Studies On The Design,Preparation And Characteristic Of A New Index Anti-guided And Gain Guided Large Mode Area Fibers

Gain guided-index antiguided?GG-IAG?fibers as a new type of LMA fiber has been concerned widely by researchers since it was proposed to the present.On the basis of GG-IAG fiber model,the composition of glass material for the core and cladding of GG-IAG fiber was designed.And the Nd³⁺doped phosphate GG-IAG fibers were made.The experiment of GG-IAG fiber amplifier was carried out.The effect of Ag coating on the gain performance of GG-IAG fiber was investigated in the experiment.Firstly,the composition of Nd³⁺doped phosphate laser glass was studied theoretically,and the composition of glass material of GG-IAG fiber was designed.And the glass materials of core and cladding were prepared.Effect of alkali metal oxide Na₂O on Tg of laser glass was studied.And the effect of La₂O₃ on the refractive index of laser glass at 1064nm was studied.By changing the content of the alkali metal oxide and the high refractive index material,the fiber glass materials have been matched to meet the requirements of the theory.The optical properties of the laser glass were tested,and the reliable experimental data are provided for the subsequent drawing of the optical fiber.Secondly,the fabrication process of rare earth doped fiber preform was investigated.And the GG-IAG fibers with different diameteris?200?m-500?m?were prepared by the preparation of the preform and the optical fiber drawing experiments.The optical properties of GG-IAG fibers,including the stimulated radiation spectrum of the optical fiber,the absorption loss of the optical fiber and so on,were also tested.The absorption coefficient of the anti guided fiber at 808nm is 0.0239/cm,the absorption loss coefficient is 0.1039dB/cm,the absorption coefficient at 1064nm is 0.0064/cm,and the absorption loss coefficient is 0.0280dB/cm.Thirdly,the relationship between the gain performance of fiber and the parameters of fiber waveguide was studied.And the experiment of GG-IAG fiber amplifier was carried out.The signal power was amplified from0.2MW to 1MW,and the gain coefficient of GG-IAG fiber is 0.1137/cm.The effect of coating Ag film on the gain performance of GG-IAG fiber was studied.The experiments were based on the GG-IAG fiber with different core diameters such as 130?m,160?m and 200?m respectively.By magnetron sputtering,a 200nm Ag film was applied on the surface of the fiber cladding as a total reflection film.The gain performance of Ag-coated and uncoated fibers was also tested.The experimental results show that the Ag film has higher signal amplification efficiency than that without Ag film under the same core diameter.And the amplification efficiency of Ag coated fiber is 50%,41.88%and 24.33%respectively,while the amplification efficiency of the unplated Ag film fiber is26.87%,22.8%and 15.87%,respectively.It shows that the optical fiber surface coating can significantly improve the gain performance of GG-IAG fiber,and the results are of guiding significance for the application of GG-IAG fiber.