纤芯掺铥均匀性对TDF及其TDFL性能的影响

Effect of Thulium Doped Fiber Core Uniformity on the Properties of TDF and TDFL

为改善掺铥光纤激光器(TDFL)的性能,对大模场双包层(LDC)铥掺杂光纤(TDF)及其搭建的TDFL的光学特性进行了实验研究。实验以两种不同类型LDC-TDF(即气相掺杂法制备的VTDF-7光纤和液相掺杂法制备的STDF-29光纤)作为试样,并以其分别搭建了TDFL。对上述TDF和TDFL光学性能分别进行详细实验研究后发现:相比STDF-29光纤,VTDF-7光纤具有更大的均匀纤芯掺杂区域;相比STDF-29光纤搭建的TDFL,VTDF-7光纤搭建的TDFL具有更高的光转换效率(53.5%,前者仅为48.7%,高出约5%)和长期稳定性(连续工作65h的功率不稳定性低于1%,前者仅工作1h就表现出了超过10%的功率衰减)。经分析,VTDF-7光纤搭建的TDFL的激光效率提高以及光子暗化效应减弱的主要原因是VTDF-7光纤中均匀的掺杂分布减少了因离子团簇而引起的损耗。由此可得,相比液相掺杂法,气相掺杂法在制备高质量大模场TDF上更具优势,可提高以其搭建的TDFL的光转换效率和耐用性。

The optical properties of large-mode-area double clad(LDC)thulium-doped fibers(TDFs)for improving the performances of TDF lasers(TDFLs)are experimentally studied.Two different LDC-TDFs are used as samples in the experiment.One of them(VTDF-7)is made by vapor-doping method and the other one(STDF-29)is fabricated by solution-doping method.Based on these two fibers,two TDFLs are constructed and performances of the lasers are investigated in detail,revealing that compared with STDF-29,the VTDF-7 owns a large uniform doping core.Therefore,VTDF-7-based TDFL has high transfer efficiency and long-term stability.The transfer efficiency of VTDF-7-based TDFL is 53.5%,which is 5% higher than that of STDF-29-based TDFL(48.7%).In addition,power instability of the VTDF-7-based TDFL is less than 1% within 65 hworking,while STDF-29-based TDFL shows more than 10%power degradation after only 1 hof operation.The efficiency improvement and photo-darkening easing of VTDF-7-based TDFL is mainly accounted for the reduction of ion-clustering related loss due to the uniform doping profile of VTDF-7.These results indicate that compared with the solution-doping method,the vapor-doping method is an attractive way for fabricate high-quality large-mode-area TDFs,which can be used for improving the transfer efficiency and robustness of TDFLs.