Fabrication And Laser Property Research Of Aluminophosphosilicate Active Fiber

High power fiber laser has become one of the most attractive laser devices due to outstanding beam quality,thermal management,compatibility and potential for further power scaling.With the dramatically improvement of output power occurred these years,nonlinear effect and photodarkening can be easily observed in fiber laser system and supposed to be the main obstructions for further power scaling.Aiming to improve the beam quality and power stability of fiber laser,this paper studied and analyzed the aluminophosphosilicate large-mode-area active fiber in terms of fiber design,perform fabrication and testing.By optimizing the fiber refractive index profile parameters,to form a low refractive index layer around core is capable of reducing the bending loss of fundamental mode.Bending loss of LP01 mode can be obviously suppressed from 0.0026dB/m to 1.2 × 10-8dB/m at 50 mm bending radius.At the same time,by depositing a high refractive index layer around core,bending loss of LP11 mode can be improved from 0.45dB/m to 36dB/m for the case of 100 mm bending radius.In this study,Al₂O₃-P₂O₅-SiO₂ glass system was applied in fiber core to weaken photodarkening effect.But high evaporation for phosphorus can easily led to center dip in fiber core.By optimizing the parameters of perform fabrication,center dip has been reduced.Mother perform was fabricated through organic chelate precursor doping technique.After sleeving and fiber draw,Yb-doped 25/400 fiber was obtained.The measurement of the parameters including preform refractive index profile,elemental analysis,fiber refractive index profile,absorption property was carried out for recipe optimization.Especially preform refractive index profile and elemental analysis play an important role in reducing core refractive index fluctuation.After laser experiment,parameters of slop efficiency,laser spectr?m,beam quality and power output stability were obtained.By comprehensive measurement,preform fabrication parameters were optimized to fabricate Yb-doped 25/400 aluminophosphosilicate fiber with Yb3+ concentration of ⁴00ppm,core n?merical aperture of 0.07.It is noted that almost no power reduction occurred within 10-hours laser experiment.which indicate that Al₂O₃-P₂O₅-SiO₂ glass system can be candidate for high power fiber laser.