Based on the rate equations describing the erbium-doped fluoride glass(ZBLAN) fibre lasers with different pumping configurations being taken into account,this paper presents theoretical calculations related to the dynamic population density and the operation performance of a high power mid-infrared all-fibre erbium-doped ZBLAN fibre laser.It shows that the ground-state absorption,excited-state absorption and energy-transfer-upconversion processes co-exist and produce a population balance,causing the laser to operate stably at a continuous wave state.A good agreement between the theoretical results and recent experimental measurement is obtained.Furthermore,the laser structure parameters including fibre length,reflectance of output fibre Bragg grating and pumping configurations are quantitatively optimised to achieve the best performance.The results show,as expected,that the slope efficiency of the fibre laser can be improved significantly through optimisation,which then provides an important guide for the design of high-performance mid-infrared erbium-doped ZBLAN fibre lasers.
An Yb3+-doped double-clad large-mode-area photonic crystal fiber(LMA PCF) laser with up to 210 W of continuous-wave output power centered at 1.05 μm is demonstrated.The length of the fiber used is 2 m and the produced laser power per meter can attain 105 W.The PCF is pumped by two diode lasers with central wavelength of 976 nm.The slope efficiency is 76%,and the beam quality factor M2 at x and y axes are measured to be 1.06 and 1.08,respectively.No thermo-optical problems and other roll-over even are observed at the highest output power.
LI JianFengDUAN KaiLiangLIU YongZhiDAI ZhiYongOU ZhongHuaLIU Yong
