solid-state nuclear magnetic resonance (NMR),Raman spectra,differential scanning calorimetry (DSC),durability test,etc.Then the luminescent properties of Er^(3+)/Yb^(3+)co-doped FSP laser glasses were characterized.Optimized laser glass was fabricated into high-gain fibers and an FL has been demonstrated.The results illustrate that the glass-forming regions of FSP systems can be quickly determined based on the thermodynamic calculation,which provides an effective and predictive method for designing novel laser glasses.Incorporating Zn(PO_(3))_(2)into FSP glass can enhance the interactions between cations and anions and increase the polymerization degree of glass structure,resulting in improved anti-crystallization ability and chemical durability,which is beneficial for preparing large-scale samples and drawing fibers.The Er^(3+)/Yb^(3+)co-doped FSP laser glasses show excellent spectroscopic properties at~1.5μm,which exhibit longer lifetime (5.9–7.5 ms),larger emission cross section (8.5×10^(-21)–9.0×10^(-21)cm^(2)) and lower saturation intensity (1.0×10^(7)W m^(2)) than some phosphate,fluorophosphate and telluroborate laser glasses.Er^(3+)/Yb^(3+)co-doped fiber based on FSP glass shows a net gain of 4.7 d B/cm@1535 nm.An FL with a threshold of~50 m W and a slope efficiency of 11.3%has been demonstrated based on such fiber.Considering its high gain characteristics,the narrow-line-width single-frequency FL and high-repetition-rate ultrafast FL are expected to be realized further.
作者
肖永宝
邝路东
王伟超
姬瑶
张勤远
姜中宏
Yongbao Xiao;Ludong Kuang;Weichao Wang;Yao Ji;Qinyuan Zhang;Zhonghong Jiang(Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques,State Key Laboratory of Luminescent Materials and Devices,South China University of Technology,Guangzhou 510640,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2022年第10期1012-1020,共9页
Chinese Science Bulletin
基金
国家自然科学基金(52130201,U1830203)
广东省珠江人才计划创新研究团队项目(2017BT01X137)资助。
关键词
光纤激光
激光玻璃
氟硫磷酸盐玻璃
玻璃性质
玻璃结构
fiber laser
laser glass
fluoro-sulfo-phosphate glass
glass property
glass structure
