A Tm-Bi Co-Doped Fiber Laser with Dual Pumping Operation

We demonstrate an efficient fiber laser operating at 1901.6nm using a newly developed thulium bismuth co-doped fiber（TBF） with dual pumping at 792nm and 1552nm.The fiber was fabricated using modified chemical vapor deposition and solution doping processes.The dopant concentrations（wt%） and compositions inside the core are0.15Bi2O3,0.3Tm2O3,l.OAl2O3 and 12.0GeO2.The TBF laser operates at 1901.6nm with a iasing efficiency of 33.2%and pump power threshold of 85mW using a 2-m-long TBF in a linear cavity with two fiber Bragg gratings（FBGs）.The high efficiency is attributed to the use of additional 1552 nm pump to complement 792nm pumping.The maximum output power of 225 mW is achieved at the pump power of 820 mW with the optimum length of 2 m.