The Research On Erbium-doped And Erbium-Ytterbium Co-doped Fibers For 1.5?m Fiber Laser

The output laser of 1.5?m high power fiber laser is located in the"eye safety"band and has low transmission loss in silica fiber and atmosphere,so it has a wide application prospect in high-capacity fiber communication system,free-space optical communication,lidar and gravitational wave detection.Erbium-ytterbium co-doped fiber and large-mode area erbium-doped fiber are important gain components for 1.5?m high-power fiber laser.In the research of the above two gain optical fibers,there are a lot of relevant reports abroad and excellent research results have been achieved,but the domestic is still in its infancy.In this paper,based on the MCVD processing combined with liquid phase doping technology,the manufacturing methods of erbium-ytterbium co-doped fiber and large mode area erbium-doped fiber are studied.Firstly,this paper introduces the MCVD processing and its influence on the properties of optical fiber preform,focusing on the effects of pre-collapse,soot deposition,pre-sintering and collapse on the realization of high p-doped fiber core.High P-doped fiber core is the key to the manufacturing of erbium-ytterbium co-doped fiber with excellent laser performance.Subsequently,the refractive index profile,optical fiber absorption,background loss and other performance analysis and characterization test of optical fiber are introduced.Based on the in-depth study of MCVD processing,a fiber preform with a core P₂O₅content of 14.12mol%was manufactured by"reverse deposition",optimizing the process parameters and combining with"central silicon layer deposition"process.Aiming at the typical central sunken of P-doped fiber,a detailed simulation analysis was carried out to clarify its impact on fiber performance.By continuously optimizing the process,the high P-doped erbium-ytterbium co-doped fiber without central sunken was manufactured.The introduction of Al₂O₃ can effectively relieve the volatilization of P₂O₅ and eliminate the core sunken,while reducing the refractive index and increasing the solubility of rare earth ions.The erbium-ytterbium co-doped optical fiber manufactured by this process successfully achieves 1.5?m laser output,and the suppression of ytterbium band amplified spontaneous emission is what the next research focus on.The research results of erbium-ytterbium co-doped optical fiber are of great significance to break the monopoly of this technology abroad.For the large-mode-area erbium-doped fiber,the core background loss at 1200nm is reduced to 4.30d B/km by controlling the purity of raw materials and optimizing the water removal process.By optimizing the deposition process and the concentration of the doping solution,a high-absorption erbium-doped fiber with a core absorption of 76.13d B/m at1530nm was manufactured.It shows that co-doping of La³⁺in the core is helpful to reduce the clustering rate of Er³⁺.At the same time,it can reduce the incorporation of Al³⁺and the numerical aperture of the core.The preform with core diameter of 3.26mm was prepared by eight passes of core layer deposition,and it was drawn into 40/125?m large-core erbium-doped fiber.This type of fiber used to build a MOPA structure to achieve a laser output of1.52W.By further optimizing the Er³⁺concentration and fiber laser system,it is expected to achieve higher power laser output.